ANTI-PRLR ANTIBODY-DRUG CONJUGATES (ADC) AND USES THEREOF

Abstract

Provided are antibody drug conjugates that bind PRLR, in particular human PRLR, their methods of making, and uses thereof.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to U.S. Provisional Patent Application Ser. No. 62/482,640, filed Apr. 6, 2017, the disclosure of which is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

[0002] Use present application pertains to, among other things, anti-prolactin receptor (PRLR) antibody drug conjugates (ADCs), compositions including ADCs, methods of making ADCs, and uses thereof.

BACKGROUND

[0003] Cancer therapies comprise a wide range of therapeutic approaches, including surgery, radiation, and chemotherapy. While the often complementary approaches allow a broad selection to be available to the medical practitioner to treat the cancer, existing therapeutics suffer from a number of disadvantages, such as a lack of selectivity of targeting cancer cells over normal, healthy cells, and the development of resistance by the cancer to the treatment.

[0004] Recent approaches to treating cancer based on targeting therapeutics, such as antibodies, have led to chemotherapeutic regimens with fewer side effects as compared to non-targeted therapies such as radiation treatment. One effective approach for enhancing the anti-tumor-potency of antibodies involved linking cytotoxic drugs or toxins to monoclonal antibodies that are capable of being internalized by a target cell. These agents are termed antibody-drug conjugates (ADCs). Upon administration to a patient, ADCs bind to target cells via their antibody portions and become internalized, allowing the drugs or toxins to exert their effect (see, e.g., U.S. Patent Appl. Publ. Nos. US2005/0180972 and US 2005/0123536).

[0005] Prolactin receptor (PRLR) is a single membrane-spanning class 1 cytokine receptor that is homologous to receptors for members of the cytokine superfamily, such as the receptors for IL2, IL3, IL4, IL6, IL7, erythropoietin, and GM-CSF. PRLR is involved in multiple biological functions, including cell growth, differentiation, development, lactation and reproduction. It has no intrinsic tyrosine kinase activity; however, ligand binding has been shown to lead to receptor dimerization, cross-phosphorylation of Jak2 and downstream signaling. Human prolactin receptor cDNA was originally isolated from hepatoma and breast cancer libraries (Boutin et al., Molec. Endocr. 3: 1455-1461, 1989). The nucleotide sequence predicted a mature protein of 598 amino acids with a much longer cytoplasmic domain than the rat liver PRL receptor. The prolactin receptor gene resides in the same chromosomal region as the growth hormone receptor gene, which has been mapped to 5;13-p12 (Arden, K. C. et al. Cytogenet Cell Gene 53: 161-165, 1990; Arden, K. C. et. al., (Abstract) AM. J. Hum. Genet. 45 (suppl.); A129 only, 1989). Growth hormone also binds to the prolactin receptor and activates the receptor.

[0006] PRLR exists in a number of different isoforms that differ in the length of their cytoplasmic domains. Four PRLR mRNA isoforms (L, I, S1a, and S1b) have been identified in human subcutaneous abdominal adipose tissue and breast adipose tissue (Ling, C. et al., J. Clin. Endocr. Metab. 88: 1804-1808, 2003). In addition, expression of both L-PRLR and I-PRLR has been detected in human subcutaneous abdominal adipose tissue and breast adipose tissue using immunoblot analysis. Recent reports have suggested PRLR is expressed and activated in human breast cancer and prostate cancer tissues (Li et al., Cancer Res., 64:4774-4782, 2004; Gill et al., J Clin Pathol., 54:956-960, 2001; Touraine et al., J Clin Endocrinol Metab., 83:667-674, 1998). Reportedly, Stat5 activation and PRLR expression is associated with high histological grade in 54% of prostate cancer specimens (Li et al., supra). Other reports suggest primary breast cancer specimens are responsive to PRL in colony formation assays, and that plasma PRL concentrations correlate with breast cancer risk (Tworoger et al., Cancer Res., 64:6814-6819, 2004; Tworoger et al., Cancer Res., 66:2476-2482, 2006). In another report, PRL transgenic mice developed malignant mammary carcinomas or prostate hyperplasia (Wennbo et al., J Clin Invest., 100:2744-2751, 1997; Wennbo et al., Endocrinology, 138:4410-4415, 1997). Blockade of PRLR signaling may be a means for treating breast and prostate cancer. (See, e.g., Damiano and Wasserman, April 2013, Clin. Cancer Res. 19(7):1644-1650).

[0007] Thus, there is a need in the art for novel PRLR antagonists for the treatment of cancer and other disorders associated with detrimental PRLR activity.

SUMMARY OF THE INVENTION

[0008] The present invention provides antibody drug conjugates (ADCs) comprising a cytotoxic and/or cytostatic agent linked to an anti-PRLR antibody by way of a linker, compositions comprising the ADCs of the invention, methods of making the ADCs of the invention and methods of treating a cancer comprising administering to a subject having cancer the ADCs of the invention. As described in more detail in the Examples, and while not intending to be bound by any particular theory of operation, data included herein demonstrate anti-PRLR ADCs comprising specific linkers and specific cytotoxic and/or cytostatic agents (i.e., a pyrrolobenzodiazepine (PBD) warhead), exert potent anti-tumor activities. Moreover, the anti-PRLR ADCs of the present invention are characterized by a low drug to antibody ratio (DAR), where low drug loading surprisingly provides a highly efficacious ADC.

[0009] Accordingly, in one aspect, the present disclosure provides ADCs that specifically bind PRLR, and in particular human PRLR (huPRLR).

[0010] In one aspect, the invention provides an antibody drug conjugate (ADC) comprising a cytotoxic and/or cytostatic agent linked to as antibody by way of a linker, wherein the antibody drug conjugate is a compound according to structural Formula (I):

[D-L-XY]n-Ab (I),

or a salt thereof, wherein D comprises a pyrrolobenzodiazepine (PBD) dimer; L is a linker; Ab is an anti-prolactin receptor (PRLR) antibody comprising (i.) a heavy chain variable region comprising a CDRH1 sequence comprising SEQ ID NO: 3, a CDRH2 sequence comprising SEQ ID NO: 4; and a CDRH3 sequence comprising SEQ ID NO: 5; (ii.) a light chain variable region comprising a CDRL1 sequence comprising SEQ ID NO: 8; a CDRL2 sequence comprising SEQ ID NO: 9, and a CDRL3 sequence comprising SEQ ID NO: 10; and (iii.) a mutation comprising S239C in a heavy chain constant region, wherein the numbering is in accordance with Kabat; XY represents a covalent linkage linking linker L to antibody Ab; and n is any integer. In one embodiment, n is 2 or 4. In one embodiment, n is 2. In preferred embodiments, n is about 2. In certain embodiments, XY is a linkage formed with it sulfhydryl group on antibody Ab. In one embodiment, XY is a maleimide-sulfhydryl linkage. In certain embodiments, L comprises the linker as described in Formula III, IV, V, VI, VII, VIII or IX. In preferred embodiments, L comprises the linker as described in Formula IX. In certain embodiments, the anti-PRLR antibody comprises an IgG1 isotype. In certain embodiments, the heavy chain constant region of the anti-PRLR antibody either lacks a C-terminal lysine or comprises an amino acid other than lysine at a C-terminus of the heavy chain constant region. In exemplary embodiments, the anti-PRLR antibody is a humanized antibody.

[0011] In another aspect, the invention provides an antibody drug conjugate (ADC) comprising a cytotoxic and/or cytostatic agent linked to an antibody by way of a linker, wherein the antibody drug conjugate is a compound according to structural Formula (I):

[D-L-XY]n-Ab (I),

[0012] or a salt thereof, wherein D comprises a pyrrolobenzodiazepine (PBD) dimer; L is a linker; Ab is an anti-prolactin receptor (PRLR) antibody comprising (i.) a heavy chain variable region comprising SEQ ID NO: 2; (ii.) a light chain variable region comprising SEQ ID NO: 7; and (iii.) a mutation comprising S239C in a heavy chain constant region, wherein the numbering is in accordance with Kabat; XY represents a covalent linkage linking linker L to antibody Ab; and n is any integer. In one embodiment, n is 2 or 4. In one embodiment, n is 2. In preferred embodiments, n is about 2. In certain embodiments, XY is a linkage formed with it sulfhydryl group on antibody Ab. In one embodiment, XY is a maleimide-sulfhydryl linkage. In certain embodiments, L comprises the linker as described in Formula III, IV, V, VI, VII, VIII or IX. In preferred embodiments, L comprises the linker as described in Formula IX. In certain embodiments, the anti-PRLR antibody comprises an IgG1 isotype. In certain embodiments, the heavy chain constant region of the anti-PRLR antibody either lacks a C-terminal lysine or comprises an amino acid other than lysine at a C-terminus of the heavy chain constant region. In exemplary embodiments, the anti-PRLR antibody is a humanized antibody.

[0013] In another aspect, the invention provides an antibody drug conjugate (ADC) comprising a cytotoxic and/or cytostatic agent linked to an antibody by way of a linker, wherein the antibody drug conjugate is a compound according to structural Formula (I):

[D-L-XY]n-Ab (I),

[0014] or a salt thereof, wherein D comprises a pyrrolobenzodiazepine (PBD) dimer; L is a linker; Ab is an anti-prolactin receptor (PRLR) antibody comprising (i.) a heavy chain comprising the amino acid sequence set forth in SEQ ID NO: 1, (ii.) a light chain variable region comprising the amino acid sequence set forth in SEQ ID NO: 6; XY represents a covalent linkage linking linker L to antibody Ab; and n is any integer. In one embodiment, n is 2 or 4. In one embodiment, n is 2. In preferred embodiments, n is about 2. In certain embodiments, XY is a linkage formed with it sulfhydryl group on antibody Ab. In one embodiment, XY is a maleimide-sulfhydryl linkage. In certain embodiments, L comprises the linker as described in Formula III, IV, V, VI, VII, VIII or IX. In preferred embodiments, L comprises the linker as described in Formula IX. In one embodiment, the anti-PRLR antibody comprises an IgG1 isotype. In certain embodiments, the anti-PRLR antibody comprises an IgG1 isotype. In certain embodiments, the heavy chain constant region of the anti-PRLR antibody either lacks a C-terminal lysine or comprises an amino acid other than lysine at a C-terminus of the heavy chain constant region. In exemplary embodiments, the anti-PRLR antibody is a humanized antibody.

[0015] In another aspect, the invention features an ADC comprising the structure of Formula (X)

##STR00001##

[0016] or a salt thereof, wherein Ab comprises an anti-PRLR antibody comprising (i.) a heavy chain variable region comprising a CDRH1 sequence comprising SEQ ID NO: 3, a CDRH2 sequence comprising SEQ ID NO: 4; and a CDRH3 sequence comprising SEQ ID NO: 5; (ii.) a light chain variable region comprising a CDRL1 sequence comprising SEQ ID NO: 8; a CDRL2 sequence comprising SEQ ID NO: 9, and a CDRL3 sequence comprising SEQ ID NO: 10; (iii.) a mutation comprising S239C in a heavy chain constant region, wherein the numbering is in accordance with Kabat; and (iv.) wherein n is 2 or about 2. In one embodiment, the heavy chain variable region comprises SEQ ID NO: 2 and the light chain variable region comprises SEQ ID NO: 7. In one embodiment, the ADC comprises a full heavy chain comprising a SEQ ID NO: 1, and a full light chain comprising SEQ ID NO: 6. In certain embodiments, the anti-PRLR antibody comprises an IgG1 isotype. In certain embodiments, the heavy chain constant region of the anti-PRLR antibody either lacks a C-terminal lysine or comprises an amino acid other than lysine at a C-terminus of the heavy chain constant region. In exemplary embodiments, the anti-PRLR antibody is a humanized antibody.

[0017] In another aspect, the invention features an ADC comprising the structure of Formula (X)

##STR00002##

[0018] or a salt thereof, wherein Ab comprises an anti-PRLR antibody comprising: (i.) a heavy chain variable region comprising SEQ ID NO: 2; (ii.) a light chain comprising SEQ ID NO: 7; (iii.) a mutation comprising S239C in a heavy chain constant region, wherein the numbering is in accordance with Kabat; and (iv.) wherein n is 2 or about 2. In one embodiment, the ADC comprises a full heavy chain comprising SEQ ID NO: 1, and a full light chain comprising SEQ ID NO: 6. In certain embodiments, the anti-PRLR antibody comprises an IgG1 isotype. In certain embodiments, the heavy chain constant region of the anti-PRLR antibody either lacks a C-terminal lysine or comprises an amino acid other than lysine at a C-terminus of the heavy chain constant region. In exemplary embodiments, the anti-PRLR antibody is a humanized antibody.

[0019] In another aspect, the invention features an ADC comprising the structure of Formula (X)

##STR00003##

[0020] or a salt thereof, wherein Ab comprises an anti-PRLR antibody comprising a heavy chain comprising SEQ ID NO: 1 and a light chain comprising SEQ ID NO: 6, wherein n is 2 or about 2.

[0021] In one aspect the invention provides a composition comprising as ADC described herein and an excipient, a carrier, and/or a diluent. In one embodiment, the composition is a pharmaceutical composition. In one embodiment the composition of the invention is formulated for pharmaceutical use in humans.

[0022] In a further aspect, the invention provides for a kit comprising at least one dose of an ADC according to any aspect of the present disclosure and at least one dose of at least one additional therapeutic, wherein the as least one additional therapeutic is optionally combined with the pharmaceutical composition.

[0023] In an even further aspect, the invention provides a method of making an ADC, comprising contacting an anti-PRLR antibody with a synthon according to structural Formula (Ia) D-L-R.sup.x, wherein D is a cytotoxic and/or cytostatic agent capable of crossing a cell membrane. L is a linker capable of being cleaved by a lysosomal enzyme, and R.sup.x comprises a functional group capable of linking the synthon to the antibody, under conditions in which the synthon covalently links the synthon to the antibody; wherein D is a PBD dimer, and wherein the antibody comprises a heavy chain comprising the amino acid sequence set forth in SEQ ID NO: 1, and a light chain comprising the amino acid sequence set forth in SEQ ID NO: 6.

[0024] In an even further aspect, the invention provides a method of making an ADC, comprising contacting an anti-PRLR antibody with a synthon according to structural Formula (Ia) D-L-R.sup.x, wherein D is a cytotoxic and/or cytostatic agent capable of crossing a cell membrane. L is a linker capable of being cleaved by a lysosomal enzyme, and R.sup.x comprises a functional group capable of linking the synthon to the antibody, under conditions in which the synthon covalently links the synthon to the antibody; wherein D is a PBD dimer, and wherein the antibody comprises (i.) a heavy chain variable region comprising a CDRH1 sequence comprising SEQ ID NO: 3, a CDRH2 sequence comprising SEQ ID NO: 4; and a CDRH3 sequence comprising SEQ ID NO: 5; (ii.) a light chain variable region comprising a CDRL1 sequence comprising SEQ ID NO: 8; a CDRL2 sequence comprising SEQ ID NO: 9, and a CDRL3 sequence comprising SEQ ID NO: 10; and (iii.) a mutation comprising S239C in a heavy chain constant region, wherein the numbering is in accordance with Kabat. In certain embodiments, the anti-PRLR antibody comprises an IgG1 isotype. In certain embodiments, the heavy chain constant region of the anti-PRLR antibody either lacks a C-terminal lysine or comprises an amino acid other than lysine at a C-terminus of the heavy chain constant region. In exemplary embodiments, the anti-PRLR antibody is a humanized antibody.

[0025] In an even further aspect, the invention provides a method of making an ADC, comprising contacting an anti-PRLR antibody with a synthon according to structural Formula (Ia) D-L-R.sup.x, wherein D is a cytotoxic and/or cytostatic agent capable of crossing a cell membrane. L is a linker capable of being cleaved by a lysosomal enzyme, and R.sup.x comprises a functional group capable of linking the synthon to the antibody, under conditions in which the synthon covalently links the synthon to the antibody; wherein D is a PBD dimer, and wherein the antibody comprises (i.) a heavy chain comprising a CDRH1 sequence comprising SEQ ID NO: 3, a CDRH2 sequence comprising SEQ ID NO: 4, and a CDRH3 sequence comprising SEQ ID NO: 5; and (ii.) a light chain variable region comprising a CDRL1 sequence comprising SEQ ID NO: 8, a CDRL2 sequence comprising SEQ ID NO: 9, and a CDRL3 sequence comprising SEQ ID NO: 10; and (iii.) a mutation comprising S239C in a heavy chain constant region, wherein the numbering is in accordance with Kabat; and wherein R.sup.x is a sulfhydryl group or maleimide-sulfhydryl group. In certain embodiments, the anti-PRLR antibody comprises an IgG1 isotype. In certain embodiments, the heavy chain constant region of the anti-PRLR antibody either lacks a C-terminal lysine or comprises an amino acid other than lysine at a C-terminus of the heavy chain constant region. In exemplary embodiments, the anti-PRLR antibody is a humanized antibody.

[0026] In an even further aspect, the invention provides a method of making an ADC, comprising contacting an anti-PRLR antibody with a synthon according to structural Formula (Ia) D-L-R.sup.x, wherein D is a cytotoxic and/or cytostatic agent capable of crossing a cell membrane. L is a linker capable of being cleaved by a lysosomal enzyme, and R.sup.x comprises a functional group capable of linking the synthon to the antibody, under conditions in which the synthon covalently links the synthon to the antibody; wherein D is a PBD dimer, wherein L comprises the linker as described in Formula III, IV, V, VI, VII, VIII or IX; and wherein the antibody comprises (i.) a heavy chain variable region comprising a CDRH1 sequence comprising SEQ ID NO: 3, a CDRH2 sequence comprising SEQ ID NO: 4, and a CDRH3 sequence comprising SEQ ID NO: 5; (ii.) a light chain variable region comprising a CDRL1 sequence comprising SEQ ID NO: 8, a CDRL2 sequence comprising SEQ ID NO: 9, and a CDRL3 sequence comprising SEQ ID NO: 10; and (iii.) a mutation comprising S239C in a heavy chain constant region, wherein the numbering is in accordance with Kabat; and wherein R.sup.x is a sulfhydryl group or maleimide-sulfhydryl group. In certain embodiments, the anti-PRLR antibody comprises an IgG1 isotype. In certain embodiments, the heavy chain constant region of the anti-PRLR antibody either lacks a C-terminal lysine or comprises an amino acid other than lysine at a C-terminus of the heavy chain constant region. In exemplary embodiments, the anti-PRLR antibody is a humanized antibody.

[0027] In an even further aspect, the invention provides a method of making an ADC, comprising contacting an anti-PRLR antibody with a synthon according to structural Formula (Ia) D-L-R.sup.x, wherein D is a cytotoxic and/or cytostatic agent capable of crossing a cell membrane. L is a linker capable of being cleaved by a lysosomal enzyme, and R.sup.x comprises a functional group capable of linking the synthon to the antibody, under conditions in which the synthon covalently links the synthon to the antibody; wherein D is a PBD dimer, wherein L comprises the linker as described in Formula IX; and wherein the antibody comprises (i.) a heavy chain variable region comprising a CDRH1 sequence comprising SEQ ID NO: 3, a CDRH2 sequence comprising SEQ ID NO: 4, and a CDRH3 sequence comprising SEQ ID NO: 5; and (ii.) a light chain variable region comprising a CDRL1 sequence comprising SEQ ID NO: 8, a CDRL2 sequence comprising SEQ ID NO: 9, and a CDRL3 sequence comprising SEQ ID NO: 10; and (iii.) a mutation comprising S239C in a heavy chain constant region, wherein the numbering is in accordance with Kabat; and wherein R.sup.x is a sulfhydryl group or maleimide-sulfhydryl group. In certain embodiments, the anti-PRLR antibody comprises an IgG1 isotype. In certain embodiments, the heavy chain constant region of the anti-PRLR antibody either lacks a C-terminal lysine or comprises an amino acid other than lysine at a C-terminus of the heavy chain constant region. In exemplary embodiments, the anti-PRLR antibody is a humanized antibody.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG. 1 shows preparation of h16f (S239C)-PBD. The conjugation process consists of reduction of the interchain disulfides, quantitative oxidation and conjugation with excess PBD drug linker, as described in Example 2.

[0029] FIG. 2 is a graph that shows a hydrophobic interaction chromatography (HIC) of h16f (S239C)-PBD. Reaction parameters were identified to provide a conjugate with >80% DAR2 drug loading, as shown in Example 2.

[0030] FIG. 3A is a graph that shows the comparison of in vivo efficacy of h16f (S239C)-PBD and h16f-MMAE using the BT-474 xenograft mode. Mice were dosed with either vehicle only. Ab-095 MMAE (3 mkd (mg/kg/day)), h16f MMAE (3 mkd), Ab-095PBD (0.5 mkd) or h16f (0.5 mkd). Mean tumor volume was measured in mm.sup.3. Arrows on the x-axis denote administration time points. Ab-05 is a human IgG.sub.1 control that recognizes tetanus toxin, which is not present as the models used. As shown and described in Example 4, the in vivo efficacy of h16f (S239C)-PBD at 0.5 mg/kg was significantly improved compared to h16f-MMAE at 3 mg/kg with a single dose (QDx1) dosing regimen.

[0031] FIG. 3B is a graph that shows the comparison of in vivo efficacy of h16f (S239C)-PBD and h16f-MMAE dosed QD7x3 (B) in the BT-474 xenograft mode. Mice were dosed with either vehicle only. Ab-095 MMAE (3 mkd (mg/kg/day)), h16f MMAE (3 mkd), Ab-095PBD (0.3 mkd) or h16f (0.3 mkd) or h16f PBD (0.2 mkd). Mean tumor volume was measured in mm.sup.3. As shown and described in Example 4, 0.3 mg/kg and 0.2 mg/kg dosing of h16f (S239C)-PBD was superior to 3 mg/kg dosing of h16f-MMAE.

