Compositions and methods for treating metastatic diseases

Abstract

The present disclosure provides anti-EPOR antibodies, anti-EPO antibodies, and fragments thereof that specifically bind to an EPOR complex with high affinity, engineered EPOs, and engineered EPOR fusion proteins for treating metastatic diseases. The anti-EPOR antibodies, anti-EPO antibodies, engineered EPOs, and / or engineered EPOR fusion proteins can be used to treat patients.

Description

Attorney Docket No. 62379-707601COMPOSITIONS AND METHODS FOR TREATING METASTATIC DISEASES CROSS-REFERENCE

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 776,795 filed on March 24, 2025, which is incorporated by reference herein in its entirety.STATEMENT AS TO FEDERALLY SPONSORED RESEARCH

[0002] This invention was made with Government support under contract CA274511 awarded by the National Institutes of Health. The Government has certain rights in the invention.BACKGROUND OF THE DISCLOSURE

[0003] Erythropoietin (EPO) induces hematopoiesis by dimerizing EPO receptor (EPOR) molecules, which leads to the activation of the EPO receptor-associated Janus tyrosine kinase 2 (Jak2) and secondary signaling molecules such as signal transducer and activator of transcription 5 (Stat5; Brines and Cerami, Nat Rev Neurosci, 2005; 6:484-94). EPO acts by binding to EPOR which is expressed on erythroid progenitor cells to inhibit apoptosis and promote cell survival, proliferation, and differentiation in production of mature red blood cells. However, EPOR expression is not restricted to erythroid tissue. EPOR is also expressed in a number of non-hematopoietic tissues and elicits tissue protective effects in ischemic injury and promotes wound healing, cardiovascular protection, angiogenesis, neuroprotection, regulation of metabolic homeostasis, and bone remodeling.

[0004] Metastasis is the leading cause of cancer-related deaths globally, with the liver being one of the most frequent and detrimental sites of metastatic spread. Moreover, multiple studies have highlighted the pivotal role of the liver in immune tolerance-mediated disease progression, in both primary hepatocellular carcinoma (HCC) and as a metastatic site for other solid tumors.SUMMARY OF THE DISCLOSURE

[0005] The present disclosure provides compositions and methods for preventing cancer metastasis by preventing the expression, formation, activation, and circulation of an erythropoietin (EPO) protein-hetero-EPO receptor complex in a subject.

[0006] In an aspect, the present disclosure provides a method for treating or inhibiting cancer metastasis in a subject, comprising administering a pharmaceutically effective amount of a composition that i) inhibits or reduces binding of an erythropoietin (EPO) protein to an EPO receptor (EPOR) complex, wherein said EPO receptor complex comprises (a) at least two EPOR subunits or (b) at least one EPOR subunit and at least one CD 131 subunit; ii) inhibits or reduces formation of an EPO receptor (EPOR) complex, wherein said EPO receptor complex comprises (a) at least two EPOR subunits or (b) at least one EPOR subunit and at least one CD 131 subunit; iii) inhibits or reduces activation of an EPO receptor (EPOR) complex on a plurality of macrophages, wherein said EPO receptor complex comprises (a) at least two EPOR subunits or (b) at least one EPOR subunit and at least one CD 131 subunit; iv) reduces an amount of circulating EPO protein in said subject; and / or v) reduces an expression level of an EPOAttorney Docket No. 62379-707601receptor (EPOR) complex on a plurality of macrophages, wherein said EPO receptor complex comprises (a) at least two EPOR subunits or (b) at least one EPOR subunit and at least one CD 131 subunit; thereby a) treating the cancer metastasis, b) inhibiting formation of a pre -metastatic niche in a distant site that is different from a location of a primary tumor, or c) inhibiting a metastatic nodule growth.

[0007] In some embodiments, said EPO receptor complex is a homo-EPO receptor complex that comprises at least two EPOR subunits. In some embodiments, said homo-EPO receptor complex comprises or consists of two EPOR subunits. In some embodiments, said EPO receptor complex is a hetero-EPO receptor complex that comprises at least one EPOR subunit and at least one CD 131 subunit. In some embodiments, said hetero-EPO receptor complex comprises or consists of an EPOR subunit and a CD131 subunit. In some embodiments, said subject has an existing metastatic cancer. In some embodiments, said subject does not have an existing metastatic cancer. In some embodiments, the method further comprises inhibiting or reducing exacerbating said primary tumor.

[0008] In some embodiments, the method further comprises increasing CD8+ T cell / regulatory T cell ratio. In some embodiments, the method further comprises inhibiting development of regulator T cells (Tregs). In some embodiments, CD8+ T cells express Cluster of Differentiation 45 (CD45), CD3, CD8, Perforin, Interferon gamma (IFNy), Granzyme B, or tumor necrosis factor alpha (TNFa). In some embodiments, Tregs express Cluster of Differentiation 4 (CD4), CD25, CD 127, Forkhead Box P3 (FoxP3), CD39, protein tyrosine phosphatase receptor type C (CD45RA), Interleukin-2 (IL-2), or a Cytotoxic T-Lymphocyte Associated Protein 4 (CTLA-4).

[0009] In some embodiments, the method further comprises rendering said cancer metastasis sensitive to an immune checkpoint inhibitor. In some embodiments, said immune checkpoint inhibitor comprises a Cytotoxic T-Lymphocyte Associated Protein 4 (CTLA-4) inhibitor, a Programmed Death 1 (PD-1) inhibitor, or a Programmed Death Ligand 1 (PD-L1) inhibitor.

[0010] In some embodiments, said distant site is different from a location of said primary tumor or said distant site is a tissue that is distinct from a tissue where said primary tumor is located. In some embodiments, said distant site is located in liver. In some embodiments, said primary tumor is located in colon. In some embodiments, said primary tumor is located in breast. In some embodiments, said primary tumor is located in pancreas. In some embodiments, said primary tumor is located in ovary.

[0011] In some embodiments, said composition comprises an antibody or a functional fragment thereof. In some embodiments, said antibody or said functional fragment thereof selectively binds to an EPO receptor subunit, a CD 131 subunit, or a combination thereof. In some embodiments, said composition comprises a compound or a salt thereof, wherein said compound is an inhibitor of hypoxia-inducible factor (HIF), IL-la, IL-1J3, TNF-a, IL-6, estrogen receptors, phospholipase C-yl, or Cbl / p85 / Episin-l pathway. In some embodiments, said composition comprises a plurality of lipid nanoparticles (LNPs) comprising siRNA directed to hetero-EPO receptor on macrophages. In some embodiments, said composition comprises an engineered EPO receptor comprising an extracellular domain (ECD) of said EPO receptor subunit. In some embodiments, said composition further comprises a second antibody or a functional fragment thereof that selectively binds to an immune checkpoint protein. In someAttorney Docket No. 62379-707601embodiments, said immune checkpoint protein comprises PD-1, PD-L1, or CTLA-4. In some embodiments, said immune checkpoint protein is PD-1.

[0012] In some embodiments, inhibiting or reducing said formation of said EPO protein-homo-EPO receptor complex, inhibiting or reducing said formation of said homo-EPO receptor between two EPO receptor subunits, inhibiting or reducing said activation of said homo-EPO receptor on said plurality of macrophages, reducing said circulating EPO protein amount, and / or reducing said expression level of homo-EPO receptor in said plurality of macrophages can inhibit formation of a pre-metastatic niche in a distant site that is different from a location of a primary tumor. In some embodiments, inhibiting or reducing said formation of said EPO protein-homo-EPO receptor complex, inhibiting or reducing said formation of said homo-EPO receptor between two EPO receptor subunits, inhibiting or reducing said activation of said homo-EPO receptor on said plurality of macrophages, reducing said circulating EPO protein amount, and / or reducing said expression level of homo-EPO receptor in said plurality of macrophages can inhibit a metastatic nodule growth.

[0013] In some aspects, provided herein is a method for treating or inhibiting cancer metastasis in a subject, comprising: administering a pharmaceutically effective amount of a composition that comprises (i) an antibody or a functional fragment thereof, or (ii) an engineered fusion protein or a functional fragment thereof, wherein said antibody or said functional fragment thereof selectively binds to a first target and a second target, wherein the first target comprises an erythropoietin (EPO) protein, an EPO receptor subunit, a CD 131 subunit, or a combination thereof, wherein the second target comprises an immune checkpoint protein, and wherein said antibody or said functional fragment thereof comprises a first antigen-binding domain and a second antigen-binding domain.

[0014] In some embodiments, said binding of said antibody or said functional fragment thereof to said first target inhibits or reduces (i) binding of an erythropoietin (EPO) protein to an EPO receptor (EPOR) complex, wherein said EPO receptor complex comprises (a) at least two EPOR subunits or (b) at least one EPOR subunit and at least one CD 131 subunit; (ii) formation of an EPO receptor (EPOR) complex, wherein said EPO receptor complex comprises (a) at least two EPOR subunits or (b) at least one EPOR subunit and at least one CD 131 subunit; (iii) activation of an EPO receptor (EPOR) complex on a plurality of macrophages, wherein said EPO receptor complex comprises (a) at least two EPOR subunits or (b) at least one EPOR subunit and at least one CD 131 subunit.

[0015] In some embodiments, said inhibiting or reducing(i) binding of an erythropoietin (EPO) protein to an EPO receptor (EPOR) complex, wherein said EPO receptor complex comprises (a) at least two EPOR subunits or (b) at least one EPOR subunit and at least one CD 131 subunit; or (ii) formation of an EPO receptor (EPOR) complex, wherein said EPO receptor complex comprises (a) at least two EPOR subunits or (b) at least one EPOR subunit and at least one CD 131 subunit inhibits immune tolerance. In some embodiments, said binding of said antibody or said functional fragment thereof to said second target inhibits immune checkpoint. In some embodiments, said inhibiting immune checkpoint inhibits immune tolerance.

[0016] In some embodiments, said first antigen-binding domain comprises: a heavy chain variable region (VH) comprising a VH complementarity determining region 1 (VH-CDR1) sequence, a VH-CDR2Attorney Docket No. 62379-707601sequence, and a VH-CDR3 sequence; and a light chain variable region (VL) comprising a VL-CDR1 sequence, a VL-CDR2 sequence, and a VL-CDR3 sequence; a VH and a kappa chain variable regions (VK); or a VH and a lambda chain variable regions. In some embodiments, said first antigen-binding domain and / or said second antigen-binding domain comprises a Fab, a Fab’, a (Fab’)2, a variable fragment (Fv), a single chain variable fragment (scFv), a scFv-Fc, a Fab-Fc, a VHH, a non-antibody scaffold, or a combination thereof. In some embodiments, said second antigen-binding domain comprises a VHH.

[0017] In some embodiments, said immune checkpoint protein comprises PD-1, PD-L1, or CTLA-4. In some embodiments, said immune checkpoint protein is PD- 1.

[0018] In some embodiments, said antibody or said functional fragment thereof is an IgG, an IgM, an IgE, an IgA, an IgD, is derived therefrom, or a combination thereof. In some embodiments, said antibody or said functional fragment thereof comprises a monoclonal antibody, a grafted antibody, a chimeric antibody, a human antibody, a humanized antibody, or a combination thereof. In some embodiments, said first antigen-binding domain and / or said second antigen-binding domain is isolated, recombinant, synthetic, or a combination thereof. In some embodiments, said antibody or a functional variant thereof further comprise a peptide linker.

[0019] In some embodiments, said engineered fusion protein or said functional fragment thereof comprises an engineered EPO receptor comprising an extracellular domain (ECD) of said EPO receptor subunit. In some embodiments, said first target comprises an EPO receptor subunit, a CD 131 subunit, or a combination thereof. In some embodiments, said subject has an existing metastatic cancer. In some embodiments, said subject does not have an existing metastatic cancer.INCORPORATION BY REFERENCE

[0020] All publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference.BRIEF DESCRIPTION OF THE DRAWINGS

[0021] A better understanding of features and advantages of the present disclosure will be obtained by reference to the following detailed description, which sets forth illustrative embodiments of the disclosure, and the accompanying drawings.

[0022] FIG. 1 shows the novel concept that immunoregulatory macrophages can be reprogrammed into co-stimulatory macrophages by restricting EPO-EPOR signaling, offering a potential strategy for treating and preventing liver metastasis. The EPO-EPOR signaling is investigated with a primary focus on macrophages in the contexts of (i) early events that enable liver metastasis, (ii) late events that lead to immune tolerance induction, and (iii) as a druggable target for treating and preventing metastatic diseases. Beyond the conceptual innovation of EPO-EPOR as a key immunoregulatory signaling axis in solid tumor liver metastases and tumor-specific immune tolerance induction, this disclosure introduces innovative model systems, technologies, concepts, and therapeutics.Attorney Docket No. 62379-707601

[0023] FIGS. 2A - 2F show the role of EPOR+macrophages in modulating immune responses and therapeutic outcomes in HCC. FIG. 2A shows immune profiling of murine spontaneous HCC models with inflamed and noninflamed TME. FIG. 2B shows a comparison of plasma EPO levels between normal and HCC-bearing mice. FIG. 2C shows overall survival analysis of wild-type (WT) mice bearing non-inflamed HCC with or without EPO deficiency. FIG. 2D illustrates macrophages that represent the dominant EPOR+cell population in both mouse and human HCC. FIG. 2E shows overall survival analysis for wild-type (WT) and EPORALysMmice in non-inflamed HCC models. FIG. 2F illustrates two weeks post-tumor induction, WT and EPORALysMmice were treated intraperitoneally with 2 mg / kg of aPD-1 or IgG serotype control every three days (5 doses total). Tumor growth was monitored using luciferase-based bioluminescence imaging, and both tumor growth and kinetics and overall survival were evaluated.

[0024] FIGS. 3A - 3E show how ablation of EPOR in macrophages reduces liver metastatic seeding and liver metastasis (LM)-mediated immune tolerance. FIG. 3A shows a schematic representation of the intrasplenic injection model for studying liver metastasis. FIG. 3B shows liver metastasis and incidence rate in wild-type (WT) and EPORALysMmice in the MC38 intrasplenic injection model. FIG. 3C shows schematic representation of the two-site injection model for studying liver metastasis. FIG. 3D shows a comparison of subcutaneous MC38 tumor growth between WT and EPORALysMmice, with and without liver metastasis (LM). FIG. 3E shows the CD8+ T cell to CD4+ Treg ratio was assessed in WT and EPOR'^M mice with LM.

[0025] FIGS. 4A - 4 F show a development and validation of a spontaneous liver metastasis model.FIG. 4A shows trichrome staining of primary PDAC tumors in mice. FIG. 4B shows a schematic representation of the generation of PLM lines, along with liver metastasis incidence rate for each line. FIG. 4C shows H& E histological analysis and bioluminescence imaging (IVIS) of liver metastases. FIG.4D shows H& E histological analysis showing how a liver metastasis (LM) module forms adjacent to the portal vein. FIG. 4E shows flow cytometry analysis of dynamic changes in macrophage populations during different stages of liver metastasis (LM). FIG. 4F shows immunofluorescence staining of F4 / 80 (macrophages) in PLM1 liver metastases.

[0026] FIGS. 5A - 5D show how ablation of EPOR in macrophages reduces liver metastasis incidence. FIG. 5A shows a schematic representation of the spontaneous liver metastasis model. FIGs.5B - 5C show the liver metastasis burden and incidence rate in wild-type (WT) and EPORALysMmice with liver metastasis (LM). FIG. 5D shows immunohistochemistry for EPOR in human liver metastases.

[0027] FIG. 6 shows the increase in Tregs during the progression of liver metastases. Evaluation of the frequency of Tregs in the spontaneous PLM model at various timepoints.

[0028] FIGS. 7A - 7D illustrates siEPOR-NPs selectively target macrophages and reduce the tumor burden of HCC-bearing mice. FIG. 7A shows the physical properties of the liposomes that were used for packaging siRNA. FIG. 7B illustrates flow cytometry analysis used to determine which myeloid cells in the liver took up the FITC-conjugated siNTC (non-target control)-NPs. FIG. 7C shows the knockdown efficiency of EPOR in liver macrophages determined by qPCR. FIG. 7D shows the effect of siEPOR-NPs on the tumor burden of non-inflamed HCC-bearing mice.Attorney Docket No. 62379-707601

[0029] FIG. 8A illustrates generation of a spontaneous HCC model by in vivo delivery of plasmids pCMV-SB13, pT3-EFla-Myc and pX330-sgRNA targeting Trp53, Pten, Keapl to mouse liver via HDTV.

[0030] FIG. 8B illustrates overall survival C57BL / 6 WT mice injected intraperitoneally (IP) with 2 mg / kg of aPD-1 (RMP1-14) or IgG Isotype control every 3 days, 2 weeks after HDTV (n = 7-9 / group).

[0031] FIG. 8C illustrates spleen weight and plasma EPO concentration of tumor-bearing mice 5 weeks after HDTV (n = 8-10 / group).

[0032] FIG. 8D illustrates data from blood samples collected from tumor-bearing mice with comparable tumor burdens and analyzed for complete blood count, 4 weeks after HDTV (n = 5 / group).

[0033] FIGs. 8E-8F illustrate correlation of EPO mRNA expression (EPOhlgh, upper quartile; EPOlow, lower quartile). FIG. 8E illustrates 5 -year overall survival and FIG. 8F illustrates immune composition in HCC patients (TCGA and LIRI-JR).

[0034] FIG. 8G illustrates data from blood samples collected from tumor-bearing mice with comparable tumor burdens and measured for plasma EPO concentration (n = 6 / group).

[0035] FIG. 8H illustrates size measurements of tumors harvested 5 weeks after HDTV of Trp53KO / MycOEand Trp53KO / EpoKO / MycOEHCC.

[0036] FIG. 81 illustrates intratumoral immune cell profiling of tumors harvested 5 weeks after HDTV for Trp53KO / MycOEand Trp53KO / EpoKO / MycOEHCC mice (n = 7-8 / group).

[0037] FIG. 8J illustrates determination of tumor size and regression rate (CR: complete regression; PR: partial regression; NR: no regression) for Hepal-6_EV (empty vector) and Hepal-6_EpoOE(EPO-overexpressing) tumors.

[0038] FIGs. 8K-8M illustrate intratumoral immune cell profiling for Hepal-6_EV (empty vector) and Hepal-6_EpoOE(EPO-overexpressing) tumors.

[0039] FIG. 8N shows tumor size and immune cell profiling of Hepal-6_EpoOEmice injected IP with aCD25, aCTLA-4, aCCR8 or IgG control.

[0040] FIG.9A illustrates the major EPOR+ populations in Hepal-6 tumors: F4 / 80+EPOR+macrophages, which consisted of CD1 lbhlMDMs, CD1 lb10MDMs and TIM-4+KCs.

[0041] FIG. 9B illustrates EPOR and MHCII levels in Hepal-6 tumors.

[0042] FIG. 9C illustrates the percentage of each F4 / 80+EPOR+macrophage subset in Hepal-6 tumors.

[0043] FIG. 9D illustrates EPOR and MHCII expression in Hepal-6 tumors.

[0044] FIG. 9E illustrates the proportion of EGFP+cells in liver KCs two weeks after orthotopic implantation of Hepal-6_EV or Hepal-6_EpoOEin Ms4a3-EGFP reporter mice.

[0045] FIG. 9F illustrates the percentage of EPOR+CD68+human macrophages and their CD14 / CD163 levels in tumors (T) and adjacent non-tumor liver tissues (NT).

[0046] FIG. 9G illustrates the EPOR expression of EPOR+CD68+human macrophages in T / NT pairs.

[0047] FIG. 9H illustrates representative immunofluorescent images showing overlapping staining pattern of EPOR and CD68 in human HCC.

[0048] FIG. 91 illustrates the correlation of EPO and EPOR mRNA expression in HCC patients (TCGA).

