WO2015081158A1 - Method of treating hiv by disrupting pd-1/pd-l1 signaling - Google Patents

Abstract

The present invention relates to methods of treating a subject infected with HIV who is currently on combination anti-retroviral therapy (cART) treatment, comprising administering to the subject a therapeutically effective amount of an antibody or an antigen-binding portion thereof that disrupts the interaction between Programmed Death-1 (PD-1) and Programmed Death Ligand-1 (PD-L1), wherein the antibody or antigen-binding portion thereof binds specifically to PD-L1.

Description

METHOD OF TREATING HIV BY DISRUPTING PD-1/PD-L1 SIGNALING

RELATED APPLICATION

This application claims the benefit of U.S. Provisional Patent Application Serial No. 61/908,961, filed on November 26, 2013, the entire contents of which are hereby incorporated by reference in their entirety.

FIELD OF THE INVENTION

This invention relates to methods for treating an HIV patient comprising administering to the patient antibodies that disrupt the PD-1/PD-L1 signaling pathway.

BACKGROUND

Programmed Death- 1 (PD-1) is a member of the Ig superfamily that is up regulated on activated lymphocytes and monocytes. PD-1 is expressed on activated CD4 and CD8 T cells, B cells and myeloid cells. Two cell surface glycoprotein ligands for PD-1 have been identified, Programmed Death Ligand-1 (PD-L1) and Programmed Death Ligand-2 (PD-L2). PD-L1 is expressed on T cells, B cells, monocytes, macrophages and dendritic cells (DCs) and its expression can be induced by activation of T lymphocytes, monocytes, mactophages and DCs. PD-L2 is expressed on non- lymphoid tissues and is up-regulated on monocytes and DCs after activation. The engagement of PD-1/PD-L1/2 inhibits CD3 -mediated T cell proliferation and cytokine production.

In both humans and primates, PD-1/PD-L1 has been shown to function as a negative regulator of immune responses to viral infections. It is known that PD-1 expression is increased on CD8 T cells during acute viral infections. However, it remains up-regulated on virus-specific CD8 T cells during chronic viral infections rendering those CD8 T cells "exhausted" with limited functional capacity.

Clearly, there is a need to restore virus-specific T cell function from exhaustion, thereby allowing the immune system to clear virus infected cells. This invention describes methods to block the PD-1/PD-L1 signaling pathway by administering anti-PD- Ll antibodies to subjects infected with HIV. SUMMARY

The present disclosure provides a method for treating a subject infected with HIV, which method comprises administering to the subject a composition comprising a therapeutically effective amount of an agent that disrupts, reduces or suppresses signaling from an inhibitory immunoregulator. In some embodiments, the agent may be an antibody (Ab). In some embodiments, the inhibitory immunoregulator may be a component of the PD-1/PD-L1 signaling pathway. In some embodiments, the Ab may disrupt the interaction between PD-1 and PD-Ll . In some embodiments, the Ab may be an anti-PD-Ll Ab.

Also provided herein are methods of treating a subject infected with HIV who is currently on combination anti-retroviral therapy (cART) treatment, comprising administering to the subject a therapeutically effective amount of an antibody or an antigen-binding portion thereof that disrupts the interaction between Programmed Death- 1 (PD-1) and Programmed Death Ligand-1 (PD-Ll), wherein the antibody or antigen- binding portion thereof binds specifically to PD-L 1.

Also provided herein are methods of treating a subject infected with HIV who is currently on combination anti-retroviral therapy (cART) treatment, comprising administering to the subject a therapeutically effective amount of an antibody or an antigen-binding portion thereof that comprises a heavy chain variable region CDR1 comprising SEQ ID NO:22, a heavy chain variable region CDR2 comprising SEQ ID NO:32, a heavy chain variable region CDR3 comprising SEQ ID NO:42, a light chain variable region CDR1 comprising SEQ ID NO: 52, a light chain variable region CDR2 comprising SEQ ID NO:62, and a light chain variable region CDR3 comprising SEQ ID NO:72.

Other features and advantages of the invention will be apparent from the following detailed description and examples which should not be construed as limiting. The contents of all cited references, including scientific articles, GENBANK® entries, patents and patent applications cited throughout this application are expressly

incorporated herein by reference. BRIEF DESCRIPTION OF THE FIGURES Figures 1A-1F. Cross-competition of FITC-conjugated human anti-hPD-Ll mAbs for binding to human PD-L1 (hPD-Ll) expressed on CHO cells as described in Example 1. A, Binding of labeled 10H10 was partially blocked by 10A5, 11E6 and 13G4 and was significantly blocked by itself; B, Binding of labeled 3G10 was significantly blocked by each of the tested anti-PD-Ll Abs except 10H10; C, Binding of labeled 10A5 was significantly blocked by each of the tested anti-PD-Ll Abs except 10H10; D, Binding of labeled 11E6 was significantly blocked by each of the tested anti-PD-Ll Abs except 10H10; and E, Binding of labeled 12A4 was significantly blocked by each of the tested anti-PD-Ll Abs except 10H10; and F, Binding of labeled 13G4 was significantly blocked by each of the tested anti-PD-Ll Abs except 10H10.

Figure 2 A and 2B. Geometric mean for viral load rebound post-ARV treatment interruption (post-TI) for BMS-936559- treated and isotype control antibody-treated SIV- infected Rhesus macaques as described in Example 2 (Fig. 2A). Geometric mean for viral load rebound post-TI of responders and non-responders within the BMS-936559- treatment group (Fig. 2B). BMS-936559-treatment responders are defined as having slower rebound and viral load <1000 RNA cp/mL for >3 weeks.

Figure 3. Kinetics of viral load rebound post-ARV treatment interruption for individual animals from the BMS-936559-treated and isotype control groups of SIV- infected Rhesus macaques as described in Example 2. The asterisks in figure legend are indicating Mama A*01, which is a Rhesus monkey HLA haplotype that may lead to spontaneous suppression of SIV.

Figure 4. Kinetics of viral load rebound post-treatment interruption for individual animals from the BMS-936559-treatment group of SIV-infected Rhesus macaques as described in Example 2.

Figure 5. Kinetics of viral load rebound post-treatment interruption for individual animals from the BMS-936559-treatment responders as described in Example 2. Black and grey bars show periods during which viral load was below detection (<50 SIV RNA copies/ml) for three of the BMS-936559-treatment responder animals for at least two consecutive VL determinations, as indicated.

Figures 6 A and 6B. Comparison of post-rebound (post-TI) with pre-ARV viral loads as described in Example 2. 4 of 8 in BMS-936559 -treated group have >2 log change in VL from pre-ARV (only 1 of 5 in isotype control group) (6A). A significant difference (p-value <0.05 in Mann- Whitney U-test) in post-rebound VL between BMS- 936559- and isotype control-treated groups was observed (6B).

Figure 7. Body weight (A), lymphocyte (B) and serum alanine aminotransferase levels (C) in ARV-suppressed SIV -infected Rhesus macques before antibody treatment (pre-mAb), during antibody administration (dose 1, 2,3, 4, 5) and after termination of ARVT (Post-TI), as indicated in Example 2.

Figure 8. SIV-peptide specific cytokine responses (Interferon-gamma [IFNy], Tumor Necrosis Factor-Alpha [TNFa] and Interleukin-2 [IL-2]) in CD8+ T cells from lymph nodes of SIV-infected Rhesus macaques pre- and post-treatment with BMS- 936559 or isotype control antibody as described in Example 2.

DETAILED DESCRIPTION

Presented herein are methods for treating a subject infected with HIV, which methods comprise administering to the subject a therapeutically effective amount of an Ab or an antigen-binding portion thereof that disrupts the interaction between the PD-1 receptor and its ligand, PD-Ll . In certain embodiments, the Ab or antigen-binding portion thereof may bind specifically to PD-Ll . Also presented herein are methods for treating a subject infected with HIV who is currently on combination anti-retro viral therapy (cART) treatment, comprising administering to the subject a therapeutically effective amount of an antibody or an antigen-binding portion thereof that disrupts the interaction between Programmed Death- 1 (PD-1) and Programmed Death Ligand-1 (PD- Ll), wherein the antibody or antigen-binding portion thereof binds specifically to PD-Ll . Definitions

In order that the present disclosure may be more readily understood, certain terms are first defined. As used in this application, except as otherwise expressly provided herein, each of the following terms shall have the meaning set forth below. Additional definitions are set forth throughout the application.

"Administering" refers to the physical introduction of a composition comprising a therapeutic agent to a subject, using any of the various methods and delivery systems known to those skilled in the art. Preferred routes of administration for Abs described herein include intravenous, intramuscular, subcutaneous or other parenteral routes of administration, for example by injection or infusion. Alternatively, an Ab described herein can be administered via a non-parenteral route, such as a topical, epidermal or mucosal route of administration, for example, intranasally, orally, vaginally, rectally, sublingually or topically. Administering can also be performed, for example, once, a plurality of times, and/or over one or more extended periods, such as once a month, once per two weeks, once a week, twice a week, or once per day.

An "antibody" (Ab) shall include, without limitation, a glycoprotein

immunoglobulin which binds specifically to an antigen and comprises at least two heavy (H) chains and two light (L) chains interconnected by disulfide bonds, or an antigen- binding portion thereof. Each H chain comprises a heavy chain variable region

(abbreviated herein as V_#) and a heavy chain constant region. The heavy chain constant region comprises three constant domains, Cm, Cm and Cm- Each light chain comprises a light chain variable region (abbreviated herein as Vi or V_K) and a light chain constant region. The light chain constant region is comprises one constant domain, C_L. The V# and V_£ regions can be further subdivided into regions of hypervariability, termed

complementarity determining regions (CDRs), interspersed with regions that are more conserved, termed framework regions (FR). Each Y_H and Vi comprises 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 Abs 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.

Antibodies typically bind specifically to their cognate antigen with high affinity, reflected by a dissociation constant (K_D) of 10^"5 to 10^"11 M or less. Any K_D greater than about 10^"4 M is generally considered to indicate nonspecific binding. As used herein, an Ab that "binds specifically" to an antigen refers to an Ab that binds to the antigen and substantially identical antigens with high affinity, which means having a K_D of 10^"7 M or less, 10^"8 M or less, 5 x 10^~9 M or less, 10^~9 M or less, or 10^"10 M or less, but does not bind with high affinity to unrelated antigens. An antigen is "substantially identical" to a given antigen if it exhibits a high degree of sequence identity to the given antigen, for example, if it exhibits at least 80%, at least 90%, at least 95%, at least 97%, or at least 99% sequence identity to the sequence of the given antigen. By way of example, an Ab that binds specifically to human PD-Ll may also have cross-reactivity with PD-Ll antigens from certain non-human primate species.

