ANTIBODIES TO HUMAN PROGRAMMED DEATH RECEPTOR PD-1

FIELD OF THE INVENTION

The present invention relates to an antibody or antigen-binding portion thereof that can bind to human programmed cell death protein 1 (PD-1). The antibody according to the present invention is further used in the preparation of a drug for treating diseases in which expression of PD-1 is detrimental.

BACKGROUND OF THE INVENTION

PD-1 (CD279) is a 288 amino acid protein inhibitory receptor expressed on activated T-cells and B-cells, natural killer cells and monocytes. PD-1 is a member of the CD28/CTLA-4 (cytotoxic T lymphocyte antigen)/ ICOS (inducible co-stimulator) family of T-cell co- inhibitory receptors. PD-1 receptor has two ligands namely, Protein Death-Ligand 1 (PD-L1) and Protein Death-Ligand 2 (PD-L2). PD-L1 (CD274, B7Ή 1) is expressed widely on both lymphoid and non-lymphoid tissues such as CD4 and CDS T-cells, macrophage lineage cells, peripheral tissues as well as on tumor cells, virally-infected cells and autoimmune tissue cells. PD-L2 (CD273, B7-DC) has a more restricted expression than PD-L1, being expressed on activated dendritic cells and macrophages (1). PD-L1 is expressed in most human cancers, including melanoma, glioma, non-small cell lung cancer, squamous cell carcinoma of head and neck, leukemia, pancreatic cancer, renal cell carcinoma, and hepatocellular carcinoma, and may be inducible in nearly all cancer types (2). PD-1 binding to its ligands results in decreased T-cell proliferation and cytokine secretion, suppressing humoral and cellular immune responses and worsening of diseases where an active immune response would have otherwise alleviated the disease state. This immune suppression can be reversed by inhibiting the local interaction of PD- 1 with PD-L1, and the effect is additive when the interaction of PD-1 with PD-L2 is blocked as well (3, 4).

Blocking PD-1 with antagonists, including monoclonal antibodies, has been studied in treatments of cancer and chronic viral infections (5).

Monoclonal antibodies to PD-1 are known in the art and have been described, for example, in patent documents W02006121168, W02009114335, WO2008156712, WO2012145493, WO2015036394, WO2015112800, WO2016015685 and WO2018128939. Three antibodies targeting human PD-1 for the treatment of various cancers in combination with conventional drugs are available commercially. These three antibodies are nivolumab, pembrolizumab and cemiplimab.

Despite the clinical success of anti-PD-1 antibodies, these therapeutic antibodies have several shortcomings, including the high cost, limited half-life and immunogenicity.

Accordingly, there is a continued need in the field of PD-1/PD-L1 pathway based disease treatment with antibodies that can effectively bind human PD-1 and block its binding with PD-L1 or PD-L2 and also improve upon some of the challenges of existing therapies. The present invention discloses such novel antibodies.

SUMMARY OF THE INVENTION

The present invention provides novel anti -PD-1 antibodies that have one or more improved characteristics, e.g., relative to known anti-PD-1 antibodies used for therapeutic purposes. The anti-PD-1 antibody or antigen binding portion thereof of the present invention binds with high affinity to human PD-1. The amino acid sequence of constant region of anti-PD-1 antibody comprises of the IgGl, IgG2, IgG3, IgG4, IgA, IgE, IgM or IgD constant region, preferably the IgGl or IgG4. Further, one or more anti-PD-1 antibodies of the present invention has modified or reduced or no ADCC and /or CDC activity. In some of the aspects, the present invention provides anti-PD-1 antibodies which has high ADCC and /or CDC activity which may lead to lysis of PD-1 expressing cells. The anti-PD-1 antibody or antigen binding portion thereof of the present invention has a K _D of 10 ^-10 M or less, more preferably 10 ^-11 M or less and even more preferably 10 ^-12 M or less for a PD-1 antigen. K _D value is a measurement of the binding affinity of the antibody towards its target antigen. The anti-PD-1 antibody or antigen binding portion thereof of the present invention can be used for the treatment of diseases where interaction of PD-1 with PDL1 and / or PDL2 is involved in modifying the disease state such as in infections and various cancers. In one aspect, the anti-PD-1 antibody or antigen binding portion thereof according to the present invention blocks PD-1 receptor interaction with its natural ligand PD-L1 and/or PD-L2. In another aspect of the invention, the anti-PD-1 antibody or antigen binding portion thereof kills the T cells that are expressing PD-1. Present invention also provides processes for preparing the novel anti-PD-1 antibodies and pharmaceutical compositions containing the same. BRIEF DESCRIPTION OF FIGURES

Figure 1 depicts a general vector map of pZRCIIhyg Anti-PD-1 LC- HC vector construct which is used to prepare full-length monoclonal anti-PD-1 antibody of the present invention.

Figure 2 depicts a general vector map of pSEX83 used in library generation to make anti-PD- 1 Fab of the present invention.

Figure 3 depicts a general vector map of pZRCIIIhyg Anti-PD-1 LC- HC vector construct which is used to prepare full-length monoclonal anti -PD-1 antibody of the anti -PD-1 Fab of the present invention.

Figure 4 depicts the results of flow cytometry experiment demonstrating that anti -PD- 1 antibodies IP-H4.2L1, IP-H4L1 (IgGl) and IP-H4L1 (IgG4) of the present invention, directed against human PD-1, bind to PD-1 on the cell surface of human PBMCs.

Figure 5 depicts the results of flow cytometry experiment using HEK 293 T cell lines demonstrating that anti-PD-1 antibodies IP-H4.2L1, IP-H4.19L1, IP-H4.36L1 of the present invention, directed against human PD-1, bind to PD-1 on the cell surface.

Figure 6 depicts the results of flow cytometry experiment using HEK 293 T cell lines demonstrating that anti -PD-1 antibodies N5NL, N6NL, N7NL, N9NL and NIONL of the present invention, directed against human PD-1, bind to PD-1 on the cell surface.

Figure 7 depicts the results of experiment demonstrating that anti -PD-1 antibodies IP-H4.2L1, IP-H4.19L1, 1P-H4.36L1 of the present invention, directed against human PD-1, promote Interieukin-2 (IL-2) secretion in a mixed lymphocyte reaction assay.

Figure 8 depicts the results of experiment demonstrating that anti -PD-1 antibodies IP-H4.2L1, IP-H4.19L1, IP-H4.36L1 of the present invention, directed against human PD-1, promote IFN-gamma (IFN-g) secretion in a mixed lymphocyte reaction assay.

Figure 9 depicts the results of experiment demonstrating that anti-PD-1 antibodies N5NL, N6NL, N9NL and NIONL of the present invention, directed against human PD-1, promote IL- 2 secretion in a mixed lymphocyte reaction assay.

Figure 10 depicts the results of experiment demonstrating that anti -PD-1 antibodies N5NL, N6NL, N9NL and NIONL of the present invention, directed against human PD-1, promote lFN-g secretion in a mixed lymphocyte reaction assay. Definitions

The term“antibody” as referred to herein includes whole antibodies and any antigen-binding fragment (i.e.,“antigen-binding portion”) or single chains thereof. An“antibody” refers to a glycoprotein comprising at least two heavy (H) chains and two light (L) chains inter- connected by disulfide bonds, or an antigen-binding portion thereof. Each heavy chain is comprised of a heavy chain variable region (abbreviated herein as VH) and a heavy chain constant region (abbreviated herein as CH). The heavy chain constant region is comprised of three domains, CHI, CH2 and CHS. Each light chain is comprised of a light chain variable region (abbreviated herein as VL) and a light chain constant region. The light chain constant region is comprised of one domain, CL. The VH and VL regions can be further subdivided into regions of hypervariability, termed complementarity determining regions (CDR), interspersed with regions that are more conserved, termed framework regions (FR). Each VH and VL is composed of three CDRs and four FRs, arranged from amino-terminus to carboxy- terminus in the following order: FR1, CDR1, FR2, CDR2, FRS, CDRS, FR4. The variable regions of the heavy and light chains contain a binding domain that interacts with an antigen. The constant regions of the antibodies may mediate the binding of the immunoglobulin to host tissues or factors, including various cells of the immune system (e.g., immune effector cells) and the first component (Clq) of the classical complement system.

The term“operatively linked” is intended to mean that an antibody gene is ligated into a vector such that transcriptional and translational control sequences within the vector serve their intended function of regulating the transcription and translation of the antibody gene.

The term“Ka” & Kd are well known to a skilled person, wherein“Ka” is the association rate of a particular antibody-antigen interaction, whereas the term“Kd” is the dissociation rate of a particular antibody-antigen interaction. The term“K _D ” is an affinity rate constant, which is obtained from the ratio of Kd to Ka. It can be measured by using surface plasmon resonance method which is well known in the art. K _D value is a measurement of the binding affinity of the antibody towards its target antigen. The term“K _D ” is also defined in WO 2006121168. This patent document is incorporated herein by reference.

The terms“monoclonal antibody” or“monoclonal antibody composition” as used herein 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“bispecific antibody” refers to a homogeneous antibody population involved in the highly specific recognition and binding of a two different antigenic determinants, or epitopes.

The term “recombinant antibody” according to the present invention, includes monoclonal antibodies which are generated recombinantly using synthetic heavy and light chain genes. Recombinant antibodies of this invention are monoclonal antibodies (mAbs) which are not produced using traditional hybridoma-based technologies, and do not need hybridomas and animals in the production process.

The term“immune effector function” as used herein is a biochemical event that results from the interaction of an antibody Fc region with an Fc receptor or ligand. Effector functions include but are not limited to ADCC, ADCP, and CDC. The term also represents a physiological event such as circulating half-life of a drug or targeting of a drug to a particular cell or tissue type.

The term“ADCC” or“antibody dependent cell-mediated cytotoxicity” as used herein is the cell-mediated reaction wherein nonspecific cytotoxic cells that express FcyRs recognize bound antibody on a target cell and subsequently cause lysis of the target cell.

The term“ADCP” or“antibody dependent cell-mediated phagocytosis” as used herein is the cell-mediated reaction wherein nonspecific cytotoxic cells that express FcyRs recognize bound antibody on a target cell and subsequently cause phagocytosis of the target cell.

The term“immune effector cell” as used herein is a cell that expresses one or more Fc receptors and mediates one or more effector functions. Effector cells include but are not limited to monocytes, macrophages, neutrophils, dendritic cells, eosinophils, mast cells, platelets, B cells, large granular lymphocytes, Langerhans' cells, natural killer (NK) cells, and gdT cells, and may be from any organism including but not limited to humans, mice, rats, rabbits, and monkeys.

The term“Fc” fragment, whose name reflects its ability to crystallize readily. In human IgG molecules, the Fc region is generated by papain cleavage N-terminal to Cys 226. The Fc region is central to the immune-effector functions of antibodies.

The term“Fc protein” as used herein refers to the portion of a single immunoglobulin heavy chain beginning in the hinge region just upstream of the papain cleavage site and ending at the C-terminus of the antibody. Accordingly, a complete Fc domain comprises at least a portion of a hinge (e.g., upper, middle, and / or lower hinge region) domain, a CH2 domain, and a CH3 domain.

The term“pharmaceutical formulation” refers to preparations, which are in such form as to permit the biological activity of the active ingredients to be unequivocally effective. The term “pharmaceutical formulation” or“pharmaceutical composition” or“composition” can be used here interchangeably.

The term“excipient” refers to an agent that may be added to a formulation to stabilize the active drug substance in the formulated form to adjust and maintain osmolality and pH of the pharmaceutical preparations. Examples of commonly used excipients include, but are not limited to, sugars, polyols, amino acids, surfactants, and polymers. “Pharmaceutically acceptable” excipients are those which can reasonably be administered to a subject mammal to provide an effective dose of the active ingredient employed.

The term“treatment” or“therapeutics” as used herein, refers to any treatment of a disease in a mammal, particularly in a human. It includes: (a) preventing the disease from occurring in a subject which may be predisposed to the disease or at risk of acquiring the disease but has not yet been diagnosed as having it; (b) inhibiting the disease, i.e., arresting its development; and (c) relieving the disease, i.e., causing regression of the disease.

The terms“patient” and“subject” are used interchangeably and are used in their conventional sense to refer to a living organism suffering from or prone to a condition that can be prevented or treated by administration of a composition of the present invention, and includes both humans and non-human animals. Examples of subjects include, but are not limited to, humans, chimpanzees and other apes and monkey species; farm animals such as cattle, sheep, pigs, goats and horses; domestic mammals such as dogs and cats; laboratory animals including rodents such as mice, rats and guinea pigs; birds, including domestic, wild and game birds such as chickens, turkeys and other gallinaceous birds, ducks, geese, and the like. The term does not denote a particular age. Thus, adult, juvenile and new bom individuals are of interest.

An“effective amount” of an antibody of the invention, or composition thereof, is an amount that is delivered to a mammalian subject, either in a single dose or as part of a series, which is effective for inducing an immune response against target antigen in said subject. This amount varies depending upon the health and physical condition of the individual to be treated, the taxonomic group of individual to be treated and other relevant factors. It is expected that the amount will fall in a relatively broad range that can be determined through routine trials.

A“pharmaceutically effective dose” or“therapeutically effective dose” is that dose required to treat or prevent, or alleviate one or more PD-1 related disorder or symptom in a subject, preferably in the present invention, for cancer or infection or autoimmune disease. The pharmaceutically effective dose depends on inter alia the specific compound (herein it is anti- PD-1 antibody or its combination or conjugate or bispecific) to administer, the severity of the symptoms, the susceptibility of the subject to side effects, the type of disease, the composition used, the route of administration, the type of mammal being treated, the physical characteristics of the specific mammal under consideration such as health and physical condition, concurrent medication, the degree of protection desired, and other factors that those skilled in the medical arts will recognize.