[0049] FIG. 9J illustrates the correlation of the signature enrichment (SE) scores of two liver macrophage subsets with EPOR mRNA expression, in human HCC-NT (TCGA).Attorney Docket No. 62379-707601

[0050] FIG. 9K illustrates the top five upregulated pathways (from 72 genes) enriched in EPOR+macrophages relative to EPOR macrophages (left), and the correlation between EPOR+macrophage signature enrichment and cell type signature for five KC subsets (right).

[0051] FIG. 10A illustrates survival of HCC-bearing WT and EporΔLysMmice (n = 8 / group).

[0052] FIG. 10B illustrates tumor growth kinetics measured by luciferin-based bioluminescence imaging (n = 7 / group) in HCC-bearing WT and EporΔLysMmice.

[0053] FIG. 10C illustrates tumor growth kinetics 2 weeks after HDTV of Keap lK0 / Myc0E-Luc+mice injected (IP) with either PBS or 50 IU of rHuEPO daily for 3 weeks (n = 8 / group).

[0054] FIG 10D illustrates overall survival in WT mice and EporΔLysMmice after HDTV (Trp53KO / MycOE-Luc+; Epow) or (Trp53KO / EpoKO / MycOE-Luc+; EpoKO) (n = 8 / group).

[0055] FIG. 10E illustrates tumor size and CR rate measurement for orthotopically implanted Hepal-6_EpoOEtumors from WT and EporΔLysMmice harvested on day 21 (n = 8-12 / group).

[0056] FIG. 10F illustrates tumor burden in Hepal-6_EpoOE(n = 6 / group) HCC bearing mice after administration of liposomes containing 50 pg of siEpor or siNTC (non-targeted control).

[0057] FIG. 10G illustrates tumor burden in Trp53KO / MycOE (n = 8 / group) HCC bearing mice after administration of liposomes containing 50 pg of siEpor or siNTC (non-targeted control).

[0058] FIG. HA illustrates total leukocyte infiltration per gram of tumor, frequency of different immune populations and functional status of TAMs (CD1 lb+F4 / 80+CD64+) in Trp53KO / MycOEtumors of WT and Epor^M harvested 5 weeks after HDTV (n = 6 / group).

[0059] FIG. 11B illustrates overall survival of C57BL / 6 WT or EporΔLysMmice 2 weeks after HDTV (Trp53KO / MycOE) injected (IP) with anti-CD8 mAb (YTS 169.4) or IgG control twice during the first week and then once weekly (total 6 doses).

[0060] FIG. 11C illustrates a UMAP plot displaying the distribution of CD8+T cells in WT and EporΔLysMgroups (n = 6 / group; 2500 CD8+T cells / sample).

[0061] FIG. HD illustrates distribution percentage of each cluster along with the expression levels of 8 DEMs in WT and EpoiALysMgroups (n = 6 / group; 2500 CD8+T cells / sample).

[0062] FIG. HE illustrates tumor growth kinetics and overall survival in C57BL / 6 WT and EporΔLysMmice 2 weeks after HDTV (Trp53KO / MycOE-Luc+), injected (IP) with 2 mg / kg of aPD-1 (RMP1-14) or IgG Isotype control every 3 days (total 5 doses). Gray area refers to the threshold level of background noise.

[0063] FIG. HF illustrates overall survival (1.5 weeks after HDTV (Trp53KO / MycOE)) in C57BL / 6 EporALYsM ERT2mice injected (IP) with 75 mg / kg tamoxifen or corn oil every 3 days (total 8 doses), in addition to the aPD-1 regimen.

[0064] FIG. 11G illustrates overall survival (2 weeks after HDTV (Trp53KO / MycOE)) in C57BL / 6 WT mice injected (IP) with 20 mg / kg mEPOR-Fc or PBS weekly (total 4 doses), in addition to the aPD-1 regimen.

[0065] FIGs. 12A-12E illustrate flow cytometry and bulk-RNAseq data from KCs isolated by FACS from adjacent liver tissues of Hepal-6_EV (KCEV) and Hepal-6_EpoOE(KCEP0) tumors at day 18 postimplantation. FIG. 12A illustrates protein levels of functional markers in KCEV and KCEpo. FIG 12B illustrates principal component analysis of gene expression profiles of KCEV and KCEpo. FIG. 12CAttorney Docket No. 62379-707601illustrates Geneset enrichment analysis for inflammatory response gene signature and heatmap for core proinflammatory cytokines enriched in KCEV. FIG 12D KCEV and KCEpo volcano plots of differentially expressed genes in KCEV and KCEpo. FIG 12E illustrates the top five upregulated and downregulated pathways enriched in KCEpo relative to KCEV.

[0066] FIG 12F illustrates correlation between EPO and KCEpo signatures in human HCC (TCGA).

[0067] FIGs. 12G-12I illustrates gene set enrichment analysis comparing the gene expression profiles of KCEV and KCEpo. FIG. 12G illustrates that the KCEpo profile was enriched for the human LILRB5+immunoregulatory KC gene signature (GenesetILIRB5_KCs). FIG. 12H illustrates core genes enriched in KCEpo for the GenesetILIRB5_KCs. FIG. 121 illustrates transcriptional factors that regulate the core genes (analyzed by ChEA3).

[0068] FIG. 13A illustrates the nucleus-to-cytoplasm ratio of NRF2 signal in KCEV and KCEpo.

[0069] FIGs. 13B-13E illustrates KCs and MDMs isolated from Hepal-6_EV and Hepal-6_EpoOEHCC-bearing WT and Epor-deficient mice. FIGs. 13B-13C illustrates mRNA expression of iron metabolism-associated genes and antioxidant genes in KCEV and KCEpo. FIG. 13D illustrates illustrates mRNA expression of iron metabolism-associated genes and antioxidant genes in MDMEV and MDMEP0. FIG. 13E illustrates illustrates mRNA expression of iron metabolism -associated genes and antioxidant genes in KCEpo with Epor deficiency.

[0070] FIG. 13F illustrates intracellular heme level in KCs isolated from Hepal-6 tumors.

[0071] FIG. 13G illustrates intracellular heme level in TAMs (both KCs and MDMs) isolated from cold HCC tumors of WT and EporΔLysMmice.

[0072] FIG. 13H illustrates tumor size and CR rate in orthotopically implanted Hepal -6_EpoOEtumors in WT and LysMCre; Nrf2£l / £1(Nrf2ALysM) mice harvested on Day 18 (n = 6 / group).

[0073] FIG. 131 illustrates representative H& E and CD8-stained images of partially regressed tumors in Nrf2: lmicc.

[0074] FIG. 13 J illustrates survival of HCC bearing WT and Nrf2ALysMmice after HDTV (Trp53KO / MycOE) (n = 8 / group).

[0075] FIG. 13K illustrates the percentages of T cell populations in HCC tumors of WT and Nrf2ALysMmice 5 weeks after HDTV (Trp53KO / MycOE) (n = 4 / group).

[0076] FIGs. 14A-14B illustrates generation of spontaneous HCC models by in vivo delivery of plasmids pCMV=SB13, pT3=EFla=Myc and pX330=sgRNA targeting Trp53, Pten, Keapl to mouse liver via HDTV. FIG. 14A illustrates plasmid uptake measured by luciferin-based bioluminescence imaging in livers, lungs and spleens harvested 2 days after HDTV. FIG. 14B illustrates total leukocyte infiltration per gram of tumor, and frequency and functional status of different immune cell types analyzed by flow cytometry (n = 8-10 / group) from HCC tumors harvested 5 weeks after HDTV.

[0077] FIG. 15 illustrates complete blood count (CBC) of mice bearing inflamed or non-inflamed HCC 4 weeks after HDTV (n = 5 / group).

[0078] FIG. 16A illustrates correlations between EPO mRNA expression and vascular invasion and Edmondson- Steiner grade.Attorney Docket No. 62379-707601

[0079] FIG. 16B illustrates correlations between EPO mRNA expression and various hypoxic markers in human HCC (TCGA), stratified by EPO expression quartiles (EPOhlgh: upper quartile, EPOlow: lower quartile).

[0080] FIG. 16C illustrates correlations between EPO mRNA expression and and 5-year overall survival in human cancers (TCGA; ACC: adrenocortical carcinoma; KIRC: kidney renal clear cell carcinoma; SKCM: skin cutaneous melanoma; BRCA: breast invasive carcinoma; COADREAD: colorectal adenocarcinoma).

[0081] FIG. 17 illustrates establishment of a spontaneous non-inflamed HCC model with EPO-deficiency using a pX333 vector, as described herein.

[0082] FIG. 18A illustrates representative immunohistochemistry images of CD8+T cells in Hepal-6 tumors from wild-type C57BL / 6 mice orthotopically implanted with allogeneic Hepal-6 cells.

[0083] FIG. 18B illustrates size of Hepal-6 tumors (day 21) in C57BL / 6 wild-type (WT) and Rag2 / _mice (n = 9 / group) orthotopically implanted with allogeneic Hepal-6 cells.

[0084] FIG. 19A illustrates characterization of Tregs in Hepal-6-EV and Hepal-6-EpoOEtumors.

[0085] FIG. 19B illustrates the effects of EPO on in vitro Treg polarization in the presence or absence of TGF[3 in Hepal-6-EV and Hepal-6-EpoOEtumors.

[0086] FIG. 19C illustrates a comparison of CD25, CCR8, and CTLA-4 expression levels between Tregs and non-Tregs from Hepal-6-EV and Hepal-6-EpoOEtumors.

[0087] FIG. 19D illustrates tumor size and regression rate measurements of Hepal-6. EpoOEon days 14, 17 and 20 after orthotopic implantation after IP injection with 2 mg / kg of aCD25, aCTLA-4, aCCR8 or IgG control. Tumors were harvested on day 21 (n = 5 / group).

[0088] FIG. 19E illustrates flow cytometry analysis of splenic Tregs.

[0089] FIG. 19F illustrates a representative Foxp3 immunohistochemistry image of aCTLA-4-treated tumors.

[0090] FIG. 19G illustrates a quantification of intratumoral Tregs and CD8+T cells.

[0091] FIG. 20A illustrates the proportion of Teri 19+CD71+ cells within the CD1 lb+Grl+ population in tumors from various spontaneous HCC models.

[0092] FIG. 20B illustrates the proportion of Teri 19+CD71+ cells within the CD1 lb+Grl+ population in tumors from spontaneous non-inflamed HCC models with EPO deficiency.

[0093] FIG. 20C illustrates the proportion of Teri 19+CD71+ cells within the CD1 lb+Grl+ population in tumors from Hepal-6 orthotopic implantation models.

[0094] FIG. 20D illustrates overall survival of mice 2 weeks after HDTV (Trp53KO / MycOE) in C57BL / 6 WT mice injected (IP) with 2 mg / kg of aPD-1 (RMP1-14), aTer-119 (TER-119) or IgG Isotype control every 3 days (total 9 doses).

[0095] FIG. 21 A illustrates expression levels of EPOR and MHCII in macrophages from non-inflamed HCC, with and without EPO deficiency.

[0096] FIG. 21B illustrates F4 / 80+EPOR+macrophages comprising CD1 lbhlMDMs and CD1 lb10MDMs in HCC tumors of Epor-tdTomato 5 weeks after HDTV (KeaplK0 / Myc0E).Attorney Docket No. 62379-707601

[0097] FIG. 21C illustrates expression levels of CLEC4F and VSIG4 in different macrophage subsets from liver tissues of HCC-bearing mice (Hepal-6 orthotopic implantation models).

[0098] FIG. 21D illustrates the proportion of EGFP+cells in the KC population of liver tissues from Ms4a3-EGFP reporter mice 2 weeks after orthotopic implantation (Hepal-6-EV or Hepal-6-EpoOE).

[0099] FIG. 22A illustrates immune profiling of EPOR+cells in liver tissues from HCC patients, and FIG. 22B illustrates the corresponding gating strategy.

[0100] FIG. 22C illustrates representative immunofluorescence images of human HCC tissues stained for EPOR and CD68.

[0101] FIG. 23 illustrates correlation of core markers of two liver macrophage subsets with EPOR mRNA expression in human HCC-NT (TCGA).

[0102] FIG. 24 illustrates differential gene expression analysis in human tumor associated EPOR+and EPOR-macrophages.

[0103] FIG. 25 illustrates differentially expressed genes EPOR+and EPOR-macrophages in human HCC.

[0104] FIG. 26 illustrates representative CD8 immunohistochemistry images of Hepal-6_EpoOEtumors in Epor11" or EporALysMmice, harvested on Day 14.

[0105] FIG. 27 illustrates the proportion of Tregs in livers of Epor" " or Epormice injected (IP) with either PBS or 50 IU of rHuEPO daily for 7 days.

[0106] FIG. 28A illustrates the physical properties of the liposomes that were used for packaging siRNA, as described herein.

[0107] FIG. 28B illustrates immune cell uptake of liposomes (FITC+population) in livers of wild-type mice injected with liposomes containing 50 pg of FITC-conjugated siNTC (non-target control) after 48 hours.

[0108] FIG. 28C illustrates the knockdown efficiency of Epor in macrophages in livers, as determined by qPCR, in wild-type mice I. V. injected with liposomes containing siNTC or siEpor.

[0109] FIG. 29 illustrates overall survival of C57BL / 6 EporALysMmice 2 weeks after HDTV (Trp53KO / MycOE), injected (IP) with 4 mg / kg of aCD8 (YTS 169.4), aCD4 (GK1.5) or IgG control twice for the first week and then once weekly (total 6 doses) (n= 8 / group).

[0110] FIG. 30A illustrates a UMAP plot of CD8+T cell populations from HCC-bearing wild-type and HCC-bearing EporALysMmice.

[0111] FIG. 30B illustrates PhenoGraph and heatmap expression analysis of CD8+T cell populations from HCC-bearing wild-type and HCC-bearing EporALysMmice.

[0112] FIG. 31 illustrates UMAP plots and PhenoGraph analysis of the CD8+T cell population identified clusters from HCC-bearing wild-type and HCC-bearing EporALysMmice.

[0113] FIG. 32 illustrates UMAP plots of the CD8+T cell populations from HCC-bearing wild-type and HCC-bearing EporALysMmice (n = 6 / group; 2500 CD8+T cells / sample). Heat mapping was used to visualize the relative expression of each marker in UMAP.Attorney Docket No. 62379-707601

[0114] FIG. 33A illustrates differential gene expression analysis among KCEVand KCEpocells isolated from adjacent liver tissues of Hepa1-6_EV (KCEV) and Hepa1-6_EpoOE(KCEpo) on day 18 postimplantation.

[0115] FIG. 33B illustrates a heatmap for all differentially expressed genes (DEGs) in KCEVand KCEpofrom adjacent liver tissues of Hepa1-6_EV (KCEV) and Hepa1-6_EpoOE(KCEpo) on day 18 postimplantation.

[0116] FIG. 33C illustrates a heatmap for the top 50 differentially expressed genes (DEGs) in KCEVand KCEpofrom adjacent liver tissues of Hepa1-6_EV (KCEV) and Hepa1-6_EpoOE(KCEpo) on day 18 postimplantation.

[0117] FIG. 34A illustrates mRNA expression of DEGs identified by bulk-RNAseq in KCs isolated from Hepa1-6_EV and Hepa1-6_EpoOEtumors in wild-type and Epor-deficient mice.

[0118] FIG. 34B illustrates mRNA expression of DEGs identified by bulk-RNAseq in MDMs isolated from Hepa1-6_EV and Hepa1-6_EpoOEtumors in wild-type and Epor-deficient mice.

[0119] FIG. 35 illustrates the KCEV profile is enriched for the human CD1C+antigen-presenting KC gene signature.

[0120] FIG. 36 illustrates signaling pathway analysis of EPO-EPOR signaling in KCs isolated from adjacent liver tissues of Hepal-6_EV (KCEV) and Hepal-6_EpoOE(KCEpo) tumors at day 18 postimplantation. Gene set enrichment analysis (Database: KEGG MEICUS) was used to compare the gene expression profiles of KCEV and KCEpo. Twenty-nine out of 226 gene sets were upregulated in KCEpo, and two gene sets were significantly enriched at nominal p-value < 5%.

[0121] FIG. 37 illustrates heme depletion in human macrophages by EPO treatment.

[0122] FIG. 38A illustrates intracellular free iron levels in bone-marrow-derived macrophages in vitro after EPO treatment in wild-type and EporΔLysMmice.

[0123] FIG. 38B illustrates intracellular free iron levels in macrophages isolated from cold HCC tumors of wild-type and EporΔLysMmice.

[0124] FIGs. 39A-39D illustrate the amino acid sequence and nucleic acid sequence of human EPOR extracellular domain (ECD) or human CD 131 ECD, human CD 131 D3D4 domains, and human EPOR (F93A) domains, including the signal peptide sequences (underlined). FIG. 39A shows the amino acid sequence (SEQ ID NO: 65) and nucleic acid sequence (SEQ ID NO: 66) of human EPOR ECD in IME020 and IME061. FIG. 39B shows the amino acid sequence (SEQ ID NO: 67) and nucleic acid sequence (SEQ ID NO: 68) of human CD131 ECD in IME062. FIG. 39C shows the amino acid sequence (SEQ ID NO: 69) and nucleic acid sequence (SEQ ID NO: 70) of human CD131 D3D4 domain in IME063. FIG. 39D shows the amino acid sequence (SEQ ID NO: 71) and nucleic acid sequence (SEQ ID NO: 72) of human EPOR (F93A) domains in IME083 and IME034.

[0125] FIG. 40 shows that ablation of EPOR in macrophages leads to reduced tumor burden in mouse liver metastasis model. A schematic representation of the intrasplenic injection model for studying liver metastasis is shown (top). LysMCre; Eporfl / fl (EporΔLysM) mice that develop EPOR-deficiency in the mature myeloid cells (primarily macrophages) were generated. Wild-type (WT) or EPORALysMC57BL / 6 mice were injected intrasplenically with 5 × 105MC38 cells (Conventional (intrasplenic) liver metastasisAttorney Docket No. 62379-707601model), followed by splenectomy. Four weeks after intrasplenic injection, liver tissues were harvested to evaluate and compare tumor burden and the incidence of liver metastasis in WT and EPORALysMmice (bottom).

[0126] FIG. 41 shows that ablation of EPOR in macrophages leads to reduced tumor burden in mouse pancreatic cancer model with liver metastasis. A schematic representation of the spontaneous liver metastasis model is shown (top). LysMCre; Eporfl / fl (EporΔLysM) mice that develop EPOR-deficiency in the mature myeloid cells (primarily macrophages) were generated. Wild-type (WT) or EPORALysMC57BL / 6 mice were orthotopically injected in the pancreas with 1 x 105PLM1 cells (spontaneous liver metastasis model). Three weeks after injection, pancreatic and liver tissues were harvested to evaluate and compare primary pancreatic ductal adenocarcinoma (PDAC) and liver metastasis burden in WT and EPORALysMmice (bottom).

[0127] FIG. 42 shows that ablation of EPOR in macrophages leads to reduced tumor burden in mouse colorectal cancer model with liver metastasis. A schematic representation of the spontaneous liver metastasis model is shown (top). LysMCre; Eporfl / fl (EporΔLysM) mice that develop EPOR-deficiency in the mature myeloid cells (primarily macrophages) were generated. Wild-type (WT) or EPORALysMC57BL / 6 mice were orthotopically injected in the colon (or cecum) with 1.5 × 105CLM1 cells (spontaneous liver metastasis model). 28 days after injection, cecum and liver tissues were harvested to evaluate primary colorectal cancer (CRC) and liver metastasis burden in WT and EporΔLysMmice (bottom).

[0128] FIG. 43 shows the treatment with anti-EPOR antibody leads to significant reduction in liver metastases in pancreatic metastasis mouse model. PLM1 cells were implanted into the pancreas of WT C57BL / 6 male mice. Animals were treated with either vehicle or anti-EPOR mouse antibody weekly at dose 1, and liver metastatic burden was measured ex vivo 21 days post tumor implantation. n=9-10 animals per group (one animal in vehicle succumbed to tumor burden prior to endpoint). * indicates p value<0.05 by one-tailed unpaired T test. EpoRmAb 1: anti-EPOR mouse antibody 1.

