WO2018102594A1

WO2018102594A1 - Methods of treating solid tumors with anti-cd200 antibodies

Info

Publication number: WO2018102594A1
Application number: PCT/US2017/064033
Authority: WO
Inventors: Xiaoping Zhang; Wei-jian PAN
Original assignee: Alexion Pharmaceuticals Inc
Current assignee: Alexion Pharmaceuticals Inc
Priority date: 2016-12-01
Filing date: 2017-11-30
Publication date: 2018-06-07
Anticipated expiration: 2019-06-01
Also published as: WO2018102594A8

Abstract

The present disclosure provides methods for treating solid tumors using an effective amount of an anti-CD200 antibody, or antigen-binding fragment thereof.

Description

METHODS OF TREATING SOLID TUMORS WITH ANTI-CD200 ANTIBODIES

RELATED APPLICATIONS

This application claims priority to, and the benefit of, U.S. Provisional Application No. 62/428,838, which was filed on December 1, 2016, and U.S. Provisional Application No.

62/466,224, which was filed on March 2, 2017. The entire contents of the aforementioned applications are incorporated herein by reference.

SEQUENCE LISTING

The instant application contains a Sequence Listing which has been submitted electronically in ASCII format and is hereby incorporated by reference in its entirety. Said ASCII copy, created on November 21, 2017 is named AXJ-230PC_SL.txt and is 17,390 bytes in size.

BACKGROUND

Antibody-based therapeutics has found a prominent place in the biopharmaceutical industry, and have contributed significantly to advancing treatment in multiple disease areas, including in inflammatory and autoimmune diseases and cancer. Advances in the understanding of the complex mechanisms of immune surveillance and regulation and the interactions between tumor cells and the immune system has helped to advance the field of immune-oncology.

Immunotherapy as a treatment for cancer holds the promise of complete and durable tumor remission, yet the immunosuppressive environment created by many tumors may limit this approach.

Tumors can create immune escape mechanisms through their ability to alter the microenvironment and suppress the immune system from eradicating the tumor. One of these mechanisms involves disrupting normal immune checkpoints to help the tumor escape immune- mediated tumor destruction. Immune checkpoints are part of the regulatory pathways induced in activated T cells that control T cell antigen responses. In the "normal" state, there is a balance of both stimulatory and inhibitory signals that provides effective immune responses while preventing autoimmunity and unrestrained T cell proliferation. However, in patients with cancer, the immune system appears to suppress T cell function, T cell responses, and natural killer (NK) cell function. In solid tumors, certain mechanisms enable immune evasion by tumor cells, providing a rationale for the use of checkpoint inhibitors, for example, like ipilimumab in melanoma, and nivolumab in nonsmall cell lung cancer.

A potential target for immunomodulation is CD200, an Ig superfamily type I

transmembrane glycoprotein, which is expressed on a variety of cells both of hematopoietic origin (myeloid and lymphoid) as well as of non-hematopoietic origin. CD200 is a regulator of the immune checkpoint and is widely distributed on a variety of tissues, including B-cells, active T cells, as well as certain vascular endothelia, kidney, and placental cells. The CD200 receptor, CD200R, is mainly expressed on myeloid cells, T- and B-cells, and polarized Th2 cells.

Interaction of CD200 and CD200R causes an immunosuppressive signal leading to inhibition of macrophages, induction of regulatory T cells, and switching of cytokine profiles. CD200 is overexpressed in multiple tumor types, and increased expression is associated with worse outcomes.

Appropriate dosing of medications, such as antibody preparations, in timing, as well as in amount or administration frequency, is a critical factor in their administration to patients and in the efficacy of medications. Accordingly, it is the object of the present disclosure to provide methods and improved methods for treating cancer patients with solid tumors with anti-CD200 antibodies, particularly with samalizumab.

SUMMARY

Provided herein are methods for treating a solid tumor {e.g., an advanced solid tumor) in a human subject comprising administering a therapeutically effective amount of an anti-CD200 antibody, or antigen binding fragment thereof, according to a particular clinical dosage regimen {i.e., at a particular dose amount and according to a specific dosing schedule).

An exemplary anti-CD200 antibody is samalizumab.

In one embodiment, the anti-CD200 antibody, or antigen-binding fragment thereof, comprises a heavy chain variable region CDRl having the sequence set forth in SEQ ID NO: 7, a heavy chain variable region CDR2 having the sequence set forth in SEQ ID NO: 8, a heavy chain variable region CDR3 having the sequence set forth in SEQ ID NO: 9, a light chain variable region CDRl having the sequence set forth in SEQ ID NO: 4, a light chain variable region CDR2 having the sequence set forth in SEQ ID NO: 5, and a light chain variable region CDR3 having the sequence set forth in SEQ ID NO: 6.

In another embodiment, the anti-CD200 antibody comprises heavy and light chain variable regions having the sequences set forth in SEQ ID NOs: 13 and 12, respectively.

In another embodiment, the anti-CD200 antibody comprises heavy and light chains having the sequences as set forth in SEQ ID NOs: 11 and 10, respectively.

In another embodiment, the anti-CD200 antibody, or antigen binding fragment thereof, comprises the CDR1, CDR2 and CDR3 domains of a heavy chain variable region having the sequence set forth in SEQ ID NO: 13, and the CDR1, CDR2 and CDR3 domains of a light chain variable region having the sequence set forth in SEQ ID NO: 12.

In another embodiment, the anti-CD200 antibody, or antigen binding fragment thereof, comprising the CDR1, CDR2 and CDR3 domains of a heavy chain region having the sequence set forth in SEQ ID NO: 11, and the CDR1, CDR2 and CDR3 domains of a light chain region having the sequence set forth in SEQ ID NO: 10.

In another embodiment, the anti-CD200 antibody is a human antibody. In another embodiment, a composition of anti-CD200 antibodies, or fragments thereof, is provided, wherein the composition {e.g., a sterile composition) comprises at least one pharmaceutically acceptable carrier.

In one embodiment, the anti-CD200 antibody, or antigen binding fragment thereof, is administered at a dose of from 5 mg/kg to 50 mg/kg (or about 5 mg/kg to about 50 mg/kg). In another embodiment, the anti-CD200 antibody, or antigen binding fragment thereof, is administered at a dose of from 10 mg/kg to 40 mg/kg (or about 10 mg/kg to about 40 mg/kg). In another embodiment, the anti-CD200 antibody, or antigen binding fragment thereof, is administered at a dose of from 15mg/kg to 30 mg/kg (or about 15 mg/kg to about 30 mg/kg). In another embodiment, the anti-CD200 antibody, or antigen binding fragment thereof, is administered at a dose of 5 mg/kg (or about 5 mg/kg). In another embodiment, the anti-CD200 antibody, or antigen binding fragment thereof, is administered at a dose of 10 mg/kg (or about 10 mg/kg). In another embodiment, the anti-CD200 antibody, or antigen binding fragment thereof, is administered at a dose of 15 mg/kg (or about 15 mg/kg). In another embodiment, the anti- CD200 antibody, or antigen binding fragment thereof, is administered at a dose of 20 mg/kg (or about 20 mg/kg). In another embodiment, the anti-CD200 antibody, or antigen binding fragment thereof, is administered at a dose of 25 mg/kg (or about 25 mg/kg). In another embodiment, the anti-CD200 antibody, or antigen binding fragment thereof, is administered at a dose of 30 mg/kg (or about 30 mg/kg). In another embodiment, the anti-CD200 antibody, or antigen binding fragment thereof, is administered at a dose of 35 mg/kg (or about 35 mg/kg). In another embodiment, the anti-CD200 antibody, or antigen binding fragment thereof, is administered at a dose of 40 mg/kg (or about 40 mg/kg). In another embodiment, the anti-CD200 antibody, or antigen binding fragment thereof, is administered at a dose of 45 mg/kg (or about 45 mg/kg). In another embodiment, the anti-CD200 antibody, or antigen binding fragment thereof, is administered at a dose of 50 mg/kg (or about 50 mg/kg). In another embodiment, the anti- CD200 antibody, or antigen binding fragment thereof, is administered at a dose of 55 mg/kg (or about 55 mg/kg). In another embodiment, the anti-CD200 antibody, or antigen-binding fragment thereof, is particularly from about 10 mg/kg to about 20 mg/kg, more particularly about 10 mg/kg, about 15 mg/kg, or about 20 mg/kg. In another embodiment, the anti-CD200 antibody, or antigen-binding fragment thereof, is particularly from 10 mg/kg to 20 mg/kg, more particularly 10 mg/kg, 15 mg/kg, or 20 mg/kg.

In one embodiment, methods of treating a patient with a solid tumor are provided, wherein the method comprises administering to the patient 10 mg/kg (or about 10 mg/kg), 15 mg/kg (or about 15 mg/kg), or 20 mg/kg (or about 10 mg/kg) of an anti-CD200 antibody, or antigen-binding fragment thereof, wherein the anti-CD200 antibody, or antigen-binding fragment thereof, comprises a heavy chain variable region CDR1 having the sequence set forth in SEQ ID NO: 7, a heavy chain variable region CDR2 having the sequence set forth in SEQ ID NO: 8, a heavy chain variable region CDR3 having the sequence set forth in SEQ ID NO: 9, a light chain variable region CDR1 having the sequence set forth in SEQ ID NO: 4, a light chain variable region CDR2 having the sequence set forth in SEQ ID NO: 5, and a light chain variable region CDR3 having the sequence set forth in SEQ ID NO: 6. In a particular embodiment, 10 mg/kg (or about 10 mg/kg) of the anti-CD200 antibody, or antigen-binding fragment thereof, is

administered to the patient. In another particular embodiment, 15 mg/kg (or about 15 mg/kg) of the anti-CD200 antibody, or antigen-binding fragment thereof, is administered to the patient. In another particular embodiment, 20 mg/kg (or about 20 mg/kg) of the anti-CD200 antibody, or antigen-binding fragment thereof, is administered to the patient. In another embodiment, methods of treating a patient with a solid tumor are provided, the method comprising administering intravenously to the patient 10 mg/kg (or about 10 mg/kg), 15 mg/kg (or about 15 mg/kg), or 20 mg/kg (or about 20 mg/kg) of an anti-CD200 antibody, or antigen-binding fragment thereof, once every fourteen (14) days or once every twenty-one days, wherein the anti-CD200 antibody, or antigen-binding fragment thereof, comprises a heavy chain variable region CDR1 having the sequence set forth in SEQ ID NO: 7, a heavy chain variable region CDR2 having the sequence set forth in SEQ ID NO: 8, a heavy chain variable region CDR3 having the sequence set forth in SEQ ID NO: 9, a light chain variable region CDR1 having the sequence set forth in SEQ ID NO: 4, a light chain variable region CDR2 having the sequence set forth in SEQ ID NO: 5, and a light chain variable region CDR3 having the sequence set forth in SEQ ID NO: 6.

In one embodiment, the anti-CD200 antibody, or antigen-binding fragment thereof, is administered every fourteen days. In another embodiment, the anti-CD200 antibody, or antigen- binding fragment thereof, is administered every twenty-one days. In another embodiment, the anti-CD200 antibody, or antigen-binding fragment thereof, is administered every two weeks. In another embodiment, the anti-CD200 antibody, or antigen-binding fragment thereof, is administered every three weeks. In another embodiment, the anti-CD200 antibody, or antigen- binding fragment thereof, is administered every four weeks. In another embodiment, the anti- CD200 antibody, or antigen-binding fragment thereof, is administered every 13 days to every 24 days (e.g., every 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, or 24 days). In another embodiment, the anti-CD200 antibody, or antigen-binding fragment thereof, is administered every 14 days or every 21 days.

In another embodiment, a treatment cycle is 21 days. In another embodiment, a treatment cycle is 14 days. In another embodiment, the treatment comprises at least 1, 2, 3, 4, or 5 cycles. In another embodiment, the treatment comprises at least 6, 7, 8, 9, 10, or 11 cycles. In another embodiment, the treatment is for the lifetime of the human patient.

In another embodiment, the anti-CD200 antibody, or antigen-binding fragment thereof, inhibits the interaction between CD200 and CD200R. In another embodiment, the method of treatment results in a CD200 saturation of at least 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81 %, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%. In one embodiment, the treatment results in a reduction in tumor burden, for example, reduction in tumor burden as assessed by a computerized tomography (CT) scan. In another embodiment, the anti-CD200 antibody, or antigen-binding fragment thereof, is administered with a frequency sufficient to provide a complete response (CR), a partial response (PR), or stable disease. In one embodiment, stable disease is 12 weeks (84 days) of tumor nonprogression. In another embodiment, the treatment results in a reduction in tumor burden according to RECIST 1.1 parameters (Response Evaluation Criteria in Solid Tumors Version 1.1 (RECIST 1.1, Eisenhauer, E.A., et al., European J. Cancer 45: 228-247(2009)) or according to irRECIST parameters (Immune-related response evaluation criteria in solid tumors, Wolchok JD, et al., Clin Cancer Res. 15 (23): 7412-20 (2009)). In another embodiment, treatment produces at least one therapeutic effect selected from the group consisting of reduction in growth rate of tumor, reduction in size of tumor, reduction in number of metastatic lesions over time, increase in duration of progression-free survival, and/or increase in overall response rate.

In one embodiment, the anti-CD200 antibody, or antigen-binding fragment thereof, is administered intravenously. In a particular embodiment, the anti-CD200 antibody, or antigen- binding fragment thereof, is administered intravenously at a rate of from about 125 to about 250 mL/hour.

Treatment with the anti-CD200 antibody, or antigen-binding fragment thereof, is continued for any suitable period of time (e.g., until a CR or a PR has been achieved). In one embodiment, the anti-CD200 antibody, or antigen-binding fragment thereof, is administered for at least about 1 month, 2 months, 3 months, 4 months, 5 months, 6 months, 7 months, 8 months, 9 months, 10 months, or 11 months. In another embodiment, the anti-CD200 antibody, or antigen-binding fragment thereof, is administered for at least one year. In another embodiment, the anti-CD200 antibody, or antigen-binding fragment thereof, is administered for at least two years. In another embodiment, the anti-CD200 antibody, or antigen-binding fragment thereof, is administered every 21 days for at least 1 month, 2 months, 3 months, 4 months, 5 months, 6 months, 7 months, 8 months, 9 months, 10 months, 11 months, one year, two years, or for the lifetime of the patient.

In one embodiment, the solid tumor is an advanced solid tumor. In another embodiment, the solid tumor is at least one of a sarcoma, carcinoma, or lymphoma. In one embodiment, the solid tumor is a tumor of the colon, stomach, salivary glands, lung (e.g., small-cell lung cancer or non-small cell lung cancer), skin, thyroid, prostate, breast, ovaries, cervix, vagina, testicles, bladder, liver, lymphatic tissue (e.g., Hodgkin's disease or non-Hodgkin's lymphomas), bone (e.g., osteogenic sarcoma or Ewing's Sarcoma), kidney (e.g., Wilms' tumor), eye (e.g., retinoblastoma), adrenal glands (e.g., neuroblastoma or adrenocortical carcinoma), soft tissue (e.g., rhabdomyosarcoma or rhabdosarcoma), ovary, pancreas, brain, head, or neck. In another embodiment, the solid tumor is at least one solid tumor selected from the group consisting of an: adrenocortical tumor, alveolar soft part sarcoma, carcinoma, chondrosarcoma, colorectal carcinoma, desmoid tumor, desmoplastic small round cell tumor, endocrine tumor, endodermal sinus tumor, epithelioid hemangioendothelioma, Ewing sarcoma, germ cell tumor,

hepatoblastoma, hepatocellular carcinoma, melanoma, nephroma, neuroblastoma, non- rhabdomyosarcoma soft tissue sarcoma (NRSTS), osteosarcoma, paraspinal sarcoma, renal cell carcinoma, retinoblastoma, rhabdomyosarcoma, synovial sarcoma, pediatric brain and extracranial solid tumor, and Wilms Tumor. In another embodiment, the tumor is derived from neural crest cells or any tumor that expresses CD200.

CD200 is highly expressed in many types of solid tumors. Elevated CD200 expression is found in many tumor types; therefore, embodiments include but are not limited to solid tumors of skin (e.g. , melanoma), lung, ovary, central nervous system, endometrial, kidney, head, and neck. Elevated CD200 expression is also observed in hematologic malignancies including leukemias, lymphomas and myeloma. In another embodiment the tumor exhibits genomic instability or a high mutational burden (Alexandrov, LB, et al., Nature, 500, 415^121 (2013)), including but not limited to melanoma, squamous lung cancer, lung adenocarcinoma, bladder carcinoma, small cell lung carcinoma, esophageal carcinoma, colorectal carcinoma, cervical carcinoma, head and neck squamous cell carcinoma, gastric cancer, uterine cancer, hepatocellular carcinoma, clear cell renal cell carcinoma, papillary renal cell carcinoma, ovarian carcinoma, prostate carcinoma, myeloma, B cell lymphoma, low grade glioma, breast cancer, pancreatic cancer, glioblastoma, neuroblastoma, chronic lymphocytic leukemia, thyroid cancer, chromophobe kidney carcinoma, acute myeloid leukemia, medulloblastoma, and acute lymphoblastic leukemia.

In another embodiment, the treatment methods described herein comprise administering the anti-CD200 antibody, or antigen binding fragment thereof, in combination with one or more other antineoplastic agents (e.g., other chemotherapeutics or other small molecule drugs). In one embodiment, no more than three other antineoplastic agents are administered within a treatment cycle. In another embodiment, no more than two other antineoplastic agents are administered within a treatment cycle. In another embodiment, no more than one other antineoplastic agent is administered within a treatment cycle. In another embodiment, no other antineoplastic agent is administered within an anti-CD200 administering treatment cycle.