Abbreviations of amino acids as used in the current application are provided in below table.

Other abbreviations used in the present application:

ACT: Adoptive cell transfer

ADCC: Antibody-dependent cellular cytotoxicity

ADCP: Antibody-dependent cellular phagocytosis

CDC: Complement-dependent cytotoxicity

CDR: Complementary Determining Region

CFU: Colony forming unit

CH: Constant region of heavy chain

cHL: Classical Hodgkin Lymphoma

CL: Constant region of light chain

dNTP: deoxyribo Nucleotide Tri Phosphate

ESCC: Esophageal Squamous Cell Carcinoma

FACS: Fluorescence-activated cell sorting

HC: Heavy Chain

HCC: Hepatocellular Carcinoma

HCVR: Heavy Chain Variable Region

HEK: Human Embryonic Kidney

hyg: hygromycin IFN-g : IFN -gamma

LC: Light Chain

LCVR: Light Chain Variable Region

mAb: monoclonal Antibody

MCC: Merkel cell carcinoma

MLR: Mixed Lymphocyte Raction

MOI: Multiplicity of Infection

NSCLC: Non-Small Cell Lung Cancer

PBMC: Peripheral blood mononuclear cells

PD-1 / PD 1: Programmed cell death receptor 1

PD-L1 /PD LI: Programmed death ligand 1

PD-L2 / PD L2: Programmed death ligand 2

Pfx: Proof reading DNA polymerase, Pfx™ from Invitrogen.

PMBCL: Primary Mediastinal Large B-Cell Lymphoma sRCA: Selective rolling circle amplification

RCC: Renal Cell Carcinoma

rpm: Round per minute

SCCHN: Squamous Cell Carcinoma of the Head and Neck

SCLC: Small Cell Lung Cancer

SEQ / seq: Sequence

SPR: Surface Plasmon Resonance

VH: Variable region of heavy chain

VL: Variable region of light chain EMBODIMENTS OF THE INVENTION

The disclosure of the present invention relates to novel anti-PD-1 antibodies that can be used for therapeutic purposes.

In one embodiment, the anti -PD- 1 antibody or antigen binding portion thereof of the present invention binds with high affinity to human PD-1.

In one embodiment, the amino acid sequence of constant region of anti-PD-1 antibody comprises of the IgGl, IgG2, IgG3, IgG4, IgG2/G4, IgA, IgE, IgM or IgD constant region, preferably the IgGl or IgG4.

In another embodiment, one or more anti -PD-1 antibodies of the present invention has modified or reduced or no ADCC and / or CDC activity. In one of the embodiments, the anti- PD-1 antibody or antigen binding portion thereof has reduced potential to cause the safety issue of ADCC and CDC. In another embodiment, the anti-PD-1 antibody or antigen binding portion thereof has ADCC and / or CDC activity.

In another embodiment, one or more anti-PD-1 antibodies of the present invention has ADCP activity.

In one of the embodiments, the anti-PD-1 antibody or antigen binding portion thereof of the present invention has a K _D of 10 ^-8 M or less, more preferably 10 ^-10 M or less and even more preferably 10 ^'11 M or less even more preferably 10 ^-12 M or less for PD-1 antigen. K _D value is a measurement of the binding affinity of the antibody towards its target antigen.

In one of the embodiments, the anti-PD-1 antibody or antigen binding portion thereof of the present invention cross-reacts with PD-1 from species other than human.

In one of the embodiments, the anti-PD-1 antibody or antigen binding portion thereof of the present invention has higher binding specificity towards human PD-1.

In one of the embodiments, an anti-PD-1 antibody or antigen binding portion thereof of the present invention has an increased half-life in subject.

In one embodiment, the anti-PD-1 antibody or antigen binding portion thereof according to the present invention blocks the function of PD-1. In one embodiment, the anti -PD- 1 antibody or antigen binding portion thereof according to the present invention prevents the binding ofPD-1 to PD-L1 expressing target cells.

In one of the embodiments, the anti-PD-1 antibody or antigen binding portion thereof according to the present invention prevents the binding of PD-1 to PD-L2 expressing target cells.

In another embodiment, the anti-PD-1 antibody or antigen binding portion thereof of the present invention kills the T cells that are expressing PD-1.

In one embodiment, the anti-PD-1 antibody or antigen binding portion thereof according to the present invention has improved circulating half-life.

In another embodiment, the anti-PD-1 antibody or antigen binding portion of the present invention is able to bind to the monkey PD-1 enabling ease of drug development by providing a relevant animal pharmacology and toxicology model.

In one embodiment, the present invention provides a nucleic acid sequence encoding the anti- PD-1 antibody or antigen-binding portion thereof of the present invention.

In one embodiment, the present invention provides an expression vector comprising the nucleic acid sequence encoding the anti-PD-1 antibody or antigen-binding portion thereof of the present invention.

In one embodiment, the present invention provides a host cell comprising the expression vector wherein the expression vector comprising the nucleic acid sequence encoding the anti- PD-1 antibody or antigen-binding portion thereof of the present invention.

In one of the embodiments, the present invention provides a composition comprising an anti- PD-1 antibody or antigen-binding portion thereof that specifically binds human PD-1 and an acceptable carrier.

In one of the embodiments, the present invention provides an immunoconjugate comprising the anti-PD-1 antibody or antigen-binding portion thereof linked to a therapeutic agent.

In one of the embodiments, the present invention provides a bispecific molecule comprising the anti-PD-1 antibody or antigen-binding portion thereof linked to a second functional moiety having a different binding specificity than said antibody, or antigen-binding portion thereof. In one of the embodiments, the present invention provides a combination comprising at least two or more antibodies or antigen binding portion thereof wherein at least one antibody or antigen binding portion thereof is the anti -PD- 1 antibody or antigen-binding portion thereof of the present invention.

In another embodiment, the anti-PD-1 antibody or antigen binding portion thereof of the present invention can be used for the treatment of disease where activity of PD-1 is detrimental such as various cancers, various infections. . In one of the embodiments, the anti- PD-1 antibody or antigen binding portion thereof of the present invention can be used for the treatment of auto-immune disorders.

In one of the embodiments, the anti-PD-1 antibody or antigen binding portion thereof of the present invention can be used for the treatment of cancer selected from NSCLC, SCLC, RCC, cHL, SCCHN, urothelial carcinoma, colorectal cancer, ESCC, primary mediastinal large b- cell lymphoma, microsatellite instability-high cancer, gastric cancer, cervical cancer, merkel cell carcinoma, endometrial carcinoma and tumor mutational burden-high (TMB-H) cancer, where PD-1 activity is amplified.

DETAILED DESCRIPTION OF THE INVENTION

In one embodiment, the anti-PD-1 antibody or antigen binding portion thereof of the present invention binds with high affinity to human PD-1.

In one embodiment, CDR1 of the heavy chain (herein after referred as CDRH1) of the anti- PD-1 antibody or antigen binding portion thereof of the present invention has an amino acid sequence of genral formula (I): X _1a -A _1a -X _2a -A _2a wherein,

X _1a is an amino acid selected from asparagine, glycine and threonine;

A1 _a is a dipeptide selected from Tyr-Tyr and Ile-Thr;

X _2a is an amino acid selected from isoleucine, leucine, valine, phenylalanine, methionine and alanine;

A _2a is single amino acid or dipeptide or tripeptide or tetrapeptide selected from tyrosine, asparagine, serine, glycine, Asn-Ser, Asn-Ser-Gly and Ser-Asn-Ser-Gly, with the proviso that asparagine as X _1a and methionine as X _2a are not present together. In one of the preferred embodiments, CDRH1 of the heavy chain of the anti-PD-1 antibody or antigen binding portion thereof of the present invention has an amino add sequence of the formula (la): X1 _a -Y-Y-X ₂ a-Y wherein,

X1a is an amino acid selected from asparagine and threonine;

X2a is an amino acid selected from isoleucine, leucine, valine, methionine and alanine, with the proviso that asparagine as X1a and methionine as X _2a are not present together.

In a more preferred embodiment, CDRH1 of the anti-PD-1 antibody or antigen binding portion thereof of the present invention is TΎUΊU.

In an alternate preferred embodiment, the CDRH1 of the anti-PD-1 antibody or antigen binding portion thereof of the present invention is GITFSNSG.

In one embodiment, CDR2 of heavy chain (herein after referred as CDRH2) of the anti-PD-1 antibody or antigen binding portion thereof of the present invention has an amino acid sequence of general formula (P) : A1b-X1b-A2b-X2b-X3b-A3b-X4b-X5b-X6b-X7b- X8b-A , wherein,

A _1b is optionally present and when present represents glycine;

Xib is an amino acid selected from methionine, isoleucine, leucine, glycine, valine and alanine;

A _1b is tripeptide or tetrapeptide selected from Asn-Pro-Ser-Asn or Trp-Tyr-Asp;

Each of X _2b and X _3b independently represents an amino acid selected from glycine and serine;

A3 _b is single amino acid or dipeptide selected from lysine or Thr-Asn;

X4 _b is an amino acid selected from tyrosine, arginine and phenylalanine;

X5 _b is an amino acid selected from serine, tyrosine and asparagine;

X6 _b may be optionally present and when present represents an amino acid selected from glutamic acid and glutamine;

X7 _b may be optionally present and when present represents an amino acid selected from asparagine and lysine; X _8b may be optionally present and when present represents an amino acid selected from tyrosine and phenylalanine;

A _4b may be optionally present and when present represents lysine.

In one of the preferred embodiments, CDRH2 of heavy chain of the anti-PD-1 antibody or antigen binding portion thereof of the present invention has an amino acid sequence of the formula (Ha): G-Xib-N-P-S-N-Xzb-X3b-T-N-X4b-X5b-X6b-X7b- Xgb -K wherein,

X _1b is an amino acid selected from methionine, isoleucine, leucine, glycine, valine and alanine;

Each of X _2b and X _3b independently represents an amino acid selected from glycine and serine;

Each of X _4b and X _8b independently represents an amino acid selected from tyrosine and phenylalanine;

X _5b is an amino acid selected from serine and asparagine;

X _6b is an amino acid selected from glutamic acid and glutamine;

X _7b is an amino acid selected from asparagine and lysine.

In a more preferred embodiment, CDRH2 of the anti-PD-1 antibody or antigen binding portion thereof of the present invention is selected from GVNPSNGGTNYNENYK, GVNPSNGGTNYNQNYK or GVNPSNSGTNYNE NYK.

In an alternate preferred embodiment, the CDRH2 of the anti-PD-1 antibody or antigen binding portion thereof of the present invention is IWYDGSKRY.

In one embodiment, the CDR3 of the heavy chain (herein after referred as CDRH3) of the anti-PD-1 antibody or antigen binding portion thereof of the present invention has an amino acid sequence of general formula (PI): A1c-X1c-A2c-X2c-A3c-X3c-A4c-X4c-X5c-A5c wherein,

A1c may be optionally present and when present represents arginine;

Xicis an amino acid selected from aspartic acid, asparagine and glutamic acid;

A2c is an amino acid or dipeptide selected from asparagine, serine and threonine or Tyr-Arg; X _2c is an amino acid selected from tyrosine, histidine, aspartic acid, glutamic acid, glycine and phenylalanine;

A _3C is an amino acid selected from aspartic acid, tyrosine, isoleucine, phenylalanine, histidine and tryptophan;

X3 _c may be optionally present and when present represents an amino acid selected from isoleucine, leucine, valine, alanine, glutamine and methionine;

A _4c may be optionally present and when present represents glycine;

X ₄ c may be optionally present and when present represents an amino acid selected from tyrosine, histidine and phenylalanine;

X _5c may be optionally present and when present represents an amino acid selected from aspartic acid and glutamic acid;

A5 _c may be optionally present and when present represents tyrosine.

In one of the embodiments, the CDRH3 of the heavy chain of the anti-PD-1 antibody or antigen binding portion thereof of the present invention has an amino acid sequence of the formula (Ilia): R-X1 _c -Y-R-X _2c -D-X _3c -G-X ₄ c-X ₅ c-Y wherein,

Each of X1 _c and Xs _c independently represents an amino acid selected from aspartic acid and glutamic acid;

Each of X _2c and X4 _c independently represents an amino acid selected from tyrosine, histidine and phenylalanine;

X3 _c is an amino acid selected from isoleucine, leucine, valine, alanine, glutamine and methionine.

In a more preferred embodiment CDRH3 of the anti-PD-1 antibody or antigen binding portion thereof of the present invention is selected from RDYRYDMGFDY or RDYRYDMGYDY or RDYRYDMGHDY.

In an alternate preferred embodiment, the CDRH3 of the anti -PD- 1 antibody or antigen binding portion thereof of the present invention is ESEY or NNDI or NSDF or NSDH or NSDY or NSGY or NTDW or NTDY. In one embodiment, CDR1 of light chain (herein after referred as CDRL1) of the anti -PD- 1 antibody or antigen binding portion thereof of the present invention has an amino acid sequence of general formula (IV): A _1D -X _1D -A _2d -X _2d -X _3d -A _3d -X _¼ -A _4d -X _5d -A _5d wherein,

A _1d is dipeptide or tripeptide selected from Gln-Ser or Arg-Ala-Ser;

X _1d is an amino acid selected from valine, glutamic acid and lysine;

A _2d is an amino acid selected from glycine and serine;

Xi _d is an amino acid selected from isoleucine, leucine, valine, alanine, serine and methionine;

X _3d is an amino acid selected from serine, tyrosine and glutamic acid;

A _3d may be optionally present and when present represents an amino acid selected from threonine;

X4 _d may be optionally present and when present represents an amino acid selected from serine, aspartic acid and glutamic acid.

