CD73 BLOCKING ANTIBODIES

Abstract

The present invention relates to antibodies and fragments thereof that bind to and inhibit CD73. The invention also relates to cells that produce such compounds; processes for preparing such compounds and antibodies, fragments, variants, and derivatives thereof; pharmaceutical compositions comprising them; and processes for using the compounds to diagnose, treat, or prevent diseases, for example, cancer.

Description

CD73 BLOCKING ANTIBODIES Cross-reference to related applications This application claims the benefit of United States Provisional Application No. US 62 / 837,214 filed on April 23, 2019, which is incorporated herein by reference in its entirety, including the drawings. Reference to the sequence list The current application is submitted together with a Sequence List in electronic format. The sequence list is provided as a file named “CD736_ST25”, created on April 1, 2020, which is 62 KB in size. The information in the electronic Sequence List is incorporated herein by reference in its entirety. Field of invention The present invention relates to antibodies and fragments thereof that bind to and inhibit CD73. The invention also relates to cells that produce such compounds; processes for preparing such compounds and antibodies, fragments, variants, and derivatives thereof; pharmaceutical compositions comprising them; and processes for using the compounds to diagnose, treat, or prevent diseases, for example, cancer. Background CD73 (ecto-5'-nucleotidase) is a 70 kDa glycosylphosphatidylinositol (GPI)-anchored protein normally expressed in endothelial cells and hematopoietic cell subsets. CD73, along with CD39, regulates adenosine triphosphate (ATP) metabolism. CD39 (NTPDase-1) converts ATP to AMP, releasing only trace amounts of ADP, while CD73 catalyzes the conversion of AMP to adenosine. Adenosine triphosphate (ATP) and its metabolites AMP and adenosine have important roles in cellular metabolism, signaling, and immune homeostasis. The release of extracellular adenosine triphosphate (ATP) in response to cell death or cellular stress activates immune responses. However, its metabolite adenosine has immunosuppressive activity. Extracellular adenosine accumulates in cancerous tissues and constitutes an important mechanism of tumor immune escape. Among other effects, tumor-derived adenosine profoundly inhibits infiltrating effector T cells via A2A receptors that activate adenylyl cyclase. CD73 expression has been reported in a variety of tumor cells, including leukemia, bladder cancer, glioma, glioblastoma, ovarian cancer, melanoma, prostate cancer, thyroid cancer, esophageal cancer, and breast cancer. CD73 expression has also been associated with a prometastatic phenotype in melanoma and breast cancer. Therapy with an antibody that binds to murine CD73 has been reported to inhibit breast tumor growth and metastasis in mice (Stagg et al. (2010) Proc. Nati. Acad. Sci. USA 104:1547-1552). Genetic suppression of A2A receptors has been shown to induce T-cell-dependent tumor rejection (Ohta et al., (2006) Proc. Nati. Acad. Sci. USA 103:13132-13137). Attenuation by siRNA or overexpression of CD73 in tumor cells can modulate tumor growth and metastasis (Beavis et al (2013 Proc. Nati. Acad. Sci. USA 110: 14711-716; Stagg et al. (2010), supra; Jin et al.(2010) Cancer Res. 70: 2245-55). CD73 - / - mice are protected from transplanted and spontaneous tumors (Stagg et al. (2010) Cancer Res. 71: 2892-2900). CD73 expression has been shown to be a negative prognostic factor for triple-negative breast cancer (Loi et al. (2013) Proc. Nati. Acad. Sci. USA 110:11091-11096). However, although CD73 is expressed on tumor cells, it is also expressed on various cells of the immune system, particularly CD4 and CD8 T cells, as well as B cells. Furthermore, an additional complicating factor is that many of the antibodies described in the literature have generally been from murine isotypes that are capable of binding to Fcγ receptors, making it difficult to separate any potential blocking effects from those mediated by Fe. Despite long-standing interest in CD73 as a therapeutic target, there remains a need for antibodies with greater potency in inhibiting CD73 enzyme activity and that are suitable for use in human therapy. The inventors provide antibodies that bind to an epitope present on CD73 expressed on the surface of cells, including tumor cells, and that inhibit the enzymatic activity (ecto-5' nucleotidase) of the CD73 enzyme. The antibodies have human-derived framework regions with minimal non-human sequence content (e.g., mouse). The antibodies can bind to CD73 in an intradimer mode and can inhibit the enzymatic activity of both soluble CD73 and the membrane-bound CD73 protein expressed on the cell surface. Advantageously, these antibodies can be used as pure CD73-blocking antibodies; for example, they inhibit the enzymatic activity of the membrane-bound CD73 protein expressed on the cell surface without substantially binding to Fcy receptors and / or without substantially directing ADCC toward a CD73-expressing cell.Optionally, the antibodies retain an Fe domain and retain binding to human FcRn. The antibodies may advantageously have a low risk of immunogenicity, for example, a low or decreased probability (compared to a parental murine antibody) of inducing a human anti-mouse antibody (HAMA) response when administered to a human. The antibodies bind to an epitope present on the human CD73 polypeptide expressed on the surface of cells, including, but not limited to, tumor cells, and inhibit the enzymatic activity (ecto-5' nucleotidase) of the CD73 enzyme. They have a particularly advantageous ability to inhibit CD73-mediated suppression of T cell proliferation and, consequently, can lead to an increase in the biological activity, including but not limited to proliferation, of cytotoxic CD4 and / or CD8 T cells, for example, as observed in a T cell proliferation assay. In one embodiment, the inhibition or neutralization of CD73 enzymatic activity is determined by assessing the ability of an antibody fragment to increase T cell proliferation when such T cells are induced to proliferate in vitro (e.g., by co-stimulation with a TCR) in the presence of an AMR (e.g., exogenously added AMP). In one embodiment, an antibody or antibody fragment, or an antigen-binding domain thereof, is provided, comprising a heavy-chain variable region comprising the amino acid sequence of SEQ ID No.: 37 and a light-chain variable region comprising an amino acid sequence selected from the group consisting of the amino acid sequences of SEQ ID No.: 33, 34, 35, or 36. In one embodiment, an antibody or antibody fragment, or an antigen-binding domain thereof, is provided, comprising a heavy-chain variable region comprising the amino acid sequence of SEQ ID No.: 37 and a light-chain variable region comprising the amino acid sequence of SEQ ID No.: 33. In one embodiment, an antibody or antibody fragment, or an antigen-binding domain thereof, is provided, comprising a heavy-chain variable region comprising the amino acid sequence of SEQ ID No.: 42 and a light-chain variable region comprising an amino acid sequence selected from the group consisting of the amino acid sequences of SEQ ID No.: 43, 44, 45, or 46. In one embodiment, an antibody or antibody fragment, or an antigen-binding domain thereof, is provided, comprising a heavy-chain variable region comprising the amino acid sequence of SEQ ID No.: 42 and a light-chain variable region comprising the amino acid sequence of SEQ ID No.: 43. In one embodiment, an anti-CD73 antibody or antibody fragment comprising a heavy chain comprising the amino acid sequence of SEQ ID No.: 38 and a light chain comprising the amino acid sequence of SEQ ID No.: 39 is provided. In one embodiment, an anti-CD73 antibody or antibody fragment comprising a heavy chain comprising the amino acid sequence of SEQ ID No.: 47 and a light chain comprising the amino acid sequence of SEQ ID No.: 48 is provided. In one embodiment, an anti-CD73 antigen-binding domain, or a protein comprising it (e.g., an antibody or antibody fragment, a multispecific binding protein, a bispecific antibody, etc.), is provided, comprising a heavy chain variable region (VH) comprising CDR1, CDR2, and CDR3 having the respective amino acid sequences shown in SEQ ID No.: 2, 3, and 4 and the amino acid sequences of frame FR1, FR2, and FR3 of the human IGHV1-3 gene (and optionally, in addition, frame 4 (FR4) amino acid sequences of the human IGHJ4 gene); and a variable light chain (VL) region CDR1, CDR2 and CDR3 having the respective amino acid sequences iviA / a / zuz ι / u iz / oa shown in SEQ ID No.: 5, 6 and 7, and the amino acid sequences of frame FR1, FR2 and FR3 of the human IGKV1-33 gene (and optionally other amino acid sequences of frame 4 (FR4) of the human IGKJ2 gene).Optionally, the residue in the variable region of the heavy chain at Kabat position 59 (HCDR2) is a leucine or glutamine residue. Optionally, the residue in the variable region of the heavy chain at Kabat position 60 (HCDR2) is a threonine or lysine residue. Optionally, the residue in the variable region of the heavy chain at Kabat position 97 (HCDR3) is a glycine or asparagine residue. Optionally, the residue in the variable region of the light chain at Kabat position 30 (LCDR1) is a serine or threonine residue. Optionally, the residue in the variable region of the light chain at Kabat position 53 (LCDR2) is a threonine or asparagine residue. In one embodiment, an anti-CD73 antigen-binding domain, or a protein comprising it (e.g., an antibody or antibody fragment, a multispecific binding protein, a bispecific antibody, etc.), is provided, comprising a heavy chain variable region (VH) comprising CDR1, CDR2, and CDR3 having the respective amino acid sequences shown in SEQ ID No.: 2, 8, and 9 and the amino acid sequences of frame FR1, FR2, and FR3 of the human IGHV1-3 gene (and optionally further the amino acid sequences of frame 4 (FR4) of the human IGHJ4 gene); and a variable light chain (VL) region CDR1, CDR2 and CDR3 having the respective amino acid sequences shown in SEQ ID No.: 10, 11 and 7, and the amino acid sequences of frame FR1, FR2 and FR3 of the human IGKV1-33 gene (and optionally other amino acid sequences of frame 4 (FR4) of the human IGKJ2 gene).In one embodiment, the VH further comprises one, two, or three of the amino acid substitutions in the Kabat heavy chain CDRs at positions selected from the group consisting of 59 (HCDR2), 60 (HCDR2), and 97 (HCDR3). Optionally, the leucine residue at position 59 is substituted with a glutamine residue. Optionally, the threonine residue at position 60 is substituted with a lysine residue. Optionally, the glycine residue at position 97 is substituted with an asparagine residue. In one embodiment, the VL further comprises an amino acid substitution in the Kabat light chain CDRs at positions 30 (LCDR1) and / or 53 (LCDR2) of the Kabat light chain, optionally further wherein the serine residue at position 30 is substituted by a threonine residue, optionally further wherein the threonine residue at position 53 is substituted by an asparagine residue. In one embodiment, an anti-CD73 antigen-binding domain, or a protein comprising it (e.g., an antibody or antibody fragment, a multispecific binding protein, a bispecific antibody, etc.), is provided, comprising a heavy chain variable region (VH) comprising CDR1, CDR2, and CDR3 having the respective amino acid sequences shown in SEQ ID No.: 2, 12, and 13 and the amino acid sequences of frame FR1, FR2, and FR3 of the human IGHV1-3 gene (and optionally further the amino acid sequences of frame 4 (FR4) of the human IGHJ4 gene); and a variable light chain (VL) region CDR1, CDR2 and CDR3 having the respective amino acid sequences shown in SEQ ID No.: 14, 15 and 7, and the amino acid sequences of frame FR1, FR2 and FR3 of the human IGKV1-33 gene (and optionally other amino acid sequences of frame 4 (FR4) of the human IGKJ2 gene). In one aspect of any embodiment hereof, a variable heavy chain (VH) region may be characterized by comprising one, two, three, four, or five amino acid substitutions at positions of the Kabat heavy chain selected from the group consisting of 2, 30, 48, 69, and 73, wherein optionally the residue present in a human sequence at the particular position is replaced by the residue present in the murine donor sequence at that particular position; and a variable light chain (VL) region may be characterized by comprising an amino acid substitution at position 67 of the Kabat light chain, optionally wherein the residue present in a human sequence at the particular position is replaced by the residue present in a murine donor sequence at that particular position.In one embodiment, the VL comprises a substitution at position 67 of the Kabat light chain, and optionally one, two, or three additional amino acid substitutions at positions of the Kabat light chain selected from the group consisting of 2, 67, and 87, optionally wherein the residue present in a human sequence at the particular position is replaced by the residue present in the murine donor sequence at that particular position. In one embodiment, an antibody or antibody-binding domain comprises a variable heavy-chain region comprising the amino acid substitutions V2I, T30A, M48I, I69L, and T73K and a variable light-chain region comprising the amino acid substitution S67Y, wherein the numbering is according to Kabat. In one aspect of any embodiment of the present, the amino acid at position 2 of Kabat's heavy chain is an isoleucine. In one aspect of any embodiment of the present, the amino acid at position 30 of Kabat's heavy chain is an alanine. In one aspect of any embodiment of the present, the amino acid at position 48 of Kabat's heavy chain is an isoleucine. In one aspect of any embodiment of the present, the amino acid at position 69 of Kabat's heavy chain is a leucine. In one aspect of any embodiment of the present, the amino acid at position 73 of Kabat's heavy chain is a lysine. In one embodiment, a VH comprises an isoleucine residue at Kabat position 2, an alanine at position 30, an isoleucine at position 48, a leucine at position 69, and a lysine at position 73. In one aspect of any embodiment of the present, the amino acid at position 67 of the Kabat light chain is a tyrosine. In one aspect of any embodiment of the present, the amino acid at position 60 of the Kabat light chain is an aspartic acid. In one aspect of any embodiment of the present, the amino acid at position 2 of the Kabat light chain is an isoleucine. In one aspect of any embodiment of the present, the amino acid at position 87 of the Kabat light chain is a phenylalanine. In one embodiment, a VL comprises a tyrosine residue at position 67 of Kabat; optionally, the VL does not comprise other substitutions in the Kabat structure by non-human residues and / or has a VL Kabat structure that is entirely human other than a substitution at residue 67. In one embodiment, a VL comprises a tyrosine residue at Kabat position 67 and an aspartic acid at position 60. In one embodiment, a VL comprises a tyrosine residue at Kabat position 67, an aspartic acid at position 60, and an isoleucine at position 2. In one embodiment, a VL comprises a tyrosine residue at Kabat position 67, an aspartic acid at position 60, an isoleucine at position 2, and a phenylalanine at position 87. In one embodiment, an anti-CD73 antigen-binding domain, or a protein comprising the antigen-binding domain (e.g., an antibody or antibody fragment, a multispecific binding protein, a bispecific antibody, etc.), is provided, comprising a heavy chain variable region (HV) comprising an amino acid sequence at least 80%, 90%, 95%, 97%, 98%, or 99% identical to the amino acid sequence of SEQ ID No. 37, and a light chain variable region (LV) comprising an amino acid sequence at least 80%, 90%, 95%, 97%, 98%, or 99% identical to the amino acid sequence of any of SEQ ID Nos. 33, 34, 35, or 36. In one embodiment, the HV comprises CDR1, CDR2, and CDR3 having the respective amino acid sequences shown in SEQ ID Nos. 2, 12, and 13. The VL comprises a CDR1, CDR2 and CDR3 that have the respective amino acid sequences shown in SEQ ID No.: 14,15 and 7.In one embodiment, VH comprises an isoleucine residue at Kabat position 2, an alanine at position 30, an isoleucine at position 48, a leucine at position 69, and a lysine at position 73. In one embodiment, VL comprises a tyrosine residue at Kabat position 67. In one embodiment, an anti-CD73 antigen-binding domain or a protein comprising the antigen-binding domain (e.g., an antibody or antibody fragment, a multispecific binding protein, a bispecific antibody, etc.) is provided, comprising a heavy chain variable region (HV) comprising CDR1, CDR2, and CDR3 having the respective amino acid sequences shown in SEQ ID No.: 2, 3, and 4 and human frames (e.g., FR1, FR2, FR3, and FR4 of human origin); and a variable light chain (VL) region CDR1, CDR2 and CDR3 comprising the respective amino acid sequences shown in SEQ ID No.: 5, 6 and 7 and human frames (e.g., FR1, FR2, FR3 and FR4 of human origin), wherein the (VH) comprises an amino acid sequence at least 80%, 90%, 95%, 97%, 98% or 99% identical to the amino acid sequence of SEQ ID No.37 or 42, and a light chain variable region (LV) comprising an amino acid sequence at least 80%, 90%, 95%, 97%, 98%, or 99% identical to the amino acid sequence of either SEQ ID No. 33-36 or 43-46). Optionally, the residue present in the heavy chain variable region at Kabat position 59 (HCDR2) is a leucine or glutamine residue. Optionally, the residue present in the heavy chain variable region at Kabat position 60 (HCDR2) is threonine or a lysine residue. Optionally, the residue present in the heavy chain variable region at Kabat position 97 (HCDR3) is a glycine or asparagine residue. Optionally, the residue present in the light chain variable region at Kabat position 30 (LCDR1) is a serine or threonine residue. Optionally, the residue present in the variable region of the light chain at position 53 of Kabat (LCDR2) is a threonine or asparagine residue.In one embodiment, VH comprises an isoleucine residue at Kabat position 2, an alanine at position 30, an isoleucine at position 48, a leucine at position 69, and a lysine at position 73. In one embodiment, VL comprises a tyrosine residue at Kabat position 67. In any embodiment, the VH domain may be characterized by comprising amino acid sequences from the human VH acceptor framework, and the VL domain comprises amino acid sequences from the human VL acceptor framework. In one embodiment, the VH segment of the human VH acceptor structure is from a segment of the human IGHV1-3 gene, and the J segment is from a segment of the human IGHJ4 gene. In one embodiment, the human VH acceptor structure is from a segment of the human IGHV13*01 gene. In one embodiment, the human VL domain acceptor structure is from a segment of the human IGKV1-33 gene; optionally, the human VL domain acceptor structure is from a segment of the human IGKV1-33*01 gene. In one embodiment, the human VL domain acceptor structure comprises the J segment from a segment of the human IGKJ2 gene. In one embodiment, an antibody or antibody fragment comprises a VH H4+ domain and a VL L1, L2, L3, or L4 domain. In one embodiment, the antibody is the H4+L1 antibody. In one embodiment, an anti-CD73 antigen-binding domain, or a protein comprising the antigen-binding domain (e.g., an antibody or antibody fragment, a multispecific binding protein, a bispecific antibody, etc.), is provided, comprising a heavy chain variable region comprising the amino acid sequence of SEQ ID No.: 37 and a light chain variable region comprising an amino acid sequence selected from the group consisting of the amino acid sequences of SEQ ID No.: 33, 34, 35 or 36. In one embodiment, an antibody or antibody fragment is provided that binds to human CD73 and neutralizes the ATPase activity of CD73, wherein the antibody or antibody fragment comprises a heavy chain variable region and a light chain variable region of the H4+L1 antibody. In one embodiment, an antibody or antibody fragment is provided that binds to a human CD73 polypeptide and neutralizes the CD73 ATPase activity, wherein the antibody or antibody fragment comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID No.: 37 and a light chain variable region comprising the amino acid sequence of SEQ ID No.: 33. In one embodiment, an antibody or antibody fragment is provided that binds to a human CD73 polypeptide and neutralizes CD73 ATPase activity, wherein the antibody or antibody fragment comprises a heavy chain comprising the amino acid sequence of SEQ ID No.: 38 and a chain comprising the amino acid sequence of SEQ ID No.: 39. In one embodiment, an antibody or antibody fragment comprises a VH 2H4+ domain and a VL 2L1, 2L2, 2L3, or 2L4 domain. In one embodiment, the antibody is the 2H4+2L1 antibody. In one embodiment, an anti-CD73 antigen-binding domain, or a protein comprising the antigen-binding domain (e.g., an antibody or antibody fragment, a multispecific binding protein, a bispecific antibody, etc.), is provided, comprising a heavy chain variable region comprising the amino acid sequence of SEQ ID No.: 42 and a light chain variable region comprising an amino acid sequence selected from the group consisting of the amino acid sequences of SEQ ID No.: 43, 44, 45 or 46. In one embodiment, an antibody or antibody fragment is provided that binds to human CD73 and neutralizes the ATPase activity of CD73, wherein the antibody or antibody fragment comprises a heavy chain variable region and a light chain variable region of the 2H4+2L1 antibody. In one embodiment, an antibody or antibody fragment is provided that binds to a human CD73 polypeptide and neutralizes the CD73 ATPase activity, wherein the antibody or antibody fragment comprises a heavy chain variable region comprising the amino acid sequence of SEQ ID No.: 42 and a light chain variable region comprising the amino acid sequence of SEQ ID No.: 43. In one embodiment, an antibody or antibody fragment is provided that binds to a human CD73 polypeptide and neutralizes the CD73 ATPase activity, wherein the antibody or antibody fragment comprises a heavy chain comprising an amino acid sequence of SEQ ID No.: 47 and a light chain comprising an amino acid sequence of SEQ ID No.: 48. In one embodiment, the antibodies do not deplete and neutralize the enzymatic activity of CD73 in the tumor environment. In one embodiment, the antibody is a human isotype IgG1, IgG2, IgG3, or IgG4 antibody. For example, the antibody may be an antibody comprising an Fe domain of the human IgG4 isotype, or an antibody comprising an Fe domain of any human IgG isotype (e.g., IgG1, IgG2, IgG3, or IgG4) modified to reduce or lack binding between the Fe domains and a human Fcy receptor (e.g., CD16), optionally modified to reduce binding between the Fe domain and a plurality of human Fcy receptors (e.g., CD16A, CD16B, CD32A, CD32B, and CD64). In one embodiment, the antibodies comprise an Fe domain of the human IgG subtype (e.g., lgG1) comprising an amino acid modification that results in a decrease (compared to the antibody comprising a wild-type human lgG1 Fe domain) or a substantially complete loss of binding to each of CD16A, CD16B, CD32A, CD32B, and CD64. In any embodiment, an antibody heavy chain comprises a human CH1 constant domain and a modified human Fe domain, optionally of the human lgG1 isotype, which optionally further comprises an amino acid sequence of any of SEQ ID No.: 16, 17, 18 or 19. In any embodiment, an antibody light chain comprises a human light chain constant domain, wherein the constant domain is optionally a human kappa domain. In one respect, disclosure antibodies do not induce or enhance the intracellular internalization of, or more generally downregulate, the cell surface-expressed