VIVO

Field of the invention

The invention relates to compounds, combinations, and kits for the cleaving of imaging or radiotherapy labels from (bio)molecules in a subject, such as

(bio)molecules that are administered to said subject for purposes such as targeted imaging and targeted radiotherapy.

Background of the invention

In many areas of medical diagnostics, imaging and radiotherapy, it is desired to selectively deliver an agent, such as a radiotherapeutic agent or a diagnostic (e.g. imaging) agent, to a specific site, or a confined region, in the body of a subject such as a patient. Targeting of an organ or a tissue is typically achieved by the conjugation of the desired imaging or radiotherapy label (i.e. a radionuclide) to a targeting agent, which binds to cell surfaces or promotes cellular uptake at or near the target site of interest. The targeting agents used to target such labels are typically constructs that have affinity for cell surface targets (e.g., membrane receptors), structural proteins (e.g., amyloid plaques), or intracellular targets (e.g., RNA, DNA, enzymes, cell signaling pathways). These targeting agents can be antibodies (and fragments), proteins, aptamers, oligopeptides, oligonucleotides, oligosaccharides, as well as peptides, peptoids and organic drug compounds known to accumulate at a particular disease or malfunction. Alternatively, an imaging or radiotherapy agent may target a metabolic pathway, which is upregulated during a disease (like infection or cancer) such as DNA, protein, and membrane synthesis and carbohydrate uptake. In diseased tissues, abovementioned markers can discriminate diseased cells from healthy tissue and offer unique possibilities for early detection, specific diagnosis and (targeted) therapy.

As radio-imaging and radiotherapeutic agents (i.e. nuclear imaging and therapy agents) comprise radionuclides, which are radioactive, it is desired to quickly, efficiently, and/or conveniently reduce the amount of radionuclides in a patient once its therapeutic and/or imaging purposes are fulfilled. For example, this will enable reducing the dose of potentially harmful radiation given to the whole body. Also, in the context of imaging, clearing the radionuclides from the patient as quickly as possible after the imaging procedure, allows starting another imaging procedure in the same patient of the same or a different imaging target (i.e. image cycling). Natural clearance, however, is very slow.

Furthermore, an important criterion for successful imaging/therapy agents in general and nuclear imaging/therapy agents in particular is that they exhibit a high target uptake while showing an efficient clearance (through renal and/or hepatobiliary systems) from non-target tissues and from the blood. However, this is often problematic, especially when using antibodies. For example, imaging studies in humans have shown that the maximum concentration of a radiolabeled antibody at the tumor site is attainable within 24 h but several more days are required before the concentration of the labeled antibody in circulation decreases to levels low enough for successful imaging to take place. In the context of radioimmunotherapy (RIT), the slow antibody clearance from blood results in high radiation doses to e.g. the bone marrow limiting the amount of radioactivity that can be safely administered, limiting the therapeutic effect.

Further, targeted imaging (e.g. optical or nuclear) or radiotherapy can be hampered by circulating fractions of the receptor that is being targeted, and which can capture the imaging or radiotherapy agents before they can reach the target receptor at the target cell surface, negatively impacting target-background ratios.

In addition, off target uptake of imaging agents (e.g. in the liver) can obscure the target uptake.

Effectively, the targeting process can be divided into three processes: (I) the administration process, in which the compound comprising a targeting agent is administered to a subject, and a fraction of said compound binds to the target;

(II) the clearance process, wherein the fraction of the compound comprising a targeting agent that circulates in the blood (rather than being bound to the target) is cleared (i.e. removed by excretion) from the blood and other non-target tissues;

(III) the imaging/therapy process, wherein the compound comprising a targeting agent present in the subject is used for imaging or therapy purposes.

It will be understood that the tumor-to-blood (T/B) ratios are increased in process (I) due to targeting, viz. the labelled compound accumulates at the targeted site, in this case a tumor.

For process (III), the T/B ratio should be sufficiently high, so that the fraction of circulating administered compound or compound bound to non-target tissues does not interfere with the imaging/therapy. Typically, this is achieved by waiting for an undesired long time during process (II), for reasons given above.

In general, it is desired to have methods to increase target-non target ratio of imaging or radiotherapy agents in the abovementioned process (II) more quickly, and to have temporal and spatial control over the action of those agents.

The poor T/B ratios for antibodies have led to pre-targeting approaches to improve image quality in radioimmunoimaging and to increase the therapeutic index in RIT. The long-circulating monoclonal antibody (mAh) is administered first, allowed to bind the tumor and slowly clear from circulation, after which a small radiolabeled probe is injected. This probe binds the tumor-bound antibody or otherwise rapidly clears from circulation, leading to improved T/B ratios.

Typically, a clearing agent is administered prior to injection of the probe, to clear any freely circulating antibody from blood, resulting in further improved T/B ratios [F.C. van de Watering et al., Front. Med. 2014, 1, 44] However, pretargeting can typically only be used with non-internalizing receptors, and is relatively complex, requiring the optimization of dosing and timing for three agents. An alternative approach is to administer a clearing agent to remove a radiolabeled antibody from circulation after sufficient amounts have bound the target, but this has not worked well in the clinic and gives high radiation doses to the liver [R.H.J. Begent et al., Br. J. Cancer 1989, 60, p. 406-412]

Another approach is to cleave the radiolabel from freely circulating antibody after sufficient amounts of radiolabeled antibody have bound and internalized in the target cells by of administering an enzyme designed to cleave the bond between antibody and label. However, the enzymatic cleavage method was rather slow and inefficient, giving only 3-fold improvements in T/B ratios [Q. Ren et al., Mol. Pharm. 2019, 16, p. 1065-1073]. In addition, three injections with the enzyme were typically required, which makes it an inconvenient method.

It is a desire to provide compounds and/or a combination of compounds that enables to quickly reduce the amount of radionuclides in a patient, e.g. after radioimaging is completed. It is also desired that a compound and/or a

combination of compounds be provided that enables an increase of the target-non target ratio of imaging or radiotherapy agents in the clearance process. It is also desired that this increase is obtained faster than in known methods.

Furthermore, it is desired to provide a compound and/or a combination of compounds that enables temporal and spatial control over the action of those agents. In addition, it is desired that this compound and/or a combination of compounds is versatile, rapid, efficient, and/or convenient.

Summary of the invention

The invention, in one aspect, pertains to a compound satisfying Formula (1):

Formula (1);

and pharmaceutically acceptable salts thereof, wherein each X ¹ , X ² , X ³ , X ⁴ is independently selected from the group consisting of

-C(R ₄₇ ) ₂ -, -NR ₃₇ -, -C(O)-, -O-, such that at most two of X ¹ , X ² , X ³ , X ⁴ are not -C(R ₄₇ ) ₂ -, and with the proviso that no sets consisting of adjacent atoms are present selected from the group consisting of -O-O-, -O-N-, -C(O)-O-, N-N-, and -C(O)-C(O)-;

X ⁵ is -C(R ₄₇ ) ₂ - or -CHR ₄₈ , preferably X ⁵ is -C(R ₄₇ ) ₂ -;

each R ₄₈ is independently selected from the group consisting of -L ^B , and -L ^A ; preferably R ₄₈ is -L ^B ;

R ₄₈ is bound to the remainder of the compound of Formula (1) via a part of R ₄₈ that is -O-, -S-, -OC(O)-, -OC(S)-, -SC(O)-, or -SC(S)-;

L ^B is a moiety satisfying Formula (2):

Formula (2); wherein

the dashed line denotes a bond to the remainder of the compound of Formula (1); S ^L is a linker, which optionally is a self-immolative linker L ^C ;

each R ₉₈ individually is a Label or a clearance- directing group;

each d independently is 0 or 1;

e is an integer in a range of from 0 to 4, preferably e is 0;

the Label is a moiety comprising a radionuclide;

the compound of Formula (1) comprises at least one Label and at least one Administration Agent;

L ^A is a moiety satisfying Formula (3):

Formula (3); wherein

the dashed line denotes a bond to the remainder of the compound of Formula (1); each s is independently 0 or 1; preferably each s is 0;

i is an integer in a range of from 0 to 4, preferably 0 or 1, most preferably 0;

each S ^P independently is a spacer, which optionally is a self-immolative linker L ^C ; A ^A denotes an Administration Agent, which is an antibody;

C ^C denotes a Construct-C, wherein each Construct-C is independently selected from the group consisting of a Label and an Administration Agent; preferably the compound of Formula (1) comprises at most one C ^C ;

provided that L ^A only comprises both the Label and the Administration Agent when L ^A is R ₄₈ ;

provided that if L ^A being R ₄₈ comprises both the Label and the Administration Agent, then the S ^P linked to said Label and said Administration Agent is a self- immolative linker;

each R ₄₇ is independently selected from the group consisting of

hydrogen, -L ^B , -L ^A , -(S ^P ) _i -C ^C , -F, -Cl, -Br, -I, -OR ₃₇ , -N(R ₃₇ ) ₂ , -SO ₃ , -PO ₃ -, -NO ₂ , - CF ₃ , -SR ₃₇ , S(=O) ₂ N(R ₃₇ ) ₂ , OC(=O)R ₃₇ , SC(=O) R ₃₇ , OC(=S)R ₃₇ , SC(=S)R ₃₇ , NR ₃₇ C(=O)-R ₃₇ , NR ₃₇ C(=S)-R ₃₇ , NR ₃₇ C(=O)O-R ₃₇ , NR ₃₇ C(=S)O-R ₃₇ ,

NR ₃₇ C(=O)S-R ₃₇ , NR ₃₇ C(=S)S-R ₃₇ , OC(=O)N(R ₃₇ ) ₂ , SC(=O)N(R ₃₇ ) ₂ ,

OC(=S)N(R ₃₇ ) ₂ , SC(=S)N(R ₃₇ ) ₂ , NR ₃₇ C(=O)N(R ₃₇ ) ₂ , NR ₃₇ C(=S)N(R ₃₇ ) ₂ , C(=O)R _37, C(=S)R _37, C(=O)N(R ₃₇ ) ₂ , C(=S)N(R ₃₇ ) ₂ , C(=O)O-R ₃₇ , C(=O)S-R ₃₇ , C(=S)O-R ₃₇ , C(=S)S-R ₃₇ , S(O)R ₃₇ , -S(O) ₂ R ₃₇ , NR ₃₇ S(O) ₂ R ₃₇ , -ON(R ₃₇ ) _2, -NR ₃₇ OR ₃₇ , C ₁ -C ₂₄ alkyl groups, C ₂ -C ₂₄ alkenyl groups, C ₂ -C ₂₄ alkynyl groups, C ₆ -C ₂₄ aryl groups, C ₂ -C ₂₄ heteroaryl groups, C ₃ -C ₂₄ cycloalkyl groups, C ₅ -C ₂₄ cycloalkenyl groups, C ₁₂ -C ₂₄ cycloalkynyl groups, C ₃ -C ₂₄ (cyclo)alkyl(hetero)aryl groups, C ₃ -C ₂₄ (hetero)aryl(cyclo)alkyl, C ₄ -C ₂₄ (cyclo)alkenyl(hetero)aryl groups, C ₄ -C ₂₄

(hetero)aryl(cyclo)alkenyl groups, C ₄ -C ₂₄ (cyclo)alkynyl(hetero)aryl groups, C ₄ - C ₂₄ (hetero)aryl(cyclo)alkynyl groups, C ₄ -C ₂₄ alkylcycloalkyl groups, and C ₄ -C ₂₄ cycloalkylalkyl groups; wherein i is an integer in a range of from 0 to 4, preferably i is an integer ranging from 0 to 1,

wherein the alkyl groups, alkenyl groups, alkynyl groups, aryl, heteroaryl, cycloalkyl groups, cycloalkenyl groups, cycloalkynyl groups,

(cyclo)alkyl(hetero)aryl groups, (hetero)aryl(cyclo)alkyl groups,

(cyclo)alkenyl(hetero)aryl groups, (hetero)aryl(cyclo) alkenyl groups, (cyclo)alkynyl(hetero)aryl groups, (hetero)aryl(cyclo)alkynyl groups, alkylcycloalkyl groups, cycloalkylalkyl groups are optionally substituted with a moiety selected from the group consisting of -Cl, -F, -Br, -I, -OR ₃₇ , -N(R ₃₇ ) ₂ , - SO ₃ R ₃₇ , -PO ₃ (R ₃₇ ) ₂ , -PO4(R ₃₇ ) ₂ , -NO ₂ , -CF ₃ , =O, =NR ₃₇ , and -SR ₃₇ , and optionally contain one or more heteroatoms selected from the group consisting of O, S, NR ₃₇ , P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized;

two R ₄₇ and/or R ₃₇ are optionally comprised in a ring,

two R ₄₇ and/or R ₃₇ are optionally comprised in a ring so as to form a ring fused to the eight membered trans-ring of Formula (1); each R ₃₇ is independently selected from the group consisting of hydrogen, -L ^B , - L ^A , -(S ^P ) _i -C ^C , C ₁ -C ₂₄ alkyl groups, C ₂ -C ₂₄ alkenyl groups, C ₂ -C ₂₄ alkynyl groups, C ₆ -C ₂₄ aryl groups, C ₂ -C ₂₄ heteroaryl groups, C ₃ -C ₂₄ cycloalkyl groups, C ₅ -C ₂₄ cycloalkenyl groups, C ₁₂ -C ₂₄ cycloalkynyl groups, C ₃ -C ₂₄ (cyclo)alkyl(hetero)aryl groups, C ₃ -C ₂₄ (hetero)aryl(cyclo)alkyl, C ₄ -C ₂₄ (cyclo)alkenyl(hetero)aryl groups, C ₄ -C ₂₄ (hetero) aryl (cyclo) alkenyl groups, C ₄ -C ₂₄ (cyclo)alkynyl(hetero)aryl groups, C ₄ -C ₂₄ (hetero) aryl (cyclo) alkynyl groups, C ₄ -C ₂₄ alkylcycloalkyl groups, and C ₄ - C ₂₄ cycloalkylalkyl groups; wherein i is an integer in a range of from 0 to 4, preferably i is 1;

the R ₃₇ groups not being hydrogen are optionally substituted with a moiety selected from the group consisting of -Cl, -F, -Br, -I, -OH, -NH ₂ , -SO ₃ H, -PO ₃ H _, - PO ₄ H _2, -NO ₂ , -CF ₃ , =O, =NH, and -SH, and optionally contain one or more heteroatoms selected from the group consisting of O, S, NH, P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized.

In another aspect, the invention relates to a combination comprising the compound according to Formula (1), and a Cleaving Agent, with the proviso that when at least one R ₄₈ in Formula (1) comprises a Label, then the Cleaving Agent does not comprise the same Label as R ₄₈ ; with the proviso that when at least one R ₄₈ in Formula (1) comprises an Administration Agent, then the Cleaving Agent does not comprise the same Administration Agent as R ₄₈ ;

wherein the Cleaving Agent is a diene. In yet another aspect, the invention pertains to the compound according to Formula (1), or the combination according to the invention for use as a

medicament.

In yet another aspect, the invention relates to the compound according to Formula (1), or the combination according to the invention, for use in the treatment of a disease, preferably cancer, in a subject, preferably a human, wherein the treatment is radiotherapy.

In a further aspect still, the invention relates to the compound according to Formula (1), or the combination according to the invention, for use in a diagnostic method comprising the steps of

(a) administering a compound according to Formula (1) as defined herein, to a subject, preferably a human;

(b) administering a Cleaving Agent as defined herein, to said subject;

(c) imaging the compound according to Formula (1) present in the subject to collect data;

(d) comparing said data to standard values;

(e) finding a significant deviation from said standard values during comparison;

(f) attributing the significant deviation to a particular clinical picture, preferably to cancer.

In yet another aspect, the invention pertains to a non-therapeutic method for imaging a compound according to Formula (1) in a subject, preferably a human, said non-therapeutic method comprising the steps of

(a) administering a compound according to Formula (1) as defined herein, to the subject;

(b) administering a Cleaving Agent as defined herein, to said subject;

(c) imaging the compound according to Formula (1) present in the subject.

In yet a further aspect, the invention relates to a use of a compound according to Formula (1), or a combination according to the invention, for imaging in a subject, preferably a human. Brief Description of the Figures

Figure 1. General scheme depicting the use of the invention in radioimmunotherapy. A radiolabelled antibody is administered, allowed to circulate and bind an internalizing cancer receptor, and after sufficient internalization has occurred a Cleaving Agent is administered that cleaves the radiolabel (e.g. a moiety comprising a radiometal-chelate complex) from the antibody, resulting in rapid renal clearance of the radioactivity from blood and non-target tissues, but not of the tumor cell-internalized radioactivity.

Figure 2. Radioactivity profiles in blood in mice injected with a mAb-trigger- Label conjugate followed by a Cleaving Agent or by vehicle. The Cleaving Agent is administered one hour or 24 hours post-mAb injection. The figure shows rapid clearance of the Label from blood upon trigger reaction with the Cleaving Agent in vivo.

Detailed Description of the Invention

In a broad sense, the invention pertains to the judicious recognition that compounds according to Formula (1), and combinations and kits as defined herein, better address one or more of the abovementioned desires. The

compounds, combinations, and kits of the invention can be used to quickly lower the amount of radionuclides in a subject. In particular, the compounds,

combinations, and kits of the invention can be used to increase the target-non target ratio of imaging or radiotherapy agents in the clearance process, and more particularly to reach such an increase more rapidly.

The invention, in one aspect, presents the concept of administering a compound according to Formula (1) comprising a label (a moiety comprising a radionuclide) and an Administration Agent, and subsequently administering a Cleaving Agent comprising a diene in the clearance phase, said dienophile and diene being capable of undergoing a bio-orthogonal reaction with each other, resulting in the decoupling of the label from the Administration Agent, preferably at specifically the non-targeted site ( e.g . the blood), and the efficient clearance of the released label from circulation and other non-target tissues, and/or the body as a whole. An Administration Agent is to be understood as any antibody, in particular those of which it is desired to image its biodistribution or target binding in vivo, or which is used as a targeting agent for therapeutic radiation.

This bio-orthogonal reaction is very fast, and readily results in good release of the moiety comprising a radionuclide. Typically, high release yields are obtained after only one administration of the Cleaving Agent, making the method efficient, and convenient for both the patient and the medical practitioner.

Thus, preferably the cleavage of the label from the compound of Formula (1) pertains to the fraction present in, or bound to non-target tissues while the portion bound to target tissues is not cleaved or does not lead to accelerated clearance.

The fact that the inverse electron demand Diels-Alder (IEDDA) reaction can be used in the abovementioned applications is surprising. Firstly, the IEDDA reaction has never been used to lower the amount of radionuclides in a subject. Instead, the IEDDA reaction has typically been used to specifically release a drug at a target site, after which the drug entered a cell, a tumor, and the like. Thus, this does not relate to radionuclides, and speaks against ways to quickly remove the released agent from the body. In addition, previously the IEDDA reaction was used to specifically release a drug at the target site specifically after the clearance process. Moreover, the IEDDA reaction was used in applications wherein no release occurs, but a clearance- directing group is used to remove the Administration Agent from circulation. By contrast, the present invention is based on the judicious insight that with the compounds and combinations of the invention, decoupling of a label and the Administration Agent occurs, preferably in the blood and other non-target sites, after which specifically the label is rapidly cleared (Figure 1).

Without wishing to be bound by theory, the inventors believe that an antibody comprised in the compounds of Formula (1) has a relatively slow clearance rate due large size and/or the binding to biomolecules and much larger structures, such as cells, which greatly reduces the clearance rate of the compound of Formula (1). By addition of a Cleaving Agent, the moiety comprising a radionuclide is released. Said moiety is by definition smaller than the compound of Formula (1), and has no specific affinity for any biomolecule and thus typically does not bind to such a biomolecule. The inventors believe that for at least these reasons, the released moiety is cleared much faster than the compound of Formula (1).

Specifically, when the Administration Agent is an intact IgG antibody, this antibody will clear very slowly from blood due to FcRn-mediated recycling. In addition, or alternatively, Administration Agents may bind to a Primary Target present in blood (e.g. on a blood cell or a shed receptor from a tumor) or other biomolecules (e.g. serum albumin) and tissues, target tissues and non-target tissues, and as a result clear slowly from the body as a whole, from the target tissues or from the non-target tissues. Also, proteins in general, including antibodies, can clear slowly due to relatively large size. On the contrary, the released moiety comprising a radionuclide is generally cleared fast, as it is much smaller and typically has low affinity to biomolecules and tissues. Reference is made to [Orcutt et al, Mol Imaging Biol. 2011, 215-221] demonstrating the fast clearance of radiolabeled chelate derivatives.

Thus, in some embodiments, a compound of Formula (1) comprising a label, particularly a radiolabeled chelate, and an Administration Agent, will be administered for the purpose of being targeted to and internalized by a certain tissue in the body, e.g. a tumor cell receptor or a brain target (Figure 1).

Subsequent injection of Cleaving Agent, preferably a non-internalizing (i.e. not cell permeable) Cleaving Agent, results in release of the radiolabeled chelate from Administration Agent in circulation and its rapid excretion, while any released chelate inside the target cell will not be excreted, leading to increased target-non-target (T-NT) ratios, that in particular are achieved more rapidly than with known methods.

In other embodiments, the compound of Formula (1) targets a non- internalizing receptor in a tissue. Then, preferably the Cleaving Agent is chosen such that it does not significantly extravasate from blood into other tissues, to enable specific release of the Label in the blood, i.e. off-target.

The compound of Formula (1) can be specifically designed as an imaging agent of a particular target or process in vivo, such as in the case of radioimmunoimaging. It can also be specifically designed to deliver therapeutic radiation to a particular target in vivo, such as in the case of

radioimmunotherapy.

A Cleaving Agent is an agent or compound that is administered to a subject for the purpose of cleaving the label from the Administration Agent resulting in a different biodistribution and pharmacokinetics of the released label compared to the label when bound to the Administration Agent. The released label has a much faster blood clearance than the compound of Formula (1) and/or the released label has a much lower retention in one or more non-target tissues such as epithelial cells, fat, muscle, and kidney and RES organs such as liver and spleen, than the compound of Formula (1).

The concept of cleaving a compound of Formula (1) in vivo is of general relevance in targeted radiotherapy and imaging.

Definitions

The present invention will further be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. Any reference signs in the claims shall not be construed as limiting the scope. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. Where an indefinite or definite article is used when referring to a singular noun e.g. "a" or "an", "the", this includes a plural of that noun unless something else is specifically stated.

The verb "to comprise", and its conjugations, as used in this description and in the claims is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. Thus, the scope of the expression "a device comprising means A and B" should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.

In addition, reference to an element by the indefinite article "a" or "an" does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there is one and only one of the elements. The indefinite article "a" or "an" thus usually means "at least one".

The compounds disclosed in this description and in the claims may comprise one or more asymmetric centres, and different diastereomers and/or enantiomers may exist of the compounds. The description of any compound in this description and in the claims is meant to include all diastereomers, and mixtures thereof, unless stated otherwise. In addition, the description of any compound in this description and in the claims is meant to include both the individual enantiomers, as well as any mixture, racemic or otherwise, of the enantiomers, unless stated otherwise. When the structure of a compound is depicted as a specific enantiomer, it is to be understood that the invention of the present application is not limited to that specific enantiomer, unless stated otherwise. When the structure of a compound is depicted as a specific

diastereomer, it is to be understood that the invention of the present application is not limited to that specific diastereomer, unless stated otherwise.

The compounds may occur in different tautomeric forms. The compounds according to the invention are meant to include all tautomeric forms, unless stated otherwise. When the structure of a compound is depicted as a specific tautomer, it is to be understood that the invention of the present application is not limited to that specific tautomer, unless stated otherwise.

The compounds disclosed in this description and in the claims may further exist as exo and endo diastereomers. Unless stated otherwise, the description of any compound in the description and in the claims is meant to include both the individual exo and the individual endo diastereomers of a compound, as well as mixtures thereof. When the structure of a compound is depicted as a specific endo or exo diastereomer, it is to be understood that the invention of the present application is not limited to that specific endo or exo diastereomer, unless stated otherwise.

Unless stated otherwise, the compounds of the invention and/or groups thereof may be protonated or deprotonated. It will be understood that it is possible that a compound may bear multiple charges which may be of opposite sign. For example, in a compound containing an amine and a carboxylic acid, the amine may be protonated while simultaneously the carboxylic acid is

deprotonated.

The present invention also provides a combination of a compound of Formula (1) and a Cleaving Agent. The term“combination” is to be understood in broad sense, not limited to a kit comprising both components. Thus, the compound of Formula (1) and the Cleaving Agent can be provided totally separately of each other. It will be understood that the function of the Cleaving Agent in particular is to act in combination with a compound of Formula (1).

In several formulae, groups or substituents are indicated with reference to letters such as“A”,“B”,“X”,“Y”, and various (numbered)“R” groups. In addition, the number of repeating units may be referred to with a letter, e.g. n in -(CH ₂ ) _n -. The definitions of these letters are to be read with reference to each formula, i.e. in different formulae these letters, each independently, can have different meanings unless indicated otherwise.

In several chemical formulae and texts below reference is made to "alkyl", "heteroalkyl", "aryl", “heteroaryl”,“alkenyl”,“alkynyl”,“alkylene”, “alkenylene”,“alkynylene”, "arylene",“cycloalkyl”,“cycloalkenyl”,“cycloakynyl ”, arenetriyl, and the like. The number of carbon atoms that these groups have, excluding the carbon atoms comprised in any optional substituents as defined herein, can be indicated by a designation preceding such terms (e.g.“C ₁ -C ₈ alkyl” means that said alkyl may have from 1 to 8 carbon atoms). For the avoidance of doubt, a butyl group substituted with a -OCH ₃ group is designated as a C ₄ alkyl, because the carbon atom in the substituent is not included in the carbon count. Unsubstituted alkyl groups have the general formula C _n H _2n+1 and may be linear or branched. Optionally, the alkyl groups are substituted by one or more substituents further specified in this document. Examples of alkyl groups include methyl, ethyl, propyl, 2-propyl, t-butyl, 1-hexyl, 1-dodecyl, etc. Unless stated otherwise, an alkyl group optionally contains one or more heteroatoms

independently selected from the group consisting of O, NR ₃₆ , S, P, and Si, wherein the N, S, and P atoms are optionally oxidized and the N atoms are optionally quaternized. In preferred embodiments, up to two heteroatoms may be consecutive, such as in for example -CH ₂ -NH-OCH ₃ and -CH ₂ -O-Si(CH ₃ ) ₃ . In some preferred embodiments the heteroatoms are not directly bound to one another. Examples of heteroalkyls include -CH ₂ CH ₂ -O-CH ₃ , -CH ₂ CH ₂ -NH-CH ₃ , - CH ₂ CH ₂ -S(O)-CH _{3 ,} -CH=CH-O-CH ₃ , -Si(CH ₃ )3. In preferred embodiments, a C ₁ - C ₄ alkyl contains at most 2 heteroatoms.

A cycloalkyl group is a cyclic alkyl group. Unsubstituted cycloalkyl groups comprise at least three carbon atoms and have the general formula C _n H _2n-1 . Optionally, the cycloalkyl groups are substituted by one or more substituents further specified in this document. Examples of cycloalkyl

groups include cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl. Unless stated otherwise, a cycloalkyl group optionally contains one or more heteroatoms independently selected from the group consisting of O, NR ₃₆ , S, P, and Si, wherein the N, S, and P atoms are optionally oxidized and the N atoms are optionally quaternized.

An alkenyl group comprises one or more carbon-carbon double bonds, and may be linear or branched. Unsubstituted alkenyl groups comprising one C-C double bond have the general formula C _n H _2n-1 . Unsubstituted alkenyl groups comprising two C-C double bonds have the general formula C _n H _2n-3 . An alkenyl group may comprise a terminal carbon-carbon double bond and/or an internal carbon-carbon double bond. A terminal alkenyl group is an alkenyl group wherein a carbon-carbon double bond is located at a terminal position of a carbon chain. An alkenyl group may also comprise two or more carbon-carbon double bonds. Examples of an alkenyl group include ethenyl, propenyl, isopropenyl, t- butenyl, 1,3-butadienyl, 1,3-pentadienyl, etc. Unless stated otherwise, an alkenyl group may optionally be substituted with one or more, independently selected, substituents as defined herein. Unless stated otherwise, an alkenyl group optionally contains one or more heteroatoms independently selected from the group consisting of O, NR ₃₆ , S, P, and Si, wherein the N, S, and P atoms are optionally oxidized and the N atoms are optionally quaternized.

An alkynyl group comprises one or more carbon-carbon triple bonds, and may be linear or branched. Unsubstituted alkynyl groups comprising one C-C triple bond have the general formula C _n H _2n-3 . An alkynyl group may comprise a terminal carbon-carbon triple bond and/or an internal

carbon-carbon triple bond. A terminal alkynyl group is an alkynyl group wherein a carbon-carbon triple bond is located at a terminal position of a carbon chain. An alkynyl group may also comprise two or more carbon-carbon triple bonds. Unless stated otherwise, an alkynyl group may optionally be substituted with one or more, independently selected, substituents as defined herein. Examples of an alkynyl group include ethynyl, propynyl, isopropynyl, t-butynyl, etc. Unless stated otherwise, an alkynyl group optionally contains one or more heteroatoms independently selected from the group consisting of O, NR ₃₆ , S, P, and Si, wherein the N, S, and P atoms are optionally oxidized and the N atoms are optionally quaternized.

An aryl group refers to an aromatic hydrocarbon ring system that comprises six to twenty-four carbon atoms, more preferably six to twelve carbon atoms, and may include monocyclic and polycyclic structures. When the aryl group is a polycyclic structure, it is preferably a bicyclic structure. Optionally, the aryl group may be substituted by one or more substituents further specified in this document. Examples of aryl groups are phenyl and naphthyl.

Arylalkyl groups and alkylaryl groups comprise at least seven carbon atoms and may include monocyclic and bicyclic structures. Optionally, the arylalkyl groups and alkylaryl may be substituted by one or more substituents further specified in this document. An arylalkyl group is for example benzyl. An alkylaryl group is for example 4-tert-butylphenyl.

Heteroaryl groups comprise at least two carbon atoms (i.e. at least C ₂ ) and one or more heteroatoms N, O, P or S. A heteroaryl group may have a monocyclic or a bicyclic structure. Optionally, the heteroaryl group may be substituted by one or more substituents further specified in this document.

Examples of suitable heteroaryl groups include pyridinyl, quinolinyl, pyrimidinyl, pyrazinyl, pyrazolyl, imidazolyl, thiazolyl, pyrrolyl, furanyl, triazolyl,

benzofuranyl, indolyl, purinyl, benzoxazolyl, thienyl, phospholyl and oxazolyl. Heteroaryl groups preferably comprise five to sixteen carbon atoms and contain between one to five heteroatoms.

Heteroarylalkyl groups and alkylheteroaryl groups comprise at least three carbon atoms (i.e. at least C ₃ ) and may include monocyclic and bicyclic structures. Optionally, the heteroaryl groups may be substituted by one or more substituents further specified in this document.

Where an aryl group is denoted as a (hetero)aryl group, the notation is meant to include an aryl group and a heteroaryl group. Similarly, an

alkyl(hetero)aryl group is meant to include an alkylaryl group and an

alkylheteroaryl group, and (hetero)arylalkyl is meant to include an arylalkyl group and a heteroarylalkyl group. A C ₂ -C ₂₄ (hetero)aryl group is thus to be interpreted as including a C ₂ -C ₂₄ heteroaryl group and a C ₆ -C ₂₄ aryl group.

Similarly, a C ₃ -C ₂₄ alkyl(hetero)aryl group is meant to include a C ₇ - C ₂₄ alkylaryl group and a C ₃ -C ₂₄ alkylheteroaryl group, and a C ₃ -C ₂₄ (hetero)arylalkyl is meant to include a C ₇ -C ₂₄ arylalkyl group and a C ₃ -C ₂₄ heteroarylalkyl group.

A cycloalkenyl group is a cyclic alkenyl group. An unsubstituted cycloalkenyl group comprising one double bond has the general formula C _n H _2n-3 . Optionally, a cycloalkenyl group is substituted by one or more substituents further specified in this document. An example of a cycloalkenyl group is cyclopentenyl. Unless stated otherwise, a cycloalkenyl group optionally contains one or more heteroatoms independently selected from the group consisting of O, NR ₃₆ , S, P, and Si, wherein the N, S, and P atoms are optionally oxidized and the N atoms are optionally quaternized.

A cycloalkynyl group is a cyclic alkynyl group. An unsubstituted cycloalkynyl group comprising one triple bond has the general formula C _n H _2n-5 . Optionally, a cycloalkynyl group is substituted by one or more substituents further specified in this document. An example of a cycloalkynyl group is cyclooctynyl. Unless stated otherwise, a cycloalkynyl group optionally contains one or more heteroatoms independently selected from the group consisting of O, NR. ₃₆ , S, P, and Si, wherein the N, S, and P atoms are optionally oxidized and the N atoms are optionally quaternized.

In general, when (hetero) is placed before a group, it refers to both the variant of the group without the prefix hetero- as well as the group with the prefix hetero-. Herein, the prefix hetero- denotes that the group contains one or more heteroatoms selected from the group consisting of O, N, S, P, and Si. It will be understood that groups with the prefix hetero- by definition contain

heteroatoms. Hence, it will be understood that if a group with the prefix hetero- is part of a list of groups that is defined as optionally containing heteroatoms, that for the groups with the prefix hetero- it is not optional to contain

heteroatoms, but is the case by definition.

Herein, it will be understood that when the prefix hetero- is used for combinations of groups, the prefix hetero- only refers to the one group before it is directly placed. For example, heteroarylalkyl denotes the combination of a heteroaryl group and an alkyl group, not the combination of a heteroaryl and a heteroalkyl group. As such, it will be understood that when the prefix hetero- is used for a combination of groups that is part of a list of groups that are indicated to optionally contain heteroatoms, it is only optional for the group within the combination without the prefix hetero- to contain a heteroatom, as it is not optional for the group within the combination with the prefix hetero- by definition (see above). For example, if heteroarylalkyl is part of a list of groups indicated to optionally contain heteroatoms, the heteroaryl part is considered to contain heteroatoms by definition, while for the alkyl part it is optional to contain heteroatoms.

Herein, the prefix cyclo- denotes that groups are cyclic. It will be understood that when the prefix cyclo- is used for combinations of groups, the prefix cyclo- only refers to the one group before it is directly placed. For example, cycloalkylalkenylene denotes the combination of a cycloalkylene group (see the definition of the suffix -ene below) and an alkenylene group, not the combination of a cycloalkylene and a cycloalkenylene group.

In general, when (cyclo) is placed before a group, it refers to both the variant of the group without the prefix cyclo- as well as the group with the prefix cyclo-.

Herein, the suffix -ene denotes divalent groups, i.e. that the group is linked to at least two other moieties. An example of an alkylene is propylene (- CH ₂ -CH ₂ -CH ₂ -), which is linked to another moiety at both termini. It is understood that if a group with the suffix -ene is substituted at one position with -H, then this group is identical to a group without the suffix. For example, an alkylene substituted with -H is identical to an alkyl group. I.e. propylene, -CH ₂ -CH ₂ -CH ₂ -, substituted with -H at one terminus, -CH ₂ -CH ₂ -CH ₂ -H, is logically identical to propyl, -CH ₂ -CH ₂ -CH ₃ .

Herein, when combinations of groups are listed with the suffix -ene, it refers to a divalent group, i.e. that the group is linked to at least two other moieties, wherein each group of the combination contains one linkage to one of these two moieties. As such, for example alkylarylene is understood as a combination of an arylene group and an alkylene group. An example of an alkylarylene group is -phenyl-CH ₂ -, and an example of an arylalkylene group is -CH ₂ -phenyl-.

Herein, the suffix -triyl denotes trivalent groups, i.e. that the group is linked to at least three other moieties. An example of an arenetriyl is depicted below:

wherein the wiggly lines denote bonds to different groups of the main compound.

It is understood that if a group with the suffix -triyl is substituted at one position with -H, then this group is identical to a divalent group with the suffix -ene. For example, an arenetriyl substituted with -H is identical to an arylene group. Similarly, it is understood that if a group with the suffix -triyl is substituted at two positions with -H, then this group is identical to a monovalent group. For example, an arenetriyl substituted with two -H is identical to an aryl group.