A4 _d may be optionally present and when present represents a tetrapeptide Gly-Tyr-Ser-Tyr;

X _5d may be optionally present and when present represents an amino acid selected from isoleucine, leucine, valine, alanine and methionine;

X _5d may be optionally present and when present represents histidine.

In one of the preferred embodiments, CDRL1 of light chain (of the anti-PD-1 antibody or antigen binding portion thereof of the present invention has an amino acid sequence of the formula (IVa): R-A-S-X1 _d -G-X _2d -X _3d -T-X _4d -G-Y-S-Y-X _5d -H wherein,

Xi _d is an amino acid selected from glutamic acid and lysine;

Each of X2 _d and Xs _d independently represents an amino acid selected from isoleucine, leucine, valine, alanine and methionine;

X _3d is an amino acid selected from serine and glutamic acid;

X4 _d is an amino acid selected from serine, aspartic acid and glutamic acid.

In a more preferred embodiment CDRL1 of the anti-PD-1 antibody or antigen binding portion thereof of the present invention is RASKGVSTSGYSYLH. In an alternate preferred embodiment CDRL1 of the anti -PD- 1 antibody or antigen binding portion thereof of the present invention is QSVSSY.

In one embodiment, CDRL2 of light chain (herein after referred as CDRL2) of anti-PD-1 antibody or antigen binding portion thereof has amino acid sequence of general formula (V): A1 _e -X1e-A2e-X2e-A3e wherein,

A1e may be optionally present and when present represents a dipeptide Leu-Ala;

X1e is an amino acid selected from serine, aspartic acid and glutamic acid;

A2e is an amino acid selected from tyrosine or alanine;

X _2c is an amino acid selected from isoleucine, leucine, valine, alanine, serine and methionine;

A _3e may be optionally present and when present represents dipeptide Glu-Ser.

In one of the preferred embodiments, CDRL2 of light chain of anti-PD-1 antibody or antigen binding portion thereof has amino acid sequence of the formula (Va): L-A-X1 _e -Y-X ₂ e-E-S wherein,

Xieis an amino acid selected from serine, aspartic acid and glutamic acid;

X2e is an amino acid selected from isoleucine, leucine, valine, alanine and methionine.

In a more preferred embodiment CDRL2 of the anti-PD-1 antibody or antigen binding portion thereof of the present invention is LASYLES.

In an alternate preferred embodiment CDRL2 of the anti-PD-1 antibody or antigen binding portion thereof of the present invention is DAS.

In one embodiment, CDR3 of light chain (herein after referred as CDRL3) of anti-PD-1 antibody or antigen binding portion thereof has amino acid sequence of general formula (VI): A1 _f X1 _f A2 _f X2 _f -X3 _f - X _4f -X5 _f X6f wherein,

Aif is dipeptide selected from Gln-His and Gln-Gln;

X1 _f is an amino acid sequence selected from serine, arginine, aspartic acid and glutamic acid;

A2 _f is an amino acid selected from arginine and serine;

X2 _f is an amino acid selected from aspartic acid, asparagine and glutamic acid; Each of X3 _f and X; _f independently represents an amino acid sequence selected from isoleucine, leucine, valine, alanine, tryptophan, arginine and methionine;

X4 _f is proline;

X6f is threonine.

In one of the preferred embodiments, CDRL3 of light chain of anti-PD-1 antibody or antigen binding portion thereof has amino acid sequence formula (Via): Q-H-X1 _f -R- X _2f -X33f-X4 _f -T wherein,

X1 _f is an amino acid sequence selected from serine, arginine, aspartic acid and glutamic acid;

X _2f is an amino acid selected from aspartic acid and glutamic acid;

Each of X3 _f and X independently represents an amino acid sequence selected from isoleucine, leucine, valine, alanine and methionine.

In a more preferred embodiment CDRL3 of the anti-PD-1 antibody or antigen binding portion thereof of the present invention is QHSRDLPLT.

In an alternate preferred embodiment CDRL3 of the anti -PD- 1 antibody or antigen binding portion thereof of the present invention is QQSSNWPRT.

In one of the preferred embodiments, CDRHl, CDRH2, CDRH3, CDRL1, CDRL2 and CDRL3 of the anti-PD-1 antibody or antigen binding portion thereof of the present invention is selected from the amino acid sequences as given in below table 1.

Table 1 : Amino acid sequences of CDR region

In one of the embodiments, the present invention provides anti-PD-1 antibody or antigen binding portion thereof comprising:

wherein,

Xi _a is an amino acid selected from asparagine, glycine and threonine;

Aia is a dipeptide selected from Tyr-Tyr and Ile-Thr;

X2a is an amino acid selected from isoleucine, leucine, valine, phenylalanine, methionine and alanine;

A2a is single amino acid or dipeptide or tripeptide or tetrapeptide selected from tyrosine, asparagine, serine, glycine, Asn-Ser, Asn-Ser-Gly and Ser-Asn-Ser-Gly;

A1 _b is optionally present and when present represents glycine;

X1 _b is an amino acid selected from methionine, isoleucine, leucine, glycine, valine and alanine;

A _2b is tripeptide or tetrapeptide selected from Asn-Pro-Ser-Asn or Trp-Tyr-Asp;

Each of X2 _b and X _3b independently represents an amino acid selected from glycine and serine;

A _3b is single amino acid or dipeptide selected from lysine or Thr-Asn;

X4 _b is an amino acid selected from tyrosine, arginine and phenylalanine;

X5 _b is an amino acid selected from serine, tyrosine and asparagine; X6 _b may be optionally present and when present represents an amino acid selected from glutamic acid and glutamine;

X7b may be optionally present and when present represents an amino acid selected from asparagine and lysine;

X8b may be optionally present and when present represents an amino acid selected from tyrosine and phenylalanine;

A4 _b may be optionally present and when present represents lysine;

A1c may be optionally present and when present represents arginine;

Xicis an amino acid selected from aspartic acid, asparagine and glutamic acid;

A _2C is an amino acid or dipeptide selected from asparagine, serine and threonine or Tyr-Arg;

X _2c is an amino acid selected from tyrosine, histidine, aspartic acid, glutamic acid, glycine and phenylalanine;

A _3C is an amino acid selected from aspartic acid, tyrosine, isoleucine, phenylalanine, histidine and tryptophan;

X _3c may be optionally present and when present represents an amino acid selected from isoleucine, leucine, valine, alanine, glutamine and methionine;

A4 _C may be optionally present and when present represents glycine;

X4c may be optionally present and when present represents an amino acid selected from tyrosine, histidine and phenylalanine;

X _5c may be optionally present and when present represents an amino acid selected from aspartic acid and glutamic acid;

A _5C may be optionally present and when present represents tyrosine;

A1 _d is dipeptide or tripeptide selected from Gln-Ser or Arg-Ala-Ser;

X1 _d is an amino acid selected from valine, glutamic acid and lysine;

A ₂ d is an amino acid selected from glycine and serine; X ₂ d is an amino acid selected from isoleucine, leucine, valine, alanine, serine and methionine;

X _3d is an amino acid selected from serine, tyrosine and glutamic acid;

A _3d may be optionally present and when present represents an amino acid selected from threonine;

X4 _d may be optionally present and when present represents an amino acid selected from serine, aspartic acid and glutamic acid;

A _4d may be optionally present and when present represents tetrapeptide Gly-Tyr-Ser-Tyr;

X ₅ d may be optionally present and when present represents an amino acid selected from isoleucine, leucine, valine, alanine and methionine;

A5 _d may be optionally present and when present represents histidine;

A1e may be optionally present and when present represents dipeptide Leu- Ala;

X1 _e is an amino acid selected from serine, aspartic acid and glutamic acid;

A _2e is an amino acid selected from tyrosine or alanine;

X _2C is an amino acid selected from isoleucine, leucine, valine, alanine, serine and methionine;

A _3e may be optionally present and when present represents dipeptide Glu-Ser;

A1 _f is dipeptide selected from Gln-His and Gln-Gln ;

X1 _f is an amino acid sequence selected from serine, arginine, aspartic acid and glutamic acid;

A _2f is an amino acid selected from arginine and serine;

X _2f is an amino acid selected from aspartic acid, asparagine and glutamic acid;

Each of X _3f and X5f independently represents an amino acid sequence selected from isoleucine, leucine, valine, alanine, tryptophan, arginine and methionine;

X4 _f is proline;

X6 _f is threonine, with the proviso that asparagine as X1a and methionine as X _2a are not present together. In one of the preferred embodiments, the present invention provides anti-PD-1 antibody or antigen binding portion thereof comprising:

(a) CDRH1 comprising amino acid sequence of the formula (la) : Xu-Y-Y-X^-Y;

(b) CDRH2 comprising amino acid sequence of the formula (IIa):G-Xi _b -N-P-S-N-X _2b -X _3b -T- N-X _4b -X _5b -X _6b -X _7b -Xto-K and

(c) CDRH3 comprising amino acid sequence of the formula (Ilia): R-Xi _c -Y-R-X _2c -D-X _3C -G- X4c-X ₅ c-Y;

(d) CDRL1 comprising amino acid sequence of the formula (IVa) : R-A-S-Xi _d -G-X _2d -X _3d -T- Xt _d -G- Y - S- Y -Xs _d -H;

(e) CDRL2 comprising amino acid sequence of the formula (Va): L-A-Xi _e -Y-X _2e -E-S;

(f) CDRL3 comprising amino acid sequence of the formula (Via): Q-H-Xi _f R- X _2f -Xs _f -P-Xtr

T wherein

Xu is an amino acid selected from asparagine and threonine;

Xia is an amino acid selected from isoleucine, leucine, valine, methionine and alanine;

Xi _b is an amino acid selected from methionine, isoleucine, leucine, glycine, valine and alanine;

Each of X _¾ and X _¾b independently represents an amino acid selected from glycine and serine;

Each of Xt _b and X» independently represents an amino acid selected from tyrosine and phenylalanine;

X _¾ is an amino acid selected from serine and asparagine;

Xe _b is an amino acid selected from glutamic acid and glutamine;

C· _¾ is an amino acid selected from asparagine and lysine;

Each of Xic and X; _c independently represents an amino acid selected from aspartic acid and glutamic acid; ach of X2c and X4 _C independently represents an amino acid selected from tyrosine, histidine and phenylalanine;

X3c is an amino acid selected from isoleucine, leucine, valine, alanine, glutamine and methionine;

X1 _d is an amino acid selected from glutamic acid and lysine

Each of X2 _d and X ₅ a independently represents an amino acid selected from isoleucine, leucine, valine, alanine and methionine;

X3 _d is an amino acid selected from serine and glutamic acid;

X4 _d is an amino acid selected from serine, aspartic acid and glutamic acid;

X1e is an amino acid selected from serine, aspartic acid and glutamic acid;

X2e is an amino acid selected from isoleucine, leucine, valine, alanine and methionine;

Xi _f is an amino acid sequence selected from serine, arginine, aspartic acid and glutamic acid;

X2 _f is an amino acid selected from aspartic acid and glutamic acid;

Each of X3 _f and X4 _f independently represents an amino acid sequence selected from isoleucine, leucine, valine, alanine and methionine, with the proviso that asparagine as X1 _a and methionine as X2 _a are not present together.

In one of the preferred embodiments, the amino acid sequences of CDRH1, CDRH2 and CDRH3 of anti -PD- 1 antibody or antigen binding portion thereof of the present invention are TYYIY, G VNP SN GGTN YNENYK and RDYRYDMGFDY respectively.

In another of the preferred embodiments, the amino acid sequences of CDRH1, CDRH2 and CDRH3 of anti -PD- 1 antibody or antigen binding portion thereof of the present invention are TYYIY, GVNP SN GGTNYNENYK and RDYRYDMGYDY respectively.

In a still another of the preferred embodiments, the amino acid sequences of CDRH1, CDRH2 and CDRH3 of anti -PD- 1 antibody or antigen binding portion thereof of the present invention are TYYIY, G VNP SN GGTNYNENYK and RDYRYDMGHDY respectively. In another of the preferred embodiments, the amino acid sequences of CDRH1, CDRH2 and CDRH3 of anti -PD- 1 antibody or antigen binding portion thereof of the present invention are TYYIY, GVNPSNSGTNYNENYK and RDYRYDMGFDY respectively.

In yet another of the preferred embodiments, the amino acid sequences of CDRH1, CDRH2 and CDRH3 of anti-PD-1 antibody or antigen binding portion thereof of the present invention are TYYIY, GVNPSNSGTNYNENYK and RDYRYDMGYDY respectively.

In still another of the preferred embodiments, the amino acid sequences of CDRH1, CDRH2 and CDRH3 of anti -PD- 1 antibody or antigen binding portion thereof of the present invention are TYYIY, GVNPSNSGTNYNENYK and RDYRYDMGHDY respectively.

In another of the preferred embodiments, the amino acid sequences of CDRH1, CDRH2 and CDRH3 of anti-PD-1 antibody or antigen binding portion thereof of the present invention are TYYIY, GVNPSNGGTNYNQNYK and RDYRYDMGFDY respectively.