polypeptide CD73, and / or do not depend on it for their CD73-inhibitory activity. Disclosure antibodies can provide greater inhibitory potency (the ability to substantially neutralize CD73 enzymatic activity) than antibodies that inhibit CD73 by causing CD73 internalization. Unlike antibodies that inhibit soluble CD73 through other mechanisms (e.g., by causing the formation of CD73 antibody oligomers), disclosure antibodies are able to inhibit CD73 enzymatic activity at a high (e.g., 10-fold) antibody-to-enzyme ratio.Furthermore, unlike antibodies that bind to an epitope on recombinant CD73 that may be modified or absent on cell surface CD73 (e.g., antibody 7G2) or with an affinity too low to be effective on CD73-expressing cells, the present antibodies bind with high affinity to an epitope that is present and / or remains intact on cell surface CD73, giving the antibodies the ability to potently neutralize the enzymatic activity of cellular CD73. The present antibodies inhibit the enzymatic activity of CD73 on cells, but can optionally also inhibit the ecto-5' nucleotidase activity of soluble recombinant CD73 (as observed in a cell-free assay using soluble dimeric CD73 polypeptide). In one respect, disclosure antibodies are able to inhibit the activity of the human CD73 polypeptide without binding to the enzymatic active site of the CD73 polypeptide, and / or are non-competitive inhibitors of CD73, for example, inhibiting the activity of the human CD73 polypeptide without detectably reducing the binding between the CD73 polypeptide and a natural substrate of the same. In one aspect, the disclosure antibodies lose binding to CD73 mutants that have a substitution at residue K136. In one aspect, the disclosure antibodies have decreased binding to CD73 mutants that have a substitution at residue K136 (with reference to the sequence of SEQ ID No.: 1; and compared to a wild-type CD73 comprising an amino acid sequence of SEQ ID No.: 1); Optionally, the antibodies also have decreased binding to CD73 mutants having substitutions at residues A99, E129, K133, E134 and A135 (with reference to the sequence of SEQ ID No.: 1; and compared to a wild-type CD73 comprising an amino acid sequence of SEQ ID No.: 1; optionally, in addition, the antibodies have decreased binding to CD73 mutants having a substitution at residues K97, E125, Q153 and K330 (with reference to the sequence of SEQ ID No.: 1; and compared to a wild-type CD73 comprising an amino acid sequence of SEQ ID No.: 1. In one embodiment, the antibodies bind to an epitope on each CD73 polypeptide chain within a CD73 dimer (i.e., they bind to CD73 in an intradimer manner), optionally further in which the epitope is present on the same face of a CD73 dimer. Thus, the antibodies can bind bivalently to a CD73 dimer, notably in a more “closed” position where the antibody binding sites are spatially more separated than in the “open” position. Given their binding to ligand-bound CD73, the antibodies described herein may be useful for binding to CD73 when bound to AMP, for example, to treat an individual or cancer characterized by (e.g., known or suspected to be characterized by) a tumor environment in which upstream ADP and / or AMP are present at significant levels prior to treatment. The antibodies may be useful for treating an individual or cancer that has (e.g.,is known or suspected to have) a tumor environment characterized by high levels of ADP (e.g., generated by dying cells, taken up by CD73 in the stromal and cellular infiltrate (e.g., Treg cells) to produce high levels of AMP), as well as more generally by AMP, by adenosine, by the presence or expression levels of CD73 or cells expressing CD73, by high numbers (e.g., compared to healthy tissue) or frequencies of cells expressing CD73 and / or high levels of CD73 expression in cells (e.g., as assessed by an immunohistochemical assay), by highly soluble CD73 polypeptides (e.g., compared to healthy tissue) (e.g., as assessed by an ELISA or generally any antibody-based screening assay),or by the presence or expression levels of the adenosine receptor or cells expressing the adenosine receptor. CD73 molecules in the tumor environment may be in the substrate-bound conformation, and the ability to bind to and inhibit substrate-bound cellular CD73 (e.g., CD73-expressing cells pre-incubated with substrate such as AMP) in addition to non-substrate-bound CD73 may provide greater capacity to inhibit CD73 in vivo. Optionally, soluble CD73 protein, the number or frequency of CD73-expressing cells, and / or CD73 expression levels in cells can be assessed in the tumor environment prior to treatment. Antibodies may have a particular advantage for treating an individual who has significant levels (e.g., high levels, compared to a reference) of soluble CD73 protein.Numbers or frequencies of cells expressing CD73 and / or levels of CD73 expression in cells in the tumor sample. Accordingly, in one aspect, the disclosure provides a humanized antibody or antibody fragment that binds to the human CD73 polypeptide expressed on the cell surface and inhibits the enzymatic activity (ecto-5' nucleotidase) of the CD73 polypeptide, wherein the antibody is capable of bivalently binding to a single CD73 polypeptide dimer (either a soluble CD73 polypeptide dimer or a cell-expressed CD73 polypeptide dimer). Optionally, the antibody binds with a first antigen-binding domain to a first CD73 polypeptide within the dimer and with a second antigen-binding domain to a second CD73 polypeptide. In one aspect, the antibody is an allosteric inhibitor of the CD73 polypeptide. The epitope on CD73 bound by antibodies is present on CD73 polypeptides expressed by a variety of cells, such as cancer cells, CD4 T cells, CD8 T cells, B cells, and transfected cells, and binds with high affinity as determined by flow cytometry. For example, an antibody may be characterized by a CE, determined by flow cytometry, of no more than 5 pg / ml, optionally no more than 2 pg / ml, no more than 1 pg / ml, no more than 0.5 pg / ml, no more than 0.1 pg / ml, or no more than 0.05 pg / ml, for binding to cells that express a CD73 polypeptide on their surface. In one embodiment, the cells are cells that are engineered to express CD73 on their surface.In one embodiment, the cells are cells that endogenously express CD73 on their surface, e.g., cancer cells, leukemia cells, bladder cancer cells, glioma cells, glioblastoma cells, ovarian cancer cells, melanoma cells, prostate cancer cells, thyroid cancer cells, esophageal cancer cells, or breast cancer cells. In one embodiment, CD73 neutralizing antibodies can be characterized by their ability to induce a decrease in CD73 5'-ectonucleotidase activity of cells by at least 60%, 75%, or 80%. In another embodiment, CD73 neutralizing antibodies can be characterized by a CSE for inhibition of CD73 5'-ectonucleotidase activity expressed by a cell of no more than 1 pg / ml, optionally no more than 0.5 pg / ml, or optionally no more than 0.2 pg / ml. Optionally, the inhibition of CD73 5'-ectonucleotidase activity expressed by a cell is determined by assessing the neutralization of 5'-ectonucleotidase activity in cells expressing CD73 (e.g., MDA-MB-231 cells) by quantifying the hydrolysis of AMP to adenosine. Optionally, inhibition of CD73 5'-ectonucleotidase activity expressed by a cell is determined by assessing the ability of an antibody or antibody fragment to increase T cell proliferation when such T cells (e.g., from a healthy human donor) are induced to proliferate in vitro (e.g., by TCR co-stimulation, stimulation of CD3 and CD28 signaling, e.g., by contacting T cells with beads functionalized with CD3 agonists and CD28 agonists) in the presence of AMP (e.g., exogenously added AMP). Optionally, T cell proliferation is assessed using the assay described in the Examples section of this document (see Example 5 and Procedures). In one respect, an anti-CD73 antibody binds to a common antigenic determinant present in both soluble CD73 and CD73 expressed on the cell surface. In one respect, an anti-CD73 antibody binds to an antigenic determinant within each CD73 polypeptide chain within a CD73 dimer (in intradimer mode), for example, in which the antigenic determinants are present on a common face of the CD73 dimer. In one respect, an anti-CD73 antibody binds to an epitope on CD73 comprising residue K136 (with reference to SEQ ID No.: 1). In one respect, an anti-CD73 antibody binds to an epitope on CD73 comprising one, two, three, or four of the residues selected from the group consisting of K97, E125, Q153, and K330 (with reference to SEQ ID No.: 1). In one respect, an anti-CD73 antibody binds to an epitope on CD73 comprising one, two, three, four, or five of the residues selected from the group consisting of A99, E129, K133, E134, and A135 (with reference to SEQ ID No.: 1). In one aspect, an anti-CD73 antibody binds at least partially within a domain or segment of amino acid residues in a human CD73 protein (e.g., a CD73 homodimer protein) comprising the amino acid residues K97, A99, E125, E129, K133, E134, A135, K136, Q153, and K330 (with reference to SEQ ID No.: 1). In another aspect, an anti-CD73 antibody binds to an epitope in CD73 comprising at least one, two, three, four, or five, or more, of the residues selected from the group consisting of K97, A99, E125, E129, K133, E134, A135, K136, Q153, and K330 (with reference to SEQ ID No.: 1). In one respect, an anti-CD73 antibody has a reduced binding to a CD73 polypeptide that has a mutation at residue K136 (with reference to ινΐΛ / a / zuz ι / u iz / oa SEQ ID No.: 1) compared to a wild-type CD73 polypeptide comprising an amino acid sequence of SEQ ID No.: 1; optionally, the mutant CD73 polypeptide has the mutation: K136A. In one aspect, an anti-CD73 antibody has reduced binding to a CD73 polypeptide having a mutation in a selected residue from the group consisting of: K97, E125, Q153 and K330 (with reference to SEQ ID No.: 1) compared to a CD73-type polypeptide comprising an amino acid sequence of SEQ ID No.: 1; optionally, the mutant CD73 polypeptide has the mutations: K97A, E125A, Q153A and / or K330A (e.g., K97A, E125A and K330A; K97A, E125A and / or Q153A). In one aspect, an anti-CD73 antibody has reduced binding to a CD73 polypeptide having a mutation in a selected residue from the group consisting of: A99, E129, K133, E134 and A135 (with reference to SEQ ID No.: 1) compared to a wild-type CD73 polypeptide comprising an amino acid sequence of SEQ ID No.: 1; optionally, the mutant CD73 polypeptide has the mutations: A99S, E129A, K133A, E134N and A135S. In one embodiment, procedures are provided for using antibodies in the treatment or prevention of diseases, for example, infectious diseases or cancer. In one aspect, antibodies are administered to an individual with cancer in sufficient quantity and frequency to neutralize CD73 activity in the tumor microenvironment. In another embodiment, antibodies are administered in sufficient quantity and frequency to decrease adenosine generation and / or concentration in the tumor microenvironment. In yet another embodiment, antibodies are administered in sufficient quantity and frequency to increase ATP generation and / or concentration in the tumor microenvironment. Finally, in yet another embodiment, antibodies are administered in sufficient quantity and frequency to neutralize CD73 activity expressed by tumor cells.In one embodiment, the antibodies are administered in sufficient quantity and frequency to neutralize the CD73 activity expressed by CD4 T cells, CD8 T cells and / or B cells. iviA / a / zuz ι / u iz / oa The antibodies will be useful for inhibiting CD73-mediated AMP catabolism to adenosine, for example, by decreasing the concentration of adenosine in the tumor microenvironment. Therefore, these antibodies will be useful for reversing the immunosuppressive effect of CD73 and / or adenosine on T cells, B cells, and other cells that express adenosine receptors, for example, in cancer treatment. In one embodiment, the anti-CD73 antibody neutralizes adenosine-mediated inhibition of proliferation, cytokine production, cytotoxicity, and / or NF-κB activity in T cells. Because CD73-mediated AMP catabolism to adenosine is irreversible, while CD73-mediated ATP to ADP and ADP to AMP catabolism is reversible (via NDK kinase and adenylate kinase, respectively), antibodies that block irreversible CD73-mediated catabolism increase the pool of AMP, making them useful for raising ADP and ATP concentrations, for example, in the tumor microenvironment. Antibodies can be useful for increasing ADP formation from AMP and ATP formation from ADP. Since ATP has immune-activating functions, anti-CD73 antibodies can be useful for activating T cells, for example, in cancer treatment. Antibodies will be useful in inhibiting the production, amounts and / or concentrations of adenosine in the tumor microenvironment. Antibodies that neutralize the activity of a soluble human CD73 polypeptide dimer can further neutralize CD73 in any other suitable context, e.g., in a reporter cell primed to express CD73, in a T cell, etc. A procedure is provided for treating an individual, the procedure comprising administering to an individual (e.g., an individual suffering from a disease, a tumor, etc.) a therapeutically active amount of any of the anti-CD73 antigen-binding compounds described herein. In one aspect, a procedure is provided for treating an individual, the procedure comprising, essentially, administering to an individual (e.g., an individual having a disease, a tumor, etc.) a therapeutically active amount of an antigen-binding compound from the disclosure. In one aspect, a method is provided for decreasing the adenosine produced by a CD73-expressing cell (e.g., an immune cell and / or a tumor cell in an individual), or a method for neutralizing cellular CD73 enzymatic activity. The method comprises, essentially consists of, or comprises: contacting the CD73-expressing cell with a disclosed antigen-binding compound (e.g., an anti-CD73 antibody or antibody fragment, or a composition comprising it). In one embodiment, the step of contacting the CD73-expressing cell with a disclosed antigen-binding compound comprises administering a therapeutically active amount of the antigen-binding compound to an individual. In one embodiment, the individual has cancer. In one aspect, a procedure is provided for decreasing adenosine present in the tumor environment (e.g., in an individual). The procedure comprises, essentially consists of, or comprises: administering to an individual a therapeutically active amount of a compound disclosed herein (e.g., an anti-CD73 antibody or antibody fragment, or a composition comprising it). In one embodiment, the individual has cancer. Optionally, the individual is a human being who has or is susceptible to having cancer. The antibodies are optionally characterized by a binding affinity (Kd) for a human CD73 polypeptide (e.g., as a CD73 dimer), as determined by SPR (e.g., according to the procedures in the Examples) of less than (better than) 10⁹M, preferably less than 10¹⁰M, or preferably less than 10¹¹M, and / or by binding the human CD73 polypeptide with a CEso less than (better than) 1 pg / ml. Optionally, the binding affinity can be specified as bivalent. In one embodiment, the antibody has an CE50 of no more than 0.5 pg / ml, optionally no more than 0.2 pg / ml, optionally no more than 0.1 pg / ml, to bind to cells (e.g., tumor cells, MDA-MB-231 cells) that express human CD73 on the cell surface. The antibodies are optionally characterized by a CEso for neutralizing the enzymatic activity of CD73 on cells expressing CD73 (e.g., tumor cells, MDA-MB-231 cells) of less than (better than) 1 pg / ml, optionally less than 0.5 pg / ml. In one embodiment, the antibody is a monoclonal antibody or a fragment thereof that retains binding specificity and the ability to neutralize the enzymatic activity of CD73 (e.g., as determined by evaluating the ability of an antibody or antibody fragment to increase T-cell proliferation when T-cell proliferation is induced in vitro in the presence of AMP (e.g., exogenously added AMP). In one embodiment, the antibody is substantially as potent as, or at least as potent as, the parental antibody having the respective amino acid sequences VH and VL of SEQ ID No. 40 and 41 for neutralizing the enzymatic activity of CD73, optionally wherein the antibody has a specificity for neutralizing the enzymatic activity of CD73 that is within 1 log to 0.5 log of the specificity of the parental antibody.In one embodiment, the antibody is more potent than the parental antibody having the respective amino acid sequences VH and VL of SEQ ID No.: 40 and 41 in neutralizing the enzymatic activity of CD73, optionally wherein the antibody has a Ce that is less potent than that of the parental antibody having the respective amino acid sequences VH and VL of SEQ ID No.: 40 and 41 in neutralizing the enzymatic activity of CD73. In one embodiment, the antibody is substantially as potent or at least as potent as the parental antibody having the respective amino acid sequences VH and VL of SEQ ID Nos. 27 and 28 for neutralizing the enzymatic activity of CD73, optionally wherein the antibody has a CEso for neutralizing the enzymatic activity of CD73 that is within 1 log or 0.5 log of the CEso of the parental antibody. In another embodiment, the antibody is more potent than the parental antibody having the respective amino acid sequences VH and VL of SEQ ID Nos. 27 and 28 for neutralizing the enzymatic activity of CD73, optionally wherein the antibody has a CEso for neutralizing the enzymatic activity of CD73 which is smaller than that of the parental antibody which has the respective amino acid sequences VH and VL of SEQ ID No.: 27 and 28. Also provided are isolated and / or recombinant nucleic acids (e.g., nucleic acid assemblies) encoding an antibody (or a heavy or light chain thereof) or a VH and / or VL domain of the disclosure, a vector or assembly of vectors comprising such a nucleic acid, a cell comprising such a vector, and a process for producing a human anti-CD73 antibody or antibody fragment, comprising culturing such a cell under conditions suitable for the expression of the anti-CD73 antibody or antibody fragment. The disclosure also refers to compositions, such as pharmaceutically acceptable compositions and kits, comprising such proteins, nucleic acids, vectors, and / or cells and typically one or more additional ingredients, which may be active or inactive ingredients that promote the formulation, delivery, stability, or other characteristics of the composition (e.g., various carriers).The disclosure also refers to several new and useful procedures that produce and use such antibodies, nucleic acids, vectors, cells, organisms and / or compositions, such as in the modulation of CD73-mediated biological activities, for example, in the treatment of related diseases, especially cancers. The disclosure also provides procedures for producing or testing an antibody or antibody fragment that binds to and neutralizes the enzymatic activity of CD73. The disclosure also provides a method for enhancing lymphocyte activity (e.g., T cells) in a subject in need, or for restoring lymphocyte activity (e.g., T cells), or a method for alleviating adenosine-mediated inhibition of lymphocyte activity (e.g., T cells), the method comprising administering an effective amount of any of the above compositions to the subject. In one embodiment, the subject is a patient suffering from cancer. For example, the patient may suffer from a solid tumor, such as colorectal cancer, renal cancer, ovarian cancer, lung cancer, breast cancer, or malignant melanoma. Alternatively, the patient may suffer from a hematopoietic cancer, such as acute myeloid leukemia, chronic myeloid leukemia, multiple myeloma, or non-Hodgkin lymphoma. These aspects are described in more detail and the additional aspects, features and advantages will become evident from the description provided in this document. Brief description of the drawings Figures 1A-1B show the titration curves obtained with humanized variants having heavy chain variable regions H0, H1, H2, H3, and H4, each combined with each of the light chain variable regions LO, L1, L2, L3, and L4, and the parental murine antibody HELP, as tested in transfected cell lines expressing human CD73 protein (Figure 1A) or cynomolgus protein (Figure 1B). Figure 2 shows the blocking of enzymatic activity by soluble recombinant CD73. The upper left panel (A) shows that a high level of luminescence was measured when the substrates ATP and CTG were mixed. When AMP was added to the reaction mixture, the CTG reaction was inhibited, resulting in a decrease in luminescence. In the presence of the rhCD73 protein, which hydrolyzes AMP, the luminescence level was restored. The blocking of CD73 enzymatic activity by the different humanized variants is shown. Figures 3A–3C and 4A–4C show two sets of experiments comparing humanized antibodies in their potency to reverse AMP-mediated inhibition of T cell proliferation. Figures 3A and 4A show the control of T cell proliferation and its inhibition by AMP for each set of experiments. Figures 3B and 4B show the efficacy of anti-CD73 antibodies in restoring CD4+ T cells, and Figures 3C and 4C show the efficacy of anti-CD73 antibodies in restoring CD8+ T cell proliferation. Cell proliferation was determined by dilution of the Cell Trace Violet marker. Data are expressed as mean of duplicates ± standard deviation. Figures 5A–5C show that T cell proliferation is restored by all anti-CD73 antibodies. Figure 5A shows the control of T cell subpopulation proliferation and its inhibition by AMP. Figure 5B shows the efficacy of H4+Lx antibodies and the parental antibody HPLP in restoring CD4+ and CD8+ T cell proliferation. Figure 5C shows the efficacy of 2H4+2Lx antibodies (the 2H4+ chain combined with the 2L1, 2L2, 2L3, or 2L4 chains) and the parental antibody 2HP2LP in restoring CD4+ and CD8+ T cell proliferation. Data are expressed as mean of duplicates ± standard deviation. Figures 6A and 6B show that T cell proliferation restored by humanized variants is reproducible in two representative human donors, respectively. The efficacy of the anti-CD73 2H4+2Lx antibody variants in restoring CD4 and CD8 T cell proliferation is shown. Data are expressed as mean of duplicates ± standard deviation. Figure 7 shows that CD4+ T cell proliferation is inhibited by ATP and restored with 2H4+2Lx antibody variants. Control of CD4+ T cell proliferation and inhibition by 100 μM of ATP, shown as demonstrated for two representative donors, D795 (Figure 7A) and D664 (Figure 7B). Data are expressed as mean of duplicates ± standard deviation. Detailed description of the invention Definitions As used in the specification, “a” or “an” may mean one or more. As used in the claim(s), when used in conjunction with the word “comprising”, the words “a” or “an” may mean one or more. As used herein, “another” may mean at least one or more. When using “comprising”, this may optionally be replaced by “consisting essentially of” or by “consisting of”. Human CD73, also known as ecto-5'-nucleotidase and 5'-primoribonucleotide phosphohydrolase, EC 3.1.3.5, encoded by the NT5E gene, exhibits 5'-nucleotidase activities, particularly AMP, NAD, and NMN-nucleosidase. CD73 catalyzes the conversion of purine 5'-primitive mononucleotides to nucleosides at neutral pH, with AMP being the preferred substrate. The enzyme consists of a dimer of two identical 70 kDa subunits linked by a glycosylphosphatidylinositol bond to the outer face of the plasma membrane. The amino acid sequence of the human CD73 preprotein (monomer), including a signal sequence at amino acids 1-26, is listed in GenBank under accession number NP_002517, the full description of which is incorporated herein by reference, and as follows: MCPRAARAPA TLLLALGAVL