Also provided are kits for treating a human patient having a solid tumor, the kit comprising:

a) a dose of an anti-CD200 antibody, or antigen-binding fragment thereof, comprising a heavy chain variable region CDR1 having the sequence set forth in SEQ ID NO: 7, a heavy chain variable region CDR2 having the sequence set forth in SEQ ID NO: 8, a heavy chain variable region CDR3 having the sequence set forth in SEQ ID NO: 9, a light chain variable region CDR1 having the sequence set forth in SEQ ID NO: 4, a light chain variable region CDR2 having the sequence set forth in SEQ ID NO: 5, and a light chain variable region CDR3 having the sequence set forth in SEQ ID NO: 6; and b) instructions for using the anti-CD200 antibody, in the methods described herein.

Other features and advantages of the methods of treatment will be apparent from the following description, the examples, and from the claims. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a graph depicting total, linear, and nonlinear clearance of samalizumab from serum.

Figure 2 is a graphic depiction of medians of conditional predictions for final samalizumab concentrations using certain dosing regimens (i.e., 5, 10, 15, and 20 mg/kg, 21 day dosing, (Q21D)).

Figures 3A-H are graphs showing median and 80% prediction intervals for percent change from baseline of CD200⁺CD2⁺ T and B-CLL CD200⁺ [MFI] cells using the dosing regimens (i.e., 5, 10, 15, and 20 mg/kg Q21D). Figure 4 is a bar graph showing the best response to samalizumab in maximum reduction in total tumor burden from baseline for patients with B-cell Chronic Lymphocytic Leukemia (CLL). Dotted lines indicate 20% increase and 30% decrease from baseline.

Figures 5A-5B are graphs showing the correlation of best response to samalizumab in maximum reduction of total tumor burden and samalizumab pharmacokinetic exposure for patients with B- Cell CLL. Figure 5A uses AUC2₈d for pharmacokinetic (PK) exposure. Figure 5B uses C_max for PK exposure. The dotted line is the line of zero, indicating tumor burden increased (above the line) or decreased (below the line) for individual data. The solid line is the linear model of predictive response. AUC_28d = population PK model predicted area under the serum

concentration-time curve after first dose for 28 days; C_max = maximum serum concentration after first dose. PK = pharmacokinetic. R = Pearson correlation coefficient.

Figure 6 is a graphic depiction of the Phase 1 clinical trial study design for treatment of solid tumors in patients with samalizumab.

Figure 7 is a graph depicting the Phase I samalizumab dose escalation (Part 1A).

Figures 8A-8B are graphs, in linear and semi-log scales, respectively, depicting serum samalizumab concentration over time with Q3W repeated intravenous dosing (10 mg/kg) in three patients with colon, lung, or renal cancer.

Figures 9A-9B are graphs, in linear and semi-log scales, respectively, depicting serum samalizumab concentration over time with Q3W repeated intravenous dosing (15 mg/kg) in four patients with colorectal cancer, neuroendocrine cancer, melanoma, or cholangiocarcinoma.

Figures 10A-10B are graphs, in linear and semi-log scales, respectively, depicting serum samalizumab concentration over time with Q3W repeated intravenous dosing (20 mg/kg) in three patients with colorectal, ovarian, or breast cancer.

Figure 11 is a chart summarizing the PK parameters for the six cancer patients who received Q3W repeated intravenous dosing of samalizumab (10 or 15 mg/kg).

Figures 12A-12B are graphs, in linear and semi-log scales, respectively, depicting serum samalizumab concentrations over time in cancer patients who received 10 mg/kg samalizumab. Figures 13A-13B are graphs, in linear and semi-log scales, respectively, depicting serum samalizumab concentration over time in cancer patients who received 15 mg/kg samalizumab.

Figures 14A-14B are graphs, in linear and semi-log scales, respectively, depicting serum samalizumab concentration over time in cancer patients who received 20 mg/kg samalizumab.

Figures 15A-15B are graphs, in linear and semi-log scales, respectively, depicting the mean serum samalizumab over time in cancer patients who received 10, 15, or 20 mg/kg samalizumab.

Figure 16 is a chart summarizing the PK paramaters for study patients who received Q3W repeated intravenous dosing of samalizumab (10, 15, or 20 mg/kg).

DETAILED DESCRIPTION

As described herein, the invention is based on the discovery that administration of an anti-CD200 antibody effectively inhibits solid tumor growth in vivo. Accordingly, the present disclosure provides methods for the treatment of a solid tumor in a subject which comprises administering to a subject (e.g. , a human) an effective amount an anti-CD200 antibody, or antigen binding fragment thereof.

I. Definitions

In order that the present description may be more readily understood, certain terms are first defined. Additional definitions are set forth throughout the detailed description. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art, and conventional methods of immunology, protein chemistry, biochemistry, recombinant DNA techniques, and pharmacology are employed.

As used herein, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. The use of "or" or "and" means "and/or" unless stated otherwise. Furthermore, use of the term "including" as well as other forms, such as "include", "includes", and "included", is not limiting.

The term "about" as used herein when referring to a measurable value such as an amount, a temporal duration and the like, is encompasses variations of up to ± 10% from the specified value. Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, etc., used herein are to be understood as being modified by the term "about".

The terms "CD200," "OX-2," and "OX-2/CD200" are used interchangeably herein and refers to the highly conserved type I transmembrane glycoprotein having an amino acid sequence of the full-length precursor human CD200 isoform A (SEQ ID NO: 1; Genbank Accession No. NP005935.2), the full-length human CD200 isoform B (SEQ ID NO: 2; Genbank Accession No. NP001004196.2), or the full-length human CD200 of SEQ ID NO: 3 (Genbank Accession No. CAA28943.1 ; FIG. 3 of McCaughan et al. (1987) Immunogenetics 25:329-335).

The term "CD200 antagonist" as used herein includes any agent that is capable of inhibiting the activity, function and/or the expression of CD200 or its receptor. In certain embodiments, the antagonist disrupts the interaction of CD200 and CD200R. In other embodiments, the CD200 antagonist is capable of decreasing the immunosuppressive effects of CD200 or is capable of targeting CD200-expressing cells for depletion or elimination.

The term "antibody" as used herein refers to polypeptides comprising at least one antibody derived antigen binding site {e.g., VH V L region or Fv, or CDR), and includes whole antibodies and any antigen binding fragments {i.e., "antigen-binding portions" or "antigen binding fragments thereof) or single chains thereof. Antibodies include known forms of antibodies. For example, the antibody can be a human antibody, a humanized antibody, a bispecific antibody, or a chimeric antibody. A "whole antibody" refers to a glycoprotein comprising at least two heavy (H) chains and two light (L) chains inter-connected by disulfide bonds, in which each heavy chain is comprised of a heavy chain variable region (abbreviated herein as VH) and a heavy chain constant region; and each light chain is comprised of a light chain variable region (abbreviated herein as VL) and a light chain constant region. The VH and VL regions can be further subdivided into regions of hypervariability, termed complementarity determining regions (CDR), interspersed with regions that are more conserved, termed framework regions (FR). Each VH and VL is composed of three CDRs and four FRs, arranged from amino-terminus to carboxy-terminus in the following order: FR1, CDR1, FR2, CDR2, FR3, CDR3, FR4. The variable regions of the heavy and light chains contain a binding domain that interacts with an antigen. The constant regions of the antibodies may mediate the binding of the immunoglobulin to host tissues or factors, including various cells of the immune system {e.g., effector cells) and the first component (Clq) of the classical complement system. The exact boundaries of CDRs can be defined differently according to different methods. In some embodiments, the positions of the CDRs or framework regions within a light or heavy chain variable domain can be as defined by Kabat et al. [(1991) "Sequences of Proteins of Immunological Interest." NIH Publication No. 91-3242, U.S. Department of Health and Human Services, Bethesda, MD]. In such cases, the CDRs can be referred to as "Kabat CDRs" {e.g., "Kabat LCDR2" or "Kabat HCDR1"). In other embodiments, the positions of the CDRs of a light or heavy chain variable region can be as defined by Chothia et al. (1989) Nature 342:877- 883. Accordingly, these regions can be referred to as "Chothia CDRs" {e.g., "Chothia LCDR2" or "Chothia HCDR3"). In other embodiments, the positions of the CDRs of the light and heavy chain variable regions can be as defined by a Kabat-Chothia combined definition. In such embodiments, these regions can be referred to as "combined Kabat-Chothia CDRs." Thomas et al. [(1996) Mol Immunol 33(17/18):1389-1401] exemplifies the identification of CDR boundaries according to Kabat and Chothia definitions. In other embodiments, the positions of the CDRs or framework regions within a light or heavy chain variable domain can be as defined by the international ImMunoGeneTics database (IMGT) standard. Marie-Paule Lefranc et al. [(2003) Developmental & Comparative Immunology 27(l):55-77] exemplifies the identification of and CDR boundaries according to IMGT standard. Accordingly, these regions can be referred to as "IMGT CDRs" {e.g., "IMGT-LCDR2" or "IMGT-HCDR3").

The antibody also can be of any of the following isotypes: IgGl, IgG2, IgG3, IgG4, IgM, IgAl, IgA2, IgAsec, IgD, and IgE. The antibody may be a naturally occurring antibody or may be an antibody that has been altered by a protein engineering technique {e.g., by mutation, deletion, substitution, and/or conjugation to a non-antibody moiety). For example, an antibody may include one or more variant amino acids (compared to a naturally occurring antibody) which change a property {e.g., at least one functional property) of the antibody. For example, numerous such alterations are known in the art which affect, e.g., half-life, effector function, and/or immune responses to the antibody in a patient. The term antibody also includes artificial or engineered polypeptide constructs which comprise at least one antibody-derived antigen binding site.

The term "human antibody," as used herein, is intended to include antibodies having variable regions in which both the framework and CDR regions are derived from human germline immunoglobulin sequences as described, for example, by Kabat et al. (See Kabat, et al. (1991) Sequences of proteins of Immunological Interest, Fifth Edition, U.S. Department of Health and Human Services, NIH Publication No. 91-3242).

The term "antigen-binding portion" of an antibody (or simply "antibody portion"), as used herein, refers to one or more fragments of an antibody that retain the ability to specifically bind to an antigen (e.g., CD200), e.g., a Fab, Fab'2, ScFv, SMIP, AFFIBODY® antibody mimetic (Affibody AB AKTIEBOLAG, Sweden), nanobody, or a domain antibody. It has been shown that the antigen-binding function of an antibody can be performed by fragments of a full- length antibody. Examples of binding fragments encompassed within the term "antigen-binding portion" of an antibody include (i) a Fab fragment, a monovalent fragment consisting of the VL, VH, CL and CHI domains; (ii) a F(ab')2 fragment, a bivalent fragment comprising two Fab fragments linked by a disulfide bridge at the hinge region; (iii) a Fd fragment consisting of the VH and CHI domains; (iv) a Fv fragment consisting of the VL and VH domains of a single arm of an antibody, (v) a dAb fragment (Ward et al., (1989) Nature 341:544-546), which consists of a VH domain; and (vi) an isolated complementarity determining region (CDR). Furthermore, although the two domains of the Fv fragment, VL and VH, are coded for by separate genes, they can be joined, using recombinant methods, by a synthetic linker that enables them to be made as a single protein chain in which the VL and VH regions pair to form monovalent molecules (known as single chain Fv (scFv); see e.g., Bird et al. (1988) Science 242:423-426; and Huston et al. (1988) Proc. Natl. Acad. Sci. USA 85:5879-5883). Such single chain antibodies are also intended to be encompassed within the term "antigen-binding portion" of an antibody. Other forms of single chain antibodies, such as diabodies are also encompassed. Diabodies are bivalent, bispecific antibodies in which VH and VL domains are expressed on a single

polypeptide chain, but using a linker that is too short to allow for pairing between the two domains on the same chain, thereby forcing the domains to pair with complementary domains of another chain and creating two antigen binding sites (see e.g., Holliger, P., et al. (1993) Proc. Natl. Acad. Sci. USA 90:6444-6448; Poljak, R. J., et al. (1994) Structure 2: 1121-1123). In one embodiment, the composition contains an antigen-binding portions described in U.S. Pat.

Nos. 6,090,382 and 6,258,562, each incorporated by reference herein.

The term "monoclonal antibody," as used herein, includes an antibody obtained from a population of substantially homogeneous antibodies, i.e., the individual antibodies comprising the population are identical except for possible naturally occurring mutations that may be present in minor amounts. Monoclonal antibodies are highly specific, being directed against a single antigenic site. Monoclonal antibodies are advantageous in that they may be synthesized by a hybridoma culture, essentially uncontaminated by other immunoglobulins. The modifier "monoclonal" indicates the character of the antibody as being amongst a substantially homogeneous population of antibodies, and is not to be construed as requiring production of the antibody by any particular method. The monoclonal antibodies to be used in accordance with the formulations disclosed herein may be made by the hybridoma method first described by Kohler, et al., (1975) Nature 256: 495, or by other methods known in the art. A "polyclonal antibody" is an antibody which was produced among or in the presence of one or more other, non-identical antibodies. In general, polyclonal antibodies are produced from a B-lymphocyte in the presence of several other B- lymphocytes which produced non-identical antibodies. Usually, polyclonal antibodies are obtained directly from an immunized animal.

An "isolated" antibody or antigen binding fragment is one which has been identified and separated and/or recovered from a component (particularly from contaminant components) of its natural environment. Contaminant components of its natural environment are materials which would interfere with research, diagnostic or therapeutic uses for the antibody, and may include enzymes, hormones, and other proteinaceous or nonproteinaceous solutes. In some

embodiments, an antibody is purified to greater than about 95% by weight of antibody, and in some embodiments, to greater than about 99% by weight of antibody.

The term "pharmaceutical formulation" or "pharmaceutical composition" refers to preparations which are in such form as to permit the biological activity of the active ingredients to be unequivocally effective, and which contain no additional components which are significantly toxic to the subjects to which the formulation would be administered.

As used herein, an "aqueous" pharmaceutical composition is a composition suitable for pharmaceutical use, wherein the aqueous carrier is water. A composition suitable for pharmaceutical use may be sterile, homogeneous, and/or isotonic. Aqueous pharmaceutical compositions may be prepared directly in an aqueous form and/or may be reconstituted from a lyophilisate.

A "sterile" composition is aseptic, or free or essentially free, from all living

microorganisms and their spores. As used herein, the terms "specific binding," "selective binding," "selectively binds," and "specifically binds," refer to antibody binding to an epitope on a predetermined antigen but not to other antigens. Typically, the antibody (i) binds with an equilibrium dissociation constant (KD) of approximately less than 10^"7 M, such as approximately less than 10 ⁸ M, 10^"9 M, or 10^"10 M or even lower when determined by, e.g. , surface plasmon resonance (SPR) technology in a BIACORE^® 2000 surface plasmon resonance instrument using the predetermined antigen, e.g., recombinant human CD200, as the analyte and the antibody as the ligand, or Scatchard analysis of binding of the antibody to antigen positive cells, and (ii) binds to the predetermined antigen with an affinity that is at least two-fold greater than its affinity for binding to a non-specific antigen (e.g., BSA, casein) other than the predetermined antigen or a closely-related antigen. Accordingly, unless otherwise indicated, an antibody that "specifically binds to human CD200" refers to an antibody that binds to soluble or cell bound human CD200 with a KD of 10^"7 M or less, such as approximately less than 10 ^"8 M, 10^"9 M, or 10^{" 10} M, or even lower.

An "epitope" refers to the site on a protein (e.g. , a human CD200 protein) that is bound by an antibody. "Overlapping epitopes" include at least one (e.g. , two, three, four, five, or six) common amino acid residue(s). In some embodiments, an anti-CD200 antibody described herein binds to an epitope within the extracellular portion of a CD200 protein. For example, in some embodiments, the anti-CD200 antibody can bind to CD200 protein at an epitope within or overlapping with: (i) amino acids 1 to 233 of the amino acid sequence depicted in SEQ ID NO: 1 ; (ii) amino acids 1 to 258 of the amino acid sequence depicted in SEQ ID NO: 2; or amino acids 1 to 229 of the amino acid sequence depicted in SEQ ID NO: 3.

In some embodiments, the anti-CD200 antibody binds to an epitope in the human CD200 protein lacking the leader sequence. For example, an anti-CD200 antibody described herein can bind to a CD200 protein at an epitope within or overlapping with amino acids 31 to 233 of the amino acid sequence depicted in SEQ ID NO: 1 , which corresponds to the extracellular portion of the mature form of human CD200 isoform A less the amino terminal leader sequence. In some embodiments, an anti-CD200 antibody described herein can bind to a CD200 protein at an epitope within or overlapping with amino acids 56 to 258 of the amino acid sequence depicted in SEQ ID NO: 2, which corresponds to the extracellular portion of the mature form of human CD200 isoform B less the amino terminal leader sequence. In some embodiments, an anti- CD200 antibody described herein can bind to a CD200 protein at an epitope within or overlapping with amino acids 27 to 229 of the amino acid sequence depicted in SEQ ID NO: 3, which corresponds to the extracellular portion of the mature form of human CD200 less the amino terminal leader sequence.

In some embodiments, the anti-CD200 antibody specifically binds to a human CD200 protein (e.g., the human CD200 protein having the amino acid sequence depicted in SEQ ID NO: 1, SEQ ID NO: 2, SEQ ID NO: 3, or the extracellular domains of the mature forms of the CD200 proteins). Methods for identifying the epitope to which a particular antibody binds are also know in the art.

The term "surface plasmon resonance", as used herein, refers to an optical phenomenon that allows for the analysis of real-time biospecific interactions by detection of alterations in protein concentrations within a biosensor matrix, for example using the BIAcore system

(Pharmacia Biosensor AB, Uppsala, Sweden and Piscataway, N.J.). For further descriptions, see Jonsson, U., et al. (1993) Ann. Biol. Clin. 51 : 19-26; Jonsson, U., et al. (1991) Biotechniqu.es 11 :620-627; Johnsson, B., et al. (1995) J. Mol. Recognit. 8: 125-131; and Johnsson, B., et al. (1991) Anal. Biochem. 198:268-277.

