NZ615308B2 - Antibody-drug conjugates - Google Patents

Abstract

Discloses an antibody-drug conjugate of the formula: Ab-(LU-D)p or a pharmaceutically acceptable salt thereof wherein; (a) Ab is an anti-5T4 antibody or antigen binding portion thereof, comprising: (i) a VH CDR1 region as shown in SEQ ID NO: 5, (ii) a VH CDR2 region as shown in SEQ ID NO: 6, (iii) a VH CDR3 region as shown in SEQ ID NO: 7, (iv) a VL CDR1 region as shown in SEQ ID NO: 8, (v) a VL CDR2 region as shown in SEQ ID NO: 9, and (vi) a VL CDR3 region as shown in SEQ ID NO: 10, (b) LU is a maleimidocaproyl linker unit, (c) p is an integer from 1 to 8, and (d) D is a Drug unit selected from the group consisting of monomethylauristatin E (MMAE) and monomethylauristatin F (MMAF); wherein the sequences are as defined in the complete specification. a VH CDR3 region as shown in SEQ ID NO: 7, (iv) a VL CDR1 region as shown in SEQ ID NO: 8, (v) a VL CDR2 region as shown in SEQ ID NO: 9, and (vi) a VL CDR3 region as shown in SEQ ID NO: 10, (b) LU is a maleimidocaproyl linker unit, (c) p is an integer from 1 to 8, and (d) D is a Drug unit selected from the group consisting of monomethylauristatin E (MMAE) and monomethylauristatin F (MMAF); wherein the sequences are as defined in the complete specification.

Description

ANTIBODY-DRUG CONJUGATES Field The present invention and the invention of NZ 712529, which was divided from the present application, generally relate to anti-5T4 antibody—drug ates for the treatment of cancer.

Background Antibody-drug conjugates (ADCs) combine the binding specificity of monoclonal 1O antibodies with the potency of chemotherapeutic agents. The logy associated with the development of monoclonal antibodies to tumor associated target molecules, the use of more effective cytotoxic agents, and the design of chemical linkers to covalently bind these components, has progressed rapidly in recent years (Ducry L., et al. Bioconjugate Chemistry, 215-13, 2010).

Promising ADCs such as SGN-75 (U82009/148942) and trastuzumab-DM1 (U82009/0226465) are currently in clinical trials. However, as other tumor associated antigens are considered for targets, numerous challenges . Each monoclonal antibody must be characterized separately, an appropriate linker designed, and a suitable cytotoxic agent identified that retains its potency upon delivery to tumor cells. One must consider the antigen density on the cancer target and whether normal tissues express the target antigen. Other considerations include whether the entire ADC is internalized upon binding the target; whether a cytostatic or cytotoxic drug is preferable when ering possible normal tissue exposure and/or the type and stage of the cancer being treated; and, r the linker ting the dy to the drug payload is a cleavable or a eavable linkage. Furthermore, the antibody to drug moiety conjugation ratio must be sufficient t compromising the binding activity of the antibody and/or the potency of the drug. It is evident that ADCs are complex biologics and the nges to develop an effective ADC remain significant.

WO 31527 The human 5T4 tumor associated antigen is the target antigen of the present invention. It has recently been shown that the 5T4 antigen is expressed in high levels on certain highly tumorlgenic cells, also called tumor—initiating cells (W02010/111659).

Tumor-initiating cells show resistance to rd therapies and are ed to be responsible for tumor recurrence and metastasis and therefore present yet another obstacle for ADC development.

The novel anti-5T4 ADCs of the present invention overcome the challenges associated with ADC technology and e highly specific and potent ADCs that bind to tumor cells sing the 5T4 antigen and deliver sufficient cytotoxic drug to the cells, thus providing an innovative and effective treatment for cancer.

Summary In one embodiment, an antibody—drug conjugate of the present invention has the a: Ab-(LU-D)p or a pharmaceutically acceptable salt thereof wherein, Ab is an anti— 5T4 antibody or antigen binding portion thereof, comprising a heavy chain variable region having a VH CDRi region as shown in SEQ ID NO: 5, a VH CDR2 region as shown in SEQ ID NO: 6, and a VH CDR3 region as shown in SEQ ID NO: 7; LU is a linker unit selected from the group consisting of maleimidocaproyl and maleimidocaproyI-Val—Cit- PABA ; p is an integer from about 1 to about 8; and D is a Drug unit ed from the group consisting of MMAE, MMAF, and MMAD.

The present invention further provides anti-5T4 antibody-drug conjugates wherein said anti-5T4 antibody or antigen binding portion thereof, comprises a heavy chain variable region having (a) a VH CDRi region as shown in SEQ ID NO: 5, (b) a VH CDR2 region as shown in SEQ ID NO: 6, and (c) a VH CDR3 region as shown in SEQ ID NO: 7.

The t invention further provides an anti-5T4 antibody-drug conjugate wherein said anti-5T4 antibody or antigen binding n thereof, ses a light chain variable region having (a) a VL CDR1 region as shown in SEQ ID NO: 8, (b) a VL CDR2 region as shown in SEQ ID NO: 9, and (c) a VL CDR3 region as shown in SEQ ID NO: 10.

The present invention further provides an anti~5T4 dy-drug ate wherein said anti—5T4 antibody or antigen binding portion thereof, further comprises a heavy chain variable region having (a) a VH CDR1 region as shown in SEQ ID NO: 5, (b) a VH CDR2 region as shown in SEQ ID NO: 6, and (c) a VH CDR3 region as shown in SEQ ID NO: 7 and a light chain variable region having (a) a VL CDR1 region as shown in SEQ ID NO: 8, (b) a VL CDR2 region as shown in SEQ ID NO: 9, and (c) a VL CDR3 region as shown in SEQ ID NO: 10.

The t invention further provides an anti—5T4 antibody-drug ate wherein said anti-5T4 antibody or antigen binding portion thereof, comprises the VH region of SEQ 1O ID NO: 3 and the VL region of SEQ ID NO: 4.

The present invention further provides an T4 antibody-drug conjugate n said anti-5T4 antibody consists of a heavy chain having SEQ ID NO: 1 and a light chain having SEQ ID NO: 2.

The present invention further provides an anti-5T4 antibody-drug conjugate wherein: (a) said anti-5T4 antibody consists of a heavy chain having SEQ ID NO:1 and a light chain having SEQ ID NO: 2, (b) said LU is maleimidocaproyl, (c) said Drug is MMAF, and (d) p is an r of about 4.

The present invention further provides an anti-5T4 antibody-drug conjugate wherein: (a) said anti-5T4 antibody consists of a heavy chain having SEQ ID N021 and a light chain having SEQ ID NO: 2, (b) said LU is maleimidocaproyI-VaI-Cit-PABA, (c) said Drug is MMAE, and (d) p is an integer of about 4.

The present invention further provides an anti-5T4 dy-drug conjugate wherein: (a) said anti—5T4 antibody consists of a heavy chain having SEQ ID NO:1 and a light chain having SEQ ID NO: 2, (b) said LU is maleimidocaproyI—VaI-Cit-PABA, (c) said Drug is MMAD, and (d) p is an integer from about 1 to about 8. 2012/051304 The present invention further provides an anti—5T4 antibody-drug conjugate wherein: (a) said anti—5T4 antibody consists of a heavy chain having SEQ ID NO:15 and a light chain having SEQ ID NO: 2, (b) said LU is maleimidocaproyl-Val—Cit—PABA, (c) said Drug is MMAE, and (d) p is an integer of about 1 to about 8.

The present invention es an anti-5T4 antibody-drug ate wherein said antibody recognizes an epitope on human 5T4 antigen wherein said epitope ses amino acid residues 173-258 and 282—361 of the amino acid sequence of SEQ ID NO: 11.

The present ion provides a pharmaceutical composition comprising an antibody-drug conjugate indicated above and a ceutically acceptable r.

The present invention further provides a method of treating a 5T4-positive cancer in a patient in need thereof, comprising administering to said patient an antibody-drug conjugate indicated above.

The present invention further provides a method of treating a 5T4-positive cancer wherein said cancer is selected from the group consisting of carcinomas of the bladder, , cervix, colon, endometrium, kidney, lung, esophagus, ovary, prostate, pancreas, liver, skin, stomach, and testes.

More preferably, the t invention provides a method of treating a 5T4-positive cancer wherein said cancer is selected from the group consisting of colorectal, breast, pancreatic, and non-small cell lung carcinomas.

The invention further provides an antibody-drug conjugate indicated above for use in therapy.

The invention further provides the use of an antibody—drug conjugate indicated above for the manufacture of a medicament.

The invention further es the use indicated above, wherein said use is for the treatment of a 5T4-positive cancer and wherein said cancer is selected from the group consisting of carcinomas of the r, breast, cervix, endometrium, kidney, lung, esophagus, ovary, prostate, pancreas, skin, h, and testes.

More preferably, the invention further provides the use indicated above, wherein said use is for the treatment of a 5T4—positive cancer wherein said Cancer is ed from the group consisting of colorectal, breast, pancreatic, and non—small cell lung carcinomas.

The invention further provides a nucleic acid that encodes an anti-5T4 antibody, a vector comprising said nucleic acid, and a host cell sing said vector.

The invention further provides a process for producing an T4 antibody comprising cultivating the host cell comprising the above mentioned vector and recovering the antibody from the cell culture.

The invention further es a process for producing an anti-5T4 antibody-drug 1O conjugate sing: (a) taking the antibody recovered from the cell culture, (b) chemically linking said antibody via a linker unit selected from the group consisting of maleimidocaproyl or maleimidocaproyl-Val-Cit to a Drug unit ed from the group consisting of MMAE, MMAD, or MMAF, and (c) purifying the antibody-drug conjugate.