[0032] FIG. 4A is a graph that shows in vivo efficacy of h16f (S239C)-PBD in a patient-derived xenograft (PDX) screen with a triple negative breast cancer (TNB) CTG-0012 tumor model. Mice were dosed with either Ab-095 naked antibody, Ab-095 PBD, h16f PBD, Ab-095 MMAE, or h16f MMAE. As shown and described in Example 4, h16f (S239C)-PBD is a more potent ADC conjugate than auristatin-based ADCs and its activity can extend to lower PRLR-expressing tumors.

[0033] FIG. 4B is a graph that shows in vivo efficacy of h16f (S239C)-PBD with a TNB CTG-0670 tumor model. Mice are dosed with either Ab-095 naked antibody, Ab-095 PBD, h16f PBD, Ab-095 MMAE, or h16f MMAE. As shown and described in Example 4, h16f (S239C)-PBD is a more potent ADC conjugate than auristatin-based ADCs and its activity can extend to lower PRLR-expressing tumors.

[0034] FIG. 4C is a graph that shows in vivo efficacy of h16f (S239C)-PBD with a TNBC CTG-0869 model. Mice were administered either Ab-095 naked antibody, Ab-095 PBD, h16f PBD, Ab-095 MMAE, or h16f MMAE. Note that for FIG. 4A, FIG. 4B, and FIG. 4C, the term "h16f-PBD" refers to h16f (S239C)-PBD. As shown and described in Example 4, h16f (S239C)-PBD is a more potent ADC conjugate than auristatin-based ADCs and its activity can extend to lower PRLR-expressing tumors.

[0035] FIG. 5A is a graph that shows protein aggregation and fragmentation for h16f (S239C). Percent (%) aggregates and % fragments are shown at time "0" (t0) and percent fragment increase per day and percent aggregate increase per day. As shown and described in Example 5, the in vitro plasma stability of the h16f (S239C) mAb and h16f (S239C)-PBD DAR2 was similar to, if not better than, h16f and h16f-vcMMAE DAR3p.

[0036] FIG. 5B is a graph that shows protein aggregation and fragmentation for h16f (S239C)-PBD DAR2. Percent (%) aggregates and % fragments are shown at time "0" (t0) and percent fragment increase per day and percent aggregate increase per day. As shown and described in Example 5, the in vitro plasma stability of the h16f (S239C) mAb and h16f (S239C)-PBD DAR2 was similar to, if not better than, h16f and h16f-vcMMAE DAR3p.

[0037] FIG. 6 provides a table describing the inhibition of in vitro proliferation of BT-474 cells with humanized PRLR ADC candidates. As shown and described in Example 1, among different ADCS containing anti-PRLR antibodies, ADCS utilizing h16f exhibited the most potent inhibitory activity in vitro.

[0038] FIG. 7 provides a table describing breast cancer cell line PRLR expression and proliferation assay summary with h16f (S239C)-PBD, h16f-MMAE and control Ab095 ADCs. An exemplary dark pink value is shown with the arrow. Light pink is denoted with a " ". As shown and described in Example 3, the PBD conjugates showed an increase in potency compared to MMAE conjugates of antibody h16f.

[0039] FIG. 8 provides a table describing PRLR expression and proliferation assay date with h16f-PBD, h16f-MMAE and control (Ab095) ADCs. An exemplary dark pink value is shown with the arrow. Light pink is denoted with a " ". As shown and described in Example 3, the h16f (S239C)-PBD conjugates showed an increase in potency compared to MMAE conjugates of h16f.

[0040] FIG. 9 provides a table describing human breast cancer PDX models with h16f ADCs. As shown and described in Example 4, h16f (S239C)-PBD is more active than h16f-MMAE in most of the PDX models evaluated.

[0041] FIG. 10 provides a comparison of specific binding (nM) to control (left) and PRLR-expressing HEK-293 cells (right) between h16f, h16f (S239C) mutant, h19e, and h19e (S239C) mutant. As shown and described in Example 6, the results demonstrate that that the h16e-S239C mutant had a 7-fold decrease in affinity to PRLR compared to h16f-S239C, whereas the h16f-S239C mutant had similar affinity as the parental h16f antibody to PRLR. Calculated EC50 (nM) values are shows on the far righthand side.

DETAILED DESCRIPTION OF THE INVENTION

[0042] The present invention relates to antibody-drug conjugates (ADCs) that target prolactin receptor (PRLR) and uses thereof. The ADCs of the present invention possess favorable attributes that provide a distinct advantage over ADCs disclosed in the prior art. For example, the ADCs of the present invention (1) are stable under a variety of conditions (see, e.g. Example 5 infra); (2) are considerably more potent than auristatin-based ADCs using essentially the same antibody backbone (see, e.g. Examples 3-4 infra); (3) display little to no reduced binding affinity to PRLR relative to a parent antibody, unlike similar antibodies also bearing an S239C mutation (see, e.g. Example 6 infra and FIG. 10); and (4) have a surprisingly low drug to antibody ratio (DAR) of about 2, e.g. 1.89, 1.96 (see Example 3 infra). Such ADCs of the present invention contain a pyrrolobenzodiazepine (PBD) warhead that is attached to an anti-PRLR antibody through a linker described in, e.g., Formula (IX) as disclosed herein. Exemplary embodiments include ADCs comprising Formula (X) as disclosed herein. Exemplary anti-PRLR antibodies include, for example, h16f (S239C).

[0043] Accordingly, the present invention pertains to antibody drug conjugates (ADCs) comprising a cytotoxic and/or cytostatic agent (e.g., PBD) linked to an anti-prolactin receptor (PRLR) antibody by way of a linker, compositions comprising the ADCs of the invention; methods of making the ADCs of the invention; and methods of using the ADCs to treat cancer associated with abnormal expression of PRLR, e.g. breast

[0044] In certain embodiments, the features an ADC comprising the structure of Formula (X)

##STR00004##

[0045] or a salt thereof, wherein Ab comprises an anti-PRLR antibody comprising: (i.) a heavy chain variable region comprising a CDRH1 sequence comprising SEQ ID NO: 3; a CDRH2 sequence comprising SEQ ID NO: 4, and a CDRH3 sequence comprising SEQ ID NO: 5; (ii.) a light chain variable region comprising a CDRL1 sequence comprising SEQ ID NO: 8, a CDRL2 sequence comprising SEQ ID NO: 9, and a CDRL3 sequence comprising SEQ ID NO: 10; (iii.) a mutation comprising S239C in a heavy chain constant region, wherein the numbering is in accordance with Kabat; and (iv.) wherein n is 2 or about 2.

[0046] In certain embodiments, the invention features an ADC comprising the structure of Formula (X)

##STR00005##

[0047] or a salt thereof, wherein Ab comprises an anti-PRLR antibody comprising: (i.) a heavy chain variable region comprising SEQ ID NO: 2; (ii.) a light chain comprising SEQ ID NO: 7; (iii.) a mutation comprising S239C in a heavy chain constant region, wherein the numbering is in accordance with Kabat; and (iv.) wherein n is 2 or about 2.

[0048] In certain embodiments, the invention features an ADC comprising the structure of Formula (X)

##STR00006##

or a salt thereof, wherein Ab comprises an anti-PRLR antibody comprising a heavy chain comprising SEQ ID NO: 1 and a light chain comprising SEQ ID NO: 6, wherein n is 2 or about 2.

[0049] In certain, embodiments, the invention features an ADC comprising a cytotoxic and/or cytostatic agent linked to an anti-PRLR antibody by way of a linker, wherein the ADC is a compound according to the structural Formula (I):

[D-L-XY].sub.n-Ab (I),

[0050] or a salt thereof, wherein D comprises a pyrrolobenzodiazepine (PBD) dimer; L is a linker, Ab is an anti-PRLR antibody comprising a heavy chain comprising SEQ ID NO: 1 and a light chain comprising SEQ ID NO: 6; XY represents a covalent linkage linking linker L to antibody Ab; and n is any integer. In particular, the anti-PRLR ADCs comprising specific linkers and specific cytotoxic and/or cytostatic agents (e.g. a pyrrolobenzodiazepine (PBD) dimer), described herein, exert surprisingly potent anti-tumor activities, in particular when compared to ADCs comprising essentially the same antibody linked to an auristatin. Moreover, the anti-PRLR ADCs of the present invention are characterized by a low drug to antibody ratio (DAR), where low drug loading surprisingly results in a highly efficacious ADC in, for example, treating cancer associated with abnormal levels of PRLR expression. As described in the Examples herein, h16f (S239C)-PBD is a more potent ADC conjugate than an h16f-auristatin ADC, and retains binding specificity to PRLR similar to non-mutated h16f. The present disclosure concerns antibody drug conjugates that specifically bind human PRLR, compositions comprising the ADCs, anti-huPRLR antibodies that can compose the ADCs: polynucleotides encoding anti-huPRLR antibodies that compose the ADCs; host cells capable of producing the antibodies and; methods and compositions useful for making the antibodies; and various methods of using the ADCs.

[0051] As will be appreciated by skilled artisans, antibodies are "modular" in nature. Throughout the disclosure, various specific embodiments of the various "modules" comprising the antibodies are described. As specific non-limiting examples, various specific embodiments of variable heavy chain (V.sub.H) CDRs, V.sub.H chains, variable light chain (V.sub.L) CDRs and V.sub.L chains are described.

[0052] The ADCs disclosed herein are also "modular" in nature. Throughout the disclosure, various specific embodiments of the various "modules" comprising the ADCs are described. As specific non-limiting examples, specific embodiments of antibodies, linkers, and cytotoxic and/or cytostatic agents that may compose the ADCs are described.

[0053] The ADCs disclosed herein may be in the form of salts, and in some specific embodiments, pharmaceutically acceptable salts. The ADCs of the present invention that possess a sufficiently acidic, sufficiently basic, or both functional groups, can react with any number of acids or bases, organic or inorganic, to form a salt.

[0054] Unless otherwise defined herein, scientific and technical terms used in connection with the present disclosure shall the meanings that are commonly understood by those of ordinary skill in the art.

[0055] The terms "human PRLR" and "human PRLR wild type" (abbreviated herein as hPRLR, hPRLRwt), as used herein, refer to a single membrane spanning class 1 cytokine receptor. Human PRLR includes an extracellular region that binds prolactin, a transmembrane region, and a cytoplasmic region. The term human PRLR is intended to include recombinant human PRLR (rhPRLR), which can be prepared by standard recombinant expression methods. Table 1 provides the amino acid sequence of human PRLR (i.e., SEQ ID NO. 12), and the extracellular domain thereof (i.e., SEQ ID NO: 13), which are known in the art. In addition, various isoforms of hPRLR are known in the art and are set forth in Table 1 below.

TABLE-US-00001 TABLE 1 Amino acid sequences of human PRLR Sequence Protein Identifier Sequence Human PRLR SEQ ID NO.: 12 MKENVASATVFTLLLFLNTCLLNGQLP PGKPEIFKCRSPNKETFTCWWRPGTDG GLPTNYSLTYHREGETLMHECPDYITG GPNSCHFGKQYTSMWRTYIMMVNATNQ MGSSFSDELYVDVTYIVQPDPPLELAV EVKQPEDRKPYLWIKWSPPTLIDLKTG WFTLLYEIRLKPEKAAEKEIHFAGQQT EFKILSLHPGQKYLVQVRCKPDHGYWS AWSPATFIQIPSDFTMNDTTVWISVAV LSAVICLIIVWAVALKGYSMVTCIFPP VPGPKIKGFDAHLLEKGKSEELLSALG CQDFPPTSDYEDLLVEYLEVDDSEDOH LMSVHSKEHPSQGMKPTYLDPDTDSGR GSCDSPSLLSEKCEEPQANPSTFYDPE VIEKPENPETTHTWDPQCISMEGKIPY FHAGGSKCSTWPLPQPSQHNPRSSYKN ITDVCELAVGPAGAPATLLNEAGKDAL KSSQTIKSREEGKATQQREVESFHSET DQDTPWLLPQEKTPFGSAKPLDYVEIH KVNKDGALSLLPKQRENSGKPKKPGTP ENNKEYAKVSGVMDNNILVLVPDPHAK NVACFEESAKEAPPSLEQNQAEKALAN FTATSSKCRLQLGGLDYLDPACFTHSF H (SEQ ID NO: 12) Human PRLR SEQ ID NO.: 13 QLPPGKPEIFKCRSPNKETFTCWKRPG Extra- TDGGLPTNYSLTYHREGETLMHECPDY cellular ITGGPNSCHFGKQYTSMWRTYIMMVNA Domain TNQMGSSFSDELYVDVTYIVQPDPPLE LAVEVKQPEDRKPYLWIKWSPPTLIDL KTGWFTLLYEIRLKPEKAAEWEIHFAG QQTEFKILSLHPGQKYLVQVRCKPDKG YWSAWSPATFIQIPSDFTMN (SEQ ID NO: 13) Human PRLR SEQ ID NO.: 14 MKENVASATVFTLLLFLNTCLLNVQPD Isoform 2 PPLELAVEVKQPEDRKPYLWIKWSPPT LIDLKTGWFTLLYEIRLKPEKAAEWEI HFAGQQTEFKILSLHPGQKYLVQVRCK PDHGYWSAWSPATFIQIPSDFTMNDTT VWISVAVLSAVICLIIVWAVALKGYSM VTCIFPPVPGPKIKGFDAHLLEKGKSE ELLSALGCQDFPPTSDYEDLLVEYLEV DDSEDQHLMSVHSKEHPSQGMKPTYLD PDTDSGRGSCDSPSLLSEKCEEPQANP STFYDPEVIEKPENPETTHTWDPQCIS MEGKIPYFHAGGSKCSTWPLPQPSQHN PRSSYKNITDVCELAVGPAGAPATLLN EAGKDALKSSQTIKSREEGKATQQREV ESSKSETDQDTPWLLPQEKTPFGSAKP LDYVEIHKVNKDGALSLLPKQRENSGK PKKPGTPENNKEYAKVSGVMDNNILVL VPDPHAKNVACFEESAKEAPPSLEQNQ AEKALANFTATSSKCRLQLGGLDYLDP ACFTHSFH (SEQ ID NO: 14) Human PRLR SEQ ID NO.: 15 MKENVASATVETLLLFLNTCLLNGQLP Isoform 3 PGKPEIFKCRSPNKETFTCWKRPGTDG GLPTNYSLTYHREGETLMHECPDYITG GPNSCHFGKQYTSMWRTYIMKVNATNQ MGSSFSDELYVDVTYIVQPDPPLELAV EVKQPEDRKPYLWIKWSPPTLIDLKTG WFTLLYEIRLKPEKAAEWEIHFAGQQT EFKILSLHPGQKYLVQVRCKPDHGYWS AWSPATFIQIPSAW (SEQ ID NO: 15) Human PRLR SEQ ID NO.: 16 MKENVASATVFTLLLFLNTCLLNGQLP Isoform 4 PGKPEIFKCRSPNKETFTCWKRPGTDG GLPTNYSLTYHREGETLMHECPDYITG GPNSCHFGKQYTSMWRTYIMMVNATNQ MGSSFSDBLYVDYTYIVQPDPPLELAY EVKQPEDRKPYLWIKWSPPTLIDLKTG WFTLLYEIRLKPEKAAEWEIHFAGQQT EFKILSLHPGQKYLVQVRCKPDHGYWS AWSPATFIQIPSDFTMNDTTVWISVAV LSAVICLIIVWAVALKGYSMVTCIFPP VPGPKIKGFDAHLLEKGKSEELLSALG CQDFPPTSDYEDLLVEYLEVDDSEDQH LMSVHSKEHPSQGDPLMLGASHYKNLK SYRPRKISSQGRLAVFTKATLTTVQ (SEQ ID NO: 16) Human PRLR SEQ ID NO.: 17 MKENVASATVFTLLLFLNTCLLNGQLP Isoform 5 PGKPEIFKCRSPNKETFTCWWRPGTDG GLPTNYSLTYHREGETLMHECPDYTTG GPNSCHFGKQYTSMWRTYIMMVNATNQ MGSSFSDELYVDVTYIVQPDPPLELAV EVKQPEDRKPYLWIKWSPPTLIDLKTG WFTLLYEIRLKPEKAAEWEIHFAGQQT EFKTLSLHPGQKYLVQVRCKPDKGYWS AWSPATFIQIPSDFTMNDTTVWISVAV LSAVICLIIVWAVALKGYSMVTCIFPP VPGPKIKGFDAHLLEKGKSEELLSALG CQDFPPTSDYEDLLVEYLEVDDSEDQH LMSVHSKEHPSQEREQRQAQEARDS (SEQ ID NO: 17) Human PRLR SEQ ID NO.: 18 MKENVASATVFTLLLFLNTCLLNGQLP Isoform 6 PGKPEIFKCRSPNXETFTCNWRPGTDG GLPTNYSLTYHREGETLMHECPDYITG GPNSCHFGKQYTSMWRTYIMMVNATNQ MGSSFSDELYVDVTYIVQPDPPLELAV EVKQPEDRKPYLWIKWSPPTLIDLKTG WFTLLYEIRLKPEKAAEWEIHFAGQQT EFKILSLHPGQKYLVQVRCKPDHGYWS AWSPATFIQIPSDFTMNDTTVWISVAV LSAVICLIIVWAVALKGYSKVTCIFPP VPGPKIKGFDAHLLEVTP (SEQ ID NO: 18) Human PRLR SEQ ID NO.: 19 MKENVASATVFTLLLFLNTCLLNGQLP Isoform 7 PGKPEIFKCRSPNKETFTCWNRPGTDG GLPTNYSLTYHREGETLMHECPDYITG GPNSCHFGKQYTSMWRTYIMMVNATNQ MGSSFSDELYVDVTYIVQPDPPLELAV EVKQPEDRKPYLWIKKSPPTLIDLKTG WFTLLYEIRLKPEKAAEWEIHFAGQQT EFKILSLHPGQKYLVQVRCKPDHGYNS AWSPATFIQIPSGDPLMLGASHYKNLK SYRPRKISSQGRLAVFTKATLTTVQ (SEQ ID NO: 19) Human PRLR SEQ ID NO.: 20 MHECPDYITGGPNSCHFGKQYTSMKRT Isoform 8 YIMMVNATNQMGSSFSDELYVDVTYIV QPDPPLELAVEVKQPEDRKPYLWIKWS PPTLIDLKTGWFTLLYEIRLKPSKAAE WEIHFAGQQTEFKILSLHPGQKYLVQV RCKPDHGYWSAWSPATFIQIPSDFTMN DTTVWISVAVLSAVICLIIVWAVALKG YSMVTCIFPPVPGPKIKGFDAHLLEVT P (SEQ ID NO: 20)

[0056] As used herein, the term "antibody" (Ab) refers to an immunoglobulin molecule that specifically binds to, or is immunologically reactive with, a particular antigen, i.e., hPRLR. Antibodies comprise complementarity determining regions (CDRs), also known as hypervariable regions, in both the light chain and heavy chain variable domains. The more highly conserved portions of the variable domains are called the framework (FR). As is known in the art, the amino acid position/boundary delineating a hypervariable region of an antibody can vary, depending on the context and the various definitions known in the art. Some positions within a variable domain may be viewed as hybrid hypervariable positions in that these positions can be deemed to be within a hypervariable region under one set of criteria, while being deemed to be outside, a hypervariable region under a different set of criteria. One or more of these positions can also be found in extended hypervariable regions. The variable domains of native heavy and light chains each comprise four FR regions, largely by adopting a .beta.-sheet configuration, connected by three CDRs, which form loops connecting, and in some cases forming part of, the .beta.-sheet structure. The CDRs in each chain are held together in close proximity by the FR regions and, with the CDRs from the other chain, contribute to the formation of the antigen binding she of antibodies. See Kabat et al., Sequences of Proteins of Immunological Interest (National Institute of Health, Bethesda, Md. 1987). As used hereby numbering of immunoglobulin amino acid residues is done according to the immunoglobulin amino acid residue numbering system of Kabat et al. unless otherwise indicated.

[0057] The term "monoconal antibody" as used herein is not limited to antibodies produced through hybridoma technology. A monoclonal antibody is derived from a single clone, including any eukaryotic, prokaryotic, or phage clone, by any means available or known in the art. Monoclonal antibodies useful with the present disclosure, including in vivo use of ADCs including anti-huPRLR antibodies in humans, chimeric, of hybridoma, recombinant, and phage display technologies, or a combination thereof. In many uses of the present disclosure , including in vivo use of ADCs including anti-huPRLR antibodies in humans, chimeric, primatized, humanized, or human antibodies can suitable be used. In exemplary embodiments, the anti-huPRLR antibodies of the present invention are humanized, e.g. h16f (S239C).

[0058] "Humanized" forms of non-human (e.g., murine) antibodies are chimeric immunoglobuins that contain minimal sequences derived from non-human immunoglobulin. In general, a humanized antibody will comprise substantially all of at least one, and typically two, variable domains, in which all or substantially all of the CDR regions correspond to those of non-human immunoglobulin and all or substantially all of the FR regions are those of a human immunoglobulin sequence. An exemplary humanized antibody of the present invention is h16f (S239C). The humanized antibody can also comprise at least a portion of an immunoglobulin constant region (Fc), typically that of a human immunoglobulin consensus sequence. Methods of antibody humanization are known in the art.

[0059] Anti-hPRLR ADCs of the invention may comprise full-length (intact) antibody molecules that are capable of specifically binding huPRLR. In one embodiment, the ADC of the invention comprises a full-length h16f (S239C) antibody.

