Zwitterionic functionalized poly(beta-aminoester) polymers and uses thereof

This application claims the benefit of European Patent Application EP21382923.7 filed on October 14th, 2021.

Technical Field

The invention relates to polymers suitable for use in the delivery of active agents. The invention also pertains to nanoparticles comprising these polymers, compositions comprising said nanoparticles and methods for their production.

Background Art

The lack of safe and efficient vectors to deliver active ingredients such as polynucleotides (DNA, RNA and the like) remains the principal handicap for the success of gene therapy. The majority of protocols for polynucleotide delivery employ viral vectors, which are highly efficient delivery systems. However, viral vectors have certain disadvantages, including safety risk, limited capacity to carry polynucleotides and high cost of large-scale production. Non-viral vectors offer potential advantages, including high packing capacity, ease of production, low toxicity and immunogenicity, but are less efficient than viral vectors.

Biodegradable poly(beta-aminoester)s (pBAE)s have been described as potential non- viral polynucleotide delivery vectors capable of condensing both DNA and RNA into discrete nanometric particles.

A continuing need exists for improved non-toxic, biodegradable, biocompatible polymers that can be used to transfect polynucleotides efficiently and that can be prepared economically. Such polymers would be useful in the packaging and delivery of DNA and RNA in gene therapy and for the packaging and delivery of other diagnostic, therapeutic and prophylactic agents.

In addition to the above, it is well-known that delivery systems such as nanoparticles (NPs), when are exposed to biological fluids, rapidly adsorb proteins. These form the so- called “hard” and “soft” corona according to their binding strength and exchange rates at the NP surface. The composition of this protein corona depends on many parameters, including particle size, surface chemistry (hydrophilicity, surface charge, etc.), environmental conditions (time, temperature, etc.) and the nature and composition of biological fluids. However, in many in vivo applications, the protein corona dictates the fate of nanocarriers and induces fast recognition by the immune system. It, therefore, reduces the circulation lifetime in the blood stream, as well as the targeting efficiency, and influences cellular uptake, biodistribution and toxicity. In view of the above, there is the need of polymers with improved properties, and which overcome the above identified problems.

Summary of Invention

The present invention provides novel zwitterionic-modified pBAEs with improved properties, making them useful in a variety of medical applications, including drug delivery.

As it is shown below, the modified pBAE polymers of the invention, hereinafter also referred as “OM-PZ-pBAE”, which are characterized by being covalently modified with zwitterionic polymeric side-chains, provide improved anti-fouling properties. In this regard, the inventors prepared nanoparticles with the polymer of the invention and performed a test simulating an in vivo environment. Table 9 below shows that the polymer of the invention (Example 6.3) can remarkably reduce the adhesion of proteins to particle’s surface. Particularly, it can be seen that the polymers of the invention give rise to an about 7-fold reduction in the protein corona formation when compared with the same polymer pBAE lacking the zwitterionic polymer (comparative example 7), besides the cationic charges of the pBAE backbone.

Not only that, but also, the data provided below show that the covalent binding of the zwitterionic polymer to the pBAE backbone is the responsible for such surprising improvement. In this regard, it is provided comparative Example 8, which differs from the polymers of the invention uniquely in the nature of the interaction between the zwitterionic polymer and the pBAE backbone: covalent (invention) vs electrostatic (comparative Example 8). As it can be concluded from Table 9 below, the behaviour of the pBAE comprising the electrostatically bound zwitterionic polymer is substantially the same as the one of the pBAE with no zwitterionic polymer in the in vivo test, being substantially less efficient in preventing the adhesion of proteins on nanoparticle’s surface than the pBAE of the invention, which is covalently modified with zwitterionic polymers. The latter means that it is not only necessary the presence of a zwitterionic polymer, but the most important, that the zwitterionic polymer has to be covalently linked (i.e. grafted) to the pBAE backbone, as it is the case of the polymers of the invention, to achieve such remarkable improvement in the anti-fouling properties.

The excellent anti-fouling properties provided by the polymers of the invention, due to the grafting of the zwitterionic polymer, confer, not only stability to the nanoparticles, but also, protection from the adherence of protein to the optional targeting moieties functionalizing the nanoparticles of the invention. Therefore, the therapeutic efficiency can also be improved. Advantageously, the inventors also found that the covalent binding of the zwitterionic polymer to the pBAE backbone did not negatively affect to the encapsulation efficiency, neither to the suitable size of the nanoparticles to be used as a delivery vehicle.

In particular, it was found that the nanoparticles of the invention had low average size, remarkably lower than 1000 nm, as it is shown in Tables 7-8 below. The above is of relevance because a size below 1000 nm guarantees that the nanoparticles can provide the biologically effect: (a) it is minimized the formation of aggregates, and (b) it is facilitated cell internalization. In addition, small sizes guarantee an appropriate stability when formulated in the form of a pharmaceutical composition and can be easily reproduced.

The administration of nanocarriers or vehicles is usually systemic and performed through parenteral routes. Therefore, nanoparticles get in contact with blood very frequently. As it is shown below, the inventors also determined the compatibility of the polymers of the invention with red blood cells (i.e. erythrocytes), which is a must before driving in vivo studies: if the nanoparticle solution is hypoosmotic, erythrocytes will explode; while hyperosmotic solution produce a shrinkage of erythrocytes.

Surprisingly, it was also found that the polymers of the invention not only extended the life of the nanoparticle, but also, they provided a lower % of haemolysis, even at high doses of active ingredient. This behaviour was not found when the zwitterionic polymer was electrostatically interacting with the pBAE polymer (Table 11 , below).

This means that the covalent grafting of zwitterionic chains into the pBAE backbone confers improved properties to the resulting nanoparticles, which are based on a remarkably stability but also on a remarkably higher security for their use in therapy, without negatively affecting to the encapsulating efficiency or ability to diffuse.

Altogether this means a great advance in the field of pharmaceuticals, especially in the development of suitable pharmaceutical carriers which are highly-efficient encapsulating systems, highly-stable due to a remarkable anti-fouling effect, and safer due to the remarkable low cytotoxicity or significant absence of any haemolytic effect.

Thus, in a first aspect the present invention provides a poly(beta-aminoester) polymer of formula (I) or a pharmaceutically salt thereof: wherein

L3 is independently selected from the group consisting of alkylene, alkenylene, heteroalkylene, heteroalkenylene, arylene, and heteroarylene; or, alternatively at least one of L3 is and T2 is selected from H, alkyl, and wherein LT is independently selected from the group consisting of:

O, S, NR _X , and a bond, wherein R _x is independently selected from the group consisting of hydrogen, halogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, and heteroaryl, and the remaining L3 groups are independently selected from the group consisting of alkylene, alkenylene, heteroalkylene, heteroalkenylene, arylene, and heteroarylene;

L4 is independently selected from the group consisting of formula (i) and (ii)

Ls is independently selected from the group consisting of alkylene, alkenylene, heteroalkylene, heteroalkenylene, arylene, and heteroarylene; each R3 is independently selected from the group consisting of hydrogen, halogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, heteroaryl, polyalkylene glycols, a moiety having a hydroxyl group (-OH), a moiety having an amine group (-NH2), and a moiety having a zwitterionic polymer, wherein:

- said polyalkylene glycol is either bound directly to the nitrogen atom to which R3 is attached or bound to the nitrogen atom to which R3 is attached via a linker moiety, wherein said linker moiety is an alkylene, cycloalkylene, alkenylene, cycloalkenylene, heteroalkylene, heterocycloalkylene, arylene or heteroarylene group;

- the moiety having a hydroxyl group (-OH) is selected from the group consisting of -(CH ₂ ) _P OH, and -(CH2)2(OCH ₂ CH ₂ )qOH;

- the moiety having an amino group (-NH ₂ ) is selected from the group consisting of -(CH ₂ ) _P NH ₂ , and -(CH ₂ ) ₂ (OCH ₂ CH ₂ ) _q NH ₂ ; and

- the moiety having a zwitterionic polymer is one of formula (II) wherein R ₄ represents R’ ₄ -C(=S)-S-; R’ ₄ represents an aryl, heteroaryl, alkyl, -SRs, -NReR? or -ORs; Rs represents aryl, heteroaryl or alkyl; Re and R7 are the same or different and represent hydrogen, halogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, and heteroaryl; Rs represents hydrogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, and heteroaryl; and R9 is a linker which binds the PZ to the -N- of the substituent of formula (i) or (ii);

PZ represents a zwitterionic polymer comprising one or more zwitterionic monomers; provided that at least one of the R3 is a moiety having a zwitterionic polymer as defined above; n is an integer from 5 to 1000, p is an integer from 1 to 20, q is an integer from 1 to 10, and r is an integer from 0 to 1 ; each Li and L2 is independently selected from the group consisting of:

O, S, NR _X , and a bond; wherein R _x is independently selected from the group consisting of hydrogen, halogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, and heteroaryl; and R3 and L5 being as defined above; and

R1, R2 and R _T are independently selected from an oligopeptide and R _y ,

R _y being selected from the group consisting of hydrogen, halogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, and heteroaryl; and provided that at least one of R1, R2 and RT is an oligopeptide.

In a second aspect the present invention provides a process for preparing a polymer as defined in the first aspect of the invention, the process comprising the step of performing a reversible addition-fragmentation chain transfer (RAFT) polymerization of a polymer of formula (Ibis) the process comprising the step of performing the RAFT polymerization of a polymer of formula (Ibis) with one or more zwitterionic monomers, in the presence of a radical initiator, wherein l_3 is independently selected from the group consisting of alkylene, alkenylene, heteroalkylene, heteroalkenylene, arylene, and heteroarylene; or, alternatively at least one of l_3 is Ti’ T ₂ ’ wherein LT’ is independently selected from the group consisting of:

O, S, NR _X , and a bond, wherein R _x is independently selected from the group consisting of hydrogen, halogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, and heteroaryl, and the remaining L’3 groups are independently selected at each occurrence from the group consisting of alkylene, alkenylene, heteroalkylene, heteroalkenylene, arylene, and heteroarylene;

L’4 is independently selected from the group consisting of

L’s is independently selected from the group consisting of alkylene, alkenylene, heteroalkylene, heteroalkenylene, arylene, and heteroarylene; each R3’ is independently selected from the group consisting of hydrogen, halogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, heteroaryl, polyalkylene glycols, a moiety having a hydroxyl group (-OH), a moiety having an amine group (-NH2), and a moiety having a chain transfer agent (CTA); provided that at least one or more of the R3’ are moieties having a CTA, wherein:

- said polyalkylene glycol is either bound directly to the nitrogen atom to which R3 is attached or bound to the nitrogen atom to which R3 is attached via a linker moiety, wherein said linker moiety is an alkylene, cycloalkylene, alkenylene, cycloalkenylene, heteroalkylene, heterocycloalkylene, arylene or heteroarylene group;

- the moiety having a hydroxyl group (-OH) is selected from the group consisting of -(CH ₂ ) _P OH, and -(CH2)2(OCH ₂ CH ₂ )qOH;

- the moiety having an amino group (-NH ₂ ) is selected from the group consisting of -(CH ₂ ) _P NH ₂ , -(CH ₂ ) ₂ (OCH ₂ CH ₂ ) _q NH ₂ ;

- the moiety having a CTA corresponds to a thio-based compound of formula (IV) wherein

Z represents an aryl, heteroaryl, alkyl, -SR’s, -NR’eR’? or -OR’s;

R’s represents aryl, heteroaryl or alkyl;

R’e and R’7 are the same or different and represent hydrogen, halogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, and heteroaryl;

R’s represents hydrogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, and heteroaryl; and R’g is a linker which binds the -S- of the thio-based compound to the -N- of the group of formula (i) or (ii); n is an integer from 5 to 1000, p is an integer from 1 to 20, q is an integer from 1 to 10, each Li and l_2 is independently selected from the group consisting of:

O, S, NR _X , and a bond; wherein R _x is independently selected from the group consisting of hydrogen, halogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, and heteroaryl; and R3’ and L’s being as defined above; and

R1, R2 and R _T are independently selected from an oligopeptide and R _y ,

R _y being selected from the group consisting of hydrogen, halogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, and heteroaryl; and provided that at least one of R1, R2 and RT is an oligopeptide.

In a third aspect the present invention provides a polymer of formula (I) obtainable by the process of the second aspect of the invention.

In a fourth aspect the present invention provides a nanoparticle, comprising one or more polymers of formula (I) as defined in the first and/or third aspects of the invention.

In a fifth aspect the present invention provides a pharmaceutical composition comprising (a) a therapeutically effective amount of the nanoparticle, as defined in the fourth aspect of the invention, comprising an active ingredient, and (b) one or more pharmaceutically acceptable excipients or carriers.

The surprising properties conferred by the polymers of the invention make them also suitable for use as a coating of any other delivery system to improve the stability (antifouling effect) as well-as as its safety.

In a sixth aspect the present invention provides the use of the polymer of formula (I) as defined in the first or third aspect of the invention, alone or in combination with one or more polymers of formula (Iter) as defined below, as a coating, particularly as anti-fouling coating.

In a seventh aspect the present invention provides a delivery system comprising an external coating comprising the polymer (I) as defined in the first or third aspect of the invention and, optionally, one or more polymers of formula (Iter) as defined below.

In an eighth aspect the present invention provides the use of the polymer as defined in the first or thrid aspect of the invention, alone or in combination with one or more polymers of formula (Iter) as defined below, as a delivery carrier.

In a ninth aspect the present invention provides the use of the polymer as defined in the first or third aspect of the invention, alone or in combination with one or more polymers of formula (Iter) as defined below, as an encapsulating agent.

In a tenth aspect the present invention provides the pharmaceutical composition as defined in the fifth aspect of the invention or the nanoparticle as defined in the fourth aspect of the invention or the coated viral particle as defined in the seventh aspect of the invention for use in therapy.

In an eleventh aspect the present invention provides a method of encapsulating an agent in a matrix of one or more polymers of formula (I) as defined in the first or third aspect of the invention, optionally in combination with one or more polymers of formula (Iter) as defined below, the method comprising steps of: providing an active agent as defined above; providing the polymer (s); and contacting the agent and the polymer under suitable conditions to form nanoparticles.

In a last aspect the present invention provides a method for the preparation of a coating viral particle as defined in the seventh aspect of the invention, the method comprising the step of mixing the viral particle with the polymer(s) as defined in the first aspect of the invention, optionally in combination with one or more polymers of formula (Iter) as defined below.

Detailed description of the invention

All terms as used herein in this application, unless otherwise stated, shall be understood in their ordinary meaning as known in the art. Other more specific definitions terms as used in the present application are as set forth below and are intended to apply uniformly throughout the specification and claims unless an otherwise expressly set out definition provides a broader definition.

It is noted that, as used in this specification and the appended claims, the singular forms ”a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise.

For the purposes of the present invention, any ranges given include both the lower and the upper end-points of the range.

The present invention provides in a first aspect, pBAE polymers covalently modified with zwitterionic polymers.

In one embodiment of the first aspect of the invention, L3 is independently selected from the group consisting of alkylene, alkenylene, heteroalkylene, heteroalkenylene, arylene, and heteroarylene; particularly L3 represents alkylene.

In another embodiment of the first aspect of the invention, optionally in combination with any of the embodiments provided above or below, L4 represents

In another embodiment of the first aspect of the invention, optionally in combination with any of the embodiments provided above or below, at least a 5% of the R3 groups in the polymer of formula (I) represents a moiety having a zwitterionic polymer of formula (II) as defined in any of the above clauses; particularly at least a 30%, 40%, 50%, 60%, 70%, 80% or 90% of the R3 groups in the polymer of formula (I) represents a moiety having a zwitterionic polymer of formula (II) as defined in any of the above clauses; particularly at least a 40% of the R3 groups in the polymer of formula (I) represents a moiety having a zwitterionic polymer of formula (II) as defined in any of the above clauses; particularly from 30 to 80%; particularly from 40 to 70% of the R3 groups in the polymer of formula (I) represents a moiety having a zwitterionic polymer of formula (II) as defined in any of the above clauses.

In another embodiment of the first aspect of the invention, optionally in combination with any of the embodiments provided above or below, at least a 5% of the R3 groups in the polymer of formula (I) represents a moiety having a zwitterionic polymer of formula (II) as defined in above and the remaining R3 groups represent a moiety having an amino group as defined above; particularly at least a 30%, 40%, 50%, 60%, 70%, 80% or 90% of the R3 groups in the polymer of formula (I) represents a moiety having a zwitterionic polymer of formula (II) as defined in above and the remaining R3 groups represent a moiety having an amino group as defined above; particularly at least a 40% of the R3 groups in the polymer of formula (I) represents a moiety having a zwitterionic polymer of formula (II) as defined above and the remaining R3 groups represent a moiety having an amino group as defined above; particularly from 30 to 80%; particularly from 40 to 70% of the R3 groups in the polymer of formula (I) represents a moiety having a zwitterionic polymer of formula (II) as defined above and the remaining R3 groups represent a moiety having an amino group as defined above.

The % of R3 groups in the polymer of formula (I) representing a moiety having a zwitterionic polymer of formula (II) is calculated dividing the number of R3 groups meaning the moiety of formula (II) by the total number of groups R3 forming part of the polymer of formula (I). The number of R3 groups is determined by 1 H-NMR, integrating the signal(s) of carbon atom of R3 located more distal from pBAE backbone.

In another embodiment of the first aspect of the invention, optionally in combination with any of the embodiments provided above or below, the remaining R3 groups forming part of the OM-PZ-pBAE, which are other than a moiety having a zwitterionic polymer, are the same or different and are selected from: -(CH2) _P OH, -(CH2)2(OCH2CH2) _q OH, -(CH2) _P NH2, and -(CH ₂ )2(OCH ₂ CH2)qNH2, wherein p and q are as defined above. In one embodiment, optionally in combination with any of the embodiments provided above or below, p and q represents from 1 to 10.

