BACKGROUND OF THE INVENTION

The present invention relates to antibodies having specificity to Nectin-4 and uses thereof.

Nectins are adhesion molecules that help organize epithelial and endothelial junctions and serve as receptors for the entry of the herpes simplex virus, mea- sle virus and poliovirus.

Nectins belong to the immunoglobulin superfamily and are homologs of the poliovirus receptor (PVR / CD155), and for this, have also been called po liovirus receptor bound proteins (PRR). To date, 5 members have been de scribed PVR / CD155, Nectin-1 / PRR1 / CD111 , Nectin-2 / PRR2 / CD112, Nectin-3 / PRR3 and Nectin-4 / PRR4 (1 ,10-13). Their ectodomain is made up of three immunoglobulin-like (Ig) -type V, C, C domains that share between 30 and 55% identity in their amino acid sequences.

Expression of Nectin / PRR molecules is generally extensive in tissues, includ ing hematopoietic, neuronal, endothelial and epithelial cells, with the exception of Nectin-3 and -4, which exhibit more restricted expression profiles.

Nectin-4 is a particularly interesting target. It is expressed during fetal devel opment, but its expression decreases and is very restricted in adult tissues in comparison to that of other members of the Nectin family. Nectin-4 is a tumor associated antigen in 83 % of bladder cancers, 78 % of breast cancers (mainly triple negative and ERBB2+), 71 % Pancreatic cancers, 55 % of lung cancers, 57% of ovarian cancers, 59% of head and neck cancers, and 55% of esopha geal cancers. Expression of Nectin-4 in these pathologies is associated with poor prognosis, probably as a consequence of the ability of Nectin-4 to confer to tumor cells in vitro, higher capacities of migration, proliferation and formation of metastases. In normal tissues, Nectin-4 is only detected in skin, salivary glands, urinary bladder and esophagus. The recent approval by heath authorities of Enfor- tumab vedotin for the 2 ^nd line treatment of advanced urothelial cancer has com pleted the validation of Nectin-4 as a target for the treatment of cancer.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to antibodies having specificity to Nectin-4, anti- gen-binding fragments thereof as well as uses thereof.

In particular, the present invention provides humanized antibodies that derive from the monoclonal anti-Nectin-4 antibody 15A7.5 mAb.

The inventors provide for the first time an antibody, i.e. 15A7.5 mAb, as well as antibodies derived therefrom, specifically binding to Nectin-4 expressed by tumors with a higher affinity in comparison to Nectin-4 expressed by human differentiated keratinocytes. In vitro, this selectivity provides mAb 15A7.5 with lower binding affinity, internalization and cytotoxic activity towards keratino cytes in comparison to tumor cells and in reference to the activity of the HA22 mAb (Enfortumab), in the same assays.

In vivo, this low binding capacity to keratinocytes endows mAb 15A7.5 with a higher half-life due to a lower absorption rate in the skin.

In a xenograft mouse model, treatment with a single dose I.V. of 4 mg/kg of mAb conjugated with Exatecan of established tumors led to a rapid and long- lasting regression.

More particularly, the inventors demonstrate that, in such configuration, 15A7.5 is more efficient than a surrogate of Enfortumab vedotin, i.e., an Enfor tumab vedotin product manufactured using non-GMP methods by a third party that is indistinguishable from the commercially available Enfortumab vedotin.

Accordingly, the antibody 15A7.5 and, in particular, humanized variants de rived therefrom, thus represents a new way to improve therapeutic index of Nectin-4 positive cancer treatment through lower associated skin toxicity and higher anti-tumor selectivity and efficacy. Thus, a first aspect of the invention relates to a monoclonal antibody or an antigen-binding fragment thereof which bind to Nectin-4 characterized by a VH region and optionally a VL region each comprising 3 CDRs designated as CDR-H1 , CDR-H2, CDR-H3, CDR-L1 , CDR-L2 and CDR-L3 defining the bind ing specificity of the antibody or the antigen-binding antibody fragment. A bind ing to human Nectin-4 is preferred.

The antibodies of the invention are monoclonal antibodies (mAb) or monoclo nal antibody fragments characterized by a specific amino acid sequence. If not indicated differently, the term “monoclonal” refers to a single species, i.e. sin gle amino acid composition of antibodies or antibody fragments.

The antigen-binding site of an inventive antibody comprises heavy chain vari able domains/regions (VH) and/or antibody light chain variable domains/re gions (VL), or pairs of VH/VL. The variable domains/region denote each of the pair of light and heavy chains which is involved directly in binding the antibody to the antigen. The variable domain of a heavy chain is abbreviated as “VH” and the variable domain of a light chain is abbreviated as “VL”.

The term “antigen-binding site” denotes the region(s) of an antibody molecule to which a ligand (e.g. the antigen, i.e. Nectin-4, or antigen fragment of it) ac tually binds and which is derived from an antibody.

An antigen-binding site of an antibody according to the invention can contain six complementarity determining regions (CDRs) which contribute in varying degrees to the affinity of the binding site for the antigen. There are three heavy chain variable domain CDRs (CDR-H1 , CDR-H2 and CDR-H3) and three light chain variable domain CDRs (CDR-L1 , CDR-L2 and CDR-L3). Also included within the scope of the invention are functional antigen binding sites comprised of fewer CDRs (i.e., where binding specificity is determined by three, four or five CDRs). For example, less than a complete set of 6 CDRs may be sufficient for binding. In some cases, a VH or a VL domain will be sufficient.

According to the present invention, a VH region or the CDRs thereof alone may constitute a complete antigen-binding site. In certain embodiments, the antibody comprises a VH region or the CDRs thereof as defined herein alone. In other embodiments, the antibody comprises a VH region or the CDRs thereof as defined herein together with a VL region or the CDRs thereof, par ticularly with a VL region or the CDRs thereof as defined herein.

The position of CDRs within a VH or VL region may be defined according to Kabat, et al. , Sequences of Proteins of Immunological Interest, 5th Ed. Public Health Service, National Institutes of Health, Bethesda, MD (1991 ) or the IMGT numbering system, both of which are known to the person skilled in the art. The IMGT numbering has been defined to compare the variable domains what ever the antigen receptor, the chain type, or the species (Lefranc M.-P., "Unique database numbering system for immunogenetic analysis" Immunol ogy Today, 18, 509 (1997); Lefranc M.-P., "The IMGT unique numbering for Immunoglobulins, T cell receptors and Ig-like domains" The Immunologist, 7, 132-136 (1999)).

A further aspect of the present invention relates to a monoclonal antibody or antigen-binding fragment thereof which binds to Nectin-4 comprising (a) a variable heavy chain (VH) region comprising complementarity-deter mining regions (CDRs) CDR-H1 , CDR-H2 and CDR-H3, wherein

(i) the CDR-H1 comprises an amino acid sequence according to SEQ ID NO: 1 or 7, or an amino acid sequence comprising a substitution, particularly a conservative substitution of 1 or 2 amino acids,

(ii) the CDR-H2 comprises an amino acid sequence according to SEQ ID NO: 2 or 8, or an amino acid sequence comprising a substitution, particularly a conservative substitution of 1 or 2 amino acids,

(iii) the CDR-H3 comprises an amino acid sequence according to SEQ ID NO: 3 or 9, or a an amino acid sequence comprising a substitution, particu larly a conservative substitution of 1 or 2 amino acids, and optionally

(b) a variable light chain (VL) region, particularly a VL region comprising complementarity-determining regions (CDRs) CDR-L1 , CDR-L2 and CDR-L3, wherein

(i) the CDR-L1 comprises an amino acid sequence according to SEQ ID NO: 4 or 10, or an amino acid sequence comprising a substitution, particularly a conservative substitution of 1 or 2 amino acids,

(ii) the CDR-L2 comprises an amino acid sequence according to SEQ ID NO: 5 or 11 , or an amino acid sequence comprising a substitution, particularly a conservative substitution of 1 or 2 amino acids,

(iii) the CDR-L3 comprises an amino acid sequence according to SEQ ID NO: 6 or 12, or an amino acid sequence comprising a substitution, particularly a conservative substitution of 1 or 2 amino acids.

Specific amino acid sequences represented by SEQ ID NO:s used herein are provided in the attached sequence listing. SEQ ID NO: 1-6 define the six CDR sequences of the inventive parental antibody according to the IMGT number ing system. SEQ ID NO: 7-12 define the six CDR sequences of the inventive parental antibody according to Kabat. If not stated otherwise, the Kabat system is used herein.