In another of the preferred embodiments, the amino acid sequences of CDRH1, CDRH2 and CDRH3 of anti -PD- 1 antibody or antigen binding portion thereof of the present invention are TYYIY, GVNPSNGGTNYNQNYK and RDYRYDMGYDY respectively.

In yet another of the preferred embodiments, the amino acid sequences of CDRH1, CDRH2 and CDRH3 of anti-PD-1 antibody or antigen binding portion thereof of the present invention are TYYIY, GVNPSNGGTNYNQNYK and RDYRYDMGHDY respectively.

In another of the preferred embodiments, the amino acid sequences of CDRH1, CDRH2 and CDRH3 of anti -PD- 1 antibody or antigen binding portion thereof of the present invention are GITFSNSG, IWYDGSKRY andNSDF respectively.

In another of the preferred embodiments, the amino acid sequences of CDRH1, CDRH2 and CDRH3 of anti-PD-1 antibody or antigen binding portion thereof of the present invention are GITFSNSG, IWYDGSKRY and NSDH respectively.

In one of the preferred embodiments, the amino acid sequences of CDRH1, CDRH2 and CDRH3 of anti -PD- 1 antibody or antigen binding portion thereof of the present invention are GITFSNSG, IWYDGSKRY and NSDY respectively. In another of the preferred embodiments, the amino acid sequences of CDRH1, CDRH2 and CDRH3 of anti -PD- 1 antibody or antigen binding portion thereof of the present invention are GITFSNSG, IWYDGSKRY and NTDW respectively.

In one of the preferred embodiments, the amino acid sequences of CDRH1, CDRH2 and CDRH3 of anti-PD-1 antibody or antigen binding portion thereof of the present invention are GITFSNSG, IWYDGSKRY and NTDY respectively.

In one of the preferred embodiments, the amino acid sequences of CDRL1, CDRL2 and CDRL3 of anti-PD-1 antibody or antigen binding portion thereof of the present invention are RASKGVSTSGYSYLH, LASYLES and QHSRDLPLT respectively.

In another of the preferred embodiments, the amino acid sequences of CDRL1, CDRL2 and CDRL3 of anti-PD-1 antibody or antigen binding portion thereof of the present invention are QSVSSY, DAS and QQSSNWPRT respectively.

In another embodiment, the present invention provides an antibody, or antigen-binding portion thereof comprising:

(a) CDRH1 comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 1, 2, 3, 4, 5, 6 and 7;

(b) CDRH2 comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 and

30;

(c) CDRH3 comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54 and 55;

(d) CDRL1 comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79,80 and 81;

(e) CDRL2 comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97 , 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110,111 and 112; and (f) CDRL3 comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135 and 136; wherein, the antibody specifically binds PD-1, preferably human PD-1.

In one of the embodiments, HCVR and LCVR of the anti -PD- 1 antibody or the antigen binding portion thereof of the present invention is selected from the amino acid sequences as given in below table 2.

Table 2: Amino acid sequences of variable region

In one of the embodiments, variable region of heavy chain of anti -PD- 1 antibody or antigen binding portion thereof of the present invention comprising of CDRH1, CDRH2 and CDRH3 comprising amino acid sequences selected from below given table 3.

Table 3: CDR regions of selected HCVR sequences

In one of the embodiments, variable region of light chain of anti -PD- 1 antibody or antigen binding portion thereof of the present invention comprising of CDRL1, CDRL2 and CDRL3 comprising amino acid sequences selected from below given table 4.

Table 4: CDR regions of selected LCVR sequences

Accordingly, the present invention provides an anti -PD- 1 antibody, or antigen-binding portion thereof, comprising a heavy chain variable region and a light chain variable region, wherein:

(a) the heavy chain variable region comprises an amino acid sequence selected from the group consisting of SEQ ID NOs: 137, 138, 139, 140, 141, 142, 143, 144, 145,146, 147, 148,149 and 150;

(b) the light chain variable region comprises an amino acid sequence of SEQ ID NO.: 151 and 152.

Preferred combinations of CDRs:

A preferred combination of CDRs of anti -PD- 1 antibody or antigen-binding portion thereof according to the present invention comprises:

(a) a heavy chain variable region CDRH1 comprising SEQ ID NO: 4;

(b) a heavy chain variable region CDRH2 comprising SEQ ID NO: 8; (c) a heavy chain variable region CDRH3 comprising SEQ ID NO: 32;

(d) a light chain variable region CDRL1 comprising SEQ ID NO: 77;

(e) a light chain variable region CDRL2 comprising SEQ ID NO: 108; and

(f) a light chain variable region CDRL3 comprising SEQ ID NO: 132

Another preferred combination of CDRs of anti -PD- 1 antibody or antigen-binding portion thereof according to the present invention comprises:

(a) a heavy chain variable region CDRH1 comprising SEQ ID NO: 4;

(b) a heavy chain variable region CDRH2 comprising SEQ ID NO: 9;

(c) a heavy chain variable region CDRH3 comprising SEQ ID NO: 32;

(d) a light chain variable region CDRL1 comprising SEQ ID NO: 77;

(e) a light chain variable region CDRL2 comprising SEQ ID NO: 108; and

(f) a light chain variable region CDRL3 comprising SEQ ID NO: 132

Another preferred combination of CDRs of anti -PD- 1 antibody or antigen-binding portion thereof according to the present invention comprises:

(a) a heavy chain variable region CDRH1 comprising SEQ ID NO: 4;

(b) a heavy chain variable region CDRH2 comprising SEQ ID NO: 26;

(c) a heavy chain variable region CDRH3 comprising SEQ ID NO: 32;

(d) a light chain variable region CDRL1 comprising SEQ ID NO: 77;

(e) a light chain variable region CDRL2 comprising SEQ ID NO: 108; and

(f) a light chain variable region CDRL3 comprising SEQ ID NO: 132

More preferred combination of CDRs of anti -PD- 1 antibody or antigen-binding portion thereof according to the present invention comprises: (a) a heavy chain variable region CDRH1 comprising SEQ ID NO: 4;

(b) a heavy chain variable region CDRH2 comprising SEQ ID NO:8;

(c) a heavy chain variable region CDRH3 comprising SEQ ID NO: 33;

(d) a light chain variable region CDRL1 comprising SEQ ID NO: 77;

(e) a light chain variable region CDRL2 comprising SEQ ID NO: 108; and

(f) a light chain variable region CDRL3 comprising SEQ ID NO: 132

More preferred combination of CDRs of anti -PD- 1 antibody or antigen-binding portion thereof according to the present invention comprises:

(a) a heavy chain variable region CDRH1 comprising SEQ ID NO: 4;

(b) a heavy chain variable region CDRH2 comprising SEQ ID NO:8;

(c) a heavy chain variable region CDRH3 comprising SEQ ID NO: 47;

(d) a light chain variable region CDRL1 comprising SEQ ID NO: 77;

(e) a light chain variable region CDRL2 comprising SEQ ID NO: 108; and

(f) a light chain variable region CDRL3 comprising SEQ ID NO: 132

Another preferred combination of CDRs of anti -PD- 1 antibody or antigen-binding portion thereof according to the present invention comprises:

(a) a heavy chain variable region CDRH1 comprising SEQ ID NO: 4;

(b) a heavy chain variable region CDRH2 comprising SEQ ID NO: 9;

(c) a heavy chain variable region CDRH3 comprising SEQ ID NO: 33;

(d) a light chain variable region CDRL1 comprising SEQ ID NO: 77;

(e) a light chain variable region CDRL2 comprising SEQ ID NO: 108; and (f) a light chain variable region CDRL3 comprising SEQ ID NO: 132

Another preferred combination of CDRs of anti -PD- 1 antibody or antigen-binding portion thereof according to the present invention comprises:

(a) a heavy chain variable region CDRH1 comprising SEQ ID NO: 4;

(b) a heavy chain variable region CDRH2 comprising SEQ ID NO: 9;

(c) a heavy chain variable region CDRH3 comprising SEQ ID NO: 47;

(d) a light chain variable region CDRL1 comprising SEQ ID NO: 77;

(e) a light chain variable region CDRL2 comprising SEQ ID NO: 108; and

(f) a light chain variable region CDRL3 comprising SEQ ID NO: 132

Another preferred combination of CDRs of anti -PD- 1 antibody or antigen-binding portion thereof according to the present invention comprises:

(a) a heavy chain variable region CDRH1 comprising SEQ ID NO: 4;

(b) a heavy chain variable region CDRH2 comprising SEQ ID NO: 26;

(c) a heavy chain variable region CDRH3 comprising SEQ ID NO: 33;

(d) a light chain variable region CDRL1 comprising SEQ ID NO: 77;

(e) a light chain variable region CDRL2 comprising SEQ ID NO: 108; and

(f) a light chain variable region CDRL3 comprising SEQ ID NO: 132

Another preferred combination of CDRs of anti -PD- 1 antibody or antigen-binding portion thereof according to the present invention comprises:

(a) a heavy chain variable region CDRH1 comprising SEQ ID NO: 4;

(b) a heavy chain variable region CDRH2 comprising SEQ ID NO: 26;

(c) a heavy chain variable region CDRH3 comprising SEQ ID NO: 47; (d) a light chain variable region CDRL1 comprising SEQ ID NO: 77;

(e) a light chain variable region CDRL2 comprising SEQ ID NO: 108; and

(f) a light chain variable region CDRL3 comprising SEQ ID NO: 132

Another preferred combination of CDRs of anti-PD-1 antibody or antigen-binding portion thereof according to the present invention comprises: a) a heavy chain variable region CDRH1 comprising SEQ ID NO: 7;

(b) a heavy chain variable region CDRH2 comprising SEQ ID NO: 30;

(c) a heavy chain variable region CDRH3 comprising SEQ ID NO: 50;

(d) a light chain variable region CDRL1 comprising SEQ ID NO: 81;

(e) a light chain variable region CDRL2 comprising SEQ ID NO: 112; and

(f) a light chain variable region CDRL3 comprising SEQ ID NO: 136

Another preferred combination of CDRs of anti-PD-1 antibody or antigen-binding portion thereof according to the present invention comprises: a) a heavy chain variable region CDRH1 comprising SEQ ID NO: 7;

(b) a heavy chain variable region CDRH2 comprising SEQ ID NO: 30;

(c) a heavy chain variable region CDRH3 comprising SEQ ID NO: 51;

(d) a light chain variable region CDRL1 comprising SEQ ID NO: 81;

(e) a light chain variable region CDRL2 comprising SEQ ID NO: 112; and

(f) a light chain variable region CDRL3 comprising SEQ ID NO: 136

Another preferred combination of CDRs of anti-PD-1 antibody or antigen-binding portion thereof according to the present invention comprises: a) a heavy chain variable region CDRH1 comprising SEQ ID NO: 7; (b) a heavy chain variable region CDRH2 comprising SEQ ID NO: 30;

(c) a heavy chain variable region CDRH3 comprising SEQ ID NO: 52;

(d) a light chain variable region CDRL1 comprising SEQ ID NO: 81;

(e) a light chain variable region CDRL2 comprising SEQ ID NO: 112; and

(f) a light chain variable region CDRL3 comprising SEQ ID NO: 136

Another preferred combination of CDRs of anti-PD-1 antibody or antigen-binding portion thereof according to the present invention comprises: a) a heavy chain variable region CDRH1 comprising SEQ ID NO: 7;

(b) a heavy chain variable region CDRH2 comprising SEQ ID NO: 30;

(c) a heavy chain variable region CDRH3 comprising SEQ ID NO: 54;

(d) a light chain variable region CDRL1 comprising SEQ ID NO: 81;

(e) a light chain variable region CDRL2 comprising SEQ ID NO: 112; and

(f) a light chain variable region CDRL3 comprising SEQ ID NO: 136

Another preferred combination of CDRs of anti-PD-1 antibody or antigen-binding portion thereof according to the present invention comprises: a) a heavy chain variable region CDRH1 comprising SEQ ID NO: 7;

(b) a heavy chain variable region CDRH2 comprising SEQ ID NO: 30;

(c) a heavy chain variable region CDRH3 comprising SEQ ID NO: 55;

(d) a light chain variable region CDRL1 comprising SEQ ID NO: 81;

(e) a light chain variable region CDRL2 comprising SEQ ID NO: 112; and

(f) a light chain variable region CDRL3 comprising SEQ ID NO: 136 Preferred combinations of variable regions:

A preferred combination of HCVR and LCVR of anti -PD- 1 antibody or antigen-binding portion thereof according to the present invention comprises:

(a) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 137; and

(b) a light chain variable region comprising the amino acid sequence of SEQ ID NO: 151

A preferred combination of HCVR and LCVR of anti -PD- 1 antibody or antigen-binding portion thereof according to the present invention comprises:

(a) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 138; and

(b) a light chain variable region comprising the amino acid sequence of SEQ ID NO: 151

A preferred combination of HCVR and LCVR of anti -PD- 1 antibody or antigen-binding portion thereof according to the present invention comprises:

(a) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 139; and

(b) a light chain variable region comprising the amino acid sequence of SEQ ID NO: 151

A preferred combination of HCVR and LCVR of anti -PD- 1 antibody or antigen-binding portion thereof according to the present invention comprises:

(a) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 140; and

(b) a light chain variable region comprising the amino acid sequence of SEQ ID NO: 151

Another preferred combination of HCVR and LCVR of anti -PD- 1 antibody or antigen- binding portion thereof according to the present invention comprises: (a) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 141; and

(b) a light chain variable region comprising the amino acid sequence of SEQ ID NO: 151