[0060] The term "cytotoxic and/or cytostatic agent", as used herein is meant to refer to any agent or drug known to inhibit the growth and/or replication of, and/or kill cells. In one embodiment, the cytotoxic and/or cytostatic agent is a cell permeating DNA minor groove-binding agent such as a pyrrolobenzodiazepine ("PBD") and PBD dimers.

[0061] The term "antibody-drug-conjugate" or "ADC" refers to as antibody chemically linked to one or more cytotoxic and/or cytostatic agents. In one embodiment, an ADC includes an antibody, cytotoxic and/or cytostatic agent, and a linker that enables attachment or conjugation of the drug to the antibody. An ADC of the present invention typically has anywhere from 1 to 3 cytotoxic and/of cytostatic agents conjugated to the antibody, including a drug loaded species of 1, 2, or 3.

[0062] The term "drug-to-antibody ratio" or "DAR" refers to the number of drugs (cytotoxic and/or cytostatic agents), e.g., PBD, attached to the antibody of the ADC. The DAR of on ADC can range from 1 to 3, although higher loads are also possible depending on the number of linkage site on an antibody. The term DAR may be used in reference to the number of drugs loaded onto an individual antibody, or, alternatively, may be used in reference to the average or mean DAR of a group of ADCs. In one embodiment, the ADC of the invention has a DAR of about 2. In this context, the term "about", means an amount within .+-.7.5% of the actual value, i.e. "about 2" means 1.85, 1.86, 1.87, 1.88, 1.89, 1.90, 1.91, 1.92, 1.93, 1.94, 1.95, 1.96, 1.97, 1.98, 1.99, 2.00, 2.01, 2.02, 2.03, 2.04, 2.05, 2.06, 2.07, 2.08, 2.09, 2.10, 2.11, 2.12, 2.13, 2.14, 2.15, and any intervening ranges.

[0063] In specific exemplary embodiments, the ADCs of the invention comprise an anti-PRLR antibody, e.g., an h16f (S239C) anti-PRLR antibody having a DAR of about 2.

[0064] In one aspect, the ADCs of the invention comprise an anti-PRLR antibody comprising a heavy chain variable region composing a CDR set (CDRH1, CDRH2 and CDRH3) as set forth in SEQ ID NOS: 3, 4, and 5, and a light chain variable region comprising a CDR set as set forth in SEQ ID NOS: 8, 9, and 10 (CDRL1, CDRL2, and CDRL3). Preferably, the anti-PRLR antibody is an IgG1 isotype having a heavy chain constant region with a cysteine mutation engineered to provide a conjugation site for a PBD. In one embodiment, the cysteine mutation is at position 239 of the heavy chain. Preferably, the mutation is S239C numbered according to Kabat. The anti-PRLR antibody "h16f (239C)" as described herein has a heavy chain variable region comprising CDRH1, CDRH2, and CDRH3 as set forth in SEQ ID NOS: 3, 4, and 5 respectively, and a light chain variable region comprising CDRL1, CDRL2, and CDRL3 as set forth in SEQ ID NOS: 8, 9, and 10 respectively. In some embodiments, the anti-PRLR antibody either lacks a C-terminal lysine or comprises an amino acid other than lysine at a C-terminus of the heavy chain constant region.

[0065] In another aspect, the ADCs of the invention comprise an anti-PRLR antibody comprising a heavy chain variable region comprising SEQ ID NO: 2, and a light chain region comprising SEQ ID NO: 7. Preferably, the anti-PRLR antibody is an IgG1 isotype having a heavy chain constant region with a cysteine mutation engineered to provide a conjugation site for a PBD. In one embodiment, the cysteine mutation is at position 239 of the heavy chain. Preferably, the mutation is S239C, numbered according to Kabat. The anti-PRLR antibody "h16f (239C)" as described herein has a heavy chain variable region comprising SEQ ID NO: 2, and a light chain variable region comprising SEQ ID NO: 7. In some embodiments, the anti-PRLR antibody either lacks a C-terminal lysine or comprises an amino acid other than lysine at a C-terminus of the heavy chain constant region.

[0066] In another aspect, the ADCs of the invention comprise an anti-PRLR antibody comprising a heavy chain comprising SEQ ID NO: 1, and a light chain region comprising SEQ ID NO: 6. The anti-PRLR antibody "h16f (239C)" as described herein has a heavy chain comprising the amino acid sequence set forth in SEQ ID NO: 1 and a light chain comprising the amino acid sequence set forth in SEQ ID NO: 6. SEQ ID NO: 1 differs from SEQ ID NO: 11 only in that SEQ ID NO: 1 contains the S239C mutation; see Table 9 infra. As described herein, the S239C mutation corresponds to amino acid residue number 242 of SEQ ID NO: 1. In some embodiments, the anti-PRLR antibody either lacks a C-terminal lysine or comprises an amino acid other than lysine at a C-terminus of the heavy chain constant region.

[0067] Antibodies of the anti-PRLR ADCs described herein may be antibodies whose sequences have been modified to alter at least one constant region-mediated biological effector function. For example, in some embodiments, an anti-PRLR antibody may be modified to reduce at least one constant region-mediated biological effector function relative to the unmodified antibody, e.g., reduced binding to the Fc receptor (Fc.gamma.R). Fc.gamma.R binding may be reduced by mutating the immunoglobulin constant region segment of the antibody at particular regions necessary for Fc.gamma.R interactions (See, e.g., Canfield and Morrison, 1991, J. Exp. Med. 173:1483-1491; and Lund et al., 1991, J. Immunol. 147:2657-2662). Reducing Fc.gamma.R binding may also reduce other effector functions which rely on Fc.gamma.R interactions, such as opsonization, phagocytosis and antigen-dependent cellular cytotoxicity ("ADCC").

[0068] Antibodies included in anti-PRLR ADCs may have low levels of, or lack, fucose. Antibodies lacking fucose have been correlated with enhance ADCC activity, especially at low doses of antibody. See Shields et al., 2002, J. Biol. Chem. 277:26733-26740; Shinkawa et al., 2003, J. Biol. Chem. 278:3466-73. Methods of preparing fucose-less antibodies include growth in rat myeloma YB2/0 cells (ATCC CRL 1662). YB2/0 cells express low levels of FUT8 mRNA, which encodes .alpha.-1,6-fucosyltransferase, an enzyme necessary for fucosylation of polypeptides.

[0069] Antibodies included in anti-PRLR ADCs may include modifications that increase or decrease their binding affinities to the neonatal Fc receptor, FcRn, for example, by mutating the immunoglobulin constant region segment at particular regions involved in FcRn interactions (see, e.g., WO 2005/123780). An anti-PRLR antibody may have one ore more amino acids inserted into one or more of its hypervariable regions, for example as described in Jung & Pluckthun, 1997, Protein Engineering 10:9, 959-966; Yazaki et al., 2004, Protein Eng. Des Sel. 17(5):481-9; and U.S. Pat. App. No. 2007/0280931.

[0070] Antibodies may be produced by any of a number of techniques, as described for example in International Publication No. WO2014/105810, incorporated by reference in its entirety herein.

[0071] Anti-PRLR antibodies with high affinity for PRLR, e.g., human PRLR, may be desirable for therapeutic uses. Accordingly, the present disclosure contemplates ADCs comprising anti-PRLR antibodies having a high binding affinity to PRLR, and in particular human PRLR. In specific embodiments, the antibodies bind PRLR with an affinity of at least about 100 nM, but may exhibit higher affinity, for example, at least 90 nM, 80 nM, 70 nM, 60 nM, 50 nM, 40 nM, 30 nM, 25 nM, 20 nM, 15 nM, 10 nM, 7nM, 6 nM, 5 nM, 4 nM, 3 nM, 2 nM, 1 nM, 0.1 nM, 0.01 nM, or even higher. In some embodiments, the antibodies bind PRLR with an affinity in the range of about 1 pM to about 100 nM, or an affinity ranging between any of the foregoing values.

[0072] Affinity of antibodies for PRLR can be determined using techniques well known in the art or described herein, such as for example, but not by way of limitation, ELISA, isothermal titration calorimetry (ITC), surface plasmon resonance, flow cytometry or fluorescent polarization assays.

[0073] Anti-PRLR antibodies can be prepared by recombinant expression of immunoglobulin light and heavy chain genes in a host cell using standard recombinant DNA methodologies known in the art, such as those described in Molecular Cloning: A Laboratory Manual, Second Edition (Sambrook, Fritsch and Maniatis (eds), Cold Spring Harbor. N.Y., 1989). For example, DNAs encoding partial or full-length light and heavy chains are inserted into expression vectors such that the genes are operatively linked to transcriptional and translational control sequences and transformed into a host cell. The antibody light chain gene and the antibody heavy chain gene can be inserted into separate vectors or more typically. Both genes are inserted into the same expression vector, accomplished by methods known in the art. Antibodies can also be produced by chemical synthesis (e.g., by the methods described in Solid Phase Peptide Synthesis, 2.sup.nd ed., 1984 The Pierce Chemical Co., Rockford, Ill.).

[0074] Anti-PRLR ADCs of the invention generally comprise an anti-PRLR antibody (e.g., h16f(S239C)) having one or more cytotoxic and/or cytostatic agents, which may be the same or different, linked thereto by way of one or more linkers, which may also be the same or different. In specific embodiments, the anti-PRLR ADCs are compounds according to structural formula (I):

[D-L-XY].sub.n-Ab (I),

or salts thereof, where each "D" represents, independently of the others, a cytotoxic and/or cytostatic agent ("drug", e.g. PBD dimer); each "L" represents, independently of the others, a linker; "Ab" represents an anti-PRLR antibody; each "XY" represents a linkage formed between a functional group R.sup.x on the linker and a "complementary" functional group R.sup.y on the antigen binding moiety; and n represents the number of drugs linked to Ab, or the drug-to-antibody ratio (DAR), of the ADC. Specific embodiments of various anti-PRLR antibodies that may compose ADCs according to structural formula (I) are described above.

[0075] In some specific embodiments of the ADCs or salts of structural formula (I), each D is the same and/or each L is the same.

[0076] Specific embodiments of cytotoxic and/or cytostatic agents (D) and linkers (L) that may compose the anti-PRLR ADCs, as well as the number of cytotoxic and/or cytostatic agents linked to the anti-PRLR ADCs, are described in more detail below.

[0077] In certain embodiments, the ADC has the structure of Formula (I), or a salt thereof, wherein D composes a pyrrolobenzodiazepine (PBD) dimer; L is a linker; Ab is an antibody comprising SEQ ID NO: 1; XY represents a covalent linkage linking linker L to antibody Ab; and n is any integer. The DAR of an ADC is equivalent to the "n" referred to in Formula I. In one embodiment, n is 2 or 4. In preferred embodiments, n is about 2. In this context, the term "about", means an amount within .+-.7.5% of the actual value, i.e. "about 2" means 1.85, 1.86, 1.87, 1.88, 1.89, 1.90, 1.91, 1.92, 1.93, 1.94, 1.95, 1.96, 1.97, 1.98, 1.99, 2.00, 2.01, 2.02, 2.03, 2.04, 2.05, 2.06, 2.07, 2.08, 2.09, 2.10, 2.11, 2.12, 2.13, 2.14, 2.15, and any intervening ranges. In exemplary embodiments, n is about 1.89 or about 1.96. Additional details regarding drugs (D of formula I) and linkers (L of Formula I) that may be used in the ADCs of the invention, as well as alternative ADC structures, are described below. In one embodiment, the cytotoxic and/or cytostatic agent is a pyrrolobenzodiazepine (PBD), e.g., a PBD dimer.

[0078] The structures of PBDs can be found, for example, in U.S. Patent Application Pub. Nos. 2013/0028917 and 2013/0028919, and in WO 2011/130598 A1, each of which are incorporated herein by reference in their entirety. The generic structure of a PBD is provided below as Formula (II).

##STR00007##

[0079] PBDs differ in the number, type and position of substituents, in both their aromatic A rings and pyrrolo C rings, and in the degree of saturation of the C ring. In the B-ring, there is generally an imine (N|C), a carbinolamine (NH--CH(OH)), or a carbinolamine methyl ether (NH--CH(OMe)) at the N10--C 11 position which is the electrophilic centre responsible for alkylating DNA. All of the known natural products have an (S)-configuration at the chiral C11a position that provides a right-handed twist when viewed from the C ring towards the A ring. The PBD examples provided herein may be conjugated to the anti-PRLR antibodies of the invention. Further examples of PBDs that may be conjugated to the anti-PRLR antibodies of the invention can be found, for example, in U.S. Patent Application Publication Nos. 2013/0028917 A1 and 2013/0028919 A1, in U.S. Pat. No 7,741,319 B2, and in WO 2011/130598 A1 and WO 2006/111759 A1, each of which are incorporated herein by reference in their entirety.

[0080] In the anti-huPRLR ADCs described herein, the cytotoxic and/or cytostatic agents are linked to the antibody by way of linkers. The linkers may be short, long, hydrophobic, hydrophilic, flexible or rigid, or may be composed of segments that each independently have one or more of the above-mentioned properties such that the linker may include segments having different properties. The linkers may be polyvalent such that they covalently link more than one agent to a single site on the antibody, or monovalent such that covalently they link a single agent to a single site on the antibody.

[0081] In certain embodiments, the linker selected is cleavable in vivo. Cleavable linkers may include chemically or enzymatically unstable or degradable linkages. Cleavable linkers generally rely on processes inside the cell to liberate the drug, such as reduction in the cytoplasm, exposure to acidic conditions in the lysosome, or cleavage by specific proteases or other enzymes within the cell. Cleavable linkers generally incorporate one or more chemical bonds that are either chemically or enzymatically cleavable while the remainder of the linker is noncleavable. In certain embodiments, a linker comprises a chemically labile group such as hydrazone and/or disulfide groups. Linkers comprising chemically labile groups exploit differential properties between the plasma and some cytoplasmic compartments. The intracellular conditions to facilitate drug release for hydrazone containing linkers are the acidic environment of endosomes and lysosomes, while the disulfide containing linkers are reduced in the cytosol, which contains high thiol concentrations, e.g., glutathione. In certain embodiments, the plasma stability of a linker comprising a chemically labile group may be increased by introducing steric hindrance using substituents near the chemically labile group.

[0082] Acid-labile groups, such as hydrazone, remain intact during systemic circulation in the blood's neutral pH environment (pH 7.3-7.5) and undergo hydrolysis and release the drug once the ADC is internalized into mildly acidic endosomal (pH 5.0-6.5) and lysosomal (pH 4.5-5.0) compartments of the cell. This pH dependent release mechanism has been associated with nonspecific release of the drug. To increase the stability of the hydrazone group of the linker, the linker may be varied by chemical modification, e.g., substitution, allowing tuning to achieve more efficient release in the lysosome with a minimized loss in circulation.

[0083] Hydrazone-containing linkers may contain additional cleavage sites, such as additional acid-labile cleavage sites and/or enzymatically labile cleavage sites ADCs including exemplary hydrazone-containing linkers include the following structures of Formulas (III), (IV), and (V):

##STR00008##

or a salt thereof, wherein D and Ab represent the cytotoxic and or cytostatic agent (drug) and antibody, respectively, and n represents the number of drug-linkers linked to the antibody. In certain linkers such as that of (Formula (III)), the linker comprises two cleavable groups-13 a disulfide and a hydrazone moiety. For such linkers, effective release of the unmodified free drug requires acidic pH or disulfide reduction and acidic pH. Linkers such as those of Formula (IV) and (V) have been shown to be effective with a single hydrazone cleavage site.

[0084] Other acid-labile groups that may be included in linkers include cis-aconityl-containing linkers, cis-Aconityl chemistry uses a carboxylic acid juxtaposed to an amide bond to accelerate amide hydrolysis under acidic conditions.

[0085] Cleavable linkers may also include a disulfide group. Disulfides are thermodynamically stable at physiological pH and are designed to release the drug upon internalization inside cells, wherein the cytosol provides a significantly more reducing environment compared to the extracellular environment. Scission of disulfide bonds generally requires the presence of a cytoplasmic thiol cofactor, such as (reduced) glutathione (GSH), such that disulfide-containing linkers are reasonably stable in circulation, selectively releasing the drug in the cytosol. The intracellular enzyme protein disulfide isomerase, or similar enzymes capable of cleaving disulfide bonds, may also contribute to the preferential cleavage of disulfide bonds inside cells. GSH is reported to be present in cells in the concentration range of 0.5-10 mM compared with a significantly lower concentration of GSH or cysteine, the most abundant low-molecular weight thiol, in circulation at approximately 5 .mu.M. Tumor cells, where irregular blood flow leads to a hypoxic state, result in enhanced activity of reductive enzymes and therefore even higher glutathione concentrations. In certain embodiments, the in vivo stability of a disulfide-containing linker may be enhanced by chemical modification of the linker, e.g., use of steric hindrance adjacent to the disulfide bond.

[0086] ADCs including exemplary disulfide-containing linkers include the following structures of Formulas (VI), (VII), and (VIII):

##STR00009##

or a salt thereof, wherein D and Ab represent the drug and antibody, respectively, n represents the number of drug-linkers linked to the antibody, and R is independently selected at each occurrence from hydrogen or alkyl, for example. In certain embodiments, increasing steric hindrance adjacent to the disulfide bond increases the stability of the linker. Structures such as (VI) and (VIII) show increased in vivo stability when one or more R groups is selected from a lower alkyl such as methyl.

[0087] Another type of cleavable linker that may be used is a linker that is specifically cleaved by an enzyme. Such linkers are typically peptide-based or include peptidic regions that act as substrates for enzymes. Peptide based linkers tend to be more stable in plasma and extracellular milieu than chemically labile linkers. Peptide bonds generally have good serum stability, as lysosomal proteolytic enzymes have very low activity in blood due to endogenous inhibitors and the unfavorably high pH value of blood compared to lysosomes. Release of a drug from an antibody occurs specifically due to the action of lysosomal proteases, e.g., cathepsin and plasmin. These proteases may be present at elevated levels in certain tumor cells.

[0088] In exemplary embodiments, the cleavable peptide is selected from tetrapeptides such as Gly-Phe-Leu-Gly, Ala-Leu-Ala-Leu, or dipeptides such as Val-Cit, Val-Ala, Met-(D)Lys, Asn-(D)Lys, Val-(D)Asp, Phe-Lys, Ile-Val, Asp-Val, His-Val, NorVal-(D)Asp, Ala-(D)Asp, Met-Lys, Asn-Lys, Ile-Pro, Me3Lys-Pro, PhenylGly-(D)-Lys, Met-(D)Lys, Asn-(D)Lys, Pro-(D)Lys, Met-(D)Lys, Asn-(D)Lys, Met-(D)Lys, Asn-(D)Lys. In certain embodiments, dipeptides are preferred over longer polypeptides due to hydrophobicity of the longer peptides.

[0089] A variety of dipeptide-based cleavable linkers useful for linking drugs such as doxorubicin, mitomycin, campotothecin, tallysomycin and auristatin/auristatin family members to antibodies have been described (see, Dubowchik et al., 1998, J. Org. Chem. 67: 1866-1872; Dubowchik et al., 1998, Bioorg. Med. Chem. Lett. 8(21):3341-3346; Walker et al., 2002, Bioorg. Med. Chem. Lett. 12:217-219; Walker et al., 2004, Bioorg. Med. Chem. Lett. 14:4323-4327; and Francisco et al., 2003, Blood 102:1458-1465, Domina et al., 2008, Bioconjugate Chemistry 19: 1960-1963, of each of which is incorporated herein by reference). All of these dipeptide linkers, or modified versions of these dipeptide linkers, may be used in the ADCs described herein. Other dipeptide linkers that may be used include those found in ADCs such as Seattle Genetics' Brentuximab Vendotin SGN-35 (Adeetris.TM.), Seattle Genetics SGN-75 (anti-CD-70, Val-Cit-MMAF), Celldex Therapeutics glembatumumab (CDX-011) (anti-NMB, Val-Cit-MMAE), and Cytogen PSMA-ADC (PSMA-ADC-1301) (anti-PSMA, Val-Cit-MMAE).

[0090] Enzymatically cleavable linkers may include a self-immolative spacer to spatially separate the drug from the site of enzymatic cleavage. The direct attachment of a drug to a peptide linker can result in proteolytic release of an amino acid adduct of the drug, thereby impairing its activity. The use of a self-immolative spacer allows for the elimination of the fully active, chemically unmodified drug upon amide bond hydrolysis.

[0091] One self-immolative spacer is the bifunctional para-aminobenzyl alcohol group, which is linked to the peptide through the amino group, forming an amide bond, while amine containing drugs may be attached through carbamate functionalities to the benzylic hydroxyl group of the linker (PABC). The resulting prodrugs are activated upon protease-mediated cleavage, leading to a 1,6-elimination reaction releasing the unmodified drug, carbon dioxide, and remnants of the linker group. the following scheme depicts the fragmentation of p-amidobenzyl ether and release of the drug.

##STR00010##

wherein X-D represents the unmodified drug.

[0092] Heterocyclic variants of this self-immolative group have also been described. See for example, U.S. Pat. No. 7,989,434, incorporated herein by reference.

[0093] In some embodiments, the enzymatically cleavable linker is a .beta.-glucuronic acid-based linker. Facile release of the drug may be realized through cleavage of the .beta.-glucuronide glycosidic bond by the lysosomal enzyme .beta.-glucuronidase. This enzyme is present abundantly within lysosomes and is overexpressed in some tumor types, while the enzyme activity outside cells is low. .beta.-Glucuronic acid-based linkers may be used to circumvent the tendency of an ADC to undergo aggregation due to the hydrophilic nature of .beta.-glucuronides. In some embodiments, .beta.-glucuronic acid-based linkers are preferred as linkers for ADCs linked to hydrophobic drugs. The following scheme depicts the release of the drug from and ADC containing a .beta.-glucuronic acid-based linker.