WPAAGAWELT ILHTNDVHSR LEQTSEDSSK CVNASRCMGG VARLFTKVQQ IRRAEPNVLL LDAGDQYQGT IWFTVYKGAE VAHFMNALRY DAMALGNHEF DNGVEGLIEP LLKEAKFPIL SANIKAKGPL ASQISGLYLP YKVLPVGDEV VGIVGYTSKE TPFLSNPGTN LVFEDEITAL QPEVDKLKTL NVNKIIALGH SGFEMDKLIA QKVRGVDVVV GGHSNTFLYT GNPPSKEVPA GKYPFIVTSD DGRKVPVVQA YAFGKYLGYL KIEFDERGNV ISSHGNPILL NSSIPEDPSI KADINKWRIK LDNYSTQELG KTIVYLDGSS QSCRFRECNM GNLICDAMIN NNLRHTDEMF WNHVSMCILN GGGIRSPIDE RNNGTITWEN LAAVLPFGGT FDLVQLKGST LKKAFEHSVH RYGQSTGEFL QVGGIHVVYD LSRKPGDRVV KLDVLCTKCR VPSYDPLKMD EVYKVILPNF LANGGDGFQM IKDELLRHDS GDQDINVVST YISKMKVIYP AVEGRIKFST GSHCHGSFSL IFLSLWAVIF VLYQ (SEQ ID NO.: 1). In the context of this document, “neutralizing the enzymatic activity of CD73” refers to a procedure in which the 5’-nucleotidase (5’-ectonucleotidase) activity of CD73 is inhibited. This includes, in particular, the inhibition of CD73-mediated adenosine generation, i.e., the inhibition of CD73-mediated AMP catabolism to adenosine. This can be measured, for example, in a cell-free assay that assesses the ability of a test compound to inhibit the conversion of AMP to adenosine, either directly or indirectly. In one embodiment, an antibody preparation causes at least a 50% decrease in the conversion of AMP to adenosine, at least a 70% decrease in the conversion of AMP to adenosine, or at least an 80% decrease in the conversion of AMP to adenosine, referring, for example, to the assays described herein. Whenever this entire specification mentions “cancer treatment” or similar terms with reference to the anti-CD73 binding agent (e.g., antibody), it shall mean: (a) cancer treatment procedure, said procedure comprising the step of administering (for at least one treatment) an anti-CD73 binding agent (preferably in a pharmaceutically acceptable carrier material) to an individual, a mammal, especially a human, who requires such treatment, in a dose that enables the treatment of the cancer (a therapeutically effective amount), preferably in a dose (amount) as specified herein; (b) the use of an anti-CD73 binding agent for the treatment of cancer, or an anti-CD73 binding agent for use in such treatment (especially in a human);(c) the use of an anti-CD73 binding agent for the manufacture of a pharmaceutical preparation for the treatment of cancer, a method of using an anti-CD73 binding agent for the manufacture of a pharmaceutical preparation for the treatment of cancer, comprising mixing an anti-CD73 binding agent with a pharmaceutically acceptable carrier, or a pharmaceutical preparation comprising an effective dose of an anti-CD73 binding agent that is appropriate for the treatment of cancer; or (d) any combination of (a), (b) and (c), in accordance with the subject matter permitted for patenting in a country where this application is filed. The term “antibody,” as used in this document, refers to both polyclonal and monoclonal antibodies. Depending on the type of constant domain in the heavy chains, antibodies are assigned to one of five major classes: IgA, IgD, IgE, IgG, and IgM. Several of these are further divided into subclasses or isotypes, such as IgG1, IgG2, IgG3, IgG4, and so on. A typical immunoglobulin (antibody) structural unit comprises a tetramer. Each tetramer consists of two identical pairs of polypeptide chains, each pair having a “light” chain (approximately 25 kDa) and a “heavy” chain (approximately 50–70 kDa). The N-terminus of each chain defines a variable region of approximately 100 to 110 or more amino acids that is primarily responsible for antigen recognition. The terms variable light chain (Vl) and variable heavy chain (Vh) refer to these light and heavy chains respectively.The heavy-chain constant domains corresponding to the different classes of immunoglobulins are designated “alpha,” “delta,” “epsilon,” “gamma,” and “mu,” respectively. The subunit structures and three-dimensional configurations of different immunoglobulin classes are well known. IgG antibodies are the exemplary class of antibodies used herein because they are the most common antibodies in physiological conditions and are most readily manufactured in a laboratory setting. Optionally, the antibody may be a monoclonal antibody. Particular examples of antibodies include humanized, chimeric, human, or otherwise human-suitable antibodies. “Antibodies” also includes any fragment or derivative of any of the antibodies described herein. The term “binds specifically to” means that an antibody can preferentially bind in a competitive binding assay to the binding partner, for example, CD73, as assessed using recombinant forms of the proteins, epitopes on the proteins, or native proteins present on the surface of isolated target cells. Competitive binding assays and other procedures for determining specific binding are described in more detail below and are well known in the art. When an antibody is said to “compete with” a particular monoclonal antibody, it means that the antibody competes with the monoclonal antibody in a binding assay using recombinant CD73 molecules or surface-expressed CD73 molecules. For example, if a test antibody reduces the binding of a reference antibody to a CD73 polypeptide or a cell expressing CD73 in a binding assay, the antibody is said to “compete” with the reference antibody, respectively. The term “affinity,” as used in this document, means the strength of an antibody’s binding to an epitope. The affinity of an antibody is given by the dissociation constant Kd, defined as [Ab] x [Ag] / [Ab-Ag], where [Ab-Ag] is the molar concentration of the antibody-antigen complex, [Ab] is the molar concentration of the unbound antibody, and [Ag] is the molar concentration of the unbound antigen. The affinity constant Ka is defined by 1 / Kd. Procedures for determining the affinity of mAbs can be found in Harlow et al., Antibodies: A Laboratory Manual, Coid Spring Harbor Laboratory Press, Coid Spring Harbor, NY, 1988; Coligan et al., Eds., Current Protocols in Immunology, Greene Publishing Assoc. and Wiley Interscience, NY, 1992, 1993; and Muller, Meth. EnzymoL 92:589-601 (1983), whose references are incorporated herein in full as a reference.A well-known standard procedure in the technique for determining mAb affinity is the use of surface plasmon resonance (SPR) screening (such as by analysis with a BIAcore™ SPR analytical device). Within the context of this document, a “determinant” designates an interaction or binding site on a polypeptide. The term “epitope” refers to an antigenic determinant and is the area or region of an antigen to which an antibody binds. A protein epitope can comprise amino acid residues directly involved in binding, as well as amino acid residues that are effectively blocked by the peptide or antibody from binding to the specific antigen—that is, amino acid residues within the antibody's “footprint.” It is the simplest form or smallest structural area of ​​a complex antigen molecule that can combine with, for example, an antibody or a receptor. Epitopes can be linear or conformational / structural. The term “linear epitope” is defined as an epitope composed of amino acid residues that are contiguous to the linear amino acid sequence (primary structure).The term “conformational or structural epitope” is defined as an epitope composed of amino acid residues that are not all contiguous and therefore represent separate parts of the linear amino acid sequence that are brought closer together by folding of the molecule (secondary, tertiary, and / or quaternary structures). A conformational epitope depends on the three-dimensional structure. Therefore, the term “conformational” is often used interchangeably with “structural.” The term “deplete” or “exhaust,” with respect to CD73-expressing cells, means a procedure, process, or compound that results in the death, elimination, lysis, or induction of such death, elimination, or lysis, so as to adversely affect the number of such CD73-expressing cells present in a sample or subject. The term “internalization,” used interchangeably with “intracellular internalization,” refers to the molecular, biochemical, and cellular events associated with the translocation of a molecule from the extracellular surface of a cell to the intracellular surface of a cell. The processes responsible for the intracellular internalization of molecules are well understood and may involve, among other things, the internalization of extracellular molecules (such as hormones, antibodies, and small organic molecules); membrane-associated molecules (such as cell-surface receptors); and complexes of membrane-associated molecules bound to extracellular molecules (for example, a ligand bound to a transmembrane receptor or an antibody bound to a membrane-associated molecule).Therefore, “inducing and / or increasing internalization” includes events in which intracellular internalization is initiated and / or the rate and / or degree of intracellular internalization is increased. The term “agent” is used herein to refer to a chemical compound, a mixture of chemical compounds, a biological macromolecule, or an extract made from biological materials. The term “therapeutic agent” refers to an agent that has biological activity. For the purposes of this document, a “humanized” or “human” antibody refers to an antibody in which the constant and variable framework regions of one or more human immunoglobulins are fused to the binding region, e.g., the CDR, of an animal immunoglobulin. Such antibodies are designed to maintain the binding specificity of the non-human antibody from which the binding regions are derived, but to avoid an immune response against the non-human antibody. Such antibodies can be obtained from transgenic mice or other animals that have been engineered to produce specific human antibodies in response to antigenic challenge (see, e.g., Green et al. (1994) Nature Genet 7:13; Lonberg et al. (1994) Nature 368: 856; Taylor et al. (1994) Int Immun 6: 579, the full texts of which are incorporated herein by reference).A fully human antibody can also be constructed by genetic or chromosomal transfection procedures, as well as phage presentation technology, all of which are known in the art (see, for example, McCafferty et al. (1990) Nature 348: 552-553). Human antibodies can also be generated by activated B cells in vitro (see, for example, U.S. Patents Nos. 5,567,610 and 5,229,275, which are incorporated herein by reference). The term “hypervariable region” when used in this document refers to the amino acid residues of an antibody that are responsible for binding to the antigen. The hypervariable region generally comprises amino acid residues from a “complementarity-determining region” or “CDR” (e.g., residues 24-34 (L1), 50-56 (L2), and 89-97 (L3) in the light-chain variable domain and 31-35 (H1), 50-65 (H2), and 95-102 (H3) in the heavy-chain variable domain; Kabat et al. 1991) and / or such residues from a “hypervariable loop” (e.g., residues 26-32 (L1), 50-52 (L2), and 91-96 (L3) in the light-chain variable domain and 26-32 (H1), 53-55 (H2), and 96-101 (H3) in the heavy-chain variable domain; Chothia and Lesk, J. Mol. Biol 1987; 196: 901-917), or a similar system to determine the essential amino acids responsible for antigen binding.Normally, the numbering of amino acid residues in this region is performed using the procedure described in Kabat et al., supra. Phrases such as “Kabat position,” “numbering of variable domain residues as in Kabat,” and “according to Kabat” herein refer to this numbering system for heavy-chain or light-chain variable domains. Using the Kabat numbering system, the actual linear amino acid sequence of a peptide may contain fewer or more amino acids due to a shortening or insertion at a residue fraction (RF) or comma-reacting residue (CDR) of the variable domain. For example, a heavy-chain variable domain may include a single-amino-acid insert (residue 52a according to Kabat) after residue 52 of CDR H2 and inserted residues (e.g., residues 82a, 82b, and 82c, etc., according to Kabat) after residue 82 of the heavy-chain FR.The Kabat residue numbering can be determined for a given antibody by alignment on homology regions of the antibody sequence with a “standard” numbered Kabat sequence. The term “frame” or “FR” residues, as used herein, refers to the region of an antibody variable domain that excludes the regions defined as CDRs. Each antibody variable domain frame can be subdivided into the contiguous regions separated by the CDRs (FR1, FR2, FR3, and FR4). The terms “Fe domain,” “Fe portion,” and “Fe region” refer to a C-terminal fragment of an antibody heavy chain, for example, from approximately amino acid (aa) 230 to approximately aa 450 of the human gamma heavy chain, or its homologous sequence in other types of antibody heavy chains (e.g., α, δ, ε, and μ for human antibodies), or a naturally occurring allotype thereof. Unless otherwise specified, the commonly accepted Kabat amino acid numbering for immunoglobulins is used throughout this description (see Kabat et al. (1991) Sequences of Protein of Immunological Interest, 5th ed., U.S. Public Health Service, National Institutes of Health, Bethesda, MD). The terms “isolated,” “purified,” or “biologically pure” refer to material that is substantially or essentially free of components that normally accompany it as found in its native state. Purity and homogeneity are typically determined using analytical chemistry techniques such as polyacrylamide gel electrophoresis or high-performance liquid chromatography. A protein that is the predominant species present in a preparation is substantially purified. The terms “polypeptide,” “peptide,” and “protein” are used interchangeably in this document to refer to a polymer of amino acid residues. These terms apply to amino acid polymers in which one or more amino acid residues are artificial chemical imitators of a corresponding naturally occurring amino acid, as well as to naturally occurring amino acid polymers and non-naturally occurring amino acid polymers. The term “recombinant,” when used with reference to, for example, a cell, nucleic acid, protein, or vector, indicates that the cell, nucleic acid, protein, or vector has been modified by the introduction of a heterologous nucleic acid or protein, or by the alteration of a native nucleic acid or protein, or that the cell is derived from a cell so modified. Thus, for example, recombinant cells express genes that are not found within the native (non-recombinant) form of the cell, or they express native genes that are otherwise abnormally expressed, underexpressed, or not expressed at all. Within the context of this document, the term antibody that “binds” to a polypeptide or epitope designates an antibody that binds to said determinant with specificity and / or affinity. The term “identity” or “identical,” when used in relation to the sequences of two or more polypeptides, refers to the degree of sequence relatedness between polypeptides, as determined by the number of matches between chains of two or more amino acid residues. “Identity” measures the percentage of identical matches between the least of two or more sequences with space alignments (if any) addressed by a particular mathematical model or computer program (i.e., “algorithms”). The identity of related polypeptides can be readily calculated using well-known procedures. Such procedures include, but are not limited to, those described in Computational Molecular Biology, Lesk, A.M., ed., Oxford University Press, New York, 1988; Biocomputing: Informatics and Genome Projects, Smith, D.W., ed., Academic Press, New York, 1993; and Computer Analysis of Sequence Data, Part 1, Griffin, A.M., and Griffin, H.G., eds., Humana Press, New Jersey, 1994; Sequence Analysis in Molecular Biology, von Heinje, G., Academic Press, 1987; Sequence Analysis Primer, Gribskov, M. and Devereux, J., eds., M. Stockton Press, New York, 1991; and Carillo et al., SIAM J. Applied Math. 48, 1073 (1988). The procedures for determining identity are designed to provide the best match between the tested sequences. These procedures are described in publicly available computer programs. Computer program procedures for determining identity between two sequences include the GCG software package, which includes GAP (Devereux et al., Nuci. Acid. Res. 12, 387 (1984); Genetics Computer Group, University of Wisconsin, Madison, Wis.), BLASTP, BLASTN, and FASTA (Altschul et al., J. Mol. Biol 215, 403-410 (1990)). The BLASTX program is publicly available from the National Center for Biotechnology Information (NCBI) and other sources (BLAST Manual, Altschul et al. NCB / NLM / NIH Bethesda, Md. 20894; Altschul et al., Supra). The well-known Smith-Waterman algorithm can also be used for identity determination. Antibody production The present invention is based, in part, on the discovery of modified human acceptor framework sequences into which antibody CDRs can be incorporated such that the resulting anti-CD73 variable region has high potency in neutralizing the enzymatic activity of human CD73. These antibodies have the advantage of having low or reduced immunogenicity in humans; for example, they have a lower capacity or likelihood of eliciting an immune response directed by an unwanted anti-CD73 antibody upon administration to a human. Examples of such antibodies disclosed herein include antibodies comprising the VH H4+ or 2H4+ domain combined with a VL L1, L2, L3, L4, 2L1, 2L2, 2L3, or 2L4 domain. Examples of antibodies in the disclosure include antibodies comprising the VH and VL domain pairs of any of the antibodies H4+L1, H4+L2, H4+L3, H4+L4, 2H4+L1, 2H4+L2, 2H4+L3, or 2H4+L4. In one aspect, an antibody or antibody fragment that binds to a human CD73 polypeptide comprises VH and VL structures (e.g., FR1, FR2, FR3, and FR4) of human origin. In one aspect, the antibody or antibody fragment comprises: an HCDR1 (heavy chain CDR1) comprising an amino acid sequence SYNMY as set out in SEQ ID No.: 2; an HCDR2 (heavy chain CDR2) comprising an amino acid sequence YIDPYNGGSSYNQKFKG as set out in SEQ ID No.: 12, optionally further wherein the glutamine residue (Q) at position 13 of SEQ ID No.: 12 may be substituted by a leucine residue (L), wherein the lysine residue (K) at position 14 of SEQ ID No.: 12 may be optionally substituted with a threonine residue (T); a HCDR3 (heavy chain CDR3) comprising an amino acid sequence GYNNYKAWFAY as set forth in SEQ ID No.: 13, optionally further wherein the asparagine residue (N) at position 3 of SEQ ID No.: 13 may be substituted by a glycine (G) residue; an LCDR1 (light chain CDR1) comprising an amino acid sequence KASQSVTNDVA iviA / a / zuz ι / u iz / oa as set out in SEQ ID No.: 14, optionally further wherein the threonine (T) residue at position 7 of SEQ ID No.: 14 may be substituted by a serine (S) residue; an LCDR2 (light chain CDR2) comprising an amino acid sequence YASNRYT as set out in SEQ ID No.: 15, wherein optionally the asparagine (N) residue at position 4 of SEQ ID No.: 15 may be substituted by a threonine (T) residue; and an LCDR3 (light chain CDR3) comprising an amino acid sequence QQDYSSLT as set out in SEQ ID No.: 7. In one embodiment, an HCDR2 comprises an amino acid sequence of Formula I: YlDPYNGGSSYN - Xaai - Xaa2- F - K - G (SEQ ID No.: 3), or a subsequence thereof, wherein Xaai is Q (Gln) or L (Leu) and wherein Xaa2 is K (Lys) or T (Thr). In one embodiment, an HCDR3 comprises an amino acid sequence of Formula II: G - Y - Xaai - N- Y- K- A- W- F- A- Y (SEQ ID No.: 4), or a subsequence thereof, wherein Xaai is N (Asp) or G (Gly). In one embodiment, an LCDR1 comprises a Formula III amino acid sequence: K - A - S - Q - S - V -Xaai - N - D - V- A (SEQ ID No.: 5), or a subsequence thereof, wherein Xaai is T (Thr) or S (Ser). In one embodiment, an LCDR2 comprises an amino acid sequence of Formula IV: Y - A - S - Xaai- R - Y - T (SEQ ID No.: 6), or a subsequence thereof, wherein Xaai is T (Thr) or N (Asn). In one aspect, an isolated antibody that binds to a human CD73 polypeptide comprises: an HCDR1 comprising an amino acid sequence SYNMY as stated in SEQ ID No.: 2; an HCDR2 comprising an amino acid sequence YIDPYNGGSSYNLTFKG as stated in SEQ ID No.: 8; an HCDR3 comprising an amino acid sequence GYGNYKAWFAY as stated in SEQ ID No.: 9; an LCDR1 comprising an amino acid sequence KASQSVSNDVA as stated in SEQ ID No.: 10; an LCDR2 comprising an amino acid sequence YASTRYT as stated in SEQ ID No.: 11; and an LCDR3 comprising an amino acid sequence QQDYSSLT as stated in SEQ ID No.: 7. In one aspect, an isolated antibody that binds to a human CD73 polypeptide comprises: an HCDR1 comprising an amino acid sequence SYNMY as stated in SEQ ID No.: 2; an HCDR2 comprising an amino acid sequence YIDPYNGGSSYNQKFKG as stated in SEQ ID No.: 12; an HCDR3 comprising an amino acid sequence GYNNYKAWFAY as stated in SEQ ID No.: 13; an LCDR1 comprising an amino acid sequence KASQSVTNDVA as stated in SEQ ID No.: 14; an LCDR2 comprising an amino acid sequence YASNRYT as stated in SEQ ID No.: 15; and an LCDR3 comprising an amino acid sequence QQDYSSLT as stated in SEQ ID No.: 7. In one embodiment, the antibody comprises a heavy chain framework of the human subgroup IGHV1-3 (optionally together with IGHJ4), optionally IGHV1-3 is IGHV1-3*01. In one embodiment, the humanized antibody comprises a light chain framework of the human subgroup IGKV1-33 (optionally together with IGKJ2), optionally from IGKV1-33*01. The antibody may further comprise one, two, three, four, five or more amino acid substitutions across the human light and / or heavy chain frameworks, to, for example, enhance affinity, stability or other properties of the antibody. Examples of VH and VL amino acid sequences of anti-CD73 antibodies are shown in Example 6 (showing the H4+ chain and Table 5 for 2H4+2Lx antibodies) and Table 1 for the L1-L4 chains. In one aspect, the invention provides an antigen-binding domain or an antibody or antibody fragment that binds to a human CD73 polypeptide, comprising: (a) a CDR-H1 comprising the amino acid sequence of SEQ ID No.: 2; (b) a CDR-H2 comprising the amino acid sequence of SEQ ID No.: 3, 8 or 12, (c) a CDR-H3 comprising the amino acid sequence of SEQ ID No.: 4, 9 or 13; (d) a CDR-LI comprising the amino acid sequence of SEQ ID No.: 5, 10 or 14; (e) a CDR-L2 comprising the amino acid sequence of SEQ ID NOS; 6, 11 or 15; (f) a CDR-L3 comprising the amino acid sequence of SEQ ID No.: 7; and (g) human light and heavy chain structural sequences. In one embodiment, the antibody comprises a heavy chain framework of the human IGHV1-3 subgroup together with IGHJ4; optionally, the antibodies comprise IGHV1-3*01 together with IGHJ4. In one embodiment, the humanized antibody comprises a light chain framework of the human IGKV1-33 subgroup, optionally IGKV1-33*01, together with IGKJ2. Optionally, in any embodiment, the antibody may be specified as an antibody other than a murine parental antibody, e.g., a murine parental antibody having the respective VH and VL of SEQ ID No. 27 and 28), or having the respective VH and VL of SEQ ID No. 40 and 41). Optionally, a human framework comprises one or more mutations, e.g., reverse mutations to introduce a residue present at the particular position in a non-human mammal (e.g., a mouse). In one aspect of any embodiment of the present, the amino acid at position 2 of Kabat's heavy chain is an isoleucine. In one aspect of any embodiment of the present, the amino acid at position 30 of Kabat's heavy chain is an alanine. In one aspect of any embodiment of the present, the amino acid at position 48 of Kabat's heavy chain is an isoleucine. In one aspect of any embodiment of the present, the amino acid at position 69 of Kabat's heavy chain is a leucine. iviA / a / zuz ι / u iz / oa In one aspect of any embodiment of the present, the amino acid at position 73 of Kabat's heavy chain is a lysine. In one embodiment, a VH comprises an isoleucine residue at Kabat position 2, an alanine at position 30, an