[0129] FIG. 44 shows the treatment with anti-EPOR antibody leads to significant reduction in liver metastases in an ovarian metastasis tumor model. Tumor cells were implanted into the peritoneal cavity of female WT mice. Animals were dosed via intraperitoneal injection with vehicle or anti-EPOR mouse antibody weekly at dose 1. Total tumor burden was measured as total tumor weight. n=9-10 animals per group. * indicates p value<0.05 by one-tailed unpaired T test. EpoRmAb 2: anti-EPOR mouse antibody 2.

[0130] FIG. 45 shows the treatment with anti-EPOR antibody demonstrates significant long-term survival benefit in liver cancer mouse model. Hydrodynamic tail vein injection (HDTV) was performed using sterile saline and plasmid mixture with a total volume corresponding to 10 % of total body weight of the mice over 8-10 seconds per animal. Animals were dosed with the indicated test article at dose 1 weekly for anti-EPOR antibody 1 or anti-EPOR antibody 2. The EPO trap was administered at dose 2, once a week and anti-PD-1 antibody was administered at dose 2, twice a week. Efficacy was measured by overall survival of animals. mAb 1 and mAb 2: anti-EPOR mouse antibody 1 and 2, respectively. KO: knock out. OE: overexpression. ** = P<0.01. ***=P<0.0005.Attorney Docket No. 62379-707601DETAILED DESCRIPTION OF THE DISCLOSURE

[0131] While various embodiments of the present disclosure are described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous modifications and changes to, and variations and substitutions of, the embodiments described herein will be apparent to those skilled in the art without departing from the disclosure. It is understood that various alternatives to the embodiments described herein can be employed in practicing the disclosure. It is also understood that every embodiment of the disclosure can optionally be combined with any one or more of the other embodiments described herein which are consistent with that embodiment.

[0132] Where elements are presented in list format (e.g., in a Markush group), it is understood that each possible subgroup of the elements is also disclosed, and any one or more elements can be removed from the list or group.

[0133] It is also understood that, unless clearly indicated to the contrary, in any method described or claimed herein that includes more than one act or step, the order of the acts or steps of the method is not necessarily limited to the order in which the acts or steps of the method are recited, but the disclosure encompasses embodiments in which the order is so limited.

[0134] It is further understood that, in general, where an embodiment in the description or the claims is referred to as comprising one or more features, the disclosure also encompasses embodiments that consist of, or consist essentially of, such feature(s).

[0135] It is also understood that any embodiment of the disclosure, e.g., any embodiment found within the prior art, can be explicitly excluded from the claims, regardless of whether or not the specific exclusion is recited in the specification.

[0136] It is further understood that reference to a peptide, a polypeptide or a protein herein, such as an antibody or a fragment thereof, includes pharmaceutically acceptable salts thereof unless specifically stated otherwise or the context clearly indicates otherwise. Such salts can have a positive net charge, a negative net charge or no net charge.

[0137] Headings are included herein for reference and to aid in locating certain sections. Headings are not intended to limit the scope of the embodiments and concepts described in the sections under those headings, and those embodiments and concepts may have applicability in other sections throughout the entire disclosure.

[0138] All patent literature and all non-patent literature cited herein are incorporated herein by reference in their entirety to the same extent as if each patent literature or non-patent literature were specifically and individually indicated to be incorporated herein by reference in its entirety.

[0139] Beyond erythroid progenitors, a growing body of evidence suggests broad EPOR expression in non-erythroid cells, such as hematopoietic stem cells (HSCs), megakaryocytes, B cells, T cells, macrophages (MΦs), endothelial cells, and neurons (Broxmeyer, J Exp Med 2013:210:205-208).Notably, the immune-modulatory role of EPO is increasingly recognized (Cantarelli et al., Am J Transplant 2019: 19:2407-2414; Peng et al., Cell Death Dis 2020: 11:79). The engagement of EPO signaling suppresses inflammatory responses by inhibiting the NFKB inducible immune pathway (Nairz etAttorney Docket No. 62379-707601al., Immunity 2011:34:61-74). Moreover, EPO primes MΦs for effective efferocytosis thereby preventing autoimmunity (Luo et al., Immunity 2016:44:287-302).

[0140] EPO is cardioprotective in ischemia reperfusion injury and myocardial infarction. EPO improves cardiac function linked to neovascularization mediated by stimulating coronary endothelial cells to activate endothelial nitric oxide (NO) synthase (eNOS) and NO production (Teng et al., Basic Res.Cardiol. 2011:106:343-354).

[0141] EPO stimulates neovascularization and angiogenesis by activating endothelial cells (ECs) and endothelial progenitor cells (EPCs) in physiological conditions and pathological conditions, e.g., ischemia cardio-vascular diseases and tumors. Activation of EPOR leads to mobilization, proliferation, migration, and differentiation of ECs and EPCs (Annese et al., Experimental Cell Research, 2019: 374(2):266-273).

[0142] In the central nervous system, EPO and EPOR are expressed by neurons, glial cells and cerebrovasculature endothelium. EPO was shown to be neurotrophic and neuroprotective in vitro and in animal models of neuronal injury associated with trauma, stroke, ischemia, inflammation and epileptic seizures. The beneficial effects of EPO were also demonstrated in clinical studies of stroke, schizophrenia and progressive multiple sclerosis. EPO protects neurons both directly, by preventing apoptosis, and indirectly, by modulating inflammatory processes and stimulating neurogenesis and angiogenesis (Wang et al., Stroke 2004:35:1732-7).

[0143] EPO regulation of metabolism extends beyond oxygen delivery and contributes to maintenance of white adipose tissue and metabolic homeostasis. EPO is protective in diet-induced obesity, improves glucose tolerance, reduces insulin resistance and regulates fat mass accumulation, particularly in male mice (Alnaeeli and Noguchi, Adipocyte 2015:4: 153-157). EPO modulates the proinflammatory response of macrophage infiltration in white adipose tissue and promotes an anti-inflammatory phenotype by inhibiting expression of proinflammatory cytokines and reducing macrophage infiltration (Alnaeeli et al., Diabetes Metab. Res. Rev. 2014:63:2415-2431).

[0144] It has been shown that some of the cytoprotective effects of EPO are mediated through its binding to heterodimers containing a canonical EPOR and a common beta receptor (βcR or CD131; Brines et al., Proc Natl Acad Sci USA 2004; 101: 14 907-14 912). Interestingly, carbamylated EPO binds to these heteroreceptors and exerts tissue-protective effects, whereas it does not bind to the classical EPOR (e.g., EPOR homodimers comprising two EPOR subunits) and does not stimulate erythropoiesis. βcR is not required for erythropoiesis. It is assumed that βcR in combination with the EPOR expressed by nonhematopoietic cells constitutes a tissue-protective receptor, thus creating a tissue-protective heteroreceptor.

[0145] The expression levels of EPO and EPOR are regulated. EPO production is induced under hypoxic conditions mediated by HIF (Semenza, Blood 2009: 114( 10):2015-9). Expression of EPOR is regulated by transcription factors Spl, GATA1, and TALI. Binding of EPO to EPOR on erythroid progenitor cells increases expression of transcription factors GATA1 and TALI, that in turn transactivate EPOR expression (Suresh et al., Front Physiol. 2020: 10: 1534). EPOR is also regulated at the protein level. P85 promotes EPOR endocytosis and degradation. Prolyl hydroxylase D3 (PHD3) mediatesAttorney Docket No. 62379-707601proline hydroxylation of EPOR leading to proteasomal degradation. TFR2 and Scribble facilitate recycling of EPOR recycling (Bhoopalan et al., FlOOORes. 2020; 9: F1000 Faculty Rev-1153).

[0146] It was recently found that EPOR plays a critical role in the induction of tumor immune tolerance by myeloid cells, including dendritic cells (DCs) and macrophages (MΦs) in a wide range of primary and metastatic tumors, including liver metastasis-induced systemic antigen-specific immune tolerance. Moreover, EPOR is indispensable in myeloid cell-mediated tolerance in transplantation of allogeneic organs such as kidney, liver, lung, heart, etc.Definitions

[0147] Unless defined otherwise or clearly indicated otherwise by their use herein, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which this application belongs.

[0148] As used in the specification and the appended claims, the indefinite articles “a” and “an” and the definite article “the” can include plural referents as well as singular referents unless specifically stated otherwise or the context clearly indicates otherwise.

[0149] The term “about” or “approximately” means an acceptable error for a particular value as determined by one of ordinary skill in the art, which depends in part on how the value is measured or determined. In certain embodiments, the term “about” or “approximately” means within one standard deviation. In some embodiments, when no particular margin of error (e.g., a standard deviation to a mean value given in a chart or table of data) is recited, the term “about” or “approximately” means that range which would encompass the recited value and the range which would be included by rounding up or down to the recited value as well, taking into account significant figures. In certain embodiments, the term “about” or “approximately” means within ± 10%, 5%, 4%, 3%, 2% or 1% of the specified value.Whenever the term “about” or “approximately” precedes the first numerical value in a series of two or more numerical values or in a series of two or more ranges of numerical values, the term “about” or “approximately” applies to each one of the numerical values in that series of numerical values or in that series of ranges of numerical values.

[0150] The term “antibody” can refer to a protein functionally defined as a binding protein and structurally defined as comprising an amino acid sequence that is recognized as being derived from the framework region of an immunoglobulin (Ig) encoding gene. An antibody can comprise one or more polypeptides substantially encoded by immunoglobulin genes or fragments of immunoglobulin genes. The recognized immunoglobulin genes can include the kappa, lambda, alpha, gamma, delta, epsilon and mu constant region genes, as well as myriad immunoglobulin variable region genes. Light chains can be classified as either kappa or lambda. Heavy chains can be classified as gamma, mu, alpha, delta, or epsilon, which in turn define the immunoglobulin classes, IgG, IgM, IgA, IgD and IgE, respectively. In some embodiments, these may be further divided into subclasses (isotypes), e.g, IgGl, IgG2, IgG3, IgG4, IgAl and IgA2.

[0151] A typical gamma immunoglobulin (antibody) structural unit is known to comprise a tetramer. Each tetramer can be composed of two identical pairs of polypeptide chains, each pair having one "light"Attorney Docket No. 62379-707601(about 25 kD) and one "heavy" chain (about 50-70 kD). The N-terminus of each chain can define a variable region of about 100 to 110 or more amino acids primarily responsible for antigen recognition. The terms variable light chain (VL) and variable heavy chain (VH) can refer to these light and heavy chains respectively.

[0152] Antibodies can exist as intact immunoglobulins or as a number of well-characterized fragments. Thus, for example, pepsin can digest an antibody below the disulfide linkages in the hinge region to produce F(ab)'2, a dimer of Fab' which itself is naturally a light chain joined to VH-CHl-Hinge by a disulfide bond. The F(ab)'2 may be reduced under mild conditions to break the disulfide linkage / s in the hinge region thereby converting the (Fab')2 dimer into an Fab' monomer. The Fab' monomer is essentially a Fab with part of the hinge region (see, Fundamental Immunology, W. E. Paul, ed., Raven Press, N. Y. (1993), for a more detailed description of other antibody fragments). While various antibody fragments are defined in terms of the digestion of an intact antibody, one of skill in the art will appreciate that fragments can be synthesized de novo either chemically or by utilizing recombinant DNA methods. Thus, the term antibody, as used herein can also include antibody fragments either produced by the modification of whole antibodies or synthesized using recombinant DNA methodologies. Preferred antibodies can include VH-VL dimers, including single chain antibodies (antibodies that exist as a single polypeptide chain), such as single chain Fv antibodies (sFv or scFv) in which a variable heavy and a variable light region are joined together (directly or through a peptide linker) to form a continuous polypeptide. The single chain Fv antibody is a covalently linked VH-VL heterodimer which may be expressed from a nucleic acid including VH- and VL-encoding sequences either joined directly or joined by a peptide-encoding linker (e.g., Huston, et al. Proc. Nat. Acad. Sci. USA, 85:5879-5883, 1988, which is hereby incorporated by reference in its entirety). While the VH and VL are connected to each as a single polypeptide chain, the VH and VL domains associate non-covalently. Alternatively, the antibody can be another fragment. Other fragments can also be generated, including using recombinant techniques. For example Fab molecules can be displayed on phage if one of the chains (heavy or light) is fused to g3 capsid protein and the complementary chain exported to the periplasm as a soluble molecule. The two chains can be encoded on the same or on different replicons; the two antibody chains in each Fab molecule assemble post-translationally and the dimer is incorporated into the phage particle via linkage to one of the chains of g3p (see, e.g., U. S. Pat. No: 5,733,743, which is hereby incorporated by reference in its entirety). The scFv antibodies and a number of other structures converting the naturally aggregated, but chemically separated light and heavy polypeptide chains from an antibody V region into a molecule that folds into a three dimensional structure substantially similar to the structure of an antigen-binding site are known to those of skill in the art (see, e.g., U. S. Pat. Nos. 5,091,513, 5,132,405, and 4,956,778, all of which are hereby incorporated by reference in their entirety). Particularly preferred antibodies can include all those that have been displayed on phage or generated by recombinant technology using vectors where the chains are secreted as soluble proteins, e.g., scFv, Fv, Fab, (Fab')2. Antibodies can also include diabodies and minibodies.

[0153] Antibodies can also include heavy chain dimers, such as antibodies from camelids. Since the VH region of a heavy chain dimer IgG in a camelid does not have to make hydrophobic interactions with aAttorney Docket No. 62379-707601light chain, the region in the heavy chain that normally contacts a light chain is changed to hydrophilic amino acid residues in a camelid. VH domains of heavy-chain dimer IgGs are called VHH domains.

[0154] In camelids, the diversity of antibody repertoire can be determined by the complementary determining regions (CDR) 1, 2, and 3 in the VH or VHH regions. The CDR3 in the camel VHH region can be characterized by its relatively long length averaging 16 amino acids (Muyldermans et al., 1994, Protein Engineering 7(9): 1129, which is hereby incorporated by reference in its entirety). This is in contrast to CDR3 regions of antibodies of many other species. For example, the CDR3 of mouse VH can have an average of 9 amino acids.

[0155] Libraries of camelid-derived antibody variable regions, which maintain the in vivo diversity of the variable regions of a camelid, can be made by, for example, the methods disclosed in U. S. Patent Application publication No. US20050037421, published Feb. 17, 2005, which is hereby incorporated by reference in its entirety.

[0156] The terms “functional fragments,” “antigen-binding portions,” “antigen-binding fragments,” “antigen-binding domains,” or “antibody fragments” can be used interchangeably herein to refer to one or more fragments of an antibody that retain the ability to specifically bind to an antigen. Representative antigen-binding fragments can include, but are not limited to, a Fab, a Fab', a (Fab')2, a Fv, a scFv, a dsFv, a variable heavy domain, a variable light domain, a variable NAR domain, bi-specific scFv, a bi-specific Fab2, a tri-specific Fab3. an AVIMER®, a minibody, a diabody, a maxibody, a camelid, a VHH, an intrabody, fusion proteins comprising an antibody portion (e.g., a domain antibody), a single chain binding polypeptide, a scFv-Fc, or a Fab-Fc.

[0157] In some instances, an antibody or functional fragment thereof can comprise an isolated antibody or functional fragment thereof, a purified antibody or functional fragment thereof, a recombinant antibody or functional fragment thereof, a modified antibody or functional fragment thereof, or a synthetic antibody or functional fragment thereof. It would be understood that the antibodies described herein can be modified as described herein or as known in the art. In some instances, antibodies and functional fragments thereof described herein can be partly or wholly synthetically produced. An antibody or functional fragment thereof can be a polypeptide or protein having a binding domain which can be or can be homologous to an antigen-binding domain. In some instances, an antibody or functional fragment thereof can be produced in an appropriate in vivo animal model and then isolated and / or purified.

[0158] The term “Fc region” can be used to define a C-terminal region of an immunoglobulin heavy chain. The “Fc region” can be a native sequence Fc region or a variant Fc region. The Fc region of an immunoglobulin generally can comprise two constant domains, CH2 and CH3.

[0159] In some instances, the Fc region of an immunoglobulin is important for many important antibody functions (e.g. effector functions), such as antigen-dependent cellular cytotoxicity (ADCC), complement dependent cytotoxicity (CDC), and antibody-dependent cell-mediated phagocytosis (ADCP), result in killing of target cells, albeit by different mechanisms. Accordingly, in some embodiments, the antibodies described herein comprise the variable domains of the invention combined with constant domains comprising different Fc regions, selected based on the biological activities of the antibody for the intended use. In certain instances, Human IgGs, for example, can be classified into four subclasses, IgGl,Attorney Docket No. 62379-707601IgG2, IgG3, and IgG4, and each these of these comprises an Fc region having a unique profile for binding to one or more of Fey receptors (activating receptors FcyRI (CD64), FcyRIIA, FcyRIIC (CD32); FcyRIIIA and FcyRIIIB (CD 16) and inhibiting receptor FcyRIIB), and for the first component of complement (Clq). Human IgGl and IgG3 bind to all Fey receptors; IgG2 binds to FcyRIIAH131, and with lower affinity to FcyRIIAR131FcyRIIIAV158; IgG4 binds to FcyRI, FcyRIIA, FcyRIIB, FcyRIIC, and FcyRIIIAV158; and the inhibitory receptor FcyRIIB has a lower affinity for IgGl, IgG2 and IgG3 than all other Fey receptors. Studies have shown that FcyRI does not bind to IgG2, and FcyRIIIB does not bind to IgG2 or IgG4. Id. In general, with regard to ADCC activity, human IgGl> IgG3»IgG4> IgG2.

[0160] In some embodiments, the antibodies of this disclosure are variants that possess reduced effector functions, which make it a desirable candidate for applications in which certain effector functions (such as complement fixation and ADCC) are unnecessary or deleterious. Such antibodies can have decreased complement-dependent cytotoxicity (CDC), antibody-dependent cell cytotoxicity (ADCC), or antibody dependent cellular phagocytosis (ADCP). In some embodiments, the antibodies of this disclosure are variants that possess increased effector functions for applications in which increased immunogenicity would be beneficial. Such antibodies can have increased CDC, ADCC, or ADCP, or a combination thereof. Non-limiting examples of in vitro assays to assess ADCC activity of a molecule of interest is described in U. S. Pat. No. 5,500,362 and 5,821,337. Alternatively, non-radioactive assays methods may be employed (e.g., ACTI™ and CytoTox 96® non-radioactive cytotoxicity assays). Useful effector cells for such assays include peripheral blood mononuclear cells (PBMC), monocytes, macrophages, and Natural Killer (NK) cells.

[0161] Antibodies can have increased half-lives and improved binding to the neonatal Fc receptor (FcRn) (See e.g., US 2005 / 0014934). Such antibodies can comprise an Fc region with one or more substitutions therein which improve binding of the Fc region to FcRn, and include those with substitutions at one or more ofFc region residues: 238, 256, 265, 272, 286, 303, 305, 307, 311, 312, 317, 340, 356, 360, 362, 376, 378, 380, 382, 413, 424 or 434 according to the EU numbering system (See e.g., U. S. Pat. No. 7,371,826). Other examples of Fc region variants are also contemplated (See e.g., Duncan & Winter, Nature 322:738-40 (1988); U. S. Pat. Nos. 5,648,260 and5,624,821; and WO94 / 29351).

[0162] ‘ ‘Antibodies” can include, but are not limited to, monoclonal antibodies, polyclonal antibodies, chimeric antibodies, bispecific antibodies, multispecific antibodies, heteroconjugate antibodies, humanized antibodies, human antibodies, deimmunized antibodies, mutants thereof, fusions thereof, immunoconjugates thereof, antigen-binding fragments thereof, functional fragments thereof, and / or any other modified configuration of the immunoglobulin molecule that comprises an antigen recognition site of the required specificity, including glycosylation variants of antibodies, amino acid sequence variants of antibodies, and / or covalently modified antibodies.

