WO2020215020A1

WO2020215020A1 - Humanized anti-pd-l1 antibodies

Info

Publication number: WO2020215020A1
Application number: PCT/US2020/028862
Authority: WO
Inventors: Shihao Chen
Original assignee: Qlsf Biotherapeutics Inc.
Priority date: 2019-04-18
Filing date: 2020-04-17
Publication date: 2020-10-22
Also published as: US20200332010A1; US11643466B2; JP2022529269A; EP3955925A4; CA3136453A1; CN114025757A; US20220112290A1; EP3955925A1; US11124572B2

Abstract

The present disclosure provides isolated binding molecules that bind to and blocks PD-L1, vectors comprising a nucleic acid molecules encoding an amino acid sequence of the binding molecules, host cells containing the vectors, methods of making the binding molecules, pharmaceutical compositions containing the binding molecules, and methods of using such antibodies, antibody fragments and derivatives and polypeptides, including methods of treating a disease requiring stimulation of immune responses including cancer.

Description

Humanized Anti-PD-Ll Antibodies

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Application No. 62/835,764, filed April 18, 2019, the disclosure of which is incorporate herein by reference in its entirety. INCORPORATION OF SEQUENCE LISTING

This application includes a Sequence Listing which is being submitted in ASCII format via EFS- Web, named "QLSF003PCT_ST25.txt,” which is 158 KB in size and created on April 17, 2020. The contents of the Sequence Listing are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION Programmed cell death protein 1 (PD-1) is a 288 amino acid cell surface protein molecule and is encoded by the PDCD1 gene in humans. PD-1 is a type I trans-membrane protein containing an immunoglobulin-variable-type-amino-terminal-extracellular domain, a transmembrane region, and a cytoplasmic tail with an immunoreceptor tyrosine-based inhibitory motif and an immunoreceptor tyrosine -based switch motif (Ishida et al., 1992). PD-1 is expressed in pro-B cells and activated T cells, but not on resting T cells in vivo. Programmed death- 1 (PD-1) acts as a checkpoint protein on immune cells. It negatively regulates the immune system through inhibition of effective T cell function by engaging PD-L1, a ligand for the PD-1 receptor.

The PD-1/PD-L1 interaction plays an important role in autoimmunity as well as in cancer immunology. PD-L1 expression has been observed in a variety of cancers including melanoma and non-small cell lung cancer. Many studies suggest that cancer cells overexpress PD-L1, which helps them evade immune attack by using the PD-l/PD-ligand (PDL) pathway. Based on the conclusion of these studies, several checkpoint blockade inhibitors for PD-l/PDL pathway were developed.

PD-1/PD-L1 blockade has achieved great clinical success in combating cancers. Several immune-therapies, such as Pembrolizumab (Keytru ) and Nivolumab (Opdivo), which target PD-1 and Atezolizumab (Tecentriq), Avelumab (Bavencio) and Durvalumab (Imfinzi) which target PD-L1, are effective in blocking the binding between PD-1 and PD-L1 which can reverse T cell dysfunction. However, in many advanced cancers, the objective response rate with monotherapy is only 20% (Xu-Monette et ah, 2017).

As a result, improved therapeutics targeting PD-1 and PD-L1 are an area of intense interest. Also, many other immunotherapies are now being tested in clinical trials as well, both alone and in combinations. Accordingly, there remains a need for more effective immunotherapy targeting PD-1/PD-L1 pathway either used alone or in combination with other therapeutic agents in drug treatment regimens.

SUMMARY OF THE INVENTION

The present disclosure provides isolated monoclonal anti-PD-L antagonist antibodies, and antigen-binding portions thereof that specifically bind to human PD-L1.

In an aspect of the invention, an isolated monoclonal anti-PD-L antagonist antibody, or antigen- binding portion thereof comprises a heavy chain variable region CDR3 comprising SEQ ID NO:43. In some embodiments, the monoclonal anti-PD-L antagonist antibody, or antigen- binding portion thereof further comprises a heavy chain variable region CDR1 comprising SEQ ID NO:31 and a heavy chain variable region CDR2 comprising SEQ ID NO:37. In preferred embodiments, the monoclonal anti-PD-L antagonist antibody, or antigen-binding portion thereof further comprises: (a) a light chain variable region CDR1 comprising SEQ ID NO: 13; (b) a light chain variable region CDR2 comprising SEQ ID NO: 19; and (c) a light chain variable region CDR3 comprising SEQ ID NO:25. In one embodiment, the antibody or portion comprises a light chain variable region amino acid sequence having at least 95% identity to SEQ ID NO: l and a heavy chain variable region amino acid sequence having at least 95% identity to SEQ ID NO:7. In another embodiment, the antibody or portion comprises a heavy chain variable region comprising an amino acid sequence that has at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to a sequence as set forth in SEQ ID NO:7.

In another aspect of the invention, an isolated monoclonal anti-PD-L antagonist antibody, or antigen-binding portion thereof comprises a heavy chain variable region CDR3 comprising SEQ ID NO:44. In some embodiments, the monoclonal anti-PD-L antagonist antibody, or antigen- binding portion thereof further comprises a heavy chain variable region CDR1 comprising SEQ ID NO:32 and a heavy chain variable region CDR2 comprising SEQ ID NO:38. In preferred embodiments, the monoclonal anti-PD-L antagonist antibody, or antigen-binding portion thereof further comprises: (a) a light chain variable region CDR1 comprising SEQ ID NO: 14; (b) a light chain variable region CDR2 comprising SEQ ID NO:20; and (c) a light chain variable region CDR3 comprising SEQ ID NO:26.

In one embodiment, the antibody or portion comprises a light chain variable region amino acid sequence having at least 95% identity to SEQ ID NO:2 and a heavy chain variable region amino acid sequence having at least 95% identity to SEQ ID NO:8. In another embodiment, the antibody or portion comprises a heavy chain variable region comprising an amino acid sequence that is at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to a sequence as set forth in SEQ ID NO:8.

In another aspect of the invention, an isolated monoclonal anti-PD-L antagonist antibody, or antigen-binding portion thereof comprises a heavy chain variable region CDR3 comprising SEQ ID NO:45. In some embodiments, the monoclonal anti-PD-L antagonist antibody, or antigen- binding portion thereof further comprises a heavy chain variable region CDR1 comprising SEQ ID NO:33 and a heavy chain variable region CDR2 comprising SEQ ID NO:39. In preferred embodiments, the monoclonal anti-PD-L antagonist antibody, or antigen-binding portion thereof further comprises: (a) a light chain variable region CDR1 comprising SEQ ID NO: 15; (b) a light chain variable region CDR2 comprising SEQ ID NO:21; and (c) a light chain variable region CDR3 comprising SEQ ID NO:27.

In one embodiment, the antibody or portion comprises a light chain variable region amino acid sequence having at least 95% identity to SEQ ID NO:3 and a heavy chain variable region amino acid sequence having at least 95% identity to SEQ ID NO:9. In another embodiment, the antibody or portion comprises a heavy chain variable region comprising an amino acid sequence that is at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to a sequence as set forth in SEQ ID NO:9.

In another aspect of the invention, an isolated monoclonal anti-PD-L antagonist antibody, or antigen-binding portion thereof comprises a heavy chain variable region CDR3 comprising SEQ ID NO:46. In some embodiments, the monoclonal anti-PD-L antagonist antibody, or antigen- binding portion thereof further comprises a heavy chain variable region CDR1 comprising SEQ ID NO:34 and a heavy chain variable region CDR2 comprising SEQ ID NO:40. In preferred embodiments, the monoclonal anti-PD-L antagonist antibody, or antigen-binding portion thereof further comprises: (a) a light chain variable region CDR1 comprising SEQ ID NO: 16; (b) a light chain variable region CDR2 comprising SEQ ID NO:22; and (c) a light chain variable region CDR3 comprising SEQ ID NO:28.