In a particular embodiment, the present invention provides an antibody-drug conjugate of the formula: Ab-(LU-D)p or a pharmaceutically acceptable salt thereof wherein; (a) Ab is an anti-5T4 antibody or antigen binding portion thereof, comprising: (i) a VH CDR1 region as shown in SEQ ID NO: 5, (ii) a VH CDR2 region as shown in SEQ ID NO: 6, (iii) a VH CDR3 region as shown in SEQ lD NO: 7, (iv) a VL CDR1 region as shown in SEQ ID NO: 8, (v) a VL CDR2 region as shown in SEQ ID NO: 9, and (vi) a VL CDR3 region as shown in SEQ ID NO: 10.(b) LU is a maleimidocaproyl linker unit, (0) p is an integer from 1 to 8, and (d) D is a Drug unit selected from the group ting of monomethylauristatin E (MMAE) and monomethylauristatin F (MMAF). in another particular embodiment, the present invention provides an antibody-drug conjugate of the formula: Ab-(LU-D)p or a ceutically acceptable salt f wherein: (a) Ab is an anti-5T4 antibody or antigen binding portion thereof, sing: (i) a VH CDR1 region as shown in SEQ ID NO: 5, (ii) a VH CDR2 region as shown in SEQ ID NO: 6, (iii) a VH CDR3 region as shown in SEQ ID NO: 7, (iv) a VL CDR1 region as shown in SEQ ID NO: 8, (v) a VL CDR2 region as shown in SEQ ID NO: 9, and (vi) a VL CDR3 (followed by page 5a) region as shown in SEQ ID NO: 10, (b) LU is a maleimidocaproyl-valine-citrulline-p- aminobenzyloxycarbonyl midocaproyl-Val-Cit-PABA) linker unit, (0) p is an integer from 1 to 8, and (d) D is a Drug unit selected from the group consisting of monomethylauristatin E (MMAE), monomethylauristatin D (MMAD), and monomethylauristatin F (MMAF).

Detailed Description The t invention provides anti—5T4 antibody-drug conjugates for the treatment of cancer. In order that the present ion is more readily understood, certain terms are first defined.

All amino acid abbreviations used in this disclosure are those accepted by the United States Patent and ark Office as set forth in 37 C.F.R. § 1.822 (B)(l). 5T4 refers to the 5T4 oncofetal antigen, a 72 kDa highly glycosylated transmenbrance glycoproteln comprising a 42 kDa non-glycosylated core (see US 5,869,053). Human 5T4 is expressed in numerous cancer types, including carcinomas of the bladder, breast, cervix, colon, endometrium, kidney, lung, gus, ovary, prostate, pancreas, liver, skin, stomach, and testes. Highly tumorigenic cells, also called cancer stem cells or tumor—initiating cells have been shown to have high levels of 5T4 expression (W02010/111659). Anti-5T4 dies of the invention include antibodies that specifically bind the human 5T4 antigen (see US 2007/0231333).

[FOLLOWED BY PAGE 6] WO 31527 2012/051304 An ody” is an immunoglobulin molecule capable of specific binding to a , such as a carbohydrate, polynucleotide, lipid, polypeptide, etc., through at least one antigen recognition site, located in the variable region of the immunoglobulin molecule. As used herein, the term ody” encompasses not only intact polyclonal or monoclonal antibodies, but also any antigen binding fragment (i.e., "antigen—binding portion") or single chain thereof, fusion proteins comprising an antibody, and any other modified configuration of the immunoglobulin molecule that ses an antigen recognition site including, for example without limitation, Fab, Fab’, F(ab’)2, an Fd nt consisting of the VH and CH1 domains, an Fv fragment consisting of the VL and VH domains of a single arm of an antibody, an isolated complementarity determining region (CDR), scFv, single domain antibodies (e.g., shark and camelid antibodies), dies, minibodies, intrabodies, diabodies, triabodies, odies, v-NAR and bis-scFv.

An antibody includes an antibody of any class, such as lgG, 19A, or lgM (or sub- class thereof), and the antibody need not be of any particular class. Depending on the antibody amino acid sequence of the nt region of its heavy chains, immunoglobulins can be assigned to different classes. There are five major classes of immunoglobulins: lgA, lgD, igE, lgG, and IgM, and several of these may be further divided into subclasses (isotypes), e.g., lgGi, lgG2, lgG3, lgG4, lgA1 and lgA2. The heavy-chain constant regions that correspond to the different classes of immunoglobulins are called alpha, delta, epsilon, gamma, and mu, respectively. The subunit structures and three-dimensional urations of different classes of immunoglobulins are weil known.

A “variable region” of an antibody refers to the variable region of the antibody light chain or the variable region of the antibody heavy chain, either alone or in ation. As known in the art, the variable regions of the heavy and light chain each consist of four framework regions (FRs) connected by three complementarity determining regions (CDRs) also known as hypervariable regions, contribute to the formation of the antigen g site of antibodies. If variants of a subject variable region are d, particularly with substitution in amino acid residues outside of a CDR region (i.e., in the framework region), appropriate amino acid substitution, preferably, conservative amino acid substitution, can be identified by comparing the subject variable region to the variable regions of other antibodies which contain CDR1 and CDR2 sequences in the same canonincal class as the subject variable region ia and Lesk, J Mol Biol 196(4): 901 ~917, 1987). When choosing FR to flank subject CDRs, e.g., when humanizing or optimizing an antibody, FRs from antibodies which contain CDR1 and CDR2 sequences in the same canonical class are preferred.

A “CDR” of a variable domain are amino acid residues within the variable region that are identified in ance with the definitions of the Kabat, Chothia, the cumulation of both Kabat and Chothia, AblVl, contact, and/or conformational definitions or any method 1O of CDR determination well known in the art. Antibody CDRs may be identified as the hypervariable regions originally defined by Kabat et al. See, e.g., Kabat et al., 1992, Sequences of Proteins of Immunological Interest, 5th ed., Public Health Service, NlH, Washington, DC. The positions of the CDRs may also be identified as the structural loop structures originally described by Chothia and . See, e.g., Chothia et al., 1989, Nature 342:877-883. Other approaches to CDR identification include the “AbM definition,” which is a compromise between Kabat and Chothia and is d using Oxford lar‘s AbM antibody modeling software (now Accelrys®), or the ct definition” of CDRs based on observed antigen contacts, set forth in MacCallum et al., 1996, J. Mol.

Biol., 262:732—745. In another approach, referred to herein as the rmational definition” of CDRs, the positions of the CDRs may be identified as the residues that make enthalpic contributions to antigen binding. See, e.g., Makabe et al., 2008, Journal of Biological Chemistry, 283:1156-1166. Still other CDR boundary definitions may not strictly follow one of the above approaches, but will nonetheless overlap with at least a portion of the Kabat CDRs, although they may be shortened or lengthened in light of prediction or experimental findings that ular residues or groups of residues or even entire CDRs do not significantly impact antigen binding. As used herein, a CDR may refer to CDRs defined by any ch known in the art, including combinations of approaches. The methods used herein may utilize CDRs defined ing to any of these approaches. For any given embodiment ning more than one CDR, the CDRs may be defined in WO 31527 accordance with any of Kabat, Chothia, extended, AbM, contact, and/or conformational definMons.

The term "menacienat antibody” {ti tab) refers to an antibody that is derived tram a singie copy or (acne, incieding (e.g., any eekaryetis, prexazyetie, cr phage stems, and not thernefimmtbyefifichitkgfibduced.teefieabw,atnenedenaianfibbdycfitheinyenfien eahmhegeneeuscrsubskwmafiyhcwmgeneeuspenumfien "Humanized" antibody refers to forms of man (e.g. murine) antibodies that are chimeric giobuiins, immunogiobulin chains, or fragments thereof (such as Fv, Fab, Fab‘, F(ab')2 or other antigen-binding subsequences of antibodies) that contain minimal sequence derived from non—human immunogiobuiin. ably, humanized antibodies are human giobuiins (recipient antibody) in which residues from a complementary determining region (CDR) of the ent are replaced by residues from a CDR of a non-human species (donor antibody) such as mouse, rat, or rabbit having the deskedspecmcfiy,afimny,andcapachy The term “chimeric antibody" is ed to refer to antibodies in which the variable region sequences are derived from one species and the constant region sequences are derived from another species, such as an antibody in which the variable region sequences are derived from a mouse antibody and the constant region sequences are derived from a human antibody.

Anabowesaffiwflnvenfiencanbegxeducedusmgtecbmquesmefikncmminthean, eg, recembinant technetegies, phage dispiay techneiogées, synthetic technetcgies er cembinatiens of such techneibgies er other teshnciegies readiiy known in the art {see for exempts, na, 5.51., Ciin‘ Chem. 45: $2860 {18%} and Fatigues, FA” et ai, J.

Mei. Bict, 3?3{43:924-40 (290?); iaMestam’zbebwdeficflxfiénafiCQRsmrmeanflxfifisbfmebmmem invenfibn.