It is understood that if a group, for example an alkyl group, contains a heteroatom, then this group is identical to a hetero- variant of this group. For example, if an alkyl group contains a heteroatom, this group is identical to a heteroalkyl group. Similarly, if an aryl group contains a heteroatom, this group is identical to a heteroaryl group. It is understood that“contain” and its

conjugations mean herein that when a group contains a heteroatom, this heteroatom is part of the backbone of the group. For example, a C ₂ alkylene containing an N refers to -NH-CH ₂ -CH ₂ -, -CH ₂ -NH-CH ₂ -, and -CH ₂ -CH ₂ -NH-.

Unless indicated otherwise, a group may contain a heteroatom at non- terminal positions or at one or more terminal positions. In this case,“terminal” refers to the terminal position within the group, and not necessarily to the terminal position of the entire compound. For example, if an ethylene group contains a nitrogen atom, this may refer to

-NH-CH ₂ -CH ₂ -, -CH ₂ -NH-CH ₂ -, and -CH ₂ -CH ₂ -NH-. For example, if an ethyl group contains a nitrogen atom, this may refer to -NH-CH ₂ -CH ₃ , -CH ₂ -NH-CH ₃ , and -CH ₂ -CH ₂ -NH ₂ .

Herein, it is understood that cyclic compounds (i.e. aryl, cycloalkyl, cycloalkenyl, etc.) are understood to be monocyclic, polycyclic or branched. It is understood that the number of carbon atoms for cyclic compounds not only refers to the number of carbon atoms in one ring, but that the carbon atoms may be comprised in multiple rings. These rings may be fused to the main ring or substituted onto the main ring. For example, C ₁₀ aryl optionally containing heteroatoms may refer to inter alia a naphthyl group (fused rings) or to e.g. a bipyridyl group (substituted rings, both containing an N atom).

Unless stated otherwise, (hetero)alkyl groups, (hetero) alkenyl groups, (hetero)alkynyl groups, (hetero)cycloalkyl groups, (hetero)cycloalkenyl groups, (hetero)cycloalkynyl groups, (hetero) alky lcycloalkyl groups,

(hetero)alkylcycloalkenyl groups, (hetero) alky lcycloalkynyl groups,

(hetero)cycloalkylalkyl groups, (hetero)cycloalkenylalkyl groups, (hetero)cycloalkynylalkyl groups, (hetero)alkenylcycloalkyl groups, (hetero)alkenylcycloalkenyl groups, (hetero)alkenylcycloalkynyl groups,

(hetero)cycloalkylalkenyl groups, (hetero)cycloalkenylalkenyl groups,

(hetero)cycloalkynylalkenyl groups, (hetero)alkynylcycloalkyl groups,

(hetero)alkynylcycloalkenyl groups, (hetero)alkynylcycloalkynyl groups,

(hetero)cycloalkylalkynyl groups, (hetero)cycloalkenylalkynyl groups,

(hetero)cycloalkynylalkynyl groups, (hetero)aryl groups, (hetero)arylalkyl groups, (hetero)arylalkenyl groups, (hetero)arylalkynyl groups, alkyl(hetero)aryl groups, alkenyl(hetero)aryl groups, alky nyl(hetero) aryl groups, cycloalkyl(hetero)aryl groups, cycloalkenyl(hetero)aryl groups, cycloalkynyl(hetero)aryl groups,

(hetero)arylcycloalkyl groups, (hetero)arylcycloalkenyl groups,

(hetero)arylcycloalkynyl groups, (hetero)alkylene groups, (hetero)alkenylene groups, (hetero)alkynylene groups, (hetero)cycloalkylene groups,

(hetero)cycloalkenylene groups, (hetero)cycloalkynylene groups, (hetero)arylene groups, alkyl(hetero)arylene groups, (hetero)arylalkylene groups,

(hetero)arylalkenylene groups, (hetero)arylalkynylene groups,

alkenyl(hetero)arylene, alkynyl(hetero)arylene, (hetero)arenetriyl groups, (hetero)cycloalkanetriyl groups, (hetero)cycloalkenetriyl and

(hetero)cycloalkynetriyl groups are optionally substituted with one or more substituents independently selected from the group consisting of -Cl, -F, -Br, -I, - OH, -NH ₂ , -SO ₃ H, -PO ₃ H, -PO4H ₂ , -NO ₂ , -CF ₃ , =O, =NR ₃₆ , -SR ₃₆ , C ₁ -C ₂₄ alkyl groups, C ₂ -C ₂₄ alkenyl groups, C ₂ -C ₂₄ alkynyl groups, C ₆ -C ₂₄ aryl groups, C ₂ -C ₂₄ heteroaryl groups, C ₃ -C ₂₄ cycloalkyl groups, C ₅ -C ₂₄ cycloalkenyl groups, C ₁₂ -C ₂₄ cycloalkynyl groups, C ₃ -C ₂₄ alkyl(hetero)aryl groups, C ₃ -C ₂₄ (hetero)arylalkyl groups, C ₄ -C ₂₄ (hetero)arylalkenyl groups, C ₄ -C ₂₄ (hetero)arylalkynyl groups, C ₄ - C ₂₄ alkenyl(hetero)aryl groups, C ₄ -C ₂₄ alkynyl(hetero)aryl groups, C ₄ -C ₂₄ alkylcycloalkyl groups, C ₆ -C ₂₄ alkylcycloalkenyl groups, C ₁₃ -C ₂₄ alkylcycloalkynyl groups, C ₄ -C ₂₄ cycloalkylalkyl groups, C ₆ -C ₂₄ cycloalkenylalkyl groups, C ₁₃ -C ₂₄ cycloalkynylalkyl groups, C ₅ -C ₂₄ alkenylcycloalkyl groups, C ₇ -C ₂₄

alkenylcycloalkenyl groups, C ₁₄ -C ₂₄ alkenylcycloalkynyl groups, C ₅ -C ₂₄

cycloalkylalkenyl groups, C ₇ -C ₂₄ cycloalkenylalkenyl groups, C ₁₄ -C ₂₄

cycloalkynylalkenyl groups, C ₅ -C ₂₄ alkynylcycloalkyl groups, C ₇ -C ₂₄ alkynylcycloalkenyl groups, C ₁₄ -C ₂₄ alkynylcycloalkynyl groups, C ₅ -C ₂₄

cycloalkylalkynyl groups, C ₇ -C ₂₄ cycloalkenylalkynyl groups, C ₁₄ -C ₂₄

cycloalkynylalkynyl groups, C ₅ -C ₂₄ cycloalkyl(hetero)aryl groups, C ₇ -C ₂₄ cycloalkenyl(hetero)aryl groups, C ₁₄ -C ₂₄ cycloalkynyl(hetero)aryl groups, C ₅ -C ₂₄ (hetero)arylcycloalkyl groups, C ₇ -C ₂₄ (hetero)arylcycloalkenyl groups, and C ₁₄ -C ₂₄ (hetero)arylcycloalkynyl groups. Unless stated otherwise, the substituents disclosed herein optionally contain one or more heteroatoms selected from the group consisting of O, S, NR ₃₆ , P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized. Preferably, these substituents optionally contain one or more heteroatoms selected from the group consisting of O, S, and NR ₃₆ .

In preferred embodiments, the substituents are selected from the group consisting of -Cl, -F, -Br, -I, -OH, -NH ₂ , -SO ₃ H, -PO ₃ H, -PO ₄ H ₂ , -NO ₂ , -CF ₃ , =O,

— NR ₃₆ , -SR ₃₆ , C ₁ -C ₁₂ alkyl groups, C ₂ -C ₁₂ alkenyl groups, C ₂ -C ₁₂ alkynyl groups, C ₆ -C ₁₂ aryl groups, C ₂ -C ₁₂ heteroaryl groups, C ₃ -C ₁₂ cycloalkyl groups, C ₅ -C ₁₂ cycloalkenyl groups, C ₁₂ cycloalkynyl groups, C ₃ -C ₁₂ alkyl(hetero)aryl groups, C ₃ - C ₁₂ (hetero)arylalkyl groups, C ₄ -C ₁₂ (hetero)arylalkenyl groups, C ₄ -C ₁₂

(hetero)arylalkynyl groups, C ₄ -C ₁₂ alkenyl(hetero)aryl groups, C ₄ -C ₁₂

alky nyl(hetero) aryl groups, C ₄ -C ₁₂ alkylcycloalkyl groups, C ₆ -C ₁₂

alkylcycloalkenyl groups, C ₁₃ -C ₁₆ alkylcycloalkynyl groups, C ₄ -C ₁₂ cycloalkylalkyl groups, C ₆ -C ₁₂ cycloalkenylalkyl groups, C ₁₃ -C ₁₆ cycloalkynylalkyl groups, C ₅ -C ₁₂ alkenylcycloalkyl groups, C ₇ -C ₁₂ alkenylcycloalkenyl groups, C ₁₄ -C ₁₆

alkenylcycloalkynyl groups, C ₅ -C ₁₂ cycloalkylalkenyl groups, C ₇ -C ₁₂

cycloalkenylalkenyl groups, C ₁₄ -C ₁₆ cycloalkynylalkenyl groups, C ₅ -C ₁₂

alkynylcycloalkyl groups, C ₇ -C ₁₂ alkynylcycloalkenyl groups, C ₁₄ -C ₁₆

alkynylcycloalkynyl groups, C ₅ -C ₁₂ cycloalkylalkynyl groups, C ₇ -C ₁₂

cycloalkenylalkynyl groups, C ₁₄ -C ₁₆ cycloalkynylalkynyl groups, C ₅ -C ₁₂

cycloalkyl(hetero)aryl groups, C ₇ -C ₁₂ cycloalkenyl(hetero)aryl groups, C ₁₄ -C ₁₆ cycloalkynyl(hetero)aryl groups, C ₅ -C ₁₂ (hetero)arylcycloalkyl groups, C ₇ -C ₁₂ (hetero)arylcycloalkenyl groups, and C ₁₄ -C ₁₆ (hetero)arylcycloalkynyl groups.

In preferred embodiments, the substituents are selected from the group consisting of -Cl, -F, -Br, -I, -OH, -NH ₂ , -SO ₃ H, -PO ₃ H, -PO ₄ H ₂ , -NO ₂ , -CF ₃ , =O, — NR ₃₆ , -SR ₃₆ , C ₁ -C ₇ alkyl groups, C ₂ -C ₇ alkenyl groups, C ₂ -C ₇ alkynyl groups, C ₆ - C ₇ aryl groups, C ₂ -C ₇ heteroaryl groups, C ₃ -C ₇ cycloalkyl groups, C ₅ -C ₇

cycloalkenyl groups, C ₁₂ cycloalkynyl groups, C ₃ -C ₇ alkyl(hetero)aryl groups, C ₃ - C ₇ (hetero)arylalkyl groups, C ₄ -C ₈ (hetero)arylalkenyl groups, C ₄ -C ₈

(hetero)arylalkynyl groups, C ₄ -C ₈ alkenyl (hetero)aryl groups, C ₄ -C ₈

alky nyl(hetero) aryl groups, C ₄ -C ₇ alkylcycloalkyl groups, C ₆ -C ₇ alkylcycloalkenyl groups, C ₁₃ -C ₁₆ alkylcycloalkynyl groups, C ₄ -C ₇ cycloalkylalkyl groups, C ₆ -C ₇ cycloalkenylalkyl groups, C ₁₃ -C ₁₆ cycloalkynylalkyl groups, C ₅ -C ₇

alkenylcycloalkyl groups, C ₇ -C ₇ alkenylcycloalkenyl groups, C ₁₄ -C ₁₆

alkenylcycloalkynyl groups, C ₅ -C ₇ cycloalkylalkenyl groups, C ₇ -C ₈

cycloalkenylalkenyl groups, C ₁₄ -C ₁₆ cycloalkynylalkenyl groups, C ₅ -C ₇

alkynylcycloalkyl groups, C ₇ -C ₈ alkynylcycloalkenyl groups, C ₁₄ -C ₁₆

alkynylcycloalkynyl groups, C ₅ -C ₇ cycloalkylalkynyl groups, C ₇ -C ₈

cycloalkenylalkynyl groups, C ₁₄ -C ₁₆ cycloalkynylalkynyl groups, C ₅ -C ₉

cycloalkyl(hetero)aryl groups, C ₇ -C ₁₁ cycloalkenyl(hetero)aryl groups, C ₁₄ -C ₁₆ cycloalkynyl(hetero)aryl groups, C ₅ -C ₉ (hetero)arylcycloalkyl groups, C ₇ -C ₁₁ (hetero)arylcycloalkenyl groups, and C ₁₄ -C ₁₆ (hetero)arylcycloalkynyl groups.

Unless stated otherwise, any group disclosed herein that is not cyclic is understood to be linear or branched. In particular, (hetero)alkyl groups,

(hetero)alkenyl groups, (hetero) alkynyl groups, (hetero)alkylene groups,

(hetero)alkenylene groups, (hetero)alkynylene groups, and the like are linear or branched, unless stated otherwise.

The general term "sugar" is herein used to indicate a monosaccharide, for example glucose (Glc), galactose (Gal), mannose (Man) and fucose (Fuc). The term "sugar derivative" is herein used to indicate a derivative of a

monosaccharide sugar, i.e. a monosaccharide sugar comprising substituents and/or functional groups. Examples of a sugar derivative include amino sugars and sugar acids, e.g. glucosamine (GlcNH ₂ ), galactosamine (GalNH ₂ ), N- acetylglucosamine (GlcNAc), N-acetylgalactosamine (GalNAc), sialic acid (Sia) which is also referred to as N-acetylneuraminic acid (NeuNAc), and N- acetylmuramic acid (MurNAc), glucuronic acid (GlcA) and iduronic acid (ldoA).

A sugar may be without further substitution, and then it is understood to be a monosaccharide. A sugar may be further substituted with at one or more of its hydroxyl groups, and then it is understood to be a disaccharide or an oligosaccharide. A disaccharide contains two monosaccharide moieties linked together. An oligosaccharide chain may be linear or branched, and may contain from 3 to 10 monosaccharide moieties.

The term "protein" is herein used in its normal scientific meaning. Herein, polypeptides comprising about 10 or more amino acids are considered proteins. A protein may comprise natural, but also unnatural amino acids. The term“protein” herein is understood to comprise antibodies and antibody fragments.

The term“peptide” is herein used in its normal scientific meaning. Herein, peptides are considered to comprise a number of amino acids in a range of from 2 to 9.

The term“peptoids” is herein used in its normal scientific meaning.

An antibody is a protein, typically generated by the immune system that is capable of recognizing and binding to a specific antigen. While antibodies or immunoglobulins derived from IgG antibodies are particularly well- suited for use in this invention, immunoglobulins from any of the classes or subclasses may be selected, e.g. IgG, IgA, IgM, IgD and IgE. Suitably, the immunoglobulin is of the class IgG including but not limited to IgG subclasses (IgGl, 2, 3 and 4) or class IgM which is able to specifically bind to a specific epitope on an antigen. Antibodies can be intact immunoglobulins derived from natural sources or from recombinant sources and can be immunoreactive portions of intact

immunoglobulins. Antibodies may exist in a variety of forms including, for example, polyclonal antibodies, monoclonal antibodies, camelized single domain antibodies, recombinant antibodies, anti-idiotype antibodies, multispecific antibodies, antibody fragments, such as, Fv, VHH, Fab, F(ab) ₂ , Fab', Fab'-SH, F(ab') ₂ , single chain variable fragment antibodies (scFv), tandem/bis-scFv, Fc, pFc', scFv-Fc, disulfide Fv (dsFv), bispecific antibodies (bc-scFv) such as BiTE antibodies, trispecific antibody derivatives such as tribodies, camelid antibodies, minibodies, nanobodies, resurfaced antibodies, humanized antibodies, fully human antibodies, single domain antibodies (sdAb, also known as Nanobody™), chimeric antibodies, antibody fusions, chimeric antibodies comprising at least one human constant region, dual-affinity antibodies such as dual-affinity retargeting proteins (DART™), and multimers and derivatives thereof, such as divalent or multivalent single-chain variable fragments (e.g. di-scFvs, tri-scFvs) including but not limited to minibodies, diabodies, triabodies, tribodies, tetrabodies, and the like, and multivalent antibodies. Reference is made to [Trends in

Biotechnology 2015, 33, 2, 65], [Trends Biotechnol. 2012, 30, 575-582], and

[Cane. Gen. Prot. 2013 10, 1-18], and [BioDrugs 2014, 28, 331—343], the contents of which are hereby incorporated by reference. "Antibody fragment" refers to at least a portion of the variable region of the immunoglobulin that binds to its target, i.e. the antigen-binding region. Other embodiments use antibody mimetics, such as but not limited to Affimers, Anticalins, Avimers, Alphabodies, Affibodies, DARPins, and multimers and derivatives thereof; reference is made to [Trends in Biotechnology 2015, 33, 2, 65], the contents of which is hereby incorporated by reference.“Antibody” as used herein also refers to antibodies with further functionalities, such as labelled antibodies, particularly radiolabeled antibodies, and antibody-drug conjugates. For the avoidance of doubt, in the context of this invention the term "antibody" is meant to encompass all of the antibody variations, fragments, derivatives, fusions, analogs and mimetics outlined in this paragraph, unless specified otherwise.

A linker is herein defined as a moiety that connects two or more elements of a compound. For example in a bioconjugate, a biomolecule and another moiety, e.g. a label, are covalently connected to each other via a linker.

A biomolecule is herein defined as any molecule that can be isolated from nature or any molecule composed of smaller molecular building blocks that are the constituents of macromolecular structures derived from nature, in particular nucleic acids, proteins, glycans and lipids. Examples of a biomolecule include an enzyme, a (non-catalytic) protein, a polypeptide, a peptide, an amino acid, an oligonucleotide, a monosaccharide, an oligosaccharide, a polysaccharide, a glycan, a lipid and a hormone.

As used herein, an organic molecule is defined as a molecule comprising a C-H bond. Organic compound and organic molecule are used synonymously. It will be understood that“organic molecule” as used herein includes biomolecules, such as nucleic acids (oligonucleotides, polynucleotides, DNA, RNA), peptides, proteins (in particular antibodies), carbohydrates

(monosaccharides, oligosaccharides, and polysaccharides), aptamers, hormones, toxins, steroids, cytokines, and lipids; small organic molecules as defined herein; polymers (in particular polyethylene glycol); LNA and PNA; amino acids;

peptoids; molecules comprising a radionuclide; fluorescent dyes; drugs; resins (in particular polystyrene and agarose); beads; particles (in particular

polymersomes, liposomes, and beads); gels; surfaces; organometallic compounds; cells; and combinations thereof.

As used herein, an inorganic molecule is defined as any molecule not being an organic molecule, i.e. not comprising a C-H bond. It will be understood that“inorganic molecule” as used herein includes surfaces (in particular chips, wafers, gold, metal, silica-based surfaces such as glass); particles such as beads (in particular magnetic beads, gold beads), silica-based particles, polymer-based materials, iron oxide particles; caron nanotubes; allotropes of carbon (in particular fullerenes such as Buckminsterfullerene; graphite, graphene, diamond, Lonsdaleite, Q-carbon, linearn acetylenic carbon, amorphous carbon, and carbon nanotubes); drugs (in particular cisplatin); and combinations thereof.

As used herein,“particle” is preferably defined as a microparticle or a nanoparticle.

The term "salt thereof’ means a compound formed when an acidic proton, typically a proton of an acid, is replaced by a cation, such as a metal cation or an organic cation and the like. The term "salt thereof’ also means a compound formed when an amine is protonated. Where applicable, the salt is a pharmaceutically acceptable salt, although this is not required for salts that are not intended for administration to a patient. For example, in a salt of a compound the compound may be protonated by an inorganic or organic acid to form a cation, with the conjugate base of the inorganic or organic acid as the anionic component of the salt.

The term "pharmaceutically accepted" salt means a salt that is acceptable for administration to a patient, such as a mammal (salts with counter- ions having acceptable mammalian safety for a given dosage regime). Such salts may be derived from pharmaceutically acceptable inorganic or organic bases and from pharmaceutically acceptable inorganic or organic acids.

"Pharmaceutically acceptable salt" refers to pharmaceutically acceptable salts of a compound, which salts are derived from a variety of organic and inorganic counter ions known in the art and include, for example, sodium, potassium, calcium, magnesium, ammonium, tetraalkylammonium, etc., and when the molecule contains a basic functionality, salts of organic or inorganic acids, such as hydrochloride, hydrobromide, formate, tartrate, besylate, mesylate, acetate, maleate, oxalate, etc.

In preferred embodiments, in relation to the invention“particle” is defined as a nanoparticle or a microparticle.

The logarithm of the partition-coefficient, i.e. Log P, is herein used as a measure of the hydrophobicity of a compound. Typically, the Log P is defined as

The skilled person is aware of methods to determine the partition-coefficient of compounds without undue experimentation. Alternatively, the skilled person knows that software is available to reliably estimate the Log P value, for example as a function within ChemDraw® software or online available tools.

The unified atomic mass unit or Dalton is herein abbreviated to Da.

The skilled person is aware that Dalton is a regular unit for molecular weight and that 1 Da is equivalent to 1 g/mol (grams per mole).

It will be understood that herein, the terms“moiety” and“group” are used interchangeably when referring to a part of a molecule. It will be understood that when a heteroatom is denoted as -X(R’) ₂ -, wherein X is the heteroatom and R’ is a certain moiety, then this denotes that two moieties R’ are attached to the heteroatom.

It will be understood that when a group is denoted as, for example, -((R ₅₁ ) ₂ -R ₅₂ ) ₂ - or a similar notation, in which R ₅₁ and R ₅₂ are certain moieties, then this denotes that first, it should be written as -R ₅₁ -R ₅₁ -R ₅₂ -R ₅₁ -R ₅₁ -R ₅₂ - before the individual R ₅₁ and R ₅₂ moieties are selected, rather than first selecting moieties R ₅₁ and R ₅₂ and then writing out the formula.

The Inverse Electron-Demand Diels-Alder reaction (IEDDA)

The established IEDDA conjugation chemistry generally involves a pair of reactants that comprise, as one reactant (i.e. one Bio-orthogonal Reactive Group), a suitable diene, such as a derivative of tetrazine (TZ), e.g. an electron- deficient tetrazine and, as the other reactant (i.e. the other Bio-orthogonal Reactive Group), a suitable dienophile, such as a trans-cyclooctene (TCO). The

exceptionally fast reaction of (substituted) tetrazines, in particular electron- deficient tetrazines, with a TCO moiety results in an intermediate that

rearranges to a dihydropyridazine Diels- Alder adduct by eliminating N2 as the sole by-product. The initially formed 4,5-dihydropyridazine product may tautomerize to a 1,4- or a 2, 5 -dihydropyridazine product, especially in aqueous environments. Below a reaction scheme is given for a [4+2] IEDDA reaction between (3,6)-di-(2-pyridyl)-s-tetrazine diene and a trans-cyclooctene dienophile, followed by a retro Diels Alder reaction in which the product and dinitrogen is formed. Because the trans-cyclooctene derivative does not contain electron withdrawing groups as in the classical Diels Alder reaction, this type of Diels Alder reaction is distinguished from the classical one, and frequently referred to as an“inverse-electron-demand Diels Alder (IEDDA) reaction”. In the following text the sequence of both reaction steps, i.e. the initial Diels-Alder cyclo-addition (typically an inverse electron-demand Diels Alder cyclo-addition) and the subsequent retro Diels Alder reaction will be referred to in shorthand as the “inverse electron-demand Diels Alder reaction” or“inverse electron- demand Diels Alder conjugation” or“IEDDA”. The product of the reaction is then the IEDDA adduct or conjugate. This is illustrated in Scheme 1 below.

Scheme 1: the IEDDA conjugation reaction

The two reactive species are abiotic and do not undergo fast metabolism or side reactions in vitro or in vivo. They are bio-orthogonal, e.g. they selectively react with each other in physiologic media. Thus, the compounds and the method of the invention can be used in a living organism. Moreover, the reactive groups are relatively small and can be introduced in biological samples or living organisms without significantly altering the size of biomolecules therein. References on the inverse electron demand Diels Alder reaction, and the behavior of the pair of reactive species include: [Thalhammer et al., Tetrahedron Lett., 1990, 31, 47, 6851-6854], [Wijnen et ah, J. Org. Chem., 1996, 61, 2001-2005], [Blackman et ah, J. Am. Chem. Soc., 2008, 130, 41, 13518-19], [Rossin et ah, Angew. Chem. Int.

Ed. 2010, 49, 3375], [Devaraj et ah, Angew. Chem. Int. Ed. 2009, 48, 7013],

[Devaraj et ah, Angew. Chem. Int. Ed., 2009, 48, 1-5].

The IEDDA Pyridazine Elimination Reaction

Below, the dienophile, a TCO, that may be comprised in kits of the invention may be referred to as a“Trigger” (T ^R ). The dienophile is connected at the ally lie position to a Construct- A. Moreover, tetrazines that are used in the IEDDA pyridazine elimination reaction may be referred to as“Cleaving Agents”. For ease of reference, the term Construct-A in this invention is used to indicate an

Administration Agent or a Label, of which it is desired to have it first in a bound state, and being able to provoke release from that state. Without wishing to be bound by theory, the inventors believe that the Cleaving Agent provokes Construct-A release via a cascade mechanism within the IEDDA adduct, i.e. the dihydropyridazine. The cascade mechanism can be a simple one step reaction, or it can be comprised in multiple steps that involves one or more intermediate structures. These intermediates may be stable for some time or may immediately degrade to the thermodynamic end-product or to the next

intermediate structure. In any case, whether it be a simple or a multistep process, the result of the cascade mechanism is that the Construct-A gets released from the IEDDA adduct. Without wishing to be bound by theory, the design of the diene is such that the distribution of electrons within the IEDDA adduct is unfavorable, so that a rearrangement of these electrons must occur.

This situation initiates the cascade mechanism, and it therefore induces the release of the Construct-A. Specifically, and without wishing to be bound by theory, the inventors believe that the NH moiety comprised in the various dihydropyridazine tautomers, such as the 1,4- dihydropyridazine tautomer, of the IEDDA adduct can initiate an electron cascade reaction, a concerted or

consecutive shift of electrons over several bonds, leading to release of the

Construct-A. Occurrence of the cascade reaction in and /or Construct-A release from the Trigger is not efficient or cannot take place prior to the IEDDA reaction, as the Trigger-Construct-A conjugate itself is relatively stable as such. The cascade can only take place after the Cleaving Agent and the Trigger- Construct conjugate have reacted and have been assembled in the IEDDA adduct.

With reference to Scheme 2 below, and without wishing to be bound by theory, the inventors believe that the pyridazine elimination occurs from the 1,4- dihydropyridazine tautomer 4. Upon formation of the 4,5-dihydropyridazine 3, tautomerization affords intermediates 4 and 7, of which the 2,5- dihydropyridazine 7 cannot eliminate the Construct-A (C ^A ). Instead it can slowly convert into aromatic 8, which also cannot eliminate C ^A or it can tautomerize back to intermediate 3. Upon formation of 4 the C ^A is eliminated near

instantaenously, affording free C ^A 8 as an amine, and pyridazine elimination products 5 and 6. This elimination reaction has been shown to work equally well in the cleavage of carbamates, carbonates, esters and ethers from the TCO trigger [Versteegen et al., Angew. Chem. Int. Ed., 2018, 57, 10494] The Trigger in Scheme 2 is also optionally bound to a Construct-B (C ^B ) , which in this case cannot release from the Trigger. Thereby Construct A can be seperated from Construct B by means of the IEDDA pyridazine elimination.

Scheme 2. IEDDA pyridazine elimination mechanism.

In preferred embodiments, the dienophile trigger moiety used in the present invention comprises a trans-cyclooctene ring. Herein, this eight-membered ring moiety will be defined as a trans-cyclooctene moiety, for the sake of legibility, or abbreviated as“TCO” moiety. It will be understood that the essence resides in the possibility of the eight-membered ring to act as a dienophile and to be released from its conjugated Construct-A upon reaction.

The tetrazines of the kits of the invention and dienophiles are capable of reacting in an inverse electron-demand Diels- Alder reaction (IEDDA). IEDDA reaction of the Trigger with the Cleaving Agent leads to release of the Construct-A through an electron-cascade-based elimination, termed the “pyridazine elimination”. When a Cleaving Agent reacts with a Trigger capable of eliminating Construct-A, the combined proces of reaction and Construct-A elimination is termed the“IEDDA pyridazine elimination”.

This invention provides a Cleaving Agent that reacts with a

Construct-A-conjugated Trigger, resulting in the cleavage of the Trigger from the Construct-A. In one prominent embodiment this results in the cleavage of

Construct-A from Construct-B. In another embodiment the Trigger cleavage results in cleavage of one Construct A from another Construct A, as the

dienophile Trigger of Formula (1) can comprise two allylic positioned Constructs- A, wherein one or both can release from the Trigger upon reaction with a diene.

In another embodiment, Trigger cleavage results in the cleavage of one or more Construct-A from one or more Construct-B. Construct-B is the Construct, i.e. either Administration Agent or Label depending on the nature of Construct-A, that is bound to the dienophile, and cannot be released from the dienophile, unless it is bound to the allylic position via a spacer or self-imolative linker that also binds Construct-A . In preferred embodiments, the Trigger is used as a reversible covalent bond between two molecular species.

Scheme 3a below is a general scheme of Construct release according to a preferred embodiment of this invention, wherein the Construct being released is termed Construct-A (C ^A ), and wherein another Construct, Construct-B (C ^B ) is bound to the dienophile but not via the allylic position, wherein Construct-B cannot be released from the dienophile, and wherein either Construct A or B is the Administration Agent and the other is the Label.

Scheme 3a: General scheme of IEDDA pyridazine elimination reaction for the release of Construct-A from Construct-B according to a preferred embodiment of this invention

Scheme 3b below is a general scheme of Construct release according to another embodiment of this invention, wherein Construct-B (C ^B ) is bound to the dienophile via a spacer or self-imolative linker that also binds Construct-A and, wherein when the spacer or self-immolative linker is released from the allylic position then Construct-B and Construct A are released from the Trigger and from each other.

Scheme 3b: General scheme of IEDDA pyridazine elimination reaction for the release of Construct-A from Construct-B according to a another embodiment of this invention

Scheme 3c below is a general scheme of Construct release according to another embodiment of this invention, wherein the Trigger is linked to two allylic positioned Construct-A's, and wherein one or both Constructs-A's can be released from the Trigger, in any case resulting in cleavage of one Construct-A from the other Construct-A, and and wherein one Construct-A is the Administration Agent and the other Construct-A is the Label.

Scheme 3c: General scheme of IEDDA pyridazine elimination reaction for the release of Construct-A from another Construct-A according to a preferred embodiment of this invention

The Construct release occurs through a powerful, abiotic, bio-orthogonal reaction of the dienenophile (Trigger) with the diene (Cleaving Agent), viz. the

aforementioned IEDDA. The bound Construct is a Construct- dienenophile conjugate. Possibly the Construct-A is linked to one or more additional

Constructs A linked via a spacer, for example a self-immolative linker. It will be understood that in Scheme 3a, 3b and 3c in the IEDDA adduct as well as in the end product after release, the indicated dienophile group and the indicated diene group are the residues of, respectively, the dienophile and diene groups after these groups have been converted in the IEDDA reaction.

The difference between C ^A and C ^B is that the bond between C ^B and the moiety holding C ^B is not broken upon reaction of the Trigger with the diene, whereas the bond between C ^A and the moiety holding C ^A is broken upon reaction of the Trigger with the diene. A person skilled in the art will understand that the moiety holding C ^A and C ^B refers to the Trigger, or a self immolative linker L ^C bound to the Trigger. For the sake of clarity, when C ^B is bound to a L ^C that is bound to the Trigger, the L ^C holding C ^B will release from the Trigger upon reaction with the diene but the C ^B will not release from the released L ^C . Likewise if C ^B is bound directly to the Trigger, C ^B will not release from the Trigger upon reaction with the diene. A person skilled in the art will understand that when it is required to seperate one Label from one Administration Agent, that preferably one of the following requirements is met:

1) one C ^A comprises the Label and another C ^A comprises the Adminstration Agent

2) either Label or Adminstration Agent is C ^A and the other is C ^B

3) Label and Adminstration Agent are both C ^B , provided that one C ^B is not part of R ₄₈ and the other is bound to a L ^C which is part of R ₄₈ , or provided that one C ^B moiety is bound to a different L ^C moiety than the other C ^B moiety.

Other than is the case with e.g. medicinally active substances, where the in vitro or in vivo action is often changed with minor structural changes, the present invention first and foremost requires the right chemical reactivity combined with sufficient stability for the intended application. Thus, the possible structures extend to those of which the skilled person is familiar with that these are reactive as dienes or dienophiles.

Targeting

A "primary target" as used in the present invention, both in relation to the Administration Agent and the Cleaving Agent, relates to a target to be detected in a diagnostic and/or imaging method, and/or to be modulated, bound, or otherwise addressed by a pharmaceutically active compound, or other

therapeutic modality. The primary target can be selected from any suitable target within the human or animal body or on a pathogen or parasite. For example, a primary target can be any molecule or tissue, which is present in an organism, tissue or cell. Targets include cells components such as cell membranes and cell walls, cell surface targets, e.g. receptors, glycoproteins; structural proteins, e.g. amyloid plaques; extracellular targets such as stroma targets, tumor microenvironment targets, extracellular matrix targets such as growth factors, and proteases; intracellular targets, e.g. surfaces of Golgi bodies, surfaces of mitochondria, RNA, DNA, enzymes, components of cell signaling pathways; and/or foreign bodies, e.g. pathogens such as viruses, viral particles, bacteria, fungi, yeast or parts thereof. Examples of primary targets include compounds such as proteins of which the presence or expression level is correlated with a certain tissue or cell type or of which the expression level is up regulated or down-regulated in a certain disorder. According to a particular embodiment of the present invention, the primary target is a protein such as a (internalizing or non-internalizing) receptor. According to a preferred embodiment of the present invention, the primary target is an internalizing receptor. According to another preferred embodiment of the present invention, the primary target is a non- internalizing receptor.

In preferred embodiments the Primary Target can be a system in the body, such as blood circulation, lymphatic system, the nervous system, the digestion system, RES system, or organs such as the heart or kidney. For example, there are imaging agents that visualize blood flow, the liver, or identify the sentinel lymph node of a tumor.

Alternatively, the primary target may be a metabolic pathway, which is upregulated during a disease, e.g. infection or cancer, such as DNA synthesis, protein synthesis, membrane synthesis and carbohydrate uptake. In diseased tissues, above-mentioned markers can differ from healthy tissue and offer unique possibilities for early detection, specific diagnosis and therapy, especially targeted therapy.

Other non-limiting examples of Primary Targets include antibodies, proteins, carbohydrates, monosacharides, polysaccharides, cytokines, hormones, steroids, somatostatin receptor, monoamine oxidase, muscarinic receptors, myocardial sympatic nerve system, leukotriene receptors, e.g. on leukocytes, urokinase plasminogen activator receptor (uPAR), folate receptor, apoptosis marker, (anti- )angiogenesis marker, gastrin receptor, dopaminergic system, serotonergic system, GABAergic system, adrenergic system, cholinergic system, opoid receptors, GPIIb/IIIa receptor and other thrombus related receptors, fibrin, calcitonin receptor, tuftsin receptor, integrin receptor, fibronectin, VEGF/EGF and VEGF/EGF receptors, TAG72, CEA, CD19, CD20,CD22, CD40, CD45, CD74, CD79, CD105, CD138, CD174, CD227, CD326, CD340, MUCl, MUC16, GPNMB, PSMA, Cripto, Tenascin C, Melanocortin-1 receptor, CD44v6, G250, HLA DR, ED-A, ED-B, TMEFF2 , EphB2, EphA2, FAP, Mesothelin, GD2, CAIX, 5T4, matrix metalloproteinase (MMP), P/E/L-selectin receptor, LDL receptor, P- glycoprotein, neurotensin receptors, neuropeptide receptors, substance P receptors, NK receptor, CCK receptors, sigma receptors, interleukin receptors, herpes simplex virus tyrosine kinase, human tyrosine kinase, MSR1, FAP,

CXCR, tumor endothelial marker (TEM), cMET, IGFR, FGFR, GPA33, hCG, According to a further particular embodiment of the invention, the primary target and targeting agent are selected so as to result in the specific or increased targeting of a tissue or disease, such as cancer, an inflammation, an infection, a cardiovascular disease, e.g. thrombus, atherosclerotic lesion, hypoxic site, e.g. stroke, tumor, cardiovascular disorder, brain disorder, apoptosis, angiogenesis, an organ, and reporter gene/enzyme. This can be achieved by selecting primary targets with tissue-, cell- or disease- specific expression. For example, membrane folic acid receptors mediate intracellular accumulation of folate and its analogs, such as methotrexate. Expression is limited in normal tissues, but receptors are overexpressed in various tumor cell types.