[0163] An antibody can be a human antibody. A human antibody can be an antibody having an amino acid sequence corresponding to that of an antibody produced by a human and / or has been made using any of the techniques for making human antibodies known in the art or disclosed herein. This definition of a human antibody includes antibodies comprising at least one human heavy chain polypeptide or at least one human light chain polypeptide. One such example is an antibody comprising murine light chain andAttorney Docket No. 62379-707601human heavy chain polypeptides. Human antibodies can be produced using various techniques known in the art. In one embodiment, the human antibody is selected from a phage library, where that phage library expresses human antibodies (Vaughan et al., 1996, Nature Biotechnology, 14:309-314; Sheets et al., 1998, PNAS USA, 95:6157-6162; Hoogenboom and Winter, 1991, J. Mol. Biol., 227:381; Marks et al., 1991, J. Mol. Biol., 222:581). Human antibodies can also be made by introducing human immunoglobulin loci into transgenic animals, e.g., mice in which the endogenous immunoglobulin genes have been partially or completely inactivated. This approach is described in U. S. Pat. Nos. 5,545,807; 5,545,806; 5,569,825; 5,625,126; 5,633,425; and 5,661,016. Alternatively, the human antibody may be prepared by immortalizing human B lymphocytes that produce an antibody directed against a target antigen (such B lymphocytes may be recovered from an subject or may have been immunized in vitro). See, e.g., Cole et al., Monoclonal Antibodies and Cancer Therapy, Alan R. Liss, p. 77 (1985); Boemer et al., 1991, J.Immunol., 147 ( 1): 86-95; and U. S. Pat. No. 5,750,373.

[0164] As used herein, the term “binding specificity” of an antibody or “antibody specificity” can refer to the identity of the antigen to which the antibody binds, preferably to the identity of the epitope to which the antibody binds.

[0165] As used herein, the term “chimeric polynucleotide” can mean that the polynucleotide comprises regions which are wild-type and regions which are mutated. It may also mean that the polynucleotide comprises wild-type regions from one polynucleotide and wild-type regions from another related polynucleotide.

[0166] As used herein, the term “complementarity-determining region” or “CDR” can refer to the art-recognized term as exemplified by Kabat and Chothia. CD Rs are also generally known as hypervariable regions or hypervariable loops (Chothia and Lesk (1987) J Mol. Biol. 196: 901; Chothia et al. (1989) Nature 342: 877; E. A. Kabat et al., Sequences of Proteins of Immunological Interest (National Institutes of Health, Bethesda, Md.) (1987); and Tramontane et al. (1990) J Mol. Biol. 215: 175, all of which are hereby incorporated by reference in their entirety). “Framework region” or “FR” can refer to the region of the V domain that flank the CDRs. The positions of the CDRs and framework regions can be determined using various well known definitions in the art, e.g., Kabat, Chothia, international ImMunoGeneTics database (IMGT), and AbM (see, e.g., Johnson et al., supra; Chothia & Lesk, 1987, Canonical structures for the hypervariable regions of immunoglobulins. J. Mol. Biol. 196, 901-917; Chothia C. et al., 1989, Conformations of immunoglobulin hypervariable regions. Nature 342, 877-883; Chothia C. et al., 1992, structural repertoire of the human VH segments J. Mol. Biol. 227, 799-817; Al-Lazikani et al., J. Mol. Biol 1997, 273(4)). Definitions of antigen combining sites are also described in the following: Ruiz et al., IMGT, the international ImMunoGeneTics database. Nucleic Acids Res., 28, 219-221 (2000); and Lefranc, M.-P. IMGT, the international ImMunoGeneTics database. Nucleic Acids Res. Jan 1;29( l):207-9 (2001); MacCallum et al, Antibody-antigen interactions: Contact analysis and binding site topography, J. Mol. Biol., 262 (5), 732-745 (1996); and Martin et al, Proc. Natl Acad. Sci. USA, 86, 9268-9272 (1989); Martin, et al, Methods Enzymol., 203, 121-153, (1991); Pedersen et al, Immunomethods, 1, 126, (1992); and Rees et al, In Sternberg M. J. E. (ed.), Protein Structure Prediction. Oxford University Press, Oxford, 141-172 1996, all of which are hereby incorporated by reference in their entirety).Attorney Docket No. 62379-707601

[0167] As used herein, the term “affinity” can refer to the equilibrium constant for the reversible binding of two agents and is expressed as binding affinity (KD). In some cases, KD can be represented as a ratio of koff, which can refer to the rate constant for dissociation of an antibody from the antibody or antigen-binding fragment / antigen complex, to kon, which can refer to the rate constant for association of an antibody, an antigen-binding domain, or an antigen-binding fragment to an antigen. Binding affinity may be determined using methods known in the art including, for example, surface plasmon resonance (SPR; Biacore™, real time molecular interaction monitoring system for analysis of affinity and / or kinetics), KinExA™ Biosensor (system for measuring binding affinity KD), scintillation proximity assays, enzyme-linked immunosorbent assay (ELISA), ORIGEN immunoassay (IGEN), fluorescence quenching, fluorescence transfer, yeast display, or any combination thereof. Binding affinity may also be screened using a suitable bioassay. The binding affinity (KD) of an antibody, antigen-binding domain, or antigenbinding fragment herein can be less than 600 nM, 590 nM, 580 nM, 570 nM, 560 nM, 550 nM, 540 nM, 530 nM, 520 nM, 510 nM, 500 nM, 490 nM, 480 nM, 470 nM, 460 nM, 450 nM, 440 nM, 430 nM, 420 nM, 410 nM, 400 nM, 390 nM, 380 nM, 370 nM, 360 nM, 350 nM, 340 nM, 330 nM, 320 nM, 310 nM, 300 nM, 290 nM, 280 nM, 270 nM, 260 nM, 250 nM, 240 nM, 230 nM, 220 nM, 210 nM, 200 nM, 190 nM, 180 nM, 170 nM, 160 nM, 150 nM, 140 nM, 130 nM, 120 nM, 110 nM, 100 nM, 90 nM, 80 nM, 70 nM, 50 nM, 50 nM, 49 nM, 48 nM, 47 nM, 46 nM, 45 nM, 44 nM, 43 nM, 42 nM, 41 nM, 40 nM, 39 nM, 38 nM, 37 nM, 36 nM, 35 nM, 34 nM, 33 nM, 32 nM, 31 nM, 30 nM, 29 nM, 28 nM, 27 nM, 26 nM, 25 nM, 24 nM, 23 nM, 22 nM, 21 nM, 20 nM, 19 nM, 18 nM, 17 nM, 16 nM, 15 nM, 14 nM, 13 nM, 12 nM, 11 nM, 10 nM, 9 nM, 8 nM, 7 nM, 6 nM, 5 nM, 4 nM, 3 nM, 2 nM, 1 nM, 990 pM, 980 pM, 970 pM, 960 pM, 950 pM, 940 pM, 930 pM, 920 pM, 910 pM, 900 pM, 890 pM, 880 pM, 870 pM, 860 pM, 850 pM, 840 pM, 830 pM, 820 pM, 810 pM, 800 pM, 790 pM, 780 pM, 770 pM, 760 pM, 750 pM, 740 pM, 730 pM, 720 pM, 710 pM, 700 pM, 690 pM, 680 pM, 670 pM, 660 pM, 650 pM, 640 pM, 630 pM, 620 pM, 610 pM, 600 pM, 590 pM, 580 pM, 570 pM, 560 pM, 550 pM, 540 pM, 530 pM, 520 pM, 510 pM, 500 pM, 490 pM, 480 pM, 470 pM, 460 pM, 450 pM, 440 pM, 430 pM, 420 pM, 410 pM, 400 pM, 390 pM, 380 pM, 370 pM, 360 pM, 350 pM, 340 pM, 330 pM, 320 pM, 310 pM, 300 pM, 290 pM, 280 pM, 270 pM, 260 pM, 250 pM, 240 pM, 230 pM, 220 pM, 210 pM, 200 pM, 190 pM, 180 pM, 170 pM, or any integer therebetween.

[0168] An antibody can selectively bind to a target if it can bind to a target with greater affinity, avidity, more readily, and / or with greater duration than it binds to other substances. For example, an anti-EPO antibody or functional fragment thereof that selectively binds to an EPO protein is an antibody or functional fragment that can bind this target with greater affinity, avidity, more readily, and / or with greater duration than it binds to a protein that is not an EPO protein.

[0169] As used herein, the term “EPO analog” can refer to a polypeptide having modifications of its polypeptide structure, or polypeptides having shorter, longer, and / or different amino acid sequence compared to wild-type human erythropoietin, and all of which bind with high affinity to the hetero-EPOR or the homo-EPOR. EPO analogs may be antagonists or agonists of the hetero-EPOR or homo-EPOR. EPO analogs may block the activity of the hetero-EPOR or the activity of the homo-EPOR. EPO analogs may activate the hetero-EPOR without activating the homo-EPOR. EPO analogs may activate the homo-Attorney Docket No. 62379-707601EPOR without activating the hetero-EPOR. EPO analogs may inhibit the hetero-EPOR without inhibiting the homo-EPOR. EPO analogs may inhibit the homo-EPOR without inhibiting the hetero-EPOR. In some embodiments, EPO analogs can comprise anti-EPO antibodies, anti-homo-EPOR antibodies, or anti-hetero-EPOR antibodies. In some embodiments, EPO analogs can comprise antagonistic or agonistic anti-EPO antibodies, anti-homo-EPOR antibodies, or anti-hetero-EPOR antibodies.

[0170] Whenever the term “at least” or “greater than” precedes the first numerical value in a series of two or more numerical values, the term “at least” or “greater than” applies to each one of the numerical values in that series of numerical values.

[0171] The term “heterologous” can refer to an amino acid or nucleotide sequence that is not naturally found in association with the amino acid or nucleotide sequence with which it is associated.

[0172] As used herein, the term “immunotherapy” can refer to particular therapies aimed at modulating immune system components, such as antibodies or immunocytes, or by drugs or other agents that stimulate, inhibit or otherwise modulate the immune system. For example, “immunotherapy” can refer to checkpoint inhibitor therapy, adoptive cell therapy and / or autologous or allogeneic CAR T-cell therapy.

[0173] Whenever the term “no more than” or “less than” precedes the first numerical value in a series of two or more numerical values, the term “no more than” or “less than” applies to each one of the numerical values in that series of numerical values.

[0174] The term “polynucleotide” can refer to a polymer composed of nucleotide units.Polynucleotides can include naturally occurring nucleic acids, such as deoxyribonucleic acid (“DNA”) and ribonucleic acid (“RNA”), as well as nucleic acid analogs. Nucleic acid analogs can include those which contain non-naturally occurring bases, nucleotides that engage in linkages with other nucleotides other than the naturally occurring phosphodiester bond, or / and bases attached through linkages other than phosphodiester bonds. Non-limiting examples of nucleotide analogs can include phosphorothioates, phosphorodithioates, phosphorotriesters, phosphoramidates, boranophosphates, methylphosphonates, chiral-methyl phosphonates, 2-O-methyl ribonucleotides, peptide-nucleic acids (PNAs), and the like. Such polynucleotides can be synthesized, e.g., using an automated DNA synthesizer. The term “nucleic acid molecule” can refer to larger polynucleotides. The term “oligonucleotide” can refer to shorter polynucleotides. In certain embodiments, an oligonucleotide can comprise no more than about 50 nucleotides. It is understood that when a nucleotide sequence is represented by a DNA sequence (i.e., A, T, G, C), this also includes an RNA sequence (i.e., A, U, G, C) in which “U” replaces “T”.

[0175] The term “polypeptide” can refer to a polymer composed of natural or / and unnatural amino acid residues, naturally occurring structural variants thereof, or / and synthetic non-naturally occurring analogs thereof, linked via peptide bonds. Synthetic polypeptides can be synthesized, e.g., using an automated polypeptide synthesizer. Polypeptides can also be produced recombinantly in cells expressing nucleic acid sequences that encode the polypeptides. The term “protein” can refer to larger polypeptides. The term “peptide” can refer to shorter polypeptides. In certain embodiments, a peptide can comprise no more than about 50, about 40, or about 30 amino acid residues. Polypeptides can include antibodies and fragments thereof. Conventional notation is used herein to portray polypeptide sequences: the left-handAttorney Docket No. 62379-707601end of a polypeptide sequence is the amino (N)-terminus; the right-hand end of a polypeptide sequence is the carboxyl (C)-terminus.

[0176] Polypeptides can include one or more modifications that may be made during the course of synthetic or cellular production of the polypeptide, such as one or more post-translational modifications, whether or not the one or more modifications are deliberate. Modifications can include, without limitation, glycosylation (e.g., N-linked glycosylation and O-linked glycosylation), lipidation, phosphorylation, sulfation, acetylation (e.g., acetylation of the N-terminus), amidation (e.g., amidation of the C-terminus), hydroxylation, methylation, formation of an intramolecular or intermolecular disulfide bond, formation of a lactam between two side chains, formation of pyroglutamate, carbamylation, and ubiquitination. As another example, a polypeptide can be attached to a natural polymer (e.g., a polysaccharide) or a synthetic polymer (e.g., polyethylene glycol [PEG]), lipidated (e.g., acylated with a C8-C20 acyl group), or labeled with a detectable agent (e.g., a radionuclide, a fluorescent dye or an enzyme). PEGylation can increase the protease resistance, stability and half-life, increase the solubility and reduce the aggregation of the polypeptide.

[0177] The term “conservative substitution” can refer to substitution of an amino acid in a polypeptide with a functionally, structurally or chemically similar natural or unnatural amino acid. In certain embodiments, the following groups each contain natural amino acids that are conservative substitutions for one another:1) Glycine (Gly / G), Alanine (Ala / A);2) Isoleucine (Ile / I), Leucine (Leu / L), Methionine (Met / M), Valine (Val / V);3) Phenylalanine (Phe / F), Tyrosine (Tyr / Y). Tryptophan (Trp / W);4) Serine (Ser / S), Threonine (Thr / T), Cysteine (Cys / C);5) Asparagine (Asn / N), Glutamine (Gln / Q);6) Aspartic acid (Asp / D), Glutamic acid (Glu / E); and7) Arginine (Arg / R), Lysine (Lys / K), Histidine (His / H).

[0178] In further embodiments, the following groups each contain natural amino acids that are conservative substitutions for one another:1) non-polar: Ala, Val, Leu, Ile, Met, Pro (proline / P), Phe, Trp;2) hydrophobic: Val, Leu, Ile, Phe, Tyr, Trp;3) aliphatic: Ala, Val, Leu, Ile;4) aromatic: Phe, Tyr, Trp, His;5) uncharged polar or hydrophilic: Gly, Ala, Pro, Ser, Thr, Cys, Asn, Gin, Tyr (tyrosine may be regarded as a hydrophobic amino acid with a polar side group);6) aliphatic hydroxyl- or sulfhydryl-containing: Ser, Thr, Cys;7) amide -containing: Asn, Gin;8) acidic: Asp, Glu;9) basic: Lys, Arg, His; and10) small: Gly, Ala, Ser, Cys.Attorney Docket No. 62379-707601

[0179] In other embodiments, amino acids may be grouped as set out below:1) hydrophobic: Val, Leu, Ile, Met, Phe, Trp, Tyr;2) aromatic: Phe, Tyr, Trp, His;3) neutral hydrophilic: Gly, Ala, Pro, Ser, Thr, Cys, Asn, Gin;4) acidic: Asp, Glu;5) basic: Lys, Arg, His; and6) residues that influence backbone orientation: Pro, Gly.

[0180] A polypeptide having one or more modifications relative to a parent polypeptide may be called an “analog”, “derivative” or “variant” of the parent polypeptide as appropriate. In some embodiments, a variant can comprise a conservatively modified amino acid sequence variant or a conservatively substituted amino acid sequence. For example, a variant of a polypeptide or an antibody can comprise one or more conservative amino acid substitutions.

[0181] The disclosure encompasses pharmaceutically acceptable salts of polypeptides, including those with a positive net charge, those with a negative net charge, and those with no net charge.

[0182] The term “pharmaceutically acceptable” can refer to a substance (e.g., an active ingredient or an excipient) that is suitable for use in contact with the tissues and organs of a subject without excessive irritation, allergic response, immunogenicity and toxicity, is commensurate with a reasonable benefit / risk ratio, and is effective for its intended use. A “pharmaceutically acceptable” excipient or carrier of a pharmaceutical composition is also compatible with the other ingredients of the composition. The term “Pharmaceutically acceptable” can refer to a material, such as a carrier or diluent, which does not abrogate the biological activity or properties of the compound, and is relatively nontoxic, i.e., the material may be administered to an individual without causing undesirable biological effects or interacting in a deleterious manner with any of the components of the composition in which it is contained. A pharmaceutically acceptable excipient can denote any pharmaceutically acceptable ingredient in a pharmaceutical composition having no therapeutic activity and being non-toxic to the subject administered, such as disintegrators, binders, fillers, solvents, buffers, tonicity agents, stabilizers, antioxidants, surfactants, carriers, diluents, excipients, preservatives or lubricants used in formulating pharmaceutical products. Pharmaceutical compositions can facilitate administration of the compound to an organism and can be formulated in a conventional manner using one or more pharmaceutically acceptable inactive ingredients that facilitate processing of the active compounds into preparations that can be used pharmaceutically. A proper formulation is dependent upon the route of administration chosen and a summary of pharmaceutical compositions can be found, for example, in Remington: The Science and Practice of Pharmacy, Nineteenth Ed (Easton, Pa.: Mack Publishing Company, 1995); Hoover, John E., Remington’s Pharmaceutical Sciences, Mack Publishing Co., Easton, Pennsylvania 1975; Liberman, H. A. and Lachman, L., Eds., Pharmaceutical Dosage Forms, Marcel Decker, New York, N. Y., 1980; and Pharmaceutical Dosage Forms and Drug Delivery Systems, Seventh Ed. (Lippincott Williams & Wilkins 1999), herein incorporated by reference. In some embodiments, pharmaceutical compositions can be formulated by dissolving active substances (e.g., anti-EPOR or anti-CD 131 antibodies described herein) in aqueous solution for injection into disease tissues or disease cells. In some embodiments,Attorney Docket No. 62379-707601pharmaceutical compositions can be formulated by dissolving active substances (e.g., anti-EPOR or anti-CD131 antibodies described herein) in aqueous solution for direct injection into disease tissues or disease cells.

[0183] The term “stringent hybridization conditions” can refer to hybridizing in 50% formamide at 5X SSC at a temperature of 42 °C and washing the filters in 0.2X SSC at 60 °C. (IX SSC is 0.15 M NaCl, 0.015 M sodium citrate.) Stringent hybridization conditions also encompasses low ionic strength and high temperature for washing, for example 0.015 M sodium chloride / 0.0015 M sodium citrate / 0.1% sodium dodecyl sulfate at 50 °C; hybridization with a denaturing agent, such as formamide, for example, 50% (v / v) formamide with 0.1% bovine serum albumin / 0.1% Ficoll / 0.1% polyvinylpyrrolidone / 50 mM sodium phosphate buffer at pH 6.5 with 750 mM sodium chloride, 75 mM sodium citrate at 42 °C; or 50% formamide, 5X SSC (0.75 M NaCl, 0.075 M sodium citrate), 50 mM sodium phosphate (pH 6.8), 0.1% sodium pyrophosphate, 5X Denhardt's solution, sonicated salmon sperm DNA (50 pg / ml), 0.1% SDS, and 10% dextran sulfate at 42 °C, with washes at 42 °C in 0.2X SSC (sodium chloride / sodium citrate) and 50% formamide at 55 °C, followed by a high-stringency wash consisting of 0.1X SSC containing EDTA at 55 °C.