##STR00011##

[0094] A variety of cleavable .beta.-glucuronic acid-based linkers useful for linking drugs such as auristatins, camtptothecin and doxorubicin analogues. CBI minor-groove binders, and psymberin to antibodies have been described (see, e.g. Nolting, Chapter 5 "Linker Technology in Antibody-Drug Conjugates." In. Antibody-Drug Conjugates: Methods in Molecular Biology, vol. 1045, pp. 71-100, Laurent Ducry (Ed.), Springer Science & Business Medica, LLC, 2013; Jeffrey et al., 2006, Bioconjug. Chem. 17:831-840; Jeffrey et al., 2007, Bioorg. Med Chem. Lett. 17.2278-2280; and Jiang et al., 2005, J. Am. Chem. Soc. 127: 11254-11255, each of which is incorporated herein by reference). All of these .beta.-glucuronic acid-based linkers may be used in the anti-PRLR ADCs described herein.

[0095] In a one embodiment, the linker used in the ADCs of the invention is shown in Formula (IX), wherein V is Val, Z is Ala, D is the drug (e.g. PBD dimer), and q is 1, 2, 3, 4, 5, 6, 7, or 8:

##STR00012##

or a salt thereof, in exemplary embodiments, q is 5.

[0096] In one aspect, the present invention describes an ADC comprising a cytotoxic and/or cytostatic agent linked to an antibody by way of a linker, wherein the antibody drug conjugate is a compound according to the structural Formula (I), or a salt thereof wherein D comprises a pyrrolobenzodiazepine (PBD) dimer; L is a linker; Ab is an antibody comprising SEQ ID NO: 1; XY represents a covalent linkage linking linker L to antibody Ab, and n is any integer. In one embodiment, XY represents a covalent linkage linking linker L to antibody Ab, where the XY is a linkage formed with a sulfhydryl group on antibody Ab. In another embodiment, XY is a maleimide-sulfhydryl linkage.

[0097] In certain, embodiments, the ADC of the present invention comprises the structure of Formula (X):

##STR00013##

[0098] or a salt thereof, wherein Ab is an antibody comprising a heavy chain variable region comprising a CDR set (CDRH1, CDRH2, and CDRH3) as set forth in SEQ ID NOS: 3, 4, and 5 respectively, and a light chain variable region comprising a CDR set (CDRL1, CDRL2, and CDRL3) as set forth in SEQ ID NOS: 8, 9, and 10 respectively, and n is about 2 to about 4. Preferably, the anti-PRLR antibody is an IgG1 isotype having a constant region with cysteine mutation engineered to provide a conjugation site for a PBD. In one embodiment, the cysteine mutation is at position 239 of the heavy chain. Preferably, the mutation is S239C, wherein the numbering is in accordance with Kabat. In one embodiment, n is about 2 or about 4. In a preferred embodiment, n is about 2. In one embodiment, the heavy chain constant region of the anti-PRLR. antibody either lacks a C-terminal lysine or comprises an amino acid other than lysine at a C-terminus of the heavy chain constant region.

[0099] In certain embodiments, the ADC of the present invention composes the structure of Formula (X):

##STR00014##

or a salt thereof, wherein Ab is an antibody comprising a heavy chain variable region comprising SEQ ID NO: 2, and a light chain variable region comprising SEQ ID NO: 7, and n is about 2 to about 4. Preferably, the anti-PRLR antibody is an IgG1 isotype having a constant region with cysteine mutation engineered to provide a conjugation site for a PBD. In one embodiment, the cysteine mutation is at position 239 of the heavy chain. Preferably, the mutation is S239C, wherein the numbering is in accordance with Kabat. In one embodiment, n is about 2 to about 4. In a preferred embodiment, n is about 2.In one embodiment, the heavy chain constant region of the anti-PRLR antibody either lacks a C-terminal lysine or comprises an amino acid other than lysine at a C-terminus of the heavy chain constant region.

[0100] In certain embodiments, the ADC of the present invention comprises the structure of Formula (X):

##STR00015##

or a salt thereof wherein Ab is an antibody comprising a heavy chain comprising the amino acid sequence set forth in SEQ ID NO: 1 and a light chain comprising the amino acid sequence set forth in SEQ ID NO: 6. In one embodiment, n is about 2 to about 4. In one embodiment, n is about 2 or about 4. In a preferred embodiment, n is about 2.

[0101] The ADCs described herein may be synthesized using chemistries that are well-known in the art. The chemistries selected will depend upon, among other things, the identity of the cytotoxic and/or cytostatic agent(s), the linker and the groups used to attach linker to the antibody. Generally, ADCs according to Formula (I) may be prepared according to the following scheme:

D-L-R.sup.x+Ab-R.sup.y.fwdarw.[D-L-XY].sub.n-Ab (Ia) (Ib) (I)

where D, L, Ab, XY and n are as previously defined above, and R.sup.x and R.sup.y represent complementary groups capable of forming covalent linkages with one another, as discussed above.

[0102] The identities of groups R.sup.x and R.sup.y will depend upon the chemistry used to link synthon D-L-R.sup.x to the antibody. Generally, the chemistry used should not alter the integrity of the antibody, for example its ability to bind its target. Preferably, the binding properties of the conjugated antibody will closely resemble those of the unconjugated antibody. A variety of chemistries and techniques for conjugating molecules to biological molecules such as antibodies are known in the art and in particular to antibodies, are well-known. See, e.g., Amon et al., "Monoclonal Antibodies for Immunotargeting of Drugs in Cancer Therapy," in: Monoclonal Antibodies and Cancer Therapy, Reisfeld et al. Eds., Alan R. Liss, Inc., 1985; Hellstrom et al., "Antibodies for Drug Delivery," in: Controlled Drug Delivery, Robinson et al. Eds., Marcel Dekker, Inc., 2nd Ed. 1987; Thorpe, "Antibody Carriers of Cytotoxic Agents in Cancer Therapy: A Review," in: Monoclonal Antibodies '84: Biological and Clinical Applications, Pinchera et al., Eds., 1985; "Analysis, Results, and Future Prospective of the Therapeutic Use of Radiolabeled Antibody in Cancer Therapy," in: Monoclonal Antibodies for Cancer Detection and Therapy, Baldwin et al., Eds., Academic Press, 1985; Thorpe et al., 1982, Immunol. Rev. 62:119-58; PCT publication WO 89/12624. Any of these chemistries may be used to link the synthons to an antibody.

[0103] A number of functional groups R.sup.x and chemistries useful for linking synthons to accessible lysine residues are known, and include by way of example and not limitation NHS-esters and isothiocyanates.

[0104] A number of functional groups R.sup.x and chemistries useful for linking synthons to accessible free sulfhydryl groups of cysteine residues are known, and include by way of example and not limitation haloacetyls and maleimides.

[0105] However, conjugation chemistries are not limited to available side chain groups. Side chains such as amines may be converted to other useful groups, such as hydroxyls, by linking an appropriate small molecule to the amine. This strategy can be used to increase the number of available linking sites on the antibody by conjugating multifunctional small molecules to side chains of accessible amino acid residues of the antibody. Functional groups R.sup.x suitable for covalently linking the synthons to these "converted" functional groups are then included in the synthons.

[0106] An antibody may also be engineered to include amino acid residues for conjugation. An approach tor engineering antibodies to include non-genetically encoded amino acid residues useful for conjugating drugs in the context of ADCs is described by Axup et al., 2012, Proc Natl Acad Sci U S A., 109(40): 16101-16106, as are chemistries and functional groups useful for linking synthons to the non-encoded amino acids.

[0107] Typically, the synthons are linked to the side chains of amino acid residues of the antibody, including, for example, the primary amino group of accessible lysine residues or the sulfhydryl group of accessible cysteine residues. Free sulfhydryl groups may be obtained by reducing interchain disulfide bonds.

[0108] For linkages where R.sup.y is a sulfhydryl group (for example, where R.sup.x is a maleimide), the antibody is generally first fully or partially reduced to disrupt interchain disulfide bridges between cysteine residues. Specific cysteine residues and interchain disulfide bridges, if present in the antibody heavy chain, may be reduced for attachment of drug-linker synthons including a group suitable for conjugation to a sulfhydryl group, and include by way of example and not limitation: residues C233, C239, and C242 (Kabat numbering system; corresponding to residues C220, C226, and C229 Eu numbering) on the human IgG.sub.1 heavy chain, and residue C214 (Kabat numbering system) on the human Ig kappa light chain. In instances where an antibody heavy chain does not contain a cysteine residue at an attachment site, however, the antibody can be engineered to contain a cysteine at a given position, e.g., position 239.

[0109] Cysteine residues for synthon attachment that do not participate in disulfide bridges may be engineered into an antibody by mutation of one or more codons. Reducing these unpaired cysteines yields a sulfhydryl group suitable for conjugation. Preferred positions for incorporating engineered cysteines include, by way of example and not limitation, positions S112C, S113C, A114C, S115C, A176C, S180C, S239C, S252C, V286C, V292C, S357C, A359C, S398C, S428C (Kabat numbering) on the human IgG1 heavy chain and positions V110C, S114C, S121C, S127C, S168C, V205C (Kabat numbering) on the human Ig kappa light chain (see, e.g., U.S. Pat. No. 7,521,541, U.S. Pat. No. 7,855,275 and U.S. Pat. No. 8,455,622). In one embodiment, residue S239 (Kabat numbering system) is mutated to a cysteine to allow conjugation of a PBD warhead to an anti-PRLR antibody, e.g. antibody h16f. This mutation is referred to herein as "S239C".

[0110] In certain embodiments, the ADCs of the invention have a DAR of about 2, via the engineered cysteines. In this context, the term "about", means an amount within .+-.7.5% of the actual value, i.e. "about 2" means 1.85, 1.86, 1.87, 1.88, 1.89, 1.90, 1.91, 1.92, 1.93, 1.94, 1.95, 1.96, 1.97, 1.98, 1.99, 2.00, 2.01, 2.02, 2.03, 2.04, 2.05, 2.06, 2.07, 2.08, 2.09, 2.10, 2.11, 2.12, 2.13, 2.14, 2.15, and any intervening ranges. For example, in certain exemplary embodiments, the ADCs of the invention have a DAR of 1.89 or 1.96, via the engineered cysteines.

[0111] In certain embodiments, the invention features a method of making an ADC, comprising contacting an antibody heavy and light chains set forth in SEQ ID NOS: 1 and 6, respectively, with a synthon according to structural Formula (Ia), wherein D is cytotoxic and/or cytostatic agent capable of crossing a cell membrane, L is a linker capable of being cleaved by a lysosomal enzyme, and R.sup.x comprises a functional group capable of covalently linking the synthon to the antibody, under conditions in which the synthon covalently links to synthon to the antibody, wherein D is, e.g., a PBD dimer.

[0112] As will be appreciated by skilled artisans, the number of cytotoxic and/or cytostatic agents linked to an antibody molecule may vary, such that an ADC preparation may be heterogeneous in nature, where some antibodies in the preparation contain one linked agent, some two, some three, etc. (and some none). The degree of heterogenity will depend upon, among other things, the chemistries used for linking the cytotoxic cytostatic agent and/or cytostatic agents. For example, where the antibodies are reduced to yield sulfhydryl groups for attachment, heterogeneous mixtures of antibodies having zero, 2, 4, 6 or 8 linked agents per molecule are often produced. Furthermore, by limiting the molar ratio of attachment compound, antibodies having zero, 1, 2, 3, 4, 5, 6, 7 or 8 linked agents per molecule are often produced. Thus, it will be understood that depending upon context, stated drug antibody ratios (DARs) may be averages for a collection of antibodies. For example, "DAR4" refers to an ADC preparation that has not been subjected to purification to isolate specific DAR peaks and comprises a heterogeneous mixture of ADC molecules having different numbers of cytostatic and/or cytostatic agents attached per antibody (e.g., 0, 2, 4, 6, 8 agents per antibody), but has an average drug-to-antibody ratio of 4.

[0113] Heterogeneous ADC preparations may be processed, for example, by hydrophobic interaction chromatography ("HIC") to yield preparations enriched in an ADC having a specified DAR of interest (or a mixture of two or more specified DARS). Such enriched preparations are designed herein as "EX," where "E" indicates the ADC preparation has been processed and is enriched in an ADC having a specific DAR and "X" represents the number of cytotoxic and/or cytostatic agents linked per ADC molecule. Preparations enriched in a mixture of ADCs having two specific DARs are designated "EX/EY," three specific DARs "EX/EY/EZ" etc., where "E" indicates the ADC preparation has been processed to enrich the specified DARs and "X," "Y" and "Z" represent the DARs enriched. As specific examples, "E2" refers to an ADC preparation that has been enriched to contain primarily ADCs having two cytotoxic and/or cytostatic agents linked per ADC molecule. "E4" refers to an ADC preparation that has been enriched to contain primarily ADCs having four cytostatic and/or cytotoxic agents linked per ADC molecule. "E2/E4" refers to an ADC preparation that has been enriched to contain primarily two ADC populations, one having two cytostatic and/or cytotoxic agents linked per ADC molecule and another having four cytostatic and/or cytotoxic agents linked per ADC molecule.

[0114] As used herein, enriched "E" preparations will generally he at least about 80% pure in the stated OAR ADCs, although higher levels of purity, such as purities of at least about 85%, 90%, 95%, 98%, or even higher, may be obtainable and desirable. For example, an "EX" preparation will generally be at least about 80% pure in ADCs having X cytostatic and/or cytotoxic agents linked pet ADC molecule, For "higher order" enriched preparations, such as, for example, "EX/EY" preparations, the sum total of ADCs having X and Y cytostatic and/or cytotoxic agents linked per ABC molecule will generally comprise at least about 80% of the total ADCs in the preparation. Similarly, in an enriched "EX/EY/EZ" preparation, the sum total of ADCs having X, Y and Z cytostatic and/or cytotoxic agents linked per ADC molecule will comprise at least about 80% of the total ADCs in the preparation.

[0115] Purity may be assessed by a variety of methods, as is known in the art. As a specific example, an ADC preparation may be analyzed via HPLC or other chromatography and the purity assessed by analyzing areas under th curves of the resultant peaks.

[0116] In one embodiment, the invention comprises a heterogenous composition comprising h16f (S293C)-PBD ADCs having a DAR of 2 (DAR E2), wherein the DAR E2 species is present at >80 percent (>80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99 percent) of all ADCs in the composition. In one embodiment, the invention comprises a heterogenous composition comprising h16f (S293C)-PBD ADCs having a DAR of 2 (DAR E2), wherein the DAR E2 species is present at >90 percent (>90, 91, 92, 93, 94, 95, 96, 97, 98, 99 percent) of the population of all ADCs in the composition.

[0117] In certain embodiments, the DAR of the ADC of the invention is about 2 or about 4. In further embodiments, the DAR of the ADC of the invention is 2.

[0118] The ADCs described herein may be in the form of pharmaceutical compositions comprising the ADC and one or more carriers, excipients and/or diluents. The compositions may be formulated for specific uses, such as for veterinary uses or pharmaceutical uses in humans.

BRIEF DESCRIPTION OF THE SEQUENCES

[0119] Incorporated by reference herein in its entirety is a Sequence Listing entitled Sequence_Listing_12367, comprising SEQ ID NO: 1 through SEQ ID NO: 31, which includes the nucleic acid and/or amino acid sequences disclosed herein. The sequence listing has been submitted herewith in ASCII test format. This sequence listing was first created on Mar. 26, 2018 and is 56 kilobytes in size.

EXAMPLES

[0120] The following Examples, which highlight certain features and properties of exemplary embodiments of anti-PRLR ADCs are provided for purposes of illustration, and not limitation.

[0121] It should be noted that, unless otherwise described, the approximate DAR of the PBD ADCs described in the examples below is about 2; see, e.g. Example 3 (DAR of 1.89 and 1.96, considered to be about 2).

Example 1

Generation of Anti-PRLR h16f (S239C)

[0122] Antibody h16f is a humanized antibody that was initially generated from a murine parent anti-PRLR antibody that was identified from a screen of anti-PRLR antibodies having inhibitory activity in, for example, a cell proliferation assay. The light chain amino acid sequence of h16f is described in SEQ ID NO: 6, the variable region is described in SEQ ID NO: 7, and the 3 CDRs are described in SEQ ID NOS: 8 to 10. The heavy chain amino acid sequence of h16f is described in SEQ ID NO: 11, the variable region is described in SEQ ID NO: 2, and the 3 CDRs are described in SEQ ID NOs: 3 to 5.

[0123] Antibody h16f was determined to have distinct properties from anti-PRLR antibody LFA-102 (Novartis). For example, antibody h16f was determined to have slower off rates to PRLR relative to antibody LFA-102, i.e., a k.sub.d of 6.23.times.10.sup.-4 s.sup.-1 and a K.sub.d of 4.6.times.10.sup.-10 M (h16f) vs. 1.10.times.10.sup.-3 s.sup.-1 and a K.sub.d of 1.3.times.10.sup.-9 M (LFA-102). Further, the structure of h16f and LFA-102 anti-PRLR antibody Fab fragments bound to PRLR was determined using X-ray crystallography to determine the epitope of each. The close contact regions for antibody h16f and LFA-102 were compared and it was determined that antibody h16f binds to the PRL ligand-binding domain, a largely non-overlapping epitope from LFA-102. Thus, antibodies h16f and LFA-102 do not have the same epitope.

[0124] A number of humanized anti-PRLR antibodies, including antibody h16f, were conjugated to an auristatin to form ADCs and evaluated for their ability to inhibit the growth of multiple breast cancer cell lines expressing different levels of PRLR. The most potent ADC candidates were then evaluated for antitumor activity against the BT-474 human breast tumor cell line. BT-474 has .about.10,000 PRLR receptors per cell, which is lower than the number typically necessary to mediate effective ADC killing, suggesting that efficient internalization may be a critical component for activity of a PRLR ADC. This tumor cell line, therefore, served as a surrogate measure of ADC internalization properties. Based on the results, the h16f antibody was identified as having the most potent inhibitory activity. The IC.sub.50 values of the anti-PRLR ADCs is described below in Table 2 and FIG. 6. Ab-05 is a human IgG.sub.1 control that recognizes tetanus toxin, which is not present in the models used.

TABLE-US-00002 TABLE 2 Inhibition of In Vitro Proliferation of BT-474 Cells with Humanized Anti-PRLR ADCs. BT-474 ADC (MMAF DAR8)* IC.sub.50 (nM) AB095 33.40 h5b** 0.68 h5d 0.61 h5e 0.55 h5f 0.58 h53e 0.27 h53f 0.40 h53b 0.37 h19e 1.04 h19f 1.02 h16a 0.68 h16c 0.74 h16f 0.19 h16g 0.30 h16h 0.22 LFA-102 1.05 *mAbs were conjugated to MMAF with DAR 8. **Multiple humanized candidates were generated from each starting murine mAb.

[0125] PRLR sequence homology is well conserved between human and primates (>95%) and is poor between human and rat or mouse (<85%). The h16f antibody binds with similar affinity to human and cynomolgus monkey. Binding of the h16f antibody to either rat or mouse PRLR is significantly lower (>1,000 fold) than to human PRLR as described in Table 3.

TABLE-US-00003 TABLE 3 Species Cross-Reactivity: Homology and Biacore. Percent Homology Affinity (K.sub.D, nM) PRLR Species to Human h16f-(S239C) h16f (S239C)-PBD Human PRLR ECD 100 1.0 0.99 Cynomolgus PRLR 98 0.72 0.71 ECD Rat PRLR ECD 72 1,400 1,600 Mouse PRLR ECD 71 400 370 Note: ECD = extracellular domain; K.sub.D = dissociation constant; PRLR = prolactin receptor

[0126] Following identification of anti-PRLR antibody h16f, the antibody was modified in order to engineer site-specific conjugation sites of the warhead PBD. Specifically, an engineered cysteine antibody (C239) was generated in order to permit site-specific conjugation of the PBD dimer with a DAR of about 2. This mutated antibody is referred to herein as h16f (S239) and includes an h16f light chain and a modified h16f (C239) heavy chain sequence. The heavy chain amino acid sequence of h16f (S239C) is described below in SEQ ID NO: 1, The CDRS (CDR1, CDR2, and CDR3) (SEQ ID Nos: 3 to 5) are underlined, and the variable region (SEQ ID NO: 2) is italicized.

TABLE-US-00004 (SEQ ID NO: 1) EVQLVQSGAEVKKPGSSVKVSCKASGYTFTTYWMHWVRQAPGQGLEWIGE IDPSDSYSNYNQKFKDRATLTVDKSTSTAYMELSSLRSEDTAVYYCARNG GLGPAWFSYWGQGTLVTVSSASTKGPSVFPLAPSSKSTSGGTAALGCLVK DYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQT YICNVNHKPSNTKVDXKVEPKSCDKTHTCPPCPAPELLGGPCVFLFPPKP KDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYN STYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQ VYTLPPSREEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPV LDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK

[0127] The heavy chain constant region of h16f (S239C) contains a modified residue relative to its parent antibody. Specifically, residue 239 (Kabat numbering) was mutated from S to a C relative to the heavy chain of h16f. This residue is underlined/bolded above in SEQ ID NO: 1. It should be noted S239C (Kabat numbering) corresponds to amino acid residue number 242 of SEQ ID NO: 1 (S242C).

[0128] The light chain amino acid sequence (SEQ ID NO: 6) of h16f (S239C) is provided below where CDRs 1, 2 and 3 (SEQ ID NOS: 8-10) are underlined, and the variable region (SEQ ID NO: 7) is italicized.