---A1 KASQSVSNDVA FATNRYT QQDYSSPWT ---A3 KASQDVDTAVA WASTRLT QQYSSYPYT Table 2 Antibody NFGMN WINTNTGEPRYAEEFKG DWDGAYFFDY SEQ ID N016 SEQ ID NO: 7 GYTFTNFGMN WINTNTGEPRYAEEFKG DWDGAYFFDY SEQ ID N016 SEQ ID NO: 7 TYAMN RIRSKSNNYATYYADSVKD QWDYDVRAMNY SEQ ID NO: 22 SEQ ID NO: 23 SEQ ID NO: 24 The present invention es an antibody or n binding portion thereof, that comprises: a) a light chain variable region comprising: i) a LCDR1 having an amino acid sequence selected from the group consisting of SEQ ID NOS: 8 and 17; ii) a LCDR2 having an amino acid sequence ed from the group consisting of SEQ ID NOS: 9 and 18; and WO 31527 iii) a LCDR3 having an amino acid sequence selected from the group consisting of SEQ ID N03: 10 and 19; and b) a heavy chain variable region comprising: i) a HCDRI having an amino acid sequence selected from the group consisting of SEQ ID NOs: 5 and 22; ii) a HCDR2 having an amino acid sequence selected from the group consisting of SEQ ID NOs: 6 and 23; and iii) a LCDRI having an amino acid sequence selected from the group consisting of SEQ ID NOs: 7 and 24.

A preferred antibody or n binding portion thereof, of the invention comprises: a) a LCVR comprising: a LCDRi of SEQ ID NO: 8, a LCDR2 of SEQ ID NO: 9, and a LCDR3 of SEQ ID NO: 10; and b) a HCVR comprising: a HCDR1 of SEQ ID NO: 5, a HCDR2 of SEQ ID NO: 6, and a HCDR3 ofSEQ ID NO: 7.

Preferred monoclonal dies of the ion are referred to herein as A1 (a humanized anti-5T4 IgGi dy); A1—IgG4 (a humanized anti—5T4 IgG4 antibody); A3 (a mouse/human chimeric antibody); and A3hu (a humanized anti—5T4 IgGi antibody). The SEQ ID NOs of the amino acid sequences encoding Mabs A1,A’I—IgG4 and A3 are provided in Table 3 below: Table 3 mun-m- gllIFII I:II--------I-__-_-A’l — 1 2 10 1 3 The phrases "an antibody recognizing an antigen" and "an antibody ic for an antigen" are used interchangeably herein with the term "an antibody which binds specifically to an antigen.” Anti-5T4 Antibody-Drug conjugate refers to an T4 antibody or antigen g portion thereof, as described herein linked to a cytotoxic drug moiety (D) via a linker unit molecule (LU).

Linker Unit (LU): LU describes the direct or indirect linkage of the dy to the drug. Attachment of a linker to a mAb can be accomplished in a variety of ways, such as through surface lysines, reductive-coupiing to oxidized carbohydrates, and through cysteine residues liberated by reducing interchain disuifide linkages. A variety of ADC linkage systems are known in the art, ing hydrazone—, disuifide- and peptide-based linkages.

Drug (D): A drug is any substance having biological or detectable activity, for example, therapeutic agents, detectable labels, binding agents, etc., and prodrugs, which are metabolized to an active agent in vivo. The terms drug and payload are used hangeably. In some embodiments, the Drug is an auristatin, such as auristatin E (also known in the art as a derivative of atin-1 O) or a tive thereof. The auristatin can be, for example, an ester formed between auristatin E and a keto acid. For example, auristatin E can be reacted with paraacetyl benzoic acid or benzoylvaleric acid to produce AEB and AEVB, respectively. Other typicai auristatins include AFP, MMAF, and MMAE. The synthesis and structure of ary atins are described in US. Patent Nos. 869, 7,098,308, 7,256,257, 7,423,116, 7,498,298 and 7,745,394, each of which is incorporated by reference herein in its entirety and for all purposes.

Auristatins have been shown to interfere with microtubuie dynamics and nuclear and cellular division and have anticancer activity. Auristatins of the present invention bind tubulin and can exert a cytotoxic or cytostatic effect on a 5T4 expressing cell or cell line.

There are a number of different assays, known in the art, that can be used for determining whether an auristatin or resultant antibody-drug conjugate exerts a cytostatic or cytotoxic effect on a desired cell or cell line. Methods for determining whether a compound binds tubulin are known in the art. See, for example, Muller et al., Anal. Chem 2006, 78, 4390- 4397; Hamel et al., Molecular Pharmacology, 1995 47: 965—976; and Hamel et al., The Journal of Biological try, 1990 26528, 17141 -1 71 49.

Examples of drugs or payloads are selected from the group consisting of DM1 (maytansine, N2'—deacetyI-N2'—(3-mercaptooxopropyl)- or acetyI-N2'—(3-mercapto- 1—oxopropyl)—maytansine), mc—MMAD (6—maleimidocaproyl-monomethylauristatin-D or N— methyl-L-valyl—N-[(1S,2R)~2~methoxy—4—[(28)[(1 R,2R)-1—methoxy-2—methyloxo-3— [[(1S)phenyl—1-(2-thiazolyl)ethyl]amino]propyl]—1~pyrrolidinyI][(1S)~1—methylpropyl} oxobutyli—N-methyl- (9Cl)- L-valinamide), mc-MMAF (maleimidocaproyl- 1O monomethylauristatin F or N-[G-(2,5-dihydro-2,5—dioxo-1H-pyrroly|)—1—oxohexyI]—N- methyl-L-valyl-L-vaIyl-(3R,48,58)-3~methoxy—5-methyl-4—(methylamino)heptanoyl- (aR,BR,2S)-B-methoxy-a-methyl-Z-pyrrolidinepropanoyl-L-phenylalanine) and mc—Val-Cit- PABA-MMAE (6-maleimidocaproyl it-(p-aminobenzyloxycarbonyl)— monomethylauristatin E or -[[N—[6—(2,5—dihydro—2,5-dioxo—1 H—pyrrol—1~yl)—1-oxohexyl]- L-vaIyI-N5-(aminocarbonyl)-L-ornithyliamino]phenyl]methoxy]carbonyl]-N~methyl-L-valyI-N- [(18,2R)~4-[(2S)—2—[(1R,2R)—3-[[(1R,28)—2—hydroxymethyl-2—phenylethyl]amino] methoxy~2~methyl—3—oxopropyl]pyrrolidinyl]—2—methoxy—1-[(1S)methy|propyl]—4— oxobutyl]~N-methyl—L-va|inamide). DM1 is a derivative of the tubulin inhibitor maytansine while MMAD, MMAE, and MMAF are auristatin derivatives. The preferred payloads of the present invention are selected from the group consisting of mc-MMAF and mc-Val—Cit— PABA-MMAE.

The term “epitopc” refers to that partian at a moiacuie capabie of being r cagni'zed by and amend by an antibody at Gi‘tét as" more cf the dy‘s aritigenntainding regions.

Epitopes often consist of a chemically active surface grouping of les such as amino acids or sugar side chains and have specific three-dimensional structural characteristics as well as specific charge characteristics. The term "antigenic epitope" as used herein, is defined as a portion of a polypeptide to which an antibody can specifically bind as determined by any method well known in the art, for example, by conventional immunoassays. A "nonlinear e" or "conformational epitope" comprises noncontiguous polypeptides (or amino acids) within the antigenic protein to which an antibody specific to the epitope binds.

The term "binding affinity $29)“ as Lissa herein, is intended to refer to the alssociaticn rate of a particuiar antigsasantibociy interaction The K9 is the ratio of tits rats of iation. also caiiso‘ the “offutats (Raff, to the association rate, or "on“ rate km)".

Tnus Kg squats kw! K0,; and is expressed as a moiar concentration (it/i}. it foiiows that the smailer this Kg. the stronger the affinity of binding. Tharefora. a an of “i 3.55% indicates waaiz. binding ty ed to 3 Kg of t nit/i. KD values for antibodies can be determined using methods well established in the art. One method for determining the KB of an antibody is by using surface plasmon resonance (SPR), typically using a biosensor system such as a e® system.

The term “specifically binds” as used herein in reference to the binding between an antibody and a 5T4 antigen and the dy binds the 5T4 n with a KD less than about 30 nM as determined by SPR at 25°C.

Pharmaceutically acceptable salt as used herein refers to pharmaceutically acceptable organic or nic salts of a molecule or macromolecule.

The term cy" is a measurement of biological activity and may be designated as |Cso, or effective concentration of antibody needed to inhibit 50% of growth of a 5T4 positive cell line as bed in Example 3. Alternatively, potency may refer to anti-tumor activity as determined in an in vivo tumor xenograph model as shown in Example 4.

The terms "polynucleotide” or "nucleic acid molecule", as used herein, are intended to include DNA les and RNA molecules. A nucleic acid molecule may be single- stranded or double-stranded, but ably is double—stranded DNA.

The polynucleotides that encode the antibodies of the present invention may include the following: only the coding sequence for the variant, the coding sequence for the variant and additional coding sequences such as a functional polypeptide, or a signal or secretory sequence or a pro—protein sequence; the coding sequence for the antibody and non-coding sequence, such as introns or non-coding sequence 5’ and/or 3’ of the coding sequence for the antibody. The term ‘polynucleotide encoding an antibody” encompasses a cleotide which includes additional coding ce for the variant but also a cleotide which includes additional coding and/or non—coding sequence. lt is known in the art that a cleotide sequence that is optimized for a ic host cell/expression system can readily be obtained from the amino acid sequence of the desired n (see GENEART® AG, Regensburg, Germany).

The polynucleotides encoding the antibodies of the present invention will typically include an sion control polynucleotide sequence operably linked to the antibody coding ces, including naturally-associated or heterologous promoter regions known in the art. Preferably, the expression control sequences will be eukaryotic promoter 1O systems in s capable of transforming or ecting eukaryotic host cells, but control sequences for prokaryotic hosts may also be used. Once the vector has been incorporated into the appropriate host cell line, the host cell is propagated under conditions suitable for expressing the nucleotide sequences, and, as desired, for the collection and purification of the antibodies. Preferred eukaryotic cell lines include the CH0 cell lines, various COS cell lines, HeLa cells, myeloma cell lines, ormed B—cells, or human embryonic kidney cell lines. The most preferred host cell is a CHO cell line.