[0184] The term “subject” can refer to an animal, including, but not limited to, a mammal, such as a primate (e.g., a human, a chimpanzee or a monkey), a rodent (e.g., a rat, a mouse, a guinea pig, a gerbil or a hamster), a lagomorph (e.g., a rabbit), a swine (e.g., a pig), an equine (e.g., a horse), a canine (e.g., a dog) or a feline (e.g., a cat). Additional examples of mammals can include, but are not limited to, any member of the mammalian class: humans, non -human primates such as chimpanzees, and other apes and monkey species; farm animals such as cattle, horses, sheep, goats, swine; domestic animals such as rabbits, dogs, and cats; laboratory animals including rodents, such as rats, mice and guinea pigs, and the like. In some cases, the mammal is a human. In some instances, the subject is an adult, a child, or an infant. In some cases, the subject may be an animal. In some cases, an animal may comprise human beings and non-human animals. In one embodiment, a non-human animal may be a non-human mammal described herein. In some instances, the subject is a companion animal. In some instances, the subject is a feline, a canine, or a rodent.

[0185] The term “substantially homologous” or “substantially identical” in the context of two polypeptides or polynucleotides can refer to two or more sequences or subsequences that have at least about 50%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid or nucleic acid residue sequence identity, when compared and aligned for maximum correspondence, as measured using a sequence comparison algorithm or by visual inspection. The terms “substantially homologous” or “substantially identical” can mean at least about 70% amino acid or nucleic acid residue identity. The term “substantially homologous” or “substantially identical” can mean at least about 85% amino acid or nucleic acid residue sequence identity. The substantial homology or identity can exist over a region of the sequences that is at least about 20, 30, 40, 50, 100, 150, or 200 residues in length. The sequences can be substantially homologous or identical over the entire length of either or both comparison biopolymers.Attorney Docket No. 62379-707601

[0186] Optimal alignment of sequences for comparison can be conducted, e.g., by the local homology algorithm of Smith and Waterman, Adv. Appl. Math., 2:482 (1981); by the homology alignment algorithm of Needleman and Wunsch, J. Mol. Biol., 48:443 (1970); by the search for similarity method of Pearson and Lipman, Proc. Natl. Acad. Sci. USA, 85:2444 (1988); by computerized implementations of these algorithms (e.g., GAP, BESTFIT, FASTA, and TFASTA in the Wisconsin Genetics Software Package, Genetics Computer Group, Madison, Wisconsin); or by visual inspection.

[0187] One example of a useful algorithm is PILEUP. PILEUP creates a multiple sequence alignment from a group of related sequences using progressive, pairwise alignments to show relationship and percent sequence identity. It also plots a tree or dendogram showing the clustering relationships used to create the alignment. PILEUP uses a simplification of the progressive alignment method of Feng and Doolittle, J. Mol. Evol., 35:351-360 (1987). The method used is similar to the method described by Higgins and Sharp, CABIOS, 5: 151-153 (1989). The program can align up to about 300 sequences, each having a maximum length of about 5,000 nucleotides or amino acids. The multiple alignment procedure begins with the pairwise alignment of the two most similar sequences, producing a cluster of two aligned sequences. This cluster is then aligned to the next most related sequence or cluster of aligned sequences. Two clusters of sequences are aligned by a simple extension of the pairwise alignment of two individual sequences. The final alignment is achieved by a series of progressive, pairwise alignments. The program is run by designating specific sequences and their amino acid or nucleotide coordinates for regions of sequence comparison and by designating the program parameters. For example, a reference sequence can be compared to other test sequences to determine the percent sequence identity relationship using the following parameters: default gap weight (3.00), default gap length weight (0.10), and weighted end gaps. Another algorithm that is useful for generating multiple alignments of sequences is Clustal W (see, e.g., Thompson et al., Nucleic Acids Research, 22:4673-4680

[1994] ).

[0188] Another 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. This algorithm involves first identifying high scoring sequence pairs (HSPs) by identifying short words of length W in the query sequence, which either match or satisfy some positive-valued threshold score T when aligned with a word of the same length in a database sequence. T is referred to as the neighborhood word score threshold (Altschul 1990). These initial neighborhood word hits act as seeds for initiating searches to find longer HSPs containing them. The word hits are then extended in both directions along each sequence for as far as the cumulative alignment score can be increased. Cumulative scores are calculated using, for nucleotide sequences, the parameters M (reward score for a pair of matching residues; always > 0) and N (penalty score for mismatching residues; always < 0). For amino acid sequences, a scoring matrix is used to calculate the cumulative score. Extension of the word hits in each direction is halted when: the cumulative alignment score falls off by the quantity X from its maximum achieved value; the cumulative score goes to zero or below, due to the accumulation of one or more negative-scoring residue alignments; or the end of either sequence is reached. The BLAST algorithm parameters W, T, and X determine the sensitivity and speed of the alignment. The BLASTNAttorney Docket No. 62379-707601program (for nucleotide sequences) uses as defaults, e.g., a wordlength (W) of 11, an expectation (E) of 10, M = 5, N = -4, and a comparison of both strands. For amino acid sequences, the BLASTP program uses as defaults, e.g., a wordlength (W) of 3, an expectation (E) of 10, and the BLOSUM62 scoring matrix (see Henikoff and Henikoff, Proc. Natl. Acad. Sci. USA, 89:10915

[1989] ).

[0189] In addition to calculating percent sequence identity, the BLAST algorithm also performs a statistical analysis of the similarity between two sequences (see, e.g., Karlin and Altschul, Proc. Natl. Acad. Sci. USA, 90:5873-5787

[1993] ). One measure of similarity provided by the BLAST algorithm is the smallest sum probability [P(N)], which provides an indication of the probability by which a match between two nucleotide or amino acid sequences would occur by chance. In certain embodiments, a polynucleotide is considered similar to a reference sequence if the smallest sum probability in a comparison of the test polynucleotide to the reference polynucleotide is less than about 0.1, 0.01 or 0.001.

[0190] A polypeptide can be substantially homologous or identical to a second polypeptide if the two polypeptides differ only by conservative amino acid substitutions. Two nucleic acid sequences can be substantially homologous or identical if the two polynucleotides hybridize to each other under stringent conditions, or under highly stringent conditions, as described herein.

[0191] The term “therapeutically effective amount” can refer to an amount of a composition or compound that, when administered to a subject, is sufficient to prevent, reduce the risk of developing, delay the onset of, slow the progression or cause regression of the medical condition being treated, or to alleviate to some extent the medical condition or one or more symptoms or complications of that condition. The term “therapeutically effective amount” can also refer to an amount of a composition or compound that is sufficient to elicit the biological or medical response of a cell, tissue, organ, system, animal or human which is sought by a researcher, veterinarian, medical doctor or clinician.

[0192] The terms “treat”, “treating” and “treatment” can include alleviating, ameliorating or abrogating a medical condition or one or more symptoms or complications associated with the condition, alleviating, ameliorating or eradicating one or more causes of the condition, preventing additional symptoms, inhibiting the disease or the condition, e.g., arresting the development of the disease or the condition, relieving the disease or the condition, causing regression of the disease or the condition, relieving a condition caused by the disease or the condition, or stopping the symptoms of the disease or the condition either prophylactically and / or therapeutically. In some embodiments, treating a disease or condition cam comprise reducing the size of disease tissues or disease cells. In some embodiments, treating a disease or a condition in a subject can comprise increasing the survival of a subject. In some embodiments, treating a disease or condition can comprise reducing or ameliorating the severity of a disease, delaying onset of a disease, inhibiting the progression of a disease, reducing hospitalization of or hospitalization length for a subject, improving the quality of life of a subject, reducing the number of symptoms associated with a disease, reducing or ameliorating the severity of a symptom associated with a disease, reducing the duration of a symptom associated with a disease, preventing the recurrence of a symptom associated with a disease, inhibiting the development or onset of a symptom of a disease, or inhibiting of the progression of a symptom associated with a disease. In some embodiments, treating a cancer can comprise reducing the size of tumor or increasing survival of a patient with a cancer. Reference to “treatment” of a medicalAttorney Docket No. 62379-707601condition can include prevention of the condition. The terms “prevent”, “preventing” and “prevention” can include precluding, reducing the risk of developing and delaying the onset of a medical condition or one or more symptoms or complications associated with the condition.Metastatic disease

[0193] Metastatic disease is the leading cause of cancer-related mortality worldwide, with the liver being one of the most frequent sites of metastasis for solid tumors. Colorectal cancer (CRC) and pancreatic ductal adenocarcinoma (PDAC) exhibit particularly high incidences of liver metastasis, affecting over 50% and 75% of patients, respectively. The liver is important in immune tolerance-mediated disease progression, both in the context of primary hepatocellular carcinoma (HCC) and as a secondary site for metastasis from other solid tumors, but the underlying mechanisms driving liver metastasis remain poorly understood.

[0194] The liver is a unique organ that inherently promotes local and systemic immune tolerance to foreign antigens. In the context of liver metastasis, the immune response to tumor antigens presented within the liver leads to systemic suppression of antitumor immunity, enabling primary tumors to evade immunosurveillance and diminishing the efficacy of immune checkpoint blockade (ICB) therapies in both patients and preclinical models. Although the underlying mechanisms are not fully understood, recent studies in tumor-bearing mice with liver metastasis have shown that tumor-specific CD8+ effector T cells undergo apoptosis, while CD4+ regulatory T cells (Tregs) are activated, through interactions with liver macrophages. Lymph node metastasis is a critical event that can trigger the development of tumor-specific Tregs, further facilitating metastatic disease progression. While metastasis-induced immune tolerance is important in disease progression, the upstream mechanisms governing these pathobiological pathways remain insufficiently understood.

[0195] Erythropoietin (EPO), a glycoprotein hormone primarily recognized for its canonical role in stimulating red blood cell production, has recently been found to mediate other biological functions. For instance, EPO promotes efferocytosis in macrophages, a process of ingesting apoptotic cells and debris without triggering an immune response against self-antigens; this is vital for preventing excessive inflammation and autoimmune disease. The analysis of human hepatocellular carcinoma (HCC samples) from The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) databases revealed that elevated EPO expression in tumors is associated with worsened survival, macrovascular invasion, and poorer tumor differentiation by Edmondson-Steiner grading. In addition, EPO binds to its cognate receptor, EPOR, on myeloid cells to induce immune tolerance. As shown in the studies, in the liver this EPO-EPOR signaling axis drives macrophages to acquire an immune-modulatory phenotype, resulting in a non-inflamed (“cold”) tumor microenvironment (TME) that evades both immunosurveillance and ICB therapies (Chiu, et al. Tumor-derived erythropoietin acts as an immunosuppressive switch in cancer immunity. Science. 2025 Apr 25;388(6745):eadr3026. doi:10.1126 / science.adr3026. Epub 2025 Apr 25. PMID: 40273234; PMCID: PMC12110762.). Based on the above, EPO-EPOR signaling can be similarly co-opted to promote liver metastasis and Examples described herein can be used to (i) investigate EPOR+ macrophages as the primary mediators permitting liver metastasis, (ii) assess whether EPO-EPOR signaling in liver metastases drives tumor-specificAttorney Docket No. 62379-707601immune tolerance induction, and (iii) examine the pharmacological inhibition of EPO-EPOR signaling as an effective strategy to prevent, inhibit, reduce or treat liver metastasis. In some embodiments, the EPO-EPOR signaling mechanism can enable metastasis to other organs and tissues in addition to the liver.

[0196] Macrophages are the dominant immune cell population in the liver, with the functional ability to induce both local and systemic immune tolerance to foreign antigens. Studies in hepatocellular carcinoma (HCC) have shown EPO secreted by tumor cells can bind to its cognate receptor (EPOR) on macrophages. This signaling pathway programs macrophages to adopt an immunoregulatory phenotype, contributing to the development of a non-inflamed (“cold”) tumor microenvironment (TME) that can evade immunosurveillance and resist immune checkpoint blockade (ICB) therapies. This EPO-EPOR signaling axis, initially characterized in HCC, can be similarly co-opted for liver metastasis and can promote tumor-specific immune tolerance. In some embodiments, EPOR+macrophages in the liver can play a critical role in the development of liver metastasis. In some embodiments, therapeutic strategies aimed at disrupting the EPO / EPOR signaling pathway can prevent, inhibit, reduce, or treat liver or other metastasis.

[0197] In some embodiments, EPOR+ macrophages can be mediators that permit liver metastasis. Primary tumors remotely activate macrophages in the liver to prime a pre-metastatic niche, enhancing the liver's susceptibility to cancer cell colonization. Examples described herein can be used to investigate the role of EPOR+ macrophages in liver metastasis. In some embodiments, syngeneic liver-tropic PDAC lines, which spontaneously metastasize to the liver following orthotopic injection into the pancreas, can be used to study EPOR+ macrophages in cancer metastasis. In some embodiments, (a) the role of macrophages as gatekeepers in liver metastatic seeding; (b) EPO-EPOR activation in macrophages as a key driver of pre-metastatic niche development in the liver; (c) spatiotemporal changes in macrophage phenotype and cell-cell interactions during pre -metastatic niche formation and early stages of liver metastases; and / or (d) the generalizability of findings from murine tissues to human disease can be studied.

[0198] In some embodiments, metastatic nodules can locally reprogram liver macrophages to promote the expansion of regulatory T cells (Tregs), which then disseminate systemically to foster tumor-specific immune tolerance. In some embodiments, two experimental liver metastasis models can be used to examine: (a) EPO-EPOR signaling at the metastatic site as a driver for immune tolerance induction; (b) macrophages as mediators of metastasis-induced tumor-specific Treg development; and / or (c) liver metastases as an educational hub for Treg development.

[0199] In some embodiments, targeting the EPO / EPOR pathway (e.g., using any compositions described herein) can serve as both a preventive and therapeutic strategy for liver metastasis. In some embodiments, targeting the EPO / EPOR pathway (e.g., using any compositions described herein) can enhance the responsiveness of liver metastasis to ICB therapy. For example, monoclonal antibodies and decoy fusion proteins against EPOR (e.g., engineered EPO trap or EPOR fusion proteins), can be used to investigate: (a) the impact of EPO / EPOR-targeted therapies on liver metastasis incidence and tumor burden; and / or (b) whether ablating EPO / EPOR signaling in macrophages sensitizes tumor-bearing mice with liver metastasis to ICB. In some embodiments, administration of any treatments described herein atAttorney Docket No. 62379-707601various time points — both before and / or after liver metastases — can prevent, inhibit, reduce, and / or treat liver or other metastatic diseases.

[0200] In some embodiments, by applying high-resolution analytical tools to syngeneic liver metastasis models, the critical mechanism(s) enabling tumor liver invasion and tolerance induction can be identified. In some embodiments, novel agents designed to prevent, inhibit, reduce, or even eliminate liver metastases can be used to treat metastatic diseases. In some embodiments, the mechanism responsible for liver metastasis and the agents that target them can be applied broadly to other sites of metastasis.

[0201] In some aspects, provided herein are methods for treating or inhibiting cancer metastasis in a subject in need thereof. In some embodiments, provided herein are methods for inhibiting formation of a pre -metastatic niche in a distant site that is different from a location of a primary tumor. In some embodiments, a distant site can comprise a site that is different from a location of said primary tumor. In some embodiments, a distant site can comprise a tissue that is distinct from a tissue where a primary tumor is located. In some embodiments, provided herein are methods for inhibiting a metastatic nodule growth. In some embodiments, the method can comprise administering a pharmaceutically effective amount of a composition that inhibits or reduces binding of an EPO protein to an EPOR complex. In some embodiments, the method can comprise administering a pharmaceutically effective amount of a composition that inhibits or reduces formation of an EPOR complex. In some embodiments, the method can comprise administering a pharmaceutically effective amount of a composition that inhibits or reduces activation of an EPOR complex on a plurality of macrophages. In some embodiments, the method can comprise administering a pharmaceutically effective amount of a composition that reduces an amount of circulating EPO protein in a subject. In some embodiments, the method can comprise administering a pharmaceutically effective amount of a composition that reduces an expression level of an EPOR complex on a plurality of macrophages.

[0202] In some embodiments, EPOR complex comprises at least two EPOR subunits (e.g., homodimer or homo-EPOR). In some embodiments, EPOR complex can comprise at least one EPOR subunit and at least one CD 131 subunit (e.g., heterodimer or hetero-EPOR). In some embodiments, an EPOR complex can comprise a homo-EPO receptor complex comprising at least two EPOR subunits. In some embodiments, a homo-EPOR complex can comprise two EPOR subunits. In some embodiments, a homo-EPOR complex can consist of two EPOR subunits. In some embodiments, an EPOR complex can comprise a hetero-EPOR complex comprising at least one EPOR subunit and at least one CD 131 subunit. In some embodiments, a hetero-EPOR complex can comprises an EPOR subunit and a CD 131 subunit. In some embodiments, a hetero-EPOR complex can consist of an EPOR subunit and a CD 131 subunit.Anti-EPOR, anti-CD131, and anti-EPO Antibodies

[0203] In some aspects, provided herein, are antibodies, antigen-binding fragments thereof, or functional fragments thereof that can selectively binds to a target. In some embodiments, antibodies, antigen-binding fragments thereof, or functional fragments thereof described herein can bind to an antigen of a target protein or an epitope on an antigen of a target protein.

[0204] In some embodiments, an antibody can be a monospecific antibody and binds a single epitope. For example, a monospecific antibody can have a plurality of immunoglobulin variable domainAttorney Docket No. 62379-707601sequences, each of which binds the same epitope. In some embodiments, an antibody can be a bispecific antibody. A bispecific antibody can have specificity for no more than two antigens. A bispecific antibody can be characterized by a first immunoglobulin variable domain sequence which has binding specificity for a first epitope and a second immunoglobulin variable domain sequence that has binding specificity for a second epitope. In some embodiments, the first and second epitopes can be on the same antigen, e.g., the same protein (or subunit of a multimeric protein). In some embodiments, the first and second epitopes can overlap. In some embodiments, the first and second epitopes do not overlap. In some embodiments, the first and second epitopes can be on different antigens, e.g., different proteins (or different subunits of a multimeric protein). In some embodiments, a bispecific antibody can comprise a heavy chain variable domain sequence and a light chain variable domain sequence which have binding specificity for a first epitope and a heavy chain variable domain sequence and a light chain variable domain sequence which have binding specificity for a second epitope. In some embodiments, a bispecific antibody can comprise a half antibody having binding specificity for a first epitope and a half antibody having binding specificity for a second epitope. In some embodiments, a bispecific antibody can comprise a half antibody, or a fragment thereof, having binding specificity for a first epitope and a half antibody, or a fragment thereof, having binding specificity for a second epitope. In some embodiments, a bispecific antibody can comprise a scFv or a Fab, or fragment thereof, have binding specificity for a first epitope and a scFv or a Fab, or fragment thereof, have binding specificity for a second epitope.

[0205] In some embodiments, an antibody can be a multispecific or multifunctional antibody. For example, a multispecific or multifunctional antibody can comprise a plurality of immunoglobulin variable domains sequences, wherein a first immunoglobulin variable domain sequence of the plurality has binding specificity for a first epitope and a second immunoglobulin variable domain sequence of the plurality has binding specificity for a second epitope. In some embodiments, the first and second epitopes are on the same antigen, e.g., the same protein (or subunit of a multimeric protein). In some embodiments, the first and second epitopes can overlap. In some embodiments, the first and second epitopes may not overlap. In some embodiments, the first and second epitopes can be on different antigens, e.g., different proteins (or different subunits of a multimeric protein). In some embodiments a multispecific antibody can comprise a third, a fourth or a fifth immunoglobulin variable domain. In some embodiments, a multispecific antibody can be a bispecific antibody, a trispecific antibody, or a tetraspecific antibody. In some embodiments, multispecific antibodies can optionally further comprise one or more additional binding domain(s) that selectively bind(s) to an IgE, a FcεRIα, a FcεRII, a tumor associated antigen (FAA), or a combination thereof. Any bispecific or multispecific antibodies described herein can be isolated, purified, recombinant, synthetic, or any combination thereof. A bispecific or mutispecific antibodies described herein can be made via any suitable method and may be recombinant, synthetic, or a combination thereof. In one aspect, provided herein can be a liquid composition or a lyophilized composition comprising one or more of bispecific or multispecific antibodies described herein. In one embodiment, a composition can comprise a population of a bispecific or multispecific antibodies. In another embodiments, a composition can comprise a population of two, three, four, five, six, seven, eight, nine, ten, or more bispecific or multispecific antibodies described above. A bispecific or multispecificAttorney Docket No. 62379-707601antibodies described herein can be utilized in an in vitro assay to, for example, identify and / or purify one or more tumor cell(s) from a mixed culture (e.g., a biological sample such as a biopsy or a blood sample). A bispecific or multispecific antibodies described herein can be utilized in an in vivo animal model to test the therapeutic efficacy of the bispecific or multispecific antibodies against a tumor.