In another embodiment of the first aspect of the invention, optionally in combination with any of the embodiments provided above or below the Li and/or L2 linking the or each oligopeptide to the polymer is a bond.

In another embodiment of the first aspect of the invention, optionally in combination with any of the embodiments provided above or below, Ry is selected from a group consisting of hydrogen, — (CH ₂ ) _m NH ₂ , — (CH ₂ )mNHMe, — (CH ₂ )mOH, — (CH ₂ )mCH ₃ , — (CH ₂ ) ₂ (OCH ₂ CH ₂ )mNH ₂ , — (CH ₂ ) ₂ (OCH ₂ CH ₂ )mOH or — (CH ₂ ) ₂ (OCH ₂ CH ₂ )mCH ₃ wherein m is an integer from 1 to 20.

In another embodiment of the first aspect of the invention, optionally in combination with any of the embodiments provided above or below, the polymer of formula (I) is one, wherein:

R1 and R2 are oligopeptides as defined below, particularly negatively charged olipeptides at pH 7;

Li and L2 represent a bond;

L3 represents alkylene;

L4 represents a substituent of formula (i), wherein:

- at least a 5% of the R3 groups represent a moiety having a zwitterionic polymer of formula (II) as defined above; R’4 being selected from alkyl, aryl, -S-alkyl, and -S- aryl; R9 representing -alkylene-C(O)-O-alkylene-, wherein the alkylene is optionally substituted; and PZ is as defined in any of the embodiments of the first aspect of the invention provided below; and

- the remaining R3 groups, which are other than the moiety of formula (II), are the same or different and are selected from -(CH2) _P OH, -(CH2)2(OCH2CH2) _q OH, -(CH ₂ ) _P NH ₂ , and -(CH ₂ )2(OCH ₂ CH2)qNH2.

The expression “Li represent a bond” means that the polymer of formula (I) is one wherein: polymer chain

The expression “L2 represent a bond” means that the polymer of formula (I) is one wherein: polymer chain

Chemical groups

The term "halogen" (or "halo") includes fluorine, chlorine, bromine and iodine.

The term "alkyl" includes monovalent, straight or branched, saturated, acyclic hydrocarbyl groups. Alkyl is suitably Ci-walkyl, or Ci-ealkyl, or Ci-4alkyl, such as methyl, ethyl, n-propyl, i-propyl or t-butyl groups. Alkyl may be substituted.

The term "cycloalkyl" includes monovalent, saturated, cyclic hydrocarbyl groups. Cycloalkyl is suitably Ca-wcycloalkyl, or Ca-ecycloalkyl such as cyclopentyl and cyclohexyl. Cycloalkyl may be substituted.

The term "alkoxy" means alkyl-O-.

The term "alkylamino" means alkyl-NH-.

The term "alkenyl" includes monovalent, straight or branched, unsaturated, acyclic hydrocarbyl groups having at least one carbon-carbon double bond and, suitably, no carbon-carbon triple bonds. Alkenyl is suitably C2-walkenyl, or C2-6alkenyl, or C2-4alkenyl. Alkenyl may be substituted.

The term "cycloalkenyl" includes monovalent, partially unsaturated, cyclic hydrocarbyl groups having at least one carbon-carbon double bond and, suitably, no carbon-carbon triple bonds. Cycloalkenyl is suitably Ca-wcycloalkenyl, or Cs-wcycloalkenyl, e.g. cyclohexenyl or benzocyclohexyl. Cycloalkenyl may be substituted. The term "alkynyl" includes monovalent, straight or branched, unsaturated, acyclic hydrocarbyl groups having at least one carbon-carbon triple bond and, suitably, no carbon-carbon double bonds. Alkynyl is suitably C2-ioalkynyl, or C2-ealkynyl, or C2-4alkynyl. Alkynyl may be substituted.

The term "alkylene" includes divalent, straight or branched, saturated, acyclic hydrocarbyl groups. Alkylene is suitably Ci-walkylene, or Ci-ealkylene, or C^alkylene, such as methylene, ethylene, n-propylene, i-propylene or t-butylene groups. Alkylene may be substituted.

The term "alkenylene" includes divalent, straight or branched, unsaturated, acyclic hydrocarbyl groups having at least one carbon-carbon double bond and, suitably, no carbon-carbon triple bonds. Alkenylene is suitably C2-ioalkenylene, or C2-6alkenylene, or C2-4alkenylene. Alkenylene may be substituted.

The term "heteroalkyl" includes alkyl groups, for example, Cvesalkyl groups, Ci-i?alkyl groups or Ci-walkyl groups, in which up to twenty carbon atoms, or up to ten carbon atoms, or up to two carbon atoms, or one carbon atom, are each replaced independently by O, S(O)t or N, provided at least one of the alkyl carbon atoms remains. The heteroalkyl group may be C-linked or hetero-linked, i.e. it may be linked to the remainder of the molecule through a carbon atom or through O, S(O)t or N, wherein t is defined below. Heteroalkyl may be substituted.

The term "heterocycloalkyl" includes cycloalkyl groups in which up to ten carbon atoms, or up to two carbon atoms, or one carbon atom, are each replaced independently by O, S(O)t or N, provided at least one of the cycloalkyl carbon atoms remains. Examples of heterocycloalkyl groups include oxiranyl, thiaranyl, aziridinyl, oxetanyl, thiatanyl, azetidinyl, tetrahydrofuranyl, tetrahydrothiophenyl, pyrrolidinyl, tetrahydropyranyl, tetrahydrothiopyranyl, piperidinyl, 1 ,4-dioxanyl, 1 ,4-oxathianyl, morpholinyl, 1 ,4-dithianyl, piperazinyl, 1 ,4-azathianyl, oxepanyl, thiepanyl, azepanyl, 1 ,4-dioxepanyl, 1 ,4- oxathiepanyl, 1 ,4-oxaazepanyl, 1 ,4-dithiepanyl, 1 ,4-thieazepanyl and 1 ,4-diazepanyl. The heterocycloalkyl group may be C-linked or N-linked, i.e. it may be linked to the remainder of the molecule through a carbon atom or through a nitrogen atom. Heterocycloalkyl may be substituted.

The term "heteroalkenyl" includes alkenyl groups, for example, Ci-6salkenyl groups, Ci- alkenyl groups or Ci-walkenyl groups, in which up to twenty carbon atoms, or up to ten carbon atoms, or up to two carbon atoms, or one carbon atom, are each replaced independently by O, S(O)t or N, provided at least one of the alkenyl carbon atoms remains. The heteroalkenyl group may be C-linked or hetero-linked, i.e. it may be linked to the remainder of the molecule through a carbon atom or through O, S(O)t or N. Heteralkenyl may be substituted.

The term "heterocycloalkenyl" includes cycloalkenyl groups in which up to three carbon atoms, or up to two carbon atoms, or one carbon atom, are each replaced independently by O, S(O)t or N, provided at least one of the cycloalkenyl carbon atoms remains. Examples of heterocycloalkenyl groups include 3,4-dihydro-2H-pyranyl, 5-6-dihydro-2H- pyranyl, 2H-pyranyl, 1 ,2,3,4-tetrahydropyridinyl and 1 ,2,5,6-tetrahydropyridinyl. The heterocycloalkenyl group may be C-linked or N-linked, i.e. it may be linked to the remainder of the molecule through a carbon atom or through a nitrogen atom. Heterocycloalkenyl may be substituted.

The term "heteroal kynyl" includes alkynyl groups, for example, Ci-esalkynyl groups, Ci- nalkynyl groups or Ci-walkynyl groups, in which up to twenty carbon atoms, or in which up to ten carbon atoms, or up to two carbon atoms, or one carbon atom, are each replaced independently by O, S(O)t or N, provided at least one of the alkynyl carbon atoms remains. The heteroalkynyl group may be C-linked or hetero-linked, i.e. it may be linked to the remainder of the molecule through a carbon atom or through O, S(O)t or N. Heteroalkynyl may be substituted.

The term "heteroalkylene" includes alkylene groups, for example, Ci-6salkylene groups, Ci- i ₇ alkylene groups or Ci-walkylene groups, in which up to twenty carbon atoms, or in which up to ten carbon atoms, or up to two carbon atoms, or one carbon atom, are each replaced independently by O, S(O)t or N, provided at least one of the alkylene carbon atoms remains. Heteroalkynylene may be substituted.

The term "heteroalkenylene" includes alkenylene groups, for example, Ci-6salkenylene groups, Cwalkenylene groups or Ci-walkenylene groups, in which up to twenty carbon atoms, or in which up to ten carbon atoms, or up to two carbon atoms, or one carbon atom, are each replaced independently by O, S(O)t or N, provided at least one of the alkenylene carbon atoms remains. Heteroalkenylene may be substituted.

The term "aryl" includes monovalent, aromatic, cyclic hydrocarbyl groups, such as phenyl or naphthyl (e.g. 1 -naphthyl or 2-naphthyl). In general, the aryl groups may be monocyclic or polycyclic fused ring aromatic groups. Preferred aryl are Ce-C^aryl. Aryl may be substituted.

Other examples of aryl groups are monovalent derivatives of aceanthrylene, acenaphthylene, acephenanthrylene, anthracene, azulene, chrysene, coronene, fluoranthene, fluorene, as-indacene, s-indacene, indene, naphthalene, ovalene, perylene, phenalene, phenanthrene, picene, pleiadene, pyrene, pyranthrene and rubicene.

The term "arylalkyl" means alkyl substituted with an aryl group, e.g. benzyl. The term “arylene” means a divalent, aromatic, cyclic hydrocarbyl groups, such as phenylene or naphthylene (e.g. 1 -naphthylene or 2-naphthylene). In general, the arylene groups may be monocyclic or polycyclic fused ring aromatic groups. Preferred arylenes are Ce-C^arylene. Arylene may be substituted.

The term "heteroaryl" includes aryl groups in which one or more carbon atoms are each replaced by heteroatoms independently selected from O, S, N, and NR ^N , where R ^N is defined below (and in one embodiment is H or alkyl (e.g. Ci-ealkyl)). Heteroaryl may be substituted.

In general, the heteroaryl groups may be monocyclic or polycyclic (e.g. bicyclic) fused ring heteroaromatic groups. Typically, heteroaryl groups contain 5-14 ring members (preferably 5-10 members) wherein 1 , 2, 3 or 4 ring members are independently selected from O, S, N, and NR ^N . A heteroaryl group is suitably a 5, 6, 9 or 10 membered, e.g. 5- membered monocyclic, 6-membered monocyclic, 9-membered fused-ring bicyclic or 10- membered fused-ring bicyclic.

Monocyclic heteroaromatic groups include heteroaromatic groups containing 5-6 ring members wherein 1 , 2, 3 or 4 ring members are independently selected from O, S, N, and NR ^N .

5-Membered monocyclic heteroaryl groups may contain 1 ring member which is an -NR ^N - group, an -O- atom or an -S- atom and, optionally, 1-3 ring members (e.g. 1 or 2 ring members) which are =N- atoms (where the remainder of the 5 ring members are carbon atoms).

Examples of 5-membered monocyclic heteroaryl groups are pyrrolyl, furanyl, thiophenyl, pyrazolyl, imidazolyl, isoxazolyl, oxazolyl, isothiazolyl, thiazolyl, 1 ,2,3 triazolyl, 1 ,2,4 triazolyl, 1 ,2,3 oxadiazolyl, 1 ,2,4 oxadiazolyl, 1 ,2,5 oxadiazolyl, 1 ,3,4 oxadiazolyl, 1 ,3,4 thiadiazolyl, pyridyl, pyrimidinyl, pyridazinyl, pyrazinyl, 1 ,3,5 triazinyl, 1 ,2,4 triazinyl, 1 ,2,3 triazinyl and tetrazolyl.

Examples of 6-membered monocyclic heteroaryl groups are pyridinyl, pyridazinyl, pyrimidinyl and pyrazinyl.

6-Membered monocyclic heteroaryl groups may contain 1 or 2 ring members which are =N- atoms (where the remainder of the 6 ring members are carbon atoms).

Bicyclic heteroaromatic groups include fused-ring heteroaromatic groups containing 9-14 ring members wherein 1 , 2, 3, 4 or more ring members are independently selected from O, S, N, and NR ^N .

9-Membered bicyclic heteroaryl groups may contain 1 ring member which is an -NR ^N - group, an-O- atom or an -S- atom and, optionally, 1-3 ring members (e.g. 1 or 2 ring members) which are =N- atoms (where the remainder of the 9 ring members are carbon atoms).

Examples of 9-membered fused-ring bicyclic heteroaryl groups are benzofuranyl, benzothiophenyl, indolyl, benzimidazolyl, indazolyl, benzotriazolyl, pyrrolo[2,3-b]pyridinyl, pyrrolo[2,3-c]pyridinyl, pyrrolo[3,2-c]pyridinyl, pyrrolo[3,2-b]pyridinyl, imidazo[4,5- b]pyridinyl, imidazo[4,5-c]pyridinyl, pyrazolo[4,3-d]pyridinyl, pyrazolo[4,3-c]pyridinyl, pyrazolo[3,4-c]pyridinyl, pyrazolo[3,4-b]pyridinyl, isoindolyl, indazolyl, purinyl, indolininyl, imidazo[1 ,2-a]pyridinyl, imidazo[1 ,5-a]pyridinyl, pyrazolo[1 ,2-a]pyridinyl, pyrrolo[1 ,2- b]pyridazinyl and imidazo[1 ,2-c]pyrimidinyl.

10-Membered bicyclic heteroaryl groups may contain 1-3 ring members which are =N- atoms (where the remainder of the 10 ring members are carbon atoms).

Examples of 10-membered fused-ring bicyclic heteroaryl groups are quinolinyl, isoquinolinyl, cinnolinyl, quinazolinyl, quinoxalinyl, phthalazinyl, 1 ,6-naphthyridinyl, 1 ,7- naphthyridinyl, 1 ,8-naphthyridinyl, 1 ,5-naphthyridinyl, 2,6-naphthyridinyl, 2,7- naphthyridinyl, pyrido[3,2-d]pyrimidinyl, pyrido[4,3-d]pyrimidinyl, pyrido[3,4-d]pyrimidinyl, pyrido[2,3-d]pyrimidinyl, pyrido[2,3-b]pyrazinyl, pyrido[3,4-b]pyrazinyl, pyrimido[5,4- d]pyrimidinyl, pyrazino[2,3-b]pyrazinyl and pyrimido[4,5-d]pyrimidinyl.

The term “heteroarylene” means divalent aryl groups in which one or more carbon atoms are each replaced by heteroatoms independently selected from O, S, N, and NR ^N , where R ^N is defined below (and in one embodiment is H or alkyl (e.g. Ci-ealkyl)). Heteroarylene may be substituted.

The term "heteroarylalkyl" means alkyl substituted with a heteroaryl group.

Examples of acyl groups include alkyl-C(=O)-, cycloalkyl-C(=O)-, alkenyl-C(=O)-, cycloalkenyl-C(=O)-, heteroalkyl-C(=O)-, heterocycloalkyl-C(=O)-, aryl-C(=O)- or heteroaryl-C(=O)-, in particular, alkyl-C(=O)- and aryl-C(=O)-.

Unless indicated explicitly otherwise, where combinations of groups are referred to herein as one moiety, e.g. arylalkyl, the last mentioned group contains the atom by which the moiety is attached to the rest of the molecule.

Where reference is made to a carbon atom of an alkyl group or other group being replaced by O, S(O)t or N, what is intended is that:

-CH= is replaced by -N=;

=C-H is replaced by =N; or -CH2- is replaced by -0-, -S(O)t- or -NR ^N -.

By way of clarification, in relation to the above mentioned heteroatom containing groups (such as heteroalkyl etc.), where a numerical of carbon atoms is given, for instance C3- eheteroalkyl, what is intended is a group based on Cs-ealkyl in which one of more of the 3- 6 chain carbon atoms is replaced by O, S(O)t or N. Accordingly, a Cs-eheteroalkyl group, for example, will contain less than 3-6 chain carbon atoms.

Where mentioned above, R ^N is H, alkyl, cycloalkyl, aryl, heteroaryl, -C(O)-alkyl, -C(O)-aryl, -C(O)-heteroaryl, -S(O)t-alkyl, -S(O)t-aryl or -S(O)t-heteroaryl. R ^N may, in particular, be H, alkyl (e.g. Ci-ealkyl) or cycloalkyl (e.g. Cs-ecycloalkyl).

Where mentioned above, t is independently 0, 1 or 2, for example 2. Typically, t is 0.

Where a group has at least 2 positions which may be substituted, the group may be substituted by both ends of an alkylene or heteroalkylene chain to form a cyclic moiety.

Optionally substituted groups (e.g. alkyl, cycloalkyl, alkoxy, alkenyl, cycloalkenyl, alkynyl, alkylene, alkenylene, heteroalkyl, heterocycloalkyl, heteroalkenyl, heterocycloalkenyl, heteroalkynyl, heteroalkylene, heteroalkenylene, aryl, arylalkyl, arylheteroalkyl, heteroaryl, heteroarylalkyl or heteroarylheteroalkyl groups etc.) may be substituted or unsubstituted, or may be unsubstituted. Typically, substitution involves the notional replacement of a hydrogen atom with a substituent group, or two hydrogen atoms in the case of substitution by =0.

Where substituted, there will generally be 1 to 3 substituents, or 1 or 2 substituents, or 1 substituent.