The present invention encompasses antibodies or antigen-binding portions thereof that bind to a specific epitope on the 5T4 antigen. The epitope fied is a ear or conformational epitope comprising a first contact with the human 5T4 antigen (SEQ lD NO: 11) between amino acid residues 173 and 252 and comprising a second contact between amino acid residues 276 and 355 (see Example 7). Thus, the CDRs and heavy and light chain variable regions described herein are used to make full-length antibodies as well as functional fragments and analogs that maintain the binding affinity of the protein employing the CDRs specific for the above mentioned epitope of the 5T4 antigen.

The binding affinity of dies of the present invention is determined using SPR (Example 6). In these experiments the 5T4 antigens are immobilized at low densities onto a BlAcore® chip and antibodies are flowed past. Build up of mass at the surface of the chip is measured. This analytical method allows the determination in real time of both on and off rates to obtain affinity (KD) for binding. The humanized antibodies of the present invention have a KB of between about 0.30 and about 30 nM; about 0.30 and about 20 nM; about 0.30 and about 10 nM; about 0.5 and about 7 nM; about 1.0 and about 5 nM; and about 1.0 and about 3 nM.

Conjugation of Drugs to an Antibody The drug has, or is modified to include, a group reactive with a conjugation point on the antibody. For example, a drug can be attached by aikylation (e.g., at the epsilon—amino group lysines or the N—terminus of antibodies), reductive amination of oxidized carbohydrate, transesterification between hydroxyl and carboxyl groups, amidation at amino groups or carboxyl groups, and conjugation to thiols. in some embodiments, the 1O number of drug es, p, conjugated per antibody le ranges from an average of 1 to 8; 1 to 7, 1 to 6, 1 to 5, 1 to 4, 1 to 3, or1 to 2. in some embodiments, p ranges from an average of 2 to 8, 2 to 7, 2 to 6, 2 to 5, 2 to 4 or 2 to 3. In other embodiments, p is an average of 1, 2, 3, 4, 5, 6, 7 or 8. In some embodiments, p ranges from an average of about1 to about 8; about1 to about 7, about 1 to about 6, about 1 to about 5, about1 to about 4, about 1 to about 3, or about 1 to about 2. In some embodiments, p ranges from about 2 to about 8, about 2 to about 7, about 2 to about 6, about 2 to about 5, about 2 to about 4 or about 2 to about 3. For examples of chemistries that can be used for ation, see, e.g., t Protocols in Protein e (John Wiley & Sons, Inc.), Chapter 15 cal Modifications of Proteins) (the disclosure of which is incorporated by reference herein in its entirety.) For example, when al activation of the protein results in formation of free thiol groups, the protein may be conjugated with a dryl reactive agent. in one aspect, the agent is one which is substantially specific forfree thiol groups. Such agents include, for example, malemide, haloacetamides (e.g., iodo, bromo or chloro), haloesters (e.g., iodo, bromo or chloro), halomethyl ketones (e.g., iodo, bromo or chloro), ic halides (e.g., iodide, bromide or chloride), vinyl sulfone and pyridylthio.

The drug can be linked to an antibody by a linker. Suitable linkers include, for example, cleavable and non-cleavable linkers. A cleavable linker is typically susceptible to cleavage under intracellular ions. Suitable cleavable s include, for example, a peptide linker ble by an intracellular protease, such as lysosomal protease or an endosomal se. ln exemplary embodiments, the linker can be a dipeptide linker, such as a -citrulline (val-cit), a phenylalanine-lysine ys) linker, or maleimidocapronic ~valine-citruline—p-aminobenzyloxycarbonyl (mc-Val—Cit—PABA) linker.

Another linker is uccinimidyI—4—[N—maleimidomethyl]cyclohexane—1~carboxylate (smcc). Sulfo—smcc conjugation occurs via a maleimide group which reacts with sulfhydryls (thiols, -SH), while its Sulfo-NHS ester is reactive toward primary amines (as found in Lysine and the protein or peptide N-terminus). Yet another linker is maleimidocaproyl (mc). Other suitable s include linkers hydrolyzable at a specific pH or a pH range, such as a hydrazone linker. Additional suitable cleavable linkers include disulfide linkers. The linker may be covalently bound to the antibody to such an extent that the antibody must be degraded ellularly in order for the drug to be released eg. the mo linker and the like.

A linker can include a group for linkage to the antibody. For example, linker can include an amino, hydroxyl, yl or sulfhydryl reactive groups (e.g., malemide, haloacetamides (e.g., iodo, bromo or chloro), haloesters (e.g., iodo, bromo or chloro), halomethyl ketones (e.g., iodo, bromo or chloro), benzylic halides (e.g., iodide, e or chloride), vinyl sulfone and pyridylthio). See generally Wong, Chemistry of Protein Conjugation and Cross-linking; CRC Press, Inc, Boca Raton, 1991.

Immunotherapy For immunotherapy, an antibody can be conjugated to a le drug, such as a cytotoxic or cytostatic agent, an immunosuppressive agent, a radioisotope, a toxin, or the like. The conjugate can be used for inhibiting the multiplication of a tumor cell or cancer cell, g apoptosis in a tumor or cancer cell, or for treating cancer in a patient. The conjugate can be used accordingly in a variety of settings for the treatment of animal cancers. The conjugate can be used to deliver a drug to a tumor cell or cancer cell.

Without being bound by theory, in some embodiments, the conjugate binds to or associates with a cancer-cell or a tumor~associated antigen, and the conjugate and/or drug can be taken up inside a tumor cell or cancer cell through receptor-mediated endocytosis.

The antigen can be attached to a tumor cell or cancer cell or can be an extracellular matrix n associated with the tumor cell or cancer cell. Once inside the cell, one or more specific peptide sequences within the conjugate (e.g., in a linker) are hydrolytlcally cleaved by one or more tumor—cell or cancer-cell-associated proteases, resulting in release of the drug. The released drug is then free to migrate within the cell and induce cytotoxic or cytostatic or other activities. In some embodiments, the drug is d from the antibody outside the tumor cell or cancer cell, and the drug subsequently penetrates the cell, or acts at the cell surface.

Therapy for Cancer As discussed above, cancers, ing, but not limited to, a tumor, metastasis, or other disease or disorder characterized by uncontrolled cell growth, can be d or prevented by administration of a protein-drug conjugate. in other embodiments, methods for ng or preventing cancer are provided, including administering to a patient in need thereof an ive amount of a conjugate and a chemotherapeutic agent. In some embodiments, the chemotherapeutic agent is that with which treatment of the cancer has not been found to be refractory. In some embodiments, the chemotherapeutic agent is that with which the treatment of cancer has been found to be refractory. The conjugate can be administered to a patient that has also undergone a treatment, such as surgery for ent for the cancer. in another embodiment, the additional method of treatment is radiation therapy.

Multi-Drug Therapy for Cancer Methods for treating cancer e administering to a patient in need thereof an effective amount of an antibody-drug conjugate and another therapeutic agent that is an ancer agent. Suitable anticancer agents include, but are not limited to, rexate, taxol, L-asparaginase, topurine, thioguanine, hydroxyurea, cytarabine, cyclophosphamide, ifosfamide, nitrosoureas, cisplatin, carboplatin, mitomycin, azine, procarbizine, topotecan, nitrogen mustards, cytoxan, etoposide, 5— fluorouracil, BCNU, irinotecan, camptothecins, bleomycin, doxorubicin, idarubicin, daunorubicin, dactinomycin, plicamycin, mitoxantrone, asparaginase, vinblastine, vincristine, vinorelbine, paclitaxel, calicheamicin, and docetaxel.

The ADCs of the present invention can be in the form of a pharmaceutical composition for administration that are formulated to be appropriate for the selected mode of administration, and pharmaceutically acceptable diluent or excipients, such as buffers, surfactants, preservatives, solubilizing agents, isotonicity agents, stabilizing agents, carriers, and the like. Remington's Pharmaceutical Sciences, Mack Publishing Co., Easton Pa., 18th ed, 1995, incorporated herein by reference, provides a compendium of formulation techniques as are lly known to practitioners.

These pharmaceutical compositions may be administered by any means known in the art that achieve the generally intended purpose to treat cancer. The preferred route of administration is parenteral, defined herein as referring to modes of administration that include but not limited to enous, intramuscular, eritoneal, subcutaneous, and rticular injection and on. The dosage administered will be dependent upon the age, health, and weight of the recipient, kind of rent treatment, if any, ncy of ent, and the nature of the effect desired.

Compositions within the scope of the invention include all compositions wherein an ADC is present in an amount that is effective to achieve the desired medical effect for treating cancer. While individual needs may vary from one patient to another, the determination of the optimal ranges of effective amounts of all of the components is within the ability of the clinician of ordinary skill.