[0206] In some embodiments, an antibody can comprise a diabody, and a single-chain molecule, as well as an antigen-binding fragment of an antibody (e.g, Fab, F(ab’)2, and Fv). For example, an antibody molecule can include a heavy (H) chain variable domain sequence (abbreviated herein as VH), and a light (L) chain variable domain sequence (abbreviated herein as VL). In some embodiments, an antibody can comprise a heavy chain and a light chain (referred to herein as a half antibody. In another example, an antibody can comprise two heavy (H) chain variable domain sequences and two light (L) chain variable domain sequence, thereby forming two antigen-binding sites, such as Fab, Fab’, F(ab’)2, Fc, Fd, Fd’, Fv, single chain antibodies (scFv for example), single variable domain antibodies, diabodies (Dab) (bivalent and bispecific), and chimeric (e.g, humanized) antibodies, which may be produced by the modification of whole antibodies orthose synthesized de novo using recombinant DNA technologies. These functional antibody fragments can retain the ability to selectively bind with their respective antigen. Antibodies and antibody fragments can be from any class of antibodies including, but not limited to, IgG, IgA, IgM, IgD, and IgE, and from any subclass (e.g., IgGl, IgG2, IgG3, and IgG4) of antibodies. A preparation of antibodies can be monoclonal or polyclonal. An antibody can also be a human, humanized, CDR-grafted, or in vitro generated antibody. An antibody can have a heavy chain constant region chosen from, e.g., IgGl, IgG2, IgG3, or IgG4. An antibody can also have a light chain chosen from, e.g., kappa or lambda. The term “immunoglobulin” (Ig) is used interchangeably with the term “antibody” herein.

[0207] Non-limiting examples of antigen-binding fragments of an antibody can include: a Fab fragment (a monovalent fragment consisting of the VL, VH, CL and CHI domains); a F(ab')2 fragment (a bivalent fragment comprising two Fab fragments linked by a disulfide bridge at the hinge region); a Fd fragment consisting of the VH and CHI domains; a Fv fragment consisting of the VL and VH domains of a single arm of an antibody; a diabody (dAb) fragment consisting of a VH domain; a camelid or camelized variable domain; a single chain Fv (scFv) (see, e.g., Bird et al. (1988) Science 242:423-426; and Huston et al. (1988) Proc. Natl. Acad. Sci. USA 85:5879-5883); and a single domain antibody. These antibody fragments can be obtained using conventional techniques known to those with skill in the art, and the fragments can be screened for utility in the same manner as are intact antibodies. For example, a singlechain antibody (scFV) can be engineered (see, for example, Colcher, D. et al. (1999) Ann N Y Acad Sci 880:263-80; and Reiter, Y. (1996) Clin Cancer Res 2:245-52). In some embodiments, a single chain antibody can be dimerized or multimerized to generate multivalent antibodies having specificities for different epitopes of the same target protein. In some embodiments, antibodies can include intact molecules as well as functional fragments thereof. Constant regions of antibodies can be altered or mutated to modify one or more properties of antibodies (e.g., to increase or decrease one or more of: Fc receptor binding, antibody glycosylation, the number of cysteine residues, effector cell function, or complement function). Methods for altering antibody constant regions are known in the art. In some embodiments, antibodies with altered function, e.g., altered affinity for an effector ligand, such as FcR onAttorney Docket No. 62379-707601a cell, or the C 1 component of complement can be produced by replacing at least one amino acid residue in the constant portion of the antibody with a different residue (see, e.g., EP 388,151 Al, U. S. Pat. No. 5,624,821 and U. S. Pat. No. 5,648,260, the contents of all of which are hereby incorporated by reference).

[0208] In some embodiments, antibodies, antigen-binding fragments thereof, or functional fragments thereof described herein can include a non-antibody scaffold. Non-limiting examples of non-antibody scaffolds include Affibodies, Affilins, Anticalins, Atrimers, Avimers, Bicyclic peptides, Cys-knots, DARPins, FN3 scaffolds (e.g., adnectins, centyrins, pronectins, Tn3), Fynomers, Kunitz domains, or OBodies.

[0209] In some embodiments, antibodies, antigen-binding fragments thereof, or functional fragments thereof described herein can be derivatized or linked to another functional molecule (e.g., another peptide or protein). As used herein, a “derivatized” antibody is an antibody that has been modified. Methods of derivatization can include, but are not limited to, the addition of a fluorescent moiety, a radionucleotide, a toxin, an enzyme or an affinity ligand such as biotin. For example, an antibody can be functionally linked to one or more other molecular entities, such as another antibody (e.g., a bispecific antibody or a diabody), a detectable agent, a cytotoxic agent, a pharmaceutical agent, and / or a protein or peptide that can mediate association of the antibody or antibody portion with another molecule (such as a streptavidin core region or a polyhistidine tag) by e.g., chemical coupling, genetic fusion, noncovalent association, or using other methods. One type of derivatized antibody can be produced by crosslinking two or more antibodies (of the same type or of different types, e.g., to create bispecific antibodies). Suitable crosslinkers can include those that are heterobifunctional, having two distinctly reactive groups separated by an appropriate spacer (e.g., m-maleimidobenzoyl-N-hydroxysuccinimide ester) or homobifunctional (e.g., disuccinimidyl suberate). Such linkers are available from Pierce Chemical Company, Rockford, Ill.

[0210] In some embodiments, antibodies can also be single domain antibodies. Single domain antibodies can include antibodies whose complementary determining regions are part of a single domain polypeptide. Non-limiting examples can include heavy chain antibodies, antibodies naturally devoid of light chains, single domain antibodies derived from conventional 4-chain antibodies, engineered antibodies and single domain scaffolds other than those derived from antibodies. Single domain antibodies can be any of the art, or any future single domain antibodies. Single domain antibodies can be derived from any species including, but not limited to mouse, human, camel, llama, fish, shark, goat, rabbit, and bovine. In some embodiments, a single domain antibody can be a naturally occurring single domain antibody known as heavy chain antibody devoid of light chains. Such single domain antibodies are disclosed in WO 94 / 04678, for example. In some embodiments, this variable domain derived from a heavy chain antibody naturally devoid of light chain is known herein as a VHH or nanobody. Such a VHH molecule can be derived from antibodies raised in Camelidae species, for example in camel, llama, dromedary, alpaca and guanaco. Other species besides Camelidae may produce heavy chain antibodies naturally devoid of light chain.

[0211] The VH and VL regions can be subdivided into regions of hypervariability, termed “complementarity determining regions” (CDR), interspersed with regions that are more conserved, termed “framework regions” (FR or FW). The extent of the framework region and CDRs has been preciselyAttorney Docket No. 62379-707601defined by a number of methods (see, Kabat, E. A., etal. (1991) Sequences of Proteins of Immunological Interest, Fifth Edition, U. S. Department of Health and Human Services, NIH Publication No. 91-3242; Chothia, C. et al. (1987) J. Mol. Biol. 196:901-917; and the AbM definition used by Oxford Molecular's AbM antibody modeling software. See, generally, e.g., Protein Sequence and Structure Analysis of Antibody Variable Domains. In: Antibody Engineering Lab Manual (Ed.: Duebel, S. and Kontermann, R., Springer-Verlag, Heidelberg). In some embodiments, CDRs can comprise amino acid sequences within antibody variable regions that confer antigen specificity and binding affinity. In some embodiments, antibodies can have three CDRs in each heavy chain variable region (VH-CDR1, VH-CDR2, and VH-CDR3) and three CDRs in each light chain variable region (VL-CDR1, VL-CDR2, and VL-CDR3). In some embodiments, boundaries of amino acid sequences of a given CDR can be determined using any of a number of known schemes, including those described by Kabat et al. (1991), “Sequences of Proteins of Immunological Interest,” 5th Ed. Public Health Service, National Institutes of Health, Bethesda, MD (“Kabat” numbering scheme), Al-Lazikani et al., (1997) JMB 273,927-948 (“Chothia” numbering scheme).

[0212] Antibodies described herein can be produced recombinantly, for example, using phage display or by using combinatorial methods. Phage display and combinatorial methods for generating antibodies are known in the art (as described in, e.g., Ladner et al. U. S. Patent No. 5,223,409; Kang et al.International Publication No. WO 92 / 18619; Dower et al. International Publication No. WO 91 / 17271; Winter et al. International Publication WO 92 / 20791; Markland et al. International Publication No. WO 92 / 15679; Breitling et al. International Publication WO 93 / 01288; McCafferty et al. International Publication No. WO 92 / 01047; Garrard et al. International Publication No. WO 92 / 09690; Ladner et al. International Publication No. WO 90 / 02809; Fuchs et al. (1991) Bio / Technology 9: 1370-1372; Hay et al. (1992) Hum Antibod Hybridomas 3:81-85; Huse et al. (1989) Science 246:1275-1281; Griffiths et al. (1993) EMBO J 12:725-734; Hawkins et al. (1992) J Mol Biol 226:889-896; Clackson et al. (1991) Nature 352:624-628; Gram et al. (1992) PNAS 89:3576-3580; Garrad et al. (1991) Bio / Technology 9: 1373-1377; Hoogenboom et al. (1991) Nuc Acid Res 19:4133-4137; and Barbas et al. (1991) PNAS 88:7978-7982, the contents of all of which are incorporated by reference herein).

[0213] In some embodiments, antibodies described herein can be fully human antibodies (e.g., antibodies made in a mouse which has been genetically engineered to produce antibodies from a human immunoglobulin sequence), or non-human antibodies, e.g., a rodent (mouse or rat), goat, primate (e.g., monkey), or camel antibodies. In some embodiments, non-human antibodies can be rodent antibodies (mouse or rat antibodies). Methods of producing rodent antibodies are known in the art.

[0214] In some embodiments, antibodies, antigen-binding fragments thereof, or functional fragments thereof described herein can be humanized antibodies or humanized antigen-binding fragments. As used herein, “humanized” antibodies refer to forms of non-human (e.g., murine) antibodies that are specific chimeric immunoglobulins, immunoglobulin chains, or fragments thereof that contain minimal sequence derived from non-human immunoglobulin. In some embodiments, humanized antibodies can be human immunoglobulins (recipient antibody) in which residues from a complementarity determining region (CDR) of the recipient are replaced by residues from a CDR of a non-human species (donor antibody)Attorney Docket No. 62379-707601such as mouse, rat, or rabbit having the desired specificity, affinity, and biological activity. In some embodiments, humanized antibodies can have at least one or two, but generally all three, recipient CD Rs (of heavy and or light immuoglobulin chains) replaced with a donor CDR. In some embodiments, antibodies may be replaced with at least a portion of a non-human CDR or only some of the CDRs may be replaced with non-human CDRs. In some embodiments, a minimal number of CDRs required for binding to the antigen can be replaced. In some embodiments, Fv framework region (FR) residues of the human immunoglobulin are replaced by corresponding non-human residues. Furthermore, humanized antibodies may comprise residues that are found neither in the recipient antibody nor in the imported CDR or framework sequences, but are included to further refine or optimize antibody performance. In general, a humanized antibody can comprise at least one, and typically two, variable domains, in which all or substantially all of the CDR regions correspond to those of a non-human immunoglobulin and all or substantially all of the FR regions are those of a human immunoglobulin consensus sequence. Humanized antibodies optimally also can comprise at least a portion of an immunoglobulin constant region or domain (Fc), typically that of a human immunoglobulin. Antibodies can have Fc regions modified as described in, for example, WO 99 / 58572. Other forms of humanized antibodies have one or more CDRs (one, two, three, four, five, or six) which are altered with respect to the original antibody, which are also termed one or more CDRs “derived from” one or more CDRs from the original antibody. Humanized antibodies can be produced, for example, by modeling the antibody variable domains and producing the antibodies using genetic engineering techniques, such as CDR grafting or CDR substitution, wherein one, two, or all CDRs of an immunoglobulin chain can be replaced. A description of various techniques for the production of humanized antibodies is found, for example, in U. S. Patent 5,225,539; Morrison et al., (1984) Proc. Nafl Acad. Sci. USA 81:6851-55; Whittle et al., (1987) Prot. Eng. 1:499-505; Co et al., (1990) J. Immunol. 148:1149-1154; Co et al., (1992) Proc. Nat'l Acad. Sci. USA 88:2869-2873; Carter et al., (1992) Proc. Nat'l Acad. Sci. USA 89:4285-4289; Routledge et al., (1991) Eur. J. Immunol. 21:2717-2725 and PCT Patent Publication Nos. WO 91 / 09967; WO 91 / 09968 and WO 92 / 113831. For example, human monoclonal antibodies can be generated using transgenic mice carrying the human immunoglobulin genes rather than the mouse system. Splenocytes from these transgenic mice immunized with the antigen of interest can be used to produce hybridomas that secrete human mAbs with specific affinities for epitopes from a human protein (see, e.g., Wood et al. International Application WO 91 / 00906, Kucherlapati et al. PCT publication WO 91 / 10741; Lonberg et al. International Application WO 92 / 03918; Kay et al.International Application 92 / 03917; Lonberg, N. et al. 1994 Nature 368:856-859; Green, L. L. et al. 1994 Nature Genet. 7:13-21; Morrison, S. L. et al. 1994 Proc. Natl. Acad. Sci. USA 81:6851-6855; Bruggeman et al. 1993 Year Immunol 7:33-40; Tuaillon et al. 1993 PNAS 90:3720-3724; Bruggeman et al. 1991 Eur J Immunol 21: 1323-1326). In some embodiments, immunocompetent transgenic mice can be used. In some embodiments, immunocompetent transgenic mice can comprise human antibody heavy chains, human antibody light chains, or combinations thereof. In some embodiments, immunocompetent transgenic mice can comprise human antibody heavy chains, human antibody lamda light chains, human antibody kappa light chains or combinations thereof. In some embodiments, one or more specific amino acids can be substituted, deleted, or added in humanized antibodies. Criteria for selecting amino acidsAttorney Docket No. 62379-707601from the donor are described in US 5,585,089, e.g., columns 12-16 of US 5,585,089, e.g., columns 12-16 of US 5,585,089, the contents of which are hereby incorporated by reference. Other techniques for humanizing antibodies are described in Padlan et al. EP 519596 Al, published on December 23, 1992.

[0215] In some embodiments, antibodies, antigen-binding fragments thereof, or functional fragments thereof described herein can comprise a CDR-grafted scaffold domain. In some embodiments, the scaffold domain can be based on a fibronectin domain, e.g., fibronectin type III domain. In some embodiments, the overall fold of the fibronectin type III (Fn3) domain can be closely related to that of the smallest functional antibody fragment, the variable domain of the antibody heavy chain. There are three loops at the end of Fn3; the positions of BC, DE and FG loops approximately correspond to those of CDR1, 2 and 3 of the VH domain of an antibody. In some embodiments, Fn3 may not have disulfide bonds; and therefore, Fn3 can be stable under reducing conditions, unlike antibodies and their fragments (see, e.g., WO 98 / 56915; WO 01 / 64942; WO 00 / 34784). An Fn3 domain can be modified (e.g., using CDRs or hypervariable loops described herein) or varied, e.g., to select domains that bind to an antigen / marker / cell described herein. In some embodiments, a scaffold domain, e.g., a folded domain, can be based on an antibody, e.g., a “minibody” scaffold created by deleting three beta strands from a heavy chain variable domain of a monoclonal antibody (see, e.g., Tramontane et al., 1994, J Mol.Recognit. 7:9; and Martin et al., 1994, EMBO J. 13:5303-5309). In some embodiments, the minibody can be used to present two hypervariable loops. In some embodiments, the scaffold domain can be a V-like domain (see, e.g., Coia et al. WO 99 / 45110) or a domain derived from tendamistatin, which is a 74 residue, six-strand beta sheet sandwich held together by two disulfide bonds (see, e.g., McConnell and Hoess, 1995, J Mol. Biol. 250:460). For example, the loops of tendamistatin can be modified (e.g., using CDRs or hypervariable loops) or varied, e.g., to select domains that bind to a marker / antigen / cell described herein. Another exemplary scaffold domain is a beta-sandwich structure derived from the extracellular domain of CTLA-4 (see, e.g., WO 00 / 60070). Other exemplary scaffold domains can include, but are not limited to, T-cell receptors, MHC proteins, extracellular domains (e.g., fibronectin Type III repeats, EGF repeats), protease inhibitors (e.g., Kunitz domains, ecotin, BPTI, and so forth), TPR repeats; trifoil structures, zinc finger domains, DNA-binding proteins, particularly monomeric DNA binding proteins, RNA binding proteins, enzymes, e.g., proteases (particularly inactivated proteases), RNase, chaperones, e.g., thioredoxin, and heat shock proteins; and intracellular signaling domains (such as SH2 and SH3 domains). See, e.g., US 20040009530 and US 7,501,121, incorporated herein by reference. In some embodiments, a scaffold domain can be evaluated and chosen, e.g., by one or more of the following criteria: (1) amino acid sequence, (2) sequences of several homologous domains, (3) 3-dimensional structure, and / or (4) stability data over a range of pH, temperature, salinity, organic solvent, oxidant concentration. In some embodiments, the scaffold domain can be a small, stable protein domain, e.g., a protein of less than 100, 70, 50, 40 or 30 amino acids. The domain may include one or more disulfide bonds or may chelate a metal, e.g., zinc.

[0216] In some embodiments, antibodies, antigen-binding fragments thereof, or functional fragments thereof described herein can comprise variable regions, or a portion thereof, e.g., CDRs, generated in a non-human organism (e.g., a rat or mouse). In some embodiments, antibodies, antigen-binding fragmentsAttorney Docket No. 62379-707601thereof, or functional fragments thereof described herein can be chimeric, CDR-grafted, or humanized antibodies. In some embodiments, antibodies, antigen-binding fragments thereof, or functional fragments thereof described herein can be generated in a non-human organism and modified. For example, antibodies, antigen-binding fragments thereof, or functional fragments thereof generated in a non-human organism (e.g., a rat or mouse) can be modified in the variable framework or constant region, to decrease antigenicity and / or immunogenicity in humans. In some embodiments, chimeric antibodies can be produced by recombinant DNA techniques known in the art (see, Robinson et al., International Patent Publication PCT / US86 / 02269; Akira, et al., European Patent Application 184,187; Taniguchi, M., European Patent Application 171,496; Morrison et al., European Patent Application 173,494; Neuberger et al., International Application WO 86 / 01533; Cabilly et al. U. S. Patent No. 4,816,567; Cabilly et al., European Patent Application 125,023; Better et al. (1988 Science 240:1041-1043); Liu et al. (1987) PNAS 84:3439-3443; Liu et al., 1987, J. Immunol. 139:3521-3526; Sun et al. (1987) PNAS 84:214-218; Nishimura et al., 1987, Cane. Res. 47:999-1005; Wood et al. (1985) Nature 314:446-449; and Shaw et al., 1988, J. Natl Cancer Inst. 80:1553-1559).