An immunoglobulin may derive from any of the commonly known isotypes, including but not limited to IgA, secretory IgA, IgG and IgM. IgG subclasses are also well known to those in the art and include but are not limited to human IgGl, IgG2, IgG3 and IgG4. "Isotype" refers to the Ab class or subclass (e.g., IgM or IgGl) that is encoded by the heavy chain constant region genes. The term "antibody" includes, by way of example, both naturally occurring and non-naturally occurring Abs; monoclonal and polyclonal Abs; chimeric and humanized Abs; human or nonhuman Abs; wholly synthetic Abs; and single chain Abs. A nonhuman Ab may be humanized by recombinant methods to reduce its immunogenicity in man. Where not expressly stated, and unless the context indicates otherwise, the term "antibody" also includes an antigen-binding fragment or an antigen-binding portion of any of the aforementioned immunoglobulins, and includes a monovalent and a divalent fragment or portion, and a single chain Ab.

An "isolated antibody" refers to an Ab that is substantially free of other Abs having different antigenic specificities (e.g., an isolated Ab that binds specifically to PD- Ll is substantially free of Abs that bind specifically to antigens other than PD-Ll). An isolated Ab that binds specifically to PD-Ll may, however, have cross-reactivity to other antigens, such as PD-Ll molecules from different species. Moreover, an isolated Ab may be substantially free of other cellular material and/or chemicals. By comparison, an "isolated" nucleic acid refers to a nucleic acid composition of matter that is markedly different, i.e., has a distinctive chemical identity, nature and utility, from nucleic acids as they exist in nature. For example, an isolated DNA, unlike native DNA, is a free-standing portion of a native DNA and not an integral part of a larger structural complex, the chromosome, found in nature. Further, an isolated DNA, unlike native genomic DNA, can typically be used in applications or methods for which native genomic DNA is unsuited, e.g., as a PCR primer or a hybridization probe for, among other things, measuring gene expression and detecting biomarker genes or mutations for diagnosing disease or assessing the efficacy of a therapeutic. An isolated nucleic acid may be purified so as to be substantially free of other cellular components or other contaminants, e.g., other cellular nucleic acids or proteins, using standard techniques well known in the art. Examples of isolated nucleic acids include fragments of genomic DNA, PCR- amplified DNA, cDNA and RNA.

The term "monoclonal antibody" ("mAb") refers to a preparation of Ab molecules of single molecular composition, i.e., Ab molecules whose primary sequences are essentially identical, and which exhibits essentially a single binding specificity and affinity for a particular epitope. A mAb is an example of an isolated Ab. MAbs may be produced by hybridoma, recombinant, transgenic or other techniques known to those skilled in the art.

A "human" antibody (HuMAb) refers to an Ab having variable regions in which both the framework and CDR regions are derived from human germline immunoglobulin sequences. Furthermore, if the Ab contains a constant region, the constant region also is derived from human germline immunoglobulin sequences. The human Abs of the invention may include amino acid residues not encoded by human germline

immunoglobulin sequences (e.g. , mutations introduced by random or site-specific mutagenesis in vitro or by somatic mutation in vivo). However, the term "human antibody," as used herein, is not intended to include Abs in which CDR sequences derived from the germline of another mammalian species, such as a mouse, have been grafted onto human framework sequences. The terms "human" Abs and "fully human" Abs and are used synonymously.

A "humanized" antibody refers to an Ab in which some, most or all of the amino acids outside the CDR domains of a non-human Ab are replaced with corresponding amino acids derived from human immunoglobulins. In one embodiment of a humanized form of an Ab, some, most or all of the amino acids outside the CDR domains have been replaced with amino acids from human immunoglobulins, whereas some, most or all amino acids within one or more CDR regions are unchanged. Small additions, deletions, insertions, substitutions or modifications of amino acids are permissible as long as they do not abrogate the ability of the Ab to bind to a particular antigen. A "humanized" Ab retains an antigenic specificity similar to that of the original Ab.

A "chimeric antibody" refers to an Ab in which the variable regions are derived from one species and the constant regions are derived from another species, such as an Ab in which the variable regions are derived from a mouse Ab and the constant regions are derived from a human Ab.

An "antigen-binding portion" of an Ab (also called an "antigen-binding fragment") refers to one or more fragments of an Ab that retain the ability to bind specifically to the antigen bound by the whole Ab.

An "immune response" refers to the action of a cell of the immune system (for example, T lymphocytes, B lymphocytes, natural killer (NK) cells, macrophages, eosinophils, mast cells, dendritic cells and neutrophils) and soluble macromolecules produced by any of these cells or the liver (including Abs, cytokines, and complement) that results in selective targeting, binding to, damage to, destruction of, and/or elimination from a 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 "immunoregulator" refers to a substance, an agent, a signaling pathway or a component thereof that regulates an immune response. "Regulating," "modifying" or

"modulating" an immune response refers to any alteration in a cell of the immune system or in the activity of such cell. Such regulation includes stimulation or suppression of the immune system which may be manifested by an increase or decrease in the number of various cell types, an increase or decrease in the activity of these cells, or any other changes which can occur within the immune system.

"Treatment" or "therapy" of a subject refers to any type of intervention or process performed on, or the administration of an active agent to, the subject with the objective of reversing, alleviating, ameliorating, inhibiting, slowing down or preventing the onset, progression, development, severity or recurrence of a symptom, complication, condition or biochemical indicia associated with a disease.

"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.

The "Programmed Death- 1 (PD-1)" receptor refers to an immunoinhibitory receptor belonging to the CD28 family. PD-1 is expressed predominantly on previously activated T cells in vivo, and binds to two ligands, PD-L1 and PD-L2. The term "PD-1" as used herein includes human PD-1 (hPD-1), variants, iso forms, and species homo logs of hPD-1, and analogs having at least one common epitope with hPD-1. The complete hPD-1 sequence can be found under GENBANK® Accession No. U64863.

"Programmed Death Ligand-1 (PD-L1)" is one of two cell surface glycoprotein ligands for PD-1 (the other being PD-L2) that downregulate T cell activation and cytokine secretion upon binding to PD-1. The term "PD-L1" as used herein includes human PD-L1 (hPD-Ll), variants, iso forms, and species homo logs of hPD-Ll, and analogs having at least one common epitope with hPD-Ll . The complete hPD-Ll sequence can be found under GENBANK® Accession No. Q9NZQ7.

A "signal transduction pathway" or "signaling pathway" refers to the biochemical relationship between a variety of signal transduction molecules that play a role in the transmission of a signal from one portion of a cell to another portion of the cell. A "cell surface receptor" includes, for example, molecules and complexes of molecules that are located on the surface of a cell and are capable of receiving a signal and transmitting such a signal across the plasma membrane of a cell. An "inhibitor" of signaling refers to a compound or agent that antagonizes or reduces the initiation, reception or transmission of a signal, be that signal stimulatory or inhibitory, by any component of a signaling pathway such as a receptor or its ligand.

"Antiretroviral" (ARV) and "combination antiretroviral therapy" (cART) refer to the drugs used to treat HIV and are herein utilized interchangeably. Called antiretrovirals because they act against the retrovirus HIV, these drugs are grouped by how they interfere with steps in HIV replication. Entry Inhibitors interfere with the virus' ability to bind to receptors on the outer surface of the cell in which it is trying to enter. When receptor binding fails, HIV cannot infect the cell. Fusion Inhibitors interfere with the virus's ability to fuse with a cellular membrane, preventing HIV from entering a cell. Reverse Transcriptase Inhibitors prevent the HIV enzyme reverse transcriptase (RT) from converting single-stranded HIV RNA into double-stranded HIV DNA (a process called reverse transcription). There are two types of RT inhibitors, nucleoside/nucleotide RT inhibitors (NRTIs) and non-nucleoside RT inhibitors (NNRTIs). NRTIs are faulty DNA building blocks. When one of these faulty building blocks is added to a growing HIV DNA chain, no further correct DNA building blocks can be added, thereby halting HIV DNA synthesis. NNRTIs bind to RT, thereby interfering with its ability to convert HIV RNA into HIV DNA. Integrase Inhibitors block the HIV enzyme integrase, which the virus uses to integrate its genetic material into the DNA of the cell it has infected.

Protease Inhibitors (Pis) interfere with the HIV enzyme called protease, which normally cuts long chains of HIV proteins into smaller individual proteins. When protease does not work properly, new virus particles cannot be assembled. Use of these drugs in

combination may be termed interchangeably anti-retroviral therapy (ART), combination anti-retro viral therapy (cART) or highly active anti-retroviral therapy (HAART).

A "subject" includes any human or nonhuman animal. The term "nonhuman animal" includes, but is not limited to, vertebrates such as nonhuman primates, sheep, dogs, cats, rabbits and ferrets, rodents such as mice, rats and guinea pigs, avian species such as chickens, amphibians, and reptiles. In some embodiments, the subject is a mammal such as a nonhuman primate, sheep, dog, cat, rabbit, ferret or rodent. In some embodiments, the subject is a primate. In some embodiments, the subject is a human such as a human patient. The terms, "subject," "patient" and "individual" are used interchangeably herein. "A subject who is currently on combination anti-retroviral therapy (cART) treatment" means that the subject is currently being treated with a cART regimen. In some embodiments, the subject who is currently being treated with a cART regimen may have been treated with a different cART regimen before switching to the current cART regimen. Thus the subject who is currently on combination anti-retroviral therapy (cART) treatment may have been on cART treatment for a period of time but with different cART regimens. A stable cART regimen means there are no changes in the components of the antiretroviral therapy for a period of time, for example, at least 30, 60, 90, 120, or 180 days, or 1, 2, or 3 years.

As described herein, any concentration range, percentage range, ratio range or integer range is to be understood to include the value of any integer within the recited range and, when appropriate, fractions thereof (such as one tenth and one hundredth of an integer), unless otherwise indicated.

Various aspects of the invention are described in further detail in the following subsections. Provided herein are methods for treating a subject infected with HIV, comprising administering to the subject a therapeutically effective amount of an Ab or an antigen- binding that binds specifically to PD-L1.