The optional substituent(s) is/are independently halogen, trihalomethyl, trihaloethyl,-OH, - NH ₂ , -NO ₂ , -CN, -N ⁺ (Ci. ₆ alkyl) ₂ O-, -CO ₂ H, -CO ₂ Ci. ₆ alkyl, -SO3H, -SOCi- ₆ alkyl, -SO2C1- ₆ alkyl, -SO ₃ Ci- ₆ alkyl, -OC(=O)OC _1-6 alkyl, -C(=O)H, -C(=O)Ci- ₆ alkyl, -OC(=O)Ci. ₆ alky), =0, -NH(Ci- ₆ alkyl), -N(Ci- ₆ alkyl) ₂ , -C(=O)NH ₂ , -C(=O)N(Ci- ₆ alkyl) ₂ , -N(Ci- ₆ alkyl)C(=O)O(Ci- ₆ alkyl), -N(Ci-6alkyl)C(=O)N(Ci- ₆ alkyl) ₂ , -OC(=O)N(Ci- ₆ alkyl) ₂ , -N(Ci-6alkyl)C(=O)C _1-6 alkyl, - C(=S)N(Ci- ₆ alkyl) ₂ , -N(C ₁ -6alkyl)C(=S)Ci- ₆ alkyl, -SO ₂ N(Ci- ₆ alkyl)2, -N(Ci-6alkyl)SO ₂ Ci- ₆ alkyl, -N(Ci-6alkyl)C(=S)N(Ci-6alkyl)2, -N(Ci.6alkyl)SO2N(Ci.6alkyl) ₂ , -Ci-ealkyl, -Ci-eheteroalkyl, - Cs-ecycloalkyl, -Cs-eheterocycloalkyl, -C2-ealkenyl, -C2-eheteroalk enyl, -Cs-ecycloalkenyl, - Cs-eheterocycloalkenyl, -C2-ealkynyl, -C2-eheteroalkynyl, -Z ^u -Ci-ealkyl,-Z ^u - Cs-ecycloalkyl, - Z ^u -C2-ealkenyl, -Z ^u -C3-ecycloalkenyl or -Z ^u -C2-ealkynyl, wherein Z ^u is independently O, S, NH or N(Ci- ₆ alkyl).

In another embodiment, the optional substituent(s) is/are independently halogen, trihalomethyl, trihaloethyl, -NO2, -CN, -N ⁺ (Ci-ealkyl)2O ^_ , -CO2H, -SO3H, -SOCi-ealkyl, - SO ₂ Ci- ₆ alkyl, -C(=O)H, -C(=O)Ci- ₆ alkyl, =0, -N(Ci- ₆ alkyl) ₂ , -C(=O)NH ₂ , -Ci- ₆ alkyl, -C ₃ . ₆ cycloalkyl, -Cs-eheterocycloalkyl, -Z ^u Ci-ealkyl or-z ^u -C3-6cycloalkyl, wherein Z ^u is defined above.

In another embodiment, the optional substituent(s) is/are independently halogen, trihalomethyl, -NO ₂ , -CN, -CO ₂ H, -C(=O)Ci- ₆ alkyl, =0, -N(Ci. ₆ alkyl) ₂ , -C(=O)NH ₂ , -Ci- ₆ alkyl, -Ca-ecycloalkyl, -Cs-eheterocycloalkyl, -Z ^u Ci-6alkyl or-Z ^u -C3-6cycloalkyl, wherein Z ^u is defined above.

In another embodiment, the optional substituent(s) is/are independently halogen, -NO ₂ , - CN, -CO ₂ H, =0, -N(Ci-6alkyl) ₂ , -Ci-ealkyl, -Cs-ecycloalkyl or -Cs-eheterocycloalkyl.

In another embodiment, the optional substituent(s) is/are independently halogen, -OH, NH ₂ , NH(Ci-6alkyl), -N(Ci-6alkyl) ₂ , -Ci-ealkyl, -Cs-ecycloalkyl or -Cs-eheterocycloalkyl.

The term "polyalkylene glycol" (PAG) refers to compounds having the general formula H- [O-C _y H _2y ]x-OH, such as H-[O-CH ₂ -CH ₂ ] _X -OH (polyethylene glycol or PEG) and H-[O- CH(CH3)-CH ₂ ] _X -OH (polypropylene glycol). When found in a compound of the invention the PAG is bound by the bond between a carbon atom and one of the terminal hydroxyl groups e.g. in the case of PEG the substituent would be H-[O-CH ₂ -CH ₂ ] _X -. The polyalkylene glycols used in the compounds of the invention, unless otherwise defined, may have a molecular weight of from 500 to 20,000 g/mol, preferably from 1 ,000 to 10,000 g/mol, more preferably from 2,000 to 5,000 g/mol, more preferably from 2,000 to 3,500 g/mol.

As used herein, the term "polymer of Formula I", “polymer of Formula Ibis”, or “polymer of Formula Iter” include pharmaceutically acceptable derivatives thereof and polymorphs, isomers and isotopically labelled variants thereof.

The term "pharmaceutically acceptable derivative" includes any pharmaceutically acceptable salt, solvate, hydrate or prodrug of a polymer of formula (I), (Ibis), (Iter) or (V). The pharmaceutically acceptable derivatives suitably refers to pharmaceutically acceptable salts, solvates or hydrates of a polymer of formula (I), (Ibis), (Iter) or (V).

As used herein, the term “pharmaceutical acceptable salt” refers to those salts which are, within the scope of sound medical judgment, suitable for use in contact with the tissues of humans and lower animals without undue toxicity, irritation, allergic response and the like, and are commensurate with a reasonable benefit/risk ratio. Pharmaceutical acceptable salts are well known in the art. Examples of pharmaceutical acceptable, nontoxic acid addition salts are salts of an amino group formed with inorganic acids such as hydrochloric acid, hydrobromic acid, phosphoric acid, sulfuric acid and perchloric acid or with organic acids such as acetic acid, trifluoroacetic acid, oxalic acid, maleic acid, tartaric acid, citric acid, succinic acid or malonic acid or by using other methods used in the art such as ion exchange. Other pharmaceutical acceptable salts include adipate, alginate, ascorbate, aspartate, benzenesulfonate, benzoate, bisulphate, borate, butyrate, camphorate, camphorsulfonate, citrate, cyclopentanepropionate, digluconate, dodecylsulphate, ethanesulfonate, formate, fumarate, glucoheptonate, glycerophosphate, gluconate, hemisulphate, heptanoate, hexanoate, hydroiodide, 2-hydroxy- ethanesulfonate, lactobionate, lactate, laurate, lauryl sulphate, malate, maleate, malonate, methanesulfonate, 2-naphthalenesulfonate, nicotinate, nitrate, oleate, oxalate, palmitate, pamoate, pectinate, persulphate, 3-phenylpropionate, phosphate, picrate, pivalate, propionate, stearate, succinate, sulphate, tartrate, thiocyanate, p-toluenesulfonate, undecanoate, valerate salts, and the like. Salts derived from appropriate bases include alkali metal, alkaline earth metal, and ammonium. Representative alkali or alkaline earth metal salts include sodium, lithium, potassium, calcium, magnesium, and the like. Further pharmaceutical acceptable salts include, when appropriate, nontoxic ammonium, quaternary ammonium, and amine cations formed using counterions such as halide, hydroxide, carboxylate, sulphate, phosphate, nitrate, lower alkyl sulfonate and aryl sulfonate.

Polymers of formula (I), (Ibis), (Iter) or (V) contain basic, e.g. amino, groups are capable of forming pharmaceutically acceptable salts with acids. Pharmaceutically acceptable acid addition salts of the polymers of formula (I), (Ibis), (Iter) or (V) may include, but are not limited to, those of inorganic acids such as hydrohalic acids (e.g. hydrochloric, hydrobromic and hydroiodic acid), sulfuric acid, nitric acid and phosphoric acids. Pharmaceutically acceptable acid addition salts of the polymers of formula (I), (Ibis), (Iter) or (V) may include, but are not limited to, those of organic acids such as aliphatic, aromatic, carboxylic and sulfonic classes of organic acids, examples of which include: aliphatic monocarboxylic acids such as formic acid, acetic acid, propionic acid or butyric acid; aliphatic hydroxy acids such as lactic acid, citric acid, tartaric acid or malic acid; dicarboxylic acids such as maleic acid or succinic acid; aromatic carboxylic acids such as benzoic acid, p-chlorobenzoic acid, phenylacetic acid, diphenylacetic acid or triphenylacetic acid; aromatic hydroxyl acids such as o-hydroxybenzoic acid, p- hydroxybenzoic acid, 1-hydroxynaphthalene-2-carboxylic acid or 3-hydroxynaphthalene-2- carboxylic acid; and sulfonic acids such as methanesulfonic acid, ethanesulfonic acid or benzenesulfonic acid. Other pharmaceutically acceptable acid addition salts of the polymers of formula (I), (Ibis), (Iter) or (V) include, but are not limited to, those of glycolic acid, glucuronic acid, furoic acid, glutamic acid, anthranilic acid, salicylic acid, mandelic acid, embonic (pamoic) acid, pantothenic acid, stearic acid, sulfanilic acid, algenic acid and galacturonic acid. Wherein the polymer of Formula I, Ibis or Iter comprises a plurality of basic groups, multiple centres may be protonated to provide multiple salts, e.g. di- or tri- salts of compounds of formula (I), (Ibis), (Iter) or (V). For example, a hydrohalic acid salt of a polymer of formula (I), (Ibis), (Iter) or (V) as described herein may be a monohydrohalide, dihydrohalide or trihydrohalide, etc. The salts include, but are not limited to those resulting from addition of any of the acids disclosed above. In one embodiment of the polymer of formula (I), (Ibis), (Iter) or (V), two basic groups form acid addition salts. In a further embodiment, the two addition salt counterions are the same species, e.g. dihydrochloride, dihydrosulphide etc. Typically, the pharmaceutically acceptable salt is a hydrochloride salt, such as a dihydrochloride salt.

Polymers of formula (I), (Ibis), (Iter) or (V) which contain acidic, e.g. carboxyl, groups are capable of forming pharmaceutically acceptable salts with bases. Pharmaceutically acceptable basic salts of the polymers of formula (I), (Ibis), (Iter) or (V) may include, but are not limited to, metal salts such as alkali metal or alkaline earth metal salts (e.g. sodium, potassium, magnesium or calcium salts) and zinc or aluminium salts.

Pharmaceutically acceptable basic salts of the polymers of formula (I), (Ibis), (Iter) or (V) may include, but are not limited to, salts formed with ammonia or pharmaceutically acceptable organic amines or heterocyclic bases such as ethanolamines (e.g. diethanolamine), benzylamines, N-methyl-glucamine, amino acids (e.g. lysine) or pyridine.

Hemisalts of acids and bases may also be formed, e.g. hemisulphate salts.

Pharmaceutically acceptable salts of polymers of Formula I, Ibis or Iter may be prepared by methods well-known in the art.

The polymers of formula (I), (Ibis), (Iter) or (V) may exist in both unsolvated and solvated forms. The term "solvate" includes molecular complexes comprising the polymer and one or more pharmaceutically acceptable solvent molecules such as water or C1-6 alcohols, e.g. ethanol. The term "hydrate" means a "solvate" where the solvent is water.

The polymers may exist in solid states from amorphous through to crystalline forms. All such solid forms are included within the invention.

The polymers may exist in one or more geometrical, optical, enantiomeric, diastereomeric and tautomeric forms, including but not limited to cis- and frans-forms, E- and Z-forms, R-, S- and meso-forms, keto- and enol-forms. All such isomeric forms are included within the invention. The isomeric forms may be in isomerically pure or enriched form, as well as in mixtures of isomers (e.g. racemic or diastereomeric mixtures).

The invention includes pharmaceutically acceptable isotopically-labelled polymers of formula (I), (Ibis), (Iter) or (V) wherein one or more atoms are replaced by atoms having the same atomic number, but an atomic mass or mass number different from the atomic mass or mass number usually found in nature. Examples of isotopes suitable for inclusion in the compounds of the invention include isotopes of hydrogen, such as ² H and ³ H, carbon, such as ¹¹ C, ¹³ C and ¹⁴ C, chlorine, such as ³⁶ CI, fluorine, such as ¹⁸ F, iodine, such as ¹²³ l and ¹²⁵ l, nitrogen, such as ¹³ N and ¹⁵ N, oxygen, such as ¹⁵ 0, ¹⁷ O and ¹⁸ O, phosphorus, such as ³² P, and sulphur, such as ³⁵ S. Certain isotopically-labelled polymers of formula (I), (Ibis), (Iter) or (V), for example, those incorporating a radioactive isotope, are useful in drug and/or substrate tissue distribution studies. The radioactive isotopes ³ H and ¹⁴ C are particularly useful for this purpose in view of their ease of incorporation and ready means of detection.

Substitution with positron emitting isotopes, such as ¹¹ C, ¹⁸ F, ¹⁵ O and ¹³ N, can be useful in Positron Emission Topography (PET) studies for examining substrate receptor occupancy.

Isotopically-labelled polymers of formula (I), (Ibis), (Iter) or (V) can generally be prepared by conventional techniques known to those skilled in the art or by processes analogous to those described herein using an appropriate isotopically-labelled reagent in place of the non-labelled reagent previously employed.

It will be appreciated that the polymers, as described herein, may be substituted with any number of substituents or functional moieties. The terms substituted, whether preceded by the term "optionally" or not, and substituent, as used herein, refer to the ability, as appreciated by one skilled in this art, to change one functional group for another functional group provided that the valency of all atoms is maintained. When more than one position in any given structure may be substituted with more than one substituent selected from a specified group, the substituent may be either the same or different at every position. The substituents may also be further substituted (e.g., an aryl group substituent may have another substituent off it, such as another aryl group, which is further substituted with fluorine at one or more positions).

The term thiohydroxyl or thiol, as used herein, refers to a group of the formula -SH.

Moiety having a zwitterionic polymer

In another embodiment of the first aspect of the invention, optionally in combination with any of the embodiments provided above or below, the moiety having a zwitterionic polymer is one wherein r represents 1.

In another embodiment of the first aspect of the invention, optionally in combination with any of the embodiments provided above or below, the moiety having a zwitterionic polymer is one where R’4 represents an aryl, alkyl or -S-R5, wherein R5 is as defined above; particularly, R’4 represents an aryl, alkyl, -S-aryl or -S-alkyl.

In another embodiment of the first aspect of the invention, optionally in combination with any of the embodiments provided above or below, the moiety having a zwitterionic polymer is one where Rg represents -alkylene-C(O)-O-alkylene-, wherein the alkylene is optionally substituted (as defined in any of the above embodiments); particularly Rg represents -(CR _y R’ _y )-(CH2)s-C(O)-O-(CH2)u-*, wherein Ry and R’y are independently selected from hydrogen, halogen, trihalomethyl, trihaloethyl, -NO2, -CN, -N ⁺ (Ci-6alkyl)2O ^_ , - CO2H, -SO3H, -SOCi- ₆ alkyl, -SO ₂ Ci. ₆ alkyl, -C(=O)H, -C(=O)Ci- ₆ alkyl, =0, -N(Ci- ₆ alkyl) ₂ , - C(=O)NH2, -Ci-ealkyl, -Ca-ecycloalkyl, -Ca-eheterocycloalkyl, -Z ^u Ci-ealkyl or-z ^u -C3-6cycloalkyl, wherein Z ^u is defined above; * indicates the binding of Rg to the -N- of the substituent of formula (i); and s and u are integers from 1 to 20. In another embodiment of the first aspect of the invention, optionally in combination with any of the embodiments provided above or below, Ry and R’y are independently selected from hydrogen, CN, and alkyl. In another embodiment of the first aspect of the invention, optionally in combination with any of the embodiments provided above or below, u represents from 1 to 10. In another embodiment of the first aspect of the invention, optionally in combination with any of the embodiments provided above or below, s represents from 1 to 10.

In another embodiment of the first aspect of the invention, optionally in combination with any of the embodiments provided above or below, the zwitterionic polymer PZ consists of zwitterionic monomers.

In another embodiment of the first aspect of the invention, optionally in combination with any of the embodiments provided above or below, the zwitterionic polymer PZ consists of from 2 to 100 monomers, particularly from 10 to 90 monomers, more particularly from 15 to 80 monomers.

The zwitterionic monomers can be derived from zwitterionic species with proton doning end groups (i.e. proton donors) or accepting end groups (i.e. proton acceptors) which are functionalized with polymerizable olefinic groups. In some cases, a zwitterionic group of a monomer can be formed by a carboxylic acid group, a sulfonic acid group, or a phosphoric acid group. In some cases, a monomer can include a zwitterionic group composed of an acrylate, a methacrylate, an acrylamide, or a methacrylamide. In some cases, a cation of a zwitterionic group can be formed by an (cyclo)aliphatic or aromatic amine, an amidine, or a guanidine. In some cases, a cation of a zwitterionic group can be a quaternary amine. In some cases, the proton donor end groups can be hydroxyl moieties. In some cases, proton accepting end groups can be amino moieties.

In another embodiment of the first aspect of the invention, optionally in combination with any of the embodiments provided above or below, the one or more zwitterionic monomers comprise(s) a positively charged nitrogen group and a negatively charged group distal to the positively charged nitrogen group on the zwitterion such that there is a separation by at least one carbon atom; particularly from 2 to 3 carbon atoms.

In some cases, a cation and an anion of a zwitterionic group can be part of the same pendant group of the monomer unit.

In one embodiment of the first aspect of the invention, optionally in combination with any of the embodiments provided above or below, the one or more zwitterionic monomers are betaine monomers, such as carboxybetaines, phosphobetaines and sulfobetaines. Illustrative non-limitative examples are carboxybetaine methacrylamide (CBMAA); sulfobetaine metacrylate; N,N-dimethyl-N-acryloyloxyethyl-N-(3-sulfopropyl)-ammonium betaine; N,N-dimethyl-N-acrylamidopropyl-N-(2-carboxymethyl)-ammonium betaine; N,N- dimethyl-N-acrylamidopropyl-N-(3-sulfopropyl)-ammonium betaine; N,N-dimethyl-N- acrylamidopropyl-N-(2-carboxymethyl)-ammonium betaine; 2-(methylthio)ethyl methacryloyl-S-(sulfopropyl)-sulfonium betaine; 1 -(3-sulfopropyl)-2-vinylpyridinium betaine; N-(4-sulfobutyl)-N-methyl-N,N-diallylamine ammonium betaine (MDABS); and N,N-diallyl-N-methyl-N-(2-sulfoethyl)ammonium betaine. In one embodiment of the first aspect of the invention, optionally in combination with any of the embodiments provided above or below, the one or more monomers are the same or different and represent sulfobetaines.