TABLE-US-00005 (SEQ ID NO: 6) DIQMTQSPSSVSASVGDRVTITCKASQYVGTAVAWYQQKPGKSPKLLIYS ASNRYTGVPSRFSDSGSGTDFTLTISSLQPEDFATYFCQQYSSYPWTFGG GTKVEIKRTVAAPSVFIFPPSDEQLKSGTASVVCLLNNFYPREAKVQWKV DNALQSGNSQESVTEQDSKDSTYSLSSTLTLSKADYEKHKVYACEVTHQG LSSPVTKSFNRGEC

[0129] h16f (S239C) was further conjugated to a PBD dimer and tested as an ADC, as described in the examples below.

Example 2

Generation and Physiochemical Characterization of PBD Conjugate

[0130] h16f (S239C)-PBD is comprised of two PBD drug-linker molecules conjugated to Cys engineered anti-PRLR antibody h16f. The structure of the PBD and linker are described in FIG. 1. FIG. 1 also describes the process by which h16f (S239C)-PBD was prepared. The conjugation process consisted of reducing the interchain disulfides, quantitative oxidation and conjugation with excess PBD drug linker. The conjugation process consisted of a quantitative reduction of the engineered and interchain disulfides. The reduction mixture was then purified to remove the excess reagant and its byproducts, followed by quantitative oxidation of the interchain disulfides and then conjugation with excess PBD drug-linker. After quenching, the reaction mixture was purified and buffer-exchanged to yield h16f (S239C)-PBD with >80% DAR2 drug loading, as described in FIG. 2. The overall yield of the h16f (S239C)-PBD ADC after purification was approximately 80%. The conjugation process required the use of approximately 4% wt loading (.about.3.5 g) of the PBD drag linker.

Example 3

In Vitro Comparison of h16f (S239C)-PBD ADC vs. h16f-MMAE ADC

[0131] h16f-MMAE and h16f (S239C)-PBD conjugates were evaluated for their ability to inhibit the growth of a panel of 25 breast cancer cell lines expressing different levels of PRLR. The results of this comparative analyses are described below in Table 4 and FIG. 7. The h16f (S239C)-PBD conjugates used in this study had a DAR of 1.89 or 1.96. The 6 day proliferation assay IC.sub.50 (nM) results are shown in Table 4 and FIG. 7.

TABLE-US-00006 TABLE 4 Breast Cancer Cell Line PRLR Expression and Proliferation Assay Summary with h16f (S239C)- PBD, h16f-MMAE and Control Antibody (Ab) 095 ADCs. 6-Day Proliferation Assay IC.sub.50 (nM)* PRLR h16f Increase in Cell line (Receptor #) RNA*** (S239C)- Ab095- PBD h16f- Ab095- PDB Breast Cancer Line (Oncomine) PBD PBD Dimer MMAE MMAE Potency**** T47D (26,000) 188 0.01 21.14 0.06 0.22 >22 21 MDAMB361.sup.+ 38 0.64 >22 0.21 0.96 9.7 1 HCC1428 26 0.54 >22 0.33 0.19 5.43 0.4 BT-474.FP2 (10,000).sup.+ 24 0.27 14.13 0.38 0.56 13.09 2 MDAMB134VI 22 0.11 26.2 0.16 0.42 11.75 4 CAMA1 17 0.01 8.6 0.09 5.16 21.71 695 MCF7 (8,000) 12 0.12 14.53 0.07 >22 >22 >183 HCC1500 8 0.28 17.43 0.1 0.97 >22 3 ZR751 8 0.04 11.31 0.05 4.07 >22 92 MDAMB415 4 0.9 13.44 0.06 >22 >22 >24 SKBR3.sup.+ 4 0.26 12.91 0.04 3.67 4.64 14 HCC70 3 0.25 7.18 0.03 >22 >22 >88 MDAMB175VII 2 30 >22 0.06 >22 >22 -- HCC38 2 25.42 32.82 0.01 >22 >22 -- UACC812 2 >22 >22 0.44 >22 >22 -- HCC1143 2 0.78 9.88 0.42 9.28 10.73 12 MDAMB468 1 0.18 3.78 0.01 14.29 13.97 80 BT549 1 8.36 19.49 0.02 >22 >22 >3 MDAMB436.FP9 1 2.09 3.02 0.06 19.22 20.95 -- (4,000) MDAMB435SLM 1 >22 >22 0.26 >22 >22 n/a MDAMB231LC3.LMC 1 >22 >22 0.16 >22 >22 n/a JIMT-1 1 9.76 6.42 0.13 17.51 17.73 n/a HCC1187 0.7 0.09 8.06 0.05 13.93 8.06 157 BT20 0.4 0.19 0.14 0.12 >22 >22 n/a SUM149PT 0.2 9.82 12.03 0.08 >22 >22 n/a *Breast cancer cell lines sensitive (bolded; >50% maximum inhibition), partially sensitive (underlined) and resistant (plain type). IC.sub.50 values were determined in cell killing titration assays starting at a concentration of 3 .mu.g/mL. **.sup.+denotes HER2+ cells lines; PRLR/cell determined by FACS-based antigen binding is shown for selected cell lines. ***Relative RNA expression based on microarray analysis. ****The increase in activity of the PBD conjugates relative to the MMAE conjugate is shown as fold-increase in potency as determined by the ratios of IC.sub.50 values

[0132] As described in Table 4 breast cancer cell lines that were shown to be sensitive to treatment with h16f (S239C)-PBD (>50% maximum inhibition) were T47D (26,000), MDAMB361, HCC1428, BT474, FP2 (10,000), MDAMB134VI, CAMA1, MCF7 (8,000), HCC1500, ZR751, MDAMB361, SKBR3, HCC70, HCC1143, MDAMB468, BT549m and HCC1187. Breast cancer cell lines that were shown to be sensitive to treatment with h16f MMAE (>50% maximum inhibition) were T47D (26,000), MDAMB361, HCC1428, BT474, FP2 (10,000), MDAMB134VI, CAMA1, MCF7 (8,000), HCC1500, ZR751. Breast cancer cell lines that were shown to be partially sensitive to treatment with h16f (S239C)-PBD were: MDAMB175VII, HCC38, UACC812 and MDAMB436.FP9 (4,000). Breast cancer cell lines that were shown to be partially sensitive to treatment with h16f (S239C)-PBD were: MCF7 (8,000) and SKBR3.

[0133] The increase in activity of the PBD conjugate relative to the MMAE conjugate is shown as fold-increase in potency as determined by the ratios of IC.sub.50 values. As shown in Table 6, the PBD conjugates showed an increase in potency compared to MMAE conjugates of antibody (h16f).

[0134] Measurement of PRLR receptor densities on these tumor cells permitted an assessment of the correlation between receptor expression and sensitivity to ADC-mediated killing. Results described in Table 4 and FIG. 7 indicated cell line sensitivity to killing by the ADC correlated with PRLR mRNA and protein expression. PRLR was overexpressed in both HER2+ and HER2- tumors. Every tumor cell line sensitive to killing by h16f-MMAE ADC was surprisingly equally or more sensitive to killing by h16f (S239C)-PBD. Additionally, several tumor cell lines with lower levels of PRLR were sensitive to killing by the PBD conjugate but were largely insensitive to h16f-MMAE. These results suggest that h16f (S239C)-PBD is more potent than h16f-MMAE and may provide additional treatment options for sensitive tumors.

[0135] BT-474 has .about.10,000 PRLR per cell, which is lower than the expression typically required to mediate effective ADC killing for other receptors such as ERBB2, MET and EGFR, though similar to levels seen with other targets such as tissue factor and LGR5. The sensitivity of BT-474 to PRLR ADC-mediated cell killing suggests that efficient internalization and/or internal processing is a critical component for ADC activity. Immunofluorescence and warhead quantification studies have confirmed rapid internalization of the ADC.

[0136] Since the PRLR/PRL axis has been implicated in other tissues, including reproductive tissues and prostate (Martei et al. (2015) Breast Cancer 7:337-343; Damiano et al. (2013) Clin Cancer Res 19:1644-1650), h16f-MMAE and -PBD conjugates were evaluated for their ability to inhibit the growth of non-breast-derived tumor cell lines as described in Table 5 and FIG. 8. Although the levels of PRLR RNA in these cell lines was generally much lower than observed for many breast cancer cell lines, several cell lines were sensitive to killing by h16f (S239C)-PBD, but not h16f-MMAE. These results suggest that h16f (S239C)-PBD may be effective in treating in tumor types other than breast cancer.

TABLE-US-00007 TABLE 5 PRLR Expression and Proliferation Assay Data with h16f-PBD, h16f-MMAE and Control (Ab095) ADCs. 6-Day Proliferation Assay IC.sub.50 (nM)* PRLR h16f Increase in Cell line (Receptor #) RNA*** (S239C)- Ab095- PBD h16f- Ab095- PDB Breast Cancer Line (Oncomine) PBD PBD Dimer MMAE MMAE Potency**** Ovarian Cancer SMOV2 (2300) n.d. 0.16 17.44 0.02 >22 >22 >138 ES2.LMC 1 15 21.52 0.18 >22 >22 >0.15 Hey A8.LMC 0.4 >22 >22 0.39 >22 >22 n/a Endometrial Cancer AN3CA 2 0.6 4.35 0.02 21.68 23.3 36 Prostate Cancer 22Rv1 2 0.01 7.56 0.09 >22 >22 >2200 PC3 0.4 >22 >22 0.09 >22 19.66 n/a Colon Cancer SW403 3 0.11 21.94 0.06 17.46 13.78 152 LoVo 2 >22 >22 0.13 >22 15.54 n/a LS174T 0.4 0.13 2.88 0.01 >22 >22 169 SW48 0.4 1.97 2.24 0.02 21.62 20.37 n/a Liver Cancer HepG2 3 8.59 15.97 0.06 >22 >22 -- HuH7 2 5.22 11.79 0.06 >22 >22 4 Hep3B 0.3 9.69 7.71 0.05 >22 >22 -- Gastric Cancer IM95 2 5.67 18.18 0.17 19.85 24.15 4 Lung Cancer NCI-H1048 2 3.09 5.32 0.03 >22 >22 -- NCI-h1395 1 >22 >22 0.63 >22 >22 n/a Recombinant Expression HEK293/Human <0.01 1.92 0.02 0.15 64.72 >15 PRLR HEK293/Vector 0.2 2.74 2.27 0.02 >22 >22 n/a *Tumor cell line sensitivity: (bold (SMOV2 (2300), ES2.LMC, AN3CA, 22Rv1, SW403, LS174T, HuH7, HEK293/Human PRLR); >50% maximum inhibition), partially sensitive (underlined (HepG2, Hep3B, NCI-H1048) and resistant (plain). IC.sub.50 values were determined in cell killing titration assays starting at a concentration of 3 .mu.g/mL. **PRLR/cell determined by FACS-based antigen binding shown for select cell line. ***Relative RNA expression based on microarray analysis ****The increase in activity of the PBD conjugate relative to the MMAE conjugate is shown as fold-increase in potency as determined by the ratios of IC.sub.50 values.

[0137] The increase in activity of the PBD conjugate relative to the MMAE conjugate is shown as fold-increase in potency as determined by the ratios of IC.sub.50 values. As shown in Table 5, the h16f (S239C)-PBD conjugates showed an increase in potency compared to MMAE conjugates of h16f.

Example 4

In Vivo Characterization of PRLR ADCs

[0138] In vivo studies using the BT-474 xenograft model in mouse subjects were perforated using both h16f conjugated auristatin payloads and PBD payloads in order to compare the activities of the two warheads in the context of a cirtually identical antibody.

[0139] BT-474 is an ER+, progesterone receptor (PR)-, HER2+ breast cancer cell line that expresses .about.10,000 PRLR receptors per cell, and in vitro efficacy of h16f (S239C)-PBD (0.27 nM) was very similar to h16f-MMAE ADC (0.56 nM) (see Table 5). In contrast, and surprisingly, the in vivo efficacy of h16f (S239C)-PBD at 0.5 mg/kg was significantly improved compared to h16f-MMAE at 3 mg/kg with a single dose (QDx1) dosing regimen as described in FIG. 3A. In a subsequent Q7Dx3 study (where mice were dosed every 7 days for 3 weeks; Q7Dx3, 0.3 mg/kg and 0.2 mg/kg dosing of h16f (S239C)-PBD was superior to 3 mg/kg dosing of h16f-MMAE, as described in FIG. 3B.

[0140] To further assess the antitumor activity of h16f (S239C)-PBD, an "n of 3" targeted study in 15 breast cancer patient-derived xenograft (PDX) primarily, but not exclusively, triple negative breast cancer (TNB) tumor models (commercially available from Champions Oncology) that express a range from weak to moderate PRLR was performed. The study and results are described in Table 8. PRLR density in this table is reflected as a comparison to the PRLR number on the MCF7 tumor cell line (8,000 receptors per cell; see Table 4). As summarized in Table 6 and FIG. 9, results surprisingly indicated that h16f (S239C)-PBD is more active than h16f-MMAE in most of the PDX models that have been evaluated. One additional TNB PDX model, BR-0851 that was evaluated was insensitive to h16f (S239C)-PBD.

TABLE-US-00008 TABLE 6 Human Breast Cancer PDX Models with h16f(S239C)-PBD vs. h16f-MMAE ADCs Gender and Species/ Doses No. per Strain and Regimen Group Noteworthy Findings CTG 1124 Mouse/ 0.2 mg/kg/day Female Expression 0.77; Efficacy High Breast PDX Harlan; at Q7Dx3 n = 3/group Model nu/nu CTG 0012 Mouse/ 0.5 mg/kg/day Female Expression 0.75; Efficacy High Breast PDX Harlan; at Q7Dx3 n = 3/group Model nu/nu CTG 00869 Mouse/ 0.5 mg/kg/day Female Expression 0.8; Efficacy High Breast PDX Harlan; at Q7Dx3 n = 3/group Model nu/nu CTG 0670 Mouse/ 0.5 mg/kg/day Female Expression 1.6; Efficacy High Breast PDX Harlan; at Q7Dx3 n = 3/group 96% Model nu/nu CTG 1019 Mouse/ 0.2 mg/kg/day Female Expression 0.33; Efficacy High Breast PDX Harlan; at Q7Dx3 n = 3/group Model nu/nu CTG 1242 Mouse/ 0.2 mg/kg/day Female Expression 1.9; Efficacy High Breast PDX Harlan; at Q7Dx3 n = 3/group Model nu/nu CTG 1171 Mouse/ 0.2 mg/kg/day Female Expression 0.89; Efficacy High Breast PDX Harlan; at Q7Dx3 n = 3/group Model nu/nu CTG 0033 Mouse/ 0.2 mg/kg/day Female Expression 1.1; Efficacy High Breast PDX Harlan; at Q7Dx3 n = 6/group Model nu/nu CTG 0017 Mouse/ 0.2 mg/kg/day Female Expression 0.29; Efficacy Breast PDX Harlan; at Q7Dx3 n = 3/group Moderate Model nu/nu CTG 0052 Mouse/ 0.2 mg/kg/day Female Expression 0.30; Efficacy Breast PDX Harlan; at Q7Dx3 n = 3/group Moderate Model nu/nu a. All in vivo efficacy studies were performed using human patient-derived xenograft models grown subcutaneously as xenografts in the mouse flank. PRLR expression level is expressed relative to MCF7, a low expressing tumor (approximately 8000 receptors/cell in culture) as a benchmark. TGI = maximum tumor growth inhibition relative to the control group. Efficacy was classified as: Low = 25-50% TGI, Moderate = 50-75% TGI or High >75% TGI.

[0141] Tumor growth inhibition for selected PDX models from the screen described in Table 6 is shown in FIG. 4A and FIG. 4B. CTG-0012 is an example of a TNB tumor model in which h16f (S239C)-PBD and h16 MMAE showed surprisingly similar efficacy although the PBD conjugate was dosed at a 10-fold lower condensation than is the MMAE conjugate, while CTG-0670 is an example of TNB tumor model where a 10-fold lower dose of h16f (S239C)-PBD has more effective than h16f-MMAE. The results from the comparative studies using the CTG-0012, CTG-0670, and CTG00869 models are described in FIG. 4A, FIGS. 4B, and 4C, respectively. Consistent with the results from the in vitro assay (Table 5), these data indicate that h16f (S239C)-PBD is a more potent ADC conjugate than auristatin-based ADCs and that its activity can extend to lower PRLR-expressing tumors.

Example 5

In Vitro Plasma Stability

[0142] The stability of fluorescently labeled h16f (S239C) antibody and h16f (S239C)-PBD DAR2 was evaluated in vitro at 37.degree. C. for 6 days in plasma from mouse, rat, cyno, and human as well as in buffer. Protein aggregation and fragmentation were measured by size exclusion chromatography (SEC); unconjugated PBD was determined by liquid chromatography-mass spectrometry (LC/MS/MS). h16f (S239C) mAb showed 2-4% initial aggregates at t0 with minimal percent increase/day (.ltoreq.0.7%) for buffer and plasma. The antibody had 0% initial fragments at t0 and minimal % increase/day (.ltoreq.0.3%) in all matrices tested. h16f (S239C)-PBD DAR2 ADC showed variable initial aggregates (0-4) and fragments (0-1.4%) at t0 in buffer and plasma. The ADC had higher percentage aggregate increase/day in plasma (0.4-4%) compared to buffer with human>cyno>rat.about.mouse plasma. The percent fragment increase/day was minimal (.ltoreq.0.2%) in all matrices as described in FIG. 5A and FIG. 5B. The PBD warhead itself was tested and found to be stable in plasma at 37.degree. C. for 6 days in all species. The unconjugated warhead released from h16f (S239C)-PBD DAR2 was below the level of quantitation at all time points and in all matrices. This corresponds to <0.7% of warhead equivalent dosed. Overall the in vitro plasma stability of the h16f (S239C) mAb and h16f (S239C)-PBD DAR2 was similar to (if not better than) h16f and h16f-vcMMAE DAR3p.

[0143] These results support the surprising and unexpected finding that h16f (S239C)-PBD ADCs of the present invention having a low drug to antibody ratio (DAR), surprisingly provide a highly efficacious ADC. Taken together, the present invention describes ADC h16f (S239C)-PBD that is a more potent ADC conjugate than an auristatin-based ADC using essentially the same antibody backbone.

Example 6

Comparison of Specific Binding to PRLR between S239C Mutants

[0144] Parental and S239C mutant antibodies were compared in a FACS titration experiment on control and PRLR-expressing HEK-293 cells. The four antibodies tested were h16f, h16e, h16f (S239C), and h16e (S239). The results are shown in FIG. 10. Briefly, h16f (S239C) mAb had similar binding to PRLR-expressing HEK-293 cells as h16f. Surprisingly, however h16e (S239C) mAb showed a 7-fold decrease in binding affinity compared to its parent, h16e. Thus, comparatively, the S239C mutation did not affect the binding affinity of h16f (S239C), but dramatically affected the binding affinity of h16e (S239C). See Tables 7 and 8 infra for a comparison between sequences between h16f, h16f (S239C), h16e, and h16e (S239C). These results support the surprising and unexpected finding that h16f (S239C) does not have a reduced binding affinity to PRLR relative to parent h16f, unlike h16e.

[0145] Taken with the findings in the previous Examples supra, the ADC construct h16f (S239C)-PBD therefore (1) is stable under a variety of conditions (see Example 5); (2) is considerably more potent than an auristatin-based ADC using essentially the same antibody backbone (see Examples 3-4, both in vitro and in vivo); (3) displays little to no reduced binding affinity to PRLR relative to its parent antibody, unlike similar antibodies bearing an S239C mutation (see Example 6 and FIG. 10); and (4) has a surprisingly low drug to antibody ratio (DAR) of about 2, e.g. 1.89, 1.96 (see Example 3).

ANTIBODY SEQUENCE TABLES:

TABLE-US-00009

[0146] TABLE 7 AMINO ACID SEQUENCES OF ANTI-PRLR ANTIBODIES h16f and h16f (S239C) SEQ ID NO Description Sequence 1 h16f (S239C) EVQLVQSGAEVKKPGSSVKVSCKASGYTFTTYWMHWVRQAPGQGLEWI heavy chain GEIDPSDSYSNYNQKFKDRATLTVDKSTSTAYMELSSLRSEDTAVYYC (HC) ARNGGLGPAWFSYWGQGTLVTVSSASTKGPSVFPLAPSSKSTSGGTAA NOTE: h16f LGCLVKDYFPEPVTVSKNSGALTSGVHTFPAVLQSSGLYSLSSVVTVP has the same SSSLGTQTYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGG HC seqence PCVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVH as h16f NAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIE (S239C) only KTISKAKGQPREPCVYTLPPSREEMTKNQVSLTCLVKGFYPSDIAVEW with a Ser ESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMH at position EALHNHYTQKSLSLSPGK (SEQ ID NO: 1) 239; see SEQ ID NO: 11 2 h16f HC EVQLVQSGAEVKKPGSSVKVSCKASGYTFTTYWMHWVRQAPGQGLEW variable IGEIDPSDSYSNYNQKFKDRATLTVDKSTSTAYMELSSLRSEDTAVY region YCARNGGLGPAWFSYWGQGTLVTVSS (SEQ ID NO: 2) 3 h16f HC GYTFTTYWMH (SEQ ID NO: 3) CDR1 antibody 4 h16f HC EIDPSDSYSNYNQKFKD (SEQ ID NO: 4) CDR2 5 h16f HC NGGLGPAWFSY (SEQ ID NO: 5) CDR3 antibody 6 h16f light DIQMTQSPSSVSASVGDRVTITCKASQYVGTAVAWYQQKPGKSPKLL chain (LC) IYSASNRYTGVPSRFSDSGSGTDFTLTISSLQPEDFATYFCQQYSSY PWTFGGGTKVEIKRTVAAPSVFIFPPSDEQLKSGTASVVCLLNNFYP REAKVQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTLTLSKADYEK HKVYACEVTHQGLSSPVTKSFNRGEC (SEQ ID NO: 6) 7 h16f LC DIQMTQSPSSVSASVGDRVTITCKASQYVGTAVAWYQQKPGKSPKLL variable IYSASNRYTGVPSRFSDSGSGTDFTLTISSLQPEDFATYFCQQYSSY region PWTFGGGTKVEIK (SEQ ID NO: 7) 8 h16f LC KASQYVGTAVA (SEQ ID NO: 8) CDR1 9 h16f LC SASNRYT (SEQ ID NO: 9) CDR2 10 h16f LC QQYSSYPWT (SEQ ID NO: 10) CDR3 11 h16f heavy EVQLVQSGAEVKKPGSSVKVSCKASGYTFTTYWMHWVRQAPGQGLEW chain (HC) IGEIDPSDSYSNYNQKFKDRATLTVDKSTSTAYMELSSLRSEDTAVY YCARNGGLGPAWFSYWGQGTLVTVSSASTKGPSVFPLAPSSKSTSGG TAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSV VTVPSSSLGTQTYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAP ELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYV DGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNK ALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQVSLTCLVKGFY PSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQG NVFSCSVMHEALHNHYTQKSLSLSPGK (SEQ ID NO: 11) NOTE: h16f (S239C) and h16f contain the same amino acid sequences in the light and heavy chain except for the single amino acid change in (S239C) in the constant region of the heavy chain, as described above.