In preferred embodiments the Primary Target equals a therapeutic target.

Preferred internalizing targets are:

Transferrin receptor, urokinase plasminogen activator receptor (uPAR), folate receptor, gastrin receptor, GPIIb/IIIa receptor, calcitonin receptor, tuftsin receptor, integrin receptor, VEGF/EGF receptors, CD19, CD20, CD22, CD25, CD30, CD33, CD40, CD45, CD56, CD70, CD74, CD79, CD105, CD123, CD138, CD163, CD174, CD184, CD227, CD269, CD326, CD340, CD352, MUCl, MUCl 6, GPNMB, PSMA, Cripto, Melanocortin-1 receptor, HLA DR, TMEFF2 , EphB2, EphA2, FAP, Mesothelin, GD2, CAIX, 5T4, matrix metalloproteinases (MMP), ADAM- 9, P/E/L-selectin receptor, LDL receptor, P-glycoprotein, neurotensin receptors, neuropeptide receptors, substance P receptors, NK receptor, CCK receptors, CXCR, tumor endothelial marker (TEM), cMET, IGFR, FGFR, GPA33, hCG, platelet- derived growth factor (PDGF), HER2, HER3, CA19, TAM, LGALS3BP, nectin-4, IFGR, cMET, PD1, PDL1, GPNMB, AGS-5, AGS-16, endosialin, ETBR, TM4SF1, BCMA, GPC2, TROP-2, AXL, HLA-DR, B7-H3, MTX3, MTX5, EFNA4, NOTCH, tissue factor (TF), PDGFR, GITR, OX40, RIG, MDA-5, NLRP1, NLRP3, AIM2, IDO, MEK, cGAS, NKG2A.

Preferred non-internalizing targets are Fibronectin ED-A, Fibronectin ED- B, VEGF, EGF , TAG72, CEA, CD20, CD25, MUCl, MUC16, Tenascin C,

CD44v6, CAIX, matrix metalloproteinase (e.g. MMP2), A33, mesothelin,

LGALS3BP, hCG, nectin-4, CD45, G250, GPA33 , GD2, PD1, PDL1, GITR, CD3, CD28, CTLA4, OX40, RIG, MDA-5, NLRP1, NLRP3, AIM2, IDO, MEK, cGAS,

NKG2A.

The person skilled in the art will understand that the preceding

classification is relative, as most targets are not completely internalizing or non- internalizing, but instead can be classified as relatively internalizing or relatively non-internalizing, as compared to other targets, such as TAG72 (non- internalizing) and HER2 (fast internalizing). The person skilled in the art will understand that internalization rate is an important factor in this classification, and that the nature of the Administration Agent or Targeting Agent T ^T can affect this rate.

Compounds of Formula (1)

The invention pertains to compounds of Formula (1) as disclosed herein. It will be understood that the compounds of Formula (1) comprise an eight- membered trans-ring, preferably a trans-cyclooctene, formed by -CHR ₄₈ , -C=C-, and X ¹ -X ⁵ .

Formula (1); R. ₄₈ is selected from the group consisting of -L ^B , and -LA

In a preferred embodiment, R ₄₈ is -L ^B .

In a preferred embodiment, R ₄₈ is -L ^A .

As is clear from the definitions of -L ^B and -L ^A herein, both -L ^B and -L ^A may comprise a moiety L ^C , which is an optional self-immolative linker, which may consist of multiple units arranged linearly and/or branched and may release one or more moieties that are denoted as C ^A moieties, while moieties that are not released from the L ^C may be denoted as C ^B . It will be understood that if L ^C comprises more than one C ^A moiety, these C ^A moieties can independently be Label or Administration Agent, optionally linked to L ^C via a spacer S ^P , since both are released due to the self-immolative character of L ^C . Preferably, if L ^C comprises one C ^B , then said C ^B moiety may be either Administration Agent or Label. Preferably, if L ^C comprises more than one C ^B , then said C ^B moieties are all either Administration Agent or Label. It will be understood that in such a way, one R ₄₈ group may comprise both a Label and an Administration Agent, that are uncoupled after reaction of the compound of Formula (1) with a Cleaving Agent due to the self-immolative character of the linker L ^C .

By way of further clarification, if R ₄₈ is L ^B and all d and e in Formula (2) are 0, the Label directly constitutes the leaving group of the release reaction, and if one of d or e in Formula (2) is 1, S ^L , which may be a self-immolative linker L ^C , constitutes the leaving group of the release reaction.

In Formula (1), R ₄₈ is bound to the remainder of the compound of Formula (1) via a part of R ₄₈ that is -O-, -S-, -OC(O)-, -OC(S)-, -SC(O)-, or -SC(S)-;

preferably -O-, or -OC(O)-, most preferably -OC(O)N- (i.e. a carbamate).

Preferably, the -O- or -S- is directly coupled to an aromatic moiety that is also part of R ₄₈ . Preferably, the -OC(O)-, -OC(S)-, -SC(O)-, or -SC(S)- are directly coupled to a carbon, oxygen, nitrogen, or sulphur atom that is also part of R ₄₈ , preferably to a secondary or tertiary amine. In a preferred embodiment, in Formula (1), R ₄₈ is bound to the remainder of the compound of Formula (1) via a part of R ₄₈ that is -O-R ₉₇ -, -S-R ₉₇ -, -OC(O)-R ₉₇ -, -OC(S)-R ₉₇ -, -SC(O)-R ₉₇ -, or -SC(S)-R ₉₇ -. In a preferred embodiment, in Formula (1), R ₄₈ is bound to the remainder of the compound of Formula (1) via a part of R ₄₈ that is -O-, -S-R ₉₉ -, - OC(O)-, -OC(O)-R ₉₉ -, -OC(S)-R ₉₉ -, -SC(O)-R ₉₉ -, or -SC(S)-R ₉₉ -.

It will be understood, that preferably this notation indicates that in e.g. -OC(O)- R ₉₉ -, the first O is attached to the eight-membered ring of Formula (1), and R ₉₉ is connected to the remainder of R ₄₈ . It will be understood that -O- denotes an ether, and can be an aromatic ether or an aliphatic ether. Likewise, -OC(O)- denotes an ester, that can be an aromatic ester or an aliphatic ester, preferably an aromatic ester. It will be understood that the part of R ₄₈ that is -O-, -OC(O)-, or -OC(S)-, could be part of a spacer S ^P or S ^L , if present, or of the Administration Agent or the Label, if no spacer S ^P or S ^L is present.

In Formula (1), when R ₄₈ is L ^B and does not comprise an Administration Agent, then R ₄₈ being L ^B preferably has a molecular weight of at most 50 kDa, and preferably of at most 5 kDa, even more preferably at most 2 kDa, even more preferably at most 1 kDa, even more preferably at most 500 Da.

In Formula (1), when R ₄₈ is L ^A and does not comprise a Label then the compound of Formula (1) without R ₄₈ preferably has a molecular weight of at most 50 kDa, and more preferably of at most 5 kDa, even more preferably at most 2 kDa, even more preferably at most 1 kDa. Preferably, when Formula (1) comprises one R ₄₈ moiety that is L ^A and does not comprise a Label, then the compound of Formula (1) without R ₄₈ being L ^A has a molecular weight of at most 50 kDa, and more preferably of at most 5 kDa, even more preferably at most 2 kDa, even more preferably at most 1 kDa. Preferably, when Formula (1) comprises two R ₄₈ moieties that are L ^A and do not comprise a Label, then the compound of Formula (1) without both R ₄₈ has a molecular weight of at most 50 kDa, and more preferably of at most 5 kDa, even more preferably at most 2 kDa, even more preferably at most 1 kDa.

The compound of Formula (1) comprises at least one Label and at least one Administration Agent. Preferably, the compound of Formula (1) comprises at most one Label and at most one Administration Agent.

Preferably, when at least one R ₄₈ is L ^B , then X ¹ , X ² , X ³ , and X ⁴ do not comprise the same Label as comprised in R ₄₈ being L ^B . Preferably, when at least one R ₄₈ is L ^A , then X ¹ , X ² , X ³ , and X ⁴ do not comprise an L ^A . In particularly favorable embodiments, one or both R ₄₈ is/are in the axial position.

Preferably, if X ⁵ is -C(R ₄₇ ) ₂ -, R ₄₈ comprises a Label, and R ₄₈ does not comprise an Administration Agent, then X - X ⁵ do not comprise the same Label as comprised in R ₄₈ .

Preferably, if X ⁵ is -C(R ₄₇ ) ₂ -, R ₄₈ comprises an Administration Agent, and R ₄₈ does not comprise a Label, then X - X ⁵ do not comprise the same

Administration Agent as comprised in R ₄₈ .

Preferably, if X ⁵ is -C(R ₄₇ ) ₂ -, and R ₄₈ comprises at least one Administration Agent and at least one Label, then X - X ⁵ optionally comprise either the same

Administration Agent as comprised in R ₄₈ or the same Label as comprised in R ₄₈ .

In Formula (1), L ^A only comprises both the Label and the Administration Agent when L ^A is R ₄₈ .

In Formula (1), if L ^A being R ₄₈ comprises both the Label and the

Administration Agent, then the S ^P linked to said Label and said Administration Agent is a self-immolative linker, preferably with the proviso that at least one of Label and Administration Agent is C ^A in the definition of L ^C or the proviso that the Label and Administration Agent are bound to different L ^C moieties within the same R ₄₈ .

Preferably, in Formula (1), L ^B only comprises both the Label and the

Administration Agent when L ^B is R ₄₈ .

Preferably, in Formula (1), if L ^B being R ₄₈ comprises both the Label and the Administration Agent, then the S ^P linked to said Label and said

Administration Agent is a self-immolative linker, preferably with the proviso that at least one of Label and Administration Agent is C ^A in the definition of L ^C or with the proviso that the Label and Administration Agent are bound to different L ^C moieties within the same R ₄₈ .

Formula (2)

In Formula (1), the moiety L ^B satisfies Formula (2):

Formula (2); wherein the dashed line denotes a bond to the remainder of the compound of Formula (1).

In Formula (2) each d independently is 0 or 1. In a preferred embodiment, at least one d is 1. In another preferred embodiment, both d are 1. In yet another preferred embodiment, both d are 0.

In Formula (2) e is an integer in a range of from 0 to 4, preferably e is at most 3, more preferably at most 2, most preferably e is at most 1. In a preferred embodiment, e is 1. In another preferred embodiment, e is 0.

In Formula (2), the Label is preferably as defined herein.

Preferably, -L ^B does not comprise an Administration Agent.

Preferably, Formula (2) is -S ^L -Label, wherein S ^L is a poly ethyleneglycol (PEG), more preferably S ^L is PEG ₄ . Linker S ^L

In Formula (2), S ^L is a linker, which may be a self-immolative linker L ^C as defined herein.

Preferably, S ^L is defined as S ^P as defined herein, wherein it will be understood that when S ^L is attached to an R ₉₈ , in some embodiments S ^L is a trivalent radical, and the suffix -ene in a preferred definition of S ^P is replaced with -triyl.

In preferred embodiments, S ^L being S ^P comprises at least one moiety selected from the group consisting of a residue of R ₃₂ , a moiety C ^M2 , and a moiety C ^x ; all as described herein. In preferred embodiments, said C ^M2 , C ^x or a residue of R ₃₂ connects the S ^P to a Label, L ^C , S ^P , R ₉₈ , or T ^R .

In a preferred embodiment, S ^L is L ^C . Preferably, when S ^L is L ^C , then e is 0, one d is 0, and one d is 1. In another preferred embodiment, S ^L is not L ^C when S ^L is comprised in any one of X ¹ -X ⁴ . In another preferred embodiment, S ^L is not L ^C . R98

In Formula (2), each R ₉₈ individually is a Label or a clearance- directing group. In a preferred embodiment, R ₉₈ is a Label. The Label of R ₉₈ is preferably as defined herein, and may be the same Label as the one comprised in L ^B that is not R ₉₈ , or a different Label.

R ₉₉

R ₉₉ is selected from the group consisting of -O-, -C(R ₃₆ ) ₂ -, -S-, and -NR ₃₆ -.

Clearance-directing group

A clearance-directing group is a moiety that directs a compound to an excretory organ, such as the kidneys or the liver. In that way, it ensures faster clearance of a compound from the blood in a subject and / or it controls which excretory organ will or will not process the compound to improve imaging procedures or non-target tissue dosimetry. In relation to the invention, it will be understood that the increased clearance rate of the Label after being separated from the Administration Agent is mainly due to this separation, and that the clearance-directing group merely further enhances the clearance rate of the Label and / or controls the clearance pathway.

In a preferred embodiment, the clearance-directing group is hexose-based. Hexose-based clearance- directing groups incorporate one or more hexoses (six carbon sugar moieties) recognized by Ashwell receptors or other receptors such as the mannose/N-acetylglucosamine receptor which are associated with

hepatocytes, endothelial cells and/or Kupffer cells of the liver or the mannose 6- phosphate receptor.

Exemplary hexoses are galactose, mannose, mannose 6-phosphate, N- acetylglucosamine, pentamannosylphosphate, and the like. Other moieties recognized by Ashwell receptors, including glucose, N-galactosamine, N- acetylgalactosamine, pentamannosyl phosphate, thioglycosides of galactose and, generally, D-galactosides and glucosides or the like may also be used in the practice of the present invention.

In a preferred embodiment, the clearance-directing group is galactose. Galactose thioglycoside conjugation is preferably accomplished following a procedure largely similar to the teachings of Lee et al., "2-Imino-2-methoxyethyl 1- 20 Thioglycosides: New Reagents for Attaching Sugars to Proteins,"

Biochemistry, (18):3956, 1976. Another useful galactose thioglycoside conjugation method is set forth in Drantz et al, "Attachment of Thioglycosides to Proteins: Enhancement of Liver Membrane Binding," Biochemistry, 15(18): 3963, 1976.

Formula (3)

In Formula (1), L ^A is a moiety satisfying Formula (3):

Formula (3); wherein the dashed line denotes a bond to the remainder of the compound of Formula (1).

In Formula (3) each s independently is 0 or 1. In a preferred embodiment, at least one s is 1. In another preferred embodiment, both s are 1. In yet another preferred embodiment, both s are 0.

In Formula (3) i is an integer in a range of from 0 to 4, preferably i is at most 3, more preferably at most 2, most preferably i is at most 1. In a preferred embodiment, i is 1. In another preferred embodiment, i is 0.

In Formula (3), A ^A denotes an Administration Agent that is an antibody.

In a preferred embodiment, Formula (3) is -S ^P -A ^A , wherein S ^P is a polyethylene glycol (PEG), more preferably S ^P is PEGs.

In a preferred embodiment, moiety L ^A has a molecular weight of at most 500 kDa, more preferably at most 200 kDa, most preferably at most 160 kDa.

In a preferred embodiment, moiety L ^A has a molecular weight of at least 0.1 kDa, more preferably at least 1 kDa, more preferably at least 10 kDa, most preferably at least 140 kDa.

In Formula (3), each S ^P independently is a spacer, which optionally is a self-immolative linker L ^C as defined herein. It will be understood that if S ^P is linked to C ^C , then S ^P is preferably a trivalent radical and the suffix -ene in the definition of S ^L is to be replaced with the suffix -triyl. Preferably, S ^P is a spacer as defined herein. Preferably, when S ^P is L ^C , then i in Formula (3) is 0, one s is 0, and one s is 1.

In Formula (3) C ^C denotes a Construct-C, wherein each Construct-C is independently selected from the group consisting of a Label, and an additional Administration Agent. The additional Administration Agent may be the same Administration Agent as comprised in L ^A not being C ^C , or it may be a different Administration Agent.

In a preferred embodiment, the compound of Formula (1) comprises at most one C ^C . Preferably, when i in Formula (3) is at least 1, then in -S ^P -C ^C , the S ^P is an L ^C .

In preferred embodiments, S ^P in Formula (3) comprises at least one moiety selected from the group consisting of a residue of R ₃₂ , a moiety C ^M2 , and a moiety C ^x ; all as described herein. In preferred embodiments, said C ^M2 , C ^x or a residue of R ₃₂ connects the S ^P to a Label, an Administration Agent, L ^C , S ^P , C ^C , or T ^R .

In a preferred embodiment, L ^A does not comprise a Label. In a preferred embodiment, X ⁵ does not comprise C ^C , L ^A , or L ^B .

Spacers S ^P

It will be understood that when herein, it is stated that“each individual S ^P is linked at all ends to the remainder of the structure” this refers to the fact that the spacer S ^P connects multiple moieties within a structure, and therefore the spacer has multiple ends by defintion. The spacer S ^P may be linked to each individual moiety via different or identical moieties that may be each

individually selected. Typically, these linking moieties are to be seen to be part of spacer S ^P itself. In case the spacer S ^P links two moieties within a structure,“all ends” should be interpreted as“both ends”. As an example, if the spacer connects a trans-cyclooctene moiety to a Construct A, then“the remainder of the molecule” refers to the trans-cylooctene moiety and Construct A, while the connecting moieties between the spacer and the trans-cyclooctene moiety and Construct A (i.e. at both ends) may be individually selected. Spacers S ^P may consist of one or multiple Spacer Units S ^U arranged linearly and/or branched and may be connected to one or more C ^A or C ^B moieties and / or one or more L ^C or T ^R moieties. The Spacer may be used to connect C ^B to one T ^R (Example A) or more T ^R (Example B and C), but it can also be used to modulate the properties, e.g. pharmacokinetic properties, of the C ^B -T ^R -C ^A conjugate (Example D). Thus a Spacer does not necessarily connect two entities together, it may also be bound to only one component, e.g. the T ^R or L ^C . Alternatively, the Spacer may comprise a Spacer Unit linking C ^A or C ^B to T ^R and in addition may comprise another Spacer Unit that is only bound to the Spacer and serves to modulate the properties of the conjugate (Example F). The Spacer may also consist of two different types of S ^U constructs, e.g. a PEG linked to a peptide, or a PEG linked to an alkylene moiety (Example E). For the sake of clarity, Example B depicts a S ^U that is branched by using a multivalent branched S ^U . Example C depicts a S ^U that is branched by using a linear S ^U polymer, such as a peptide, whose side chain residues serve as conjugation groups.

The Spacer may be bound to the Cleaving Agent in similar designs such as depicted in above examples A- F.

The Spacer Units include but are not limited to amino acids, nucleosides, nucleotides, and biopolymer fragments, such as oligo- or polypeptides, oligo- or polypeptoids, or oligo- or polylactides, or oligo- or poly-carbohydrates, varying from 2 to 200, particularly 2 to 113, preferably 2 to 50, more preferably 2 to 24 and more preferably 2 to 12 repeating units. Exemplary preferred biopolymer S ^U are peptides.

Yet other examples are alkyl, alkylene, alkenyl, alkenylene, alkynyl, alkynylene, cycloalkyl, cycloalkylene, cycloalkenyl, cycloalkenylene, cycloalkynyl, cycloalkynylene, aryl, arylene, alkylaryl, alkylarylene, arylalkyl, arylalkylene, arylalkenyl, arylalkenylene, arylalkynyl, arylalkynylene , polyethyleneamino, polyamine, which may be substituted or unsubstituted, linear or branched, may contain further cyclic moieties and / or heteroatoms, preferably O, N, and S, more preferably O; wherein in some embodiments these example S ^U comprise at most 50 carbon atoms, more preferably at most 25 carbon atoms, more preferably at most 10 carbon atoms. In preferred embodiments the S ^U is independently selected from the group consisting of (CH ₂ ) _r , (C ₃ -C ₈ carbocyclo), O-(CH ₂ ) _r , arylene, (CH ₂ ) _r -arylene, arylene- (CH ₂ ) _r , (CH ₂ ) _r -(C ₃ -C ₈ carbocyclo), (C ₃ -C ₈ carbocyclo)- (CH ₂ ) _r , (C ₃ -C ₈ heterocyclo, (CH ₂ ) _r -(C ₃ -C ₈ heterocyclo), (C ₃ -C ₈ heterocyclo)-(CH ₂ ) _r , - (CH ₂ ) _r C(O)NR ₄ (CH ₂ ) _r , (CH ₂ CH ₂ O) _r , (CH ₂ CH ₂ O) _r CH ₂ ,(CH ₂ ) _r C(O)NR ₄ (CH ₂ CH ₂ O) _r , (CH ₂ ) _r C(O)NR ₄ (CH ₂ CH ₂ O) _r CH ₂ , (CH ₂ CH ₂ O) _r C(O)NR ₄ (CH ₂ CH ₂ O) _r , (CH ₂ CH ₂ O) _r C(O)NR ₄ (CH ₂ CH ₂ O) _r CH ₂ , (CH ₂ CH ₂ O) _r C(O)NR ₄ CH ₂ , -(CH ₂ ) _r C(O)NR ₃₇ (CH ₂ ) _r , (CH ₂ CH ₂ O) _r , (CH ₂ CH ₂ O) _r CH ₂ ,(CH ₂ ) _r C(O)NR ₃₇ (CH ₂ CH ₂ O) _r ,

(CH ₂ ) _r C(O)NR ₃₇ (CH ₂ CH ₂ O) _r CH ₂ , (CH ₂ CH ₂ O) _r C(O)NR ₃₇ (CH ₂ CH ₂ O) _r , (CH ₂ CH ₂ O) _r C(O)NR ₃₇ (CH ₂ CH ₂ O) _r CH ₂ , (CH ₂ CH ₂ O) _r C(O)NR ₃₇ CH ₂ ; wherein r is independently an integer from 1 -10, R ₄ is as defined herein, and R ₃₇ is as defined herein.

Other examples of Spacer Units S ^U are linear or branched polyalkylene glycols such as polyethylene glycol (PEG) or polypropylene glycol (PPG) chains varying from 2 to 200, particularly 2 to 113, preferably 2 to 50, more preferably 2 to 24 and more preferably 2 to 12 repeating units. It is preferred that when polyalkylene glycols such as PEG and PPG polymers are only bound via one end of the polymer chain, that the other end is terminated with -OCH ₃ , -OCH ₂ CH ₃ , - OCH ₂ CH ₂ CO ₂ H.

Other polymeric Spacer Units are polymers and copolymers such as poly- (2-oxazoline), poly( N-(2-hydroxypropyl)methacrylamide) (HPMA), polylactic acid (PLA), polylactic-glycolic acid (PLGA), polyglutamic acid (PG), dextran, polyvinylpyrrolidone (PVP), poly(l-hydroxymethylethylene hydroxymethyl- formal (PHF). Other exemplary polymers are polysaccharides,

glycopolysaccharides, glycolipids, polyglycoside, polyacetals, polyketals, polyamides, polyethers, polyesters. Examples of naturally occurring

polysaccharides that can be used as S ^U are cellulose, amylose, dextran, dextrin, levan, fucoidan, carraginan, inulin, pectin, amylopectin, glycogen, lixenan, agarose, hyaluronan, chondroitinsulfate, dermatansulfate, keratansulfate, alginic acid and heparin. In yet other exemplary embodiments, the polymeric S ^U comprises a copolymer of a polyacetal/polyketal and a hydrophilic polymer selected from the group consisting of polyacrylates, polyvinyl polymers, polyesters, polyorthoesters, polyamides, oligopeptides, polypeptides and derivatives thereof. Exemplary preferred polymeric S ^U are PEG, HPMA, PLA, PLGA, PVP, PHF, dextran, oligopeptides, and polypeptides.

In some aspects of the invention polymers used in a S ^U have a molecular weight ranging from 2 to 200 kDa, from 2 to 100 kDa, from 2 to 80 kDa, from 2 to 60 kDa, from 2 to 40 kDa, from 2 to 20 kDa, from 3 to 15 kDa, from 5 to 10 kDa, from 500 dalton to 5 kDa.

Other exemplary S ^U are dendrimers, such as poly(propylene imine) (PPI) dendrimers, PAMAM dendrimers, and glycol based dendrimers.

The S ^U of the invention expressly include but are not limited to conjugates prepared with commercially available cross-linker reagents such as BMPEO, BMPS, EMCS, GMBS, HBVS, LC-SMCC, MBS, MPBH, SBAP, SIA, SIAB,

SMCC, SMPB, SMPH, sulfo-EMCS, sulfo-GMBS, sulfo-KMUS, sulfo-MBS, sulfo- SIAB, sulfo-SMCC, sulfo-SMPB, and SVSB, DTME, BMB, BMDB, BMH, BMOE, BM(PEO) ₃ and BM(PEO) ₄ .

To construct a branching Spacer one may use a S ^U based on one or several natural or non-natural amino acids, amino alcohol, aminoaldehyde, or polyamine residues or combinations thereof that collectively provide the required

functionality for branching. For example serine has three functional groups, i.e. acid, amino and hydroxyl groups and may be viewed as a combined amino acid an aminoalcohol residue for purpose of acting as a branching S ^U . Other exemplary amino acids are lysine and tyrosine. In preferred embodiments, the Spacer consist of one Spacer Unit, therefore in those cases S ^P equals S ^U . In preferred embodiments the Spacer consist of two, three or four Spacer Units.

In some aspects of the invention S ^P has a molecular weight ranging from 2 to 200 kDa, from 2 to 100 kDa, from 2 to 80 kDa, from 2 to 60 kDa, from 2 to 40 kDa, from 2 to 20 kDa, from 3 to 15 kDa, from 5 to 10 kDa, from 500 dalton to 5 kDa. In some aspects of the invention, the S ^P has a mass of no more than 5000 daltons, no more than 4000 daltons, no more than 3000 daltons, no more than 2000 daltons, no more than 1000 daltons, no more than 800 daltons, no more than 500 daltons, no more than 300 daltons, no more than 200 daltons. In some aspects the S ^P has a mass from 100 daltons, from 200 daltons, from 300 daltons to 5000 daltons. In some aspects of the S ^P has a mass from 30, 50, or 100 daltons to 1000 daltons, from about 30, 50, or 100 daltons to 500 daltons.

Preferably, each S ^P is independently selected from the group consisting of R ₉₇ , -O-, -OC(O)-, -OC(O)-R ₉₉ -, -OC(S)-R ₉₉ -, -OR ₉₇ -, -OC(O)-R ₉₇ -, -OC(O)-R ₉₉ -R ₉₇ -, -OC(S)-R ₉₉ -R ₉₇ -, and L ^C . In another preferred embodiment, S ^P is not L ^C when S ^P is comprised in any one of X ¹ -X ⁴ . In a preferred embodiment, S ^P is not L ^C .

In preferred embodiments, S ^P comprises a residue of R ₃₂ , a moiety C ^M2 or a moiety C ^x ; all as described herein. In preferred embodiments, said C ^M2 , C ^x or a residue of R ₃₂ connects the S ^P to a Label, an Administration Agent, L ^C , S ^P , C ^C , R ₉₈ , or T ^R . R ₉₇

In a preferred embodiment, each R ₉₇ is independently selected from the group consisting of C ₁ -C ₂₄ alkylene groups, C ₂ -C ₂₄ alkenylene groups, C ₂ -C ₂₄ alkynylene groups, C ₆ -C ₂₄ arylene, C ₂ -C ₂₄ heteroarylene, C ₃ -C ₂₄ cycloalkylene groups, C ₅ -C ₂₄ cycloalkenylene groups, and C ₁₂ -C ₂₄ cycloalkynylene groups, which are optionally further substituted with one or more substituents selected from the group consisting of -Cl, -F, -Br, -I, -OH, -NH ₂ , -SO ₃ H, -PO ₃ H, -PO ₄ H ₂ , -NO ₂ , - CF ₃ , =O,— NR ₃₆ , -SR ₃₆ , C ₁ -C ₂₄ alkyl groups, C ₂ -C ₂₄ alkenyl groups, C ₂ -C ₂₄ alkynyl groups, C ₆ -C ₂₄ aryl groups, C ₂ -C ₂₄ heteroaryl groups, C ₃ -C ₂₄ cycloalkyl groups, C ₅ - C ₂₄ cycloalkenyl groups, C ₁₂ -C ₂₄ cycloalkynyl groups, C ₃ -C ₂₄ alkyl(hetero)aryl groups, C ₃ -C ₂₄ (hetero)arylalkyl groups, C ₄ -C ₂₄ (hetero)arylalkenyl groups, C ₄ -C ₂₄ (hetero)arylalkynyl groups, C ₄ -C ₂₄ alkenyl(hetero)aryl groups, C ₄ -C ₂₄

alky nyl(hetero) aryl groups, C ₄ -C ₂₄ alkylcycloalkyl groups, C ₆ -C ₂₄

alkylcycloalkenyl groups, C ₁₃ -C ₂₄ alkylcycloalkynyl groups, C ₄ -C ₂₄ cycloalkylalkyl groups, C ₆ -C ₂₄ cycloalkenylalkyl groups, C ₁₃ -C ₂₄ cycloalkynylalkyl groups, C ₅ -C ₂₄ alkenylcycloalkyl groups, C ₇ -C ₂₄ alkenylcycloalkenyl groups, C ₁₄ -C ₂₄

alkenylcycloalkynyl groups, C ₅ -C ₂₄ cycloalkylalkenyl groups, C ₇ -C ₂₄

cycloalkenylalkenyl groups, C ₁₄ -C ₂₄ cycloalkynylalkenyl groups, C ₅ -C ₂₄

alkynylcycloalkyl groups, C ₇ -C ₂₄ alkynylcycloalkenyl groups, C ₁₄ -C ₂₄

alkynylcycloalkynyl groups, C ₅ -C ₂₄ cycloalkylalkynyl groups, C ₇ -C ₂₄

cycloalkenylalkynyl groups, C ₁₄ -C ₂₄ cycloalkynylalkynyl groups, C ₅ -C ₂₄

cycloalkyl(hetero)aryl groups, C ₇ -C ₂₄ cycloalkenyl(hetero)aryl groupsC, ₁ 4-C ₂₄ cycloalkynyl(hetero)aryl groups, C ₅ -C ₂₄ (hetero)arylcycloalkyl groups, C ₇ -C ₂₄ (hetero)arylcycloalkenyl groups, and C ₁₄ -C ₂₄ (hetero)arylcycloalkynyl groups, wherein the substituents optionally contain one or more heteroatoms selected from the group consisting of O, S, NR ₃₆ , P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized;

and wherein preferably the alkylene groups, alkenylene groups, alkynylene groups, cycloalkylene groups, cycloalkenylene groups, and cycloalkynylene groups optionally contain one or more heteroatoms selected from the group consisting of O, S, NR ₃₆ , P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized.

In a preferred embodiment, each R ₉₇ is independently selected from the group consisting ofC ₁ -C ₁₂ alkylene groups, C ₂ -C ₁₂ alkenylene groups, C ₂ -C ₁₂ alkynylene groups, C ₆ -C ₁₂ arylene, C ₂ -C ₁₂ heteroarylene, C ₃ -C ₁₂ cycloalkylene groups, C ₅ -C ₁₂ cycloalkenylene groups, and C ₁₂ cycloalkynylene groups;

and wherein preferably the alkylene groups, alkenylene groups, alkynylene groups, cycloalkylene groups, cycloalkenylene groups, and cycloalkynylene groups optionally contain one or more heteroatoms selected from the group consisting of O, S, NR ₃₆ , P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized.

In a preferred embodiment, each R ₉₇ is independently selected from the group consisting of C ₁ -C ₆ alkylene groups, C ₂ -C ₆ alkenylene groups, C ₂ -C ₆ alkynylene groups, C ₆ -C ₆ arylene, C ₂ -C ₆ heteroarylene, C ₃ -C ₆ cycloalkylene groups, and C ₅ -C ₆ cycloalkenylene groups;

and wherein preferably the alkylene groups, alkenylene groups, alkynylene groups, cycloalkylene groups, cycloalkenylene groups, and cycloalkynylene groups optionally contain one or more heteroatoms selected from the group consisting of O, S, NR ₃₆ , P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized.

In a preferred embodiment, the R ₉₇ groups are optionally further substituted with one or more substituents selected from the group consisting of - Cl, -F, -Br, -I, -OH, -NH ₂ , -SO ₃ H, -PO ₃ H, -PO4H ₂ , -NO ₂ , -CF ₃ , =O, =NR ₃₆ , -SR ₃₆ , C ₁ -C ₁₂ alkyl groups, C ₂ -C ₁₂ alkenyl groups, C ₂ -C ₁₂ alkynyl groups, C ₆ -C ₁₂ aryl groups, C ₂ -C ₁₂ heteroaryl groups, C ₃ -C ₁₂ cycloalkyl groups, C ₅ -C ₁₂ cycloalkenyl groups, C ₁₂ cycloalkynyl groups, C ₃ -C ₁₂ alkyl(hetero)aryl groups, C ₃ -C ₁₂

(hetero)arylalkyl groups, C ₄ -C ₁₂ (hetero)arylalkenyl groups, C ₄ -C ₁₂

(hetero)arylalkynyl groups, C ₄ -C ₁₂ alkenyl(hetero)aryl groups, C ₄ -C ₁₂

alky nyl(hetero) aryl groups, C ₄ -C ₁₂ alkylcycloalkyl groups, C ₆ -C ₁₂

alkylcycloalkenyl groupsC, ₁ 3-C18 alkylcycloalkynyl groups, C ₄ -C ₁₂ cycloalkylalkyl groups, C ₆ -C ₁₂ cycloalkenylalkyl groups, C ₁₃ -C ₁₈ cycloalkynylalkyl groups, C ₅ -C ₁₂ alkenylcycloalkyl groups, C ₇ -C ₁₂ alkenylcycloalkenyl groups, C ₁₄ -C ₁₆

alkenylcycloalkynyl groups, C ₅ -C ₁₂ cycloalkylalkenyl groups, C ₇ -C ₁₂

cycloalkenylalkenyl groups, C ₁₄ -C ₁₆ cycloalkynylalkenyl groups, C ₅ -C ₁₂

alkynylcycloalkyl groups, C ₇ -C ₁₂ alkynylcycloalkenyl groups, C ₁₄ -C ₁₆

alkynylcycloalkynyl groups, C ₅ -C ₁₂ cycloalkylalkynyl groups, C ₇ -C ₁₂

cycloalkenylalkynyl groups, C ₁₄ -C ₁₆ cycloalkynylalkynyl groups, C ₅ -C ₁₂

cycloalkyl(hetero)aryl groups, C ₇ -C ₁₂ cycloalkenyl(hetero)aryl groups, C ₁₄ -C ₁₆ cycloalkynyl(hetero)aryl groups, C ₅ -C ₁₂ (hetero)arylcycloalkyl groups, C ₇ -C ₁₂ (hetero)arylcycloalkenyl groups, and C ₁₄ -C ₁₆ (hetero)arylcycloalkynyl groups, wherein the substituents optionally contain one or more heteroatoms selected from the group consisting of O, S, NR ₃₆ , P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized. In preferred embodiments, the R ₉₇ groups are optionally further substituted with one or more substituents selected from the group consisting of - Cl, -F, -Br, -I, -OH, -NH ₂ , -SO ₃ H, -PO ₃ H, -PO4H ₂ , -NO ₂ , -CF ₃ , =O, =NR ₃₆ , -SR ₃₆ , C ₁ -C ₆ alkyl groups, C ₂ -C ₆ alkenyl groups, C ₂ -C ₆ alkynyl groups, C ₆ aryl groups, C ₂ -C ₆ heteroaryl groups, C ₃ -C ₆ cycloalkyl groups, C ₅ -C ₆ cycloalkenyl groups, C ₃ - C ₆ alkyl(hetero)aryl groups, C ₃ -C ₆ (hetero)arylalkyl groups, C ₄ -C ₆

(hetero)arylalkenyl groups, C ₄ -C ₆ (hetero)arylalkynyl groups, C ₄ -C ₆

alkenyl(hetero)aryl groups, C ₄ -C ₆ alkynyl(hetero)aryl groups, C ₄ -C ₆

alkylcycloalkyl groups, C f ; alkylcycloalkenyl groups, C ₄ -C ₆ cycloalkylalkyl groups, C ₆ cycloalkenylalkyl groups, C ₅ -C ₆ alkenylcycloalkyl groups, C ₇

alkenylcycloalkenyl groups, C ₅ -C ₆ cycloalkylalkenyl groups, C ₇

cycloalkenylalkenyl groups, C ₅ -C ₆ alkynylcycloalkyl groups, C ₇

alkynylcycloalkenyl groups, C ₅ -C ₆ cycloalkylalkynyl groups, C ₅ -C ₆

cycloalkyl(hetero)aryl groups, and C ₅ -C ₆ (hetero)arylcycloalkyl groups, wherein the substituents optionally contain one or more heteroatoms selected from the group consisting of O, S, NR ₃₆ , P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized.