In one embodiment, the antibody or portion comprises a light chain variable region amino acid sequence having at least 95% identity to SEQ ID NO:4 and a heavy chain variable region amino acid sequence having at least 95% identity to SEQ ID NO: 10. In another embodiment, the antibody or portion comprises a heavy chain variable region comprising an amino acid sequence that is at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to a sequence as set forth in SEQ ID NO: 10.

In another aspect of the invention, an isolated monoclonal anti-PD-L antagonist antibody, or antigen-binding portion thereof comprises a heavy chain variable region CDR3 comprising SEQ ID NO:47. In some embodiments, the monoclonal anti-PD-L antagonist antibody, or antigen- binding portion thereof further comprises a heavy chain variable region CDR1 comprising SEQ ID NO:35 and a heavy chain variable region CDR2 comprising SEQ ID NO:41. In preferred embodiments, the monoclonal anti-PD-L antagonist antibody, or antigen-binding portion thereof further comprises: (a) a light chain variable region CDR1 comprising SEQ ID NO: 17; (b) a light chain variable region CDR2 comprising SEQ ID NO:23; and (c) a light chain variable region CDR3 comprising SEQ ID NO:29.

In one embodiment, the antibody or portion comprises a light chain variable region amino acid sequence having at least 95% identity to SEQ ID NO:5 and a heavy chain variable region amino acid sequence having at least 95% identity to SEQ ID NO: 11. In another embodiment, the antibody or portion comprises a heavy chain variable region comprising an amino acid sequence that is at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to a sequence as set forth in SEQ ID NO: 11.

In another aspect of the invention, an isolated monoclonal anti-PD-L antagonist antibody, or antigen-binding portion thereof comprises a heavy chain variable region CDR3 comprising SEQ ID NO:48. In some embodiments, the monoclonal anti-PD-L antagonist antibody, or antigen- binding portion thereof further comprises a heavy chain variable region CDR1 comprising SEQ ID NO:36 and a heavy chain variable region CDR2 comprising SEQ ID NO:42. In preferred embodiments, the monoclonal anti-PD-L antagonist antibody, or antigen-binding portion thereof further comprises: (a) a light chain variable region CDR1 comprising SEQ ID NO: 18; (b) a light chain variable region CDR2 comprising SEQ ID NO:24; and (c) a light chain variable region CDR3 comprising SEQ ID NO:30.

In one embodiment, the antibody or portion comprises a light chain variable region amino acid sequence having at least 95% identity to SEQ ID NO:6 and a heavy chain variable region amino acid sequence having at least 95% identity to SEQ ID NO: 12. In another embodiment, the antibody or portion comprises a heavy chain variable region comprising an amino acid sequence that is at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to a sequence as set forth in SEQ ID NO: 12.

In another aspect of the invention, an isolated monoclonal anti-PD-L antagonist antibody or an antigen-binding portion thereof comprises a heavy chain variable region comprising an amino sequence selected from the group consisting of SEQ ID NOs:65-67 and a light chain variable region comprising an amino sequence selected from the group consisting of SEQ ID NOs:49-51.

In another aspect of the invention, an isolated monoclonal anti-PD-L antagonist antibody or an antigen -binding portion thereof comprises: a heavy chain variable region comprising an amino sequence selected from the group consisting of SEQ ID NOs: 68-70 and a light chain variable region comprising an amino sequence selected from the group consisting of SEQ ID NOs:55-58. In another aspect of the invention, an isolated monoclonal anti-PD-L antagonist antibody or an antigen -binding portion thereof comprises: a heavy chain variable region comprising an amino sequence selected from the group consisting of SEQ ID NOs: 71-76 and a light chain variable region comprising an amino sequence selected from the group consisting of SEQ ID NOs:59-61.

In another aspect of the invention, an isolated monoclonal anti-PD-L antagonist antibody or an antigen -binding portion thereof comprises: a heavy chain variable region comprising an amino sequence selected from the group consisting of SEQ ID NOs: 77-78 and a light chain variable region comprising an amino sequence selected from the group consisting of SEQ ID NOs:62-63.

In another aspect of the invention, an isolated monoclonal anti-PD-L antagonist antibody or an antigen -binding portion thereof comprises: a heavy chain variable region comprising an amino sequence selected from the group consisting of SEQ ID NOs: 79-80 and a light chain variable region comprising an amino sequence selected from the group consisting of SEQ ID NOs:64.

In another aspect of the invention, an isolated monoclonal anti-PD-L antagonist antibody or an antigen -binding portion thereof comprises: a heavy chain variable region comprising an amino sequence selected from the group consisting of SEQ ID NOs: 81-83 and a light chain variable region comprising an amino sequence selected from the group consisting of SEQ ID NOs:52-54.

In another aspect of the invention, an isolated monoclonal antibody or antigen binding portion thereof, comprising a light chain comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 84-99 and a heavy chain comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 100-118.

The antibodies of the disclosed invention can be further engineered into formats suitable for human therapeutics by modifications that minimize immunogenicity. Suitable antibodies include, but are not limited to chimeric antibodies and humanized antibodies. The affinity, stability and specificity of the disclosed antibodies can also be further optimized by techniques known to one of skill in the art. Other formats can involve oligomerization, drug conjugation and fusion of the disclosed antibodies with other functional proteins.

The antibodies of the disclosed invention can be, for example, full-length antibodies, for example of an IgGl, IgG2, IgG3, or IgG4 isotype. Alternatively, the disclosed antibodies can be antibody fragments, such as Fab, Fab' and F(ab')2 fragments, diabody, triabody, tetrabody, single-chain variable region fragment (scFv), disulfide- stabilized variable region fragment (dsFv), and half antibodies. Alternatively, the disclosed antibodies can be bispecific antibodies.

In another aspect of the invention, the antibody or antigen-binding fragment thereof has an affinity (KD) for PD-L1 in the range of 5x 10^_8 M to 1x10 ¹⁰ M, or 1.32x 10^-9 M to 2.68x10^-10 M.

In some embodiments, the anti-PD-L antagonist antibody, or antigen-binding portion thereof binds to and blocks human PD-L1. Therefore the antibody, or antigen-binding portion can stimulate an anti-tumor immune response. In some embodiments, the anti-PD-L antagonist antibody, or antigen-binding portion thereof binds to and blocks non-human primate PD-L1. In another aspect of the invention, a composition comprising the isolated anti-PD-L antagonist monoclonal antibody, or antigen-binding portion thereof is also provided.

In another aspect of the invention, a pharmaceutical composition comprising the isolated anti- PD-L antagonist monoclonal antibody, or antigen-binding portion thereof and a pharmaceutically acceptable carrier are also provided. Compositions comprising an immunoconjugate of the invention and a pharmaceutically acceptable carrier are also provided.

In another aspect of the invention, a vector comprising an isolated nucleic acid molecule encoding the antibody, or antigen-binding portion thereof, and a host cell comprising an expression vector comprising said nucleic acid molecule are also provided. The present invention further provides a method of stimulating immune responses using the anti- PD-L antagonist antibodies of the disclosed invention. For example, in one embodiment, the disclosed invention provides a method for treating a subject in need thereof, comprising the step of administering to the subject an effective amount of the antibody or antigen-binding portion of the disclosed invention. In another aspect, the disclosed invention provides a method for treating cancer in a human comprising the step of administering to the human the anti-PD-L antagonist antibody or antigen-binding portion of the disclosed invention in an amount effective to treat said cancer.

In another aspect, the disclosed invention provides a method for treating infectious diseases in a human comprising the step of administering to the human the anti-PD-L antagonist antibody or antigen-binding portion of the disclosed invention in an amount effective to treat said infectious diseases.

Other features and advantages of the instant disclosure will be apparent from the following detailed description and examples, which should not be construed as limiting. The contents of all references, GenBank entries, patents and published patent applications cited throughout this application are expressly incorporated herein by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments are illustrated in referenced figures. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than restrictive. Figure 1 shows Anti-PD-L Lead candidates bind to PD-L1 on A431 cells

Figure 2 shows Anti-PD-L Lead candidates block PD-1 interaction on HEK293/huPD-L cells.