Other suitable zwitterionic monomers that may be used to form zwitterionic include, but are not limited to, 2-Methacryloyloxyethyl phosphorylcholine; [3- (Methacryloylamino)propyl]dimethyl(3-sulfopropyl)ammonium hydroxide inner salt (also known as 3-(dimethyl{3-[(2-methylacryloyl)amino]propyl}ammonio)propan e-1 -sulfonate), [2-(Methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (also known as dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]-(3-sulfopropyl)a zanium); 2-[(2- acryloylethyl)dimethylammonio]ethyl 2-methyl phosphate; 2-(acryloyloxyethyl)-2'- (trimethylammonium)ethyl phosphate; [(2-acryloylethyl)dimethylammonio]methyl phosphonic acid; 2-methacryloyloxyethyl phosphorylcholine (MPC); 2-[(3- acrylamidopropyl)dimethylammonio]ethyl 2'-isopropyl phosphate (AAPI); 1 -vinyl-3-(3- sulfopropyl)imidazolium hydroxide; and (2-acryloxyethyl)carboxymethyl methylsulfonium chloride as well as any derivative, salt, copolymer and combinations thereof.

In one embodiment of the first aspect of the invention, optionally in combination with any of the embodiments provided above or below, the zwitterionic polymer PZ is a homopolymer, which means that it is composed by the same zwitterionic monomer. In an alternative embodiment of the first aspect of the invention, optionally in combination with any of the embodiments provided above or below, the zwitterionic polymer PZ is a heteropolymer, which means that it is composed of two or more different zwitterionic monomers, creating random-, block-, or alternating-copolymer systems. In some cases, zwitterionic monomers can be used to prepare linear architectures, combs, stars, brushes, hyperbranched/arborescent, and crosslinked gel systems may also be used. The length of the graft and density of the graft chains can be optimized.

Oligopeptide

In one embodiment of the first aspect of the invention, optionally in combination with any of the embodiments provided above or below, Ri and R2 are both oligopeptides.

In another embodiment of the first aspect of the invention, optionally in combination with any of the embodiments provided above or below, R1 and R2 represent the same oligopeptide.

According to the present invention, an "oligopeptide" comprises a string of at least three amino acids linked together by peptide bonds. Such peptides can contain only natural amino acids, although non-natural amino acids (i.e. , compounds that do not occur in nature but that can be incorporated into a polypeptide chain) and/or amino acid analogues as are known in the art may alternatively be employed. Also, one or more of the amino acids in such peptides may be modified, for example, by the addition of a chemical entity such as a carbohydrate group, a phosphate group, a farnesyl group, an isofarnesyl group, a fatty acid group, or a linker for conjugation, functionalization, or other modification, etc.

In one embodiment of the first aspect of the invention, optionally in combination with any of the embodiments provided above or below, the oligopeptides in the polymers defined herein typically comprise from 3 to 20 amino acid residues, particularly from 3 to 10 amino acid residues, more particularly from 3 to 6 amino acid residues. Alternatively, the oligopeptides in the polymers defined herein may comprise from 4 to 20 amino acid residues, particularly from 4 to 10 amino acid residues, more particularly from 4 to 6 amino acid residues.

In one embodiment of the first aspect of the invention, optionally in combination with any of the embodiments provided above or below, the or each oligopeptide may be hydrophobic. The or each oligopeptide may comprise naturally occurring amino acids that are hydrophobic such as valine, leucine, isoleucine, methionine, tryptophan, phenylalanine, cysteine, tyrosine and alanine; in particular, the or each oligopeptide may comprise valine, leucine, isoleucine, methionine, tryptophan and phenylalanine.

In another embodiment of the first aspect of the invention, optionally in combination with any of the embodiments provided above or below, the or each oligopeptide may be hydrophilic. The or each oligopeptide may comprise naturally occurring amino acids that are hydrophilic such as serine, threonine, cysteine, asparagine and glutamine, and may further comprise naturally occurring amino acids that are charged at pH7. In another embodiment of the first aspect of the invention, optionally in combination with any of the embodiments provided above or below, the or each oligopeptide has a net positive charge at pH 7. The or each oligopeptide may comprise naturally occurring amino acids that are positively charged at pH 7, that is, lysine, arginine and histidine. In one embodiment of the first aspect of the invention, optionally in combination with any of the embodiments provided above or below, the or each oligopeptide consists of homooligopeptides consisting of naturally occurring amino acids that are positively charged at pH 7, that is, lysine, arginine and/or histidine. For example, the or each oligopeptide may be selected from the group consisting of polylysine, polyarginine, and polyhistidine, each of which may be terminated with cysteine. I

In another embodiment of the first aspect of the invention, optionally in combination with any of the embodiments provided above or below, the or each oligopeptide is a compound of Formula III: wherein p is an integer from 2 to 19, typically from 3 to 9 or from 3 to 5, and wherein R _a is selected at each occurrence from the group consisting of H2NC(=NH)-NH(CH2)3-, H2N(CH2)4-, and (1/7-imidazol-4-yl)-CH2-; and the wavy line points out that the oligopeptide is bound to the pBAE backbone through -S-.

Where the or each oligopeptide is a compound of Formula III, the Li and/or l_2 (and/or LT, when present) linking the or each oligopeptide to the polymer is a bond and the terminal cysteine residue provides a means of coupling the or each oligopeptide to the acrylate terminated compound of the pBAE backbone. The thiol functionality provides faster, more efficient and more easily controlled addition to the double bond. By contrast, where the or each oligopeptide is terminated in an amine functionality for coupling, an excess of this compound is required in the coupling step.

Alternatively, the or each oligopeptide may have a net negative charge at pH 7. The or each oligopeptide may comprise naturally occurring amino acids that are negatively charged at pH 7, that is, aspartic acid and glutamic acid. For example, the or each oligopeptide may be selected from polyaspartic acid and polyglutamic acid, each of which may be terminated with cysteine. In this embodiment, the or each oligopeptide may be a compound of Formula 11 Ibis

(lllbis) wherein p’ is an integer from 2 to 19, typically from 3 to 9 or from 3 to 5, and wherein R _a ’ is HO ₂ C(CH ₂ ) ₂ - or HO ₂ C-CH ₂ -. In this case, the Li and/or l_ ₂ linking the or each oligopeptide to the polymer is a bond as the terminal cysteine residue provides a means of coupling the or each oligopeptide to the acrylate terminated pBAE backbone.

Alternatively, the or each oligopeptide may comprise a mixture of naturally occurring amino acids that are negatively charged at pH 7 and naturally occurring amino acids that are positively charged at pH 7.

Cell-targeting moiety

In another embodiment of the first aspect of the invention, optionally in combination with any of the embodiments provided above or below, the polymer OM-pZ-pBAE of the invention further includes one or more cell-targeting moieties.

In the context of the present invention, the term “cell-targeting moiety" means a moiety that binds a cell. In certain embodiments, cell-targeting ligands are selective for one or more particular cell type. In certain embodiments, cell-targeting moieties selectively bind a receptor, such as a cell surface receptor.

Illustrative non-limitative examples of cell-targeting moieties include, but are not limited to, an antibody, a receptor ligand, a hormone, a vitamin, and an antigen, however, the present invention is not limited by the nature of the targeting agent. In some embodiments, the cell-targeting moiety is a receptor ligand, such as a ligand for CFTR, EGFR, the estrogen receptor, FGR2, folate receptor, IL-2 receptor, glycoprotein, the retinol binding protein and VEGFR.

In another embodiment of the first aspect of the invention, optionally in combination with any of the embodiments provided above or below, the receptor ligand is a carbohydrate (such as a lectine) or a sugar (such as mannose or galactose). In another embodiment, optionally in combination with any of the embodiments provided above or below, the cell-targeting moiety comprises a targeting group linker.

In another embodiment, optionally in combination with any of the embodiments provided above or below, the cell-targeting group linker comprises one or more groups selected from among: phosphate, amide, ether, ester, pyrrolidine, disulfide, and methylene.

In another embodiment, optionally in combination with any of the embodiments provided above or below, the cell-targeting moiety is bound to R3. The binding of the cell-targeting moiety to R3 can be performed following well-known protocols. The skilled person, using their general knowledge, is able to select the most appropriate conditions/reagents, depending on the particular cell-targeting moiety and the particular meaning of R3. For example, the cell-targeting moiety can be firstly modified to incorporate a thiol group, preferably at a terminal position, and then, reacting the thiol derivative with the polymer of formula (I), under appropriate conditions to promote the generation of a -S-S-. The reaction can be based on the aminolysis on the Z group of the compound of formula (IV) by preparing a thiol-derivative which reacts with the cell-targeting moiety previously thiol- functionalized. Reaction conditions and reagents useful to perform the aminolysis are widely known for those skilled in the art (Hess A. et al., 2020; Boyer C. et al., 2009).

An example of the appropriate conditions to allow the derivatization are provided below, wherein the polymer of formula (I) is modified to include retinol as cell-targeting moiety.

Nanoparticles

The present invention further provides nanoparticles comprising one or more polymers of formula (I) as defined above. All the embodiments provided above for the polymers of the first aspect of the invention, are also embodiments of the nanoparticles of the fourth aspect of the invention.

Such nanoparticles are suitable for encapsulation of a particular molecule (compound of interest), such as a diagnostic and imaging reagents or an active agent, and show improved pharmacological properties.

Diagnostic and imaging agents include contrast agents, magnetic materials, agents sensitive to light, radiolabels, and fluorescent compounds, such as carboxyfluorescein. Such agents may be used for biodistribution studies in vitro and in vivo. Delivery of nanoparticles of the present invention to the brain has been demonstrated by such studies. For example, paclitaxel-loaded nanoparticles comprising surface-modifying agents have been detected in the brain in biodistribution studies in vivo. Moreover, fluorescently labelled nanoparticles can be used in a cellular study simulating the bloodbrain barrier. The active agent(s) may be present within the nanoparticles or on the surfaces of the nanoparticles. Typically the active agent is present within the nanoparticles. The interaction between the active agent(s) and the nanoparticle is typically non-covalent, for example, hydrogen bonding, electrostatic interaction or physical encapsulation. Typically the interaction is electrostatic

The nanoparticles are biocompatible and sufficiently resistant to their environment of use that a sufficient amount of the nanoparticles remain substantially intact after entry into the mammalian body so as to be able to reach the desired target and achieve the desired physiological effect. The polymers described herein are biocompatible and preferably biodegradable.

Herein, the term ‘biocompatible’ describes as substance which may be inserted or injected into a living subject without causing an adverse response. For example, it does not cause inflammation or acute rejection by the immune system that cannot be adequately controlled. It will be recognized that “biocompatible” is a relative term, and some degree of immune response is to be expected even for substances that are highly compatible with living tissue. An in vitro test to assess the biocompatibility of a substance is to expose it to cells; biocompatible substances will typically not result in significant cell death (for example, >20%) at moderate concentrations (for example, 29 pg/10<4 >cells).

Herein, the term ‘biodegradable’ describes a polymer which degrades in a physiological environment to form monomers and/or other non-polymeric moieties that can be reused by cells or disposed of without significant toxic effect. Degradation may be biological, for example, by enzymatic activity or cellular machinery, or may be chemical, typically a chemical process that takes place under physiological conditions. Degradation of a polymer may occur at varying rates, with a half-life in the order of days, weeks, months, or years, depending on the polymer or copolymer used. The components preferably do not induce inflammation or other adverse effects in vivo. In certain preferred embodiments, the chemical reactions relied upon to break down the biodegradable compounds are uncatalysed.

Herein, the term “nanoparticles” refers to a solid particle with a diameter of from about 1 to about 1000 nm, particularly from 50 to 800nm, particularly from 100 to 500 nm. The mean diameter of the nanoparticles of the present invention may be determined by methods known in the art, preferably by dynamic light scattering. In particular, the invention relates to nanoparticles that are solid particles with a diameter of from about 1 to about 1000nm when analysed by dynamic light scattering at a scattering angle of 173° and at a temperature of 25°C, using a sample appropriately diluted with filtered water and a suitable instrument such as the Zetasizer™ instruments from Malvern Instruments (UK). Where a particle is said to have a diameter of x nm, there will generally be a distribution of particles about this mean, but at least 50% by number (e.g. >60%, >70%, >80%, >90%, or more) of the particles will have a diameter within the range x±20%.

Nanoparticles of the present disclosure may be formed with high active agent content and high encapsulation efficiency, as explained above and showed below.

Herein, the active agent encapsulation efficiency refers to the active agent incorporated into the nanoparticles as a weight percentage of the total active agent used in the method of preparation of the active agent-containing nanoparticles. It is typically up to and including 95%, more typically from 70% to 95%.

Herein, active agent entrapment refers to the weight percentage of the active agent in the active agent-loaded nanoparticles. Active agent entrapment is preferably at least 2 wt %, more preferably at least 5 wt %, more preferably at least 10 wt % and typically in the range of from 2 wt % to 20 wt %, more preferably from 5 wt % to 20 wt %, more preferably from 10 wt % to 20 wt %.

In one embodiment of the fourth aspect of the invention, optionally in combination with any of the embodiments provided above or below, the compound of interest is an active ingredient.

In one embodiment of the fourth aspect of the invention, optionally in combination with any of the embodiments provided above or below, the compound of interest, particularly the active ingredient, is negatively charged at biological pH.

In an alternative embodiment of the fourth aspect of the invention, optionally in combination with any of the embodiments provided above or below, the compound of interest, particularly the active ingredient, is positively charged at biological pH.

The “positively charged at biological pH” in the context of the invention is meant to include any compound, particularly any pharmacologically active substance, that bear negative charges in the molecule in an aqueous solution at a biological pH (about 7).

The “negatively charged at biological pH” in the context of the invention is meant to include any compound, particularly any pharmacologically active substance, that bear negative charges in the molecule in an aqueous solution at a biological pH (about 7). In one embodiment, the anionic nature can be imparted from one or more functional groups selected from the group consisting of carboxyl, phosphate and sulphate groups. In one embodiment of the present invention, optionally in combination with any of the embodiments provided above or below, the negatively charged compound of interest is a polyanionic small molecule, a nucleic acid, polypeptide or protein. As used herein, the term “small molecule” refers to organic compounds, whether naturally-occurring or artificially created (e.g., via chemical synthesis) that have relatively low molecular weight and that are not proteins, polypeptides, or polynucleotides. Typically, small molecules have a molecular weight of less than about 1500 g/mol. Examples of the polyanionic small molecules may include heparin, calcitonin, etc.

The nucleic acid may be a nucleic acid drug, such as deoxyribonucleic acid, ribonucleic acid, or a polynucleotide derivative wherein the backbone, sugar or base is chemically modified or the end of the nucleic acid is modified. Particularly, it may be one or more nucleic acid selected from the group consisting of RNA, DNA (such as a gene or oligonucleotide), siRNA (small interfering RNA), an aptamer, antisense oligodeoxynucleotide (ODN), antisense RNA, ribozyme, DNAzyme, ASO, ribozyme, oligonucleotide RNA inhibitor, immune modulating oligonucleotide or other desired negatively charged nucleic acid.

Also, in order to increase the stability of the nucleic acid in blood or weaken the immune response, the backbone, sugar or base of the nucleic acid may be chemically modified or the end of the nucleic acid may be modified. Specifically, a portion of the phosphodiester bond of the nucleic acid may be substituted by a phosphorothioate or boranophosphate bond, or the nucleic acid may include at least one nucleotide wherein various functional groups such as a methyl group, a methoxyethyl = 30 group or fluorine are introduced in the 2'-OH position of some riboses. Therefore, the polynucleotide may be derived from natural nucleosides (i.e., adenosine, thymidine, guanosine, cytidine, uridine, inosine, xanthosine, deoxyadenosine, deoxythymidine, deoxyguanosine, deoxyinosine, and deoxycytidine), nucleoside analogues (e.g., 2-aminoadenosine, 2-thiothymidine, inosine, pyrrolo-pyrimidine, 3-methyl adenosine, C5-propynylcytidine, C5-propynyluridine, C5- bromouridine, C5-fluorouridine, C5-iodouridine, C5-methylcytidine, 7-deazaadenosine, 7- deazaguanosine, 8-oxoadenosine, 8-oxoguanosine, O(6)-methylguanine, and 2- thiocytidine), or mixtures thereof. The nucleotides may be derived from chemically modified bases, biologically modified bases (e.g., methylated bases), intercalated bases, unmodified or modified sugars (e.g., 2 '-fluororibose, ribose, 2'-deoxyribose, arabinose, and hexose), and/or unmodified or modified phosphate groups (e.g., phosphorothioates and 5'-N-phosphoramidite linkages).

Typically, a polynucleotide comprises at least three nucleotides. Preferably, the polynucleotide is 20-30 nucleotides in length, more preferably 20-25 nucleotides in length, for example, 22 nucleotides in length. In another embodiment, optionally in combination with any of the embodiments provided above or below, one or more ends of the nucleic acid may be modified with one or more selected from the group consisting of cholesterol, tocopherol, a fatty acid having 10-24 carbon atoms, and any analogue, derivative and metabolite thereof. For example, siRNA may be modified at the 5' end or at the 3' end or at both ends of the sense and/or antisense strand, and preferably at the end of the sense strand.

In another embodiment, optionally in combination with any of the embodiments provided above or below, the nanoparticle comprises a polymeric shell comprising the polymer(s) of formula (I); and a core comprising the compound(s) encapsulated therein.