TABLE-US-00010 TABLE 8 AMINO ACID SEEQUENCES OF ANTI-PRLR ANTIBODIES h16e and h16e (S239C) SEQ ID NO Description Sequence 21 h16e (S239C) EVQLVQSGAEVKKPGASVKVSCKASGYTFTDYNIHWVRQAPGQGLEWI heavy chain GYIYPKNDGTGYNQKFKSRATLTVDKSTSTAYMELRSLRSDDTAVYYC (HC) ARGDGNYVGDMDYWGQGTTVTVSSASTKGPSVFPLAPSSKSTSGGTAA NOTE: LGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVP h16e has the SSSLGTQTYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGG same HC PCVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFKWYVDGVEVH sequence as NAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIE h16e (S239C) KTISKAKGQPREPQVYTLPPSREEMTKNQVSLTCLVKGFYPSDIAVEW only with a Ser ESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMH at position 239; EALHNHYTQKSLSLSPGK (SEQ ID NO: 21) see SEQ ID NO: 30 22 h16e HC EVQLVQSGAEVKKPGASVKVSCKASGYTFTDYNIHWVRQAPGQGLEW variable IGYIYPNNDGTGYNQKFKSRATLTVDNSTSTAYMELRSLRSDDTAVY region YCARGDGNYVGDMDYWGQGTTVTVSS (SEQ ID NO: 22) 23 h16e (HC) GYTFTDYNIH (SEQ ID NO: 23) CDR1 antibody 24 h16e (HC) YIYPNNDGTGYNQKFKS (SEQ ID NO: 24) CDR2 25 h16e (HC) GDGNYVGDMDY (SEQ ID NO: 25) CDR3 antibody 26 h16e light DIQMTQSPSSLSASVGDRVTITCRASENIYSYLAWYQQKPGKPPKLL chain (LC) VYNAKTLAEGVPSRFSGSGSGTDFTLTISSLQPEDFATYYCQHHYAT PFTFGQGTKLEIKRTVAAPSVFIFPPSDEQLKSGTASvvCLLNNFYP REAKVQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTLTLSKADYEK HKVYACEVTHQGLSSPVTKSFNRGEC (SEQ ID NO: 26) 27 h16e LC DIQMTQSPSSLSASVGDRVTITCRASENIYSYLAWYQQKPGKPPKLL variable VYNAKTLAEGVPSRFSGSGSGTDFTLTISSLQPEDFATYYCQHHYAT region PFTFGQGTKLEIK (SEQ ID NO: 27) 28 h16e LC RASENIYSYLA (SEQ ID NO: 28) CDR1 29 h16e LC NAKTLAE (SEQ ID NO: 29) CDR2 30 h16e LC QHHYATPFT (SEQ ID NO: 30) CDR3 31 h16e heavy EVQLVQSCAEVKKPGASVKV0CKA5GYTFTDYNIHKVRQAPGQGLEW chain (HC) IGYIYPNNDGTGYNQKFKSRATLTVDNSTSTAYMELRSLRSDDTAVY YCARGDGNYVGDMDYWGQGTTVTVSSASTKGPSVFPLAPSSKSTSGG TAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSV VTVPSSSLGTQTYICNVNKKPSNTKVDKKVEPKSCDKTHTCPPCPAP ELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYV DGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNK ALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQVSLTCLVKGFY PSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQG NVFSCSVMHEALHNHYTQKSLSLSPGK (SEQ ID NO: 31) NOTE: h16e (S239C) and h16e contain the same amino acid sequences in the light and heavy chain except for the single amino acid change in (S239C) in the constant region of the heavy chain, as described above.

[0147] All publications, patents, patent applications and other documents cited in this application are hereby incorporated by reference in their entireties for all purposes to the same extent as if each individual publication, patent, patent application or other document were individually indicated to be incorporated by reference for all purposes.

[0148] While various specific embodiments have been illustrated and described, it will be appreciated that various changes can be made without departing from the spirit and scope of the invention(s).

Sequence CWU 1

1

311450PRTArtificial SequenceSynthetic 1Glu Val Gln Leu Val Gln Ser Gly Ala Glu Val Lys Lys Pro Gly Ser 1 5 10 15 Ser Val Lys Val Ser Cys Lys Ala Ser Gly Tyr Thr Phe Thr Thr Tyr 20 25 30 Trp Met His Trp Val Arg Gln Ala Pro Gly Gln Gly Leu Glu Trp Ile 35 40 45 Gly Glu Ile Asp Pro Ser Asp Ser Tyr Ser Asn Tyr Asn Gln Lys Phe 50 55 60 Lys Asp Arg Ala Thr Leu Thr Val Asp Lys Ser Thr Ser Thr Ala Tyr 65 70 75 80 Met Glu Leu Ser Ser Leu Arg Ser Glu Asp Thr Ala Val Tyr Tyr Cys 85 90 95 Ala Arg Asn Gly Gly Leu Gly Pro Ala Trp Phe Ser Tyr Trp Gly Gln 100 105 110 Gly Thr Leu Val Thr Val Ser Ser Ala Ser Thr Lys Gly Pro Ser Val 115 120 125 Phe Pro Leu Ala Pro Ser Ser Lys Ser Thr Ser Gly Gly Thr Ala Ala 130 135 140 Leu Gly Cys Leu Val Lys Asp Tyr Phe Pro Glu Pro Val Thr Val Ser 145 150 155 160 Trp Asn Ser Gly Ala Leu Thr Ser Gly Val His Thr Phe Pro Ala Val 165 170 175 Leu Gln Ser Ser Gly Leu Tyr Ser Leu Ser Ser Val Val Thr Val Pro 180 185 190 Ser Ser Ser Leu Gly Thr Gln Thr Tyr Ile Cys Asn Val Asn His Lys 195 200 205 Pro Ser Asn Thr Lys Val Asp Lys Lys Val Glu Pro Lys Ser Cys Asp 210 215 220 Lys Thr His Thr Cys Pro Pro Cys Pro Ala Pro Glu Leu Leu Gly Gly 225 230 235 240 Pro Cys Val Phe Leu Phe Pro Pro Lys Pro Lys Asp Thr Leu Met Ile 245 250 255 Ser Arg Thr Pro Glu Val Thr Cys Val Val Val Asp Val Ser His Glu 260 265 270 Asp Pro Glu Val Lys Phe Asn Trp Tyr Val Asp Gly Val Glu Val His 275 280 285 Asn Ala Lys Thr Lys Pro Arg Glu Glu Gln Tyr Asn Ser Thr Tyr Arg 290 295 300 Val Val Ser Val Leu Thr Val Leu His Gln Asp Trp Leu Asn Gly Lys 305 310 315 320 Glu Tyr Lys Cys Lys Val Ser Asn Lys Ala Leu Pro Ala Pro Ile Glu 325 330 335 Lys Thr Ile Ser Lys Ala Lys Gly Gln Pro Arg Glu Pro Gln Val Tyr 340 345 350 Thr Leu Pro Pro Ser Arg Glu Glu Met Thr Lys Asn Gln Val Ser Leu 355 360 365 Thr Cys Leu Val Lys Gly Phe Tyr Pro Ser Asp Ile Ala Val Glu Trp 370 375 380 Glu Ser Asn Gly Gln Pro Glu Asn Asn Tyr Lys Thr Thr Pro Pro Val 385 390 395 400 Leu Asp Ser Asp Gly Ser Phe Phe Leu Tyr Ser Lys Leu Thr Val Asp 405 410 415 Lys Ser Arg Trp Gln Gln Gly Asn Val Phe Ser Cys Ser Val Met His 420 425 430 Glu Ala Leu His Asn His Tyr Thr Gln Lys Ser Leu Ser Leu Ser Pro 435 440 445 Gly Lys 450 2120PRTArtificial SequenceSynthetic 2Glu Val Gln Leu Val Gln Ser Gly Ala Glu Val Lys Lys Pro Gly Ser 1 5 10 15 Ser Val Lys Val Ser Cys Lys Ala Ser Gly Tyr Thr Phe Thr Thr Tyr 20 25 30 Trp Met His Trp Val Arg Gln Ala Pro Gly Gln Gly Leu Glu Trp Ile 35 40 45 Gly Glu Ile Asp Pro Ser Asp Ser Tyr Ser Asn Tyr Asn Gln Lys Phe 50 55 60 Lys Asp Arg Ala Thr Leu Thr Val Asp Lys Ser Thr Ser Thr Ala Tyr 65 70 75 80 Met Glu Leu Ser Ser Leu Arg Ser Glu Asp Thr Ala Val Tyr Tyr Cys 85 90 95 Ala Arg Asn Gly Gly Leu Gly Pro Ala Trp Phe Ser Tyr Trp Gly Gln 100 105 110 Gly Thr Leu Val Thr Val Ser Ser 115 120 310PRTArtificial SequenceSynthetic 3Gly Tyr Thr Phe Thr Thr Tyr Trp Met His 1 5 10 417PRTArtificial SequenceSynthetic 4Glu Ile Asp Pro Ser Asp Ser Tyr Ser Asn Tyr Asn Gln Lys Phe Lys 1 5 10 15 Asp 511PRTArtificial SequenceSynthetic 5Asn Gly Gly Leu Gly Pro Ala Trp Phe Ser Tyr 1 5 10 6214PRTArtificial SequenceSynthetic 6Asp Ile Gln Met Thr Gln Ser Pro Ser Ser Val Ser Ala Ser Val Gly 1 5 10 15 Asp Arg Val Thr Ile Thr Cys Lys Ala Ser Gln Tyr Val Gly Thr Ala 20 25 30 Val Ala Trp Tyr Gln Gln Lys Pro Gly Lys Ser Pro Lys Leu Leu Ile 35 40 45 Tyr Ser Ala Ser Asn Arg Tyr Thr Gly Val Pro Ser Arg Phe Ser Asp 50 55 60 Ser Gly Ser Gly Thr Asp Phe Thr Leu Thr Ile Ser Ser Leu Gln Pro 65 70 75 80 Glu Asp Phe Ala Thr Tyr Phe Cys Gln Gln Tyr Ser Ser Tyr Pro Trp 85 90 95 Thr Phe Gly Gly Gly Thr Lys Val Glu Ile Lys Arg Thr Val Ala Ala 100 105 110 Pro Ser Val Phe Ile Phe Pro Pro Ser Asp Glu Gln Leu Lys Ser Gly 115 120 125 Thr Ala Ser Val Val Cys Leu Leu Asn Asn Phe Tyr Pro Arg Glu Ala 130 135 140 Lys Val Gln Trp Lys Val Asp Asn Ala Leu Gln Ser Gly Asn Ser Gln 145 150 155 160 Glu Ser Val Thr Glu Gln Asp Ser Lys Asp Ser Thr Tyr Ser Leu Ser 165 170 175 Ser Thr Leu Thr Leu Ser Lys Ala Asp Tyr Glu Lys His Lys Val Tyr 180 185 190 Ala Cys Glu Val Thr His Gln Gly Leu Ser Ser Pro Val Thr Lys Ser 195 200 205 Phe Asn Arg Gly Glu Cys 210 7107PRTArtificial SequenceSynthetic 7Asp Ile Gln Met Thr Gln Ser Pro Ser Ser Val Ser Ala Ser Val Gly 1 5 10 15 Asp Arg Val Thr Ile Thr Cys Lys Ala Ser Gln Tyr Val Gly Thr Ala 20 25 30 Val Ala Trp Tyr Gln Gln Lys Pro Gly Lys Ser Pro Lys Leu Leu Ile 35 40 45 Tyr Ser Ala Ser Asn Arg Tyr Thr Gly Val Pro Ser Arg Phe Ser Asp 50 55 60 Ser Gly Ser Gly Thr Asp Phe Thr Leu Thr Ile Ser Ser Leu Gln Pro 65 70 75 80 Glu Asp Phe Ala Thr Tyr Phe Cys Gln Gln Tyr Ser Ser Tyr Pro Trp 85 90 95 Thr Phe Gly Gly Gly Thr Lys Val Glu Ile Lys 100 105 811PRTArtificial SequenceSynthetic 8Lys Ala Ser Gln Tyr Val Gly Thr Ala Val Ala 1 5 10 97PRTArtificial SequenceSynthetic 9Ser Ala Ser Asn Arg Tyr Thr 1 5 109PRTArtificial SequenceSynthetic 10Gln Gln Tyr Ser Ser Tyr Pro Trp Thr 1 5 11450PRTArtificial SequenceSynthetic 11Glu Val Gln Leu Val Gln Ser Gly Ala Glu Val Lys Lys Pro Gly Ser 1 5 10 15 Ser Val Lys Val Ser Cys Lys Ala Ser Gly Tyr Thr Phe Thr Thr Tyr 20 25 30 Trp Met His Trp Val Arg Gln Ala Pro Gly Gln Gly Leu Glu Trp Ile 35 40 45 Gly Glu Ile Asp Pro Ser Asp Ser Tyr Ser Asn Tyr Asn Gln Lys Phe 50 55 60 Lys Asp Arg Ala Thr Leu Thr Val Asp Lys Ser Thr Ser Thr Ala Tyr 65 70 75 80 Met Glu Leu Ser Ser Leu Arg Ser Glu Asp Thr Ala Val Tyr Tyr Cys 85 90 95 Ala Arg Asn Gly Gly Leu Gly Pro Ala Trp Phe Ser Tyr Trp Gly Gln 100 105 110 Gly Thr Leu Val Thr Val Ser Ser Ala Ser Thr Lys Gly Pro Ser Val 115 120 125 Phe Pro Leu Ala Pro Ser Ser Lys Ser Thr Ser Gly Gly Thr Ala Ala 130 135 140 Leu Gly Cys Leu Val Lys Asp Tyr Phe Pro Glu Pro Val Thr Val Ser 145 150 155 160 Trp Asn Ser Gly Ala Leu Thr Ser Gly Val His Thr Phe Pro Ala Val 165 170 175 Leu Gln Ser Ser Gly Leu Tyr Ser Leu Ser Ser Val Val Thr Val Pro 180 185 190 Ser Ser Ser Leu Gly Thr Gln Thr Tyr Ile Cys Asn Val Asn His Lys 195 200 205 Pro Ser Asn Thr Lys Val Asp Lys Lys Val Glu Pro Lys Ser Cys Asp 210 215 220 Lys Thr His Thr Cys Pro Pro Cys Pro Ala Pro Glu Leu Leu Gly Gly 225 230 235 240 Pro Ser Val Phe Leu Phe Pro Pro Lys Pro Lys Asp Thr Leu Met Ile 245 250 255 Ser Arg Thr Pro Glu Val Thr Cys Val Val Val Asp Val Ser His Glu 260 265 270 Asp Pro Glu Val Lys Phe Asn Trp Tyr Val Asp Gly Val Glu Val His 275 280 285 Asn Ala Lys Thr Lys Pro Arg Glu Glu Gln Tyr Asn Ser Thr Tyr Arg 290 295 300 Val Val Ser Val Leu Thr Val Leu His Gln Asp Trp Leu Asn Gly Lys 305 310 315 320 Glu Tyr Lys Cys Lys Val Ser Asn Lys Ala Leu Pro Ala Pro Ile Glu 325 330 335 Lys Thr Ile Ser Lys Ala Lys Gly Gln Pro Arg Glu Pro Gln Val Tyr 340 345 350 Thr Leu Pro Pro Ser Arg Glu Glu Met Thr Lys Asn Gln Val Ser Leu 355 360 365 Thr Cys Leu Val Lys Gly Phe Tyr Pro Ser Asp Ile Ala Val Glu Trp 370 375 380 Glu Ser Asn Gly Gln Pro Glu Asn Asn Tyr Lys Thr Thr Pro Pro Val 385 390 395 400 Leu Asp Ser Asp Gly Ser Phe Phe Leu Tyr Ser Lys Leu Thr Val Asp 405 410 415 Lys Ser Arg Trp Gln Gln Gly Asn Val Phe Ser Cys Ser Val Met His 420 425 430 Glu Ala Leu His Asn His Tyr Thr Gln Lys Ser Leu Ser Leu Ser Pro 435 440 445 Gly Lys 450 12622PRTHomo sapiens 12Met Lys Glu Asn Val Ala Ser Ala Thr Val Phe Thr Leu Leu Leu Phe 1 5 10 15 Leu Asn Thr Cys Leu Leu Asn Gly Gln Leu Pro Pro Gly Lys Pro Glu 20 25 30 Ile Phe Lys Cys Arg Ser Pro Asn Lys Glu Thr Phe Thr Cys Trp Trp 35 40 45 Arg Pro Gly Thr Asp Gly Gly Leu Pro Thr Asn Tyr Ser Leu Thr Tyr 50 55 60 His Arg Glu Gly Glu Thr Leu Met His Glu Cys Pro Asp Tyr Ile Thr 65 70 75 80 Gly Gly Pro Asn Ser Cys His Phe Gly Lys Gln Tyr Thr Ser Met Trp 85 90 95 Arg Thr Tyr Ile Met Met Val Asn Ala Thr Asn Gln Met Gly Ser Ser 100 105 110 Phe Ser Asp Glu Leu Tyr Val Asp Val Thr Tyr Ile Val Gln Pro Asp 115 120 125 Pro Pro Leu Glu Leu Ala Val Glu Val Lys Gln Pro Glu Asp Arg Lys 130 135 140 Pro Tyr Leu Trp Ile Lys Trp Ser Pro Pro Thr Leu Ile Asp Leu Lys 145 150 155 160 Thr Gly Trp Phe Thr Leu Leu Tyr Glu Ile Arg Leu Lys Pro Glu Lys 165 170 175 Ala Ala Glu Trp Glu Ile His Phe Ala Gly Gln Gln Thr Glu Phe Lys 180 185 190 Ile Leu Ser Leu His Pro Gly Gln Lys Tyr Leu Val Gln Val Arg Cys 195 200 205 Lys Pro Asp His Gly Tyr Trp Ser Ala Trp Ser Pro Ala Thr Phe Ile 210 215 220 Gln Ile Pro Ser Asp Phe Thr Met Asn Asp Thr Thr Val Trp Ile Ser 225 230 235 240 Val Ala Val Leu Ser Ala Val Ile Cys Leu Ile Ile Val Trp Ala Val 245 250 255 Ala Leu Lys Gly Tyr Ser Met Val Thr Cys Ile Phe Pro Pro Val Pro 260 265 270 Gly Pro Lys Ile Lys Gly Phe Asp Ala His Leu Leu Glu Lys Gly Lys 275 280 285 Ser Glu Glu Leu Leu Ser Ala Leu Gly Cys Gln Asp Phe Pro Pro Thr 290 295 300 Ser Asp Tyr Glu Asp Leu Leu Val Glu Tyr Leu Glu Val Asp Asp Ser 305 310 315 320 Glu Asp Gln His Leu Met Ser Val His Ser Lys Glu His Pro Ser Gln 325 330 335 Gly Met Lys Pro Thr Tyr Leu Asp Pro Asp Thr Asp Ser Gly Arg Gly 340 345 350 Ser Cys Asp Ser Pro Ser Leu Leu Ser Glu Lys Cys Glu Glu Pro Gln 355 360 365 Ala Asn Pro Ser Thr Phe Tyr Asp Pro Glu Val Ile Glu Lys Pro Glu 370 375 380 Asn Pro Glu Thr Thr His Thr Trp Asp Pro Gln Cys Ile Ser Met Glu 385 390 395 400 Gly Lys Ile Pro Tyr Phe His Ala Gly Gly Ser Lys Cys Ser Thr Trp 405 410 415 Pro Leu Pro Gln Pro Ser Gln His Asn Pro Arg Ser Ser Tyr His Asn 420 425 430 Ile Thr Asp Val Cys Glu Leu Ala Val Gly Pro Ala Gly Ala Pro Ala 435 440 445 Thr Leu Leu Asn Glu Ala Gly Lys Asp Ala Leu Lys Ser Ser Gln Thr 450 455 460 Ile Lys Ser Arg Glu Glu Gly Lys Ala Thr Gln Gln Arg Glu Val Glu 465 470 475 480 Ser Phe His Ser Glu Thr Asp Gln Asp Thr Pro Trp Leu Leu Pro Gln 485 490 495 Glu Lys Thr Pro Phe Gly Ser Ala Lys Pro Leu Asp Tyr Val Glu Ile 500 505 510 His Lys Val Asn Lys Asp Gly Ala Leu Ser Leu Leu Pro Lys Gln Arg 515 520 525 Glu Asn Ser Gly Lys Pro Lys Lys Pro Gly Thr Pro Glu Asn Asn Lys 530 535 540 Glu Tyr Ala Lys Val Ser Gly Val Met Asp Asn Asn Ile Leu Val Leu 545 550 555 560 Val Pro Asp Pro His Ala Lys Asn Val Ala Cys Phe Glu Glu Ser Ala 565 570 575 Lys Glu Ala Pro Pro Ser Leu Glu Gln Asn Gln Ala Glu Lys Ala Leu 580 585 590 Ala Asn Phe Thr Ala Thr Ser Ser Lys Cys Arg Leu Gln Leu Gly Gly 595 600 605 Leu Asp Tyr Leu Asp Pro Ala Cys Phe Thr His Ser Phe His 610 615 620 13209PRTHomo sapiens 13Gln Leu Pro Pro Gly Lys Pro Glu Ile Phe Lys Cys Arg Ser Pro Asn 1 5 10 15 Lys Glu Thr Phe Thr Cys Trp Trp Arg Pro Gly Thr Asp Gly Gly Leu 20 25 30 Pro Thr Asn Tyr Ser Leu Thr Tyr His Arg Glu Gly Glu Thr Leu Met 35 40 45 His Glu Cys Pro Asp Tyr Ile Thr Gly Gly Pro Asn Ser Cys His Phe 50 55 60 Gly Lys Gln Tyr Thr Ser Met Trp Arg Thr Tyr Ile Met Met Val Asn 65 70 75 80 Ala Thr Asn Gln Met Gly Ser Ser Phe Ser Asp Glu Leu Tyr Val Asp 85 90 95 Val Thr Tyr Ile Val Gln Pro Asp Pro Pro Leu Glu Leu Ala Val Glu 100 105 110 Val Lys Gln Pro Glu Asp Arg Lys Pro Tyr Leu Trp Ile Lys Trp Ser 115 120 125 Pro Pro Thr Leu Ile Asp Leu Lys Thr Gly Trp Phe Thr Leu Leu Tyr 130 135 140 Glu Ile Arg Leu Lys Pro Glu Lys Ala Ala Glu Trp Glu Ile His Phe 145 150 155 160 Ala Gly Gln Gln Thr Glu Phe Lys Ile Leu Ser Leu His Pro Gly Gln 165 170 175 Lys Tyr Leu Val Gln Val Arg Cys Lys Pro Asp His Gly Tyr Trp Ser 180 185 190 Ala Trp Ser Pro Ala Thr Phe Ile Gln Ile Pro Ser Asp Phe Thr Met 195 200 205 Asn 14521PRTHomo sapiens 14Met Lys Glu Asn Val Ala Ser Ala Thr Val Phe Thr