Figure 3 show Anti-PD-L antibodies potentiated IL-2 release by SEB stimulation

Figure 4 show PD-L1 Antibodies Potentiated IFN gamma Secretion in Mixed Lymphocyte Reaction Assays indicating that the lead anti-PD-L antibodies blocked PD-l-mediated inhibition.

Figure 5 shows PD-L1 blockade by lead antibodies enhanced interferon gamma production by T cells in CMV peptide- specific recall response assays.

Figure 6 shows thermal stability of humanized anti-PD-L lead antibodies DETAILED DESCRIPTION OF THE INVENTION

The following embodiments and aspects thereof are described and illustrated in conjunction with systems, compositions and methods which are meant to be exemplary and illustrative, not limiting in scope.

DEFINITIONS As used herein the term“comprising” or“comprises” is used in reference to compositions, methods, and respective component(s) thereof, that are useful to an embodiment, yet open to the inclusion of unspecified elements, whether useful or not. It will be understood by those within the art that, in general, terms used herein are generally intended as“open” terms (e.g., the term “including” should be interpreted as“including but not limited to,” the term“having” should be interpreted as“having at least,” the term“includes” should be interpreted as“includes but is not limited to,” etc.).

Unless stated otherwise, the terms“a” and“an” and“the” and similar references used in the context of describing a particular embodiment of the application (especially in the context of claims) can be construed to cover both the singular and the plural. The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (for example,“such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the application and does not pose a limitation on the scope of the application otherwise claimed. The abbreviation,“e.g.” is derived from the Latin exempli gratia, and is used herein to indicate a non-limiting example. Thus, the abbreviation“e.g.” is synonymous with the term“for example.” No language in the specification should be construed as indicating any non-claimed element essential to the practice of the application.

As used herein, the term“about” refers to a measurable value such as an amount, a time duration, and the like, and encompasses variations of ±20%, ±10%, ±5%, ±1%, ±0.5% or ±0.1% from the specified value.

The term "epitope" as used herein can include any protein determinant capable of specific binding to an immunoglobulin or T-cell receptor. Epitopic determinants usually consist of chemically active surface groupings of molecules such as amino acids or sugar side chains and usually have specific three-dimensional structural characteristics, as well as specific charge characteristics. An antibody is said to specifically bind an antigen when the equilibrium dissociation constant is < 1 mM, preferably £ 100 nM and most preferably £ 10 nM.

The term "KD" can refer to the equilibrium dissociation constant of a particular antibody- antigen interaction. The term "immune response" as used herein can refer to the action of, for example, lymphocytes, antigen presenting cells, phagocytic cells, granulocytes, and soluble macromolecules produced by the above cells or the liver (including antibodies, cytokines, and complement) that results in selective damage to, destruction of, or elimination from an organism of invading pathogens, cells or tissues infected with pathogens, cancerous cells, or, in cases of autoimmunity or pathological inflammation, normal organismal cells or tissues.

An "antigen- specific T cell response" as used herein can refer to responses by a T cell that result from stimulation of the T cell with the antigen for which the T cell is specific. Non-limiting examples of responses by a T cell upon antigen- specific stimulation include proliferation and cytokine production (e.g., IL-2 production). As used herein, the term“antibody” refers to an intact immunoglobulin or to a monoclonal or polyclonal antigen-binding fragment with the Fc (crystallizable fragment) region or FcRn binding fragment of the Fc region, referred to herein as the“Fc fragment” or“Fc region”. Antigen-binding fragments may be produced by recombinant DNA techniques or by enzymatic or chemical cleavage of intact antibodies. Antigen-binding fragments include, inter alia, Fab, Fab', F(ab')2, Fv, dAb, and complementarity determining region (CDR) fragments, single-chain antibodies (scFv), single region antibodies, chimeric antibodies, diabodies and polypeptides that contain at least a portion of an immunoglobulin that is sufficient to confer specific antigen binding to the polypeptide. The Fc region includes portions of two heavy chains contributing to two or three classes of the antibody. The Fc region may be produced by recombinant DNA techniques or by enzymatic (e.g. papain cleavage) or via chemical cleavage of intact antibodies.

The term“antibody fragment,” as used herein, refers to a protein fragment that comprises only a portion of an intact antibody, generally including an antigen binding site of the intact antibody and thus retaining the ability to bind antigen. Examples of antibody fragments encompassed by the present definition include: (i) the Fab fragment, having VL, CL, VH and CH 1 regions; (ii) the Fab' fragment, which is a Fab fragment having one or more cysteine residues at the C- terminus of the CH 1 region; (iii) the Fd fragment having VH and CH 1 regions; (iv) the Fd' fragment having VH and CH 1 regions and one or more cysteine residues at the C-terminus of the CH 1 region; (v) the Fv fragment having the VL and VH regions of a single arm of an antibody;

(vi) the dAb fragment (Ward et al., Nature 341, 544-546 (1989)) which consists of a VH region;

(vii) isolated CDR regions; (viii) F(ab')2 fragments, a bivalent fragment including two Fab' fragments linked by a disulfide bridge at the hinge region; (ix) single chain antibody molecules (e.g., single chain Fv; scFv) (Bird et al., Science 242:423-426 (1988); and Huston et al., PNAS (USA) 85:5879-5883 (1988)); (x) "diabodies" with two antigen binding sites, comprising a heavy chain variable region (VH) connected to a light chain variable region (VL) in the same polypeptide chain (see, e.g., EP 404,097; WO 93/11161; and Hollinger et al., Proc. Natl. Acad. Sci. USA, 90:6444-6448 (1993)); (xi) "linear antibodies" comprising a pair of tandem Fd segments (VH-CH1-VH-CH1) which, together with complementary light chain polypeptides, form a pair of antigen binding regions (Zapata et al. Protein Eng. 8(10):1057-1062 (1995); and U.S. Pat. No. 5,641,870). “Single-chain variable fragment”, “single-chain antibody variable fragments” or “scFv” antibodies as used herein refers to forms of antibodies comprising the variable regions of only the heavy (VH) and light (VL) chains, connected by a linker peptide. The scFvs are capable of being expressed as a single chain polypeptide. The scFvs retain the specificity of the intact antibody from which it is derived. The light and heavy chains may be in any order, for example, VH-linker-VL or VL-linker-VH, so long as the specificity of the scFv to the target antigen is retained.

An "isolated antibody", as used herein, can refer to an antibody that is substantially free of other antibodies having different antigenic specificities (e.g., an isolated antibody that specifically binds a PD-L1 protein can be substantially free of antibodies that specifically bind antigens other than PD-L1 proteins). An isolated antibody that specifically binds a human PD-L1 protein can, however, have cross-reactivity to other antigens, such as PD-L1 proteins from other species. Moreover, an isolated antibody can be substantially free of other cellular material and/or chemicals.

Anti-PD-L antagonist antibody-producing cells, e.g., hybridomas, can be selected, cloned and further screened for desirable characteristics, including robust growth, high antibody production and desirable antibody characteristics. Hybridomas can be expanded in vivo in syngeneic animals, in animals that lack an immune system, e.g., nude mice, or in cell culture in vitro. Methods of selecting, cloning and expanding hybridomas are well known to those of ordinary skill in the art.

The terms "monoclonal antibody" or "monoclonal antibody composition" as used herein can refer to a preparation of antibody molecules of single molecular composition. A monoclonal antibody composition displays a single binding specificity and affinity for a particular epitope.