Example 1 Preparation of an anti-5T4 ADC 5T4—A1 antibody drug conjugate (ADC) is ed via partial reduction of the mAb with —carboxyethyl)phosphine (TCEP) followed by reaction of reduced Cys residues with the desired maleimide terminated linker-payload. in particular, 5T4-A1 mAb is partially reduced via addition of 2.8 molar excess of -carboxyethyl)phosphine (TCEP) ii 100 HIM HEPEg :"!Cfi’t’kx‘wfxmii :‘ “w"? ~§3§ erazineethai:esutf—ozsis SEEK}? buller H 7.0 al d t . . )j} . , 1 mM diethylenetriaminepentaacetic acid (DTPA) for 2 h at 37 °C. The desired - payload is then added to the reaction mixture at a linker~payloadlmAb—thiol molar ratio of .5 (ma|eimidocapronic-monomethylauristatin F [mc~MMAF]) or 8 (maleimidocapronic — valine—citruline-p—aminobenzyloxycarbonyl- monomethylauristatin E [mc—Val-Cit—PABA- MMAED and reacted for an additional 1 h at 25°C in the presence of 15% v/v of dimethylacetamide (DMA). After the 1 h incubation period, N—ethylmaleimide (4.5 fold excess for F and 2 fold excess for mc—Val-Cit-PABA-MMAE) is added to cap the ted thiols and is d to react for 15 s followed by addition of 6 fold excess L-Cys to quench any unreacted linker-payload. The reaction mixture is dialyzed overnight at 4 °C in phosphate buffered saline (PBS), pH 7.4, and purified via SEC (AKTA explorer, Superdex 200 10/30 GL column). The ADC is further characterized via size exclusion chromatography (SEC ) for purity, hobic interaction chromatography (HIC), and liquid tography electrospray ionisation tandem mass spectrometry I MS) to calculate loading, and the concentration is determined via UV spectrophotometer.

Example 2 Binding Studies Cells expressing the 5T4 antigen, and the negative control Rail cells, are plated at a density of 500,000 cells/well on non-tissue culture treated 96 well plates and kept on ice.

Dilutions of the A1 and A1-lgG4 antibodies or A1-mcMMAF ADC are made in 3% bovine serum albumin BSA in Dulbecco’s phosphate buffered saline (DPBS) and added to the plate at a final concentration of L. The plates are then incubated on ice for 1 hour followed by 2 washes. The secondary antibody, PE (phycoerythrin) conjugated Goat Anti- Human lgG F0 is added to the wells. After 30 minutes of incubation at 4°C, the mean fluorescence intensity is then measured using a flow cytometer.

The data in Table 4 indicates that the A1 antibody binds a diverse panel of 5T4 positive cell lines. The data in Table 5 indicates that r binding on several different cell lines is observed with the A1 and A1 -lgG4 antibodies as well as the A1-mchVlAF ADC.

Table 4 Human Cell Lines A1 antibody Mean Fluorescent Intensity /5T4 oma) MDAMB468 (breast) 3000 MDAMD361-DYT2 (breast) 4500 NCl-H157 (lung) 4100 A431 (epithelial) 2000 Caki (kidney) 2500 PC3mm2 (prostate) 4500 PC14PE6 (lung) 3200 Panc1 (pancreatic) 3500 Su8686 (pancreatic) 3700 H1975 1600 37622A— (Primary Lung cancer cells) 10600 Raji (negative control) <100 Table 5 Cell Lines A1 -mcMMAF A1 -IGG4 A1 -lGG4-CM lgG control MDAMD361- DYT2 MDAMB468 Example 3 Cytotoxicity Assay Cell lines expressing 5T4, and the negative control Raji cell line, are cultured with increasing concentrations of ADC. After four days, viability of each e is assessed. 1050 values are calculated by logistic non-linear regression and are presented as ng Ab/mL. A1 ~mcMMAF, A1—chMAE, A3—mcMMAF and A3-mcMMAE are shown to t the growth of 5T4 sing cell lines (MDAMB435/5T4, MDAMB468, and MDAMBB61DYT2), while being inactive on 5T4 negative cells (Raji), Table 6.

Table 6 [C50 (ng Ab/ml) MDAMB435/5T4 MDAMB361DYT2 68 Raji(5T4-) A1-mcMMAF 1.3 >45,000 A1 -chMAE 6.8 A3-mcMMAF 0.3 A3-chMAE 3.5 86.8 160.6 0 Nonbinding 21258 ~50,000 73059 >45,000 Ab~mcMMAF Nonbinding 7979 >45,000 Ab- chMAE Additionally, 5T4+ primary lung tumor 376223 cells are isolated and grown in culture. Cells are cultured with increasing concentrations of ADC. Ten days later, viability of each culture is assessed using the MTS method. leo values were calculated by logistic non-linear regression and are presented as ng Ab/ml. A1-mcMMAF, A1-chMAE, A3- mcMMAF, and AE inhibit the growth of the primary lung tumor cells, Table 7.

Table 7 37622a primary lung ADC [Cso (n9 Ab/ml) A1—mcMMAF 504.1 A1—chMAE A3—mcMMAF A3—chMAE Nonbinding Ab- >45,000 mcMMAF Example 4 Subcutaneous Xenograft Model Female, athymic (nude) mice (or another strain of immunosupressed mice) are injected s.c. with MDAMB435/5T4, MDAMB361DYT2, or H1975 tumor cells. Mice with staged tumors, approximately 0.1 to 0.3 g (n=6 to 10 mice/treatment group) are administered intravenously Q4Dx4 with normal saline le), A1-mcMMAF, A1- chMAE, A1—mcMMAD, A1—smchM1, A3—mcMMAF, A3—vclVlMAE, ora nonbinding 1O control antibody conjugated to either mcMMAF or chMAE, at the dose of 3 mg Ab/kg. All ADCs are dosed based on Ab content. Tumors are measured at least once a week and their size (mm2 1r SEM) is calculated as mm2 = 0.5 x (tumor width?) x (tumor length).

The data in Table 8 tes that A1-mcMMAF, A1 —chMAE, A1—chMAD, A3— mcMMAF, and A3-chMAE inhibit the growth of MDAMB435/5T4 xenografts while A1 - mcMMAD and A1-smchM1 were not active in this model.

The data in Table 9 indicates that MAF, A1 —chMAE, A1 ~chMAD, A1— smchM1, A3-mcMMAF, and A3-chMAE inhibit the growth of MDAMBB61DYT2 afts while A1 -mcMMAD was not active in this model.

The data in Table 10 tes that A1-mcMMAF, A1 -chMAE, A1 , A3- , and A3—chMAE inhibit the growth of H1975 xenografts while A1-mcMMAD and A1-smchM1 were not active in this model.

Table 8 /5T4 xenog rafts Tumor volume(m.mx+sem) Compound Day 0 Day 17 Day 42 Day 65 Day 85 (3 mg/kg Q4dx4) Vehicle 169 + 8 531 + 73 1255-+ 190 GT A1 168v15 67i56 174:119 3642278 mCMMAF A1 168i8 10i10 91i91 200i200 chMAE A1168+12 390+112 GT GT A1 174+ 10 429+62 12554227 1781 i388 A1 169 + 12 A3 174+12 105+27 216+143 448+220 A3 172 + 13 Nonbinding Ab 170 +11 100 +15 314 +121 838 + 381 Nonbinding Ab 172 +11 168 + 53 461 + 178 GT: group terminated due to large tumor size Table 9 MDAMBB61DYT2 xenografts Tumor volume (mma, x t sem ) Compound Day 19 Day 47 Day 90 Day 131 (3 mg/kg Q4dx4) Vehide 363i58 558i149 48 GT A1 0:0 7i? 111-11 mcMMAF A1 0&0 9:9 34:27 chMAE A1 352:26 130i15 0:0 0:0 0:0 voMMAD A3 342 i 23 128 i 10 79 i 30 105 t 49 353 i 234 mcMMAF --A3 3541-21 111120 21:21 --72i72 155+155 --A1 347 i 15 775 i 199 GT -GT A1 352 i 26 0 1r 0 chMAD A1 353 i 25 330 i- 146 smchM1 --Nonbinding Ab 342 i 38 869 i 198 ----Nonbinding Ab 344 i 20 303 i 78 346 i 185 595 i 362 GT= group terminated due to large tumor size PCT/IBZOIZ/051304 Table 10 - H1975 Xenografts Tumor volume (mm3, x i sem) Compound Dose(()mg/kg Day 15 Day 22 Day 40 Vehicle 1154 i 136_—- A1 519 + 45 581 + 79 2840 + 207 mcMMAF A1 929 i 90 926 i- 116 GT chMAE A1 467i19 240114 625i317 chMAD A3 426 +10 980 + 79 1343 +140 1261 + 203 A3 431 +14 944 + 52 993 + 71 A1427+16 837 + 69 1468 +139 GT 423 +18 901+ 83 1852-+ 167 GT ding 1026 i 68 1861 + 224 GT mcMMAF Nonbinding 3 427 t 13 1213 t 67 1959..+ 139 GT GT: group terminated due to large tumor size Alternatively, nude mice with 37622a primary tumor cell xenografts established subcutaneously are treated iv Q4Dx4 with A1 -mcMMAF, MAD, A1 -chMAD, or A3—mcMMAF at the dose of 3 mg Ab/kg and the tumor growth is monitored over the period WO 31527 of 96 days. Table 11 demonstrates that A1-mcMMAF, A1-chMAD and A3—mcMMAF inhibit the growth of 37622a primary tumor afts ed to vehicle l treated animals while A1—mcMMAD was not active in this model.

Table 11 37622a Primary Tumor Xenografts Tumorvolume(mm3, x+sem) Compound Day 22 Day 46 Day 68 Day 96 Vehicle -——— A1- .111+18 67211 124+47 2_33+1053—57+150 mCMMAF A1- 127+28 862+377.- 3764-119 mcMMAD - — 108+14---160+121 131 +28 211 +128 463 +210 mCMMAF GT: group terminated due to large tumor size Unexpectedly, the data in Tables 8-11 show that ADCs with the same antibody and drug payload but with different linkers had a dissimilar efficacy profile i.e. A1 -mcMMAD vs 1O A1-chMAD in all four aft models. In addition, the data show that ADCs with the same antibody and linker but with different drug payloads also had a different efficacy profile i.e. A1-mcMMAF vs A1-mcMMAD, in all four xenograft models. Thus, the drug MMAD is effective in all four xenograft models when linked to the A1 antibody by the vc linker but has no activity in any of the xenograft models tested when linked by the mo linker. in contrast, the drug MMAF is highly effective in all 4 xenograft models when linked 2012/051304 to the A1 dy with the mo linker while the chemically related drug MMAD has no ty in all 4 xenograft models when linked to the same antibody by the same .