In some embodiments, the subject may be currently on combination anti-retro viral therapy (cART) treatment. In some embodiments, the cART treatment (or regimen) may comprise at least two drugs. In some embodiments, the cART treatment (or regimen) may comprise at least three drugs. In some embodiments, the cART treatment may comprise at least three anti-retroviral drugs selected from entry inhibitors, fusion inhibitors, reverse transcriptase (RT) inhibitors, nucleoside/nucleotide RT inhibitors, non- nucleoside RT inhibitors, integrase inhibitors, and protease inhibitors. In some

embodiments, the cART treatment or regimen may comprise an integrase inhibitor, a non-nucleoside reverse transcriptase inhibitor (NNRTI), and a protease inhibitor (PI). In some embodiments, the cART treatment or regimen may comprise at least four drugs. In some embodiments, the patient may have been on cART treatment for at least 1, 2, 3, 4, 5, 6, 8, 9, 12, 18, 24, 36 or 48 months. In some embodiments, the patient may have been on cART treatment for at least 1 year. In some embodiments, the patient may have been on cART treatment for at least 2 years. In some embodiments, the patient may have been on a stable cART regimen with no changes in the components of the antiretroviral therapy for at least 30, 60, 90, 120, 180 days or 1 year. In some embodiments, the patient may have been on a stable cART regimen with no changes in the components of the

antiretroviral therapy for at least 90 days.

In some embodiments, the subject may have a suppressed viral load (VL). The term "suppressed VL" means a reduced VL as compared to the VL before the patient started any cART treatment (pre-cART treatment VL). In some embodiments, the subject may have a suppressed VL before the antibody or an antigen-binding portion thereof is administered. For example, the subject may have a suppressed VL of less than 2000, less than 1000, less than 500, less than 200, less than 100, less than 50, less than 40, less than 30, less than 20, or less than 10 RNA copies/mL. In some embodiments, the subject may have a suppressed VL of less than 1000 RNA copies/mL before the antibody or an antigen-binding portion thereof is administered. In some embodiments, the subject may have a suppressed VL of less than 100 RNA copies/mL before the antibody or an antigen- binding portion thereof is administered. In some embodiments, the subject may have a suppressed VL of less than 50 RNA copies/mL before the antibody or an antigen-binding portion thereof is administered. In some embodiments, the subject may have a fully suppressed VL. For HIV-1 infected patients, "fully suppressed VL" means VL below the limit of detection for commonly used commercial and FDA approved methods. In some embodiments, a suppressed VL is less than 20 or 40 RNA copies/mL, which is the limit of detection for the tests typically used to quantify HIV VL in infected patients (e.g. <40 copies/mL obtained by the Abbott m2000 assay or <20 copies/mL by the Roche

TAQMAN® v2.0 assay).

In some embodiments, the method may further comprise removing the cART treatment after the antibody or an antigen-binding portion thereof is administered.

"Removing" the cART treatment means stopping or suspending temporarily, or permanently, the cART treatment. In some embodiments, the viral load of the subject may be suppressed after the cART treatment is removed ("post-ARV interruption"). The term "suppressed VL" means a reduced VL as compared to the pre-cART treatment VL. In some embodiments, the viral load, after the cART treatment is removed, may be less than 2000, less than 1000, less than 500, less than 200, less than 100, less than 50 RNA, or less than 20 copies/mL or below the limit of detection for commonly used commercial and FDA approved methods.

In some embodiments, the viral load may be suppressed for at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 36, or 48 weeks, or at least 1, 2, or 3 years after the cART treatment is removed. In some embodiments, the viral load may be suppressed for at least 3 weeks after the cART treatment is removed. In some embodiments, the viral load may be suppressed for at least 4 weeks after the cART treatment is removed. In some embodiments, the viral load may be suppressed for at least 6 weeks after the cART treatment is removed. In some embodiments, the viral load may be suppressed for at least 3 months after the cART treatment is removed. In some embodiments, the viral load may be suppressed for at least 6 months after the cART treatment is removed.

In some embodiments, the viral load, after the cART treatment is removed, may be less than 2000, less than 1000, less than 500, less than 200, less than 100, less than 50 RNA, or less than 20 copies/mL or below the limit of detection for commonly used commercial and FDA approved methods, for at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 36, or 48 weeks, or at least 1, 2, or 3 years. In some embodiments, the viral load, after the cART treatment is removed, may be less than 1000 RNA copies/mL for at least 6 weeks, or 3, 6, 9, 12, 18, 24, or 36 months. In some embodiments, the viral load, after the cART treatment is removed, may be less than 1000 RNA copies/mL for at least 6 weeks. In some embodiments, the viral load, after the cART treatment is removed, may be less than 1000 RNA copies/mL for at least 3 months. In some embodiments, the viral load, after the cART treatment is removed, may be less than 1000 RNA copies/mL for 3-6 months. In some embodiments, the viral load, after the cART treatment is removed, may be less than 1000 RNA copies/mL for at least 6 months.

In some embodiments, the viral load, after the cART treatment is removed, may be less than 50 RNA copies/mL for at least 6 weeks, or 3, 6, 9, 12, 18, 24, or 36 months. In some embodiments, the viral load, after the cART treatment is removed, may be less than 50 RNA copies/mL for at least 6 weeks. In some embodiments, the viral load, after the cART treatment is removed, may be less than 50 RNA copies/mL for at least 3 months. In some embodiments, the viral load, after the cART treatment is removed, may be less than 50 RNA copies/mL for 3-6 months. In some embodiments, the viral load, after the cART treatment is removed, may be less than 50 RNA copies/mL for at least 6 months. In some embodiments, the viral load, after the cART treatment is removed, may be less than 20 RNA copies/mL for at least 3 months. In some embodiments, the viral load, after the cART treatment is removed, may be less than 20 RNA copies/mL for at least 6 months. In some embodiments, the viral load, after the cART treatment is removed, may be below the limit of detection for a commonly used commercial and FDA approved method for at least 3 months. In some embodiments, the sustained viral load of the subject is below the limit of detection for a commonly used commercial and FDA approved method for at least 6 months.

In some embodiments, the viral load may be suppressed following an initial viral load rebound after the cART treatment is removed. The term "initial viral load rebound" means an increase in VL as compared to the VL before the cART treatment is removed.

Anti-PD-Ll Antibodies Each of the anti-PD-Ll HuMAbs disclosed in U.S. Patent No. 7,943,743, which is incorporated by reference herein in its entirety, has been demonstrated to exhibit one or more of the following characteristics (a) binds to human PD-Ll with a K_D of 1 x 10^~7 M or less; (b) inhibits the binding of PD-Ll to PD-1; (c) reverses exhaustion of virus- specific T cell observed during chronic infections and (d) reverses the suppressive effect of T regulatory cells on T cell effector cells and/or dendritic cells.

In some embodiments, an anti-PD-Ll Ab or antigen-binding portion thereof may bind specifically to human PD-Ll wherein the antibody exhibits at least one of the following properties:

(a) binds to human PD-Ll with a K_D of lxlO^"7M or less;

(b) increases T-cell proliferation in a mixed lymphocyte reaction (MLR) or similar assay;

(c) increases interferon-γ production in an MLR or similar assay; or

(d) increases interleukin-2 (IL-2) secretion in an MLR or similar assay.

Exemplary anti-PD-Ll Abs include the anti-PD-Ll HuMAbs 3G10, 12A4, 10A5, 5F8, 10H10, 1B12, 7H1, 11E6, 12B7, and 13G4 disclosed in U.S. Patent No. 7,943,743. In some embodiments, the antibody or an antigen-binding portion thereof may be an IgGl, IgG2 or IgG4 isotype. In some embodiments, the antibody or an antigen-binding portion thereof may be an antibody fragment or a single chain antibody. In some embodiments, the antibody or an antigen-binding portion thereof may bind to human PD- Ll with a K_D of lx 10^"8M or less, 5xlO^~9M or less, 2xlO^~9M or less, or lxlO^~9M or less. In some embodiments, the antibody or an antigen-binding portion thereof may bind to human PD-Ll with a K_D of 2xlO^~9M or less.

In some embodiments, an anti-PD-Ll Ab or antigen-binding portion thereof may bind specifically to human PD-Ll and comprise: (a) a human heavy chain variable region comprising the sequence set forth in SEQ ID NO: 1 and a human light chain variable region comprising the sequence set forth in SEQ ID NO: 11; (b) a human heavy chain variable region comprising the sequence set forth in SEQ ID NO: 2 and a human light chain variable region comprising the sequence set forth in SEQ ID NO: 12; (c) a human heavy chain variable region comprising the sequence set forth in SEQ ID NO: 3 and a human light chain variable region comprising the sequence set forth in SEQ ID NO: 13; (d) a human heavy chain variable region comprising the sequence set forth in SEQ ID NO: 4 and a human light chain variable region comprising the sequence set forth in SEQ ID NO: 14; (e) a human heavy chain variable region comprising the sequence set forth in SEQ ID NO: 5 and a human light chain variable region comprising the sequence set forth in SEQ ID NO: 15; (f) a human heavy chain variable region comprising the sequence set forth in SEQ ID NO: 6 and a human light chain variable region comprising the sequence set forth in SEQ ID NO: 16; (g) a human heavy chain variable region comprising the sequence set forth in SEQ ID NO: 7 and a human light chain variable region comprising the sequence set forth in SEQ ID NO: 17; (h) a human heavy chain variable region comprising the sequence set forth in SEQ ID NO: 8 and a human light chain variable region comprising the sequence set forth in SEQ ID NO: 18; (i) a human heavy chain variable region comprising the sequence set forth in SEQ ID NO: 9 and a human light chain variable region comprising the sequence set forth in SEQ ID NO: 19; or (j) a human heavy chain variable region comprising the sequence set forth in SEQ ID NO: 10 and a human light chain variable region comprising the sequence set forth in SEQ ID NO: 20.

Given that each of these Abs can bind to PD-L1, the V# and Y_L sequences can be "mixed and matched" to create other anti-PD-Ll Abs of the invention. PD-L1 binding of such "mixed and matched" Abs can be tested using binding assays e.g., ELISAs, western blots, radioimmunoassays and BIACORE® analysis that are well known in the art {see, e.g., U.S. Patent No. 7,943,743). In some embodiments, when and Y_L chains are mixed and matched, a Y_H sequence from a particular V#/V _L pairing may be replaced with a structurally similar Y_H sequence. Likewise, a Y_L sequence from a particular V#/V _L pairing may be replaced with a structurally similar Y_L sequence. In some embodiments, an anti-PD-Ll Ab, or antigen binding portion thereof, may bind specifically to human PD-L1 and comprise:

(a) a heavy chain variable region comprising an amino acid sequence selected from SEQ ID NOs: l, 2, 3, 4, 5, 6, 7, 8, 9, and 10; and

(b) a light chain variable region comprising an amino acid sequence selected from SEQ ID NOs: 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20. In some embodiments, the anti-PD-Ll Abs or antigen-binding portions thereof may bind specifically to PD-L1 and comprise a heavy chain variable region derived from a particular germline heavy chain immunoglobulin and/or a light chain variable region derived from a particular germline light chain immunoglobulin. In some embodiments, the anti-PD-Ll Abs may comprise: (a) a heavy chain variable region comprising a sequence derived from a human Y_H 1-18, 1-69, 1-3 or 3-9 germline sequence, and/or a light chain variable region comprising a sequence derived from a human V_K L6, LI 5, A27 or LI 8 germline sequence. Exemplary amino acid sequences of the and V_K regions encoded by the Y_H 1-18, Y_H 1-3, V_H 1-69, Y_H 3-9, V_K L6, V_K L15 and V_K A27 germline genes are provided in U.S. Patent No. 7,943,743.