In preferred embodiments, the R ₉₇ groups are optionally further

substituted with one or more substituents selected from the group consisting of - Cl, -F, -Br, -I, -OH, -NH ₂ , -SO ₃ H, -PO ₃ H, -PO ₄ H ₂ , -NO ₂ , -CF ₃ , =O, =NR ₃₆ , -SR ₃₆ , C ₁ -C ₆ alkyl groups, C ₂ -C ₆ alkenyl groups, C ₂ -C ₆ alkynyl groups, C ₆ aryl groups, C ₂ -C ₆ heteroaryl groups, C ₃ -C ₆ cycloalkyl groups, C ₅ -C ₆ cycloalkenyl groups, C ₃ - C ₇ alkyl(hetero)aryl groups, C ₃ -C ₇ (hetero)arylalkyl groups, C ₄ -C ₈

(hetero)arylalkenyl groups, C ₄ -C ₈ (hetero)arylalkynyl groups, C ₄ -C ₈

alkenyl(hetero)aryl groups, C ₄ -C ₈ alkynyl(hetero)aryl groups, C ₄ -C ₆

alkylcycloalkyl groups, C ₆ -C ₇ alkylcycloalkenyl groups, C ₄ -C ₆ cycloalkylalkyl groups, C ₆ -C ₇ cycloalkenylalkyl groups, C ₅ -C ₆ alkenylcycloalkyl groups, C ₇ -C ₈ alkenylcycloalkenyl groups, C ₅ -C ₆ cycloalkylalkenyl groups, C ₇ -C ₈

cycloalkenylalkenyl groups, C ₅ -C ₆ alkynylcycloalkyl groups, C ₇ -C ₈

alkynylcycloalkenyl groups, C ₅ -C ₆ cycloalkylalkynyl groups, C ₅ -C ₉

cycloalkyl(hetero)aryl groups, and C ₅ -C ₉ (hetero)arylcycloalkyl groups, wherein the substituents optionally contain one or more heteroatoms selected from the group consisting of O, S, NR ₃₆ , P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized.

In a preferred embodiment, the R ₉₇ groups are not substituted. In a preferred embodiment, the R ₉₇ groups do not contain a heteroatom.

Linker L ^C

L ^C is an optional self-immolative linker, which may consist of multiple units arranged linearly and/or branched and may release one or more C ^A moieties.

It will be understood that if L ^C comprises more than one C ^A moiety, these C ^A moieties can independently be Label or Administration Agent, optionally linked to L ^C via a spacer S ^P , since both are released due to the self- immolative character of L ^C . Preferably, if L ^C comprises more than one C ^B , then said C ^B moieties are all either Administration Agent or Label.

By way of further clarification, if R ₄₈ is L ^B and all d and e in Formula (2) are 0, the Label directly constitutes the leaving group of the release reaction, and if one of d or e in Formula (2) is 1, S ^L , which may be a self-immolative linker L ^C , constitutes the leaving group of the release reaction. The possible L ^C structures, their use, position and ways of attachment of linkers L ^C , constructs C ^A and C ^B , and the T ^R are known to the skilled person, see for example [Papot et al., Anticancer Agents Med. Chem., 2008, 8, 618-637]. Nevertheless, typical but non- limiting examples of self-immolative linkers L ^C are benzyl-derivatives, such as those drawn below. There are two main self-immolation mechanisms: electron cascade elimination and cyclization-mediated elimination. The preferred example below on the left functions by means of the cascade mechanism, wherein the bond to the Y ^C between Trigger and L ^C , here termed Y ^C1 , is cleaved, and an electron pair of Y ^C1 , for example an electron pair of NR ⁶ , shifts into the benzyl moiety resulting in an electron cascade and the formation of 4-hydroxybenzyl alcohol, CO ₂ and the liberated C ^A also comprising an Y ^c , here termed Y ^C2 . The preferred example in the middle functions by means of the cyclization mechanism, wherein cleavage of the bond to the amine of Y ^C1 leads to nucleophilic attack of the amine on the carbonyl, forming a 5-ring l,3-dimethylimidazolidin-2-one and liberating the C ^A including Y ^C2 . The preferred example on the right combines both mechanisms, this linker will degrade not only into CO ₂ and one unit of 4- hydroxybenzyl alcohol (when Y ^C1 is O), but also into one 1,3- dimethylimidazoli din-2 -one unit.

Herein, C ^A is optionally linked to the remainder of L ^C via a spacer S ^P .

By substituting the benzyl groups of aforementioned self-immolative linkers L ^C , it is possible to tune the rate of release of the construct C ^A , caused by either steric and/or electronic effects on the cyclization and/or cascade release. Synthetic procedures to prepare such substituted benzyl- derivatives are known to the skilled person (see for example [Greenwald et al, J. Med. Chem., 1999, 42, 3657-

3667] and [Thornthwaite et al, Polym. Chem., 2011, 2, 773-790]. Preferred substituted benzyl- derivatives with different release rates are drawn below.

Herein, C ^A is optionally linked to the remainder of L ^C via a spacer S ^P .

In preferred embodiments the L ^C satisfies one of the following Formulae 23a-c

Formula 23a Formula 23b Formula 23c wherein Y ^C1 is O, S or NR ⁶ ; V, U, W, Z are each independently CR ⁷ or N; Y ^C2 is O, S, secondary amine or tertiary amine, wherein these Y ^C2 moieties are part of C ^A ; with R ⁶ , R ⁷ , R ⁸ , R ⁹ as defined herein, and wherein, C ^A is optionally linked to the remainder of L ^C via a spacer S ^P .

In preferred embodiments it is preferred that R ⁶ is H or methyl, R ⁷ is H, R ⁸ is H or methyl and R ⁹ is H. In preferred embodiments the R ⁷ comprised in Formula 23c is CF ₃ and Z is N. In preferred embodiments the L ^C satisfies the following Formula 23d

Formula 23d wherein Y ^C1 is O, S or NR ⁶ ; Y ^C2 is O, S, secondary amine or tertiary amine, wherein these Y ^C2 moieties are part of C ^A ; with R ⁶ , R ⁷ , R ⁸ , R ⁹ as defined herein; preferably R ⁷ is C ₁ -C ₈ alkyl, C ₆ -C ₁₂ aryl, C ₁ -C ₈ O-alkyl, C ₆ -C ₁₂ O-aryl , NO ₂ , F, Cl, Br, I, CN, with m being an integer from 0 to 4; preferably each R ⁸ and R ⁹ are independently H, C ₁ -C ₈ alkyl, C ₆ -C ₁ 2 aryl, C ₁ -C ₈ O-alkyl, C ₆ -C ₁₂ O-aryl , NO ₂ , F, Cl, Br, I, CN; and wherein, C ^A is optionally linked to the remainder of L ^C via a spacer S ^P . Preferably R ⁷ is electron donating and preferably m is an integer between 0 and 2, more preferably m is 0. Preferably R ⁸ is H and R ⁹ is H or methyl.

Self-immolative linkers that undergo cyclization include but are not limited to substituted and unsubstituted aminobutyric acid amide, appropriately

substituted bicyclo[2.2.1] and bicyclo[2.2.2] ring system, 2-aminophenylpropionic acid amides, and trimethyl lock-based linkers, see e.g. [Chem. Biol. 1995, 2, 223], [J. Am. Chem. Soc. 1972, 94, 5815], [J. Org. Chem. 1990, 55, 5867], the contents of which are hereby incorporated by reference. Preferably, with an L ^C that releases C ^A by means of cyclization, the remainder of C ^A is bound to L ^C via Y ^C1 being an aromatic oxygen of sulfur. It will be understood that e.g. aromatic oxygen means an oxygen that is directly attached to an aromatic group.

In preferred embodiments such cyclization L ^C satisfies one of the following Formulae 24a-f.

Formula 24a Formula 24b Formula 24c Formula 24d

Formula 24f

Wherein Y ^C1 is NR ⁶ ; Y ^C2 is O or S, wherein these Y ^C2 moieties are part of C ^A ; a is independently 0 or 1; R ⁶ and R ⁷ are as defined herein, and wherein, C ^A is optionally linked to the remainder of L ^C via a spacer S ^P . Preferably R ⁶ and R ⁷ are H, unsubstituted C ₁ -C ₈ alkyl, C ₆ aryl, more preferably R ⁶ is H or methyl and R ⁷ is

H.

In a preferred embodiment, the remainder of C ^A in Formula 24a,

24b, 24c, 24d and 24e is bound to Y ^C2 via an aromatic moiety, said moiety being a part of C ^A . In a preferred embodiment, the remainder of C ^A in Formula 24f is bound to Y ^C2 via an aliphatic moiety, said moiety being a part of C ^A .

Several preferred structures of L ^C are shown below. In these examples C ^A is preferably bound to L ^C via an Y ^C2 that is O or S, wherein O or S is part of C ^A . For the avoidance of doubt, in these examples Y ^C1 is not denoted as such but is embodied by the relevant NH, NR ⁶ , S, O groups.

Herein, C ^A is optionally linked to the remainder of L ^C via a spacer S ^P ; and R ⁶ is as defined herein

Several other preferred structures of L ^C are shown below. In these examples C ^A is preferably bound to L ^C via an Y ^C2 that is a secondary or primary amine, and wherein said Y ^C2 is part of C ^A . For the avoidance of doubt, in these examples Y ^C1 is not denoted as such but is embodied by the relevant NH, NR ⁶ , S, O groups, and C ^A is optionally linked to the remainder of L ^C via a spacer S ^P .

Herein, R ⁶ is as defined herein.

Further preferred structures of L ^C can be found in

WO2009017394(A1), US7375078, WO2015038426A1, WO2004043493, Angew.

Chem. Int. Ed. 2015, 54, 7492— 7509, the contents of which are hereby incorporated by reference.

In preferred embodiments of the invention the L ^C has a mass of no more than 1000 daltons, no more than 500 daltons, no more than 400 daltons, no more than 300 daltons, or from 10, 50 or 100 to 1000 daltons, from 10, 50, 100 to 400 daltons, from 10, 50, 100 to 300 daltons, from 10, 50, 100 to 200 daltons, e.g., 10-1000 daltons, such as 50-500 daltons, such as 100 to 400 daltons.

A person skilled in the art will know that one L ^C may be connected to another L ^C that is bound to C ^A , wherein upon reaction of the Cleaving Agent with the Trigger T ^R , L ^C -L ^C -C ^A is released from the T ^R , leading to self-immolative release of both L ^C moieties and the C ^A moiety. With respect to the L ^C formulas disclosed herein, the L ^C linking the T ^R to the other L ^C then does not release C ^A but an L ^C that is bound via Y ^C1 and further links to a C ^A .

R ⁶ , R ⁷ , R ⁸ , R ⁹ are as defined herein.

In a preferred embodiment, L ^C is selected from the group consisting of linkers according to Group I, Group II, and Group III,

wherein linkers according to Group I are

, wherein U, V, W, Z are each independently selected from the group consisting of -CR ⁷ -, and -N-. Herein, e is either 0 or 1, and X is selected from the group consisting of -O-, -S- and -NR ⁶ -. Preferably, each R ⁸ and R ⁹ are independently selected from the group consisting of hydrogen, C ₁ -C ₄ alkyl groups, C ₂ -C ₄ alkenyl groups, and C _4-6 (hetero)aryl groups, wherein for R ⁸ and R ⁹ the alkyl groups, alkenyl groups, and (hetero)aryl groups are optionally substituted with a moiety selected from the group consisting of -Cl, -F, -Br, -I, -OH, -NH ₂ , =O, -SH, -SO ₃ H, - PO ₃ H, -PO ₄ H ₂ and -NO ₂ and optionally contain at most two heteroatoms selected from the group consisting of -O-, -S-, -NH-, -P-, and -Si-, wherein the N, S, and P atoms are optionally oxidized. For linkers according to Group I C ^A is linked to L ^C via a moiety selected from the group consisting of -O-, -N-, -C-, and -S-, preferably from the group consisting of secondary amines and tertiary amines, wherein said moieties are part of C ^A .

The linker according to Group II is

, wherein m is an integer between 0 and 2, preferably m is 0, and wherein e is either 0 or 1. For linkers according to Group II C ^A is linked to L ^C via a moiety selected from the group consisting of -O-, -N-, -C-, and -S-, preferably from the group consisting of secondary amines and tertiary amines, wherein said moieties are part of C ^A .

Linkers according to Group III are

wherein for linkers according to Group III C ^A is linked to L ^C via a moiety selected from the group consisting of -O- and -S-, preferably -O- or -S- bound to a C ₄ -6 (hetero)aryl group, wherein said moieties are part of C ^A .

For linkers according to Groups I-III preferably each R ⁶ is independently selected from the group consisting of hydrogen, C ₁ -C ₄ alkyl groups, C ₂ -C ₄ alkenyl groups, and C _4-6 (hetero)aryl groups, wherein for R ⁶ the alkyl groups, alkenyl groups, and (hetero)aryl groups are optionally substituted with a moiety selected from the group consisting of -Cl, -F, -Br, -I, -OH, -NH ₂ , =O, -SH, -SO ₃ H, -PO ₃ H _, - PO4H ₂ and -NO ₂ and optionally contain at most two heteroatoms selected from the group consisting of -O-, -S-, -NH-, -P-, and -Si-, wherein the N, S, and P atoms are optionally oxidized. For linkers of Groups I-III preferably each R ⁷ is independently selected from the group consisting of hydrogen and C ₁ -C ₃ alkyl groups, C ₂ -C ₃ alkenyl groups, and C ₄ -6 (hetero)aryl groups, wherein for R ⁷ the alkyl groups, alkenyl groups, and (hetero)aryl groups are optionally substituted with a moiety selected from the group consisting of -Cl, -F, -Br, -I, -OH, -NH ₂ , =O, =NH, -N(CH ₃ ) ₂ , - S(O) ₂ CH ₃ , and -SH, and are optionally interrupted by at most one heteroatom selected from the group consisting of -O-, -S-, -NH-, -P-, and -Si-, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized, wherein R ⁷ is preferably selected from the group consisting of hydrogen, methyl, -CH ₂ -CH ₂ -N(CH ₃ ) ₂ , and -CH ₂ -CH ₂ -S(O) ₂ -CH ₃ .

R ⁶ , R ⁷ , R ⁸ , R ⁹ comprised in said Group I, II and III, can optionally also be -

(S ^P )i-C ^B .

For all linkers according to Group I and Group II Y ^C1 is selected from the group consisting of -O-, -S-, and -NR ⁶ -, preferably -NR ⁶ -. For all linkers according to Group III, Y ^C1 is -NR ⁶ -. For all linkers according to Group I, Group II, and Group III, Y ^C2 is selected from the group consisting of O and S, preferably O.

Preferably, in Groups I-III when two L ^C are linked to each other, then the L ^C attached to the -O- or -S- at the allylic position of the trans-cyclooctene is selected from the group consisting of linkers according to Group I and Group II, and the L ^C between the L ^C attached to the -O- or -S- at the allylic position of the trans-cyclooctene and C ^A is selected from Group III, and that the wiggly line in the structures of Group III then denotes a bond to the L ^C attached to the -O- or -S- at the allylic position of the trans-cyclooctene instead of a bond to the allylic -O- or -S- on the trans-cyclooctene ring, and that the double dashed line in the structures of Groups I and II then denotes a bond to the L ^C between the L ^C attached to the -O- or -S- at the allylic position of the trans-cyclooctene and the C ^A instead of a bond to C ^A .

In preferred embodiments, L ^C is selected from the group consisting of linkers according to Group IV, Group V, Group VI, and Group VII.

Linkers according to Group IV are

, wherein C ^A is linked to L ^C via a moiety selected from the group consisting of -O- and -S-, preferably from the group consisting of -O-C _5-8 -arylene- and -S-C _5-8 - arylene-, wherein said moieties are part of C ^A .

Linkers according to Group V are

, wherein C ^A is linked to L ^C via a moiety selected from the group consisting of -O- and -S-, wherein said moieties are part of C ^A .

Linkers according to Group VI are

, wherein C ^A is linked to L ^C via a moiety selected from the group consisting of -O-, -N-, and -S-, preferably a secondary or a tertiary amine, wherein said moieties are part of C ^A .

Linkers according to Group VII are

, wherein C ^A is linked to L ^C via a moiety selected from the group consisting of -O-, -N-, and -S-, preferably from the group consisting of secondary amines and tertiary amines, wherein said moieties are part of C ^A , wherein when multiple double dashed lines are shown within one L ^C , each C ^A moiety is independently selected.

For all linkers according to Group IV, Group V, Group VI, and Group VII, Y ^C1 is selected from the group consisting of -O-, -S-, and -NR ⁶ -. For all linkers according to Groups IV- VII R ⁶ and R ⁷ are as defined herein; i is an integer in a range of from 0 to 4, preferably 0 or 1; and j is 0 or 1.

In preferred embodiments, R ⁶ , R ⁷ , R ⁸ and R ⁹ in L ^C formulas, in particular in any one of Groups I- VII, are hydrogen.

Preferably, each R ⁶ is independently selected from the group consisting of hydrogen, -(S ^P ) _i -C ^C , C ₁ -C ₂₄ alkyl groups, C ₂ -C ₂₄ alkenyl groups, C ₂ -C ₂₄ alkynyl groups, C ₆ -C ₂₄ aryl groups, C ₂ -C ₂₄ heteroaryl groups, C ₃ -C ₂₄ cycloalkyl groups, C ₅ - C ₂₄ cycloalkenyl groups, C ₁₂ -C ₂₄ cycloalkynyl groups, C ₃ -C ₂₄

(cyclo)alkyl(hetero)aryl groups, C ₃ -C ₂₄ (hetero)aryl(cyclo)alkyl, C ₄ -C ₂₄

(cyclo)alkenyl(hetero)aryl groups, C ₄ -C ₂₄ (hetero)aryl(cyclo)alkenyl groups, C ₄ -C ₂₄ (cyclo)alkynyl(hetero)aryl groups, C ₄ -C ₂₄ (hetero)aryl(cyclo) alkynyl groups, C ₄ -C ₂₄ alkylcycloalkyl groups, and C ₄ -C ₂₄ cycloalkylalkyl groups; wherein i is an integer in a range of from 0 to 4, preferably i is 1;

the R ⁶ groups not being hydrogen are optionally substituted with a moiety selected from the group consisting of -Cl, -F, -Br, -I, -OH, -NH ₂ , -SO ₃ H, -PO ₃ H _, - PO ₄ H _2, -NO ₂ , -CF ₃ , =O, =NH, and -SH, and optionally contain one or more heteroatoms selected from the group consisting of O, S, NH, P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized.

In preferred embodiments, each R ⁶ is individually selected from the group consisting of hydrogen, C ₁ -C ₈ alkyl groups, C ₂ -C ₈ alkenyl groups, C ₂ -C ₈ alkynyl groups, C ₆ -C ₁₂ aryl, C ₂ -C ₁₂ heteroaryl, C ₃ -C ₈ cycloalkyl groups, C ₅ -C ₈ cycloalkenyl groups, C ₃ -C ₁₂ alkyl(hetero)aryl groups, C ₃ -C ₁₂ (hetero)arylalkyl groups, C ₄ -C ₁₂ alkylcycloalkyl groups, C ₄ -C ₁₂ cycloalkylalkyl groups, C ₅ -C ₁₂

cycloalkyl(hetero)aryl groups and C ₅ -C ₁₂ (hetero)arylcycloalkyl groups, wherein the R ⁶ groups not being hydrogen are optionally substituted with a moiety selected from the group consisting of -Cl, -F, -Br, -I, -OH, -NH ₂ , -SO ₃ H, -PO ₃ H _, - PO ₄ H _2, -NO ₂ , -CF ₃ , =O, =NH, and -SH, and optionally contain one or more heteroatoms selected from the group consisting of O, S, NH, P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized.

In preferred embodiments, R ⁶ is selected from the group consisting of hydrogen, C ₁ -C ₄ alkyl groups, C ₂ -C ₄ alkenyl groups, C ₂ -C ₄ alkynyl groups, C ₆ -C ₈ aryl, C ₂ -C ₈ heteroaryl, C ₃ -C ₆ cycloalkyl groups, C ₅ -C ₆ cycloalkenyl groups, C ₃ -C ₁₀ alkyl(hetero)aryl groups, C ₃ -C ₁₀ (hetero)arylalkyl groups, C ₄ -C ₈ alkylcycloalkyl groups, C ₄ -C ₈ cycloalkylalkyl groups, C ₅ -C ₁₀ cycloalkyl(hetero)aryl groups and C ₅ - C ₁₀ (hetero)arylcycloalkyl groups, wherein the R ⁶ groups not being hydrogen are optionally substituted with a moiety selected from the group consisting of -Cl, -F, -Br, -I, -OH, -NH ₂ , -SO ₃ H, -PO ₃ H, -PO ₄ H _2, -NO ₂ , -CF ₃ , =O, =NH, and -SH, and optionally contain one or more heteroatoms selected from the group consisting of O, S, NH, P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized.

In preferred embodiments, R ⁶ is selected from the group consisting of hydrogen, C ₁ -C ₄ alkyl groups, C ₂ -C ₄ alkenyl groups, and C _4-6 (hetero)aryl groups, wherein for R ⁶ the alkyl groups, alkenyl groups, and (hetero)aryl groups are optionally substituted with a moiety selected from the group consisting of -Cl, -F, -Br, -I, -OH, -NH ₂ , =O, -SH, -SO ₃ H, -PO ₃ H, -PO ₄ H ₂ and -NO ₂ and optionally contain at most two heteroatoms selected from the group consisting of -O-, -S-, - NH-, -P-, and -Si-, wherein the N, S, and P atoms are optionally oxidized.

In preferred embodiments, R ⁶ is selected from the group consisting of hydrogen, ₁ -C ₃ alkyl groups, C ₂ -C ₃ alkenyl groups, and C _4-6 (hetero)aryl groups, wherein for R ⁶ the alkyl groups, alkenyl groups, and (hetero)aryl groups are optionally substituted with a moiety selected from the group consisting of -Cl, -F, -Br, -I, -OH, -NH ₂ , =O, -SH, -SO ₃ H, -PO ₃ H, -PO ₄ H ₂ and -NO ₂ and optionally contain at most two heteroatoms selected from the group consisting of -O-, -S-, - NH-, -P-, and -Si-, wherein the N, S, and P atoms are optionally oxidized.

In preferred embodiments, the R ⁶ groups not being hydrogen are not substituted. In preferred embodiments, the R ⁶ groups not being hydrogen do not contain heteroatoms. In preferred embodiments, the R ⁶ groups are hydrogen.

RI

In preferred embodiments, each R ⁷ is independently selected from the group consisting of hydrogen, -(S ^P )i-C ^C , -F, -Cl, -Br, -I, -OR ₃₇ , -N(R ₃₇ ) ₂ , -SO ₃ , -PO ₃ , -NO ₂ , -CF ₃ , -SR ₃₇ , S(=O) ₂ N(R ₃₇ ) ₂ , OC(=O)R ₃₇ , SC(=O) R ₃₇ , OC(=S)R ₃₇ , SC(=S)R ₃₇ ,

NR ₃₇ C(=O)-R ₃₇ , NR ₃₇ C(=S)-R ₃₇ , NR ₃₇ C(=O)O-R ₃₇ , NR ₃₇ C(=S)O-R ₃₇ , NR ₃₇ C(=O)S- R ₃₇ , NR ₃₇ C(=S)S-R ₃₇ , OC(=O)N(R ₃₇ ) ₂ , SC(=O)N(R ₃₇ ) ₂ , OC(=S)N(R ₃₇ ) ₂ ,

SC(=S)N(R ₃₇ ) ₂ , NR ₃₇ C(=O)N(R ₃₇ ) ₂ , NR ₃₇ C(=S)N(R ₃₇ ) ₂ , C(=O)R _37, C(=S)R _37,

C(=O)N(R ₃₇ ) ₂ , C(=S)N(R ₃₇ ) ₂ , C(=O)O-R ₃₇ , C(=O)S-R ₃₇ , C(=S)O-R ₃₇ , C(=S)S-R ₃₇ , S(O)R ₃₇ , -S(O) ₂ R ₃₇ , NR ₃₇ S(O) ₂ R ₃₇ , -ON(R ₃₇ ) ₂ , -NR ₃₇ OR ₃₇ , C- ₁ C ₂₄ alkyl groups, C ₂ - C ₂₄ alkenyl groups, C ₂ -C ₂₄ alkynyl groups, C ₆ -C ₂₄ aryl groups, C ₂ -C ₂₄ heteroaryl groups, C ₃ -C ₂₄ cycloalkyl groups, C ₅ -C ₂₄ cycloalkenyl groups, C ₁₂ -C ₂₄ cycloalkynyl groups, C ₃ -C ₂₄ (cyclo)alkyl(hetero)aryl groups, C ₃ -C ₂₄ (hetero)aryl(cyclo) alkyl, C ₄ - C ₂₄ (cyclo)alkenyl(hetero)aryl groups, C ₄ -C ₂₄ (hetero)aryl(cyclo) alkenyl groups, C ₄ -C ₂₄ (cyclo)alkynyl(hetero)aryl groups, C ₄ -C ₂₄ (hetero)aryl(cyclo)alkynyl groups, C ₄ -C ₂₄ alkylcycloalkyl groups, and C ₄ -C ₂₄ cycloalkylalkyl groups; wherein i is an integer in a range of from 0 to 4, preferably i is 1,

wherein the alkyl groups, alkenyl groups, alkynyl groups, aryl, heteroaryl, cycloalkyl groups, cycloalkenyl groups, cycloalkynyl groups,

(cyclo)alkyl(hetero)aryl groups, (hetero)aryl(cyclo) alkyl groups,

(cyclo)alkenyl(hetero)aryl groups, (hetero)aryl(cyclo)alkenyl groups,

(cyclo)alkynyl(hetero)aryl groups, (hetero)aryl(cyclo)alkynyl groups,

alkylcycloalkyl groups, cycloalkylalkyl groups are optionally substituted with a moiety selected from the group consisting of -Cl, -F, -Br, -I, -OR ₃₇ , -N(R ₃₇ ) ₂ , - SO ₃ R ₃₇ , -PO ₃ (R ₃₇ ) ₂ , -PO ₄ (R ₃₇ ) ₂ , -NO ₂ , -CF ₃ , =O, =NR ₃₇ , and -SR ₃₇ , and optionally contain one or more heteroatoms selected from the group consisting of O, S, NR ₃₇ , P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized.

In preferred embodiments, each R ⁷ is independently selected from the group consisting hydrogen, -F, -Cl, -Br, -I, -OR ₃₇ , -N(R ₃₇ ) ₂ , -SO ₃ , -PO ₃ , -NO ₂ , -CF ₃ , -SR ₃₇ , S(=O) ₂ N(R ₃₇ ) ₂ , OC(=O)R ₃₇ , SC(=O) R ₃₇ , OC(=S)R ₃₇ , SC(=S)R ₃₇ , NR ₃₇ C(=O)- R ₃₇ , NR ₃₇ C(=S)-R ₃₇ , NR ₃₇ C(=O)O-R ₃₇ , NR ₃₇ C(=S)O-R ₃₇ , NR ₃₇ C(=O)S-R ₃₇ ,

NR ₃₇ C(=S)S-R ₃₇ , OC(=O)N(R ₃₇ ) ₂ , SC(=O)N(R ₃₇ ) ₂ , OC(=S)N(R ₃₇ ) ₂ , SC(=S)N(R ₃₇ ) ₂ , NR ₃₇ C(=O)N(R ₃₇ ) ₂ , NR ₃₇ C(=S)N(R ₃₇ ) ₂ , C(=O)R _37, C(=S)R _37, C(=O)N(R ₃₇ ) ₂ ,

C(=S)N(R ₃₇ ) ₂ , C(=O)O-R ₃₇ , C(=O)S-R ₃₇ , C(=S)O-R ₃₇ , C(=S)S-R ₃₇ , S(O)R ₃₇ , - S(O) 2R ₃₇ , NR ₃₇ S(O) ₂ R ₃₇ , -ON(R ₃₇ ) ₂ , -NR ₃₇ OR ₃₇ , C ₁ -C ₈ alkyl groups, C ₂ -C ₈ alkenyl groups, C ₂ -C ₈ alkynyl groups, C ₆ -C ₁₂ aryl groups, C ₂ -C ₁₂ heteroaryl groups, C ₃ -C ₈ cycloalkyl groups, C ₅ -C ₈ cycloalkenyl groups, C ₃ -C ₁₂ alkyl(hetero)aryl groups, C ₃ - C ₁₂ (hetero)arylalkyl groups, C ₄ -C ₁₂ alkylcycloalkyl groups, C ₄ -C ₁₂ cycloalkylalkyl groups, C ₅ -C ₁₂ cycloalkyl(hetero)aryl groups and C ₅ -C ₁₂ (hetero)arylcycloalkyl groups, wherein the alkyl groups, alkenyl groups, alkynyl groups, aryl,

heteroaryl, cycloalkyl groups, cycloalkenyl groups, alkyl(hetero)aryl groups, (hetero)arylalkyl groups, alkylcycloalkyl groups, cycloalkylalkyl groups, cycloalkyl(hetero)aryl groups and (hetero)arylcycloalkyl groups are optionally substituted with a moiety selected from the group consisting of -Cl, -F, -Br, -I, - OR ₃₇ , -N(R ₃₇ ) ₂ , -SO ₃ R ₃₇ , -PO ₃ (R ₃₇ ) ₂ , -PO4(R ₃₇ ) ₂ , -NO ₂ , -CF ₃ , =O, =NR ₃₇ , and -SR ₃₇ , and optionally contain one or more heteroatoms selected from the group

consisting of O, S, NR ₃₇ , P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized.

In preferred embodiments, each R ⁷ is independently selected from the group consisting of hydrogen, -F, -Cl, -Br, -I, -OR ₃₇ , -N(R ₃₇ ) ₂ , -SO ₃ , -PO ₃ ^· , -NO ₂ , - CF ₃ , -SR ₃₇ , S(=O) ₂ N(R ₃₇ ) ₂ , OC(=O)R ₃₇ , SC(=O) R ₃₇ , OC(=S)R ₃₇ , SC(=S)R ₃₇ ,

NR ₃₇ C(=O)-R ₃₇ , NR ₃₇ C(=S)-R ₃₇ , NR ₃₇ C(=O)O-R ₃₇ , NR ₃₇ C(=S)O-R ₃₇ , NR ₃₇ C(=O)S- R ₃₇ , NR ₃₇ C(=S)S-R ₃₇ , OC(=O)N(R ₃₇ ) ₂ , SC(=O)N(R ₃₇ ) ₂ , OC(=S)N(R ₃₇ ) ₂ ,

SC(=S)N(R ₃₇ ) ₂ , NR ₃₇ C(=O)N(R ₃₇ ) ₂ , NR ₃₇ C(=S)N(R ₃₇ ) ₂ , C(=O)R _37, C(=S)R _37,

C(=O)N(R ₃₇ ) ₂ , C(=S)N(R ₃₇ ) ₂ , C(=O)O-R ₃₇ , C(=O)S-R ₃₇ , C(=S)O-R ₃₇ , C(=S)S-R ₃₇ , S(O)R ₃₇ , -S(O) ₂ R ₃₇ , NR ₃₇ S(O) ₂ R ₃₇ , -ON(R ₃₇ ) ₂ , -NR ₃₇ OR ₃₇ , C- ₁ C ₄ alkyl groups, C ₂ -C ₄ alkenyl groups, C ₂ -C ₄ alkynyl groups, C ₆ -C ₈ aryl groups, C ₂ -C ₈ heteroaryl groups, C ₃ -C ₆ cycloalkyl groups, C ₅ -C ₆ cycloalkenyl groups, C ₃ -C ₁₀ alkyl(hetero)aryl groups, C ₃ -C ₁₀ (hetero)arylalkyl groups, C ₄ -C ₁₀ alkylcycloalkyl groups, C ₄ -C ₁₀ cycloalkylalkyl groups, C ₅ -C ₁₀ cycloalkyl(hetero)aryl groups and C ₅ -C ₁₀

(hetero)arylcycloalkyl groups, wherein the alkyl groups, alkenyl groups, alkynyl groups, aryl, heteroaryl, cycloalkyl groups, cycloalkenyl groups, alkyl(hetero)aryl groups, (hetero)arylalkyl groups, alkylcycloalkyl groups, cycloalkylalkyl groups, cycloalkyl(hetero)aryl groups and (hetero)arylcycloalkyl groups are optionally substituted with a moiety selected from the group consisting of -Cl, -F, -Br, -I, - OR ₃₇ , -N(R ₃₇ ) ₂ , -SO ₃ R ₃₇ , -PO ₃ (R ₃₇ ) ₂ , -PO4(R ₃₇ ) ₂ , -NO ₂ , -CF ₃ , =O, =NR ₃₇ , and -SR ₃₇ , and optionally contain one or more heteroatoms selected from the group consisting of O, S, NR ₃₇ , P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized.

In preferred embodiments, each R ⁷ is independently selected from the group consisting of hydrogen andC ₁ -C ₃ alkyl groups, C ₂ -C ₃ alkenyl groups, and C _4-6 (hetero)aryl groups, wherein the alkyl groups, alkenyl groups, and

(hetero)aryl groups are optionally substituted with a moiety selected from the group consisting of -Cl, -F, -Br, -I, -OH, -NH ₂ , =O, =NH, -N(CH ₃ ) ₂ , -S(O) ₂ CH ₃ , and -SH, and are optionally interrupted by at most one heteroatom selected from the group consisting of -O-, -S-, -NH-, -P-, and -Si-, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized.

In preferred embodiments, R ⁷ is preferably selected from the group consisting of hydrogen, methyl, -CH ₂ -CH ₂ -N(CH ₃ ) ₂ , and -CH ₂ -CH ₂ -S(O) ₂ -CH ₃ . In preferred embodiments, the R ⁷ groups not being hydrogen are not substituted. In preferred embodiments, the R ⁷ groups not being hydrogen do not contain heteroatoms. In preferred embodiments, the R ⁷ groups are hydrogen.

R ⁸ and R ⁹

R ⁸ and R ⁹ are as defined for R ⁷ . In preferred embodiments, at least one or all R ⁸ are -H. In preferred embodiments, at least one or all R ⁸ are -CH ₃ . In preferred embodiments, at least one or all R ⁹ are -H. In preferred embodiments, at least one or all R ⁹ are -CH ₃ . In preferred embodiments, the R ₈ and R ₉ groups not being hydrogen are not substituted. In preferred embodiments, the R ₈ and R ₉ groups not being hydrogen do not contain heteroatoms. In preferred embodiments, the R ⁸ and R ⁹ groups are hydrogen. X ¹ , X ² , X ³ , X ⁴ . and X ⁵

In Formula (1), each X ¹ , X ² , X ³ , X ⁴ is independently selected from the group consisting of -C(R ₄₇ ) ₂ -, -NR ₃₇ -, -C(O)-, -O-, such that at most two of X ¹ , X ² , X ³ , X ⁴ are not -C(R ₄₇ ) ₂ -, and with the proviso that no sets consisting of adjacent atoms are present selected from the group consisting of -O-O-, -O-N-, -C(O)-O-, N-N-, and -C(O)-C(O)-.

In a preferred embodiment, X ¹ , X ² , X ³ , and X ⁴ are -C(R ₄₇ ) ₂ -, and preferably at most four R ₄₇ , more preferably at most two R ₄₇ , most preferably at most one R ₄₇ , are not H. In Formula (1) X ⁵ is -C(R ₄₇ ) ₂ - or -CHR ₄₈ . In a preferred

embodiment, X ⁵ is -C(R ₄₇ ) ₂ -; more preferably X ⁵ is -CHR ₄₇ , and most preferably X ⁵ is -CH ₂ . In a preferred embodiment X ⁵ is CHR ₄₈ . R ₃₆

In a preferred embodiment, R ₃₆ is as defined for R ₃₇ .

In Formula (1) R ₃₆ is preferably selected from the group consisting of hydrogen, C ₁ -Ce alkyl groups, C ₂ -C ₈ alkenyl groups, and C _4-6 (hetero)aryl groups, wherein the alkyl groups, alkenyl groups, and (hetero)aryl groups are optionally

substituted with a moiety selected from the group consisting of -Cl, -F, -Br, -I, - OH, -NH ₂ , =O, -SH, -SO ₃ H, -PO ₃ H, -PO ₄ H ₂ and -NO ₂ and optionally contain at most two heteroatoms selected from the group consisting of -O-, -S-, -NH-, -P-, and -Si-, wherein the N, S, and P atoms are optionally oxidized. In preferred embodiments, the R ₃₆ groups not being hydrogen are not substituted. In

preferred embodiments, the R ₃₆ groups not being hydrogen do not contain heteroatoms. In some preferred embodiments, R ₃₆ is hydrogen.