The term "K_0ff," as used herein, is intended to refer to the off rate constant for dissociation of an antibody from the antibody/antigen complex.

The term "Kd," as used herein, is intended to refer to the dissociation constant of a particular antibody-antigen interaction.

The terms "treat," "treating," and "treatment," as used herein, refer to therapeutic measures described herein. The methods of treatment employ administration to a subject (such as a human) the combination disclosed herein in order to cure, delay, reduce the severity of, or ameliorate one or more symptoms of the disease or disorder or recurring disease or disorder, or in order to prolong the survival of a subject beyond that expected in the absence of such treatment.

The term "subject" or "patient" are used interchangeably herein, and refer to a mammal such as a human, mouse, rat, hamster, guinea pig, rabbit, cat, dog, monkey, cow, horse, pig, llama, and the like.

The terms "effective amount" or "therapeutically effective amount" are used

interchangeably and refer to an amount of formulation, of antibody, or of antigen-binding fragment thereof, effective to alleviate or ameliorate one or more symptom(s) of disease (such as cancer and/or solid tumors) or to prolong the survival of the subject being treated. Determination of a therapeutically effective amount is well within the capability of those skilled in the art, especially in light of the detailed disclosure provided herein. Therapeutically effective dosages may be determined by using in vitro and in vivo methods.

The term "prophylaxis" refers to decreasing the likelihood of, or prevention of, a disease or condition (e.g., cancer, tumor burden, autoimmune disease, and allograft rejection).

As used herein, the term "chronically" (e.g., to chronically administer a compound), or similar terms, refers to a method of administration in which an agent (e.g., an anti-CD200 antibody) is administered to a subject in an amount and with a frequency sufficient to maintain an effective amount of the agent in the subject for at least seven (e.g., at least eight, nine, 10, 1 1 , 12, 13, 14, 15, 16, 17, 18, 19, 20, 21 , 22, 23, or 24) days. In some embodiments, an agent can be chronically administered to a subject for at least one (e.g. , at least two, three, four, five, or six) month(s). In some embodiments, an agent can be chronically administered to a subject for a year or more. In some embodiments, an agent can be administered to a subject for the lifetime of the patient.

An "immune response" refers to a biological response within a vertebrate against foreign agents, which response protects the organism against these agents and diseases caused by them. An immune response is mediated by the action of a cell of the immune system (for example, a T lymphocyte, B lymphocyte, natural killer (NK) cell, macrophage, eosinophil, mast cell, dendritic cell or neutrophil) and soluble macromolecules produced by any of these cells or the liver (including antibodies, cytokines, and complement) that results in selective targeting, binding to, damage to, destruction of, and/or elimination from the vertebrate's body of invading pathogens, cells or tissues infected with pathogens, cancerous or other abnormal cells, or, in cases of autoimmunity or pathological inflammation, normal human cells or tissues. An immune response or reaction includes, e.g. , activation or inhibition of a T cell, e.g. , an effector T cell or a Th cell, such as a CD4⁺ or CD8⁺ T cell, or the inhibition of a Treg cell.

"Immunotherapy" refers to the treatment of a subject afflicted with, or at risk of contracting or suffering a recurrence of, a disease by a method comprising inducing, enhancing, suppressing or otherwise modifying an immune response. "Immunostimulating therapy" or "immunostimulatory therapy" refers to a therapy that results in increasing (inducing or enhancing) an immune response in a subject for, e.g. , treating cancer and/or tumors. "Potentiating an endogenous immune response" means increasing the effectiveness or potency of an existing immune response in a subject. This increase in effectiveness and potency may be achieved, for example, by overcoming mechanisms that suppress the endogenous host immune response or by stimulating mechanisms that enhance the endogenous host immune response.

As used herein, the term "T cell-mediated response" refers to a response mediated by T cells, including effector T cells (e.g. , CD8⁺ cells) and helper T cells (e.g. , CD4⁺ cells). T cell mediated responses include, for example, T cell cytotoxicity and proliferation. As used herein, the term "cytotoxic T lymphocyte (CTL) response" refers to an immune response induced by cytotoxic T cells. CTL responses are mediated primarily by CD8⁺ T cells.

As used herein, the terms "inhibits" or "blocks" (e.g., referring to inhibition blocking of CD200 binding or activity) are used interchangeably, and encompass both partial and complete inhibition/blocking as well as antagonism of the binding between CD200 and CD200R.

As used herein, "cancer" refers to a broad group of diseases characterized by the uncontrolled growth of abnormal cells in the body. Unregulated cell division may result in the formation of malignant tumors or cells that invade neighboring tissues and may metastasize to distant parts of the body through the lymphatic system or bloodstream. As used herein, the term includes pre-malignant as well as malignant cancers.

As used herein, "solid tumor" refers to a subset of cancers characterized by abnormal mass of tissue which does not contain cysts or liquid areas. Examples include but are not limited to malignant sarcomas, carcinomas, and lymphomas.

As used herein, the term "hematological malignancy" includes a lymphoma, leukemia, myeloma or a lymphoid malignancy, as well as a cancer of the spleen and the lymph nodes. Exemplary lymphomas include both B cell lymphomas and T cell lymphomas.

An "ECOG performance status" is an attempt to quantify cancer patients' general well- being and activities of daily life. This measure is used to determine whether they can receive chemotherapy, whether dose adjustment is necessary, and as a measure for the required intensity of palliative care. It is also used in oncological randomized controlled trials as a measure of quality of life. A score of zero equals Fully active, able to carry on all pre-disease performance without restriction. A score of 1 equals Restricted in physically strenuous activity, but ambulatory and able to carry out work of a light or sedentary nature, e.g. , light house work or office work. A score of 2 equals Ambulatory and capable of all self-care but unable to carry out any work activities; up and about more than 50% of waking hours. A score of 3 equals Capable of only limited self-care and confined to bed or chair more than 50% of waking hours. A score of 4 equals Completely disabled; cannot carry on any self-care; totally confined to bed or chair. A score of 5 equals Dead.

Various aspects described herein are described in further detail in the following subsections.

II. Anti-CD200 Antibodies

Anti-CD200 antibodies for use in the methods provided herein are CD200 antagonists and include whole antibodies, or antibody fragments capable of binding to CD200, particularly anti-CD200 antibodies which disrupt the interaction between CD200 and CD200R. Exemplary anti-CD200 antibodies, or antigen binding fragments thereof .which can be used in the methods described herein include, but are not limited to, those disclosed in U.S. Patent Nos. 7,408,041 and 8,075,884; and WO 2012/106634 (the contents of each of which are herein incorporated by reference in their entirety).

In one embodiment, the anti-CD200 antibody, or antigen binding fragment thereof, comprises the CDRl, CDR2, and CDR3 domains of a heavy chain variable region having the sequence set forth in SEQ ID NO: 13, and the CDRl, CDR2, and CDR3 domains of a light chain variable region having the sequence set forth in SEQ ID NO: 12.

In another embodiment, the anti-CD200 antibody, or antigen binding fragment thereof, comprising the CDRl, CDR2 and CDR3 domains of a heavy chain region having the sequence set forth in SEQ ID NO: 11, and the CDRl, CDR2 and CDR3 domains of a light chain region having the sequence set forth in SEQ ID NO: 10.

In another embodiment, the anti-CD200 antibody, or antigen binding fragment thereof, comprises: (a) a light chain variable domain that comprises (i) a light chain CDRl comprising the sequence set forth in SEQ ID NO: 4, (ii) a light chain CDR2 comprising the sequence set forth in SEQ ID NO: 5, and (iii) a light chain CDR3 comprising the sequence set forth in SEQ ID NO: 6; and (b) a heavy chain variable domain comprising (i) a heavy chain CDRl comprising the sequence set forth in SEQ ID NO: 7, (ii) a heavy chain CDR2 comprising the sequence set forth in SEQ ID NO: 8 and (iii) a heavy chain CDR3 comprising the sequence set forth in SEQ ID NO: 9. In another embodiment, the antibody comprises a light chain region sequence as set forth in SEQ ID NO: 10 and/or a heavy chain variable region sequence as set forth in SEQ ID NO: 11. In one embodiment, the antibody comprises a light chain sequence as set forth in SEQ ID NO: 12 and/or a heavy chain sequence as set forth in SEQ ID NO: 13. In one embodiment, the anti- CD200 antibody is samalizumab (also known as ALXN6000; Alexion Pharmaceuticals, Inc., New Haven, CT).

Antibodies and antigen binding fragments thereof may be obtained according to established hybridoma and recombinant procedures. Suitable methods for producing an antibody (e.g. , an anti-CD200 antibody) or antigen-binding fragments thereof may be obtained according to established hybridoma and recombinant procedures as previously disclosed (see, e.g., U.S. Pat. Nos. 7,427,665; 7,435,412; and 7,408,041). For example, a process for the production of an antibody disclosed herein includes culturing a host (e.g., E. coli or a mammalian cell), which has been transformed with a hybrid vector. The vector includes one or more expression cassettes containing a promoter operably linked to a first DNA sequence encoding a signal peptide linked in the proper reading frame to a second DNA sequence encoding the antibody protein. The antibody protein is then collected and isolated. Optionally, the expression cassette may include a promoter operably linked to polycistronic, for example bicistronic, DNA sequences encoding antibody proteins each individually operably linked to a signal peptide in the proper reading frame.

Multiplication of hybridoma cells or mammalian host cells in vitro is carried out in suitable culture media, which include the customary standard culture media (such as, for example Dulbecco's Modified Eagle Medium (DMEM) or RPMI 1640 medium), optionally replenished by a mammalian serum (e.g. , fetal calf serum), or trace elements and growth sustaining supplements (e.g., feeder cells such as normal mouse peritoneal exudate cells, spleen cells, bone marrow macrophages, 2-aminoethanol, insulin, transferrin, low density lipoprotein, oleic acid, or the like). Multiplication of host cells which are bacterial cells or yeast cells is likewise carried out in suitable culture media known in the art. For example, for bacteria suitable culture media include medium LE, NZCYM, NZYM, NZM, Terrific Broth, SOB, SOC, 2xYT, or M9 Minimal Medium. For yeast, suitable culture media include medium YPD, YEPD, Minimal Medium, or Complete Minimal Dropout Medium. In vitro production provides relatively pure antibody preparations and allows scale-up to give large amounts of the desired antibodies. Techniques for bacterial cell, yeast, plant, or mammalian cell cultivation are known in the art and include homogeneous suspension culture {e.g., in an airlift reactor or in a continuous stirrer reactor), and immobilized or entrapped cell culture {e.g., in hollow fibers, microcapsules, on agarose microbeads or ceramic cartridges).

Large quantities of the desired antibodies can also be obtained by multiplying mammalian cells in vivo. For this purpose, cells producing the desired antibodies are injected into histocompatible mammals to cause growth of antibody-producing tumors. Optionally, the animals are primed with a hydrocarbon, especially mineral oils such as pristane (tetramethyl- pentadecane), prior to the injection. After one to three weeks, the antibodies are isolated from the body fluids of those mammals. For example, hybridoma cells obtained by fusion of suitable myeloma cells with antibody-producing spleen cells from Balb/c mice, or transfected cells derived from hybridoma cell line Sp2/0 that produce the desired antibodies are injected intraperitoneally into Balb/c mice optionally pre-treated with pristine. After one to two weeks, ascitic fluid is taken from the animals.

The antibody which is formulated is preferably essentially pure and desirably essentially homogeneous {e.g., free from contaminating proteins, etc.). "Essentially pure" antibody means a composition comprising at least about 90% by weight of the antibody, based on total weight of the composition, preferably at least about 95% by weight of the antibody. "Essentially homogeneous" antibody means a composition comprising at least about 99% by weight of antibody, based on total weight of the composition.

Techniques for purification of therapeutic antibodies to pharmaceutical grade are well known in the art. Exemplary techniques are discussed in, for example, Kohler and Milstein, (1975) Nature 256:495-497; U.S. Pat. No. 4,376,1 10; Harlow and Lane, Antibodies: A

Laboratory Manual (1988), Cold Spring Harbor, the disclosures of which are all incorporated herein by reference. Techniques for the preparation of recombinant antibody molecules are described in the above references and also in, for example WO97/08320; U.S. Pat. Nos. and Smith, 1985, Science, 225: 1315-1317; Parmley and Smith 1988, Gene 73, pp 305-318; De La Cruz et al, 1988, J.. Biol. Chem., 263:4318-4322; U.S. Pat. Nos. 5,223,409; 5,403,484;

5,427,908; 5,508,717; 5,571,698; 5,780,279; and 6,040,136; WO 88/06630; WO 92/15679; Davis et al., Cancer Metastasis Rev., 1999;18(4):421-5; Taylor, et al., Nucleic Acids Research 20 (1992): 6287-6295; Tomizuka et al., Proc. Nat. Academy of Sciences USA 97(2) (2000): 722-727 (the contents of each are incorporated herein by reference).

III. Compositions

In one aspect, the present disclosure provides a composition comprising an anti-CD200 antibody. In one embodiment, the anti-CD200 antibody is samalizumab. In another

embodiment, the composition comprises a anti-CD200 antibody, wherein the anti-CD200 antibody comprises the CDR1, CDR2, and CDR3 domains in a heavy chain variable region having the sequence set forth in SEQ ID NO: 11 and the CDR1, CDR2, and CDR3 domains in a light chain variable region having the sequence set forth in SEQ ID NO: 10.

Pharmaceutical compositions suitable for administration to human patients are typically formulated for parenteral administration, e.g., in a liquid carrier, or suitable for reconstitution into liquid solution or suspension for intravenous administration.

The compositions can be formulated according to standard methods. Pharmaceutical formulations are further described in, e.g., Gennaro (2000) "Remington: The Science and Practice of Pharmacy," 20^th Edition, Lippincott, Williams & Wilkins (ISBN: 0683306472); Ansel et al. (1999) Pharmaceutical Dosage Forms and Drug Delivery Systems, 7^th Edition, Lippincott Williams & Wilkins Publishers (ISBN: 0683305727); and Kibbe (2000) Handbook of Pharmaceutical Excipients American Pharmaceutical Association, 3^rd Edition (ISBN:

091733096X).

In general, such compositions typically comprise a pharmaceutically acceptable carrier. As used herein, the term "pharmaceutically acceptable" means approved by a government regulatory agency or listed in the U.S. Pharmacopeia or another generally recognized pharmacopeia for use in animals, particularly for use in humans. The term "carrier" refers to a diluent, adjuvant, excipient, or vehicle with which the agent is administered. Such

pharmaceutical carriers can be sterile liquids, such as water and oils, including those of petroleum, animal, vegetable or synthetic origin, such as peanut oil, soybean oil, mineral oil, sesame oil, glycerol polyethylene glycol ricinoleate, and the like. Water or aqueous solution saline and aqueous dextrose and glycerol solutions may be employed as carriers, particularly for injectable solutions. Liquid compositions for parenteral administration can be formulated for administration by injection or continuous infusion. Routes of administration by injection or infusion include intravenous, intraperitoneal, intramuscular, intrathecal and subcutaneous. For oral use, the pharmaceutical compositions of the present disclosure may be administered, for example, in the form of tablets or capsules, powders, dispersible granules, or cachets, or as aqueous solutions or suspensions. In the case of tablets for oral use, carriers which are commonly used include lactose, corn starch, magnesium carbonate, talc, and sugar, and lubricating agents such as magnesium stearate are commonly added. For oral administration in capsule form, useful carriers include lactose, corn starch, magnesium carbonate, talc, and sugar. When aqueous suspensions are used for oral administration, emulsifying and/or suspending agents are commonly added.

In addition, sweetening and/or flavoring agents may be added to the oral compositions. For intramuscular, intraperitoneal, subcutaneous and intravenous use, sterile solutions of the active ingredient(s) are usually employed, and the pH of the solutions should be suitably adjusted and buffered. For intravenous use, the total concentration of the solute(s) should be controlled in order to render the preparation isotonic.

For preparing suppositories according to the disclosure, a low melting wax such as a mixture of fatty acid glycerides or cocoa butter is first melted, and the active ingredient is dispersed homogeneously in the wax, for example by stirring. The molten homogeneous mixture is then poured into conveniently sized molds and allowed to cool and thereby solidify.

Liquid preparations include solutions, suspensions and emulsions. Such preparations are exemplified by water or water/propylene glycol solutions for parenteral injection. Liquid preparations may also include solutions for intranasal administration.

Also included are solid preparations which are intended for conversion, shortly before use, to liquid preparations for either oral or parenteral administration, including lyophylisates. Such liquid forms include solutions, suspensions and emulsions.

IV. Patient Populations

Provided herein are effective methods for treating cancer, particularly solid tumors (e.g., an advanced solid tumor), in a patient, e.g., using an anti-CD200 antibody. Cancers for which the disclosed methods may be used include but are not limited to a solid tumor of the colon, stomach, salivary glands, lung (e.g. , small-cell lung cancer or non-small cell lung cancer), skin, thyroid, prostate, breast, ovaries, cervix, vagina, testicles, bladder, liver, lymphatic tissue (e.g., Hodgkin's disease or non-Hodgkin's lymphomas), bone (e.g., osteogenic sarcoma or Ewing's Sarcoma), kidney (e.g., Wilms' tumor), eye (e.g., retinoblastoma), adrenal glands (e.g., neuroblastoma or adrenocortical carcinoma), soft tissue (e.g., rhabdomyosarcoma or

rhabdosarcoma), ovary, pancreas, brain, head, or neck. In another embodiment, the solid tumor is selected from the group consisting of an: adrenocortical tumor, alveolar soft part sarcoma, carcinoma, chondrosarcoma, colorectal carcinoma, desmoid tumor, desmoplastic small round cell tumor, endocrine tumor, endodermal sinus tumor, epithelioid hemangioendothelioma, Ewing sarcoma, germ cell tumor, hepatoblastoma, hepatocellular carcinoma, melanoma, nephroma, neuroblastoma, non-rhabdomyosarcoma soft tissue sarcoma (NRSTS), osteosarcoma, paraspinal sarcoma, renal cell carcinoma, retinoblastoma, rhabdomyosarcoma, synovial sarcoma, pediatric brain and extracranial solid tumor, and Wilms Tumor. In another embodiment, the tumor is derived from neural crest cells and any tumor that expresses CD200.