The term "recombinant human antibody", as used herein, can refer to all human antibodies that are prepared, expressed, created or isolated by recombinant means, such as (a) antibodies isolated from an animal (e.g., a mouse) that is transgenic or transchromosomal for human immunoglobulin genes or a hybridoma prepared therefrom (described below), (b) antibodies isolated from a host cell transformed to express the human antibody, e.g., from a transfectoma, (c) antibodies isolated from a recombinant, combinatorial human antibody library, and (d) antibodies prepared, expressed, created or isolated by any other means that involve splicing of human immunoglobulin gene sequences to other DNA sequences. Such recombinant human antibodies have variable regions in which the framework and CDR regions are derived from human germline immunoglobulin sequences. In certain embodiments, however, such recombinant human antibodies can be subjected to in vitro mutagenesis (or, when an animal transgenic for human Ig sequences is used, in vivo somatic mutagenesis) and thus the amino acid sequences of the VH and VL regions of the recombinant antibodies are sequences that, while derived from and related to human germline VH and VL sequences, may not naturally exist within the human antibody germline repertoire in vivo.

The term "isotype" can refer to the antibody class (e.g., IgM or IgG 1) that is encoded by the heavy chain constant region genes. An antibody can be an immunoglobulin G (IgG), an IgM, an IgE, an IgA or an IgD molecule, or is derived therefrom.

The phrases "an antibody recognizing an antigen" and "an antibody specific for an antigen" are used interchangeably herein with the term "an antibody which binds specifically to an antigen."

As used herein, an antibody that "specifically binds human PD-L1" can refer to an antibody that binds to a human PD-L1 protein (and possibly a PD-L1 protein from one or more non-human species) but does not substantially bind to non-PD-Ll proteins. Preferably, the antibody binds to a human PD-L1 protein with "high affinity," namely with a K_D of 1x10- M or less, more preferably 5x10^-8 M or less, more preferably 3x10^-8 M or less, more preferably 1x10^-8 M or less, more preferably 5x 10^-9 M or less or even more preferably 1x10^-9 M or less.

The term "does not substantially bind" to a protein or cells, as used herein, can mean that it cannot bind or does not bind with a high affinity to the protein or cells, i.e., binds to the protein or cells with an K_D of 2x 10^-6 M or more, more preferably 1 x 10^-5 M or more, more preferably 1 x 10^-4 M or more, more preferably 1x10^-3 M or more, even more preferably 1 x 10 ^-2 M or more. The term "high affinity" for an IgG antibody can refer to an antibody having a K_D of 1x10^-6 M or less, preferably 1x10^-7 M or less, more preferably 1x10^-8 M or less, even more preferably 1x10^-9 M or less, even more preferably 1x10^-10 M or less for a target antigen. However, "high affinity" binding can vary for other antibody isotypes.

The term“pharmaceutical formulation” refers to a preparation which is in such form as to permit the biological activity of an active ingredient contained therein to be effective, and which contains no additional components which are unacceptably toxic to a subject to which the formulation would be administered.

A“therapeutically effective amount” of an agent, e.g., a pharmaceutical formulation or cells, refers to an amount effective, at dosages and for periods of time necessary, to achieve a desired therapeutic result, such as for treatment of a disease, condition, or disorder, and/or pharmacokinetic or pharmaco-dynamic effect of the treatment. The therapeutically effective amount may vary according to factors such as the disease state, age, sex, and weight of the subject, and the populations of cells administered. In some embodiments, the provided methods involve administering the cells and/or compositions at effective amounts, e.g., therapeutically effective amounts.

An "antagonist antibody" as used herein, is an antibody blocks or dampens a biological response by binding to and blocking a ligand (for example, PD-L1) to which the antibody binds. An antagonist may, for example, bind to PD-L1 and block the binding of PD-L1 with PD-1, which thereby inhibits PD-1 receptor's phosphorylation or may inhibit the signal/cells activation. In one embodiment, the antibodies of the invention are antagonistic anti-PD-L antibodies.

A "CDR grafted antibody" is an antibody comprising one or more CDRs derived from an antibody of a particular species or isotype and the framework of another antibody of the same or different species or isotype.

A "humanized antibody" has a sequence that differs from the sequence of an antibody derived from a non-human species by one or more amino acid substitutions, deletions, and/or additions, such that the humanized antibody is less likely to induce an immune response, and/or induces a less severe immune response, as compared to the non-human species antibody, when it is administered to a human subject. In one embodiment, certain amino acids in the framework and constant regions of the heavy and/or light chains of the non-human species antibody are mutated to produce the humanized antibody. In another embodiment, the constant region(s) from a human antibody are fused to the variable region(s) of a non-human species. In another embodiment, a humanized antibody is a CDR grafted antibody comprising one or more CDRs derived from an antibody of a particular species or isotype and the framework of human antibodies. In another embodiment, one or more amino acid residues in one or more CDR sequences of a non-human antibody are changed to reduce the likely immunogenicity of the non-human antibody when it is administered to a human subject, wherein the changed amino acid residues either are not critical for immuno specific binding of the antibody to its antigen, or the changes to the amino acid sequence that are made are conservative changes, such that the binding of the humanized antibody to the antigen is not significantly worse than the binding of the non-human antibody to the antigen. Examples of how to make humanized antibodies may be found in U.S. Pat. Nos. 6,054,297, 5,886, 152 and 5,877,293.

The term "chimeric antibody" (cAb) refers to an antibody that contains one or more regions from one antibody and one or more regions from one or more other antibodies. In one embodiment, one or more of the PD-L1 are derived from a human anti-PD-L antibody. In another embodiment, all of the CDRs are derived from a human anti-PD-L antibody. In another embodiment, the CDRs from more than one human anti-PD-L antibodies are mixed and matched in a chimeric antibody. Lor instance, a chimeric antibody may comprise a CDR1 from the light chain of a first human anti-PD-L antibody, a CDR2 and a CDR3 from the light chain of a second human anti-PD-L antibody, and the CDRs from the heavy chain from a third anti- PD-L antibody. In the context of the present disclosure, cAbs represent variable regions of mouse monoclonal antibodies fused to the Lc regions of human antibodies. In another embodiment, other combinations are also possible.

The term "subject" can refer to any human or non-human animal. The subject can be male or female and can be any suitable age, including infant, juvenile, adolescent, adult, and geriatric subjects. The term "nonhuman animal" includes all vertebrates, e.g., mammals and non- mammals, such as nonhuman primates, sheep, dogs, cats, cows, horses, chickens, rabbits, mice, rats, amphibians, and reptiles, although mammals are preferred, such as non-human primates, sheep, dogs, cats, cows and horses.

The binding of an antibody of the disclosed invention to PD-L1 can be assessed using one or more techniques well established in the art. Lor example, in a preferred embodiment, an antibody can be tested by ELISA assays, for example using a recombinant PD-L1 protein. Still other suitable binding assays include but are not limited to a flow cytometry assay in which the antibody is reacted with a cell line that expresses human PD-L1, such as Expi293 or ExpiCHO cells that have been transfected to express PD-L1 (e.g., human PD-L1) on their cell surface. Additionally or alternatively, the binding of the antibody, including the binding kinetics (e.g., K_D value) can be tested in BIAcore binding assays, Octet Red96 (Pall) and the like.

Preferably, an antibody of the disclosed invention binds to a human PD-L1 protein with a K_D of 5x10 ⁸

- M or less, binds to a human PD-L1 protein with a K_D of 2x10 ⁸

- M or less, binds to a human PD-L1 protein with a K_D of 5x10^-9 M or less, binds to a human PD-L1 protein with a K_D of 4x10^-9 M or less, binds to a human PD-L1 protein with a K_D of 3x10^-9 M or less, binds to a human PD-L1 protein with a K_D of 2x10^-9 M or less, binds to a human PD-L1 protein with a K_D of 1x10^-9 M or less.

