Formulations of antibodies that bind human CD137 and uses thereof

Abstract

The present disclosure relates to, inter alia, stable formulations comprising an antibody that binds human CD 137 or antigen binding fragments thereof, and to use of the formulations in methods for treating, or ameliorating various diseases and conditions, including cancer, that are amenable to treatment with a CD 137 antibody.

Description

FORMULATIONS OF ANTIBODIES THAT BIND HUMAN CD137 AND USES THEREOF CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application Serial No. 62 / 793,342 filed on January 16, 2019, and U.S. Provisional Patent Application Serial No. 62 / 960,501 filed on January 13, 2020, the contents of each of which are herein incorporated by reference in their entireties. BACKGROUND In recent years, an increasing body of evidence suggests the immune system operates as a significant barrier to tumor formation and progression. The principle that naturally-occurring T cells with anti-tumor potential or activity exist in a patient with cancer has rationalized the development of immunotherapeutic approaches in oncology. Immune cells, such as T cells, macrophages, and natural killer cells, can exhibit anti-tumor activity and effectively control the occurrence and growth of malignant tumors. Tumor-specific or -associated antigens can induce immune cells to recognize and eliminate malignancies (Chen & Mellman, (2013) Immunity 39(1):1-10). In spite of the existence of tumor-specific immune responses, malignant tumors often evade or avoid immune attack through a variety of immunomodulatory mechanisms resulting in the failure to control tumor occurrence and progression (Motz & Coukos, (2013) Immunity 39(1):61-730). Indeed, an emerging hallmark of cancer is the exploitation of these immunomodulatory mechanisms and the disablement of anti-tumor immune responses, resulting in tumor evasion and escape from immunological killing (Hanahan and Weinberg (2011) Cell 144(5):646-674). Novel approaches in the immunotherapy of cancer involve counteracting these immune evasion and escape mechanisms and inducing the endogenous immune system to reject tumors. CD137 (alternatively known as “tumor necrosis factor receptor superfamily member 9” (TNFRSF9), 4-1BB, and “induced by lymphocyte activation” (ILA)) is a transmembrane co- stimulatory receptor protein belonging to the tumor necrosis factor superfamily. CD137 is a T cell co-stimulatory receptor induced upon TCR activation (Nam et al., (2005) Curr Cancer Drug Targets 5:357-363; Watts et al., (2005) Annu Rev Immunol 23:23-68). In addition to its expression on activated CD4+ and CD8+ T cells, CD137 is also expressed on CD4+CD25+ regulatory T cells, activated natural killer (NK) and NK-T cells, monocytes, neutrophils, and dendritic cells. Under physiological conditions, CD137 is ligated by CD137 ligand (CD137L), an agonist membrane molecule present on antigen-presenting cells including B cells, monocytes, macrophages, and dendritic cells (Watts et al., (2005) Annu Rev Immunol 23:23-68). Upon interaction with its ligand, CD137 leads to increased TCR-induced T-cell proliferation, cytokine production, functional maturation, and prolonged CD8+ T-cell survival. The potential of CD137 co-stimulation using various agonists (e.g. agonistic antibodies, recombinant CD137L protein, and CD137-specific aptamers) in enabling the immune system to attack tumors has been documented in numerous models (Dharmadhikari et al., (2016) Oncoimmunology 5(4):e1113367 and references therein). A recent report on the clinical evaluation of an agonistic CD137 antibody (Urelumab, BMS-663513; Bristol-Myers Squibb) documented the observation of treatment- related adverse events in human subjects, including indications of severe hepatotoxicity (transaminitis) correlating with antibody dose (Segal et al., (2016) Clin Cancer Res 23(8):1929- 1936). In contrast, a different agonistic CD137 antibody (Utomilumab, PF-05082566; Pfizer) tested in combination with an anti-PD-1 antibody (pembrolizumab), though not resulting in any dose-limiting toxicities, showed comparable results to anti-PD-1 antibody therapy alone (Tolcher, A. etal., (2017) Clin Cancer Res 23(18): 5349-5357). One of the challenges in developing therapeutic antibodies is protein stability. Antibodies have a three-dimensional structure, known as the tertiary structure, that is sensitive to the balance of intra- and intermolecular interactions between amino acid functional groups and the external environment. Non-covalent interactions are critical to maintaining the native folded structure of the antibody. Furthermore, the folded antibody structure is in a state of dynamic equilibrium and any factors shifting the interaction balance can cause the structure to change. This results in unstable large molecules. For example, when the native antibody structure is unfolded to an intermediate state or to a denatured state, the protein variants are prone to aggregation. (Awwad et al., Pharmaceutics, 2018, 10, 83; doi:10.3390 / pharmaceutics10030083). Many factors can lead to protein aggregation, these include temperature, mechanical, physical, and freeze / thaw stress. Thus, one of the barriers to antibody development is the development of stable antibody formulations. Excipients have been used to increase the stability of antibody formulations by reducing protein dynamics and motion, increasing confirmation stability of the antibodies, and inhibiting aggregation. However, the excipient used in one antibody formulation may not be suitable for another antibody due to differences in antibody sequence (Awwad er al.). Thus, there continues to be an unmet need for the development of stable antibody formulations, including stable formulations comprising novel agonistic antibodies that bind to human CD137. SUMMARY OF THE INVENTION The present disclosure is based, at least in part, on the discovery of novel agonist anti- CD137 antibodies exhibiting protective anti-tumor immunity in animals, and formulations thereof. Notably, the antibodies described herein are efficacious against diverse tumor types, and over a wide dose range. Moreover, as exemplified in the working examples, the antibodies described herein are therapeutically effective against very large tumors. For example, treatment of tumor-bearing mice with agonist anti-CD137 antibodies described herein resulted in complete regression of tumors as large as 1,800 mm?, As set forth in FIG. 15, treatment of such mice also resulted in protective immunity. And coincident with the observed efficacy were positive immunophenotypic changes in the tumor microenvironment, such as increased immune cell infiltration with concomitant reductions in regulatory T cell and exhausted T cell populations (see, e.g., FIGs. 22A-22D). As described above, agonism of CD137 has been associated with certain adverse events, including hepatotoxicity-related deaths in humans (see, e.g., Segal et al. (2017) Clin Cancer Res 23(8): 1929-1935). Similar toxicities resulting from treatment with agonist anti-CD137 antibodies (such as the 3H3 antibody) have also been observed in animal models (see, e.g., Bartkowiak et al. (2018) Clin Cancer Res 24(5):1138-1151). Yet, the agonist anti-CD137 antibodies described herein have minimal effects on the liver, as determined by, e.g., plasma levels of liver enzymes (e.g., alanine aminotransferase (ALT)) and immune cell infiltration. For example, there was no evidence of increased intrahepatic or intrasplenic immune cell infiltration in mice treated with the antibodies. Thus, the antibodies described herein are not only highly efficacious, but also sparing of certain toxicities associated with CD137 agonism. While the disclosure is not bound by any particular theory or mechanism of action, the superior therapeutic and toxicity-sparing properties of the antibodies described herein are believed to derive in part from one or both of their affinity and the novel epitope to which they bind. That is, the antibodies described herein share a common, novel epitope that is distinct from that of other agonist anti-CD137 antibodies. And, as exemplified in the working examples, engagement of this epitope by the antibodies described herein gives rise to differentiated in vitro activity, such as effects on regulatory T cell proliferation, cytokine production by CD8* T cells and macrophages, and intracellular signaling, as compared to agonist antibodies that bind to different epitopes of CD137. Furthermore, it has been demonstrated that an affinity range (a “sweet spot”) for antibodies is particularly optimal for anti-tumor activity. For example, antibodies of intermediate affinity were shown to be more efficacious against large tumors as compared to antibodies with higher or lower affinity. The disclosure relates, at least in part, to stable anti-CD137 antibody formulations. Notably, the anti-CD137 antibody formulations of the disclosure maintain the stability of the antibody, or antigen binding fragment thereof, minimize the formation of antibody aggregates (high molecular weight species) and particulates, reduce the percentage of charge variants, and maintain the structural integrity of the antibody. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises a heavy chain CDR3 of SEQ ID NO: 126, wherein X is any amino acid, and a buffer comprising histidine. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises a heavy chain CDR3 of SEQ ID NO: 126, wherein X is any amino acid, a buffer comprising histidine; and a disaccharide sugar. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises a heavy chain CDR3 of SEQ ID NO: 126, wherein X is any amino acid, and a buffer comprising histidine, wherein the formulation has a pH of about 5.0-7.0. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises a heavy chain CDR3 of SEQ ID NO: 126, wherein X is any amino acid, a buffer comprising histidine, a disaccharide sugar, a non-ionic surfactant, and a salt, wherein the pH of the formulation is about 5.0 to about 7.0. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises a heavy chain CDR3 of SEQ ID NO: 126, wherein X is any amino acid, a buffer comprising histidine, a disaccharide sugar at about 5%-about 15% weight / volume, a non- ionic surfactant at about 0.01%-about 0.1% weight / volume (w / v), and a salt at about 50 mM — 200 mM, wherein the pH of the formulation is about 5.0 to about 7.0. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises a heavy chain CDR3 of SEQ ID NO: 126, wherein X is any amino acid, a buffer comprising about 10 mM to about 100 mM histidine, sucrose at about 5%-about 15% weight / volume, polysorbate-80 at about 0.01%-about 0.1% weight / volume (w / v), and NaCl at about 50 mM — 200 mM, wherein the pH of the formulation is about 5.0 to about 7.0. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises a heavy chain CDR3 of SEQ ID NO: 126, wherein X is any amino acid, a buffer comprising histidine, a disaccharide sugar, a non-ionic surfactant, and a salt, wherein the pH of the formulation is about 5.0 to about 7.4. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises a heavy chain CDR3 of SEQ ID NO: 126, wherein X is any amino acid, a buffer comprising histidine, a disaccharide sugar at about 5%-about 15% weight / volume, a non- ionic surfactant at about 0.01%-about 0.1% weight / volume (w / v), and a salt at about 50 mM — 200 mM, wherein the pH of the formulation is about 5.0 to about 7.4. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises a heavy chain CDR3 of SEQ ID NO: 126, wherein X is any amino acid, a buffer comprising about 10 mM to about 100 mM histidine, sucrose at about 5%-about 15% weight / volume, polysorbate-80 at about 0.01%-about 0.1% weight / volume (w / v), and NaCl at about 50 mM — 200 mM, wherein the pH of the formulation is about 5.0 to about 7.4. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises a heavy chain CDR3 of SEQ ID NO: 126, wherein X is any amino acid, a buffer comprising about 20 mM histidine, sucrose at about 10% weight / volume (w / v), polysorbate-80 at about 0.03% weight / volume (w / v), and NaCl at about 100mM, wherein the pH of the formulation is about 6.0. In any of the foregoing or related aspects of the disclosure, the anti-CD137 antibody comprises a heavy chain CDR3 of DXPFXLDXXYYYYYX (SEQ ID NO: 127), wherein X is any amino acid. In any of the foregoing or related aspects of the disclosure, the anti-CD137 antibody comprises a heavy chain CDR3 of DX X>X3X4LX5XeX7XsYX9YYX10 (SEQ ID NO: 128), wherein Xi is any amino acid, wherein Xz is a non-polar amino acid, wherein X3 is a non- polar amino acid, wherein X4is any amino acid, wherein Xs is a polar amino acid, wherein X¢is any amino acid, wherein X7 is any amino acid, wherein Xs is a polar amino acid, wherein Xo is a polar amino acid, and wherein Xois any amino acid. In any of the foregoing or related aspects of the disclosure, X2 is proline, X3 is phenylalanine or tryptophan, Xs is aspartic acid or glutamic acid, Xy is tyrosine, and Xo is tyrosine. In any of the foregoing or related aspects of the disclosure, the anti-CD137 antibody of the formulation of the disclosure comprises a heavy chain CDR3 of SEQ ID NO: 68. In any of the foregoing or related aspects of the disclosure, the anti-CD137 antibody comprises a comprises a heavy chain CDR1 of SEQ ID NO: 48, a heavy chain CDR2 of SEQ ID NO: 56, and a heavy chain CDR3 of SEQ ID NO: 68, and a light chain CDR1 of SEQ ID NO: 69, a light chain CDR2 of SEQ ID NO: 78, and a light chain CDR3 of SEQ ID NO: 89. In any of the foregoing or related aspects of the disclosure, the anti-CD137 antibody comprises a comprises a heavy chain CDR1 of SEQ ID NO: 51, a heavy chain CDR2 of SEQ ID NO: 108, and a heavy chain CDR3 of SEQ ID NO: 68, and a light chain CDR1 of SEQ ID NO: 69, a light chain CDR2 of SEQ ID NO: 78, and a light chain CDR3 of SEQ ID NO: 89. In any of the foregoing or related aspects of the disclosure, the anti-CD137 antibody comprises heavy and light chain sequences comprising amino acid sequences having at least 90% identity to SEQ ID NOs: 4 and 6, respectively. In some aspects, the anti-CD137 antibody comprises heavy and light chain sequences having amino acid sequences set forth in SEQ ID NOs: 4 and 6, respectively. In any of the foregoing or related aspects of the disclosure, the anti-CD137 antibody comprises heavy and light chain sequences comprising amino acid sequences having at least 90% identity to SEQ ID NOs: 101 and 6, respectively. In some aspects, the anti-CD137 antibody comprises heavy and light chain sequences having amino acid sequences set forth in SEQ ID NOs: 101 and 6, respectively. In any of the foregoing or related aspects of the disclosure, the antibody comprises an IgG1 heavy chain constant region. In some aspects, the IgG1 heavy chain constant region is a wild-type human IgG1 heavy chain constant region. In some aspects, the IgG1 heavy chain constant region comprises an amino acid substitution relative to a wild-type human IgG1 heavy chain constant region. In any of the foregoing or related aspects of the disclosure, the antibody comprises an 1gG4 heavy chain constant region. In some aspects, the [gG4 heavy chain constant region is a wild-type human IgG4 heavy chain constant region. In some aspects, the [gG4 heavy chain constant region comprises an amino acid substitution relative to a wild-type human IgG4 heavy chain constant region. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 56 and 68, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 69, 78 and 89, respectively, and a buffer comprising histidine. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 135, 139 and 143, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 144, 147 and 150, respectively, and a buffer comprising histidine. [new paragraph] In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 154 and 159, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 144, 147, 150, respectively, and a buffer comprising histidine. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 56 and 68, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 69, 78 and 89, respectively, a buffer comprising histidine, and a disaccharide sugar. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 135, 139 and 143, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 144, 147 and 150, respectively, a buffer comprising histidine, and a disaccharide sugar. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 154 and 159, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 144, 147 and 150, respectively, a buffer comprising histidine, and a disaccharide sugar. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 56 and 68, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 69, 78 and 89, respectively, and a buffer comprising histidine, wherein the formulation has a pH of about 5.0-7.0. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 135, 139 and 143, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 144, 147 and 150, respectively, and a buffer comprising histidine, wherein the formulation has a pH of about 5.0-7.0. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 154 and 159, respectively, and light chain CDR 1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 144, 147 and 150, respectively, and a buffer comprising histidine, wherein the formulation has a pH of about 5.0-7.0. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 56 and 68, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 69, 78 and 89, respectively, a buffer comprising histidine, a disaccharide sugar, a non- ionic surfactant, and a salt, wherein the pH of the formulation is about 5.0 to about 7.0. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 135, 139 and 143, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 144, 147 and 150, respectively, a buffer comprising histidine, a disaccharide sugar, a non-ionic surfactant, and a salt, wherein the pH of the formulation is about 5.0 to about 7.0. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 154 and 159, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 144, 147 and 150, respectively, a buffer comprising histidine, a disaccharide sugar, a non-ionic surfactant, and a salt, wherein the pH of the formulation is about 5.0 to about 7.0. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 56 and 68, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 69, 78 and 89, respectively, a buffer comprising histidine, a disaccharide sugar at about 5%-about 15% weight / volume, a non-ionic surfactant at about 0.01%-about 0.1% weight / volume (w / v), and a salt at about 50 mM — 200 mM, wherein the pH of the formulation is about 5.0 to about 7.0. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 135, 139 and 143, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 144, 147 and 150, respectively, a buffer comprising histidine, a disaccharide sugar at about 5%-about 15% weight / volume, a non-ionic surfactant at about 0.01%-about 0.1% weight / volume (w / v), and a salt at about 50 mM — 200 mM, wherein the pH of the formulation is about 5.0 to about 7.0. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 154 and 159, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 144, 147 and 150, respectively, a buffer comprising histidine, a disaccharide sugar at about 5%-about 15% weight / volume, a non-ionic surfactant at about 0.01%-about 0.1% weight / volume (w / v), and a salt at about 50 mM — 200 mM, wherein the pH of the formulation is about 5.0 to about 7.0. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 56 and 68, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 69, 78 and 89, respectively, a buffer comprising about 10 mM to about 100 mM histidine, sucrose at about 5%-about 15% weight / volume, polysorbate-80 at about 0.01%-about 0.1% weight / volume (w / v), and NaCl at about 50 mM — 200 mM, wherein the pH of the formulation is about 5.0 to about 7.0. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 135, 139 and 143, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 144, 147 and 150, respectively, a buffer comprising about 10 mM to about 100 mM histidine, sucrose at about 5%-about 15% weight / volume, polysorbate-80 at about 0.01%- about 0.1% weight / volume (w / v), and NaCl at about 50 mM — 200 mM, wherein the pH of the formulation is about 5.0 to about 7.0. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 154 and 159, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 144, 147 and 150, respectively, a buffer comprising about 10 mM to about 100 mM histidine, sucrose at about 5%-about 15% weight / volume, polysorbate-80 at about 0.01%- about 0.1% weight / volume (w / v), and NaCl at about 50 mM — 200 mM, wherein the pH of the formulation is about 5.0 to about 7.0. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 56 and 68, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 69, 78 and 89, respectively, and a buffer comprising histidine, wherein the formulation has a pH of about 5.0-7.4. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 135, 139 and 143, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 144, 147 and 150, respectively, and a buffer comprising histidine, wherein the formulation has a pH of about 5.0-7.4. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 154 and 159, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 144, 147 and 150, respectively, and a buffer comprising histidine, wherein the formulation has a pH of about 5.0-7.4. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 56 and 68, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 69, 78 and 89, respectively, a buffer comprising histidine, a disaccharide sugar, a non- ionic surfactant, and a salt, wherein the pH of the formulation is about 5.0 to about 7.4. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 135, 139 and 143, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 144, 147 and 150, respectively, a buffer comprising histidine, a disaccharide sugar, a non-ionic surfactant, and a salt, wherein the pH of the formulation is about 5.0 to about 74. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 154 and 159, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 144, 147 and 150, respectively, a buffer comprising histidine, a disaccharide sugar, a non-ionic surfactant, and a salt, wherein the pH of the formulation is about 5.0 to about T4. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 56 and 68, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 69, 78 and 89, respectively, a buffer comprising histidine, a disaccharide sugar at about 5%-about 15% weight / volume, a non-ionic surfactant at about 0.01%-about 0.1% weight / volume (w / v), and a salt at about 50 mM — 200 mM, wherein the pH of the formulation is about 5.0 to about 7.4. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 135, 139 and 143, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 144, 147 and 150, respectively, a buffer comprising histidine, a disaccharide sugar at about 5%-about 15% weight / volume, a non-ionic surfactant at about 0.01%-about 0.1% weight / volume (w / v), and a salt at about 50 mM — 200 mM, wherein the pH of the formulation is about 5.0 to about 7.4. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 154 and 159, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 144, 147 and 150, respectively, a buffer comprising histidine, a disaccharide sugar at about 5%-about 15% weight / volume, a non-ionic surfactant at about 0.01%-about 0.1% weight / volume (w / v), and a salt at about 50 mM — 200 mM, wherein the pH of the formulation is about 5.0 to about 7.4. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 56 and 68, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 69, 78 and 89, respectively, a buffer comprising about 10 mM to about 100 mM histidine, sucrose at about 5%-about 15% weight / volume, polysorbate-80 at about 0.01%-about 0.1% weight / volume (w / v), and NaCl at about 50 mM — 200 mM, wherein the pH of the formulation is about 5.0 to about 7.4. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 135, 139 and 143, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 144, 147 and 150, respectively, a buffer comprising about 10 mM to about 100 mM histidine, sucrose at about 5%-about 15% weight / volume, polysorbate-80 at about 0.01%- about 0.1% weight / volume (w / v), and NaCl at about 50 mM — 200 mM, wherein the pH of the formulation is about 5.0 to about 7.4. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 154 and 159, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 144, 147 and 150, respectively, a buffer comprising about 10 mM to about 100 mM histidine, sucrose at about 5%-about 15% weight / volume, polysorbate-80 at about 0.01%- about 0.1% weight / volume (w / v), and NaCl at about 50 mM — 200 mM, wherein the pH of the formulation is about 5.0 to about 7.4. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 56 and 68, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 69, 78 and 89, respectively, a buffer comprising about 20 mM histidine, sucrose at about 10% weight / volume (w / v), polysorbate-80 at about 0.03% weight / volume (w / v), and NaCl at about 100mM, wherein the pH of the formulation is about 6.0. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 135, 139 and 143, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 144, 147 and 150, respectively, a buffer comprising about 20 mM histidine, sucrose at about 10% weight / volume (w / v), polysorbate-80 at about 0.03% weight / volume (w / v), and NaCl at about 100mM, wherein the pH of the formulation is about 6.0. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 154 and 159, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 144, 147 and 150, respectively, a buffer comprising about 20 mM histidine, sucrose at about 10% weight / volume (w / v), polysorbate-80 at about 0.03% weight / volume (w / v), and NaCl at about 100mM, wherein the pH of the formulation is about 6.0. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises the heavy and light chain variable sequences set forth in SEQ ID NOs: 4 and 6, respectively, and a buffer comprising histidine. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises the heavy and light chain variable sequences set forth in SEQ ID NOs: 4 and 6, respectively, a buffer comprising histidine, and a disaccharide sugar. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises the heavy and light chain variable sequences set forth in SEQ ID NOs: 4 and 6, respectively, and a buffer comprising histidine, wherein the formulation has a pH of about 5.0- 7.0. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises the heavy and light chain variable sequences set forth in SEQ ID NOs: 4 and 6, respectively, a buffer comprising histidine, a disaccharide sugar, a non-ionic surfactant, and a salt, wherein the pH of the formulation is about 5.0 to about 7.0. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises the heavy and light chain variable sequences set forth in SEQ ID NOs: 4 and 6, respectively, a buffer comprising histidine, a disaccharide sugar at about 5%-about 15% weight / volume, a non-ionic surfactant at about 0.01%-about 0.1% weight / volume (w / v), and a salt at about 50 mM — 200 mM, wherein the pH of the formulation is about 5.0 to about 7.0. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises the heavy and light chain variable sequences set forth in SEQ ID NOs: 4 and 6, respectively, a buffer comprising about 10 mM to about 100 mM histidine, sucrose at about 5%-about 15% weight / volume, polysorbate-80 at about 0.01%-about 0.1% weight / volume (w / v), and NaCl at about 50 mM — 200 mM, wherein the pH of the formulation is about 5.0 to about 7.0. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises the heavy and light chain variable sequences set forth in SEQ ID NOs: 4 and 6, respectively, and a buffer comprising histidine, wherein the formulation has a pH of about 5.0- 7.4. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises the heavy and light chain variable sequences set forth in SEQ ID NOs: 4 and 6, respectively, a buffer comprising histidine, a disaccharide sugar, a non-ionic surfactant, and a salt, wherein the pH of the formulation is about 5.0 to about 7.4. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises the heavy and light chain variable sequences set forth in SEQ ID NOs: 4 and 6, respectively, a buffer comprising histidine, a disaccharide sugar at about 5%-about 15% weight / volume, a non-ionic surfactant at about 0.01%-about 0.1% weight / volume (w / v), and a salt at about 50 mM — 200 mM, wherein the pH of the formulation is about 5.0 to about 7.4. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises the heavy and light chain variable sequences set forth in SEQ ID NOs: 4 and 6, respectively, a buffer comprising about 10 mM to about 100 mM histidine, sucrose at about 5%-about 15% weight / volume, polysorbate-80 at about 0.01%-about 0.1% weight / volume (w / v), and NaCl at about 50 mM — 200 mM, wherein the pH of the formulation is about 5.0 to about 7.4.In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises the heavy and light chain variable sequences set forth in SEQ ID NOs: 4 and 6, respectively, a buffer comprising about 20 mM histidine, sucrose at about 10% weight / volume (w / v), polysorbate-80 at about 0.03% weight / volume (w / v), and NaCl at about 100mM, wherein the pH of the formulation is about 6.0. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy and light chain amino acid sequences set forth in SEQ ID NOs: 129 and 133, respectively, and a buffer comprising histidine. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy and light chain amino acid sequences set forth in SEQ ID NOs: 129 and 133, respectively, a buffer comprising histidine, and a disaccharide sugar. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy and light chain amino acid sequences set forth in SEQ ID NOs: 129 and 133, respectively, and a buffer comprising histidine, wherein the formulation has a pH of about 5.0-7.0. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy and light chain amino acid sequences set forth in SEQ ID NOs: 129 and 133, respectively, a buffer comprising histidine, a disaccharide sugar, a non-ionic surfactant, and a salt, wherein the pH of the formulation is about 5.0 to about 7.0. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy and light chain amino acid sequences set forth in SEQ ID NOs: 129 and 133, respectively, a buffer comprising histidine, a disaccharide sugar at about 5%-about 15% weight / volume, a non-ionic surfactant at about 0.01%-about 0.1% weight / volume (w / v), and a salt at about 50 mM — 200 mM, wherein the pH of the formulation is about 5.0 to about 7.0. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy and light chain amino acid sequences set forth in SEQ ID NOs: 129 and 133, respectively, a buffer comprising about 10 mM to about 100 mM histidine, sucrose at about 5%-about 15% weight / volume, polysorbate-80 at about 0.01%-about 0.1% weight / volume (w / v), and NaCl at about 50 mM — 200 mM, wherein the pH of the formulation is about 5.0 to about 7.0. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy and light chain amino acid sequences set forth in SEQ ID NOs: 129 and 133, respectively, and a buffer comprising histidine, wherein the formulation has a pH of about 5.0-7.4. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy and light chain amino acid sequences set forth in SEQ ID NOs: 129 and 133, respectively, a buffer comprising histidine, a disaccharide sugar, a non-ionic surfactant, and a salt, wherein the pH of the formulation is about 5.0 to about 7.4. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy and light chain amino acid sequences set forth in SEQ ID NOs: 129 and 133, respectively, a buffer comprising histidine, a disaccharide sugar at about 5%-about 15% weight / volume, a non-ionic surfactant at about 0.01%-about 0.1% weight / volume (w / v), and a salt at about 50 mM — 200 mM, wherein the pH of the formulation is about 5.0 to about 7.4. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy and light chain amino acid sequences set forth in SEQ ID NOs: 129 and 133, respectively, a buffer comprising about 10 mM to about 100 mM histidine, sucrose at about 5%-about 15% weight / volume, polysorbate-80 at about 0.01%-about 0.1% weight / volume (w / v), and NaCl at about 50 mM — 200 mM, wherein the pH of the formulation is about 5.0 to about 7.4. In some aspects, the disclosure provides a formulation comprising an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises heavy and light chain amino acid sequences set forth in SEQ ID NOs: 129 and 133, respectively, a buffer comprising about 20 mM histidine, sucrose at about 10% weight / volume (w / v), polysorbate-80 at about 0.03% weight / volume (w / v), and NaCl at about 100mM, wherein the pH of the formulation is about 6.0. In any of the foregoing or related aspects of the disclosure, the formulation of the disclosure comprises histidine. In some aspects, the formulation of the disclosure comprises about 10 mM histidine to about 100 mM histidine. In some aspects, the formulation comprises about 20 mM histidine. In any of the foregoing or related aspects of the disclosure, the formulation of the disclosure comprises a disaccharide sugar. In some embodiments, the disaccharide sugar is selected from sucrose, lactose, maltose, and trehalose. In some embodiments, the disaccharide sugar is sucrose. In some embodiments, the formulation of the disclosure comprises the disaccharide sugar at about 5%-about 15% weight / volume. In some embodiments, the formulation of the disclosure comprises the disaccharide sugar at about 10% weight / volume. In any of the foregoing or related aspects of the disclosure, the formulation of the disclosure comprises a salt. In some aspects, the salt is NaCl. In some aspects, the formulation of the disclosure comprises salt at a concentration of about 50 mM - 200 mM. In some aspects, the formulation of the disclosure comprises salt at a concentration of about 100 mM. In any of the foregoing or related aspects of the disclosure, the formulation of the disclosure has a pH of about 5.0-7.0. In some embodiments, the formulation of the disclosure has a pH of about 6.0. In any of the foregoing or related aspects of the disclosure, the formulation of the disclosure has a pH of about 5.0-8.0. In some embodiments, the formulation of the disclosure has a pH of about 5.0-7.4. In any of the foregoing or related aspects of the disclosure, the formulation of the disclosure comprises a non-ionic surfactant. In some aspects, the non-ionic surfactant is a polysorbate. In some aspects, the polysorbate is polysorbate-80. In some aspects, the formulation of the disclosure comprises the non-ionic surfactant is at about 0.01%-about 0.1% weight / volume (w / v). In some aspects, the formulation of the disclosure comprises the non-ionic surfactant is at about 0.03% weight / volume (w / v). In any of the foregoing or related aspects of the disclosure, the formulation of the disclosure comprises an anti-CD137 antibody at a concentration of about 1mg / ml to about 100 mg / ml. In some aspects, the formulation of the disclosure comprises the anti-CD137 antibody at a concentration of about 5 mg / ml to about 15 mg / ml. In some aspects, the formulation of the disclosure comprises the anti-CD137 antibody at a concentration of about 15 mg / ml to about 30 mg / ml. In some aspects, the formulation of the disclosure comprises the anti-CD137 antibody at a concentration of about 30 mg / ml to about 45 mg / ml. In some aspects, the formulation of the disclosure comprises the anti-CD137 antibody at a concentration of about 45 mg / ml to about 60 mg / ml. In some aspects, the formulation of the disclosure comprises the anti-CD137 antibody at a concentration of about 60 mg / ml to about 75 mg / ml. In some aspects, the formulation of the disclosure comprises the anti-CD137 antibody at a concentration of about 75 mg / ml to about 90 mg / ml. In some aspects, the formulation of the disclosure comprises the anti-CD137 antibody at a concentration of about 85 mg / ml to about 100 mg / ml. In some aspects, the formulation of the disclosure comprises the anti-CD137 antibody at a concentration of about 5 mg / ml. In some aspects, the formulation of the disclosure comprises the anti-CD137 antibody at a concentration of about 10 mg / ml. In some aspects, the formulation of the disclosure comprises the anti-CD137 antibody at a concentration of about 15 mg / ml. In some aspects, the formulation of the disclosure comprises the anti-CD137 antibody at a concentration of about 20 mg / ml. In some aspects, the disclosure provides a method for inducing or enhancing dimerization of human CD137 trimers in a subject, comprising administering to a subject in need thereof, an effective amount of the formulation of the disclosure. In some aspects, the disclosure provides a method for inducing or enhancing multimerization of human CD137 trimers in a subject, comprising administering to a subject in need thereof, an effective amount of the formulation of the disclosure. In some aspects, the disclosure provides a method for inducing or enhancing T cell activation in a subject, comprising administering to a subject in need thereof, an effective amount of the formulation of the disclosure. In some aspects, the T cell activation occurs in a tumor microenvironment. In some aspects, the disclosure provides a method for inducing or enhancing a cytotoxic T cell response in a subject, comprising administering to a subject in need thereof, an effective amount of the formulation of the disclosure. In some aspects, the cytotoxic T cell response occurs in a tumor microenvironment. In some aspects, the disclosure provides a method for inducing or enhancing cytokine production of an immune cell in a subject, comprising administering to a subject in need thereof, an effective amount of the formulation of the disclosure. In some aspects, the cytokine produced is IL-2, TNFa, IL-13, IFN-y, or combinations thereof. In some aspects, the cytokine production occurs in a tumor microenvironment. In some aspects, the disclosure provides a method for inducing or enhancing T cell proliferation in a subject, comprising administering to a subject in need thereof, an effective amount of the formulation of the disclosure. In some aspects, the T cell proliferation occurs in a tumor microenvironment. In some aspects, the