In one embodiment, the subject treated according to the methods provided herein has a cancer which over-expresses CD200 relative to normal cells of the same histological type as the cells from which the cancer cells are derived. Methods of determining the expression of CD200 are known and described, for example, in U.S. Patent No. 7,435,412; U.S. Patent No. 8,709,415; and U.S. Patent No. 9,085,623.

V. Additional Agents/Therapies

The anti-CD200 antibodies provided herein can also be administered in combination with other immunomodulatory compounds, vaccines, or chemotherapy. As used herein, adjunctive or combined administration (coadministration) includes simultaneous administration of the compositions with the immunomodulatory compound, vaccine or chemotherapy, in the same or different dosage form, or separate administration of the compounds (e.g., sequential

administration). Such concurrent or sequential administration preferably results in both the anti- anti-CD200 antibodies and the one or more agents being simultaneously present in treated patients. Thus, the anti-CD200 composition and immunomodulatory compounds, vaccines or chemotherapy, can be simultaneously administered in a single formulation. Alternatively, the anti-CD200 composition and immunomodulatory compounds, vaccines or chemotherapy, can be formulated for separate administration and are administered concurrently or sequentially.

In one embodiment, the treatment methods described herein comprise administering the anti-CD200 antibodies in combination with one or more other antineoplastic agents (e.g. , other chemotherapeutics or other small molecule drugs). In one embodiment, no more than three other antineoplastic agents are administered within a treatment cycle. In another embodiment, no more than two other antineoplastic agents are administered within a treatment cycle. In another embodiment, no more than one other antineoplastic agent is administered within a treatment cycle. In another embodiment, no other antineoplastic agent is administered within a treatment cycle.

Illustrative examples of suitable immunomodulatory therapies include the administration of agents that block negative regulation of T cells or antigen presenting cells (e.g., anti-CTLA4 antibodies, anti-PD-Ll antibodies, anti-PDL-2 antibodies, anti-PD- 1 antibodies and the like) or the administration of agents that enhance positive co-stimulation of T cells (e.g. , anti-CD40 antibodies or anti 4-1BB antibodies). Furthermore, immunomodulatory therapy could be cancer vaccines such as dendritic cells loaded with tumor cells, tumor RNA or tumor DNA, tumor protein or tumor peptides, patient derived heat-shocked proteins (HSPs) or general adjuvants stimulating the immune system at various levels such as CpG, Luivac, Biostim, Ribominyl, Imudon, Bronchovaxom or any other compound activating receptors of the innate immune system (e.g. , toll-like receptors). Also, immunomodulatory therapy could include treatment with cytokines such as IL-2, GM-CSF, and IFN-gamma.

Accordingly in some embodiments, the methods of treatment provided herein enhance the immune response to cancer cells by the administration of the anti-CD200 compositions provided herein, alone or in combination with one of the previously mentioned

immunomodulatory therapies. For example, in certain embodiments, the compositions provided herein may be used in combination with a monoclonal antibody (e.g. , rituximab, trastuzumab, alemtuzumab, cetuximab, or bevacizumab), including a conjugated monoclonal antibody (e.g., gemtuzumab, ozogamicin, ibritumomab tiuxetan, or tositumomab).

The anti-CD200 antibodies of the present disclosure (e.g., samalizumab) may also be used in conjunction with other therapies that are selected for their particular usefulness against the cancer that is being treated. Combinations of the present disclosure may alternatively be used sequentially with known pharmaceutically acceptable agent(s) when inappropriate.

For example, the anti-CD200 antibodies described herein can further be used in combination (e.g. , simultaneously or separately) with an additional treatment, such as irradiation, chemotherapy (e.g. , using cytarabine, daunorubicin, camptothecin (CPT-11), 5-fluorouracil (5- FU), cisplatin, doxorubicin, irinotecan, paclitaxel, gemcitabine, cisplatin, paclitaxel, doxorubicin, 5-fu, or camptothecin + apo21/TRAIL (a 6X combo)), one or more proteasome inhibitors (e.g., bortezomib or MG132), one or more Bcl-2 inhibitors (e.g., BH3I-2' (bcl-xl inhibitor), AT-101 (R-(-)-gossypol derivative), ABT-263 (small molecule), GX- 15-070 (obatoclax), or MCL- 1 (myeloid leukemia cell differentiation protein- 1) antagonists), iAP (inhibitor of apoptosis protein) antagonists (e.g., smac7, smac4, small molecule smac mimetic, synthetic smac peptides (see Fulda et al, Nat Med 2002;8:808-15), ISIS23722 (LY2181308), or AEG-35156 (GEM- 640)), HDAC (histone deacetylase) inhibitors, anti-CD20 antibodies (e.g., rituximab), angiogenesis inhibitors (e.g. , bevacizumab), anti-angiogenic agents targeting VEGF and

VEGFR, synthetic triterpenoids (see Hyer et al, Cancer Research 2005;65:4799-808), c-FLIP (cellular FLICE-inhibitory protein) modulators (e.g., natural and synthetic ligands of PPARy (peroxisome proliferator-activated receptor γ), kinase inhibitors (e.g. , Sorafenib, Vemurafenib), and/or genotoxic drugs.

The anti-CD200 antibodies described herein can further be used in combination with one or more anti-proliferative cytotoxic agents. Classes of compounds that may be used as antiproliferative cytotoxic agents include, but are not limited to, the following:

Alkylating agents (including, without limitation, nitrogen mustards, ethylenimine derivatives, alkyl sulfonates, nitrosoureas and triazenes): Uracil mustard, Chlormethine, Cyclophosphamide (CYTOXAN^®), fosfamide, Melphalan, Chlorambucil, Pipobroman,

Triethylenemelamine, Triethylenethiophosphoramine, Busulfan, Carmustine, Lomustine, Streptozocin, Dacarbazine, and Temozolomide.

Antimetabolites (including, without limitation, folic acid antagonists, pyrimidine analogs, purine analogs and adenosine deaminase inhibitors): methotrexate, 5-Fluorouracil, floxuridine, dytarabine, 6-Mercaptopurine, 6-Thioguanine, fludarabine phosphate, pentostatine, and gemcitabine.

Suitable anti-proliferative agents for use in the methods of disclosed herein, include, without limitation, taxanes, paclitaxel (paclitaxel is commercially available as

TAXOL^®)(tamoxifen), docetaxel, discodermolide (DDM), dictyostatin (DCT), Peloruside A, epothilones, epothilone A, epothilone B, epothilone C, epothilone D, epothilone E, epothilone F, furanoepothilone D, desoxyepothilone Bl, [17]-dehydrodesoxyepothilone B,

[18]dehydrodesoxyepothilones B, C12,13-cyclopropyl-epothilone A, C6-C8 bridged epothilone A, trans-9, 10-dehydroepothilone D, cis-9, 10-dehydroepothilone D, 16-desmethylepofhilone B, epothilone B 10, discoderomolide, patupilone (EPO-906), KOS-862, KOS- 1584, ZK-EPO, ABJ- 789, XAA296A (Discodermolide), TZT-1027 (soblidotin), ILX-651 (tasidotin hydrochloride), Halichondrin B, Eribulin mesylate (E-7389), Hemiasterlin (HTI-286), E-7974, Cy tophycins, LY-355703, Maytansinoid immunoconjugates (DM-1), MKC- 1, ABT-751 , Tl-38067, T-900607, SB-715992 (ispinesib), SB-743921 , MK-0731 , STA-5312, eleutherobin, 17-p-acetoxy-2-ethoxy- 6-oxo-B-homo-estra- l,3,5(10)-trien-3-ol, cyclostreptin, isolaulimalide, laulimalide, 4-epi-7- dehydroxy-14, 16-didemethyl-(+)-discodermolides, and cryptothilone 1, in addition to other microtubule stabilizing agents known in the art.

In cases where it is desirable to render aberrantly proliferative cells quiescent in conjunction with or prior to treatment with the chemotherapeutic methods of the disclosure, hormones and steroids (including synthetic analogs), such as 17a-Ethinylestradiol,

Diethylstilbestrol, Testosterone, Prednisone, Fluoxymesterone, Dromostanolone propionate, Testolactone, Megestrolacetate, Methylprednisolone, Methyl-testosterone, Prednisolone, Triamcinolone, Chlorotrianisene, Hydroxyprogesterone, Aminoglutethimide, Estramustine, Medroxyprogesteroneacetate, Leuprolide, Flutamide, Toremifene, ZOLADEX® (goserelin acetate), can also be administered to the patient. When employing the methods or compositions of the present disclosure, other agents used in the modulation of tumor growth or metastasis in a clinical setting, such as antimimetics, can also be administered as desired.

Methods for the safe and effective administration of chemotherapeutic agents are known to those skilled in the art and described in the literature. For example, chemotherapeutic agent administration is described in the Physicians' Desk Reference (PDR), e.g. , 1996 edition (Medical Economics Company, Montvale, N.J. 07645- 1742, USA); the disclosure of which is incorporated herein by reference.

The chemotherapeutic agent(s) and/or radiation therapy can be administered according to known therapeutic protocols. The administration of the chemotherapeutic agent(s) and/or radiation therapy can be varied depending on the disease being treated and the known effects of the chemotherapeutic agent(s) and/or radiation therapy on that disease. Also, in accordance with the knowledge of the skilled clinician, the therapeutic protocols (e.g. , dosage amounts and times of administration) can be varied in view of the observed effects of the administered therapeutic agents on the patient, and in view of the observed responses of the disease to the administered therapeutic agents. VI. Treatment Protocols

Suitable treatment protocols for treating a solid tumor (e.g., advanced solid tumor) in a patient (e.g., human) include, for example, administering to the patient an effective amount of an anti-CD200 antibody, or antigen-binding fragment thereof.

In one embodiment, the anti-CD200 antibody, or antigen binding fragment thereof, is administered at a dose of 5 mg/kg to 50 mg/kg (or about 5 mg/kg to about 50 mg/kg). In another embodiment, the anti-CD200 antibody, or antigen binding fragment thereof, is administered at a dose of 10 mg/kg to 40 mg/kg (or about 10 mg/kg to about 40 mg/kg). In another embodiment, the anti-CD200 antibody, or antigen binding fragment thereof, is administered at a dose of 15mg/kg to 30 mg/kg (or about 15 mg/kg to about 30 mg/kg). In another embodiment, the anti- CD200 antibody, or antigen binding fragment thereof, is administered at a dose of 5 mg/kg (or about 5 mg/kg). In another embodiment, the anti-CD200 antibody, or antigen binding fragment thereof, is administered at a dose of 10 mg/kg (or about 10 mg/kg). In another embodiment, the anti-CD200 antibody, or antigen binding fragment thereof, is administered at a dose of 15 mg/kg (or about 15 mg/kg). In another embodiment, the anti-CD200 antibody, or antigen binding fragment thereof, is administered at a dose of 20 mg/kg (or about 20 mg/kg). In another embodiment, the anti-CD200 antibody, or antigen binding fragment thereof, is administered at a dose of 25 mg/kg (or about 25 mg/kg). In another embodiment, the anti-CD200 antibody, or antigen binding fragment thereof, is administered at a dose of 30 mg/kg (or about 30 mg/kg). In another embodiment, the anti-CD200 antibody, or antigen binding fragment thereof, is administered at a dose of 35 mg/kg (or about 35 mg/kg). In another embodiment, the anti- CD200 antibody, or antigen binding fragment thereof, is administered at a dose of 40 mg/kg (or about 40 mg/kg). In another embodiment, the anti-CD200 antibody, or antigen binding fragment thereof, is administered at a dose of 45 mg/kg (or about 45 mg/kg). In another embodiment, the anti-CD200 antibody, or antigen binding fragment thereof, is administered at a dose of 50 mg/kg (or about 50 mg/kg). In another embodiment, the anti-CD200 antibody, or antigen binding fragment thereof, is administered at a dose of 55 mg/kg (or about 55 mg/kg).

In another embodiment, the amount of the anti-CD200 antibody administered is constant for each dose. In another embodiment, the amount of the anti-CD200 antibody varies with each dose. For example, at least one maintenance (or follow-on) dose of the antibody can be higher or the same as the loading dose which is first administered. In another embodiment, the maintenance dose can be lower than the loading dose. A clinician may utilize preferred dosages as warranted by the condition of the patient being treated. The dose of may depend upon a number of factors, including stage of disease, DLTs, AEs, etc. Generally, treatment is initiated with smaller dosages which are less than the optimum dose of the compound. Thereafter, the dosage is increased by small amounts until the optimum effect under the circumstances is reached. For convenience, the total daily dosage may be divided and administered in portions during the day if desired. The total weekly dosage may similarly be divided over several administrations over one day or over several days. Intermittent therapy (e.g., one week out of three weeks or three out of four weeks) may also be used.

In one embodiment, methods of treating a patient with a solid tumor are provided, wherein the method comprises administering to the patient about 10 mg/kg, about 15 mg/kg, or about 20 mg/kg of an anti-CD200 antibody, or antigen-binding fragment thereof, wherein the anti-CD200 antibody, or antigen-binding fragment thereof, comprises a heavy chain variable region CDRl having the sequence set forth in SEQ ID NO: 7, a heavy chain variable region CDR2 having the sequence set forth in SEQ ID NO: 8, a heavy chain variable region CDR3 having the sequence set forth in SEQ ID NO: 9, a light chain variable region CDRl having the sequence set forth in SEQ ID NO: 4, a light chain variable region CDR2 having the sequence set forth in SEQ ID NO: 5, and a light chain variable region CDR3 having the sequence set forth in SEQ ED NO: 6. In a particular embodiment, 10 mg/kg of the anti-CD200 antibody, or antigen- binding fragment thereof, is administered to the patient. In another particular embodiment, 15 mg/kg of the anti-CD200 antibody, or antigen-binding fragment thereof, is administered to the patient. In another particular embodiment, 20 mg/kg of the anti-CD200 antibody, or antigen- binding fragment thereof, is administered to the patient.

In another embodiment, methods of treating a patient with a solid tumor are provided, the method comprising administering intravenously to the patient about 10 mg/kg, about 15 mg/kg, or about 20 mg/kg of an anti-CD200 antibody, or antigen-binding fragment thereof, once every twenty-one days, wherein the anti-CD200 antibody, or antigen-binding fragment thereof, comprises a heavy chain variable region CDRl having the sequence set forth in SEQ ID NO: 7, a heavy chain variable region CDR2 having the sequence set forth in SEQ ID NO: 8, a heavy chain variable region CDR3 having the sequence set forth in SEQ ID NO: 9, a light chain variable region CDRl having the sequence set forth in SEQ ID NO: 4, a light chain variable region CDR2 having the sequence set forth in SEQ ID NO: 5, and a light chain variable region CDR3 having the sequence set rorth in i>hiQ ID J L): 6.

In one embodiment, the anti-CD200 antibody, or antigen-binding fragment thereof, is administered every two weeks. In another embodiment, the anti-CD200 antibody, or antigen- binding fragment thereof, is administered every three weeks. In another embodiment, the anti- CD200 antibody, or antigen-binding fragment thereof, is administered every four weeks. In another embodiment, the anti-CD200 antibody, or antigen-binding fragment thereof, is administered every 13 days to every 24 days (e.g., every 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, or 24 days). In another embodiment, the anti-CD200 antibody, or antigen-binding fragment thereof, is administered every 21 days.

In another embodiment, a treatment cycle is 21 days. In another embodiment, a treatment cycle is 14 days. In another embodiment, the treatment comprises at least 1, 2, 3, 4, or 5 cycles.

In another embodiment, the anti-CD200 antibody, or antigen-binding fragment thereof, inhibits the interaction between CD200 and CD200R. In another embodiment, treatment results in a CD200 saturation of≥ 90%. In another embodiment, the CD200 is saturated from about 80% to about 100%. In other embodiments, the CD200 is saturated from about 80% to about 90%. In another embodiment, the method of treatment results in a CD200 saturation of at least 60%, 61 %, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71 %, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81 %, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% .

Treatment with the anti-CD200 antibody, or antigen-binding fragment thereof, is continued for any suitable period of time (e.g., until a CR or a PR has been achieved). In one embodiment, the anti-CD200 antibody, or antigen-binding fragment thereof, is administered for at least 1 month, 2 months, 3 months, 4 months, 5 months, 6 months, 7 months, 8 months, 9 months, 10 months, or 11 months. In another embodiment, the anti-CD200 antibody, or antigen- binding fragment thereof, is administered for at least one year. In another embodiment, the anti- CD200 antibody, or antigen-binding fragment thereof, is administered for at least two years. In another embodiment, the anti-CD200 antibody, or antigen-binding fragment thereof, is administered every 21 days for at least 1 month, 2 months, 3 months, 4 months, 5 months, 6 months, 7 months, 8 months, 9 months, 10 months, 1 1 months, one year, or two years, up to the lifetime of the human patient.

In another aspect, treatment produces a median change from baseline for

CD200⁺CD4⁺Tcells of about 80% to about 90%. In another embodiment, the treatment produces a change from baseline for CD200⁺CD4⁺Tcells of about 80% to about 100%. In other embodiments, the change from baseline is at least about 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91 , 92, 93, 94, 95, 96, 97, 98, 99, or 100%.