isoleucine at position 48, a leucine at position 69, and a lysine at position 73. In one aspect of any embodiment of the present, the amino acid at position 67 of the Kabat light chain is a tyrosine. In one aspect of any embodiment of the present, the amino acid at position 60 of the Kabat light chain is either serine or aspartic acid. In one aspect of any embodiment of the present, the amino acid at position 2 of the Kabat light chain is either valine or isoleucine. In one aspect of any embodiment of the present, the amino acid at position 87 of the Kabat light chain is either tyrosine or phenylalanine. In one embodiment, a VL comprises a tyrosine residue at Kabat position 67, a serine at position 60, an isoleucine at position 2, and a tyrosine at position 87. In one aspect of any embodiment of the present, the amino acid at position 28 of Kabat's heavy chain is threonine (T). In one aspect of any embodiment of the present, the amino acid at position 66 of Kabat's heavy chain is arginine (R). In one aspect of any embodiment of the present, the amino acid at position 67 of Kabat's heavy chain is valine (V). In one aspect of any embodiment of the present, the amino acid at position 71 of Kabat's heavy chain is arginine (R). Positions in the VH and VL domains of this document are described using the Kabat numbering system (Kabat et al. (1991) Sequences of Protein of Immunological Interest, 5th ed., United States Public Health Service, National Institute of Health, Bethesda, MD). In one respect, the anti-CD73 antibody comprises a VH domain that has at least approximately 80% sequence identity (e.g., at least approximately 85%, 90%, 95%, 97%, 98% or 99% identity, or 100% identity) with the VH domain of SEQ ID No.: 37 or 42. In one respect, the anti-CD73 antibody or antibody fragment comprises a VL domain having at least approximately 80% sequence identity (e.g., at least approximately 85%, 90%, 95%, 97%, 98% or 99% identity, or 100% identity) with the VL domain of any of SEQ ID No.: 33-36 or 43-46. In one aspect, the anti-CD73 antibody or antibody fragment comprises a VH domain having at least approximately 80% sequence identity (e.g., at least approximately 85%, 90%, 95%, 97%, 98% or 99% identity, or 100% identity) with the VH domain of SEQ ID No.: 42, and a VL domain having at least approximately 80% sequence identity (e.g., at least approximately 85%, 90%, 95%, 97%, 98% or 99% identity, or 100% identity) with the VL domain of any of SEQ ID No.: 43-46. In one aspect, the anti-CD73 antibody or antibody fragment comprises a heavy chain having at least approximately 80% sequence identity (e.g., at least approximately 85%, 90%, 95%, 97%, 98%, or 99% identity, or 100% identity) with the heavy chain of SEQ ID No.: 38 of the H4+L1 antibody. In one embodiment, the antibody or antibody fragment comprises a light chain having at least approximately 80% sequence identity (e.g., at least approximately 85%, 90%, 95%, 97%, 98%, or 99% identity, or 100% identity) with the light chain of SEQ ID No.: 39 of the H4+L1 antibody. In one aspect, the anti-CD73 antibody or antibody fragment comprises a heavy chain having at least approximately 80% sequence identity (e.g., at least approximately 85%, 90%, 95%, 97%, 98%, or 99% identity, or 100% identity) with the heavy chain of SEQ ID No.: 47 of antibody 2H4+2L1. In one embodiment, the antibody or antibody fragment comprises a light chain having at least approximately 80% sequence identity (e.g., at least approximately 85%, 90%, 95%, 97%, 98%, or 99% identity, or 100% identity) with the light chain of SEQ ID No.: 48 of antibody 2H4+2L1. The DNA encoding an antibody can be prepared and placed into an appropriate expression vector for transfection into a suitable host. The host is then used for recombinant production of the antibody, or variants thereof, such as a humanized version of that monoclonal antibody, active fragments of the antibody, chimeric antibodies comprising the antigen-recognizing portion of the antibody, or versions comprising a detectable fraction. The DNA encoding the monoclonal antibodies described herein can be easily isolated and sequenced using conventional procedures (e.g., using oligonucleotide probes that can specifically bind to genes encoding the heavy and light chains of murine antibodies). In one aspect, a nucleic acid encoding either a heavy or light chain of an anti-CD73 antibody of any embodiment herein is provided. Once isolated, the DNA can be placed into expression vectors, which are then transfected into host cells such as E. coli cells, simian COS cells, Chinese hamster ovary (CHO) cells, or myeloma cells that do not otherwise produce immunoglobulin protein, to achieve monoclonal antibody synthesis in the recombinant host cells.Such DNA sequences can be modified for any number of purposes, for example, to humanize antibodies, produce fragments or derivatives, or to modify the antibody sequence, for example, at the antigen-binding site to optimize the antibody's binding specificity. In one embodiment, an isolated nucleic acid sequence encoding a light and / or heavy chain of an antibody is provided, as well as a recombinant host cell comprising (for example, in its genome) such nucleic acid. Recombinant expression in bacteria of antibody-encoding DNA is well known in the art (see, for example, Skerra et al., Curr. Opinion in Immunol., 5, p. 256 (1993); and Pluckthun, Immunol. 130, p. 151 (1992)). Antibody fragments and derivatives (which are encompassed by the term “antibody” or “antibodies” as used in this application, unless otherwise stated or clearly contradicted by the context) may be produced by techniques known in the art. “Fragments” comprise a portion of the intact antibody, usually the antigen-binding site or variable region. Examples of antibody fragments include Fab, Fab', Fab'-SH, F(ab')2, and Fv fragments; diabodies; any antibody fragment that is a polypeptide having a primary structure consisting of an uninterrupted sequence of contiguous amino acid residues (referred to herein as a “single-chain antibody fragment” or “single-chain polypeptide”); and multispecific (e.g., bispecific) antibodies formed from antibody fragments. Typically, an anti-CD73 antibody provided herein has an affinity for a CD73 polypeptide (e.g., a CD73 polypeptide as produced in the Examples herein) in the range of approximately 10⁴ to approximately 10¹¹ M⁻¹ (e.g., approximately 10⁸ to approximately 10¹⁰ M⁻¹). For example, in one particular aspect, the disclosure provides an anti-CD73 antibody that has an average dissociation constant (Kd) of less than 1 x 10⁹ M with respect to CD73, as determined, for example, by surface plasmon resonance (SPR) scanning (such as by analysis with a BIAcore™ SPR analytical device). In a more particular exemplary aspect, the disclosure provides anti-CD73 antibodies that have a Kd of approximately 1 x10'8M to approximately 1 x 10'10M, or approximately 1 x 10'9M to approximately 1 x 10'11M, for CD73. Antibodies can be characterized, for example, by a mean Kd of no more than approximately (i.e., better affinity than) 100, 60, 10, 5, or 1 nanomolar, preferably subnanomolar, or optionally no more than approximately 500, 200, 100, or 10 picomolar. The Kd can be determined, for example, by immobilizing recombinantly produced human CD73 proteins on the surface of a chip, followed by application of the antibody to be tested in solution. In one embodiment, the procedure further comprises a step (d), selecting antibodies from (b) that are capable of competing for binding to CD73 with the control antibody. In one embodiment, anti-CD73 antibodies can be prepared so that they do not have substantial binding to human Fcy receptors (e.g., any one or more of CD16A, CD16B, CD32A, CD32B, and / or CD64). Such antibodies may comprise constant regions of various heavy chains that are known to lack or have low binding to Fcy receptors. Alternatively, antibody fragments that do not comprise (or comprise portions of) constant regions, such as F(ab')2 fragments, can be used to avoid binding to the Fe receptor. Binding to the Fe receptor can be assessed according to procedures known in the art, including, for example, testing the binding of an antibody to the Fe receptor protein in a BIACORE assay.Furthermore, any IgG antibody isotype in which the Fe portion is modified (e.g., by introducing 1, 2, 3, 4, 5, or more amino acid substitutions) to minimize or eliminate binding to Fe receptors can generally be used (see, for example, WO 03 / 101485, a description of which is incorporated herein by reference). Assays for evaluating Fe receptor binding are well known in the art and are described, for example, in WO 03 / 101485. In one embodiment, the antibody may comprise one or more specific mutations in the Fe region that result in “silent Fe” antibodies that have minimal interaction with effector cells. Silenced elicitor functions can be obtained by mutation in the Fe region of the antibodies and have been described in the art: N297A mutation, LALA mutations (Strohl, W., 2009, Curr. Opin. Biotechnol. Vol. 20(6): 685-691); and D265A (Baudino et al., 2008, J. Immunol. 181: 6664-69). See also Heusser et al., WO2012 / 065950, whose descriptions are incorporated herein by reference. In one embodiment, an antibody comprises one, two, three, or more amino acid substitutions in the hinge region. In one embodiment, the antibody is an IgG1 or IgG2 and comprises one, two, or three substitutions at residues 233-236, optionally 233-238 (EU numbering). In one embodiment, the antibody is an IgG4 and comprises one, two, or three substitutions at residues 327,330 and / or 331 (EU numbering). Examples of silent Fe IgG1 antibodies include the LALA mutation, which comprises the L234A and L235A mutations in the Fe amino acid sequence of IgG1. Another example of a silent Fe mutation is a mutation at residue D265, or at D265 and P329, for example, as used in an IgG1 antibody such as the DAPA mutation (D265A, P329A) (US 6,737,056). Another silent IgG1 antibody comprises a mutation at residue N297 (for example, N297A, N297S mutation), resulting in aglycosylated / non-glycosylated antibodies. Other silent mutations include substitutions at residues L234 and G237 (L234A / G237A); Substitutions in waste products S228, L235 and R409 (S228P / L235E / R409K, T, M, L); substitutions in waste products H268, V309, A330 and A331 (H268Q / V309L / A330S / A331S); substitutions in waste products C220, C226, C229 and P238 (C220S / C226S / C229S / P238S); substitutions in waste products C226, C229, E233,L234 and L235 (C226S / C229S / E233P / L234V / L235A); substitutions in wastes K322, L235 and L235 (K322A / L234A / L235A); substitutions in wastes L234, L235E and P331 (L234F / L235E / P331S); substitutions in wastes 234, 235 and 297; substitutions in wastes E318, K320 and K322 (L235E / E318A / K320A / K322A); substitutions in wastes (V234A, G237A, P238S); substitutions in wastes 243 and 264; substitutions in wastes 297 and 299; substitutions such that Residues 233, 234, 235, 237 and 238 as defined by the EU numbering system comprise a selected sequence of PAAAP, PAAAS and SAAAS (see WO2011 / 066501). In one embodiment, the antibody may comprise one or more specific mutations in the Fe region. For example, such an antibody may comprise an Fe domain of human IgG1 origin, comprising a mutation in Kabat residues 234, 235, 237, 330, and / or 331. One example of such an Fe domain comprises substitutions in Kabat residues L234, L235, and P331 (e.g., L234A / L235E / P331S or L234F / L235E / P331S). Another example of such an Fe domain comprises substitutions in Kabat residues L234, L235, G237, and P331 (e.g., L234A / L235E / G237A / P331S). Yet another example of such an Fe domain comprises substitutions in Kabat residues L234, L235, G237, A330, and P331 (for example, L234A / L235E / G237A / A330S / P331S).In one embodiment, the antibody comprises an Fe domain, optionally of human IgG1 type, comprising: an L234Xi substitution, an L235X2 substitution, and a P331Xs substitution, wherein Xi is any amino acid residue other than leucine, X2 is any amino acid residue other than leucine, and X3 is any amino acid residue other than proline; optionally wherein X1 is an alanine or phenylalanine or a conservative substitution thereof; optionally wherein X2 is glutamic acid or a conservative substitution thereof; optionally wherein X3 is a serine or a conservative substitution thereof.In another embodiment, the antibody comprises an Fe domain, optionally of the human IgG1 isotype, comprising: an L234X1 substitution, an L235X2 substitution, a G237X4 substitution, and a P331X4 substitution, wherein X1 is any amino acid residue other than leucine, X2 is any amino acid residue other than leucine, X3 is any amino acid residue other than glycine, and X4 is any amino acid residue other than proline; optionally wherein X1 is alanine or phenylalanine or a conservative substitution thereof; optionally wherein X2 is glutamic acid or a conservative substitution thereof; optionally, X3 is alanine or a conservative substitution thereof; optionally, X4 is serine or a conservative substitution thereof.In another embodiment, the antibody comprises an Fe domain, optionally of the human IgG1 isotype, comprising: an L234Xi substitution, an L235X2 substitution, a G237X4 substitution, a G330X4 substitution, and a P331Xs substitution, wherein X1 is any amino acid residue other than leucine, X2 is any amino acid residue other than leucine, X3 is any amino acid residue other than glycine, X4 is any amino acid residue other than alanine, and X5 is any amino acid residue other than proline; optionally wherein X1 is alanine or phenylalanine or a conservative substitution thereof; optionally wherein X2 is glutamic acid or a conservative substitution thereof; optionally, X3 is alanine or a conservative substitution thereof; optionally, X4 is serine or a conservative substitution thereof; optionally, X5 is serine or a conservative substitution thereof. In the abbreviated notation used here, the format is: wild-type residue: position in the polypeptide: mutant residues, where the residue positions are indicated according to the EU numbering according to Kabat. In one embodiment, an antibody comprises a heavy-chain constant region comprising the amino acid sequence below, or an amino acid sequence at least 90%, 95%, or 99% identical thereto but retaining the amino acid residues at Kabat positions 234, 235, and 331 (underlined): ASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPV TVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLG TQTYICNVNHKPSNTKVDKRVEPKSCDKTHTCPPCPAPEA EGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKF NWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWL NGKEYKCKVSNKALPASIEKTISKAKGQPREPQVYTLPPSR EEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTP PVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNH YTQKSLSLSPGK (SEQ ID No.: 16). In one embodiment, an antibody comprises a heavy-chain constant region comprising the amino acid sequence below, or an amino acid sequence at least 90%, 95%, or 99% identical thereto but retaining amino acid residues at Kabat positions 234, 235, and 331. (underlined): ASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPV TVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLG TQTYICNVNHKPSNTKVDKRVEPKSCDKTHTCPPCPAPEF EGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKF NWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWL NGKEYKCKVSNKALPASIEKTISKAKGQPREPQVYTLPPSR EEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTP PVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNH YTQKSLSLSPGK (SEQ ID No.: 17). In one embodiment, an antibody comprises a heavy-chain constant region comprising the amino acid sequence below, or an amino acid sequence at least 90%, 95%, or 99% identical thereto but retaining amino acid residues at Kabat positions 234, 235, 237, 330, and 331 (underlined): > κ C ι\ 44 j ASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPV ~ σ TVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLG “ TQTYICNVNHKPSNTKVDKRVEPKSCDKTHTCPPCPAPEA EGAPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKF NWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWL NGKEYKCKVSNKALPSSIEKTISKAKGQPREPQVYTLPPSR EEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTP PVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNH YTQKSLSLSPGK (SEQ ID No.: 18). In one embodiment, an antibody comprises a heavy-chain constant region comprising the following amino acid sequence, or a sequence at least 90%, 95%, or 99% identical thereto but retaining amino acid residues at Kabat positions 234, 235, 237, and 331. (underlined): ASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPV TVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLG TQTYICNVNHKPSNTKVDKRVEPKSCDKTHTCPPCPAPEA EGAPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKF NWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWL NGKEYKCKVSNKALPASIEKTISKAKGQPREPQVYTLPPSR EEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTP PVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNH YTQKSLSLSPGK (SEQ ID No.: 19). Fe-silent antibodies result in low or no ADCC activity, meaning that an Fe-silent antibody exhibits ADCC activity below 50% specific cell lysis. Preferably, an antibody substantially lacks ADCC activity; for example, the Fe-silent antibody exhibits ADCC (specific cell lysis) activity below 5% or below 1%. Fe-silent antibodies can also result in the absence of FcνR-mediated crosslinking of CD73 on the surface of a CD73-expressing cell. In one embodiment, the antibody has a substitution in a heavy chain constant region in one, two, three, four, five or more of the selected residues from the group consisting of: 220, 226, 229, 233, 234, 235, 236, 237, 238, 243, 264, 268, 297, 298, 299, 309, 310, 318, 320, 322, 327, 330, 331 and 409 (the numbering of the residues in the heavy chain constant region is according to the EU numbering according to Kabat). In one embodiment, the antibody comprises a substitution at residues 234, 235, and 322. In one embodiment, the antibody comprises a substitution at residues 234, 235, and 331. In one embodiment, the antibody comprises a substitution at residues 234, 235, 237, and 331. In one embodiment, the antibody comprises a substitution at residues 234, 235, 237, 330, and 331. In one embodiment, the Fe domain is of the human IgG1 subtype. Amino acid residues are indicated according to the EU numbering according to Kabat. In one embodiment, the antibody comprises an Fe domain that includes an amino acid substitution that enhances binding to human FcRn polypeptides to increase the antibody's in vivo half-life. Exemplary mutations are described in Strohl, W., 2009, Curr. Opin. BiotechnoL Vol. 20 (6): 685-691, a description of which is incorporated herein by reference. Examples of substitutions used in human IgG1 isotype antibodies are substitutions at Kabat residues M252, S254, and T256; substitutions at residues T250 and M428; substitutions at residue N434; substitutions at residues H433 and N434; substitutions at residues T307, E380, and N434; and substitutions at residues T307, E380, and N434. Substitutions in wastes M252, S254, T256, H433, N434 and 436; substitutions in waste I253; substitutions in wastes P257, N434, D376 and N434.An antigen-binding compound can be evaluated at any desired stage for its ability to inhibit the enzymatic activity of CD73, in particular to block the 5'-nucleotidase activity of CD73 and reduce adenosine production by a CD73-expressing cell, and in turn restore lymphocyte activity and / or alleviate adenosine-mediated lymphocyte inhibition. The ability of an antibody to inhibit the enzymatic activity of CD73 can be tested in a cell-free assay using recombinant soluble human CD73 (as dimers) and AMP, where the conversion of AMP to adenosine (and / or inhibition thereof) is detected either directly (e.g., by measuring substrates and products, i.e., AMP, adenosine, and / or phosphate) or indirectly. In one example, AMP and / or adenosine are detected by HPLC before and after incubation of the test compound with recombinant CD73. The CD73-inhibitory activity of an antibody can also be assessed in many other ways. For example, in an indirect assay, a luciferase-based reagent (e.g., the CelITiter-Glo® system available from Promega) is used to detect the disappearance of AMP. The luciferase reaction in the assay is inhibited by AMP. The addition of the CD73 enzyme to the reaction degrades the AMP and relieves the inhibition, producing a detectable signal. Assays using soluble CD73 will include tests under conditions where antibodies are provided in substantial molar excess (e.g., 10x, 20x, 50x, 100x, etc.) against CD73 polypeptide dimers. When provided in molar excess relative to the enzyme, anti-CD73 antibodies will no longer be able to form multimeric complexes of antibodies and CD73 dimers; antibodies that retain inhibition of CD73 enzyme activity can then be selected. The ability of an antibody to inhibit the enzymatic activity of CD73 5'-ectonucleotidase can also be tested alternatively or additionally in a cell assay (using cells expressing CD73). Advantageously, antibodies can first be tested or screened in the cell-free assay to identify antibodies that block the enzyme's activity, thus reducing the likelihood of selecting antibodies that inhibit CD73 by causing CD73 internalization, and then tested as purified antibodies in cell assays. Cell assays can be carried out as shown in the Examples in this document or as disclosed in PCT Publication No. WO2016 / 055609, which is incorporated herein by reference. For example, CD73-expressing cells (e.g., the MDA-MB-231 cell line) are seeded in 96-well flat-bottom plates in the presence of anti-CD73 antibodies and incubated, as detailed in WO2016 / 055609.AMP is added to the cells and incubated at 4°C (to avoid downregulation of CD73). The plates are then centrifuged and the supernatant transferred to a 96-well flat-bottom culture plate. The free phosphate produced by the hydrolysis of AMP to adenosine is then quantified. A decrease in the hydrolysis of AMP to adenosine in the presence of the antibody indicates that the antibody inhibits cellular CD73. In one embodiment, an antibody preparation causes at least a 50% decrease in the enzymatic activity of a CD73 polypeptide, preferably a decrease of at least 60%, 70% or 80% in the enzymatic activity of a CD73 polypeptide (e.g., a soluble homodimeric CD73 polypeptide; cell-expressed CD73). The activity of an antibody can also be measured in an indirect assay to determine its ability to modulate lymphocyte activity, for example, to alleviate adenosine-mediated inhibition of lymphocyte activity, or to induce activation of lymphocyte activity. This can be addressed, for example, using a cytokine release assay. In another example, an antibody can be evaluated in an indirect assay for its ability to modulate lymphocyte proliferation. In one embodiment, an antibody neutralizes the 5'-ectonucleotidase activity of a homodimeric human CD73 polypeptide in solution. In another embodiment, the antibody binds to and inhibits the enzymatic activity of a soluble human CD73 polypeptide, specifically an antibody that neutralizes CD73-mediated AMP catabolism to adenosine. In yet another embodiment, the antibody binds bivalently to CD73. In another embodiment, the antibody is a non-depleted antibody, for example, an Fe silent antibody that substantially lacks binding to human Fcγ receptors. In yet another embodiment, the antibody neutralizes CD73 in solution without relying on the induction of CD73 polypeptide oligomers: anti-CD73 antibody. In one embodiment, an antibody specifically binds to human CD73 on the surface of a cell and is able to neutralize the 5'-ectonucleotidase activity of a soluble human CD73 polypeptide. In one embodiment, the antibody does not induce oligomerization of the soluble CD73. In one embodiment, an antibody