In another embodiment, optionally in combination with any of the embodiments provided above or below, the nanoparticle may comprise one or more polymers of formula (Iter):

L”3 is independently selected from the group consisting of alkylene, alkenylene, heteroalkylene, heteroalkenylene, arylene, and heteroarylene; or, alternatively at least one of L3” is wherein LT” is independently selected from the group consisting of:

»

O, S, NR _X , and a bond, wherein R _x is independently selected from the group consisting of hydrogen, halogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, and heteroaryl, and the remaining L ₃ ” groups are independently selected at each occurrence from the group consisting of alkylene, alkenylene, heteroalkylene, heteroalkenylene, arylene, and heteroarylene;

L’ 4 is independently selected from the group consisting of (v) and (vi)

(v) (vi)

Ls” is independently selected from the group consisting of alkylene, alkenylene, heteroalkylene, heteroalkenylene, arylene, and heteroarylene; each R ₃ ” is independently selected from the group consisting of hydrogen, halogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, heteroaryl, polyalkylene glycols, a moiety having a hydroxyl group (-OH), and a moiety having an amine group (-NH2), wherein:

- said polyalkylene glycol is either bound directly to the nitrogen atom to which R ₃ ” is attached or bound to the nitrogen atom to which R ₃ ” is attached via a linker moiety, wherein said linker moiety is an alkylene, cycloalkylene, alkenylene, cycloalkenylene, heteroalkylene, heterocycloalkylene, arylene or heteroarylene group;

- the moiety having a hydroxyl group (-OH) is selected from the group consisting of - (CH ₂ ) _P OH, and -(CH2)2(OCH ₂ CH ₂ )qOH; and

- the moiety having an amino group (-NH ₂ ) is selected from the group consisting of -(CH ₂ )pNH ₂ , and -(CH ₂ ) ₂ (OCH ₂ CH ₂ ) _q NH ₂ ; n is an integer from 5 to 1000, p is an integer from 1 to 20, and q is an integer from 1 to 10, each Li and l_ ₂ is independently selected from the group consisting of:

O, S, NR _X , and a bond; wherein R _x is independently selected from the group consisting of hydrogen, halogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, and heteroaryl; and R3” and L5” being as defined above; and

R1, R ₂ and R _T are independently selected from an oligopeptide and R _y ,

R _y being selected from the group consisting of hydrogen, halogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, and heteroaryl; and provided that at least one of R1, R ₂ and RT is an oligopeptide.

In one embodiment, optionally in combination with any of the embodiments provided above, or below, the polymer of formula (Iter) is one wherein L3” presents alkylene.

In one embodiment, optionally in combination with any of the embodiments provided above, or below, the polymer of formula (Iter) is one wherein L4” presents a group of formula (v), wherein R3” is as defined above.

In one embodiment, optionally in combination with any of the embodiments provided above or below, the polymer of formula (Iter) is one of formula (v) wherein R”3 groups are the same or different and are selected from -(CH ₂ ) _P OH, -(CH ₂ ) ₂ (OCH ₂ CH ₂ ) _q OH, -(CH ₂ ) _P NH ₂ , and -(CH ₂ ) ₂ (OCH ₂ CH ₂ ) _q NH ₂ , wherein p and q are as defined above.

All the embodiments provided under the first aspect of the invention for the polymer of formula (I), regarding Li, l_ ₂ , R1 and R ₂ , including the oligopeptides useful in the context of the invention, are also embodiments of the polymer of formula (Iter).

In another embodiment, optionally in combination with any of the embodiments provided above or below, the polymer of formula (Iter) is one wherein:

R1 and R ₂ are oligopeptides as defined above, particularly having negative charge at pH 7;

Li and l_ ₂ represent a bond; L3” represents alkylene; and

L4” represents a substituent of formula (i), wherein R3” are the same or different and are selected from -(CH ₂ ) _P OH, -(CH ₂ ) ₂ (OCH ₂ CH ₂ ) _q OH, -(CH ₂ ) _P NH ₂ , and -(CH ₂ ) ₂ (OCH ₂ CH ₂ ) _q NH ₂ .

As it can be derived from Table 8 below, the incorporation of one or more polymers of formula (Iter), further reduced the average size of the resulting polyplexes.

In another embodiment, optionally in combination with any of the embodiments provided above or below, the nanoparticle comprises a polymeric shell comprising the polymer(s) of formula (I) and one or more polymer(s) of formula (Iter); and a core comprising the compound(s) encapsulated therein.

In one embodiment, optionally in combination with any of the embodiments provided above or below, the nanoparticle may comprise a negatively charged compound of interest, as defined above, and one or more polymers of formula (I) and optionally one or more polymers of formula (Iter), having a net positive charge at pH 7. The positively charged oligopeptides interact with negatively charged compound during the process of nanoparticle formation and facilitate encapsulation of the compound in the nanoparticles.

In an alternative embodiment, optionally in combination with any of the embodiments provided above or below, the nanoparticles may comprise polymers of formula (I) and optionally polymers of formula (Iter) wherein the or each oligopeptide has a net negative charge at pH 7 and a compound of interest having a net positive charge at pH7. The negatively charged oligopeptides interact with positively charged compound during the process of nanoparticle formation and facilitate encapsulation of the compound in the nanoparticles.

The present invention further provides a method of encapsulating a compound of interest, such as an active ingredient, in a matrix of polymers of formula I and optionally of formula (Iter) to form nano particles, the method comprising steps of: providing a charged compound of interest; providing the polymer(s) as defined in any of the above embodiments; and contacting the agent and the polymer under suitable conditions to form nanoparticles. The skilled person, using their general knowledge, can routinely adjust the parameters to obtain the nanoparticles. An illustrative example is provided below, in the Examples. Pharmaceutical Compositions

The compositions of the invention comprise a therapeutically effective amount of the nanoparticles of the invention, when they incorporate an active ingredient, together with pharmaceutically acceptable excipients and/or carriers.

The expression "therapeutically effective amount" as used herein, refers to the amount of the nanoparticles of the invention that, when administered passes to blood stream and is sufficient to prevent development of, or alleviate to some extent, one or more of the symptoms of the disease which is addressed. The particular dose of the nanoparticles administered according to this invention will of course be determined by the particular circumstances surrounding the case, including the compound administered, the route of administration, the particular condition being treated, and the similar considerations.

The term “pharmaceutically acceptable” refers to that excipients or carriers suitable for use in the pharmaceutical technology for preparing compositions with medical use.

The expression "excipients and/or carriers" refers to acceptable materials, compositions or vehicles. Each component must be pharmaceutically acceptable in the sense of being compatible with the other ingredients of the composition. It must also be suitable for use in contact with the tissue or organ of humans and non-human animals without excessive toxicity, irritation, allergic response, immunogenicity or other problems or complications commensurate with a reasonable benefit/risk ratio. Examples of suitable acceptable excipients are solvents, dispersion media, diluents, or other liquid vehicles, dispersion or suspension aids, surface active agents, isotonic agents, thickening or emulsifying agents, preservatives, solid binders, lubricants and the like. Except insofar as any conventional excipient medium is incompatible with a substance or its derivatives, such as by producing any undesirable biological effect or otherwise interacting in a deleterious manner with any other component(s) of the pharmaceutical composition, its use is contemplated to be within the scope of this invention.

The formulations of the pharmaceutical compositions described herein may be prepared by any method known or hereafter developed in the art of pharmacology. In general, such preparatory methods include the step of bringing the nanoparticles into association with an excipient and/or one or more other accessory ingredients, and then, if necessary and/or desirable, shaping and/or packaging the product into a desired single- or multidose unit.

A pharmaceutical composition of the invention may be prepared, packaged, and/or sold in bulk, as a single unit dose, and/or as a plurality of single unit doses. As used herein, a “unit dose” is discrete amount of the pharmaceutical composition comprising a predetermined amount of the nanoparticles.

The relative amounts of the active ingredient (i.e. , the peptide as defined in any of the previous aspects and embodiments), the acceptable excipients, and/or any additional ingredients in the composition of the invention will vary, depending upon the identity, size, and/or condition of the subject treated and further depending upon the route by which the composition is to be administered.

Acceptable excipients used in the manufacture of these compositions include, but are not limited to, inert diluents, dispersing and/or granulating agents, surface active agents and/or emulsifiers, disintegrating agents, binding agents, preservatives, buffering agents, lubricating agents, and/or oils. Such excipients may optionally be included in the inventive formulations. Excipients such as cocoa butter and suppository waxes, coloring agents, coating agents, sweetening, flavoring, and perfuming agents can be present in the composition, according to the judgment of the formulator.

Obtaining of the polymers of formula (I)

The obtaining of this new family of polymers can involve the synthesis of acrylate- terminated polymers (pBAE), the modification of the acrylate ends with oligopeptides and the subsequent modification of the hydroxyl group of the side chain with the Chain Transfer Agent (CTA). Through a final grafting process of the zwitterionic monomer on the pBAE backbone.

As pointed out above, the present invention provides, in a second aspect, a process for obtaining the polymer of formula (I) which comprises the RAFT polymerization of a polymer of formula (Ibis), as defined above, which is characterized by incorporating at least one moiety comprising a CTA compound corresponding to a thio-based compound of formula (IV), together with one or more zwitterionic monomers, in the presence of a radical initiator. The skilled person, using their general knowledge will be able to routinary choose the more appropriate conditions to perform the polymerization. An illustrative example of the appropriate reaction conditions is provided below.

In one embodiment of the second aspect of the invention, optionally in combination with any of the embodiments provided above or below, the polymer (Ibis) is one wherein L/ represents a bond.

In one embodiment of the second aspect of the invention, optionally in combination with any of the embodiments provided above or below, the polymer (Ibis) is one wherein L2’ represents a bond. In one embodiment of the second aspect of the invention, optionally in combination with any of the embodiments provided above or below, the polymer (Ibis) is one wherein L3’ represents alkylene.

In one embodiment of the second aspect of the invention, optionally in combination with any of the embodiments provided above or below, the polymer (Ibis) is one wherein L4’ represents a group of formula (iii).

In one embodiment of the second aspect of the invention, optionally in combination with any of the embodiments provided above or below, the polymer (Ibis) is one wherein at least a 5% of the R’3 groups in the polymer of formula (Ibis) represents a moiety of formula (IV) as defined above; particularly at least a 30%, 40%, 50%, 60%, 70%, 70%, 80% or 90% of the R’3 groups in the polymer of formula (Ibis) represents a moiety of formula (IV) as defined above; particularly at least a 40% of the R’3 groups in the polymer of formula (Ibis) represents a moiety of formula (IV) as defined above; particularly from 30 to 80%; particularly from 40 to 70% of the R’3 groups in the polymer of formula (Ibis) represents a moiety of formula (IV) as defined above.

In one embodiment of the second aspect of the invention, optionally in combination with any of the embodiments provided above or below, the polymer (Ibis) is one wherein the remaining R’3 groups, which are other than a moiety of formula (IV), are the same or different and are selected from -(CH2) _P OH, -(CH2)2(OCH2CH2) _q OH, -(CH2) _P NH2, and -(CH ₂ )2(OCH ₂ CH2)qNH2, wherein p and q are as defined above.

In one embodiment of the second aspect of the invention, optionally in combination with any of the embodiments provided above or below, the polymer (Ibis) is one wherein the thio-based compound (IV) is one where Z represents an aryl, alkyl or -S-R’s, wherein R’s is as defined above; particularly, R’s represents an aryl, alkyl, -S-aryl or -S-alkyl.

In one embodiment of the second aspect of the invention, optionally in combination with any of the embodiments provided above or below, the polymer (Ibis) is one wherein the thio-based compound (IV) is one where R’9 represents -alkylene-C(O)-O-alkylene-, wherein the alkylene is optionally substituted; particularly R’g represents -(CR _w R’w)- (CH ₂ )V-C(O)-O-(CH ₂ )W-*, wherein R _w and R’ _w are independently selected from hydrogen, hydrogen, halogen, trihalomethyl, trihaloethyl, -NO2, -CN, -N ⁺ (Ci-6alkyl)2O ^_ , -CO2H, -SO3H, -SOCi- ₆ alkyl, -SO ₂ Ci. ₆ alkyl, -C(=O)H, -C(=O)Ci- ₆ alkyl, =0, -N(Ci- ₆ alkyl) ₂ , -C(=O)NH ₂ , -C1- ealkyl, -Cs-ecycloalkyl, -Cs-eheterocycloalkyl, -Z ^u Ci-6alkyl and -z ^u -C3-6cycloalkyl, wherein Z ^u is defined above; * indicates the binding of R’9 to the -N- of the substituent of formula (i); and v and w are integers from 1 to 20.

In another embodiment of the second aspect of the invention, optionally in combination with any of the embodiments provided above or below, the polymer of formula (Ibis) is one wherein R _w and R’ _w are independently selected from hydrogen, CN and alkyl.

In another embodiment of the second aspect of the invention, optionally in combination with any of the embodiments provided above or below, the polymer of formula (Ibis) is one wherein the thio-based compound (IV) is one where v is from 1 to 10.

In another embodiment of the second aspect of the invention, optionally in combination with any of the embodiments provided above or below, the polymer of formula (Ibis) is one wherein the thio-based compound (IV) is one wherein w is from 1 to 10.

In another embodiment of the second aspect of the invention, optionally in combination with any of the embodiments provided above or below, the polymer of formula (Ibis) is one wherein the oligopeptide(s) are as defined in any of the previous embodiments.

In one embodiment of the second aspect of the invention, optionally in combination with any of the embodiments provided above or below, the polymer (Ibis) is one wherein:

Ri and R2 are oligopeptides as defined in any of the embodiments provided above, under the first aspect of the invention, particularly negatively charged olipeptides at pH 7;

Li’and L2’ represent a bond;

L3’ represents alkylene;

L4’ represents a substituent of formula (iii), wherein:

- at least 5% of the R3’ groups represent a moiety of formula (IV) as defined above; Z being selected from alkyl, aryl, -S-alkyl, and -S-aryl; and R’9 representing -alkylene-C(O)-O-alkylene-, wherein the alkylene is optionally substituted; and

- the remaining R3’ groups, which are other than the moiety of formula (II), are the same or different and are selected from -(CH2) _P OH, -(CH2)2(OCH2CH2) _q OH, -(CH ₂ ) _P NH ₂ , and -(CH ₂ )2(OCH ₂ CH2)qNH2.

The RAFT polymerization is performed using zwitterionic monomer(s). Suitable zwitterionic monomers in the context of the invention are as they have been defined in above.

As the skilled person knows, the RAFT polymerization requires the presence of a radical initiator. Any of the well-known radical initiators suitable in the context of the RAFT polymerization can be used to polymerize the zwitterionic monomers in the CTA-based moiety of formula (IV). Illustrative non-limitative examples are azo polymerization initiators such as azobisisobutyronitrile (AIBN), 4,4'-azobis(4-cyanovaleric acid) (ACVA), also called 4,4'-azobis(4-cyanopentanoic acid), which are widely used, but also other azo polymerization initiators manufactured by companies such as Fujifilm or Otsuka Chemical Co. Ltd. (series of azo polymerization initiators “V”).

In one embodiment of the process of the second aspect of the invention, optionally in combination with any of the embodiments provided above or below, the RAFT polymerization is performed at room temperature.

In one embodiment of the process of the second aspect of the invention, optionally in combination with any of the embodiments provided above or below, the RAFT polymerization is performed under agitation.

The polymer of formula (Ibis), which is characterized by being activated to perform the RAFT polymerization (due to the CTA moiety), can be obtained using well-known protocols. For example, they can be obtained by: (1) reacting a polymer of formula (V) or a pharmaceutical salt thereof with any suitable chain transfer agent, as defined above; and (2) the resulting polymer is then reacted with the oligopeptides.

The pBAE polymer of formula (V) is one wherein: wherein L3 is independently selected from the group consisting of alkylene, alkenylene, heteroalkylene, heteroalkenylene, arylene, and heteroarylene; or at least one occurrence of L3 is wherein Ti is and T2 is selected from H, alkyl, and wherein LT is independently selected from the group consisting of:

O, S, NR _X , and a bond, wherein R _x is independently selected from the group consisting of hydrogen, halogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, and heteroaryl, and the remaining l_3 groups are independently selected at each occurrence from the group consisting of alkylene, alkenylene, heteroalkylene, heteroalkenylene, arylene, and heteroarylene; l_6 is independently selected from the group consisting of (vii) and (viii)

L? is independently selected from the group consisting of alkylene, alkenylene, heteroalkylene, heteroalkenylene, arylene, and heteroarylene;

RT is independently selected from an oligopeptide and R _y ; and wherein R _y is selected from the group consisting of hydrogen, halogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, and heteroaryl; each Rw is independently selected from the group consisting of hydrogen, halogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, heteroaryl, polyalkylene glycols, a moiety having a hydroxyl group (-OH), and a moiety having an amine group (-NH2),; provided that at least one or more of the R« are moieties having a a hydroxyl group, wherein:

- said polyalkylene glycol is either bound directly to the nitrogen atom to which R3 is attached or bound to the nitrogen atom to which R3 is attached via a linker moiety, wherein said linker moiety is an alkylene, cycloalkylene, alkenylene, cycloalkenylene, heteroalkylene, heterocycloalkylene, arylene or heteroarylene group;

- the moiety having a hydroxyl group (-OH) is selected from the group consisting of -(CH ₂ ) _P OH, and -(CH2)2(OCH ₂ CH ₂ )qOH;

- the moiety having an amino group (-NH ₂ ) is selected from the group consisting of -(CH ₂ ) _P NH ₂ , -(CH ₂ ) ₂ (OCH ₂ CH ₂ ) _q NH ₂ ; n is an integer from 5 to 1,000, p is an integer from 1 to 20, and q is an integer from 1 to 10.

In one embodiment, optionally in combination with any of the embodiments provided above or below, the polymer (V) is one wherein L3 represents alkylene.

In one embodiment, optionally in combination with any of the embodiments provided above or below, the polymer (V) is one wherein l_6 represents a group of formula (vii).