In some embodiments, determining whether an anti-CD200 antibody has produced a desired immunomodulatory effect in a human can be performed by querying whether the post- treatment CD200⁺ leukocyte or CD200⁺ bone marrow cell concentration falls within a predetermined range indicative of the occurrence of a desired immunomodulatory effect by an anti-CD200 antibody in a human. In some embodiments, determining whether an anti-CD200 antibody has produced a desired immunomodulatory effect in a human can include querying if the post-treatment CD200⁺ leukocyte or CD200⁺ bone marrow cell concentration for a given histological type of CD200⁺ leukocytes or CD200⁺ bone marrow cells falls above or below a predetermined cut-off value. A cut-off value is typically the concentration of CD200⁺ leukocytes or CD200⁺ bone marrow cells of a given histological type above or below which is considered indicative of a certain phenotype— namely the occurrence of a desired

immunomodulatory effect in a human produced by an anti-CD200 antibody.

In some embodiments, the methods described herein can include the step of determining whether one or more cancer cells of a human patient's cancer express CD200. In some embodiments, the methods can include determining whether one or more cancer cells of the human's cancer overexpress CD200, relative to a control sample. In some embodiments, the control sample is obtained from the same human and comprises normal cells of the same tissue type as the human's cancer. In some embodiments, the control sample can be the expression level (or average expression level) of cells obtained from one or more humans who do not have cancer. In some embodiments, the cancer comprises cells (e.g. , a plurality or even a majority of cells) that express or overexpress CD200 (e.g., CD200 protein and/or CD200 mRNA). In some embodiments, at least (or greater than) 10% (e.g. , 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, or 95%) of the cancer cells of the human's cancer overexpress CD200. In some embodiments, all assayed cancer cells overexpress CD200 relative to normal cells. In some embodiments, a cancer cell (e.g. , a plurality of cancer cells, at least 10% of cancer cells, or all assayed cancer cells) can express CD200 protein at levels at least about 1.4 (e.g. , at least about 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.2, 2.5, 3.0, 3.5, 4.0, 4.5, or 5 or more) -fold higher than the expression levels found on normal cells of the same histological type or higher than the average expression of normal cells from one or more patients who do not have cancer.

In some embodiments, an anti-CD200 antibody blocks immune suppression in cancer by targeting cancer cells that express CD200. Eradication, or inhibition, of these cancer cells can stimulate the immune system and allow further eradication of cancer cells. In some

embodiments, the combination of direct cancer cell killing and driving the immune response towards a Thl profile provides enhanced efficacy in cancer treatment. Thus, in one embodiment, a cancer treatment is provided wherein a CD200 antibody or antigen-binding fragment thereof, both a) blocks the interaction between CD200 and its receptor and b) directly kills the cancer cells expressing CD200, and is administered to a cancer patient. The mechanism by which the cancer cells are killed can include, but is not limited to, ADCC or CDC; fusion with a toxin; fusion with a toxic radioactive agent; fusion with a toxic polypeptide such as granzyme B or perforin; fusion with a cytotoxic virus (e.g. , cytotoxic reovirus such as REOLYSIN^®); or fusion with a cytokine such as TNF-a or IFN-a. In an alternative embodiment, a cancer treatment involves administering an antibody that both a) blocks the interaction between CD200 and its receptor and b) enhances cytotoxic T cell or NK cell activity against the tumor. Such

enhancement of the cytotoxic T cell or NK cell activity may, for example, be combined by fusing the antibody with cytokines such as, e.g. , IL-2, IL-12, IL-18, IL-13, and IL-5. In addition, such enhancement may be achieved by administration of an anti-CD200 antibody in combination with inhibitors such as DVliDs, thalidomide, or thalidomide analogs.

VII. Outcomes

Patients, e.g., humans, treated according to the methods disclosed herein preferably experience improvement in at least one sign of cancer (e.g., a solid tumor). In one embodiment, improvement is measured by a reduction in the quantity and/or size of measurable tumor lesions. In another embodiment, lesions can be measured on X-rays, chest X-rays, or CT or MRI films. In another embodiment, cytology or histology can be used to evaluate responsiveness to a therapy.

In another embodiment, the treatment results in a reduction in tumor burden as assessed by a computerized tomography (CT) scan. In another embodiment, the treatment results in a complete response (CR), a partial response (PR), or stable disease. In one embodiment, stable disease is 12 weeks (84 days) of tumor nonprogression. In another embodiment, the treatment results in a reduction in tumor burden according to RECIST 1.1 parameters (Response

Evaluation Criteria in Solid Tumors Version 1.1 (RECIST 1.1, Eisenhauer, E.A., et al., European J. Cancer 45: 228-247(2009)) or to irRECIST parameters (Immune-related response evaluation criteria in solid tumors, Wolchok JD, et al., Clin Cancer Res. 15 (23): 7412-20 (2009)). In another embodiment, treatment produces at least one therapeutic effect selected from the group consisting of reduction in growth rate of tumor, reduction in size of tumor, reduction in number of metastatic lesions over time, increase in duration of progression-free survival, and/or increase in overall response rate. In another embodiment, the patient treated experiences tumor shrinkage and/or decrease in growth rate, i.e., suppression of tumor growth. In another embodiment, unwanted cell proliferation is reduced or inhibited. In yet another embodiment, one or more of the following can occur: the number of cancer cells can be reduced; tumor size can be reduced; cancer cell infiltration into peripheral organs can be inhibited, retarded, slowed, or stopped; tumor metastasis can be slowed or inhibited; tumor growth can be inhibited; recurrence of tumor can be prevented or delayed; one or more of the symptoms associated with cancer can be relieved to some extent.

In another aspect, the treatment produces a desired immunomodulatory effect in a human (e.g., a patient with a solid tumor). The immunomodulatory effect can be characterized by a change (e.g., an increase or a decrease) in at least one biomarker, e.g., an anti-CD200 antibody- associated immunomodulatory biomarker described herein, the change selected from the group consisting of: (i) a reduced concentration of regulatory T cells, relative to the concentration of regulatory T cells of the same histological type in the human prior to the first administration of the antibody; (ii) an increased concentration of CD8⁺ T cells, relative to the concentration of CD8⁺ T cells of the same histological type in the human prior to the first administration of the antibody; (iii) an increased concentration of activated T cells, relative to the concentration of activated T cells of the same histological type in the human prior to the first administration of the antibody; (iv) a reduced concentration of CD200⁺ leukocytes (e.g., CD200⁺ T cells), relative to the concentration of CD200⁺ leukocytes of the same histological type in the human prior to the first administration of the antibody; (v) an increase in the concentration of CD200R⁺ leukocytes (e.g. , CD200R⁺ T cells), relative to the concentration of CD200R⁺ leukocytes of the same histological type in the human prior to the first administration of the antibody; (vi) a ratio of percent activated T cells to percent regulatory T cells (Tregs) of at least 2: 1 (e.g., at least 3: 1, at least 4: 1, at least 5: 1, at least 6: 1 , or at least 7: 1), relative to the ratio of activated T cells to Tregs in the human prior to the first administration of the antibody; (vii) a decreased level of CD200 expression by a plurality of leukocytes in a biological sample obtained from a patient prior to administration to the patient of an anti-CD200 antibody, relative to the level of CD200 expression by a plurality of leukocytes of the same histological type in a biological sample from the patient prior to administration of the antibody; and (viii) an increased level of CD200R expression by a plurality of leukocytes in a biological sample from a patient administered an anti-CD200 antibody, relative to the level of CD200R expression by a plurality of leukocytes in a biological sample from the patient prior to administration of the anti-CD200 antibody.

In another embodiment, administration of an anti-CD200 antibody results in at least a 1.5-fold (e.g., a 1.6, 1.7, 1.8, or 1.9-fold), two-fold (e.g., a 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, or 2.9-fold), three-fold (e.g., a 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, or 3.9-fold), or four-fold (e.g., a 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, or 4.9-fold) reduction in tumor volume, e.g., relative to tumor growth on the first day of treatment or immediately before initiation of treatment.

In a further embodiment, administration of an anti-CD200 antibody results in tumor growth inhibition of at least 80%, e.g. , relative to tumor growth on the first day of treatment or immediately before initiation of treatment.

In certain embodiments, administration of an anti-CD200 antibody reduces tumor mass by at least about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 99% relative to the tumor mass prior to initiation of the treatment or on the first day of treatment. In some embodiment, the tumor mass is no longer detectable following treatment as described herein. In some embodiments, a subject is in partial or full remission. In certain embodiments, a subject has an increased overall survival, median survival rate, and/or progression free survival.

In some embodiments, a reduction in CD200 expression by a plurality of leukocytes (e.g. , bone marrow cells or splenocytes) in a biological sample obtained from the patient after administration of the anti-CD200 antibody, as compared to a control expression level (e.g. , the level of CD200 expression in a plurality of leukocytes of the same histological type in a biological sample obtained from the patient prior to administration of the anti-CD200 antibody) indicates that the anti-CD200 antibody has produced a desired immunomodulatory effect in the human. It is understood that any of the methods described herein can involve determining whether there has been a change (e.g. , an increase or a decrease) in two or more (e.g. , three, four, five, six, seven, eight, nine, 10, or more) of the anti-CD200 antibody-associated biomarkers described herein. Where interrogation of more than one of the biomarkers is practiced, any combination of two or more (e.g. , three, four, five, six, seven, eight, nine, 10, or more) of the biomarkers can be analyzed.

In embodiments in which at least two (e.g. , at least three, four, five, six, seven, eight, nine, 10, 1 1 , 12, 13, 14, or more) doses of the anti-CD200 antibody are administered to the human prior to detecting a change (e.g. , an increase or a decrease) in the at least one biomarker, the detecting can occur, e.g. , within (or less than) two months (e.g. , less than eight weeks, seven weeks, six weeks, five weeks, one month, four weeks, three weeks, two weeks or 13 days, 12 days, 11 days, 10 days, nine days, eight days, seven days, six days, five days, or less than 5 days), and/or not until at least 1 day (e.g. , at least two days, three days, four days, five days, six days, seven days, eight days, nine days, 10 days, 1 1 days, 12 days, 13 days, 14 days, 15 days, 16 days, 17 days, 18 days, 19 days, 20 days, or three weeks, four weeks, a month, five weeks, six weeks, seven weeks, or eight weeks or more) after, the last dose of the multiple dose anti-CD200 antibody regimen is administered to the human. In some embodiments, the detecting can occur between dosing (e.g. , between the first and second dose, between the second and third dose, between the third and fourth dose, between the fifth and six dose, and/or between the seventh and eighth dose). Such detection can be useful for determining a dosing schedule for the human that is effective to maintain the immunomodulatory effect (e.g. , the peak or maximum level of the immunomodulatory effect) in the human over the course of treatment.

In some embodiments of any of the methods described herein, the regulatory T cells can be FoxP3⁺, e.g. , CD3⁺CD4⁺CD25⁺FoxP3⁺ T cells or CD3⁺CD4⁺FoxP3⁺ T cells. In some embodiments of any of the methods described herein, the activated T cells can be, e.g. ,

CD3⁺CD4⁺CD25⁺FoxP3^neg T cells or CD3⁺CD4⁺FoxP3^neg T cells. Methods for measuring the concentration of CD200⁺ cells (e.g., CD200⁺ T cells) are well known in the art and include, among other methods, flow cytometry. See, e.g. , Chen et al.

(2009) Mol Immunol 46( 10) : 1951 - 1963. In some embodiments, a practitioner can interrogate a biological sample obtained from a post-treatment patient (a patient to which an anti-CD200 antibody has already been administered) for the concentration of cells of a particular subset of CD200⁺ leukocytes (e.g., T cells). For example, a practitioner can determine the concentration of CD200⁺/CD4⁺ T cells and/or the concentration of activated CD200⁺/CD4⁺ T cells present in a biological sample from a post-treatment patient. In some embodiments, a practitioner can determine the concentration of CD200⁺/CD8⁺ cells. In each case, a reduction in the

concentration of CD200⁺ T cells of a given subset, as compared to control concentration of CD200⁺ T cells of the same histological type, indicates that the anti-CD200 antibody has produced in the human a desired immunomodulatory effect.

Methods for quantifying the expression level of CD200 and/or CD200R by a cell or a population of cells are well known in the art and include, among other methods, Western blotting, dot blotting, and flow cytometry, which are useful for quantifying expression of protein, or reverse transcriptase polymerase chain reaction (RT-PCR) and Northern blotting analysis for quantifying expression of mRNA. See, e.g. , Walker et al. (2009) Exp Neurol 215(1):5-19;

Rijkers et al. (2008) Mol Immunol 45(4): 1 126-1135; and Voehringer et al. (2004) J Biol Chem 279(52):541 17-54123, and generally Sambrook et al. (1989) "Molecular Cloning: A Laboratory Manual, 2^nd Edition," Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y. and Ausubel et al. (1992) "Current Protocols in Molecular Biology," Greene Publishing Associates.

In some embodiments, a practitioner can interrogate a biological sample (e.g., a blood sample) obtained from a post-treatment patient (a patient to which an anti-CD200 antibody has been administered) for the CD200 and/or CD200R expression level (e.g. , the average expression level) by a plurality of leukocytes of a given histological type. For example, a practitioner can determine the expression level or average expression level of CD200R by a plurality of CD4⁺ T cells, CD8⁺ T cells, activated CD4⁺ T cells, NK T cells, or CD217CD257Fox3P⁺ T cells. In one instance, an increase in CD200R expression by a given subset of leukocytes, as compared to control expression level (e.g., the average level of expression of leukocytes of the same histological type in a biological sample obtained from the patient prior to administration of the antibody), indicates that the anti-CD200 antibody has produced in the human a desired immunomodulatory effect.

In some embodiments, immune competence can be determined by quantifying the absolute number of certain lymphocyte populations in a biological sample (e.g., a blood sample) obtained from a patient as measured by, e.g., flow cytometry. See, e.g., Shearer et al. (2003) J Allergy Clin Immunol 112(5):973-980 and Paglieroni and Holland (1994) Transfusion 34:512- 516. For example, in some embodiments, immune competence is indicated by a CD45⁺ lymphocyte count, by flow cytometry, of: 0.66-4.60xl0³ cells/μL (for patients 0 to 17 years of age); 0.99-3.15xl0³ cells/uL (for patients aged 18 to 55 years); or 1.00-3.33xl0³ cells/uL (for patients older than 55 years).

In some embodiments, immune competence can be determined by quantifying the absolute number of CD3⁺ T cells, by flow cytometry, in a biological sample obtained from a patient. For example, in some embodiments, immune competence is indicated by a CD3⁺ lymphocyte count, by, e.g. , flow cytometry, of: 2,500-5,500 cells/μL (for patients 0 to 2 months of age); 2,500-5,600 cells/uL (for patients aged 3 to 5 months); 1,900-5,900 cells/μL (for patients aged 6 to 1 1 months); 2, 100-6,200 cells/μL (for patients aged 12 to 23 months); 1 ,400-3,700 cells/μL (for patients aged 2 to 5 years); 1,200-2,600 cells/μL (for patients aged 6 to 11 years); 1 ,000-2,200 cells/^L (for patients aged 12 to 17 years); 677-2,383 cells/μL (for patients aged 18 to 55 years); or 617-2,254 cells/μL (for patients older than 55 years of age).

In some embodiments, immune competence can be determined by quantifying the absolute number of CD19⁺ B cells, by, e.g., flow cytometry, in a biological sample obtained from a patient. For example, in some embodiments, immune competence is indicated by a CD19⁺ B cell count, by flow cytometry, of: 300-2,000 cells/μL (for patients 0 to 2 months of age); 430-3,000 cells/μL (for patients aged 3 to 5 months); 610-2,600 cells/uL (for patients aged 6 to 1 1 months); 720-2,600 cells/μL (for patients aged 12 to 23 months); 390-1,400 cells/μL (for patients aged 2 to 5 years); 270-860 cells/μL (for patients aged 6 to 11 years); 110-570 cells^L (for patients aged 12 to 17 years); 99-527 cells/ uL (for patients aged 18 to 55 years); or 31-409 cells/μL (for patients older than 55 years of age).

In some embodiments, immune competence can be determined by quantifying the absolute number of CD16⁺CD56⁺ Natural Killer (NK) cells, by, e.g., flow cytometry, in a biological sample obtained from a patient. For example, in some embodiments, immune competence is indicated by a CD16⁺CD56⁺ NK cell count, by flow cytometry, of: 170-1,100 (for patients 0 to 2 months of age); 170-830 cells/μL (for patients aged 3 to 5 months); 160-950 cells/μL (for patients aged 6 to 11 months); 180-920 cells/μΐ- (for patients aged 12 to 23 months); 130-720 cells/μL (for patients aged 2 to 5 years); 100-480 cells/μL (for patients aged 6 to 1 1 years); 1 10-570 cells/ uL (for patients aged 12 to 17 years); 101-678 cells/uL (for patients aged 18 to 55 years); or 1 10-657 cells/μL (for patients older than 55 years of age).

In some embodiments, immune competence can be determined by quantifying the absolute number of CD4⁺ Helper T cells, by, e.g. , flow cytometry, in a biological sample obtained from a patient. For example, in some embodiments, immune competence is indicated by a CD4⁺ Helper T cell count, by flow cytometry, of: 1 ,600-4,000 (for patients 0 to 2 months of age); 1,800-4,000 cells/uL (for patients aged 3 to months); 1,400-4,300 cells/uL (for patients aged 6 to 11 months); 1 ,300-3,400 cells/μL (for patients aged 12 to 23 months); 700-2,200 cells/μL (for patients aged 2 to 5 years); 650- 1 ,500 cells/μL (for patients aged 6 to 11 years); 530-1 ,300 cells/μL (for patients aged 12 to 17 years); 424-1,509 cells/μΐ. (for patients aged 18 to 55 years); or 430-1,513 cells/uL (for patients older than 55 years of age).