disclosure provides a method for reducing or inhibiting tumor growth, comprising administering to a subject in need thereof, an effective amount of the formulation of the disclosure. In some aspects, the disclosure provides a method for treating a disorder mediated by human CD137 in a subject, comprising administering to a subject in need thereof, an effective amount of the formulation of the disclosure. In some aspects, the disclosure provides a method for treating cancer in a subject, comprising administering to a subject in need thereof, an effective amount of the formulation of the disclosure. In any of the foregoing aspects, infiltration of immune cells into a tumor microenvironment is increased after administration of the formulation. In some aspects, the immune cells express CD45. In any of the forgoing aspects, the quantity of T regulatory (Treg) cells is reduced in a tumor microenvironment after administration of the formulation. In some aspects, the Treg cells express CD4, FOXP-3 and CD25. In any of the forgoing aspects, the quantity of macrophages is reduced in a tumor microenvironment after administration of the isolated monoclonal antibody or antigen binding portion. In some aspects, the macrophages express CD45 and CD11b. In any of the forgoing aspects, T cell exhaustion is reduced in a tumor microenvironment after administration of the isolated monoclonal antibody or antigen binding portion. In some aspects, reduction of T cell exhaustion comprises a decrease in expression of TIGIT, PD-1, LAG-3, or combinations thereof. In any of the foregoing aspects, the cancer is selected from the group consisting of melanoma, glioma, renal, breast, hematological, and head and neck cancer. In some aspects, the hematological cancer is a B cell lymphoma. In some aspects, the disclosure provides a method of inducing an anti-tumor memory immune response, comprising administering to a subject in need thereof, an effective amount of the formulation of the disclosure. In any of the foregoing aspects, the anti-CD137 antibody binds Fc gamma receptor. In any of the foregoing aspects, depletion of CD4+ T cells, CD8+ T cells, Natural Killer cells, or combinations thereof, reduces the efficacy of the formulation. In some aspects, the disclosure provides a kit comprising a container comprising the formulation of the disclosure, and a package insert comprising instructions for administration of the formulation, for treating or delaying progression of cancer or reducing or inhibiting tumor growth in a subject in need thereof. In some aspects, the disclosure provides a kit comprising a container comprising the formulation of the disclosure, and a package insert comprising instructions for administration of the formulation alone or in combination with another agent, for treating or delaying progression of cancer or reducing or inhibiting tumor growth in a subject in need thereof. In some aspects, the disclosure provides for the use of the formulation of the disclosure, for the manufacture of a medicament for treating or delaying progression of cancer or reducing or inhibiting tumor growth in a subject in need thereof. In some aspects, the disclosure provides a formulation of the disclosure for use in the manufacture of a medicament for treating or delaying progression of cancer or reducing or inhibiting tumor growth in a subject in need thereof. In some aspects, the disclosure provides a formulation of the disclosure for use as a medicament. In view of the foregoing, in some aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds human CD137, wherein the antibody or antigen binding portion binds human CD137 with an affinity (Kp) of between about 40 nM to about 100 nM. In some aspects, the disclosure provides an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds to human CD137, wherein the antibody or antigen binding portion binds human CD137 with an affinity (Kp) of about 30-100 nM (e.g., between about 30 nM and about 110 nM). In some aspects, the affinity of the anti-CD137 antibody to human CD137 is at least two (e.g., at least three, four, five, six, seven, eight, nine, or 10) fold higher than the affinity of mAb10 for mouse CD137. In some aspects, the affinity of the anti-CD137 antibody is no greater than 500, 450, 400, 350, 300, 250, 200, 250, 200, 175, 150, 125, 110, or 100 nM. In some aspects, the affinity of the anti-CD137 antibody to human CD137 is at least two (e.g., at least three, four, five, six, seven, eight, nine, or 10) fold higher than the affinity of mAb10 for mouse CD137, but no greater than 500, 450, 400, 350, 300, 250, 200, 250, 200, 175, 150, 125, 110, or 100 nM. In some aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds to human CD137, wherein the antibody or antigen binding portion binds to an epitope on human CD137 comprising one or more (e.g., one, two, three, four, five, six, seven, eight, nine, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or all 25) of amino acids 111-132 of SEQ ID NO:3. In some aspects, the disclosure provides an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds to human CD137, wherein the antibody or antigen binding portion binds to an epitope within amino acids 111-132 of SEQ ID NO:3. In some aspects, the disclosure provides an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds to human CD137, wherein the antibody or antigen binding portion binds to all or a portion of amino acids 111-132 of SEQ ID NO:3. In some aspects, the epitope comprises K114 of SEQ ID NO: 3. In some aspects, the epitope comprises residues E111, T113, and K114 of SEQ ID NO: 3. In some aspects, the epitope comprises residues E111, T113, K114, N126 and 1132 of SEQ ID NO: 3. In some aspects, the epitope comprises residues E111, T113, K114 and P135 of SEQ ID NO: 3. In some aspects, the epitope comprises residues E111, T113, K114, N126, 1132 and P135 of SEQ ID NO: 3. In some aspects, the antibody or antigen binding portion thereof binds to human CD137 with an affinity of between about 30 nM and about 100 nM (e.g., between about 30 nM and about 110 nM). In some aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds to human CD137, wherein the antibody or antigen binding portion binds human CD137 with an affinity (Kp) of about 40- 100 nM (e.g., between about 40 nM and about 100 nM) and binds to an epitope on human CD137 comprising K114 of SEQ ID NO: 3. In some aspects, the disclosure provides an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds to human CD137, wherein the antibody or antigen binding portion binds human CD137 with an affinity (Kp) of about 30-100 nM (e.g., between about 30 nM and about 100 nM) and binds to an epitope on human CD137 comprising K114 of SEQ ID NO: 3. In some aspects, the epitope comprises residues E111, T113, and K114 of SEQ ID NO: 3. In some aspects, the epitope comprises residues E111, T113, K114, N126 and I132 of SEQ ID NO: 3. In some aspects, the epitope comprises residues E111, T113, K114 and P135 of SEQ ID NO: 3. In some aspects, the epitope comprises residues E111, T113, K114, N126, 1132 and P135 of SEQ ID NO: 3. In some aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds to human CD137, wherein the antibody or antigen binding portion binds human CD137 with an affinity (Kp) of about 30- 100 nM (e.g., about 30 nM to about 100 nM) and binds to an epitope on human CD137 comprising a sequence of one or more amino acid residues corresponding to amino acid positions 111 to 135 of SEQ ID NO: 3. In some aspects, the epitope comprises 2, 3,4, 5, 6,7, 8,9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 amino acid residues corresponding to amino acid positions 111 to 135 of SEQ ID NO: 3. In some aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds to human CD137, wherein the antibody or antigen binding portion binds human CD137 with an affinity (Kp) of about 30- 100 nM (e.g., between about 30 nM and about 100 nM) and binds to an epitope on human CD137 located within amino acid residues 111-135 of SEQ ID NO: 3. In some aspects, the epitope is at least 3,4, 5, 6,7, 8,9, 10, 11, 12, 13, 14 or 15 amino acids. In some aspects, the epitope is fewer than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13,12, 11, 10,9, 8,7,6 or 5 amino acids. In some aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds to human CD137, wherein the antibody or antigen binding portion binds human CD137 with an affinity (Kp) of about 30- 100 nM (e.g., between about 30 nM and about 100 nM) and binds to an epitope on human CD137 comprising ELTK (corresponding to amino acid residues 111-114 of SEQ ID NO: 3). In some aspects, the epitope further comprises one or more residues N126, 1132 and P135 of SEQ 1D NO: 3. In any of the foregoing aspects, the epitope is a non-linear epitope. In any of the foregoing aspects, mutation of residue K114 of SEQ ID NO: 3 abrogates binding of the antibody or antigen binding portion thereof to human CD137. In any of the foregoing aspects, the antibody or antigen binding portion described herein binds human CD137 with an affinity (Kp) of about 30-100 nM, 30-95 nM, 45-95 nM, 50-90 nM, 55-85 nM, 60-80 nM, 65-75 nM, 55-75 nM, 40-70 nM, 50-80 nM, or 60-90 nM. In some aspects, the antibody or antigen binding portion binds to a non-ligand binding region of the extracellular domain of human CD137. In some aspects, the antibody or antigen binding portion does not inhibit the interaction between CD137 and CD137L. In some aspects, the non-ligand binding region spans cysteine rich domain (CRD) III and CRD IV. In any of the foregoing aspects, the antibody or antigen binding portion does not inhibit the formation of a trimer of CD137:CD137L monomers. In some aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds human CD137, wherein the antibody or antigen binding portion: (i) binds human CD137 with an affinity (Kp) of about 30-100 nM (e.g., between about 30 nM and about 100 nM); (ii) binds to a non-ligand binding region of the extracellular domain of human CD137; and (iii) binds to an epitope on human CD137 comprising K114 of SEQ ID NO: 3. In some aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds human CD137, wherein the antibody or antigen binding portion: (i) binds human CD137 with an affinity (Kp) of about 30-100 nM (e.g., between about 30 nM and about 100 nM); (ii) does not inhibit the interaction between human CD137 and human CD137 ligand; and (iii) binds to an epitope on human CD137 comprising K114 of SEQ ID NO: 3. In some aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds human CD137, wherein the antibody or antigen binding portion: (i) binds human CD137 with an affinity (Kp) of about 30- 100 nM (e.g., between about 30 nM and about 100 nM) and (ii) does not inhibit the formation of a trimer of CD137:CD137L monomers (that is, a CD137:CD137L trimer:trimer complex). In some aspects, the disclosure features an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds human CD137, wherein the antibody or antigen binding portion: (i) binds human CD137 with an affinity (Kp) of about 30-100 nM (e.g., between about 30 nM and about 100 nM) and (ii) binds to a non-ligand binding region of the extracellular domain of human CD137. In some aspects, the disclosure features an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds human CD137, wherein the antibody or antigen binding portion: (i) binds human CD137 with an affinity (Kp) of about 30-100 nM (e.g., between about 30 nM and about 100 nM) and (ii) does not inhibit the interaction between human CD137 and CD137 ligand. In any of the foregoing aspects, the antibody or antigen binding portion comprises a heavy chain CDR3 comprising the amino acid sequence DXXXXLXXXXYXYYX (SEQ ID NO: 126), wherein X is any amino acid. In some aspects, the antibody or antigen binding portion comprises a heavy chain CDR3 comprising the amino acid sequence DXPFXLDXXYYYYYX (SEQ ID NO: 127), wherein X is any amino acid. In any of the foregoing aspects, mutation of residues D95, L100, Y100E, Y100G, Y100H, or combinations thereof, of the heavy chain CDR3, to alanine results in loss of binding to human CD137. In any of the foregoing aspects, mutation of residues P97, F98, D100A, Y100D, Y 100F, or combinations thereof, to alanine results in reduction of binding to human CD137. In any of the foregoing aspects, the antibody or antigen binding portion comprises heavy and light chain CDRs, wherein heavy chain CDR3 comprises the amino acid sequence set forth in SEQ ID NO: 68. In other aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds to human CD137, wherein (i) the antibody or antigen binding portion binds human CD137 with an affinity (Kp) of about 30-100 nM (e.g., between about 30 nM and about 100 nM); and (ii) the antibody or antigen binding portion comprises a heavy chain CDR3 comprising the amino acid sequence DXXXXLXXXXYXYYX (SEQ ID NO: 126), wherein X is any amino acid. In some embodiments, X is any amino acid except alanine. In another aspect, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds to human CD137, wherein (i) the antibody or antigen binding portion binds human CD137 with an affinity (Kp) of about 30-100 nM (e.g., between about 30 nM and about 100 nM); and (ii) the antibody or antigen binding portion comprises a heavy chain CDR3 comprising the amino acid sequence DX 1X>X3X4LX5X6X7XsYXsYYX10 (SEQ ID NO: 128), wherein X is any amino acid, wherein Xz is a non-polar amino acid, wherein X3 is a non-polar amino acid, wherein Xa4is any amino acid, wherein Xs is a polar amino acid, wherein Xe is any amino acid, wherein X7 is any amino acid, wherein Xs is a polar amino acid, wherein Xg is a polar amino acid, and wherein Xiois any amino acid. In some aspects, X2is proline, X3 is phenylalanine or tryptophan, Xs is aspartic acid or glutamic acid, Xs is tyrosine, and Xo is tyrosine. In other aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds to human CD137, wherein (i) the antibody or antigen binding portion binds human CD137 with an affinity (Kp) of about 30-100 nM (e.g., between about 30 nM and about 100 nM); and (ii) the antibody or antigen binding portion thereof specifically binds to an epitope on human CD137 comprising one or more residues E111, T113, K114, N126, 1132 and P135 of SEQ ID NO: 3. In other aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds to human CD137, wherein (i) the antibody or antigen binding portion binds human CD137 with an affinity (Kp) of about 30-100 nM (e.g., between about 30 nM and about 100 nM); (ii) the antibody or antigen binding portion thereof specifically binds to an epitope on human CD137 comprising one or more residues E111, T113, K114, N126, 1132 and P135 of SEQ ID NO: 3; (iii) the antibody or antigen binding portion comprises a heavy chain CDR3 comprising the amino acid sequence DXXXXLXXXXYXYYX (SEQ ID NO: 126), wherein X is any amino acid; or (iv) combinations thereof. In some aspects, X is any amino acid except alanine. In other aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds to human CD137, wherein (i) the antibody or antigen binding portion binds human CD137 with an affinity (Kp) of about 30-100 nM (e.g., between about 30 nM and about 100 nM); (ii) the antibody or antigen binding portion thereof specifically binds to an epitope on human CD137 comprising one or more residues E111, T113, K114, N126, 1132 and P135 of SEQ ID NO: 3; (iii) the antibody or antigen binding portion comprises a heavy chain CDR3 comprising the amino acid sequence DX 1X>X3X4LX5X6X7XsYXsYYX10 (SEQ ID NO: 128), wherein X is any amino acid, wherein Xz is a non-polar amino acid, wherein X3 is a non-polar amino acid, wherein X4 is any amino acid, wherein Xs is a polar amino acid, wherein Xe is any amino acid, wherein X7 is any amino acid, wherein Xs is a polar amino acid, wherein Xo is a polar amino acid, and wherein Xo is any amino acid; or (iv) combinations thereof. In some aspects, Xa is proline, X3 is phenylalanine or tryptophan, Xs is aspartic acid or glutamic acid, Xs is tyrosine, and Xo is tyrosine. In other aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds to human CD137, wherein (i) the antibody or antigen binding portion binds human CD137 with an affinity (Kp) of about 30-100 nM (e.g., between about 30 nM and about 100 nM); (ii) the antibody or antigen binding portion thereof specifically binds to an epitope on human CD137 comprising one or more residues E111, T113, K114, N126, 1132 and P135 of SEQ ID NO: 3; and (iii) the antibody or antigen binding portion comprises a heavy chain CDR3 comprising the amino acid sequence DXXXXLXXXXYXYYX (SEQ ID NO: 126), wherein X is any amino acid. In some aspects, X is any amino acid except alanine. In other aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds to human CD137, wherein (i) the antibody or antigen binding portion binds human CD137 with an affinity (Kp) of about 30-100 nM (e.g., between about 30 nM and about 100 nM); (ii) the antibody or antigen binding portion thereof specifically binds to an epitope on human CD137 comprising one or more residues E111, T113, K114, N126, 1132 and P135 of SEQ ID NO: 3; and (iii) the antibody or antigen binding portion comprises a heavy chain CDR3 comprising the amino acid sequence DX) XoX3X4LXsX6X7XsYXoYYX 10 (SEQ ID NO: 128), wherein Xi is any amino acid, wherein X is a non-polar amino acid, wherein X3 is a non-polar amino acid, wherein X4 is any amino acid, wherein Xs is a polar amino acid, wherein Xe is any amino acid, wherein X7 is any amino acid, wherein Xs is a polar amino acid, wherein Xo is a polar amino acid, and wherein Xjois any amino acid. In some aspects, Xz is proline, X3 is phenylalanine or tryptophan, Xs is aspartic acid or glutamic acid, Xs is tyrosine, and Xo is tyrosine. In any of the foregoing aspects, the epitope comprises K114. In any of the foregoing aspects, the epitope comprises E111, T113 and K114. In any of the foregoing aspects, the epitope comprises E11, T113, K114, N126 and 1132. In any of the foregoing aspects, the epitope comprises residues E111, T113, K114, N126, 1132 and P135 of SEQ ID NO: 3. In other aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds to human CD137, wherein (i) the antibody or antigen binding portion binds human CD137 with an affinity (Kp) of about 30-100 nM (e.g., between about 30 nM and about 100 nM); and (ii) the antibody or antigen binding portion thereof specifically binds to an epitope comprising a sequence of one or more amino acid residues corresponding to amino acid positions 111 to 135 of SEQ ID NO: 3. In other aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds to human CD137, wherein (i) the antibody or antigen binding portion binds human CD137 with an affinity (Kp) of about 30-100 nM (e.g., between about 30 nM and about 100 nM); (ii) the antibody or antigen binding portion thereof specifically binds to an epitope comprising a sequence of one or more amino acid residues corresponding to amino acid positions 111 to 135 of SEQ ID NO: 3; (iii) the antibody or antigen binding portion comprises a heavy chain CDR3 comprising the amino acid sequence DXXXXLXXXXYXYYX (SEQ ID NO: 126), wherein X is any amino acid; or (iv) combinations thereof. In some aspects, X is any amino acid except alanine. In other aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds to human CD137, wherein (i) the antibody or antigen binding portion binds human CD137 with an affinity (Kp) of about 30-100 nM (e.g., between about 30 nM and about 100 nM); (ii) the antibody or antigen binding portion thereof specifically binds to an epitope comprising a sequence of one or more amino acid residues corresponding to amino acid positions 111 to 135 of SEQ ID NO: 3; (iii) the antibody or antigen binding portion comprises a heavy chain CDR3 comprising the amino acid sequence DX 1X>X3X4LX5X6X7XsYXsYYX10 (SEQ ID NO: 128), wherein X is any amino acid, wherein Xz is a non-polar amino acid, wherein X3 is a non-polar amino acid, wherein X4 is any amino acid, wherein Xs is a polar amino acid, wherein Xe is any amino acid, wherein X7 is any amino acid, wherein Xs is a polar amino acid, wherein Xo is a polar amino acid, and wherein Xo is any amino acid; or (iv) combinations thereof. In some aspects, Xa is proline, X3 is phenylalanine or tryptophan, Xs is aspartic acid or glutamic acid, Xs is tyrosine, and Xo is tyrosine. In another aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds to human CD137, wherein (i) the antibody or antigen binding portion binds human CD137 with an affinity (Kp) of about 30-100 nM (e.g., between about 30 nM and about 100 nM); (ii) the antibody or antigen binding portion thereof specifically binds to an epitope comprising a sequence of one or more amino acid residues corresponding to amino acid positions 111 to 135 of SEQ ID NO: 3; and (iii) the antibody or antigen binding portion comprises a heavy chain CDR3 comprising the amino acid sequence DXXXXLXXXXYXYYX (SEQ ID NO: 126), wherein X is any amino acid. In some aspects, X is any amino acid except alanine. In another aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds to human CD137, wherein (i) the antibody or antigen binding portion binds human CD137 with an affinity (Kp) of about 30-100 nM (e.g., between about 30 nM and about 100 nM); (ii) the antibody or antigen binding portion thereof specifically binds to an epitope comprising a sequence of one or more amino acid residues corresponding to amino acid positions 111 to 135 of SEQ ID NO: 3; and (iii) the antibody or antigen binding portion comprises a heavy chain CDR3 comprising the amino acid sequence DX) XoX3X4LXsX6X7XsYXoYYX 10 (SEQ ID NO: 128), wherein Xi is any amino acid, wherein X is a non-polar amino acid, wherein X3 is a non-polar amino acid, wherein X4 is any amino acid, wherein Xs is a polar amino acid, wherein Xe is any amino acid, wherein X7 is any amino acid, wherein Xs is a polar amino acid, wherein Xo is a polar amino acid, and wherein Xjois any amino acid. In some aspects, Xa is proline, X3 is phenylalanine or tryptophan, Xs is aspartic acid or glutamic acid, Xs is tyrosine, and Xo is tyrosine. In any of the foregoing aspects, the epitope comprises 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 amino acid residues corresponding to amino acid positions 111 to 135 of SEQ ID NO: 3. In some aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds to human CD137, wherein (i) the antibody or antigen binding portion binds human CD137 with an affinity of about 30-100 nM (e.g., between about 30 nM and about 100 nM); and (ii) the antibody or antigen binding portion thereof specifically binds to an epitope comprising ELTK (corresponding to amino acid residues 111-114 of SEQ ID NO: 3). In some aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds to human CD137, wherein (i) the antibody or antigen binding portion binds human CD137 with an affinity (Kp) of about 30-100 nM (e.g., between about 30 nM and about 100 nM); (ii) the antibody or antigen binding portion thereof specifically binds to an epitope comprising ELTK (corresponding to amino acid residues 111-114 of SEQ ID NO: 3); (iii) the antibody or antigen binding portion comprises a heavy chain CDR3 comprising the amino acid sequence DXXXXLXXXXYXYYX (SEQ ID NO: 126), wherein X is any amino acid; or (iv) combinations thereof. In some aspects, X is any amino acid except alanine. In some aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds to human CD137, wherein (i) the antibody or antigen binding portion binds human CD137 with an affinity (Kp) of about 30-100 nM (e.g., between about 30 nM and about 100 nM); (ii) the antibody or antigen binding portion thereof specifically binds to an epitope comprising ELTK (corresponding to amino acid residues 111-114 of SEQ ID NO: 3); (iii) the antibody or antigen binding portion comprises a heavy chain CDR3 comprising the amino acid sequence DX; XoX3X4LXsX6X7XsYXoYYX 10 (SEQ ID NO: 128), wherein Xi is any amino acid, wherein X is a non-polar amino acid, wherein X3 is a non-polar amino acid, wherein X4 is any amino acid, wherein Xs is a polar amino acid, wherein Xe is any amino acid, wherein X57 is any amino acid, wherein Xs is a polar amino acid, wherein Xy is a polar amino acid, and wherein Xjois any amino acid; or (iv) combinations thereof. In some aspects, Xz is proline, X3 is phenylalanine or tryptophan, Xs is aspartic acid or glutamic acid, Xs is tyrosine, and Xo is tyrosine. In some aspects, the disclosure provides an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds to human CD137, wherein (i) the antibody or antigen binding portion binds human CD137 with an affinity (Kp) of about 30-100 nM (e.g., between about 30 nM and about 100 nM); (ii) the antibody or antigen binding portion thereof specifically binds to an epitope comprising ELTK (corresponding to amino acid residues 111-114 of SEQ ID NO: 3); and (iii) the antibody or antigen binding portion comprises a heavy chain CDR3 comprising the amino acid sequence DXXXXLXXXXYXYYX (SEQ ID NO: 126), wherein X is any amino acid. In some aspects, X is any amino acid except alanine. In some aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds to human CD137, wherein (i) the antibody or antigen binding portion binds human CD137 with an affinity (Kp) of about 30-100 nM (e.g., between about 30 nM and about 100 nM); (ii) the antibody or antigen binding portion thereof specifically binds to an epitope comprising ELTK (corresponding to amino acid residues 111-114 of SEQ ID NO: 3); and (iii) the antibody or antigen binding portion comprises a heavy chain CDR3 comprising the amino acid sequence DX; XoX3X4LXsX6X7XsYXoYYX 10 (SEQ ID NO: 128), wherein Xi is any amino acid, wherein X is a non-polar amino acid, wherein X3 is a non-polar amino acid, wherein X4 is any amino acid, wherein Xs is a polar amino acid, wherein Xe is any amino acid, wherein X7 is any amino acid, wherein Xs is a polar amino acid, wherein Xs is a polar amino acid, and wherein Xjois any amino acid. In some aspects, X2 is proline, X3 is phenylalanine or tryptophan, Xs is aspartic acid or glutamic acid, Xs is tyrosine, and Xo is tyrosine In any of the foregoing aspects, the epitope comprises the residues ELTK of SEQ ID NO: 3 (corresponding to amino acid residues 111-114 of SEQ ID NO: 3). In some aspects, the epitope comprises ELTK of SEQ ID NO: 3 (corresponding to amino acid residues 111-114 of SEQ ID NO: 3) and residues N126, 1132 and P135 of SEQ ID NO: 3. In any of the foregoing aspects, the epitope is a non-linear epitope. In some aspects, mutation of residue K114 of human CD137 (SEQ ID NO: 3) abrogates binding of the antibody or antigen binding portion thereof to human CD137. In any of the foregoing aspects, the antibody or antigen binding portion thereof comprises a heavy chain CDR3 comprising the amino acid sequence DXPFXLDXXYYYYYX (SEQ ID NO: 128), wherein X is any amino acid. In some aspects, mutation of residues D935, L100, Y100E, Y100G, Y100H, or combinations thereof, of the heavy chain CDR3 of the antibody or antigen binding portion described herein, results in loss of binding to human CD137. In some aspects, mutation of residues P97, F98, D100A, Y100D, Y100F, or combinations thereof, of the heavy chain CDR3 of the antibody or antigen binding portion described herein, to alanine results in reduction of binding to human CD137. In other aspects, mutation of residues P97, F98, D100A, Y100D, Y100F, or combinations thereof, of the heavy chain CDR3 of the antibody or antigen binding portion described herein, to any residue except alanine, results in an increase in binding to human CD137. In any of the foregoing aspects, the antibody or antigen binding portion thereof, binds human CD137 with an (Kp) of about 45-95 nM, 50-90 nM, 55-85 nM, 60-80 nM, 65-75 nM, 55- 75 nM, 40-70 nM, 50-80 nM, or 60-90 nM. In any of the foregoing aspects, the antibody or antigen binding portion thereof, binds human CD137 with an (Kp) of about 45 nM to about 95 nM, about 50 to about 90 nM, about 55 to about 85 nM, about 60 to about 80 nM, about 65 to about 75 nM, about 55 to about 75 nM, about 40 to about 70 nM, about 50 to about 80 nM, or about 60 to about 90 nM. In any of the foregoing aspects, the antibody or antigen binding portion thereof comprises heavy and light chain CDRs, wherein heavy chain CDR3 comprises the amino acid sequence set forth in SEQ ID NO: 68. In any of the foregoing aspects, the antibody or antigen binding portion thereof comprises heavy and light chain CDRs selected from the group consisting of: (a) heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 56 and 68, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 69, 78 and 89, respectively; and (b) heavy chain CDR 1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 51, 108 and 68, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 69, 78 and 89, respectively. In some embodiments, the agonistic isolated monoclonal antibody or antigen-binding portion thereof comprises heavy and light chain CDRs selected from the group consisting of: (a) heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 135, 139 and 143, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 144, 147 and 150, respectively; and (b) heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 137, 141 and 143, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 144, 147 and 150, respectively. In some embodiments, the agonistic isolated monoclonal antibody or antigen-binding portion thereof comprises heavy and light chain CDRs selected from the group consisting of: (a) heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 154 and 159, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 144, 147 and 150, respectively; and (b) heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 51, 156 159 respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 144, 147 and 150, respectively. In any of the foregoing aspects, the antibody or antigen binding portion thereof comprises heavy and light chain variable regions, wherein the heavy chain variable region comprises an amino acid sequence selected from the group consisting of SEQ ID NOs: 4 and 101; and wherein the light chain variable region comprises an amino acid sequence of SEQ ID NO: 6. In any of the foregoing aspects, the antibody or antigen binding portion thereof comprises heavy and light chain variable regions, comprising amino acid sequences selected from the group consisting of: (a) SEQ ID NO: 4 and 6, respectively; and (b) SEQ ID NO: 101 and 6, respectively. In any of the foregoing aspects, the antibody or antigen binding portion thereof comprises heavy and light chain variable regions, wherein the heavy chain variable region comprises an amino acid sequence which is at least 90% identical to the amino acid sequence selected from the group consisting of SEQ ID NOs: 4 and 101; and wherein the light chain variable region comprises an amino acid sequence which is at least 90% identical to the amino acid sequence of SEQ ID NO: 6. In any of the foregoing aspects, the antibody or antigen binding portion thereof comprises heavy and light chain variable regions comprising amino acid sequences at least 90% identical to the amino acid sequences selected from the group consisting of: (a) SEQ ID NO: 4 and 6, respectively; and (b) SEQ ID NO: 101 and 6, respectively. In any of the foregoing aspects, the antibody or antigen binding portion comprises heavy and light chains comprising amino acid sequences selected from the group consisting of: (a) SEQ ID NOs: 129 and 133, respectively; and (b) SEQ ID NOs: 131 and 133, respectively. In any of the foregoing aspects, the isolated monoclonal antibody, or antigen binding portion thereof described herein, is an agonist of human CD137 activity. In any of the foregoing aspects, the isolated monoclonal antibody, or antigen binding portion thereof described herein, competes with mAb]1 or an antigen binding fragment of mAb1, for binding to the epitope of human CD137. In some aspects, the formulations described herein comprise an isolated monoclonal antibody that specifically binds CD137, or an antigen binding portion thereof, wherein the antibody or antigen binding portion thereof comprises heavy and light chain CDRs selected from the group consisting of: (a) heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 56 and 68, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 69, 78 and 89, respectively; (b) heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 56 and 68, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 70, 79 and 90, respectively; (c) heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 56 and 68, respectively, and light chain CDR 1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 71, 80 and 91, respectively; (d) heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 56 and 68, respectively, and light chain CDR 1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 72, 81 and 92, respectively; (e) heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 56 and 68, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 73, 82 and 91, respectively; ® heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 56 and 68, respectively, and light chain CDR 1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 74, 83 and 93, respectively; (g) heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 56 and 68, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 75, 84 and 91, respectively; (h) heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 56 and 68, respectively, and light chain CDR 1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 74, 85 and 94, respectively; (i) heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 56 and 68, respectively, and light chain CDR 1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 76, 86 and 95, respectively; (j) heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 56 and 68, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 77, 87 and 93, respectively; (k) heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 56 and 68, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 69, 88 and 90, respectively; (1) heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 49, 57 and 68, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 69, 78 and 89, respectively; (m) heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 49, 58 and 68, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 69, 78 and 89, respectively; (n) heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 49, 59 and 68, respectively, and light chain CDR 1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 69, 78 and 89, respectively; (0) heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 49, 60 and 68, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 69, 78 and 89, respectively; (p) heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 50, 61 and 68, respectively, and light chain CDR 1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 69, 78 and 89, respectively; (q) heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 50, 58 and 68, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 69, 78 and 89, respectively; (r) heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 51, 62 and 68, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 69, 78 and 89, respectively; (s) heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 52, 63 and 68, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 69, 78 and 89, respectively; (t) heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 50, 64 and 68, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 69, 78 and 89, respectively; (u) heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 50, 65 and 68, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 69, 78 and 89, respectively; (v) heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 51, 108 and 68, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 69, 78 and 89, respectively; (w) heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 107, 56 and 68, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 69, 78 and 89, respectively; and (x) heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 56 and 68, respectively, and light chain CDR 1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 109, 110 and 92, respectively. In other aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds human CD137, wherein the antibody or antigen binding portion thereof comprises heavy and light chain variable regions, wherein the heavy chain variable region comprises an amino acid sequence selected from the group consisting of SEQ ID NOs: 4, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 101 and 103; and wherein the light chain variable region comprises an amino acid sequence selected from the group consisting of SEQ ID NOs: 6, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46 and 105. In other aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds human CD137, wherein the antibody or antigen binding portion comprises heavy and light chain variable regions encoded by nucleotide sequences selected from the group consisting of: (a) SEQ ID NOs: 5 and 7, respectively; and (b) SEQ ID NOs: 102 and 7, respectively. In other aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds human CD137, wherein the antibody or antigen binding portion thereof comprises heavy and light chain variable regions encoded by nucleotide sequences selected from the group consisting of: (a) SEQ ID NO: 5 and 7, respectively; (b) SEQ ID NO: 5 and 29, respectively; (¢) SEQ ID NO: 5 and 31, respectively; (d) SEQ ID NO: 5 and 33, respectively; (e) SEQ ID NO: 5 and 35, respectively; (f) SEQ ID NO: 5 and 37, respectively; (g) SEQ ID NO: 5 and 39, respectively; (h) SEQ ID NO: 5 and 41, respectively; (i) SEQ ID NO: 5 and 43, respectively; (j) SEQ ID NO: 5 and 45, respectively; (k) SEQ ID NO: 5 and 47, respectively; (1) SEQ ID NO: 9 and 7, respectively; (m) SEQ ID NO: 11 and 7, respectively; (n) SEQ ID NO: 13 and 7, respectively; (0) SEQ ID NO: 15 and 7, respectively; (p) SEQ ID NO: 17 and 7, respectively; (q) SEQ ID NO: 19 and 7, respectively; (r) SEQ ID NO: 21 and 7, respectively; (s) SEQ ID NO: 23 and 7, respectively; (t) SEQ ID NO: 25 and 7, respectively; (u) SEQ ID NO: 27 and 7, respectively; (v) SEQ ID NO: 102 and 7, respectively; (w) SEQ ID NO: 104 and 7, respectively; and (x) SEQ ID NO: 5 and 106, respectively. In yet other aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds human CD137, wherein the antibody or antigen binding portion thereof comprises heavy and light chain CDRs, wherein heavy chain CDR3 comprises the amino acid sequence set forth in SEQ ID