The present disclosure relates to isolated monoclonal antibodies, or antigen binding portions thereof, which binds to and blocks PD-L1, and uses thereof. In certain embodiments, the antibodies of the disclosed invention are derived from identified heavy and light chain germline sequences and/or comprise identified structural features such as CDR regions comprising identified amino acid sequences. This disclosure provides isolated antibodies, methods of making such antibodies and antigen-binding portions thereof of the disclosed invention. This disclosure also relates to methods of using the antibodies, such as using the anti-PD-L antibodies of the disclosed invention to stimulate immune responses, alone or in combination with other immunostimulatory or therapeutic antibodies. Accordingly, also provided are methods of using the anti-PD-L antagonist antibodies of the disclosed invention for example, including but not limited to, treating cancer in a human. Various aspects of the invention relate to antibodies and antibody fragments, pharmaceutical compositions, nucleic acids, recombinant expression vectors, and host cells for making such antibodies and fragments. Methods of using the antibodies of the invention to detect human PD-L1, to inhibit PD-L1 activity, either in vitro or in vivo, and to prevent or treat disorders such as cancer are also encompassed by the invention.

Complementarity determining regions (CDRs) are known as hypervariable regions both in the light chain and the heavy chain variable regions. The more highly conserved portions of variable regions are called the framework (FR). Complementarity determining regions (CDRs) and framework regions (FR) of a given antibody may be identified using the system described by Kabat et al. supra; Lefranc et al., supra and/or Honegger and Pluckthun, supra. Also familiar to those in the art is the numbering system described in Kabat et al. (1991, NIH Publication 91- 3242, National Technical Information Service, Springfield, Va.). In this regard Kabat et al. defined a numbering system for variable region sequences that is applicable to any antibody. One of ordinary skill in the art can unambiguously assign this system of "Kabat numbering" to any variable region amino acid sequence, without reliance on any experimental data beyond the sequence itself.

In certain embodiment, the present invention provides anti-PD-L antagonist antibodies or antigen-binding portions thereof. In one embodiment, the mouse antibody or portion comprises (a) a light chain variable region CDR1 comprising SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 16; SEQ ID NO: 17, SEQ ID NO: 18, (b) a light chain variable region CDR2 comprising SEQ ID NO: 19, SEQ ID NO:20, SEQ ID NO:21, SEQ ID NO:22, SEQ ID NO:23, SEQ ID NO:24; (c) a light chain variable region CDR3 comprising SEQ ID NO:25, SEQ ID NO:26, SEQ ID NO:27, SEQ ID NO:28, SEQ ID NO:29, SEQ ID NO:30; (d) a heavy chain variable region CDR1 comprising SEQ ID NO:31, SEQ ID NO:32, SEQ ID NO:33, SEQ ID NO:34, SEQ ID NO:35, SEQ ID NO:36 ; (e) a heavy chain variable region CDR2 comprising SEQ ID NO:37, SEQ ID NO:38 , SEQ ID NO:39, SEQ ID NO:40, SEQ ID NO:41, SEQ ID NO:42 ; (f) a heavy chain variable region CDR3 comprising SEQ ID NO:43 , SEQ ID NO:44, SEQ ID NO:45 , SEQ ID NO:46, SEQ ID NO:47, SEQ ID NO:48.

In one embodiment, the present disclosure provides a monoclonal antibody or antigen-binding portion thereof that binds to a PD-L1 epitope, that comprises a light chain variable region amino acid sequence having at least 95% identity to SEQ ID NOs: 1, 49, 50 or 51; and a heavy chain variable region amino acid sequence having at least 95% identity to SEQ ID NOs: 7, 65, 66 or 67.

In another embodiment, the present disclosure provides a monoclonal antibody or antigen- binding portion thereof that binds to a PD-L1 epitope, that comprises a light chain variable region amino acid sequence having at least 95% identity to SEQ ID NOs: 2, 55, 56, 57 or 58; and a heavy chain variable region amino acid sequence having at least 95% identity to SEQ ID NOs:8, 68. 69 or 70

In yet another embodiment, the present disclosure provides a monoclonal antibody or antigen- binding portion thereof that binds to a PD-L1 epitope, that comprises a light chain variable region amino acid sequence having at least 95% identity to SEQ ID NOs: 3, 59, 60 or 61 and a heavy chain variable region amino acid sequence having at least 95% identity to SEQ ID NOs: 9, 71, 72, 73, 74, 75 or 76. In yet another embodiment, the present disclosure provides a monoclonal antibody or antigen- binding portion thereof that binds to a PD-L1 epitope, that comprises a light chain variable region amino acid sequence having at least 95% identity to SEQ ID NOs: 4, 62 or 63 and a heavy chain variable region amino acid sequence having at least 95% identity to SEQ ID NOs: 10, 77 or 78.

In yet another embodiment, the present disclosure provides a monoclonal antibody or antigen- binding portion thereof that binds to a PD-L1 epitope, that comprises a light chain variable region amino acid sequence having at least 95% identity to SEQ ID NOs: 5 or 64 and a heavy chain variable region amino acid sequence having at least 95% identity to SEQ ID NOs: 11, 79 or 80.

In yet another embodiment, the present disclosure provides a monoclonal antibody or antigen- binding portion thereof that binds to a PD-L1 epitope, that comprises a light chain variable region amino acid sequence having at least 95% identity to SEQ ID NOs: 6, 52, 53 or 54 and heavy chain variable region amino acid sequence having at least 95% identity to SEQ ID NOs: 12, 81, 82 or 83.

Given that each of these antibody Fabs can bind to human PD-L1, the VH and VL sequences can be "mixed and matched" to create other anti-PD-L binding molecules of the invention. Preferably, when VH and VL chains are mixed and matched, a VH sequence from a particular VH/VL pairing is replaced with a structurally similar VH sequence. Likewise, preferably a VL sequence from a particular VH/VL pairing is replaced with a structurally similar VL sequence.

In some embodiments, the humanized anti-PD-L antibody or antigen binding portion thereof comprises a heavy chain variable region comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 65-67 and a light chain variable region comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 49-51. Preferred heavy and light chain combinations include but not limited to:

(a) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:65 and a light chain variable region comprising the amino acid sequence of SEQ ID NO:49;

(b) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:66 and a light chain variable region comprising the amino acid sequence of SEQ ID NO:50; (c) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:67 and a light chain variable region comprising the amino acid sequence of SEQ ID NO:51;

In some embodiments, the humanized anti-PD-L antibody or antigen binding portion thereof comprises a heavy chain variable region comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 68-70 and a light chain variable region comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 55-58. Preferred heavy and light chain combinations include but not limited to:

(a) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:68 and a light chain variable region comprising the amino acid sequence of SEQ ID NO:55;

(b) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:69 and a light chain variable region comprising the amino acid sequence of SEQ ID NO:56;

(c) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:70 and a light chain variable region comprising the amino acid sequence of SEQ ID NO:57;

In some embodiments, the humanized anti-PD-L antibody or antigen binding portion thereof comprises a heavy chain variable region comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 71-76 and a light chain variable region comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 59-61. Preferred heavy and light chain combinations include but not limited to:

(a) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:71 and a light chain variable region comprising the amino acid sequence of SEQ ID NO:59;

(b) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:72 and a light chain variable region comprising the amino acid sequence of SEQ ID NO:60;

(c) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:73 and a light chain variable region comprising the amino acid sequence of SEQ ID NO:61;

In some embodiments, the humanized anti-PD-L antibody or antigen binding portion thereof comprises a heavy chain variable region comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 77-78 and a light chain variable region comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 62-63. Preferred heavy and light chain combinations include but not limited to:

(a) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:77 and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 62;

(b) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:78 and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 63;

In some embodiments, the humanized anti-PD-L antibody or antigen binding portion thereof comprises a heavy chain variable region comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 79-80 and a light chain variable region comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 64. Preferred heavy and light chain combinations include but not limited to:

(a) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:79 and a light chain variable region comprising the amino acid sequence of SEQ ID NO:64;

In some embodiments, the humanized anti-PD-L antibody or antigen binding portion thereof comprises a heavy chain variable region comprising an amino acid sequence selected from the group consisting of SEQ ID NOs:81-83 and a light chain variable region comprising an amino acid sequence selected from the group consisting of SEQ ID NOs:52-54. Preferred heavy and light chain combinations include but not limited to:

(a) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:81 and a light chain variable region comprising the amino acid sequence of SEQ ID NO:52;

(b) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:82 and a light chain variable region comprising the amino acid sequence of SEQ ID NO:53;

(c) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO:83 and a light chain variable region comprising the amino acid sequence of SEQ ID NO:54;

In some embodiments, the humanized anti-PD-L antibody or antigen binding portion thereof comprises a light chain comprising an amino acid sequence selected from the group consisting of SEQ ID NOs:84-99 and a heavy chain comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 100-118. In one embodiment, the invention provides an anti-PD-L antibody, or an antigen-binding fragment thereof, comprising a heavy chain comprising a CDR3 region as set forth in SEQ ID NO: 43 and comprising a heavy chain variable region comprising an amino acid sequence that has at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to a sequence as set forth in any one of SEQ ID NOs: 7 or 65-67.