Another preferred combination of HCVR and LCVR of anti -PD- 1 antibody or antigen- binding portion thereof according to the present invention comprises:

(a) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 142; and

(b) a light chain variable region comprising the amino acid sequence of SEQ ID NO: 151

Another preferred combination of HCVR and LCVR of anti -PD- 1 antibody or antigen- binding portion thereof according to the present invention comprises:

(a) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 143; and

(b) a light chain variable region comprising the amino acid sequence of SEQ ID NO: 151

Another preferred combination of HCVR and LCVR of anti -PD- 1 antibody or antigen- binding portion thereof according to the present invention comprises:

(a) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 144; and

(b) a light chain variable region comprising the amino acid sequence of SEQ ID NO: 151

Another preferred combination of HCVR and LCVR of anti -PD- 1 antibody or antigen- binding portion thereof according to the present invention comprises:

(a) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 145; and

(b) a light chain variable region comprising the amino acid sequence of SEQ ID NO: 151 Another preferred combination of HCVR and LCVR of anti -PD- 1 antibody or antigen- binding portion thereof according to the present invention comprises:

(a) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 146; and

(b) a light chain variable region comprising the amino acid sequence of SEQ ID NO: 152

Another preferred combination of HCVR and LCVR of anti -PD- 1 antibody or antigen- binding portion thereof according to the present invention comprises:

(a) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 147; and

(b) a light chain variable region comprising the amino acid sequence of SEQ ID NO: 152

Another preferred combination of HCVR and LCVR of anti-PD-1 antibody or antigen- binding portion thereof according to the present invention comprises:

(a) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 148; and

(b) a light chain variable region comprising the amino acid sequence of SEQ ID NO: 152

Another preferred combination of HCVR and LCVR of anti-PD-1 antibody or antigen- binding portion thereof according to the present invention comprises:

(a) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 149; and

(b) a light chain variable region comprising the amino acid sequence of SEQ ID NO: 152

Another preferred combination of HCVR and LCVR of anti-PD-1 antibody or antigen- binding portion thereof according to the present invention comprises:

(a) a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 150; and (b) a light chain variable region comprising the amino acid sequence of SEQ ID NO: 152

In one of the embodiments, the antibody or antigen binding portion thereof of the present invention comprising at least one of the following characteristics:

(a) cross-reacts with PD-1 from species other than human;

(b) higher binding specificity towards human PD-1;

(c) promotes IL-2 cytokine secretion;

(d) promotes higher IFN-gamma secretion;

(e) blocks PD-1 receptor interaction with its natural ligand PD-L1 and/or PD-L2;

(f) promotes T cell proliferation and

(g) has improved circulating half-life.

In one of the embodiments, the anti-PD-1 antibody or antigen binding portion thereof has a K _D of 10 ^'10 M or less, more preferably 10 ^'11 M or less for a PD-1 antigen. In a preferred embodiment, the anti-PD-1 antibody or antigen binding portion thereof of the present invention binds to human PD-1 with a K _D of 10 ^'10 M or less, preferably 10 ^'u M or less. K _D value is a measurement of the binding affinity of the antibody towards its target antigen. Such binding affinity and binding kinetics of anti-PD-1 antibodies can be examined by SPR analysis. The said analysis is very well known in the art to measure affinity of the antibody or antigen binding portion thereof towards its target antigen and a skilled person is well aware of the techniques for performing such analysis.

In one of the embodiments, the anti-PD-1 antibody or antigen binding portion thereof of the present invention has high specificity towards PD-1. The anti-PD-1 antibody according to the present invention has high affinity towards human PD-1 antigen/epitope. In another embodiment, the anti-PD-1 antibody or antigen binding portion thereof of the present invention has high binding specificity towards human PD-1. Binding specificity is examined by SPR method. The“high specificity towards PD-1 or towards human PD-1” means the antibody or antigen binding portion thereof does not bind to the other T cell co-inhibitory receptors with the same affinity.

In one of the embodiments, the anti-PD-1 antibody or antigen binding portion thereof cross- reacts with PD-1 from other species such as cynomolgus monkey, etc. with enough affinity. In another embodiment, the anti-PD-1 antibody or antigen binding portion thereof of the present invention blocks interaction of PD-1 with its ligand in surface plasmon resonance assay.

In another embodiment, the anti-PD-1 antibody or antigen binding portion thereof of the present invention kills the T cells that are expressing PD-1.

In one embodiment, the anti-PD-1 antibody or antigen binding portion thereof according to the present invention promotes IL-2 cytokine secretion. In such embodiment, the anti-PD-1 antibody or antigen binding portion thereof according to the present invention when available during MLR, results in an increased production of IL-2 as measured by ELISA.

In one embodiment, the anti-PD-1 antibody or antigen binding portion thereof according to the present invention promotes higher IFN-gamma secretion. The term“higher” refers herein is with reference to known anti-PD-1 antibody. In another embodiment, the anti-PD-1 antibody or antigen binding portion thereof of the present invention when available during MLR, results in an increased production of IFN-gamma as measured by ELISA. Bone marrow transplant experiments using IFN-yR-/- mice implicated IFN-g as a crucial nexus for controlling PD-1 -mediated tumor infiltration by T cells. It is also evaluated and confirmed that other PN-g inducible chemokines may also play a role in the synergistic effect of anti- PD-1 on ACT. (7) In addition, IFN-g is reported as an important marker for prediction of response to immune checkpoint blockade (8).

In one embodiment, the anti-PD-1 antibody or antigen binding portion thereof according to the present invention promotes T cell proliferation. In such embodiment, the anti-PD-1 antibody or antigen binding portion thereof according to the present invention when available during MLR, results in an increased T cell proliferation as measured by proliferation measurement assay. Such assays are known to the person skilled in the art.

In one of the embodiments, the anti-PD-1 antibody or antigen binding portion thereof according to the present invention has improved pharmacokinetic properties.

In one of the embodiments, the anti-PD-1 antibody or antigen binding portion thereof according to the present invention has an increased half-life in humans. The pharmacokinetic profile of anti-PDl of the present invention is determined in the cynomolgus monkey. Since the intended route of administration in patients is intravenous, anti-PDl antibody is administered intravenously to the animals in the studies in a buffer solution. In brief, the study includes 3 animals/sex/group which are administered at dose levels up to 50 mg/Kg. PD effects of the anti-PDl antibody such as peripheral immune cell population modulation, and change in absolute lymphocyte count (ALC) are studied.

In one embodiment, the anti-PD-1 antibody or antigen binding portion thereof according to the present invention blocks PD-1 receptor interaction with its natural ligands PD-L1 and/or PD-L2. The anti-PD-1 antibodies of the present invention are tested for their ability to block binding of the ligands PD-L1 and PD-L2 to PD-1 expressed on cells by using a mixed lymphocyte reaction (MLR). The anti-PD-1 antibodies of the present invention are tested for their ability to block binding of the ligands PD-L1 and PD-L2 to PD-1 by SPR.

In one of the embodiments, effect of binding of anti -PD- 1 antibody or antigen binding portion thereof of the present invention to PD-1 on T cell activation is analysed by suitable assays known in the art. An anti-PD-1 antibody or antigen binding portion thereof according to the present invention binds to PD-1 expressed on PD-1 expressing transfected cell line. Further, anti-PD-1 antibodies or antigen binding portion thereof according to the present invention binds to peripheral blood mononuclear cells (PBMC).

The antibodies according to the present invention can be full-length (for example, an IgGl or lgG4 antibody) or may comprise only an antigen- binding portion (for example, a Fab, F(ab')2 or scFv fragment), and optionally be modified to effect functionality, e.g., to eliminate residual effector functions such as ADCC and CDC activity.

In one of the embodiments, the amino acid sequences of constant region of anti-PD-1 antibody is the IgGl, IgG2, IgG3, IgG4, IgA, IgE, IgM, IgD constant region or hybrid of mentioned constant regions such as IgG2/IgG4, preferably IgGl or IgG4, more preferably IgG4.

In another embodiment, the Fc region of the antibodies of the present invention is altered by replacing at least one amino acid residue with a different amino acid residue to alter the effector function(s) of the antibody.

In one of the preferred embodiments, the amino acid sequences of the heavy chain constant region of the anti-PD-1 antibody of the present invention has mutation in its hinge region, preferably a serine to proline mutation in the hinge region of IgG4 constant region of the antibody. Human IgG4 antibodies can exist in two forms that are associated with hinge heterogeneity. In one form, an antibody comprises a stable four-chain construct of approximately 150-160 kDa in which the dimers are held together by an inter chain heavy chain disulfide bond. In a second form, the dimers are not linked via inter chain disulfide bonds and a molecule of about 75- 80 kDa is formed composed of a covalently coupled light and heavy chain (half-antibody). The latter forms have been extremely difficult to separate from the full antibody, even after affinity purification. The frequency of appearance of the second form in various intact IgG4 isotypes is due to, but not limited to, structural differences associated with the hinge region isotype of the antibody. A single amino acid substitution in the hinge region of the human lgG4 hinge can significantly reduce the appearance of the second form (6) to levels typically observed using a human IgGl hinge. Full-length antibodies comprising CDRs or variable regions of the present invention further comprise said single amino acid substitution (i.e., S228P) when it is developed in IgG4 form.

In one embodiment, the anti -PD- 1 antibody of the present invention has ADCC and /or CDC activity. In a preferred embodiment, the anti-PD-1 antibody of the present invention with modified or reduced or no ADCC and/or CDC activity is an anti-PD-1 antibody with IgGl or IgG4 or IgG2 / IgG4 constant region. In another embodiment, the Fc region of the antibodies of the present invention is altered by replacing at least one amino acid residue with a different amino acid residue to increase ADCC and/or CDC activity. In one of the preferred embodiment, the anti-PD-1 antibody of the present invention with increased ADCC and/or CDC activity is an anti-PD-1 antibody with IgGl or IgGl with at least one altered amino acid residue constant region. IgGl with at least one altered amino acid residue constant region as referred herein is a modified IgGl which may provide higher ADCC and/or CDC activity as compared to IgGl without such modification.

In another preferred embodiment, the anti -PD- 1 antibody of the present invention with reduced or no ADCC and/or CDC activity is an anti -PD- 1 antibody with IgGl or IgGl with at least one altered amino acid residue constant region. IgGl with at least one altered amino acid residue constant region as referred herein is a modified IgGl which may provide reduced or no ADCC and/or CDC activity as compared to IgGl without such modification.

In another preferred embodiment, the anti-PD-1 antibody of the present invention with reduced or no ADCC and/or CDC activity is an anti-PD-1 antibody with IgG4 or IgG4 with at least one altered amino acid residue constant region. IgG4 with at least one altered amino acid residue constant region as referred herein is a modified IgG4 which may provide reduced or no ADCC and/or CDC activity as compared to IgG4 without such modification.

In another aspect, anti- PD-1 antibody according to the present invention has increased FcRn binding and increased half -life with modified or reduced or no ADCC and/or CDC activity. In one of the embodiments, the anti-PD-1 antibody according to the present invention has amino acid sequences of constant region of IgGl or IgG4 with P329G and/or M428L & N434S mutation. The constant region of anti-PD-1 antibody with mentioned all three mutations in IgGl and IgG4 constant region are referred herein as IgGl(GLS) and IgG4(GLS), respectively.

In a preferred embodiment, the anti- PD-1 antibody according to the present invention comprising single amino acid substitution selected from S228P, P329G, M428L, N434S and suitable combination thereof.

In one of the embodiments, the anti-PD-1 antibody according to the present invention is monoclonal antibody or bispecific antibody or polyclonal antibody, preferably monoclonal antibody.

In one of the embodiments, the antibody or antigen-binding portion thereof targeting PD-1 antigen according to the present invention is murine, chimeric, recombinant or humanized in nature, preferably recombinant in nature.

Immunoconjugates and Bi specific antibodies

In one of the embodiments, the anti -PD-1 antibody of the present invention is conjugated to drug, preferably cytotoxic agent optionally through linker. The present invention also provides an immunoconjugate comprising an antibody of the invention, or antigen-binding portion thereof, linked to another therapeutic agent, such as a cytotoxin or a radioactive isotope. Such immunoconjugates prepared according to the present invention specifically bind to PD1 expressing immune cells leading to their lysis. These immune cells can include T cells, NK cells, B cells, monocytes and the like expressing PD-1. Thus, the immunoconjugates prepared according to the current invention help to treat disease where an activity of PD-1 expressing immune cells is detrimental. In one of the embodiments, the anti -PD- 1 antibody of the present invention is used to make a bispecific molecule. A bispecific molecule comprising an antibody, or antigen binding portion thereof, of the present invention, having two unique antigen-binding arms or functional moieties such that one binds PD-1 and the other with a different binding specificity. In one of the embodiments, the second functional moiety according to the present invention can bind to antigen selected from CTLA-4, PD-L1, LAG-3, TIGIT and HER2.

Nucleic acid molecules encoding anti -PD-1 antibodies, vectors and host cells

The present invention provides nucleic acid molecules or nucleic acid sequences encoding the antibodies, or antigen-binding portions thereof of the present invention as well as expression vectors comprising such nucleic acid sequences and host cells comprising such expression vectors. In the present application, pZRCH as well as pZRCIII vectors are used for the cloning and expression of anti -PD-1 antibodies of the present invention. pZRCH vector (pZRCIIhyg) and pZRCin vector are described in patent documents WO 2007/017903 and WO 2012/046255 A2, respectively. The host cell according to the present invention is prokaryotic or eukaryotic cell, preferably the host cell is an E. coli cell or a mammalian cell, such as a CHO cell orNSO cell or CHO-GS cell or CHO-S cell or CHO-K1 cell.