NO: 68. In another aspect, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds human CD137, wherein the antibody or antigen binding portion thereof comprises heavy and light chain CDRs, wherein heavy chain CDR3 comprises the amino acid sequence DXXXXILXXXXYXYYX (SEQ ID NO: 126), wherein X is any amino acid. In some aspects, X is any amino acid except for alanine. In some aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds human CD137, wherein the antibody or antigen binding portion thereof comprises heavy and light chain CDRs, wherein heavy chain CDR3 comprises the amino acid sequence DXPFXLDXXYYYYYX (SEQ ID NO: 127), wherein X is any amino acid. In some aspects, X is any amino acid except for alanine. In yet other aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds human CD137, wherein the antibody or antigen binding portion thereof comprises heavy and light chain CDRs, wherein heavy chain CDR3 comprises the amino acid sequence DXXXXLXXXXYXYYX (SEQ ID NO: 126), wherein X is any amino acid, and wherein mutation of residues D95, L100, Y100E, Y100G, Y100H, or combinations thereof, results in loss of binding to human CD137. In other aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds human CD137, wherein the antibody or antigen binding portion thereof comprises heavy and light chain CDRs, wherein heavy chain CDR3 comprises the amino acid sequence DXPFXLDXXYYYYYX (SEQ ID NO: 127), wherein X is any amino acid, and wherein mutation of residues P97, F98, D100A, Y100D, Y100F, or combinations thereof to alanine results in reduction of binding to human CD137. In some aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds human CD137, wherein the antibody or antigen binding portion thereof comprises heavy and light chain CDRs, wherein heavy chain CDR3 comprises the amino acid sequence DXPFXLDXXYYYYYX (SEQ ID NO: 127), wherein X is any amino acid, and wherein mutation of residues P97, F98, D100A, Y100D, Y100F, or combinations thereof to any residue except alanine, results in an increase in binding to human CD137. In yet other aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds human CD137, wherein the antibody or antigen binding portion thereof comprises heavy and light chain CDRs, wherein heavy chain CDR3 comprises the amino acid sequence DX1X2X3X4LX5X6X7X8YX9YYX10 (SEQ ID NO: 128) wherein X1 is any amino acid, wherein X2 is a non-polar amino acid, wherein X3 is a non-polar amino acid, wherein X4 is any amino acid, wherein X5 is a polar amino acid, wherein X6 is any amino acid, wherein X7 is any amino acid, wherein X8 is a polar amino acid, wherein X09 is a polar amino acid, and wherein X10 is any amino acid. In some aspects, wherein X2 is proline, wherein X3 is phenylalanine or tryptophan, wherein X35 is aspartic acid or glutamic acid wherein X8 is tyrosine, and wherein X9 is tyrosine. In some aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds human CD137, wherein the antibody or antigen binding portion thereof comprises heavy and light chain variable regions comprising amino acid sequences selected from the group consisting of: (a) SEQ ID NO: 4 and 6, respectively; (b) SEQ ID NO: 4 and 28, respectively; (c) SEQ ID NO: 4 and 30, respectively; (d) SEQ ID NO: 4 and 32, respectively; (e) SEQ ID NO: 4 and 34, respectively; ® SEQ ID NO: 4 and 36, respectively; (2 SEQID NO: 4 and 38, respectively; (h) SEQ ID NO: 4 and 40, respectively; i) SEQ ID NO: 4 and 42, respectively; [0] SEQ ID NO: 4 and 44, respectively; k) SEQ ID NO: 4 and 46, respectively; 0 SEQ ID NO: 8 and 6, respectively; (m) SEQID NO: 10 and 6, respectively; (n) SEQ ID NO: 12 and 6, respectively; (0) SEQ ID NO: 14 and 6, respectively; (p) SEQ ID NO: 16 and 6, respectively; (q@) SEQID NO: 18 and 6, respectively; @ SEQ ID NO: 20 and 6, respectively; (s) SEQ ID NO: 22 and 6, respectively; (t) SEQ ID NO: 24 and 6, respectively; (u) SEQ ID NO: 26 and 6, respectively; w) SEQ ID NO: 101 and 6, respectively; (w) SEQID NO: 103 and 6, respectively; and (x) SEQ ID NO: 4 and 105, respectively. In other aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds human CD137wherein the antibody or antigen binding portion thereof comprises heavy and light chain variable regions, wherein the heavy chain variable region comprises an amino acid sequence which is at least 90% identical to the amino acid sequence selected from the group consisting of SEQ ID NOs: 4, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 101 and 103; and wherein the light chain variable region comprises an amino acid sequence which is at least 90% identical to the amino acid sequence selected from the group consisting of SEQ ID NOs: 6, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46 and 105. In some aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds human CD137, wherein the antibody or antigen binding portion thereof comprises heavy and light chain variable regions comprising amino acid sequences at least 90% identical to the amino acid sequences selected from the group consisting of: (a) SEQ ID NO: 4 and 6, respectively; (b) SEQ ID NO: 4 and 28, respectively; (c) SEQ ID NO: 4 and 30, respectively; (d) SEQ ID NO: 4 and 32, respectively; (e) SEQ ID NO: 4 and 34, respectively; ®) SEQ ID NO: 4 and 36, respectively; (2) SEQ ID NO: 4 and 38, respectively; (h) SEQ ID NO: 4 and 40, respectively; (i) SEQ ID NO: 4 and 42, respectively; G) SEQ ID NO: 4 and 44, respectively; k) SEQ ID NO: 4 and 46, respectively; On SEQ ID NO: 8 and 6, respectively; (m) SEQID NO: 10 and 6, respectively; (n) SEQ ID NO: 12 and 6, respectively; (0) SEQ ID NO: 14 and 6, respectively; (p) SEQ ID NO: 16 and 6, respectively; [G)) SEQ ID NO: 18 and 6, respectively; (r) SEQ ID NO: 20 and 6, respectively; (s) SEQ ID NO: 22 and 6, respectively; (t) SEQ ID NO: 24 and 6, respectively; (u) SEQID NO: 26 and 6, respectively; (v) SEQID NO: 101 and 6, respectively; (w) SEQID NO: 103 and 6, respectively; and (x) SEQ ID NO: 4 and 105, respectively. In some aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds human CD137, wherein the antibody or antigen binding portion thereof comprises heavy and light chain sequences comprising amino acid sequences selected from the group consisting of: (a) SEQ ID NOs: 129 and 133, respectively; and (b) SEQ ID NOs: 131 and 133, respectively. In some aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds human CD137, wherein the antibody or antigen binding portion thereof comprises heavy and light chain sequences having amino acid sequences set forth in SEQ ID NOs: 129 and 133, respectively. In some aspects, the formulations described herein comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds human CD137, wherein the antibody or antigen binding portion thereof comprises heavy and light chain sequences having amino acid sequences set forth in SEQ ID NOs: 131 and 133, respectively In any of the foregoing aspects, the antibody or antigen binding portion specifically binds to and agonizes human CD137. In any of the foregoing aspects, the isolated monoclonal antibody or antigen binding portion thereof, exhibits at least one or more of the following properties selected from the group consisting of: (a) induces or enhances dimerization of CD137 trimers; (b) induces or enhances multimerization of CD137 trimers; (c) induces or enhances T cell activation; (d induces or enhances a cytotoxic T cell response; (e) induces or enhances T cell proliferation; ® induces or enhances cytokine production; and © any combination of properties (a)-(f). In any of the foregoing aspects, the isolated monoclonal antibody or antigen binding portion thereof, exhibits at least one or more of the following properties relative to a reference antibody that binds human CD137, selected from the group consisting of: (a) does not induce or enhance intrahepatic T cell activation; (b) does not induce or enhance intrahepatic T cell proliferation; (c) does not induce or enhance intrasplenic T cell activation; (d@ does not induce or enhance intrasplenic T cell proliferation; (e) does not induce or enhance macrophage activation; 6 does not induce or enhance macrophage differentiation; @ does not induce or enhance alanine aminotransferase (ALT) activity; and (h) any combination of properties (a) — (g). In some aspects, the reference antibody is urelumab. In any of the foregoing aspects, the isolated monoclonal antibody or antigen binding portion thereof, induces or enhances human CD137-mediated T cell activation in the tumor microenvironment, but does not significantly induce or enhance human CD137-mediated T cell activation in the spleen and / or liver. In any of the foregoing aspects, the isolated monoclonal antibody or antigen binding portion thereof, induces or enhances T cell activation in the tumor microenvironment, but does not significantly induce or enhance T cell activation in the spleen and / or liver. In any of the foregoing aspects, the isolated monoclonal antibody or antigen binding portion thereof, induces or enhances human CD137-mediated cytotoxic T cell response in the tumor microenvironment, but does not significantly induce or enhance human CD137-mediated cytotoxic T cell response in the spleen and / or liver. In any of the foregoing aspects, the isolated monoclonal antibody or antigen binding portion thereof, induces or enhances a cytotoxic T cell response in the tumor microenvironment, but does not significantly induce or enhance a T cell response in the spleen and / or liver. In any of the foregoing aspects, the isolated monoclonal antibody or antigen binding portion thereof, induces human CDI137-mediated T cell proliferation in the tumor microenvironment, but does not significantly induce human CD137-mediated T cell proliferation in the spleen and / or liver. In any of the foregoing aspects, the isolated monoclonal antibody or antigen binding portion thereof, induces T cell proliferation in the tumor microenvironment, but does not significantly induce T cell proliferation in the spleen and / or liver. In any of the foregoing aspects, the isolated monoclonal antibody or antigen binding portion thereof, induces human CDI137-mediated T cell infiltration in the tumor microenvironment, but does not significantly induce human CD137-mediated T cell infiltration in the spleen and / or liver. In any of the foregoing aspects, the isolated monoclonal antibody or antigen binding portion thereof, induces T cell infiltration in the tumor microenvironment, but does not significantly induce T cell infiltration in the spleen and / or liver. In any of the foregoing aspects, the isolated monoclonal antibody or antigen binding fragment thereof, induces or enhances human CD137-mediated cytokine production in the tumor microenvironment, but does not significantly induce or enhance human CD137-mediated cytokine production in the spleen and / or liver. In any of the foregoing aspects, the properties of the antibody or antigen binding portion described herein, are not Fc gamma receptor binding dependent. In some aspects, the properties of the antibody or antigen binding portion described herein, are enhanced by Fc gamma receptor binding. In any of the foregoing aspects, the isolated monoclonal antibody or antigen binding portion thereof cross competes with mAb] (i.e., an antibody comprising the heavy and light chain variable sequences of SEQ ID NOs: 4 and 6, respectively). In some aspects, the isolated monoclonal antibody or antigen binding portion thereof cross competes with mAbl (ie., an antibody comprising the heavy and light chain variable sequences of SEQ ID NOs: 4 and 6, respectively), mab8 (i.e., an antibody comprising the heavy and light chain variable sequences of SEQ ID NOs: 101 and 6, respectively) or mAb10 (i.e., an antibody comprising the heavy and light chain variable sequences of SEQ ID NOs: 26 and 6, respectively). In some aspects, the isolated monoclonal antibody or antigen binding portion thereof cross competes with mab8 (i.e., an antibody comprising the heavy and light chain variable sequences of SEQ ID NOs: 101 and 6, respectively). In some aspects, the isolated monoclonal antibody or antigen binding portion thereof cross competes with mAbl0 (i.e., an antibody comprising the heavy and light chain variable sequences of SEQ ID NOs: 26 and 6, respectively). In any of the foregoing aspects, the isolated monoclonal antibody or antigen binding portion thereof comprises at least the functional properties of mAbl (i.e., an antibody comprising the heavy and light chain variable sequences of SEQ ID NOs: 4 and 6, respectively). In some aspects, the isolated monoclonal antibody or antigen binding portion thereof comprises at least the functional properties of mAbl (i.e., an antibody comprising the heavy and light chain variable sequences of SEQ ID NOs: 4 and 6, respectively), mab8 (i.e., an antibody comprising the heavy and light chain variable sequences of SEQ ID NOs: 101 and 6, respectively) or mAbl10 (i.e., an antibody comprising the heavy and light chain variable sequences of SEQ ID NOs: 26 and 6, respectively). In some aspects, the isolated monoclonal antibody or antigen binding portion thereof comprises at least the functional properties of mab8 (i.e., an antibody comprising the heavy and light chain variable sequences of SEQ ID NOs: 101 and 6, respectively). In some aspects, the isolated monoclonal antibody or antigen binding portion thereof comprises at least the functional properties of mAb10 (i.e., an antibody comprising the heavy and light chain variable sequences of SEQ ID NOs: 26 and 6, respectively). In any of the foregoing aspects, the isolated monoclonal antibody or antigen binding portion thereof has a Kp value at least equivalent to mAb] (i.e., an antibody comprising the heavy and light chain variable sequences of SEQ ID NOs: 4 and 6, respectively). In some aspects, the isolated monoclonal antibody or antigen binding portion thereof has a Kp value at least equivalent to mAbl (i.e., an antibody comprising the heavy and light chain variable sequences of SEQ ID NOs: 4 and 6, respectively), mab8 (i.e., an antibody comprising the heavy and light chain variable sequences of SEQ ID NOs: 101 and 6, respectively) or mAb10 (i.e., an antibody comprising the heavy and light chain variable sequences of SEQ ID NOs: 26 and 6, respectively). In some aspects, the isolated monoclonal antibody or antigen binding portion thereof has a Kp value at least equivalent to mab8 (i.e., an antibody comprising the heavy and light chain variable sequences of SEQ ID NOs: 101 and 6, respectively). In some aspects, the isolated monoclonal antibody or antigen binding portion thereof has a Kp value at least equivalent to mAb10 (i.e., an antibody comprising the heavy and light chain variable sequences of SEQ ID NOs: 26 and 6, respectively). In any of the foregoing aspects, the isolated monoclonal antibody or antigen binding portion thereof, cross-reacts with cynomolgus CD137 and / or mouse CD137. In any of the foregoing aspects, the isolated monoclonal antibody, or antigen binding portion thereof, is selected from the group consisting of an IgG1, an IgG2, and IgG3, an IgG4, and IgM, and IgA1, and IgA2, and IgD, and an IgE antibody. In some aspects, the isolated monoclonal antibody, or antigen binding portion thereof, is an IgG1 antibody or IgG4 antibody. In any of the foregoing aspects, the isolated monoclonal antibody comprises a wild-type 1gG1 or wild-type IgG4 heavy chain constant region. In some aspects, the isolated monoclonal antibody comprises a mutant IgG1 heavy chain constant region. In some aspects, the isolated monoclonal antibody comprises a mutant IgG4 heavy chain constant region. In some aspects, the mutant IgG4 heavy chain constant region comprises a substitution at Ser228. In some aspects, the mutant IgG4 heavy chain constant region comprises substitution S228P. In any of the foregoing aspects, the isolated monoclonal antibody, or antigen binding portion thereof, binds to an epitope of CD137, wherein the amino acid residues comprising the epitope bound by the antibody are located within 4 angstroms of the amino acid residues comprising the paratope of the mAbl antibody, described herein. In any of the foregoing aspects, the isolated monoclonal antibody, or antigen binding portion thereof, binds to an epitope of CD137, wherein a mutation of the epitope bound by the antibody inhibits, reduces, or blocks binding to both the antibody and to antibody mAbl. In any of the foregoing aspects, the isolated antibody, or antigen binding portion thereof, is fully human or humanized (i.e., a fully human or humanized antibody or antigen binding portion thereof). In some aspects, the disclosure provides a pharmaceutical composition comprising an isolated monoclonal antibody or antigen binding portion thereof, as described herein, and a pharmaceutically acceptable carrier. In other aspects, the disclosure provides a nucleic acid comprising a nucleotide sequence encoding the light chain, heavy chain, or both light and heavy chains of an isolated monoclonal antibody, or antigen binding portion thereof, described herein. In some aspects, the nucleic acid comprises SEQ ID NOs: 5 and 7. In some aspects, the nucleic acid comprises SEQ ID NOs: 102 and 7. In some aspects, the disclosure provides an expression vector comprising the nucleic acid described herein. In other aspects, the disclosure provides a cell transformed with an expression vector described herein. In another aspect, the disclosure provides a method for producing an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds human CD137, the method comprising maintaining a cell described herein under conditions permitting expression of the monoclonal antibody or antigen binding portion thereof. In some aspects, the method for producing the monoclonal antibody that specifically binds human CD137, or antigen binding portion thereof, further comprises obtaining the monoclonal antibody or antigen binding portion thereof. In yet another aspect, the disclosure provides a method for inducing or enhancing dimerization of human CD137 trimers in a subject, comprising administering to a subject in need thereof, an effective amount of an isolated monoclonal antibody, or antigen binding portion thereof, as described herein, or a pharmaceutical composition described herein. In another aspect, the disclosure provides a method for inducing or enhancing multimerization of human CD137 trimers in a subject, comprising administering to a subject in need thereof, an effective amount of an isolated monoclonal antibody, or antigen binding portion thereof, as described herein, or a pharmaceutical composition described herein. In other aspects, the disclosure provides a method for inducing or enhancing T cell activation mediated by human CD137 in a subject, comprising administering to a subject in need thereof, an effective amount of an isolated monoclonal antibody, or antigen binding portion thereof, as described herein, or a pharmaceutical composition described herein. In some aspects, T cell activation occurs in a tumor microenvironment. In other aspects, T cell activation does not significantly occur in the spleen and / or liver of the subject. In another aspect, the disclosure provides a method for inducing or enhancing a cytotoxic T cell response mediated by human CD137 in a subject, comprising administering to a subject in need thereof, an effective amount of an isolated monoclonal antibody, or antigen binding portion thereof, as described herein, or a pharmaceutical composition described herein. In some aspects, the cytotoxic T cell response occurs in a tumor microenvironment. In other aspects, the cytotoxic T cell response does not significantly occur in the spleen and / or liver of the subject. In some aspects, the disclosure provides a method for inducing or enhancing cytokine production mediated by human CD137 in a subject, comprising administering to a subject in need thereof, an effective amount of an isolated monoclonal antibody, or antigen binding portion thereof, as described herein, or a pharmaceutical composition described herein. In some embodiments, the cytokine produced is IL-2, TNFa, IL-13, IFN-y, or combinations thereof. In some embodiments, the cytokine produced is IL-2. In some embodiments, the cytokine produced is TNFo. In some embodiments, the cytokine produced is IL-13. In some embodiments, the cytokine produced is IFN-y. In some embodiments, the cytokine produced is IL-2 and TNFa. In some embodiments, the cytokine produced is IL-2 and IL-13. In some embodiments, the cytokine produced is IL-2 and IFN-y. In some embodiments, the cytokine produced is TNFa, and IL-13. In some embodiments, the cytokine produced is TNFa and IFN-y. In some embodiments, the cytokine produced is IL-13 and IFN-y. In some embodiments, the cytokine produced is IL-2, TNFa and IL-13. In some embodiments, the cytokine produced is IL-2, TNFa and IFN-y. In some embodiments, the cytokine produced is IFN-y TNFa and IL-13. In other embodiments, cytokine production occurs in a tumor microenvironment. In yet other embodiments, cytokine production does not significantly occur in the spleen and / or liver of the subject. In another aspect, the disclosure provides a method for inducing or enhancing T cell proliferation mediated by human CD137 in a subject, comprising administering to a subject in need thereof, an effective amount of an isolated monoclonal antibody, or antigen binding portion thereof, as described herein, or a pharmaceutical composition described herein. In some embodiments, T cell proliferation occurs in a tumor microenvironment. In other embodiments, T cell proliferation does not significantly occur in the spleen and / or liver of the subject. In another aspect, the disclosure provides a method for reducing or inhibiting tumor growth, comprising administering to a subject in need thereof, an effective amount of an isolated monoclonal antibody, or antigen binding portion thereof, as described herein, or a pharmaceutical composition described herein. In yet another aspect, the disclosure provides a method for treating a disorder mediated by human CD137 in a subject, comprising administering to a subject in need thereof, an effective amount of an isolated monoclonal antibody, or antigen binding portion thereof, as described herein, or a pharmaceutical composition described herein. In some aspects, the disclosure provides a method for treating cancer in a subject, comprising administering to a subject in need thereof, an effective amount of an isolated monoclonal antibody, or antigen binding portion thereof, as described herein, or a pharmaceutical composition described herein. In some embodiments, the cancer is selected from the group consisting of melanoma, glioma, renal, breast, hematological and head and neck cancer. In some embodiments, the hematological cancer is a B cell lymphoma. In some aspects, the disclosure provides a method of inducing an anti-tumor memory immune response, comprising administering to a subject in need thereof, an effective amount of an isolated monoclonal antibody, or antigen binding portion thereof, as described herein, or a pharmaceutical composition described herein. In any of the foregoing aspects, infiltration of immune cells into a tumor microenvironment is increased after administration of an antibody or antigen binding portion. In some aspects, immune cells express CD45. In any of the foregoing aspects, quantity of T regulatory (Treg) cells is reduced in a tumor microenvironment after administration of an antibody or antigen binding portion. In some aspects, Treg cells express CD4, FOXP-3 and CD24. In any of the foregoing aspects, quantity of macrophages cells is reduced in a tumor microenvironment after administration of a monoclonal antibody or antigen binding portion. In some aspects, macrophages express CD45 and CD11b. In any of the foregoing aspects, T cell exhaustion is reduced after administration of an antibody or antigen binding portion. In some aspects, reduction of T cell exhaustion comprises a decrease in expression of TIGIT, PD-1, LAG-3 or a combination thereof. In some aspects, reduction of T cell exhaustion comprises a decrease in expression of TIGIT and PD-1. In any of the foregoing aspects, depletion of CD4+ T cells, CD8+ T cells, Natural Killer cells, or combinations thereof, reduces the efficacy of the antibody or antigen binding portion thereof. In another aspect, the disclosure provides a method for detecting the presence or absence of human CD137 in a biological sample, comprising: (a) contacting a biological sample with an antibody or antigen-binding portion described herein, wherein the antibody or antigen-binding portion is labeled with a detectable substance; and (b) detecting the antibody or antigen-binding portion bound to human CD137 to thereby detect the presence or absence of human CD137 in the biological sample. In another aspect, the disclosure provides a kit comprising a container comprising an antibody or antigen-binding portion described herein, and an optional pharmaceutically acceptable carrier, or a pharmacentical composition described herein, and a package insert comprising instructions for administration of the antibody or pharmaceutical composition, for treating or delaying progression of cancer or reducing or inhibiting tumor growth in a subject in need thereof. In another aspect, the disclosure provides a kit comprising a container comprising an antibody or antigen-binding portion described herein, and an optional pharmaceutically acceptable carrier, or a pharmaceutical composition described herein, and a package insert comprising instructions for administration of the antibody or pharmaceutical composition alone or in combination with another agent, for treating or delaying progression of cancer or reducing or inhibiting tumor growth in a subject in need thereof. In another aspect, the disclosure provides use of an isolated monoclonal antibody, or antigen binding portion thereof, as described herein, to induce or enhance T cell activation mediated by human CD137 in a subject. In other aspects, the disclosure provides use of an isolated monoclonal antibody, or antigen binding portion thereof, as described herein, to induce or enhance multimerization of human CD137 trimers in a subject. In another aspect, the disclosure provides use of an isolated monoclonal antibody, or antigen binding portion thereof, as described herein, to induce or enhance a cytotoxic T cell response mediated by human CD137 in a subject. In other aspects, the disclosure provides use of an isolated monoclonal antibody, or antigen binding portion thereof, as described herein, to induce or enhance cytokine production mediated by human CD137 in a subject. In another aspect, the disclosure provides use of an isolated monoclonal antibody, or antigen binding portion thereof, as described herein, to induce or enhance T cell proliferation mediated by human CD137 in a subject. In another aspect, the disclosure provides use of an isolated monoclonal antibody, or antigen binding portion thereof, as described herein, to reduce or inhibit tumor growth in a subject in need thereof. In other aspects, the disclosure provides use of an isolated monoclonal antibody, or antigen binding portion thereof, as described herein, to treat a disorder mediated by human CD137 in a subject in need thereof. In another aspect, the disclosure provides use of an isolated monoclonal antibody, or antigen binding portion thereof, as described herein, to treat cancer in a subject in need thereof. In another aspect, the disclosure provides use of an isolated monoclonal antibody, or antigen binding portion thereof, as described herein, for the manufacture of a medicament for treating or delaying progression of cancer or reducing or inhibiting tumor growth in a subject in need thereof. In other aspects, the disclosure provides an isolated monoclonal antibody, or antigen binding portion thereof, as described herein, in the manufacture of a medicament for treating or delaying progression of cancer or reducing or inhibiting tumor growth in a subject in need thereof. In another aspect, the disclosure provides an isolated monoclonal antibody or antigen binding portion thereof, as described herein, for use as a medicament. BRIEF DESCRIPTION OF THE DRAWINGS The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee. FIG. 1 provides graphs depicting the distribution of binding affinities of affinity matured clones of the parental anti-CD137 antibody mAbl. FIG. 2 provides a schematic showing the results of mAbl CDRH3 alanine scanning, as measured by binding affinity (Kp) to human or mouse CD137. FIG. 3A shows the amino acid sequence of human CD137 wherein residues comprising an epitope bound by mAb1, mAb4 or mADbS are indicated in bold. FIG. 3B is a graph depicting kinetic binding data of mAb] to the extracellular domain of mouse and rat CD137 as determined by surface plasmon resonance. FIG. 3C provides x-ray crystallography images of human CDI137 bound to CD137L (shown in grey) and residues E111, T113, K114 and P135 shown as spheres. FIG. 3D provides x-ray crystallography images of human CD137 bound to CD137L (shown in grey) in trimeric formation, and residues E111, T113, K114 and P135 shown as spheres. FIG. 4A provides a scatterplot of flow cytometric data depicting an increase in TIGIT (top) or PD-1 (bottom) expression on CD44+ T cells in response to anti-CD137 antibodies. FIG. 4B provides graphs depicting the quantification of CD8+ CD44+ T cells expressing TIGIT (top) or PD-1 (bottom) in the spleen of mice after treatment with anti-CD137 antibodies. FIG. 4C provides graphs depicting the quantification of CD8+ T cells in the spleen of mice after treatment with anti-CD137 antibodies, as percentage of CD45+ cells (left) or cell number per spleen (right). FIG. 5A provides graphs showing individual CT26 tumor volumes in mice after treatment with anti-CD137 antibodies at indicated dosages. FIG. 5B is a graph showing the mean tumor volumes provided in FIG. 5A. FIG. 5C is a Kaplan-Meier graph showing overall survival of mice with tumors after treatment with anti-CD137 antibodies. FIG. 5D is a graph showing tumor volume in mice re-challenged with tumorigenic CT26 cells. FIG. 6A provides graphs showing individual CT26 tumor volumes in mice after treatment with parental and affinity-matured anti-CD137 antibodies. FIG. 6B is a graph providing the mean tumor volumes provided in FIG. 6A. FIG. 7 provides graphs depicting the percentage of CD8+ or CD4+ T cells, from splenic T cells (top) and tumor infiltrating leukocytes (bottom) after treatment with anti-CD137 antibodies at indicated dosages. FIG. 8 provides graphs showing individual tumor volumes when mice were treated with mAbl, with or without lymphocyte depleting antibodies. CD4+ T cells were depleted with GK1.5 (middle graph), CD8+ T cells were depleted with YTS169.4 (second graph from the right), and NK cells were depleted with an anti-asialo-GM1 antibody (last graph on the right). FIG. 9 provides graphs showing individual tumor volumes in mice having either CT26 tumors (colon carcinoma), EMT-6 tumors (breast carcinoma), A20 tumors (B cell lymphoma), or MC38 tumors (colon carcinoma) and treated with mAb8 or isotype control antibody. FIGs. 10A-10C show the in vivo anti-tumor efficacy of anti-CD137 antibodies administered at 150 pig / mouse. Individual tumor volumes are shown in 10A, mean tumor volumes are shown in 10B and percent survival is shown in 10C. FIGs. 11A-11C show the in vivo anti-tumor efficacy of anti-CD137 antibodies administered at 20 pg / mouse. Individual tumor volumes are shown in 11A, mean tumor volumes are shown in 11B and percent survival is shown in 11C. FIG. 12 provides graphs showing individual tumor volumes in mice having CT26 tumors and treated with varying doses of mAb1 (i.e, 12.5, 25, 50, 100 or 200g) or isotype control. FIGs. 13A and 13B show the contribution of Fc binding in the anti-tumor efficacy of mAbl. FIG. 13A shows mAb] as an IgG4 isotype or an IgG4 aglycosylated isotype. Mean tumor volumes are shown on the top and individual tumor volumes are shown on the bottom. FIG. 13B shows mAbl1 as an IgG4 isotype or an IgGl aglycosylated isotype. Mean tumor volumes are shown on the top and individual tumor volumes are shown on the bottom. FIGs. 14A-14D show the in vivo anti-tumor efficacy of anti-CD137 antibodies in mice with large established tumors (i.e., 500mm?) prior to receiving treatment. Individual tumor volumes are shown in 14A and 14D, mean tumor volumes are shown in 14B and percent survival 1s shown in 14C. FIG. 15 provides a Kaplan-Meier survival graph showing protective anti-tumor immunity in mice previously treated with mAbl, mAb8 or isotype control from FIGs. 14A-14C and considered cured, re-challenged with CT26 cells in an opposing flank. FIG. 16A provides scatterplots of flow cytometric data showing the expansion of CD45+ intrahepatic T cells following treatment with anti-CD137 antibodies at indicated dosages. FIG. 16B provides graphs depicting the quantification of intrahepatic CD8+ T cells (left) and CD4+ T cells (right) following treatment with anti-CD137 antibodies at indicated dosages. FIG. 17A provides graphs depicting the percentage of CD3+, CD4+, or CD8+ T cells, from splenic T cells after treatment of mice with affinity-matured anti-CD137 antibodies. FIG. 17B provides graphs depicting the percentage of CD3+, CD4+, or CD8+ T cells from liver T cells after treatment of mice with affinity-matured anti-CD137 antibodies. FIG. 18A provides graphs depicting the percentage of splenic CD8+CD44+ T cells expressing TIGIT, PD-1, or LAG3 after treatment of mice with affinity-matured anti-CD137 antibodies. FIG. 18B provides graphs depicting the percentage of liver CD8+CD44+ T cells expressing TIGIT, PD-1, or LAG3 after treatment of mice with affinity-matured anti-CD137 antibodies. FIG. 19A provides graphs depicting the percentage of splenic CD4+CD44+ T cells expressing TIGIT, PD-1, or LAG3 after treatment of mice with affinity-matured anti-CD137 antibodies. FIG. 19B provides graphs depicting the percentage of liver CD4+CD44+ T cells expressing TIGIT, PD-1, or LAG3 after treatment of mice with affinity-matured anti-CD137 antibodies. FIGs. 20A-20C provide graphs of in vivo indicators of toxicity resulting from multiple administrations of anti-CD137 antibodies mAbl, mAb8 or 3H3 at varying doses. FIG. 20A is a graph showing percentage of CD8+ T cells in the liver after administration of the anti-CD137 antibodies. FIG. 20B is a graph showing alanine aminotransferase (ALT) activity in the plasma of mice administered anti-CD137 antibodies. FIG. 20C is a graph showing the levels of TNFo, in the plasma of mice administered anti-CD137 antibodies. FIG. 21 provides representative images of sectioned livers stained with hematoxylin and eosin (H&E) from mice treated with mAbl, mAb8, 3H3 or isotype control as described in FIGs. 20A-20C. Arrows indicate infiltration of immune cells. FIGs. 22A-22D provide representative FACS plots showing immune cell reprogramming in the tumor microenvironment. Mice having CT26 tumors were administered multiple doses of mADb8 or isotype control (days 0, 3, 6 and 9). FIG. 22A shows overall immune cell infiltration based on CD45 expression. FIG. 22B shows reduction in Treg cells as measured by FOXP-3 and CD25 expression. FIG. 22C shows reduction of T-cell exhaustion as measured by PD-1 and TIGIT expression. FIG. 22D shows reduction of tumor-associated macrophages as measured by F4 / 80 and CD11b expression. FIG. 23 shows immunophenotyping analysis of spleens from mice having CT26 tumors and treated with either anti-CD137 antibodies mAb1 and 3H3, or isotype control. FIG. 24 is a graph showing the concentration of IL-2 (pg / ml) produced by murine T cells in an OVA stimulation assay, when stimulated with the anti-CD137 antibodies indicated. Along with Atezolizumab (anti-PD-L1 antibody), a murine anti-PD-1 (RMP1-14) was used as a comparator. FIGs. 25A and 25B are graphs showing the percentage of murine CD8+ T cells expressing either CD25 (25A) or TIGIT (25B) when stimulated with the anti-CD137 antibodies indicated, in an OVA stimulation assay. Along with Atezolizumab (anti-PD-L1 antibody), a murine anti-PD-1 (RMP1-14) and murine anti-CD137 (3H3) were used as comparators. FIG. 26 provides bar graphs depicting the quantification of cytokines (IL-2, TNFa, IL-13, and IFN-y) produced by CD3+ T cells following incubation with plate-bound anti-CD137 antibodies. Cytokine levels are shown as fold increase over baseline activation by an anti-CD3 antibody. FIGs. 27A-27C provide graphs depicting the dose-response of IFN-y production in a mixed lymphocyte reaction following treatment with anti-CD137 antibodies. An anti-PD1 antibody (Keytruda; Merck) was used as a control. FIG. 28 is a graph showing IFN-y production from human T cells co-cultured with CHO cells engineered to express CD32 (CHO-CD32 cells) in the presence of anti-CD137 antibodies mAb1, mAb8, mAb4 or mAb35, or isotype control. FIG. 29 is a graph showing proliferation of Treg cells when co-cultured with CHO cells engineered to express CD32 (CHO-CD32 cells) in the presence or absence of anti-CD137 antibodies mAb1l, mAb8, mAb4 or mAbS3, isotype control. FIG. 30 provides graphs showing NFkf and SRF signaling in CCL-119 cells transduced with luciferase reporters for NFP or SRF in the presence of mAbl, mAB8, mAb4 or mAbS at varying concentrations. FIG. 31 provides graphs showing induction of IL-6, TNFa, or IL-27 by bone marrow- derived mouse macrophages stimulated with TLR9 agonist CpG in the presence of anti-CD137 antibodies mAb1, 3H3 or LOB12.3, or isotype control. FIG. 32 provides a graph showing induction of TNFa by human monocyte derived macrophages stimulated with LPS in the presence of anti-CD137 antibodies mAbl, mAb4 or mADbS, or isotype control. FIG. 33 provides a graph showing effect of anti-CD137 antibodies on macrophage differentiation as determined by CD64 expression of THP1 monocytes cultured with PMA in the presence of anti-CD137 antibodies mAb1, mAb4 or mAbS, or isotype control. FIGs. 34A-34C provides graphs showing percentage of hCD45+, hCD8+ or hCD4+ from immunocompetent mice that received human PBMCs and anti-CD137 antibodies mAbl, mAb4 or mADbS, or isotype control. FIG. 35 graphically depicts cIEF charge variants analysis of mAb] at high concentration (100 mg / mL) in three buffers with different pH and stored at either 4°C or 25°C temperatures up to 