According to the present invention, a substitution of 1 or 2 amino acids in these CDR sequences is possible. In particular embodiments, a conservative amino acid substitution is preferable, i.e. a substitution of an amino acid by another amino acid with similar biochemical properties, for example a substitution of an aliphatic amino acid, e.g. Gly, Ala, Val, Leu or lie, for another aliphatic amino acid, a basic amino acid, e.g. His, Lys or Arg, against another basic amino acid, an acidic amino acid or an amide thereof, e.g. Asp, Glu, Asn or Gin, against another acidic amino acid or an amide thereof, an aromatic amino acid, e.g. Phe, Tyr or Trp, against another aromatic amino acid, or a hydroxy or sulfur containing amino acid, e.g. Ser, Thr, Met or Cys, against another hy droxy or sulfur containing amino acid.

An "antigen-binding fragment" of an antibody refers to a molecule comprising a portion of an intact antibody that binds the antigen to which the intact anti body binds. Examples of antibody fragments include but are not limited to Fv, Fab, Fab ^' , Fab ^' -SH, F(ab’)2; diabodies; linear antibodies; single-chain anti body molecules (e.g. scFv); and multi-specific antibodies formed from antibody fragments. The term also encompasses a fusion protein, e.g. a fusion protein with a non-immunoglobulin peptide or polypeptide, and a conjugate with a non- proteinaceous structure, e.g. a label or a toxin. The terms “antigen-binding fragment of an antibody”, “antigen-binding fragment thereof”, “fragment of an antibody” or “fragment thereof” may be used interchangeably herein.

The inventive antibody or the antigen-binding fragment thereof may be mono- or multivalent, i.e. it may comprise a single antigen-binding site or multiple an tigen-binding sites. For example, Fab fragments have single antigen-binding site, antibodies of the IgG class or Fv or scFv fragments have two antigen binding sites and antibodies of the IgM class have 5 antigen-binding sites. The term “antibody” also encompasses hetero-specific antibodies, e.g. hetero bispecific antibodies, which have different antigen-binding sites, particularly antibodies, which are directed to two different epitopes on the antigen. As used herein, “epitope” is a region of an antigen that is bound by an antibody. The term “epitope” includes any polypeptide determinant capable of specific bind ing to an antibody. According to a further preferred embodiment, the antibody or antigen-binding fragment thereof comprises according to the IMGT numbering system

(i) a VH region comprising the CDR-H1 of SEQ ID NO:1 , the CDR- H2 of SEQ ID NO:2 , and the CDR-H3 of SEQ ID NO:3, and op tionally

(ii) a VL region comprising the CDR-L1 of SEQ ID NO:4 , the CDR- L2 of the SEQ ID NO:5 and the CDR-L3 of the SEQ ID NO:6.

According to another preferred embodiment, the antibody or antigen-binding fragment thereof comprises according to Kabat

(i) a VH region comprising the CDR-H1 of SEQ ID NO:7 , the CDR- H2 of SEQ ID NO:8 , and the CDR-H3 of SEQ ID NO:9, and optionally

(ii) a VL region comprising the CDR-L1 of SEQ ID NO:10 , the CDR- L2 of the SEQ ID NO:11 and the CDR-L3 of the SEQ ID NO:12.

More particularly, the antibody or antigen-binding fragment thereof may com prise

(a) a VH region comprising an amino acid sequence according to SEQ ID NO: 13 or an amino acid sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99% over the whole length of the sequence, and optionally

(b) a VL region, particularly a VL region comprising an amino acid sequence according to SEQ ID NO: 14 or an amino sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99% over the whole length of the sequence.

"Percent (%) amino acid sequence identity" with respect to a peptide or poly peptide sequence is defined as the percentage of amino acid residues in a candidate sequence that are identical with the amino acid residues in the spe cific peptide or polypeptide sequence, after aligning the sequences and intro ducing gaps, if necessary, to achieve the maximum percent sequence identity, Alignment for purposes of determining percent amino acid sequence identity can be achieved in various ways that are within the skill in the art, for instance, using publicly available computer software such as BLAST.

The antibody of the invention may be a chimeric antibody, a multispecific anti body, in particular a bispecific antibody, a human antibody, a humanized anti body or an antigen-binding fragment thereof.

According to the present invention, a “chimeric” antibody refers to an antibody in which a portion of the heavy and/or light chain is derived from a particular source or species, while the remainder of the heavy and/or light chain is de rived from a different source or species.

“Multispecific antibodies” bind two or more different epitopes. The epitopes may be on the same or different antigens. A preferred example of a multi specific antibody is a “bispecific antibody” which binds two different epitopes

In preferred embodiments, the antibody of the invention is a humanized anti body.

The term "humanized antibody" or "humanized version of an antibody" refers to antibodies for which both heavy and light chains are humanized as a result of antibody engineering. A humanized chain is typically a chain in which the V- region amino acid sequence has been changed so that, analyzed as a whole, is closer in homology to a human germline sequence than to the germline se quence of the species of origin. For example, a murine CDR may be grafted into the framework region of a human antibody to prepare the “humanized an tibody.” See, e.g., Riechmann, L, et al. , Nature 332 (1988) 323-327; and Neu- berger, M. S., et al., Nature 314 (1985) 268-270. Other forms of humanized antibodies encompassed by the present invention are those in which the con stant region has been additionally modified or changed from that of the original antibody to generate the properties according to the invention. Humanization assessment is based on the resulting amino acid sequence and not on the methodology per se.

Another preferred embodiment refers to human antibodies.

The term “human antibody”, as used herein, is intended to include antibodies having variable and constant regions derived from human germ line immuno globulin sequences. Human antibodies are well-known in the state of the art (van Dijk, M. A., and van de Winkel, J. G., Curr. Opin. Chem. Biol. 5 (2001) 368-374). Human antibodies can also be produced in transgenic animals (e.g., mice) that are capable, upon immunization, of producing a full repertoire or a selection of human antibodies in the absence of endogenous immunoglobulin production.

The antibody of the present invention may be of any suitable class. The term “class” refers to the type of constant domain or constant region possessed by its heavy chain. As used herein, “constant domain” or “constant region” de notes the sum of the domains of an antibody other than the variable region. The constant region is not directly involved in binding of an antigen, but exhib its various effector functions. The antibody may be of any of the five major classes of antibodies: IgA, IgD, IgE, IgG, and IgM, or any subclass thereof (iso type), e.g., lgG1 , lgG2, lgG3, lgG4, lgA1 , and lgA2. The heavy chain constant domains that correspond to the different classes of immunoglobulins are called a, d, e, g and m, respectively. According to the present invention, an antibody of the class IgG, IgA or IgM or a fragment thereof is particularly suitable.

According to a preferred embodiment, an antibody of the invention is selected from class IgG, e.g. of subclass lgG1 , lgG2, lgG3 of lgG4, of class IgM, of class IgA or an antigen-binding fragment thereof. In particular embodiments, the inventive humanized or human antibodies are defined by combination of at least 3, preferably 6, complementarity-determin ing regions (CDRs), i.e. relate to antibodies or antigen-binding fragments thereof comprising

(a) a variable heavy chain (VH) region comprising complementarity determining regions (CDRs) CDR-H1, CDR-H2 and CDR-H3, wherein

(i) the CDR-H1 comprises an amino acid sequence according to SEQ ID NO: 21, 35, 49 or 63, or an amino acid sequence comprising a substitution, particularly a conservative substitution of 1 or 2 amino acids,

(ii) the CDR-H2 comprises an amino acid sequence according to SEQ ID NO: 22, 36, 50 or 64 or an amino acid sequence comprising a substitution, particularly a conservative substitution of 1 or 2 amino acids,

(iii) the CDR-H3 comprises an amino acid sequence according to SEQ ID NO: 23, 37, 51 or 65, or an amino acid sequence comprising a substitution, particularly a conservative substitution of 1 or 2 amino acids, and optionally

(b) a variable light chain (VL) region, particularly a VL region com prising complementarity-determining regions (CDRs) CDR-L1, CDR-L2 and CDR-L3, wherein

(i) the CDR-L1 comprises an amino acid sequence according to SEQ ID NO: 24, 38, 52 or 66, or an amino acid sequence comprising a substitution, particularly a conservative substitution of 1 or 2 amino acids,

(ii) the CDR-L2 comprises an amino acid sequence according to SEQ ID NO: 25, 39, 53 or 67, or an amino acid sequence comprising a substitution, particularly a conservative substitution of 1 or 2 amino acids, (iii) the CDR-L3 comprises an amino acid sequence according to SEQ ID NO: 26, 40, 54 or 68, or an amino acid sequence comprising a substitution, particularly a conservative substitution of 1 or 2 amino acids.