In some embodiments, the antibody or antigen-binding portions thereof may comprise: (a) a heavy chain variable region that comprises a sequence derived from a human Y 1-18 germline sequence, and a light chain variable region that comprises a sequence derived from a human V_K L6 germline sequence; (b) a heavy chain variable region that comprises a sequence derived from a human Y_H 1-69 germline sequence, and a light chain variable region that comprises a sequence derived from a human V_K L6 germline sequence; (c) a heavy chain variable region that comprises a sequence derived from a human Y 1-3 germline sequence, and a light chain variable region that comprises a sequence derived from a human V_K L15 germline sequence; (d) a heavy chain variable region that comprises a sequence derived from a human Y_H 1-69 germline sequence, and a light chain variable region that comprises a sequence derived from a human V_K A27 germline sequence; (e) a heavy chain variable region that comprises a sequence derived from a human Y 3-9 germline sequence, and a light chain variable region that comprises a sequence derived from a human V_K L15germline sequence; or (f) a heavy chain variable region that comprises a sequence derived from a human 3-9 germline sequence, and a light chain variable region that comprises a sequence derived from a human V_K

L18germline sequence.

An example of an Ab having a Y_H and a V_K derived from Y_H 1-18 and V_K L6 germline sequences, respectively, is 3G10. Examples of Abs having and V_K regions derived from Y_H 1-69 and V_K L6 germline sequences, respectively, include 12A4, 1B12, 7H1 and 12B7. An example of an Ab having a Y_H and a V_K derived from Y_H 1-3 and V_K L15 germline sequences, respectively, is 10A5. Examples of Abs having Y_H and V_K regions derived from V_H 1-69 and V_K A27 germline sequences, respectively, include 5F8, 11E6 and 1 lE6a. An example of an Ab having a V_# and a V_K derived from V_H 3-9 and V_K L15 germline sequences, respectively, is 10H10. An example of an Ab having a Y_H and a V_K derived from 1-3 and V_K L15 germline sequences, respectively, is 10A5. An example of an Ab having a V# and a V_K derived from V# 3-9 and V_K LI 8 germline sequences, respectively, is 13G4.

In certain embodiments, anti-PD-Ll Abs or antigen-binding portion thereof may comprise heavy and light chain variable regions having amino acid sequences that are highly similar, homologous or identical to the amino acid sequences of the exemplary anti-PD-Ll Abs described herein, wherein the Ab retains the functional properties of the exemplary anti-PD-Ll Abs. For example, the anti-PD-Ll Abs may include mAbs comprising a heavy chain variable region and a light chain variable region, wherein the heavy chain variable region comprises a sequence that is at least 80%, 85%, 90%, 95%, 96%), 97%), 98%o or 99% identical to an amino acid sequence selected from SEQ ID NOs. 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10, and the light chain variable region comprises a sequence that is at least 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99% identical to an amino acid sequence selected from the group consisting of SEQ ID NOs. 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20. In some embodiments, the anti-PD-Ll Abs may comprise a heavy chain variable region comprising a sequence that is at least 95% identical to an amino acid sequence selected from SEQ ID NOs. 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10, and a light chain variable region comprising a sequence that is at least 95% identical to an amino acid sequence selected from the group consisting of SEQ ID NOs. 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20. In some embodiments, the anti-PD-Ll Abs may comprise a heavy chain variable region comprising a sequence that is at least 98% identical to an amino acid sequence selected from SEQ ID NOs. 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10, and a light chain variable region comprising a sequence that is at least 98% identical to an amino acid sequence selected from the group consisting of SEQ ID NOs. 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20.

In some embodiments, the anti-PD-Ll Abs may comprise (a) a heavy chain variable region comprising an amino acid sequence that is at least 95% identical to SEQ ID NO: l, and a light chain variable region comprising an amino acid sequence that is at least 95% identical to SEQ ID NO: l 1; (b) a heavy chain variable region comprising an amino acid sequence that is at least 95% identical to SEQ ID NO:2, and a light chain variable region comprising an amino acid sequence that is at least 95% identical to SEQ ID NO: 12; (c) a heavy chain variable region comprising an amino acid sequence that is at least 95% identical to SEQ ID NO:3, and a light chain variable region comprising an amino acid sequence that is at least 95% identical to SEQ ID NO: 13; (d) a heavy chain variable region comprising an amino acid sequence that is at least 95% identical to SEQ ID NO:4, and a light chain variable region comprising an amino acid sequence that is at least 95% identical to SEQ ID NO: 14; (e) a heavy chain variable region comprising an amino acid sequence that is at least 95% identical to SEQ ID NO:5, and a light chain variable region comprising an amino acid sequence that is at least 95% identical to SEQ ID NO: 15; (f) a heavy chain variable region comprising an amino acid sequence that is at least 95% identical to SEQ ID NO:6, and a light chain variable region comprising an amino acid sequence that is at least 95% identical to SEQ ID NO: 16; (g) a heavy chain variable region comprising an amino acid sequence that is at least 95% identical to SEQ ID NO:7, and a light chain variable region comprising an amino acid sequence that is at least 95% identical to SEQ ID NO: 17; (h) a heavy chain variable region comprising an amino acid sequence that is at least 95% identical to SEQ ID NO: 8, and a light chain variable region comprising an amino acid sequence that is at least 95% identical to SEQ ID NO: 18; (i) a heavy chain variable region comprising an amino acid sequence that is at least 95% identical to SEQ ID NO:9, and a light chain variable region comprising an amino acid sequence that is at least 95% identical to SEQ ID NO: 19; or j) a heavy chain variable region comprising an amino acid sequence that is at least 95% identical to SEQ ID NO: 10, and a light chain variable region comprising an amino acid sequence that is at least 95% identical to SEQ ID NO:20.

In some embodiments, the anti-PD-Ll Abs or antigen-binding portion thereof may comprise a heavy chain variable region comprising an amino acid sequence that is at least 95% identical to SEQ ID NO:2, and a light chain variable region comprising an amino acid sequence that is at least 95% identical to SEQ ID NO: 12. In some embodiments, the anti-PD-Ll Abs or antigen-binding portion thereof may comprise a heavy chain variable region comprising SEQ ID NO:2, and a light chain variable region comprising SEQ ID NO: 12. The CDR domains of the above anti-PD-Ll HuMAbs have been delineated using the Kabat system, and these Abs may also be defined by combinations of their 3 heavy chain and 3 light chain CDRs (for example, see U.S. Patent No. 7,943,743). Since each of these Abs can bind to PD-Ll and antigen-binding specificity is provided primarily by the CDRl , CDR2, and CDR3 regions, the V_H CDRl , CDR2, and CDR3 sequences and V_K CDRl, CDR2, and CDR3 sequences can be "mixed and matched" (i.e., CDRs from different Abs can be mixed and match, although each Ab contains a V_H CDRl, CDR2, and CDR3 and a V_K CDRl, CDR2, and CDR3) to create other anti-PD-Ll Abs that also constitute Abs of the invention. PD-Ll binding of such "mixed and matched" Abs can be tested using, for example, ELISAs, western blots, radioimmunoassays and BIACORE® analysis.

Certain embodiments of the anti-PD-Ll Abs may comprise heavy and light chain variable regions each comprising CDRl, CDR2 and CDR3 domains, wherein one or more of these CDR domains comprise sequences that are the same as the CDR sequences of the anti-PD-Ll Abs described herein (e.g., 3G10, 12A4, 10A5, 5F8, 10H10, 1B12, 7H1, 11E6, 12B7 and 13G4), or conservative modifications thereof, and wherein the Abs retain the desired functional properties of the preferred anti-PD-Ll Abs of the invention.

On the basis of the evidence that the heavy chain CDR3 is the primary

determinant of binding specificity and affinity of an Ab, it is generally true that once the heavy chain CDR3 sequence of a given Ab is defined, variability in the other five CDR sequences will not greatly affect the binding specificity of that Ab. Accordingly, anti- PD-Ll Abs of the invention include isolated Abs comprising 6 CDRs, wherein the Abs are defined by specifying the sequence of the heavy chain CDR3 domain.

In some embodiments, the V_H and/or V_L amino acid sequences may exhibit at least 95%, 96%, 97%, 98% or 99% identity to the sequences described herein and have the same V_H CDRl, CDR2, and CDR3 or V_K CDRl, CDR2, and CDR3 as the sequences. In some embodiments, the anti-PD-Ll Abs or antigen-binding portion thereof may comprise a heavy chain variable region comprising an amino acid sequence that is at least 95% identical to SEQ ID NO:2, and a light chain variable region comprising an amino acid sequence that is at least 95% identical to SEQ ID NO: 12; and (a) a heavy chain variable region CDRl comprising SEQ ID NO:22; (b) a heavy chain variable region CDR2 comprising SEQ ID NO:32; (c) a heavy chain variable region CDR3 comprising SEQ ID NO:42; (d) a light chain variable region CDR1 comprising SEQ ID NO:52; (e) a light chain variable region CDR2 comprising SEQ ID NO: 62; and (f) a light chain variable region CDR3 comprising SEQ ID NO: 72.

In some embodiments, the anti-PD-Ll Abs or antigen-binding portion thereof may comprise (a) a heavy chain variable region CDR1 comprising SEQ ID NO:22; (b) a heavy chain variable region CDR2 comprising SEQ ID NO:32; (c) a heavy chain variable region CDR3 comprising SEQ ID NO:42; (d) a light chain variable region CDR1 comprising SEQ ID NO:52; (e) a light chain variable region CDR2 comprising SEQ ID NO:62; and (f) a light chain variable region CDR3 comprising SEQ ID NO:72.