In one embodiment, the polymer (V) is one wherein at least a 5% of the R« groups in the polymer of formula (V) represents a moiety having a hydroxyl group (-OH) as defined above; particularly at least a 30%, 40%, 50%, 60%, 70%, 70%, 80% or 90% of the R« groups in the polymer of formula (V) represents a moiety having a hydroxyl group (-OH) as defined above; particularly at least a 40% of the R« groups in the polymer of formula (V) represents a moiety having a hydroxyl group (-OH) as defined above; particularly from 30 to 80%; particularly from 40 to 70% of the R« groups in the polymer of formula (V) represents a moiety having a hydroxyl group (-OH) as defined above.

In one embodiment, the polymer (V) is one wherein at least a 5% of the R« groups in the polymer of formula (V) represents a moiety having a hydroxyl group (-OH) as defined above and the remaining R« groups present a moiety having an amino group as defined above; particularly at least a 30%, 40%, 50%, 60%, 70%, 70%, 80% or 90% of the R ₁₀ groups in the polymer of formula (V) represents a moiety having a hydroxyl group (-OH) as defined above and the remaining R ₁₀ groups present a moiety having an amino group as defined above; particularly at least a 40% of the R« groups in the polymer of formula (V) represents a moiety having a hydroxyl group (-OH) as defined above and the remaining R« groups present a moiety having an amino group as defined above; particularly from 30 to 80%; particularly from 40 to 70% of the R« groups in the polymer of formula (V) represents a moiety having a hydroxyl group (-OH) as defined above and the remaining R« groups present a moiety having an amino group.

The compound of formula (V) is firstly “activated” by performing a sterification reaction between the one or more -OH of the R« groups and the particular CTA, thus obtaining a “CTA-modified pBAE”. Appropriate reaction conditions can be routinary optimized by the skilled person. The present invention provides illustrative reaction conditions in the Examples below, using two different CTAs.

And, subsequently, the resulting CTA-modified pBAE of formula reacts with the corresponding oligopeptide(s) which are as defined in any of the above embodiments, in the presence of a polar solvent, such as DMSO, at room temperature and agitation, thus obtaining the polymer of formula (Ibis). Illustrative reaction conditions to perform the end modification of the CTA-modified pBAE with the oligopeptides have been widely disclosed, such as in US20180250410. Further exemplary conditions are also provided in Examples below.

The obtaining of polymers of formula (V) has been widely disclosed in the prior art, for example in the US2018025410.

An alternative process to the one of the second aspect of the invention is based on reacting the pBAE of formula (Iter), wherein one or more of the L4” represents (v) and one or more of the R3” represents a moiety having a hydroxyl group (-OH), as defined above and the zwitterionic polymeric chain, previously formed by RAFT polymerization or any other appropriate polymerization technique.

The present invention also provides a poly(beta-aminoester) polymer of formula (I) or a pharmaceutically salt thereof which is obtainable by any of the above processes.

The term "obtainable" and "obtained" have the same meaning and are used interchangeably. In any case, the expression "obtainable" encompasses the term “obtained”.

In one aspect the present invention provides the use of the polymers as coating agents.

The polymer of the invention can be applied on so non-related surfaces such as the one of an adenoviral vector, such as a AAV, or on the surface of a device, for example a stent. In any case, the polymer of the invention will provide the surprising anti-fouling and safety properties.

The coating can be based on the immobilization of the polymer chains of formula (I) due to covalent, electrostatic or hydrogen bonds.

In the case of using the polymers of the invention to coat a AAV surface, the skilled person could routinary find the more appropriate conditions to react and bind the polymers to the amino groups of viral capsid proteins. The polymers of formula (I), and of formula (Iter), the latter if present, can be non- covalently bound to the viral vector. There are well-known protocols to achieve such kind of binding. For example, EP3406265 provides reactions conditions which can also be followed in the context of the invention.

Alternatively, the polymer(s) of formula (I), and of formula (Iter), the latter if present, can be covalently bound to the viral vector. In this embodiment, the polymer of the invention is firstly carboxyl-activated and, then it is subjected to reaction with the viral vector under conditions promoting the reaction between the carboxylic acid of the polymer and the amino group of the viral capsid, to form an amide group.

As used herein, the term "carboxyl-activated" refers to the incorporation of a carboxyl group in which one hydroxyl group has been replaced by a carboxyl activating group. There are well-known protocols to perform such modification.

As used herein, the term "carboxyl activating group" means a group that modifies a carboxyl group to be susceptible to react later on, for instance, to form an amide group with an amino group of a viral capsid proteins. Commonly, a carboxyl activating group is an electron withdrawing moiety that substitutes the hydroxyl moiety of a carboxyl group. Such electron withdrawing moiety enhances polarization and thereby the electrophilicity at the carbonyl carbon.

In particular, the AAV vector and the acid activated PBAE as defined herein above may be mixed in solution of Hepes from 10 mM to 40 mM, such as 20 mM, and a pH from 7 to 9 such as of 7.4 at concentrations appropriate to obtain the desired ratio AAV vector/acid activated PBAE and to enable the reaction between the acid activated residues of the PBAEs and the amino groups of the viral capsid proteins and, consequently, to obtain a coating covalently attached to the AAV vector. Thus, to form the AAV vector particles a ratio from 1E-9 to 5E-8 pg pBAE/vp, for example of 1E-8 pg pBAE/vp, is used.

A PBAE-covalently coated AAV vector obtainable by the process as defined above also forms part of the invention.

The viral particle can be any vector suitable for use in therapy, particularly an AAV.

Throughout the description and claims the word "comprise" and variations of the word, are not intended to exclude other technical features, additives, components, or steps.

Furthermore, the word “comprise” encompasses the case of “consisting of”. Additional objects, advantages and features of the invention will become apparent to those skilled in the art upon examination of the description or may be learned by practice of the invention. The following examples are provided by way of illustration, and they are not intended to be limiting of the present invention. Furthermore, the present invention covers all possible combinations of particular and preferred embodiments described herein.

Examples

I. MATERIALS

5-amino-1 -pentanol (ref:123048, Merck), hexylamine (ref:8.04326, Merck), 1 ,4-butanediol (ref:493732, Merck), 4-Cyano-4-(dodecylsulfanyl thiocarbonyl) sulfanylpentanoic acid (ref: 723274, Merck), 4- Cyano- 4- (phenylcarbonothioylthio) pentanoic acid (ref: 722995, Merck), A/,A/'-Dicyclohexylcarbodiimide, (ref: 36650, Merck), 4- (Dimethylamino)pyridine (ref: 8,51055, Merck), ([2-(Methacryloyloxy)ethyl]dimethyl-(3- sulfopropyl)ammonium hydroxide (ref: 494158, FluoroChem). Cys-His-His-His and Cys- Lys-Lys-Lys were ordered to Ontores. pDNA for polyplex formulation was amplified by using a Nucleobond PC 10000 EF kit (ref: 740548, Cultek). Sodium Acetate buffer was purchased at Merck (ref:S7899) and diluted to appropriate concentration using MilliQ water.

Cell Culture: AML-12 (ATCC CRL-2254) cells were cultured in DMEM-F12 supplemented with 10% (v/v) FBS, 100 units mL-1 penicillin G, 100 pg mL-1 streptomycin, and 2 mmol L-1 l-glutamine. AML-12 culture media, also included 10 pg mL-1 insulin, 5.5 pg mL-1 transferrin, 5 ng mL-1 selenium, and 40 ng mL-1 dexamethasone. All were cultured at 37oC under a 5% CO2/95% air atmosphere until 80-90% confluence before passaging or starting transfection.

II. METHODS

1H-RMN was performed using a 400 MHz Varian (NMR Instruments, Claredon Hills, IL)

IR was performed using FT-IR Nicolet iZ10 (Thermoscientific)..

The mean diameter of the polyplexes were determined using Zetasizer ZS Nano from Malvern Instruments (UK). The dynamic light scattering was measured at a scattering angle of 173° and at a temperature of 25 ° C, using a sample diluted with MilliQ water.

UV reading of electrophoretic gels was performed using Tecan Infinite 200 Pro plate reader.

Flow cytometry (NovoCyte, ACEA Bioscience) was used to quantify uptake efficiency. Briefly, at the end of the experiment, cells were trypsinized and fixed with 1% paraformaldehyde. At least 2000 cells were analyzed for each well. Results correspond to the mean standard deviation of at least three independent experiments, each consisting on an experiment triplicate.

III. SYNTHESIS OF THE POLYMERS OF THE INVENTION Example 1. Synthesis of poly(beta-a mi noester) C6-50 backbone (pBAE)

Synthesis of the pBAE backbone was performed according following the procedure of US20180250410. Briefly, it was performed the addition reaction of the hexylamine (0.422 g) to 1 ,4-butanediol diacrylate (2.0 g) and 5-amino-1 -pentanol (0.426 g) under magnetic stirring at 200 rpm, at a temperature of 90 °C for 20 h. The resulting polymer was characterized by 1H-RMN:(400MHz, chloroform- , TMS) (ppm): 5 =6,40 (d, CH2=CH-), 6,10 (d, CH2=CH-), 5,83 (d, CH2=CH-), 4.18 (br, CH2-O-C(=O)-CH=CH2), 4,09 (t, -CH2- CH2-O-), 3.62 (t, CH2-CH2-OH), 2.78 (br, -CH2-CH2-N-), 2.45 (br, -N-CH2-CH2-C(=O)- O), 1.83 - 1.60 (br, -O-CH2-CH2-CH2-CH2-O), 1.40- 1.18 (br, - CH2-CH2-CH2-CH2-OH, N-(CH2)2-CH2-(CH2)2-OH), 0.88 (t, CH2-CH2-CH3).

Example 2. Synthesis of the chain transfer agent-modified poly(beta-aminoester) C6-50 (CTA-pBAE)

The CTA-poly(beta-aminoester) was synthesized by esterification of the hydroxyl group of the side chain of the pBAE obtained in Example 1 with the terminal acid of a CTA selected from 4-cyano-4-(dodecylsulfanyl thiocarbonyl)sulfanylpentanoic acid (DCTP) and 4-cyano- 4- (phenylcarbonothioylthio) pentanoic acid. Briefly, pBAE (0.1 g) was dissolved in anhydrous dichloromethane (2.5 ml_), and dicyclohexylcarbodiimide (DCC, 0.96 g), 4- dimethylaminopyridine (DMAP, 0.005 g) and the corresponding CTA (0.096 g) were added while keeping the reaction on ice. After 15 min, the set up was let at room temperature for 18h under stirring. Molar ratio of hydroxyl:CTA 1 :1 ensure 100% of esterification of hydroxyl groups from the initial backbone.

TABLE 1

Example 3 Synthesis of the oligopeptide modified CT A poly(beta-aminoester) (OM-

CTA-pBAE) oligopeptide oligopeptide

OM-CTA-pBAEs were obtained by end-modification of the acrylate-terminated groups of either pBAE (as disclosed in Ex. 1) or CTA-pBAE (as disclosed in Ex. 2), with thiol- terminated oligopeptides (comprising lysine (K) or histidine (H) residues) at a 1 : 2.5 molar ratio in dimethylsulfoxide. The mixture was stirred overnight at 200 rpm, at room temperature, and the resulting polymer was obtained by precipitation in a mixture of diethyl ether and acetone (7 : 3; v/v). Following this procedure, the following oligopeptide-modified pBAEs were obtained:

SUBSTITUTE SHEET (RULE 26) TABLE 2 Example 4. RAFT polymerization grafting for zwitterionic poly(beta-aminoester) obtention (OM-PZ-pBAE)

For 25-monomer length zwitterionic chains, the corresponding OM-CTA-pBAE (0.1 g) and sulfobetaine methacrylate (SBMA, 0.423 g) were dissolved in trifluoroethanol (TFE) and bubbled with N2 for 15 min. The reaction was heated until 50 °C and V044 (0.005 g) was added as initiator. The reaction was stirred for 18h at 50 °C and under nitrogen atmosphere. The product was precipitated in diethyl ether/acetone 7:3, washed with cold methanol, and dried over vacuum to obtain the desired OM-pZ-pBAE as a yellowish powder. For 50-monomer length zwitterionic chains, same conditions were applied but 0.843g of SBMA were initially added.

Following the above procedure, the following zwitterionic pBAE polymers were obtained and characterized:

TABLE 3

IV. SYNTHESIS OF DNA POLYPLEXES AND BIOPHYSICAL CHARACTERIZATION

Example 5: DNA polyplexes with a OM-PZ-pBAE of the invention

Nanoparticles were formulated by mixing the corresponding OM-PZ-pBAE resulting from Example 4 with plasmidic DNA. The plasmidic DNA was obtained using a GigaPrep kit and following manufacturer’s instructions. Briefly, 2L media for growing the bacteria was prepared (LB media) and autoclaved. Next, a plaque was seeded with bacteria previously transformed with the required plasmid and kept in glycerols. Following, a preculture, followed by a culture of bateria were prepared. When the optical density was significantly increased, bacteria were centrifuged and the DNA extracted from the pellet. Finally, a solution of 1mg/ml_ of plasmid DNA was obtained.

On the other hand, 100 mg of each one of the OM-PZ-pBAE were dissolved in 1 mL of milliQ water.

Polyplexes were formed by mixing equal volumes of polymer and plasmidic DNA, with acetate buffer at 12.5 mM (most convenient formulation although it can be increased up to 25 mM), 5.2 pH adjusted by adding acetic acid 1 M. The plasmidic DNA was added to the polymer solution, mixed with pipetting for a few seconds and incubated at room temperature for 20 min (accepted range from 5 minutes to 1 hour). Finally, polyplexes were precipitated in the same volume of water.

Several formulations were prepared on the basis of different weight ratio polymenplasmidic DNA, from 10:1 and 300:1 as provided in the table below.

TABLE 4

Example 6: DNA polyplex combination comprising OM-PZ-pBAEs of the invention

As nanoparticles are internalized in endosomes by cells, it has been postulated that endosome lysis is necessary to produce gene release and cell transfection. For this reason, once the optimal ratio of zwitterionic modified pBAE and plasmid was obtained, each one of the lysine modified zwitterionic pBAEs of Examples 4.1 to 4.4 was mixed with histidine modified pBAE of Ex. 3.3, in order to ease the endosomal scape through the proton sponge effect.

The preparation protocol was the same as the one disclosed in Example 5 above with the following minor changes: separate solutions were prepared dissolving 0.1 g of the OM-PZ- pBAE of Examples 4.1 to 4.4 or of the one of Ex. 3.3, dissolved in 1 mL of miliQ water and

DMSO respectively, and the resulting two solutions were mixed at different volume ratios, as summarized in Table 5a-5c below, to optimize the physicochemical properties:

TABLE 5a

TABLE 5b Example 4.2; OM- pBAE**= Example 3.3

TABLE 5c

OM-pBAE*= Example 3.3 The resulting solutions were then mixed with the plasmid and the same reaction conditions as the ones disclosed in Example 5 were followed to obtain the polyplexes of the invention.

Example 7. DNA polyplexes with pBAE of Ex. 3. (comparative purpose)

In order to determine the effect of covalently binding the zwitterionic polymer to the pBAE backbone, a comparative test was performed using OM-pBAEs of Example 3 (which do not incorporate neither the zwitterionic polymer nor the chain transfer agent) to form the DNA polyplexes. The same protocol as the one provided under Example 5 was followed in order to prepare a solution for each one of the OM-pBAE, the histidine-modified pBAE (Ex. 3.3, also referred as “H” solution) and the lysine-modified pBAE (Ex. 3.4, also referred as “K” solution).

Then, both solutions were mixed at a K solutiomH solution weight ratio of 60:40, in acetate buffer at 12.5 mM, 5.2 pH, adjusted by adding acetic acid 1 M. Thus, obtaining a polymeric solution K-H.

The polyplexes were formed by mixing equal volumes of polymeric solution K-H and the plasmid solution (the latter being obtained as explained in previous sections, but at different weight ratio polymergenetic material, from 10:1 and 300:1. The genetic material was added to polymer solution, mixed with pipetting for a few seconds and incubated at room temperature for 20 min (accepted range from 5 minutes to 1 hour). Finally, polyplexes were precipitated in the same volume of water.

Example 8. DNA polyplexes with a pBAE coated with a zwitterionic polymer (comparative purpose)

In order to determine how the interaction between the pBAE and the zwitterionic polymer affects to the properties of the resulting DNA polyplexes, a comparative one, based on electrostatic interactions (instead of covalent interaction) was prepared as follows.

The same protocol as the one provided under Example 5 was followed in order to prepare a solution for each one of the OM-pBAE, the histidine-modified pBAE (Ex. 3.3, also referred as “H” solution) and the lysine-modified pBAE (Ex. 3.4, also referred as “K” solution).

Then, both solutions were mixed at a K solutiomH solution weight ratio of 60:40, in acetate buffer at 12.5 mM, 5.2 pH, adjusted by adding acetic acid 1 M. Thus, obtaining a polymeric solution K-H.

The polyplexes were formed by mixing equal volumes of polymeric solution K-H and the plasmid solution (the latter being obtained as explained in previous sections) but at different weight ratio polymengenetic material, from 10:1 and 300:1. The genetic material was added to polymer solution, mixed with pipetting for a few seconds and incubated at room temperature for 20 min (accepted range from 5 minutes to 1 hour). After 10 minutes, different percentages of pSBMA (chain length 25 monomers) were added into the acetate buffer medium and gently resuspended. After 10 minutes, polyplexes were precipitated in the same volume of water. TABLE 6

Example 9. Biophysical characterization of the polyplexes

A) Encapsulation efficiency

In order to confirm the encapsulation efficiency of the polyplexes obtained as disclosed in the above Examples 5 to 8, an agarose gel electrophoresis was performed. Briefly, 8 uL of the polyplexes resulting from Examples 5-8 were added to wells of agarose gel (2.5%, containing 1 g ml’ ¹ ethidium bromide). Samples were run at 80 for 45 min and visualized by UV illumination.