Specific humanized or human antibodies according to the present invention may comprise

(a) (i) a VH region comprising the CDR-H1 of SEQ ID NO:21 , the CDR-

H2 of SEQ ID NO:22, and the CDR-H3 of SEQ ID NO:23, and optionally

(ii) a VL region comprising the CDR-L1 of SEQ ID NO:24, the CDR- L2 of the SEQ ID NO:25, and the CDR-L3 of the SEQ ID NO:26, or

(b) (i) a VH region comprising the CDR-H1 of SEQ ID NO:35, the CDR-

H2 of SEQ ID NO:36, and the CDR-H3 of SEQ ID NO:37, and optionally

(ii) a VL region comprising the CDR-L1 of SEQ ID NO:38, the CDR- L2 of the SEQ ID NO:39, and the CDR-L3 of the SEQ ID NO:40, or

(c) (i) a VH region comprising the CDR-H1 of SEQ ID NO:49, the CDR-

H2 of SEQ ID NO:50 , and the CDR-H3 of SEQ ID NO:51 , and optionally

(ii) a VL region comprising the CDR-L1 of SEQ ID NO:52, the CDR- L2 of the SEQ ID NO:53, and the CDR-L3 of the SEQ ID NO:54, or

(d) (i) a VH region comprising the CDR-H1 of SEQ ID NO:63, the CDR-

H2 of SEQ ID NO:64, and the CDR-H3 of SEQ ID NO:65, and optionally

(ii) a VL region comprising the CDR-L1 of SEQ ID NO:66, the CDR- L2 of the SEQ ID NO:67 and the CDR-L3 of the SEQ ID NO:68, or

(e) (i) a VH region comprising the CDR-H1 of SEQ ID NO:21 , the CDR- H2 of SEQ ID NO:22, and the CDR-H3 of SEQ ID NO:23, and optionally

(ii) a VL region comprising the CDR-L1 of SEQ ID NO:38, the CDR- L2 of the SEQ ID NO:39 and the CDR-L3 of the SEQ ID NO:40, or

(f) (i) a VH region comprising the CDR-H1 of SEQ ID NO:21 , the CDR-

H2 of SEQ ID NO:22, and the CDR-H3 of SEQ ID NO:23, and optionally

(ii) a VL region comprising the CDR-L1 of SEQ ID NO:52, the CDR- L2 of the SEQ ID NO:53 and the CDR-L3 of the SEQ ID NO:54, or

(g) (i) a VH region comprising the CDR-H1 of SEQ ID NO:21 , the CDR-

H2 of SEQ ID NO:22, and the CDR-H3 of SEQ ID NO:23, and optionally

(ii) a VL region comprising the CDR-L1 of SEQ ID NO:66, the CDR- L2 of the SEQ ID NO:67 and the CDR-L3 of the SEQ ID NO:68, or

(h) (i) a VH region comprising the CDR-H1 of SEQ ID NO:35 , the CDR-

H2 of SEQ ID NO:36, and the CDR-H3 of SEQ ID NO:37, and optionally

(ii) a VL region comprising the CDR-L1 of SEQ ID NO:24, the CDR- L2 of the SEQ ID NO:25 and the CDR-L3 of the SEQ ID NO:26, or

(j) (i) a VH region comprising the CDR-H1 of SEQ ID NO:35, the CDR-

H2 of SEQ ID NO:36, and the CDR-H3 of SEQ ID NO:37, and optionally

(ii) a VL region comprising the CDR-L1 of SEQ ID NO:52, the CDR- L2 of the SEQ ID NO:53 and the CDR-L3 of the SEQ ID NO:54, or

(k) (i) a VH region comprising the CDR-H1 of SEQ ID NO:35, the CDR-

H2 of SEQ ID NO:36, and the CDR-H3 of SEQ ID NO:37, and optionally (ii) a VL region comprising the CDR-L1 of SEQ ID NO:66, the CDR- L2 of the SEQ ID NO:67 and the CDR-L3 of the SEQ ID NO:68, or

(L) (i) a VH region comprising the CDR-H1 of SEQ ID NO:49, the CDR-

H2 of SEQ ID NO:50, and the CDR-H3 of SEQ ID NO:51 , and optionally

(ii) a VL region comprising the CDR-L1 of SEQ ID NO:24, the CDR- L2 of the SEQ ID NO:25 and the CDR-L3 of the SEQ ID NO:26, or

(m) (i) a VH region comprising the CDR-H1 of SEQ ID NO:49, the CDR-

H2 of SEQ ID NO:50, and the CDR-H3 of SEQ ID NO:51 , and optionally

(ii) a VL region comprising the CDR-L1 of SEQ ID NO:38, the CDR- L2 of the SEQ ID NO:39 and the CDR-L3 of the SEQ ID NO:40, or

(n) (i) a VH region comprising the CDR-H1 of SEQ ID NO:49, the CDR-

H2 of SEQ ID NO:50, and the CDR-H3 of SEQ ID NO:51 , and optionally

(ii) a VL region comprising the CDR-L1 of SEQ ID NO:66, the CDR- L2 of the SEQ ID NO:67 and the CDR-L3 of the SEQ ID NO:68, or

(o) (i) a VH region comprising the CDR-H1 of SEQ ID NO:63, the CDR-

H2 of SEQ ID NO:64, and the CDR-H3 of SEQ ID NO:65, and optionally

(ii) a VL region comprising the CDR-L1 of SEQ ID NO:24, the CDR- L2 of the SEQ ID NO:25 and the CDR-L3 of the SEQ ID NO:26, or

(p) (i) a VH region comprising the CDR-H1 of SEQ ID NO:63, the CDR-

H2 of SEQ ID NO:64, and the CDR-H3 of SEQ ID NO:65, and optionally

(ii) a VL region comprising the CDR-L1 of SEQ ID NO:38, the CDR- L2 of the SEQ ID NO:39 and the CDR-L3 of the SEQ ID NQ:40, OG

(q) (i) a VH region comprising the CDR-H1 of SEQ ID NO:63, the CDR-

H2 of SEQ ID NO:64, and the CDR-H3 of SEQ ID NO:65, and optionally

(ii) a VL region comprising the CDR-L1 of SEQ ID NO:52, the CDR- L2 of the SEQ ID NO:53 and the CDR-L3 of the SEQ ID NO:54.

In particular preferred are the humanized antibodies (a), (b), (c), (d), (j), (k), (n) and (q) as defined above.

Of course, the humanized or human antibodies according to the invention may be also defined by their VH and/or VL regions.

Such antibodies may comprise

(i) a VH region comprising an amino acid sequence selected from SEQ ID NO:27, 41, 55 or 69 or an amino acid sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%, and optionally

(ii) a VL region, particularly a VL region comprising an amino acid sequence selected from SEQ ID NO:28, 42, 56, 70 or 103 or an amino sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%.

Specific humanized or human antibodies according to the invention may be defined by their VH and/or VL regions, wherein such antibodies comprise (a) (i) a VH region comprising an amino acid sequence according to

SEQ ID NO:27 or an amino acid sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%, and optionally

(ii) a VL region, particularly a VL region comprising an amino acid sequence according to SEQ ID NO:28 or an amino sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least

99%, or

(b) (i) a VH region comprising an amino acid sequence according to SEQ ID NO:41 or an amino acid sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%, and optionally

(ii) a VL region, particularly a VL region comprising an amino acid sequence according to SEQ ID NO:42 or an amino sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%, or

(c) (i) a VH region comprising an amino acid sequence according to SEQ ID NO:55 or an amino acid sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%, and optionally

(ii) a VL region, particularly a VL region comprising an amino acid sequence according to SEQ ID NO:56 or an amino sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%, or

(d) (i) a VH region comprising an amino acid sequence according to SEQ ID NO:69 or an amino acid sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%, and optionally

(ii) a VL region, particularly a VL region comprising an amino acid sequence according to SEQ ID NO:70 or 103 or an amino sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%, or (e) (i) a VH region comprising an amino acid sequence according to SEQ ID NO:27 or an amino acid sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%, and optionally

(ii) a VL region, particularly a VL region comprising an amino acid sequence according to SEQ ID NO:42 or an amino sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%, or

(f) (i) a VH region comprising an amino acid sequence according to SEQ ID NO:27 or an amino acid sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%, and optionally

(ii) a VL region, particularly a VL region comprising an amino acid sequence according to SEQ ID NO:56 or an amino sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%, or

(g) (i) a VH region comprising an amino acid sequence according to SEQ ID NO:27 or an amino acid sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%, and optionally

(ii) a VL region, particularly a VL region comprising an amino acid sequence according to SEQ ID NO:70 or 103 or an amino sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%, or