In some embodiments, the anti-PD-Ll Abs or antigen-binding portion thereof may comprise (a) a heavy chain variable region CDR1 comprising SEQ ID NO:21; (b) a heavy chain variable region CDR2 comprising SEQ ID NO:31; (c) a heavy chain variable region CDR3 comprising SEQ ID NO:41; (d) a light chain variable region CDR1 comprising SEQ ID NO:51; (e) a light chain variable region CDR2 comprising SEQ ID NO:61; and (f) a light chain variable region CDR3 comprising SEQ ID NO:71.

In some embodiments, the anti-PD-Ll Abs or antigen-binding portion thereof may comprise (a) a heavy chain variable region CDR1 comprising SEQ ID NO:23; (b) a heavy chain variable region CDR2 comprising SEQ ID NO:33; (c) a heavy chain variable region CDR3 comprising SEQ ID NO:43; (d) a light chain variable region CDR1 comprising SEQ ID NO:53; (e) a light chain variable region CDR2 comprising SEQ ID NO: 63; and (f) a light chain variable region CDR3 comprising SEQ ID NO: 73.

In some embodiments, the anti-PD-Ll Abs also include isolated Abs that bind specifically to human PD-Ll and cross-compete for binding to human PD-Ll with any of HuMAbs 3G10, 12A4, 10A5, 5F8, 10H10, 1B12, 7H1, 11E6, 12B7 and 13G4. Thus, the anti-PD-Ll Abs include isolated Abs or antigen-binding portions thereof that cross- compete for binding to PD-Ll with a reference Ab or a reference antigen-binding portion thereof comprising: (a) a human heavy chain variable region comprising the sequence set forth in SEQ ID NO: 1 and a human light chain variable region comprising the sequence set forth in SEQ ID NO: 11; (b) a human heavy chain variable region comprising the sequence set forth in SEQ ID NO: 2 and a human light chain variable region comprising the sequence set forth in SEQ ID NO: 12; (c) a human heavy chain variable region comprising the sequence set forth in SEQ ID NO: 3 and a human light chain variable region comprising the sequence set forth in SEQ ID NO: 13; (d) a human heavy chain variable region comprising the sequence set forth in SEQ ID NO: 4 and a human light chain variable region comprising the sequence set forth in SEQ ID NO: 14; (e) a human heavy chain variable region comprising the sequence set forth in SEQ ID NO: 5 and a human light chain variable region comprising the sequence set forth in SEQ ID NO: 15; (f) a human heavy chain variable region comprising the sequence set forth in SEQ ID NO: 6 and a human light chain variable region comprising the sequence set forth in SEQ ID NO: 16; (g) a human heavy chain variable region comprising the sequence set forth in SEQ ID NO: 7 and a human light chain variable region comprising the sequence set forth in SEQ ID NO: 17; (h) a human heavy chain variable region comprising the sequence set forth in SEQ ID NO: 8 and a human light chain variable region comprising the sequence set forth in SEQ ID NO: 18; (i) a human heavy chain variable region comprising the sequence set forth in SEQ ID NO: 9 and a human light chain variable region comprising the sequence set forth in SEQ ID NO: 19; or (j) a human heavy chain variable region comprising the sequence set forth in SEQ ID NO: 10 and a human light chain variable region comprising the sequence set forth in SEQ ID NO: 20.

The ability of an Ab to cross-compete with any of 3G10, 12A4, 10A5, 5F8, 10H10, 1B12, 7H1, 11E6, 12B7 and 13G4 for binding to human PD-Ll demonstrates that such Ab binds to the same epitope region of each of 3G10, 12A4, 10A5, 5F8, 10H10, 1B12, 7H1, 11E6, 12B7 and 13G4, respectively. All isolated Abs that bind to the same epitope region of human PD-Ll as does HuMAb 3G10, 12A4, 10A5, 5F8, 10H10, 1B12, 7H1, 11E6, 12B7 or 13G4 are included among the Abs of the invention. These cross- competing Abs are expected to have very similar functional properties by virtue of their binding to the same epitope region of PD-Ll . For example, cross-competing anti-PD-Ll mAbs 3G10, 1B12, 13G4, 12A4 (BMS-936559), 10A5, 12B7, 11E6 and 5F8 have been shown to have similar functional properties (see U.S. Patent No. 7,943,743 at Examples 3-11), whereas mAb 10H10, which binds to a different epitope region, behaves differently (U.S. Patent No. 7,943,743 at Example 11). The higher the degree of cross- competition, the more similar may the functional properties be. Further, cross-competing Abs can be identified in standard PD-Ll binding assays, e.g., BIACORE® analysis, ELISA assays or flow cytometry, that are well known to persons skilled in the art. In some embodiments, the Abs that cross-compete for binding to human PD-Ll with, or bind to the same epitope region of human PD-L1 as, 3G10, 12A4, 10A5, 5F8, 10H10, 1B12, 7H1, 11E6, 12B7 or 13G4 may be mAbs, preferably chimeric Abs, or humanized or human Abs. Such human mAbs can be prepared and isolated as described in U.S. Patent No. 7,943,743.

Data provided in Example 1 show that each of the anti-PD-Ll HuMAbs 5F8,

7H1, 1B12, 3G10, 10A5, 11E6, 12A4, 12B7 and 13G4, i.e., all of the HuMAbs tested except 10H10, substantially blocked binding of mAbs 3G10, 10A5, 11E6, 12A4 and 13G4 to Chinese Hamster Ovary (CHO) cells expressing PD-L1 cells. HuMAb 10H10 substantially blocked the binding only of itself to CHO/PD-Ll cells. These data show that 3G10, 10A5, 11E6, 12A4 and 13G4 cross-compete with all of the HuMAbs tested, except for 10H10, for binding to the same epitope region of human PD-L1 (Figures 1A-F).

In some embodiments, the antibody or an antigen-binding portion thereof may cross-compete for binding to PD-L1 with a reference antibody which comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:2 and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 12. In some embodiments, the antibody or an antigen-binding portion thereof may bind to the same epitope as a reference antibody which comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:2 and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 12.

Anti-PD-Ll Abs provided herein also include antigen-binding portions of the above Abs, including Fab, F(ab')₂ Fd, Fv, and scFv, di-scFv or bi-scFv, and scFv-Fc fragments, diabodies, triabodies, tetrabodies, and isolated CDRs {see Hollinger and Hudson, 2005; Olafsen and Wu, 2010, for further details). Nucleic Acid Molecules Encoding Antibodies

Another aspect of the present disclosure pertains to isolated nucleic acid molecules that encode any of the Abs described herein. These nucleic acids may be present in whole cells, in a cell lysate, or in a partially purified or substantially pure form.

A nucleic acid of the invention can be, for example, DNA or RNA, and may or may not contain intronic sequences. In a some embodiments embodiment, the nucleic acid is a cDNA. Nucleic acids provided herein can be obtained using standard molecular biology techniques. For Abs expressed by hybridomas (e.g., hybridomas prepared from transgenic mice carrying human immunoglobulin genes as described further below), cDNAs encoding the light and heavy chains of the Ab made by the hybridoma can be obtained by standard PCR amplification or cDNA cloning techniques. Nucleic acids encoding Abs obtained from an immunoglobulin gene library (e.g., using phage display techniques) can be recovered from the library.

In some embodiments, the nucleic acids molecules described herein include those encoding the and V_K sequences of the anti-PD-Ll HuMAbs, 3G10, 12A4, 10A5, 5F8, 10H10, 1B12, 7H1, 11E6, 12B7, and 13G4 (disclosed in U.S. Patent No. 7,943,743). An isolated DNA encoding the V_H region can be converted to a full-length heavy chain gene by operatively linking the V^-encoding DNA to another DNA molecule encoding heavy chain constant regions (Cm, Cm and Cm), the sequences of which are known in the art and can be obtained by standard PCR amplification. The heavy chain constant region can be an IgGl, IgG2, IgG3, IgG4, IgA, IgE, IgM or IgD constant region. In some embodiments, the heavy chain constant region may be an IgGl, IgG2 or IgG4 constant region. Similarly, an isolated DNA encoding the Vi region can be converted to a full- length light chain gene by operatively linking the Vi-encoding DNA to another DNA molecule encoding the light chain constant region (C_L), the sequence of which is known in the art and can be obtained by standard PCR amplification. The light chain constant region can be a kappa or lambda constant region. In some embodiments, the light chain constant region may be a kappa constant region.

Pharmaceutical Compositions

Antibodies of the present invention may be constituted in a composition, e.g. , a pharmaceutical composition, containing one Ab or a combination of Abs, or an antigen- binding portion(s) thereof, and a pharmaceutically acceptable carrier. As used herein, a "pharmaceutically acceptable carrier" includes any and all solvents, dispersion media, coatings, antibacterial and antifungal agents, isotonic and absorption delaying agents, and the like that are physiologically compatible. Preferably, the carrier is suitable for intravenous, intramuscular, subcutaneous, parenteral or epidermal administration (e.g., by injection or infusion). A pharmaceutical composition of the invention may include one or more pharmaceutically acceptable salts, anti-oxidant, aqueous and nonaqueous carriers, and/or adjuvants such as preservatives, wetting agents, emulsifying agents and dispersing agents.

Dosage regimens are adjusted to provide the optimum desired response, e.g., a therapeutic response or minimal adverse effects. For administration of an anti-PD-Ll Ab or an antigen-binding portion thereof, the dosage may range from about 0.0001 to about 100 mg/kg, usually from about 0.001 to about 50 mg/kg, from about 0.01 to about 20 mg/kg, or from about 0.1 to about 10 mg/kg, of the subject's body weight. In some embodiments, the dosage is within the range of 0.1-10 mg/kg body weight. For example, dosages can be about 0.1, 0.3, 1, 3, 5 or 10 mg/kg body weight. In some embodiment, the dosage is about 0.1, 0.3, 3, or 10 mg/kg body weight. In some embodiments, the dosage may a fixed dose ranging from 0.001 to 2000 mg, from 0.01 to 1500 mg, from 0.1 to 1000 mg, from 1 to 1000 mg, from 1 to 500 mg, from 1 to 100 mg, from 100 to 200 mg, from 200 to 300 mg, from 300 to 400 mg, from 400 to 500 mg, from 500 to 600 mg, from 600 to 700 mg, from 700 to 800 mg, from 800 to 900 mg, or from 900 to 1000 mg.

The dosing schedule is typically designed to achieve exposures that result in sustained receptor occupancy (RO) based on typical pharmacokinetic properties of an Ab. An exemplary treatment regime may entail administration once per week, once every two weeks, once every three weeks, once every four weeks, once a month, once every 3 months or once every three to 6 months.