In order to determine the efficiency from the electrophoretic data, bands were quantified using Imaged software. The naked plasmid was used as control, to normalize the intensity of the bands corresponding to the encapsulated plasmid and determine the percentage that has not been encapsulated (the one that runs in the gel). Then, by difference, the percentage encapsulated was calculated.

In this way, it was found that the amount of polymer guaranteeing the encapsulation of the DNA sample n the case of using the polymers of the invention, was the same as for pBAE alone, (Ex. 7) i.e., 20:1. This means that the covalent binding of the zwitterionic polymeric chains does not negatively affect the “innate” encapsulation ability of pBAE.

On the other hand, the inventors found that the encapsulation efficiency was not neither negatively affected by the length of the zwitterionic polymer. To that end, they compared the results from Ex. 5.23 (C6CTPKRSBMA50), having a zwitterionic polymer with 50 SBMA monomers, vs Ex. 5.24 (C6CTPKPSBMA25), having a zwitterionic polymer with 25 SBMA monomers: both were able to substantially encapsulate the same amount of nucleic acid. B) Size analysis

Polyplexes were synthesized as disclosed in previous examples. After 20 min of incubation at room temperature, 100 pl of nanoparticles were diluted with 900 pl of PBS 1 x for further hydrodynamic size analysis. On one hand, it was found that the polyplexes of the invention had low average size, remarkably lower than 1000 nm, as it is shown in Table 7 below, make them suitable to be used as delivery vehicles:

Table 7

In view of the above, the inventors confirmed the effect of adding a second polymer, OM- pBAE to the polyplexe. Thus, the inventors compared the polyplexes of Example 5.5 with those of Example 6, formulated at the same weight ratio of pBAE polymers:pDNA. The results are summarized in Table 8 below:

Table 8

As it can be derived from Table 8 above, the incorporation of a second pBAE polymer, in particular a OM-pBAE polymer, further reduced the average size of the resulting polyplexes.

This is of importance because a size below 900 nm guarantees that the polyplexes can provide the biologically effect: (a) it is minimized the formation of aggregates, and (b) it is facilitated cell internalization. In addition, small sizes guarantees an appropriate stability when formulated in the form of a pharmaceutical composition and can be easily reproduced.

C) Anti-fouling properties

Protein coronas were formed following a modification of the Sempf protocol (Sempf K. ^et al., “Adsorption of plasma proteins on uncoated PLGA nanoparticles”, European Journal of Pharmaceutics and Biopharmaceutics, vol. 85(1), 2013, pages 53-60). Briefly, 100 pL of fresh polyplexes obtained as disclosed in previous Examples 5 to 8 were incubated with 185 pL of FBS plus 1 mL phosphate buffered saline (PBS), to simulate blood conditions, for 18 h, at 37 °C. After this time, they were centrifuged for 15 min at 15 000 x g, followed by the addition of 100 pL of PBS obtaining a first supernatant (S1) with the unbound protein and a first pellet (including the nanoparticles), the latter being redispersed and then recentrifuged at same conditions. In this way, a second supernatant (S2) including the soft corona was obtained. The second pellet (hard corona pellet) was redispersed with 100 pL of PBS + 10 wt% SDS, and incubated for 5 min, at 37 °C, to separate hard protein corona in a third supernatant (S3). Finally, protein concentration was determined by using a colorimetric BCA kit, following manufacturer’s instructions.

The following table summarizes the protein amount determined for the tested polyplexes: Table 9

Protein corona (%) = concentration of soft+hard protein corona/total concentration of protein, wherein the “total concentration of protein” is determined adding the protein concentration determined in supernatants S1+S2+S3.

As it can be derived from the above, the polyplexes of the invention, due to the grafting of the zwitterionic polymer into pBAE backbone, shows a substantially lower amount of protein adhered to the surface of the polyplexes. Particularly, it can be seen that the polyplexes of the invention had a protein corona content at least 7-fold lower than those provided by the pBAE of Example 7 (which lacks the zwitterionic polymer) and those of Example 8 (which differ from the one of Ex. 6.3 in the nature of the interaction between the pBAE and the zwitterionic polymer).

As it is also concluded from the above table 9, when the polyplex was based on an electrostatic zwitterionic polymer (comparative Example 8), there were not significant differences with respect to the pBAE with no zwitterionic polymer (comparative Example 7). This means that it is not only necessary the presence of a zwitterionic polymer, but, the most important, that the zwitterionic is covalently linked (i.e. grafted) to the pBAE backbone, as it is the case of the polymers of the invention, to achieve such remarkable improvement in the anti-fouling properties.

Since there were not significant differences between the polyplex with an electrostatic zwitterionic polymer (comparative Ex. 8) vs the pBAE with no zwitterionic polymer (comparative Ex. 7), the following tests were only performed with the polyplex just comprising the pBAE with no zwitterionic polymer.

D) Cell viability assay

HeLa cells were grown in 96 well plates at an initial seeding density of 10000 cells per well in 200 pL cell culture media (density of 5-10 ⁴ cells/mL). Cells were grown for 24 h, transfected with different polymer formulations at 4 ug/well DNA. 24 h post-transfection, the medium was removed, cells were washed with PBS, and complete medium supplemented with 20% MTT reagent (v/v) was added. Cells were incubated at 37 °C for 2 hours and DMSO was added to solubilize the purple crystals. Absorbance was measured at 550 nm using a microplate reader. Cell viability was expressed as a relative percentage compared with untreated cells.

Table 10

As it is derived from the above table, the polyplexes of the invention, characterized by incorporating grafted zwitterionic polymers, are substantially less cytotoxic than the polyplexes obtained using just pBAE (comparative Ex. 7), at any time and even using higher concentrations of the polyplex.

Not only that, but also, the polyplexes of the invention are safer vehicles to carry high amounts of the active ingredient.

E) Hemolysis assay

The administration of nanocarriers is usually systemic and performed through parenteral routes. Therefore, particles get in contact with blood very frequently. For this reason, proving their compatibility with red blood cells (i.e. erythrocytes) is a must before driving in vivo studies. If the nanoparticle solution is hypoosmotic, erythrocytes will explode; while hyperosmotic solution produce a shrinkage of erythrocytes. Sometimes, even when adjusting salt concentration, particles produce hemolysis, this is, the lysis of erythrocytes. Since they are full of hemoglobin, when they are broken, they release hemoglobin; therefore, we can quantify hemoglobin release, by measuring absorbance at 540 nm. The higher the hemoglobin release, the higher the hemolysis percentage.

Human blood was centrifuged twice to isolate erythrocytes and the pellet was diluted in PBS to a concentration of 8x10 ⁹ cell/mL. Cells were seeded in a 96 well plate and incubated for 10 min and 24 hours with the desired concentration of DNA. The samples were centrifuged at 3000 rpm for 5 minutes and the absorbance of the supernatant was measured at 540 nm to determine the amount of hemoglobin in the supernatant of the samples.

The following table summarizes the results thus obtained: Table 11

As it is derived from the above, the polymer of the invention provides a % of haemolysis remarkable lower, especially when significant concentrations of the polyplexes are used.

This means that the grafting of zwitterionic chains in a pBAE backbone makes the resulting polymer remarkably safer for their use in therapy.

F) Transfection efficiency

Transfection efficiency of different formulations of polyplexes was assessed in AML12 cells, from mouse liver. Zwitterionic grafted pBAE particles (OM-pZ-pBAE) were not expected to present high transfections percentages, due to their stealth properties, while retinol modified zwitterionic pBAE :pBAE particles (KzHHret) were expected to selectively transfect AML12 cells. Retinol is highly affinity for retinol binding protein (RBP), a blood circulating protein which presents receptors in the liver. Therefore, the rational of this strategy was to make nanoparticles that naturally attached to RBP; this is, that RBP forms a protein corona in the nanoparticles of the invention to direct them to correspondent liver receptor. As a negative control, glucosamine modified zwitterionic pBAE:pBAE (KzHHglu) particles were used to transfect AML12 cells as they do not present specific receptors for this moiety. Results were compared to pBAE particles, which were previously proved to have high and non-specific transfection capacity in several cell lines.

Thus, first of all the zwitterionic pBAE polymers of the invention, as well as the comparative backbone of Ex. 3 above was modified to incorporate retinol moieties as previously reported by Fornaguera C et al., 2019.

Then, the synthesis and isolation of the polyplexes were performed following the protocol already provided above.

AML12 cells were grown in 96 well plates at an initial seeding density of 10000 cells per well in 200 pL cell culture media (5-10 ⁴ cells/ml_). Cells were grown for 24 h and transfected with different polyplex formulations encapsulating green fluorescent protein plasmid. After 48h, cells were trypsinized and flow cytometry was performed. The results are provided below in Table 12: the polyplexes incorporating the polymer of the invention, at different percentages of retinol (KzHHret) shows a clear positive trend to transfection, this trend increasing with the concentration of retinol.

Table 12

It is remarkable that the polymer of the invention has not transfection ability and that only when it incorporates retinol, this effect is observed. Not only that, but also, the polymer of the invention does not mask the cell-targeting moiety therein incorporated: the greater the concentration of cell-targeting moiety, the greater the transfection rate. Citation List

Sempf K. et al., “Adsorption of plasma proteins on uncoated PLGA nanoparticles”, European Journal of Pharmaceutics and Biopharmaceutics, vol. 85(1), 2013, pages 53- 60).

Hess A. et al., “Aminolysis induced functionalization of (RAFT) polymer-dithioester with thiols and disulfides”, Polym. Chem., 2020,11 , 7677-7684.

Boyer C. et al., “Modification of RAFT-polymers via thiol-ene reactions: A general route to functional polymers and new architectures”, Polym. Chem., 2009, 47(15), 3773-3794.

Fornaguera C. et al., “In Vivo Retargeting of Poly(beta aminoester) (OM-PBAE) Nanoparticles is Influenced by Protein Corona”, Advanced Healthcare Materials, 2019, 8(19), 1900849.

Clauses

For reasons of completeness, various aspects of the invention are set out in the following numbered clauses:

Clause 1. A poly(beta-aminoester) polymer of formula (I) or a pharmaceutically salt thereof: wherein

L3 is independently selected from the group consisting of alkylene, alkenylene, heteroalkylene, heteroalkenylene, arylene, and heteroarylene; or, alternatively at least one of L3 is and T2 is selected from H, alkyl, and wherein LT is independently selected from the group consisting of:

O, S, NR _X , and a bond, wherein R _x is independently selected from the group consisting of hydrogen, halogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, and heteroaryl, and the remaining L3 groups are independently selected from the group consisting of alkylene, alkenylene, heteroalkylene, heteroalkenylene, arylene, and heteroarylene;

L4 is independently selected from the group consisting of formula (i) and (ii)

Ls is independently selected from the group consisting of alkylene, alkenylene, heteroalkylene, heteroalkenylene, arylene, and heteroarylene; each R3 is independently selected from the group consisting of hydrogen, halogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, heteroaryl, polyalkylene glycols, a moiety having a hydroxyl group (-OH), a moiety having an amine group (-NH2), and a moiety having a zwitterionic polymer, wherein:

- said polyalkylene glycol is either bound directly to the nitrogen atom to which R3 is attached or bound to the nitrogen atom to which R3 is attached via a linker moiety, wherein said linker moiety is an alkylene, cycloalkylene, alkenylene, cycloalkenylene, heteroalkylene, heterocycloalkylene, arylene or heteroarylene group;

- the moiety having a hydroxyl group (-OH) is selected from the group consisting of -(CH ₂ ) _P OH, and -(CH2)2(OCH ₂ CH ₂ )qOH;

- the moiety having an amino group (-NH ₂ ) is selected from the group consisting of -(CH ₂ ) _P NH ₂ , and -(CH ₂ ) ₂ (OCH ₂ CH ₂ ) _q NH ₂ ; and

- the moiety having a zwitterionic polymer is one of formula (II) wherein F represents R’4-C(=S)-S-; R’4 represents an aryl, heteroaryl, alkyl, -SRs, -NReR? or -ORs; Rs represents aryl, heteroaryl or alkyl; Re and R7 are the same or different and represent hydrogen, halogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, and heteroaryl; Rs represents hydrogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, and heteroaryl; and R9 is a linker which binds the PZ to the -N- of the substituent of formula (i) or (ii);

PZ represents a zwitterionic polymer comprising one or more zwitterionic monomers; provided that at least one of the R3 is a moiety having a zwitterionic polymer as defined above; n is an integer from 5 to 1000, p is an integer from 1 to 20, q is an integer from 1 to 10, and r is an integer from 0 to 1 ; each Li and L2 is independently selected from the group consisting of:

O, S, NR _X , and a bond; wherein R _x is independently selected from the group consisting of hydrogen, halogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, and heteroaryl; and R3 and Ls being as defined above; and

R1, R2 and R _T are independently selected from an oligopeptide and R _y ,

R _y being selected from the group consisting of hydrogen, halogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, and heteroaryl; and provided that at least one of R1, R2 and RT is an oligopeptide.

Clause 2. The polymer of clause 1 , wherein L3 is independently selected from the group consisting of alkylene, alkenylene, heteroalkylene, heteroalkenylene, arylene, and heteroarylene; particularly L3 represents alkylene. Clause 3. The polymer of any one of the preceding clauses, wherein L4 represents wherein R3 is as defined in any one of the above clauses.

Clause 4. The polymer of any one of the preceding clauses, wherein at least a 5% of the R3 groups in the polymer of formula (I) represents a moiety having a zwitterionic polymer of formula (II) as defined in any of the above clauses; particularly at least a 30%, 40%, 50%, 60%, 70%, 70%, 80% or 90% of the R3 groups in the polymer of formula (I) represents a moiety having a zwitterionic polymer of formula (II) as defined in any of the above clauses; particularly at least a 40% of the R3 groups in the polymer of formula (I) represents a moiety having a zwitterionic polymer of formula (II) as defined in any of the above clauses; particularly from 30 to 80%; particularly from 40 to 70% of the R3 groups in the polymer of formula (I) represents a moiety having a zwitterionic polymer of formula (II) as defined in any of the above clauses.

Clause 5. The polymer of any one of the preceding clauses, wherein the remaining R3 groups, which are other than a moiety of formula (II), are the same or different and are selected from -(CH ₂ ) _P OH, -(CH2)2(OCH ₂ CH ₂ )qOH, -(CH ₂ ) _P NH ₂ , and -(CH ₂ ) ₂ (OCH ₂ CH ₂ ) _q NH ₂ , wherein p and q are as defined above.

Clause 6. The polymer of any one of the preceding clauses, wherein the moiety having a zwitterionic polymer is one as defined in clause 1 , wherein r represents 1 .

Clause 7. The polymer of any one of the preceding clauses, wherein the moiety having a zwitterionic polymer of formula (II) is one where R’4 represents an aryl, alkyl or -S-Rs, wherein Rs is as defined above; particularly, R’4 represents an aryl, alkyl, -S-aryl or -S- alkyl.

Clause 8. The polymer of any one of the preceding clauses, wherein the moiety having a zwitterionic polymer is one where R9 represents -alkylene-C(O)-O-alkylene-, wherein the alkylene is optionally substituted; particularly R9 represents -(CR _y R’ _y )-(CH ₂ ) _s -C(O)-O- (CH ₂ ) _U -*, wherein Ry and R’y are independently selected from hydrogen, halogen, trihalomethyl, trihaloethyl, -NO ₂ , -CN, -N ⁺ (Ci-6alkyl) ₂ O ^_ , -CO ₂ H, -SO3H, -SOCi-ealkyl, - SO ₂ Ci- ₆ alkyl, -C(=O)H, -C(=O)Ci- ₆ alkyl, =0, -N(Ci- ₆ alkyl) ₂ , -C(=O)NH ₂ , -C^alkyl, -C ₃ . ecycloalkyl, -Cs-eheterocycloalkyl, -Z ^u Ci-6alkyl and -z ^u -C3-6cycloalkyl, wherein Z ^u is defined above; * indicates the binding of Rg to the -N- of the substituent of formula (i); and s and u are integers from 1 to 20.

Clause 9. The polymer of clause 8, wherein R _y and R’ _y are independently selected from hydrogen, CN, and alkyl.

Clause 10. The polymer of any one of the preceding clauses 8-9, wherein s is from 1 to 10.

Clause 11. The polymer of any one of the preceding clauses 8-10, wherein u is from 1 to 10.

Clause 12. The polymer of any one the preceding clauses, wherein:

Ri and R2 are oligopeptides as defined in any of the above clauses, particularly negatively charged olipeptides at pH 7;

Li and L2 represent a bond;

L3 represents alkylene;

L4 represents a substituent of formula (i), wherein:

- at least 5% of the R3 groups represent a moiety having a zwitterionic polymer of formula (II) as defined above; R’4 being selected from alkyl, aryl, -S-alkyl, and -S- aryl; R9 representing -alkylene-C(O)-O-alkylene-, wherein the alkylene is optionally substituted; and PZ is as defined in any of the above clauses; and

- the remaining R3 groups, which are other than the moiety of formula (II), are the same or different and are selected from -(CH2) _P OH, -(CH2)2(OCH2CH2) _q OH, -(CH ₂ ) _P NH ₂ , and -(CH ₂ )2(OCH2CH2)qNH ₂ ;

Clause 13. The polymer of any one of the preceding clauses, wherein the zwitterionic polymer PZ consists of from 2 to 100 monomers, particularly from 10 to 90 monomers, more particularly from 15 to 80 monomers.

Clause 14. The polymer of any one of the preceding clauses, wherein the zwitterionic polymer PC comprises one or more zwitterionic monomers comprising a positively charged nitrogen group and a negatively charged group distal to the positively charged nitrogen group on the zwitterion such that there is a separation by at least one carbon atom; particularly from 2 to 3 carbon atoms.