(h) (i) a VH region comprising an amino acid sequence according to SEQ ID NO:41 or an amino acid sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%, and optionally (ii) a VL region, particularly a VL region comprising an amino acid sequence according to SEQ ID NO:28 or an amino sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%, or

(j) (i) a VH region comprising an amino acid sequence according to SEQ ID NO:41 or an amino acid sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%, and optionally

(ii) a VL region, particularly a VL region comprising an amino acid sequence according to SEQ ID NO:56 or an amino sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%, or

(k) (i) a VH region comprising an amino acid sequence according to SEQ ID NO:41 or an amino acid sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%, and optionally

(ii) a VL region, particularly a VL region comprising an amino acid sequence according to SEQ ID NO:70 or 103 or an amino sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%, or

(L) (i) a VH region comprising an amino acid sequence according to SEQ ID NO:55 or an amino acid sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%, and optionally

(ii) a VL region, particularly a VL region comprising an amino acid sequence according to SEQ ID NO:28 or an amino sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%, or (m) (i) a VH region comprising an amino acid sequence according to SEQ ID NO:55 or an amino acid sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%, and optionally

(ii) a VL region, particularly a VL region comprising an amino acid sequence according to SEQ ID NO:42 or an amino sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%, or

(n) (i) a VH region comprising an amino acid sequence according to SEQ ID NO:55 or an amino acid sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%, and optionally

(ii) a VL region, particularly a VL region comprising an amino acid sequence according to SEQ ID NO:70 or 103 or an amino sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%,

(o) (i) a VH region comprising an amino acid sequence according to SEQ ID NO:69 or an amino acid sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%, and optionally

(ii) a VL region, particularly a VL region comprising an amino acid sequence according to SEQ ID NO:28 or an amino sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%, or

(p) (i) a VH region comprising an amino acid sequence according to SEQ ID NO:69 or an amino acid sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%, and optionally

(ii) a VL region, particularly a VL region comprising an amino acid sequence according to SEQ ID NO:42 or an amino sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least

99%, or

(q) (i) a VH region comprising an amino acid sequence according to

SEQ ID NO:69 or an amino acid sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%, and optionally

(ii) a VL region, particularly a VL region comprising an amino acid sequence according to SEQ ID NO:56 or an amino sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%.

In particular preferred are the humanized antibodies (a), (b), (c), (d), (j), (k), (n) and (q) as defined above.

According to an especially preferred embodiment, the inventive antibodies and antigen-binding fragments thereof bind to Nectin-4 expressed by tumors with a higher affinity in comparison to Nectin-4 expressed by human differentiated keratinocytes. Such specific binding allows, inter alia, less side effects, in par ticular reduced skin toxicity, during a treatment based on the inventive antibod ies.

As used herein, the terms “binding” and “specific binding” refer to the binding of the inventive antibody or fragment thereof to an epitope of the Nectin-4 an tigen. The measure of the binding strength of an antibody is referred to as affinity. Methods for determining such a binding and/or affinity using in vitro assays are known to the person skilled in the art. According to the present invention, detection with flow cytometry, immuno-histochemistry and/or fluo rescence are described and in particular preferred herein.

The affinity of the binding of an antibody to an antigen is defined by the terms Ka (rate constant for the association of the antibody from the antibody/antigen complex), KD (dissociation constant), and K _di s (kD/ka). Antibodies according to the invention and antigen-binding fragments thereof preferably show a dissociation constant KD of at least 40, preferably at least 45, more preferably at least 50 and most preferably at least 55 (nM).

An especially preferred embodiment of the invention relates to a humanized antibody and antigen-binding fragments thereof, comprising

(i) a VH region comprising the CDR-H1 of SEQ ID NO:1 , the CDR-H2 of SEQ ID NO:2 , and the CDR-H3 of SEQ ID NO:3, and optionally

(ii) a VL region comprising the CDR-L1 of SEQ ID NO:4 , the CDR-L2 of the SEQ ID NO:5 and the CDR-L3 of the SEQ ID NO:6, wherein the antibody and antigen-binding fragments thereof bind to Nectin-4 expressed by tumors with a higher affinity in comparison to Nectin-4 expressed by human differentiated keratinocytes.

Further aspects of the present invention relate to the monoclonal anti-Nectin- 4 antibodies 9A2.7, 3A1.4 as well as 8F06 and antigen-binding fragments thereof as described herein. Flumanized variants of those antibodies are pre ferred.

Thus, the present invention also provides monoclonal antibodies or antigen binding fragment thereof which bind to Nectin-4 comprising (a) a variable heavy chain (VH) region comprising complementarity-deter mining regions (CDRs) CDR-H1 , CDR-H2 and CDR-H3, wherein

(i) the CDR-H1 comprises an amino acid sequence according to SEQ ID NO:79, 87 or 95, or an amino acid sequence comprising a substitution, particularly a conserva tive substitution of 1 or 2 amino acids,

(ii) the CDR-H2 comprises an amino acid sequence according to SEQ ID NO:80, 88 or 96, or an amino acid sequence comprising a substitution, particularly a conserva tive substitution of 1 or 2 amino acids, (iii) the CDR-H3 comprises an amino acid sequence according to SEQ ID NO:81, 89 or 97, or a an amino acid sequence comprising a substitution, particularly a con servative substitution of 1 or 2 amino acids, and optionally

(b) a variable light chain (VL) region, particularly a VL region comprising complementarity-determining regions (CDRs) CDR-L1, CDR-L2 and CDR-L3, wherein

(i) the CDR-L1 comprises an amino acid sequence according to SEQ ID NO:83, 91 or 99, or an amino acid sequence comprising a substitution, particularly a conserva tive substitution of 1 or 2 amino acids,

(ii) the CDR-L2 comprises an amino acid sequence according to SEQ ID NO:84, 92 or 100 or an amino acid sequence comprising a substitution, particularly a conserva tive substitution of 1 or 2 amino acids,

(iii) the CDR-L3 comprises an amino acid sequence according to SEQ ID NO:85, 93 or 101. or an amino acid sequence comprising a substitution, particularly a conserva tive substitution of 1 or 2 amino acids.

One embodiment, relates to an anti-Nectin 4 antibody or antigen-binding frag ment thereof comprising

(i) a VH region comprising the CDR-H1 of SEQ ID NO:79 , the CDR-H2 of SEQ ID NO:80 , and the CDR-H3 of SEQ ID NO:81 , and optionally

(ii) a VL region comprising the CDR-L1 of SEQ ID NO:83 , the CDR-L2 of the SEQ ID NO:84 and the CDR-L3 of the SEQ ID NO:85; or

(a) a VH region comprising an amino acid sequence according to SEQ ID NO:82 or an amino acid sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%, and optionally (b) a VL region, particularly a VL region comprising an amino acid se quence according to SEQ ID NO:86 or an amino sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%.

Antibody 9A2.7 is characterized by such VH region and VL region sequences.

One embodiment, relates to an anti-Nectin 4 antibody or antigen-binding frag ment thereof comprising

(i) a VH region comprising the CDR-H1 of SEQ ID NO:87 , the CDR-H2 of SEQ ID NO:88 , and the CDR-H3 of SEQ ID NO:89, and optionally

(ii) a VL region comprising the CDR-L1 of SEQ ID NO:91 , the CDR-L2 of the SEQ ID NO:92 and the CDR-L3 of the SEQ ID NO:93; or

(a) a VH region comprising an amino acid sequence according to SEQ ID NO:90 or an amino acid sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%, and optionally

(b) a VL region, particularly a VL region comprising an amino acid se quence according to SEQ ID NO:94 or an amino sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%.

Antibody 3A1.4 is characterized by such VH region and VL region sequences.

One embodiment, relates to an anti-Nectin 4 antibody or antigen-binding frag ment thereof comprising

(i) a VH region comprising the CDR-H1 of SEQ ID NO:95 , the CDR-H2 of SEQ ID NO:96 , and the CDR-H3 of SEQ ID NO:97, and optionally

(ii) a VL region comprising the CDR-L1 of SEQ ID NO:99 , the CDR-L2 of the SEQ ID NO:100 and the CDR-L3 of the SEQ ID NO:101; or

(a) a VH region comprising an amino acid sequence according to SEQ ID NO:98 or an amino acid sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%, and optionally (b) a VL region, particularly a VL region comprising an amino acid se quence according to SEQ ID NO:102 or an amino sequence having an identity thereof of at least 85%, at least 90%, at least 95% or at least 99%.

Antibody 8F06 is characterized by such VH region and VL region sequences.

SEQ ID NO: s 79-86 characterize mAb 9A2.7.

SEQ ID NO:s 87-94 characterize mAb 3A1.4.