Actual dosage levels of the active ingredients in the pharmaceutical compositions described herein may be varied so as to obtain an amount of the active ingredient which is effective to achieve the desired therapeutic response for a particular patient, composition, and mode of administration, without being unduly toxic to the patient. The selected dosage level will depend upon a variety of pharmacokinetic factors including the activity of the particular compositions of the present invention employed, the route of

administration, the time of administration, the rate of excretion of the particular compound being employed, the duration of the treatment, other drugs, compounds and/or materials used in combination with the particular compositions employed, the age, sex, weight, condition, general health and prior medical history of the patient being treated, and like factors well known in the medical arts. A composition of the present invention can be administered via one or more routes of administration using one or more of a variety of methods well known in the art. As will be appreciated by the skilled artisan, the route and/or mode of administration will vary depending upon the desired results.

Uses and Methods

In patients who are effectively treated with combination antiretroviral therapy

(cART), HIV-1 persists in latently-infected resting CD4+T-cells and possibly other tissues or cellular reservoirs. Elimination of replication competent pro-virus (i.e., HIV viral DNA that has been integrated into the human genome, typically within active human genes) within latently infected cells is necessary to cure HIV-1 infection. Consequently, reduction or elimination of HIV-1 reservoirs that persist on suppressive cART may require the combination of multiple therapeutic modalities. Hence, the testing of interventions that have the potential both to impact persistent HIV-1 and be combined with other interventions that may be additive or synergistic is a necessary step in a comprehensive strategy for cure research.

cART clearly has been effective at suppressing plasma HIV-1 RNA to well below the limits of detection by conventional tests in most treated HIV-infected patients.

However, despite effective cART, low level HIV-1 viremia persists in most patients, likely arising from long-lived HIV-1 reservoirs. Why this persistent viremia and the resulting antigenemia fail to stimulate effective HIV-1 specific T-cell responses and why virus-producing cells are ineffectively cleared is not completely understood. It is known that chronic antigen stimulation results in marked down regulation of the antigen-specific cellular immune responses in HIV-1 and other chronic viral infections. The molecular mechanisms behind this "immune exhaustion" in the context of chronic infection are only recently coming to light (Wherry E.J., "T cell exhaustion", Nat. Immunol., 12(6):492-499 (2011)).

T-cell Exhaustion in HIV

An important factor in the ineffective HIV-1 specific immune response is that chronic HIV-1 infection leads to up-regulation of inhibitory co-receptors on T-cells (e.g. PD-1 and CTLA4), which are cellular makers of immune exhaustion. The expression of PD-1 and CTLA4, on CD4+ and/or CD8+ T-cells, is associated with disease progression in untreated HIV-1 infection. PD-1 expression on HIV-1 specific CD 8+ and CD4+ T- cells is reduced by antiretroviral therapy, but its expression remains elevated compared to uninfected participants, especially in patients with less robust CD4+ T-cell responses (Day 2006, Trautman 2006, Petrova 2006). Expression of PD-L1, a ligand for PD-1, in addition to being inducibly expressed on antigen-presenting cells, is also up-regulated on both CD4+ and CD8+ HIV-1 specific T cells in response to HIV-1 infection, and levels of PD-L1 on T-cells in this context remain elevated despite suppression of HIV-1 by cART (Sachdeva et al, J. Acquir. Immune. Defic. Syndr., 54(5):447-454 (2010);

Rosignoli et al, Clin. Exp. Immunol, 157(l):90-97 (2009)). Whether blockade of the PD-1/PD-L1 axis can restore the function of exhausted T-cells in chronic HIV-1 is an important unanswered question.

PD-1 and PD-L1 Blockade in Animal Models

Blocking the PD-1 pathway using an antibody to PD-1 in a macaque model of SIV infection (Velu et al, Nature, 458(7235):206-210 (2009)) resulted in rapid expansion of virus-specific CD8+ T-cells with improved functional quality of antiviral CD8+ T- cells in the blood and gut as demonstrated by the generation of poly- functional cells capable of co-producing cytokines IFN-γ, TNF-a and IL-2. These immune responses were associated with significant changes in plasma SIV RNA and prolonged survival in the absence of antiretroviral therapy. Further, anti-PD-Ll (BMS-936559 also known as MDX-1105) resulted in large reductions in HIV-1 replication in vivo, as well as increases in the percentage of CD4+ T-cells, in HIV-infected humanized mice in the absence of antiretroviral therapy (Palmer et al., J. Immunol., 190(1):211-219 (2013)).

Data provided in Example 2 show that virally suppressed monkeys while on ARV treated with an anti-PD-Ll Ab (BMS-936559) achieve durable suppression (Figure 2). Further, upon removal of ARV, there is a 7-10 day delay in the rebound of viral load in anti-PD-Ll treated group compared to the iso-type control group. Additionally, the anti- PD-Ll treated group had about 2-4 logio lower viral load at 6 weeks post- ARV interruption compared to the corresponding pre -ARV viral load (Figure 3, Figure 6). Unexpectedly, 2 of the anti-PD-Ll treated animals appeared to have spontaneously suppressed virus to below the limit of detection (<50 SIV copies/ml) for 3 to 4 weeks before returning to detectable viremia, and 4 (including aforementioned two) of the anti- PD-Ll treated animals had spontaneously suppressed virus below 1000 SIV copies/ml for >6 weeks. In contrast, none of the iso-type control group had undetectable viral load following the initial rebound of viremia post-ARV treatment interruption (Figure 5), with the exception of an animal within the isotype control group that reached undetectable after 170 days post-ARV treatment interruption. In the anti-PD-Ll treatment group, both the degree of reduction in viral load following the initial rebound of viremia post-ARV treatment interruption and the duration of the suppression were unexpected. The large proportion of the animals that responded to anti-PD-Ll treatment (4 of 8) also was unexpected.

The following examples should not be construed as further limiting.

EXAMPLE 1

Cross-Competition Between Anti-PD-Ll HuMAbs for Binding to

CHO Cells Expressing Human PD-L1

CHO cells transfected to express hPD-Ll (CHO/PD-L1 cells) were incubated with 10 μg/ml of each of ten unconjugated human anti-PD-Ll mAbs (5F8, 7H1, 10H10, 1B12, 3G10, 10A5, 11E6, 12A4, 12B7, and 13G4) or human IgGl (hlgGl) isotype control Ab for 20 min at 4°C. FITC-conjugated 10H10 (A), 3G10 (B), 10A5 (C), 11E6 (D), 12A4 (E) or 13G4 (F) was added to the cells to a final concentration of 0.09 μg/ml (B, D), 0.27 μg/ml (A, C), 0.91 μg/ml (F), or 2.73 μg/ml (E) for an additional 20 min at 4°C without prior washout of unbound, unconjugated Ab. Different quantities of the various FITC- conjugated HuMAbs were used due to differences in binding efficiency following labeling, and the optimal amounts of these FITC-conjugated HuMAbs were previously determined by dose-titration analysis of binding to CHO/PD-L1 cells. Binding of FITC- conjugated 10H10, 3G10, 10A5, 11E6, 12A4 or 13G4 to the CHO/PD-L1 cells was measured by flow cytometry.

The results are depicted in Figure 1. Binding of labeled 10H10 was partially blocked by 10A5, 11E6 and 13G4, but was substantially blocked only by itself (Figure 1A). Conversely, 10H10 substantially blocked the binding only of itself to CHO/PD-L1 cells. Each of anti-PD-Ll HuMAbs 5F8, 7H1, 1B12, 3G10, 10A5, 11E6, 12A4, 12B7 and 13G4 substantially blocked binding of labeled mAbs 3G10 (Figure IB), 10A5 (Figure 1C), 11E6 (Figure ID), 12A4 (Figure IE) and 13G4 (Figure IF) to CHO/PD-L1 cells as measured by MFI, though mAbs 5F8 and 13G4 generally blocked binding of the labeled mAbs to a slightly lesser extent.

EXAMPLE 2

The hypothesis was that treatment of virally suppressed monkeys with anti-PD-Ll might alter their immune system in a way that could reduce their latent reservoir and/or allow for control of virus once the antiretrovirals (ARV) were interrupted.

13 chronically SIV -infected Rhesus macaques were treated with ARV (PMPA 20 mg/kg QD, FTC 30 mg/kg QD, RAL 200 mg BID, ATV 400mg BID) in order to suppress their viral load. After approximately 6 months on ARV (range 4-8 months), 8 animals received 5 doses of the anti-PD-Ll Ab (BMS-936559 also referred to herein and in U.S. Patent No. 7,943,743 as 12A4) at 10 mg/kg over a 2 week period (day 0, 4, 7, 11, 14) and 5 animals received the same dose regimen of an isotype control antibody. The animals continued on ARV throughout the period of antibody administration and for an additional 4 weeks post-antibody administration, after which ARV was stopped and the viral loads (VL) were monitored for rebound. Blood was drawn throughout for VL, receptor occupancy (RO), PK, Chem/CBC, PAXGENE®, PBMC. Tissue biopsies (lymph node, rectal) were collected before administration of the antibody, before termination of ARV and post termination of ARV.

The results are depicted in Figures 2-7. The VL for all animals in the isotype control group rebounded within 7-10 days of ARV treatment interruption. Four of the animals in the BMS-936559-treatment group had VL rebound kinetics similar to the isotype control-treated group. Interestingly, 3 of 8 animals treated with BMS-936559 had a 7-10 day delay in VL rebound compared to the isotype control group. One additional animal, after an initial small increase in VL, returned to undetectable, rebounded again with a delay similar to the other 3 animals noted above. In addition, the same 4 anti-PD- Ll treated animals had -1.5-4 logio lower VL at 6 weeks post-ARV interruption compared to their pre-ARV VL (Figures 6A and 6B). This group of animals (M568, P294, P310, and P604) constitute the BMS-936559-treatment responder group (Figures 2- 5) as they had viral load <1000 RNA cp/mL for >6 weeks. Most unexpectedly, after an initial delayed rebound of VL, 2 of the BMS-936559-treated animals appear to have suppressed virus to below the limit of detection (50 SIV copies/mL) for a period of 3-4 weeks. No animals in the isotype control group had undetectable VL and only 1 of 5 animals in this control group had a 2 logio decline in VL compared to pre-ARV (Figure 6). EXAMPLE 3

Design of Phase 1 Clinical Study Utilizing an Anti-PD-Ll Antibody Study Design The trial is a phase I, dose-escalating, placebo-controlled study of the safety, pharmacokinetics and immunotherapeutic activity of single doses of anti-PD-Ll antibody (BMS-936559, also referred to herein and in U.S. Patent No. 7,943,743 as 12A4) in HIV- 1 infected patients on cART who have a CD4+ cell count of > 350 cells^L and a plasma HIV-1 RNA < 40 copies/mL (Abbott M2000 or Roche TAQMAN® v2.0 assay), but measureable HIV-1 RNA by SCA >0.4 copies/mL. Four dose cohorts of the anti-PD-Ll antibody (0.3, 1, 3 and 10 mg/kg) will be studied. Dose cohort 1 (0.3 mg/kg BMS- 936559) will have 8 participants (6 active and 2 placebo) while the remaining dose cohorts each will have 16 participants (12 active and 4 placebo). Anti-PD-Ll antibody /placebo infusion will occur over 60 minutes via IV infusion. The study will enroll sequential dose-rising cohorts. Participants will be followed for 48 weeks with frequent safety evaluations in the first 4 weeks.