Clause 15. The polymer of any one of the preceding clauses, wherein the one or more zwitterionic monomers are betaine derivatives; particularly a betaine derivative selected from: a carboxybetaine, a phosphobetaine, and a sulfobetaine; particularly the one or more zwitterionic monomers are sulfobetaine derivatives.

Clause 16. The polymer of any one of the preceding clauses, wherein the zwitterionic polymer PZ is a homopolymer. Clause 17. The polymer of any one of the preceding clauses, wherein the zwitterionic polymer PZ consists of zwitterionic monomers as defined in any of the previous clauses 14-16.

Clause 18. The polymer of any one of the preceding clauses, wherein the or each oligopeptide comprises from 3 to 20 amino acid residues.

Clause 19. The polymer of any one of the preceding clauses, wherein the or each oligopeptide has a net positive charge at pH 7.

Clause 20. The polymer of any one of the clauses 1-19, wherein the or each oligopeptide has a net negative charge at pH 7.

Clause 21. The polymer of any one of the preceding clauses 1-19, wherein the or each oligopeptide comprises a mixture of naturally occurring amino acids that are negatively charged at pH 7 and naturally occurring amino acids that are positively charged at pH 7.

Clause 22. The polymer of any one of the clauses 19 and 21 , wherein the or each oligopeptide comprises amino acid residues selected from the group consisting of lysine, arginine, and histidine.

Clause 23. The polymer of any one of the clauses 20 and 21 , wherein the or each oligopeptide comprises amino acid residues selected from the group consisting of glutamic acid and aspartic acid.

Clause 24. The polymer of any one of the preceding clauses, wherein the or each oligopeptide is thiol-terminally functionalised.

Clause 25. The polymer of the preceding clause, wherein the or each oligopeptide is of formula (III): wherein p is an integer from 2 to 19 and wherein Ra is selected from the group consisting of H2NC(=NH)— NH(CH ₂ ) ₃ - , H2N(CH2)4— or (1H-imidazol-4-yl)-CH2 — , and the wavy line points out that the oligopeptide is bound to the pBAE backbone through -S-. Clause 26. The polymer of any one of the preceding clauses, wherein Ri and R2 are both oligopeptides.

Clause 27. The polymer of any one of the preceding clauses, wherein R1 and R2 represent the same oligopeptides.

Clause 28. The polymer of any one of the preceding clauses, wherein Ry is selected from a group consisting of hydrogen, — (CH2) _m NH2, — (CH2)mNHMe, -(CH2)mOH, -(CH2)mCH3, — (CH ₂ ) ₂ (OCH ₂ CH ₂ )mNH ₂ , — (CH ₂ ) ₂ (OCH ₂ CH ₂ )mOH or — (CH ₂ ) ₂ (OCH ₂ CH ₂ )mCH3 wherein m is an integer from 1 to 20.

Clause 29. The polymer of any one of the preceding clams, which is functionalised with one or more cell-targeting moieties.

Clause 30. A process for preparing a polymer as defined in any one of the preceding clauses, the process comprising the step of performing a reversible additionfragmentation chain transfer (RAFT) polymerization of a polymer of formula (Ibis) with one or more zwitterionic monomers, in the presence of a radical initiator, wherein

L3 is independently selected from the group consisting of alkylene, alkenylene, heteroalkylene, heteroalkenylene, arylene, and heteroarylene; or, alternatively at least one of L3 is

T1’ T ₂ ’ wherein and T2’ is selected from H, alkyl, and wherein LT’ is independently selected from the group consisting of:

O, S, NR _X , and a bond, wherein R _x is independently selected from the group consisting of hydrogen, halogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, and heteroaryl, and the remaining L’3 groups are independently selected at each occurrence from the group consisting of alkylene, alkenylene, heteroalkylene, heteroalkenylene, arylene, and heteroarylene;

L’4 is independently selected from the group consisting of (iii) and (iv)

(iii) (iv)

L’s is independently selected from the group consisting of alkylene, alkenylene, heteroalkylene, heteroalkenylene, arylene, and heteroarylene; each R3’ is independently selected from the group consisting of hydrogen, halogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, heteroaryl, polyalkylene glycols, a moiety having a hydroxyl group (-OH), a moiety having an amine group (-NH2), and a moiety having a chain transfer agent (CTA); provided that at least one or more of the R3’ are moieties having a CTA, wherein:

- said polyalkylene glycol is either bound directly to the nitrogen atom to which R3 is attached or bound to the nitrogen atom to which R3 is attached via a linker moiety, wherein said linker moiety is an alkylene, cycloalkylene, alkenylene, cycloalkenylene, heteroalkylene, heterocycloalkylene, arylene or heteroarylene group;

- the moiety having a hydroxyl group (-OH) is selected from the group consisting of -(CH ₂ ) _P OH, and -(CH2)2(OCH ₂ CH ₂ )qOH;

- the moiety having an amino group (-NH ₂ ) is selected from the group consisting of -(CH ₂ ) _P NH ₂ , and -(CH ₂ ) ₂ (OCH ₂ CH ₂ ) _q NH ₂ ;

- the moiety having a CTA corresponds to a thio-based compound of formula (IV) wherein

Z represents an aryl, heteroaryl, alkyl, -SR’s, -NR’eR’? or -OR’s;

R’s represents aryl, heteroaryl or alkyl;

R’s and R’7 are the same or different and represent hydrogen, halogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, and heteroaryl;

R’s represents hydrogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, and heteroaryl; and

R’9 is a linker which binds the -S- of the thio-based compound to the -N- of the group of formula (i) or (ii); n is an integer from 5 to 1000, p is an integer from 1 to 20, q is an integer from 1 to 10, each Li and l_ ₂ is independently selected from the group consisting of: O, S, NR _X , and a bond; wherein R _x is independently selected from the group consisting of hydrogen, halogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, and heteroaryl; and R3’ and L’s being as defined above; and

R1, R2 and R _T are independently selected from an oligopeptide and R _y ,

R _y being selected from the group consisting of hydrogen, halogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, and heteroaryl; and provided that at least one of R1, R2 and RT is an oligopeptide.

Clause 31. The process of clause 30, wherein the polymer of formula (Ibis) is one wherein at least a 5% of the R’3 groups in the polymer of formula (Ibis) represents a moiety of formula (IV) as defined above; particularly at least a 30%, 40%, 50%, 60%, 70%, 70%, 80% or 90% of the R’3 groups in the polymer of formula (Ibis) represents a moiety of formula (IV) as defined above; particularly at least a 40% of the R’3 groups in the polymer of formula (Ibis) represents a moiety of formula (IV) as defined above; particularly from 30 to 80%; particularly from 40 to 70% of the R’3 groups in the polymer of formula (Ibis) represents a moiety of formula (IV) as defined above..

Clause 32. The process of any one of the clauses 30-31 , wherein the polymer of formula (Ibis) is one wherein the remaining R’3 groups, which are other than a moiety of formula (IV), are the same or different and are selected from -(CH2) _P OH, -(CH2)2(OCH2CH2) _q OH, -(CH2) _P NH2, and -(CH2)2(OCH2CH2) _q NH2, wherein p and q are as defined above.

Clause 33. The process of any one of the clauses 30-32, wherein the thio-based compound (IV) is one where Z represents an aryl, alkyl or -S-R’s, wherein R’s is as defined above; particularly, R’s represents an aryl, alkyl, -S-aryl or -S-alkyl.

Clause 34. The process of any one of the clauses 30-33, wherein the thio-based compound (IV) is one where R’9 represents -alkylene-C(O)-O-alkylene-, wherein the alkylene is optionally substituted; particularly R’g represents -(CR _w R’w)-(CH2)v-C(O)-O- (CH2) _W -*, wherein Rw and R’w are independently selected from hydrogen, hydrogen, halogen, trihalomethyl, trihaloethyl, -NO2, -CN, -N ⁺ (Ci-6alkyl)2O ^_ , -CO2H, -SO3H, -SOC1. ealkyl, -SO ₂ Ci- ₆ alkyl, -C(=O)H, -C(=O)Ci. ₆ alkyl, =0, -N(Ci- ₆ alkyl) ₂ , -C(=O)NH ₂ , -Ci- ₆ alkyl, - Cs-ecycloalkyl, -Cs-eheterocycloalkyl, -Z ^u Ci-6alkyl and -z ^u -C3-6cycloalkyl, wherein Z ^u is defined above; * indicates the binding of R’g to the -N- of the substituent of formula (i); and v and w are integers from 1 to 20.

Clause 35. The polymer of clause 34 wherein R _w and R’ _w are independently selected from hydrogen, CN and alkyl.

Clause 36. The process of any one of the clauses 30-35, wherein the polymer of formula (Ibis) is one wherein:

Ri and R2 are oligopeptides as defined in any of the embodiments provided above, under the first aspect of the invention, particularly negatively charged olipeptides at pH 7;

Li’and L2’ represent a bond;

L3’ represents alkylene;

L4’ represents a substituent of formula (iii), wherein:

- at least 5% of the R3’ groups represent a moiety of formula (IV) as defined above;

Z being selected from alkyl, aryl, -S-alkyl, and -S-aryl; and R’9 representing -alkylene-C(O)-O-alkylene-, wherein the alkylene is optionally substituted; and

- the remaining R3’ groups, which are other than the moiety of formula (II), are the same or different and are selected from -(CH2) _P OH, -(CH2)2(OCH2CH2) _q OH, -(CH ₂ ) _P NH ₂ , and -(CH ₂ )2(OCH2CH2)qNH ₂ ;

Clause 37. The process of any one of the clauses 30-36, wherein the thio-based compound (IV) is one where v is from 1 to 10.

Clause 38. The process of any one of the clauses 30-37, wherein the thio-based compound (IV) is one wherein w is from 1 to 10.

Clause 39. The process of any one of the clauses 30-38, wherein the oligopeptide(s) are as defined in any of the previous clauses 18-27.

Clause 40. The process of any one of the clauses 30-39, wherein the zwitterionic monomer(s) are as defined in clauses 14-15.

Clause 41. The process of any one of the clauses 30-40, which is performed at room temperature.

Clause 42. The process of any one of the clauses 30-41 , which is performed under agitation.

Clause 43. The polymer of formula (I) obtainable by the process of any one of the clauses 30-42.

Clause 44. A nanoparticle, comprising one or more polymers of formula (I) as defined in any one of the preceding clauses or as defined in clause 43.

Clause 45. The nanoparticle of clause 44, which further comprises one or more polymers of formula (Iter):

L” ₃ is independently selected from the group consisting of alkylene, alkenylene, heteroalkylene, heteroalkenylene, arylene, and heteroarylene; or, alternatively at least one of L3” is and T2” is selected from H, alkyl, and wherein LT” is independently selected from the group consisting of:

O, S, NR _X , and a bond, wherein R _x is independently selected from the group consisting of hydrogen, halogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, and heteroaryl, and the remaining L3” groups are independently selected at each occurrence from the group consisting of alkylene, alkenylene, heteroalkylene, heteroalkenylene, arylene, and heteroarylene;

L’ 4 is independently selected from the group consisting of (v) and (vi)

(V) (Vi)

L5” is independently selected from the group consisting of alkylene, alkenylene, heteroalkylene, heteroalkenylene, arylene, and heteroarylene; each R3” is independently selected from the group consisting of hydrogen, halogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, heteroaryl, polyalkylene glycols, a moiety having a hydroxyl group (-OH), and a moiety having an amine group (-NH2), wherein:

- said polyalkylene glycol is either bound directly to the nitrogen atom to which R3” is attached or bound to the nitrogen atom to which R3” is attached via a linker moiety, wherein said linker moiety is an alkylene, cycloalkylene, alkenylene, cycloalkenylene, heteroalkylene, heterocycloalkylene, arylene or heteroarylene group;

- the moiety having a hydroxyl group (-OH) is selected from the group consisting of - (CH ₂ ) _P OH, and -(CH2)2(OCH ₂ CH ₂ )qOH; and

- the moiety having an amino group (-NH ₂ ) is selected from the group consisting of -(CH ₂ ) _P NH ₂ , -(CH ₂ ) _P OH; n is an integer from 5 to 1000, p is an integer from 1 to 20, and q is an integer from 1 to 10, each Li and l_ ₂ is independently selected from the group consisting of:

O, S, NR _X , and a bond; wherein R _x is independently selected from the group consisting of hydrogen, halogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, and heteroaryl; and R3” and Ls” being as defined above; and

R1, R2 and R _T are independently selected from an oligopeptide and R _y ,

R _y being selected from the group consisting of hydrogen, halogen, alkyl, cycloalkyl, alkenyl, cycloalkenyl, heteroalkyl, heterocycloalkyl, acyl, aryl, and heteroaryl; and provided that at least one of R1, R2 and RT is an oligopeptide.

Clause 46. The nanoparticle of clause 45, wherein the polymer of formula (Iter) is one wherein R”3 groups are the same or different and are selected from -(CH2) _P OH, -(CH2)2(OCH ₂ CH ₂ )qOH, -(CH ₂ ) _P NH ₂ , and -(CH ₂ )2(OCH ₂ CH2)qNH2, wherein p and q are as defined above.

Clause 47. The nanoparticle of any one of the clauses 45-46, wherein the polymer of formula (Iter) is one wherein:

R1 and R2 are oligopeptides as defined in any of the above clauses;

Li and L2 represent a bond;

L3” represents alkylene; and

L4” represents a substituent of formula (v), wherein R3” are the same or different and are selected from -(CH ₂ ) _P OH, -(CH2)2(OCH ₂ CH ₂ )qOH, -(CH ₂ ) _P NH ₂ , and -(CH ₂ )2(OCH ₂ CH2)qNH2.

Clause 48. The nanoparticle of any one of the clauses 45-47, wherein the polymer of formula (Iter) is one wherein the oligopeptide(s) are as defined in any of the previous clauses 18-27.

Clause 49. The nanoparticle of any one of the preceding clauses 45-48, which comprises one or more compounds of interest selected from a diagnostic reagent, an imaging reagent and an active ingredient.

Clause 50. The nanoparticle of clause 49, wherein the compound of interest has a net positive charge, or alternatively, a net negative charge, at pH 7.

Clause 51. The nanoparticle of clause 50, wherein:

R1 and R2 represent, in the polymer of formula (I) and optionally in the polymer of formula (Iter), oligopeptides having a net positive charge at pH 7, and the compound has a net negative charge at pH 7; or, alternatively,

R1 and R2 represent, in the polymer of formula (I) and optionally in the polymer of formula (Iter), oligopeptides having a net negative charge at pH 7, and the compound has a net positive charge at pH 7.

Clause 52. The nanoparticle of clause 51, which encapsulates a nucleic acid having negative net charge at biological pH, particularly a RNA, DNA, siRNA, such as gene, an oligonucleotide, ASO, ribozyme, oligonucleotide RNA inhibitor, immune modulating oligonucleotide or other desired negatively charged nucleic acid; peptide or protein.

Clause 53. The nanoparticle of any one of the clauses 45-52, which comprises a polymeric shell comprising the polymer(s) of formula (I) and optionally of formula (Iter); and a core comprising the compound(s) of interest encapsulated therein.

Clause 54. The nanoparticle of any one of the clauses 45-53, which has an average diameter below 1000 nm, particularly from particularly from 50 to 800 nm, particularly from 100 to 500 nm.

Clause 55. A pharmaceutical composition comprising a therapeutically effective amount of the nanoparticle as defined in any one of the clauses 45-54, together with one or more pharmaceutically acceptable excipients or carriers.

Clause 56. A delivery system comprising an external coating comprising the polymer (I) as defined in any one of the clauses 1-29 or 43 and, optionally, one or more polymers of formula (Iter) as defined in any one of the clauses 45-49.

Clause 57. The delivery system of clause 56, which is a viral particle particularly suitable for use in therapy, particularly an AAV.

Clause 58. The delivery system of any one of the clauses 56-57, wherein the one or more polymers of formula (I) are covalently bound to the viral particle’s surface.

Clause 59. The delivery system of any one of the clauses 56-58, wherein the one or more polymers of formula (Iter) are covalent bound to the viral particle’s surface.

Clause 60. The delivery system of clause 56, which is a medical device suitable for use in humans or animals, such as an implantable medical device.

Clause 61. Use of the polymer as defined in any one of the clauses 1-29 or 43, alone or in combination with one or more polymers of formula (Iter) as defined in any of the clauses 45-49 as a coating, particularly as anti-fouling coating.

Clause 62. Use of the polymer as defined in any one of the clauses 1-29 or 43, alone or in combination with one or more polymers of formula (Iter) as defined in any of the clauses 45-49, as a delivery carrier. Clause 63. Use of the polymer as defined in any one of the clauses 1-29 or 43, alone or in combination with one or more polymers of formula (Iter) as defined in any of the clauses 45-49, as an encapsulating agent.

Clause 64. The nanoparticle as defined in any one of the clauses 44-54 or the pharmaceutical composition as defined in clause 55 or the delivery device as defined in any one of the clauses 56-60 for use in therapy.

Clause 65. A method of encapsulating an agent in a matrix of polymers of any one of the clauses 1-29 or 43 to form nanoparticles, the method comprising steps of: providing an active agent as defined above; providing the polymer (s); and contacting the agent and the polymer under suitable conditions to form nanoparticles.

Clause 66. The method of clause 65, wherein the step of contacting comprises (a) spray drying a mixture of the agent and the polymer, (b) double emulsion solvent evaporation techniques or (c) a phase inversion technique.

Clause 67. A method for the preparation of a coating viral particle as defined in any one of the clauses 56-59, the method comprising the step of mixing the viral particle with the polymer(s) as defined in any one of the clauses 1-29 or 43 optionally in combination with one or more polymers of formula (Iter) as defined in any one of the clauses 45-49.

Clause 68. The method of clause 67, wherein when the polymer(s) of formula (I), alone or in combination with the ones of formula (Iter), are covalently bound to the viral surface, then the method comprises a previous step wherein the polymer(s) of formula (I) and/or (Iter) are acid activated.