R ₄₇

In Formula (1) each R47 is independently selected from the group consisting of hydrogen, -L ^B , -L ^A , -(S ^P )i-C ^C , -F, -Cl, -Br, -I, -OR ₃₇ , -N(R ₃₇ ) ₂ , -SO ₃ , -PO ₃ -, -NO ₂ , - CF ₃ , -SR ₃₇ , S(=O) ₂ N(R ₃₇ ) ₂ , OC(=O)R ₃₇ , SC(=O) R ₃₇ , OC(=S)R ₃₇ , SC(=S)R ₃₇ ,

NR ₃₇ C(=O)-R ₃₇ , NR ₃₇ C(=S)-R ₃₇ , NR ₃₇ C(=O)O-R ₃₇ , NR ₃₇ C(=S)O-R ₃₇ , NR ₃₇ C(=O)S- R ₃₇ , NR ₃₇ C(=S)S-R ₃₇ , OC(=O)N(R ₃₇ ) ₂ , SC(=O)N(R ₃₇ ) ₂ , OC(=S)N(R ₃₇ ) ₂ ,

SC(=S)N(R ₃₇ ) ₂ , NR ₃₇ C(=O)N(R ₃₇ ) ₂ , NR ₃₇ C(=S)N(R ₃₇ ) ₂ , C(=O)R _37, C(=S)R _37,

C(=O)N(R ₃₇ ) ₂ , C(=S)N(R ₃₇ ) ₂ , C(=O)O-R ₃₇ , C(=O)S-R ₃₇ , C(=S)O-R ₃₇ , C(=S)S-R ₃₇ , S(O)R ₃₇ , -S(O) ₂ R ₃₇ , NR ₃₇ S(O) ₂ R ₃₇ , -ON(R ₃₇ ) ₂ , -NR ₃₇ OR ₃₇ , C- ₁ C ₂₄ alkyl groups, C ₂ - C ₂₄ alkenyl groups, C ₂ -C ₂₄ alkynyl groups, C ₆ -C ₂₄ aryl groups, C ₂ -C ₂₄ heteroaryl groups, C ₃ -C ₂₄ cycloalkyl groups, C ₅ -C ₂₄ cycloalkenyl groups, C ₁₂ -C ₂₄ cycloalkynyl groups, C ₃ -C ₂₄ (cyclo)alkyl(hetero)aryl groups, C ₃ -C ₂₄ (hetero)aryl(cyclo) alkyl, C ₄ - C ₂₄ (cyclo)alkenyl(hetero)aryl groups, C ₄ -C ₂₄ (hetero)aryl(cyclo) alkenyl groups, C ₄ -C ₂₄ (cyclo)alkynyl(hetero)aryl groups, C ₄ -C ₂₄ (hetero)aryl(cyclo)alkynyl groups, C ₄ -C ₂₄ alkylcycloalkyl groups, and C ₄ -C ₂₄ cycloalkylalkyl groups; wherein i is an integer in a range of from 0 to 4, preferably i is an integer ranging from 0 to 1, wherein the alkyl groups, alkenyl groups, alkynyl groups, aryl, heteroaryl, cycloalkyl groups, cycloalkenyl groups, cycloalkynyl groups,

(cyclo)alkyl(hetero)aryl groups, (hetero)aryl(cyclo) alkyl groups,

(cyclo)alkenyl(hetero)aryl groups, (hetero)aryl(cyclo)alkenyl groups,

(cyclo)alkynyl(hetero)aryl groups, (hetero)aryl(cyclo)alkynyl groups,

alkylcycloalkyl groups, cycloalkylalkyl groups are optionally substituted with a moiety selected from the group consisting of -Cl, -F, -Br, -I, -OR ₃₇ , -N(R ₃₇ ) ₂ , - SO ₃ R ₃₇ , -PO ₃ (R ₃₇ ) ₂ , -PO ₄ (R ₃₇ ) ₂ , -NO ₂ , -CF ₃ , =O, =NR ₃₇ , and -SR ₃₇ , and optionally contain one or more heteroatoms selected from the group consisting of O, S, NR ₃₇ , P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized.

In preferred embodiments, each R ₄₇ is independently selected from the group consisting of hydrogen, -L ^B , -L ^A , -(S ^P )i-C ^C , -F, -Cl, -Br, -I, -OR ₃₇ , -N(R ₃₇ ) ₂ , - SO ₃ , -PO ₃ -, -NO ₂ , -CF ₃ , -SR ₃₇ , S(=O) ₂ N(R ₃₇ ) ₂ , OC(=O)R ₃₇ , SC(=O) R ₃₇ , OC(=S)R ₃₇ , SC(=S)R ₃₇ , NR ₃₇ C(=O)-R ₃₇ , NR ₃₇ C(=S)-R ₃₇ , NR ₃₇ C(=O)O-R ₃₇ , NR ₃₇ C(=S)O-R ₃₇ , NR ₃₇ C(=O)S-R ₃₇ , NR ₃₇ C(=S)S-R ₃₇ , OC(=O)N(R ₃₇ ) ₂ , SC(=O)N(R ₃₇ ) ₂ , OC(=S)N(R ₃₇ ) ₂ , SC(=S)N(R ₃₇ ) ₂ , NR ₃₇ C(=O)N(R ₃₇ ) ₂ , NR ₃₇ C(=S)N(R ₃₇ ) ₂ , C(=O)R _37, C(=S)R _37,

C(=O)N(R ₃₇ ) ₂ , C(=S)N(R ₃₇ ) ₂ , C(=O)O-R ₃₇ , C(=O)S-R ₃₇ , C(=S)O-R ₃₇ , C(=S)S-R ₃₇ , S(O)R ₃₇ , -S(O) ₂ R ₃₇ , NR ₃₇ S(O) ₂ R ₃₇ , -ON(R ₃₇ ) ₂ , -NR ₃₇ OR ₃₇ , C ₁ -C ₈ alkyl groups, C ₂ -C ₈ alkenyl groups, C ₂ -C ₈ alkynyl groups, C ₆ -C ₁₂ aryl groups, C ₂ -C ₁₂ heteroaryl groups, C ₃ -C ₈ cycloalkyl groups, C ₅ -C ₈ cycloalkenyl groups, C ₃ -C ₁₂

alkyl(hetero)aryl groups, C ₃ -C ₁₂ (hetero)arylalkyl groups, C ₄ -C ₁₂ alkylcycloalkyl groups, C ₄ -C ₁₂ cycloalkylalkyl groups, C ₅ -C ₁₂ cycloalkyl(hetero)aryl groups and C ₅ -C ₁₂ (hetero)arylcycloalkyl groups, wherein the alkyl groups, alkenyl groups, alkynyl groups, aryl, heteroaryl, cycloalkyl groups, cycloalkenyl groups, alkyl(hetero)aryl groups, (hetero)arylalkyl groups, alkylcycloalkyl groups, cycloalkylalkyl groups, cycloalkyl(hetero)aryl groups and (hetero)arylcycloalkyl groups are optionally substituted with a moiety selected from the group

consisting of -Cl, -F, -Br, -I, -OR ₃₇ , -N(R ₃₇ ) ₂ , -SO ₃ R ₃₇ , -PO ₃ (R ₃₇ ) ₂ , -PO4(R ₃₇ ) ₂ , -NO ₂ , -CF ₃ , =O,— NR ₃₇ , and -SR ₃₇ , and optionally contain one or more heteroatoms selected from the group consisting of O, S, NR ₃₇ , P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized.

In preferred embodiments, each R47 is independently selected from the group consisting of hydrogen, -L ^B , -L ^A , -(S ^P )i-C ^C , -F, -Cl, -Br, -I, -OR ₃₇ , -N(R ₃₇ ) ₂ , - SO ₃ , -PO ₃ -, -NO ₂ , -CF ₃ , -SR ₃₇ , S(=O) ₂ N(R ₃₇ ) ₂ , OC(=O)R ₃₇ , SC(=O) R ₃₇ , OC(=S)R ₃₇ , SC(=S)R ₃₇ , NR ₃₇ C(=O)-R ₃₇ , NR ₃₇ C(=S)-R ₃₇ , NR ₃₇ C(=O)O-R ₃₇ , NR ₃₇ C(=S)O-R ₃₇ , NR ₃₇ C(=O)S-R ₃₇ , NR ₃₇ C(=S)S-R ₃₇ , OC(=O)N(R ₃₇ ) ₂ , SC(=O)N(R ₃₇ ) ₂ , OC(=S)N(R ₃₇ ) ₂ , SC(=S)N(R ₃₇ ) ₂ , NR ₃₇ C(=O)N(R ₃₇ ) ₂ , NR ₃₇ C(=S)N(R ₃₇ ) ₂ , C(=O)R _37, C(=S)R _37,

C(=O)N(R ₃₇ ) ₂ , C(=S)N(R ₃₇ ) ₂ , C(=O)O-R ₃₇ , C(=O)S-R ₃₇ , C(=S)O-R ₃₇ , C(=S)S-R ₃₇ , S(O)R ₃₇ , -S(O) ₂ R ₃₇ , NR ₃₇ S(O) ₂ R ₃₇ , -ON(R ₃₇ ) ₂ , -NR ₃₇ OR ₃₇ , C- ₁ C ₄ alkyl groups, C ₂ -C ₄ alkenyl groups, C ₂ -C ₄ alkynyl groups, C ₆ -C ₈ aryl groups, C ₂ -C ₈ heteroaryl groups, C ₃ -C ₆ cycloalkyl groups, C ₅ -C ₆ cycloalkenyl groups, C ₃ -C ₁₀ alkyl(hetero)aryl groups, C ₃ -C ₁₀ (hetero)arylalkyl groups, C ₄ -C ₁₀ alkylcycloalkyl groups, C ₄ -C ₁₀ cycloalkylalkyl groups, C ₅ -C ₁₀ cycloalkyl(hetero)aryl groups and C ₅ -C ₁₀

(hetero)arylcycloalkyl groups, wherein the alkyl groups, alkenyl groups, alkynyl groups, aryl, heteroaryl, cycloalkyl groups, cycloalkenyl groups, alkyl(hetero)aryl groups, (hetero)arylalkyl groups, alkylcycloalkyl groups, cycloalkylalkyl groups, cycloalkyl(hetero)aryl groups and (hetero)arylcycloalkyl groups are optionally substituted with a moiety selected from the group consisting of -Cl, -F, -Br, -I, - OR ₃₇ , -N(R ₃₇ ) ₂ , -SO ₃ R ₃₇ , -PO ₃ (R ₃₇ ) ₂ , -PO4(R ₃₇ ) ₂ , -NO ₂ , -CF ₃ , =O, =NR ₃₇ , and -SR ₃₇ , and optionally contain one or more heteroatoms selected from the group consisting of O, S, NR ₃₇ , P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized. R ₃₇

In Formula (1) each R ₃₇ is independently selected from the group consisting of hydrogen, -L ^B , -L ^A , -(S ^P )i-C ^C , C ₁ -C ₂₄ alkyl groups, C ₂ -C ₂₄ alkenyl groups, C ₂ -C ₂₄ alkynyl groups, C ₆ -C ₂₄ aryl groups, C ₂ -C ₂₄ heteroaryl groups, C ₃ -C ₂₄ cycloalkyl groups, C ₅ -C ₂₄ cycloalkenyl groups, C ₁₂ -C ₂₄ cycloalkynyl groups, C ₃ -C ₂₄

(cyclo)alkyl(hetero)aryl groups, C ₃ -C ₂₄ (hetero)aryl(cyclo)alkyl, C ₄ -C ₂₄

(cyclo)alkenyl(hetero)aryl groups, C ₄ -C ₂₄ (hetero)aryl(cyclo)alkenyl groups, C ₄ -C ₂₄ (cyclo)alkynyl(hetero)aryl groups, C ₄ -C ₂₄ (hetero)aryl(cyclo) alkynyl groups, C ₄ -C ₂₄ alkylcycloalkyl groups, and C ₄ -C ₂₄ cycloalkylalkyl groups; wherein i is an integer in a range of from 0 to 4, preferably i is 1; the R ₃₇ groups not being hydrogen are optionally substituted with a moiety selected from the group consisting of -Cl, -F, -Br, -I, -OH, -NH ₂ , -SO ₃ H, -PO ₃ H, -PO ₄ H _2, -NO ₂ , -CF ₃ , =O, =NH, and -SH, and optionally contain one or more heteroatoms selected from the group consisting of O, S, NH, P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized.

In preferred embodiments, R ₃₇ is selected from the group consisting of hydrogen, -L ^B , -L ^A , -(S ^P )i-C ^C , C ₁ -C ₈ alkyl groups, C ₂ -C ₈ alkenyl groups, C ₂ -C ₈ alkynyl groups, C ₆ -C ₁₂ aryl, C ₂ -C ₁₂ heteroaryl, C ₃ -C ₈ cycloalkyl groups, C ₅ -C ₈ cycloalkenyl groups, C ₃ -C ₁₂ alkyl(hetero)aryl groups, C ₃ -C ₁₂ (hetero)arylalkyl groups, C ₄ -C ₁₂ alkylcycloalkyl groups, C ₄ -C ₁₂ cycloalkylalkyl groups, C ₅ -C ₁₂ cycloalkyl(hetero)aryl groups and C ₅ -C ₁₂ (hetero)arylcycloalkyl groups, wherein the R ₃₇ groups not being hydrogen are optionally substituted with a moiety selected from the group consisting of -Cl, -F, -Br, -I, -OH, -NH ₂ , -SO ₃ H, -PO ₃ H _, - PO ₄ H _2, -NO ₂ , -CF ₃ , =O, =NH, and -SH, and optionally contain one or more heteroatoms selected from the group consisting of O, S, NH, P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized.

In preferred embodiments, R ₃₇ is selected from the group consisting of hydrogen, -L ^B , -L ^A , -(S ^P )i-C ^C , C ₁ -C ₄ alkyl groups, C ₂ -C ₄ alkenyl groups, C ₂ -C ₄ alkynyl groups, C ₆ -C ₈ aryl, C ₂ -C ₈ heteroaryl, C ₃ -C ₆ cycloalkyl groups, C ₅ -C ₆ cycloalkenyl groups, C ₃ -C ₁₀ alkyl(hetero)aryl groups, C ₃ -C ₁₀ (hetero)arylalkyl groups, C ₄ -C ₈ alkylcycloalkyl groups, C ₄ -C ₈ cycloalkylalkyl groups, C ₅ -C ₁₀ cycloalkyl(hetero)aryl groups and C ₅ -C ₁₀ (hetero)arylcycloalkyl groups, wherein the R ₃₇ groups not being hydrogen are optionally substituted with a moiety selected from the group consisting of -Cl, -F, -Br, -I, -OH, -NH ₂ , -SO ₃ H, -PO ₃ H _, - PO ₄ H _2, -NO ₂ , -CF ₃ , =O, =NH, and -SH, and optionally contain one or more heteroatoms selected from the group consisting of O, S, NH, P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized.

In preferred embodiments, the R ₃₇ groups not being hydrogen are not

substituted. In preferred embodiments, the R ₃₇ groups not being hydrogen do not contain heteroatoms. In some preferred embodiments, R ₃₇ is hydrogen. S ^P is a spacer as defined herein and C ^C is a Construct-C as defined herein.

In Formula (1) two R ₄₇ and /or R ₃₇ are optionally comprised in a ring.

In Formula (1) two R ₄₇ and /or R ₃₇ are optionally comprised in a ring so as to form a ring fused to the eight-membered trans-ring of Formula (1). It is preferred that when two R ₄₇ and /or R ₃₇ groups are comprised in a ring so as to form a ring fused to the eight-membered trans-ring, that these rings fused to the eight-membered trans-ring are C ₃ -C ₇ cycloalkylene groups and C ₄ -C ₇

cycloalkenylene groups, optionally substituted and containing heteroatoms as described for R ₄₇ . Label

The compound of Formula (1) comprises a Label that is capable of providing the desired diagnostic, imaging, and/or radiotherapeutic effect.

The Label is a moiety comprising a radionuclide.

Especially for imaging applications, it is preferred that the Label is a detectable label. A "detectable label" as used herein relates to the part of the compound of Formula (1) which allows detection of the compound of Formula (1) when present in a cell, tissue or organism. One type of detectable label envisaged within the context of the present invention is a contrast providing label. Different types of detectable labels are envisaged within the context of the present invention and are described hereinbelow.

Thus, according to a particular embodiment of the present invention, the compounds, combinations, kits, and methods of the present invention are used in imaging, especially medical imaging. In order to identify the Primary Target and/or to evaluate the biodistribution of the compound of Formula (1), use is made of a detectable Label.

Preferred detectable labels for imaging are contrast-providing moieties used in traditional imaging systems.

Preferably, the radionuclide comprised in a Label for imaging is an isotope selected from the group consisting of ³ H, ¹¹ C, ¹³ N, ¹⁵ O, ¹⁸ F, ¹⁹ F, ⁴⁴ Sc, ⁵¹ Cr, ⁵² Fe, ⁵² Mn, ⁵⁵ Co, ⁶⁰ Cu, ⁶¹ Cu, ⁶² Zn, ⁶² Cu, ⁶³ Zn, ⁶⁴ Cu, ⁶⁶ Ga, ⁶⁷ Ga, ⁶⁸ Ga, ⁷⁰ As, ⁷¹ As,

⁷² As, ⁷⁴ As, ⁷⁵ Se, ⁷⁵ Br, ⁷⁶ Br, ⁷⁷ Br, ^8O Br, ⁸² Br, ⁸² Rb, ⁸⁶ Y, ⁸⁸ Y, ⁸⁹ Sr, ⁸⁹ Zr, ⁹⁷ Ru, ^99m Tc, ¹¹⁰ In, ¹¹¹ In, ¹¹³ In, ¹¹⁴ In, ¹¹⁷ Sn, ¹²⁰ I, ¹²² Xe, ¹²³ I, ¹²⁴ I, ¹²⁵ I, ¹⁶⁶ Ho, ¹⁶⁷ Tm, ¹⁶⁹ Yb, ¹⁹³ Pt, ¹⁹⁵ Pt, ²⁰¹ Tl, and ²⁰³ Pb.

More preferably, the radionuclide comprised in a Label for imaging is an isotope selected from the group consisting of ¹⁸ F, ⁴⁴ Sc, ⁶⁴ Cu, ⁶⁸ Ga, ⁸⁹ Zr, ^99m Tc, ¹¹¹ In, ¹²³ I, and ¹²⁴ I.

Other elements and isotopes, such as being used for therapy may also be applied for imaging in certain applications.

In one embodiment the detectable labels comprise small size organic PET and SPECT radioisotopes, such as ¹⁸ F, ¹¹ C , ¹²³ I or ¹²⁴ I. Due to their small size, organic PET or SPECT radioisotopes are ideally suited for monitoring intracellular events as they do not greatly affect the properties of the Administration Agent in general and its membrane transport in particular.

In preferred embodiments, especially when the compound of Formula (1) is used in therapeutic applications, the Label is a therapeutic Label, said Label comprising a radioactive isotope for radiation therapy. A radionuclide used for therapy is preferably an isotope selected from the group consisting of ²⁴ Na, ³² P, ³³ P, ⁴⁷ Sc, ⁵⁹ Fe, ⁶⁷ Cu, ⁷⁶ As, ⁷⁷ As, ⁸⁰ Br, ⁸² Br, ⁸⁹ Sr, ⁹⁰ Nb, ⁹⁰ Y, ¹⁰³ Ru, ¹⁰⁵ Rh, ¹⁰⁹ Pd, ¹¹¹ Ag, ¹¹¹ In, ¹²¹ Sn, ¹²⁷ Te, ¹³¹ I, ¹⁴⁰ La, ¹⁴¹ Ce, ¹⁴² Pr, ¹⁴³ Pr, ¹⁴⁴ Pr, ¹⁴⁹ Pm, ¹⁴⁹ Tb, ¹⁵¹ Pm, ₁ ⁵ ₃ Sm, ¹⁵⁹ Gd, ¹⁶¹ Tb, ¹⁶⁵ Dy, ¹⁶⁶ Dy, ₁₆₆ Ho, ¹⁶⁹ Er, ¹⁷² Tm, ¹⁷⁵ Yb, ¹⁷⁷ Lu,

¹⁸⁶ Re, ¹⁸⁸ Re, ¹⁹⁸ Au, ¹⁹⁹ Au, ²¹¹ At, ²¹¹ Bi, ²¹² Bi, ²¹² Pb, ²¹³ Bi, ²¹⁴ Bi, ²²³ Ra, ²²⁴ Ra, ²²⁵ Ac, and ²²⁷ Th.

More preferably, the radionuclide comprised in a Label for therapy is an isotope selected from the group consisting of ⁹⁰ Y, ¹¹¹ In, ¹³¹ I, ¹⁷⁷ Lu, ¹⁸⁶ Re, ¹⁸⁸ Re, ²¹¹ At, ²¹² Pb, ²¹³ Bi, ²²⁵ Ac, and ²²⁷ Th.

When the Label is intended to comprise a metal, such as ¹¹¹ In for SPECT imaging, such is preferably provided in the form of a chelate. In such a case the Label preferably comprises a structural moiety capable of forming a coordination complex with such a metal. A good example hereof are macrocylic lanthanide(III) chelates derived from l,4,7,10-tetraazacyclododecane-l,4,7,10-tetraacetic acid (H ₄ dota).

In preferred embodiments, the Label is selected from the group consisting of -OR ₃₇ , -N(R ₃₇ ) ₂ , -CF ₃ , -SR ₃₇ , S(=O) ₂ N(R ₃₇ ) ₂ , OC(=O)R ₃₇ , SC(=O) R ₃₇ , OC(=S)R ₃₇ , SC(=S)R ₃₇ , NR ₃₇ C(=O)-R ₃₇ , NR ₃₇ C(=S)-R ₃₇ , NR ₃₇ C(=O)O-R ₃₇ , NR ₃₇ C(=S)O-R ₃₇ , NR ₃₇ C(=O)S-R ₃₇ , NR ₃₇ C(=S)S-R ₃₇ , OC(=O)N(R ₃₇ ) ₂ , SC(=O)N(R ₃₇ ) ₂ , OC(=S)N(R ₃₇ ) ₂ , SC(=S)N(R ₃₇ ) ₂ , NR ₃₇ C(=O)N(R ₃₇ ) ₂ , NR ₃₇ C(=S)N(R ₃₇ ) ₂ , C(=O)R _37, C(=S)R _37,

C(=O)N(R ₃₇ ) ₂ , C(=S)N(R ₃₇ ) ₂ , C(=O)O-R ₃₇ , C(=O)S-R ₃₇ , C(=S)O-R ₃₇ , C(=S)S-R ₃₇ , S(O)R ₃₇ , -S(O) ₂ R ₃₇ , NR ₃₇ S(O) ₂ R ₃₇ , -ON(R ₃₇ ) _2, -NR ₃₇ OR ₃₇ , C _I -C ₂₄ alkyl groups, C ₂ - C ₂₄ alkenyl groups, C ₂ -C ₂₄ alkynyl groups, C ₆ -C ₂₄ aryl groups, C ₂ -C ₂₄ heteroaryl groups, C ₃ -C ₂₄ cycloalkyl groups, C ₅ -C ₂₄ cycloalkenyl groups, C ₁₂ -C ₂₄ cycloalkynyl groups, C ₃ -C ₂₄ (cyclo)alkyl(hetero)aryl groups, C ₃ -C ₂₄ (hetero)aryl(cyclo) alkyl, C ₄ - C ₂₄ (cyclo)alkenyl(hetero)aryl groups, C ₄ -C ₂₄ (hetero)aryl(cyclo)alkenyl groups, C ₄ - C ₂₄ (cyclo)alkynyl(hetero)aryl groups, C ₄ -C ₂₄ (hetero)aryl(cyclo)alkynyl groups, C ₄ -C ₂₄ alkylcycloalkyl groups, and C ₄ -C ₂₄ cycloalkylalkyl groups;

the R ₃₇ groups, alkyl groups, alkenyl groups, alkynyl groups, aryl, heteroaryl, cycloalkyl groups, cycloalkenyl groups, cycloalkynyl groups,

(cyclo)alkyl(hetero)aryl groups, (hetero)aryl(cyclo) alkyl groups,

(cyclo)alkenyl(hetero)aryl groups, (hetero)aryl(cyclo)alkenyl groups,

(cyclo)alkynyl(hetero)aryl groups, (hetero)aryl(cyclo)alkynyl groups,

alkylcycloalkyl groups, cycloalkylalkyl groups comprise, are substituted with, and/or chelating at least one isotope selected from the group consisting of ³ H, ¹¹ C, ¹³ N, ¹⁵ O, ¹⁸ F, ¹⁹ F, ⁵¹ Cr, ⁵² Fe, ⁵² Mn, ⁵⁵ Co, ⁶⁰ Cu, ⁶¹ Cu, ⁶² Zn, ⁶² Cu, ⁶³ Zn, ⁶⁴ Cu, ⁶⁶ Ga, ⁶⁷ Ga, ⁶⁸ Ga, ⁷⁰ As, ⁷¹ As, ⁷² As, ⁷⁴ As, ⁷⁵ Se, ⁷⁵ Br, ⁷⁶ Br, ⁷⁷ Br, ⁸⁰ Br, ⁸² Br, ⁸² Rb, ⁸⁶ Y, ⁸⁸ Y, ⁹ °Y, ⁸⁹ Sr, ⁸⁹ Zr, ⁹⁷ Ru, ^99m Tc, ¹¹⁰ In, ¹¹¹ In, ¹¹³ In, ¹¹⁴ In, ¹¹⁷ Sn, ¹²⁰ I, ¹²² Xe, ¹²³ I, ¹²⁴ I, ¹²⁵ I, ¹⁶⁶ Ho, ¹⁶⁷ Tm, ¹⁶⁹ Yb, ¹⁹³ Pt, ¹⁹⁵ Pt, ²⁰¹ T1, ²⁰³ Pb, ²⁴ Na, ³² P, ³³ P, ⁴⁷ Sc, ⁵⁹ Fe, ⁶⁷ Cu, ⁷⁶ As, ⁷⁷ As, ⁹⁰ Nb, ¹⁰³ Ru, ¹⁰⁵ Rh, ¹⁰⁹ Pd, ¹¹¹ Ag, ¹²¹ Sn, ¹²⁷ Te, ¹³¹ I, ¹⁴⁰ La, ¹⁴¹ Ce, ¹⁴² Pr,

¹⁴³ Pr, ¹⁴⁴ Pr, ₁₄₉ Pm, ¹⁴⁹ Tb, ¹⁶¹ Pm, ¹⁵³ Sm, ¹⁵⁹ Gd, ¹⁶¹ Tb, ¹⁶⁵ Dy, ¹ ₆ ⁶ Dy ₁₆₆ Ho, ¹⁶⁹ Er,

¹⁷² Tm, ¹⁷⁵ Yb, ¹⁷⁷ Lu, ¹⁸⁶ Re, ¹⁸⁸ Re, ¹⁹⁸ Au, ¹⁹⁹ Au, ²¹¹ At, ²¹¹ Bi, ²¹² Bi, ²¹² Pb, ²¹³ Bi, ²¹⁴ Bi, ²²³ Ra, ²²⁴ Ra, ²²⁵ Ac and ²²⁷ Th,

and are optionally further substituted with a moiety selected from the group consisting of -Cl, -F, -Br, -I, -OR ₃₇ , -N(R ₃₇ ) ₂ , -SO ₃ R ₃₇ , -PO ₃ (R ₃₇ ) ₂ , -PO4(R ₃₇ ) ₂ , -NO ₂ , - CF ₃ , =O,— NR ₃₇ , and -SR ₃₇ , and optionally contain one or more heteroatoms selected from the group consisting of O, S, NR ₃₇ , P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized.

In another preferred embodiment, the Label is selected from the group consisting of -OR ₃₇ , -N(R ₃₇ ) ₂ , -CF ₃ , -SR ₃₇ , S(=O) ₂ N(R ₃₇ ) ₂ , OC(=O)R ₃₇ , SC(=O)R ₃₇ , OC(=S)R ₃₇ , SC(=S)R ₃₇ , NR ₃₇ C(=O)-R ₃₇ , NR ₃₇ C(=S)-R ₃₇ , NR ₃₇ C(=O)O-R ₃₇ ,

NR ₃₇ C(=S)O-R ₃₇ , NR ₃₇ C(=O)S-R ₃₇ , NR ₃₇ C(=S)S-R ₃₇ , OC(=O)N(R ₃₇ ) ₂ ,

SC(=O)N(R ₃₇ ) ₂ , OC(=S)N(R ₃₇ ) ₂ , SC(=S)N(R ₃₇ ) ₂ , NR ₃₇ C(=O)N(R ₃₇ ) ₂ ,

NR ₃₇ C(=S)N(R ₃₇ ) ₂ , C(=O)R _37, C(=S)R _37, C(=O)N(R ₃₇ ) ₂ , C(=S)N(R ₃₇ ) ₂ , C(=O)O-R ₃₇ , C(=O)S-R ₃₇ , C(=S)O-R ₃₇ , C(=S)S-R ₃ 7,C ₁ -C ₁₂ alkyl groups, C ₂ -C ₁₂ alkenyl groups, C ₂ -C ₁₂ alkynyl groups, C ₆ -C ₁₂ aryl groups, C ₂ -C ₁₂ heteroaryl groups, C ₃ -C ₁₂ cycloalkyl groups, C ₅ -C ₁₂ cycloalkenyl groups, C ₁₂ -C ₁₂ cycloalkynyl groups, C ₃ -C ₁₂ (cyclo)alkyl(hetero)aryl groups, C ₃ -C ₁₂ (hetero)aryl(cyclo)alkyl, C ₄ -C ₁₂ (cyclo)alkenyl(hetero)aryl groups, C ₄ -C ₁₂ (hetero)aryl(cyclo) alkenyl groups, C ₄ -C ₁₂ (cyclo)alkynyl(hetero)aryl groups, C ₄ -C ₁₂ (hetero)aryl(cyclo)alkynyl groups, C ₄ -C ₁₂ alkylcycloalkyl groups, and C ₄ -C ₁₂ cycloalkylalkyl groups;

the R ₃₇ groups, alkyl groups, alkenyl groups, alkynyl groups, aryl, heteroaryl, cycloalkyl groups, cycloalkenyl groups, cycloalkynyl groups,

(cyclo)alkyl(hetero)aryl groups, (hetero)aryl(cyclo) alkyl groups,

(cyclo)alkenyl(hetero)aryl groups, (hetero)aryl(cyclo)alkenyl groups,

(cyclo)alkynyl(hetero)aryl groups, (hetero)aryl(cyclo)alkynyl groups,

alkylcycloalkyl groups, cycloalkylalkyl groups comprise, are substituted with, and/or chelating at least one isotope selected from the group consisting of ³ H, ¹¹ C, ¹³ N, ¹⁵ 0, ¹⁸ F, ¹⁹ F, ⁴⁴ Sc, ⁵¹ Cr, ⁵² Fe, ⁵² Mn, ⁵⁵ Co, ⁶⁰ Cu, ⁶¹ Cu, ⁶² Zn, ⁶² Cu, ⁶³ Zn, ⁶⁴ Cu, ⁶⁶ Ga, ⁶⁷ Ga, ⁶⁸ Ga, ⁷⁰ As, ⁷¹ As, ⁷² As, ⁷⁴ As, ⁷⁵ Se, ⁷⁵ Br, ⁷⁶ Br, ⁷⁷ Br, ⁸ °Br, ⁸² Br, ⁸² Rb, ⁸⁶ Y, ⁸⁸ Y, ⁹⁰ Y, ⁸⁹ Sr, ⁸⁹ Zr, ⁹⁷ Ru, ^99m Tc, ¹¹⁰ In, ¹¹¹ In, ¹¹³ In, ¹¹⁴ In, ¹¹⁷ Sn, ¹²⁰ I, ¹²² Xe, ¹²³ I, ¹²⁴ I, ¹²⁵ I, ¹⁶⁶ Ho, ¹⁶⁷ Tm, ¹⁶⁹ Yb, ¹⁹³ Pt, ¹⁹⁵ Pt, ²⁰¹ T1, ²⁰³ Pb, ²⁴ Na, ³² P, ³³ P, ⁴⁷ Sc, ⁵⁹ Fe, ⁶⁷ Cu,

⁷⁶ As, ⁷⁷ As, ⁹⁰ Nb, ¹⁰³ Ru, ¹⁰⁵ Rh, ¹⁰⁹ Pd, ¹¹¹ Ag, ¹²¹ Sn, ¹²⁷ Te, ¹³¹ I, ¹⁴⁰ La, ¹⁴¹ Ce, ¹⁴² Pr, ¹⁴³ Pr, ¹⁴⁴ Pr, ¹⁴⁹ Pm, ₁ ⁴ ₉ Tb, ¹⁵¹ Pm, ¹⁵³ Sm, ¹⁵⁹ Gd, ¹⁶¹ Tb, ¹⁶⁵ Dy, ¹⁶⁶ Dy, ¹⁶⁶ Ho, ¹⁶⁹ Er, ¹⁷² Tm, ¹⁷⁵ Yb, ¹⁷⁷ Lu, ¹⁸⁶ Re, ¹⁸⁸ Re, ¹⁹⁸ Au, ¹⁹⁹ Au, ²¹¹ At, ²¹¹ Bi, ²¹² Bi, ²¹² Pb, ²¹³ Bi, ²¹⁴ Bi, ²²³ Ra, ²²⁴ Ra, ²²⁵ Ac, and ²²⁷ Th,

and are optionally further substituted with a moiety selected from the group consisting of -Cl, -F, -Br, -I, -OR ₃₇ , -N(R ₃₇ ) ₂ , -SO ₃ R ₃₇ , -PO ₃ (R ₃₇ ) ₂ , -PO ₄ (R ₃₇ ) ₂ , -NO ₂ , - CF ₃ , =O,— NR ₃₇ , and -SR ₃₇ , and optionally contain one or more heteroatoms selected from the group consisting of O, S, NR ₃₇ , P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized.