In some embodiments, immune competence can be determined by quantifying the absolute number of CD8⁺ T cells, by, e.g., flow cytometry, in a biological sample obtained from a patient. For example, in some embodiments, immune competence is indicated by a CD8⁺ T cell count, by flow cytometry, of: 560-1,700 (for patients 0 to 2 months of age); 590-1 ,600 cells/μL (for patients aged 3 to 5 months); 500- 1,700 cells/μL (for patients aged 6 to 1 1 months); 620-2,000 cells/μL (for patients aged 12 to 23 months); 490-1 ,300 cells/μL (for patients aged 2 to 5 years); 370-1 , 100 cells/μΐ, (for patients aged 6 to 11 years); 330-920 cells/μL (for patients aged 12 to 17 years); 169-955 cells/μL (for patients aged 18 to 55 years); or 101-839 cells^L (for patients older than 55 years of age).

Methods for determining immune response following treatment with an ani-CD200 antibody, or antigen-binding fragment thereof, are elaborated on in, e.g., U.S. Pat. No. 9,180, 186. VIII. Kits and Unit Dosage Forms

Also provided herein are kits which include a pharmaceutical composition containing an anti-CD200 antibody in a therapeutically effective amount adapted for use in methods described herein. In one embodiment, the anti-CD200 antibody is samalizumab. The kits optionally also can include instructions, e.g. , comprising administration schedules, to allow a practitioner (e.g. , a physician, nurse, or patient) to administer the composition contained therein to a patient having a solid tumor. The kit also can include a syringe.

Optionally, the kits include multiple packages of the single-dose pharmaceutical compositions each containing an effective amount of the anti-CD200 antibody, or antigen- binding fragment thereof for administration in accordance with the methods provided herewith. Instruments or devices necessary for administering the pharmaceutical composition(s) also may be included in the kits. For instance, a kit may provide one or more pre-filled syringes containing an amount of the anti-CD200 antibody.

In one embodiment, the anti-CD200 antibody comprises the CDRl, CDR2, and CDR3 domains in a heavy chain variable region having the sequence set forth in SEQ ID NO: 11, and the CDRl, CDR2, and CDR3 domains in a light chain variable region having the sequence set forth in SEQ ID NO: 10.

In one embodiment, the kit for treating a solid tumor in a human patient comprises: a dose of an anti-CD200 antibody, or antigen-binding fragment thereof, comprising a heavy chain variable region CDRl having the sequence set forth in SEQ ID NO: 7, a heavy chain variable region CDR2 having the sequence set forth in SEQ ID NO: 8, a heavy chain variable region CDR3 having the sequence set forth in SEQ ID NO: 9, a light chain variable region CDRl having the sequence set forth in SEQ ID NO: 4, a light chain variable region CDR2 having the sequence set forth in SEQ ID NO: 5, and a light chain variable region CDR3 having the sequence set forth in SEQ ID NO: 6; and instructions for using the anti-CD200 antibody, in the methods described herein.

The following examples are merely illustrative and should not be construed as limiting the scope of this disclosure in any way as many variations and equivalents will become apparent to those skilled in the art upon reading the present disclosure.

The contents of all references, Genbank entries, patents and published patent applications cited throughout this application are expressly incorporated herein by reference. EXAMPLES

Example 1: Dosing regimen and PK/PD analysis

Based on pharmacokinetic (PK) and pharmacodynamic (PD) studies, the following dosing regimen was identified as sufficient to achieve an adequate PK concentration range and to saturate CD200 receptors.

• Dose Regimen (021D, mg/kg dosing. Part Al):

o 10 mg kg, 15 mg/kg, or 20 mg/kg of samalizumab was administered IV on Day 0, and every 21 days thereafter

o Maximum tolerated dose (MTD) was determined

• Dose Regimen (dose confirmation for recommended Phase 2 dose, RP2D, Part A2): o MTD, or 20 mg/kg

o Tumor biopsy evaluation

Estimated PK values are shown in Table 1. Estimated PD parameters for B-CLL

CD200⁺[MFI] and CD200⁺CD4⁺Tcells are shown in Tables 2 and 3. Additionally, Figure 1 demonstrates the dependence of total, linear, and nonlinear clearance (CL) on samalizumab serum concentration. Figure 1 further shows that samalizumab receptor mediated clearance is saturated at > 100 μg/ml serum concentration.

Analysis of the dosing regimen was conducted to determine (1) estimated mean exposure, (2) median drug concentration predictions over time, and (3) percent change in B-CLL

CD200⁺[MFI] and CD200⁺CD4⁺Tcells over time. Table 4 shows the Mean (SD) exposure estimates for certain dosing regimens (i.e., 5 mg/kg, 10 mg/kg, 15 mg/kg, or 20 mg/kg of the drug).

Table 1: Samalizumab PK Parameter Estimates

Table 2: PD Parameter Estimates (B-CLL CD200⁺[MFI])

Table 3: PD Parameter Estimates (CD200⁺CD4⁺ Tcells %)

Table 4: Mean (SD) Exposure Estimates for Dosing Regimens

Figure 2 demonstrates model prediction for drug concentrations using the dosing regimens (i.e., 5 mg/kg, 10 mg/kg, 15 mg/kg, or 20 mg/kg of the drug by IV every 21 days). Specifically, Figure 2 demonstrates that samalizumab PK exposures increase as dose increases from 5 to 20 mg/kg, and steady state is reached after the 4^th dose. Accumulation ratio for AUC was found to be 2.2, 2.6, 2.7, and 2.8-fold for each of 5, 10, 15, and 20 mg/kg doses, respectively. Additionally, samalizumab concentrations are > 100 pg/mL for 10, 15 and 20 mg/kg doses at steady state. Additionally, for the 5 mg/kg dose, the samalizumab concentration was < 100 μg/mL at steady state.

Figure 3 demonstrates median and 80% prediction intervals for percent change from baseline of CD200⁺CD4⁺ T cells and B-CLL CD200⁺[MFI] for the dosing regimens.

In summary, PK simulation suggested that these dosing regimens would provide PK exposures in an adequate PK concentration range to saturate receptors. PK accumulation at steady state was comparable to that after the 1^st dose, and was 2.2 to 2.8 for the Q3W dosing regimen. The dose reached maximum reduction of CD200⁺CD4⁺ T cells (~ 80%) after the 2^nd dose and maintained reduction during a 21 -day dosing interval. A dose-dependent reduction of B-CLL CD200⁺(MFI) cells was also shown.

Example 2: Clinical trial of samalizumab in CLL and MM

The first-in-human trial of samalizumab was conducted in patients with CLL under protocol C07-003 (ClinicalTrials.gov: NCT00648739). This was a Phase I/II open-label, dose- escalation study in patients with refractory, relapsing, or previously untreated advanced CLL evaluating safety, PK, pharmacodynamics (PD), and preliminary observations of efficacy. Twenty-three CLL patients were enrolled in 6 cohorts at doses ranging from 50-500 mg/m². Three extremely advanced patients with Multiple Myeloma (MM) were enrolled toward the end of the trial: 2 at 500 mg/m² and 1 at 600 mg/m². Patients received a single initial intravenous (IV) dose of samalizumab and could receive additional doses at 28-day cycles (1 dose/cycle) if the first dose was well tolerated (over 6 weeks) and if the patient exhibited at least stable disease (SD). The trial was originally designed to allow a maximum of 4 cycles of therapy, and later amended to allow ongoing every 4-week cycles as long as the therapy continued to be well tolerated and the patients maintained SD or better. SD was defined as <50% increase in the sum of the products of at least 2 lymph nodes, no new lesions, <50% increase in absolute blood lymphocyte count, and no transition to aggressive histology. Assessments performed throughout cycle 1 and then every 2 weeks, included standard safety measures, anti-drug antibody (ADA), PK, PD, complete blood count (CBC), and follow up computerized

tomography (CT) scans (at end of cycle 1, cycle 4 and every other cycle thereafter). No maximum tolerated dose (MTD) was identified during this trial.

Of the 26 patients treated with samalizumab, 25 (96%) patients experienced at least one adverse event (AE), 5 (19%) patients reported AEs that led to drug discontinuation, and 6 (23%) patients reported serious adverse events (SAE). A total of 6 (23%) patients reported AEs not related to study drug. Fifteen (58%) patients reported AEs that were possibly related to the study drug, and 4 (15%) patients reported AEs that were probably or definitely study drug-related. Samalizumab dosing was not associated with potent cytokine adverse reactions at any time point. Generally, AEs were mild and moderate in severity (>50% of patients) and manageable; 7 (27%) patients reported severe AEs and 3 (12%) patients experienced life-threatening or disabling AEs. There was 1 (4%) death in this clinical study, which was judged unrelated to the study medication.

A total of 256 treatment-related adverse events were reported by 25 (96%) patients enrolled in the study. The most frequent event was fatigue reported by 12 patients (46%), followed by headache, pyrexia, and rash, each reported by 5 patients (19%). One event (dose group 200 mg/m²) was judged to be definitely related. This event was an allergic reaction associated with a pre-dose positive anti-drug antibody level.

Evidence for anti-tumor effect was observed in 77% (17/22) of evaluable CLL patients following samalizumab dosing (16 patients with SD and one with confirmed partial response [PR]). Disease progression was observed in 5 patients. The 16 patients who achieved SD were found across all dosing cohorts after 29-525 days of dosing. Most of these patients (13/16, 81%) had 4 or fewer dosing cycles; only 3 SD patients received 6 or more cycles; 2 received 6 cycles and one received 18 cycles. Twenty-two of the 23 CLL patients in the trial had bulky disease evaluable by CT scan. Of the 22 patients whose target lesions were measured at baseline, 14 (64%) showed a decrease in measureable lesions at any time following treatment with samalizumab. Of these 14 patients, 1 1 (79%) did so after Cycle 1, between Days 28-42. Three did not have any reduction in lesion size after the initial dose, but did have reduction at a later cycle of dosing: Patient 102-303 (200 mg/m²) at Cycle 3, Patient 102-401 (300 mg/m²) at Cycle 14, and Patient 101-606 (500 mg/m²) at Cycle 4. Nine patients (41%) had a sustained cumulative maximal decrease in tumor burden (World Health Organization [WHO] criteria) of >10%. The maximum percent change from baseline in bulky adenopathy burden (sum of the bi-dimensional products of all target lesions) for each patient is shown in Figure 4.

A >30% decrease in tumor burden was observed in two of 22 (9%) evaluable CLL (two of 7 at the highest doses) patients. Patient 102-601 (500 mg/m²) had a maximum decrease of 40.5%, and Patient 102-502 (400 mg/m²) had a maximum decrease of 63.4%. These responses correlated with comparatively robust CD200 target down-regulation on tumor cells and T cells. In evaluable patients, biomarker and PD marker findings included:

• Decreased CD200 on peripheral B-cell chronic lymphocytic leukemia (B-CLL) cells in 86% (18/21 patients) (sustained at higher doses)

• Decreased CD200 expression on CD4+ T cells in 95% (19/20 patients) (sustained at higher doses) and concomitant increase in CD200R+ T cells in 42% (8/19 patients)

• A reduction in peripheral Tregs in 36% (9/25 patients)

• A modest first-dose Thl cytokine response in 40% (10/25 patients); 88% (22/25 patients) with detectable Thl cytokines at one or more time points during the study

Example 3: Phase 1 dose escalation study in patients with solid tumors

An open-label Phase 1 clinical study is conducted, wherein samalizumab is administered to patients at least 18 years of age with solid tumors, (e.g., at least one solid tumor or at least one advanced solid luiiiui).

A. Objectives

The primary objective is to determine a safe, well-tolerated, biologically active dose (BAD) and any dose limiting toxicity of samalizumab with a twenty-one day schedule of dosing (Q21D) in patients with solid tumors, particularly advanced solid tumors. The efficacy of samaiizumab against solid tumors is evaluated.

Additionally, the study characterizes samaiizumab pharmacokinetics (PK) following administration of samaiizumab in patients at least 18 years of age.

Exploratory biomarkers are assessed (including markers of immune function and inflammatory pathways) and exploring PK/pharmacodynamic exposure-response relationships. B. Trial Design Summary

The overall study design is depicted in schematically in Figure 6. The doses for this study are 10, 15, and 20 mg/kg given intravenously Q21D. This study employs a standard 3 + 3 design for dose escalation. During Part Al, cohorts of 3 or 6 patients are enrolled sequentially at escalating doses of 10, 15, and 20 mg/kg (see Figure 7). Enrollment at each dose level and assessment of DLTs is completed prior to enrolling patients at the next dose level; intrapatient dose escalation is not allowed.

Enrollment at subsequent dose levels occurs under the following conditions: a) None of the 3 patients experiences a DLT within Cycle 1 ; and b) All 3 patients complete the Day 21 visit.

The maximum dose received is either 20 mg kg or the MTD + 5 mg/kg, whichever occurs first. The MTD is defined as the dose level at which less than one-third of patients experiences DLTs during the first 21 days of treatment and immediately below the dose at which at least one third of patients experience DLTs. If there are no DLTs reported or there is no evidence of clinical benefit at 20 mg/kg, an alternate dosing schedule is explored. Patients may continue dosing with samaiizumab until either disease progression is confirmed or until an unacceptable toxicity occurs.

Once the dose-escalation (Part Al) is completed, additional patients are enrolled in Part A2 to: 1) characterize the PK and to evaluate the PK/pharmacodynamic relationship more fully; 2) further evaluate the clinical and pharmacodynamic responses; and 3) further evaluate safety and tolerability at the MTD. Safety data is reviewed periodically. Patients are replaced if they do not reach Day 21 due to a non-DLT event (such as disease progression). Tumor evaluation, including assessments at baseline and throughout the study for response and disease progression, is performed using Eisenhauer EA, et al. (New response evaluation criteria in solid tumors: Revised RECIST guideline (versionl.l), Eur J of Cancer. 45:228-247 (2009)(RECIST 1.1)).

Primary Outcome Measures: 1. Number of patients experiencing Dose Limiting Toxicity graded according Common Terminology Criteria for Adverse Events (CTCAE) Version 4.03, observed in Cycle 1 in order to meet the objective of assessment of the MTD.

2. Maximum Plasma Concentration (C_max) after administration of samalizumab

3. Area under the plasma drug concentration-time curve (AUC) after

administration of samalizumab

Secondary Outcome Measures:

1. Objective Response Rate using Response Evaluation Criteria in Solid Tumors 1.1 (RECIST)

2. Disease Control Rate using RECIST 1.1

3. Duration of Response

4. Progression Free Survival

5. Overall Survival

C. Patient Inclusion Criteria

Patients must meet all of the following criteria to be enrolled in this study:

1. Male or female patients are at least 18 years of age at the time of screening.

2. Eastern Cooperative Oncology Group (ECOG) performance status 0, 1, or 2. Subjects or their legal representative must be able to understand and provide written informed consent.

3. Patient has advanced/metastatic cancer with disease progression after treatment with all available therapies known to confer clinical benefit.

4. Patient has a life expectancy of greater than 12 weeks.

D. Patient Exclusion Criteria

Patients meeting any of the following criteria are excluded from the study:

1. Patient has a symptomatic brain metastasis.

2. Patient has active gastrointestinal bleeding as evidenced by either hematemesis or melena.

3. Patient has acute gastrointestinal ulcers.

4. Patient has a history of any cancer other than the present condition (except nonmelanoma skin cancer or carcinoma in situ of the cervix), unless in complete remission and off all therapy for that disease for a minimum of 3 years. 5. Patient with a condition requiring systemic treatment with either corticosteroids (> 10 mg daily prednisone equivalents) or other immunosuppressive medications within 14 days of study drug administration. Inhaled or topical steroids, adrenal replacement doses > 10 mg daily prednisone equivalents, and systemic corticosteroids to manage treatment-emergent adverse events are permitted in the absence of active autoimmune disease.

6. Patient has an active infection requiring therapy.

7. Patient is positive for Human Immunodeficiency Virus (HIV) (HIV 1/2 antibodies), active hepatitis B, or hepatitis C.

8. Patient has significant cardiovascular impairment (history of New York Heart

Association Functional Classification system Class III or IV) or a history of myocardial infarction or unstable angina within the past 6 months prior to study drug treatment.

9. The patient's most recent test values within 14 days before the date of entry meet the following standards:

a. Bone marrow function: neutrophil count≤ 1500/mm³, hemoglobin≤ 9.0 g/dL, platelet count≤ 100,000/mm³.

b. Liver function: total bilirubin≥ 1.5 x the upper limit of normal (ULN) based on the standard value of each institution, aspartate aminotransferase and alanine aminotransferase ≥ 2.5 x ULN based on the reference laboratory.

c. Renal function: serum creatinine≥ 1.5 x ULN based on the reference laboratory

10. Patient has ongoing immune-stimulated adverse events (AEs) from other

immunotherapies (e.g. , pneumonitis, thyroiditis, or hepatitis) or a history of pneumonitis.

1 1. Patient has received chemotherapy, targeted therapy, and/or immunotherapy within the 28 days prior to first dose of study drug.

12. Patient has toxicities from previous immunotherapy that have not resolved to Grade 1.

Patient Withdrawal Criteria

Patients are allowed to withdraw consent at any time. A patient's treatment may be discontinued because of AEs or SAEs, as well as conditions or intercurrent illnesses that preclude compliance with the protocol from the standpoint of the patient's safety or wellbeing. Patients that experience disease progression or a DLT may not receive additional doses of samalizumab. If a patient develops an AE of≥ Grade 3 toxicity that is not related to the disease under study or its sequelae after Cycle 1 that would have been considered a DLT during planned cycles, no additional samalizumab is given to that patient. If a patient becomes pregnant, the study drug must be immediately discontinued and the Sponsor must be notified. The pregnancy is followed to term and the Sponsor is notified regarding the outcome. Patients who discontinue treatment prior to completion of a cycle for reasons other than DLTs are replaced.