To be included in the study, the subject should have been receiving a stable cART regimen containing at least three agents (not including ritonavir if less than a 200mg total daily dose) with no changes in the components of their antiretroviral therapy for at least 90 days prior to study entry. One of the agents includes an integrase inhibitor, NNRTI (Non-Nucleoside Reverse Transcriptase Inhibitors), or a boosted-PI (protease inhibitor). Plasma HIV-1 RNA level of the subject should be below detected limit obtained by FDA- approved assays (limit of detection: 75, 50, 40 or 20) for >2 years on cART. Participants must have at least one documented HIV-1 RNA level less than the limit of detection 12- 24 months prior to screening and one HIV-1 RNA level less than the limit of detection within 12 months prior to screening, but a single unconfirmed plasma HIV-1 RNA level > limit of detection but <1000 copies/mL is allowed if followed by HIV-1 RNA level below detectable limits, but none in the 6 months prior to screening. Plasma HIV-1 RNA level of the subject should be <40 copies/mL obtained by the Abbott m2000 assay or <20 copies/mL by the Roche TAQMAN® v2.0 assay within 90 days prior to entry. Primary Objectives

Assess the safety of single dose administration of four different dose levels (0.3, 1, 3 and 10 mg/kg) of BMS-936559 versus placebo in HIV-1 infected participants on cART.

Evaluate the change in magnitude of HIV-1 Gag-specific CD8+ T cells by intracellular staining for IFN-gamma prior to and after administration of a single-dose of BMS-936559 or placebo.

Assess whether administration of a single-dose of BMS-936559 will significantly reduce persistent plasma viremia measured by SCA in participants on suppressive cART.

Secondary Objectives

Describe the pharmacokinetics of BMS-936559 antibody after single-dose administration to cART -treated HIV-1 infected participants.

Explore the changes in total HIV-1 DNA, 2LTR circle DNA, cell-associated HIV- 1 RNA and RNA/DNA ratios in total CD4+ cells prior to and following BMS-936559 administration.

Explore relationships between BMS-936559 exposure (AUC, C_max) and changes in biomarkers including, but not limited to, HIV-1 RNA by SCA, HIV-1 DNA, 2LTR circle DNA, cell-associated HIV-1 RNA and RNA/DNA ratios in total CD4+ cells, receptor occupancy, and markers of immune response.

Measure PD-L1 receptor occupancy following single dose administration of BMS-936559 at four escalating dose levels.

Explore the proportion of total and HIV-1 gag-specific CD8+ T-cells that express PD-1, PD-L1, and other exhaustion markers by multi-parameter flow cytometry. The expression profile of PD-L2 on dendritic cells and monocyte derived-macrophages will also be determined.

Explore changes in cytolytic potential (CD 107a mobilization) and proliferation (CFSE dilution) of HIV-1 Gag-specific CD8+ T-cells.

Explore changes in poly-functionality of HIV-1 specific CD8+ and CD4+ T-cells as defined by changes in at least 3 different T-cell functions detected in multi-parameter flow cytometry. Explore changes in immune activation of CD8+ T-cells by quantifying CD38+ HLA-DR+ expression prior to and following BMS-936559 administration by flow cytometry.

Explore gene expression profiles in whole blood before and after administration of BMS-936559 with the aim of identifying changes in gene expression associated with increases in HIV-1 specific immune function and reduction in plasma viremia or CD4+ T-cell-associated HIV-1 RNA.

Explore whether single doses of BMS-936559 elicit an immunogenic response. Regimens

56 HIV-1 infected participants will be sequentially assigned to one of four cohorts, beginning with the lowest dose cohort:

Cohort 1 : Participants will receive 0.3 mg/kg of BMS-936559 or placebo, administered as a single 60 minute infusion one time.

Cohort 2: Participants will receive 1 mg/kg of BMS-936559 or placebo, administered as a single 60 minute infusion one time.

Cohort 3 : Participants will receive 3 mg/kg of BMS-936559 or placebo, administered as a single 60 minute infusion one time.

Cohort 3: Participants will receive 10 mg/kg of BMS-936559 or placebo, administered as a single 60 minute infusion one time.

Participants will be followed for a total of 48 weeks.

Formulation

BMS-936559 will be supplied as an injection, 100 mg/vial (10 mg/mL). It is a colorless, clear to slightly opalescent, essentially free of particles, sterile, non-pyrogenic solution contained in 10-mL Type I glass vials, stoppered with 20-mm stoppers, and sealed with 20-mm aluminum seals. Each vial of drug product contains the labeled amount of BMS-936559 drug substance and sodium citrate, sodium chloride, mannitol, diethylenetriamine pentaacetic acid (pentetic acid), and polysorbate 80. The concentration of each vial is 10 mg/mL at a pH of 6.5. A 5% overfill is included in each vial. Placebo for BMS-936559 will be sodium chloride for injection 0.9%, USP. EXAMPLE 4

Measurements of IL-2, IFNy, and TNFa production by CD4+ and CD8+ T cells were conducted using freshly isolated lymphocytes derived from the blood and lymph nodes of SIV-infected Rhesus macaques pre- and post-treatment with BMS-936559 or isotype control antibody as described in Example 2. Lymphocytes were counted using a Guava EasyCyte automatic cytometer (Millipore) and approximately 2 x 10⁶ lymphocytes were used per sample in a 96-well V-bottom plate. Cells were stimulated with 2μg/mL of SIVmac239 Gag peptide pool (NIH AIDS reagent Program, cat# 6204) and 1 μg/mL each of anti-CD28 and anti-CD49d antibodies (BD Biosciences). Cells were incubated at 37°C for 6 hours, with the addition GOLGISTOP® and GOLGIPLUG® (BD Biosciences) at a final dilution of 1 : 1 ,500 and 1 : 1 ,000, respectively, after the first hour.

The following conjugated antibodies and staining reagents were used: CD3- Horizon V450, CD4-PerCP-Cy5.5, CD8-APC-Cy7, CD69-ECD (Beckman Coulter), IL- 2-APC, IFNy-PE-Cy, and TNFa-FITC and Yellow LIVE/DEAD Fixable Dead Cell Stain (Invitrogen). All antibodies were from BD Biosciences unless otherwise indicated. The value of percentage cytokine positive cells, in un-stimulated samples, was subtracted from corresponding value in stimulated samples.

Overall, the percent of cytokine -producing T cells was higher in cells from lymph node samples than cytokine responses measured from peripheral blood. Within a compartment, the percent of cytokine -producing cells was similar between CD4⁺ and CD8 T cells. There was a limited change in cytokine production by CD4 T cells between pre- and post- BMS-936559 treatment in either lymph node or peripheral blood samples. Limited changes were also noted in cytokine production by CD8⁺ T cells between pre- and post-treatment in peripheral blood samples. There was however, an increase in cytokine production by CD8⁺ T cells in lymph node samples. All BMS- 936559-treated animals showed increases in IFN-γ and/or TNFa production post- treatment in comparison to control animals (Figure 8). Additionally, 2 of 4 responder animals showed increased poly-functionality, with changes in all three measured cytokines, IFNy, TNFa and IL2, post-treatment compared to pre -treatment. Two animals in the isotype group also had increased poly- functionality. However, the animal with the best post-TI viral load response, P294, had the greatest change in poly-functionality post- treatment.

Sequence Listing Summary

SEQ ID NO: SEQUENCE SEQ ID NO: SEQUENCE

51 VKCDRl a.a.3G10 79 VK CDR3 a.a.12B7

52 VKCDRl a.a.12A4 80 VKCDR3 a.a.13G4

53 VKCDRl a.a.10A5

54 VK CDR1 a.a.5F8 81 VH n.t.3G10

55 VKCDRl a.a.10H10 82 VHn.t.12A4

56 VKCDRl a.a.1B12 83 VHn.t.10A5

57 VK CDR1 a.a.7H1 84 VH n.t.5F8

58 VKCDRl a.a.11E6 85 VHn.t.10H10

59 VK CDR1 a.a.12B7 86 VHn.t.1B12

60 VKCDRl a.a.13G4 87 VH n.t.7H1

88 VHn.t.11E6

61 VK CDR2 a.a.3G10 89 VH n.t.12B7

62 VKCDR2 a.a.12A4 90 VHn.t.13G4

63 VKCDR2 a.a.10A5

64 VK CDR2 a.a.5F8 91 VKn.t.3G10

65 VK CDR2 a.a.10H10 92 VKn.t.12A4

66 VK CDR2 a.a. IB 12 93 VKn.t.10A5

67 VK CDR2a.a.7H1 94 VKn.t.5F8

68 VKCDR2 a.a.11E6 95 VKn.t.10H10

69 VK CDR2 a.a.12B7 96 VKn.t.1B12

70 VKCDR2 a.a.13G4 97 VKn.t.7H1

98 VKn.t.11E6

71 VK CDR3 a.a.3G10 99 VKn.t.12B7

72 VKCDR3 a.a.12A4 100 VKn.t.13G4

73 VKCDR3 a.a.10A5

74 VK CDR3 a.a.5F8 101 VH 1-18 germline a.a.

75 VKCDR3 a.a.10H10 102 VH 1-69 germline a.a.

76 VKCDR3 a.a. IB 12 103 VH 1-3 germline a.a.

77 VK CDR3 a.a.7H1 104 VH 3-9 germline a.a.

78 VK CDR3 a.a.HE6 SEQ ID NO: SEQUENCE

105 VK L6 germline a. a.

106 VK LI 5 germline a.a.

107 VK A27 germline a.a.

108 VK LI 8 germline a.a.

109 VK a.a. HE6a

Claims

CLAIMS What is claimed is:

1. A method of treating a subject infected with HIV who is currently on combination anti-retroviral therapy (cART) treatment, comprising administering to the subject a therapeutically effective amount of an antibody or an antigen-binding portion thereof that disrupts the interaction between Programmed Death- 1 (PD-1) and Programmed Death Ligand-1 (PD-L1), wherein the antibody or antigen-binding portion thereof binds specifically to PD-L1.