specifically binds to human CD73 on the surface of a cell and is able to neutralize the 5'-ectonucleotidase activity of Cellular CD73 (CD73 expressed by cells). In one embodiment, an antibody specifically binds to and neutralizes the 5'-ectonucleotidase activity of human CD73 on the cell surface and is not internalized into CD73-expressing cells upon binding to CD73. The antibody does not cause multimerization and subsequent internalization of CD73. In another embodiment, an antibody binds to and is able to inhibit the enzymatic activity of a recombinant human CD73 polypeptide in solution, wherein said antibody is not internalized into CD73-expressing cells. In another embodiment, the non-internalizing antibody binds to CD73 bivalently. In another embodiment, the antibody is a non-depleting antibody, e.g., an iron-silenced antibody. The antibody is able to neutralize the 5'-ectonucleotidase activity of a dimeric human CD73 polypeptide in solution, furthermore, without relying on the induction of CD73 polypeptide oligomers: anti-CD73 antibodies. In one embodiment, an antibody specifically binds bivalently to human CD73 polypeptides and inhibits the enzymatic activity of cellular human CD73 (and optionally recombinant soluble human CD73), wherein said antibody does not induce or enhance intracellular internalization of CD73 in CD73-expressing cells. Preferably, the antibody substantially lacks binding to the Fcy receptor (e.g., via its Fe domain). In one aspect, an antibody binds specifically to human CD73 on the surface of a cell pre-incubated with AMP and is able to neutralize its 5'-ectonucleotidase activity. Alternatively, the neutralization of 5'-ectonucleotidase activity is determined by assessing the neutralization of 5'-ectonucleotidase activity in cells expressing CD73 (e.g., MDA-MB-231 cells) by quantifying the hydrolysis of AMP to adenosine. In one aspect, the neutralization of CD73 5'-ectonucleotidase activity expressed by a cell is determined by assessing the ability of an antibody to increase T cell proliferation when such T cells are induced to proliferate in vitro (e.g., by TCR co-stimulation, stimulation of CD3 and CD28 signaling, e.g., by contacting T cells with beads functionalized with CD3 agonists and CD28 agonists) in the presence of AMP (e.g., exogenously added AMP). In another aspect, the neutralization of the 5'-ectonucleotidase activity assay is assessed using the T cell proliferation assay described in the section entitled “Procedures” in the Examples. Antibodies can be characterized by their ability to bind to cells transfected with CD73 mutants, compared to the ability of the anti-CD73 antibody to bind to the wild-type CD73 polypeptide (e.g., SEQ ID No.: 1). A reduction in the binding between an anti-CD73 antibody and a mutant CD73 polypeptide means there is a reduction in binding affinity (e.g., as measured by procedures known as the FACS test of cells expressing a particular mutant, or the Biacore test of binding to mutant polypeptides) and / or a reduction in the total binding capacity of the anti-CD73 antibody (e.g., as evidenced by a decrease in Bmax on a graph of anti-CD73 antibody concentration versus polypeptide concentration).A significant reduction in binding indicates that the mutated residue is directly involved in binding to the anti-CD73 antibody or is very close to the binding protein when the anti-CD73 antibody binds to CD73. In some embodiments, a significant reduction in binding means that the affinity and / or binding capacity between an anti-CD73 antibody and a mutant CD73 polypeptide is reduced by more than 40%, more than 50%, more than 55%, more than 60%, more than 65%, more than 70%, more than 75%, more than 80%, more than 85%, more than 90%, or more than 95% relative to the binding between the antibody and a wild-type CD73 polypeptide. In certain embodiments, binding is reduced below detectable limits. In some embodiments, a significant reduction in binding is evident when the binding of an anti-CD73 antibody to a mutant CD73 polypeptide is less than 50% (e.g., less than 45%, 40%, 35%, 30%, 25%, 20%, 15%, or 10%) of the binding observed between the anti-CD73 antibody and a wild-type CD73 polypeptide. In one respect, anti-CD73 antibodies have reduced binding to a CD73 polypeptide that has a mutation at residue K136 (with reference to SEQ ID No.: 1); optionally, the mutant CD73 polypeptide has the mutation: K136A. In one respect, anti-CD73 antibodies have reduced binding to a CD73 polypeptide that has a mutation in a selected residue from the group consisting of: K97, E125, Q153 and K330 (with reference to SEQ ID No.: 1); optionally, the mutant CD73 polypeptide has the mutations: K97A, E125A, Q153A and / or K330A (e.g., K97A, E125A and K330A; K97A, E125A and / or Q153A). In one aspect, anti-CD73 antibodies have reduced binding to a CD73 polypeptide that has a mutation in a selected residue from the group consisting of: A99, E129, K133, E134 and A135 (with reference to SEQ ID No.: 1); optionally, the mutant CD73 polypeptide has the mutations: A99S, E129A, K133A, E134N and / or A135S. Optionally, in one aspect, anti-CD73 antibodies do not have reduced binding to a CD73 polypeptide having a mutation in a selected residue from the group consisting of: Q70, R73, A74, A107 and R109 (with reference to SEQ ID No.: 1); optionally, the mutant CD73 polypeptide has the mutations: A99S, Q70S, R73A, A74E, A107I and / or R109G. In one respect, anti-CD73 antibodies bind to an epitope on CD73 comprising residue K136 (with reference to SEQ ID No.: 1). In one respect, anti-OD73 antibodies bind to an epitope on CD73 comprising one, two, three, or four of the residues selected from the group consisting of K97, E125, Q153, and K330 (with reference to SEQ ID No.: 1). In one respect, anti-CD73 antibodies bind to an epitope on CD73 comprising one, two, three, four, or five of the residues selected from the group consisting of A99, E129, K133, E134, and A135 (with reference to SEQ ID No.: 1). In one aspect, anti-CD73 antibodies bind to an epitope on CD73 comprising one, two, three, four, five, or more of the residues selected from the group consisting of K97, A99, E125, E129, K133, E134, A135, and K136 (with reference to SEQ ID No.: 1). Optionally, in one aspect, anti-CD73 antibodies do not bind to an epitope on CD73 comprising one, two, three, four, or five of the residues selected from the group consisting of Q70, R73, A74, A107, and R109 (with reference to SEQ ID No.: 1). An anti-CD73 antibody may be incorporated into a pharmaceutical formulation comprising a concentration of 1 mg / mL to 500 mg / mL, wherein said formulation has a pH of 2.0 to 10.0. The formulation may further comprise a buffer system, preservative(s), tonicity agent(s), chelating agent(s), stabilizers, and surfactants. In one embodiment, the pharmaceutical formulation is an aqueous formulation, i.e., a formulation comprising water. Typically, said formulation is a solution or a suspension. In a further embodiment, the pharmaceutical formulation is an aqueous solution. The term “aqueous formulation” is defined as a formulation comprising at least 50% w / w water. Likewise, the term “aqueous solution” is defined as a solution comprising at least 50% w / w water, and the term “aqueous suspension” is defined as a suspension comprising at least 50% w / w water. In another embodiment, the pharmaceutical formulation is a lyophilized formulation, to which the physician or patient adds solvents and / or diluents before use. In another embodiment, the pharmaceutical formulation is a dry formulation (e.g., lyophilized or spray-dried) ready to use without prior dissolution. In an additional aspect, the pharmaceutical formulation comprises an aqueous solution of said antibody and a buffer, wherein the antibody is present at a concentration of 1 mg / ml or higher, and wherein said formulation has a pH of approximately 2.0 to approximately 10.0. In another embodiment, the pH of the formulation is in the selected range from the list consisting of approximately 2.0 to approximately 10.0, approximately 3.0 to approximately 9.0, approximately 4.0 to approximately 8.5, approximately 5.0 to approximately 8.0, and approximately 5.5 to approximately 7.5. In a further embodiment, the buffer is selected from the group consisting of sodium acetate, sodium carbonate, citrate, glycylglycine, histidine, glycine, lysine, arginine, sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium phosphate, and tris(hydroxymethyl)-aminomethane, bicine, tricine, malic acid, succinate, maleic acid, fumaric acid, tartaric acid, aspartic acid, or mixtures thereof. Each of these specific buffers constitutes an alternative embodiment. In a further embodiment, the formulation further comprises a pharmaceutically acceptable preservative. In a further embodiment, the formulation further comprises an isotonic agent. In a further embodiment, the formulation also comprises a chelating agent. In a further embodiment, the formulation further comprises a stabilizer. In a further embodiment, the formulation further comprises a surfactant. For convenience, reference is made to Remington: The Science and Practice of Pharmacy, 19th edition, 1995. Other ingredients may be present in the peptide's pharmaceutical formulation. These additional ingredients may include wetting agents, emulsifiers, antioxidants, bulking agents, tonicity modifiers, chelating agents, metal ions, oily vehicles, proteins (e.g., human serum albumin, gelatin, or other proteins), and a hybrid ion (e.g., an amino acid such as betaine, taurine, arginine, glycine, lysine, or histidine). These additional ingredients should not adversely affect the overall stability of the pharmaceutical formulation. Pharmaceutical compositions containing an antibody can be administered to a patient requiring such treatment at various sites, such as topical sites (e.g., on the skin and mucous membranes), sites that prevent absorption (e.g., intravascular, intravenous, intramuscular, intramuscular, intravenous, lingual, sublingual, buccal, oral, intragastric, nasal, pulmonary (e.g., via the bronchioles and alveoli or a combination thereof), epidermal, dermal, transdermal, vaginal, rectal, ocular (e.g., via the conjunctiva), urethral, ​​and parenteral routes. Diagnosis and treatment of neoplasms iviA / a / zuz ι / u iz / oa Procedures are also provided for treating an individual, particularly a human patient, using an anti-CD73 antibody or antibody fragment as described herein. In one embodiment, the disclosure provides for the use of an antibody or antibody fragment as described herein in the preparation of a pharmaceutical composition for administration to a human patient. Typically, the patient suffers from or is at risk of cancer or an infectious disease (e.g., viral or bacterial infection). For example, in one aspect, a procedure is provided for restoring or enhancing the activity of immune cells (e.g., lymphocytes) in a patient in need, comprising the step of administering a neutralizing anti-CD73 antibody to that patient. In another embodiment, the procedure is aimed at increasing the activity of immune cells (e.g., T cells) in patients who have a disease such as cancer or an infectious disease in which increased immune cell activity and / or infiltration at a disease site (e.g., tumor environment or site of infection) is beneficial or is caused or characterized by immunosuppression, immunosuppressive cells, or, for example, adenosine-generated CD4 T cells, CD8 T cells, or B cells. These procedures will be particularly useful for treating individuals with tumors where the tumor microenvironment (and CD73-mediated adenosine production within the tumor) is suspected of contributing to a lack of recognition by the immune system (immune escape). The tumor environment may, for example, be characterized by immune cells expressing CD73, such as CD4 T cells, CD8 T cells, B cells, and / or tumor cells expressing CD73. Anti-CD73 procedures and antibodies can be used for the treatment and / or prevention of a variety of cancers and other proliferative diseases. Because these procedures work by reducing adenosine, which inhibits the antitumor activity of lymphocytes, and possibly additionally increasing ATP, which can enhance lymphocyte antitumor activity, they are applicable to a wide range of cancers, including, in particular, solid tumors in which adenosine in the tumor microenvironment may play an important role in suppressing the antitumor immune response. In one embodiment, a human patient treated with an anti-CD73 antibody has liver cancer, bone cancer, pancreatic cancer, skin cancer, head or neck cancer, breast cancer, lung cancer, non-small cell lung cancer (NSCLC), castration-resistant prostate cancer (CRPC), melanoma, uterine cancer, colon cancer,rectal cancer, anal region cancer, stomach cancer, testicular cancer, uterine cancer, fallopian tube carcinoma, endometrial carcinoma, cervical carcinoma, vaginal carcinoma, vulvar carcinoma, non-Hodgkin lymphoma, esophageal cancer, small bowel cancer, endocrine system cancer, thyroid gland cancer, parathyroid gland cancer, adrenal gland cancer, soft tissue sarcoma, urethral cancer, penile cancer, childhood solid tumors, lymphocytic lymphoma, bladder cancer, kidney or ureter cancer, renal pelvis carcinoma, central nervous system (CNS) neoplasm, primary CNS lymphoma, tumor angiogenesis, spinal cord tumor, brainstem glioma, pituitary adenoma, Kaposi's sarcoma, squamous cell carcinoma, environmentally induced cancers, including asbestos-induced cancers, neoplasms hematological conditions that include, for example, multiple myeloma,B-cell lymphoma, Hodgkin lymphoma / primary mediastinal B-cell lymphoma, non-Hodgkin lymphomas, acute myeloid lymphoma, chronic myelogenous leukemia, chronic lymphoid leukemia, follicular lymphoma, diffuse large B-cell lymphoma, Burkitt lymphoma, large cell lymphoma, precursor of B-cell lymphoblastic lymphoma, mantle cell lymphoma, acute lymphoblastic leukemia, mycosis fungoides, anaplastic large cell lymphoma, T-cell lymphoma and precursor of T-cell lymphoblastic lymphoma, and any combination of these cancers. This disclosure also applies to the treatment of metastatic cancers. Patients may be evaluated or selected for one or more of the clinical attributes described above before, during, or after treatment. Because anti-CD73 procedures and antibodies operate by reducing adenosine, which inhibits the activity and / or infiltration of immune cells (e.g., lymphocytes), and possibly additionally increasing ATP, which can increase lymphocyte activity, they are applicable to a wide range of infectious diseases, including preferably any infection caused by viruses, bacteria, protozoa, molds, or fungi. In one embodiment, the anti-CD73 antibody is administered in an amount effective to achieve and / or maintain in an individual (e.g., for 1, 2, 3, or 4 weeks and / or until subsequent administration of the antigen-binding compound) a blood concentration of at least CE0, optionally CE70, and optionally substantially CE100, for the neutralization of CD73 enzyme activity. In one embodiment, the active amount of anti-CD73 antibody is an amount effective to achieve CE0, optionally CE70, and optionally substantially CE100, for the neutralization of CD73 enzyme activity in an extravascular tissue of an individual. In one embodiment, the active amount of anti-CD73 antibody is an amount effective to achieve (or maintain) in an individual CE0, optionally CE70, and optionally substantially CE100, for the inhibition or neutralization of CD73 enzyme activity. In one embodiment, the anti-CD73 antibody is administered in an amount effective to achieve and / or maintain (e.g., for 1, 2, 3, 4 weeks and / or until subsequent administration of anti-CD73 antibody) in an individual a blood concentration of at least CEso, optionally CE70, and optionally substantially CE100, for the inhibition of CD73-mediated AMP to adenosine catabolism (e.g., by assessing the neutralization of 5'-ectonucleotidase activity in MDA-MB-231 cells by quantifying the hydrolysis of AMP to adenosine). In another embodiment, the amount of anti-CD73 antibody is an amount effective to achieve (or maintain) CEso, optionally CE70, and optionally substantially CE100, for the inhibition of CD73-mediated AMP to adenosine catabolism in an individual's extravascular tissue. In one embodiment, a method is provided for treating or preventing cancer in an individual. The method comprises administering to an individual suffering from a disease an anti-CD73 antibody in an amount that achieves or maintains, for a specified time period, a circulating concentration, optionally in an extravascular tissue of interest (e.g., the tumor or tumor environment), that is greater than the concentration required for 50%, 70%, or whole CD73-expressing cells with receptor saturation in circulation (e.g., 90%) (e.g., as assessed in PBMC). Optionally, the concentration achieved is at least 20%, 50%, or 100% greater than the concentration required for the specified receptor saturation. In one embodiment, a method is provided for treating or preventing cancer in an individual. The method comprises administering to the individual an anti-CD73 antibody in an amount that achieves or maintains, for a specified time period, a circulating concentration, optionally in an extravascular tissue of interest (e.g., the tumor or tumor environment), that is higher than CE50, optionally CE70, or optionally CE100, for binding to CD73-expressing cells (e.g., as assessed by titrating the anti-CD73 antibody in CD73-expressing cells, e.g., MDA-MB-231 cells). Optionally, the concentration achieved is at least 20%, 50%, or 100% higher than CE50, optionally CE70, or optionally CE100, for binding to CD73-expressing cells. In any embodiment, the antibody may have, for example, a CE50, optionally CE70 or optionally CE100, to bind to cells expressing CD73 in human PBMCs of between 0.5-100 ng / ml, optionally 1-100 ng / ml, optionally 30-100 ng / ml, for example, approximately 30-90 ng / ml, (for example, as assessed by titrating the anti-CD73 antibody in cells expressing CD73, for example, MDA-MB-231 cells). The EC50 for neutralizing CD73 enzyme activity with the anti-CD73 antibody can be, for example, between approximately 0.01 pg / ml and 1 pg / ml, optionally between 0.1 pg / ml and 10 pg / ml, or optionally between 0.1 pg / ml and 1 pg / ml. For example, the EC50 can be approximately 0.1 pg / ml, approximately 0.2 pg / ml, or approximately 0.3 pg / ml. Therefore, a quantity of this anti-CD73 antibody is administered, for example, to achieve and / or maintain a blood concentration of at least 0.1 pg / ml, optionally at least 0.2 pg / ml, optionally at least 1 pg / ml, or optionally at least 2 pg / ml. When targeting tissues outside the vasculature (the tumor environment, for example, in the treatment of solid tumors), a dose approximately 10 times greater is typically considered to be required compared to the dose that provides the corresponding concentration in the circulation. An amount of anti-CD73 antibody administered to achieve (and / or maintain) a circulating (blood) concentration of approximately 1 pg / ml, 2 pg / ml, 10 pg / ml, or 20 pg / ml is expected to achieve (and / or maintain) an extravascular tissue (e.g., tumor tissue) concentration of approximately 0.1 pg / ml, 0.2 pg / ml, 1 pg / ml, or 2 pg / ml, respectively. In one embodiment, an anti-CD73 antibody is administered, for example, in an amount suitable for achieving and / or maintaining a concentration in the tissue (e.g., tumor environment) of at least 0.1 pg / ml, optionally at least 0.2 pg / ml, optionally at least 1 pg / ml, or optionally at least 2 pg / ml. The antibody can be administered, for example, in an amount to achieve and / or maintain a blood concentration of at least approximately 1 pg / ml, 2 pg / ml, 10 pg / ml, or 20 pg / ml, for example, between 1-100 pg / ml, 10-100 pg / ml, 1-50 pg / ml, 1-20 pg / ml, or 110 pg / ml. The administered amount can be adjusted to provide maintenance of the desired concentration for a specific period of time after administration (e.g., 1, 2, 3, 4 weeks, etc.). In some embodiments, an amount of anti-CD73 antibody is administered to achieve a concentration in blood (serum) or in extravascular tissue (e.g., tumor environment) that corresponds at least to EC70 or EC100 for neutralizing the enzymatic activity of CD73. The antibody may be administered, for example, in an amount to achieve and / or maintain a concentration in blood or extravascular tissue (e.g., tumor environment) of at least approximately 1 pg / ml, 2 pg / ml, 10 pg / ml, or 20 pg / ml. The EC50, EC70, or EC100 can be evaluated, for example, in a cell assay for the neutralization of CD73 enzyme activity (e.g., neutralization of 5' ectonucleotidase activity in MDA-MB-231 cells by quantifying the hydrolysis of AMP to adenosine). “EC50” with respect to the neutralization of CD73 enzyme activity refers to the efficient concentration of anti-CD73 antibody that produces 50% of its maximum response or effect with respect to neutralizing the enzyme activity. “EC70” with respect to the neutralization of CD73 enzyme activity refers to the efficient concentration of anti-CD73 antibody that produces 70% of its maximum response or effect. “CE100” with respect to the neutralization of CD73 enzyme activity, refers to the efficient concentration of anti-CD73 antibody that produces its substantially maximum response or effect with respect to such neutralization of enzyme activity. In some embodiments, particularly for the treatment of solid tumors, the concentration achieved is designed to lead to a concentration in the tissues (outside the vasculature, for example, in the tumor or tumor environment) that corresponds at least to EC50 for neutralization of enzymatic activity, optionally to approximately, or at least approximately, EC100. In one embodiment, the amount of anti-CD73 antibody is between 1 and 20 mg / kg of body weight. In one embodiment, the amount is administered to an individual weekly, every two weeks, monthly, or every two months. In one embodiment, a method is provided for treating a human individual, comprising administering to the individual an effective quantity of an anti-CD73 antibody from the disclosure during at least one administration cycle (optionally at least 2, 3, 4, or more administration cycles), wherein the cycle is a period of eight weeks or less, and wherein for each of the at least one cycle, one, two, three, or four doses of the anti-CD73 antibody are administered at a dose of 1-20 mg / kg of body weight. In one embodiment, the anti-CD73 antibody is administered by intravenous infusion. Suitable treatment protocols for treating a human include, for example, administering to the patient an amount of an anti-CD73 antibody as described herein, wherein the procedure comprises at least one administration cycle in which at least one dose of the anti-CD73 antibody is administered. Optionally, at least 2, 3, 4, 5, 6, 7, or 8 doses of the anti-CD73 antibody are administered. In one embodiment, the administration cycle is between 2 and 8 weeks. A patient with cancer can be treated with the anti-CD73 antibody without a prior screening step to assess CD73 expression in cells within the tumor microenvironment (e.g., tumor cells, CD4 T cells, CD8 T cells, B cells). Optionally, treatment procedures may include a screening step for the CD73 nucleic acid or polypeptide in a biological sample from an individual's tumor (e.g., cancerous tissue, tissue proximal to or at the periphery of a cancer, tissue adjacent to the cancer, adjacent non-tumor tissue, or adjacent normal tissue). A determination that a biological sample comprises cells expressing CD73 (e.g., expressing CD73 at a high level, high-intensity staining with an anti-CD73 antibody, compared to a reference, e.g., healthy tissue) indicates that the patient has a cancer that may greatly benefit