F. Study Drug Preparation and Administration

Samalizumab is formulated at pH 5.2 in 50 mM citrate, 75mM sodium chloride (NaCl), 2% mannitol, and 0.02% polysorbate 80. The solution is clear liquid and practically free from particles. Samalizumab is provided as a sterile solution in clear glass 20-ml open label vials containing 20 ml of formulated active agent at a concentration of 5 mg/ml, for a total of 100 mg per vial. Vials are tracked via unique tracking numbers.

Each patient's dosage is calculated based on body weight and the patient's assigned dosage cohort. All doses are individualized to the patient's body weight in milligrams per kilogram (mg kg). If a patient's baseline weight does not fluctuate by > 10%, the baseline weight is used to calculate dose. However, if a postbaseline weight measurement collected during physical examinations varies from baseline by > 10%, then it is used to calculate the dose instead of the baseline weight. The drug is diluted aseptically with an equal volume of 0.9% NaCl Injection, USP.

The drug is not administered as an IV push or bolus injection. Samalizumab is administered intravenously (after being inspected visually for particulate matter and/or discoloration) at from about 125 to about 250 mL/hour via any approved infusion pump and includes an IV filter of 0.20-0.22 microns between the infusion container and the patient.

G. Infusion Reactions and Management

Samalizumab is an antibody that has been designed to be compatible with the human immune system; however, the possibility of allergic reactions including anaphylaxis, anaphylactic reactions, skin rash and hives exists. Humanized proteins, including some monoclonal antibodies, can be toxic; therefore, physicians should be vigilant for signs and symptoms of acute toxicity. Physical examination also includes inspection of infusion site for any potential reaction. H. Treatment Plan and Procedures

Approximately 33 patients are enrolled, with the following assumptions: a single DLT is observed at each initial dose cohort requiring expansion; a 10% drop-out rate; and a 10% tumor progression rate. The final sample size depends on the number of doses explored, the frequency of tumor progression, the number of patients with DLTs, and the actual number of drop-outs. Due to the uncertainty of predicting the aforementioned variables, it is possible that more than 33 patients may be enrolled to determine the MTD. All patients who meet all of the inclusion criteria and none of the exclusion criteria are eligible to enroll in this study. This is an open- label study with sequential escalating dose cohorts; assignment to a particular dose is based on the time of enrollment.

Dosing begins with the 10-mg/kg dose cohort and proceeds sequentially in Part Al. Decisions about dose escalation and expansion are based on the number of patients experiencing DLTs. An initial cohort of 3 patients is enrolled into a dose cohort.

If none of 3 patients develop DLTs within Cycle 1, enrollment begins at the next higher dose level (dose increased by 5 mg/kg) to a maximum of 20 mg/kg.

If one of 3 patients develops a DLT within Cycle 1 , the dose cohort is expanded to include 3 new patients.

If none of 3 new patients develop a DLT (for a total of 1 of 6 patients with a DLT at this dose level), enrollment begins at the next higher dose level (dose increased by 5 mg/kg) to a maximum of 20 mg/kg.

If≥ 1 of 3 new patients develop a DLT within Cycle 1 (for a total of≥ 2 of 6 patients with a DLT at this dose level), the dose-escalation component of the study (Part Al) is terminated, and the dose level 5 mg/kg below the current dose is considered the MTD.

If≥ 2 of 3 patients develop DLTs within Cycle 1, the dose-escalation component of the study (Part Al) is terminated, and the dose level 5 mg/kg below the current dose is considered the MTD.

The anticipated maximum dose received in this study is either 20 mg/kg or the MTD + 5 mg/kg, whichever occurs first. Patients may continue dosing with samalizumab until either disease progression is confirmed or until an unacceptable toxicity occurs.

The MTD is further evaluated in the dose confirmation cohort (Part A2), which is subsequently considered the recommended Phase 2 dose (RP2D), and used in future studies with samalizumab. The cohort in which the RP2D is determined is thereby referred to as the RP2D cohort.

Once the MTD is determined, additional patients are enrolled until a total of 12 patients treated at the RP2D. These patients are evaluated to: 1) characterize the PK profile and evaluate the PK/pharmacodynamic relationship more fully; 2) further evaluate the clinical and

pharmacodynamic effects; and 3) further evaluate safety and tolerability at the MTD (Figure 6 and Table 5). Thus, in addition to the initial 3 or 6 patients who are evaluated during the dose- escalation component of the study (Part Al), an additional 6 or 9 patients are evaluated in the Dose Confirmation Cohort, for a maximum of 12 patients (Part A2). The Dose-Confirmation Cohort includes 6 or 9 additional patients to reach a total of 12 patients at MTD, including a subset of at least 3 patients with pre- and post-treatment tumor biopsies treated at the RP2D (Tumor Biopsy Evaluation Cohort). Enrollment in the Tumor Biopsy Evaluation Cohort requires that patients have tumors accessible for biopsies. In addition, 3 patients treated at 5 mg/kg below the RP2D with pre- and postdose biopsies are enrolled. If DLTs are experienced by patients in the Dose-Confirmation Cohort, decisions about further dose expansion and escalation follow the Part Al treatment scheme. A total of 12 patients are enrolled at the MTD (RP2D) for assessment of clinical and pharmacodynamic responses (including tumor biopsy evaluation) and safety and tolerability.

Patients are followed until disease progression or occurrence of unacceptable toxicity.

Table 5: Pharmacokinetic, Pharmacodynamic, and Clinical Evaluation in the Dose'

Confirmation Cohort (Part A2)

A Dose-Limiting Toxicity (DLT) is a study drug-related adverse event (AE) defined based on NCI CTCAE Version 4.03, encompassing one or more of the following: • Grade 4 hematologic toxicity lasting > 14 days,

• Grade 4 nonhematologic treatment-related toxicity (not laboratory),

• Grade 3 nonhematologic toxicity (not laboratory) lasting > 3 days despite optimal supportive care,

• Any Grade 3 nonhematological laboratory value if:

o Medical intervention is required to treat the patient, or

o The abnormality leads to hospitalization, or

o The abnormality persists for > 1 week.

• Grade 5 toxicity (death).

• Any toxicity that results in a treatment delay exceeding 21 days.

Patients are followed until all AEs have recovered to baseline, or are deemed medically stable or irreversible in the opinion of the Investigator or until initiation of a new treatment, whichever occurs first. Other safety assessments include, but are not limited to, the following: serious AEs (SAEs), clinical laboratory evaluations, thyroid function assessments, vital sign measurements, physical examination, electrocardiogram (ECG), and pregnancy tests.

I. Safety Reporting

Safety data of samalizumab in patients with advanced solid tumors are evaluated, and assessment of AEs are based on criteria described by the National Cancer Institute (NCI) Common Terminology Criteria for Adverse Events (CTCAE) Version 4.03. Adverse events are assessed continuously during the study and for 100 days after the last study drug administration or until initiation of a new anticancer treatment, whichever occurs first.

J. Criteria for Evaluation

Efficacy of samalizumab in patients with advanced solid tumors is evaluated using endpoints of objective responses (OR). Objective responses are assessed according to RECIST 1.1. Stable disease requires 12 weeks (84 days) of tumor non-progression. For this study, classification of response is either OR, which includes complete response (CR) or partial response (PR), or clinical benefit response, consisting of CR, PR, or stable disease.

Patients with at least one lesion measurable that can be accurately assessed at baseline by computerized tomography (CT), magnetic resonance imaging (MRI) or plain X-ray are included in this study. Measurable Lesions: At least one lesion, not previously irradiated, that can be accurately measured at baseline as≥ 10 mm in the longest diameter (except lymph nodes which must have short access≥ 15mm) with CT or MRI, which is suitable for accurate repeated measurements.

All other lesions, including small lesions (longest diameter < 10 mm or pathological lymph nodes with≥ 10 mm to < 15 mm short axis at baseline. Nodes with < 10 mm short axis are considered nonpathological and are not recorded as nontarget lesions (NTLs).

Truly nonmeasurable lesions include the following: bone lesions, leptomeningeal disease, ascites, pleural/pericardial effusion, inflammatory breast disease, lymphangitic involvement of skin or lung, and abdominal masses/abdominal organomegaly identified by physical examination that are not measurable by CT or MRI.

Previously irradiated lesions as localized post radiation changes, which affect lesion sizes, may occur. Therefore, lesions that have been previously irradiated are not considered measurable and are selected as NTLs at baseline and followed up as part of the NTL assessment.

Skin lesions assessed by clinical examination.

Brain metastases are measured by any method, but particularly by MRI.

Lytic bone lesions or mixed lytic-blastic lesions, with identifiable soft tissue

components, are considered measurable if the soft tissue component meets the definition of measurability. Blastic lesions are considered nonmeasurable.

Cystic metastases are considered measurable lesions if they meet the criteria for measurability from a radiological point of view but if noncystic lesions are present in the same patient, these noncystic lesions are selected as the target lesions (TLs).

A maximum of five measurable lesions (with a maximum of two lesions per organ), representative of all lesions involved suitable for accurate repeated measurement, are identified as TLs at baseline. All other lesions (or sites of disease) not recorded as TLs are identified as NTLs at baseline.

The same method of assessment and the same technique are used to characterize each identified and reported lesion at baseline and during follow-up. The methods for RECIST assessment are summarized in Table 6 and those excluded for tumor assessments are discussed below, with the rationale provided. Table 6. Summary of Methods of Assessment

Abbreviations: CT = computerized tomography; FDG = fluorodeoxyglucose; MRI = magnetic resonance imaging; PET = positron emission tomography.

Computerized tomography and MRI are generally considered to be the best currently available and reproducible methods to measure TLs selected for response assessment and to assess NTLs and identification of new lesions. CT examinations of the chest and abdomen are typically be used to assess tumor burden at baseline and follow-up visits. Computerized tomography examination with intravenous contrast media administration is the preferred method. Magnetic resonance imaging is used where CT is not feasible or if it is medically

contraindicated. For assessment of brain lesions, MRI is the preferred method.

Plain X-rays may be used as a method of assessment for bone NTLs and to identify the presence of new bone lesions.

Chest X-rays are not used for assessment of TLs, as they are assessed by CT or MRI examination. However, chest X-rays are used to assess NTLs and to identify the presence of new lesions.

Clinical examination is not used for assessment of TLs. Clinically detected lesions are selected as TLs if they are then assessed by CT or MRI scans. Clinical examination is used to assess NTLs in patients that also have other lesions assessable by CT, MRI, or plain X-ray and to identify the presence of new lesions.

Ultrasound examination is not used for assessment of TLs and NTLs, as it is not a reproducible method, does not provide an accurate assessment of tumor size, and it is subjective and operator dependent. However, ultrasound examination is used to identify the presence of new lesions. If new clinical symptoms occur, and an ultrasound is performed, then new lesions should be confirmed by CT or MRI examination. Endoscopy and laparoscopy are not used for tumor assessments as they are not validated in the context ot tumor measurements.

Tumor markers are not used for tumor response assessments per RECIST 1.1.

Histology is not used as part of the tumor response assessment per RECIST 1.1.

Cytological confirmation of the neoplastic origin of any effusion that appears or worsens during treatment is required when the measurable tumor has met criteria for response or stable disease. In such circumstances, the cytology is necessary to differentiate between response/stable disease (an effusion may be a side effect of the treatment) and progressive disease (if the neoplastic origin of the fluid is confirmed). Where cytology findings are not available, any effusion that significantly worsens (from trace to large) or the appearance of a clinically significant effusion (requiring change in drug therapy) during the study drug is considered to be progression of NTLs or disease progression due to new lesions.

Bone lesions identified on an isotopic bone scan at baseline and confirmed by CT, MRI, or X-ray at baseline are recorded as NTLs and followed by the same method as per baseline assessment. Isotopic bone scans are used as a method of assessment to identify the presence of new bone lesions at Follow-up Visits. New lesions are recorded where a positive hotspot that was not present on the baseline bone scan assessment is identified on a bone scan performed at any time during the study. A positive hotspot(s) is/are considered to be a significant new site of malignant disease and represent true disease progression in order to record the new lesion.

Confirmation by CT, MRI, and X-ray is recommended where bone scan findings are equivocal.

Fluorodeoxyglucose-positron emission tomography (FDG-PET) scans are used as a method for identifying new lesions, according to the following algorithm: new lesions are recorded where there is positive FDG uptake (defined as when an uptake greater than twice that of the surrounding tissue is observed) not present on the baseline FDG-PET scan or in a location corresponding to a new lesion on CT/MRI at the same Follow-up Visit. If there is no baseline FDG-PET scan available, and no evidence of new lesions on CT MRI scans, then follow-up CT/MRI assessments are continued, scheduled as per protocol or clinical indicated, in order to confirm new lesions.

Computerized tomography examination of the chest and abdomen (including liver adrenal glands) is used to assess tumor burden at baseline and Follow-up Visits. Computerized tomography examination with intravenous contract media administration is the preferred method. Magnetic resonance imaging is used where CT is not feasible or if it is medically contraindicated. Baseline tumor assessments encompass all areas ot known predilection tor metastases in the disease under evaluation and additionally investigate areas that may be involved based on signs and symptoms of individual patients and are performed no more than 28 days before the start of study drug. Any other sites at which new disease is suspected is also adequately imaged at Follow-up. If an unscheduled assessment is performed, and the patient has not progressed, every attempt is made to perform the subsequent assessments as their scheduled visits. This schedule is to be followed in order to minimize any unintentional bias caused by some patients being assessed at different frequency than other patients.

A maximum of 5 measurable lesions, with a maximum of 2 lesions per organ (including lymph nodes), representative of all lesions involved, are identified as target lesions (TLs) at baseline. Target lesions are selected on the basis of their size (longest diameter for non-nodal lesions or short axis for nodal lesions) but in addition are those that lend themselves to reproducible repeated measurements. Where the largest lesion does not lend itself to

reproducible measurement, the next largest lesion that can be measured reproducibly is selected. The site and location of each TL is documented as well as the longest diameter for non-nodal lesions (or short axis for lymph nodes) in millimeters. At baseline, the sum of the diameters for all TLs is calculated and reported as the baseline sum of diameters. At follow-up visits, the sum of diameters for all TLs are calculated and reported as the follow-up sum of diameters.

For TLs measurable in 2 or 3 dimensions, longest diameter is reported. For pathological lymph nodes measurable in 2 or 3 dimensions, the short axis is reported. If the CT/MRI slice thickness used is > 5mm, the minimum size of measurable disease at baseline is twice the slice thickness of the baseline scan. If a lesion has completely disappeared, the longest diameter is recorded as 0 mm. If a TL splits into two or more parts, then record the sum of the diameters of those parts. If two or more TLs merge then the sum of the diameters of the combined lesion is recorded for one of the lesions and 0 mm recorded for the other lesions. If a TL is believed to be present and is faintly seen but too small to measure, a default value of 5mm is assigned. If an accurate measure can be given, this is recorded, even if it is below 5mm. If a TL cannot be measured accurately due to it being too large, an estimate of the size of the lesion is provided. When a TL has had any intervention e.g. , radiotherapy, embolization, or surgery, during the study, the size of the TL should still be provided where possible. Table 7 provides the definitions of the criteria used to determine objective tumor visit response for TLs.

Table 7. Overall Visit Response for Target Lesions

All other lesions (or sites of disease) not recorded as TLs are identified as NTLs at baseline. Measurements are not required for these lesions but their status is followed at subsequent visits. At each visit, an overall assessment of the NTL response is recorded by the Investigator. Table 8 provides the definitions of the criteria used to determine and record overall response for NTLs at the investigational site at each visit.

Table 8. Overall Visit Response for Nontarget Lesions

Details of any new lesions are also recorded with the date of assessment. The presence of one or more new lesions is assessed as progression. A lesion identified at a foiiow-up assessment in an anatomical location that was not scanned at baseline is considered a new lesion and indicates disease progression. The finding of a new lesion should be unequivocal (i.e., not attributable to differences in scanning technique, change in imaging modality or findings thought to represent something other than tumor). For example, if a new lesion is equivocal because of its small size, the treatment and tumor assessments continue until the new lesion is confirmed. If repeat scans confirm there is a new lesion, then the progression date is declared using the date of the initial scan.

Symptomatic deterioration is not a descriptor of an objective response: it is a reason for stopping study therapy. Patients with 'symptomatic deterioration' requiring discontinuation of study drug without objective evidence of disease progression at that time continue to undergo RECIST 1.1 assessments according to the clinical study protocol until objective disease progression is observed.

The overall visit response is derived using the algorithm shown in Table 9, where CR = complete response; NA = not applicable (relevant when no nontarget lesions at baseline); NE = not evaluable; PD = progressive disease; and PR = partial response.

Table 9. Overall Visit Response

The use of standardized protocols for CT and MRI allows comparability both within and between ditterent studies, irrespective ol where the examination has been undertaken.

Computerized tomography scans of chest and abdomen (including liver and adrenal glands) are contiguous throughout all the anatomical regions of interest. Optimal anatomic coverage for most solid tumors is the chest, abdomen, and pelvis. Coverage encompasses all areas of known predilection for metastases in the disease under evaluation and additionally includes areas that may be involved based on signs and symptoms of individual patients.

Because a lesion later identified in a body part not scanned at baseline is considered as a new lesion representing disease progression, careful consideration is given to the extent of imaging coverage at baseline and at subsequent follow-up time points, enabling better consistency not only of tumor measurements but also of identification of new disease.