4 weeks. FIG. 36 graphically depicts the cIEF charge variants analysis of mAbl at 5 mg / mL in three buffers with different pH at 40°C for up to 4 weeks. FIG. 37 depicts the size-exclusion chromatography profile of mAb] after diluting 10-fold into 5%, 0.5% or 0.1% dextrose solutions, 0.9% saline, or pure water and incubating at room temperature for three days. The term dextrose is used interchangeably with the term glucose. FIG. 38 graphically depicts the Dynamic Light Scattering (DLS) results of mAb] after diluting 10-fold into 5%, 0.5% or 0.1% dextrose solutions, 0.9% saline, or pure water and incubating at room temperature for 3 days FIG. 39 graphically depicts the micro-flow imaging analysis of subvisible particles between 2-80 mm. The analysis was performed using mAb! at 10 mg / mL in a formulation of the disclosure after going through three cycles of freeze-thaw between -30°C / room temperature and three passes through a needle with a built in Sum filter or a vented needle with a built in Sum filter. DETAILED DESCRIPTION The present disclosure provides various formulations of an anti-CD137 antibody, or antigen binding fragments thereof, that specifically bind to human CD137 and agonize human CD137. In some embodiments, the formulations of the disclosure include (i) an anti-CD137 antibody or antigen binding fragment thereof, (ii) a buffer (e.g., histidine), (iii) a disaccharide sugar (e.g., sucrose); (iv) a non-ionic surfactant (e.g., polysorbate 80); and (v) a salt (e.g., NaCl). In some embodiments, the formulations of the disclosure have a pH of about 5.0 to about 7.0. In some embodiments, the formulations of the disclosure have a pH of about 5.0 to about 7.4. The disclosure also provides methods for treating cancer, or reducing or inhibiting tumor growth in a patient comprising administering a formulation of the disclosure to the patient. The disclosure also provides methods for inducing or enhancing T cell activation in a patient comprising administering a formulation of the disclosure to the patient. The present disclosure is based, at least in part, on the discovery that the formulations of the disclosure are stable and minimize the formation of antibody aggregates and particulates. In particular, the formulations of the disclosure were shown to provide an anti-CD137 agonist antibody, mAb1, with excellent stability, no significant loss of monomeric antibody, and no significant amount of degradation. In particular, it was surprisingly discovered that an anti- CD137 antibody was stable at high concentrations and under forced degradation conditions (e.g., elevated temperature) when formulated in histidine buffer at pH 5.8. Likewise, it was discovered that there was a reduction in acidic / basic species when the anti-CD137 antibody was formulated in a buffer at pH 6.0 and at pH 6.5. It was also discovered that the anti-CD137 formulations of the disclosure had excellent stability with no significant loss of monomeric antibody. Furthermore, it was discovered that the addition of sucrose to the anti-CD137 formulations of the disclosure resulted in improved antibody stability at elevated temperatures. Accordingly, in some embodiments, the present disclosure provides stable anti-CD137 antibody formulations. In some embodiments, the present disclosure provides stable anti-CD137 antibody formulations comprising (i) a buffer comprising about 10 mM to about 100 mM histidine, (ii) sucrose at about 5%-about 15% weight / volume, (iii) polysorbate-80 at about 0.01%-about 0.1% weight / volume (w / v), and (iv) NaCl at about 50 mM — 200 mM, wherein the pH of the formulation is about 5.0 to about 7.0. In some embodiments, the pH of the formulation is about 5.0 to about 7.4. In some embodiments, the pH of the formulation is about 5.0 to about 8.0. Cancer therapy with agonist anti-CD137 antibodies has been shown to induce immune- mediated tumor rejections in mice, and analogous agents of this kind are currently being tested in cancer patients. Previous reports have indicated that administration of anti-CD137 antibodies can induce significant accumulations of polyclonal infiltrates of T lymphocytes in the liver (Dubrot et al,, (2010) Cancer Immunology, Immunotherapy 59(8):1223-1233), suggestive of hepatic inflammation and the potential for drug-induced liver toxicity. A recent report on the clinical evaluation of an agonistic anti-CD137 antibody (Urelumab, BMS-663513; Bristol-Myers Squibb) documented the observation of treatment-related adverse events in human subjects, including indications of severe hepatotoxicity (transaminitis) correlating with antibody dose (Segal et al., (2016) Clin Cancer Res 23(8):1929-1936). The present disclosure provides isolated monoclonal antibodies, or antigen binding portions thereof, that specifically bind to an epitope of human CD137 and agonize human CD137, and formulations thereof. In some embodiments, the antibody or antigen binding portion thereof competes with mAb] for binding to the epitope of human CD137. In some aspects, the anti-CD137 agonist antibodies of the disclosure induce cytokine production and expansion of CD8+ T cells in the tumor microenvironment, and protective anti-tumor immunity in vivo with a concomitant reduction in the potential for toxicity-related events, as compared to the anti-mouse CD137 3H3 antibody (Melero et al. (1997) Nature Medicine 3(6):682-685; Uno et al. (2006) Nature Medicine 12(6):693-696) and to at least two anti-human CD137 antibodies in clinical development (BMS- 663513 / Urelumab, Bristol-Meyers Squibb, and PF-05082566 / Utomilumab, Pfizer). Definitions Terms used in the claims and specification are defined as set forth below unless otherwise specified. It must be noted that, as used in the specification and the appended claims, the singular forms "a," "an" and "the" include plural referents unless the context clearly dictates otherwise. Further, unless otherwise required by context, singular terms shall include pluralities and plural terms shall include the singular. As used herein, "about" will be understood by persons of ordinary skill and will vary to some extent depending on the context in which it is used. If there are uses of the term which are not clear to persons of ordinary skill given the context in which it is used, "about" will mean up to plus or minus 10% of the particular value. As used herein, the term "agonist" refers to any molecule that partially or fully promotes, induces, increases, and / or activates a biological activity of a native polypeptide disclosed herein (e.g., CD137). Suitable agonist molecules specifically include agonist antibodies or antibody fragments, fragments or amino acid sequence variants of native polypeptides, peptides, antisense oligonucleotides, small organic molecules, etc. In some embodiments, activation in the presence of the agonist is observed in a dose-dependent manner. In some embodiments, the measured signal (e.g., biological activity) is at least about 5%, at least about 10%, at least about 15%, at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or at least about 100% higher than the signal measured with a negative control under comparable conditions. Also disclosed herein, are methods of identifying agonists suitable for use in the methods of the disclosure. For example, these methods include, but are not limited to, binding assays such as enzyme-linked immuno-absorbent assay (ELISA), FORTE BIO© systems, and radioimmunoassay (RIA). These assays determine the ability of an agonist to bind the polypeptide of interest (e.g., a receptor or ligand, e.g., CD137) and therefore indicate the ability of the agonist to promote, increase or activate the activity of the polypeptide. Efficacy of an agonist can also be determined using functional assays, such as the ability of an agonist to activate or promote the function of the polypeptide. For example, a functional assay may comprise contacting a polypeptide with a candidate agonist molecule and measuring a detectable change in one or more biological activities normally associated with the polypeptide. The potency of an agonist is usually defined by its ECso value (concentration required to activate 50% of the agonist response). The lower the ECso value the greater the potency of the agonist and the lower the concentration that is required to activate the maximum biological response. As used herein, the term “alanine scanning” refers to a technique used to determine the contribution of a specific wild-type residue to the stability or function(s) (e.g., binding affinity) of a given protein or polypeptide. The technique involves the substitution of an alanine residue for a wild-type residue in a polypeptide, followed by an assessment of the stability or function(s) (e.g., binding affinity) of the alanine-substituted derivative or mutant polypeptide and comparison to the wild-type polypeptide. Techniques to substitute alanine for a wild-type residue in a polypeptide are known in the art. The term "ameliorating" refers to any therapeutically beneficial result in the treatment of a disease state, e.g., cancer, including prophylaxis, lessening in the severity or progression, remission, or cure thereof. As used herein, the term "amino acid" refers to naturally occurring and synthetic amino acids, as well as amino acid analogs and amino acid mimetics that function in a manner similar to the naturally occurring amino acids. Naturally occurring amino acids are those encoded by the genetic code, as well as those amino acids that are later modified, e.g., hydroxyproline, y- carboxyglutamate, and O-phosphoserine. Amino acid analogs refer to compounds that have the same basic chemical structure as a naturally occurring amino acid, i.e., a carbon that is bound to a hydrogen, a carboxyl group, an amino group, and an R group, e.g., homoserine, norleucine, methionine sulfoxide, methionine methyl sulfonium. Such analogs have modified R groups (e.g., norleucine) or modified peptide backbones, but retain the same basic chemical structure as a naturally occurring amino acid. Amino acid mimetics refers to chemical compounds that have a structure that is different from the general chemical structure of an amino acid, but that function in a manner similar to a naturally occurring amino acid. Amino acids can be referred to herein by either their commonly known three letter symbols or by the one-letter symbols recommended by the IUPAC-IUB Biochemical Nomenclature Commission. Nucleotides, likewise, can be referred to by their commonly accepted single-letter codes. As used here, a “polar amino acid” refers to an amino acid comprising a side chain that prefers to reside in an aqueous environment. In some embodiments, a polar amino acid is selected from the group consisting of: arginine, asparagine, aspartic acid, glutamic acid, glutamine, histidine, lysine, serine, theronine and tyrosine. Polar amino acids can be positive, negatively or neutrally charged. As used herein, a “non-polar amino acid” refers to an amino acid selected from the group consisting of: alanine, cysteine, glycine, isoleucine, leucine, methionine, phenylalanine, proline, tryptophan and valine. As used herein, an "amino acid substitution” refers to the replacement of at least one existing amino acid residue in a predetermined amino acid sequence (an amino acid sequence of a starting polypeptide) with a second, different "replacement" amino acid residue. An "amino acid insertion" refers to the incorporation of at least one additional amino acid into a predetermined amino acid sequence. While the insertion will usually consist of the insertion of one or two amino acid residues, larger "peptide insertions," can also be made, e.g. insertion of about three to about five or even up to about ten, fifteen, or twenty amino acid residues. The inserted residue(s) may be naturally occurring or non- naturally occurring as disclosed above. An "amino acid deletion" refers to the removal of at least one amino acid residue from a predetermined amino acid sequence. As used herein, the term “amount” or “level” refers to a detectable quantity, level or abundance of a substance (e.g., a protein). When referring to a polypeptide, such as those described herein, the terms “level of expression” or “expression level” in general are used interchangeably and generally refer to a detectable amount of a polypeptide in a biological sample (e.g., on the surface of a cell). As used herein, the term "anti-CD137 agonist antibody" (used interchangeably with the term "anti-CD137 antibody") refers to an antibody that specifically binds to CD137 and partially or fully promotes, induces, increases, and / or activates CD137 biological activity, response, and / or downstream pathway(s) mediated by CD137 signaling or other CD137-mediated function. In some embodiments, an anti-CD137 agonist antibody binds to CD137 and allows binding of CD137L. In some embodiments, an anti-CD137 agonist antibody binds to CD137 and induces multimerization of CD137. In some embodiments, an anti-CD137 agonist antibody binds to CD137 and induces the dimerization of CD137 trimers. In some embodiments, an anti-CD137 agonist antibody binds to CD137 and induces the multimerization of CD137 trimers. Examples of anti-CD137 agonist antibodies are provided herein. Methods for detecting formation of a trimer:trimer complex are known to those of skill in the art. For example, electron microscopy has been shown to detect such complexes, see, e.g., Won, E. The Journal of Biological Chemistry, Vol. 285 (12): 9202-9210 (2010) As used herein, the term “anti-CD137 mAb1” (used interchangeably with “mAb1”) refers to an exemplary anti-CD137 agonist antibody that comprises the variable heavy chain (Vx) amino acid sequence: EVQLLESGGGLVQPGGSLRLSCAASGFTFSSYAMSWVRQAPGKGLEW VSAISGSGGSTY YADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCAKDSPFLLDDYYYYYYMDVW GKGTTVTVSS (SEQ ID NO: 4), and the variable light chain (V1) amino acid sequence: DIQMTQSPSSVSASVGDRVTITCRASQGISSWLAWYQQKPGKAPKLLIYAASSLQSGVPS RFSGSGSGTDFTLTISSLQPEDFATYYCQQGHLFPITFGGGTKVEIK (SEQ ID NO: 6). As used herein, the term “anti-CD137 mAb8” (used interchangeably with “mAb8”) refers to an exemplary anti-CD137 agonist antibody that comprises the variable heavy chain ((Vu) amino acid sequence: EVQLLESGGGLVQPGGSLRLSCAASGFTFRNYAMSWVRQAPGKGLEWVSAISGSGDTT YYADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCAKDSPFLLDDYYYYYYMDV WGKGTTVTVSS (SEQ ID NO: 101); and the variable light chain (V1) amino acid sequence: DIQMTQSPSSVSASVGDRVTITCRASQGISSWLAWYQQKPGKAPKLLIYAASSLQSGVPS RFSGSGSGTDFTLTISSLQPEDFATY YCQQGHLFPITFGGGTKVEIK (SEQ ID NO: 6). As used herein, the term “anti-CD137 mAbl10” (used interchangeably with “mAb10”) refers to an exemplary anti-CD137 agonist antibody that comprises the variable heavy chain (Vu) amino acid sequence: EVQLLESGGGLVQPGGSLRLSCAASGFTFYGYAMSWVRQAPGKGLEWVAAISGSGDST YYADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCAKDSPFLLDDYYYYYYMDV WGKGTTVTVSS (SEQ ID NO: 26); and the variable light chain (VL) amino acid sequence: DIQMTQSPSSVSASVGDRVTITCRASQGISSWLAWYQQKPGKAPKLLIYAASSLQSGVPS RESGSGSGTDFTLTISSLOPEDFATY YCQQGHLFPITFGGGTKVEIK (SEQ ID NO: 6). As used herein, the term “antibody” refers to a whole antibody comprising two light chain polypeptides and two heavy chain polypeptides. Whole antibodies include different antibody isotypes including IgM, IgG, IgA, IgD, and IgE antibodies. The term “antibody” includes a polyclonal antibody, a monoclonal antibody, a chimerized or chimeric antibody, a humanized antibody, a primatized antibody, a deimmunized antibody, and a fully human antibody. The antibody can be made in or derived from any of a variety of species, e.g., mammals such as humans, non-human primates (e.g., orangutan, baboons, or chimpanzees), horses, cattle, pigs, sheep, goats, dogs, cats, rabbits, guinea pigs, gerbils, hamsters, rats, and mice. The antibody can be a purified or a recombinant antibody. As used herein, the terms “antibody fragment,” “antigen-binding fragment,” “antigen binding portion” or similar terms refer to a fragment of an antibody that retains the ability to bind to a target antigen (e.g., CD137) and inhibit the activity of the target antigen. Such fragments include, e.g., a single chain antibody, a single chain Fv fragment (scFv), an Fd fragment, a Fab fragment, a Fab’ fragment, or an F(ab’), fragment. An scFv fragment is a single polypeptide chain that includes both the heavy and light chain variable regions of the antibody from which the scFv is derived. In addition, intrabodies, minibodies, triabodies, and diabodies are also included in the definition of antibody and are compatible for use in the methods described herein. See, e.g., Todorovska et al., (2001) J. Immunol. Methods 248(1):47-66; Hudson and Kortt, (1999) J. Immunol. Methods 231(1):177-189; Poljak, (1994) Structure 2(12):1121-1123; Rondon and Marasco, (1997) Annu. Rev. Microbiol. 51:257-283, the disclosures of each of which are incorporated herein by reference in their entirety. As used herein, the term “antibody fragment” also includes, e.g., single domain antibodies such as camelized single domain antibodies. See, e.g., Muyldermans et al., (2001) Trends Biochem. Sci. 26:230-235; Nuttall et al., (2000) Curr. Pharm. Biotech. 1:253-263; Reichmann et al., (1999) J. Immunol. Meth. 231:25-38; PCT application publication nos. WO 94 / 04678 and WO 94 / 25591; and U.S. Patent No:. 6,005,079, all of which are incorporated herein by reference in their entireties. In some embodiments, the disclosure provides single domain antibodies comprising two VH domains with modifications such that single domain antibodies are formed. In some embodiment, an antigen-binding fragment includes the variable region of a heavy chain polypeptide and the variable region of a light chain polypeptide. In some embodiments, an antigen-binding fragment described herein comprises the CDRs of the light chain and heavy chain polypeptide of an antibody. The term “antigen presenting cell” or “APC” is a cell that displays foreign antigen complexed with MHC on its surface. T cells recognize this complex using T cell receptor (TCR). Examples of APCs include, but are not limited to, dendritic cells (DCs), peripheral blood mononuclear cells (PBMC), monocytes (such as THP-1), B lymphoblastoid cells (such as C1R.A2, 1518 B-LCL) and monocyte-derived dendritic cells (DCs). Some APCs internalize antigens either by phagocytosis or by receptor-mediated endocytosis. The term “antigen presentation” refers to the process by which APCs capture antigens and enables their recognition by T cells, e.g., as a component of an MHC-I and / or MHC-II conjugate. As used herein, the term "apoptosis" refers to the process of programmed cell death that occurs in multicellular organisms (e.g. humans). The highly-regulated biochemical and molecular events that result in apoptosis can lead to observable and characteristic morphological changes to acell, including membrane blebbing, cell volume shrinkage, chromosomal DNA condensation and fragmentation, and mRNA decay. A common method to identify cells, including T cells, undergoing apoptosis is to expose cells to a fluorophore-conjugated protein (Annexin V). Annexin V is commonly used to detect apoptotic cells by its ability to bind to phosphatidylserine on the outer leaflet of the plasma membrane, which is an early indicator that the cell is undergoing the process of apoptosis. As used herein, the term “binds to immobilized CD137,” refers to the ability of a human antibody of the disclosure to bind to CD137, for example, expressed on the surface of a cell or which is attached to a solid support. As used herein, the term “bispecific” or “bifunctional antibody” refers to an artificial hybrid antibody having two different heavy / light chain pairs and two different binding sites. Bispecific antibodies can be produced by a variety of methods including fusion of hybridomas or linking of Fab' fragments. See, e.g., Songsivilai & Lachmann, (1990) Clin. Exp. Immunol. 79:315- 321; Kostelny et al., (1992) J. Immunol. 148:1547-1553. Traditionally, the recombinant production of bispecific antibodies is based on the co- expression of two immunoglobulin heavy-chain / light-chain pairs, where the two heavy chain / light-chain pairs have different specificities (Milstein and Cuello, (1983) Nature 305:537- 539). Antibody variable domains with the desired binding specificities (antibody-antigen combining sites) can be fused to immunoglobulin constant domain sequences. The fusion of the heavy chain variable region is preferably with an immunoglobulin heavy-chain constant domain, including at least part of the hinge, CH2, and CH3 regions. For further details of illustrative currently known methods for generating bispecific antibodies see, e.g., Suresh et al., (1986) Methods Enzymol. 121:210; PCT Publication No. WO 96 / 27011; Brennan et al., (1985) Science 229:81; Shalaby et al., J. Exp. Med. (1992) 175:217-225; Kostelny et al., (1992) J. Immunol. 148(5):1547-1553; Hollinger et al., (1993) Proc. Natl. Acad. Sci. USA 90:6444-6448; Gruber et al., (1994) J. Immunol. 152:5368; and Tutt et al., (1991) J. Immunol. 147:60. Bispecific antibodies also include cross-linked or heteroconjugate antibodies. Heteroconjugate antibodies may be made using any convenient cross-linking methods. Suitable cross-linking agents are well known in the art, and are disclosed in U.S. Pat. No. 4,676,980, along with a number of cross-linking techniques. Various techniques for making and isolating bispecific antibody fragments directly from recombinant cell culture have also been described. For example, bispecific antibodies have been produced using leucine zippers. See, e.g., Kostelny et al. (1992) J Immunol 148(5):1547-1553. The leucine zipper peptides from the Fos and Jun proteins may be linked to the Fab' portions of two different antibodies by gene fusion. The antibody homodimers may be reduced at the hinge region to form monomers and then re-oxidized to form the antibody heterodimers. This method can also be utilized for the production of antibody homodimers. The “diabody” technology described by Hollinger et al. (1993) Proc Natl Acad Sci USA 90:6444-6448 has provided an alternative mechanism for making bispecific antibody fragments. The fragments comprise a heavy-chain variable domain (VH) connected to a light-chain variable domain (VL) by a linker which is too short to allow pairing between the two domains on the same chain. Accordingly, the VH and VL domains of one fragment are forced to pair with the complementary VL and VH domains of another fragment, thereby forming two antigen-binding sites. Another strategy for making bispecific antibody fragments by the use of single-chain Fv (scFv) dimers has also been reported. See, e.g., Gruber et al. (1994) J Immunol 152:5368. Alternatively, the antibodies can be “linear antibodies” as described in, e.g., Zapata et al. (1995) Protein Eng. 8(10):1057-1062. Briefly, these antibodies comprise a pair of tandem Fd segments (VH-CH1-VH-CH1) which form a pair of antigen binding regions. Linear antibodies can be bispecific or monospecific. Antibodies with more than two valencies (e.g., trispecific antibodies) are contemplated and described in, e.g., Tutt et al. (1991) J Immunol 147:60. The disclosure also embraces variant forms of multi-specific antibodies such as the dual variable domain immunoglobulin (DVD-Ig) molecules described in Wu et al. (2007) Nat Biotechnol 25(11): 1290-1297. The DVD-Ig molecules are designed such that two different light chain variable domains (VL) from two different parent antibodies are linked in tandem directly or via a short linker by recombinant DNA techniques, followed by the light chain constant domain. Similarly, the heavy chain comprises two different heavy chain variable domains (VH) linked in tandem, followed by the constant domain CHI and Fc region. Methods for making DVD-Ig molecules from two parent antibodies are further described in, e.g., PCT Publication Nos. WO 08 / 024188 and WO 07 / 024715. In some embodiments, the bispecific antibody is a Fabs-in- Tandem immunoglobulin, in which the light chain variable region with a second specificity is fused to the heavy chain variable region of a whole antibody. Such antibodies are described in, e.g., International Patent Application Publication No. WO 2015 / 103072. As used herein, "cancer antigen" or “tumor antigen” refers to (i) tumor- specific antigens, (ii) tumor- associated antigens, (iii) cells that express tumor- specific antigens, (iv) cells that express tumor- associated antigens, (v) embryonic antigens on tumors, (vi) autologous tumor cells, (vii) tumor- specific membrane antigens, (viii) tumor- associated membrane antigens, (ix) growth factor receptors, (x) growth factor ligands, and (xi) any other type of antigen or antigen-presenting cell or material that is associated with a cancer. The term "carcinoma" is art recognized and refers to malignancies of epithelial or endocrine tissues including respiratory system carcinomas, gastrointestinal system carcinomas, genitourinary system carcinomas, testicular carcinomas, breast carcinomas, prostatic carcinomas, endocrine system carcinomas, and melanomas. The anti-CD137 antibodies described herein can be used to treat patients who have, who are suspected of having, or who may be at high risk for developing any type of cancer, including renal carcinoma or melanoma. Exemplary carcinomas include those forming from tissue of the cervix, lung, prostate, breast, head and neck, colon and ovary. The term also includes carcinosarcomas, which include malignant tumors composed of carcinomatous and sarcomatous tissues. An "adenocarcinoma" refers to a carcinoma derived from glandular tissue or in which the tumor cells form recognizable glandular structures. As used herein the term "compete", when used in the context of antigen-binding proteins (e.g., immunoglobulins, antibodies, or antigen-binding fragments thereof) that compete for binding to the same epitope, refers to a interaction between antigen-binding proteins as determined by an assay (e.g., a competitive binding assay; a cross-blocking assay), wherein a test antigen- binding protein (e.g., a test antibody) inhibits (e.g., reduces or blocks) specific binding of a reference antigen-binding protein (e.g., a reference antibody, such as mAb1) to a common antigen (e.g., CD137 or a fragment thereof). In some embodiments, the antibodies described herein cross compete with mAb] (i.e., an antibody comprising the heavy and light chain variable sequences of SEQ ID NOs: 4 and 6, respectively), mab8 (i.e., an antibody comprising the heavy and light chain variable sequences of SEQ ID NOs: 101 and 6, respectively) or mAblO (i.e., an antibody comprising the heavy and light chain variable sequences of SEQ ID NOs: 26 and 6, respectively). A polypeptide or amino acid sequence "derived from" a designated polypeptide or protein refers to the origin of the polypeptide. Preferably, the polypeptide or amino acid sequence which is derived from a particular sequence has an amino acid sequence that is essentially identical to that sequence or a portion thereof, wherein the portion consists of at least 10-20 amino acids, preferably at least 20-30 amino acids, more preferably at least 30-50 amino acids, or which is otherwise identifiable to one of ordinary skill in the art as having its origin in the sequence. Polypeptides derived from another peptide may have one or more mutations relative to the starting polypeptide, e.g., one or more amino acid residues which have been substituted with another amino acid residue or which has one or more amino acid residue insertions or deletions. A polypeptide can comprise an amino acid sequence which is not naturally occurring. Such variants necessarily have less than 100% sequence identity or similarity with the starting molecule. In certain embodiments, the variant will have an amino acid sequence from about 75% to less than 100% amino acid sequence identity or similarity with the amino acid sequence of the starting polypeptide, more preferably from about 80% to less than 100%, more preferably from about 85% to less than 100%, more preferably from about 90% to less than 100% (e.g., 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%) and most preferably from about 95% to less than 100%, e.g., over the length of the variant molecule. In certain embodiments, there is one amino acid difference between a starting polypeptide sequence and the sequence derived there from. Identity or similarity with respect to this sequence is defined herein as the percentage of amino acid residues in the candidate sequence that are identical (i.e., same residue) with the starting amino acid residues, after aligning the sequences and introducing gaps, if necessary, to achieve the maximum percent sequence identity. In certain embodiments, a polypeptide consists of, consists essentially of, or comprises an amino acid sequence selected from a sequence set forth in any one of Tables 22-27. In certain embodiments, a polypeptide includes an amino acid sequence at least 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%. or 99% identical to an amino acid sequence selected from a sequence set forth in any one of Tables 22-27. In certain embodiments, a polypeptide includes a contiguous amino acid sequence at least 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 91%, 98%, or 99% identical to a contiguous amino acid sequence selected from a sequence set forth in any one of Tables 22-27. In certain embodiments, a polypeptide includes an amino acid sequence having at least 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 200, 300, 400, or 500 (or any integer within these numbers) contiguous amino acids of an amino acid sequence selected from a sequence set forth in any one of Tables 22-27. In certain embodiments, the antibodies of the disclosure are encoded by a nucleotide sequence. Nucleotide sequences of the invention can be useful for a number of applications, including: cloning, gene therapy, protein expression and purification, mutation introduction, DNA vaccination of a host in need thereof, antibody generation for, e.g., passive immunization, PCR, primer and probe generation, and the like. In certain embodiments, the nucleotide sequence of the invention comprises, consists of, or consists essentially of, a nucleotide sequence selected from a sequence set forth in any one of Tables 22-27. In certain embodiments, a nucleotide sequence includes a nucleotide sequence at least 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%. 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identical to a nucleotide sequence selected from a sequence set forth in any one of Tables 22-27. In certain embodiments, a nucleotide sequence includes a contiguous nucleotide sequence at least 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identical to a contiguous nucleotide sequence selected from a sequence set forth in any one of Tables 22-27. In certain embodiments, a nucleotide sequence includes a nucleotide sequence having at least 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 200, 300, 400, or 500 (or any integer within these numbers) contiguous nucleotides of a nucleotide sequence selected from a sequence set forth in any one of Tables 22-27. It will also be understood by one of ordinary skill in the art that the antibodies suitable for use in the methods disclosed herein may be altered such that they vary in sequence from the naturally occurring or native sequences from which they were derived, while retaining the desirable activity of the native sequences. For example, nucleotide or amino acid substitutions leading to conservative substitutions or changes at "non-essential" amino acid residues may be made. Mutations may be introduced by standard techniques, such as site-directed mutagenesis and PCR-mediated mutagenesis. The antibodies suitable for use in the methods disclosed herein may comprise conservative amino acid substitutions at one or more amino acid residues, e.g., at essential or non-essential amino acid residues. A "conservative amino acid substitution" is one in which the amino acid residue is replaced with an amino acid residue having a similar side chain. Families of amino acid residues having similar side chains have been defined in the art, including basic side chains (e.g., lysine, arginine, histidine), acidic side chains (e.g., aspartic acid, glutamic acid), uncharged polar side chains (e.g., glycine, asparagine, glutamine, serine, threonine, tyrosine, cysteine), nonpolar side chains (e.g., alanine, valine, leucine, isoleucine, proline, phenylalanine, methionine, tryptophan), beta-branched side chains (e.g., threonine, valine, isoleucine) and aromatic side chains (e.g., tyrosine, phenylalanine, tryptophan, histidine). Thus, a nonessential amino acid residue in a binding polypeptide is preferably replaced with another amino acid residue from the same side chain family. In certain embodiments, a string of amino acids can be replaced with a structurally similar string that differs in order and / or composition of side chain family members. Alternatively, in certain embodiments, mutations may be introduced randomly along all or part of a coding sequence, such as by saturation mutagenesis, and the resultant mutants can be incorporated into binding polypeptides of the invention and screened for their ability to bind to the desired target. As used herein, the term antigen “cross-presentation” refers to presentation of exogenous protein antigens to T cells via MHC class I and class II molecules on APCs. As used herein, the term “cross-reacts” refers to the ability of an antibody of the disclosure to bind to CD137 from a different species. For example, an antibody of the present disclosure which binds human CD137 may also bind another species of CD137. As used herein, cross- reactivity is measured by detecting a specific reactivity with purified antigen in binding assays (e.g., SPR, ELISA) or binding to, or otherwise functionally interacting with, cells physiologically expressing CD137. Methods for determining cross-reactivity include standard binding assays as described herein, for example, by BIACORE™ surface plasmon resonance (SPR) analysis using a BIACORE™ 2000 SPR instrument (Biacore AB, Uppsala, Sweden), or flow cytometric techniques. As used herein, the term “cytotoxic T lymphocyte (CTL) response” refers to an immune response induced by cytotoxic T cells. CTL responses are mediated primarily by CD8* T cells. As used herein, the term "dimerization" refers to the formation of a macromolecular complex by two, usually non-covalently bound, macromolecules, such as proteins or multimers of proteins. Homodimerization refers to the process of dimerization when the macromolecules (e.g., proteins) are identical in nature. Heterodimerization refers to the process of dimerization when the macromolecules (e.g., proteins) are non-identical in nature. Methods for determining dimerization are known to those of skill in the art. For example, such methods include, but are not limited to, yeast two-hybrid assay, fluorescence resonance energy transfer (FRET), bioluminescence resonance energy transfer (BRET), protein mass spectrometry, evanescent wave methods, size exclusion chromatography, analytical ultracentrifugation, scattering techniques, NMR spectroscopy, isothermal titration calorimetry, fluorescence anisotropy, fluorescence correlation spectroscopy (FCS), fluorescence recovery after photobleaching (FRAP), proximity imaging (PRIM) and bimolecular fluorescence complementation (BiFC) (see e.g., Gell D.A., Grant R.P., Mackay J.P. (2012) The Detection and Quantitation of Protein Oligomerization. In: Matthews J.M. (eds) Protein Dimerization and Oligomerization in Biology. Advances in Experimental Medicine and Biology, vol 747. Springer, New York, NY; and Xie, Q. et al. Methods Mol Biol, 2011; 680: 3-28). As used herein, the terms "dimerization of CD137" refers to the dimerization of two CD137 trimers. In some embodiments, the anti-CD137 agonist antibodies described herein induce or enhance dimerization of CD137. In some embodiments, the anti-CD137 agonist antibodies described herein induce or enhance dimerization of CD137 relative to the amount of dimerization in the absence of an anti-CD137 agonist antibody. In some embodiments, the anti-CD137 agonist antibodies described herein induce or enhance dimerization of CD137 relative to the amount of dimerization in the presence of a reference anti-CD137 agonist antibody. In some embodiments, dimerization is increased by at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 715%, 80%, 85%, 90%, 95%, or 100%. As used herein, the term “ECso” refers to the concentration of an antibody or an antigen- binding portion thereof, which induces a response, either in an in vitro or an in vivo assay, which is 50% of the maximal response, i.e., halfway between the maximal response and the baseline. As used herein, the term “effective dose” or “effective dosage” is defined as an amount sufficient to achieve or at least partially achieve the desired effect. The term “therapentically effective dose” is defined as an amount sufficient to cure or at least partially arrest the disease and its complications in a patient already suffering from the disease. Amounts effective for this use will depend upon the severity of the disorder being treated and the general state of the patient's own immune system. As used herein, the term “epitope” or “antigenic determinant” refers to a determinant or site on an antigen (e.g., CD137) to which an antigen-binding protein (e.g., an immunoglobulin, antibody, or antigen-binding fragment) specifically binds. The epitopes of protein antigens can be demarcated into “linear epitopes” and “conformational epitopes”. As used herein, the term “linear epitope” refers to an epitope formed from a contiguous, linear sequence of linked amino acids. Linear epitopes of protein antigens are typically retained upon exposure to chemical denaturants (e.g., acids, bases, solvents, cross-linking reagents, chaotropic agents, disulfide bond reducing agents) or physical denaturants (e.g. thermal heat, radioactivity, or mechanical shear or stress). In some embodiments, an epitope is non-linear, also referred to as an interrupted epitope. As used herein, the term “conformational epitope” or “non-linear epitope” refers to an epitope formed from