In preferred embodiments, each Label is independently selected from the group consisting of -OR ₃₇ , -N(R ₃₇ ) ₂ , -CF ₃ , -SR ₃₇ , S(=O) ₂ N(R ₃₇ ) ₂ , OC(=O)R ₃₇ , SC(=O)R ₃₇ , OC(=S)R ₃₇ , SC(=S)R ₃₇ , NR ₃₇ C(=O)-R ₃₇ , NR ₃₇ C(=S)-R ₃₇ , NR ₃₇ C(=O)O- R ₃₇ , NR ₃₇ C(=S)O-R ₃₇ , NR ₃₇ C(=O)S-R ₃₇ , NR ₃₇ C(=S)S-R ₃₇ , OC(=O)N(R ₃₇ ) ₂ ,

SC(=O)N(R ₃₇ ) ₂ , OC(=S)N(R ₃₇ ) ₂ , SC(=S)N(R ₃₇ ) ₂ , NR ₃₇ C(=O)N(R ₃₇ ) ₂ ,

NR ₃₇ C(=S)N(R ₃₇ ) ₂ , C(=O)R _37, C(=S)R _37, C(=O)N(R ₃₇ ) ₂ , C(=S)N(R ₃₇ ) ₂ , C(=O)O-R ₃₇ , C(=O)S-R ₃₇ , C(=S)O-R ₃₇ , C(=S)S-R ₃ 7,C ₁ -C ₆ alkyl groups, C ₂ -C ₆ alkenyl groups, C ₂ - C ₆ alkynyl groups, C ₆ aryl groups, C ₂ -C ₆ heteroaryl groups, C ₃ -C ₆ cycloalkyl groups, C ₅ -C ₆ cycloalkenyl groups, C ₈ cycloalkynyl groups, C ₃ -C ₆ (cyclo)alkyl(hetero)aryl groups, C ₃ -C ₆ (hetero)aryl(cyclo)alkyl, C ₄ -C ₆ (cyclo)alkenyl(hetero)aryl groups, C ₄ -C ₆ (hetero)aryl(cyclo)alkenyl groups, C ₄ -C ₆ (cyclo)alkynyl(hetero)aryl groups, C ₄ -C ₆ (hetero)aryl(cyclo)alkynyl groups, C ₄ -C ₆ alkylcycloalkyl groups, and C ₄ -C ₆ cycloalkylalkyl groups;

the R ₃₇ groups, alkyl groups, alkenyl groups, alkynyl groups, aryl, heteroaryl, cycloalkyl groups, cycloalkenyl groups, cycloalkynyl groups,

(cyclo)alkyl(hetero)aryl groups, (hetero)aryl(cyclo) alkyl groups,

(cyclo)alkenyl(hetero)aryl groups, (hetero)aryl(cyclo)alkenyl groups,

(cyclo)alkynyl(hetero)aryl groups, (hetero)aryl(cyclo)alkynyl groups,

alkylcycloalkyl groups, cycloalkylalkyl groups comprise, are substituted with and/or chelating at least one isotope selected from the group consisting of ³ H, ¹¹ C, ¹³ N, ¹⁵ O, ¹⁸ F, ¹⁹ F, ⁴⁴ Sc, ⁵¹ Cr, ⁵² Fe, ⁵² Mn, ⁵⁵ Co, ⁶⁰ Cu, ⁶¹ Cu, ⁶² Zn, ⁶² Cu, ⁶³ Zn, ⁶⁴ Cu, ⁶⁶ Ga, ⁶⁷ Ga, ⁶⁸ Ga, ⁷⁰ As, ⁷¹ As, ⁷² As, ⁷⁴ As, ⁷⁵ Se, ⁷⁵ Br, ⁷⁶ Br, ⁷⁷ Br, ^8O Br, ⁸² Br, ⁸² Rb, ⁸⁶ Y, ⁸⁸ Y, ⁹ °Y, ⁸⁹ Sr, ⁸⁹ Zr, ⁹⁷ Ru, ^99m Tc, ¹¹⁰ In, ¹¹¹ In, ¹¹³ In, ¹¹⁴ In, ¹¹⁷ Sn, ¹²⁰ I, ¹²² Xe, ¹²³ I, ¹²⁴ I, ¹²⁵ I, ¹⁶⁶ Ho, ¹⁶⁷ Tm, ¹⁶⁹ Yb, ¹⁹³ Pt, ¹⁹⁵ Pt, ²⁰¹ T1, ²⁰³ Pb, ²⁴ Na, ³² P, ³³ P, ⁴⁷ Sc, ⁵⁹ Fe, ⁶⁷ Cu,

⁷⁶ As, ⁷⁷ As, ⁹⁰ Nb, ¹⁰³ Ru, ¹⁰⁵ Rh, ¹⁰⁹ Pd, ¹¹¹ Ag, ¹²¹ Sn, ¹²⁷ Te, ¹³¹ I, ¹⁴⁰ La, ¹⁴¹ Ce,

¹⁴² Pr, ¹⁴³ Pr, ₁ ⁴ ₄ Pr, ₁ ⁴ ₉ Pm, ₁ ⁴ ₉ Tb, ¹⁵¹ Pm, ¹⁵³ Sm, ¹⁵⁹ Gd, ¹⁶¹ Tb, ¹⁶⁵ Dy, ¹⁶⁶ Dy, ¹⁶⁶ Ho, ¹⁶⁹ Er, ¹⁷² Tm, ¹⁷⁵ Yb, ¹⁷⁷ Lu, ¹⁸⁶ Re, ¹⁸⁸ Re, ¹⁹⁸ Au, ¹⁹⁹ Au, ²¹¹ At, ²¹¹ Bi, ²¹² Bi, ²¹² Pb, ²¹³ Bi, ²¹⁴ Bi, ²²³ Ra, ²²⁴ Ra, ²²⁵ Ac, and ²²⁷ Th,

and are optionally further substituted with a moiety selected from the group consisting of -Cl, -F, -Br, -I, -OR ₃₇ , -N(R ₃₇ ) ₂ , -SO ₃ R ₃₇ , -P0 ₃ (R ₃₇ ) ₂ , -P04(R ₃₇ ) ₂ , -NO ₂ , - CF ₃ , =O,— NR ₃₇ , and -SR ₃₇ , and optionally contain one or more heteroatoms selected from the group consisting of O, S, NR ₃₇ , P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized.

In a preferred embodiment the Label is derived from a prosthetic group. The person skilled in the art will understand that a prosthetic group is a precursor that can be radiolabeled with a radionuclide like ¹³¹ I thus forming the Label.

In another preferred embodiment, the Label is selected from the group consisting of C ₁ -C ₁₂ alkyl groups, C ₂ -C ₁₂ alkenyl groups, C ₂ -C ₁₂ alkynyl groups, C ₆ -C ₁₂ aryl groups, C ₂ -C ₁₂ heteroaryl groups, C ₃ -C ₁₂ cycloalkyl groups, C ₅ -C ₁₂ cycloalkenyl groups, C ₁₂ -C ₁₂ cycloalkynyl groups, C ₃ -C ₁₂ (cyclo)alkyl(hetero)aryl groups, C ₃ -C ₁₂ (hetero)aryl(cyclo)alkyl, C ₄ -C ₁₂ (cyclo)alkenyl(hetero)aryl groups, C ₄ -C ₁₂ (hetero)aryl(cyclo)alkenyl groups, C ₄ -C ₁₂ (cyclo)alkynyl(hetero)aryl groups, C ₄ -C ₁₂ (h etero) aryl (cyclo) alky nyl groups, C ₄ -C ₁₂ alkylcycloalkyl groups, and C ₄ - C ₁₂ cycloalkylalkyl groups; said groups comprise, or are substituted with, at least one isotope selected from the group consisting of ³ H, ¹¹ C, ¹³ N, ¹⁵ O, ¹⁸ F, ¹⁹ F, ⁷⁵ Br, ⁷⁶ Br, ⁷⁷ Br, ⁸⁰ Br, ⁸² Br, ¹²⁰ I, ¹²³ I, ¹²⁴ I, ¹²⁵ I, ³² P, ³³ P, ¹³¹ I, and ²¹¹ At;

and are optionally further substituted with a moiety selected from the group consisting of -Cl, -F, -Br, -I, -OR ₃₇ , -N(R ₃₇ ) ₂ , -SO ₃ R ₃₇ , -PO ₃ (R ₃₇ ) ₂ , -PO4(R ₃₇ ) ₂ , -NO ₂ , - CF ₃ , =O,— NR ₃₇ , and -SR ₃₇ , and optionally contain one or more heteroatoms selected from the group consisting of O, S, NR ₃₇ , P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized.

In a preferred embodiment the Label comprises a chelating moiety.

In a preferred embodiment, the Label is a chelating moiety selected from the group consisting of conjugates of DTPA (diethylenetriaminepentaacetic acid), DOTA (1,4,7,10- tetraazacyclododecane-N,N',N",N"-tetraacetic acid), DOTAGA anhydride (2,2',2”-(10-(2,6-dioxotetrahydro-2H-pyran-3-yl)-l,4,7,10- tetraazacyclododecane-l,4,7-triyl)triacetic acid), NOTA (1,4,7-triazacyclononane- N,N',N"-triacetic acid), TETA (l,4,8,ll-tetraazacyclotetradecane-N,N',N",N'- tetraacetic acid), OTTA (Nl-(p-isothiocyanatobenzyl)-diethylenetriamine- Ni,N2,N3,N3-tetraacetic acid), deferoxamine or DFO (N'- [5- [[4-[[5- (acetylhy droxy amino)pentyl] amino] - 1 , 4- dioxobutyl] hydroxy amino] pentyl] - N- (5 - aminopentyl)-N-hydroxybutanediamide), and the DFO derivative called DFO*, and HYNIC (hydrazino nicotinamide); and the chelating moiety chelates a metal selected from the group consisting of ⁴⁴ Sc, ⁵¹ Cr, ⁵² Fe, ⁵² Mn, ⁵⁵ Co, ⁶⁰ Cu, ⁶¹ Cu, ⁶² Zn, ⁶² Cu, ⁶³ Zn, ⁶⁴ Cu, ⁶⁶ Ga, ⁶⁷ Ga, ⁶⁸ Ga, ⁷⁰ As, ⁷¹ As, ⁷² As, ⁷⁴ As, ⁷⁵ Se, ⁸² Rb, ⁸⁶ Y, ⁸⁸ Y, ⁸⁹ Sr, ⁸⁹ Zr, ⁹⁷ Ru, ^99m Tc, ¹¹⁰ In, ¹¹¹ In, ¹¹³ In, ¹¹⁴ In, ¹¹⁷ Sn, ¹²² Xe, ¹⁶⁶ Ho, ¹⁶⁷ Tm, ¹⁶⁹ Yb, ¹⁹³ Pt, ¹⁹⁶ Pt, ²⁰¹ T1, ²⁰³ Pb, ²⁴ Na, ⁴⁷ Sc, ⁵⁹ Fe, ⁶⁷ Cu, ⁷⁶ As, ⁷⁷ As, ⁸⁹ Sr, ⁹⁰ Nb, ⁹⁰ Y, ¹⁰³ Ru, ¹⁰⁵ Rh, ¹⁰⁹ Pd, ¹¹¹ Ag, ¹¹¹ In, ¹²¹ Sn, ¹²⁷ Te, ¹⁴⁰ La, ¹⁴¹ Ce, ¹⁴² Pr, ¹⁴³ Pr, ¹⁴⁴ Pr, ¹⁴⁹ Pm, ¹⁴⁹ Tb, ¹⁵¹ Pm, ¹⁵³ Sm, ¹⁵⁹ Gd, ¹⁶¹ Tb, ¹⁶⁵ Dy, ¹⁶⁶ Dy, ¹⁶⁶ Ho, ¹⁶⁹ Er, ¹⁷² Tm, ¹⁷⁵ Yb, ¹⁷⁷ Lu,

¹⁸⁶ Re, ¹⁸⁸ Re, ¹⁹⁸ Au, ¹⁹⁹ Au, ²¹¹ At, ²¹¹ Bi, ²¹² Bi, ²¹² Pb, ²¹³ Bi, ²¹⁴ Bi, ²²³ Ra, ²²⁴ Ra, ²²⁵ Ac, and ²²⁷ Th. In a preferred embodiment the metal chelate comprises an acyclic derivative of ethylenediaminotetraacetic acid (EDTA) or diethylenediaminotetraacetic acid (DTP A):

, wherein the dashed line denotes a bond to the rest of the molecule.

In another preferred embodiment the metal chelate comprises an acyclic chelator containing carboxy-pyridine groups:

, wherein the dashed line denotes a bond to the rest of the molecule.

In another preferred embodiment the metal chelate comprises a cyclic derivative of 1,4,7, 10-tetraazadodecane (cyclen):

, wherein the dashed line denotes a bond to the rest of the molecule.

In another preferred embodiment the metal chelate comprises a derivative of 1,4,7-triazacyclononane (TACN):

, wherein the dashed line denotes a bond to the rest of the molecule.

In yet another preferred embodiment the metal chelate comprises a macrocyclic chelator containing N and O heteroatoms:

, wherein the dashed line denotes a bond to the rest of the molecule.

In another preferred embodiment the metal chelate comprises a derivative of the cryptand agent sarcophagine (Sar):

, wherein the dashed line denotes a bond to the rest of the molecule.

In another preferred embodiment the metal chelate comprises a linear or cyclic chelator containing hydroxamate groups:

, wherein the dashed line denotes a bond to the rest of the molecule.

In yet another preferred embodiment the metal chelate comprises a linear or cyclic chelator containing 3-hydroxy-4-pyridinone (3,4-HOPO) groups:

, wherein the dashed line denotes a bond to the rest of the molecule.

In another preferred embodiment the metal chelate comprises a linear or cyclic chelator containing N, S and P heteroatoms:

, wherein the dashed line denotes a bond to the rest of the molecule M denotes a radionuclide selected from the group consisting of ^99m Tc, ¹⁸⁶ Re, and ¹⁸⁸ Re.

In another preferred embodiment the metal chelate comprises glycine, serine, cysteine, lysine and alanine residues:

, wherein the dashed line denotes a bond to the rest of the molecule M denotes a radionuclide selected from the group consisting of ^99m Tc, ¹⁸⁶ Re, and ¹⁸⁸ Re.

In another preferred embodiment the metal chelate contains

hydrazinonicotinic acid (HYNIC) and a co-ligand:

, wherein the dashed line denotes a bond to the rest of the molecule M denotes a radionuclide selected from the group consisting of ^99m Tc, ¹⁸⁶ Re, and ¹⁸⁸ Re.

In another preferred embodiment the chelate comprises carbonyl groups and a chelator containing N, O and S heteroatoms or a cyclopentadienyle:

, wherein the dashed line denotes a bond to the rest of the molecule M denotes a radionuclide selected from the group consisting of ^99m Tc, ¹⁸⁶ Re, and ¹⁸⁸ Re.

In some preferred embodiments of the present invention the label contains ¹⁸ F and can be produced by the skilled person on the basis of known synthesis routes using known labeled synthons or prosthetic groups. Several non limiting examples of ¹⁸ F-containing labels are depicted below:

, wherein the dashed line denotes a bond to the rest of the molecule.

In preferred embodiments of the present invention the label contains at least one isotope selected from the group consisting of ¹²³ I, ¹²⁴ I, ¹²⁵ I, ¹³¹ I, and ²¹¹ At; and is synthesized by the skilled person on the basis of known synthesis routes using prosthetic groups. Several preferred embodiments of such labels are depicted below:

, wherein the dashed line denotes a bond to the rest of the molecule and X denotes ¹²³ I, ¹²⁴ I, ¹²⁵ I, ¹³¹ I or ²¹¹ At.

In yet another preferred embodiment of the present invention the label contains at least one isotope selected from the group consisting of ¹²³ I, ¹²⁴ I, ¹²⁵ I, ¹³¹ I, and ²¹¹ At;and is synthetized by the skilled person on the basis of known synthesis routes using a closo-decaborate(2-) group:

, wherein the dashed line denotes a bond to the rest of the molecule and X denotes ¹²³ I, ¹²⁴ I, ¹²⁵ I, ¹³¹ I or ²¹¹ At.

Administration Agent

The Administration Agent is an antibody. The Administration Agent can be any construct of which it is desired to modify it with a Label for radio-imaging or radiotherapy and of which it is desired to remove its imaging or radiotherapy label at a particular time after injection. This particularly is the case in the event of targeted imaging and radiotherapy to a site, such as a tumor, within the body of a subject, notably a human subject. The sole requirement is that it can be provided with a Trigger T ^R , which is further linker to a Label. The precise linkage of the Trigger to the Administration Agent will depend on the molecular structure of both, but it should be noted that this does not normally present a particular challenge to the person skilled in the art, as many proven conjugation methods and linkage moieties for various biomolecules exist. The linkage can, optionally, be via a spacer such as a polyethylene glycol (PEG) chain.

Typically the Administration Agent can bind to a Primary Target, as defined herein. Said Primary Target can be a target to which a Targeting Agent binds or it can be a therapeutic target upon which a drug has its effect. In a preferred embodiment the Primary Target is a therapeutic target and the

Targeting Agent is a drug and binds said Primary Target.

In preferred embodiments, the Administration Agent is a Targeting Agent as defined herein, insofar the Targeting Agent is described as an antibody.

In other preferred embodiments, the Administration Agent equals a Targeting Agent, and the Targeting Agent is radiolabeled with a therapeutic radioisotope in order to target therapeutic radiation to tissues expressing a Primary Target. In other preferred embodiments, the Administration Agent equals a Targeting Agent, and the Targeting Agent is radiolabeled with a diagnostic radioisotope in order to image tissues expressing a Primary Target.

In preferred embodiments, the Administration Agent is an antibody that comprises an FcRn binding domain, more preferably an intact IgG antibody. Preferably, the Administration Agent is an intact antibody.

In other preferred embodiments, the Administration Agent is an antibody that comprises an albumin-binding moiety.

In other preferred embodiments the Administration Agent equals a drug. In other preferred embodiments the Administration Agent equals a drug and the drug is labeled using the presented invention for the purpose of imaging in vivo drug distribution. Drugs that can be used in an Administration Agent relevant to this invention are pharmaceutically active compounds.

In a preferred embodiment the pharmaceutically active compound or drug is selected from the group consisting of cytotoxins, antiproliferative/antitumor agents, antiviral agents, antibiotics, anti-inflammatory agents, chemosensitizing agents, radiosensitizing agents, immunomodulators, immunosuppressants, immunostimulants, anti-angiogenic factors, and enzyme inhibitors.

In other preferred embodiments the drug is designed to act in the central neural system, for example in the context of Alzheimer’s disease and Parkinsons’ disease, for example antibodies against beta-amyloid and Tau proteins.

Exemplary cytotoxic drug types, for example for use in cancer therapy, include but are not limited to DNA damaging agents, DNA crosslinkers, DNA binders, DNA alkylators, DNA intercalators, DNA cleavers, microtubule stabilizing and destabilizing agents, topoisomerases inhibitors, radiation sensitizers, anti-metabolites, natural products and their analogs, peptides, oligonucleotides, enzyme inhibitors such as dihydrofolate reductase inhibitors and thymidylate synthase inhibitors.

Exemplary immunemodulators are antibodies against PD-L1, PD-1, LAG- 3, OX40, TIGIT, TIM-3, B7H4, Vista, CTLA-4, APRIL, GITR, CD3, CD28, CD40, CD74, RIG, MDA-5, NLRP1, NLRP3, AIM2, IDO, MEK, cGAS, and CD25, NKG2A. It will be understood that chemical modifications may also be made to the

Administration Agent in order to make reactions of that compound more convenient for purposes of preparing conjugates of the invention.

In a preferred embodiment, the Administration Agent before conjugation to the remainder of the compound of Formula (1) comprises at least one moiety selected from the group consisting of -OH, -NHR’, -CO ₂ H, -SH, -S-S-, -SCH ₃ -, -N ₃ , terminal alkynyl, terminal alkenyl, -C(O)R', C ₈ -C ₁₂ (hetero)cycloalkynyl, nitrone, nitrile oxide, (imino)sydnone, isonitrille, and (oxa)norbornene, tetrazine, wherein R' equals R ₃₇ , said moiety used for conjugation to a moiety comprising the dienophile, the Label and R ₃₂ so as to form the compound satisfying Formula (1), and comprising a C ^M2 or C ^x moiety.

In preferred embodiments the Administration Agent is bound to the remainder of the compound of Formula (1) via a C ^M2 selected from the group consisting of amine, amide, thioamide, aminooxy, carbamate, thiocarbamate, urea, thiourea, sulfonamide, and sulfoncarbamate.

In preferred embodiments C ^M2 equals R ₁₀ as defined herein.

In a preferred embodiment, when the Administration Agent is conjugated via -SH or -S-S-, then C ^M2 is selected from the group consisting of

wherein the wiggly line denotes a bond to the remaining part of the molecule, and wherein the dashed line denotes a bond to the Administration Agent, wherein R' equals R ₃₇ as defined herein. In a preferred embodiment, when the Administration Agent is conjugated via -SCH ₃ - then C ^M2 preferably is:

wherein the wiggly line denotes a bond to the remaining part of the molecule, and wherein the dashed line denotes a bond to the Administration Agent.

In a preferred embodiment, when the Administration Agent is conjugated via -NR’-, then C ^M2 is selected from the group consisting of

wherein R' equals R ₃₇ as defined herein, wherein the wiggly line denotes a bond to the remaining part of the molecule, and wherein the dashed line denotes a bond to the Administration Agent.

In a preferred embodiment, when the Administration Agent is conjugated via -C- derived from a moiety that was -C(O)R’ or -C(O)R’-, then C ^M2 is selected from the group consisting of

wherein the wiggly line denotes a bond to the remaining part of the molecule, and wherein the dashed line denotes a bond to the Administration Agent.

In a preferred embodiment, when the Administration Agent is conjugated via -C(O)- derived from a moiety that was -C(O)OH, then C ^M2 is selected from the group consisting of wherein R' equals R ₃₇ as defined herein, wherein

the wiggly line denotes a bond to the remaining part of the molecule, and wherein the dashed line denotes a bond to the Administration Agent.

In a preferred embodiment, when the Administration Agent is conjugated via -O-, then C ^M2 is selected from the group consisting of wherein R' equals R ₃₇ as defined herein, wherein the wiggly line denotes a bond to the remaining part of the molecule, and wherein the dashed line denotes a bond to the Administration Agent.

In a preferred embodiment, when the Administration Agent is conjugated via -N ₃ that was reacted with an R ₃₂ that comprised an alkyne group, then the resulting C ^x comprises a triazole ring, wherein each C ^x is independently selected from the group consisting of

, and ; wherein the wiggly line denotes a bond to the remaining part of the molecule, and wherein the dashed line denotes a bond to the Administration Agent.

Preferably, the Administration Agent is modified with further moieties that equal Formula (1), except that these further moieties do not comprise an Administration Agent (as the first mentioned Administration Agent is already coupled to said moiety). In a preferred embodiment, the Administration Agent is coupled to further moieties as defined in this paragraph at 1 to 8 positions, more preferably from 1 to 6 positions, even more preferably at 1 to 4 positions.

Further embodiments in relation to the compound of Formula (1)

In the compound of the invention the Administration Agent is an antibody.

In a preferred embodiment, in the compound of the invention the Label is a radiolabel, preferably a chelating moiety that chelates a radioisotope.

The skilled person is familiar with the fact that the dienophile activity is not necessarily dependent on the presence of all carbon atoms in the ring, since also heterocyclic monoalkenylene eight-membered rings are known to possess dienophile activity. Thus, in general, the invention is not limited to strictly trans- cyclooctene. The person skilled in organic chemistry will be aware that other eight-membered ring-based dienophiles exist, which comprise the same

endocyclic double bond as the trans-cyclooctene, but which may have one or more heteroatoms elsewhere in the ring. I.e., the invention generally pertains to eight- membered non-aromatic cyclic alkenylene moieties, preferably a cyclooctene moiety, and more preferably a trans-cyclooctene moiety.

Trans-cyclooctene or E-cyclooctene derivatives are very suitable as

Triggers, especially considering their high reactivity. Optionally, the trans- cyclooctene (TCO) moiety comprises at least two exocyclic bonds fixed in substantially the same plane, preferably as described in WO 2012/156919A1, and/or it optionally comprises at least one substituent in the axial position, and not the equatorial position. The person skilled in organic chemistry will understand that the term“fixed in substantially the same plane” refers to bonding theory according to which bonds are normally considered to be fixed in the same plane. Typical examples of such fixations in the same plane include double bonds and strained fused rings. E.g., the at least two exocyclic bonds can be the two bonds of a double bond to an oxygen (i.e. C=O). The at least two exocyclic bonds can also be single bonds on two adjacent carbon atoms, provided that these bonds together are part of a fused ring (i.e. fused to the TCO ring) that assumes a substantially flat structure, therewith fixing said two single bonds in substantially one and the same plane. Examples of the latter include strained rings such as cyclopropyl and cyclobutyl. Without wishing to be bound by theory, the inventors believe that the presence of at least two exocyclic bonds in the same plane will result in an at least partial flattening of the TCO ring, which can lead to higher reactivity in the IEDDA reaction. A background reference providing further guidance is WO 2012/153254. The at least two exocyclic bonds fixed in substantially the same plane are preferably as described on page 16 and further of WO 2012/156919 Al.

TCO moieties may consist of multiple isomers, also comprising the equatorial vs. axial positioning of substituents on the TCO. In this respect, reference is made to Whitham et al. J. Chem. Soc. (C), 1971, 883-896, describing the synthesis and characterization of the equatorial and axial isomers of trans- cyclo-oct-2-en-ol, identified as (IRS, 2RS) and (1SR, 2RS), respectively. In these isomers the OH substituent is either in the equatorial or axial position. Without wishing to be bound by theory, the inventors believe that the presence of an axial substituent increases the TCO ring strain resulting in higher reactivity in the IEDDA reaction. A background reference providing further guidance is WO 2012/049624.

Furthermore, in case of allylic substituents on the TCO in some

embodiments it is preferred that these are positioned axially and not

equatorially.

It should be noted that, depending on the choice of nomenclature, the TCO dienophile may also be denoted E-cyclooctene. With reference to the conventional nomenclature, it will be understood that, as a result of substitution on the cyclooctene ring, depending on the location and molecular weight of the substituent, the same cyclooctene isomer may formally become denoted as a Z- isomer. In the present invention, any substituted variants of the invention, whether or not formally“E” or“Z,” or“cis” or“trans” isomers, will be considered derivatives of unsubstituted trans-cyclooctene, or unsubstituted E-cyclooctene. The terms’’trans-cyclooctene” (TCO) as well as E-cyclooctene are used

interchangeably and are maintained for all dienophiles according to the present invention, also in the event that substituents would formally require the opposite nomenclature. I.e., the invention relates to cyclooctene in which carbon atoms 1 and 6 as numbered below are in the E ( entgegen ) or trans position.

The dienophiles for use in the invention can be synthesized by the skilled person, on the basis of known synthesis routes to cyclooctenes and corresponding hetero atom(s) -containing rings. The skilled person further is aware of the wealth of cyclooctene derivatives that can be synthesized via the ring closing metathesis reaction using Grubbs catalysts. As mentioned above, the TCO possibly includes one or more heteroatoms in the ring. This is as such sufficiently accessible to the skilled person [e.g. WO2016025480]. Reference is made, e.g., to the presence of a thioether in TCO: [Cere et al. J. Org. Chem. 1980, 45, 261]. Also, e.g., an - O-S1R ₂ - O moiety in TCO: [Prevost et al. J. Am. Chem. Soc. 2009, 131, 14182] References to TCO syntheses wherein the allylic positioned leaving group (R ₄₈ ) is an ether, ester, carbonate, carbamate or a thiocarbamate are: [Versteegen et al Angew. Chem. Int. Ed. 2018, 57, 10494], and [Steiger et al Chem Comm 2017, 53, 1378]. Exemplary TCOs include the following structures, indicated below with

literature references. Where a cyclooctene derivative is depicted as a Z- cyclooctene it is conceived that this can be converted to the E-cyclooctene analog.

In a preferred embodiment, the compound of Formula (1) satisfies any one of the following structures:

= rest of attached C ^B or S ^P -C ^B

= rest of attached C ^A or L ^C -C ^A , optionally comprising C ^B or S ^P -C ^B , wherein C ^A is optionally bound to remainder of the molecule via S ^P

rest of attached C ^B or S ^P -C ^B

rest of attached C ^A or L ^C -C ^A , optionally comprising C ^B or S ^P -C ^B , wherein C ^A is optionally bound to remainder of the molecule via S ^P

= rest of attached C ^B or S ^P -C ^B

= rest of attached C ^A or L ^C -C ^A , optionally comprising C ^B orS ^P -C ^B ,

wherein C ^A is optionally bound to remainder of the molecule via S ^P

In a preferredembodiment,the compoundof Formula(1) is any one of the racemic and enantiomericallypure compounds listed below:

wherein the wiggly line indicates a bond to the remainder of the compound of Formula (1).

Especially preferred compounds of Formula (1) are the enantiomerically pure compounds listed below:

wherein the wiggly line indicates a bond to the remainder of the compound of Formula (1).

Other preferred compounds of Formula (1) are:

- - - = bond to remainder of R ₄₇

In preferred embodiments, L ^A not being R ₄₈ , L ^B not being R ₄₈ , the Label, the Administration Agent, R ₉₈ , and/or C ^C are bound to the remainder of the compound of Formula (1) via a residue of R ₃₂ , or a moiety C ^M2 or C ^x as defined herein, wherein preferably said residue of R ₃₂ or a moiety C ^M2 or C ^x equals or is comprised in a Spacer. A person skilled in the art will understand that "residue of R ₃₂ " means the conjugation reaction product of R ₃₂ with another chemical group so as to form a conjugate, for example between C ^C with the remainder of the compound according to Formula (1).

In preferred embodiments, L ^A not being R ₄₈ , L ^B not being R ₄₈ , the Label, the Administration Agent, R ₉₈ , and/or C ^C are bound to the remainder of the molecule via C ^M2 as defined herein, wherein preferably C ^M2 equals or is comprised in a Spacer.

In yet other preferred embodiments, L ^A not being R ₄₈ , L ^B not being R ₄₈ , the Label, the Administration Agent, R ₉₈ , and/or C ^C are bound to the remainder of the molecule via C ^x as defined herein, wherein preferably C ^x equals or is comprised in a Spacer. In preferred embodiments, moiety C ^x , C ^M2 and the said residue of R ₃₂ are comprised in L ^A not being R ₄₈ , L ^B not being R ₄₈ , the Label, the Administration Agent, R ₉₈ , and/or C ^C .

C ^M2

In preferred embodiments, C ^M2 is selected from the group consisting of amine, amide, thioamide, aminooxy, carbamate, thiocarbamate, urea, thiourea, ether, sulfonamide, and sulfoncarbamate. In preferred embodiments C ^M2 equals R ₁₀ .

In preferred embodiments, C ^M2 is:

wherein the dashed line denotes a bond to or towards L ^A not being R ₄₈ , L ^B not being R ₄₈ , the Label, the Administration Agent, S ^P , L ^C , R ₉₈ , or C ^C and the wiggly line denotes a bond to the remaining part of the dienophile. In preferred embodiments the wiggly line denotes a bond to or towards L ^A not being R ₄₈ , L ^B not being R ₄₈ , the Label, the Administration Agent, S ^P , L ^C , R ₉₈ , or C ^C and the dashed line denotes a bond to the remaining part of the dienophile.

With reference to above schemes with examples of C ^M2 and C ^x , in some embodiments it is preferred that when L ^A not being R ₄₈ , L ^B not being R ₄₈ , the Label, the Administration Agent, R ₉₈ , or C ^C is a protein, such as an antibody, that the dashed line denotes a bond to or towards L ^A not being R ₄₈ , L ^B not being R ₄₈ , the Label, the Administration Agent, R ₉₈ , or C ^C .

Intermediates for the preparation of compounds of Formula (1)

Preferred intermediates to prepare compounds of Formula (1) of the invention are listed below. Particularly preferred intermediates from the below are enantiomerically pure compounds A-F, in particular A, D, E, F. A person skilled in the art will understand that compounds E and F still need to be isomerized to E-cyclooctenes, after which the enantiomer with the axial OH can be separated from the enantiomer with the equatorial OH as described by Rossin et al Bioconj.Chem., 2016 27(7):1697-1706.

A general synthesis method of a TCO trigger and its corresponding compound of Formula (l)s is shown directly below. The synthesis method is as reported in Rossin et al Nature Communications 2018, 9, 1484 and Rossin et al Bioconj.Chem., 2016 27(7):1697-1706 with the exception of the conversion of D to F, which now is conducted by mixing D with hydroxide solution in methanol, followed by evaporation and reaction with iodomethane. Please note that for sake of clarity only one of the two enantiomers of E-K is shown. A person skilled in the art will understand that the enantiomers can be separated at various stages in the synthesis using established chiral resolution methods to obtain

enantiomerically pure B, E, F, H, for example, such as chiral salts.

wherein the wiggly line denotes the bond to the remainder of R ₄₈ and the dashed line denotes the bond to the remainder of the molecule.

Cleaving Agent

The compound used to release one or more moieties R ₄₈ from the structure of Formula (1) is herein referred to as“Cleaving Agent”.

In a preferred embodiment, the combination of the invention comprises a Cleaving Agent with the proviso that when at least one R ₄₈ in Formula (1) is L ^B , then the Cleaving Agent does not comprise the Label of L ^B ; with the proviso that when at least one R ₄₈ in Formula (1) is L ^A , then the Cleaving Agent does not comprise the Administration Agent of L ^A ;

wherein the Cleaving Agent is a diene.

In a preferred embodiment, the Cleaving Agent does not comprise a Label.

In a preferred embodiment, the Cleaving Agent does not comprise an Administration Agent.

In preferred embodiments wherein the Primary Target is an internalizing receptor and it is desired to selectively cleave the Label in blood and not at the Primary Target, the Cleaving Agent is preferentially designed to be cell impermeable. In said embodiment, wherein the Label is a chelate then the Cleaving Agent can be either internalizing or non-internalizing ,as the cleaved chelate cannot escape the target cell.

In preferred embodiments, wherein the Primary Target is a non

internalizing receptor and it is desired to cleave the Label in blood and not at the Primary Target, the Cleaving Agent is preferentially designed to extravasate poorly into tissues and rapidly clear, to minimize reaction at the Primary Target while achieving cleavage in blood.

In a preferred embodiment, the combination of the invention is a kit.

In some embodiments, preferably, the Cleaving Agent has a molecular weight of at most 150 kDa, when at least one R ₄₈ in Formula (1) is L ^A that does not comprise a Label; more preferably at most 70 kDa, most preferably at most 1 kDa.

In other embodiments, preferably, the Cleaving Agent has a molecular weight of at least 300 kDa, to minimize extravasation.

In preferred embodiments the Cleaving Agent is cell-impermeable, to further increase the selective cleavage of a compound of Formula (1) present in non-target sites ( e.g . blood).

In preferred embodiments, the properties of the Cleaving Agent (e.g. level of cell permeability and extravasation) are achieved by a suitably chosen R ⁸⁷ group (vide infra), comprised in the Clearing Agent formulas below.

Preferably, the reaction of the Cleaving Agent with the Administration Agent present in a tissue of interest in vivo results in at least 20 % reduction of radioactivity, more preferably at least 40 %, more preferably at least 60 %, even more preferably at least 80 %.

In a preferred embodiment, the Cleaving Agent is a tetrazine. Tetrazines are dienes and are highly reactive towards dienophiles, especially the TCO constructs (vide supra). The diene of the Cleaving Agent is selected so as to be capable of reacting with the dienophile, e.g. the TCO, by undergoing a Diels- Alder cycloaddition followed by a retro Diels-Alder reaction, giving the IEDDA adduct. This intermediate adduct then releases the Construct-A.

Synthesis routes to tetrazines in general are readily available to the skilled person, based on standard knowledge in the art. References to tetrazine synthesis routes include for example Lions et al, J. Org. Chem., 1965, 30, 318- 319; Horwitz et al, J. Am. Chem. Soc., 1958, 80, 3155-3159; Hapiot et al, New J. Chem., 2004, 28, 387-392, Kaim et al, Z. Naturforsch., 1995, 50b, 123-127, Yang et al., Angew. Chem. 2012, 124, 5312 -5315; Mao et al., Angew. Chem. Int. Ed. 2019, 58, 1106-1109; Qu et al. Angew. Chem. Int. Ed. 2018, 57, 12057 -12061; Selvaraj et al., Tetrahedron Lett. 2014, 55, 4795-4797; Fan et al., Angew. Chem. Int. Ed. 2016, 55, 14046-14050.

Preferably, the Cleaving Agent is a tetrazine satisfying Formula (4) and preferably including pharmaceutically accepted salts thereof:

Formula (4) ; wherein each moiety Q ₁ and Q ₂ is independently selected from the group consisting of hydrogen, -F, -Cl, -Br, -I, -OR ₃₇ , -N(R ₃₇ ) ₂ , -SO ₃ , -PO ₃ -, -NO ₂ , -CF ₃ , -SR ₃₇ ,

S(=O) ₂ N(R ₃₇ ) ₂ , OC(=O)R ₃₇ , SC(=O) R ₃₇ , OC(=S)R ₃₇ , SC(=S)R ₃₇ , NR ₃₇ C(=O)-R ₃₇ , NR ₃₇ C(=S)-R ₃₇ , NR ₃₇ C(=O)O-R ₃₇ , NR ₃₇ C(=S)O-R ₃₇ , NR ₃₇ C(=O)S-R ₃₇ , NR ₃₇ C(=S)S- R ₃₇ , OC(=O)N(R ₃₇ ) ₂ , SC(=O)N(R ₃₇ ) ₂ , OC(=S)N(R ₃₇ ) ₂ , SC(=S)N(R ₃₇ ) ₂ ,

NR ₃₇ C(=O)N(R ₃₇ ) ₂ , NR ₃₇ C(=S)N(R ₃₇ ) ₂ , C(=O)R _37, C(=S)R _37, C(=O)N(R ₃₇ ) ₂ ,

C(=S)N(R ₃₇ ) ₂ , C(=O)O-R ₃₇ , C(=O)S-R ₃₇ , C(=S)O-R ₃₇ , C(=S)S-R ₃₇ , S(O)R ₃₇ , - S(O) 2R ₃₇ , NR ₃₇ S(O) ₂ R ₃₇ , -ON(R ₃₇ ) ₂ , -NR ₃₇ OR ₃₇ , alkyl groups, alkenyl groups, alkynyl groups, aryl groups, heteroaryl groups, cycloalkyl groups, cycloalkenyl groups, cycloalkynyl groups, (cyclo)alkyl(hetero)aryl groups,

(hetero)aryl(cyclo)alkyl, (cyclo)alkenyl(hetero)aryl groups,

(hetero)aryl(cyclo)alkenyl groups, (cyclo)alkynyl(hetero)aryl groups,

(hetero)aryl(cyclo)alkynyl groups, alkylcycloalkyl groups, and cycloalkylalkyl groups.