Optimal visualization and measurement of metastases in solid tumors requires consistent administration (dose and rate) of intravenous contrast as well as timing of scanning. Typically, most abdominal imaging is performed during the portal venous phase and (optimally) about the same time frame after injection on each examination. An adequate volume of a suitable contrast agent is given so that the metastases are demonstrated to best effect and a consistent method is used on subsequent examinations for any given patient. The same technique is used at baseline and on follow- up examinations for a given patient. For patients who develop contraindications to contrast after baseline contrast CT is done, the decision as to whether noncontrast CT or MRI (enhanced or nonenhanced) is performed is based on the tumor type, anatomic location of the disease and is optimized to allow for comparison to the prior studies if possible. Each case is discussed with the radiologist to determine if substitution of these other approaches is possible and, if not, the patient is considered not evaluable from that point forward. Care must be taken in measurement of TLs on a different modality and interpretation of nontarget disease or new lesions, since the same lesion may appear to have a different size using a new modality. Oral contrast is recommended to help visualize and differentiate structures in the abdomen. If iodine contrast media is medically contraindicated at baseline or at any time during the course of the study then the recommended methods are: CT thoracic examination without contrast, and abdominal and pelvic MRI with contrast. If MRI cannot be performed, then CT without intravenous contrast is an option for the thorax, abdomen, and pelvic examinations. For assessment of brain lesions, MRI is the preferred method. CT scans are performed at 5 mm contiguous slice thickness, and this guideline presumes a minimum i> mm thickness in recommendations for the measurable lesion definition.

Exceptionally, particular institutions may perform medically acceptable scans at slice thicknesses greater than 5 mm. If this occurs, the minimum size of measurable lesions at baseline is twice the slice thickness of the baseline scans. All window settings are included in the assessment, particularly in the thorax where lung and soft tissue windows should be considered. When measuring lesions, the TLs are measured on the same window setting for repeated examinations throughout the study. All images from each examination are included in the assessment.

Magnetic resonance imaging has excellent contrast, spatial and temporal resolution; however, there are many image acquisition variables involved in MRI, which greatly impact image quality, lesion conspicuity and measurement. Furthermore, the availability of MRI is variable globally. The modality used at follow-up is the same as was used at baseline, and the lesions are measured/assessed on the same pulse sequence. Generally, axial imaging of the abdomen and pelvis with Tl and T2 weighted imaging along with gadolinium-enhanced imaging is performed. The field of view, matrix, number of excitations, phase encode steps, use of fat suppression and fast sequences are optimized for the specific body part being imaged as well as the scanner utilized. It is beyond the scope of this study to prescribe specific MRI pulse sequence parameters for all scanners, body parts and diseases. Ideally, the same type of scanner is used and the image acquisition protocol is followed as closely as possible to prior scans. Body scans are performed with breath-hold scanning techniques if possible. For these reasons, CT is the imaging modality of choice.

Fluorodeoxyglucose positron emission tomography has gained acceptance as a valuable tool for detecting, staging and restaging several malignancies. If FDG-PET scans are included in a protocol, an FDG uptake period of 60 minutes prior to imaging has been decided as the most appropriate for imaging of patients with malignancy. Whole-body acquisition is important since this allows for sampling of all areas of interest and can assess if new lesions have appeared thereby determining the possibility of interval progression of disease. Images from the base of the skull to the level of the mid-thigh are obtained 60 minutes postinjection. Positron emission tomography camera specifications are variable and manufacturer specific, so every attempt is made to use the same scanner, or the same model scanner, for serial scans on the same patient. Whole-body acquisitions are performed in either 2- or 3-dimensional mode with attenuation correction, as long as the method is consistent across all patients and serial scans in the clinical studies.

At present, low dose or attenuation correction CT portions of a combined PET-CT are of limited use in anatomically based efficacy assessments and it is thereby suggested that they are not substituted for dedicated diagnostic contrast enhanced CT scans for tumor measurements by RECIST 1.1. In exceptional situations, if a site can document that the CT performed as part of a PET-CT is of identical diagnostic quality to a diagnostic CT (with IV and oral contrast), then the CT portion of the PET-CT is used for RECIST measurements. However, this is not

recommended because the PET portion of the CT introduces additional data that may bias an Investigator if it is not routinely or serially performed.

Pharmacokinetic parameters to be estimated using model independent methods following single-dose administration in Cycle 1 include:

• Systemic clearance (CL)

• Maximum observed serum concentration (Cmax)

• Time to reach Cmax after drug administration (T_max)

• Minimum concentration at the end of a dosing interval

• Terminal elimination half-life (Ti/₂)

• Volume of distribution (V)

• Area under the serum concentration-time curve during a 21 -day dosing interval at steady state (AUC2 id)

• Area under the serum concentration-time curve from time zero to the last measurable concentration (AUGast)

Cmax and the minimum observed serum concentration at the end of a dosing interval (C_min) is estimated following multiple-dose administration from Cycle 2 to Cycle 5.

The status of anti-samalizumab antibody is determined for all patients. Assay results are reported as positive or negative for the confirmatory and neutralizing assays, and the proportion of patients with positive results are summarized.

Pre- and post-treatment tumor biopsies are collected to assess the penetrance of samalizumab in tumors at the MTD/RP2D (and at 5 mg/kg below the MTD/RP2D if the RP2D is either 15 or 20 mg/kg) in the Tumor Biopsy Evaluation Cohort, a subset of the Dose

Confirmation Cohort (Part A2). The presence of tumor-infiltrating lymphocytes is also assessed. If the RP2D is 10 mg/kg, 6 pre- and post-treatment tumor biopsies are taken from 6 additional patients at Day 1 and at Day 8 ot Cycle 2. If the RP2D is either lb or 20 mg kg, 6 pre- and post- treatment tumor biopsies are taken from 6 additional patients (3 patients at the RP2D and 3 patients at the next lower dose [i.e., RP2D reduced by 5 mg/kg]) at Day 1 and at Day 8 of Cycle 2.

The pharmacodynamic assessments of tumor biopsies may include, but are not limited to, samalizumab binding to CD200.

In addition, peripheral blood is collected for evaluation of samalizumab binding to peripheral blood mononuclear cells (PBMC) as a surrogate tissue of samalizumab binding in tumors. Samples are analyzed by flow cytometry, and evaluations may include, but are not limited to, the proportion of CD200 bound by samalizumab in cellular subsets (e.g., CD3+, CD4+, CD8+, activated T cells, and regulatory T cells). The effect of samalizumab on the number of cells in cellular subsets may also be assessed. The absolute number of lymphocytes and leukocytes relative to baseline may also be evaluated.

Peripheral blood samples are collected to enable evaluation of exploratory biomarkers which may include but are not limited to serum cytokines associated with activation of the immune system or inflammatory pathway. Additional exploratory biomarkers may include, but are not limited to, markers of the CD200 signaling pathway, immune checkpoint signaling, immune function, and inflammatory signaling. To understand the relationship between exploratory biomarkers in solid tumors and the clinical response to samalizumab, archival biopsy material from previous surgical resection is also requested, where available. Biomarker analyses may include, but are not limited to, CD200 protein expression, presence of CD200 receptor (CD200R), soluble CD200 in plasma, the presence of tumor infiltrating lymphocytes, and/or the evaluation of candidate gene signature to predict the response to samalizumab. Where predose and postdose tumor biopsies are available, biopsy tissue may be evaluated for tumor localization of samalizumab, expression of CD200, presence of tumor infiltrating lymphocytes, or other markers of immune checkpoint signaling.

Safety data of samalizumab in patients with advanced solid tumors are evaluated, and assessment of AEs are based on criteria described by the National Cancer Institute (NCI) Common Terminology Criteria for Adverse Events (CTCAE) Version 4.03. Adverse events are assessed continuously during the study and for 100 days after the last study drug administration, or until initiation of a new anticancer treatment, whichever occurs first.

K. Statistical and Pharmacokinetic Methods

For continuous variables, descriptive statistics (mean, standard deviation [SD], interquartiles, and ranges) are presented; for categorical variables, counts and percentages are tabulated by cohort. Assessment of CR, PR, and stable disease are also presented in tabular format. For safety-related parameters (i.e., clinical signs/symptoms, clinical laboratory toxicities, and ECG and vital sign abnormalities), both tabular summary and by-patient listings are provided.

For a series of PK data following first dose administration in Cycle 1, PK parameters are estimated using noncompartmental analysis method. All PK data collected from Cycle 1 to Cycle 5 are analyzed using a nonlinear mixed effect modeling technique. Individual post hoc PK parameters are estimated using final population PK model. All PK parameters are summarized using descriptive statistics by dose level. Descriptive statistics are include number of patients (N), mean, SD, median, minimum, maximum, and coefficient of variation. Samalizumab serum concentration data is summarized by dose level and treatment cycle with descriptive statistics at each scheduled time point. Individual and mean concentration-time profiles are provided in linear and log-linear scale.

Dose Proportionality Test is performed by a Power Model Analysis, in which the natural logarithm (Ln) C_max and area under the serum concentration-time curve from time zero to the last measurable concentration (AUCiast) values are regressed against Ln dose values. The 95% confidence interval (CI) is constructed for β value. Inclusion of null value of 1.0 within the 95% CI suggests that a dose-proportional increase cannot be ruled out.

The PK/pharmacodynamic relationships are explored. This also includes the effect of anti-drug antibody on PK, pharmacodynamic/efficacy, ECG, and other safety parameters.

There are three analysis populations for this study, as follows: the Full Analysis (FA) Population, the Safety Population, and the PK Population.

Full Analysis Population: The FA Population includes all enrolled patients that had at least one postbaseline observation and have received at least one dose of study drug. Full Analysis Population analyses are based upon the treatment regimens patients were to receive. Safety Population: All patients treated with study drug are included in the Safety Population. Safety analyses are based upon the treatment regimens actually received.

Pharmacokinetic Population: All patients treated with samalizumab who provide at least one valid concentration value comprise the PK Population. The PK Population is used for the analysis of PK data. The PK exposure-response analysis includes patients who have both available PK and PK/pharmacodynamics response data.

Interim analysis is conducted as needed.

Example 4: Preliminary PK Results (Study ALXN6000-ONC-102)

Initial PK results were obtained for cancer patients treated with samalizumab (Q3W repeated IV dosing). Three doses were assessed: 10, 15, and 20 mg/kg. In patients who received 10 mg/kg samalizumab, variable serum samalizumab concentration was observed after the first dose, but stabilized thereafter (see Figures 8A-8B). No anti-drug antibodies (ADA) were detected and limited accumulation of samalizumab was observed after repeated dosing. In patients who received 15 mg/kg samalizumab, variable serum samalizumab concentration was observed after the first dose, but stabilized thereafter, and limited accumulation of samalizumab was observed after repeated dosing (see Figures 9A-9B). Persistent ADA was observed in a single patient, which may have reduced PK values in this particular patient. Figures 10A-10B show data for patients who received 20 mg/kg samalizumab. No ADA was detected in these patients.

In summary, the observed PK under all three dosing regimens (10, 15, and 20 mg/kg) were in the linear range, although PK parameters for the 20 mg/kg cohort were not calculated due to limited data availability (see Figure 11). Similar ti/₂ were observed for patients who received 10 or 15 mg/kg doses and the C_max did not correlate with the given dose (even excluding the outlier patient). While some inter-subject variability was observed after the first dose, the serum concentration of samalizumab stabilized thereafter, and limited accumulation of samalizumab was observed alter repeated dosing. However, some differences in PK values were observed between patients with different tumor types, suggesting that target-mediated deposition may be occurring and higher dosing of samalizumab may be beneficial in some patients (e.g. , at 40 mg/kg). Example 5: Extended PK Results (Study ALXN6000-ONC-102)

Additional PK results were obtained from the cancer patients treated with samalizumab (Q3W repeated IV dosing). Figures 12A-12B are graphs showing serum samalizumab concentration over time in patients treated with 10 mg/kg samalizumab. Figures 13A-13B are graphs showing serum samalizumab concentration over time in patients who received 15 mg/kg samalizumab. Figures 14A-14B are graphs showing serum samalizumab concentration over time in patients who received 20 mg/kg samalizumab. Figures 15A-15B are graphs showing the mean serum samalizumab concentration over time in patients who received 10, 15, or 20 mg/kg samalizumab. Figure 16 is a chart summarizing the PK paramaters for the study patients who received Q3W repeated intravenous dosing of samalizumab (10, 15, or 20 mg/kg).

Claims

CLAIMS What is claimed is:

1. A method of treating a human patient having a solid tumor, the method comprising administering to the patient about 5 mg/kg to about 50 mg/kg; particularly from about 10 mg/kg to about 20 mg/kg; more particularly about 10 mg/kg, about 15 mg/kg, or about 20 mg/kg, of an anti-CD200 antibody, or antigen-binding fragment thereof, with a frequency sufficient to provide a partial response, a complete response, or stable disease, wherein the anti-CD200 antibody, or antigen-binding fragment thereof, comprises a heavy chain variable region CDRl having the sequence set forth in SEQ ID NO: 7, a heavy chain variable region CDR2 having the sequence set forth in SEQ ID NO: 8, a heavy chain variable region CDR3 having the sequence set forth in SEQ ID NO: 9, a light chain variable region CDRl having the sequence set forth in SEQ ID NO: 4, a light chain variable region CDR2 having the sequence set forth in SEQ ID NO: 5, and a light chain variable region CDR3 having the sequence set forth in SEQ ID NO: 6.

2. The method of claim 1, wherein the frequency is once every fourteen days or once every twenty-one days.

3. The method of claim 1 or 2, wherein the anti-CD200 antibody comprises heavy and light chain variable regions having the sequences set forth in SEQ ID NOs: 13 and 12, respectively.

4. The method of any one of the preceding claims, wherein the anti-CD200 antibody comprises heavy and light chains having the sequences as set forth in SEQ ID NOs: 11 and 10, respectively.

5. The method of any one of the preceding claims, wherein the anti-CD200 antibody is samalizumab or an antigen-binding fragment thereof.

6. The method of any one of the preceding claims, wherein the anti-CD200 antibody or antigen-binding fragment thereof inhibits the interaction between CD200 and CD200R.

7. The method of any one of the preceding claims wherein the treatment results in a CD200 saturation of at least about 70, 75, 80, 85, 90, or 95%.

8. The method of any one of the preceding claims, wherein the solid tumor is at least one of a sarcoma, carcinoma, and lymphoma.

9. The method of any one of the preceding claims, wherein the solid tumor is an advanced solid tumor.

10. The method of any one of claims 1-9, wherein the solid tumor is at least one tumor selected from the group consisting of a tumor of the colon, stomach, salivary glands, lung (including small-cell lung cancer and non-small cell lung cancer), skin, thyroid, prostate, breast, ovaries, cervix, vagina, testicles, bladder, liver, lymphatic tissue (including Hodgkin's disease and non-Hodgkin's lymphomas), bone (including osteogenic sarcoma and Ewing' s Sarcoma), kidney, eye (including retinoblastoma), adrenal glands (including neuroblastoma and

adrenocortical carcinoma), soft tissue (including rhabdomyosarcoma and rhabdosarcoma), ovary, pancreas, brain, head, and neck.

11. The method of any one of claims 1-9, wherein the solid tumor is at least one tumor selected from the group consisting of an adrenocortical tumor, alveolar soft part sarcoma, carcinoma, chondrosarcoma, colorectal carcinoma, desmoid tumor, desmoplastic small round cell tumor, endocrine tumor, endodermal sinus tumor, epithelioid hemangioendothelioma, Ewing sarcoma, germ cell tumor, hepatoblastoma, hepatocellular carcinoma, melanoma, nephroma, neuroblastoma, non-rhabdomyosarcoma soft tissue sarcoma (NRSTS), osteosarcoma, paraspinal sarcoma, renal cell carcinoma, retinoblastoma, rhabdomyosarcoma, synovial sarcoma, pediatric brain tumor, extracranial solid tumor, Wilms' tumor, melanoma, squamous lung cancer, lung adenocarcinoma, bladder carcinoma, small cell lung carcinoma, esophageal carcinoma, colorectal carcinoma, cervical carcinoma, head and neck squamous cell carcinoma, gastric cancer, uterine cancer, hepatocellular carcinoma, clear cell renal cell carcinoma, papillary renal cell carcinoma, ovarian carcinoma, prostate carcinoma, myeloma, B cell lymphoma, low grade glioma, breast cancer, pancreatic cancer, glioblastoma, neuroblastoma, chronic lymphocytic leukemia, thyroid cancer, chromophobe kidney carcinoma, acute myeloid leukemia, medulloblastoma, and acute lymphoblastic leukemia.

12. The method of any one of the preceding claims, wherein the treatment results in a reduction in tumor burden according to RECIST 1.1 parameters.

13. The method of any one of the preceding claims, wherein the treatment results in a reduction in tumor burden according to irRECIST parameters.

14. The method of any one of the preceding claims, wherein the anti-CD200 antibody, or antigen binding portion thereof, is administered intravenously.

15. The method of claim 14, wherein the intravenous administration is at a rate of from about 125 to about 250 mL/hour.

16 The method of any of the preceding claims, wherein the anti-CD200 antibody, or antigen- binding fragment thereof, is administered every twenty-one days for at least 1 year.

17. The method of any one of claims 1-14, wherein the anti-CD200 antibody, or antigen- binding fragment thereof, is administered every twenty-one days for at least 2 years.

18. A kit for treating a human patient having a solid tumor, the kit comprising:

a) a dose of an anti-CD200 antibody, or antigen-binding fragment thereof, comprising a heavy chain variable region CDRl having the sequence set forth in SEQ ID NO: 7, a heavy chain variable region CDR2 having the sequence set forth in SEQ ID NO: 8, a heavy chain variable region CDR3 having the sequence set forth in SEQ ID NO: 9, a light chain variable region CDRl having the sequence set forth in SEQ ID NO: 4, a light chain variable region CDR2 having the sequence set forth in SEQ ID NO: 5, and a light chain variable region CDR3 having the sequence set forth in SEQ ID NO: 6; and b) instructions for using the anti-CD200 antibody, in the method of any one of the preceding claims.