from treatment with the anti-CD73 antibody.In one embodiment, the procedure comprises determining the expression level of a nucleic acid or CD73 polypeptide in a biological sample and comparing the level to a reference level corresponding to a healthy individual. A determination that a biological sample comprises cells expressing the nucleic acid or CD73 polypeptide at a level that is elevated compared to the reference level (e.g., healthy tissue) indicates that the patient has a cancer that may be advantageously treated with an anti-CD73 antibody of the disclosure. Optionally, detecting a CD73 polypeptide in a biological sample comprises detecting the CD73 polypeptide expressed on the surface of a malignant cell, or a CD4 T cell, a CD8 T cell, or a B cell. Determining whether an individual has a cancer characterized by cells expressing a CD73 polypeptide may involve, for example, obtaining a biological sample (e.g., by performing a biopsy) from the individual comprising cells from the cancer environment (e.g., tumor or tissue adjacent to the tumor), contacting these cells with an antibody that binds to a CD73 polypeptide, and detecting whether the cells express CD73 on their surface. Optionally, determining whether an individual has cells expressing CD73 may involve performing an immunohistochemical assay. iviA / a / zuz ι / u iz / oa Antibody compositions can be used advantageously in combination with one or more other therapeutic agents, including agents normally used for the specific therapeutic purpose for which the antibody is administered. The additional therapeutic agent will normally be administered in amounts and treatment regimens typically used for that agent as monotherapy for the particular disease or condition being treated. Such therapeutic agents include, but are not limited to, anticancer agents and chemotherapeutic agents. In one embodiment, anti-CD73 antibodies enhance the efficacy of agents that neutralize the inhibitory activity of human PD-1, for example, by inhibiting the interaction between PD-1 and PD-L1. Accordingly, in one embodiment, the second or additional therapeutic agent is an antibody or other agent that neutralizes the inhibitory activity of human PD-1. Programmed cell death 1 (PD-1) (also called programmed cell death 1) is an inhibitory member of the CD28 receptor family. The full human PD-1 sequence can be found using the GenBank accession number U64863. Inhibition or neutralization of PD-1 inhibitory activity may involve the use of a polypeptide agent (e.g., an antibody, a polypeptide fused to an Fe domain, an immunoadhesin, etc.) that prevents PD-L1-induced PD-1 signaling. Currently, at least six agents that block the PD-1 / PD-L1 pathway are marketed or under clinical evaluation. One such agent is BMS-936558 (Nivolumab / ONO-4538, Bristol-Myers Squibb; formerly MDX-1106).Nivolumab (trade name Opdivo®) is an FDA-approved, fully human anti-PD-L1 IgG4 mAb that inhibits the binding of PD-L1 ligand to PD-1 and CD80 and is described as a 5C4 antibody in WO 2006 / 121168, which is incorporated herein by reference. For patients with melanoma, the most significant odds ratio (OR) was observed with a dose of 3 mg / kg, while for other cancers it was with 10 mg / kg. Nivolumab is typically dosed at 10 mg / kg every 3 weeks until cancer progression. The terms “reduces the inhibitory activity of human PD-1,” “neutralizes PD-1,” or “neutralizes the inhibitory activity of human PD-1” refer to a process in which the PD-1's signal transduction capacity is inhibited as a result of its interaction with one or more of its binding partners, such as PD-L1 or PD-L2. An agent that neutralizes the inhibitory activity of PD-1 decreases, blocks, inhibits, abolishes, or interferes with the signal transduction resulting from the interaction of PD-1 with one or more of its binding partners, such as PD-L1 and PD-L2. Such an agent can thus reduce the negative costimulatory signal mediated by or through cell surface proteins expressed on T lymphocytes, thereby enhancing T cell effector functions such as proliferation, cytokine production, and / or cytotoxicity. MK-3475 (Merck's human anti-PD1 IgG4 mAb), also known as lambrolizumab or pembrolizumab (brand name Keytruda®), has been approved by the FDA for the treatment of melanoma and is being tested in other cancers. Pembrolizumab was tested at 2 mg / kg or 10 mg / kg every 2 to 3 weeks until disease progression. MK-3475, also known as Merck 3745 or SCH-900475, is also described in WO2009 / 114335. MPDL3280A / RG7446 (atezolizumab, trade name Tecentriq™, an anti-PD-L1 from Roche / Genentech) is a human anti-PD-L1 mAb containing an Fe domain designed to optimize efficacy and safety by minimizing FcyR binding and, consequently, antibody-dependent cell-mediated cytotoxicity (ADCC). Doses of <1, 10, 15, and 25 mg / kg of MPDL3280A were administered every 3 weeks for up to 1 year. In the phase 3 trial, MPDL3280A was administered at 1200 mg by intravenous infusion every three weeks in NSCLC. AMP-224 (Ampliimmune and GSK) is an immunoadhesin comprising an extracellular PD-L2 domain fused to an Fe domain. Other examples of PD-1-neutralizing agents include an antibody that binds to PD-L2 (an anti-PD-L2 antibody) and blocks the interaction between PD-1 and PD-L2. Pidlizumab (CT-011; CureTech) (humanized anti-PD1 lgG1 mAb from CureTech / Teva), Pidlizumab (CT-011; CureTech) (see for example, WO2009 / 101611) is another example; The agent was tested in thirty patients with relapsing rituximab-responsive LF who were treated with 3 mg / kg of CT-011 intravenously every 4 weeks during infusions in combination with rituximab dosed at 375 mg / m2 weekly for 4 weeks, starting 2 weeks after the first CT-011 infusion. Other known PD-1 antibodies and other PD-1 inhibitors include AMP224 (a B7-DC / IgG1 fusion protein licensed by GSK), AMP-514 described in WO 2012 / 145493, antibody MEDI-4736 (durvalumab, trade name Imfinzi™, an anti-PD-L1 developed by AstraZeneca / Medimmune) described in WO2011 / 066389 and US2013 / 034559, antibody YW243.55.S70 (an anti-PD-L1) described in WO2010 / 077634, MDX-1105, also known as BMS936559, is an anti-PD-L1 antibody developed by Bristol-Myers Squibb described in WO2007 / 005874, and antibodies and inhibitors described in WO2006 / 121168. WO2009 / 014708, WO2009 / 114335 and WO2013 / 019906, the disclosures of which are incorporated herein by reference. Other examples of anti-PD1 antibodies are described in WO2015 / 085847 (Shanghai Hengrui Pharmaceutical Co. Ltd.), e.g. antibodies having the light chain variable domain CDR1, 2 and 3 of SEQ ID No.: 6, SEQ ID No.: 7 and / or SEQ ID No.8, respectively, and the variable heavy chain domain of antibody CDR1, 2, and 3 of SEQ ID No.: 3, SEQ ID No.: 4, or SEQ ID No.: 5, respectively, wherein the references in SEQ ID No.: are the numbering in accordance with WO2015 / 085847, the disclosure of which is incorporated herein by reference. Antibodies that compete with any of these antibodies for binding to PD-1 or PD-L1 may also be used. In some embodiments, the PD-1 neutralizing agent is an anti-PD-L1 antibody that inhibits the binding of PD-L1 to PD-1. An exemplary anti-PD-1 antibody is pembrolizumab (marketed by Merck & Co. as Keytruda™, see also WO 2009 / 114335, disclosure of which is incorporated herein by reference). An exemplary anti-PD-L1 antibody is MEDI-4736 (durvalumab, trade name Imfinzi™, an anti-PD-L1 developed by AstraZeneca / Medimmune). In treatment procedures, the CD73-binding compound and the second therapeutic agent can be administered separately, together, sequentially, or in a cocktail. In some embodiments, the antigen-binding compound is administered before the second therapeutic agent. For example, the CD73-binding compound can be administered approximately 0 to 30 days before the second therapeutic agent. In other embodiments, a CD73-binding compound is administered from approximately 30 minutes to approximately 2 weeks, from approximately 30 minutes to approximately 1 week, from approximately 1 hour to approximately 2 hours, from approximately 2 hours to approximately 4 hours, from approximately 4 hours, from approximately 6 hours to approximately 8 hours, from approximately 8 hours to 1 day, or from approximately 1 to 5 days before the second therapeutic agent.In some embodiments, a CD73-binding compound is administered concurrently with the therapeutic agents. In other embodiments, a CD73-binding compound is administered after the second therapeutic agent. For example, a CD73-binding compound may be administered approximately 0 to 30 days after the second therapeutic agent. In other embodiments, a CD73-binding compound is administered approximately 30 minutes to approximately 2 weeks, approximately 30 minutes to approximately 1 week, approximately 1 hour to approximately 2 hours, approximately 2 hours to approximately 4 hours, approximately 4 hours to approximately 6 hours, approximately 6 hours to approximately 8 hours, approximately 8 hours to 1 day, or approximately 1 to 5 days after the second therapeutic agent. Examples of Procedures Cloning, production and purification of recombinant huCD73 Molecular Biology The huCD73 protein was cloned from MIAPACA-2 cDNA using the following primers TACGACTCACAAGCTTGCCGCCACCATGTGTCCCCGAGCCGCGCG (SEQ ID No.: 20) (Direct) and CCGCCCCGACTCTAGAtcaGTGATGGTGATGATGGTGcttgatccgaccttcaactg iviA / a / zuz ι / u iz / oa (SEQ ID No.: 21) (Reverse). Next, the purified PCR product was cloned into an expression vector using the InFusion cloning system. A 6xHis tag was added to the C-terminus of the protein for the purification step. Amino acid sequence of the cloned huCD73: MCPRAARAPATLLLALGAVLWPAAGAWELTILHTNDVHSRLEQTSEDSSKV NASRCMGGVARLFTKVQQIRRAEPNVLLLDAGDQYQGTIWFTVYKGAEVAHFMNAL RYDAMALGNHEFDNGVEGLIEPLLKEAKFPILSANIKAKGPLASQILKVLPYLPVLPV GDEVVGIVGYTSKETPFLSNPGTNLVFEDEITALQPEVDKLKTLNVNKIIALGHSGFE MDKLIAQKVRGVDVVVGGHSNTFLYTGNPPSKEVPAGKYPFIVTSDDGRKVPVQA YAFGKYLGYLKIEFDERGNVISSHGNPINSPENKSINKSINKSILLDIKWW GKTIVYLDGSSQSCRFRECNMGNLICDAMINNNLRHTDEMFWNHVSMCILNGGGIR SPIDERNNGTITWENLAAVLPFGGTFDLVQLKGSTLKKAFEHSVHRYGQSTGEFLQV GGIHVVYDLSRKPGDRVVKLDVLCTKCRVPSYDPLYKGFLGFLGFLGGGTFDLVQLKGSTLKKAFEHSVHRYGQSTGEFLQV QMIKdELLRHDSGDQDINVVSTYISKMKVIYPAVEGRIKHHHHHH (SEQ ID No.: 22). Expression and purification of huCD73 proteins After validation of the cloned sequence, the cells were nucleofected, and the producing set was subcloned to obtain a cell clone that produced the huCD73 protein. The supernatant of the huCD73 clone grown on a roller was collected and purified using a Ni-NTA column and eluted with 250 mM imidazole. The purified proteins were then loaded onto an S200 size-exclusion chromatography column. The purified protein corresponding to a dimer was formulated in a buffer of 20 mM Tris pH 7.5, 120 mM NaCl, and 4 mM CaCl₂ for enzyme activity assays, while the formulation buffer was supplemented with 20% glycerol. SPR analysis to evaluate Ab Kd in recombinant CD73 protein SPR measurements were performed on a Biacore™ T200 instrument at 25 °C. Protein A (GE Healthcare) was immobilized on a CM5 Sensor Chip (GE Healthcare). The chip surface was activated with EDC / NHS (N-ethyl-N'-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide) (Biacore™, GE Healthcare). Protein A was diluted to 10 pg / ml in coupling buffer (10 mM acetate, pH 5.6) and injected until the appropriate immobilization level was reached (i.e., 2000 RU). Deactivation of the remaining activated groups was performed using 100 mM ethanolamine, pH 8 (Biacore™, GE Healthcare). The affinity study was conducted according to a standard capture-kinetic protocol recommended by the manufacturer (Biacore™, GE Healthcare Kinetic Assistant). Sequential serial dilutions of recombinant human soluble CD73 protein, ranging from 1.23 to 300 nM, were injected onto the captured anti-CD73 antibodies and allowed to dissociate for 10 min before regeneration. All sets of sensograms were fitted using the 1:1 kinetic binding model. Bivalent affinities and kinetic association and dissociation rate constants were calculated. Flow cytometry analysis to assess the recognition of anti-CD73 by antibodies One hundred and five MDA-MB-231 cells resuspended in FCSB were distributed into 96W round-bottom microplates (50 µL per well). An interval dose of anti-CD73 mAb was added to the plates, and the cells were incubated for 1 hour at +5 ± 3 °C. The cells were washed three times in FCSB by rotating the plates at 400 g for 3 minutes at 4 °C. A PE-conjugated goat F(ab')2 anti-human IgG (H+L) secondary Ab diluted in FCSB was added to the cells, and the plates were incubated for an additional 30 minutes at +5 ± 3 °C. The cells were washed three times as described above and analyzed by flow cytometry. The median fluorescence intensity versus mAb concentration was plotted and the CEso was calculated using GraphPad Prism™ software. In vitro enzyme assay with recombinant human CD73 or cynomolge Briefly, recombinant human or cynomolgo CD73 was incubated in 96 W flat-bottom white microplates in the presence of a dose interval of anti-CD73 mAb or isotype control. The plates were incubated for 1 hour at +37 ± 1 °C. ATP (12.5 µM) and AMP (125 µM) were added to each well, and the plates were incubated at +37 ± 1 °C for an additional 30 minutes. CelITiter-Glo™ (Promega), containing luciferase / luciferin, was added to the wells, the plates were incubated for 5 minutes at room temperature in the dark, and the emitted light was measured using an Enspire™ instrument (Perkin Elmer). iviA / a / zuz ι / u iz / oa • Conditions: • ATP + AMP: maximum inhibition of luciferase (100%) • CD73 + ATP + AMP: no inhibition of luciferase (0%) Residual enzyme activity versus anti-CD73 antibody concentration was represented in graphs using GraphPad Prism7™ software. T cell proliferation assay Peripheral blood was obtained from healthy donors, and mononuclear cells were isolated in a Ficoll gradient. Lymphocytes were further enriched in a 52% Percoll™ gradient (cell pellets) and stained with CelITrace™ Violet 2 μM (Thermofisher). 5 x 10⁴ to 1 x 10⁵ stained cells were distributed onto 96 W round-bottom plates, incubated for 1 h at 37 °C with anti-CD73 antibodies, and activated for 3 to 5 days by the addition of anti-CD3 / anti-CD28 coated beads. Inhibition of T cell proliferation was achieved by the addition of 200 μM AMP. T cell proliferation and the ability of the antibodies to block the immunosuppressive effect of AMP were assessed by flow cytometry, quantifying the dye dilution in proliferating T cells. The percentage of proliferating T cells versus the concentration of anti-CD73 antibodies was represented in graphs using GraphPad Prism™ software.Some experiments were performed on complete PBMCs from healthy donors or cancer patients; the protocol was as described above, except that T cell suppression was achieved by adding 0.5 to 1 mM ATP. To compare donors or patients, T cell proliferation was normalized using the following formula: (activated cells + AT(M)P + Ab — (activated cells + AT(M)P) (activated cells) — (activated cells + AT(M)P) Allogeneic mixed lymphocyte reaction (MLR) assay Mononuclear cells were isolated from healthy donors on a Ficoll gradient, and monocytes were purified by immunomagnetic selection using CD14 microbeads (Miltenyi Biotec). Monocytes were differentiated into dendritic cells (MoDCs) by 5–7 days of culture in the presence of GM-CSF (400 ng / ml) and IL-4 (20 ng / ml). On the day of DC retrieval, CD4+ T cells from allogeneic donors were purified by immunomagnetic exhaustion of non-CD4+ T cells (Miltenyi Biotec) and stained with Cell Trace™ Violet. DCs (10⁴ cells / well) and T cells (5 × 10⁴ cells / well) were pooled in 96 W round-bottom microplates in the presence of interval doses of anti-huCD73 antibodies and a fixed dose of ATP. T cell proliferation and the ability of Ab to reverse ATP-mediated suppression were evaluated as described for the T cell proliferation assay. Example 1: Modeling and generation of anti-huCD73 antibodies with human structural sequences The parental antibody 3C12 described in PCT publication WO2016 / 055609, which has amino acid sequences VH and VL of SEQ ID No.: 27 and 28, respectively, was modified by introducing heavy chain structures (FR1, FR2, FR3) from subgroup IGHV1-3*01 along with IGHJ4*01 (FR4) into VH, and by introducing light chain structures (FR1, FR2, FR3) from human subgroup IGKV1-33*01, along with IGKJ2*01 (FR4) into VL. Three-dimensional models based on different segments of the human VH and VL genes were superimposed, and all amino acid differences were examined individually. In silico molecular design was challenged using 3D models of both parenteral chimeric (HPLP) and humanized (HOLO) antibodies. Intra- and extra-chain connections between residues were also evaluated to identify and avoid disruption of any important low-energy bonds. The VH and VL sequences of each engineered domain were cloned into vectors containing the hulgGI-derived constant domains with L234A / L235E / G237A / A330S / P331S substitutions and the huCk constant domain, respectively. The two resulting vectors were co-transfected into a CHO cell line. The established cell pool was used to produce the antibody in CHO medium. The antibody was then purified using protein A. The heavy and light chain sequences used to model a chimeric Fab version of 3C12 with human IgG1 constant regions, including an Fe domain comprising iviA / a / zuz ι / u iz / oa L234A / L235E / G237A / A330S / P331S substitutions (N297-linked glycosylation retention), were as follows: HP Fab heavy chain (underlined variable domain) QIQLQQSGPELVKPGASVKVSCKASGYAFASYNMNWVKQSHGKSLDWIGYI DPYNGGSSYNLTFKGKATLTVDKSSTTAYMHLNSLTSEDSAVYYCARGYGNYKAWF AYWGQGTLVTVSAASTKGPSVFPLAPSSKSTSGGTAALGCLVKdYFPEPVTVSWNS GALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDK (SEQ ID No.: 23). LP Fab Light Chain (underlined variable domain) DVVMTQTPKFLLVSAGDRVTITCKASQSVSNDVAWYQQKPGQSPKLLIYYAS TRYTGVPDRFTGSGYGTDFTFTISTVQAEDLAVYFCQQDYSSLTFGAGTKLELKRTV AAPSVFIFPPSDEQLKSGTASVVCLLNNFYPREAKVQWKVDNALQSGNSQESVTEQ DSKDSTYSLSSTLTLSKADYEKHKVYACEVTHQGLSSPVTKSFNRGEC (SEQ ID No.: 24). Heavy chain H0 Fab (underlined variable domain) QVQLVQSGAEVKKPGASVKVSCKASGYTFTSYNMYWVRQAPGQRLEWMG YIDPYNGGSSYNLTFKGRVTITRDTSASTAYMELSSLRSEDTAVYYCARGYGNYKA WFAYWGQGTLVTVSSASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVS WNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDK (SEQ ID No.: 25). Light chain LO Fab (underlined variable domain) DIQMTQSPSSLSASVGDRVTITCKASQSVSNDVAWYQQKPGKAPKLLIYYAS TRYTGVPSRFSGSGSGTDFTFTISSLQPEDIATYYCQQDYSSLTFGQGTKLEIKRTVA APSVFIFPPSDEQLKSGTASVVCLLNNFYPREAKVQWKVDNALQSGNSQESVTEQD SKDSTYSLSSTLTLSKADYEKHKVYACEVTHQGLSSPVTKSFNRGEC (SEQ ID No.: 26). The sequences of the heavy chain variable region and the light chain variable region of the parental HPLP antibody are shown below: HP VH QIQLQQSGPELVKPGASVKVSCKASGYAFASYNMNWVKQSHGKSLDWIGYI DPYNGGSSYNLTFKGKATLTVDKSSTTAYMHLNSLTSEDSAVYYCARGYGNYKAWF AYWGQGTLVTVSA (SEQ ID No.: 27). LP VL DVVMTQTPKFLLVSAGDRVTITCKASQSVSNDVAWYQQKPGQSPKLLIYYAS TRYTGVPDRFTGSGYGTDFTFTISTVQAEDLAVYFCQQDYSSLTFGAGTKLELK (SEQ ID No.: 28). Heavy chain design To investigate whether residue I2 (also position 2 according to Kabat's numbering) forms a hydrophobic bond with CDR_H3-Y109 and plays a role in the positioning or flexibility of CDR_H3, the valine residue at position 2 was replaced with an isoleucine. The V2 and I2 side chains do not match in the two models. V2 also forms a hydrophobic bond with H0-Y109 (Kabat Y108), but the Y109 position is slightly modified, and H0-Y109 forms a β-bond with LC-Y55 (Kabat Y54). Y55 is a CDR_L2 residue. The substitution of V2 can influence the position of both CDR_H3 and CDR_L2. To investigate whether residues at positions 28 and 30 (frame 1, also positions 28 and 30 according to Kabat) influence antigen binding, these positions were replaced with an alanine. The parental antibody has the sequence YAFA compared to YTFT in the HOLO antibody. Residues A28 and A30 are exposed on the molecular surface near the paratope. It appears likely that a threonine at position 28 would negatively influence antigen binding. On the other hand, it seems unlikely that A30 is critical. To investigate whether the residue at position 44 (also Kabat 44) plays a role at the VH / VL interface, this residue was re-mutated, thus preserving the serine present in the parental antibody. The parental antibody has the sequence GKS compared to GQR in the holo antibody. R44 is located at the VH / VL interface, very close to the L45 side chain. To investigate whether the residue at position 48 (also Kabat 48) is important, this residue was remutated, thus preserving the residue present in the parental antibody. The parental antibody has the sequence WIG compared to WMG in the H0L0 antibody. I48 and M48 appear to occupy critical positions just below CDR_H2 and are involved in a complex hydrophobic network. To investigate the significance of residues at positions 67 (Kabat position 66) and 68 (Kabat position 67), these residues were remutated, thus preserving the residues present in the parental antibody. The parental antibody has the sequence KAT compared to RVT in the holo antibody. The loop between F64 (Kabat F63) and K67 / R67 (Kabat K66 / R66) shows very different conformations in the two models. A68 (Kabat 67) is a Vernier residue. In order to investigate the role of the residue at position 70 of Abnum (position 69 of Kabat), this residue was remutated, thus preserving the leucine present in the parental antibody. The parental antibody has the sequence TLT compared to TIT in the holo antibody. L70 and I70 (Kabat L69 and I69) are involved in a complex hydrophobic network. To investigate the role of the residue at position 72 (Kabat 71), this residue was remutated, thus preserving the serine present in the parental antibody. The parental antibody has the TVD sequence compared to the TRD sequence of the holoantibody. V72 and R72 (Kabat V71 and R71) occupy critical positions just below CDR_H2. The distal hydrophilic side chain of residue V72 projects onto the molecular surface and forms an α-bond with N55 (Kabat N54). N55 occupies the same position in both models. However, the α-bond with R72 (Kabat R71) may reduce the flexibility of the corresponding loop. Based on the above, the impact on antigen binding of replacing the parental valine with an arginine in the holoantibody cannot be predicted. To investigate whether the residue at position 74 (Kabat 73) influences antigen binding, this residue was re-mutated, thus preserving the serine present in the parental antibody. The parental antibody has the sequence DKS compared to DTS in the holo antibody. K74 and T74 (Kabat K73 and T73) are exposed on the molecular surface near the paratope and may be involved in antigen binding. A first heavy chain variant (H1) having the amino acid sequence shown in SEQ ID No.: 29 had a V2I and T73K substitution. A second heavy chain variant (H2) having the amino acid sequence shown in SEQ ID No.: 30 had the V2I, T28A, R71V, and T73K substitutions. A third heavy chain variant (H3) having the amino acid sequence shown in SEQ ID No.: 31 had the V2I, T28A, M48I, R66K, V67A, R71V, and T73K substitutions. A fourth heavy chain variant (H4) having the amino acid sequence shown in SEQ ID No.: 32 had the V2I, T28A, T30A, M48I, R66K, V67A, I69L, R71V, and T73K substitutions. The numbering of substitutions is done according to Kabat. Lightweight chain design The parental antibody has the sequence DVVM compared to DIQM of the holo antibody. Residue V2 forms a hydrophobic bond with A25. Residue I2 may be exposed on the paratope surface, but its impact on paratope organization cannot be predicted. I2 does not form a hydrophobic bond with A25, and this may slightly modify the position of CDR-L1. Therefore, the isoleucine in residue 2 was replaced with a valine. The parental antibody has the PDR sequence compared to PSR in the holo antibody. Residue R61 occupies