In Formula (4), the Q ₁ and Q ₂ groups not being H, -F, -Cl, -Br, -I, -OH, -

NH ₂ , -SO ₃ , -PO ₃ , -NO ₂ , -CF ₃ , are optionally substituted, preferably with a moiety selected from the group consisting of -Cl, -F, -Br, -I, -OR ₃₇ , -N(R ₃₇ ) ₂ , -SO ₃ R ₃₇ , - PO ₃ (R ₃₇ ) ₂ , -PO ₄ (R ₃₇ ) ₂ , -NO ₂ , -CF ₃ , =O, =NR ₃₇ , and -SR ₃₇ , and optionally contain one or more heteroatoms selected from the group consisting of O, S, NR ₃₇ , P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized.

In Formula (4), the Q ₁ and Q ₂ groups are optionally bound to a polymer, a particle, a peptide, a peptoid, a dendrimer, a protein, an aptamer, a

carbohydrate, an oligonucleotide, an oligosaccharide, a lipid, a steroid, a liposome, a micelle, a Targeting Agent T ^T , a— (S ^P ) _D -R ⁸⁷ , an albumin-binding moiety, and a chelating moiety; wherein D is 0 or 1.

In Formula (4), preferably, at least one of moieties Q ₁ and Q ₂ is not hydrogen.

In Formula (4), preferably each moiety Q ₁ and Q ₂ is independently selected from the group consisting of hydrogen, -F, -Cl, -Br, -I, -OR ₃₇ , -N(R ₃₇ ) ₂ , -SO ₃ , -PO _{3 ,} -NO ₂ , -CF ₃ , -SR ₃₇ , S(=O) ₂ N(R ₃₇ ) ₂ , OC(=O)R ₃₇ , SC(=O) R ₃₇ , OC(=S)R ₃₇ , SC(=S)R ₃₇ , NR ₃₇ C(=O)-R ₃₇ , NR ₃₇ C(=S)-R ₃₇ , NR ₃₇ C(=O)O-R ₃₇ , NR ₃₇ C(=S)O-R ₃₇ , NR ₃₇ C(=O)S- R ₃₇ , NR ₃₇ C(=S)S-R ₃₇ , OC(=O)N(R ₃₇ ) ₂ , SC(=O)N(R ₃₇ ) ₂ , OC(=S)N(R ₃₇ ) ₂ ,

SC(=S)N(R ₃₇ ) ₂ , NR ₃₇ C(=O)N(R ₃₇ ) ₂ , NR ₃₇ C(=S)N(R ₃₇ ) ₂ , C(=O)R _37, C(=S)R _37,

C(=O)N(R ₃₇ ) ₂ , C(=S)N(R ₃₇ ) ₂ , C(=O)O-R ₃₇ , C(=O)S-R ₃₇ , C(=S)O-R ₃₇ , C(=S)S-R ₃₇ , S(O)R ₃₇ , -S(O) ₂ R ₃₇ , NR ₃₇ S(O) ₂ R ₃₇ , -ON(R ₃₇ ) ₂ , -NR ₃₇ OR ₃₇ , C- ₁ C ₂₄ alkyl groups, C ₂ - C ₂₄ alkenyl groups, C ₂ -C ₂₄ alkynyl groups, C ₆ -C ₂₄ aryl groups, C ₂ -C ₂₄ heteroaryl groups, C ₃ -C ₂₄ cycloalkyl groups, C ₅ -C ₂₄ cycloalkenyl groups, C ₁₂ -C ₂₄ cycloalkynyl groups, C ₃ -C ₂₄ (cyclo)alkyl(hetero)aryl groups, C ₃ -C ₂₄ (hetero)aryl(cyclo) alkyl, C ₄ - C ₂₄ (cyclo)alkenyl(hetero)aryl groups, C ₄ -C ₂₄ (hetero)aryl(cyclo) alkenyl groups, C ₄ -C ₂₄ (cyclo)alkynyl(hetero)aryl groups, C ₄ -C ₂₄ (hetero)aryl(cyclo)alkynyl groups, C ₄ -C ₂₄ alkylcycloalkyl groups, and C ₄ -C ₂₄ cycloalkylalkyl groups.

In preferred embodiments, the Q ₁ and Q ₂ groups not being hydrogen are not substituted.

In a preferred embodiment, Q ₁ and Q ₂ in Formula (4) are selected from the group of hydrogen, -F, -Cl, -Br, -I, -OR ₃₇ , -N(R ₃₇ ) ₂ , -SO ₃ , -PO ₃ -, -NO ₂ , -CF ₃ , -SR ₃₇ , S(=O) ₂ N(R ₃₇ ) ₂ , OC(=O)R ₃₇ , SC(=O) R ₃₇ , OC(=S)R ₃₇ , SC(=S)R ₃₇ , NR ₃₇ C(=O)-R ₃₇ , NR ₃₇ C(=S)-R ₃₇ , NR ₃₇ C(=O)O-R ₃₇ , NR ₃₇ C(=S)O-R ₃₇ , NR ₃₇ C(=O)S-R ₃₇ , NR ₃₇ C(=S)S- R ₃₇ , OC(=O)N(R ₃₇ ) ₂ , SC(=O)N(R ₃₇ ) ₂ , OC(=S)N(R ₃₇ ) ₂ , SC(=S)N(R ₃₇ ) ₂ ,

NR ₃₇ C(=O)N(R ₃₇ ) ₂ , NR ₃₇ C(=S)N(R ₃₇ ) ₂ , C(=O)R _37, C(=S)R _37, C(=O)N(R ₃₇ ) ₂ ,

C(=S)N(R ₃₇ ) ₂ , C(=O)O-R ₃₇ , C(=O)S-R ₃₇ , C(=S)O-R ₃₇ , C(=S)S-R ₃₇ , S(O)R ₃₇ , - S(O) 2R ₃₇ , NR ₃₇ S(O) ₂ R ₃₇ , -ON(R ₃₇ ) ₂ , -NR ₃₇ OR ₃₇ , C ₁ -C ₈ alkyl groups, C ₂ -C ₈ alkenyl groups, C ₂ -C ₈ alkynyl groups, C ₆ -C ₁₂ aryl groups, C ₂ -C ₁₂ heteroaryl groups, C ₃ -C ₈ cycloalkyl groups, C ₅ -C ₈ cycloalkenyl groups, C ₃ -C ₁₂ alkyl(hetero)aryl groups, C ₃ - C ₁₂ (hetero)arylalkyl groups, C ₄ -C ₁₂ alkylcycloalkyl groups, C ₄ -C ₁₂ cycloalkylalkyl groups, C ₅ -C ₁₂ cycloalkyl(hetero)aryl groups and C ₅ -C ₁₂ (hetero)arylcycloalkyl groups.

In a preferred embodiment, Q ₁ and Q ₂ in Formula (4) are selected from the group of hydrogen, -F, -Cl, -Br, -I, -OR ₃₇ , -N(R ₃₇ ) ₂ , -SO ₃ , -PO ₃ -, -NO ₂ , -CF ₃ , -SR ₃₇ , S(=O) ₂ N(R ₃₇ ) ₂ , OC(=O)R ₃₇ , SC(=O) R ₃₇ , OC(=S)R ₃₇ , SC(=S)R ₃₇ , NR ₃₇ C(=O)-R ₃₇ , NR ₃₇ C(=S)-R ₃₇ , NR ₃₇ C(=O)O-R ₃₇ , NR ₃₇ C(=S)O-R ₃₇ , NR ₃₇ C(=O)S-R ₃₇ , NR ₃₇ C(=S)S- R ₃₇ , OC(=O)N(R ₃₇ ) ₂ , SC(=O)N(R ₃₇ ) ₂ , OC(=S)N(R ₃₇ ) ₂ , SC(=S)N(R ₃₇ ) ₂ ,

NR ₃₇ C(=O)N(R ₃₇ ) ₂ , NR ₃₇ C(=S)N(R ₃₇ ) ₂ , C(=O)R _37, C(=S)R _37, C(=O)N(R ₃₇ ) ₂ ,

C(=S)N(R ₃₇ ) ₂ , C(=O)O-R ₃₇ , C(=O)S-R ₃₇ , C(=S)O-R ₃₇ , C(=S)S-R ₃₇ , S(O)R ₃₇ , - S(O) 2R ₃₇ , NR ₃₇ S(O) ₂ R ₃₇ , -ON(R ₃₇ ) _2, -NR ₃₇ OR ₃₇ , C-C _{1 4} alkyl groups, C ₂ -C ₄ alkenyl groups, C ₂ -C ₄ alkynyl groups, C ₆ -C ₈ aryl groups, C ₂ -C ₈ heteroaryl groups, C ₃ -C ₆ cycloalkyl groups, C ₅ -C ₆ cycloalkenyl groups, C ₃ -C ₁₀ alkyl(hetero)aryl groups, C ₃ - C ₁₀ (hetero)arylalkyl groups, C ₄ -C ₁₀ alkylcycloalkyl groups, C ₄ -C ₁₀ cycloalkylalkyl groups, C ₅ -C ₁₀ cycloalkyl(hetero)aryl groups and C ₅ -C ₁₀ (hetero)arylcycloalkyl groups.

In a preferred embodiment, Q ₁ and Q ₂ in Formula (4) are selected from the group of hydrogen, phenyl, 2-pyridyl, 3-pyridyl, 4-pyridyl, 2,6-pyrimidyl, 2,5- pyrimidyl, 3,5-pyrmidyl, and 2,4-pyrimidyl; and Q ₁ and Q ₂ not being hydrogen are optionally substituted with a moiety selected from the group consisting of -F, -Cl, -Br, -I, -OR ₃₇ , -N(R ₃₇ ) ₂ , -SO ₃ , -PO ₃ -, -NO ₂ , -CF ₃ , -SR ₃₇ , S(=O) ₂ N(R ₃₇ ) ₂ ,

OC(=O)R ₃₇ , SC(=O) R ₃₇ , OC(=S)R ₃₇ , SC(=S)R ₃₇ , NR ₃₇ C(=O)-R ₃₇ , NR ₃₇ C(=S)-R ₃₇ , NR ₃₇ C(=O)O-R ₃₇ , NR ₃₇ C(=S)O-R ₃₇ , NR ₃₇ C(=O)S-R ₃₇ , NR ₃₇ C(=S)S-R ₃₇ ,

OC(=O)N(R ₃₇ ) ₂ , SC(=O)N(R ₃₇ ) ₂ , OC(=S)N(R ₃₇ ) ₂ , SC(=S)N(R ₃₇ ) ₂ , NR ₃₇ C(=O)N(R ₃₇ ) ₂ , NR ₃₇ C(=S)N(R ₃₇ ) ₂ , C(=O)R _37, C(=S)R _37, C(=O)N(R ₃₇ ) ₂ , C(=S)N(R ₃₇ ) ₂ , C(=O)O-R ₃₇ , C(=O)S-R ₃₇ , C(=S)O-R ₃₇ , C(=S)S-R ₃₇ , S(O)R ₃₇ , -S(O) ₂ R ₃₇ , NR ₃₇ S(O) ₂ R ₃₇ , -ON(R ₃₇ ) _2, - NR ₃₇ OR ₃₇ , C ₁ -C ₂₄ alkyl groups, C ₂ -C ₂₄ alkenyl groups, C ₂ -C ₂₄ alkynyl groups, C ₆ - C ₂₄ aryl groups, C ₂ -C ₂₄ heteroaryl groups, C ₃ -C ₂₄ cycloalkyl groups, C ₅ -C ₂₄ cycloalkenyl groups, C ₁₂ -C ₂₄ cycloalkynyl groups, C ₃ -C ₂₄ (cyclo)alkyl(hetero)aryl groups, C ₃ -C ₂₄ (hetero)aryl(cyclo)alkyl, C ₄ -C ₂₄ (cyclo)alkenyl(hetero)aryl groups, C ₄ -C ₂₄ (hetero) aryl (cyclo) alkenyl groups, C ₄ -C ₂₄ (cyclo)alkynyl(hetero)aryl groups, C ₄ -C ₂₄ (hetero) aryl (cyclo) alkynyl groups, C ₄ -C ₂₄ alkylcycloalkyl groups, and C ₄ - C ₂₄ cycloalkylalkyl groups; preferably with a moiety selected from the group consisting of -F, -Cl, -Br, -I, -OR ₃₇ , -N(R ₃₇ ) ₂ , -SO ₃ , -PO ₃ , -NO ₂ , -CF ₃ , -SR ₃₇ , S(=O) ₂ N(R ₃₇ ) ₂ , OC(=O)R ₃₇ , SC(=O) R ₃₇ , OC(=S)R ₃₇ , SC(=S)R ₃₇ , NR ₃₇ C(=O)-R ₃₇ , NR ₃₇ C(=S)-R ₃₇ , NR ₃₇ C(=O)O-R ₃₇ , NR ₃₇ C(=S)O-R ₃₇ , NR ₃₇ C(=O)S-R ₃₇ , NR ₃₇ C(=S)S- R ₃₇ , OC(=O)N(R ₃₇ ) ₂ , SC(=O)N(R ₃₇ ) ₂ , OC(=S)N(R ₃₇ ) ₂ , SC(=S)N(R ₃₇ ) ₂ ,

NR ₃₇ C(=O)N(R ₃₇ ) ₂ , NR ₃₇ C(=S)N(R ₃₇ ) ₂ , C(=O)R _37, C(=S)R _37, C(=O)N(R ₃₇ ) ₂ ,

C(=S)N(R ₃₇ ) ₂ , C(=O)O-R ₃₇ , C(=O)S-R ₃₇ , C(=S)O-R ₃₇ , C(=S)S-R ₃₇ , S(O)R ₃₇ , - S(O) ₂ R ₃₇ , NR ₃₇ S(O) ₂ R ₃₇ , -ON(R ₃₇ ) _2, -NR ₃₇ OR ₃₇ , C ₁ -C ₈ alkyl groups, C ₂ -C ₈ alkenyl groups, C ₂ -C ₈ alkynyl groups, C ₆ -C ₁₂ aryl groups, C ₂ -C ₁₂ heteroaryl groups, C ₃ -C ₈ cycloalkyl groups, C ₅ -C ₈ cycloalkenyl groups, C ₃ -C ₁₂ alkyl(hetero)aryl groups, C ₃ - C ₁₂ (hetero)arylalkyl groups, C ₄ -C ₁₂ alkylcycloalkyl groups, C ₄ -C ₁₂ cycloalkylalkyl groups, C ₅ -C ₁₂ cycloalkyl(hetero)aryl groups, and C ₅ -C ₁₂ (hetero)arylcycloalkyl groups; more preferably with a moiety selected from the group consisting of -F, - Cl, -Br, -I, -OR ₃₇ , -N(R ₃₇ ) ₂ , -SO ₃ , -PO ₃ -, -NO ₂ , -CF ₃ , -SR ₃₇ , S(=O) ₂ N(R ₃₇ ) ₂ ,

OC(=O)R ₃₇ , SC(=O) R ₃₇ , OC(=S)R ₃₇ , SC(=S)R ₃₇ , NR ₃₇ C(=O)-R ₃₇ , NR ₃₇ C(=S)-R ₃₇ , NR ₃₇ C(=O)O-R ₃₇ , NR ₃₇ C(=S)O-R ₃₇ , NR ₃₇ C(=O)S-R ₃₇ , NR ₃₇ C(=S)S-R ₃₇ ,

OC(=O)N(R ₃₇ ) ₂ , SC(=O)N(R ₃₇ ) ₂ , OC(=S)N(R ₃₇ ) ₂ , SC(=S)N(R ₃₇ ) ₂ , NR ₃₇ C(=O)N(R ₃₇ ) ₂ , NR ₃₇ C(=S)N(R ₃₇ ) ₂ , C(=O)R _37, C(=S)R _37, C(=O)N(R ₃₇ ) ₂ , C(=S)N(R ₃₇ ) ₂ , C(=O)O-R ₃₇ , C(=O)S-R ₃₇ , C(=S)O-R ₃₇ , C(=S)S-R ₃₇ , S(O)R ₃₇ , -S(O) ₂ R ₃₇ , NR ₃₇ S(O) ₂ R ₃₇ , -ON(R ₃₇ ) _2, - NR ₃₇ OR ₃₇ , C ₁ -C ₄ alkyl groups, C ₂ -C ₄ alkenyl groups, C ₂ -C ₄ alkynyl groups, C ₆ -C ₈ aryl groups, C ₂ -C ₈ heteroaryl groups, C ₃ -C ₆ cycloalkyl groups, C ₅ -C ₆ cycloalkenyl groups, C ₃ -C ₁₀ alkyl(hetero)aryl groups, C ₃ -C ₁₀ (hetero)arylalkyl groups, C ₄ -C ₁₀ alkylcycloalkyl groups, C ₄ -C ₁₀ cycloalkylalkyl groups, C ₅ -C ₁₀

cycloalkyl(hetero)aryl groups, and C ₅ -C ₁₀ (hetero)arylcycloalkyl groups.

In a preferred embodiment, in Formula (4):

(a) Q ₁ and Q ₂ are selected from the group consisting of 2-pyridyl, 3-pyridyl, and 4- pyridyl;

(b) Q ₁ is selected from the group consisting of 2,6-pyrimidyl, 2,5-pyrimidyl, 3,5- pyrmidyl, and 2,4-pyrimidyl; and Q ₂ is (hetero)alkyl; or

(c) Q ₁ is phenyl and Q ₂ is hydrogen;

(d) Q ₁ is alkyl and Q ₂ is alkyl;

(e) Q ₁ is phenyl and Q ₂ is alkyl;

(f) Q ₁ is phenyl and Q ₂ is phenyl;

and in (a)-(f) all Q ₁ and Q ₂ not being hydrogen are optionally substituted as defined in the previous paragraph.

In a preferred embodiment, in Formula (4) the alkyl is a C ₁ -C ₂₄ alkyl group, preferably a C ₁ -C ₁₂ alkyl group, more preferably a C ₁ -C ₆ (hetero)alkyl group.

In a preferred embodiment, in Formula (4) the (hetero)aryl is a C ₆ -C ₂₄ aryl group, preferably a C ₆ -C ₁₂ aryl, more preferably a phenyl.

In a preferred embodiment, in Formula (4) the (hetero)aryl is a C ₂ -C ₂₄ heteroaryl, preferably a C ₂ -C ₁₂ heteroaryl, more preferably a C ₂ -C ₅ heteroaryl.

In a preferred embodiment, in Formula (4) the alkenyl is a C ₂ -C ₂₄ alkenyl, preferably a C ₂ -C ₁₂ alkenyl, more preferably a C ₂ -C ₆ alkenyl.

In a preferred embodiment, in Formula (4) the alkynyl is a C ₂ -C ₂₄ alkynyl, preferably a C ₂ -C ₁₂ alkynyl, more preferably a C ₂ -C ₆ alkynyl.

In a preferred embodiment, in Formula (4) the cycloalkyl is a C ₃ -C ₂₄ cycloalkyl, preferably a C ₃ -C ₁₂ cycloalkyl, more preferably a C ₃ -C ₆ cycloalkyl.

In a preferred embodiment, in Formula (4) the cycloalkenyl, C ₅ -C ₂₄ cycloalkenyl groups, preferably a C ₅ -C ₁₂ cycloalkenyl, more preferably a C ₅ -C ₆ cycloalkenyl.

In a preferred embodiment, in Formula (4) the cycloalkynyl is a C ₆ -C ₂₄ cycloalkynyl, preferably a C ₈ -C ₁₂ cycloalkynyl, more preferably a C ₈ cycloalkyl.

In preferred embodiments, the Cleaving Agent can be a multimeric compound, comprising a plurality of dienes as defined herein. These multimeric compounds include but are not limited to biomolecules, proteins, peptides, peptoids, polymers, dendrimers, liposomes, micelles, particles, gels, polymer particles, or other polymeric constructs.

Preferred tetrazines

Formula (4a)

Preferred tetrazines are in accordance with Formula (4a), and preferably include pharmaceutically accepted salts thereof:

Formula (4a)

, wherein each moiety Q ₁ and Q ₂ is independently selected from the group consisting of hydrogen and moieties according to Formula (5):

Formula (5)

, wherein the dashed line indicates a bond to the remainder of the molecule, and wherein R ₁₀ , R ₁₁ , and R ₁₂ are as defined herein.

As will be understood herein, in relation to Formula (5), the dashed line may indicate a bond to a tetrazine group of Formula (4a), another moiety according to Formula (5), or to the remainder of the compound according to Formulae (6)-(13) as defined below.

In a preferred embodiment, each f in Formula (5) is an integer

independently selected from a range of from 0 to 24, preferably in a range of from 1 to 12, more preferably in a range of from 2 to 6, even more preferably from 1 to 3. In a preferred embodiment, f is 1. In other preferred embodiments f is an integer in the range from 12 to 24.

In a preferred embodiment, in Formula (5) g is an integer in a range of from 0 to 12, preferably in a range of from 1 to 6, more preferably in a range of from 2 to 4.

In a preferred embodiment, in Formula (5) each h is independently 0 or 1. In a preferred embodiment, g is 0, and f is 1. In a preferred embodiment, g is 1, and f is 1.

In case the compound according to the invention comprises more than one moiety satisfying Formula (5), each g, h, and f is independently selected.

In a preferred embodiment, the moiety according to Formula (5) is optionally substituted with another independently selected moiety according to Formula (5). In another preferred embodiment, the moiety according to Formula (5) is not substituted with another independently selected moiety according to Formula (5). In a preferred embodiment, the moiety according to Formula (5) is a R ⁸⁷ , as defined further below.

In a preferred embodiment, the moiety according to Formula (5) satisfies molecules from Group R ^M shown further below

It is preferred that at least one of moieties Q ₁ and Q ₂ in Formula (4a) is not hydrogen.

In preferred embodiments, Q ₁ in Formula (4a) is selected from the group consisting of C ₆ -C ₂₄ aryl, and C ₂ -C ₂₄ heteroaryl, and is optionally further substituted with a moiety according to Formula (5), preferably not more than one moiety according to Formula (5).

In preferred embodiments, Q ₁ in Formula (4a) is selected from the group consisting of C ₆ -C ₂₄ aryl, and C ₂ -C ₂₄ heteroaryl, and is optionally further substituted with a moiety according to Formula (5), preferably not more than one moiety according to Formula (5), and Q ₂ in Formula (4a) is selected from the group consisting of C ₆ -C ₂₄ aryl, and C ₂ -C ₂₄ heteroaryl, and is optionally further substituted with a moiety according to Formula (5), preferably not more than one moiety according to Formula (5).

In preferred embodiments, Q ₁ in Formula (4a) is selected from the group consisting of C ₆ aryl, and C ₃ -C ₅ heteroaryl, and is optionally further substituted with at least one moiety according to Formula (5), preferably not more than one moiety according to Formula (5). Herein, preferred heteroaryls are 2-pyridyl, 3- pyridyl, 4-pyridyl, 2,6-pyrimidyl, 3,5-pyrimidyl, 2,5-pyrimidyl, 2,4-pyrimidyl, 2,4 imidazyl, 2,5 imidazyl, phenyl, 2,3-pyrazyl, 3,4-pyrazyl, oxazol, isoxazol, thiazol, oxazoline, 2-pyrryl, 3-pyrryl, 2-thiophene, and 3-thiophene.

In preferred embodiments, Q ₁ in Formula (4a) is C ₃ -C ₅ heteroaryl, and is optionally further substituted with at least one moiety according to Formula (5), preferably not more than one moiety according to Formula (5), and Q ₂ is C ₃ -C ₅ heteroaryl, and is optionally further substituted with a moiety according to Formula (5), preferably not more than one moiety according to Formula (5).

Herein, preferred heteroaryls are 2-pyridyl, 3-pyridyl, 4-pyridyl, 2,6-pyrimidyl, 3,5-pyrimidyl, 2,5-pyrimidyl, 2,4-pyrimidyl, 2,4 imidazyl, 2,5 imidazyl, phenyl, 2,3-pyrazyl, 3,4-pyrazyl, oxazol, isoxazol, thiazol, oxazoline, 2-pyrryl, 3-pyrryl, 2- thiophene, and 3-thiophene.

In preferred embodiments, Q ₁ in Formula (4a) is C ₃ -C ₅ heteroaryl, and is optionally further substituted with at least one moiety according to Formula (5), preferably not more than one moiety according to Formula (5), and Q ₂ is H.

In preferred embodiments, Q ₁ in Formula (4a) is a phenyl ring, and is optionally further substituted with at least one moiety according to Formula (5), preferably not more than one moiety according to Formula (5), and Q ₂ is -H.

In preferred embodiments, Q ₁ in Formula (4a) is a phenyl ring, and is optionally further substituted with at least one moiety according to Formula (5), preferably not more than one moiety according to Formula (5), and Q ₂ is a phenyl ring, and is optionally further substituted with at least one moiety according to Formula (5), preferably not more than one moiety according to Formula (5).

In preferred embodiments, Q ₁ in Formula (4a) is a phenyl ring, and is optionally further substituted with at least one moiety according to Formula (5), preferably not more than one moiety according to Formula (5), and Q ₂ is selected from the group consisting of C ₆ aryl, and C ₃ -5 heteroaryl, and is optionally further substituted with at least one moiety according to Formula (5), preferably not more than one moiety according to Formula (5).

In preferred embodiments, Q ₁ in Formula (4a) is C ₁ -C ₁₂ alkyl, and is optionally further substituted with at least one moiety according to Formula (5), preferably not more than one moiety according to Formula (5), and Q ₂ selected from the group consisting of C ₆ aryl, and C ₃ -5 heteroaryl, and is optionally further substituted with at least one moiety according to Formula (5), preferably not more than one moiety according to Formula (5).

In preferred embodiments, Q ₁ in Formula (4a) is C ₁ -C ₁₂ alkyl, and is optionally further substituted with at least one moiety according to Formula (5), preferably not more than one moiety according to Formula (5), and Q ₂ in Formula (4a) is C ₁ -C ₁₂ alkyl, and is optionally further substituted with at least one moiety according to Formula (5), preferably not more than one moiety according to Formula (5).

In preferred embodiments Q ₂ equals Q ₁ . R ₁₀

In preferred embodiments, each R ₁₀ is independently selected from the group consisting of -O-, -S-, -SS-, -NR ₄ -, -N=N-, -C(O)-, -C(O)NR ₄ -, -OC(O)-, -C(O)O-, -OC(O)O-, -OC(O)NR ₄ -, -NR ₄ C(O)-, -NR ₄ C(O)O-, -NR ₄ C(O)NR ₄ -, -SC(O)-, -C(O)S-, -SC(O)O-, -OC(O)S-, -SC(O)NR ₄ -, -NR ₄ C(O)S-, -S(O)-, -S(O) ₂ -, -OS(O) ₂ -, -S(O ₂ )O-, -OS(O) ₂ O-, -OS(O) ₂ NR ₄ -, -NR ₄ S(O) ₂ O-, -C(O)NR ₄ S(O) ₂ NR ₄ -, -OC(O)NR ₄ S(O) ₂ NR ₄ -, -OS(O)-, -OS(O)O-, -OS(O)NR ₄ -, -ONR ₄ C(O)-, -ONR ₄ C(O)O-, -ONR ₄ C(O)NR ₄ -, -NR ₄ OC(O)-, -NR ₄ OC(O)O-, -NR ₄ OC(O)NR ₄ -, -ONR ₄ C(S)-, -ONR ₄ C(S)O-,

-ONR ₄ C(S)NR ₄ -, -NR ₄ OC(S)-, -NR ₄ OC(S)O-, -NR ₄ OC(S)NR ₄ -, -OC(S)-, -C(S)O-, -OC(S)O-, -OC(S)NR ₄ -, -NR ₄ C(S)-, -NR ₄ C(S)O-, -SS(O) ₂ -, -S(O) ₂ S-, -OS(O ₂ )S-, -SS(O) ₂ O-, -NR ₄ OS(O)-, -NR ₄ OS(O)O-, -NR ₄ OS(O)NR ₄ -, -NR ₄ OS(O) ₂ -,

-NR ₄ OS(O) ₂ O-, -NR ₄ OS(O) ₂ NR ₄ -, -ONR ₄ S(O)-, -ONR ₄ S(O)O-, -ONR ₄ S(O)NR ₄ -, -ONR ₄ S(O) ₂ O-, -ONR ₄ S(O) ₂ NR ₄ -, -ONR ₄ S(O) ₂ -, -OP(O)(R ₄ ) ₂ -, -SP(O)(R ₄ ) ₂ -,

-NR ₄ P(O)(R ₄ ) ₂ -, and combinations thereof, wherein R ₄ is defined as described herein.

In preferred embodiments, each R ₁₀ is independently selected from the group consisting of -O-, -S-, -SS-, -NR ₄ -, -N=N-, -C(O)-, -C(O)NR ₄ -, -OC(O)-, - C(O)O-, -OC(O)NR ₄ -, -NR ₄ C(O)-, -NR ₄ C(O)O-, -NR ₄ C(O)NR ₄ -, -SC(O)-, -C(O)S-, - SC(O)O-, -OC(O)S-, -SC(O)NR ₄ -, -NR ₄ C(O)S-, -SCO)-, -S(O) ₂ -, -C(O)NR ₄ S(O) ₂ NR ₄ -, -OC(O)NR ₄ S(O) ₂ NR ₄ -, -OC(S)-, -C(S)O-, -OC(S)O-, -OC(S)NR ₄ -, -NR ₄ C(S)-, - NR ₄ C(S)O-, and -SS(O) ₂ -.

R ₁₁

In preferred embodiments, each R ₁₁ is independently selected from the group consisting of C ₁ -C ₂₄ alkylene groups, C ₂ -C ₂₄ alkenylene groups, C ₂ -C ₂₄ alkynylene groups, C ₆ -C ₂₄ arylene, C ₂ -C ₂₄ heteroarylene, C ₃ -C ₂₄ cycloalkylene groups, C ₅ -C ₂₄ cycloalkenylene groups, and C ₁₂ -C ₂₄ cycloalkynylene groups, which are optionally further substituted with one or more substituents selected from the group consisting of -Cl, -F, -Br, -I, -OH, -NH ₂ , -SO ₃ H, -PO ₃ H _, -PO ₄ H ₂ , -NO ₂ , -CF ₃ , =O, =NR ₃₆ , -SR ₃₆ , C ₁ -C ₂₄ alkyl groups, C ₂ -C ₂₄ alkenyl groups, C ₂ -C ₂₄ alkynyl groups, C ₆ -C ₂₄ aryl groups, C ₂ -C ₂₄ heteroaryl groups, C ₃ -C ₂₄ cycloalkyl groups, C ₅ -C ₂₄ cycloalkenyl groups, C ₁₂ -C ₂₄ cycloalkynyl groups, C ₃ -C ₂₄ alkyl(hetero)aryl groups, C ₃ -C ₂₄ (hetero)arylalkyl groups, C ₄ -C ₂₄ (hetero)arylalkenyl groups, C ₄ -C ₂₄

(hetero)arylalkynyl groups, C ₄ -C ₂₄ alkenyl(hetero)aryl groups, C ₄ -C ₂₄

alky nyl(hetero) aryl groups, C ₄ -C ₂₄ alkylcycloalkyl groups, C ₆ -C ₂₄

alkylcycloalkenyl groups, C ₁₃ -C ₂₄ alkylcycloalkynyl groups, C ₄ -C ₂₄ cycloalkylalkyl groups, C ₆ -C ₂₄ cycloalkenylalkyl groups, C ₁₃ -C ₂₄ cycloalkynylalkyl groups, C ₅ -C ₂₄ alkenylcycloalkyl groups, C ₇ -C ₂₄ alkenylcycloalkenyl groups, C ₁₄ -C ₂₄

alkenylcycloalkynyl groups, C ₅ -C ₂₄ cycloalkylalkenyl groups, C ₇ -C ₂₄

cycloalkenylalkenyl groups, C ₁₄ -C ₂₄ cycloalkynylalkenyl groups, C ₅ -C ₂₄

alkynylcycloalkyl groups, C ₇ -C ₂₄ alkynylcycloalkenyl groups, C ₁₄ -C ₂₄

alkynylcycloalkynyl groups, C ₅ -C ₂₄ cycloalkylalkynyl groups, C ₇ -C ₂₄

cycloalkenylalkynyl groupsC, ₁ 4-C ₂₄ cycloalkynylalkynyl groups, C ₅ -C ₂₄

cycloalkyl(hetero)aryl groups, C ₇ -C ₂₄ cycloalkenyl(hetero)aryl groups, C ₁₄ -C ₂₄ cycloalkynyl(hetero)aryl groups, C ₅ -C ₂₄ (hetero)arylcycloalkyl groups, C ₇ -C ₂₄ (hetero)arylcycloalkenyl groups, and C ₁₄ -C ₂₄ (hetero)arylcycloalkynyl groups, wherein the substituents optionally contain one or more heteroatoms selected from the group consisting of O, S, NR ₃₆ , P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized;

and wherein preferably the alkylene groups, alkenylene groups, alkynylene groups, cycloalkylene groups, cycloalkenylene groups, and cycloalkynylene groups optionally contain one or more heteroatoms selected from the group consisting of O, S, NR ₃₆ , P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized.

In preferred embodiments, each R ₁₁ is independently selected from the group consisting of C ₁ -C ₁₂ alkylene groups, C ₂ -C ₁₂ alkenylene groups, C ₂ -C ₁₂ alkynylene groups, C ₆ -C ₁₂ arylene, C ₂ -C ₁₂ heteroarylene, C ₃ -C ₁₂ cycloalkylene groups, C ₅ -C ₁₂ cycloalkenylene groups, and C ₁₂ cycloalkynylene groups;

and wherein preferably the alkylene groups, alkenylene groups, alkynylene groups, cycloalkylene groups, cycloalkenylene groups, and cycloalkynylene groups optionally contain one or more heteroatoms selected from the group consisting of O, S, NR ₃₆ , P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized. In preferred embodiments, each R ₁₁ is independently selected from the group consisting of C ₁ -C ₆ alkylene groups, C ₂ -C ₆ alkenylene groups, C ₂ -C ₆ alkynylene groups, C ₆ -C ₆ arylene, C ₂ -C ₆ heteroarylene, C ₃ -C ₆ cycloalkylene groups, and C ₅ -C ₆ cycloalkenylene groups;

and wherein preferably the alkylene groups, alkenylene groups, alkynylene groups, cycloalkylene groups, cycloalkenylene groups, and cycloalkynylene groups optionally contain one or more heteroatoms selected from the group consisting of O, S, NR ₃₆ , P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized.