noncontiguous amino acids juxtaposed by tertiary folding of a polypeptide. Conformational epitopes are typically lost upon treatment with denaturants. An epitope typically includes at least 3,4,5,6,7,8,9, 10, 11, 12, 13, 14 or 15 amino acids in a unique spatial conformation. In some embodiments, an epitope includes fewer than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6 or 5 amino acids in a unique spatial conformation. Generally, an antibody, or antigen-binding fragment thereof, specific for a particular target molecule will preferentially recognize and bind to a specific epitope on the target molecule within a complex mixture of proteins and / or macromolecules. In some embodiments, an epitope does not include all amino acids of the extracellular domain of human CD137. Also encompassed by the present disclosure are antibodies that bind to an epitope on CD137 which comprises all or a portion of an epitope recognized by the particular antibodies described herein (e.g., the same or an overlapping region or a region between or spanning the region). As used herein, the term “epitope mapping” refers to a process or method of identifying the binding site, or epitope, of an antibody, or antigen binding fragment thereof, on its target protein antigen. Epitope mapping methods and techniques are provided herein. As used herein, the term "CD137" refers to a specific member of the tumor necrosis factor receptor (TNFR) family of transmembrane proteins. Alternative names and acronyms for CD137 in the art include “tumor necrosis factor receptor superfamily member 9” (TNFRSF9), 4-1BB and “induced by lymphocyte activation” (ILA) (Alderson et al., (1994) Eur J Immunol 24(9):2219- 2227; Schwarz et al., (1993) Gene 134(2):295-298). An exemplary amino acid sequence of full- length human CD137, including leader, transmembrane, and cytoplasmic domains is set forth in Table 23 (SEQ ID NO: 3) and here: MGNSCYNIVATLLLVLNFERTRSLQDPCSNCPAGTFCDNNRNQICSPCPPNSFSSAGGQR TCDICRQCKGVFRTRKECSSTSNAECDCTPGFHCLGAGCSMCEQDCKQGQELTKKGCK DCCFGTFNDQKRGICRPWTNCSLDGKSVLVNGTKERDVVCGPSPADLSPGASSVTPPAP AREPGHSPQIISFFLALTSTALLFLLFFLTLRFSVVKRGRKKLLYIFKQPFMR PVQTTQEEDGCSCRFPEEEEGGCEL. As used herein, the term “CD137L" or “CD137 ligand” refers to a member of the tumor necrosis factor (TNF) family of transmembrane proteins. Alternative names and acronyms for CD137L in the art include “tumor necrosis factor superfamily member 9” (TNFSF9) and 4-1BB ligand (4-1BBL) (Alderson et al., (1994) Eur J Immunol 24(9):2219-2227). An exemplary amino acid sequence of full-length CD137L is set forth in Table 23 (SEQ ID NO: 97). As used herein, the terms “Fc-mediated effector functions” or “Fc effector functions” refer to the biological activities of an antibody other than the antibody’s primary function and purpose. For example, the effector functions of a therapeutic agnostic antibody are the biological activities other than the activation of the target protein or pathway. Examples of antibody effect functions include Clq binding and complement dependent cytotoxicity; Fc receptor binding; antibody- dependent cell-mediated cytotoxicity (ADCC); phagocytosis; down regulation of cell surface receptors (e.g., B cell receptor); lack of activation of platelets that express Fc receptor; and B cell activation. Many effector functions begin with Fc binding to an Fcy receptor. As used herein, the term “Fc receptor” refers to a polypeptide found on the surface of immune effector cells, which is bound by the Fc region of an antibody. In some embodiments, the Fc receptor is an Fey receptor. There are three subclasses of Fey receptors, FcyRI (CD64), FeyRIL (CD32) and FycRIII (CD16). All four IgG isotypes (IgGl, IgG2, IgG3 and IgG4) bind and activate Fc receptors FcyRI, FcyRIIA and FcyRIIA. FcyRIIB is an inhibitory receptor, and therefore antibody binding to this receptor does not activate complement and cellular responses. FcyRI is a high affinity receptor that binds to IgG in monomeric form, whereas FcyRIIA and FcyRIIA are low affinity receptors that bind IgG only in multimeric form and have slightly lower affinity. The binding of an antibody to an Fc receptor and / or Clq is governed by specific residues or domains within the Fc regions. Binding also depends on residues located within the hinge region and within the CH2 portion of the antibody. In some embodiments, the agonistic and / or therapeutic activity of the antibodies described herein is dependent on binding of the Fc region to the Fc receptor (e.g., FcyR). In some embodiments, the agonistic and / or therapeutic activity of the antibodies described herein is enhanced by binding of the Fc region to the Fc receptor (e.g., FcyR). As used herein, the term “glycosylation pattern” is defined as the pattern of carbohydrate units that are covalently attached to a protein, more specifically to an immunoglobulin protein. A glycosylation pattern of a heterologous antibody can be characterized as being substantially similar to glycosylation patterns which occur naturally on antibodies produced by the species of the nonhuman transgenic animal, when one of ordinary skill in the art would recognize the glycosylation pattern of the heterologous antibody as being more similar to said pattern of glycosylation in the species of the nonhuman transgenic animal than to the species from which the CH genes of the transgene were derived. As used herein, the term “hematological cancer” includes a lymphoma, leukemia, myeloma or a lymphoid malignancy, as well as a cancer of the spleen and lymph nodes. Exemplary lymphomas include both B cell lymphomas (a B-cell hematological cancer) and T cell lymphomas. B-cell lymphomas include both Hodgkin's lymphomas and most non-Hodgkin's lymphomas. Non- limiting examples of B cell lymphomas include diffuse large B-cell lymphoma, follicular lymphoma, mucosa-associated lymphatic tissue lymphoma, small cell lymphocytic lymphoma (overlaps with chronic lymphocytic leukemia), mantle cell lymphoma (MCL), Burkitt's lymphoma, mediastinal large B cell lymphoma, Waldenstrom macroglobulinemia, nodal marginal zone B cell lymphoma, splenic marginal zone lymphoma, intravascular large B-cell lymphoma, primary effusion lymphoma, lymphomatoid granulomatosis. Non-limiting examples of T cell lymphomas include extranodal T cell lymphoma, cutaneous T cell lymphomas, anaplastic large cell lymphoma, and angioimmunoblastic T cell lymphoma. Hematological malignancies also include leukemia, such as, but not limited to, secondary lenkemia, chronic lymphocytic leukemia, acute myelogenous leukemia, chronic myelogenous leukemia, and acute lymphoblastic leukemia. Hematological malignancies further include myelomas, such as, but not limited to, multiple myeloma and smoldering multiple myeloma. Other hematological and / or B cell- or T-cell- associated cancers are encompassed by the term hematological malignancy. As used herein, the term “human antibody” includes antibodies having variable and constant regions (if present) of human germline immunoglobulin sequences. Human antibodies of the disclosure can include amino acid residues not encoded by human germline immunoglobulin sequences (e.g., mutations introduced by random or site-specific mutagenesis in vitro or by somatic mutation in vivo) (See, e.g., Lonberg et al., (1994) Nature 368(6474): 856-859); Lonberg, (1994) Handbook of Experimental Pharmacology 113:49-101; Lonberg & Huszar, (1995) Intern. Rev. Immunol. 13:65-93, and Harding & Lonberg, (1995) Ann. N.Y. Acad. Sci. 764:536-546). However, the term “human antibody” does not include antibodies in which CDR sequences derived from the germline of another mammalian species, such as a mouse, have been grafted onto human framework sequences (i.e. humanized antibodies). As used herein, the term “heterologous antibody” is defined in relation to the transgenic non-human organism producing such an antibody. This term refers to an antibody having an amino acid sequence or an encoding nucleic acid sequence corresponding to that found in an organism not consisting of the transgenic non-human animal, and generally from a species other than that of the transgenic non-human animal. The terms “inducing an immune response” and “enhancing an immune response” are used interchangeably and refer to the stimulation of an immune response (i.e., either passive or adaptive) to a particular antigen. The term “induce” as used with respect to inducing CDC or ADCC refer to the stimulation of particular direct cell killing mechanisms. As used herein, a subject “in need of prevention,” “in need of treatment,” or “in need thereof,” refers to one, who by the judgment of an appropriate medical practitioner (e.g., a doctor, a nurse, or a nurse practitioner in the case of humans; a veterinarian in the case of non-human mammals), would reasonably benefit from a given treatment (such as treatment with a composition comprising an anti-CD137 antibody). The term "in vivo" refers to processes that occur in a living organism. As used herein, the term “isolated antibody” is intended to refer to an antibody which is substantially free of other antibodies having different antigenic specificities (e.g., an isolated antibody that specifically binds to human CD137 is substantially free of antibodies that specifically bind antigens other than CD137). An isolated antibody that specifically binds to an epitope may, however, have cross-reactivity to other CD137 proteins from different species. However, the antibody continues to display specific binding to human CD137 in a specific binding assay as described herein. In addition, an isolated antibody is typically substantially free of other cellular material and / or chemicals. In some embodiments, a combination of “isolated” antibodies having different CD137 specificities is combined in a well-defined composition. As used herein, the term “isolated nucleic acid molecule” refers to nucleic acids encoding antibodies or antibody portions (e.g., Vu, Vi, CDR3) that bind to CD137, is intended to refer to a nucleic acid molecule in which the nucleotide sequences encoding the antibody or antibody portion are free of other nucleotide sequences encoding antibodies or antibody portions that bind antigens other than CD137, which other sequences may naturally flank the nucleic acid in human genomic DNA. For example, a sequence selected from a sequence set forth in any one of Tables 22- 27corresponds to the nucleotide sequences comprising the heavy chain (Vu) and light chain (VL) variable regions of anti-CD137 antibody monoclonal antibodies described herein. As used herein, “isotype” refers to the antibody class (e.g., IgM or IgGl) that is encoded by heavy chain constant region genes. In some embodiments, a human monoclonal antibody of the disclosure is of the IgGl isotype. In some embodiments, a human monoclonal antibody of the disclosure is of the IgGl isotype and comprises a mutation. In some embodiments, a human monoclonal antibody of the disclosure is of the IgG2 isotype. In some embodiments, a human monoclonal antibody of the disclosure is of the IgG3 isotype. In some embodiments, a human monoclonal antibody of the disclosure is of the IgG4 isotype. In some embodiments, a human monoclonal antibody of the disclosure is of the IgG4 isotype and comprises a mutation. In some embodiments, the mutation is a substitution at Ser228. In some embodiments, the substitution at Ser228 is S228P. As used herein, the term “isotype switching” refers to the phenomenon by which the class, or isotype, of an antibody changes from one Ig class to one of the other Ig classes. As used herein the term “KD” or “Kp” refers to the equilibrium dissociation constant of a binding reaction between an antibody and an antigen. The value of Kp is a numeric representation of the ratio of the antibody off-rate constant (kd) to the antibody on-rate constant (ka). The value of Kp is inversely related to the binding affinity of an antibody to an antigen. The smaller the Kp value the greater the affinity of the antibody for its antigen. Affinity is the strength of binding of a single molecule to its ligand and is typically measured and reported by the equilibrium dissociation constant (Kp), which is used to evaluate and rank order strengths of bimolecular interactions. As used herein, the term “kd” or “kq” (alternatively “koff” or “kot”) is intended to refer to the off-rate constant for the dissociation of an antibody from an antibody / antigen complex. The value of kd is a numeric representation of the fraction of complexes that decay or dissociate per second, and is expressed in units secl. As used herein, the term “ka” or “k.” (alternatively “kon” or “kon”) is intended to refer to the on-rate constant for the association of an antibody with an antigen. The value of ka is a numeric representation of the number of antibody / antigen complexes formed per second in a 1 molar (IM) solution of antibody and antigen, and is expressed in units Msec™’. As used herein, the terms "linked," "fused", or "fusion", are used interchangeably. These terms refer to the joining together of two more elements or components or domains, by whatever means including chemical conjugation or recombinant means. Methods of chemical conjugation (e.g., using heterobifunctional crosslinking agents) are known in the art. As used herein, “local administration” or “local delivery,” refers to delivery that does not rely upon transport of the composition or agent to its intended target tissue or site via the vascular system. For example, the composition may be delivered by injection or implantation of the composition or agent or by injection or implantation of a device containing the composition or agent. Following local administration in the vicinity of a target tissue or site, the composition or agent, or one or more components thereof, may diffuse to the intended target tissue or site. As used herein, “MHC molecules” refers to two types of molecules, MHC class I and MHC class II. MHC class I molecules present antigen to specific CD8+ T cells and MHC class II molecules present antigen to specific CD4+ T cells. Antigens delivered exogenously to APCs are processed primarily for association with MHC class II. In contrast, antigens delivered endogenously to APCs are processed primarily for association with MHC class I. As used herein, the term “monoclonal antibody” refers to an antibody which displays a single binding specificity and affinity for a particular epitope. Accordingly, the term “human monoclonal antibody” refers to an antibody which displays a single binding specificity and which has variable and optional constant regions derived from human germline immunoglobulin sequences. In some embodiments, human monoclonal antibodies are produced by a hybridoma which includes a B cell obtained from a transgenic non-human animal, e.g., a transgenic mouse, having a genome comprising a human heavy chain transgene and a light chain transgene fused to an immortalized cell. As used herein, the term “multimerization” refers to the formation of a macromolecular complex comprising more than two macromolecules such as proteins, typically bound by non- covalent interactions. Methods for determining multimerization are known to those of skill in the art and are described supra for dimerization. In some embodiments, the anti-CD137 agonist antibodies described herein induce or enhance multimerization of CD137. In some embodiments, the anti-CD137 agonist antibodies described herein induce or enhance multimerization of CD137 relative to the amount of multimerization in the absence of an anti-CD137 agonist antibody. In some embodiments, the anti-CD137 agonist antibodies described herein induce or enhance multimerization of CD137 relative to the amount of multimerization in the presence of a reference anti-CD137 agonist antibody. In some embodiments, multimerization is increased by at least 5%, 10%, 15%, 20%, 25%, 30%. 35%, 40%, 45%, 50%, 55%, 60%, 65%, 10%, 15%, 80%, 85%, 90%, 95%, or 100%. As used herein, the term “naturally-occurring” as applied to an object refers to the fact that an object can be found in nature. For example, a polypeptide or polynucleotide sequence that is present in an organism (including viruses) that can be isolated from a source in nature and which has not been intentionally modified by man in the laboratory is naturally-occurring. As used herein, the term “nonswitched isotype” refers to the isotypic class of heavy chain that is produced when no isotype switching has taken place; the CH gene encoding the nonswitched isotype is typically the first CH gene immediately downstream from the functionally rearranged VDJ gene. Isotype switching has been classified as classical or non-classical isotype switching. Classical isotype switching occurs by recombination events which involve at least one switch sequence region in the transgene. Non-classical isotype switching may occur by, for example, homologous recombination between human 6, and human ¥ (8-associated deletion). Alternative non-classical switching mechanisms, such as intertransgene and / or interchromosomal recombination, among others, may occur and effectuate isotype switching. As used herein, the term "nucleic acid" refers to deoxyribonucleotides or ribonucleotides and polymers thereof in either single- or double- stranded form. Unless specifically limited, the term encompasses nucleic acids containing known analogues of natural nucleotides that have similar binding properties as the reference nucleic acid and are metabolized in a manner similar to naturally occurring nucleotides. Unless otherwise indicated, a particular nucleic acid sequence also implicitly encompasses conservatively modified variants thereof (e.g., degenerate codon substitutions) and complementary sequences and as well as the sequence explicitly indicated. Specifically, degenerate codon substitutions can be achieved by generating sequences in which the third position of one or more selected (or all) codons is substituted with mixed-base and / or deoxyinosine residues (Batzer et al., Nucleic Acid Res. 19:5081, 1991; Ohtsuka et al., Biol. Chem. 260:2605-2608, 1985; and Cassol et al, 1992; Rossolini et al, Mol. Cell. Probes 8:91-98, 1994). For arginine and leucine, modifications at the second base can also be conservative. The term nucleic acid is used interchangeably with gene, cDNA, and mRNA encoded by a gene. Polynucleotides used herein can be composed of any polyribonucleotide or polydeoxribonucleotide, which can be unmodified RNA or DNA or modified RNA or DNA. For example, polynucleotides can be composed of single- and double-stranded DNA, DNA that is a mixture of single- and double- stranded regions, single- and double- stranded RNA, and RNA that is mixture of single- and double- stranded regions, hybrid molecules comprising DNA and RNA that can be single- stranded or, more typically, double-stranded or a mixture of single- and double- stranded regions. In addition, the polynucleotide can be composed of triple-stranded regions comprising RNA or DNA or both RNA and DNA. A polynucleotide can also contain one or more modified bases or DNA or RNA backbones modified for stability or for other reasons. "Modified" bases include, for example, tritylated bases and unusual bases such as inosine. A variety of modifications can be made to DNA and RNA; thus, "polynucleotide" embraces chemically, enzymatically, or metabolically modified forms. A nucleic acid is “operably linked” when it is placed into a functional relationship with another nucleic acid sequence. For instance, a promoter or enhancer is operably linked to a coding sequence if it affects the transcription of the sequence. With respect to transcription regulatory sequences, operably linked means that the DNA sequences being linked are contiguous and, where necessary to join two protein coding regions, contiguous and in reading frame. For switch sequences, operably linked indicates that the sequences are capable of effecting switch recombination. As used herein, the term “paratope”, also “antigen-binding site” refers to a portion of an antibody, or antigen-binding fragment thereof, which recognizes and binds to an epitope on an antigen, comprising the set of complementarity determining regions (CDRs) located within variable heavy and light chains. As used herein, “parenteral administration,” “administered parenterally,” and other grammatically equivalent phrases, refer to modes of administration other than enteral and topical administration, usually by injection, and include, without limitation, intravenous, intranasal, intraocular, intramuscular, intraarterial, intrathecal, intracapsular, intraorbital, intracardiac, intradermal, intraperitoneal, transtracheal, subcutaneous, subcuticular, intraarticular, subcapsular, subarachnoid, intraspinal, epidural, intracerebral, intracranial, intracarotid and intrasternal injection and infusion. As used herein, the term “patient” includes human and other mammalian subjects that receive either prophylactic or therapeutic treatment. The term "percent identity," in the context of two or more nucleic acid or polypeptide sequences, refer to two or more sequences or subsequences that have a specified percentage of nucleotides or amino acid residues that are the same, when compared and aligned for maximum correspondence, as measured using one of the sequence comparison algorithms described below (e.g., BLASTP and BLASTN or other algorithms available to persons of skill) or by visual inspection. Depending on the application, the "percent identity" can exist over a region of the sequence being compared, e.g., over a functional domain, or, alternatively, exist over the full length of the two sequences to be compared. For sequence comparison, typically one sequence acts as a reference sequence to which test sequences are compared. When using a sequence comparison algorithm, test and reference sequences are input into a computer, subsequence coordinates are designated, if necessary, and sequence algorithm program parameters are designated. The sequence comparison algorithm then calculates the percent sequence identity for the test sequence(s) relative to the reference sequence, based on the designated program parameters. Optimal alignment of sequences for comparison can be conducted, e.g., by the local homology algorithm of Smith & Waterman, Adv. Appl. Math. 2:482 (1981), by the homology alignment algorithm of Needleman & Wunsch, J. Mol. Biol. 48:443 (1970), by the search for similarity method of Pearson & Lipman, Proc. Natl. Acad. Sci. USA 85:2444 (1988), by computerized implementations of these algorithms (GAP, BESTFIT, FASTA, and TFASTA in the Wisconsin Genetics Software Package, Genetics Computer Group, 575 Science Dr., Madison, ‘Wis.), or by visual inspection (see generally Ausubel et al., infra). One example of an algorithm that is suitable for determining percent sequence identity and sequence similarity is the BLAST algorithm, which is described in Altschul et al., J. Mol. Biol. 215:403-410 (1990). Software for performing BLAST analyses is publicly available through the National Center for Biotechnology Information website. As generally used herein, “pharmaceutically acceptable” refers to those compounds, materials, compositions, and / or dosage forms which are, within the scope of sound medical judgment, suitable for use in contact with the tissues, organs, and / or bodily fluids of human beings and animals without excessive toxicity, irritation, allergic response, or other problems or complications commensurate with a reasonable benefit / risk ratio. As used herein, a “pharmaceutically acceptable carrier” refers to, and includes, any and all solvents, dispersion media, coatings, antibacterial and antifungal agents, isotonic and absorption delaying agents, and the like that are physiologically compatible. The compositions can include a pharmaceutically acceptable salt, e.g., an acid addition salt or a base addition salt (see, e.g., Berge et al. (1977) J Pharm Sci 66:1-19). As used herein, the terms "polypeptide," "peptide", and "protein" are used interchangeably to refer to a polymer of amino acid residues. The terms apply to amino acid polymers in which one or more amino acid residue is an artificial chemical mimetic of a corresponding naturally occurring amino acid, as well as to naturally occurring amino acid polymers and non-naturally occurring amino acid polymer. As used herein, the term “preventing” when used in relation to a condition, refers to administration of a composition which reduces the frequency of, or delays the onset of, symptoms of a medical condition in a subject relative to a subject which does not receive the composition. As used herein, the term “purified” or “isolated” as applied to any of the proteins (antibodies or fragments) described herein refers to a polypeptide that has been separated or purified from components (e.g., proteins or other naturally-occurring biological or organic molecules) which naturally accompany it, e.g., other proteins, lipids, and nucleic acid in a prokaryote expressing the proteins. Typically, a polypeptide is purified when it constitutes at least 60 (e.g., at least 65, 70, 75, 80, 85, 90, 92, 95, 97, or 99) %, by weight, of the total protein in a sample. As used herein, the term “rearranged” refers to a configuration of a heavy chain or light chain immunoglobulin locus wherein a V segment is positioned immediately adjacent to a D-J or J segment in a conformation encoding essentially a complete Vy or VL domain, respectively. A rearranged immunoglobulin gene locus can be identified by comparison to germline DNA; a rearranged locus will have at least one recombined heptamer / nonamer homology element. As used herein, the term “receptor clustering” refers to a cellular process that results in grouping or local accumulation of a set of receptors at a particular cellular location, often to induce or amplify a signaling response. Many protein receptors bind cognate ligands and cluster, i.e., form dimers, trimers, oligomers or multimers, upon binding their cognate ligands. For example, the PDGF receptor and TNF receptor superfamily members form dimers and trimers upon ligand binding, respectively. Cognate ligand-induced clustering (e.g., dimerization, multimerization) induces signal transduction through the receptor. Accordingly, the antibodies, or antigen-binding fragments thereof, of the present disclosure can activate a receptor by binding to more than one receptor and induce or stabilize dimerization, trimerization, and / or multimerization with or without cognate ligand binding. Receptor clustering and multimerization is needed for TNFR signaling (Wajant (2015) Cell Death Differ 22(11):1727-1741), and in particular for TNFRSF activation. 4-1BB (CD137), CD40, GITR, CD27, DR3, DRS, and Fas are some of the TNFESF receptors known to require clustering in order to trigger downstream signaling. Experimental evidence that the 4-1BB receptor must be cross-linked to signal comes from Rabu et al. These authors reported that a 1-trimer form of human 4-1BBL had no activating effects on human T cells whereas cross-linking the protein into 2- or more trimers led to a strongly activating protein (Rabu et al., (2005) J Biol Chem 280:41472- 41481). Accordingly, in some embodiments, an anti-CD137 agonist antibody induces the multimerization of 2 or more trimers of CD137. As used herein, the term “recombinant host cell” (or simply “host cell”) is intended to refer to a cell into which a recombinant expression vector has been introduced. It should be understood that such terms are intended to refer not only to the particular subject cell but to the progeny of such a cell. Because certain modifications may occur in succeeding generations due to either mutation or environmental influences, such progeny may not, in fact, be identical to the parent cell, but are still included within the scope of the term “host cell” as used herein. As used herein, the term “recombinant human antibody” includes all human antibodies that are prepared, expressed, created or isolated by recombinant means, such as (a) antibodies isolated from an animal (e.g., a mouse) that is transgenic or transchromosomal for human immunoglobulin genes or a hybridoma prepared therefrom, (b) antibodies isolated from a host cell transformed to express the antibody, e.g., from a transfectoma, (¢) antibodies isolated from a recombinant, combinatorial human antibody library, and (d) antibodies prepared, expressed, created or isolated by any other means that involve splicing of human immunoglobulin gene sequences to other DNA sequences. Such recombinant human antibodies comprise variable and constant regions that utilize particular human germline immunoglobulin sequences are encoded by the germline genes, but include subsequent rearrangements and mutations which occur, for example, during antibody maturation. As known in the art (see, e.g., Lonberg (2005) Nature Biotech. 23(9):1117-1125), the variable region contains the antigen binding domain, which is encoded by various genes that rearrange to form an antibody specific for a foreign antigen. In addition to rearrangement, the variable region can be further modified by multiple single amino acid changes (referred to as somatic mutation or hypermutation) to increase the affinity of the antibody to the foreign antigen. The constant region will change in further response to an antigen (i.e., isotype switch). Therefore, the rearranged and somatically mutated nucleic acid molecules that encode the light chain and heavy chain immunoglobulin polypeptides in response to an antigen may not have sequence identity with the original nucleic acid molecules, but instead will be substantially identical or similar (i.e., have at least 80% identity). As used herein, the term “reference antibody” (used interchangeably with “reference mAb”) or “reference antigen-binding protein” refers to an antibody, or an antigen-binding fragment thereof, that binds to a specific epitope on human CD137 and is used to establish a relationship between itself and one or more distinct antibodies. In some embodiments, the relationship is the binding of the reference antibody and the one or more distinct antibodies to the same epitope on CD137. As used herein, the term connotes an anti-CD137 antibody that is useful in a test or assay, such as those described herein, (e.g., a competitive binding assay), as a competitor, wherein the assay is useful for the discovery, identification or development, of one or more distinct antibodies that bind to the same epitope. The variable heavy (Vu) and light chain (VL) amino acid sequences of an exemplary reference antibody (mAb1) are provided in Table 23 (Vul, SEQ ID NO. 4; Vu2, SEQ ID NO. 6). In some embodiments, the term connotes an anti- CD137 antibody that is useful in a test or assay, as a comparator, wherein the assay is useful for distinguishing characteristics of the antibodies (e.g., hepatotoxicity, anti-tumor efficacy). In some embodiments, the reference antibody is urelumab. In some embodiments, the reference antibody 1s utomilumab. As used herein, the terms “specific binding,” “selective binding,” “selectively binds,” and “specifically binds,” refer to antibody binding to an epitope on a predetermined antigen. Typically, the antibody binds with an equilibrium dissociation constant (Kp) of approximately less than 10 M, such as approximately less than 107, 10% M, 10° M or 101° M or even lower when determined by surface plasmon resonance (SPR) technology in a BIACORE 2000 instrument using recombinant human CD137 as the analyte and the antibody as the ligand and binds to the predetermined antigen with an affinity that is at least two-fold greater than its affinity for binding to a non-specific antigen (e.g., BSA, casein) other than the predetermined antigen or a closely- related antigen. The phrases “an antibody recognizing an antigen” and “an antibody specific for an antigen” are used interchangeably herein with the term “an antibody which binds specifically to an antigen.” As used herein, the term “switch sequence” refers to those DNA sequences responsible for switch recombination. A “switch donor” sequence, typically a pu switch region, will be §' (i.e., upstream) of the construct region to be deleted during the switch recombination. The “switch acceptor” region will be between the construct region to be deleted and the replacement constant region (e.g., ¥, €, etc.). As there is no specific site where recombination always occurs, the final gene sequence will typically not be predictable from the construct. As used herein, the term “subject” includes any human or non-human animal. For example, the methods and compositions of the present invention can be used to treat a subject with an immune disorder. The term “non-human animal” includes all vertebrates, e.g., mammals and non- mammals, such as non-human primates, sheep, dog, cow, chickens, amphibians, reptiles, etc. For nucleic acids, the term “substantial homology” indicates that two nucleic acids, or designated sequences thereof, when optimally aligned and compared, are identical, with appropriate nucleotide insertions or deletions, in at least about 80% of the nucleotides, usually at least about 90% to 95%, and more preferably at least about 98% to 99.5% of the nucleotides. Alternatively, substantial homology exists when the segments will hybridize under selective hybridization conditions, to the complement of the strand. The percent identity between two sequences is a function of the number of identical positions shared by the sequences (i.e., % homology = # of identical positions / total # of positions x 100), taking into account the number of gaps, and the length of each gap, which need to be introduced for optimal alignment of the two sequences. The comparison of sequences and determination of percent identity between two sequences can be accomplished using a mathematical algorithm, as described in the non-limiting examples below. The percent identity between two nucleotide sequences can be determined using the GAP program in the GCG software package (available at http: / / www.gcg.com), using a NWSgapdna.CMP matrix and a gap weight of 40, 50, 60, 70, or 80 and a length weight of 1, 2, 3, 4,5, or 6. The percent identity between two nucleotide or amino acid sequences can also be determined using the algorithm of E. Meyers and W. Miller (CABIOS, 4:11-17 (1989)) which has been incorporated into the ALIGN program (version 2.0), using a PAM120 weight residue table, a gap length penalty of 12 and a gap penalty of 4. In addition, the percent identity between two amino acid sequences can be determined using the Needleman and Wunsch (J. Mol. Biol. (48):444- 453 (1970)) algorithm which has been incorporated into the GAP program in the GCG software package (available at http: / / www.gcg.com), using either a Blossum 62 matrix or a PAM250 matrix, and a gap weight of 16, 14, 12, 10, 8, 6, or 4 and a length weight of 1, 2, 3, 4, 5, or 6. The nucleic acid and protein sequences of the present disclosure can further be used as a “query sequence” to perform a search against public databases to, for example, identify related sequences. Such searches can be performed using the NBLAST and XBLAST programs (version 2.0) of Altschul, er al. (1990) J. Mol. Biol. 215:403-10. BLAST nucleotide searches can be performed with the NBLAST program, score = 100, wordlength = 12 to obtain nucleotide sequences homologous to the nucleic acid molecules of the invention. BLAST protein searches can be performed with the XBLAST program, score = 50, wordlength = 3 to obtain amino acid sequences homologous to the protein molecules of the invention. To obtain gapped alignments for comparison purposes, Gapped BLAST can be utilized as described in Altschul et al., (1997) Nucleic Acids Res. 25(17):3389-3402. When utilizing BLAST and Gapped BLAST programs, the default parameters of the respective programs (e.g., XBLAST and NBLAST) can be used. See http: / / www .ncbi.nlm.nih.gov. The nucleic acids may be present in whole cells, in a cell lysate, or in a partially purified or substantially pure form. A nucleic acid is “isolated” or “rendered substantially pure” when purified away from other cellular components or other contaminants, e.g., other cellular nucleic acids or proteins, by standard techniques, including alkaline / SDS treatment, CsCl banding, column chromatography, agarose gel electrophoresis and others well known in the art. See, F. Ausubel, et al., ed. Current Protocols in Molecular Biology, Greene Publishing and Wiley Interscience, New York (1987). The nucleic acid compositions of the present disclosure, while often in a native sequence (except for modified restriction sites and the like), from either cDNA, genomic or mixtures thereof may be mutated, in accordance with standard techniques to provide gene sequences. For coding sequences, these mutations, may affect amino acid sequence as desired. In particular, DNA sequences substantially homologous to or derived from native V, D, J, constant, switches and other such sequences described herein are contemplated (where "derived" indicates that a sequence is identical or modified from another sequence). As used herein, the term “tumor microenvironment” (alternatively “cancer microenvironment”; abbreviated TME) refers to the cellular environment or milieu in which the tumor or neoplasm exists, including surrounding blood vessels as well as non-cancerous cells including, but not limited to, immune cells, fibroblasts, bone marrow-derived inflammatory cells, and lymphocytes. Signaling molecules and the extracellular matrix also comprise the TME. The tumor and the surrounding microenvironment are closely related and interact constantly. Tumors can influence the microenvironment by releasing extracellular signals, promoting tumor angiogenesis and inducing peripheral immune tolerance, while the immune cells in the microenvironment can affect the growth and evolution of tumor cells. The term “T cell” refers to a type of white blood cell that can be distinguished from other white blood cells by the presence of a T cell receptor on the cell surface. There are several subsets of T cells, including, but not limited to, T helper cells (a.k.a. Tu cells or CD4* T cells) and subtypes, including Tul, Tu2, Tu3, Tul7, Tu9, and Tru cells, cytotoxic T cells (i.e., Tc cells, CD8* T cells, cytotoxic T lymphocytes, T-killer cells, killer T cells), memory T cells and subtypes, including central memory T cells (Tcum cells), effector memory T cells (Tem and Temra cells), and resident memory T cells (Tru cells), regulatory T cells (a.k.a. Treg cells or suppressor T cells) and subtypes, including CD4* FOXP3* Trg cells, CD4*FOXP3™ Th, cells, Trl cells, Th3 cells, and Treg17 cells, natural killer T cells (a.k.a. NKT cells), mucosal associated invariant T cells (MAITs), and gamma delta T cells (v8 T cells), including Vy9 / V82 T cells. Any one or more of the aforementioned or unmentioned T cells may be the target cell type for a method of use of the invention. As used herein, the term “T cell activation” or “activation of T cells” refers to a cellular process in which mature T cells, which express antigen-specific T cell receptors on their surfaces, recognize their cognate antigens and respond by entering the cell cycle, secreting cytokines or lytic enzymes, and initiating or becoming competent to perform cell-based effector functions. T cell activation requires at least two signals to become fully activated. The first occurs after engagement of the T cell antigen-specific receptor (TCR) by the antigen-major histocompatibility complex (MHC), and the second by subsequent engagement of co-stimulatory molecules (e.g., CD28). These signals are transmitted to the nucleus and result in clonal expansion of T cells, upregulation of activation markers on the cell surface, differentiation into effector cells, induction of cytotoxicity or cytokine secretion, induction of apoptosis, or a combination thereof. As used herein, the term “T cell-mediated response” refers to any response mediated by T cells, including, but not limited to, effector T cells (e.g., CD8* cells) and helper T cells (e.g., CD4* cells). T cell mediated responses include, for example, T cell cytotoxicity and proliferation. As used herein, the terms “therapeutically effective amount” or “therapeutically effective dose,” or similar terms used herein are intended to mean an amount of an agent (e.g., an anti- CD137 antibody or an antigen-binding fragment thereof) that will elicit the desired biological or medical response (e.g., an improvement in one or more symptoms of a cancer). The terms “treat,” “treating,” and “treatment,” as used herein, refer to therapeutic or preventative measures described herein. The methods of “treatment” employ administration to a subject, in need of such treatment, a human antibody of the present disclosure, for example, a subject in need of an enhanced immune response against a particular antigen or a subject who ultimately may acquire such a disorder, in order to prevent, cure, delay, reduce the severity of, or ameliorate one or more symptoms of the disorder or recurring disorder, or in order to prolong the survival of a subject beyond that expected in the absence of such treatment. As used herein, the term “unrearranged” or “germline configuration” refers to the configuration wherein the V segment is not recombined so as to be immediately adjacent to a D or J segment. As used herein, the term “vector” is intended to refer to a nucleic acid molecule capable of transporting another nucleic acid to which it has been linked. One type of vector is a “plasmid,” which refers to a circular double stranded DNA loop into which additional DNA segments may be ligated. Another type of vector is a viral vector, wherein additional DNA segments may be ligated into the viral genome. Certain vectors are capable of autonomous replication in a host cell into which they are introduced (e.g., bacterial vectors having a bacterial origin of replication and episomal mammalian vectors). Other vectors (e.g., non-episomal mammalian vectors) can be integrated into the genome of a host cell upon introduction into the host cell, and thereby are replicated along with the host genome. Moreover, certain vectors are capable of directing the expression of genes to which they are operatively linked. Such vectors are referred to herein as “recombinant expression vectors” (or simply, “expression vectors”). In general, expression vectors of utility in recombinant DNA techniques are often in the form of plasmids. In the present specification, “plasmid” and “vector” may be used interchangeably as the plasmid is the most commonly used form of vector. However, the invention is intended to include such other forms of expression vectors, such as viral vectors (e.g., replication defective retroviruses, adenoviruses and adeno-associated viruses), which serve equivalent functions. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. Preferred methods and materials are described below, although methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the presently disclosed methods and compositions. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. Anti-CD137 Formulations The disclosure provides formulations comprising an antibody or antigen binding fragments thereof that bind to human CD137 [hereinafter an “anti-CD137 antibody” or an “anti- human CD137 antibody”]. The anti-CD137 antibody formulations of the disclosure maintain the antibody, or antigen binding fragment thereof, under stable conditions, minimize the formation of antibody aggregates (high molecular weight species) and particulates, reduce the percentage of charge variants, and maintain the structural integrity of the antibody. In one aspect, the disclosure provides, at least in part, various formulations of an anti- CD137 antibody, or antigen binding fragment thereof. In some embodiments, the formulations of the disclosure comprising anti-CD137, or an antigen binding fragment thereof, also include: (i) a buffer (e.g., histidine), (ii) a disaccharide sugar (e.g., sucrose), (iii) a non-ionic surfactant (e.g., polysorbate 80), and / or (iv) a salt (e.g., NaCl). In some embodiments, the formulations of the disclosure have a pH of about 5.0 to about 7.0. In some embodiments, the formulations of the disclosure have a pH of about 5.0 to about 7.4. In some embodiments, the pH of the formulation is about 5.0 to about 8.0. In some embodiments, the formulations of the disclosure further contain one or more solubilizers, diluents, binders, stabilizers, salts, lipophilic solvents, amino acids, chelators, or preservatives. (i) Buffering Agents In some embodiments, buffering agents are included in antibody formulations to improve stability and / or control the pH of the formulation. As exemplified in the working examples described herein, the anti-CD137 antibody was stable at high concentrations and under forced degradation conditions when formulated in histidine buffer. In some embodiments, buffering agents useful in the formulations described herein include, e.g., salts of citric acid, ascorbic acid, gluconic acid, carbonic acid, tartaric acid, succinic acid, acetic acid, or phthalic acid. In some embodiments, the buffer is a Tris-based or phosphate buffer. In some embodiments, the formulations described herein include one or more amino acids, which can, among other things, provide buffering capacity. Suitable amino acids for use in the formulations of the disclosure include, e.g., histidine, glycine, and serine. In some embodiments, the formulations of the disclosure do not include a free amino acid as a buffering agent. In some embodiments, the formulations of the disclosure include one free amino acid (e.g., histidine) as a buffering agent. In some embodiments, the formulations of the disclosure include two or more (e.g., two, three, four, five, six, or seven or more) different amino acids as buffering agents, e.g., serine and histidine. The buffering agents are generally used at concentrations between approximately 10 mM and 100 mM, depending, in part, on the buffering capacity required. In some embodiments, a formulation described herein includes a buffering agent at a concentration of less than, or approximately, 100 (e.g., less than, or approximately, 90, 80, 70, 60, 50, 40, 30, 25, 20, 15, or 10) mM. In some embodiments, a formulation described herein contains a buffering agent at a concentration of at least 10 (e.g., at least 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100 or more) mM. In some embodiments, a formulation described herein includes a buffering agent at a concentration of between about 10 mM to 20 mM, 15 mM to 20 mM, 10 mM to 25 mM, 15 mM to 25 mM, 20 mM to 25 mM, 10 mM to 30 mM, 15 mM to 30 mM, 20 mM to 30 mM, 25 mM to 30 mM, 10 mM to 40 mM, 15 mM to 40 mM, 20 mM to 40 mM, 25 mM to 40 mM, 30 mM to 40 mM, 10 mM to 50 mM, 15 mM to 50 mM, 20 mM to 50 mM, 25 mM to 50 mM, 30 mM to 50 mM, 40 mM to 50 mM, 10 mM to 100 mM, 15 mM to 100 mM, 20 mM to 100 mM, 25 mM to 100 mM, 30 mM to 100 mM, 40 mM to 100 mM, or 50 to 100 mM. It is understood that in embodiments where a formulation of the disclosure contains two or more (e.g., at least two, three, four, five, six, seven, eight, nine, or 10 or more) different buffering agents, each of the two or more buffering agents can independently be present at, e.g., one of the above described concentrations. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 10-100 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 15-100 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 20-100 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 25-100 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine concentration of about 30-100 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 40-100 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 50-100 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 10-50 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 15-50 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 20-50 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 25-50 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 30-50 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 40-50 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 10-40 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 15-40 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 20-40 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 25-40 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 30-40 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 10-30 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 15-30 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 20-30 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 25-30 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 10-25 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 15-25 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 20-25 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 10-20 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 15-20 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 10 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 11 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 12 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 13 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 14 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 15 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 16 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 17 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 18 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 19 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 20 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 21 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 22 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 23 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 24 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 25 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 26 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 27 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 28 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 29 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 30 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 35 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 40 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 45 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 50 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 55 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 60 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 65 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 70 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 75 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 80 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 85 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 90 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 95 mM. In some embodiments, the formulation of the disclosure includes a buffer comprising histidine at a concentration of about 100 mM. (ii) Carbohydrate Excipients In some embodiments, carbohydrate excipients are added to antibody formulations of the disclosure to improve stability. As provided in the working examples, it was discovered that the addition of sucrose to the anti-CD137 formulations of the disclosure resulted in improved stability at elevated temperatures. In some embodiments, any of the formulations described herein contain a carbohydrate excipient. Suitable carbohydrate excipients are described in, e.g., Katakam and Banga (1995) J Pharm Pharmacol 47(2):103-107; Andya et al. (2003) AAPS PharmSci 5(2): Article 10; and Shire (2009) “Current Trends in Monoclonal Antibody Development and Manufacturing,” Volume 11, Springer, 354 pages. Carbohydrate excipients suitable for use in the formulations described herein include, without limitation, monosaccharides such as fructose, maltose, galactose, glucose, D-mannose, and sorbose; disaccharides such as lactose, sucrose, trehalose, and cellobiose; polysaccharides such as maltodextrins, dextrans, and starches; and sugar alcohols such as mannitol, xylitol, maltitol, lactitol, and sorbitol. In some embodiments, the carbohydrate excipient is a disaccharide or disaccharide sugar. In some embodiments, the disaccharide sugar is sucrose. In some embodiments, a carbohydrate excipient is present in a formulation of the disclosure at a concentration of at least, or approximately, 5 (e.g., at least, or approximately, 5.0, 5.5,6.0,6.5,7.0,75,8.0,85,9.0,9.5,10.0, 10.5, 11.0, 11.5, 12.0, 12.5, 13.0, 13.5, 14.0, 14.5, 15.0 or more) % weight / volume (w / v). In embodiments where a formulation of the disclosure contains two or more (e.g., at least two, three, four, five, six, seven, eight, nine, or 10 or more) different carbohydrate excipients (e.g., sorbitol and mannitol), each excipient can, independently, be present at any of the above-described concentrations. In some embodiments of the disclosure, the carbohydrate excipient is present in an amount of from about 5-15% (w / v) (5, 6,7, 8,9, 10, 11, 12, 13, 14, or 15%). In some embodiments, the carbohydrate excipient is present in an amount from about 6% to about 15% (w / v). In some embodiments, the carbohydrate excipient is present in an amount from about 8% to about 15% (w / v). In some embodiments, the carbohydrate excipient is present in an amount from about 10% to about 15% (w / v). In some embodiments, the carbohydrate excipient is present in an amount from about 12% to about 15% (w / v). In some embodiments, the carbohydrate excipient is present in an amount from about 14% to about 15% (w / v). In some embodiments, the carbohydrate excipient is present in an amount from about 5% to about 12% (w / v). In some embodiments, the carbohydrate excipient is present in an amount from about 6% to about 12% (w / v). In some embodiments, the carbohydrate excipient is present in an amount from about 8% to about 12% (w / v). In some embodiments, the carbohydrate excipient is present in an amount from about 10% to about 12% (w / v). In some embodiments, the carbohydrate excipient is present in an amount from about 5% to about 10% (w / v). In some embodiments, the carbohydrate excipient is present in an amount from about 6% to about 10% (w / v). In some embodiments, the carbohydrate excipient is present in an amount from about 8% to about 10% (w / v). In some embodiments, the carbohydrate excipient is a disaccharide sugar. In some embodiments, the carbohydrate excipient is sucrose. In some embodiments, the carbohydrate excipient is present in an amount of about 5% (w / v). In some embodiments, the carbohydrate excipient is present in an amount of about 6% (w / v). In some embodiments, the carbohydrate excipient is present in an amount of about 7% (w / v). In some embodiments, the carbohydrate excipient is present in an amount of about 8% (w / v). In some embodiments, the carbohydrate excipient is present in an amount of about 9% (w / v). In some embodiments, the carbohydrate excipient is present in an amount of about 10% (w / v). In some embodiments, the carbohydrate excipient is present in an amount of about 11% (w / v). In some embodiments, the carbohydrate excipient is present in an amount of about 12% (w / v). In some embodiments, the carbohydrate excipient is present in an amount of about 13% (w / v). In some embodiments, the carbohydrate excipient is present in an amount of about 14% (w / v). In some embodiments, the carbohydrate excipient is present in an amount of about 15% (w / v). In some embodiments, the carbohydrate excipient is a disaccharide sugar. In some embodiments, the carbohydrate excipient is sucrose. In some embodiments, the carbohydrate excipient is trehalose. In some embodiments, the formulation of the disclosure includes a disaccharide sugar. In some embodiments, the formulation of the disclosure includes sucrose. In some embodiments, the carbohydrate excipient is trehalose. In some embodiments, the formulations of the disclosure include sucrose in an amount from about 5% to about 15% (w / v). In some embodiments, the formulations of the disclosure include sucrose in an amount from about 6% to about 15% (w / v). In some embodiments, the formulations of the disclosure include sucrose in an amount from about 8% to about 15% (w / v). In some embodiments, the formulations of the disclosure include sucrose in an amount from about 10% to about 15% (w / v). In some embodiments, the formulations of the disclosure include sucrose in an amount from about 12% to about 15% (w / v). In some embodiments, the formulations of the disclosure include sucrose in an amount from about 14% to about 15% (w / v). In some embodiments, the formulations of the disclosure include sucrose in an amount from about 5% to about 12% (w / v). In some embodiments, the formulations of the disclosure include sucrose in an amount from about 6% to about 12% (w / v). In some embodiments, the formulations of the disclosure include sucrose in an amount from about 8% to about 12% (w / v). In some embodiments, the formulations of the disclosure include sucrose in an amount from about 10% to about 12% (w / v). In some embodiments, the formulations of the disclosure include sucrose in an amount from about 5% to about 10% (w / v). In some embodiments, the formulations of the disclosure include sucrose in an amount from about 6% to about 10% (w / v). In some embodiments, the formulations of the disclosure include sucrose in an amount from about 8% to about 10% (w / v). In some embodiments, the formulations of the disclosure include sucrose at about 5% (w / v). In some embodiments, the formulations of the disclosure include sucrose at about 6% (w / v). In some embodiments, the formulations of the disclosure include sucrose at about 7% (w / v). In some embodiments, the formulations of the disclosure include sucrose at about 8% (w / v). In some embodiments, the formulations of the disclosure include sucrose at about 9% (w / v). In some embodiments, the formulations of the disclosure include sucrose at about 10% (w / v). In some embodiments, the formulations of the disclosure include sucrose at about 11% (w / v). In some embodiments, the formulations of the disclosure include sucrose at about 12% (w / v). In some embodiments, the formulations of the disclosure include sucrose at about 13% (w / v). In some embodiments, the formulations of the disclosure include sucrose at about 14% (w / v). In some embodiments, the formulations of the disclosure include sucrose at about 15% (wiv). (iii) Surfactants In some embodiments, the antibody formulations of the disclosure comprise a surfactant. As used herein, a surfactant is a surface active agent that is amphipathic in nature. In some embodiments, surfactants are added to the formulations herein to provide stability, reduce and / or prevent aggregation or to prevent and / or inhibit protein damage during processing conditions such as purification, filtration, freeze-drying, transportation, storage, and delivery. In some embodiments of the present disclosure, a surfactant is useful for providing stability to the active ingredient(s). In some embodiments, the formulations of the disclosure contain a surfactant such as an anionic, cationic, or non-ionic surfactant. In some embodiments, the surfactant is polyoxyethylene sorbitan fatty acid esters (Polysorbates, sold under the trade name TWEEN®) including Polysorbate-20 (polyoxyethylene sorbitan monolaurate), Polysorbate-40 (polyoxyethylene sorbitan monopalmitate), Polysorbate-60 (polyoxyethylene sorbitan monostearate), and Polysorbate-80 (polyoxyethylene sorbitan monooleate); polyoxyethylene alkyl ethers such as BRIJ® 58 and BRIJ® 35; poloxamers (e.g., poloxamer 188); TRITON® X- 100 and TRITON® X-114; NP40; Span 20, Span 40, Span 60, Span 65, Span 80 and Span 85; copolymers of ethylene and propylene glycol (e.g., the PLURONIC® series of nonionic surfactants such as PLURONIC® F68, PLURONIC® 10RS, PLURONIC® F108, PLURONIC® F127, PLURONIC® F38, PLURONIC® L44, PLURONIC® L62; and sodium dodecyl sulfate (SDS). In some embodiments, the surfactant is a non-ionic surfactant. In some embodiments, the surfactant is a polysorbate. In some embodiments, the surfactant is polysorbate 80. The amount of surfactant to be included in the formulations of the invention is an amount sufficient to perform the desired function, i.e. a minimal amount necessary to stabilize the active pharmaceutical ingredient (i.e., the anti-CD137 antibody or antigen binding fragment thereof) in the formulation. All percentages for the surfactant are listed as w / v %. In some embodiments, the formulations described herein contain a surfactant (e.g., any of the pharmaceutically-acceptable surfactants described herein or known in the art) at a concentration of at least, or approximately, 0.01 (e.g., at least, or approximately, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, or more) w / v %. In some embodiments, formulation of the disclosure contains no more than 0.1 (e.g., no more than 0.09, 0.08, 0.07, 0.06, 0.05, 0.04, 0.03, 0.02, or 0.01) w / v % of a pharmaceutically-acceptable surfactant. In some embodiments, the formulation of the disclosure includes a surfactant at a concentration of from about 0.01% to about 0.1% w / v. In some embodiments, the formulation of the disclosure includes a surfactant in an amount from about 0.01% to about 0.09% w / v; from about 0.01% to about 0.08% w / v; from about 0.01% to about 0.07% w / v; from about 0.01% to about 0.06% w / v; from about 0.01% to about 0.05% w / v; from about 0.01% to about 0.04% w / v; from about 0.01% to about 0.03% w / v, or from about 0.01% to about 0.02% w / v. In some embodiments, the formulation of the disclosure includes a surfactant in an amount of about 0.01% w / v. In some embodiments, the formulation of the disclosure includes a surfactant in an amount of about 0.02% w / v. In some embodiments, the formulation of the disclosure includes a surfactant in an amount of about 0.025% w / v. In some embodiments, the formulation of the disclosure includes a surfactant in an amount of about 0.03% w / v. In some embodiments, the formulation of the disclosure includes a surfactant in an amount of about 0.035% w / v. In some embodiments, the formulation of the disclosure includes a surfactant in an amount of about 0.04% w / v. In some embodiments, the formulation of the disclosure includes a surfactant in an amount of about 0.05% w / v. In some embodiments, the formulation of the disclosure includes a surfactant in an amount of about 0.06% w / v. In some embodiments, the formulation of the disclosure includes a surfactant in an amount of about 0.07% w / v. In some embodiments, the formulation of the disclosure includes a surfactant in an amount of about 0.08% w / v. In some embodiments, the formulation of the disclosure includes a surfactant in an amount of about 0.09% w / v. In some embodiments, the formulation of the disclosure includes a surfactant in an amount of about 0.1% w / v. In some embodiments, the surfactant in the formulation of the disclosure is polysorbate 80. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount from about 0.01% to about 0.1% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount from about 0.01% to about 0.09% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount from about 0.01% to about 0.08% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount from about 0.01% to about 0.07% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount from about 0.01% to about 0.06% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount from about 0.01% to about 0.05% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount from about 0.01% to about 0.04% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount from about 0.01% to about 0.03% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount from about 0.01% to about 0.02% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount from about 0.02% to about 0.1% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount from about 0.02% to about 0.09% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount from about 0.02% to about 0.08% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount from about 0.02% to about 0.07% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount from about 0.02% to about 0.06% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount from about 0.02% to about 0.05% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount from about 0.02% to about 0.04% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount from about 0.02% to about 0.035% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount from about 0.02% to about 0.03% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount from about 0.025% to about 0.05% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount from about 0.025% to about 0.04% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount from about 0.025% to about 0.035% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount from about 0.025% to about 0.03% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount from about 0.03% to about 0.1% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount from about 0.03% to about 0.09% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount from about 0.03% to about 0.08% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount from about 0.03% to about 0.07% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount from about 0.03% to about 0.06% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount from about 0.03% to about 0.05% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount from about 0.03% to about 0.04% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount of about 0.01% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount of about 0.015% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount of about 0.02% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount of about 0.025% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount of about 0.03% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount of about 0.035% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount of about 0.04% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount of about 0.045% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount of about 0.05% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount of about 0.055% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount of about 0.06% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount of about 0.065% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount of about 0.07% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount of about 0.075% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount of about 0.08% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount of about 0.085% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount of about 0.09% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount of about 0.095% w / v. In some embodiments, the formulation of the disclosure includes polysorbate 80 in an amount of about 0.1% w / v. (iv) Salts In some embodiments, a salt can be included in the antibody formulations described herein to provide stability to the formulation. In some embodiments, the formulations described herein contain a salt, e.g., sodium chloride, potassium chloride, or magnesium chloride. In some embodiments, a formulation described herein contains a salt at a concentration of at least 50 (e.g., at least 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, 180, 185, 190, 195, or 200, or more) mM. In some embodiments, a formulation of the disclosure includes a salt at a concentration of less than, or approximately, 200 (e.g., less than, or approximately, 195, 190, 185, 180, 175, 170, 165, 160, 155, 150, 145, 140, 135, 130, 125, 120, 115, 110, 105, 100, 95, 90, 85, 80, 75, 70, 65, 60, 55, or 50) mM. In some embodiments, a formulation of the disclosure includes a salt at a concentration of between about 50 mM to 100 mM, 60 mM to 100 mM, 70 mM to 100 mM, 80 mM to 100 mM, 90 mM to 100 mM, 50 mM to 120 mM, 60 mM to 120 mM, 70 mM to 120 mM, 80 mM to 120 mM, 90 mM to 120 mM, 100 mM to 120 mM, 110 mM to 120 mM, 50 mM to 150 mM, 60 mM to 150 mM, 70 mM to 150 mM, 80 mM to 150 mM, 90 mM to 150 mM, 100 mM to 150 mM, 110 mM to 150 mM, 120 mM to 150 mM, 130 mM to 150 mM, 140 mM to 150 mM, 50 mM to 200 mM, 60 mM to 200 mM, 70 mM to 200 mM, 80 mM to 200 mM, 90 mM to 200 mM, 100 mM to 200 mM, 110 mM to 200 mM, 120 mM to 200 mM, 130 mM to 200 mM, 140 mM to 200 mM, 150 mM to 200 mM, 160 mM to 200 mM, 170 mM to 200 mM, 180 mM to 200 mM, or 190 mM to 200 mM. It is understood that in embodiments where a formulation of the disclosure contains two or more (e.g., at least two, three, four, five, six, seven, eight, nine, or 10 or more) different salts, each of the two or more salts can independently be present at, e.g., one of the above described concentrations. In some embodiments, the formulations of the disclosure comprise NaCl. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 50-100 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 60-100 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 70-100 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 80-100 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 90-100 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 90-110 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 95-105 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 50-120 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 80-120 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 100-120 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 50-150 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 80-150 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 100- 150 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 120-150 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 50-200 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 80-200 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 100-200 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 120- 200 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 150-200 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 50 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 60 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 70 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 75 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 80 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 85 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 90 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 95 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 100 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 105 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 110 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 115 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 120 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 125 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 130 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 140 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 150 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 160 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 170 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 180 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 190 mM. In some embodiments, the formulations of the disclosure include NaCl at a concentration of about 200 mM. (v) pH It was discovered that the pH of the anti-CD137 antibody formulations of the disclosure affect the stability of the formulations. As provided in the working examples, improved stability was observed when the anti-CD137 antibody was formulated in histidine buffer at pH 5.8 as compared to formulations comprising glutamic acid at pH 4.5 or Tris at pH 7.5. In some embodiments, the formulations described herein include a buffering or pH- adjusting agent. In some embodiments, any of the formulations described herein have, or can be adjusted to have, a physiologically acceptable pH. As used herein, “physiologically acceptable pH” is a pH that is between, and inclusive of, pH 5 and pH 7, and in some embodiments of the formualtions described herein, a pH that is between, and inclusive of, pH 5 and pH 8. Accordingly, as used herein, a physiologically acceptable pH is inclusive of particular pH values suchas 5.0,5.1,5.2,5.3,5.4,5.5,5.6,5.7,5.8,5.9,6.0,6.1,6.2,6.3,6.4,6.5,6.6,6.7, 6.8, 6.9, 70,7.1,72,7.3,74,7.5,7.6,7.7,7.8,7.9, and 8.0. In some embodiments, physiologically acceptable pH is at least pH 5 (e.g., at least pH 5.1, 5.2,5.3,5.4,5.5,5.6,5.7, 5.8 or 5.9), but less than pH 7 (e.g., less than pH 6.9, 6.8, 6.7, 6.6, 6.5, 6.4, 6.3, 6.2, or 6.1). That is, in some embodiments physiologically acceptable pH is, e.g., at least pH 5.0, but less than pH 7.0. In some embodiments, a physiologically acceptable pH is between pH 5.0 and pH 7.0. In some embodiments, a physiologically acceptable pH is between pH 5.5 and pH 6.5. In some embodiments, a physiologically acceptable pH is, e.g., pH 6. In some embodiments, the pH of an antibody formulation described herein is between approximately 5.0 and 7.0, inclusive (e.g., approximately 5.0, 5.1,5.2,5.3,5.4,5.5,5.6,5.7,5.8,5.9,6.0,6.1,6.2,6.3,6.4,6.5,6.6,6.7, 6.8, 6.9, and 7.0). In some embodiments, physiologically acceptable pH is at least pH 5 (e.g., at least pH 5.1,5.2,5.3,5.4,5.5,5.6,5.7,5.8 or 5.9), but less than pH 8 (e.g., less than pH 7.9, 7.8, 77,7.6,7.5,7.4,7.3,7.2,0r 7.1). That is, in some embodiments physiologically acceptable pH is, e.g., at least pH 5.0, but less than pH 8.0. In some embodiments, a physiologically acceptable pH is between pH 5.0 and pH 8.0. In some embodiments, a physiologically acceptable pH is between pH 5.5 and pH 7.5. In some embodiments, a physiologically acceptable pH is, e.g., pH 6. In some embodiments, a physiologically acceptable pH is, e.g., pH 7.4. In some embodiments, the pH of an antibody formulation described herein is between approximately 5.0 and 8.0, inclusive (e.g., approximately 5.0, 5.1, 5.2,5.3,5.4,5.5,5.6,5.7,5.8,5.9, 6.0, 6.1, 6.2, 6.3,6.4,6.5,6.6,6.7,6.8,69,7.0,7.1,7.2,7.3,7.4,7.5,7.6,7.7,7.8,7.9, and 8.0). In some embodiments, the formulation of the disclosure has a pH of about 5.0 to about 7.0. In some embodiments, the formulation of the disclosure has a pH of about 5.5 to about 7.0. In some embodiments, the formulation of the disclosure has a pH of about 6.0 to about 7.0. In some embodiments, the formulation of the disclosure has a pH of about 6.5 to about 7.0. In some embodiments, the formulation of the disclosure has a pH of about 5.0 to about 6.5. In some embodiments, the formulation of the disclosure has a pH of about 5.5 to about 6.5. In some embodiments, the formulation of the disclosure has a pH of about 6.0 to about 6.5. In some embodiments, the formulation of the disclosure has a pH of about 5.0 to about 6.0. In some embodiments, the formulation of the disclosure has a pH of about 5.5 to about 6.0. In some embodiments, the formulation of the disclosure has a pH of about 5.0 to about 5.5. In some embodiments, the formulation of the disclosure has a pH of about 5.8 to about 6.2. In some embodiments, the formulation of the disclosure has a pH of about 5.0. In some embodiments, the formulation of the disclosure has a pH of about 5.1. In some embodiments, the formulation of the disclosure has a pH of about 5.2. In some embodiments, the formulation of the disclosure has a pH of about 5.3. In some embodiments, the formulation of the disclosure has a pH of about 5.4. In some embodiments, the formulation of the disclosure has a pH of about 5.5. In some embodiments, the formulation of the disclosure has a pH of about 5.6. In some embodiments, the formulation of the disclosure has a pH of about 5.7. In some embodiments, the formulation of the disclosure has a pH of about 5.8. In some embodiments, the formulation of the disclosure has a pH of about 5.9. In some embodiments, the formulation of the disclosure has a pH of about 6.0. In some embodiments, the formulation of the disclosure has a pH of about 6.1. In some embodiments, the formulation of the disclosure has a pH of about 6.2. In some embodiments, the formulation of the disclosure has a pH of about 6.3. In some embodiments, the formulation of the disclosure has a pH of about 6.4. In some embodiments, the formulation of the disclosure has a pH of about 6.5. In some embodiments, the formulation of the disclosure has a pH of about 6.6. In some embodiments, the formulation of the disclosure has a pH of about 6.7. In some embodiments, the formulation of the disclosure has a pH of about 6.8. In some embodiments, the formulation of the disclosure has a pH of