rotameric positions. The loops appear to be oriented the same way, but not overlapping (lateral translation corresponding to the global translation of the entire domain). In the parental antibody, D60 forms a salt bridge and an H-bond with CDR-L2-R54. In the holo antibody, residue S60 does not contact R54. R54 occupies rotameric positions. Contact with D60 may be critical for imposing a specific and appropriate position on the CDR-L2 residues. Therefore, the aspartic acid residue at position 60 of the holo antibody was replaced with a serine. The parental antibody has the sequence GYG compared to GSG in the HOLO antibody. To investigate whether residue Y67 contributes to the paratope, the serine in the HOLO antibody was replaced with a tyrosine. The parental antibody has the sequence YFC compared to YYC in the HOLO antibody. Although Y87 does not appear to form a α-bond with adjacent residues, the function of this residue will be investigated, and the tyrosine at position 87 in the HOLO was replaced with a phenylalanine. iviA / a / zuz ι / u iz / oa A first light chain variant (L1) having the amino acid sequence shown in SEQ ID No.: 33 had the S67Y substitution. A second light chain variant (L2) having the amino acid sequence shown in SEQ ID No.: 34 had the S60D and S67Y substitutions. A third light chain variant (L3) having the amino acid sequence shown in SEQ ID No.: 35 had the I2V, S60D, and S67Y substitutions. A fourth light chain variant (L4) having the amino acid sequence shown in SEQ ID No.: 36 had the I2V, S60D, S67Y, and Y87F substitutions. The amino acids of respect to the region's variables include 10 types (H" cadena in the Tabla 1) and a ligera (the "L" cadena in the Tabla 1) se more often in the Tabla 1 continuation. Tabla 1 Cade na SEQ ID NO Secuencia (sustituciones de aminoácidos en negrita, CDR de Kabat subrayadas) H1 29 QIQLVQSGAEVKKPGASVKVSCKASGYTFTSYNMYWVRQAPG QRLEWMGYIDPYNGGSSYN LTFKGRVTITRD KS AST AYM ELSS L RS E DT AV YYC A RGYGNYK AWFAYWGQGTLVTVSS H2 30 QIQLVQSGAEVKKPGASVKVSCKASGYAFTSYNMYWVRQAP GQSLEWMGYIDPYNGGSSYN LTFKGRVTITVDKSASTAYMELSSLRSEDTAVYYCARGYGNYK AWFAYWGQGTLVTVSS H3 31 QIQLVQSGAEVKKPGASVKVSCKASGYAFTSYNMYWVRQAP GQSLEWIGYIDPYNGGSSYN LTFKGKATITVDKSASTAYMELSS L RS E DT AV YYC A RGYGNYK AWFAYWGQGTLVTVSS H4 32 QIQLVQSGAEVKKPGASVKVSCKASGYAFASYNMYWVRQAP GQSLEWIGYIDPYNGGSSYN LTFKGKATLTVDKSASTAYMELSSLRSEDTAVYYCARGYGNY KAWFAYWGQGTLVTVSS L1 33 DIQMTQSPSSLSASVGDRVTITCKASQSVSNDVAWYQQKPGK APKLLIYYASTRYTGVPSR FSGSGYGTDH IH IISSLQPEDIATYYCQQDYSSLTFGQGTKLEI K L2 34 DIQMTQSPSSLSASVGDRVTITCKASQSVSNDVAWYQQKPGK APKLLIYYASTRYTGVPDR FSGSGYGTDH I Η IISSLQPEDIATYYCQQDYSSLTFGQGTKLEI K L3 35 DVQMTQSPSSLSASVGDRVTITCKASQSVSNDVAWYQQKPG KAPKLLIYYASTRYTGVPDR FSGSGYGTDFTFTISSLQPEDIATYYCQQDYSSLTFGQGTKLEI K L4 36 DVQMTQSPSSLSASVGDRVTITCKASQSVSNDVAWYQQKPG KAPKLLIYYASTRYTGVPDR FSGSGYGTDF I Η IISSLQPEDIATYFCQQDYSSLTFGQGTKLEI K iviA / a / ¿u¿ ι / u iz / oa This product produces anti-allergic devices that contain many combinations of old and more expensive items in the tab 2 times a day. Tabla 2 Lightweight chains LO L1 L2 L3 L4 Heavy chains HO HOLO H0L1 H0L2 H0L3 H0L4 H1 H1L0 H1L1 H1L2 H1L3 H1L4 H2 H2L0 H2L1 H2L2 H2L3 H2L4 H3 H3L0 H3L1 H3L2 H3L3 H3L4 H4 H4L0 H4L1 H4L2 H4L3 H4L4 Ejemplo 2: Add the soluble CD73 protein to SPR The binding of the antibodies in Table 2 of Example 1 was assayed to determine their binding to soluble human dimeric CD73 proteins, and these antibodies were cloned, produced, and purified. The affinity and association / dissociation constants of the humanized variants were evaluated by SPR analysis. Table 3 summarizes all the calculated constants. The H0L0 antibody with a fully human IGHV1-3*01 and IGHJ4*01 heavy chain frame and a fully human IGKV1-33*01 and IGKJ2*01 light chain frame resulted in a Kd of 65 nM. As shown in Table 3, the humanized HxLO variants (H1L0, H2L0, H3L0, and H4L0) exhibited an association constant equivalent to other variants but had a faster dissociation profile. Consistent with this, the Kd of the HxLO variants was higher than that observed for all other variants (Table 3). The introduction of the amino acid sequences of the full human IGKV1-33*01 and IGKJ2*01 light chains into the humanized variants thus appears to be detrimental to the affinity for the CD73-humanized Ab. However, all other humanized vahants had an affinity for CD73 similar to that of the chimeric parental antibody 3C12 (0.68 nM). In particular, all heavy chains, including the fully human unmodified heavy chain structure IGHV1-3*01 and IGHJ4*01, provided high-affinity binding to CD73. Table 3 iviA / a / zuz ι / u iz / oa humanized variants Kd (nM) ka (1 / Ms) kd (1 / s) HOLO 65 1.36E+05 8.82E-03 H0L1 0.9 1.44E+05 1.27E-04 H0L2 0.7 1.68E+05 1.19E-04 H0L3 0.6 1.70E+05 9.49E-05 H0L4 0.6 1.37E+05 8.65E-05 H1LO 28.7 1.03E+05 2.96E-03 H1L1 0.8 1.00E+05 8.43E-05 H1L2 0.6 1.35E+05 8.3E-080.81L 9.26E+04 7.20E-05 H1L4 0.7 9.82E+04 6.77E-05 H2L0 5.6 2.38E+05 3.20E-03 H2L1 1.4 8.37E+04 1.18E-04 H18.13+05 1.55E-04 H2L3 1 1.20E+05 1.23E-04 H2L4 0.9 1.20E+05 1.06E-04 H3L0 29.4 2.71 E+05 7.97E-03 H3L1 1.8 7.89E-04 H3L1-304 1.4 8.66E+04 1.22E-04 H3L3 1.1 9.57E+04 1.05E-04 H3L4 1 9.04E+04 8.91 E-05 H4L0 7.8 1.58E+05 1.23E-031 H3L0 1.76E+05 1.79E-04 H4L2 0.9 7.75E+04 7.12E-05 H4L3 0.7 1.10E+05 7.69E-05 H4L4 1.2 6.01 E+04 7.14E-05 iviA / a / ¿u¿ ι / υ ιζ / oa Example 3: Binding to cells expressing human CD73 by flow cytometry The binding of the humanized antibodies in Table 2 to CD73-expressing cells was assayed by flow cytometry. As shown in Figure 1, all the tested antibodies recognized human CD73 proteins. Binding efficiency to human CD73 was similar among the humanized variants and the chimeric format, except for HOLO, H2L0, and H3L0, which were less efficient than the parental antibody. These observations are consistent with SPR data showing lower affinity for the HxLO variants (H1LO, H2L0, H3L0, and H4L0). Accordingly, all the heavy chains, including the structured IGHV1-3*01 heavy chain and the unmodified, fully human IGHJ4*01 heavy chain, provided excellent binding to CD73-expressing cells, comparable to the parental antibody. Example 4: In vitro enzyme assay with recombinant soluble human CD73 protein The effectiveness of the humanized variants was compared with that of the parental antibody in inhibiting the enzymatic activity of the recombinant CD73 protein (Figure 2). As shown in Figure 2 (panel A), high levels of luminescence were measured when the ATP and CTG substrates were mixed. When AMP was added to the reaction mixture, the CTG reaction was inhibited, resulting in a decrease in luminescence. In the presence of the AMP-hydrolyzing protein rhCD73, the luminescence level was restored. The blocking of CD73 enzyme activity by the humanized variants is shown in Figure 2. The results showed that, with the exception of the LO variants (HOLO, H1L0, H2L0, H3L0, and H4L0), which exhibited reduced activity compared to the parental antibody, all humanized variants strongly inhibited the enzymatic activity of the soluble CD73 protein. However, surprisingly, for most antibodies, the potency was somewhat lower than that of the parental antibody. Only H1L4 and all H4 variants blocked enzymatic activity with a potency similar to that of the parental antibody. These experiments demonstrated that, regardless of the number of reverse mutations in the heavy chain, the absence of mutation in the light chain when using the IGKV1-33*01 and IGKJ2*01 sequences as an acceptor framework leads to a significant decrease in the ability to inhibit the activity of the soluble CD73 protein. The best effectiveness in blocking CD73 protein activity was achieved with H1L4 and H4Lx variants other than H4L0 (i.e., H4L1, H4L2, H4L3, and H4L4). Example 5: T cell proliferation assay The concentration of AMP capable of inhibiting T cell proliferation was tested in two series of experiments to establish an AMP concentration that induces a high suppressive effect and allows for the restoration of proliferation in the presence of the parental 3C12 antibody. The enriched lymphocyte fraction was incubated for 3 days in the presence of anti-CD3 / anti-CD28 beads and a range of AMP doses (from 50 μM to 1.6 mM to 50 μM). The highest percentage of CD4+ and CD8+ T cell restoration was observed with 0.2 to 0.8 mM and 0.2 to 1 mM of AMP, respectively, in the two series of experiments. The ability of the humanized variants and the parental antibody was evaluated in the two series of experiments to compare their ability to restore T cell proliferation inhibited by AMP 0.8 mM. As shown in Figure 3, with the exception of the HxLO variants, the chimeric and humanized antibodies were able to restore T cell proliferation (for both CD4+ and CD8+ subpopulations). Despite their ability to restore proliferation, the potency of most humanized variants was lower compared to the parental antibody. The H0L4, H1L4, and H4L4 variants demonstrated a similar level of potency to the parental antibody, although they did not reach the full potency of the parental antibody. A second experiment was conducted under the same experimental conditions, except that the LO variants were replaced by isotype controls. The results are presented in Figure 4. Similar to what is shown in Figure 3, with the exception of the HxLO variants, the chimeric and humanized antibodies were able to restore T cell proliferation (for both CD4+ and CD8+ subpopulations). However, despite their ability to restore proliferation, the potency of most of the humanized variants was again somewhat lower compared to the parental antibody. The H0L4, H1L4, and H4L4 variants came closest to the efficacy of the parental antibody. Example 6: Designing new framework variants and CDRs Surprisingly, the preceding examples showed no direct correlation between flow cytometry assessment and potency in inhibiting CD73 enzyme activity. Interestingly, while variants H1, H2, H3, and H4 were essentially indistinguishable based on binding affinity to recombinant CD73 protein in SPR assays and flow cytometry in CD73-expressing cells, variants H2 and H3 were less potent in functional assays than variant H4 in their ability to restore T cell proliferation in Example 5. One possibility is that mutations introduced into H2 and H3 frames that were detrimental to potency in inhibiting CD73 (but not detrimental to CD73 binding affinity) were compensated for by mutations introduced into variant H4 frames.Based on the above, new variants were designed with substitutions within the heavy chain and / or RDF residues. Based on these observations, the substitutions made in chains H2, H3, and H4 were classified as residues considered critical to function, residues that likely do not affect function, residues that negatively impact function, and residues that restore function. A new heavy chain variant, designated Ή4+”, having the amino acid sequence shown below (SEQ ID No.: 37; amino acid substitutions in bold, Kabat CDR underlined), was designed and combined with L1, L2, L3 and L4 Light Chains (from SEQ ID No.: 33, 34, 35 and 36, respectively) to generate four new antibodies, H4+L1, H4+L2, H4+L3 and H4+L4. H4+ VH: QIQLVQSGAEVKKPGASVKVSCKASGYTFASYNMYWVRQAPGQRLEWIGYI DPYNGGSSYNLTFKGRVT LT RD KS AST AYM ELSSLRSE DTAVYYCARGYGNYKAW FAYWGQGTLVTVSS (SEQ ID No.: 37). The complete H4+ heavy chain amino acid sequence comprising a human lgG1 Fe domain with L234A / L235E / G237A / A330S / P331S substitutions is shown below: QIQLVQSGAEVKKPGASVKVSCKASGYTFASYNMYWVRQAPGQRLEWIGYI DPYNGGSSYNLTFKGRVTLTRDKSASTAYMELSSLRSEDTAVYYCARGYGNYKAW FAYWGQGTLVTVSSASTKGPSVFPLAPSSKSTSGGTAALGCLVKdYFPEPVTVSWN SGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKRVE PKSCDKTHTCPPCPAPEAEGAPSVFLFPPKPKdTLMISRTPEVTCVVVDVSHEDPEV KFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKAL PSSIEKTISKAKGQPREPQVYTLPPSREEMTKNQVSLTCLVKGFYPSDIAVEWESNG QPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKS LSLSPGK (SEQ ID No.: 38). The H4+L1 antibody contained an L1 light chain comprising a human Ckappa domain, the full sequence of which is shown below: DIQMTQSPSSLSASVGDRVTITCKASQSVSNDVAWYQQKPGKAPKLLIYYAS TRYTGVPSR (SEQ ID No.: 39). To investigate how the same frameshift substitutions would affect an antibody with differences in its heavy and light chain CDRs, an additional series of four antibodies was produced, each sharing a common heavy chain and one of four different light chains. The common heavy chain, designated “2H4+”, had a glutamine at Kabat position 59 (Q59) in HCDR2 (i.e., an L59Q substitution, compared to the H4+ chain), a lysine at Kabat residue 60 (K60) in HCDR2 (i.e., a T60K substitution, compared to the H4+ chain), and an asparagine at Kabat position 97 (N97) in HCDR3 (i.e., a substitution G97N, compared to the H4+ chain). The four light chains designated 2L1, 2L2, 2L3, and 2L4 had the same structural residues as the L1, L2, L3, and L4 chains, respectively, and differed in their CDRs from the L1-L4 chains by the presence of a threonine at the Kabat 30 position (T30) in LCDR1 (i.e., a substitution S30T, compared to chains L1–L4), and an asparagine at the Kabat residue (N53) in LCDR2 (i.e., a T53N substitution, compared to chains L1–L4). The four resulting novel antibodies are designated 2H4+2L1, 2H4+2L2, 2H4+2L3, and 2H4+2L4 (see Table 4 below). A parental antibody sharing the CDRs was produced in murine frames with variable heavy- and light-chain regions designated 2HP and 2LP (amino acid sequences shown in Table 5 below). As in Example 1, all antibodies were produced as human IgG1 isotype with L234A / L235E / G237A / A330S / P331S substitutions to reduce Fe receptor binding. Table 4 Reference mAb VH VL 2H4+L1 2H4+ 2L1 (SEQ ID No.: 42) (SEQ ID No.:43) 2H4+L2 2H4+ 2L2 (SEQ ID No.: 42) (SEQ ID No.: 44) 2H4+L3 2H4+ 2L3 (SEQ ID No.: 42) (SEQ ID No.: 45) 2H4+L4 2H4+ 2L4 (SEQ ID No.: 42) (SEQ ID No.: 46) 2HP2LP 2HP 2LP (SEQ ID No.: 40) (SEQ ID No.: 41) Table 5 Cade na SEQ ID No.: Variable amino acids from the region (sustituciones of amino acids in the network, CDR from Kabat subrayadas) 2HP 40 EIQLQQSGPELVKPGASVKVSCKASGYAFTSYNMYWVKQSH GKRLEWIGYIDPYNG 11- IISTMQAEDLAVYFCQQDYSSLTFGAGTKL ELK 2H4+ 42 QIQLVQSGAEVKKPGASVKVSCKASGYTFASYNMYWVRQAP GQRLEWIGYIDPYNG GSSYNQKFKGRVTLTRDKSASTAYMELSSLRSEDTAVYYCAR GYNNYKAWFAYWGQ GTLVTVSS 2L1 43 DIQMTQS PSSLSAS VG DR VTITCKASQS VTN D VA WYQQK PG K APKLLIYYASNRYT GVPSRFSGSGYGTDFTFTISSLQPEDIATYYCQQDYSSLTFGQ GTKLEIK 2L2 44 D IQMTQS PSSLSAS VG DR VTITCKASQS VTN D VA WYQQK PG K APKLLIYYASNRYT GVPDRFSGSGYGTDFTFTISSLQPEDIATYYCQQDYSSLTFGQ GTKLEIK 2L3 45 DVQMTQSPSSLSASVGDRVTITCKASQSVTNDVAWYQQKPG KAPKLLIYYASNRYT GVPDRFSGSGYGTDFTFTISSLQPEDIATYYCQQDYSSLTFGQ GTKLEIK 2L4 46 DVQMTQSPSSLSASVGDRVTITCKASQSVTNDVAWYQQKPG KAPKLLIYYASNRYT GVPDRFSGSGYGTDFTFTISSLQPEDIATYFCQQDYSSLTFGQ GTKLEIK iviA / a / zuz ι / u iz / oa The amino acid sequence of the full 2H4+ heavy chain comprising an Fe domain of human lgG1 with L234A / L235E / G237A / A330S / P331S substitutions is shown below: QIQLVQSGAEVKKPGASVKVSCKASGYTFASYNMYWVRQAPGQRLEWIGYI DPYNGGSSYNQKFKGRVTLTRDKSASTAYMELSlRSEDTAVYCARGYNNYKAW FAYWGQGTLVSSASTKGPSVFPLAPSSKSTVKTAVKGFPWGFPTV SGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSSLGTQTYICNVNHKPSNTKVDKRVE PKSCDKTHTCPPCPAPEAEGAPSVFLFPPKPKdTLMISRTPEVTCVVVDVSHEDPEV KFNWYVDGVVHNACTKPREEQYNSTYVKVLVKVLKVLKVLK PSSIEKTISKAKGQPREPQVYTLPPSREEMTKNQVSLTCLVKGFYPSDIAVEWESNG QPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKS LSLSPGK (SEQ ID No.: 47). The amino acid sequence of the complete 2L1 light chain of the antibody comprising a human Ckappa domain is shown below: DIQMTQSPSSLSASVGDRVTITCKASQSVTNDVAWYQQKPGKAPKLLIYYAS NRYTGVPSRFSGSGYGTDFTFTISSLQPEDIATYYCQQDYSSLTFGQGTKLEIKRTV AAPSVFIFPPSDEQLKSGTASVVCLLNNFYPREAKVQWKVDNALQSGNSQESVTEQ DSKDSTYSLSSTLTLSKADYEKHKVYACEVTHQGLSSPVTKSFNRGEC (SEQ ID No.: 48). Example 7: Study of new variants of in vitro enzyme assay with recombinant CD73 protein The efficacy of the humanized variants was compared with that of the parental antibody in inhibiting the enzymatic activity of the recombinant CD73 protein, using the procedures described in Example 4. All the new humanized variants produced in Example 6 potently inhibited the activity of the CD73 protein. The H4+Lx antibodies were as effective as their parental counterparts. Furthermore, all 2H4+2Lx variants (2H4+L1, 2H4+L2, 2H4+L3, and 2H4+L4) showed increased potency in inhibiting CD73 compared to the H4+Lx variants. The 2H4+2Lx variants inhibited CD73 activity with similar efficacy to the parental 2HP2LP antibody. An additional experiment was performed using different concentrations of the CD73 protein (50, 100, 200, 400 ng / ml). The aim of this experiment was to study the ability of humanized antibodies to block the activity of large amounts of CD73 protein. Again, the 2H4+2Lx variants were as potent as the parental 2HP2LP antibody. Example 8: Study of new variants to determine the effectiveness of the cynomolgus CD73 protein An experiment was performed on the recombinant cyCD73 rec protein with variants 2H1Lx and 2H4+2Lx. The experimental conditions were the same as in the experiments with human protein except for the concentration of cyCD73 protein that was used (400 ng / ml). The effectiveness of the humanized variants in blocking the enzymatic activity of the cyCD73 protein was the same as that of the parental (chimeric) antibody. Example 9: Study of new variants in the T cell proliferation assay The ability of humanized variants of different antibodies to restore T cell proliferation inhibited by AMP was tested. Figure 5A shows the inhibitory effect of AMP on T cell proliferation. All humanized variants potently blocked the inhibitory effect of AMP on T cell proliferation (Figures 5B and C). While most humanized variants generally appear to be as efficient as their chimeric parental counterpart in reversing AMP-mediated T cell suppression, the 2H4+2Lx variants were the most potent among all variants and, surprisingly, were even more potent than the parental antibody 2HP2LP in blocking the suppressive effects of AMP. Example 10: Comparative study of new variants in the T-cell proliferation assay in two human donors Based on the results obtained previously, the humanized variants of 2H4+2Lx were further characterized in additional series of T cell proliferation experiments. Figures 6A and 6B show the results obtained in a T-cell proliferation assay using cells from two healthy donors, respectively. As noted previously, the 2H4+2Lx variants were each more potent than the parental 2HP2LP in restoring T-cell proliferation (Figure 6A and B, right-hand panels). No clear differences were observed between the different 2H4+2Lx variants. Therefore, once again, the 2H4+2Lx variants were more potent than the parental 2HP2LP antibody in blocking the suppressive effects of AMP. Taken together, the results obtained in the T cell proliferation assay indicate that the humanized variants having the H4+ and H4+ chain frames are the most potent antibody variants, and that the 2H4+2Lx variants in general have the highest potency among all antibodies. Example 11: Study of new variants in the mixed lymphocyte allogeneic reaction (MLR) assay The 2H4+2Lx antibody variant was tested in an allogeneic MLR to confirm the results previously obtained in T cell proliferation assays. T cell proliferation was inhibited by adding 100 μM of ATP (which is degraded to ADP and AMP by CD39), as shown in Figure 7 for two human donor samples. As shown in Figure 7, left panel, T cell proliferation was inhibited by the addition of ATP. T cell proliferation was restored in the presence of anti-CD73 antibodies (center and right panels). All humanized variants of 2H4+2Lx were able to restore T cell proliferation with comparable or better efficacy than the parental 2HP2LP antibody. All 2H4+2Lx variants were more potent than the parental 2HP2LP in restoring T cell proliferation in these environments. These results were consistent with those obtained in the T cell proliferation assay using AMP as an inhibitor. In summary, the substitutions introduced in the H4+ and 2H4+ variable regions, along with the substitutions introduced in the L1 and 2L1 chains (and the L2, L3, L4, 2L2, 2L3, and 2L4 chains), appear to restore (and even improve) important functional properties of their parental murine antibodies, but they have human framework regions and therefore a lower risk of immunogenicity in humans. The 2H4+2Lx antibodies are the most potent of all. One possible explanation for the surprising finding that binding affinity for CD73 did not directly correlate with potency in functionally inhibiting CD73 activity may be related to the fact that these antibodies bind to CD73 and act as allosteric inhibitors. The antibodies bind to CD73 in an intradimer binding mode in a 1:1 stoichiometry between an intact full-length antibody and a CD73 dimer. Previous structural studies of CD73 have shown that its enzymatic activity requires extensive rotation of the N-terminal domain that defines the open (inactive) and closed (active, substrate-bound) states of the enzyme (Knapp et al., 2012 Structure 20 (12): 2161-73).Based on the crystal structure of the parental anti-CD73 F(ab) complexed with the CD73 ectodomain, and considering the 1:1 stoichiometry between an intact antibody and a CD73 dimer, steric hindrance would likely make it improbable that the intact antibody could bind to open conformers of CD73. Instead, the intact antibody constrains CD73 to an intermediate state in which AMP cannot be hydrolyzed. Since CD73 is thus bound by the antibodies while in an energetically unstable conformation, small changes that alter the rigidity of the antibody structure may be affecting the antibody's ability to adapt to the changing conformation of the CD73 dimer. Accordingly, these changes may impair the antibody's ability to inhibit CD73 activity in the presence of substrate.However, these small changes in antibody structure would not be observed in SPR or other binding assays, which are also performed in the absence of substrate. The heavy- and light-chain variable regions described herein appear to be able to capture (and even enhance) the full CD73 interaction dynamics of the parental antibodies, while incorporating human frameworks. All references, including publications, patent applications, and patents, cited in this document are incorporated herein by reference in their entirety and to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and set forth in full in this document (to the maximum extent permitted by law), irrespective of any separate incorporation of particular documents made elsewhere in this document. The use of the terms “a” and “an” and “the” and similar references should be interpreted to cover both the singular and the plural, unless otherwise stated herein or clearly contradicted by the context. Unless otherwise stated, all exact values ​​provided in this document are representative of the corresponding approximate values ​​(e.g., all exact example values ​​provided with respect to a particular factor or measure may be considered as also providing a corresponding approximate measure, modified by "approximately", where appropriate). The description herein of any aspect or embodiment that uses terms such as “comprising”, “having”, “including” or “containing” with reference to an element or elements is intended to provide support for a similar aspect or embodiment herein that “consists of”, “consists essentially of”, or “substantially comprises” that particular element or elements, unless otherwise stated or clearly contradicted by the context (e.g., a composition described herein as comprising a particular element should be understood as also describing a composition consisting of that element, unless otherwise stated or clearly contradicted by the context). The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended simply to better illuminate the invention and does not impose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any element not claimed as essential to the practice of the invention.