Leu Leu Leu Phe 1 5 10 15 Leu Asn Thr Cys Leu Leu Asn Val Gln Pro Asp Pro Pro Leu Glu Leu 20 25 30 Ala Val Glu Val Lys Gln Pro Glu Asp Arg Lys Pro Tyr Leu Trp Ile 35 40 45 Lys Trp Ser Pro Pro Thr Leu Ile Asp Leu Lys Thr Gly Trp Phe Thr 50 55 60 Leu Leu Tyr Glu Ile Arg Leu Lys Pro Glu Lys Ala Ala Glu Trp Glu 65 70 75 80 Ile His Phe Ala Gly Gln Gln Thr Glu Phe Lys Ile Leu Ser Leu His 85 90 95 Pro Gly Gln Lys Tyr Leu Val Gln Val Arg Cys Lys Pro Asp His Gly 100 105 110 Tyr Trp Ser Ala Trp Ser Pro Ala Thr Phe Ile Gln Ile Pro Ser Asp 115 120 125 Phe Thr Met Asn Asp Thr Thr Val Trp Ile Ser Val Ala Val Leu Ser 130 135 140 Ala Val Ile Cys Leu Ile Ile Val Trp Ala Val Ala Leu Lys Gly Tyr 145 150 155 160 Ser Met Val Thr Cys Ile Phe Pro Pro Val Pro Gly Pro Lys Ile Lys 165 170 175 Gly Phe Asp Ala His Leu Leu Glu Lys Gly Lys Ser Glu Glu Leu Leu 180 185 190 Ser Ala Leu Gly Cys Gln Asp Phe Pro Pro Thr Ser Asp Tyr Glu Asp 195 200 205 Leu Leu Val Glu Tyr Leu Glu Val Asp Asp Ser Glu Asp Gln His Leu 210 215 220 Met Ser Val His Ser Lys Glu His Pro Ser Gln Gly Met Lys Pro Thr 225 230 235 240 Tyr Leu Asp Pro Asp Thr Asp Ser Gly Arg Gly Ser Cys Asp Ser Pro 245 250 255 Ser Leu Leu Ser Glu Lys Cys Glu Glu Pro Gln Ala Asn Pro Ser Thr 260 265 270 Phe Tyr Asp Pro Glu Val Ile Glu Lys Pro Glu Asn Pro Glu Thr Thr 275 280 285 His Thr Trp Asp Pro Gln Cys Ile Ser Met Glu Gly Lys Ile Pro Tyr 290 295 300 Phe His Ala Gly Gly Ser Lys Cys Ser Thr Trp Pro Leu Pro Gln Pro 305 310 315 320 Ser Gln His Asn Pro Arg Ser Ser Tyr His Asn Ile Thr Asp Val Cys 325 330 335 Glu Leu Ala Val Gly Pro Ala Gly Ala Pro Ala Thr Leu Leu Asn Glu 340 345 350 Ala Gly Lys Asp Ala Leu Lys Ser Ser Gln Thr Ile Lys Ser Arg Glu 355 360 365 Glu Gly Lys Ala Thr Gln Gln Arg Glu Val Glu Ser Phe His Ser Glu 370 375 380 Thr Asp Gln Asp Thr Pro Trp Leu Leu Pro Gln Glu Lys Thr Pro Phe 385 390 395 400 Gly Ser Ala Lys Pro Leu Asp Tyr Val Glu Ile His Lys Val Asn Lys 405 410 415 Asp Gly Ala Leu Ser Leu Leu Pro Lys Gln Arg Glu Asn Ser Gly Lys 420 425 430 Pro Lys Lys Pro Gly Thr Pro Glu Asn Asn Lys Glu Tyr Ala Lys Val 435 440 445 Ser Gly Val Met Asp Asn Asn Ile Leu Val Leu Val Pro Asp Pro His 450 455 460 Ala Lys Asn Val Ala Cys Phe Glu Glu Ser Ala Lys Glu Ala Pro Pro 465 470 475 480 Ser Leu Glu Gln Asn Gln Ala Glu Lys Ala Leu Ala Asn Phe Thr Ala 485 490 495 Thr Ser Ser Lys Cys Arg Leu Gln Leu Gly Gly Leu Asp Tyr Leu Asp 500 505 510 Pro Ala Cys Phe Thr His Ser Phe His 515 520 15230PRTHomo sapiens 15Met Lys Glu Asn Val Ala Ser Ala Thr Val Phe Thr Leu Leu Leu Phe 1 5 10 15 Leu Asn Thr Cys Leu Leu Asn Gly Gln Leu Pro Pro Gly Lys Pro Glu 20 25 30 Ile Phe Lys Cys Arg Ser Pro Asn Lys Glu Thr Phe Thr Cys Trp Trp 35 40 45 Arg Pro Gly Thr Asp Gly Gly Leu Pro Thr Asn Tyr Ser Leu Thr Tyr 50 55 60 His Arg Glu Gly Glu Thr Leu Met His Glu Cys Pro Asp Tyr Ile Thr 65 70 75 80 Gly Gly Pro Asn Ser Cys His Phe Gly Lys Gln Tyr Thr Ser Met Trp 85 90 95 Arg Thr Tyr Ile Met Met Val Asn Ala Thr Asn Gln Met Gly Ser Ser 100 105 110 Phe Ser Asp Glu Leu Tyr Val Asp Val Thr Tyr Ile Val Gln Pro Asp 115 120 125 Pro Pro Leu Glu Leu Ala Val Glu Val Lys Gln Pro Glu Asp Arg Lys 130 135 140 Pro Tyr Leu Trp Ile Lys Trp Ser Pro Pro Thr Leu Ile Asp Leu Lys 145 150 155 160 Thr Gly Trp Phe Thr Leu Leu Tyr Glu Ile Arg Leu Lys Pro Glu Lys 165 170 175 Ala Ala Glu Trp Glu Ile His Phe Ala Gly Gln Gln Thr Glu Phe Lys 180 185 190 Ile Leu Ser Leu His Pro Gly Gln Lys Tyr Leu Val Gln Val Arg Cys 195 200 205 Lys Pro Asp His Gly Tyr Trp Ser Ala Trp Ser Pro Ala Thr Phe Ile 210 215 220 Gln Ile Pro Ser Ala Trp 225 230 16376PRTHomo sapiens 16Met Lys Glu Asn Val Ala Ser Ala Thr Val Phe Thr Leu Leu Leu Phe 1 5 10 15 Leu Asn Thr Cys Leu Leu Asn Gly Gln Leu Pro Pro Gly Lys Pro Glu 20 25 30 Ile Phe Lys Cys Arg Ser Pro Asn Lys Glu Thr Phe Thr Cys Trp Trp 35 40 45 Arg Pro Gly Thr Asp Gly Gly Leu Pro Thr Asn Tyr Ser Leu Thr Tyr 50 55 60 His Arg Glu Gly Glu Thr Leu Met His Glu Cys Pro Asp Tyr Ile Thr 65 70 75 80 Gly Gly Pro Asn Ser Cys His Phe Gly Lys Gln Tyr Thr Ser Met Trp 85 90 95 Arg Thr Tyr Ile Met Met Val Asn Ala Thr Asn Gln Met Gly Ser Ser 100 105 110 Phe Ser Asp Glu Leu Tyr Val Asp Val Thr Tyr Ile Val Gln Pro Asp 115 120 125 Pro Pro Leu Glu Leu Ala Val Glu Val Lys Gln Pro Glu Asp Arg Lys 130 135 140 Pro Tyr Leu Trp Ile Lys Trp Ser Pro Pro Thr Leu Ile Asp Leu Lys 145 150 155 160 Thr Gly Trp Phe Thr Leu Leu Tyr Glu Ile Arg Leu Lys Pro Glu Lys 165 170 175 Ala Ala Glu Trp Glu Ile His Phe Ala Gly Gln Gln Thr Glu Phe Lys 180 185 190 Ile Leu Ser Leu His Pro Gly Gln Lys Tyr Leu Val Gln Val Arg Cys 195 200 205 Lys Pro Asp His Gly Tyr Trp Ser Ala Trp Ser Pro Ala Thr Phe Ile 210 215 220 Gln Ile Pro Ser Asp Phe Thr Met Asn Asp Thr Thr Val Trp Ile Ser 225 230 235 240 Val Ala Val Leu Ser Ala Val Ile Cys Leu Ile Ile Val Trp Ala Val 245 250 255 Ala Leu Lys Gly Tyr Ser Met Val Thr Cys Ile Phe Pro Pro Val Pro 260 265 270 Gly Pro Lys Ile Lys Gly Phe Asp Ala His Leu Leu Glu Lys Gly Lys 275 280 285 Ser Glu Glu Leu Leu Ser Ala Leu Gly Cys Gln Asp Phe Pro Pro Thr 290 295 300 Ser Asp Tyr Glu Asp Leu Leu Val Glu Tyr Leu Glu Val Asp Asp Ser 305 310 315 320 Glu Asp Gln His Leu Met Ser Val His Ser Lys Glu His Pro Ser Gln 325 330 335 Gly Asp Pro Leu Met Leu Gly Ala Ser His Tyr Lys Asn Leu Lys Ser 340 345 350 Tyr Arg Pro Arg Lys Ile Ser Ser Gln Gly Arg Leu Ala Val Phe Thr 355 360 365 Lys Ala Thr Leu Thr Thr Val Gln 370 375 17349PRTHomo sapiens 17Met Lys Glu Asn Val Ala Ser Ala Thr Val Phe Thr Leu Leu Leu Phe 1 5 10 15 Leu Asn Thr Cys Leu Leu Asn Gly Gln Leu Pro Pro Gly Lys Pro Glu 20 25 30 Ile Phe Lys Cys Arg Ser Pro Asn Lys Glu Thr Phe Thr Cys Trp Trp 35 40 45 Arg Pro Gly Thr Asp Gly Gly Leu Pro Thr Asn Tyr Ser Leu Thr Tyr 50 55 60 His Arg Glu Gly Glu Thr Leu Met His Glu Cys Pro Asp Tyr Ile Thr 65 70 75 80 Gly Gly Pro Asn Ser Cys His Phe Gly Lys Gln Tyr Thr Ser Met Trp 85 90 95 Arg Thr Tyr Ile Met Met Val Asn Ala Thr Asn Gln Met Gly Ser Ser 100 105 110 Phe Ser Asp Glu Leu Tyr Val Asp Val Thr Tyr Ile Val Gln Pro Asp 115 120 125 Pro Pro Leu Glu Leu Ala Val Glu Val Lys Gln Pro Glu Asp Arg Lys 130 135 140 Pro Tyr Leu Trp Ile Lys Trp Ser Pro Pro Thr Leu Ile Asp Leu Lys 145 150 155 160 Thr Gly Trp Phe Thr Leu Leu Tyr Glu Ile Arg Leu Lys Pro Glu Lys 165 170 175 Ala Ala Glu Trp Glu Ile His Phe Ala Gly Gln Gln Thr Glu Phe Lys 180 185 190 Ile Leu Ser Leu His Pro Gly Gln Lys Tyr Leu Val Gln Val Arg Cys 195 200 205 Lys Pro Asp His Gly Tyr Trp Ser Ala Trp Ser Pro Ala Thr Phe Ile 210 215 220 Gln Ile Pro Ser Asp Phe Thr Met Asn Asp Thr Thr Val Trp Ile Ser 225 230 235 240 Val Ala Val Leu Ser Ala Val Ile Cys Leu Ile Ile Val Trp Ala Val 245 250 255 Ala Leu Lys Gly Tyr Ser Met Val Thr Cys Ile Phe Pro Pro Val Pro 260 265 270 Gly Pro Lys Ile Lys Gly Phe Asp Ala His Leu Leu Glu Lys Gly Lys 275 280 285 Ser Glu Glu Leu Leu Ser Ala Leu Gly Cys Gln Asp Phe Pro Pro Thr 290 295 300 Ser Asp Tyr Glu Asp Leu Leu Val Glu Tyr Leu Glu Val Asp Asp Ser 305 310 315 320 Glu Asp Gln His Leu Met Ser Val His Ser Lys Glu His Pro Ser Gln 325 330 335 Glu Arg Glu Gln Arg Gln Ala Gln Glu Ala Arg Asp Ser 340 345 18288PRTHomo sapiens 18Met Lys Glu Asn Val Ala Ser Ala Thr Val Phe Thr Leu Leu Leu Phe 1 5 10 15 Leu Asn Thr Cys Leu Leu Asn Gly Gln Leu Pro Pro Gly Lys Pro Glu 20 25 30 Ile Phe Lys Cys Arg Ser Pro Asn Lys Glu Thr Phe Thr Cys Trp Trp 35 40 45 Arg Pro Gly Thr Asp Gly Gly Leu Pro Thr Asn Tyr Ser Leu Thr Tyr 50 55 60 His Arg Glu Gly Glu Thr Leu Met His Glu Cys Pro Asp Tyr Ile Thr 65 70 75 80 Gly Gly Pro Asn Ser Cys His Phe Gly Lys Gln Tyr Thr Ser Met Trp 85 90 95 Arg Thr Tyr Ile Met Met Val Asn Ala Thr Asn Gln Met Gly Ser Ser 100 105 110 Phe Ser Asp Glu Leu Tyr Val Asp Val Thr Tyr Ile Val Gln Pro Asp 115 120 125 Pro Pro Leu Glu Leu Ala Val Glu Val Lys Gln Pro Glu Asp Arg Lys 130 135 140 Pro Tyr Leu Trp Ile Lys Trp Ser Pro Pro Thr Leu Ile Asp Leu Lys 145 150 155 160 Thr Gly Trp Phe Thr Leu Leu Tyr Glu Ile Arg Leu Lys Pro Glu Lys 165 170 175 Ala Ala Glu Trp Glu Ile His Phe Ala Gly Gln Gln Thr Glu Phe Lys 180 185 190 Ile Leu Ser Leu His Pro Gly Gln Lys Tyr Leu Val Gln Val Arg Cys 195 200 205 Lys Pro Asp His Gly Tyr Trp Ser Ala Trp Ser Pro Ala Thr Phe Ile 210 215 220 Gln Ile Pro Ser Asp Phe Thr Met Asn Asp Thr Thr Val Trp Ile Ser 225 230 235 240 Val Ala Val Leu Ser Ala Val Ile Cys Leu Ile Ile Val Trp Ala Val 245 250 255 Ala Leu Lys Gly Tyr Ser Met Val Thr Cys Ile Phe Pro Pro Val Pro 260 265 270 Gly Pro Lys Ile Lys Gly Phe Asp Ala His Leu Leu Glu Val Thr Pro 275 280 285 19268PRTHomo sapiens 19Met Lys Glu Asn Val Ala Ser Ala Thr Val Phe Thr Leu Leu Leu Phe 1 5 10 15 Leu Asn Thr Cys Leu Leu Asn Gly Gln Leu Pro Pro Gly Lys Pro Glu 20 25 30 Ile Phe Lys Cys Arg Ser Pro Asn Lys Glu Thr Phe Thr Cys Trp Trp 35 40 45 Arg Pro Gly Thr Asp Gly Gly Leu Pro Thr Asn Tyr Ser Leu Thr Tyr 50 55 60 His Arg Glu Gly Glu Thr Leu Met His Glu Cys Pro Asp Tyr Ile Thr 65 70 75 80 Gly Gly Pro Asn Ser Cys His Phe Gly Lys Gln Tyr Thr Ser Met Trp 85 90 95 Arg Thr Tyr Ile Met Met Val Asn Ala Thr Asn Gln Met Gly Ser Ser 100 105 110 Phe Ser Asp Glu Leu Tyr Val Asp Val Thr Tyr Ile Val Gln Pro Asp 115 120 125 Pro Pro Leu Glu Leu Ala Val Glu Val Lys Gln Pro Glu Asp Arg Lys 130 135 140 Pro Tyr Leu Trp Ile Lys Trp Ser Pro Pro Thr Leu Ile Asp Leu Lys 145 150 155 160 Thr Gly Trp Phe Thr Leu Leu Tyr Glu Ile Arg Leu Lys Pro Glu Lys 165 170 175 Ala Ala Glu Trp Glu Ile His Phe Ala Gly Gln Gln Thr Glu Phe Lys 180 185 190 Ile Leu Ser Leu His Pro Gly Gln Lys Tyr Leu Val Gln Val Arg Cys 195 200 205 Lys Pro Asp His Gly Tyr Trp Ser Ala Trp Ser Pro Ala Thr Phe Ile 210 215 220 Gln Ile Pro Ser Gly Asp Pro Leu Met Leu Gly Ala Ser His Tyr Lys 225 230 235 240 Asn Leu Lys Ser Tyr Arg Pro Arg Lys Ile Ser Ser Gln Gly Arg Leu 245 250 255 Ala Val Phe Thr Lys Ala Thr Leu Thr Thr Val Gln 260 265 20217PRTHomo sapiens 20Met His Glu Cys Pro Asp Tyr Ile Thr Gly Gly Pro Asn Ser Cys His 1 5 10 15 Phe Gly Lys Gln Tyr Thr Ser Met Trp Arg Thr Tyr Ile Met Met Val 20 25 30 Asn Ala Thr Asn Gln Met Gly Ser Ser Phe Ser Asp Glu Leu Tyr Val 35 40 45 Asp Val Thr Tyr Ile Val Gln Pro Asp Pro Pro Leu Glu Leu Ala Val 50 55 60 Glu Val Lys Gln Pro Glu Asp Arg Lys Pro Tyr Leu Trp Ile Lys Trp 65 70 75 80 Ser Pro Pro Thr Leu Ile Asp Leu Lys Thr Gly Trp Phe Thr Leu Leu 85 90 95 Tyr Glu Ile Arg Leu Lys Pro Glu Lys Ala Ala Glu Trp Glu Ile His 100 105 110 Phe Ala Gly Gln Gln Thr Glu Phe Lys Ile Leu Ser Leu His Pro Gly 115 120 125 Gln Lys Tyr Leu Val Gln Val Arg Cys Lys Pro Asp His Gly Tyr Trp 130 135 140 Ser Ala Trp Ser Pro Ala Thr Phe Ile Gln Ile Pro Ser Asp Phe Thr 145 150 155 160 Met Asn Asp Thr Thr Val Trp Ile Ser Val Ala Val Leu Ser Ala Val 165 170 175 Ile Cys Leu Ile Ile Val Trp Ala Val Ala Leu Lys Gly Tyr Ser Met 180 185 190 Val Thr Cys Ile Phe Pro Pro Val Pro Gly Pro Lys Ile Lys Gly Phe 195 200 205 Asp Ala His Leu Leu Glu Val Thr Pro 210 215 21450PRTartificialSynthetic 21Glu Val Gln Leu Val Gln Ser Gly Ala Glu Val Lys Lys Pro Gly Ala 1 5 10 15 Ser Val Lys Val Ser Cys Lys Ala Ser Gly Tyr Thr Phe Thr Asp Tyr 20 25 30 Asn Ile His Trp Val Arg Gln Ala Pro Gly Gln Gly Leu Glu Trp Ile 35