about 6.9. In some embodiments, the formulation of the disclosure has a pH of about 7.0. In some embodiments, the formulation of the disclosure has a pH of about 5.0 to about 8.0. In some embodiments, the formulation of the disclosure has a pH of about 6.5 to about 8.0. In some embodiments, the formulation of the disclosure has a pH of about 6.0 to about 8.0. In some embodiments, the formulation of the disclosure has a pH of about 6.5 to about 8.0. In some embodiments, the formulation of the disclosure has a pH of about 5.0 to about 7.5. In some embodiments, the formulation of the disclosure has a pH of about 5.5 to about 7.5. In some embodiments, the formulation of the disclosure has a pH of about 6.0 to about 7.5. In some embodiments, the formulation of the disclosure has a pH of about 5.0 to about 7.0. In some embodiments, the formulation of the disclosure has a pH of about 5.5 to about 7.0. In some embodiments, the formulation of the disclosure has a pH of about 5.0 to about 7.5. In some embodiments, the formulation of the disclosure has a pH of about 5.8 to about 6.2. In some embodiments, the formulation of the disclosure has a pH of about 5.8 to about 7.4. In some embodiments, the formulation of the disclosure has a pH of about 5.0. In some embodiments, the formulation of the disclosure has a pH of about 5.1. In some embodiments, the formulation of the disclosure has a pH of about 5.2. In some embodiments, the formulation of the disclosure has a pH of about 5.3. In some embodiments, the formulation of the disclosure has a pH of about 5.4. In some embodiments, the formulation of the disclosure has a pH of about 5.5. In some embodiments, the formulation of the disclosure has a pH of about 5.6. In some embodiments, the formulation of the disclosure has a pH of about 5.7. In some embodiments, the formulation of the disclosure has a pH of about 5.8. In some embodiments, the formulation of the disclosure has a pH of about 5.9. In some embodiments, the formulation of the disclosure has a pH of about 6.0. In some embodiments, the formulation of the disclosure has a pH of about 6.1. In some embodiments, the formulation of the disclosure has a pH of about 6.2. In some embodiments, the formulation of the disclosure has a pH of about 6.3. In some embodiments, the formulation of the disclosure has a pH of about 6.4. In some embodiments, the formulation of the disclosure has a pH of about 6.5. In some embodiments, the formulation of the disclosure has a pH of about 6.6. In some embodiments, the formulation of the disclosure has a pH of about 6.7. In some embodiments, the formulation of the disclosure has a pH of about 6.8. In some embodiments, the formulation of the disclosure has a pH of about 6.9. In some embodiments, the formulation of the disclosure has a pH of about 7.0. In some embodiments, the formulation of the disclosure has a pH of about 7.1. In some embodiments, the formulation of the disclosure has a pH of about 7.2. In some embodiments, the formulation of the disclosure has a pH of about 7.3. In some embodiments, the formulation of the disclosure has a pH of about 7.4. In some embodiments, the formulation of the disclosure has a pH of about 7.5. In some embodiments, the formulation of the disclosure has a pH of about 7.6. In some embodiments, the formulation of the disclosure has a pH of about 7.7. In some embodiments, the formulation of the disclosure has a pH of about 7.8. In some embodiments, the formulation of the disclosure has a pH of about 7.9. In some embodiments, the formulation of the disclosure has a pH of about 8.0. (vi) Concentration of Anti-CD137 Antibody In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation of the disclosure at a concentration of about 1 mg / ml to about 100 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 5 mg / ml to about 15 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 15 mg / ml to about 30 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 30 mg / ml to about 45 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 45 mg / ml to about 60 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 60 mg / ml to about 75 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 75 mg / ml to about 90 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 85 mg / ml to about 100 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation of the disclosure at a concentration of about 1 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 2 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 3 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 4 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 5 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 6 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 7 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 8 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 9 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 10 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 11 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 12 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 13 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 14 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 15 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 16 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 17 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 18 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 19 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 20 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 21 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 22 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 23 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 24 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 25 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 30 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 35 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 40 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 45 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 50 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 55 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 60 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 65 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 70 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 75 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 80 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 85 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 90 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 95 mg / ml. In some embodiments, the anti-CD137 antibody or antigen binding fragment thereof is present in the formulation at a concentration of about 100 mg / ml. (vii) Exemplary formulations In some embodiments, a formulation of the disclosure comprises the following elements: a buffer comprising histidine and an anti-CD137 antibody or antigen binding fragment thereof. In some embodiments, the formulation comprises about 10 mM histidine to about 100 mM histidine. In some embodiments, the formulation includes an anti-CD137 antibody or antigen binding fragment thereof at a concentration of about 1 mg / ml to about 100 mg / ml. In some embodiments, the formulation of the disclosure comprises the following elements: a buffer comprising histidine, a disaccharide sugar, and an anti-CD137 antibody or antigen binding fragment thereof. In some embodiments, the formulation comprises about 10 mM histidine to about 100 mM histidine. In some embodiments, the disaccharide sugar is sucrose. In some embodiments, the formulation comprises the disaccharide sugar at about 5-15% (w / v). In some embodiments, the formulation includes an anti-CD137 antibody or antigen binding fragment thereof at a concentration of about 1 mg / ml to about 100 mg / ml. In some embodiments, a formulation of the disclosure comprises the following elements: a buffer comprising histidine and an anti-CD137 antibody or antigen binding fragment thereof. In some embodiments, the formulation has a pH of about 5.0 to 7.0. In some embodiments, the formulation comprises about 10 mM histidine to about 100 mM histidine. In some embodiments, the formulation includes an anti-CD137 antibody or antigen binding fragment thereof at a concentration of about 1 mg / ml to about 100 mg / ml. In some embodiments, the formulation of the disclosure comprises the following elements: a buffer comprising histidine, a disaccharide sugar, a non-ionic surfactant, a salt, and an anti-CD137 antibody or antigen binding fragment thereof. In some embodiments, the formulation has a pH of about 5.0 to 7.0. In some embodiments, the formulation comprises about 10 mM histidine to about 100 mM histidine. In some embodiments, the disaccharide sugar of the formulation is sucrose. In some embodiments, the formulation comprises the disaccharide sugar at about 5-15% (w / v). In some embodiments, the non-ionic surfactant of the formulation is polysorbate. In some embodiments, the polysorbate is polysorbate 80. In some embodiments, the formulation comprises the non-ionic surfactant at about 0.01% to about 0.1% (w / v). In some embodiments, the salt of the formulation is NaCl. In some embodiments, the formulation comprises salt at a concentration of about 50 mM to about 200 mM. In some embodiments, the formulation includes an anti-CD137 antibody or antigen binding fragment thereof at a concentration of about 1 mg / ml to about 100 mg / ml. In some embodiments, the formulation of the disclosure comprises the following elements: a buffer comprising histidine, a disaccharide sugar at about 5% to about 15 % (w / v), a non-ionic surfactant at about 0.01% to about 0.1% w / v, a salt at about 50 mM to about 200 mM, and an anti-CD137 antibody or antigen binding fragment thereof. In some embodiments, the formulation has a pH of about 5.0 to 7.0. In some embodiments, the formulation comprises about 10 mM histidine to about 100 mM histidine. In some embodiments, the disaccharide sugar of the formulation is sucrose. In some embodiments, the disaccharide sugar of the formulation is lactose. In some embodiments, the disaccharide sugar of the formulation is maltose. In some embodiments, the disaccharide sugar of the formulation is trehalose. In some embodiments, the non-ionic surfactant of the formulation is polysorbate. In some embodiments, the polysorbate is polysorbate 80. In some embodiments, the salt of the formulation is NaCl. In some embodiments, the formulation includes an anti-CD137 antibody or antigen binding fragment thereof at a concentration of about 1 mg / mlto about 100 mg / ml. In some embodiments, the formulation of the disclosure comprises the following elements: a buffer comprising about 10 mM to about 100 mM histidine, sucrose at about 5% to about 15 % (w / v), polysorbate 80 at about 0.01% to about 0.1% w / v, NaCl at about 50 mM to about 200 mM, and an anti-CD137 antibody or antigen binding fragment thereof. In some embodiments, the formulation has a pH of about 5.0 to 7.0. In some embodiments, the formulation has a pH of about 5.0 to 7.4. In some embodiments, the formulation includes an anti-CD137 antibody or antigen binding fragment thereof at a concentration of about 1 mg / ml to about 100 mg / ml. In some embodiments, the formulation of the disclosure comprises the following elements: a buffer comprising about 20 mM histidine, sucrose at about 10% (w / v), polysorbate 80 at about 0.03% w / v, NaCl at about 100 mM, and an anti-CD137 antibody or antigen binding fragment thereof. In some embodiments, the formulation has a pH of about 6.0. In some embodiments, the formulation includes an anti-CD137 antibody or antigen binding fragment thereof at a concentration of about 1 mg / ml to about 100 mg / ml. In some embodiments, the formulation includes an anti-CD137 antibody or antigen binding fragment thereof at a concentration of about 5 mg / ml to about 15 mg / ml. In some embodiments, the formulation includes an anti-CD137 antibody or antigen binding fragment thereof at a concentration of about 15 mg / ml to about 30 mg / ml. In some embodiments, the formulation includes an anti-CD137 antibody or antigen binding fragment thereof at a concentration of about 30 mg / ml to about 45 mg / ml. In some embodiments, the formulation includes an anti-CD137 antibody or antigen binding fragment thereof at a concentration of about 45 mg / ml to about 60 mg / ml. In some embodiments, the formulation includes an anti-CD137 antibody or antigen binding fragment thereof at a concentration of about 60 mg / ml to about 75 mg / ml. In some embodiments, the formulation includes an anti-CD137 antibody or antigen binding fragment thereof at a concentration of about 75 mg / ml to about 90 mg / ml. In some embodiments, the formulation includes an anti-CD137 antibody or antigen binding fragment thereof at a concentration of about 85 mg / ml to about 100 mg / ml. In some embodiments, the formulation includes an anti-CD137 antibody or antigen binding fragment thereof at a concentration of about 5 mg / ml. In some embodiments, the formulation includes an anti-CD137 antibody or antigen binding fragment thereof at a concentration of about 10 mg / ml. In some embodiments, the formulation includes an anti-CD137 antibody or antigen binding fragment thereof at a concentration of about 15 mg / ml. In some embodiments, the formulation includes an anti-CD137 antibody or antigen binding fragment thereof at a concentration of about 20 mg / ml. The formulations of the disclosure as described herein provide the anti-CD137 antibody or antigen binding fragments thereof with marked stability, minimize the formation of antibody aggregates (high molecular weight species) and particulates, minimize charge variants, and maintain the structural integrity of the antibody. (viii) Stability of Anti-CD137 Formulations In some embodiments, the formulations described herein are capable of maintaining the structural integrity of an anti-CD137 antibody or antigen binding fragment thereof in a solution for an extended period of time. In some embodiments, an anti-CD137 antibody in a formulation of the disclosure remains stable after storage for at least four weeks (e.g., at least five weeks, six weeks, seven weeks, eight weeks, nine weeks, 10 weeks, 11 weeks, 12 weeks, 13 weeks, 14 weeks, 15 weeks, 16 weeks, 17 weeks, 18 weeks, 19 weeks, 20 weeks, 21 weeks, 22 weeks, 23 weeks, or 24 weeks, or at least one month, two months, three months, four months, five months, six months, seven months, eight months, nine months, 10 months, 11 months, 12 months, 13 months, 14 months, 15 months, 16 months, 17 months, 18 months, 19 months, 20 months, 21 months, 22 months, 23 months, 24 months, or more) at approximately 2°C to 40°C (e.g., storage at, e.g., 1,2,3,4,5,6,7,8,9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40°C). In some embodiments, an anti-CD137 antibody in a formulation of the disclosure remains stable after storage for at least four weeks at approximately 2°C to 9°C. In some embodiments, an anti-CD137 antibody in a formulation of the disclosure remains stable after storage for at least four weeks at approximately 10°C to 19°C. In some embodiments, an anti-CD137 antibody in a formulation of the disclosure remains stable after storage for at least four weeks at approximately 20°C to 29°C. In some embodiments, an anti-CD137 antibody in a formulation of the disclosure remains stable after storage for at least four weeks at approximately 30°C to 40°C. In some embodiments, an anti-CD137 antibody in a formulation of the disclosure remains stable after storage for at least four weeks at approximately 4°C. In some embodiments, an anti-CD137 antibody in a formulation of the disclosure remains stable after storage for at least four weeks at approximately 25°C. In some embodiments, an anti- CD137 antibody in a formulation of the disclosure remains stable after storage for at least four weeks at approximately 40°C. As exemplified in the working examples described herein, the inventors provide formulations suitable for maintaining an anti-CD137 antibody or antigen binding fragments thereof at approximately 10 mg / mL in predominantly monomeric form for at least 24 weeks at 4°C, at least 12 weeks at 25°C, and at least four weeks at 40°C. As used herein, an anti-CD137 antibody or antigen binding fragment thereof in a formulation of the disclosure is “predominantly monomeric,” or in “predominantly monomeric form,” if the antibody present in the solution is at least 95 (e.g., at least 95.1, 95.2, 95.3, 95.4, 95.5, 95.6, 95.7, 95.8, 95.9, 96, 96.1, 96.2, 96.3, 96.4, 96.5, 96.6, 96.7, 96.8, 96.9, 97, 97.1, 97.2, 97.3, 97.4, 97.5, 97.6, 97.7, 97.8,97.9, 98, 98.1, 98.2, 98.3, 98.4, 98.5, 98.6, 98.7, 98.8, 98.9, 99, 99.1, 99.2, 99.3, 99.4, 99.5, 99.6, 99.7, 99.8, or 99.9 or greater) % monomeric, e.g., as determined using size exclusion chromatography (SEC). That is: less than 5 (e.g., less than 4.9. 4.8,4.7,4.6,4.5,4.4,4.3, 4.2, 4.1,4.0,39,3.8.37.36,35.34,33.32.31, 3.0,29,28,27.28,25,24,23.22:21.2 19,1.8,1.7,1.6,1.5,1.4,1.3,1.2,1.1,1,0.9,0.8,0.7, 0.6, 0.5, 0.4, 0.3, 0.2, or 0.1) % of the antibody in the solution is oligomeric, aggregated, and / or fragmented. As used herein, antibody fragmentation refers to improperly assembled constituents or degradation products of a whole antibody having a lower molecular weight than the whole antibody. Such fragmentation forms include, but are not limited to, a free monomeric heavy chain polypeptide, a dimeric heavy chain polypeptide (e.g., disulfide-linked heavy chain polypeptide), a dimeric heavy chain polypeptide bound to one light chain polypeptide, a monomeric heavy chain polypeptide bound to one light chain polypeptide, or further degradation product(s) or fragment(s) of a light chain or heavy chain polypeptide. In some embodiments, less than 2 (e.g., less than 1.9, 1.8, 1.7, 1.6, 1.5, 1.4, 1.3,1.2,1.1,1,0.9,0.8,0.7, 0.6, 0.5, 0.4, 0.3, 0.2, or 0.1) % of the antibody is aggregated after storage for at least four weeks (e.g., at least five weeks, six weeks, seven weeks, eight weeks, nine weeks, 10 weeks, 11 weeks, 12 weeks, 13 weeks, 14 weeks, 15 weeks, 16 weeks, 17 weeks, 18 weeks, 19 weeks, 20 weeks, 21 weeks, 22 weeks, 23 weeks, or 24 weeks, or at least one month two months, three months, four months, five months, six months, seven months, eight months, nine months, 10 months, 11 months, 12 months, 13 months, 14 months, 15 months, 16 months, 17 months, 18 months, 19 months, 20 months, 21 months, 22 months, 23 months, 24 months, or more) at 2°C to 8°C. Methods for determining the amount of monomeric antibody, as well as the amount of oligomeric, aggregated, or fragmented forms of the anti-CD137 antibody or antigen binding fragment thereof present in solution are described herein and exemplified in the working examples. For example, a skilled artisan can determine the percentage of whole, fragmented, unfolded intermediates, and / or aggregated antibody species present in a given solution using, e.g., size exclusion chromatography (SEC), size exclusion chromatography high- performance liquid chromatography (SEC-HPLC), static light scattering (SLS), Fourier transform infrared spectroscopy (FTIR), circular dichroism (CD), urea-induced protein unfolding techniques, intrinsic tryptophan fluorescence, non-reducing sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), and differential scanning calorimetry (DSC). Anti-CD137 Antibodies and Antigen-binding Fragments Thereof The present disclosure provides formulations comprising antibodies and antigen binding fragments thereof that specifically bind to and agonize CD137. In some embodiments, the formulations of the disclosure comprise any of the anti-CD137 antibodies or antigen binding fragments thereof that are described herein. In some aspects, the disclosure provides formulations comprising anti-CD137 agonist antibodies and antigen binding fragments thereof that are useful for the treatment of cancer. In some embodiments, the formulations of the disclosure comprise anti-CD137 agonist antibodies an antigen binding fragments thereof that induce cytokine production. In some embodiments, the formulations of the disclosure comprise anti-CD137 agonist antibodies that increase the number of CD8+ T cells in the tumor microenvironment. In some embodiments, the formulations of the disclosure comprise anti-CD137 agonist antibodies and antigen binding fragments thereof that induce protective anti-tumor immunity. The disclosure also provides formulations comprising anti-CD137 agonist antibodies and antigen binding fragments thereof that, upon administration in vivo, do not substantially increase intrasplenic or intrahepatic CD4+ and / or CD8+ T cell populations. Human CD137 is a 255 amino acid transmembrane polypeptide (SEQ ID NO: 3; Accession No. NM_001561; NP_001552) and a member of the phylogenetically-conserved tumor necrosis factor receptor (TNFR) superfamily. CD137 (alternatively 4-1BB, TNFR superfamily 9) and its ligand (CD137L) are involved in the regulation of a wide range of immune activities. CD137 ligand cross-links its receptor, CD137, which is expressed on activated T cells, and co-stimulates T cell activities. CD137 is an activation-induced co-stimulatory molecule. Recent studies have revealed that CD137-mediated anti-cancer effects are largely based on its ability to activate T cells, in particular, to induce a cytotoxic T lymphocyte (CTL) response, and induce cytokine production, in particular, high amounts of IFN-y (Ye et al., (2014) Clin Cancer Res 20(1):44-55). CD137 ligand is a transmembrane protein on the cell surface and transmit signals into the cells on which it is expressed, a phenomenon referred to as “reverse signaling” or “back signaling”). CD137 ligand expression is found on most types of leukocytes and on some nonimmune cells. In monocytic cells (monocytes, macrophages, and DCs), CD137 ligand signaling induces activation, migration, survival, and differentiation. Accordingly, in some embodiments, an isolated anti-CD137 agonist antibody, or antigen- binding fragment thereof, described herein, binds to and agonizes CD137 and allows or promotes CD137L binding. In some embodiments, an isolated anti-CD137 agonist antibody, or antigen- binding fragment thereof, described herein, binds to and agonizes CD137. In some embodiments, the anti-CD137 antibodies provided by the disclosure bind to and agonize CD137 and co-stimulate activation of T cells. In some embodiments, the formulations of the disclosure comprise an isolated anti-CD137 agonist antibody, or antigen-binding fragment thereof, described herein, that has one or more of the following properties or characteristics: a) specifically binds to human CD137; b) binds to human and cynomolgus CD137; and ¢) binds to human and mouse CD137. In some embodiments, an anti-CD137 agonist antibody, or antigen-binding fragment thereof, described herein, binds to CD137 and co-stimulates T cell activities. In some embodiments, an anti-CD137 agonist antibody, or antigen-binding fragment thereof, described herein, binds to CD137 and induces or enhances T cell activation, a cytotoxic T lymphocyte (CTL) response, T cell proliferation, cytokine production, or a combination thereof. In some embodiments, an anti-CD137 agonist antibody, or antigen-binding fragment thereof, described herein, binds to CD137 and induces or enhances T cell activation, a cytotoxic T lymphocyte (CTL) response, T cell proliferation, cytokine production, or a combination thereof, in a tumor microenvironment. In some embodiments, an anti-CD137 antibody, or antigen-binding fragment thereof, described herein, does not significantly induce or enhance intrahepatic and / or intrasplenic T cell activation and / or T cell proliferation. In some embodiments, an anti-CD137 antibody, described herein, binds to CD137 and induces the production of IFN-y. In some embodiments, the antibodies provided by the disclosure bind to CD137 and induce the production of IL-2, TNF-a, IL-13, or a combination thereof. In some embodiments, the formulations of the disclosure comprise anti-CD137 antibodies described herein that specifically bind to and agonize CD137. In some embodiments, agonism of CD137 is measured by determining the concentration of cytokines produced by immune cells. Methods for analyzing cytokine production are known in the art and utilized in the Examples. In some embodiments, an increase in cytokine production by immune cells indicates CD137 agonism. In some embodiments, agonism of CD137 is measured by analyzing T cell proliferation. In some embodiments, an increase in T cell proliferation indicates CD137 agonism. In some embodiments, agonism of CD137 is measured by measuring the level of cell signaling either through quantitation of phosphorylation of relevant molecules or expression of a gene reporter after a relevant promoter. In some embodiments, an increase in cell signaling indicates CD137 agonism. In some embodiments, agonism of CD137 is measured by measuring the volume of a tumor. In some embodiments, a decrease in the volume of a tumor indicates CD137 agonism. In some embodiments, the formulations of the disclosure comprise anti-CD137 antibodies described herein that induce, increase or stabilize oligomerization, multimerization, or other higher order clustering of CD137. In some embodiments, the clustering of CD137 on the cell surface is observed via fluorescence microscopy. Provided herein are formulations comprising isolated monoclonal antibodies or antigen binding fragments thereof, that bind to and agonize CD137. In some embodiments, the antibodies or antigen binding fragments thereof, (i) bind human CD137 with an affinity (Kp) of about 30-100 nM (e.g., between about 30 nM and about 100 nM); (ii) bind an epitope on human CD137 described herein; and / or (iii) comprise a heavy chain CDR3 comprising the amino acid sequence DXXXXLXXXXYXYYX (SEQ ID NO: 126). Affinity for CD137 In some embodiments, the formulations of the disclosure comprise an isolated anti- CD137 agonist antibody, or antigen binding fragment thereof, described herein, that binds human CD137 with an affinity (Kp) of about 30-100 nM (e.g., between about 30 nM and about 100 nM or between about 40 nM and about 100 nM). In some embodiments, the affinity of the anti-CD137 antibody to human CD137 is at least two (e.g., at least three, four, five, six, seven, eight, nine, or 10) fold higher than the affinity of mAb10 for mouse CD137. In some embodiments, the affinity of the anti-CD137 antibody is no greater than 500, 450, 400, 350, 300, 250, 200, 250, 200, 175, 150, 125, 110, or 100 nM. In some embodiments, the affinity of the anti-CD137 antibody to human CD137 is at least two (e.g., at least three, four, five, six, seven, eight, nine, or 10) fold higher than the affinity of mAb10 for mouse CD137, but no greater than 500, 450, 400, 350, 300, 250, 200, 250, 200, 175, 150, 125, 110, or 100 nM. The affinity of the antibody is the strength of binding to a single CD137 polypeptide. In some embodiments, affinity is indicated by the equilibrium dissociation constant (Kp). The value of Kp is inversely related to the binding affinity of an antibody to an antigen. Accordingly, the smaller the Kp value, the greater the affinity of the antibody for its antigen. Methods for determining the affinity of an antibody for its antigen are known in the art. An exemplary method for determining binding affinity employs surface plasmon resonance. Surface plasmon resonance is an optical phenomenon that allows for the analysis of real time biospecific interactions by detection of alterations in protein concentrations within a biosensor matrix, for example using the BIAcore system (Pharmacia Biosensor AB, Uppsala, Sweden and Piscataway, N.J.). For further descriptions, see Jonsson, U., et al. (1993) Ann. Biol. Clin. 51: 19- 26; Jonsson, U., i (1991) Biotechniques 11 :620-627; Johnsson, B., et al. (1995) J. Mol. Recognit. 8: 125-131; and Johnsson, B., et al. (1991) Anal. Biochem. 198:268-277. In some embodiments, the anti-CD137 antibodies described herein bind human CD137 with an affinity (Kp) of about 30-100 nM (e.g., between about 30 nM and about 100 nM). In some embodiments, the anti-CD137 antibodies described herein bind human CD137 with an affinity (Kp) of about 40-100 nM. In some embodiments, the anti-CD137 antibodies described herein bind human CD137 with an affinity (Kp) of about 30-40 nM, 40-50 nM, 50-60 nM, 60-70 nM, 70-80 nM, 80-90 nM, 90-100 nM, 45-55 nM, 55-65 nM, 75-85 nM, 85-95 nM, 45-95 nM, 50-90 nM, 55-85 nM, 60-80 nM, 65-75 nM, 55-75 nM, 40-70 nM, 50-80 nM, or 60-90 nM. In some embodiments, the anti-CD137 antibodies described herein bind human CD137 with an affinity (Kp) of about 60-80 nM. In some embodiments, the anti-CD137 antibodies described herein bind human CD137 with an affinity (Kp) of about 60-75 nM. In some embodiments, the anti-CD137 antibodies described herein bind human CD137 with an affinity (Kp) of about 60-90 nM. In some embodiments, the anti-CD137 antibodies described herein bind human CD137 with an affinity (Kp) of about 50-80 nM. In some embodiments, the anti-CD137 antibodies described herein bind human CD137 with an affinity (Kb) of about 40-70 nM. In some embodiments, the anti-CD137 antibodies described herein bind human CD137 with an affinity (Kp) of about 55-75 nM. In some embodiments, the anti- CD137 antibodies described herein bind human CD137 with an affinity (Kp) of about 65-75 nM. In some embodiments, the anti-CD137 antibodies described herein bind human CD137 with an affinity (Kp) of about 60-80 nM. In some embodiments, the anti-CD137 antibodies described herein bind human CD137 with an affinity (Kp) of about 55-85 nM. In some embodiments, the anti-CD137 antibodies described herein bind human CD137 with an affinity (Kp) of about 50-90 nM. In some embodiments, the anti-CD137 antibodies described herein bind human CD137 with an affinity (Kp) of about 45-95 nM. In some embodiments, the anti-CD137 antibodies described herein bind human CD137 with an affinity (Kp) of about 85-95 nM. In some embodiments, the anti-CD137 antibodies described herein bind human CD137 with an affinity (Kp) of about 75-85 nM. In some embodiments, the anti-CD137 antibodies described herein bind human CD137 with an affinity (Kp) of about 75-85 nM. In some embodiments, the anti-CD137 antibodies described herein bind human CD137 with an affinity (Kp) of about 55-65 nM. In some embodiments, the anti-CD137 antibodies described herein bind human CD137 with an affinity (Kb) of about 45-55 nM. In some embodiments, the anti-CD137 antibodies described herein bind human CD137 with an affinity (Kp) of about 80-90 nM. In some embodiments, the anti- CD137 antibodies described herein bind human CD137 with an affinity (Kp) of about 70-80 nM. In some embodiments, the anti-CD137 antibodies described herein bind human CD137 with an affinity (Kp) of about 60-70 nM. In some embodiments, the anti-CD137 antibodies described herein bind human CD137 with an affinity (Kp) of about 50-60 nM. In some embodiments, the anti-CD137 antibodies described herein bind human CD137 with an affinity (Kp) of about 40-50 nM. In some embodiments, the anti-CD137 antibodies described herein bind human CD137 with an affinity (Kp) of about 30-40 nM. In some embodiments, the anti-CD137 antibodies described herein bind human CD137 with an affinity (Kp) of about 30 nM, about 31 nM, about 32 nM, about 33 nM, about 34 nM, about 35 nM, about 36 nM, about 37 nM, about 38 nM, about 39 nM, about 40 nM, about 41 nM, about 42 nM, about 43 nM, about 44 nM, about 45 nM, about 46 nM, about 47 nM, about 48 nM, about 49 nM, about 50 nM, about 51 nM, about 52 nM, about 53 nM, about 54 nM, about 55 nM, about 56 nM, about 57 nM, about 58 nM, about 59 nM, about 60 nM, about 61 nM, about 62 nM, about 63 nM, about 64 nM, about 65 nM, about 66 nM, about 67 nM, about 68 nM, about 69 nM, about 70 nM, about 71 nM, about 72 nM, about 73 nM, about 74 nM, about 75 nM, about 76 nM, about 77 nM, about 78 nM, about 79 nM, about 80 nM, about 81 nM, about 82 nM, about 83 nM, about 84 nM, about 85 nM, about 86 nM, about 87 nM, about 88 nM, about 89 nM, about 90 nM, about 91 nM, about 92 nM, about 93 nM, about 94 nM, about 95 nM, about 96 nM, about 97 nM, about 98 nM, about 99 nM, about 100 nM, about 101 nM, about 102 nM, about 103 nM, about 104 nM, about 105 nM, about 106 nM, about 107 nM, about 108 nM, about 109 nM or about 110 nM. In some embodiments, the anti-CD137 antibodies described herein bind human CD137 with an affinity (Kp) of at least 30 nM but less than about 110 nM, at least 31 nM but less than about 109 nM, at least 32 nM but less than about 108 nM, at least 33 nM but less than about 107 nM, at least 34 nM but less than about 106 nM, at least 35 nM but less than about 105 nM, at least 36 nM but less than about 104 nM, at least 37 nM but less than about 103 nM at least 38 nM but less than about 102 nM, at least 39 nM but less than about 101 nM, at least 40 nM but less than about 100 nM; at least 41 nM but less than about 99 nM; least 42 nM but less than about 98 nM; least 43 nM but less than about 97 nM; at least 44 nM but less than about 96 nM; at least 45 nM but less than about 95 nM; at least 46 nM but less than about 94 nM; at least 47 nM but less than about 93 nM; at least 48 nM but less than about 92 nM; at least 49 nM but less than about 91 nM; at least 50 nM but less than about 90 nM; at least 51 nM but less than about 89 nM; at least 52 nM but less than about 88 nM; at least 53 nM but less than about 87 nM; at least 54 nM but less than about 86 nM; at least 55 nM but less than about 85 nM; at least 56 nM but less than about 84 nM; at least 57 nM but less than about 83 nM; at least 58 nM but less than about 82 nM; at least 59 nM but less than about 81 nM; at least 60 nM but less than about 80 nM; at least 61 nM but less than about 79 nM; at least 62 nM but less than about 78 nM; at least 63 nM but less than about 77 nM; at least 64 nM but less than about 76 nM; or at least 65 nM but less than about 75 nM. In some embodiments, the anti-CD137 antibodies described herein bind human CD137 with an affinity (Kp) of at least 40 nM but less than about 100 nM. In some embodiments, the anti-CD137 antibodies described herein cross-react with CD137 polypeptides from more than one species. In some embodiments, the anti-CD137 antibodies described herein bind cynomolgus CD137 and human CD137. In some embodiments, the anti-CD137 antibodies described herein bind mouse CD137 and human CD137. In some embodiments, the anti-CD137 antibodies described herein bind human CD137, mouse CD137 and cynomolgus CD137. CD137 Epitope Binding In some embodiments, the formulations of the disclosure comprise an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds to human CD137. In some embodiments, the formulations of the disclosure comprise an isolated monoclonal antibody, or antigen binding portion thereof, that binds to an epitope on human CD137. In some embodiments, the isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds to human CD137, binds to an epitope on human CD137 comprising one or more (e.g., one, two, three, four, five, six, seven, eight, nine, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or all 25) of amino acids 111-132 of SEQ ID NO:3. In some embodiments, the isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds to human CD137, binds to an epitope within amino acids 111-132 of SEQ ID NO:3. In some aspects, the disclosure provides an isolated monoclonal antibody, or antigen binding portion thereof, that specifically binds to human CD137, binds to all or a portion of amino acids 111-132 of SEQ ID NO:3. In some embodiments, an isolated anti-CD137 agonist antibody, or antigen binding fragment thereof, described herein, binds to an epitope of human CD137 comprising residue K114 of SEQ ID NO: 3. In some embodiments, an isolated anti-CD137 agonist antibody, or antigen binding fragment thereof, described herein, binds to an epitope of human CD137 comprising residues E111, T113 and K114 of SEQ ID NO: 3. In some embodiments, an isolated anti-CD137 agonist antibody, or antigen binding fragment thereof, described herein, binds to an epitope of human CD137 comprising residues E111, T113, K114, N126 and 1132 of SEQ ID NO: 3. In some embodiments, an isolated anti-CD137 agonist antibody, or antigen binding fragment thereof, described herein, binds to an epitope of human CD137 comprising E111, T113, K114, N126, 1132 and P135 of SEQ ID NO: 3. In some embodiments, an isolated anti-CD137 agonist antibody, or antigen binding fragment thereof, described herein, binds to an epitope of human CD137 comprising one or more residues E111, T113,K114,N126, 1132 and P135 of SEQ ID NO: 3. In some embodiments, an isolated anti-CD137 agonist antibody, or antigen binding fragment thereof, described herein, binds to an epitope of human CD137 comprising a sequence of one or more amino acid residues corresponding to amino acid positions 100 to 135, 101 to 135, 102 to 135, 103 to 135, 104 to 135, 105 to 135, 106 to 135, 107 to 135, 108 to 135, 109 to 135, 110to0 135, 0r 111 to 135 of SEQ ID NO: 3. In some embodiments, an isolated anti-CD137 agonist antibody, or antigen binding fragment thereof, described herein, binds to an epitope of human CD137 comprising a sequence of one or more amino acid residues corresponding to amino acid positions 111 to 135 of SEQ ID NO: 3. In some embodiments, the epitope comprises 2, 3, 4, 5, 6, 7, 8,9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 amino acid residues corresponding to amino acid positions 111 to 135 of SEQ ID NO: 3. In some embodiments, an isolated anti-CD137 agonist antibody, or antigen binding fragment thereof, described herein, binds to an epitope of human CD137 within amino acid positions 100 to 135, 101 to 135, 102 to 135, 103 to 135, 104 to 135, 105 to 135, 106 to 135, 107 to 135, 108 to 135, 109 to 135, 110 to 135, or 111 to 135 of SEQ ID NO: 3. In some embodiments, an isolated anti-CD137 agonist antibody, or antigen binding fragment thereof, described herein, binds to an epitope of human CD137 within amino acid positions 111 to 135 of SEQ ID NO: 3. In some embodiments, the epitope comprises 2, 3, 4, 5, 6,7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 amino acid residues corresponding to amino acid positions 111 to 135 of SEQ ID NO: 3. In some embodiments, an isolated anti-CD137 agonist antibody, or antigen b...