In preferred embodiments, the R ₁₁ groups are optionally further

substituted with one or more substituents selected from the group consisting of - Cl, -F, -Br, -I, -OH, -NH ₂ , -SO ₃ H, -PO ₃ H, -PO4H ₂ , -NO ₂ , -CF ₃ , =O, =NR ₃₆ , -SR ₃₆ , C1-C ₁₂ alkyl groups, C ₂ -C ₁₂ alkenyl groups, C ₂ -C ₁₂ alkynyl groups, C ₆ -C ₁₂ aryl groups, C ₂ -C ₁₂ heteroaryl groups, C ₃ -C ₁₂ cycloalkyl groups, C ₅ -C ₁₂ cycloalkenyl groups, C ₁₂ cycloalkynyl groups, C ₃ -C ₁₂ alkyl(hetero)aryl groups, C ₃ -C ₁₂

(hetero)arylalkyl groups, C ₄ -C ₁₂ (hetero)arylalkenyl groups, C ₄ -C ₁₂

(hetero)arylalkynyl groups, C ₄ -C ₁₂ alkenyl(hetero)aryl groups, C ₄ -C ₁₂

alky nyl(hetero) aryl groups, C ₄ -C ₁₂ alkylcycloalkyl groups, C ₆ -C ₁₂

alkylcycloalkenyl groups, C ₁₃ -C ₁₈ alkylcycloalkynyl groups, C ₄ -C ₁₂ cycloalkylalkyl groups, C ₆ -C ₁₂ cycloalkenylalkyl groups, C ₁₃ -C ₁₈ cycloalkynylalkyl groups, C ₅ -C ₁₂ alkenylcycloalkyl groups, C ₇ -C ₁₂ alkenylcycloalkenyl groups, C ₁₄ -C ₁₆

alkenylcycloalkynyl groups, C ₅ -C ₁₂ cycloalkylalkenyl groups, C ₇ -C ₁₂

cycloalkenylalkenyl groups, C ₁₄ -C ₁₆ cycloalkynylalkenyl groups, C ₅ -C ₁₂

alkynylcycloalkyl groups, C ₇ -C ₁₂ alkynylcycloalkenyl groups, C ₁₄ -C ₁₆

alkynylcycloalkynyl groups, C ₅ -C ₁₂ cycloalkylalkynyl groups, C ₇ -C ₁₂

cycloalkenylalkynyl groups, C ₁₄ -C ₁₆ cycloalkynylalkynyl groups, C ₅ -C ₁₂

cycloalkyl(hetero)aryl groups, C ₇ -C ₁₂ cycloalkenyl(hetero)aryl groups, C ₁₄ -C ₁₆ cycloalkynyl(hetero)aryl groups, C ₅ -C ₁₂ (hetero)arylcycloalkyl groups, C ₇ -C ₁₂ (hetero)arylcycloalkenyl groups, and C ₁₄ -C ₁₆ (hetero)arylcycloalkynyl groups, wherein the substituents optionally contain one or more heteroatoms selected from the group consisting of O, S, NR ₃₆ , P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized. In preferred embodiments, the R ₁₁ groups are optionally further substituted with one or more substituents selected from the group consisting of - Cl, -F, -Br, -I, -OH, -NH ₂ , -SO ₃ H, -PO ₃ H, -PO ₄ H ₂ , -NO ₂ , -CF ₃ , =O, =NR ₃₆ , -SR ₃₆ , C ₁ -C ₆ alkyl groups, C ₂ -C ₆ alkenyl groups, C ₂ -C ₆ alkynyl groups, C ₆ aryl groups, C ₂ -C ₆ heteroaryl groups, C ₃ -C ₆ cycloalkyl groups, C ₅ -C ₆ cycloalkenyl groups, C ₃ - C ₆ alkyl(hetero)aryl groups, C ₃ -C ₆ (hetero)arylalkyl groups, C ₄ -C ₆

(hetero)arylalkenyl groups, C ₄ -C ₆ (hetero)arylalkynyl groups, C ₄ -C ₆

alkenyl(hetero)aryl groups, C ₄ -C ₆ alkynyl(hetero)aryl groups, C ₄ -C ₆

alkylcycloalkyl groups, Ce alkylcycloalkenyl groups, C ₄ -C ₆ cycloalkylalkyl groups, C ₆ cycloalkenylalkyl groups, C ₅ -C ₆ alkenylcycloalkyl groups, C ₇

alkenylcycloalkenyl groups, C ₅ -C ₆ cycloalkylalkenyl groups, C ₇

cycloalkenylalkenyl groups, C ₅ -C ₆ alkynylcycloalkyl groups, C ₇

alkynylcycloalkenyl groups, C ₅ -C ₆ cycloalkylalkynyl groups, C ₅ -C ₆

cycloalkyl(hetero)aryl groups, and C ₅ -C ₆ (hetero)arylcycloalkyl groups, wherein the substituents optionally contain one or more heteroatoms selected from the group consisting of O, S, NR ₃₆ , P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized.

In preferred embodiments, the R ₁₁ groups are optionally further

substituted with one or more substituents selected from the group consisting of - Cl, -F, -Br, -I, -OH, -NH ₂ , -SO ₃ H, -PO ₃ H, -PO ₄ H ₂ , -NO ₂ , -CF ₃ , =O, =NR ₃₆ , -SR ₃₆ , C ₁ -C ₆ alkyl groups, C ₂ -C ₆ alkenyl groups, C ₂ -C ₆ alkynyl groups, C ₆ aryl groups, C ₂ -C ₆ heteroaryl groups, C ₃ -C ₆ cycloalkyl groups, C ₅ -C ₆ cycloalkenyl groups, C ₃ - C ₇ alkyl(hetero)aryl groups, C ₃ -C ₇ (hetero)arylalkyl groups, C ₄ -C ₈

(hetero)arylalkenyl groups, C ₄ -C ₈ (hetero)arylalkynyl groups, C ₄ -C ₈

alkenyl(hetero)aryl groups, C ₄ -C ₈ alkynyl(hetero)aryl groups, C ₄ -C ₆

alkylcycloalkyl groups, C ₆ -C ₇ alkylcycloalkenyl groups, C ₄ -C ₆ cycloalkylalkyl groups, C ₆ -C ₇ cycloalkenylalkyl groups, C ₅ -C ₆ alkenylcycloalkyl groups, C ₇ -C ₈ alkenylcycloalkenyl groups, C ₅ -C ₆ cycloalkylalkenyl groups, C ₇ -C ₈

cycloalkenylalkenyl groups, C ₅ -C ₆ alkynylcycloalkyl groups, C ₇ -C ₈

alkynylcycloalkenyl groups, C ₅ -C ₆ cycloalkylalkynyl groups, C ₅ -C ₉

cycloalkyl(hetero)aryl groups, and C ₅ -C ₆ (hetero)arylcycloalkyl groups, wherein the substituents optionally contain one or more heteroatoms selected from the group consisting of O, S, NR ₃₆ , P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized.

It is preferred that when f > 2, that R ₁₁ is independently selected from the group consisting of C ₁ -C ₆ alkylene groups, C ₂ -C ₆ alkenylene groups, C ₂ -C ₆ alkynylene groups, C ₆ -C ₆ arylene, C ₂ -C ₆ heteroarylene, C ₃ -C ₆ cycloalkylene groups, and C ₅ -C ₆ cycloalkenylene groups; and wherein preferably the alkylene groups, alkenylene groups, alkynylene groups, cycloalkylene groups,

cycloalkenylene groups, and cycloalkynylene groups optionally contain one or more heteroatoms selected from the group consisting of O, S, NR ₃₆ , P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized.

In a preferred embodiment, the R ₁₁ substituents do not contain heteroatoms.

In a preferred embodiment, the R ₁₁ groups are not substituted.

In another preferred embodiment, the R ₁₁ groups do not contain heteroatoms.

R12

R ₁₂ is selected from the group consisting of -H, -OH, -NH ₂ , -N ₃ , -Cl, -Br, -F, -I, a polymer, a particle, a peptide, a peptoid, a dendrimer, a protein, a biomolecule, a carbohydrate, an oligonucleotide, an oligosaccharide, a lipid, a liposome, a micelle, an imaging moiety, a Targeting Agent T ^T , a R ⁸⁷ , an albumin-binding moiety, and a chelating moiety.

Non-limiting examples of chelating moieties for use in R ₁₂ are DTPA (diethylenetriaminepentaacetic acid),

DOTA (1,4,7,10- tetraazacyclododecane-N,N',N",N"-tetraacetic acid),

NOTA (l,4,7-triazacyclononane-N,N',N"-triacetic acid),

TETA (1,4,8, ll-tetraazacyclotetradecane-N,N',N",N'-tetraacetic acid),

OTTA (Nl-(p-isothiocyanatobenzyl)-diethylenetriamine-Ni,N ₂ ,N ₃ ,N ₃ -tetraacetic acid), deferoxamine or DFO (N'-[5-[[4-[[5-(acetylhydroxyamino)pentyl]amino]-l,4- dioxobutyl] hydroxy amino] pentyl] -N- (5 - aminopentyl) - N -hy droxybutanediamide) or HYNIC (hydrazino nicotinamide).

In a preferred embodiment, when R ¹² is a polymer, a particle, a peptide, a peptoid, a dendrimer, a protein, a biomolecule, an oligonucleotide, an oligosaccharide, a lipid, a liposome, a micelle, a Targeting Agent T ^T , or a R ⁸⁷ , then f is at most 2, preferably at most 1.

Formulae (6) ( 7 ) (8) ( 9 ) (10) (11 ) (12) and (13)

In preferred embodiments of the invention the tetrazine is in accordance with any one of the Formulae (6), (7), (8), (9), (10), (11), (12), or (13):

wherein each moiety Q, Q ₁ , Q ₂ , Q ₃ , and Q ₄ is independently selected from the group consisting of hydrogen and moieties according to Formula (5) as defined herein; and wherein R ₁ , R ₂ , and R ₃ are as defined herein.

In preferred embodiments, in the tetrazines according to any one of Formulae (6), (7), (8), (9), (10), (11), (12), and (13), at most one moiety selected from the group consisting of Q, Q ₁ , Q ₂ , Q ₃ , and Q ₄ is hydrogen.

In preferred embodiments, in the tetrazines according to any one of Formulae (7), (8), (9), (10), (11), (12), and (13), at most two moieties selected from the group consisting of Q, Q ₁ , Q ₂ , Q ₃ , and Q ₄ are hydrogen.

In preferred embodiments, in the tetrazines according to any one of Formulae (7), (8), (9), (10), (11), (12), and (13), at most three moieties selected from the group consisting of Q, Q ₁ , Q ₂ , Q ₃ , and Q ₄ are hydrogen.

In preferred embodiments, in the tetrazines according to any one of Formulae (7), (8), (9), (10), (11), (12), and (13), all moieties selected from the group consisting of Q, Q ₁ , Q ₂ , Q ₃ , and Q ₄ are hydrogen. In preferred embodiments, in the tetrazines according to any one of

Formulae (7), (8), (9), (10), (11), (12), and (13), at most one moiety selected from the group consisting of Q, Q ₁ , Q ₂ , Q ₃ , and Q ₄ is not hydrogen.

In preferred embodiments, in the tetrazines according to any one of

Formulae (7), (8), (9), (10), (11), (12), and (13), at most two moieties selected from the group consisting of Q, Q ₁ , Q ₂ , Q ₃ , and Q ₄ is not hydrogen.

Molecular weight

Preferably, for all compounds disclosed herein comprising a group Q, Q ₁ , Q ₂ , Q ₃ , Q ₄ or -(CH ₂ ) _y -((R ₁ )p-R ₂ )n-(R ₁ )p-R ₃ , at least one of these groups has a molecular weight in a range of from 100 Da to 3000 Da. Preferably, at least one of these groups has a molecular weight in a range of from 100 Da to 2000 Da. More preferably, at least one of these groups has a molecular weight in a range of from 100 Da to 1500 Da, even more preferably in a range of from 150 Da to 1500 Da. Even more preferably still, at least one of these groups has a molecular weight in a range of from 150 Da to 1000 Da, most preferably in a range of from 200 Da to 1000 Da.

Preferably, for all compounds disclosed herein, comprising a group Q, Q1, Q2 , Q3 , Q4 or -(CH ₂ ) _y -((R ₁ ) _p -R ₂ )n-(Ri)p-R ₃ , none of these groups has a molecular weight of more than 3000 Da, in particular in the case the Clearing Agent needs to efficiently extravasate into tissues.

GrOUP -(CH ₂ ) -((R ₁ ) _p -R ₂ )n-(R ₁ ) _p -R ₃

In preferred embodiments, y is an integer in a range of from 1 to 12, preferably from 1 to 10, more preferably from 1 to 8, even more preferably from 2 to 6, most preferably from 2 to 4. In preferred embodiments, y is at least 2, preferably y is at least 3. In preferred embodiments, p is 0 or 1, wherein each p is independently selected. In preferred embodiments, each n is an integer independently selected from a range of from 0 to 24, preferably from 1 to 12, more preferably from 1 to 6, even more preferably from 1 to 3, most preferably n is 0 or 1. In preferred embodiments n is preferably an integer from 12 to 24. In preferred embodiments, n is 1. In preferred embodiments, the entire group -((R ₁ ) _p -R ₂ ) _n -(R ₁ ) _p -R ₃ has a molecular weight in a range of from 100 Da to 3000 Da. Preferably, the entire group -((R ₁ ) _p -R ₂ ) _n -(R ₁ )p-R ₃ has a molecular weight in a range of from 100 Da to 2000 Da. More preferably, the entire group -((R ₁ ) _p -R ₂ ) _n -(R ₁ ) _P -R ₃ has a molecular weight in a range of from 100 Da to 1500 Da, even more preferably in a range of from 150 Da to 1500 Da. Even more preferably still, the entire group -((R ₁ ) _p -R ₂ ) _n - (R _I ) _P -R ₃ has a molecular weight in a range of from 150 Da to 1000 Da, most preferably in a range of from 200 Da to 1000 Da.

It is preferred that when n > 2, that R ₂ is independently selected from the group consisting of C ₁ -C ₆ alkylene groups, C ₂ -C ₆ alkenylene groups, C ₂ -C ₆ alkynylene groups, C ₆ -C ₆ arylene, C ₂ -C ₆ heteroarylene, C ₃ -C ₆ cycloalkylene groups, and C ₅ -C ₆ cycloalkenylene groups; and wherein preferably the alkylene groups, alkenylene groups, alkynylene groups, cycloalkylene groups,

cycloalkenylene groups, and cycloalkynylene groups optionally contain one or more heteroatoms selected from the group consisting of O, S, NR ₃₆ , P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized.

In preferred embodiments, the entire group -((R ₁ ) _p -R ₂ )n-(R ₁ ) _p -R ₃ satisfies molecules from Group R ^M shown below. R ^M :

, wherein the wiggly line denotes a bond to a tetrazine group as disclosed herein or to a group R ₁ or R ₂ .

In preferred embodiments, the group -((Ri) _p -R ₂ )n-(Ri) _P -R3 satisfies molecules from Group R ^M , wherein it is understood that when n is more than 1, -((R ₁ ) _p -R ₂ ) _n -(R ₁ ) _p -R ₃ may be preceded by a group -((R ₁ ) _p -R ₂ ) - so as to form a group -((Ri) _p -R ₂ )-((Ri) _P -R ₂ )n-i-(Ri) _P -R3. It is understood that this follows from the definition of how to write out the repeating units, i.e. -((R ₁ ) _p -R ₂ ) ₂ - would first be written as - (R ₁ ) _p -R ₂ - (R ₁ ) _p -R ₂ - before Ri, p, and R ₂ are independently selected.

R ₁ R ₂ . and R ₃

R ₁ is as defined for R ₁₀ . R ₂ is as defined for R ₁₁ . R ₃ is as defined for R _12.

R ₄

Preferably, each R ₄ is independently selected from the group consisting of hydrogenC, ₁ -C ₂₄ alkyl groups, C ₂ -C ₂₄ alkenyl groups, C ₂ -C ₂₄ alkynyl groups, C ₆ - C ₂₄ aryl, C ₂ -C ₂₄ heteroaryl, C ₃ -C ₂₄ cycloalkyl groups, C ₅ -C ₂₄ cycloalkenyl groups, and C ₁₂ -C ₂₄ cycloalky nyl groups.

In a preferred embodiment, each R ₄ is independently selected from the group consisting of hydrogenC, ₁ -C ₁₂ alkyl groups, C ₂ -C ₁₂ alkenyl groups, C ₂ -C ₁₂ alkynyl groups, C ₆ -C ₁₂ aryl, C ₂ -C ₁₂ heteroaryl, C ₃ -C ₁₂ cycloalkyl groups, C ₅ -C ₁₂ cycloalkenyl groups, and C ₁₂ cycloalkynyl groups.

In a preferred embodiment, each R ₄ is independently selected from the group consisting of hydrogenC, ₁ -C ₄ alkyl groups, C ₂ -C ₄ alkenyl groups, C ₂ -C ₄ alkynyl groups, C ₆ aryl, C ₂ -C ₆ heteroaryl, C ₃ -C ₈ cycloalkyl groups, C ₅ -C ₈ cycloalkenyl groups, and C ₈ cycloalkynyl groups.

Preferably, the R ₄ groups not being hydrogen, optionally contain one or more heteroatoms selected from the group consisting of O, S, NR5, P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized.

Preferably, the R ₄ groups not being hydrogen, are optionally further substituted with one or more substituents selected from the group consisting of - Cl, -F, -Br, -I, -OH, -NH ₂ , -SO ₃ H, -PO ₃ H, -PO ₄ H ₂ , -NO ₂ , -CF ₃ , =O, =NR ₅ , -SR ₆ , C ₁ - C ₂₄ alkyl groups, C ₂ -C ₂₄ alkenyl groups, C ₂ -C ₂₄ alkynyl groups, C ₆ -O ₂₄ aryl groups, C ₂ -C ₂₄ heteroaryl groups, C ₃ -C ₂₄ cycloalkyl groups, C ₅ -C ₂₄ cycloalkenyl groups, C ₁₂ -C ₂₄ cycloalkynyl groups, C ₃ -C ₂₄ alkyl(hetero)aryl groups, C ₃ -C ₂₄ (hetero)arylalkyl groups, C ₄ -C ₂₄ (hetero)arylalkenyl groups, C ₄ -C ₂₄

(hetero)arylalkynyl groups, C ₄ -C ₂₄ alkenyl(hetero)aryl groups, C ₄ -C ₂₄

alky nyl(hetero) aryl groups, C ₄ -C ₂₄ alkylcycloalkyl groups, C ₆ -O ₂₄

alkylcycloalkenyl groups, C ₁₃ -C ₂₄ alkylcycloalkynyl groups, C ₄ -C ₂₄ cycloalkylalkyl groups, C ₆ -C ₂₄ cycloalkenylalkyl groups, C ₁₃ -C ₂₄ cycloalkynylalkyl groups, C ₅ -C ₂₄ alkenylcycloalkyl groups, C ₇ -C ₂₄ alkenylcycloalkenyl groups, C ₁₄ -C ₂₄

alkenylcycloalkynyl groups, C ₅ -C ₂₄ cycloalkylalkenyl groups, C ₇ -C ₂₄

cycloalkenylalkenyl groups, C ₁₄ -C ₂₄ cycloalkynylalkenyl groups, C ₅ -C ₂₄

alkynylcycloalkyl groups, C ₇ -C ₂₄ alkynylcycloalkenyl groups, C ₁₄ -C ₂₄

alkynylcycloalkynyl groups, C ₅ -C ₂₄ cycloalkylalkynyl groups, C ₇ -C ₂₄

cycloalkenylalkynyl groups, C ₁₄ -C ₂₄ cycloalkynylalkynyl groups, C ₅ -C ₂₄

cycloalkyl(hetero)aryl groups, C ₇ -C ₂₄ cycloalkenyl(hetero)aryl groups, C ₁₄ -C ₂₄ cycloalkynyl(hetero)aryl groups, C ₅ -C ₂₄ (hetero)arylcycloalkyl groups, C ₇ -C ₂₄ (hetero)arylcycloalkenyl groups, and C ₁₄ -C ₂₄ (hetero)arylcycloalkynyl groups; wherein the substituents optionally contain one or more heteroatoms selected from the group consisting of O, S, NR ₅ , P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized.

Preferably, the R ₄ groups not being hydrogen, are optionally further substituted with one or more substituents selected from the group consisting of - Cl, -F, -Br, -I, -OH, -NH ₂ , -SO ₃ H, -PO ₃ H, -PO ₄ H ₂ , -NO ₂ , -CF ₃ , =O, =NR ₅ , -SR ₅ , C ₁ - C ₄ alkyl groups, C ₂ -C ₄ alkenyl groups, C ₂ -C ₄ alkynyl groups, C ₆ aryl groups, C ₂ -C ₄ heteroaryl groups, C ₃ -C ₄ cycloalkyl groups, C ₅ -C ₄ cycloalkenyl groups, C ₁₂ cycloalkynyl groups, C ₃ -C ₁₂ alkyl(hetero)aryl groups, C ₃ -C ₁₂ (hetero)arylalkyl groups, C ₄ -C ₁₂ (hetero)arylalkenyl groups, C ₄ -C ₁₂ (hetero)arylalkynyl groups, C ₄ - C ₁₂ alkenyl(hetero)aryl groups, C ₄ -C ₁₂ alkynyl(hetero)aryl groups, C ₄ -C ₁₂ alkylcycloalkyl groups, C ₆ -C ₁₂ alkylcycloalkenyl groups, C ₁₃ -C ₁₂ alkylcycloalkynyl groups, C ₄ -C ₁₂ cycloalkylalkyl groups, C ₆ -C ₁₂ cycloalkenylalkyl groups, C ₁₃ cycloalkynylalkyl groups, C ₅ -C ₁₂ alkenylcycloalkyl groups, C ₇ -C ₁₂ alkenylcycloalkenyl groups, C ₁₄ alkenylcycloalkynyl groups, C ₅ -C ₁₂

cycloalkylalkenyl groups, C ₇ -C ₁₂ cycloalkenylalkenyl groups, C ₁₄

cycloalkynylalkenyl groups, C ₅ -C ₁₂ alkynylcycloalkyl groups, C ₇ -C ₁₂

alkynylcycloalkenyl groups, C ₁₄ -C ₁₂ alkynylcycloalkynyl groups, C ₅ -C ₁₂

cycloalkylalkynyl groups, C ₇ -C ₁₂ cycloalkenylalkynyl groups, C ₁₄

cycloalkynylalkynyl groups, C ₅ -C ₁₂ cycloalkyl(hetero)aryl groups, C ₇ -C ₁₂ cycloalkenyl(hetero)aryl groups, C ₁₄ cycloalkynyl(hetero)aryl groups, C ₅ -C ₁₂ (hetero)arylcycloalkyl groups, C ₇ -C ₁₂ (hetero)arylcycloalkenyl groups, and C ₁₄ (hetero)arylcycloalkynyl groups;

wherein the substituents optionally contain one or more heteroatoms selected from the group consisting of O, S, NR ₅ , P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized.

In a preferred embodiment, the R ₄ substituents do not contain

heteroatoms. In a preferred embodiment, the R ₄ groups are not substituted.

In another preferred embodiment, the R ₄ groups do not contain heteroatoms.

R ₅

Preferably, each R ₅ is independently selected from the group consisting of hydrogen, C ₁ -C ₈ alkyl groups, C ₂ -C ₈ alkenyl groups, C ₂ -C ₈ alkynyl groups, C ₆ -C ₁₂ aryl, C ₂ -C ₁₂ heteroaryl, C ₃ -C ₈ cycloalkyl groups, C ₅ -C ₈ cycloalkenyl groups, C ₃ -C ₁₂ alkyl(hetero)aryl groups, C ₃ -C ₁₂ (hetero)arylalkyl groups, C ₄ -C ₁₂ alkylcycloalkyl groups, C ₄ -C ₁₂ cycloalkylalkyl groups, C ₅ -C ₁₂ cycloalkyl(hetero)aryl groups and C ₅ -C ₁₂ (hetero)arylcycloalkyl groups, wherein the R ₅ groups not being hydrogen are optionally substituted with a moiety selected from the group consisting of -Cl, -F, -Br, -I, -OH, -NH ₂ , -SO ₃ H, -PO ₃ H, -PO ₄ H _2, -NO ₂ , -CF ₃ , =O, =NH, and -SH, and optionally contain one or more heteroatoms selected from the group consisting of O, S, NH, P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized.

In a preferred embodiment, the R ₅ groups are not substituted.

In another preferred embodiment, the R ₅ groups do not contain heteroatoms. Moieties Q, Q ₁ , Q ₂ , Q ₃ , Q ₄

In preferred embodiments, g is an integer in a range of from 0 to 12, preferably from 0 to 10, more preferably from 0 to 8, even more preferably from 1 to 6, most preferably from 2 to 4. In other preferred embodiments g is 0. In case more than one moiety selected from the group consisting of Q, Q ₁ , Q ₂ , Q ₃ , and Q ₄ within one compound satisfies Formula (5), each g is independently selected.

In preferred embodiments, h is 0 or 1. In case more than one moiety selected from the group consisting of Q, Q ₁ , Q ₂ , Q ₃ , and Q ₄ within one compound satisfies Formula (5), each h is independently selected.

In preferred embodiments, each f belonging to a moiety Q, Q ₁ , Q ₂ , Q ₃ , or Q ₄ is an integer independently selected from a range of from 0 to 24, preferably from 1 to 12, more preferably from 1 to 6, even more preferably from 1 to 3, most preferably f is 0 or 1. In preferred embodiments f is preferably an integer from 12 to 24. In other preferred embodiments, f is 1.

In preferred embodiments, the group -((R ₁₀ )h-R ₁₁ )n-(R ₁₀ )h-R ₁₂ satisfies molecules from Group R ^M shown above.

In preferred embodiments, the group -((R ₁₀ ) _h -R ₁₁ ) _n -(R ₁₀ ) _h -R ₁₂ satisfies molecules from Group R ^M , wherein it is understood that when n is more than 1, e.g. -((R ₁₀ ) _h -R ₁₁ ) _n-i -(R ₁₀ ) _h -Ri2 may be preceded by a group -(R ₁₀ ) _h -R ₁₁ - so as to form a group -(R ₁₀ )h-R ₁₁ -((R ₁₀ )h-R ₁₁ )n-i-(R ₁₀ )h-Ri2. It is understood that this follows from the definition of how to write out the repeating units, i.e. -((R ₁₀ ) _h -Ru) ₂ - would first be written as -(R ₁₀ ) _h -R ₁₁ -(R ₁₀ ) _h -R ₁₁ - before R ₁₀ , h, and R ₁₁ are independently selected.

Formulae (14), (14a), (14b), (14c), (14d), (14e), and (14f)

In a preferred embodiment, the Cleaving Agent is a tetrazine satisfying Formula (14):

Formula (14)

and preferably including pharmaceutically acceptable salts thereof,

wherein, Y _a is selected from the group consisting of Y ₁ , Y ₂ , Y ₃ , Y ₄ , Y ₅ and Ub:

wherein, Y _b is selected from the group consisting of Y ₁ , Y ₂ , Y ₃ , Y ₄ , Y ₅ , Ub, hydrogen, X ₄₇ , and -(S ^P )D-R ⁸⁷ ; wherein SP is a spacer, preferably as defined herein, wherein D is 0 or 1, preferably D is 0; wherein when Y _a is Ub, then Y _b is hydrogen, wherein each Q ₁ and Q ₅ , are individually selected from the group consisting of X _45, hydrogen, X ₄₇ and -(S ^P )D-R ⁸⁷ ; wherein each Q ₂ and Q ₄ , are individually selected from the group consisting of X ₄₆ , hydrogen, X ₄₇ , and— (S ^P )D— R ⁸⁷ ; wherein each Q ₃ is individually selected from the group consisting of hydrogen, X ₄₇ , and— (S ^P )D— R ⁸⁷ ; wherein preferably the compound of Formula (14) comprises at least one X ₄₅ or X ₄₆ group, wherein each X ₄₅ individually is selected from the group consisting of N(X ₅₀ ) ₂ , C(X ₅₁ ) ₂ N(X ₅₀ ) ₂ , NX ₅₀ C(O)X5i, NX ₅₀ C(S)X5i, OH, SH, C(0)OH, C(S)OH, C(0)SH, C(S)SH, NX ₅₀ C(O)OX _5I, NX ₅₀ C(S)OX _5I, NX ₅₀ C(0)SX _5I , NX ₅₀ C(S)SX6i, NX ₅₀ C(O)N(X _5I ) ₂ , NX _5O C(S)N(X _5I ) ₂ , NX ₅₀ SO ₂ X _5I , NX ₅₀ SO ₃ X _5I , NX ₅₀ OX _5I , SO ₃ H, , S0 ₂ N(X _5I ) ₂ , and PO ₃ H ₂ ; wherein each X ₄₆ individually is selected from the group consisting of N(Xso) ₂ , 0(C _5ΐ ) ₂ N(C _d o) ₂ , NX ₅₀ C(O)X _5I , NX ₅₀ C(S)X _5I „ OH, SH, C(0)OH, C(S)OH, C(0)SH, C(S)SH,

NX ₅₀ C(O)OX _5I, NX6OC(S)OX _6I, NX ₅₀ C(O)SX _5I, NX ₅₀ C(S)SX _5I, NX _5O C(0)N(X _5I ) ₂ , NX _5O C(S)N(X _5I ) ₂ , NX ₅₀ SO ₂ X _5I , NX ₅₀ SO ₃ X _5I , NX ₅₀ OX _5I , SO ₃ H, and PO ₃ H ₂ ; wherein each X ₅₀ and X ₅₁ individually is selected from the group consisting of hydrogen, X ₄₈ , and— (S ^P )D—R ⁸⁷ ; wherein each X ₄₈ is preferably independently selected from the group consisting of hydrogen, C ₁ -C ₄ alkyl groups, C ₂ -C ₄ alkenyl groups, and C _4-6 (hetero)aryl groups; wherein for X ₄₈ the alkyl groups, alkenyl groups, and (hetero)aryl groups are optionally substituted with a moiety selected from the group consisting of -Cl, -F, -Br, -I, -OH, -NH ₂ , =O, -SH, -SO ₃ H, -PO ₃ H, -PO ₄ H ₂ , and -NO ₂ ; and optionally contain at most two heteroatoms selected from the group consisting of -O-, -S-, -NH-, -P-, and -Si-, wherein the N, S, and P atoms are optionally oxidized, wherein each X ₄₇ is selected from the group consisting of -F, - Cl, -Br, -I, -OX ₄₉ , -N(X ₄₉ ) ₂ , -SO ₃ , -PO ₃ -, -NO ₂ , -CF ₃ , -SX ₄₉ , S(=O) ₂ N(X ₄₉ ) _2,

OC(=O)X ₄₉ , SC(=O) X ₄₉ , OC(=S)X ₄₉ , SC(=S)X _49, NX ₄₉ C(=O)-X ₄₉ , NX ₄₉ C(=S)-X ₄₉ , NX ₄₉ C(=O)O-X ₄₉ , NX ₄₉ C(=S)O-X ₄₉ , NX ₄₉ C(=O)S-X ₄₉ , NX ₄₉ C(=S)S-X ₄₉ ,

OC(=O)N(X ₄₉ ) ₂ , SC(=O)N(X ₄₉ ) ₂ , OC(=S)N(X ₄₉ ) ₂ , SC(=S)N(X ₄₉ ) ₂ , NX ₄₉ C(=O)N(X ₄₉ ) ₂ , NX ₄₉ C(=S)N(X ₄₉ ) _2, C(=O)X _49, C(=S)X _49, C(=O)N(X ₄₉ ) ₂ , C(=S)N(X ₄₉ ) ₂ , C(=O)O-X ₄₉ , C(=O)S-X ₄₉ , C(=S)O-X ₄₉ , C(=S)S-X ₄₉ , -S(O)X ₄₉ , -S (O) ₂ X ₄₉ , NX ₄₉ S(O) ₂ X ₄₉ , -ON(X ₄₉ ) _2, -NX ₄₉ OX ₄₉ , C ₁ -C ₈ alkyl groups, C ₂ -C ₈ alkenyl groups, C ₂ -C ₈ alkynyl groups, C ₆ - C ₁₂ aryl, C ₂ -C ₁₂ heteroaryl, C ₃ -C ₈ cycloalkyl groups, C ₅ -C ₈ cycloalkenyl groups, C ₃ -C ₁₂ alkyl(hetero)aryl groups, C ₃ -C ₁₂ (hetero)arylalkyl groups, C ₄ -C ₁₂

alkylcycloalkyl groups, C ₄ -C ₁₂ cycloalkylalkyl groups, C ₅ -C ₁₂

cycloalkyl(hetero)aryl groups and C ₅ -C ₁₂ (hetero)arylcycloalkyl groups,

wherein the alkyl groups, alkenyl groups, alkynyl groups, aryl, heteroaryl, cycloalkyl groups, cycloalkenyl groups, alkyl(hetero)aryl groups, (hetero)arylalkyl groups, alkylcycloalkyl groups, cycloalkylalkyl groups, cycloalkyl(hetero)aryl groups and (hetero)arylcycloalkyl groups are optionally substituted with a moiety selected from the group consisting of -Cl, -F, -Br, -I, -OX ₄₉ , -N(X ₄₉ ) ₂ , -SO ₃ X ₄₉ , - PO ₃ (X ₄₉ ) _2, -PO ₄ (X ₄₉ ) _2, -NO ₂ , -CF ₃ , =O, =NX ₄₉ , and -SX ₄₉ , and optionally contain one or more heteroatoms selected from the group consisting of O, S, NX ₄₉ , P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized; wherein X ₄₉ is selected from the group consisting of hydrogen, C ₁ -C ₈ alkyl groups, C ₂ -C ₈ alkenyl groups, C ₂ -C ₈ alkynyl groups, C ₆ -C ₁₂ aryl, C ₂ -C ₁₂ heteroaryl, C ₃ -C ₈ cycloalkyl groups, C ₅ -C ₈ cycloalkenyl groups, C ₃ -C ₁₂ alkyl(hetero)aryl groups, C ₃ -C ₁₂ (hetero)arylalkyl groups, C ₄ -C ₁₂ alkylcycloalkyl groups, C ₄ -C ₁₂ cycloalkylalkyl groups, C ₅ -C ₁₂ cycloalkyl(hetero)aryl groups and C ₅ -C ₁₂ (hetero)arylcycloalkyl groups, wherein the X ₄₉ groups not being hydrogen are optionally substituted with a moiety selected from the group consisting of -Cl, -F, -Br, -I, -OH, -NH ₂ , -SO ₃ H, -PO ₃ H, -PO ₄ H _2, -NO ₂ , -CF ₃ , =O, =NH, and -SH, and optionally contain one or more heteroatoms selected from the group consisting of O, S, NH, P, and Si, wherein the N, S, and P atoms are optionally oxidized, wherein the N atoms are optionally quaternized; wherein for each individual Y _a and Y _b preferably at most two, more preferably at most one of Q ₁ , Q ₂ , Q ₃ , Q _4, and Q ₅ are said R ⁸⁷ ; wherein the compound according to Formula (14) preferably comprises at most four R ⁸⁷ moieties, more preferably at most two R ⁸⁷ moieties, most preferably at most one R ⁸⁷ ; wherein the compound according to Formula (14) preferably comprises at least one R ⁸⁷ ; wherein preferably for each individual Y _a and Y _b at most three, more preferably at most two of Q ₁ , Q ₂ , Q ₃ , Q _4, and Q ₅ are not hydrogen; wherein preferably for each individual Y _a and Y _b at most two of Q ₁ , Q ₂ , Q ₃ , Q _4, and Q ₅ are X ₄₅ or X ₄₆ , wherein preferably for each individual Y _a and Y _b one of Q ₁ , Q ₂ , Q _4, and Qs is X ₄ 5 or X ₄₆ , wherein preferably both Y _a and Y _b comprise at least one X ₄ 5 or X ₄₆ , wherein preferably both Y _a and Y _b comprise one X ₄₅ or X ₄₆ , wherein preferably both Y _a and Y _b comprise one X ₄₅ or X ₄₆ , wherein preferably the X ₄₅ comprised in Y _a is the same as the X ₄₅ comprised in Y _b , and/or the X ₄₆ comprised in Y _a is the same as the X ₄₆ comprised in Y _b , wherein

preferably Y _a and Y _b are both independently selected Yi, or both independently selected Y ₂ , or both independently selected Y ₃ , or both independently selected Y ₄ , or both independently selected Y5.

In a preferred embodiment, in Formula (14) or in any one of Formulae (14a)-(14f), when Q ₁ is a X ₄ 7 or -(S ^P ) _D -R ⁸⁷ , then for Q ₁ the X ₄₇ and the R ⁸⁷ are not a group in accordance with the definition of X ₄₅ .

In a preferred embodiment, in Formula (14) or in any one of Formulae (14a)-(14f), when Q5 is a X ₄ 7 or -(S ^P ) _D -R ⁸⁷ , then for Q5 the X ₄₇ and the R ⁸⁷ are not a group in accordance with the definition of X ₄₅ .

In a preferred embodiment, in Formula (14) or in any one of Formulae (14a)-(14f), when Q ₂ is a X ₄ 7 or -(S ^P ) _D -R ⁸⁷ , then for Q ₂ the X ₄₇ and the R ⁸⁷ are not a group in accordance with the definition of X ₄₆ .

In a preferred embodiment, in Formula (14) or in any one of Formulae (14a)-(14f), when Q ₄ is a X ₄ 7 or -(S ^P ) _D -R ⁸⁷ , then for Q ₄ the X ₄₇ and the R ⁸⁷ are not a group in accordance with the definition of X ₄₆ . In preferred embodiments Y _a equals Y _b . In preferred embodiments Y _a is selected from Yi, Y2, Y3, Y4 or Y5 and Y _b is hydrogen, X ₄₇ or -(S ^P )D-R ⁸⁷ . In preferred embodiments Y _a is selected from Yi, Y ₂ , Y ₃ , Y ₄ or Y ₅ and Y _b is hydrogen. In preferred embodiments the compound according to Formula (14) does not comprise a R ⁸⁷ . In preferred embodiments, X ₅₀ is hydrogen. In preferred