SEQ ID NO:s 95-102 characterize mAb 8F06.

Beside a lower binding affinity, the inventive antibodies and fragments pro vided herein show also preferably lower internalization and/or cytotoxic activity towards keratinocytes in comparison to tumor cells.

According to an especially preferred embodiment, the inventive antibodies and fragments show lower binding affinity, lower internalization and lower cytotoxic activity towards keratinocytes in comparison to tumor cells.

Of course, a specific binding to human Nectin-4 expressed by tumors is pre ferred. Thus, the antibodies provided herein show preferably specific binding to Nectin-4 and no essential or no cross reactivity to other proteins, in particular to proteins of the human Nectin-family such as Nectin-1 .

According to a further aspect, the present invention also relates to a monoclo nal antibody or antigen-binding fragment thereof characterized by binding to human Nectin-4 expressed by tumors with a higher affinity in comparison to Nectin-4 expressed by human differentiated keratinocytes. For comparison, the binding affinity may be detected by flow cytometry, immuno-histochemistry and/or fluorescence.

According to a further embodiment, inventive antibodies or antigen-binding fragments thereof comprise a labeling group and/or an effector group being coupled to the antibody or antigen-binding fragment. The labeling group may be, for example, a dye, a paramagnetic, radioactive or fluorogenic group that is detectable upon imaging. A preferred effector group is a therapeutic group, in particular a cytotoxic agent, such as chemotherapeutically active agents, drugs, anti-inflammatory agents, radioactive isotopes, toxins such as topoiso- merase poisons, enzymes and fragments thereof such as nucleolytic enzymes, growth inhibitory agents, antibiotics as wells as all suitable anticancer and an titumor agents known to the person skilled in the art. Especially preferred is the topoisomerase poison Camptothecin and derivatives and/or structural an alogues thereof like Exatecan as well as derivatives thereof like Deruxtecan.

A preferred embodiment of an antitumor agent relates to antitumor immune stimulating agents including but not restricted to toll-like receptor (TLR) ago nists or stimulators of interferon genes (STING) pathways.

According to another preferred embodiment an anti-inflammatory agent may be selected from group comprising steroids and corticosteroids such as gluco corticoids, e.g. cortisol and derivatives thereof, or mineralocorticoids such as aldosterone and derivatives thereof.

According to a further aspect of the invention, the antibody or antigen-binding fragment thereof is for use in medicine, particularly for therapeutic or diagnos tic applications including in vitro and in vivo diagnostic applications.

The antibody or antigen-binding fragment thereof may be of use in a method of preventing and/or treating cancer and/or inflammatory disorders, wherein the cancer and/or inflammatory disorder is preferably associated with Nectin- 4 overexpression.

The cancer to be prevented and/or treated may be any kind of cancer, wherein the term “cancer” is used herein to refer to proliferative diseases. The cancer to be prevented and/or treated according to the present invention is preferably selected from the group consisting of urothelial, endometrial, cervical, colorec tal, liver, bladder, thyroid, breast, pancreatic, lung, ovarian head and neck and/or esophagus cancer.

Being highly specific for Nectin-4 expressed on tumors, the inventive antibod ies and fragments thereof may be also used in diagnostics, for example being coupled to a labeling group as described above.

According to a further aspect, the antibody or antigen-binding fragment thereof as described herein may be used in a method of preventing and/or treating an inflammatory disorder, wherein the inflammatory disorder is preferably associ ated with Nectin-4 expression. Such treatment may be preferably combined with an anti-inflammatory agent known to the person skilled in the art. Pre ferred anti-inflammatory agents are described above.

Another aspect of the present invention is a combination of at least 2 different monoclonal antibodies or fragments as described herein.

Further, the present invention relates to a nucleic acid molecule, e.g. a DNA molecule, encoding an antibody VH region, or an antibody VL region, or en coding a complete antibody or an antibody fragment as indicated above, a vector or vector system, i.e. a plurality of vectors, comprising said nucleic acid molecule(s) as indicated above, preferably in operative linkage with an expres sion control sequence, particularly with a heterologous expression control se quence.

Furthermore, the invention relates to a cell comprising a nucleic acid molecule or a vector or vector system as described above. The term “vector,” as used herein, refers to a nucleic acid molecule capable of propagating another nu cleic acid to which it is linked. According to a preferred embodiment, the vector is an expression vector. An “expression vector” is a vector are capable of di recting the expression of nucleic acids to which they are operatively linked. Vectors, in particular expression vectors, for the recombinant production of an tibodies are well known in the art.

The cell may be a known host cell for producing antibodies or antibody frag ments, e.g. a prokaryotic cell such as an E. coli cell, a yeast cell, an insect cell or a mammalian cell, e.g. a CHO cell or a hybridoma cell.

Still a further aspect of the present invention relates to a pharmaceutical com position comprising an antibody or antigen-binding fragment thereof as de scribed herein. Typically, the antibody or antibody-fragment is administered as a pharmaceutical composition comprising the active agent and a pharmaceu tically acceptable carrier or excipient. Examples of suitable carriers and excip ients for formulating antibodies or antibody fragments include saline and aque ous buffer solutions and are well known in the art.

Depending on the stage and the severity of the disorder to be treated, the pharmaceutical composition may be administered once or several times during the course of the disorder. For example, it may be administered daily, each second day, two times weekly or weekly for a suitable period of time.

In certain embodiments, the pharmaceutical composition is administered par- enterally, e.g. by subcutaneous, intramuscular or intravenous injection or by infusion. In further embodiments, the pharmaceutical composition may be ad ministered locally, e.g. orally, nasally or pulmonally, for example as an aerosol.

Further, the present invention is explained in more detail by the following Ta bles, Figures and Examples. FIGURES

FIG. 1: Ch-15A7.5 recognizes human Nectin-4. Detection by flow cytom etry.

Flow cytometry analysis of MDA-MB231 transfected with the N- terminal Flag-tagged epitope of Nectin-4 using a dose range (0.3 ng/mL - 5 pg/mL) of Ch-15A7 antibody. Parental MDA-MB231 cells are included as controls. Cells were then stained with phy- coerythrin conjugate goat anti human Fc antibody. The normal ized mean fluorescence intensity is shown. Inlay: staining of pa rental MDA-MB231 cells with anti Nectin-1, -2 and -3 mAbs (5 pg/mL). Mean fluorescence intensity is represented.

FIG. 2: Ch-15A7.5 recognizes IgV-like domain of human Nectin-4. De tection by ELISA.

Ninety-six-wells plates were coated, as indicated, with 5 pg/mL Nectin-1 extracellular domain Fc fusion recombinant protein (Ned-VCC), or Nectin-4 IgV-like domain Fc fusion recombinant protein (Nec4-V), or Nectin-4 extracellular domain Fc fusion re combinant protein (Nec4-VCC) overnight at 4°C. Ch15A7.5 rec ognizes the Nectin-4 extracellular domain, more precisely the Nectin-4 IgV-like domain and not the Nectin-1 extracellular do main.

FIG. 3: Characterization of Ch-15A7.5 epitope. Competition assay was performed by ELISA.

Ninety-six-wells plates were coated with 5 pg/mL of Nectin-4 ex tracellular domain Fc fusion recombinant protein (Nec4-VCC) overnight at 4°C. Binding of peroxidase-conjugated Ch-15A7.5 mAb (5 pg/mL) was measured in presence of increasing concen- trations (2.75 ng/mL - 6 pg/mL) of Rituximab, Ch-15A7 mAb, En- fortumab (HA22), Ch-N41 mAb and Ch-14A5 mAb. HA22, Ch- N41 and CH-14A5 recognize the IgV domain of Nectin-4.

FIG. 4: Competition of Ch-15A7.5 mAb with Nectin-1 for Nectin-4 bind ing. Competition was assessed by flow cytometry. Ninety-six-wells plates were seeded with 50,000 CHO cells trans fected with human Nectin-4 cDNA. Cells were incubated 45 minutes with increasing concentrations of isotypic control or Ch- 15A7.5 mAb (8 ng/mL - 5 pg/mL). After washing, plates were incubated with 20 pg/mL of Nectin-1 extracellular domain Fc fu sion recombinant protein (Ned-VCC). Nectin-1 binding was re vealed after incubation with goat anti human Fc antibody coupled to phycoerythrin.

FIG. 5: Cross-reactivity with Nectin-4 from cynomolgus monkey, rat and mouse. Detection by flow cytometry.