Preparation of antibodies

In the present invention, the anti -PD-1 antibody or antigen binding portion thereof is produced using recombinant techniques. In recombinant technique according to the present invention, suitable expression vectors are used. Vector to prepare antibodies of the present invention can be a vector which is readily known to the person skilled in the art. The expression vector and expression control sequences are chosen to be compatible with the expression host cell used. The antibody light chain gene and the antibody heavy chain gene can be inserted into separate vector or, more typically, both genes are inserted into the same expression vector. The antibody genes are inserted into the expression vector by standard methods (e.g., ligation of complementary restriction sites on the antibody gene fragment and vector, or blunt end ligation if no restriction sites are present) known to persons skilled in the art. For example, to express the antibodies, or antibody fragments thereof, DNAs encoding partial or full-length light and heavy chains, can be obtained by standard molecular biology techniques (e.g., PCR amplification or cDNA cloning using a hybridoma that expresses the antibody of interest) and the DNAs can be inserted into expression vectors such that the genes are operatively linked to transcriptional and translational control sequences. In addition to the antibody chain genes and regulatory sequences, the recombinant expression vectors of the invention may carry additional sequences, such as sequences that regulate replication of the vector in host cells (e.g., origins of replication) and selectable marker genes. The heavy chain variable regions of the antibodies described herein can be used to create full-length antibody genes of any antibody isotype by inserting them into expression vectors already encoding heavy chain constant and full-length light chain of the desired isotype such that the V _H segment is operatively linked to the C _H segments) within the vector. Additionally or alternatively, the recombinant expression vector can encode a signal peptide that facilitates secretion of the antibody chain from a host cell. For expression of the light and heavy chains, the expression vector(s) encoding the heavy and light chains is transfected into a host cell by standard techniques such as lipid mediated transfection, electroporation, calcium-phosphate precipitation, DEAE-dextran transfection and the like. Preferred mammalian host cells for expressing the recombinant antibodies of the invention include Chinese Hamster Ovary (CHO cells) (including DHFR- CHO cells), NSO myeloma cells, COS cells and SP2 cells. In particular, for use with NSO myeloma cells, another preferred expression system is the GS gene expression system. Antibodies produced according to the present invention can be further produced by known cell culture techniques for large scale antibody production. Antibodies can be recovered from the culture medium using standard protein purification methods. When using recombinant techniques, the antibody can be produced intracellularly, in the periplasmic space, or directly secreted into the medium. If the antibody is produced intracellularly, as a first step, the particulate debris, either host cells or lysed fragments, is removed, for example, by centrifugation or ultrafiltration. Antibodies of the invention can be tested for binding to PD-1 by, for example, standard ELISA.

Anti-PD-1 antibodies of the present invention is also prepared using phage display library approach after making Fab libraries using site directed mutagenesis approach as described herein examples. In this method, anti-PD-1 Fab regions are generated using phage library approach which are further converted into full-length using expression vector based recombinant techniques as described in this application.

Combination of anti-PD-1 of the present invention with other drugs The present invention provides a combination comprising at least two or more antibodies or antigen binding portion thereof wherein at least one antibody or antigen binding portion thereof is anti-PD-1 antibody of the present invention. The combination according to the present invention may comprise second antibody or antigen binding portion thereof selected from anti-LAG3 antibody, anti-CTLA4 antibody, anti-HER2 antibody, anti-VEGF antibody, anti-PDLl antibody, anti-PD-1 antibody, in combination with anti-PD-1 antibody or antigen binding portion thereof the present invention. In another embodiment, the present invention provides a combination comprising of anti-PD-1 antibody or antigen binding portion(s) thereof and a peptide or a combination comprising anti-PD-1 antibody or antigen binding portion(s) thereof and a cytokine (preferably interleukin).

Pharmaceutical compositions

A pharmaceutical composition, containing one or a combination of monoclonal antibodies or antigen-binding portion(s) thereof or a combination of anti-PD-1 antibody or antigen binding portion(s) thereof and a peptide or a combination of anti-PD-1 antibody or antigen binding portion(s) thereof and a cytokine (preferably interleukin), of the present invention, formulated together with a pharmaceutically acceptable carrier can be developed. Present invention also provides a composition, e.g., a pharmaceutical composition, containing one or a combination of monoclonal antibodies, or antigen-binding portion(s) thereof, or a combination of anti-PD- 1 antibody or antigen binding portion(s) thereof and a peptide or a combination of anti-PD-1 antibody or antigen binding portion(s) thereof and a cytokine (preferably interleukin), of the present invention, formulated together with a pharmaceutically acceptable carrier. Such compositions may include one or a combination of (e.g., two or more different) antibodies, or immunoconjugates or bispecific molecules of the invention. For example, a pharmaceutical composition of the invention can comprise a combination of antibodies (or immunoconjugates or bispecifics) that bind to different epitopes on the target antigen or to different epitopes on different target antigens or that have complementary activities.

In one of the embodiments, the anti-PD-1 antibody or antigen binding portion thereof can be combined with other suitable drug for the treatment of various cancers, infections or autoimmune disorders.

The anti-PD-1 antibody or antigen binding portion thereof of the present invention can be combined or can be used in combination with other suitable chemically synthesised therapeutic drug(s). The said chemically synthesised therapeutic drug can be anti -cancer or anti-infective drugs or combination of such drugs.

The anti-PD-1 antibody or antigen binding portion thereof of the present invention can be combined with chemotherapeutic agent(s) in clinical setting.

The anti -PD- 1 antibody or antigen binding portion thereof of the present invention can be used in combination with vaccine(s) to induce T and B cell immune responses, possibly by prolonging vaccine-induced T- or B-cell proliferation, in both prophylactic and therapeutic settings.

Therapeutic Uses

In one of the embodiments, the anti-PD-1 antibody or antigen binding portion thereof or combination or conjugate or bispecific antibody of the present invention can be used for the treatment of disease where activity of PD-1 or an expression of PD-1 is detrimental. Such diseases are readily known to the person skilled in the art.

The anti-PD-1 antibody or antigen-binding portion thereof or combination or conjugate or bispecific antibody of the present invention can be used to treat various cancers such as NSCLC, SCLC, RCC, cHL, SCCHN, breast cancer, urothelial carcinoma, colorectal cancer, ESCC, primary mediastinal large b-cell lymphoma, microsatellite instability-high cancer, gastric cancer, ovarian cancer, prostate cancer, gliomas, glioblastoma, astrocytomas, glioblastoma multiforme, Bannayan-Zonana syndrome, Cowden disease, Lhermitte-Duclos disease, inflammatory breast cancer, Wilm's tumor, Ewing's sarcoma, Rhabdomyosarcoma, ependymoma, medulloblastoma, kidney cancer, liver cancer, melanoma, pancreatic cancer, sarcoma, osteosarcoma, giant cell tumor of bone, thyroid cancer, lymphoblastic T cell leukemia, Chronic myelogenous leukemia, Chronic lymphocytic leukemia, Hairy -cell leukemia, acute lymphoblastic leukemia, acute myelogenous leukemia, AML, Chronic neutrophilic leukemia, Acute lymphoblastic T cell leukemia, plasmacytoma, Immunoblastic large cell leukemia, Mantle cell leukemia, Multiple myeloma Megakaryoblastic leukemia, multiple myeloma, acute megakaryocyte leukemia, promyelocytic leukemia, Erythroleukemia, malignant lymphoma, hodgkins lymphoma, non-hodgkins lymphoma, lymphoblastic T cell lymphoma, Burkitt's lymphoma, follicular lymphoma, neuroblastoma, cervical cancer, merkel cell carcinoma, endometrial carcinoma, tumor mutational burden-high (TMB-H) cancer, vulval cancer, salivary gland cancer, nasopharangeal cancer, buccal cancer, cancer of the mouth, GIST (gastrointestinal stromal tumor), and testicular cancer.

The anti -PD- 1 antibody or antigen-binding portion thereof or combination or conjugate or bispecific antibody of the present invention can be used to treat various infections. Examples of such infection can be infections are the infection caused by pathogens selected from HIV, Hepatitis (A, B, & C), Influenza, Herpes, Giardia, Malaria, Leishmania, Staphylococcus aureus, Pseudomonas aeruginosa, SARS-CoV, MERS-CoV, SARS-CoV-2, Ebola, etc.

The anti -PD- 1 antibody or antigen-binding portion thereof or combination or conjugate or bispecific antibody of the present invention can be used to treat various autoimmune disorders. Examples of such autoimmune disorder are rheumatoid arthritis, psoriasis, psoriatic arthritis, ankylosing spondylitis, juvenile rheumatoid arthritis, Crohn’s disease, ulceritive colitis, sepsis, atopic disease such as asthma, eczema, allergies, multiple sclerosis, systemic lupus erythematosus, vasculitis, myasthenia gravis, Graves disease, Hashimoto’s thyroiditis, sepsis, Autoimmune hemolytic anemia, Pernicious anemia, Idiopathic thrombocytopenic purpura, Goodpasture's syndrome, Bullous pemphigoid, Pemphigous vulgaris, Hashimoto's thyroiditis, Insulin- dependent diabetes mellitus (1DDM), CIDP Diabetes, Antianemics (Beta-Thalassemia), Hematopoietic Agents, Ophthalmic Drugs, Bone Diseases, Neurological Genetic Disorders, Age-related macular degeneration, Diabetic Retinopathy, Macular diseases, Ocular Genetic Disorders, Hemophilia B, Agents for (Coagulation factor IX (9) deficiency) Cardiovascular Diseases, Type 2 Diabetes, Immunosuppressants, Treatment of Transplant Rejection, Myelodysplastic Syndrome Therapy, Retinopathy, Aplastic anemia, Analgesic Drugs, , Hematologic Genetic Disorders, Multisystem Genetic Disorders, Osteoarthritis, Scleroderma, Treatment of Autoimmune Diseases, Treatment of Gout, Urticaria, Heart Failure Therapy, Lymphoma Therapy, Nephritis, Respiratory Disorders and Therapy of Inborn Errors of Metabolism.

In a preferred embodiment, the present invention provides effective amount of an anti-PD-1 antibody or antigen binding portion(s) thereof as disclosed in the current invention which can reduce PD-1 mediated-immunosuppression . These antibodies can be administered in conventional routes and dosages such as“pharmaceutically effective dose” or“therapeutically effective dose”.

Examples

The following examples are illustrative and should not be construed as limiting the scope of this disclosure in any way as many variations and equivalents will become apparent to those skilled in the art upon reading the present disclosure. All patents, patent applications and publications cited herein are incorporated herein by reference in their entireties.

Example 1: Generation of pZRCII hyg Anti-PD-1 light and heavy chain vectors

Construction of pZRCII hygIgG4 vector

Chemically synthesized Human IgG4 constant region (SEQ ID No.: 156) was amplified to incorporate restriction enzymes Sail, Apal overhangs at 5’ and Noil overhangs at 3’ termini by 30 cycles of PCR using 0.2 pM of specific oligonucleotide primers containing the above restriction sites in a volume of 50 mΐ containing lx Pfx buffer, 1.5 mM MgSC>4, 2.5 mM each of the 4 dNTPs and 1 unit of Pfx Polymerase. Each PCR amplification cycle consisted of incubations at 95 °C for 30 seconds (denaturation), 55 °C for 45 seconds (annealing) and 72 °C for 1 minute (extension). Amplified product of the PCR reaction was resolved on a 1% Agarose gel. The desired fragment of approximately 980 base pairs in size was excised out from the gel and purified using Qiagen Gel extraction kit. This purified PCR fragment and pZRCII vector with hygromycin resistance gene, were digested with restriction enzymes Sail and Noil. pZRCII vector was prepared as described in patent publication WO 2007/017903. The vector fragment of approximately 7692 base pair was purified from the gel by using Qiagen Gel extraction kit. The digested PCR fragment was also purified using Qiagen gel extraction kit. Digested and purified PCR product and pZRCII hyg vector were ligated and ligation product was transformed in E. coli Top 10F' strain. Transformants were scored on the basis of kanamycin resistance. Plasmid DNA isolated from such colonies was analyzed for the presence of IgG4 constant region fragment by restriction digestion using Sail and Noil restriction enzyme. One of the plasmids showing the expected restriction profile having the IgG4 constant region fragment integrated in the pZRCII vector was named, pZRC P IgG4 constant. In the same manner, chemically synthesized IgGl Fc (SEQ ID No.: 157) was cloned in pZRCII vector and named as pZRCIIhyg. IgGl vector.