2. The method of claim 1, wherein the cART treatment comprises at least three anti- retroviral drugs.

3. The method of claim 1 or 2, wherein the cART treatment comprises at least three anti-retroviral drugs selected from entry inhibitors, fusion inhibitors, reverse transcriptase

(RT) inhibitors, nucleoside/nucleotide RT inhibitors, non-nucleoside RT inhibitors, integrase inhibitors, and protease inhibitors.

4. The method of any one of the foregoing claims, wherein the subject has been on cART treatment for at least one year.

5. The method of any one of the foregoing claims, wherein the subject has been on cART treatment for at least two years.

6. The method of any one of the foregoing claims, wherein the subject has a suppressed viral load (VL) which is less than 1000 RNA copies/mL before the antibody or antigen-binding portion thereof is administered.

7. The method of any one of the foregoing claims, wherein the subject has a suppressed VL which is less than 50 RNA copies/mL before the antibody or antigen- binding portion thereof is administered.

8. The method of any one of the foregoing claims, further comprising removing the cART treatment after the antibody or antigen-binding portion thereof is administered.

9. The method of claim 8, wherein the viral load is suppressed after the cART treatment is removed.

10. The method of claim 9, wherein the viral load is suppressed following an initial viral load rebound after the cART treatment is removed.

11. The method of claim 9 or 10, wherein the viral load is suppressed for at least 3 weeks after the cART treatment is removed.

12. The method of any one of claims 9-11, wherein the viral load is suppressed for at least 6 weeks after the cART treatment is removed.

13. The method of any one of claims 9-12, wherein the viral load is suppressed for at least 6 months after the cART treatment is removed.

14. The method of any one of claims 8-13, wherein the viral load, after the cART treatment is removed, is less than 1000 RNA copies/mL for at least 6 weeks.

15. The method of any one of claims 8-14, wherein the viral load, after the cART treatment is removed, is less than 1000 RNA copies/mL for at least 6 months.

16. The method of any one of the foregoing claims, wherein the antibody or an antigen-binding portion thereof cross-competes for binding to PD-Ll with a reference antibody which comprises:

a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:2 and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 12.

17. The method of any one of the foregoing claims, wherein the antibody or an antigen-binding portion thereof comprises a heavy chain variable region comprising an amino acid sequence that is at least 95% identical to SEQ ID NO:2, and a light chain variable region comprising an amino acid sequence that is at least 95% identical to SEQ ID NO: 12.

18. The method of any one of the foregoing claims, wherein the antibody or antigen- binding portion thereof comprises:

a heavy chain variable region comprising an amino acid sequence that is at least 95% identical to SEQ ID NO:2, and

a light chain variable region comprising an amino acid sequence that is at least 95% identical to SEQ ID NO:12; and

wherein the heavy chain variable region comprises:

(a) a heavy chain variable region CDR1 comprising SEQ ID NO:22; (b) a heavy chain variable region CDR2 comprising SEQ ID NO:32; and

(c) a heavy chain variable region CDR3 comprising SEQ ID NO:42; and the light chain variable region comprises:

(d) a light chain variable region CDR1 comprising SEQ ID NO:52; (e) a light chain variable region CDR2 comprising SEQ ID NO:62; and

(f) a light chain variable region CDR3 comprising SEQ ID NO: 72.

19. The method of any one of the foregoing claims, wherein the antibody or antigen- binding portion thereof comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:2 and a human light chain variable region comprising the amino acid sequence of SEQ ID NO: 12.

20. The method of any one of claims 1-15, wherein the antibody or antigen-binding portion thereof comprises: (a) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 1 and a light chain variable region comprising the amino acid sequence of SEQ ID NO: l l;

(b) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:2 and a light chain variable region comprising the amino acid sequence of SEQ ID

NO: 12;

(c) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 3 and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 13;

(d) a heavy chain variable region comprising the amino acid sequence of SEQ

ID NO:4 and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 14;

(e) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 5 and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 15;

(f) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 6 and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 16;

(g) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 7 and a light chain variable region comprising the amino acid sequence of SEQ ID

NO: 17;

(h) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 8 and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 18;

(i) a heavy chain variable region comprising the amino acid sequence of SEQ

ID NO: 9 and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 19; or

j) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 10 and a light chain variable region comprising the amino acid sequence of SEQ ID NO:20.

21. The method of any one of claims 1-15, wherein the antibody or antigen-binding portion thereof comprises:

(a) a heavy chain variable region CDR1 comprising SEQ ID NO:21;

(b) a heavy chain variable region CDR2 comprising SEQ ID NO: 31 ;

(c) a heavy chain variable region CDR3 comprising SEQ ID NO:41;

(d) a light chain variable region CDR1 comprising SEQ ID NO:51 ;

(e) a light chain variable region CDR2 comprising SEQ ID NO:61; and

(f) a light chain variable region CDR3 comprising SEQ ID NO:71.

22. The method of any one of claims 1-15, wherein the antibody or antigen-binding portion thereof comprises:

(a) a heavy chain variable region CDR1 comprising SEQ ID NO:22;

(b) a heavy chain variable region CDR2 comprising SEQ ID NO:32;

(c) a heavy chain variable region CDR3 comprising SEQ ID NO:42;

(d) a light chain variable region CDR1 comprising SEQ ID NO:52;

(e) a light chain variable region CDR2 comprising SEQ ID NO:62; and

(f) a light chain variable region CDR3 comprising SEQ ID NO: 72.

23. The method of any one of claims 1-15, wherein the antibody or antigen-binding portion thereof comprises:

(a) a heavy chain variable region CDR1 comprising SEQ ID NO:23;

(b) a heavy chain variable region CDR2 comprising SEQ ID NO:33;

(c) a heavy chain variable region CDR3 comprising SEQ ID NO:43;

(d) a light chain variable region CDR1 comprising SEQ ID NO:53;

(e) a light chain variable region CDR2 comprising SEQ ID NO: 63; and

(f) a light chain variable region CDR3 comprising SEQ ID NO: 73.

24. A method of treating a subject infected with HIV who is currently on combination anti-retroviral therapy (cART) treatment, comprising

administering to the subject a therapeutically effective amount of an antibody or an antigen-binding portion thereof that comprises

(a) a heavy chain variable region CDR1 comprising SEQ ID NO:22, (b) a heavy chain variable region CDR2 comprising SEQ ID NO:32, (c) a heavy chain variable region CDR3 comprising SEQ ID NO:42, (d) a light chain variable region CDR1 comprising SEQ ID NO:52,

(e) a light chain variable region CDR2 comprising SEQ ID NO:62, and

(f) a light chain variable region CDR3 comprising SEQ ID NO: 72.

25. The method of claim 24, further comprising removing the cART treatment after the antibody or antigen-binding portion thereof is administered.

26. The method of claim 25, wherein the viral load is suppressed after the cART treatment is removed.

27. The method of any one of claims 24-26, wherein the antibody or antigen-binding portion thereof comprises:

a heavy chain variable region comprising an amino acid sequence that is at least 95% identical to SEQ ID NO:2, and

a light chain variable region comprising an amino acid sequence that is at least 95% identical to SEQ ID NO:12.

28. The method of any one of claims 24-27, wherein the antibody or antigen-binding portion thereof comprises:

a heavy chain variable region comprising SEQ ID NO:2, and

a light chain variable region comprising SEQ ID NO: 12.

29. The method of any one of claims 24-28, wherein the cART treatment comprises at least three anti-retroviral drugs.

30. The method of any one of claims 24-29, wherein the cART treatment comprises at least three anti-retroviral drugs selected from entry inhibitors, fusion inhibitors, reverse transcriptase (RT) inhibitors, nucleoside/nucleotide RT inhibitors, non-nucleoside RT inhibitors, integrase inhibitors and protease inhibitors.

31. The method of any one of claims 26-30, wherein the subject has been on cART treatment for at least one year.

32. The method of any one of claims 26-31 , wherein the subject has been on cART treatment for at least two years.

33. The method of any one of claims 26-32, wherein the subject has a suppressed viral load (VL) which is less than 1000 RNA copies/mL before the antibody or antigen- binding portion thereof is administered.

34. The method of any one of claims 26-33, wherein the subject has a suppressed VL which is less than 50 RNA copies/mL before the antibody or antigen-binding portion thereof is administered.

35. The method of any one of claims 26-34, wherein the viral load is suppressed following an initial viral load rebound after the cART treatment is removed.

36. The method of any one of claims 26-35, wherein the viral load is suppressed for at least 3 weeks after the cART treatment is removed.

37. The method of any one of claims 26-36, wherein the viral load is suppressed for at least 6 weeks after the cART treatment is removed.

38. The method of any one of claims 26-37, wherein the viral load is suppressed for at least 6 months after the cART treatment is removed.

39. The method of any one of claims 26-38, wherein the viral load of the subject, after the cART treatment is removed, is less than 1000 RNA copies/mL for at least 6 weeks.

40. The method of any one of claims 26-39, wherein the viral load of the subject, after the cART treatment is removed, is less than 1000 RNA copies/mL for at least 6 months.

41. The method of any one of the foregoing claims, wherein the antibody or antigen- binding portion thereof is linked to a therapeutic agent.

42. The method of claim 41, wherein the therapeutic agent is a cytotoxin.

43. The method of claim 41, wherein the therapeutic agent is a radioactive isotope.

44. The method of claim 41, wherein the therapeutic agent is a second functional moiety having a different binding specificity than said antibody or antigen binding portion thereof.

45. The method of any one of the foregoing claims, wherein the therapeutically effective amount of the antibody or antigen-binding portion thereof comprises a dose ranging from 0.01 to 100.0 mg/kg body weight.

46. The method of any one of the foregoing claims, wherein the therapeutically effective amount of the antibody or antigen-binding portion thereof comprises a dose ranging from 0.1 to 50.0 mg/kg body weight.

47. The method of any one of the foregoing claims, wherein the antibody or antigen- binding portion thereof is administered at about 0.3 mg/kg, 1 mg/kg, 3 mg/kg, 5 mg/kg, or 10 mg/kg body weight.

48. The method of any one of the foregoing claims, wherein the antibody or an antigen-binding portion thereof is administered in combination with at least one other antiretroviral agent.