40 45 Gly Tyr Ile Tyr Pro Asn Asn Asp Gly Thr Gly Tyr Asn Gln Lys Phe 50 55 60 Lys Ser Arg Ala Thr Leu Thr Val Asp Asn Ser Thr Ser Thr Ala Tyr 65 70 75 80 Met Glu Leu Arg Ser Leu Arg Ser Asp Asp Thr Ala Val Tyr Tyr Cys 85 90 95 Ala Arg Gly Asp Gly Asn Tyr Val Gly Asp Met Asp Tyr Trp Gly Gln 100 105 110 Gly Thr Thr Val Thr Val Ser Ser Ala Ser Thr Lys Gly Pro Ser Val 115 120 125 Phe Pro Leu Ala Pro Ser Ser Lys Ser Thr Ser Gly Gly Thr Ala Ala 130 135 140 Leu Gly Cys Leu Val Lys Asp Tyr Phe Pro Glu Pro Val Thr Val Ser 145 150 155 160 Trp Asn Ser Gly Ala Leu Thr Ser Gly Val His Thr Phe Pro Ala Val 165 170 175 Leu Gln Ser Ser Gly Leu Tyr Ser Leu Ser Ser Val Val Thr Val Pro 180 185 190 Ser Ser Ser Leu Gly Thr Gln Thr Tyr Ile Cys Asn Val Asn His Lys 195 200 205 Pro Ser Asn Thr Lys Val Asp Lys Lys Val Glu Pro Lys Ser Cys Asp 210 215 220 Lys Thr His Thr Cys Pro Pro Cys Pro Ala Pro Glu Leu Leu Gly Gly 225 230 235 240 Pro Cys Val Phe Leu Phe Pro Pro Lys Pro Lys Asp Thr Leu Met Ile 245 250 255 Ser Arg Thr Pro Glu Val Thr Cys Val Val Val Asp Val Ser His Glu 260 265 270 Asp Pro Glu Val Lys Phe Asn Trp Tyr Val Asp Gly Val Glu Val His 275 280 285 Asn Ala Lys Thr Lys Pro Arg Glu Glu Gln Tyr Asn Ser Thr Tyr Arg 290 295 300 Val Val Ser Val Leu Thr Val Leu His Gln Asp Trp Leu Asn Gly Lys 305 310 315 320 Glu Tyr Lys Cys Lys Val Ser Asn Lys Ala Leu Pro Ala Pro Ile Glu 325 330 335 Lys Thr Ile Ser Lys Ala Lys Gly Gln Pro Arg Glu Pro Gln Val Tyr 340 345 350 Thr Leu Pro Pro Ser Arg Glu Glu Met Thr Lys Asn Gln Val Ser Leu 355 360 365 Thr Cys Leu Val Lys Gly Phe Tyr Pro Ser Asp Ile Ala Val Glu Trp 370 375 380 Glu Ser Asn Gly Gln Pro Glu Asn Asn Tyr Lys Thr Thr Pro Pro Val 385 390 395 400 Leu Asp Ser Asp Gly Ser Phe Phe Leu Tyr Ser Lys Leu Thr Val Asp 405 410 415 Lys Ser Arg Trp Gln Gln Gly Asn Val Phe Ser Cys Ser Val Met His 420 425 430 Glu Ala Leu His Asn His Tyr Thr Gln Lys Ser Leu Ser Leu Ser Pro 435 440 445 Gly Lys 450 22120PRTArtificial SequenceSynthetic 22Glu Val Gln Leu Val Gln Ser Gly Ala Glu Val Lys Lys Pro Gly Ala 1 5 10 15 Ser Val Lys Val Ser Cys Lys Ala Ser Gly Tyr Thr Phe Thr Asp Tyr 20 25 30 Asn Ile His Trp Val Arg Gln Ala Pro Gly Gln Gly Leu Glu Trp Ile 35 40 45 Gly Tyr Ile Tyr Pro Asn Asn Asp Gly Thr Gly Tyr Asn Gln Lys Phe 50 55 60 Lys Ser Arg Ala Thr Leu Thr Val Asp Asn Ser Thr Ser Thr Ala Tyr 65 70 75 80 Met Glu Leu Arg Ser Leu Arg Ser Asp Asp Thr Ala Val Tyr Tyr Cys 85 90 95 Ala Arg Gly Asp Gly Asn Tyr Val Gly Asp Met Asp Tyr Trp Gly Gln 100 105 110 Gly Thr Thr Val Thr Val Ser Ser 115 120 2310PRTArtificial SequenceSynthetic 23Gly Tyr Thr Phe Thr Asp Tyr Asn Ile His 1 5 10 2417PRTArtificial SequenceSynthetic 24Tyr Ile Tyr Pro Asn Asn Asp Gly Thr Gly Tyr Asn Gln Lys Phe Lys 1 5 10 15 Ser 2511PRTArtificial SequenceSynthetic 25Gly Asp Gly Asn Tyr Val Gly Asp Met Asp Tyr 1 5 10 26214PRTArtificial SequenceSynthetic 26Asp Ile Gln Met Thr Gln Ser Pro Ser Ser Leu Ser Ala Ser Val Gly 1 5 10 15 Asp Arg Val Thr Ile Thr Cys Arg Ala Ser Glu Asn Ile Tyr Ser Tyr 20 25 30 Leu Ala Trp Tyr Gln Gln Lys Pro Gly Lys Pro Pro Lys Leu Leu Val 35 40 45 Tyr Asn Ala Lys Thr Leu Ala Glu Gly Val Pro Ser Arg Phe Ser Gly 50 55 60 Ser Gly Ser Gly Thr Asp Phe Thr Leu Thr Ile Ser Ser Leu Gln Pro 65 70 75 80 Glu Asp Phe Ala Thr Tyr Tyr Cys Gln His His Tyr Ala Thr Pro Phe 85 90 95 Thr Phe Gly Gln Gly Thr Lys Leu Glu Ile Lys Arg Thr Val Ala Ala 100 105 110 Pro Ser Val Phe Ile Phe Pro Pro Ser Asp Glu Gln Leu Lys Ser Gly 115 120 125 Thr Ala Ser Val Val Cys Leu Leu Asn Asn Phe Tyr Pro Arg Glu Ala 130 135 140 Lys Val Gln Trp Lys Val Asp Asn Ala Leu Gln Ser Gly Asn Ser Gln 145 150 155 160 Glu Ser Val Thr Glu Gln Asp Ser Lys Asp Ser Thr Tyr Ser Leu Ser 165 170 175 Ser Thr Leu Thr Leu Ser Lys Ala Asp Tyr Glu Lys His Lys Val Tyr 180 185 190 Ala Cys Glu Val Thr His Gln Gly Leu Ser Ser Pro Val Thr Lys Ser 195 200 205 Phe Asn Arg Gly Glu Cys 210 27107PRTArtificial SequenceSynthetic 27Asp Ile Gln Met Thr Gln Ser Pro Ser Ser Leu Ser Ala Ser Val Gly 1 5 10 15 Asp Arg Val Thr Ile Thr Cys Arg Ala Ser Glu Asn Ile Tyr Ser Tyr 20 25 30 Leu Ala Trp Tyr Gln Gln Lys Pro Gly Lys Pro Pro Lys Leu Leu Val 35 40 45 Tyr Asn Ala Lys Thr Leu Ala Glu Gly Val Pro Ser Arg Phe Ser Gly 50 55 60 Ser Gly Ser Gly Thr Asp Phe Thr Leu Thr Ile Ser Ser Leu Gln Pro 65 70 75 80 Glu Asp Phe Ala Thr Tyr Tyr Cys Gln His His Tyr Ala Thr Pro Phe 85 90 95 Thr Phe Gly Gln Gly Thr Lys Leu Glu Ile Lys 100 105 2811PRTArtificial SequenceSynthetic 28Arg Ala Ser Glu Asn Ile Tyr Ser Tyr Leu Ala 1 5 10 297PRTArtificial SequenceSynthetic 29Asn Ala Lys Thr Leu Ala Glu 1 5 309PRTArtificial SequenceSynthetic 30Gln His His Tyr Ala Thr Pro Phe Thr 1 5 31450PRTArtificial SequenceSynthetic 31Glu Val Gln Leu Val Gln Ser Gly Ala Glu Val Lys Lys Pro Gly Ala 1 5 10 15 Ser Val Lys Val Ser Cys Lys Ala Ser Gly Tyr Thr Phe Thr Asp Tyr 20 25 30 Asn Ile His Trp Val Arg Gln Ala Pro Gly Gln Gly Leu Glu Trp Ile 35 40 45 Gly Tyr Ile Tyr Pro Asn Asn Asp Gly Thr Gly Tyr Asn Gln Lys Phe 50 55 60 Lys Ser Arg Ala Thr Leu Thr Val Asp Asn Ser Thr Ser Thr Ala Tyr 65 70 75 80 Met Glu Leu Arg Ser Leu Arg Ser Asp Asp Thr Ala Val Tyr Tyr Cys 85 90 95 Ala Arg Gly Asp Gly Asn Tyr Val Gly Asp Met Asp Tyr Trp Gly Gln 100 105 110 Gly Thr Thr Val Thr Val Ser Ser Ala Ser Thr Lys Gly Pro Ser Val 115 120 125 Phe Pro Leu Ala Pro Ser Ser Lys Ser Thr Ser Gly Gly Thr Ala Ala 130 135 140 Leu Gly Cys Leu Val Lys Asp Tyr Phe Pro Glu Pro Val Thr Val Ser 145 150 155 160 Trp Asn Ser Gly Ala Leu Thr Ser Gly Val His Thr Phe Pro Ala Val 165 170 175 Leu Gln Ser Ser Gly Leu Tyr Ser Leu Ser Ser Val Val Thr Val Pro 180 185 190 Ser Ser Ser Leu Gly Thr Gln Thr Tyr Ile Cys Asn Val Asn His Lys 195 200 205 Pro Ser Asn Thr Lys Val Asp Lys Lys Val Glu Pro Lys Ser Cys Asp 210 215 220 Lys Thr His Thr Cys Pro Pro Cys Pro Ala Pro Glu Leu Leu Gly Gly 225 230 235 240 Pro Ser Val Phe Leu Phe Pro Pro Lys Pro Lys Asp Thr Leu Met Ile 245 250 255 Ser Arg Thr Pro Glu Val Thr Cys Val Val Val Asp Val Ser His Glu 260 265 270 Asp Pro Glu Val Lys Phe Asn Trp Tyr Val Asp Gly Val Glu Val His 275 280 285 Asn Ala Lys Thr Lys Pro Arg Glu Glu Gln Tyr Asn Ser Thr Tyr Arg 290 295 300 Val Val Ser Val Leu Thr Val Leu His Gln Asp Trp Leu Asn Gly Lys 305 310 315 320 Glu Tyr Lys Cys Lys Val Ser Asn Lys Ala Leu Pro Ala Pro Ile Glu 325 330 335 Lys Thr Ile Ser Lys Ala Lys Gly Gln Pro Arg Glu Pro Gln Val Tyr 340 345 350 Thr Leu Pro Pro Ser Arg Glu Glu Met Thr Lys Asn Gln Val Ser Leu 355 360 365 Thr Cys Leu Val Lys Gly Phe Tyr Pro Ser Asp Ile Ala Val Glu Trp 370 375 380 Glu Ser Asn Gly Gln Pro Glu Asn Asn Tyr Lys Thr Thr Pro Pro Val 385 390 395 400 Leu Asp Ser Asp Gly Ser Phe Phe Leu Tyr Ser Lys Leu Thr Val Asp 405 410 415 Lys Ser Arg Trp Gln Gln Gly Asn Val Phe Ser Cys Ser Val Met His 420 425 430 Glu Ala Leu His Asn His Tyr Thr Gln Lys Ser Leu Ser Leu Ser Pro 435 440 445 Gly Lys 450

Claims

1-11. (canceled)

12. An antibody-drug conjugate (ADC) comprising the structure of Formula (IX), or a salt thereof ##STR00016## wherein Formula (IX) comprises a monoclonal anti-PRLR antibody (Ab) conjugated to at least one cytotoxic warhead, wherein D comprises a pyrrolobenzodiazepine (PBD) dimer; Y is Val, Z is Ala, and q is 1, 2, 3, 4, 5, 6, 7, or 8, and wherein said monoclonal anti-PRLR antibody comprises: i. a heavy chain variable region comprising a CDRH1 sequence comprising SEQ ID NO: 3, a CDRH2 sequence comprising SEQ ID NO: 4, and a CDRH3 sequence comprising SEQ ID NO: 5; ii. a light chain variable region comprising a CDRL1 sequence comprising SEQ ID NO: 8, a CDRL2 sequence comprising SEQ ID NO: 9, and a CDRL3 sequence comprising SEQ ID NO: 10; and iii. a mutation comprising S239C in a heavy chain constant region, wherein the numbering is in accordance with Kabat, and wherein said monoclonal anti-PRLR antibody is conjugated to said at least one cytotoxic warhead through said S239C mutation in said heavy chain constant region.

13. The ADC of claim 12, wherein q is 5.

14-15. (canceled)

16. The ADC of claim 12, wherein said monoclonal anti-PRLR antibody comprises an IgG1 isotype.

17. The ADC of claim 12, wherein said heavy chain constant region of said monoclonal anti-PRLR antibody either lacks a C-terminal lysine or comprises an amino acid other than lysine at a C-terminus of the heavy chain constant region.

18. The ADC of claim 12, wherein said monoclonal anti-PRLR antibody is a humanized antibody.

19. The ADC of claim 12, wherein said ADC has a drug load of two cytotoxic warheads per anti-PRLR antibody.

20. The ADC of claim 13, wherein said monoclonal antibody comprises an IgG1 isotype.

21. The ADC of claim 13, wherein said heavy chain constant region of said monoclonal anti-PRLR antibody either lacks a C-terminal lysine or comprises an amino acid other than lysine at a C-terminus of the heavy chain constant region.

22. The ADC of claim 13, wherein said monoclonal anti-PRLR antibody is a humanized antibody.

23. The ADC of claim 13, wherein said ADC has a drug load of two cytotoxic warheads per anti-PRLR antibody.

24. An antibody-drug conjugate (ADC) comprising the structure of Formula (IX), or a salt thereof, ##STR00017## wherein Formula (IX) comprises a monoclonal anti-PRLR antibody (Ab) conjugated to at least one cytotoxic warhead, wherein D comprises a pyrrolobenzodiazepine (PBD) dimer; Y is Val, Z is Ala, and q is 1, 2, 3, 4, 5, 6, 7, or 8, and wherein said monoclonal anti-PRLR antibody comprises: i. a heavy chain variable region comprising SEQ ID NO: 2; ii. a light chain variable region comprising SEQ ID NO: 7; and iii. a mutation comprising S239C in a heavy chain constant region, wherein the numbering is in accordance with Kabat, and wherein said monoclonal anti-PRLR antibody is conjugated to said at least one cytotoxic warhead through said S239C mutation in said heavy chain constant region.

25. The ADC of claim 24, wherein q is 5.

26. The ADC of claim 24, wherein said monoclonal antibody comprises an IgG1 isotype.

27. The ADC of claim 24, wherein said heavy chain constant region of said monoclonal anti-PRLR antibody either lacks a C-terminal lysine or comprises an amino acid other than lysine at a C-terminus of the heavy chain constant region.

28. The ADC of claim 24, wherein said monoclonal anti-PRLR antibody is a humanized antibody.

29. The ADC of claim 24, wherein said ADC has a drug load of two cytotoxic warheads per anti-PRLR antibody.

30. The ADC of claim 25, wherein said monoclonal antibody comprises an IgG1 isotype.

31. The ADC of claim 25, wherein said heavy chain constant region of said monoclonal anti-PRLR antibody either lacks a C-terminal lysine or comprises an amino acid other than lysine at a C-terminus of the heavy chain constant region.

32. The ADC of claim 25, wherein said monoclonal anti-PRLR antibody is a humanized antibody.

33. The ADC of claim 25, wherein said ADC has a drug load of two cytotoxic warheads per anti-PRLR antibody.

34. An antibody-drug conjugate (ADC) comprising the structure of Formula (IX), or a salt thereof, ##STR00018## wherein Formula (IX) comprises a monoclonal anti-PRLR antibody (Ab) conjugated to at least one cytotoxic warhead, wherein D comprises a pyrrolobenzodiazepine (PBD) dimer; Y is Val, Z is Ala, and q is 1, 2, 3, 4, 5, 6, 7, or 8, and wherein said monoclonal anti-PRLR antibody comprises: i. a full heavy chain comprising SEQ ID NO: 1; and ii. a full light chain comprising SEQ ID NO: 6; wherein said monoclonal anti-PRLR antibody is conjugated to said at least one cytotoxic warhead through amino acid residue 242 of SEQ ID NO: 1.

35. The ADC of claim 34, wherein q is 5.

36. The ADC of claim 34, wherein said heavy chain constant region of said monoclonal anti-PRLR antibody either lacks a C-terminal lysine or comprises an amino acid other than lysine at a C-terminus of the heavy chain constant region.

37. The ADC of claim 34, wherein said ADC has a drug load of two cytotoxic warheads per anti-PRLR antibody.

38. The ADC of claim 35, wherein said heavy chain constant region of said monoclonal anti-PRLR antibody either lacks a C-terminal lysine or comprises an amino acid other than lysine at a C-terminus of the heavy chain constant region.

39. The ADC of claim 35, wherein said ADC has a drug load of two cytotoxic warheads per anti-PRLR antibody.

40. An antibody-drug conjugate (ADC) comprising the structure of Formula (IX), ##STR00019## wherein Formula (IX) comprises a monoclonal anti-PRLR antibody (Ab) conjugated to a cytotoxic warhead, wherein D comprises a pyrrolobenzodiazepine (PBD) dimer; Y is Val, Z is Ala, and q is 5 and wherein said monoclonal anti-PRLR antibody comprises: i. a heavy chain variable region comprising a CDRH1 sequence comprising SEQ ID NO: 3, a CDRH2 sequence comprising SEQ ID NO: 4, and a CDRH3 sequence comprising SEQ ID NO: 5; ii. a light chain variable region comprising a CDRL1 sequence comprising SEQ ID NO: 8, a CDRL2 sequence comprising SEQ ID NO: 9, and a CDRL3 sequence comprising SEQ ID NO: 10; and iii. a mutation comprising S239C in a heavy chain constant region, wherein the numbering is in accordance with Kabat, wherein said monoclonal anti-PRLR antibody is conjugated to said cytotoxic warhead through said S239C mutation in said heavy chain constant region, and wherein said ADC has a drug load of two cytotoxic warheads per anti-PRLR antibody.

41. The ADC of claim 40, wherein said monoclonal antibody comprises an IgG1 isotype.

42. The ADC of claim 40, wherein said heavy chain constant region of said monoclonal anti-PRLR antibody either lacks a C-terminal lysine or comprises an amino acid other than lysine at a C-terminus of the heavy chain constant region.

43. The ADC of claim 40, wherein said monoclonal anti-PRLR antibody is a humanized antibody.

44. An antibody-drug conjugate (ADC) comprising the structure of Formula (IX), ##STR00020## wherein Formula (IX) comprises a monoclonal anti-PRLR antibody (Ab) conjugated to a cytotoxic warhead, wherein D comprises a pyrrolobenzodiazepine (PBD) dimer; Y is Val, Z is Ala, and q is 5 and wherein said monoclonal anti-PRLR antibody comprises: i. a heavy chain variable region comprising SEQ ID NO: 2; ii. a light chain variable region comprising SEQ ID NO: 7; and iii. a mutation comprising S239C in a heavy chain constant region, wherein the numbering is in accordance with Kabat, wherein said monoclonal anti-PRLR antibody is conjugated to said cytotoxic warhead through said S239C mutation in said heavy chain constant region, and wherein said ADC has a drug load of two cytotoxic warheads per anti-PRLR antibody.

45. The ADC of claim 44, wherein said monoclonal antibody comprises an IgG1 isotype.

46. The ADC of claim 44, wherein said heavy chain constant region of said monoclonal anti-PRLR antibody either lacks a C-terminal lysine or comprises an amino acid other than lysine at a C-terminus of the heavy chain constant region.

47. The ADC of claim 44, wherein said monoclonal anti-PRLR antibody is a humanized antibody.

48. An antibody-drug conjugate (ADC) comprising the structure of Formula (IX), ##STR00021## wherein Formula (IX) comprises a monoclonal anti-PRLR antibody (Ab) conjugated to a cytotoxic warhead, wherein D comprises a pyrrolobenzodiazepine (PBD) dimer; Y is Val, Z is Ala, and q is 5, and wherein said monoclonal anti-PRLR antibody comprises: i. a full heavy chain comprising SEQ ID NO: 1; and ii. a full light chain comprising SEQ ID NO: 6; wherein said monoclonal anti-PRLR antibody is conjugated to said cytotoxic warhead through amino acid residue 242 of SEQ ID NO: 1, and wherein said ADC has a drug load of two cytotoxic warheads per anti-PRLR antibody.

49. The ADC of claim 48, wherein said heavy chain constant region of said monoclonal anti-PRLR antibody either lacks a C-terminal lysine or comprises an amino acid other than lysine at a C-terminus of the heavy chain constant region.