In one embodiment, the invention provides an anti-PD-L antibody, or an antigen-binding fragment thereof, comprising a heavy chain comprising a CDR3 region as set forth in SEQ ID NO: 44, and comprising a heavy chain variable region comprising an amino acid sequence that has at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to a sequence as set forth in any one of SEQ ID NOs:8 or 68-70.

In one embodiment, the invention provides an anti-PD-L antibody, or an antigen-binding fragment thereof, comprising a heavy chain comprising a CDR3 region as set forth in SEQ ID NO: 45, and comprising a heavy chain variable region comprising an amino acid sequence that has at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to a sequence as set forth in any one of SEQ ID NOs: 9 or 71-76.

In one embodiment, the invention provides an anti-PD-L antibody, or an antigen-binding fragment thereof, comprising a heavy chain comprising a CDR3 region as set forth in SEQ ID NO: 46, and comprising a heavy chain variable region comprising an amino acid sequence that has at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to a sequence as set forth in any one of SEQ ID NOs: 10 or 77-78.

In one embodiment, the invention provides an anti-PD-L antibody, or an antigen-binding fragment thereof, comprising a heavy chain comprising a CDR3 region as set forth in SEQ ID NO: 47, and comprising a heavy chain variable region comprising an amino acid sequence that has at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to a sequence as set forth in any one of SEQ ID NOs: 11 or 79-80.

In one embodiment, the invention provides an anti-PD-L antibody, or an antigen-binding fragment thereof, comprising a heavy chain comprising a CDR3 region as set forth in SEQ ID NO: 48, and comprising a heavy chain variable region comprising an amino acid sequence that has at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to a sequence as set forth in any one of SEQ ID NOs: 12 or 81-83.

In one embodiment, the invention provides an anti-PD-L antibody, or an antigen-binding fragment thereof, comprising a light chain comprising a CDR3 region as set forth in SEQ ID NO:

25, and having a light chain variable region comprising an amino acid sequence that has at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to a sequence as set forth in any one of SEQ ID NOs: 1 or 49-51.

26, and having a light chain variable region comprising an amino acid sequence that has at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to a sequence as set forth in any one of SEQ ID NOs: 2 or 55-58.

27, and having a light chain variable region comprising an amino acid sequence that has at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to a sequence as set forth in any one of SEQ ID NOs: 3 or 59-61.

28, and having a light chain variable region comprising an amino acid sequence that has at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to a sequence as set forth in any one of SEQ ID NOs: 4 or 62-63.

29, and having a light chain variable region comprising an amino acid sequence that has at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to a sequence as set forth in any one of SEQ ID NOs: 5 or 64.

In one embodiment, the invention provides an anti-PD-L antibody, or an antigen-binding fragment thereof, comprising a light chain comprising a CDR3 region as set forth in SEQ ID NO: 30, and having a light chain variable region comprising an amino acid sequence that has at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to a sequence as set forth in any one of SEQ ID NOs: 6 or 52-54.

Thus, in certain embodiments, the CDR3 region is held constant, while variability may be introduced into the remaining CDRs and/or framework regions of the heavy and/or light chains, while the antibody, or antigen binding fragment thereof, retains the ability to bind to PD-L1 and retains the functional characteristics, e.g., binding affinity, of the parent.

In one embodiment, the substitutions made within a heavy or light chain that is at least 95% identical (or at least 96% identical, or at least 97% identical, or at least 98% identical, or at least 99% identical) are conservative amino acid substitutions. A "conservative amino acid substitution" is one in which an amino acid residue is substituted by another amino acid residue having a side chain (R group) with similar chemical properties (e.g., charge or hydrophobicity). In general, a conservative amino acid substitution will not substantially change the functional properties of a protein. In cases where two or more amino acid sequences differ from each other by conservative substitutions, the percent sequence identity or degree of similarity may be adjusted upwards to correct for the conservative nature of the substitution. Means for making this adjustment are well-known to those of skill in the art. See, e.g., Pearson (1994) Methods Mol. Biol. 24: 307-331, herein incorporated by reference. Examples of groups of amino acids that have side chains with similar chemical properties include (1) aliphatic side chains: glycine, alanine, valine, leucine and isoleucine; (2) aliphatic -hydroxyl side chains: serine and threonine; (3) amide-containing side chains: asparagine and glutamine; ( 4) aromatic side chains: phenylalanine, tyrosine, and tryptophan; (5) basic side chains: lysine, arginine, and histidine; (6) acidic side chains: aspartate and glutamate, and (7) sulfur-containing side chains are cysteine and methionine. In addition to chemically- conserved amino acids, substitutions may include any amino acid which occurs in similar positions within related evolutionary-conserved human variable heavy chain sequences, human variable light chain sequences, and orthologous sequences from non-human species.

Unless stated otherwise, or implicit from context, the following terms and phrases include the meanings provided below. Unless explicitly stated otherwise, or apparent from context, the terms and phrases below do not exclude the meaning that the term or phrase has acquired in the art to which it pertains. The definitions are provided to aid in describing particular embodiments, and are not intended to limit the claimed invention, because the scope of the invention is limited only by the claims. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

All publications herein are incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference. The following description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

WORKING EXAMPLES:

The following examples are not intended to limit the scope of the claims to the invention but is rather intended to be exemplary of certain embodiments. Any variations in the exemplified methods which occur to the skilled artisan are intended to fall within the scope of the present invention.

Vector Construction:

Vector pcDNA3.4TOPO (Invitrogen) was ligated to a short polylinker containing EcoRI, Xhol, and NotI. The resulting plasmid was digested with EcoRI and Notl restriction enzymes and purified by gel electrophoresis. For heavy chain cloning, we assembled using Gibson assembly the prepared vector, a gblock encoding and VH region (IDT), and human IgG2 gblock encoding an Xhol site at the junction of the J-chain and CH 1 domain. The plasmid was prepared and digested with EcoRI and Xhol to accommodate all the humanized variable heavy (VH) domains with an IgG2 isotype. All assembly was done with the Gibson method (NEB). Variable light regions were constructed with a similar method using gblocks to assemble Vkappa regions with a gblock fragment which encoded the constant kappa (Ck).

Protein Expression, Purification, and Binding characterization: Plasmids were prepped and transfected into Expi293 or ExpiCHO cells using the transient expression system (Thermo Fisher). Briefly plasmids were transfected into 3e6 cells/ml cells at 1 ug plasmid DNA total/ml culture. Heavy chain and light chain plasmids were mixed in a 1:1 ratio. Cultures were incubated at 37°C, shaking. After 16 hours, we added Transfection Enhancer 1 and 2 to the cultures and continued incubation for six days. Supernatant were filtered, and protein titers were determined by an IgG quantitation protocol using the Octet Red96 (Pall). IgG was purified by Mab Select Sure Protein-A column purification on an ACTA PURE system and dialyzed overnight in PBS. Purified antibodies were characterized for affinity to the antigen by Octet Red96 by loading purified antibodies onto anti-human Heavy Chain (AHC) capture sensors and measuring rates of association and dissociation of PDL1 histidine tagged target at three concentrations. (Table 1).