Claims

1. An antibody or antibody fragment capable of specifically binding to a human CD73 polypeptide, wherein the antibody or antibody fragment comprises a heavy chain variable region (VH) comprising the amino acid sequence of SEQ ID No.: 42 (chain 2H4+), and a light chain variable region (VL) comprising an amino acid sequence selected from the group consisting of SEQ ID No.: 43 (chain 2L1), 44 (chain 2L2), 45 (chain 2L3) and 46 (chain 2L4).

2. The antibody or antibody fragment of claim 1, wherein the antibody or antibody fragment comprises a heavy chain variable region (VH) comprising the amino acid sequence of SEQ ID No.: 42 (2H4+ chain) and a light chain variable region (VL) comprising the amino acid sequence of SEQ ID No.: 43 (2L1 chain).

3. The antibody or antibody fragment of claim 1, wherein the antibody or antibody fragment comprises a heavy chain comprising the amino acid sequence of SEQ ID No.: 47 and a light chain comprising the amino acid sequence of SEQ ID No.:

48.

4. An antibody or antibody fragment capable of specifically binding to a human CD73 polypeptide, wherein the antibody or antibody fragment comprises a heavy chain variable region (HV) comprising the amino acid sequence of SEQ ID No.: 37 (H4+ chain) and a chain variable region (LV) comprising an amino acid sequence selected from the group consisting of SEQ ID No.: 33 (L1 chain), 34 (L2 chain), 35 (L3 chain) and 36 (L4 chain).

5. The antibody or antibody fragment of claim 4, wherein the antibody or antibody fragment comprises a heavy chain variable region (VH) comprising the amino acid sequence of SEQ ID No.: 37 (H4+ chain) and a light chain variable region (VL) comprising the amino acid sequence of SEQ ID No.: 33 (L1 chain).

6. The antibody or antibody fragment of claim 4, wherein the antibody or antibody fragment comprises a heavy chain comprising the amino acid sequence of SEQ ID No.: 38 and a light chain comprising the amino acid sequence of SEQ ID No.:

39.

7. The antibody or antibody fragment of any of the preceding claims, wherein the antibody or antibody fragment is capable of neutralizing the 5'-ectonucleotidase activity of a CD73 polypeptide.

8. An antibody or antibody fragment capable of specifically binding to a human CD73 polypeptide on the cell surface and neutralizing the 5'-ectonucleotidase activity of the cell surface CD73 polypeptide, wherein the antibody or antibody fragment comprises a heavy chain variable region (HV) comprising an amino acid sequence at least 95% identical to the amino acid sequence of SEQ ID No.: 42, and a light chain variable region (LV) comprising an amino acid sequence at least 95% identical to an amino acid sequence selected from the group consisting of SEQ ID No.:

43.

9. An antibody or antibody fragment that is capable of specifically binding to a human CD73 polypeptide on the surface of a cell and neutralizing the 5'-ectonucleotidase activity of the cell surface CD73 polypeptide, wherein the antibody or antibody fragment comprises a heavy chain comprising an amino acid sequence at least 95% identical to the amino acid sequence of SEQ ID No.: 47, and a light chain comprising an amino acid sequence at least 95% identical to an amino acid sequence selected from the group consisting of SEQ ID No.:

48.

10. The antibody or antibody fragment of claim 8 or 9, wherein the VH comprises a CDR1, CDR2 and CDR3 having the respective amino acid sequences shown in SEQ ID No.: 2, 3 and 4; and the VL comprises a CDR1, CDR2 and CDR3 having the respective amino acid sequences shown in SEQ ID No.: 5, 6 and 7.

11. The antibody or antibody fragment of any one of claims 8 to 10, wherein the VH comprises the amino acid sequences of the FR1, FR2 and FR3 frame of the human IGHV1-3 gene and the VL comprises the amino acid sequences of the FR1, FR2 and FR3 frame of the human IGKV1-33 gene.

12. The antibody or antibody fragment of any one of claims 8-11, wherein the VH comprises a CDR1, CDR2 and CDR3 having the respective amino acid sequences shown in SEQ ID Nos. 2, 8 and 9; and the VL comprises a CDR1, CDR2 and CDR3 having the respective amino acid sequences shown in SEQ ID Nos. 10, 11 and 7.

13. The antibody or antibody fragment of claim 12, wherein the antibody or antibody fragment comprises a heavy chain variable region (HV) comprising an amino acid sequence at least 90%, 95%, 97%, 98% or 99% identical to the amino acid sequence of SEQ ID No.: 37, and a light chain variable region (LV) comprising an amino acid sequence at least 90%, 95%, 97%, 98% or 99% identical to an amino acid sequence selected from the group consisting of SEQ ID No.:

33.

14. The antibody or antibody fragment of claim 12, wherein the antibody or antibody fragment comprises a heavy chain comprising an amino acid sequence at least 90%, 95%, 97%, 98% or 99% identical to the amino acid sequence of SEQ ID No.: 38, and a light chain comprising an amino acid sequence at least 90%, 95%, 97%, 98% or 99% identical to an amino acid sequence selected from the group consisting of SEQ ID No.:

39.

15. The antibody or antibody fragment of any one of claims 8-11, wherein the VH comprises a CDR1, CDR2 and CDR3 having the respective amino acid sequences shown in SEQ ID No.: 2, 12 and 13; and the VL comprises a CDR1, CDR2 and CDR3 having the respective amino acid sequences shown in SEQ ID No.: 14, 15 and 7.

16. The antibody or antibody fragment of claim 15, wherein the antibody or antibody fragment comprises a heavy chain variable region (HV) comprising an amino acid sequence at least 90%, 95%, 97%, 98% or 99% identical to the amino acid sequence of SEQ ID No.: 42, and a light chain variable region (LV) comprising an amino acid sequence at least 90%, 95%, 97%, 98% or 99% identical to an amino acid sequence selected from the group consisting of SEQ ID No.:

43.

17. The antibody or antibody fragment of claim 15, wherein the antibody or antibody fragment comprises a heavy chain comprising an amino acid sequence at least 90%, 95%, 97%, 98% or 99% identical to the amino acid sequence of SEQ ID No.: 47, and a light chain comprising an amino acid sequence at least 90%, 95%, 97%, 98% or 99% identical to an amino acid sequence selected from the group consisting of SEQ ID No.:

48.

18. The antibody or antibody fragment of any one of the preceding claims, wherein: the amino acid at position 2 of the Kabat heavy chain is an isoleucine.

19. The antibody or antibody fragment of any one of the preceding claims, wherein the amino acid at position 30 of the Kabat heavy chain is an alanine.

20. The antibody or antibody fragment of any one of the preceding claims, wherein the amino acid at position 48 of the Kabat heavy chain is an isoleucine.

21. The antibody or antibody fragment of any one of the preceding claims, wherein the amino acid at position 69 of the Kabat heavy chain is a leucine.

22. The antibody or antibody fragment of any one of the preceding claims, wherein the amino acid at position 73 of the Kabat heavy chain is a lysine.

23. The antibody or antibody fragment of any one of the preceding claims, wherein the heavy chain comprises an isoleucine residue at Kabat position 2, an alanine at position 30, an isoleucine at position 48, a leucine at position 69, and a lysine at position 73.

24. The antibody or antibody fragment of any one of the preceding claims, wherein the amino acid at position 67 of the Kabat light chain is a tyrosine.

25. The antibody or antibody fragment of any one of the preceding claims, wherein the amino acid at position 60 of the Kabat light chain is serine or aspartic acid.

26. The antibody or antibody fragment of any one of the preceding claims, wherein the amino acid at position 2 of the Kabat light chain is valine or isoleucine.

27. The antibody or antibody fragment of any one of the preceding claims, wherein the amino acid at position 87 of the Kabat light chain is either tyrosine or phenylalanine.

28. The antibody or antibody fragment of any one of the preceding claims, wherein the light chain comprises a tyrosine residue at Kabat position 67, a serine at position 60, an isoleucine at position 2, and a tyrosine at position 87.

29. The antibody or antibody fragment of any one of the preceding claims, wherein the amino acid at position 28 of the Kabat heavy chain is threonine (T), the amino acid at position 66 of the Kabat heavy chain is arginine (R), the amino acid at position 67 of the Kabat heavy chain is valine (V), and the amino acid at position 71 of the Kabat heavy chain is arginine (R).

30. The antibody or antibody fragment of any one of the preceding claims, wherein the antibody or antibody fragment specifically binds to a human CD73 polypeptide on the surface of a cell and is capable of neutralizing the 5'-ectonucleotidase activity thereof, wherein the antibody or antibody fragment inhibits the activity of the human CD73 polypeptide without detectably reducing the binding between the CD73 polypeptide and a substrate thereof.

31. The antibody or antibody fragment of any one of the preceding claims, wherein the antibody or antibody fragment has reduced binding to a mutant CD73 polypeptide comprising the K136A mutation and / or the A99S, E129A, K133A, E134N and A135S mutations (with reference to SEQ ID No.: 1), in relation to the binding between the antibody or antibody fragment and a wild-type CD73 polypeptide comprising the amino acid sequence of SEQ ID No.:

1.

32. The antibody or antibody fragment of any one of the preceding claims, wherein the antibody or antibody fragment comprises a human-derived Fe domain modified to reduce the binding between the Fe domain and a human Fcy receptor.

33. The antibody or antibody fragment of any one of the preceding claims, wherein the antibody or antibody fragment comprises a human lgG1 Fe domain comprising amino acid substitutions at residues 234, 235 and 331 or comprising amino acid substitutions at residues 234, 235 and 322. (EU numbering according to Kabat).

34. The antibody of any one of the preceding claims, wherein the antibody is a full-length antibody.

35. The antibody or antibody fragment of any one of the preceding claims, wherein the antibody is an antibody fragment.

36. A pharmaceutical composition comprising an antibody or antibody fragment of any one of the preceding claims and a pharmaceutically acceptable carrier.

37. A kit comprising the antibody or antibody fragment of any of the preceding claims, optionally further comprising a labeled secondary antibody that specifically recognizes the antibody or antibody fragment of any of the preceding claims.

38. A nucleic acid or set of nucleic acids encoding a heavy and / or light chain of an antibody or antibody fragment of any one of claims 1 to 35.

39. A recombinant host cell producing the antibody or antibody fragment of any one of claims 1 to 35.

40. A method for treating or preventing a disease in a patient in need thereof, the method comprising administering to said patient an effective amount of an antibody, antibody fragment or a composition of any one of claims 1-36.

41. The process of claim 40, wherein said disease is cancer or an infectious disease.

42. The process of any one of claim 40 or 41, wherein the disease or cancer is leukemia, bladder cancer, glioma, glioblastoma, ovarian cancer, melanoma, prostate cancer, thyroid cancer, stomach cancer, esophageal cancer, pancreatic cancer or breast cancer.