[0217] In some embodiments, antibodies, antigen-binding fragments thereof, or functional fragments thereof described herein that can selectively binds to an antigen of a target protein or an epitope on an antigen of a target protein. In some embodiments, the target can comprise an erythropoietin (EPO) protein, an EPO receptor subunit of a homo-EPOR or a hetero-EPOR, a CD 131 subunit of a hetero-EPOR, or a combination thereof. In some embodiments, the target can comprise a homo-EPOR complex comprising two EPOR subunits, or a hetero-EPOR complex comprising an EPOR subunit and a CD 131 subunit. For example, antibodies, antigen-binding fragments thereof, or functional fragments thereof described herein can selectively binds to a hetero-EPOR complex comprising an EPOR subunit and a CD131 subunit. In this embodiment, antibodies, antigen-binding fragments thereof, or functional fragments thereof described herein can bind to an EPOR subunit and / or a CD 131 subunit of a hetero-EPOR complex. In some embodiments, antibodies, antigen-binding fragments thereof, or functional fragments thereof described herein can be non-naturally occurring. In some embodiments, antibodies, antigen-binding fragments thereof, or functional fragments thereof described herein can be isolated and / or purified. In some embodiments, antibodies, antigen-binding fragments thereof, or functional fragments thereof described herein can be used in in vitro assays (e.g., binding assays, functional assays, etc.).

[0218] In some embodiments, antibodies or functional fragments thereof described herein can bind to a target and can act as an antagonist. In one example, an anti-EPO antibody can bind an EPO protein and can prevent, inhibit, or reduce formation of a complex between an EPO protein and an EPOR complex. In another example, an anti-EPOR antibody can bind an EPO receptor subunit and can prevent, inhibit, or reduce complex formation of an EPOR complex or complex formation between an EPO protein and an EPOR complex. In some embodiments, preventing, inhibiting, or reducing complex formation of a homo-EPOR or complex formation between an EPO protein and an EPOR complex can lead to prevention, inhibition, or reduction of EPOR activation or function. In some embodiments, an anti-EPO antibody can bind an EPO protein and inhibit or decrease the level of an activity of an EPOR without affecting binding of the EPO protein to the EPOR. In some embodiments, an anti-EPOR antibody can bind to an EPOR andAttorney Docket No. 62379-707601inhibit or decrease the level of an activity of the EPOR without affecting the complex formation of the EPOR or complex formation between an EPO protein and the EPOR.

[0219] In some embodiments, an EPOR activity can include, but are not limited to, phosphorylation of an intracellular domain of an EPOR, Janus tyrosine kinase 2 (Jak2), or Signal transducer and activator of transcription 5 (Stat5). In some embodiments, an EPOR activity can include, but are not limited to, activation of Jak2, Jak2 pathway, Stat5 pathway, mitogen-activated protein kinase (MAPK), MAPK pathway, extracellular signal-regulated kinase (ERK), ERK pathway, phosphatidylinositol 3-kinase (PI3K), PI3K pathway, v-Akt Murine Thymoma Viral Oncogene / Protein Kinase-B (Akt / PKB), Akt / PKB pathway, Mammalian Target of rapamycin (mTOR), or mTOR pathway. In some embodiments, antibodies or functional fragments thereof described herein can inhibit activation or phosphorylation of homo-EPOR, hetero-EPOR, Jak2, Stat5, MAPK, ERK, PI3K, Akt / PKB, or mTOR. In some embodiments, antibodies or functional fragments thereof described herein can inhibit activation of Jak2, Jak2 pathway, Stat5, Stat5 pathway, MAPK, MAPK pathway, ERK, ERK pathway, PI3K, PIK3 pathway, Akt / PKB, Akt / PKB pathway, mTOR, or mTOR pathway. In some embodiments, antibodies or functional fragments thereof described herein can promote activation or phosphorylation of EPOR, Jak2, Stat5, or mTOR. In some embodiments, antibodies or functional fragments thereof described herein can promote activation of Jak2, Jak2 pathway, Stat5, Stat5 pathway, MAPK, MAPK pathway, ERK, ERK pathway, PI3K, PIK3 pathway, Akt / PKB, Akt / PKB pathway, mTOR, or mTOR pathway. In some embodiments, antibodies or functional fragments thereof described herein may not affect activation or phosphorylation of EPOR, Jak2, Stat5, MAPK, ERK, PI3K, Akt / PKB, or mTOR. In some embodiments, antibodies or functional fragments thereof described herein may not affect activation of Jak2, Jak2 pathway, Stat5, Stat5 pathway, MAPK, MAPK pathway, ERK, ERK pathway, PI3K, PIK3 pathway, Akt / PKB, Akt / PKB pathway, mTOR, or mTOR pathway. In some embodiments, activation or phosphorylation of EPOR, Jak2, Stat5, MAPK, ERK, PI3K, Akt / PKB, or mTOR can be measured using any methods known in the art. Examples of methods to measure Jak2, Stat5, MAPK, ERK, PI3K, Akt / PKB, or mTOR activation level include, but are not limited to, western blotting, a flow cytometry assay, a cell proliferation assay, an apoptosis assay, or enzyme-linked immunosorbent assay (ELISA).

[0220] In some embodiments, anti -EPO antibodies, anti -EPOR antibodies, anti-CD131 antibodies, or functional fragments thereof described herein can bind to a target and can act as antagonists for an EPOR comprising an EPOR subunit and a CD 131 subunit. In some embodiments, anti -EPO antibodies, anti-EPOR antibodies, anti-CD131 antibodies, or functional fragments thereof described herein can be antagonists for an EPOR comprising an EPOR subunit and a CD 131 subunit and can selectively bind the EPOR and have binding specificity or selectivity for the EPOR. In some embodiments, anti-EPO antibodies, anti -EPOR antibodies, anti-CD131 antibodies, or functional fragments thereof can be antagonists for an EPOR comprising an EPOR subunit and a CD 131 subunit and can have a higher binding affinity, specificity, or selectivity to the EPOR than to an EPOR comprising two EPOR subunits. For example, anti-EPO antibodies, anti -EPOR antibodies, anti-CD131 antibodies, or functional fragments thereof described herein can be antagonists for an EPOR comprising an EPOR subunit and a CD 131 subunit and can have an EPOR binding affinity, specificity, or selectivity that is higher than a bindingAttorney Docket No. 62379-707601affinity, specificity, or selectivity for an EPOR comprising two EPOR subunits. In some embodiments, anti-EPO antibodies, anti -EPOR antibodies, anti-CD131 antibodies, or functional fragments thereof described herein can be antagonists for an EPOR comprising an EPOR subunit and a CD 131 subunit and have an EPOR binding affinity, specificity, or selectivity that is at least about 1%, at least about 2%, at least about 3%, at least about 4%, at least about 5%, at least about 6%, at least about 7%, at least about 8%, at least about 9%, at least about 10%, at least about 11%, at least about 12%, at least about 13%, at least about 14%, at least about 15%, at least about 16%, at least about 17%, at least about 18%, at least about 19%, at least about 20%, at least about 21%, at least about 22%, at least about 23%, at least about 24%, at least about 25%, at least about 26%, at least about 27%, at least about 28%, at least about 29%, at least about 30%, at least about 31%, at least about 32%, at least about 33%, at least about 34%, at least about 35%, at least about 36%, at least about 37%, at least about 38%, at least about 39%, at least about 40%, at least about 41%, at least about 42%, at least about 43%, at least about 44%, at least about 45%, at least about 46%, at least about 47%, at least about 48%, at least about 49%, 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 99% higher than a binding affinity, specificity or selectivity for an EPOR comprising two EPOR subunits.

[0221] In some embodiments, anti-EPO antibodies, anti-EPOR antibodies, or functional fragments thereof described herein can bind to a target and can act as antagonists for an EPOR comprising two EPOR subunits. In some embodiments, anti-EPO antibodies, anti-EPOR antibodies, or functional fragments thereof described herein can be antagonists for an EPOR comprising two EPOR subunits and can selectively bind to homo-EPOR. In some embodiments, anti-EPO antibodies, anti-EPOR antibodies, or functional fragments thereof can be antagonists for an EPOR comprising two EPOR subunits and can have a higher binding affinity to the EPOR than to an EPOR comprising an EPOR subunit and a CD 131 subunit. For example, anti-EPO antibodies, anti-EPOR antibodies, or functional fragments thereof described herein can be antagonists for an EPOR comprising two EPOR subunits and can have an EPOR binding affinity, specificity, or selectivity that is higher than a binding affinity, specificity, or selectivity for an EPOR comprising an EPOR subunit and a CD 131 subunit. In some embodiments, anti-EPO antibodies, anti-EPOR antibodies, or functional fragments thereof described herein can be antagonists for an EPOR comprising two EPOR subunits and have an EPOR binding affinity, specificity, or selectivity that is at least about 1%, at least about 2%, at least about 3%, at least about 4%, at least about 5%, at least about 6%, at least about 7%, at least about 8%, at least about 9%, at least about 10%, at least about 11%, at least about 12%, at least about 13%, at least about 14%, at least about 15%, at least about 16%, at least about 17%, at least about 18%, at least about 19%, at least about 20%, at least about 21%, at least about 22%, at least about 23%, at least about 24%, at least about 25%, at least about 26%, at least about 27%, at least about 28%, at least about 29%, at least about 30%, at least about 31%, at least about 32%, at least about 33%, at least about 34%, at least about 35%, at least about 36%, at least about 37%, at least about 38%, at least about 39%, at least about 40%, at least about 41%, at least about 42%, at least about 43%, at least about 44%, at least about 45%, at least about 46%, at least about 47%, at least about 48%, at least about 49%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least aboutAttorney Docket No. 62379-70760170%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or at least about 99% higher than a binding affinity, specificity or selectivity for an EPOR comprising an EPOR subunit and a CD 131.

[0222] In some aspects, antibodies described herein have specificity for EPO, hetero-EPOR, or homo-EPOR and include all the forms described above. The antibody can be engineered for use in a particular organism. The organism can be a human, canine, or a commercially valuable livestock, such as, for example, pigs, horses, dogs, cats, chickens, or other birds. Such engineering of the antibody can include, for example, CDR splicing, humanization, humaneering, chimerization, or isolating human (or other organism) antibodies using any of the repertoire technologies or monoclonal technologies known in the art.

[0223] Certain examples of antibodies with alternative scaffolds can include, but are not limited to, nanobodies, affibodies, microbodies, evibodies, and domain antibodies. Certain examples of alternative scaffolds useful for creating antibodies can include, but are not limited to, single domain antibodies from camelids; protease inhibitors; human serum transferrin; CTLA-4; fibronectin, including, but not limited to, the fibronectin type III domain; C-type lectin-like domains; lipocalin family proteins; ankyrin repeat proteins; the Z-domain of Protein A; gamma-crystallin; Tendamistat; Neocarzinostatin; CBM4-2; the T-cell receptor; Im9; designed AR proteins; designed TPR proteins; zinc finger domains; pVIII; Avian Pancreatic Polypeptide; GCN4; WW domains; Src Homology 3 (SH3) domains; Src Homology 2 (SH2) domains; PDZ domains; TEM-1 beta-lactamase; GFP; Thioredoxin; Staphylcoccal nuclease; PHD-finger domains; CI-2; BPTI; APPI; HPSTI; Ecotin; LACI-D1; LDTI; MTI-II; scorpion toxins; Insect Defensin A Peptide; EETI-II; Min-23; CBD; PBP; Cytochrome b Transferrin; LDL Receptor Domain A; and ubiquitin. Certain examples of alternative scaffolds are discussed in Hey et al., “Artificial, non-antibody binding proteins for pharmaceutical and industrial applications” Trends in Biotechnology, 23:514-22 (2005) and Binz et al., “Engineering novel binding proteins from nonimmunoglobulin domains” Nature Biotechnology, 23: 1257-68 (2005), both of which are incorporated by reference in their entirety for all purposes.

[0224] A bispecific or bifiinctional antibody can comprise two different heavy / light chain pairs and two different binding sites. Bispecific antibodies may be produced by a variety of methods including, but not limited to, fusion of hybridomas or linking of Fab’ fragments. See, e.g., Songsivilai & Lachmann Clin. Exp. Immunol 79: 315-321 (1990), Kostelny et al. J. Immunol. 148:1547-1553 (1992), which is incorporated by reference in its entirety for all purposes.

[0225] Bispecific antibody molecules can be classified into five different structural groups: (i) bispecific immunoglobulin G (BsIgG); (ii) IgG appended with an additional antigen-binding moiety; (iii) bispecific antibody fragments; (iv) bispecific fusion proteins; and (v) bispecific antibody conjugates. BsIgG is a format that is monovalent for each antigen. Exemplary BsIgG formats include but are not limited to crossMab, DAF (two-in-one), DAF (four-in-one), DutaMab, DT-IgG, knobs-in-holes common LC, knobs-in-holes assembly, charge pair, Fab-arm exchange, SEEDbody, triomab, LUZ-Y, Fcab, KA-body, orthogonal Fab. See Spiess et al. Mol. Immunol. 67(2015): 95 -106. Exemplary BsIgGs includeAttorney Docket No. 62379-707601catumaxomab (Fresenius Biotech, Trion Pharma, Neopharm), which contains an anti-CD3 arm and an anti-EpCAM arm; and ertumaxomab (Neovii Biotech, Fresenius Biotech), which targets CD3 and HER2. In some embodiments, BsIgG comprises heavy chains that are engineered for heterodimerization. For example, heavy chains can be engineered for heterodimerization using a “knobs-into-holes” strategy, a SEED platform, a common heavy chain (e.g., in KA-bodies). and use of heterodimeric Fc regions. See Spiess et al. Mol. Immunol. 67(2015):95-106. Strategies that have been used to avoid heavy chain pairing of homodimers in BsIgG include knobs-in-holes, duobody, azymetric, charge pair, HA-TF, SEEDbody, and differential protein A affinity. See Id. BsIgG can be produced by separate expression of the component antibodies in different host cells and subsequent purification / assembly into a BsIgG. BsIgG can also be produced by expression of the component antibodies in a single host cell. BsIgG can be purified using affinity chromatography, e.g., using protein A and sequential pH elution. IgG appended with an additional antigen-binding moiety is another format of bispecific antibody molecules. For example, monospecific IgG can be engineered to have bispecificity by appending an additional antigenbinding unit onto the monospecific IgG, e.g., at the N- or C- terminus of either the heavy or light chain. Exemplary additional antigen-binding units include single domain antibodies (e.g., variable heavy chain or variable light chain), engineered protein scaffolds, and paired antibody variable domains (e.g., single chain variable fragments or variable fragments). See Id. Examples of appended IgG formats include dual variable domain IgG (DVD-Ig), IgG(H)-scFv, scFv-(H)IgG, IgG(L)-scFv, scFv-(L)IgG, IgG(L, H)-Fv, IgG(H)-V, V(H)-IgG, IgG(L)-V, V(L)-IgG, KIH IgG-scFab, 2scFv-IgG, IgG-2scFv, scFv4-Ig, zybody, and DVI-IgG (four-in-one). See Spiess et al. Mol. Immunol. 67(2015):95-106. An example of an IgG-scFv is MM-141 (Merrimack Pharmaceuticals), which binds IGF-1R and HER3. Examples of DVD-Ig include ABT-981 (AbbVie), which binds IL-la and IL- IP; and ABT-122 (AbbVie), which binds TNF and IL-17A.

[0226] Bispecific antibody fragments (BsAb) are a format of bispecific antibody molecules that lack some or all of the antibody constant domains. For example, some BsAb lack an Fc region. In some embodiments, bispecific antibody fragments include heavy and light chain regions that are connected by a peptide linker that permits efficient expression of the BsAb in a single host cell. Exemplary bispecific antibody fragments include but are not limited to nanobody, nanobody-HAS, BiTE, Diabody, DART, TandAb, scDiabody, scDiabody-CH3, Diabody-CH3, triple body, miniantibody, minibody, TriBi minibody, scFv-CH3 KIH, Fab-scFv, scFv-CH-CL-scFv, F(ab’)2, F(ab’)2-scFv2, scFv-KIH, Fab-scFv-Fc, tetravalent HCAb, scDiabody-Fc, Diabody-Fc, tandem scFv-Fc, and intrabody. For example, the BiTE format comprises tandem scFvs, where the component scFvs bind to CD3 on T cells and a surface antigen on cancer cells. Bispecific fusion proteins include antibody fragments linked to other proteins, e.g., to add additional specificity and / or functionality. An example of a bispecific fusion protein is an immTAC, which comprises an anti-CD3 scFv linked to an affinity-matured T-cell receptor that recognizes HLA-presented peptides. In some embodiments, the dock-and-lock (DNL) method can be used to generate bispecific antibody molecules with higher valency. Also, fusions to albumin binding proteins or human serum albumin can be extend the serum half-life of antibody fragments. In some embodiments, chemicalAttorney Docket No. 62379-707601conjugation, e.g., chemical conjugation of antibodies and / or antibody fragments, can be used to create BsAb molecules. An exemplary bispecific antibody conjugate includes the CovX-body format, in which a low molecular weight drug is conjugated site-specifically to a single reactive lysine in each Fab arm or an antibody or fragment thereof. In some embodiments, the conjugation improves the serum half-life of the low molecular weight drug. An exemplary CovX-body is CVX-241 (NCT01004822), which comprises an antibody conjugated to two short peptides inhibiting either VEGF or Ang2. In some instances, bispecific antibodies can further comprise a linker. In some instances, bispecific antibodies can further comprise a Fc domain. The Fc domain can be, for example, a human IgGl Fc domain. The Fc domain can comprise a knob-in-hole. In some instances, bispecific antibodies can further comprise a linker and an Fc domain. In some embodiments, a linker can be a peptide linker. Non-limiting examples of peptide linkers can include (GS)n(SEQ ID NO: 73), (GGS)n(SEQ ID NO: 74), (GGGS)n(SEQ ID NO: 75), (GGSG)n (SEQ ID NO: 76), (GGSGG)n(SEQ ID NO: 77), or (GGGGS)n(SEQ ID NO: 78), wherein n can be 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10. For example, a linking peptide can be (GGGGS)3(SEQ ID NO: 79) or (GGGGS)4 (SEQ ID NO: 80). Linkers described herein can be used for multispecific antibodies. In this embodiment, multispecific antibodies can have more than one linker. In this embodiment, the linker can be the same. Alternatively, the linkers can be different.

[0227] The antibody molecules can be produced by recombinant expression, e.g., of at least one or more component, in a host system. Exemplary host systems include eukaryotic cells (e.g., mammalian cells, e.g., CHO or HEK293 cells, or insect cells, e.g., SF9 or S2 cells) and prokaryotic cells (e.g., E. col ). Bispecific antibody molecules can be produced by separate expression of the components in different host cells and subsequent purification / assembly. Alternatively, the antibody molecules can be produced by expression of the components in a single host cell. Purification of bispecific antibody molecules can be performed by various methods such as affinity chromatography, e.g., using protein A and sequential pH elution. In other embodiments, affinity tags can be used for purification, e.g., histidine-containing tag, myc tag, or streptavidin tag.

[0228] In an aspect, an antibody may be part of a conjugate molecule comprising all or part of the antibody and a prodrug. The term “prodrug” refers to a precursor or derivative form of a pharmaceutically active substance. A prodrug can be less cytotoxic to cells compared to the parent drug and capable of being enzymatically activated or converted into the more active cytotoxic parent form. Exemplary prodrugs can include, but are not limited to, phosphate-containing prodrugs, thiophosphate-containing prodrugs, sulfate-containing prodrugs, peptide -containing prodrugs, D-amino acid-modified prodrugs, glycosylated prodrugs, beta-lactam-containing prodrugs, optionally substituted phenoxyacetamide-containing prodrugs and optionally substituted phenylacetamide-containing prodrugs, 5 -fluorocytosine and other 5 -fluorouridine prodrugs which can be converted into a more active cytotoxic free drug. Examples of cytotoxic drugs that can be derivatized into a prodrug form can include, but are not limited to, those cytotoxic agents described above. See, e.g., U. S. Pat. No. 6,702,705.