Table 1. Mono-valent binding kinetics of humanized anti-PD-L Antibodies were compared to benchmark controls as determined by Octet.

Flow Cytometry Binding Analysis of anti-PD-L Antibodies to PD-L1 expressing A431 Cancer Cells

Two days prior to the FACS analysis, A431 cancer cells were seeded into 24-well plates at 30-60% confluence in the absence or the presence of 1000 U/ml of recombinant human IFN-g to stimulate PD-L1 expression. On the day of the FACS analysis, wells were washed with PBS and harvested with Trypsin/EDTA. Detached cells were washed twice, resuspended in FACS buffer at 5E6 cells/ml, and aliquoted into in 96 well plates at 1E5 cells/well. Cells were stained with 5 ug/ml anti-PD-L antibodies, positive control antibody“C 1-IgG 1”, or isotype IgGl on ice for 45 minutes followed by washing and secondary staining with 1:500 diluted Goat anti-human IgG- AF647. Cells were analyzed by flow cytometry following a final wash and addition of 7-AAD

(FIG. 1).

PD-1 His Tag Blocking assay on hPDLl/HEK293 cells testing humanized anti-PD-L

For screening hybridomas, hPD-L expressing 293 cells were harvested by Accutase and resuspend at 4E6 cells/ml cells with FACS Wash buffer. To compare blocking abilities of antibodies, we mixed 30 ul cells/well (120,000), 30 ul of 6 ug/ml rhPD-1 His tag protein (2 ug/ml final concentration), and 30 ul of serially titrated anti-PDLl antibodies and incubated for 20 min on ice. Following incubation, cells were washed and bound PD-1 was detected with anti-His Tag-APC Mouse IgGl (R&D Cat# IC050A). Cells were analyzed by flow cytometry following a final wash and addition of 7-AAD. Blocking abilities of humanized antibodies were compared with the same assay using rhPD-1 Fc-biotin at 0.5 ug/ml final concentration and detection with Streptavidin-APC (R&D cat# F0050) (FIG.2) (Table 2).

SEB Stimulation Assay Fresh PBMCs were diluted to 2E6 cells/ml in X-Vivo 15 medium (Lonza cat# 04-744Q). SEB (Millipore cat# 324798) was added to the PBMCs at 200 ng/ml (2x). Cells were treated with antibodies by adding 100 ul of diluted antibodies and 100 ul of PBMC/SEB antigen mixture into 96-well flat-bottom plates. Following incubation at 37 °C for 48 hours, supernatants were analyzed for IL-2 with an ELISA kit (R&D Systems) (FIG.3).

Mixed Lymphocyte Reaction Assay

PBMCs were isolated from human buffy coat using Density Gradient Centrifugation (Miltenyi Biotec) and washed 4 times with PBS. CD4+ T cells were isolated (Miltenyi Biotec cat# 130- 096-533) from the PBMCs and resuspended in X-Vivo 15 medium at 4E6 cells/ml. Monocyte-derived dendritic cells were generated from positively selected CD 14+ monocytes (Monocyte Isolation Kit II, Cat no. 130-091-153, Miltenyi Biotec). Cells were seeded at 5E5 cells/ml in complete RPMI-1640 media supplemented with 10% fetal bovine serum (FBS) for 7 days. Cultures were supplemented with recombinant human (rh-) IL-4 (1000 U/ml) (R&D Systems) and rh granulocyte-macrophage colony- stimulating factor (rh-GMCSF) (500 U/ml) (R&D Systems) on days 0, 2 and 5. Immature DCs were harvested on Day 7 and resuspended in 5 ml RPMI-1640, 10% FBS medium. Cells were incubated with occasional mixing with 20 ug/ml mitomycin C (Roche REF 10107409001) for 1 hour at 37 oC followed by washing and resuspension in X-Vivo 15 media to 4E5 cells/ml.

In 96 well flat bottom plates, we mixed 50 ul DC cells (2E4 DCs/well), 100 ul serial diluted anti- PD-L1 antibodies, and controls at a 2x concentration, and 50 ul purified CD4+ T cells (2E5 CD4+ T cells/per well) at 1:10 ratio (DCs : T cells). Plates were incubated for 5 days and the supernatants were analyzed by ELISA for IFNg release (R&D Systems) (FIG.4).

CMV Antigen Recall Response in vitro with anti-PDLl treatment

Thawed PBMCs from a CMV+ donor (Astarte Biologies) were counted and resuspended in AIM-V medium with b-Mercaptoethanol (1:1000) at 2E6 cells/ml. In a 96-well flat-bottom plate, we mixed 100 ul CMV+ PBMCs (2E5 cells/well), 50 ul of 5 ug/ml CMV antigen (Astarte cat# 1004), and 50 ul serially diluted anti-PDLl antibodies and controls. Plates were incubated for 4 days and the supernatants were analyzed by ELISA for IFNg release (R&D Systems) (FIG.5). Protein thermal shift of humanized anti-PDLl antibodies

Ten (10) ug/ml anti-PD-L antibodies were mixed with 2 ul 50X protein thermal shift dye, and PBS to a final volume of 100 ul. Samples were aliquoted into a PCR 96-tube plate in quadruplicate (25 ul/well). Protein Thermal Shift reactions were measured on an Applied Biosystems StepOne Real-Time PCR instrument using a continuous temperature gradient of 1 °C change per 1 min 5 sec from 22 - 95 °C. Tm was analyzed using the derivative method (FIG.6).

Sequence Listing

Mouse antibodies

Claims

CLAIMS What is claimed is:

1. An isolated monoclonal anti-PD-L antibody, or an antigen-binding portion thereof comprising a heavy chain variable region CDR3 comprising SEQ ID NO:43.

2. An isolated monoclonal anti-PD-L antibody, or an antigen-binding portion thereof comprising a heavy chain variable region CDR3 comprising SEQ ID NO:44.

3. An isolated monoclonal anti-PD-L antibody, or an antigen-binding portion thereof comprising a heavy chain variable region CDR3 comprising SEQ ID NO:45.

4. An isolated monoclonal anti-PD-L antibody, or an antigen-binding portion thereof comprising a heavy chain variable region CDR3 comprising SEQ ID NO:46.

5. An isolated monoclonal anti-PD-L antibody, or an antigen-binding portion thereof comprising a heavy chain variable region CDR3 comprising SEQ ID NO:47.

6. An isolated monoclonal anti-PD-L antibody, or an antigen-binding portion thereof comprising a heavy chain variable region CDR3 comprising SEQ ID NO:48.

7. The monoclonal antibody, or an antigen-binding portion thereof, of claim 1, which further comprises a heavy chain variable region CDR1 comprising SEQ ID NO:31 and a heavy chain variable region CDR2 comprising SEQ ID NO:37 respectively.

8. The monoclonal antibody, or an antigen-binding portion thereof, of claim 2, which further comprises a heavy chain variable region CDR1 comprising SEQ ID NO:32 and a heavy chain variable region CDR2 comprising SEQ ID NO:38 respectively.

9. The monoclonal antibody, or an antigen-binding portion thereof, of claim 3, which further comprises a heavy chain variable region CDR1 comprising SEQ ID NO:33 and a heavy chain variable region CDR2 comprising SEQ ID NO:39 respectively.

10. The monoclonal antibody, or an antigen-binding portion thereof, of claim 4, which further comprises a heavy chain variable region CDR1 comprising SEQ ID NO:34 and a heavy chain variable region CDR2 comprising SEQ ID NO:40 respectively.

11. The monoclonal antibody, or an antigen-binding portion thereof, of claim 5, which further comprises a heavy chain variable region CDR1 comprising SEQ ID NO:35 and a heavy chain variable region CDR2 comprising SEQ ID NO:41 respectively.

12. The monoclonal antibody, or an antigen-binding portion thereof, of claim 6, which further comprises a heavy chain variable region CDR1 comprising SEQ ID NO:36 and a heavy chain variable region CDR2 comprising SEQ ID NO:42 respectively.