Yet another unexpected observation is seen with the ADC A1 Vl‘l (Tables 8— ). This ADC was very effective against the MDAMBB61DYT2 xenograft but had essentially no effect against the MDAMB435/5T4 and the H1975 xenografts even though all the xenografts have a high expression of the 5T4 target antigen. This data illustrates that the effectiveness of the linker-payload could not be predicted even when the same high affinity antibody is utilized or even when the same ADC is used. 1O Example 5 Antibody Dependent Cell-Mediated Cytotoxicity (ADCC) ADCC assay: Blood from a healthy volunteer is collected into a BD Vacutainer CPT cell preparation tube with sodium heparin. Human peripheral blood mononucleocytes (PBMC) are harvested and resuspended in assay buffer (RPMI 1640 supplemented with 10 mM HEPES) at 2.5 x 107 cells/ml. Target cells (MDAMB435/5T4 or MDAMB435/neo) are seeded at a density of 1 x 104L cells/well in a 96 well assay plate. A1 antibody or A1— mchVlAF are added, then human PBMC effector cells (5 x 105) are dispensed into the wells for an orztarget cell ratio (EzT) of 50:1. The assay plate is incubated at 37 °C for 4 hours for ADCC activity. The plate is harvested by adding equal volume of CytoTox-One reagent (Promega). Stop solution (Promega; 50 ul) is added to each well and lactate dehydrogenase release was quantified by measuring fluorescence intensity. As a positive control, 2 pl of lysis buffer per well is added to generate a maximum LDH release (100% cytotoxicity) in control wells. Percent cytotoxicity is calculated using the ing equation: mental — effector spontaneous — target spontaneous % Specific Cytotoxicity = X 100 target maximum — target spontaneous Where “experimental” corresponds to the signal measured in one of the experimental conditions, “effector spontaneous” corresponds to the signal measured in the presence of PBMC alone, “target neous” corresponds to the signal measured in the presence of target cells alone, and “target m” corresponds to the signal measured in the ce of detergent-lysed target cells alone.

The ADCC activity of A1-lgG1 Ab and A1 F compared to A1 —lgG4 Ab is shown in Table 12. Both the A1 antibody and A1emcMMAF demonstate comparable ADCC activity indicating that the ADCC activity of A1 -mcM MAF may contribute to its anti- tumor activity.

Table 12 3 _ Example 6 Binding Affinity Surface plasmon resonance (SPR) analysis is performed utilizing the BlAcore® to determine the affinity constants for A1 —lgG1 and A1 —lgG4 binding to either human or cynomolgus 5T4 at pH 6.0 and pH 7.4. BlAcore® technology utilizes changes in the tive index at the surface layer upon binding of the huA1 antibody ts to the human 5T4 protein immobilized on the e layer. Binding is detected by SPR of laser light refracting from the surface. is of the signal kinetics on-rate and off-rate allows the discrimination between non-specific and specific interactions. The 5T4 proteins used for this analysis consisted of the human or cynomolgus 5T4 ectodomain fused to the human IgG1-Fc domain and low densities (45.1 and 45.4 RU for human and cynomolgus respectively) are immobilized onto a CM5 chip to accurately measure affinity constants.

The measurement of specific binding to the 5T4 ectodomain is attained by subtracting binding to a reference surface that had only human c protein immobilized onto the CM5 chip at the same y to that on the 5T4—Fc surfaces. Next, various concentrations of A1, A1 -lgG4, or A3 antibodies in either HBS—EP pH 7.4 or MES- EP pH 6.0 buffer are injected over the surface. The surface is regenerated two times with Glycine pH 1.7 + 0.05% Surfactant P20 (GE care, BR—1000—54) between injection Results show that the A1 has a slightly higher affinity for human 5T4 using the low— density 5T4 surface at both pH 6.0 and pH 7.4 relative to A1-lgG4 (1 .5~fold and 1.2-fold 1O respectively, Table 13). Additionally, A1 exhibited slightly better g to cynomolgus 5T4 at both pH 6.0 and pH 7.4 compared to A1 ~lgG4 (1.7-fold and 1.2-fold respectively) and both A1 and A1 -IgG4 bound human 5T4, 3 -— 4 fold better than cynomolgus 5T4 (Table 12).

Table 13 Antibody Antigen pH ka(1/Ms) kd(1/s) KD(nM) A1-lgG1 hu5T4 6.0 4.31E+O5 4595 . 6.26E+05 8.93E 2.33E+05 6.41E—04- 2.02E+05 9.50E—04 4.70 05 1.32E-04 0.48 7.4 3.28E+05 1.72E—04- A1-igG1 cyno5T4 7.4 05 2.73E A1-lgG4 cyno5T4 7.4 1.81E+05 3.82E Comparing the A1 and A3 antibodies, it is apparent that the A1 antibody binds human and cynomolgus 5T4 better at pH 7.4 relative to pH 6.0 while the A3 antibody exhibits enhanced binding at pH 6.0 compared to pH 7.4, Table 14.

WO 31527 2012/051304 Table 14 Antibody ka (1/Ms)on kd (1/s)off KD (nM) hu5T4 ” 4.31 E+05 4.59E—04 1.06 hu5T4 6.0 3.51 E+05 4.17E-05 0.12 cyn05T4 6.0 2.33E+05 6.41E-04 2.76 cyno5T4 4.58E+05 hu5T4 7 4 2.75E+05 hu5T4 7 4 1.79E+05 cyn05T4 74 1.51 E+05 cyn05T4 1.98E+05 1.62E-O4 0.82 1.98E+05 Example 7 Epitope Mapping Using 5T4 Chimeras To identify the epitopes to which each of the A1 and A3 antibodies bind, an enzyme linked sorbent assay (ELISA) is performed using (1) 5T4 ectodomain Fc construct and (2) human/mouse 5T4 chimera constructs transiently sed in COS-1 cells. The ectodomain includes the amino—terminal region, two leucine-rich s, and the 1O intervening hydrophilic region. Mouse and rat 5T4 ectodomains contain a 6 amino acid direct repeat within their hydrophilic region.

Fusion proteins containing a 5T4 ectodomain and 3 Fc constant region from human lgG1 are prepared using human 5T4 (amino acids 1-355), mouse 5T4 (amino acids 1- 361), rat 5T4 (amino acids 1-361), cynomologus monkey 5T4 (amino acids 1-355), chimpanzee 5T4 (amino acids 1-355), and black-tailed marmoset (amino acids 1-355).

The binding results with human/mouse 5T4 chimera constructs are summarized in Table 14, which indicates specific g, partial binding, or lack of binding, by the A1 and A3 antibodies.

Table 15 refers to binding ability of the antibodies to the various human/mouse chimeras and the nomenclature is designated by mouse 5T4 content. When no binding is observed, this indicates where the antibody binds human 5T4 since these antibodies do not bind mouse 5T4. For example, the A3 antibody has the most N-terminal binding e en 83 - 163) and this is shown by lack of binding to the 5T4 chimera that has es 83 — 163 replaced by mouse 5T4, hence A3 can no longer bind. Based upon these results, it is determined that humanized A1 antibody has a first contact with human 5T4 between amino acid residues 173 and 252 and a second contact with human 5T4 between amino acid residues 276 and 355. The A3 antibody binds the first leucine-rich repeat region of human 5T4 n amino acid residues 83 h 163. The number of amino acid residues corresponds to the human 5T4 antigen amino acid sequence of SEQ 1O lD NO: 11.

Table 15 5T4 Antigen Construct Human/mouse 83-163 Human/mouse 173—361 Human/mouse 173-258 Human/mouse 282-361 Example 8 Comparison of A1 -mcMMAF ADC with A1 -lgG4-CM ADC A1 -mcMMAF is ed to A1—lgG4—AcBut calicheamicin (A1-lGG4—CM) for both safety and efficacy. A1—4—CM is comprised of the A1-lgG4 antibody ated with the linker, AcBut [—(4’ acetylphenoxy) butanoic acid], to a calicheamicin payload. The calicheamicins are potent antitumor agents of a class of enediyne antibiotics derived from the bacterium Micromonospora echinospora.

The cell binding activity of A1 Ab, A1 -lgG4 Ab, A1-mcMMAF ADC and A1 -|gG4-CM ADC are compared using several 5T4 positive cell lines (see Example 2, Table 5). The data indicates that similar binding is ed with the A1 and A1 -lgG4 antibodies as well as the A1-mcMMAF ADC, all of which have a higher mean fluorescent intensity than A1- lgG4—CM for all the 5T4 ve cell lines tested.

A1—mcMMAF and A‘l-lgG4-CM are tested side—by-side in the MDAMB435/5T4 subcutaneous xenograft model. Both ADCs are given iv (Q4dx2) when the tumors reach approximately 200 mm2 in size. The anti-tumor activity of A1—lgG4-CM at a dose of 3 mg/kg is similar to the anti~tumor activity of A1—mcMMAF administered at dose of 10 mg/kg (Table 16). Based upon these results, the anti-tumor activity of A1-lgG4-CM is approximately 3.3 fold more potent than A1 -mcMMAF.