Flow cytometry analysis of CHO cells transfected with human, cynomolgus monkey, rat or mouse Nectin-4 using a dose range of Ch-15A7 (A), Ch-3A1.4 (B), Ch-9A2.7 (C) or Enfortumab (HA22, D) antibodies (0.05 ng/mL - 5 pg/mL). Cells were then stained with phycoerythrin conjugate goat anti human Fc anti body. Normalized mean fluorescence intensity is shown. Tables report the estimated ECso values determined by GraphPad Prism 9 software using non-linear curve fitting (4 parameters). ~ symbol indicates that the reported value is ambiguous due to poor curve fitting.

FIG. 6: Differential binding to Nectin-4 expressed by tumor cell line and normal differentiated human keratinocytes. Detection by flow cy tometry. Flow cytometry analysis of TNBC cell line (SUM190, plain sym bols) and normal differentiated (0.1 mM CaCh) human keratino- cytes (NHEK, open symbols) using a dose range (1.2 ng/mL - 5 pg/mL)) of Enfortumab (HA22, squares), Ch-15A7.5 (circles), Ch-3A1.4 (triangles) and Ch-9A2.7 (diamonds). Cells were then stained with phycoerythrin conjugate goat anti human Fc anti body. Normalized mean fluorescence intensities are shown. Non linear curve fitting (4 parameters) was done with GraphPad Prism 9 software. Florizontal bar is placed at 50% of maximum staining intensity obtained with FIA22 antibody on SUM190 cells.

FIG. 7: Differential binding to Nectin-4 expressed by tumor cell line and normal differentiated human keratinocytes. Detection by flow cy tometry.

Flow cytometry analysis of TNBC cell line (SUM190, A) and nor mal differentiated (0.1 mM CaCh) human keratinocytes (NFIEK, B) using 5 pg/mL of FIA22 (Enfortumab), Ch-15A7.5, and Ch- 8F06. Cells were then stained with phycoerythrin conjugate goat anti human Fc antibody. Normalized mean fluorescence intensi ties are shown.

FIG. 8: Differential binding to Nectin-4 expressed by tumor cell line and human keratinocytes. Detection by immuno-histochemistry. Cryo-preserved OCT-embedded blocks of high expressing levels of Nectin-4 tumor cell line (SUM190), low expressing levels of Nectin-4 tumor cell line (SUM149), human and cynomolgus skin were processed for staining with 15A7.5 mAb (A) and 9A2.7 mAb (B). Quick score reported for each mAb are shown (A, B). C, ratio of quick score SUM190 over human skin.

FIG. 9: Differential internalization in tumor cell line and human keratino cytes. Detection by fluorescence Enfortumab (HA22), Ch-15A7.5 and Isotypic control mAbs were coupled to pHAB thiol reactive dye to reach dye antibody ratio comprised between 4.58 and 5.55. A dose range of each of these antibody dye conjugates (1.6 ng/mL - 5 pg/mL) was incubated in duplicates with SUM190PT Nectin-4-expressing cell line (A) nor mal human differentiated (0.1 mM CaCh) keratinocytes (B). In tracellular fluorescence was recorded after 24 hours with flo rescence microplate reader (ClarioStar). Reported are the fluo rescence intensities in function of dye antibody conjugate con centration.

FIG. 10: Differential in vitro cytotoxic activity to tumor cells and normal dif ferentiated human keratinocytes. Cell survival measured by MTT assay.

Enfortumab (HA22, diamonds), Ch-15A7.5 (triangles) and Ch- 9A2.7 (squares) mAbs were coupled to a-amanitin to generate antibody drug conjugates which cytotoxic activity of a dose range (7.7 pg/mL - 15 pg/mL) was comparatively evaluated on SUM190PT Nectin-4-expressing cell line (A, D) or normal human differentiated (0.1 mM CaCh) keratinocytes (B, E). Viability (MTT assay) after a 5-days incubation period is reported. ECso values were determined by GraphPad Prism 9 software using non-linear curve fitting (4 parameters). For each condition, the ratio of ECso of Ch-15A7.5 ADC (C) or Ch-9A2.7 ADC (F) to that of HA22-ADC was calculated and reported. Data shown is representative of 2 different Nectin-4 expressing tumor cell lines (SUM190PT and MDA-MB468) and 3 independent donors for human keratino cytes.

FIG. 11: Treatment of SUM190 grafted NSG mice with Ch-15A7.5-MA-

PS-BGIu-Exatecan ADC induces a long-lasting tumor regression period. NSG mice (n=5/group) were orthotopically xenografted bilaterally with the SUM190PT cells embedded in Matrigel. Three different ADC were tested: Isotypic Control, ICT- and Ch-15A7.5-MA-PS- BGIu-Exatecan and Enfortumab vedotin surrogate, HA22-MC-vc- PABC-MMAE. Treatment of mice (single intravenous injection) started when tumors reached approximately 150 mm ³ . Ch- 15A7.5-MA-PS-BGIu-Exatecan (Ch-15A7.5-Ex) was evaluated at 2 doses (4 or 8 mg/kg), ICT-MA-PS-BGIu-Exatecan (ICT-Ex) was given at 8 mg/kg and Enfortumab vedotin (EV) surrogate was given at 4 mg/kg. Tumor sizes (n=10/group) were monitored with a caliper twice a week thereafter and sizes were reported with the following formula (LxlxhxPi/6).

FIG. 12: Apparent affinity of humanized variants to tumor cells. Detection by flow cytometry.

T47D human tumor cells expressing Nectin-4 were numbered and incubated with a dose range (169 pg/mL - 30 pg/mL) of Ch- 15A7.5 or indicated humanized variants. Numbers associated with H and L refer to the number of back mutations introduced. Cells were then stained with phycoerythrin conjugate goat anti human Fc antibody and analyzed by flow cytometry. Mean fluo rescence intensities are reported. GraphPad Prism 9 software was used non-linear curve fitting (4 parameters).

FIG. 13: Treatment of SUM 190 grafted NSG mice with HA22-MA-PS-

BGIu-Exatecan ADC induces a long-lasting tumor regression pe riod.

NSG mice (n=5/group) were orthotopically xenografted bilaterally with the SUM190PT cells embedded in Matrigel. Three different ADC were tested: Isotypic Control, ICT- and HA22-MA-PS-BGIu- Exatecan and Enfortumab vedotin surrogate, HA22-MC-vc- PABC-MMAE. Treatment of mice (single intravenous injection) started when tumors reached approximately 150 mm ³ . HA22MA- PS-BGIu-Exatecan (HA22-Ex) was evaluated at 2 doses (4 or 8 mg/kg), ICT- MA-PS-BGIu-Exatecan (ICT-Ex) was given at 8 mg/kg and Enfortumab vedotin (EV) surrogate was given at 4 mg/kg. Tumor sizes (n=10/group) were monitored with a caliper twice a week thereafter and sizes were reported with the follow ing formula (LxlxhxPi/6).

FIG. 14: Treatment of SUM 190 grafted NSG mice with HA22-MA-PS-

BGIu-Exatecan and HA22-MC-GGFG-DX8951 ADC induces a long-lasting tumor regression period.

NSG mice (n=5/group) were orthotopically xenografted bilaterally with the SUM190PT cells embedded in Matrigel. Five different ADC were tested: Isotypic Control, ICT- and FIA22 coupled either with MA-PS-BGIu-Exatecan (ICT-Ex and FIA22-Ex) or MC- GGFG-DX8951 (ICT- and FIA22-Dxd) and Enfortumab vedotin surrogate, FIA22-MC-vc-PABC-MMAE (EV). Treatment of mice (single intravenous injection) started when tumors reached ap proximately 150 mm ³ . FIA22-Ex and FIA22-Dxd were evaluated at 2 doses (4 or 8 mg/kg), ICT-EX and ICT-Dxd were given at 8 mg/kg and Enfortumab vedotin (EV) surrogate was given at 4 mg/kg. Tumor sizes (n=10/group) were monitored with a caliper twice a week thereafter and sizes were reported with the follow ing formula (LxlxhxPi/6).

FIG. 15: Treatment of SUM190 grafted NOD-Scid mice with Ch-15A7.5- a-amanitin ADC induces a long-lasting tumor regression period. NOD-Scid mice (n=10/group) were orthotopically xenografted with the SUM190PT cells embedded in Matrigel. Three different ADC were tested: Isotypic Control, ICT- and Ch-15A7.5-a-ama- nitin and Enfortumab vedotin surrogate, FIA22-MC-vc-PABC- MMAE (EV surrogate). Treatment of mice (2 intravenous injec tions at a 7-days interval, arrow heads) started when tumors reached approximately 120 mm ³ . Ch-15A7.5-a-amanitin was evaluated at 2 doses (0.5 or 1 mg/kg), ICT-a-amanitin was given at 1 mg/kg and Enfortumab vedotin (EV) surrogate was given at 0.5 or 2 mg/kg. Tumor sizes (n=10/group) were monitored with a caliper twice a week thereafter and sizes were reported with the following formula (LxlxhxPi/6).