Claims

CLAIMS 1. A formulation comprising: (a) an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises a heavy chain CDR3 of SEQ ID NO: 126, wherein X is any amino acid, and (b) a buffer comprising histidine.

2. A formulation comprising: (a) an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises a heavy chain CDR3 of SEQ ID NO: 126, wherein X is any amino acid, (b) a buffer comprising histidine; and (c) a disaccharide sugar.

3. A formulation comprising: (a) an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises a heavy chain CDR3 of SEQ ID NO: 126, wherein X is any amino acid, and (b) a buffer comprising histidine; wherein the formulation has a pH of about 5.0-7.

0. 4, A formulation comprising: (a) an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises a heavy chain CDR3 of SEQ ID NO: 126, wherein X is any amino acid, and (b) a buffer comprising histidine; wherein the formulation has a pH of about 5.0-7.

4.

5. A formulation comprising: (a) an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises a heavy chain CDR3 of SEQ ID NO: 126, wherein X is any amino acid, (b) a buffer comprising histidine, (c) a disaccharide sugar, (d) a non-ionic surfactant, and (e) a salt, wherein the pH of the formulation is about 5.0 to about 7.

0.

6. A formulation comprising: (a) an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises a heavy chain CDR3 of SEQ ID NO: 126, wherein X is any amino acid, (b) a buffer comprising histidine, (c) a disaccharide sugar, (d) a non-ionic surfactant, and (e) a salt, wherein the pH of the formulation is about 5.0 to about 7.

4.

7. A formulation comprising: (a) an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises a heavy chain CDR3 of SEQ ID NO: 126, wherein X is any amino acid, (b) a buffer comprising histidine, (c) a disaccharide sugar at about 5%-about 15% weight / volume, (d) a non-ionic surfactant at about 0.01%-about 0.1% weight / volume (w / v), and (e) a salt at about 50 mM —- 200 mM, wherein the pH of the formulation is about 5.0 to about 7.

0.

8. A formulation comprising: (a) an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises a heavy chain CDR3 of SEQ ID NO: 126, wherein X is any amino acid, (b) a buffer comprising histidine, (c) a disaccharide sugar at about 5%-about 15% weight / volume, (d) a non-ionic surfactant at about 0.01%-about 0.1% weight / volume (w / v), and (e) a salt at about 50 mM — 200 mM, wherein the pH of the formulation is about 5.0 to about 7.

4.

9. A formulation comprising: (a) an anti-CD137 antibody at a concentration of about 1mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises a heavy chain CDR3 of SEQ ID NO: 126, wherein X is any amino acid, (b) a buffer comprising about 10 mM to about 100 mM histidine, (c) sucrose at about 5%-about 15% weight / volume, (d) polysorbate-80 at about 0.01%-about 0.1% weight / volume (w / v), and (e) NaCl at about 50 mM — 200 mM, wherein the pH of the formulation is about 5.0 to about 7.

0.

10. A formulation comprising: (a) an anti-CD137 antibody at a concentration of about 1mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises a heavy chain CDR3 of SEQ ID NO: 126, wherein X is any amino acid, (b) a buffer comprising about 10 mM to about 100 mM histidine, (c) sucrose at about 5%-about 15% weight / volume, (d) polysorbate-80 at about 0.01%-about 0.1% weight / volume (w / v), and (e) NaCl at about 50 mM — 200 mM, wherein the pH of the formulation is about 5.0 to about 7.

4.

11. A formulation comprising: (a) an anti-CD137 antibody at a concentration of about 1 mg / ml to about 100 mg / ml, wherein the anti-CD137 antibody comprises a heavy chain CDR3 of SEQ ID NO: 126, wherein X is any amino acid, (b) a buffer comprising about 20 mM histidine, (c) sucrose at about 10% weight / volume (w / v), (d) polysorbate-80 at about 0.03% weight / volume (w / v), and (e) NaCl at about 100mM, wherein the pH of the formulation is about 6.

0.

12. The formulation of any one of claims 1-11, wherein the anti-CD137 antibody comprises a heavy chain CDR3 of DXPFXLDXXYYYYYX (SEQ ID NO: 127), wherein X is any amino acid.

13. The formulation of any one of claims 1-11, wherein the anti-CD137 antibody comprises a heavy chain CDR3 of DX X2X3X4LX5X6X7XsYXoYYX10 (SEQ ID NO: 128), wherein X| is any amino acid, wherein Xz is a non-polar amino acid, wherein X3 is a non-polar amino acid, wherein X41s any amino acid, wherein Xs is a polar amino acid, wherein Xe is any amino acid, wherein X7 1s any amino acid, wherein Xs is a polar amino acid, wherein Xs is a polar amino acid, and wherein Xjois any amino acid.

14. The formulation of claim 13, wherein X» is proline, X3 is phenylalanine or tryptophan, Xs is aspartic acid or glutamic acid, Xg is tyrosine, and Xo is tyrosine.

15. The formulation of any one of claims 1-14, wherein the anti-CD137 antibody comprises a heavy chain CDR3 of SEQ ID NO:

68.

16. The formulation of any one of claims 1-15, wherein the anti-CD137 antibody comprises a comprises a heavy chain CDR1 of SEQ ID NO: 48, a heavy chain CDR2 of SEQ ID NO: 56, and a heavy chain CDR3 of SEQ ID NO: 68, and a light chain CDR1 of SEQ ID NO: 69, a light chain CDR2 of SEQ ID NO: 78, and a light chain CDR3 of SEQ ID NO:

89.

17. The formulation of any one of claims 1-15, wherein the anti-CD137 antibody comprises heavy and light chain CDRs selected from the group consisting of: (a) heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 56 and 68, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 69, 78 and 89, respectively; (b) heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 51, 108 and 68, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 69, 78 and 89, respectively; (©) heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 135, 139 and 143, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 144, 147 and 150, respectively; (d) heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 137, 141 and 143, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 144, 147 and 150, respectively. (e) heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 48, 154 and 159, respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 144, 147 and 150, respectively; and 6) heavy chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 51, 156 159 respectively, and light chain CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 144, 147 and 150, respectively.

18. The formulation of any one of claims 1-16, wherein the anti-CD137 antibody comprises heavy and light chain sequences comprising amino acid sequences having at least 90% identity to SEQ ID NOs: 4 and 6, respectively.

19. The formulation of claim 18, wherein the anti-CD137 antibody comprises heavy and light chain sequences having amino acid sequences set forth in SEQ ID NOs: 4 and 6, respectively.

20. The formulation of any one of claims 1-15 and 17, wherein the anti-CD137 antibody comprises heavy and light chain sequences comprising amino acid sequences having at least 90% identity to SEQ ID NOs: 101 and 6, respectively.

21. The formulation of claim 20, wherein the anti-CD137 antibody comprises heavy and light chain sequences having amino acid sequences set forth in SEQ ID NOs: 101 and 6, respectively.

22. The formulation of any one of claims 1-19, wherein the antibody comprises an IgG1 heavy chain constant region.

23. The formulation of claim 22, wherein the IgG1 heavy chain constant region is a wild-type human IgG1 heavy chain constant region 24. The formulation of claim 22, wherein the IgG1 heavy chain constant region comprises an amino acid substitution relative to a wild-type human IgG1 heavy chain constant region.

25. The formulation of any one of claim 1-19, wherein the antibody comprises an IgG4 heavy chain constant region.

26. The formulation of claim 25, wherein the IgG4 heavy chain constant region is a wild-type human IgG4 heavy chain constant region 27. The formulation of claim 25, wherein the IgG4 heavy chain constant region comprises an amino acid substitution relative to a wild-type human IgG4 heavy chain constant region.

28. The formulation of any one of claims 1-27, comprising about 10 mM histidine to about 100 mM histidine.

29. The formulation of any one of claims 1-28, comprising about 20 mM histidine.

30. The formulation of any one of claims 1, 3-4, 9-10, and 12-28, further comprising a disaccharide sugar.

31. The formulation of any one of claims 2, 5-8, and 30, wherein the disaccharide sugar is selected from sucrose, lactose, maltose, and trehalose.

32. The formulation of claim 31, wherein the disaccharide sugar is sucrose.

33. The formulation of any one of claims 2, 5-6, and 30-32, wherein the disaccharide sugar is at about 5%-about 15% weight / volume.

34. The formulation of any one of claims 2, 5-8, and 30-32, wherein the disaccharide sugar is at about 10% weight / volume.

35. The formulation of any one of claims 1-4 and 12-28, further comprising a salt.

36. The formulation of any one of claims 5-8, and 35, wherein the salt is NaCl.

37. The formulation of any one of claims 5 and 35-36, wherein the salt is at a concentration of about 50 mM - 200 mM.

38. The formulation of any one of claims 5-10 and 35-36, wherein the salt is at a concentration of about 100 mM.

39. The formulation of any one of claims 1, 2, and 12-28, wherein the formulation has a pH of about 5.0-7.

0.

40. The formulation of any one of claims 1, 2, and 12-28, wherein the formulation has a pH of about 5.0-7.

4.

41. The formulation of any one of claims 3-4, 7-10, and 39-40 wherein the pH is about 6.

0.

42. The formulation of any one of claims 1-4 and 12-41, further comprising a non-ionic surfactant.

43. The formulation of any one of claims 5-8, and 42, wherein the non-ionic surfactant is a polysorbate. 44, The formulation of claim 43, wherein the polysorbate is polysorbate-80.

45. The formulation of any one of claims 5-6 and 42-43, wherein the non-ionic surfactant is at about 0.01%-about 0.1% weight / volume (w / v).

46. The formulation of any one of claims 5-8, and 42-43, wherein the non-ionic surfactant is at about 0.03% weight / volume (w / v).

47. The formulation of any one of claims 1-46, comprising the anti-CD137 antibody at a concentration of about 5 mg / ml to about 15 mg / ml.

48. The formulation of any one of claims 1-46, comprising the anti-CD137 antibody at a concentration of about 15 mg / ml to about 30 mg / ml.

49. The formulation of any one of claims 1-46, comprising the anti-CD137 antibody at a concentration of about 30 mg / ml to about 45 mg / ml.

50. The formulation of any one of claims 1-46, comprising the anti-CD137 antibody at a concentration of about 45 mg / ml to about 60 mg / ml.

51. The formulation of any one of claims 1-46, comprising the anti-CD137 antibody at a concentration of about 60 mg / ml to about 75 mg / ml.

52. The formulation of any one of claims 1-46, comprising the anti-CD137 antibody at a concentration of about 75 mg / ml to about 90 mg / ml.

53. The formulation of any one of claims 1-46, comprising the anti-CD137 antibody at a concentration of about 85 mg / ml to about 100 mg / ml.

54. The formulation of any one of claims 1-46, comprising the anti-CD137 antibody at a concentration of about 5 mg / ml.

55. The formulation of any one of claims 1-46, comprising the anti-CD137 antibody at a concentration of about 10 mg / ml.

56. The formulation of any one of claims 1-46, comprising the anti-CD137 antibody at a concentration of about 15 mg / ml.

57. The formulation of any one of claims 1-46, comprising the anti-CD137 antibody at a concentration of about 20 mg / ml.

58. A method for inducing or enhancing dimerization of human CD137 trimers in a subject, comprising administering to a subject in need thereof, an effective amount of the formulation of any one of claims 1-57.

59. A method for inducing or enhancing multimerization of human CD137 trimers in a subject, comprising administering to a subject in need thereof, an effective amount of the formulation of any one of claims 1-57.

60. A method for inducing or enhancing T cell activation in a subject, comprising administering to a subject in need thereof, an effective amount of the formulation of any one of claims 1-57.

61. The method of claim 60, wherein the T cell activation occurs in a tumor microenvironment.

62. A method for inducing or enhancing a cytotoxic T cell response in a subject, comprising administering to a subject in need thereof, an effective amount of the formulation of any one of claims 1-57.

63. The method of claim 62, wherein the cytotoxic T cell response occurs in a tumor microenvironment.

64. A method for inducing or enhancing cytokine production of an immune cell in a subject, comprising administering to a subject in need thereof, an effective amount of the formulation of any one of claims 1-57.

65. The method of claim 64, wherein the cytokine produced is IL-2, TNFa, IL-13, IFN-y, or combinations thereof.

66. The method of claim 64 or claim 65, wherein the cytokine production occurs in a tumor microenvironment.

67. A method for inducing or enhancing T cell proliferation in a subject, comprising administering to a subject in need thereof, an effective amount of the formulation of any one of claims 1-57.

68. The method of claim 67, wherein the T cell proliferation occurs in a tumor microenvironment.

69. A method for reducing or inhibiting tumor growth, comprising administering to a subject in need thereof, an effective amount of the formulation of any one of claims 1-57.

70. A method for treating a disorder mediated by human CD137 in a subject, comprising administering to a subject in need thereof, an effective amount of the formulation of any one of claims 1-57.

71. A method for treating cancer in a subject, comprising administering to a subject in need thereof, an effective amount of the formulation of any one of claims 1-57.

72. The method of any one of claims 69-71, wherein infiltration of immune cells into a tumor microenvironment is increased after administration of the formulation.

73. The method of claim 72, wherein the immune cells express CD45.

74. The method of any one of claims 69-73, wherein the quantity of T regulatory (Treg) cells is reduced in a tumor microenvironment after administration of the formulation.

75. The method of claim 74, wherein the Treg cells express CD4, FOXP-3 and CD25.

76. The method of any one of claims 69-75, wherein the quantity of macrophages is reduced in a tumor microenvironment after administration of the isolated monoclonal antibody or antigen binding portion.

77. The method of claim 76, wherein the macrophages express CD45 and CD11b.

78. The method of any one of claims 69-77, wherein T cell exhaustion is reduced in a tumor microenvironment after administration of the isolated monoclonal antibody or antigen binding portion, optionally wherein reduction of T cell exhaustion comprises a decrease in expression of TIGIT, PD-1, LAG-3, or combinations thereof.

79. The method of any one of claims 71-78, wherein the cancer is selected from the group consisting of melanoma, glioma, renal, breast, hematological, and head and neck cancer.

80. The method of claim 79, wherein the hematological cancer is a B cell lymphoma.

81. A method of inducing an anti-tumor memory immune response, comprising administering to a subject in need thereof, an effective amount of the formulation of claims 1-57.

82. The method of any one of claims 58-81, wherein the anti-CD137 antibody binds Fc gamma receptor.

83. The method of any one of claims 58-82, wherein depletion of CD4+ T cells, CD8+ T cells, Natural Killer cells, or combinations thereof, reduces the efficacy of the formulation.

84. AXkit comprising a container comprising the formulation of any one of claims 1-57, and a package insert comprising instructions for administration of the formulation, for treating or delaying progression of cancer or reducing or inhibiting tumor growth in a subject in need thereof.

85. Akit comprising a container comprising the formulation of any one of claims 1-57, and a package insert comprising instructions for administration of the formulation alone or in combination with another agent, for treating or delaying progression of cancer or reducing or inhibiting tumor growth in a subject in need thereof.

86. The use of the formulation of any one of claims 1-57, for the manufacture of a medicament for treating or delaying progression of cancer or reducing or inhibiting tumor growth in a subject in need thereof.

87. A formulation according to any one of claims 1-57, in the manufacture of a medicament for treating or delaying progression of cancer or reducing or inhibiting tumor growth in a subject in need thereof.

88. A formulation according to any one of claims 1-57, for use as a medicament.

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