Table 16 olume((mm, x+sem) Compound Dose ) Day 0 Day 7 Day 21 Day 31 Day 45 Q4dx4 Vehicle O 123i8 195+36 402+56 6354—111 1309+332 A1~ 166:29 227:42 361i89 mcMMAF A1- 123i14 761-11 mcMMAF A1-IGG4— It could be expected that the 3.3 fold enhanced potency of A1-lgG4-CM over that of A1-mcMMAF would translate into a 3.3 fold enhanced safety margin of At—mcMMAF over that of A1-lgG4-CM in an animal toxicity study. However, when the safety profile of A1- lgG4-CM in cynomolgus s is ed, it is determined that A1-lgG4-CM is at least 100 fold more toxic than A1-mcMMAF in the cynomolgus macque. When A1-lgG4~CM is stered at 0.032, 0.095 and 0.32 mg Ab/kg/cycle (2, 6, 20 pg calicheamicin/kg/cycle) to male (n=3) and female (n=3) cynomolgus macques, toxicity is observed at each dose level. After 2 cycles (2 doses), 4 out of 6 animals in the 0.095 treatment group are either euthanized or found dead. On the other hand, no deaths are observed at dosages up to mg/kg with A1 F (247 pg mclVlMAF/kg/cycle), after 2 cycles (2 doses), over the same 4 week time period. In summary, the 10 mg/kg dosage group ofA1—mcMMAF is safe while the 0.096 mg/kg dosage group ofA‘l—IgG4—CM is deemed toxic when both are administered twice to cynomolgus s in a 4 week observation period.

Unexpectedly, these results demonstrate a 105 fold (10/0.095=105) safety margin of MAF over that of A1—lgG4~CM, rather than the expected 3.3 fold safety margin based on the relative anti-tumor potency of each ADC. This data reveals the unpredictable nature of antibody-drug ates that utilize antibodies to the same antigen target but are conjugated to a different drug payload.

Example 9 A1 -mcMMAF Mouse PKlPD Modeling and al Dose Predictions PK/PD modeling has been used to quantify the tumor response of A1 ~mcMMAF in mouse xenograft studies, in order to ine efficacious concentration across cell lines.

The transit compartment tumor kill PK/PD model used was previously described by Simeoni etal. (Simeoni et al, Cancer Res, 64:1094, (2004)). The model has been modified to account for , exponential and logistic growth of tumor, and saturative killing by the drug. PK/PD model parameters include: kg ex exponential growth kg logistic growth wo initial tumor volume tau transduction rate kmax maximum kill rate szo concentration at half max kill rate WO 31527 2012/051304 The PK/PD modeling results are used to calculate the Tumor Static Concentration (TSC, Equation 1). This is the drug concentration where tumor growth is equal to tumor death rates and tumor volume remains ged. TSC can be d as the minimal concentration ed for efficacy. T80 is used to give guidance on clinical dose selection, with concentrations of >TSC required for efficacy in the clinic.

For A1~mcMMAF, mouse PK was determined in a separate study (3mg/kg lV, female athymic nu/nu mice). Mouse xenograft studies were completed using 3 different 5T4 cell lines with A1-mcMMAF administered at dose levels between 1 and 30 mg/kg every 4 days: cell line MDAMB435/5T4 (closed at 1, 3, 10, and 30 mg/kg), cell line H1975 1O (dosed at 1, 3, and 10 mg/kg) and cell line 37622A (dosed at 1 and 10 mg/kg). PK/PD modeling was performed as described and TSCs are reported in Table 17.

Mouse PK/PD parameters for each xenograft cell line were combined with predicted human PK of A1-mcMMAF to simulate doses required for efficacy in the . Using this methodology, A1-mcMMAF has a predicted minimally efficacious clinical dose of about 0.22 to about 2.3 mg/kg Q3 weeks [every three weeks] (Table 17). in an embodiment of the present invention, dose ranges can be in the range from about 0.18 mg/kg to about 2.7 mg/kg, from about 0.22 mg/kg to about 2.6 mg/kg, from about 0.27 mg/kg to about 2.5 mg/kg, from about 0.32 mg/kg to about 2.3 mg/kg, from about 0.37 mg/kg to about 2.15 mg/kg, from about 0.42 mg/kg to about 2.10 mg/kg, from about 0.47 mg/kg to about 2.05 mg/kg, from about 0.52 mg/kg to about 2.00 mg/kg, from about 0.57 mg/kg to about 1.95 mg/kg, from about 0.62 mg/kg to about 1.90 mg/kg, from about 0.67 mg/kg to about 1.85 mg/kg, from about 0.72 mg/kg to about 1.80 mg/kg, from about 0.82 mg/kg to about 1.70 mg/kg, from about 0.92 mg/kg to about 1.60 mg/kg, from about 1.02 mg/kg to about 1.50 mg/kg, from about 1.12 mg/kg to about 1.40 mg/kg, or from about 1.20 mg/kg to about 1.30 mg/kg, with dosing at Q3 weeks. Preferably, dose ranges can be in the range from about 0.22 mg/kg to about 2.3 mg/kg.

Equation 1 gEX k -k.