FIG. 16: Treatment of SUM190 grafted NOD-Scid mice with HA22-a-am- anitin ADC induces a long-lasting tumor regression period. NOD-Scid mice (n=10/group) were orthotopically xenografted with the SUM190PT cells embedded in Matrigel. Three different ADC were tested: Isotypic Control, ICT- and HA22-a-amanitin and Enfortumab vedotin surrogate, HA22-MC-vc-PABC-MMAE (EV surrogate). Treatment of mice (2 intravenous injections at a 7-days interval, arrow heads) started when tumors reached ap proximately 120 mm ³ . HA22-a-amanitin was evaluated at 2 doses (0.5 or 1 mg/kg), ICT-a-amanitin was given at 1 mg/kg and Enfortumab vedotin (EV) surrogate was given at 0.5 or 2 mg/kg. Tumor sizes (n=10/group) were monitored with a caliper twice a week thereafter and sizes were reported with the following for mula (LxlxhxPi/6).

FIG. 17: Treatment of SUM190 grafted NOD-Scid mice with Ch-15A7.5- a-amanitin ADC induces a long-lasting tumor regression period. NOD-Scid mice (n=10/group) were orthotopically xenografted with the SUM190PT cells embedded in Matrigel. Three different ADC were tested: Isotypic Control, ICT- and Ch-15A7.5-a-ama- nitin and Enfortumab vedotin surrogate, HA22-MC-vc-PABC- MMAE (EV surrogate). Treatment of mice (1 intravenous injec tion, arrow head) started when tumors reached approximately 120 mm ³ . Ch-15A7.5-a-amanitin was evaluated at 3 doses (2, 4 and 8 mg/kg), ICT-a-amanitin was given at 8 mg/kg and Enfor- tumab vedotin (EV) surrogate was given at 4 mg/kg. Tumor sizes (n=10/group) were monitored with a caliper twice a week there after and sizes were reported with the following formula (LxlxhxPi/6).

FIG. 18: Treatment of SUM190 grafted NOD-Scid mice with HA22-a-am- anitin ADC induces a long-lasting tumor regression period. NOD-Scid mice (n=10/group) were orthotopically xenografted with the SUM190PT cells embedded in Matrigel. Three different ADC were tested: Isotypic Control, ICT- and HA22-a-amanitin and Enfortumab vedotin surrogate, HA22-MC-vc-PABC-MMAE (EV surrogate). Treatment of mice (1 intravenous injection, arrow head) started when tumors reached approximately 120 mm ³ . HA22-a-amanitin was evaluated at 3 doses (2, 4 and 8 mg/kg), ICT-a-amanitin was given at 8 mg/kg and Enfortumab vedotin (EV) surrogate was given at 4 mg/kg. Tumor sizes (n=10/group) were monitored with a caliper twice a week thereafter and sizes were reported with the following formula (LxlxhxPi/6).

FIG. 19: Differential binding of Ch-15A7.5 and its humanized variants to

Nectin-4 expressed by tumor cell line and normal differentiated human keratinocytes. Detection by flow cytometry.

Flow cytometry analysis of TNBC cell line (SUM190, upper pan els) and normal differentiated (0.1 mM CaC ) human keratino cytes (NHEK, lower panels) using a dose range (8 pM - 33 nM) of Ch-5A12.2, Ch-15A7.5 and its humanized variants 15A7.5- H1L2, -H1L3, -H2L2, -H2L3, -H3L0, -H3L2, -H3L3. Cells were then stained with phycoerythrin conjugate goat anti human Fc antibody. Normalized mean fluorescence intensities are shown. Non-linear curve fitting (4 parameters) was done with GraphPad Prism 9 software. Note the much lower apparent ECso of Ch- 15A7.5 and its humanized variants towards keratinocytes (lower panels) in comparison to that of Ch-5A12.2.

FIG. 20: Amino acid sequence of the variable heavy chain (VH) and vari able light chain (VK) of the parental antibody clone 5A12.2. The H-CDR and L-CDR sequences according to the IMTG nomencla ture are underlined.

FIG 21 : Amino acid sequences of the variable heavy chains (VH) and var iable light chains (VK) of humanized variants of 9A2.7. The H- CDR and L-CDR sequences according to the IMTG nomencla ture are underlined

FIG 22: Amino acid sequences of the variable heavy chains (VH) and var iable light chains (VK) of humanized variants of 3A1.4. The H- CDR and L-CDR sequences according to the IMTG nomencla ture are underlined.

FIG 23: Amino acid sequences of the variable heavy chains (VH) and var iable light chains (VK) of humanized variants of 8F06. The H- CDR and L-CDR sequences according to the IMTG nomencla ture are underlined

FIG 24: Amino acid sequences of the variable heavy chains (VH) and var iable light chains (VK) of parental antibody clone 15A7.5. The H- CDR and L-CDR sequences according to the IMTG nomencla ture are gray-shaded.

FIG 25: Amino acid sequences of the variable heavy chains (VH) and var iable light chains (VL) of humanized variants of 15A7.5. The H- CDR and L-CDR sequences according to the IMTG nomencla ture are gray-shaded.

FIG 26: Affinity values of humanized 15A7.5 variants

EXAMPLES

Materials and Methods

Cell lines:

Human breast carcinoma cell line MDA-MB231 (ATCC, Manassas, VA) was cultured in DMEM supplemented with 10% fetal bovine serum, 50 lll/mL pen icillin, 50 pg/mL streptomycin and 2 mM glutamine. The cells were transfected with expression vector p3XFLR4.C1 containing a PVRL4 cDNA. Human triple negative breast cancer cell line SUM190PT (BiolVT, Westbury, NY) was cul tures in Ham's F12 medium with 5% fetal bovine serum, 1 % non-essential amino acids, 1 % Hepes, 1 % insulin, 1 pg/mL hydrocortisone, 6.8 ng/mL Triiodo L-tyrosine, 100 lll/mL penicillin, 100 pg/mL streptomycin and 2 mM glutamine. Chinese hamster ovary CHO cell line was cultured in DMEM supplemented with 10% fetal bovine serum, 100 lll/mL penicillin, 100 pg/mL streptomycin and 2 M gluta mine. Human breast carcinoma MDA-MB-468 cell line and T47D cell line were cul tured in RPMI supplemented with 10% fetal bovine serum, 100 lll/mL penicillin, 100 pg/mL streptomycin.

ELISA:

A sandwich enzyme-linked immunosorbent assay was used to control speci ficity of Ch-15A7.5 antibody and to perform competition assays between dif ferent mabs. Ninety-six-wells plates were coated with 10 nM of Nectin-4-VCC- Fc, Nectin-1-VCC-Fc (entire extracellular part) or Nectin-4-V-Fc (comprising only the IgV domain) overnight at +4° C. After washes and saturation with PBS 1 % BSA, cells were incubated for 2 hours at 25°C with 10 nM of peroxidase- conjugated Ch-15A7.5 mab. In the case of competition, binding of 0.5 nM of peroxidase conjugated Ch-15A7.5 mab was measured in the presence of var iable concentration (0.018 nM to 40 nM) of "cold" mab. One hundred pL of peroxidase substrate was added (One Step ABST, Pierce), and OD was red at 405 nm. Flow Cytometry:

Cells or cell lines (10,000 - 50,000) expressing Nectin-4 (naturally or trans fected) were incubated with dose range of the indicated antibodies. After wash ing, cells were then stained with phycoerythrine-conjugated goat anti human antibody (5 pg/mL) Jackson Immuno Research). After fixation, cells were stained with a viability dye (e780, Invitrogen) before flow cytometry acquisition.