Construction of pZRCIIhyg Anti -PD- 1 LC- HC vector constructs

Anti- PD1 light chain and heavy chain genes were chemically synthesized and cloned into a cloning vector pMA (Geneart, Germany). To clone light chain gene in the pZRCIIhyg.IgG4 constant region vector, pMA with light chain and pZRCIIhyg. IgG4 vectors were digested with Xhol and kpnl restriction enzymes. The light chain of approximately 737 bp (SEQ ID No.: 163) and pZRCIIhyg. IgG4 vector of approximately 8672 base pairs in size was excised from the gel and purified using Qiagen Gel extraction kit. The digested and purified light chain and pZRCIIhyg.IgG4 vector were ligated and transformed in E. coli Top 10F' strain. Transformants were selected on the basis of kanamycin resistance. Plasmid DNA isolated from about 20 such colonies was analyzed for the presence of light chain gene by restriction digestion using various restriction enzymes. One such plasmid, having the light chain gene integrated in the first transcription assembly of pZRCIIhyg.IgG4 vector was selected to prepare pZRCIIhyg. LC- HC vectors. To clone heavy chain genes, chemically synthesized heavy chain gene variable fragments (SEQ ID No.:158, 159, 160, 161 and 162), all of approximately 446 base pairs in size and pZRCII hyg. LC- IgG4 vector having light chain of SEQ ID NO.: 163 were digested with SalI and ApaI. The digested and purified, heavy chain gene variable region fragments (SEQ ID No.: 158, 159, 160, 161 and 162) were individually ligated into pZRCIIhyg Anti-PD-1 LC IgG4 vector and transformed in E. coli Top 10F'. Transformants were selected on the basis of kanamycin resistance. Plasmid DNA isolated from the transformants was analyzed for the presence of heavy chain gene by restriction digestion using Sail and Noil. Final vectors containing light chain of SEQ ID No.: 163 and heavy chain of SEQ ID No.: 158, light chain of SEQ ID No.: 163 and heavy chain of SEQ ID No.: 159, light chain of SEQ ID No.: 163 and heavy chain of SEQ ID No.: 160, light chain of SEQ ID No.: 163 and heavy chain of SEQ ID No.: 161, light chain of SEQ ID No.: 163 and heavy chain of SEQ ID No.: 162 were confirmed by nucleotide sequencing of heavy and light chains. The final constructs comprising different combinations of heavy chain and light chain were named as IP-H4L1, IP-H4.2L1, IP-H4.2(Y.H)L1, IP-H4.19L1, and IP-H4.36L1, respectively. The said different constructs encode amino acid sequences of HCVR and LCVR of anti-PD-1 antibodies of the present invention as described in table 5.

Table 5: List of anti-PD-1 antibody constructs with their respective SEQ ID NO.s of HCVR and LCVR

A general vector map of the said construct is represented in figure 1. IP-H4L1 is also generated with IgGl isotype as illustrated herein using chemically synthesized Human IgGl constant region (SEQ ID No. : 157).

Amino acid sequences of variable regions of heavy chains and light chain are provided in table 2 and constant region of IgGl, IgG4 and light chain are given at end of the present specification. In the same manner, nucleotide sequences of variable regions of heavy chains, constant region of IgGl and IgG4 and light chain are also given at end of the present specification.

Example 2: Generation of Anti-PD-1 mAbs synthesized using pZRCII vector

To generate material for proof of concept studies, different Anti-PD-1 antibodies constructs as prepared in Example 1 (IP-H4L1, IP-H4.2L1, IP-H4.2(Y.H)L1, IP-H4.19L1, and IP-H4.36L1) were expressed using ExpiCHO™ expression system (Gibco). On the day prior to transfection, ExpiCHO-S™ cells were seeded to a final density of 3 ^c 10 ⁶ viable cells/mL in a shake flask/ culti-tube and allowed to grow overnight. On the next day, the cells were counted and adjusted to a final density of 6 x 10 ⁶ viable cells/mL with fresh ExpiCHO™ Expression Medium, pre- warmed to 37 °C. ExpiFectamine™ CHO transfection reagent and plasmid DNA complexes were prepared. The solution was slowly added to the cell suspension with gentle mixing. Cells were incubated in a 37 °C incubator with a humidified atmosphere and 5% CO2 in an orbital shaker. Temperature was shifted to 32 °C on Day 1. ExpiFectamine™ CHO Enhancer and feed were added on Day 1 followed by a second feeding on Day 5 post- transfection. Cultures were harvested (on Day 8-12) and one step purification was carried out using agarose-Protein A matrix (MAbselect SuRe antibody purification resin, GE). The bound antibody was eluted using Glycine Buffer, pH 2.5 and neutralized to pH 7 with Tris Buffer pH 9. The protein concentration of the purified antibody was determined by Protein A HPLC method.

Example 3: Phage display Fab library preparation

(a) Fab plasmid generation

For library generation, E. coli optimized Fab region with overhangs of EcoRI and BamHI was chemically synthesized and cloned in pMA / pMK vectors obtained from Geneart, Germany. Fab gene (SEQ ID No. 164) was isolated from pMA vector construct after digestion with EcoRI and BamHI. An amino sequence of cloned Fab gene is provided herein as SEQ ID NOs. : 165 for VH and 166 for VL.

The pSEX8l (Cat No: PR3005, Progen) phagemid vector was modified in which pIII gene of phagemid vector was truncated and digested with EcoRI and BamHI and the linearized vector was ligated with the digested Fab gene. The resultant modified vector is referred herein as pSEX83. Vector map of pSEX83 is given herein as Figure 2. The digested Fab and pSEX83 vector fragments were analyzed on agarose gel and purified from the gel using QIAquick gel extraction kit (Qiagen cat no 28706). The ligation products of both Fab (insert) and pSEX83 (vector) were transformed in electro-competent E. coli TGI cells (Cat No: 60502-1, Lucigen). Transformed cells were plated on 2xYT agar plates containing ampicillin (100 mg / mL). The clones were analysed by EcoRI and BamHI restriction digestion and DNA sequencing using Sanger’s method.

(b) Preparation of libraries

Two steps were followed to prepare Fab phage display library.

Step 1 : PCR Primer based site directed mutagenesis in the CDRH1

Here CDRH1 region of the Fab was targeted for making variants. The mutations in the selected regions were introduced by using PCR with respective primer pair (NI-CDRHIF and NI-CDRH1R) having Sapl restriction site (Table 6). Each primer pair was designed in such a way that they amplified a complete plasmid in a linear form which after restriction digestion by Sapl followed by ligation with T4 DNA ligase resulted in a circular plasmid with mutations introduced by the primer pair.

100 ng of the template DNA of Fab gene in pSEX83 vector was used for amplification using the primer pairs mentioned in table 6. Once the template was amplified using the randomized primers the product was digested with Sapl to obtain sticky ends. After PCR purification, the digested product was ligated overnight at 16 °C. Ligated DNA was then transformed to freshly prepared electrocompetent cells (TGI). Transformed cells were cultured for the production of phages. The phage production was done separately for each library as explained earlier (9).

Table 6: List of primers used in PCR Primer based site directed mutagenesis

Step 2: Kunkel mutagenesis and sRCA

Kunkel mutagenesis was performed with sRCA following Huovinen et al 2012. Small culture of CJ236 cells was infected with phages carrying plasmid of the CDRH1 mutated Fab gene. The infected cells were grown in 2xYT containing uridine (6 mg / ml) and carbenicillin antibiotic (100 mg / ml). Phages were produced after superinfection with VCS M13 helper phage (Agilent technologies, USA) and purified by precipitating with PEG6000 (4%) and NaCl (500 mM). Single-stranded uridyl ated DNA (ss(U)DNA), was extracted from the purified phages by using M13 purification kit from E.Z.N.A. ^® M13 DNA mini kit (OMEGA bio-tek, USA) following the manufacturer’s instructions.

This ss(U)DNA was used as a template in Kunkel mutagenesis and different primers with random mutations were used for making the library. Primers targeting different CDRs i.e., CDRH2, CDRH3 and CDRL3 of nivolumab Fab (Table 6) were hybridized separately to the ss(U)DNA template and extended by Kunkel mutagenesis method. The product was UDG- treated and selectively amplified by RCA (10). The RCA product was digested with Hind IP, circularized using T4 DNA ligase and transformed in SS320 cells. Phages (the secondary library) were produced separately for each mutagenesis primer by superinfection with helper phage as described below.

Example 4: Mutant Fab phage production and purification thereof

Flasks containing 2xYT media with carbenicillin or ampicillin (100 mL / mL) were inoculated with the cells from the glycerol stock of the above described library at the initial concentration of 0.06 ODeoo. Cultures were grown at 37 °C with shaking at 250 rpm till they reach an OD600 of up to ~ 0.4-0.6. Helper phages either, VCSM13 (Agilent, Cat no. 200251) or M13K07 (GE healthcare, Cat no. 27152401), were then added to the culture at a multiplicity of infection (MOI) of 20, and incubated first without shaking at 37 °C for 40 minutes, followed by another 40 minutes of incubation at 37 °C with shaking. Kanamycin was then added to the media and culture was grown overnight at 26 °C at 150 rpm. Overnight phage culture was centrifuged at 4000g and cell pellet was discarded. PEG (20 %) / NaCl (2.5M) solution at a ratio of 1:5 was added to the supernatant in order to precipitate the phages. Resuspended solution was incubated on ice for 20 minutes followed by centrifugation at 14,000g for 15 minutes at 4 °C. Supernatant was discarded and pellet was resuspended in 1 mL of sterile PBS with 0.01 % sodium azide. Phages were stored at 4 °C until further use.

Example 5: Biopanning of phages expressing high affinity Fab variants

The library (lx10 ¹² pfu) prepared in example 4 was screened for high affinity Fab binders to PD1 receptor. First round of panning against recombinant PD1 receptor antigen (Sino biological, Cat No, 10377-H08H) at pH 7.4, was performed using antigen-immobilized, Immunotubes (Quidel, USA) that were prepared by incubating them with a 5 pg / mL PD1 protein solution in carbonate buffer (0.1 M, pH 9.6) overnight at 4 °C. Immunotubes were washed 3 times with PBS and then incubated with phages in PBS for 2 h at 25 °C with constant rotation. The tubes were washed ten times with 4 mL PBS with tween 20 (0.1 %) and subsequently 10 times with PBS. The bound phages were eluted with glycine-HCL pH 2.1 (0.1 M). The eluted phages were rescued by infection of TGI E coli cells, plated, and phages produced as described in example 4. Second and third round of panning were performed on the PD1 antigen coated immunotubes in such a manner that output phages from first round of panning (1x10 ¹¹ CFU) and second (1x10 ¹⁰ CFU) round of panning were used, as input phages for second and third round of panning, respectively. Phages after third round of panning were infected in TGI cells as mentioned before and phagemid DNA was isolated for anti-PD-1 cloning in suitable expression vector.

Example 6: Screening of individual anti-PD-1 clones as soluble Fab proteins

Cloning into expression vector and protein production

The anti-PD-1 genes from the enriched library produced after 3 rounds of panning were cloned into the expression vector pOPE101 (carbenicillin resistant) (Progen, Germany) such that the individual anti-PD-1 clones could be produced as His-tagged fusion products. Both the vector DNA (pOPElOl) and phagemid DNA were digested with restriction enzymes (EcoRI and BamHI) to isolate vector and anti-PD-1 genes, respectively. Both restriction digested vector and anti-PD-1 gene were ligated and transformed to TGI electrocompetent cells. Transformed cells were plated on to the 2xYT agar plates containing carbenicillin antibiotic. Individual clones were picked from the 2xYT agar plates and cultured in 15 mL tube with 5 mL of 2xYT media containing carbenicillin or ampicillin (100 pL / mL) overnight at 32 °C at 200 rpm. Next day, cultures were reinoculated to fresh 2xYT medium containing carbenicillin (100 pg / mL) and glucose (0.1 %) at a volumetric ratio of 1:200. Cultures were grown until the OD600 reached 0.6-0.8. After that ImM Isopropyl b-D-l- thiogalactopyranoside (IPTG) was added to the culture and grown overnight at 30 °C at 200 rpm. Overnight culture was spun at 10,800g for 15 minutes and supernatant was removed. Cell pellet was resuspended in 1 / 20 ^th volume of the original culture in lx PBS buffer pH-7.4 containing 2mg / ml lysozyme, 0.1% triton X and 1 U / 100 mL benzonase and incubated at 37 °C for 1 h. Resuspended pellet was centrifuged at 10,800g for 15 minutes and supernatant was collected as the cell lysate containing the soluble His-tagged Fab variants. This cell lysate fraction was used in immunoassays to study Anti-PD-1 binding after quantifying the soluble Fab in the periplasmic fraction.

Determination of concentration of soluble anti-PD-1 Fabs in periplasmic fractions

Clones were cultured individually for the production of soluble Fab variants as described above. Total Fab in cell lysate or periplasmic fraction was quantified by immobilizing the soluble Fabs on maxisorp plates pre-coated with goat anti -Human IgG antibody (Fab specific) (Sigma-Aldrich, Cat no. 15260). Coating was done overnight with the goat anti-Human IgG antibody (Fab specific) (Sigma-Aldrich, Cat no. 15260) at concentrations of 1mg / mL (IOOmI / well) in coating buffer (0.1M NaHCO3, pH 9.6). After washing the plate twice, cell lysate 100 mL (1 / 20 v / v in lx PBS) was added and incubated for 1 h at 25 °C. Known concentrations of serially diluted human Fabs were used as standards for the calculation of amount of Fab protein in cell lysate. The plate was washed 3 time with PBST (0.1% Tween20 in lx PBS). 100 mΐ (1:10000) of HRP conjugated goat anti-Human IgG antibody (Fab specific) (Sigma- Aldrich, Cat no. A0293) was added to each well of the plate and incubated for lh. Plate was then washed 5 times with PBST followed by addition of substrate o-phenylenediamine dihydrochloride (OPD) (100mL / well) for 15 minutes at 37 °C. The reaction was stopped using IN H2SO4 (lOOuL / well) and optical density (OD) was measured at 450nm using TEC AN INFINITE ^® MlOOOpro. Concentration of Fab in cell lysate was then calculated using reference standards.