13. The monoclonal antibody, or an antigen-binding portion thereof, of claim 7, which further comprises

(a) a light chain variable region CDR1 comprising SEQ ID NO: 13;

(b) a light chain variable region CDR2 comprising SEQ ID NO: 19; and

(c) a light chain variable region CDR3 comprising SEQ ID NO:25;

wherein said antibody or portion specifically binds to human PD-L1.

14. The monoclonal antibody, or an antigen-binding portion thereof, of claim 8, which further comprises

(a) a light chain variable region CDR1 comprising SEQ ID NO: 14;

(b) a light chain variable region CDR2 comprising SEQ ID NO:20; and

(c) a light chain variable region CDR3 comprising SEQ ID NO:26;

wherein said antibody or portion specifically binds to human PD-L1.

15. The monoclonal antibody, or an antigen-binding portion thereof, of claim 9, which further comprises

(a) a light chain variable region CDR1 comprising SEQ ID NO: 15;

(b) a light chain variable region CDR2 comprising SEQ ID NO:21; and

(c) a light chain variable region CDR3 comprising SEQ ID NO:27;

wherein said antibody or portion specifically binds to human PD-L1.

16. The monoclonal antibody, or an antigen -binding portion thereof, of claim 10, which further comprises (a) a light chain variable region CDR1 comprising SEQ ID NO: 16;

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

(c) a light chain variable region CDR3 comprising SEQ ID NO:28;

wherein said antibody or portion specifically binds to human PD-L1.

17. The monoclonal antibody, or an antigen -binding portion thereof, of claim 11, which further comprises

(a) a light chain variable region CDR1 comprising SEQ ID NO: 17;

(b) a light chain variable region CDR2 comprising SEQ ID NO:23; and

(c) a light chain variable region CDR3 comprising SEQ ID NO:29;

wherein said antibody or portion specifically binds to human PD-L1.

18. The monoclonal antibody, or an antigen -binding portion thereof, of claim 12, which further comprises

(a) a light chain variable region CDR1 comprising SEQ ID NO: 18;

(b) a light chain variable region CDR2 comprising SEQ ID NO:24; and

(c) a light chain variable region CDR3 comprising SEQ ID NO:30;

wherein said antibody or portion specifically binds to human PD-L1.

19. The monoclonal antibody, or antigen-binding portion thereof, of claim 1, which comprises a light chain variable region amino acid sequence having at least 95% identity to SEQ ID NO: 1 and a heavy chain variable region amino acid sequence having at least 95% identity to SEQ ID NO:7.

20. The monoclonal antibody, or an antigen -binding portion thereof, of claim 1, which comprises a heavy chain variable region comprising an amino acid sequence that has at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to a sequence as set forth in SEQ ID NO:7.

21. The monoclonal antibody, or antigen-binding portion thereof, of claim 2, which comprises a light chain variable region amino acid sequence having at least 95% identity to SEQ ID NO:2 and a heavy chain variable region amino acid sequence having at least 95% identity to SEQ ID NO:8.

22. The monoclonal antibody, or an antigen-binding portion thereof, of claim 2, which comprises a heavy chain variable region comprising an amino acid sequence that has at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to a sequence as set forth in SEQ ID NO:8.

23. The monoclonal antibody, or antigen-binding portion thereof, of claim 3, which comprises a light chain variable region amino acid sequence having at least 95% identity to SEQ ID NO:3 and a heavy chain variable region amino acid sequence having at least 95% identity to SEQ ID NO:9.

24. The monoclonal antibody, or an antigen -binding portion thereof, of claim 3, which comprises a heavy chain variable region comprising an amino acid sequence that has at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to a sequence as set forth in SEQ ID NO:9.

25. The monoclonal antibody, or antigen-binding portion thereof, of claim 4, which comprises a light chain variable region amino acid sequence having at least 95% identity to SEQ ID NO:4 and a heavy chain variable region amino acid sequence having at least 95% identity to SEQ ID NO: 10.

26. The monoclonal antibody, or an antigen-binding portion thereof, of claim 4, which comprises a heavy chain variable region comprising an amino acid sequence that has at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to a sequence as set forth in SEQ ID NO: 10.

27. The monoclonal antibody, or antigen-binding portion thereof, of claim 5, which comprises a light chain variable region amino acid sequence having at least 95% identity to SEQ ID NO:5 and a heavy chain variable region amino acid sequence having at least 95% identity to SEQ ID NO: 11.

28. The monoclonal antibody, or an antigen -binding portion thereof, of claim 5, which comprises a heavy chain variable region comprising an amino acid sequence that has at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to a sequence as set forth in SEQ ID NO: 11.

29. The monoclonal antibody, or antigen-binding portion thereof, of claim 6, which comprises a light chain variable region amino acid sequence having at least 95% identity to SEQ ID NO:6 and a heavy chain variable region amino acid sequence having at least 95% identity to SEQ ID NO: 12.

30. The monoclonal antibody, or an antigen-binding portion thereof, of claim 6, which comprises a heavy chain variable region comprising an amino acid sequence that has at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to a sequence as set forth in SEQ ID NO: 12.

31. The monoclonal antibody, or antigen-binding portion thereof, of claim 1, which comprises: a heavy chain variable region comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 65-67 and a light chain variable region comprising an amino acid sequence selected from the group consisting of SEQ ID NOs:49-51.

32. The monoclonal antibody, or antigen-binding portion thereof, of claim 2, which comprises: a heavy chain variable region comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 68-70 and a light chain variable region comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 55-58.

33. The monoclonal antibody, or antigen-binding portion thereof, of claim 3, which comprises: a heavy chain variable region comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 71-76 and a light chain variable region comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 59-61

34. The monoclonal antibody, or antigen-binding portion thereof, of claim 4, which comprises: a heavy chain variable region comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 77-78 and a light chain variable region comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 62-63

35. The monoclonal antibody, or antigen-binding portion thereof, of claim 5, which comprises: a heavy chain variable region comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 79-80 and a light chain variable region comprising an amino acid sequence selected from the group consisting of SEQ ID NO: 64.

36. The monoclonal antibody, or antigen-binding portion thereof, of claim 6, which comprises: a heavy chain variable region comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 81-83 and a light chain variable region comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 52-54.

37. An isolated monoclonal antibody or antigen binding portion thereof, comprising a light chain comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 84-99 and a heavy chain comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 100-118.

38. The monoclonal antibody, or antigen-binding portion thereof, of any one of claims 1-37, which is a Fab fragment, an F(ab')2 fragment, an Fv fragment, a single chain antibody, or a bispecific antibody.

39. The monoclonal antibody of any one of claims 1-37, which is a chimeric antibody or humanized antibody.

40. The monoclonal antibody of any one of claims 1-37, which is an immunoglobulin G (IgG), an IgM, an IgE, an IgA or an IgD molecule.

41. The monoclonal antibody of claim 39, which is an IgG 1, IgG2, IgG3, or IgG4.

42. An immunoconjugate comprising the antibody, or antigen-binding portion thereof, of any one of claims 1-41, linked to a therapeutic agent.

43. A pharmaceutical composition comprising the antibody, or antigen-binding portion thereof, according to any one of claims 1-41 and a pharmaceutically acceptable carrier.

44. A method of stimulating immune responses in a subject, comprising the step of administering to the subject the pharmaceutical composition according to claim 43 in therapeutically effective amount to stimulate an immune response in said subject.

45. A method of treating infectious diseases in a subject, comprising the step of administering to the subject the pharmaceutical composition according to claim 43 in therapeutically effective amount to treat said infectious diseases.

46. A method of treating cancer in a subject, comprising the step of administering to the subject the pharmaceutical composition according to claim 43 in therapeutically effective amount to treat said cancer.

47. The antibody or antigen-binding fragment thereof according to any one of claims 1-41, wherein the antibody or antigen-binding fragment thereof has an affinity (KD) for PD-L1 in the range of 5x10^-8 M to 1x10^-10 M.