Immuno histo chemistry:

Frozen samples stored at -80°C were kept on dry ice and placed in plastic cryomolds in a way that would allow to maximize the number of subsequent sections and were embedded in Optimal Cutting Temperature (OCT) medium. Frozen blocks of OCT were mounted on disks with OCT and cryosection were performed at -20°C on a NX70 cryostat (Thermo Scientific). Cryosections (7pm) were mounted on superfrost + slides (VWR). Only the requested num ber of slides for each sery of test were prepared and stored at -80°C until use. Remaining blocks were stored at -80°C until further use. Sections were ar ranged on the slide and fixed in Acetone at -20°C for 10 minutes. Endogenous peroxidases were inhibited by immersing the slides in hydrogen peroxide (FI2O2) as part of Roche DAB kit protocol. Several dilution of each mab were tested to optimize noise to signal ratio and 0.5 pg/mL of mouse 15A7.5 mab and 10 pg/mL of mouse 9A2.7 mab were determined as optimal. In order to mitigate the non specific binding of the secondary antibody to the mouse tis sue, a Rabbit anti-mouse IgG (4 pg/mL, Abeam) was added following primary Ab incubation. The omni-map anti -rabbit FIRP (Roche) was then used to per form the DAB staining according to manufacturer’s instruction (Ventana auto mat). An assessment of both the staining intensity and the proportion of stained cells was performed. Two trained technicians observed the same microscope field independently and sequentially. Both the stained cells proportion and the staining intensity were evaluated for each field. For each staining, 10 fields were chosen randomly at the magnification which allowed the best visualiza tion of tissues. Scoring procedure was as follows: (i) The proportion of cells stained positively was estimated and a score from 0 to 4 was be assigned for each field ( 0= 0-5%; 1 = 5- 25%; 2= 25-50%; 3= 50-75%; and 4= 75-100%); and (ii) The staining intensity was scored as 0, 1 , 2, or 3 corresponding to the presence of negative, weak, intermediate, and strong brown staining, respec tively. The final Score for each field and for each observer was the multiplica tion of the two values (0 = No staining in the tissue; 12= tissue contains strongly stained cells). For each tissue type, on each of the 5 slides of each set of slides, 10 independent observation fields were scored in parallel for both stain ing intensity and percentage of labeled cells. Technicians simultaneously ob served a given field (virtual slide, on computer screen) and independently scored, blind of the other observer results. For each slide, the 10 scores of each technician were averaged to set the final score for each observer. Final scores of the two observers were averaged yielding the tissue score for the given slide. For the human skin, only results from the first set of the repeata bility are presented.

Internalization assay

Ten thousand SUM190PT or human differentiated keratinocytes (0.1 mM CaCI2) were seeded in 96-wells plates and subsequently incubated for 24 hours at 37°C, with a dose range (1 .6 ng/mL - 5 pg/mL) of anti Nectin-4 mAbs and isotypic control conjugated with pFIAB thiol reactive dye. Upon internaliza tion and endo-lysosomal processing, the acidic environment causes the dye to fluoresce. Fluorescence intensity was monitored on a plate reader with an ex citation at 532 nm and an emission at 560 nm.

In vitro cytotoxic assay

To analyze the in vitro cytotoxic activity of ADC, cell viability was assessed using the AlamarBlue staining protocol as recommended by the manufacturer (Biosource, CA, USA). The test incorporates a fluorescent oxidation-reduction indicator. Fluorescence intensity is proportional to cellular metabolic reduction. Experiments were done by incubating 3000 cells/well (SUM190PT or differen tiated NFIEK) in triplicate with serial dilutions of ADC at Day 0 in 96-wells plates. AlamarBlue was measured at Day 5 by incubating 1/10 volume of ala- marBlue solution for 2 h at 37° C and read at 595 nm (FLUOstar Optima, BMG Labtech).

Mouse experiments

NOD/SCID (nonobese diabetic/severe combined immunodeficient)/gc null mice (NSG) were obtained from Charles River Laboratory (Margate, UK). Six to seven-weeks old females (n=5/group) were orthotopically xenografted bilat erally with the SUM190PT (0.5 x 10 ⁶ ) cells embedded in Matrigel. Treatment with ADC was performed as mentioned in the respective experiments. Tumor sizes (n=10/group) were monitored with a caliper twice a week thereafter and sizes were reported with the following formula (LxlxhxPi/6)

Hybridoma sequencing

For hybridoma sequencing, RNA was first extracted from hybridoma cell pel lets. cDNA was generated by reverse transcription and VH and VL domains were amplified by polymerase chain reaction using Prime STARMax DNA Pol ymerase (Takara). PCR products were subsequently cloned into dedicated heavy and light chain expression vector and then sequenced.

Chimeric antibodies generation, production, purification and control Light chain expression vector is coding for a V kappa chain. Depending on the payload used, 2 different heavy chain expression vectors were used, one cod ing for a Fc fragment with D265C (ThiomAb) L234A and L235A mutations, one coding for a Fc fragment with P331 S, L234Q and L235F mutations. Both Fc fragments are “Fc-silent”. The sequences of anti-Nectin-4 Enfortumab (HA22) were also cloned in the same vectors.

Light and heavy chain vectors were transfected in HEK293 seeded with a 1 .2/1 ratio. After 6 days of production, culture supernatants were clarified and mAbs were purified using MabSelect PrismA resin (GE Healthcare) according to the manufacturer’s instructions. 0.5M Glycine, 3M NaCI, pH8.9 was used as bind ing buffer, and 0.1 M Citrate pH 3 was used for elution. Instant neutralization was done with 10% (V/V) 1 M Tris-HCI pH 9. Monoclonal chimeric antibodies were then dialyzed against PBS 1X pH 7.4 (Mini dialysis devices, 2 ml_-10k, Thermo Scientific) followed by filtration on 0.22 mM filter (Milelex GV hydro philic PVDF, Millipore). Concentration was determined with a Nanodrop 2000 Spectrophotometer (Thermo Scientific) taking into account the specific extinc tion coefficient (E ^{1 %} 280nm) of each monoclonal antibody. Purity was determined by UPLC-SEC using an Acquity UPLC-HClass Bio (Waters) using a Protein- BEH 200A column equilibrated in 0.2 M NaPC , 0.3 M NaCI pH 6.9 supple mented with 10% isopropanol. The mass of the antibodies was determined in a Xevo G2-S Q-Tof mass spectrophoyometer (Waters) using a reversed- phase column (PLRP-S 4000A, Agilent technologies). All samples were ana lyzed after deglycosylation with PNGase F glycosidase (New England Biolabs) at 37°C, according to the manufacturer’s instructions. Fragmentation and/or aggregation of the final material was evaluated by SDS-PAGE. Endotoxin load was determined using a chromogenic LAL-kinetic assay (Charles River En- dosafe).

Antibody conjugation

The thiol reactive dye pHAB (Promega) was conjugated to cysteine of selected anti-Nectin-4 ThiomAb (D265C, L234A, L235A) antibodies using maleimide chemistry according to manufacturer’s instructions. Briefly, antibodies were di alyzed against 0.1 M Phosphate buffer pH 7.0 before being reduced with 2.5 mM for 1 h at room temperature under mild agitation. Subsequently, DTT was removed by washing/centrifugation twice on Zeba spin desalting columns (7 MWCO). 1.2 L of pHdye reagent (10 pg/mL DMSO) was added to 100 pg of antibody and incubated 1 hour at room temperature protected form light. After removal of excess dye with Zeba desalting columns, Dye antibody ratio were calculated to verify equivalent conjugation between different antibodies. A cysteine reactive linker-amanitin compound (Heidelberg Pharma) with a cleavable linker (valine alanine) or with a non-cleavable linker was conjugated to engineered cysteine residues of selected anti-Nectin-4 ThiomAb (D265C, L234A, L235A) antibodies using maleimide chemistry. Briefly, ThiomAb anti bodies in PBS 1X pH 7.4 were reduced with TCEP and interchains disulfides were re-oxidized by dehydroascorbic acid. Subsequently, the engineered cys teines were used for conjugation with cysteine reactive linker amanitin com pound HDP 30.1699. The conjugates were purified by dialysis. The drug-anti- body ratio (DAR) according to LC-MS analysis was comprised between 1 .44 and 1 .79 toxins per conjugated mAb. As determined by SEC-HPLC, less than 2% material was aggregated.

The cysteine reactive linker-exatecan compound Maleimide-Gly-PSAR10-glu- curonide-exatecan (MabLink) was conjugated to cysteine residues of selected anti-Nectin-4 mAbs (P331 S, L234Q and L235F). In brief, mAbs in PBS 1X, 1 mM EDTA were reduced with 14 molar equivalent of TCEP for 2 hours at 37°C, after which the buffer was exchanged (Amicon ultra 30 kDa) to 100 mM KPO4, 1 mM EDTA pH 7.4. Twelve molar equivalents of the cysteine reactive linker- exatecan compound were used for conjugation with reactive cysteines for 35 min at room temperature. Buffer was then exchanged to 100 mM KPO4 pH 8.0, before incubation at 37°C for 24 hours in absence of oxygen to allow the ma leimide to self-hydrolyze. The final exchange buffer was performed in 20 mM His pH 6.0 before filtration 0.22 mM filter. The drug-antibody ratio (DAR) ac cording to LC-MS analysis was comprised between 7.77 and 7.82 toxins per conjugated mAb. As determined by SEC-HPLC, less than 8% material was aggregated.