Qualitative analysis of anti-PD-1 Fab binders

Recombinant PD1 antigen was coated on polystyrene plate (100 ng / 100 pL / well), overnight at 4 °C in coating buffer (0.1M NaHC03, pH 9.6). After washing the plate twice, 100 ng of Fab binder diluted in IOOmI PBS pH 6.0 was added to each well and incubated for 1 h at 25 °C. Plates were washed 4 times with PBST (0.1% Tween20 in lx PBS pH 6.0) followed by addition of 100 mΐ (1:10000) of HRP conjugated goat anti-Human IgG antibody (Fab specific) (Sigma-Aldrich, Cat no. A0293) and incubated for 1 h at 25 °C. Plate was then washed 5 times with PBST followed by addition of substrate o-phenylenediamine dihydrochloride (OPD) (lOOpL / well) for 15 minutes at 37 °C. The reaction was stopped using IN H ₂ S04 (lOOuL / well) and optical density was measured at 450 nm using TECAN INFINITE ^® MlOOOpro. Individual clones with relatively high OD signal compared to the parent Fab were shortlisted for further characterization.

Example 7: Generation of pZRCIII hyg Anti-PD-1 light and heavy chain vectors

Five clones were shortlisted based on the results obtained from the qualitative analysis of anti- PD-1 Fab binders. These five clones are referred herein as N5, N6, N7, N9 and N10 based on HCVR region of Fab binders. Genes encoding heavy chain variable regions of N5, N6, N7, N9 and N10 (Amino acid sequences SEQ ID No.:146-150 and nucleotide sequences SEQ ID No.: 169-173, respectively) and light chain gene (SEQ ID No. : 167 and 174 are amino acid and nucleotide sequence, respectively.) were chemically synthesized and cloned into pMA vector (GeneArt, Germany). To clone light chain, in mammalian expression vector, pZRCin hyg.IgG4 vector was digested with Xhol and Kpnl restriction enzymes. The light chain insert digested with same restriction enzymes was ligated to Xhol and Kpnl digested pZRCin hyg.IgG4 vector and transformed in E. coli Top 10F' strain. Transformants were selected on the basis of kanamycin resistance. Plasmid DNA isolated from such colonies was analyzed for the presence of light chain gene by restriction digestion using Xhol and Kpnl restriction enzyme. One of the plasmids showing the expected restriction profile was further digested with Sail and Apal restriction enzymes to insert genes encoding heavy chain variable regions of N5, N6, N7, N9 and N10 (Amino acid sequences SEQ ID No.: 146-150 and nucleotide sequences SEQ ID No.: 169-173, respectively) in frame with IgG4 constant region (SEQ ID No. : 168 and 175 are amino acid and nucleotide sequence, respectively) of pZRCIII hyg.IgG4 vector. The vector and insert digested with Sail and Apal restriction enzymes were ligated and transformed in E coli Top lOF' strain. Transformants were selected on the basis of kanamycin resistance. The plasmid DNA from transformants was digested with Sail and Apal restriction enzymes to confirm the presence of the respective variable region. Final vectors containing light chain of SEQ ID No.: 174 and heavy chain of SEQ ID No.: 169; light chain of SEQ ID No.: 174 and heavy chain of SEQ ID No.: 170; light chain of SEQ ID No.: 174 and heavy chain of SEQ ID No.: 171; light chain of SEQ ID No.: 174 and heavy chain of SEQ ID No.: 172; and light chain of SEQ ID No.: 174 and heavy chain of SEQ ID No.: 173, were confirmed by nucleotide sequencing of heavy and light chains. These final vectors are named as N5NL, N6NL, N7NL, N8NL, N9NL and N10NL, respectively.

The said different constructs encode amino acid sequences of HCVR and LCVR of anti-PD-1 antibodies of the present invention as described in table 7.

Table 7: List of anti-PD-1 antibody constructs with their respective SEQ ID NO.s of amino acid sequences of HCVR and LCVR

A general vector map of the said construct is represented in figure 3.

Amino acid sequences of variable regions of heavy chains and light chain are provided in table 2 and constant region of IgGl, IgG4 and light chain are given at end of the present specification. In the same maimer, nucleotide sequences of variable regions of heavy chains, constant region of IgGl and IgG4 and light chain are also given at end of the present specification.

Example 8: Generation of Anti-PD-l mAbs synthesized using pZRCIII vector

To generate material for proof of concept studies, different Anti-PD-1 antibodies constructs as prepared in Example 7 (N5NL, N6NL, N7NL, N9NL and N10NL) were expressed in CHO-S cells (Invitrogen). Cells were routinely cultured in CDM media from Lonza. Cells were seeded ~24 hours prior to transfection. Transfections were done by electroporation using Neon Transfection system (Invitrogen) using pre-optimized conditions. Post transfection, cells were plated in 24 well plate containing 1 ml prewarmed serum free media. Cells were incubated in humidified incubator at 37 °C in presence of 5% CO2. The selection of transfected pool was done in the presence of 600 mg /ml of Hygromycin in serum free medium. The cell number of the pool was monitored regularly during the selection process over a period of 2-3 weeks and regular media exchanges were given. Anti-PD-1 expressing stable transfectant pools were expanded and the antibodies were produced using fed batch cultures. Cells were seeded at a density of 0.3 ^c 10 ⁶ cells/ml in 125 ml Erienmeyer shake flasks in chemically defined media Flasks were incubated in a humidified Kuhner incubator shaker at 37 °C temperature, 5% CO2 level with shaking speed of 110 RPM. A fixed daily feeding regimen was followed during the entire culture. Chemically defined feeds from Hyclone, GE were used. Feeding was initiated post 72 hours of culture and continued till the culture was harvested. Cultures were harvested (on Day 8-12) and one step purification was carried out using agarose-Protein A matrix (MAbselect SuRe antibody purification resin, GE). The bound antibody was eluted using Glycine Buffer, pH 2.5 and neutralized to pH 7 with Tris Buffer pH 9. The protein concentration of the purified antibody was determined by Protein A HPLC method. Example 9: Affinity analysis of anti- Human PD-1 Antibody by Surface Plasmon Resonance (SPR) method

Affinity rate constants for the binding of anti -PD-1 antibody candidates (IP-H4L1 (IgG4), IP- H4L1 (IgGl), IP-H4.2L1, IP-H4.19L1, IP-H4.36L1, N5NL, N6NL, N7NL, N9NL and N10NL) to the human PD-1 were determined using Proteon XPR (Biorad).

Human PD-1 (AcroBiosy stems) was directly immobilized onto the GLC Chip (ProteOn) using amine-coupling method to obtain a ligand immobilization level of about 500 RU. lOmM Phosphate Buffered Saline (PBS) (lOmM phosphate buffer, pH 7.4, 300mM NaCl, 0.005% Surfactant P20) was used as the running buffer to carry out the kinetic measurements. All the one step purified antibody samples were diluted in running buffer described above at a suitable concentration in series of concentrations from 10 nM to 0.09 nM. These samples were injected over the chip at a flow rate of 50 pL / min with an association time of 300s and dissociation time of 1800s. After each sample run, the chip surface was regenerated with lOmM Glycine Buffer pH 1.5 for 18 sec at a flow rate of 100 pL / min.

K _D values (Kinetic constants) were determined as the ratio of dissociation rate (kd) to association rate (ka), i.e. K _D = kd/ka using ProteOn manager software v3.1.0.6.

The results are presented in table 8. The data was analysed using Langmuir binding model.

Table 8: Results of affinity analysis of anti-PD-1 antibodies by Surface Plasmon Resonance

Example 10: Analysis of anti-PD-1 antibodies using flow cytometric assay in PBMC cells

Human peripheral blood mononuclear cells (PBMC) depleted of monocytes were activated with plate-coated anti-CD3 antibody (clone UCHT-1; BD Biosciences) for 3 days. After washing, the cells were incubated with different concentrations of the anti-PD-1 antibodies IP- H4.2L1, IP-H4L1 (IgGl) and IP-H4L1 (IgG4). The binding of these anti-PD-1 antibodies to PD1 expressed on activated cells was assessed using R-phycoerythrin conjugated F(ab) ² Fragment Goat Anti-Human IgG, Fey Fragment specific as a secondary reagent and evaluating the samples using a flow cytometer (BD FACS Cant II). The binding data is shown in Figure 4. It demonstrates the binding specificity of IP- H4.2L, IP-H4L1 (IgGl) and IP-H4L1 (IgG4) for human PD1, expressed on the cells.

Example 11: Analysis of anti-PD-1 antibodies using flow cytometric assay in HEK-293T cells

HEK 293 T cells stably transfected to express human PD-1 were incubated with different concentrations of the anti-PD-1 antibodies IP- H4.19L1, IP- H4.2L1 and IP-H4.36L1. The binding of these antibodies to PD1 on HEK-293T cells was assessed using R-phycoerythrin conjugated F(ab) ² Fragment Goat Anti-Human IgG, Fcy fragment specific as a secondary reagent evaluated in a flow cytometer (BD FACS CantoTM II) using. The data is shown in Figure 5. It demonstrates the binding specificity of IP- H4.19L1, IP- H4.2L1 and IP-H4.36L1 for human PD1 expressed on the cells.

In the similar manner, other anti-PD-1 antibodies N5NL, N6NL, N7NL, N9NL and N10NL were analysed using flow cytometric assay in HEK-293T cells. The data is shown in Figure 6.

Example 12: Analysis of anti-PD-1 antibody in mixed lymphocyte reaction

Dendritic cells (DC) were generated by culturing monocytes isolated from PBMCs in vitro for 7 days with 50 ng/mL interleukin-4 (IL-4) and 100 ng/mL GM-CSF (11). Monocyte depleted PBMCs (5 x 10 ⁴ ) and allogeneic DCs (1 x 10 ⁴ ) were co-cultured with or without different concentration of anti PD1 antibodies IP- H4.2L1, IP- H4.36L1, IP- H4.19L1, IP-H4L1 (IgG4) and nivolumab analogue, added at the initiation of the assay. After 5 days, culture supernatants were collected and analysed for IL2 and IFN gamma secretion by ELISA (BD Biosciences). The increased secretion of either IL-2 or IFN gamma due to the given anti PD-1 antibody was calculated after subtracting the values obtained with the IgG4 isotype control from the respective group. The results of IL2 and IFN gamma are shown in Figures 7 and 8 respectively. The obtained results demonstrate that the anti -PD 1 anti -PD- 1 antibodies of the present invention are able promote secretion of IL-2 and IFN- gamma by T cells in an MLR.

In the similar manner, other anti-PD-1 antibodies N5NL, N6NL, N9NL and N10NL were analysed in mixed lymphocyte reaction for the analysis of increased IL2 and IFN gamma secretion by ELISA (BD Biosciences). The results of IL2 and IFN gamma are shown in Figures 9 and 10 respectively.

List of amino acid sequences used in the present invention:

SEQ ID No.: 153 - IgG4 constant region

SEQ ID No.: 154 - IgGl constant region

References incorporated in current patent application:

1. Dong et al, B7-H1, a third member of the B7 family, co-stimulates T-cell proliferation and interieukin-10 secretion, Nature Med., 1999 Dec;5(12): 1365-9, 1999

2. Zou et al, Inhibitory B7-family molecules in the tumour microenvironment, Nature Review Immunol., Jun;8(6):467-77, 2008

3. Iwai et al., Involvement of PD-L1 on Tumor Cells in the Escape From Host Immune System and Tumor Immunotherapy by PD-L1 Blockade, Proc. Nat 7. Acad. ScL USA 99: 12293-7, 2002

4. Brown et al., Blockade of Programmed Death-1 Ligands on Dendritic Cells Enhances T Cell Activation and Cytokine Production, J. Immunol. 170:1257-66, 2003

5. Sheridan et al, Cautious optimism surrounds early clinical data for PD-1 blocker, Nature Biotechnology 30: 729-730, 2012

6. Angal S, King DJ, Bodmer MW, Turner A, Lawson AD, Roberts G, Pedley B, Adair JR. A single amino acid substitution abolishes the heterogeneity of chimeric mouse/human (IgG4) antibody. Mol Immunol. 1993; 30(1): 105-8.

7. Weiyi Peng, Chengwen Liu, et al, PD-1 blockade enhances T cell migration to tumors by elevating IFN-g inducible chemokines Cancer Res. 2012 October 15; 72(20): 5209- 5218

8. Niki Karachaliou, Maria Gonzalez-Cao, Guillermo Crespo, et al, Interferon gamma, an important maiker of response to immune checkpoint blockade in non-small cell lung cancer and melanoma patients Therapeutic Advances in Medical Oncology, 2018, Vol. 10: 1-23, 2018 9. Brockmann et al, Synthetic single-framework antibody library integrated with rapid affinity maturation by VL shuffling, Protein Engineering, Design & Selection vol. 24 no. 9 pp. 691-700, 2011

10. Huovinen T, Brockmann E-C, Akter S, Perez-Gamarra S, Yla ^' -Pelto J, et al., Primer Extension Mutagenesis Powered by Selective Rolling Circle Amplification., Volume 7, Issue 2 , e31817, 2012

11. Palucka et al., Dendritic Cells as the Terminal Stage ofMonocyte Differentiation, J Immunology, 160 :4587-4595,1998

Incorporation by reference

The entire disclosure of each of the patent documents and scientific articles referred to herein is incorporated by reference for all purposes.

Equivalents

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The foregoing embodiments are therefore to be considered in all respects illustrative rather than limiting the invention described herein. Scope of the invention is thus indicated by the appended claims rather than by the foregoing description, and all changes that come within the meaning and range of equivalency of the claims are intended to be embraced therein.

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