If “0 WO 3 1, TSC =———gE* kg kmax —kgEx 95‘ k 2k _ If wO >1, TSC =—g-—€3°— kg wO km; vkg Table 17 TSC ted Stasis Dose Cell Line [80% confidence] [80% confidence] (ug/ml) (mg/kg QB weeks) MDAMB435/5T4 1.1 [0.9, 1.4] 0.22 [0.18, 0.28] 37622A 5.1 [2.1, 9.9} 1.1 [0.6, 2.0] 11.6 [9.6, 14.1] 2.3 [2.0, 2.7] PCT/1B2012/051304 CE LISTING SEQ ID NO:1 Humanized Al human IgG1 heavy chain EVQLVESGGGLVQPGGSLRLSCAASGYTFTNFGMNWVRQAPGKGLEWVAWINTNTGEPRYAEEFKG RFTISRDNAKNSLYLQMNSLRAEDTAVYYCARDWDGAYFFDYWGQGTLVTVSSASTKGPSVFPLAP SSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQ TYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCV VVDVSHEDPEVKFNWYVDGVEVflNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKAL PAPIEKTISKAKGQPREPQVYT;PPSREEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTT PPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK SEQ ID NO:2 Humanized A1 human Kappa light chain: SPSSLSASVGDRVTITCKASQSVSNDVAWYQQKPGKAPKLLIYFATNRYTGVPSRFSGSG YGTDFTLTISSLQPEDFATYYCQQDYSSPWTFGQGTKVE:KRTVAAPSVFIFPPSDEQLKSGTASV VCLLNNFYPREAKVQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTLTLSKADYEKHKVYACEVTH QGLSSPVTKSFNRGEC SEQ ID N013 Al—VH EVQLVESGGGLVQPGGSLRLSCAASGYTFTNFGMNWVRQAPGKGLEWVAWINTNTGEPRYAEEFKG RFTISRDNAKNSLYLQMNSLRAEDTAVYYCARDWDGAYFFDYWGQGTLVTVSS SEQ ID NO:4 Al—VL DIQMTQSPSSLSASVGDRVTITCKASQSVSNDVAWYQQKPGKAPKLLIYFATNRYTGVPSRFSGSG YGTDFTLTISSLQPEDFATYYCQQDYSSPWTFGQGTKVEIK SEQ ID NO:5 Al-HC CDRl NFGMN SEQ ID N016 Al—HC CDR2 WINTNTGEPRYAEEFKG SEQ ID N027 Al-HC CDR3 DWDGAYFFDY SEQ ID NO:8 Al~LC~CDRl SNDVA 1O SEQ ID N029 Al-LC-CDRZ FATNRYT SEQ ID N0:10 Al-LC-CDR3 QQDYSSPWT SEQ ID NO:11 Human 5T4 antigen MPGGCSRGPAAGDGRLRLARLALVLLGWVSSSSPTSSASS FSSSAPFLASAVSAQPPLPDQCPALCECSEAARTVKCVNR NLTEVPTDLPAYVRNLFLTGNQLAVLPAGAFARRPPLAEL AALNLSGSRLDEVRAGAFEHLPSLQQLDLSHNPLADLSPF ASVSAPSPLVELILNHIVPPEDERQNRSFEGMVV AALLAGRALQGLRRLELASNHFLYLPRDVLAQLPSLRHLD LSNNSLVSLTYVSFRNLTHLESLHLEDNALKVLHNGTLAE LQGLPHIRVFLDNNPWVCDCHMADMVTWLKETEVVQGKDR LTCAYPEKMRNRVLLELNSADLDCDP:LPPSLQTSYVFLG IVLALIGAIFLLVLYLNRKGIKKWMHNIRDACRDHMEGYH YRYEINADPRLTNLSSNSDV SEQ ID NO:12 Humanized Al human IgG4m heavy chain: EVQLVESGGGLVQPGGSLRLSCAASGYTFTNFGMNWVRQAPGKGLEWVAWINTNTGEPRYAEEFKG RFTISRDNAKNSLYLQMNSLRAEDTAVYYCARDWDGAYFFDYWGQGTLVTVSSASTKGPSVFPLAP CSRSTSESTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTK TYTCNVDHKPSNTKVDKRVESKYGPPCPPCPAPEFLGGPSVFLFPPKPKDTLMISRTPEVTCVVVD VSQEDPEVQFNWYVDGVEVHNAKTKPREEQFNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKGLPSS IEKTISKAKGQPREPQVYTLPPSQEEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPV FFLYSRLTVDKSRWQEGNVFSCSVMHEALHNHYTQKSLSLSLGK SEQ ID NO:13 A1 human IgG4m VH (Al—IGG4—VH) EVQLVESGGGLVQPGGSLRLSCAASGYTFTNFGMNWVRQAPGKGLEWVAW:NTNTGEPRYAEEFKG RFTISRDNAKNSLYLQMNSLRAEDTAVYYCARDWDGAYFFDYWGQGTLVTVSS SEQ ID NO:14 Al-IgG4-VH-CDR1 NFGMN SEQ ID NO:15 Chimeric A3 heavy chain (muA3—hngG1) EVQLVESGGGLVQPKGSLKLSCAASGFTFNTYAMNWVRQAPGKGLEWVARIRSKSNNYATYYADSV KDRFTISRDDSQSMLYLQMNNLKTEDTAMYYCVRQWDYDVRAMNYWGQGTLVTVSSASTKGPSVFP LAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSL GTQTYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEV VSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSN KALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNY KTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK SEQ ID N0216 Chimeric A3 VH EVQLVESGGGLVQPKGSLKLSCAASGFTFNTYAMNWVRQAPGKGLEWVARIRSKSNNYATYYADSV KDRFTISRDDSQSMLYLQMNNLKTEDTAMYYCVRQWDYDVRAMNYWGQGTLVTVSS SEQ ID NO:17 Chimeric A3 VH-CDRl TYAMN SEQ ID NO:18 Chimeric A3 Z RIRSKSNNYATYYADSVKD SEQ ID NO:19 Chimeric A3 VH—CDR3 QWDYDVRAMNY 1O SEQ ID N0220 Chimeric A3 light chain (muA3~huKappa) DIVMTQSHIFMSTSVGDRVSITCKASQDVDTAVAWYQQKPGQSPKLLIYWASTRLTGVPDRFTGSG SGTDFTLTISNVQSEDLADYFCQQYSSYPYTFGQGTKLEIKRTVAAPSVFIFPPSDEQLKSGTASV VCLLNNFYPREAKVQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTLTLSKADYEKHKVYACEVTH QGLSSPVTKSFNRGEC SEQ ID NO:21 ic A3 VL DIVMTQSHIFMSTSVGDRVSITCKASQDVDTAVAWYQQKPGQSPKLLIYWASTRLTGVPDRFTGSG SGTDFTLTISNVQSEDLADYFCQQYSSYPYTFGQGTKLE2K SEQ ID NO:22 Chimeric A3 VL—CDRl KASQDVDTAVA SEQ ID NO:23 Chimeric A3 VL—CDRZ WASTRLT SEQ ID NO:24 Chimeric A3 VL—CDR3 QQYSSYPYT SEQ ID N0225 Humanized A3 human IgG1 heavy chain: EVQLVESGGGLVQPGGSLRLSCAASGFTFNTYAMNWVRQAPGKGLEWVARIRSKSNNYATYYADSV KDRFTISRDDAKNSLYLQMNSLRAEDTAVYYCVRQWDYDVRAMNYWGQGTLVTVSSASTKGPSVFP LAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSL GTQTYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEV TCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSN KALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNY KTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK SEQ ID NO:26 Humanized A3 VH: EVQLVESGGGLVQPGGSLRLSCAASGFTFNTYAMNWVRQAPGKGLEWVARIRSKSNNYATYYADSV KDRFTISRDDAKNSLYLQMNSLRAEDTAVYYCVRQWDYDVRAMNYWGQGTLVTVSS SEQ ID NO:27 Humanized A3 VH-CDRl: TYAMN SEQ ID NO:28 Humanized A3 VH—CDRZ: NNYATYYADSVKD SEQ ID NO:29 Humanized A3 VH-CDR3: QWDYDVRAMNY SEQ ID NO:30 Humanized A3 human Kappa light chain: DIQMTQSPSSLSASVGDRVTITCKASQDVDTAVAWYQQKPGKAPKLLIYWASTRLTGVPSRFSGSG LTISSLQPEDFATYYCQQYSSYPYTFGQGTKLEIKRTVAAPSVFIFPPSDEQLKSGTASV VCLLNNFYPREAKVQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTLTLSKADYEKHKVYACEVTH QGLSSPVTKSFNRGEC SEQ ID NO:31 Humanized A3 VL: DIQMTQSPSSLSASVGDRVT I TCKASQDVDTAVAWYQQKPGKAPKLLIYWASTRLTGVPSRFSGSG SGTDFTLTISSLQPEDFATYYCQQYSSYPYTFGQGTKLE IK SEQ ID NO:32 Humanized A3 VL-CDRl: KASQDVDTAVA SEQ ID NO:33 Humanized A3 VL—CDRZ: WASTRLT 1O SEQ ID N0234 zed A3 VL—CDRB: QQYSSYPYT

Claims (20)

What is claimed

1. An dy-drug conjugate of the formula: Ab—(LU-D)p or a pharmaceutically acceptable salt thereof wherein; (a) Ab is an anti—5T4 antibody or antigen binding portion thereof, comprising: (i) a VH CDR1 region as shown in SEQ lD NO: 5, (ii) a VH CDR2 region as shown in SEQ lD NO: 6, (iii) a VH CDR3 region as shown in SEQ ID NO: 7, (iv) a VL CDR1 region as shown in SEQ ID NO: 8, (v) a VL CDR2 region as shown in SEQ lD NO: 9, and (vi) a VL CDR3 region as shown in SEQ lD NO: 10, (b) LU is a maleimidocaproyl linker unit, (0) p is an r from 1 to 8, and (d) D is a Drug unit selected from the group consisting of monomethylauristatin E (MMAE) and monomethylauristatin F (MMAF).

2. An antibody-drug conjugate of the formula: -D)p 20 or a pharmaceutically acceptable salt thereof wherein: (a) Ab is an T4 antibody or antigen binding portion thereof, comprising: (i) a VH CDR1 region as shown in SEQ lD NO: 5, (ii) a VH CDR2 region as shown in SEQ ID NO: 6, (iii) a VH CDR3 region as shown in SEQ lD NO: 7, 25 (iv) a VL CDR1 region as shown in SEQ ID NO: 8, (v) a VL CDR2 region as shown in SEQ lD NO: 9, and (vi) a VL CDR3 region as shown in SEQ ID NO: 10, (b) LU is a maleimidocaproyl-valine-citrulline-p-aminobenzyloxycarbonyl (maleimidocaproyl-Val-Cit-PABA) linker unit, 30 (0) p is an integer from 1 to 8, and (d) D is a Drug unit selected from the group ting of monomethylauristatin E (MMAE), monomethylauristatin D (MMAD), and thylauristatin F (MMAF).

3. The antibody-drug conjugate of Claim 1 or 2, wherein said anti-5T4 antibody or antigen binding portion thereof, comprises the VH region of SEQ lD NO: 3 and the VL region of SEQ ID NO: 4.

4. The antibody-drug conjugate of any one of Claims 1-3 wherein said anti—5T4 antibody 1O or antigen binding n thereof, consists of a heavy chain having SEQ ID N021 and a light chain having SEQ lD NO: 2.

5. The antibody-drug conjugate of any one of Claims 1-4, wherein said antibody or antigen binding portion thereof, recognizes an epitope on human 5T4 antigen, wherein said 15 epitope comprises amino acid es 173-258 and 282-361 of the amino acid sequence of SEQ lD NO:11.

6. The antibody—drug conjugate of any one of Claims 1-5, wherein said Drug is MMAF. 20

7. The antibody-drug conjugate of any one of Claims 1-6, wherein p is an integer from 1 to 4.

8. The antibody-drug conjugate of Claim 1 wherein: (a) said anti-5T4 antibody consists of a heavy chain having SEQ ID N021 and a 25 light chain having SEQ lD NO: 2, (b) said LU is maleimidocaproyl, (c) said Drug is MMAF, and (d) p is an r from 1 to 8. 30

9. The antibody-drug conjugate of Claim 1 wherein: (a) said anti-5T4 antibody ts of a heavy chain having SEQ ID NO:1 and a light chain having SEQ lD NO: 2, (b) said LU is idocaproyl, (c) said Drug is MMAF, and (d) p is an integer from 1 to 4.

10. A pharmaceutical composition comprising the antibody-drug conjugate of any one of Claims 1-9 and a pharmaceutically acceptable carrier. 10

11. The antibody-drug conjugate of any one of Claims 1-9 for use in therapy.

12. The use of the antibody-drug ate of any one of Claims 1-9 for the manufacture of a ment for the ent of 5T4-positive cancer. 15

13. The use according to Claim 12, wherein said cancer is selected from the group consisting of colorectal, breast, pancreatic and non-small cell lung carcinomas.

14. A process for producing an anti-5T4 antibody-drug conjugate comprising: (a) chemically linking a linker unit selected from the group consisting of 20 maleimidocaproyl or maleimidocaproyl-valine-citrulline-p-aminobenzyloxycarbonyl (maleimidocaproyl—Val-Cit-PABA) to a Drug unit selected from the group consisting of MMAE, MMAD, or MMAF; (b) ating said linker-drug to the anti-5T4 antibody or antigen binding portion thereof as defined in any one of Claims 1-9, and; 25 (c) purifying the antibody-drug conjugate.

15. The antibody-drug conjugate of Claim 1, substantially as herein described with reference to any one of the Examples thereof.

16. The antibody-drug conjugate of any one of Claims 1-9 or 11, substantially as herein described.

17. The pharmaceutical composition of Claim 10, ntially as herein described.

18. The use of Claim 12 or 13, substantially as herein described.

19. The process of Claim 14, substantially as herein described with reference to any one of the Examples thereof.

20. The process of Claim 14, substantially as herein described.