[0229] In some aspect, an anti-EPOR, anti-CD131, or anti-EPO antibody can comprise an antigenbinding domain or an antigen-binding fragment. In some embodiments, an antigen-binding domain or an antigen-binding fragment can comprise a heavy chain variable region (VH), a light chain variable regionAttorney Docket No. 62379-707601(VL), or a combination thereof. In some embodiments, a heavy chain variable region (VH) can comprise an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VH sequences listed in Table 1-1, 4, 6, 8, 13, 15, or 17. In some embodiments, a VH can comprise an amino acid sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of VH sequences listed in Table 1-1, 4, 6, 8, 13, 15, or 17. In some embodiments, a VH can comprise an amino acid sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of VH sequences listed in Table 1-1, 4, 6, 8, 13, 15, or 17. In some embodiments, a VH can comprise any one of VH sequences listed in Table 1-1, 4, 6, 8, 13, 15, or 17, or a variant thereof. In some embodiments, a VH can comprise an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 3, 147-334, 523-651, 781-916, 3824-3921, 4020-4050, 4088-4245, or 5616-5803. In some embodiments, a VH can comprise an amino acid sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of SEQ ID NOs: 3, 147-334, 523-651, 781-916, 3824-3921, 4020-4050, 4088-4245, or 5616-5803. In some embodiments, a VH can comprise an amino acid sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of SEQ ID NOs: 3, 147-334, 523-651, 781-916, 3824-3921, 4020-4050, 4088-4245, or 5616-5803. In some embodiments, a VH can comprise an amino acid sequence of any one of SEQ ID NOs: 3, 147-334, 523-651, 781-916, 3824-3921, 4020-4050, 4088-4245, or 5616-5803, or a variant thereof. In some embodiments, a variant can comprise a conservatively modified or substituted amino acid sequence variant.

[0230] In some embodiments, a light chain variable region (VL) can comprise an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VL sequences listed in Table 1-1, 4, 6, 8, 13, 15, or 17. In some embodiments, a VL can comprise an amino acid sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%,Attorney Docket No. 62379-70760197%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of VL sequences listed in Table 1-1, 4, 6, 8, 13, 15, or 17. In some embodiments, a VL can comprise an amino acid sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of VL sequences listed in Table 1-1, 4, 6, 8, 13, 15, or 17. In some embodiments, a VL can comprise any one of VL sequences listed in Table 1-1, 4, 6, 8, 13, 15, or 17, or a variant thereof. In some embodiments, a light chain variable region (VL) can comprise an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 4, 335-522, 652-780, 917-1052, 3922-4019, 4051-4087, 4246-4403, or 5804-5991. In some embodiments, a VL can comprise an amino acid sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of SEQ ID NOs: 4, 335-522, 652-780, 917-1052, 3922-4019, 4051-4087, 4246-4403, or 5804-5991. In some embodiments, a VL can comprise an amino acid sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of SEQ ID NOs: 4, 335-522, 652-780, 917-1052, 3922-4019, 4051-4087, 4246-4403, or 5804-5991. In some embodiments, a VL can comprise an amino acid sequence of any one of SEQ ID NOs: 4, 335-522, 652-780, 917-1052, 3922-4019, 4051-4087, 4246-4403, or 5804-5991, or a variant thereof. In some embodiments, a variant can comprise a conservatively modified or substituted amino acid sequence variant.

[0231] In some embodiments, an anti-EPOR, anti-CD131, or anti-EPO antibody can comprise a VH comprising an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VH sequences listed in Table 1-1, 4, 6, 8, 13, 15, or 17 and a VL comprising an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VL sequences listed in Table 1-1, 4, 6, 8, 13, 15, or 17. In some embodiments, an anti-EPOR, anti-CD131, or anti-EPO antibody can comprise a VH comprising an amino acid sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of VH sequences listed in Table 1-1, 4, 6, 8, 13, 15, or 17 and a VL comprising an amino acidAttorney Docket No. 62379-707601sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of VL sequences listed in Table 1-1, 4, 6, 8, 13, 15, or 17. In some embodiments, an anti-EPOR, anti-CD131, or anti-EPO antibody can comprise a VH comprising an amino acid sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of VH sequences listed in Table 1-1, 4, 6, 8, 13, 15, or 17 and a VL comprising an amino acid sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of VL sequences listed in Table 1-1, 4, 6, 8, 13, 15, or 17. In some embodiments, an anti-EPOR, anti-CD131, or anti-EPO antibody can comprise a VH comprising an amino acid sequence of any one of VH sequences listed in Table 1-1, 4, 6, 8, 13, 15, or 17, or a variant thereof and a VL comprising an amino acid sequence of any one of VL sequences listed in Table 1-1, 4, 6, 8, 13, 15, or 17, or a variant thereof. In some embodiments, a variant can comprise a conservatively modified or substituted amino acid sequence variant.

[0232] In some embodiments, an anti-EPOR, anti-CD131, or anti-EPO antibody can comprise a VH comprising an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 3, 147-334, 523-651, 781-916, 3824-3921, 4020-4050, 4088-4245, or 5616-5803 and a VL comprising an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 4, 335-522, 652-780, 917-1052, 3922-4019, 4051-4087, 4246-4403, or 5804-5991. In some embodiments, an anti-EPOR, anti-CD131, or anti-EPO antibody can comprise a VH comprising an amino acid sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of SEQ ID NOs: 3, 147-334, 523-651, 781-916, 3824-3921, 4020-4050, 4088-4245, or 5616-5803 and a VL comprising an amino acid sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of SEQ ID NOs: 4, 335-522, 652-780, 917-1052, 3922-4019, 4051-4087, 4246-4403, or 5804-5991. In some embodiments, an anti-EPOR, anti-CD131, or anti-EPO antibody can comprise a VH comprising an amino acid sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%,Attorney Docket No. 62379-70760183%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of SEQ ID NOs: 3, 147-334, 523-651, 781-916, 3824-3921, 4020-4050, 4088-4245, or 5616-5803 and a VL comprising an amino acid sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of SEQ ID NOs: 4, 335-522, 652-780, 917-1052, 3922-4019, 4051-4087, 4246-4403, or 5804-5991. In some embodiments, an anti-EPOR, anti-CD131, or anti-EPO antibody can comprise a VH comprising an amino acid sequence of any one of SEQ ID NOs: 3, 147-334, 523-651, 781-916, 3824-3921, 4020-4050, 4088-4245, or 5616-5803, or a variant thereof and a VL comprising an amino acid sequence of any one of SEQ ID NOs: 4, 335-522, 652-780, 917-1052, 3922-4019, 4051-4087, 4246-4403, or 5804-5991, or a variant thereof. In some embodiments, a variant can comprise a conservatively modified or substituted amino acid sequence variant.

[0233] In some embodiments, a VH can comprise a VH complementarity determining region 1 (VH-CDR1), a VH-CDR2, or a VH-CDR3. In some embodiments, a VH can comprise a VH complementarity determining region 1 (VH-CDR1), a VH-CDR2, and a VH-CDR3. In some embodiments, VH-CDR1, VH-CDR2, and / or VH-CDR3 can be defined according to Kabat, Chothia, IMGT, AbM, or Contact.

[0234] In some embodiments, a VH-CDR1 can comprise an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VH-CDR1 sequences listed in Table 5, 7, 9, or 18. In some embodiments, a VH-CDR1 can comprise an amino acid sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of VH-CDR1 sequences listed in Table 5, 7, 9, or 18. In some embodiments, a VH-CDR1 can comprise an amino acid sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of VH-CDR1 sequences listed in Table 5, 7, 9, or 18. In some embodiments, a VH-CDR1 can comprise any one of VH-CDR1 sequences listed in Table 5, 7, 9, or 18, or a variant thereof. In some embodiments, a VH-CDR1 can comprise an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 1087-1274, 2215-2343, 2989-3124, or 4668-4825. In some embodiments, a VH-CDR1 can comprise an amino acid sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%,Attorney Docket No. 62379-70760198.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of SEQ ID NOs: 1087-1274, 2215-2343, 2989-3124, or 4668-4825. In some embodiments, a VH-CDR1 can comprise an amino acid sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of SEQ ID NOs: 1087-1274, 2215-2343, 2989-3124, or 4668-4825. In some embodiments, a VH-CDR1 can comprise an amino acid sequence of any one of SEQ ID NOs: 1087-1274, 2215-2343, 2989-3124, or 4668-4825, or a variant thereof. In some embodiments, an anti-EPOR or an anti-CD 131 antibody that binds to EPO receptor subunit, CD 131 subunit, or both subunits of a hetero- EPOR can comprise a VH-CDR1 sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VH-CDR1 sequences listed in Table 5, 7, 9, or 18. In some embodiments, an anti-EPOR or an anti-CD131 antibody that binds to EPO receptor subunit, CD 131 subunit, or both subunits of a hetero-EPOR can comprise a VH-CDR1 sequence at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of VH-CDR1 sequences listed in Table 5, 7, 9, or 18. In some embodiments, an anti-EPOR or an anti-CD131 antibody that binds to EPO receptor subunit, CD 131 subunit, or both subunits of a hetero-EPOR can comprise a VH-CDR1 sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of VH-CDR1 sequences listed in Table 5, 7, 9, or 18. In some embodiments, an anti-EPOR or an anti-CD131 antibody that binds to EPO receptor subunit, CD 131 subunit, or both subunits of a hetero-EPOR can comprise any one of VH-CDR1 sequences listed in Table 5, 7, 9, or 18, or a variant thereof. In some embodiments, a variant can comprise a conservatively modified or substituted amino acid sequence variant.

[0235] In some embodiments, a VH-CDR2 can comprise an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VH-CDR2 sequences listed in Table 5, 7, 9, or 18. In some embodiments, a VH-CDR2 can comprise an amino acid sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of VH-CDR2 sequences listed in Table 5, 7, 9, or 18. In some embodiments, a VH-CDR2 can comprise an amino acid sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%,Attorney Docket No. 62379-70760199%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of VH-CDR2 sequences listed in Table 5, 7, 9, or 18. In some embodiments, a VH-CDR2 can comprise any one of VH-CDR2 sequences listed in Table 5, 7, 9, or 18, or variant thereof. In some embodiments, a VH-CDR2 can comprise an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 1275-1462, 2344-2472, 3125-3260, or 4826-4983. In some embodiments, a VH-CDR2 can comprise an amino acid sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of SEQ ID NOs: 1275-1462, 2344-2472, 3125-3260, or 4826-4983. In some embodiments, a VH-CDR2 can comprise an amino acid sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of SEQ ID NOs: 1275-1462, 2344-2472, 3125-3260, or 4826-4983. In some embodiments, a VH-CDR2 can comprise an amino acid sequence of any one of SEQ ID NOs: 1275-1462, 2344-2472, 3125-3260, or 4826-4983, or a variant thereof. In some embodiments, an anti-EPOR or an anti-CD 131 antibody that binds to EPO receptor subunit, CD 131 subunit, or both subunits of a hetero- EPOR can comprise a VH-CDR2 sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VH-CDR2 sequences listed in Table 5, 7, 9, or 18. In some embodiments, an anti-EPOR or an anti-CD 131 antibody that binds to EPO receptor subunit, CD131 subunit, or both subunits of a hetero-EPOR can comprise a VH-CDR2 sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of VH-CDR2 sequences listed in Table 5, 7, 9, or 18. In some embodiments, an anti-EPOR or an anti-CD 131 antibody that binds to EPO receptor subunit, CD 131 subunit, or both subunits of a hetero-EPOR can comprise a VH-CDR2 sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of VH-CDR2 sequences listed in Table 5, 7, 9, or 18. In some embodiments, an anti-EPOR or an anti-CD131 antibody that binds to EPO receptor subunit, CD 131 subunit, or both subunits of a hetero-EPOR can comprise any one of VH-CDR2 sequences listed in Table 5, 7, 9, or 18, or a variant thereof. In some embodiments, a variant can comprise a conservatively modified or substituted amino acid sequence variant.Attorney Docket No. 62379-707601

[0236] In some embodiments, a VH-CDR3 can comprise an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VH-CDR3 sequences listed in Table 5, 7, 9, 14, 16, or 18. In some embodiments, a VH-CDR3 can comprise an amino acid sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of VH-CDR3 sequences listed in Table 5, 7, 9, 14, 16, or 18. In some embodiments, a VH-CDR3 can comprise an amino acid sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of VH-CDR3 sequences listed in Table 5, 7, 9, 14, 16, or 18. In some embodiments, a VH-CDR3 can comprise any one of VH-CDR3 sequences listed in Table 5, 7, 9, 14, 16, or 18, or a variant thereof. In some embodiments, a VH-CDR3 can comprise an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 1463-1650, 2473-2601, 3261-3396, 4404-4501, 4600-4630, or 4984-5141. In some embodiments, a VH-CDR3 can comprise an amino acid sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of SEQ ID NOs: 1463-1650, 2473-2601, 3261-3396, 4404-4501, 4600-4630, or 4984-5141. In some embodiments, a VH-CDR3 can comprise an amino acid sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of SEQ ID NOs: 1463-1650, 2473-2601, 3261-3396, 4404-4501, 4600-4630, or 4984-5141. In some embodiments, a VH-CDR3 can comprise an amino acid sequence of any one of SEQ ID NOs: 1463-1650, 2473-2601, 3261-3396, 4404-4501, 4600-4630, or 4984-5141, or a variant thereof. In some embodiments, an anti-EPOR or an anti-CD131 antibody that binds to EPO receptor subunit, CD131 subunit, or both subunits of a hetero-EPOR can comprise a VH-CDR3 sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VH-CDR3 sequences listed in Table 5, 7, 9, 14, 16, or 18. In some embodiments, an anti-EPOR or an anti-CD131 antibody that binds to EPO receptor subunit, CD 131 subunit, or both subunits of a hetero-EPOR can comprise a VH-CDR3 sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%,Attorney Docket No. 62379-70760197%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of VH-CDR3 sequences listed in Table 5, 7, 9, 14, 16, or 18. In some embodiments, an anti-EPOR or an anti-CD 131 antibody that binds to EPO receptor subunit, CD 131 subunit, or both subunits of a hetero-EPORcan comprise a VH-CDR3 sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of VH-CDR3 sequences listed in Table 5, 7, 9, 14, 16, or 18. In some embodiments, an anti-EPOR or an anti-CD 131 antibody that binds to EPO receptor subunit, CD 131 subunit, or both subunits of a hetero-EPOR can comprise any one of VH-CDR3 sequences listed in Table 5, 7, 9, 14, 16, or 18, or a variant thereof. In some embodiments, a variant can comprise a conservatively modified or substituted amino acid sequence variant.

[0237] In some embodiments, an anti-EPOR, anti-CD 131, or anti -EPO antibody can comprise a VH-CDR1 sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VH-CDR1 sequences listed in Table 5, 7, 9, or 18, a VH-CDR2 sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VH-CDR2 sequences listed in Table 5, 7, 9, or 18, and a VH-CDR3 sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VH-CDR3 sequences listed in Table 5, 7, 9, 14, 16, or 18. In some embodiments, an anti-EPOR, anti-CD 131, or anti -EPO antibody can comprise any one of VH-CDR1 sequences listed in Table 5, 7, 9, or 18, or a variant thereof, VH-CDR2 sequences listed in Table 5, 7, 9, or 18, or a variant thereof, and VH-CDR3 sequences listed in Table 5, 7, 9, 14, 16, or 18, or a variant thereof. In some embodiments, a variant can comprise a conservatively modified or substituted amino acid sequence variant.

[0238] In some embodiments, an anti-EPOR, anti-CD 131, or anti -EPO antibody can comprise a VH-CDR1 comprising an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 1087-1274, 2215-2343, 2989-3124, or 4668-4825, a VH-CDR2 comprising an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 1275-1462, 2344-2472, 3125-3260, or 4826-4983, and a VH-CDR3 comprising an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%,Attorney Docket No. 62379-70760192%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 1463-1650, 2473-2601, 3261-3396, 4404-4501, 4600-4630, or 4984-5141.

[0239] In some embodiments, an anti-EPOR, anti-CD131, or anti-EPO antibody can comprise a VH- CDR1 comprising an amino acid sequence with at most about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at most about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 1087-1274, 2215-2343, 2989-3124, or 4668- 4825, a VH-CDR2 comprising an amino acid sequence with at most about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at most about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 1275-1462, 2344-2472, 3125-3260, or 4826-4983, and a VH-CDR3 comprising an amino acid sequence with at most about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at most about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 1463-1650, 2473-2601, 3261-3396, 4404-4501, 4600-4630, or 4984-5141.

[0240] In some embodiments, an anti-EPOR, anti-CD131, or anti-EPO antibody can comprise a VH- CDR1 comprising an amino acid sequence with about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 1087-1274, 2215-2343, 2989-3124, or 4668-4825, a VH-CDR2 comprising an amino acid sequence with about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 1275-1462, 2344-2472, 3125-3260, or 4826-4983, and a VH-CDR3 comprising an amino acid sequence with about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 1463-1650, 2473-2601, 3261-3396, 4404-4501, 4600-4630, or 4984-5141.

[0241] In some embodiments, an anti-EPOR, anti-CD131, or anti-EPO antibody can comprise a VH-CDR1 comprising an amino acid sequence of any one of SEQ ID NOs: 1087-1274, 2215-2343, 2989-3124, or 4668-4825, or a variant thereof, a VH-CDR2 comprising an amino acid sequence of any one of SEQ ID NOs: 1275-1462, 2344-2472, 3125-3260, or 4826-4983, or a variant thereof, and a VH-CDR3 comprising an amino acid sequence of any one of SEQ ID NOs: 1463-1650, 2473-2601, 3261-3396, 4404-4501, 4600-4630, or 4984-5141, or a variant thereof. In some embodiments, a variant can comprise a conservatively modified or substituted amino acid sequence variant.Attorney Docket No. 62379-707601

[0242] In some embodiments, a VL can comprise a VL complementarity determining region 1 (VL-CDR1), a VL-CDR2, or a VL-CDR3. In some embodiments, a VL can comprise a VL complementarity determining region 1 (VL-CDR1), a VL-CDR2, and a VL-CDR3. In some embodiments, VL-CDR1, VL-CDR2, and / or VL-CDR3 can be defined according to Kabat, Chothia, IMGT, AbM, or Contact.

[0243] In some embodiments, a VL-CDR1 can comprise an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VL-CDR1 sequences listed in Table 5, 7, 9, or 19. In some embodiments, a VL-CDR1 can comprise an amino acid sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of VL-CDR1 sequences listed in Table 5, 7, 9, or 19. In some embodiments, a VL-CDR1 can comprise an amino acid sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of VL-CDR1 sequences listed in Table 5, 7, 9, or 19. In some embodiments, a VL-CDR1 can comprise any one of VL-CDR1 sequences listed in Table 5, 7, 9, or 19, or a variant thereof. In some embodiments, a VL-CDR1 can comprise an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 1651-1838, 2602-2730, 3397-3532, or 5142-5299. In some embodiments, a VL-CDR1 can comprise an amino acid sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of SEQ ID NOs: 1651-1838, 2602-2730, 3397-3532, or 5142-5299. In some embodiments, a VL-CDR1 can comprise an amino acid sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of SEQ ID NOs: 1651-1838, 2602-2730, 3397-3532, or 5142-5299. In some embodiments, a VL-CDR1 can comprise an amino acid sequence of any one of SEQ ID NOs: 1651-1838, 2602-2730, 3397-3532, or 5142-5299, or a variant thereof. In some embodiments, an anti-EPOR or an anti-CD 131 antibody that binds to EPO receptor subunit, CD 131 subunit, or both subunits of a hetero-EPOR can comprise a VL-CDR1 sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VL-CDR1 sequences listed in Table 5, 7, 9, or 19. In some embodiments, an anti-EPOR or an anti-CD 131 antibody that binds to EPO receptor subunit, CD 131Attorney Docket No. 62379-707601subunit, or both subunits of a hetero-EPOR can comprise a VL-CDR1 sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of VL-CDR1 sequences listed in Table 5, 7, 9, or 19. In some embodiments, an anti-EPOR or an anti-CD131 antibody that binds to EPO receptor subunit, CD 131 subunit, or both subunits of a hetero-EPOR can comprise a VL-CDR1 sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of VL-CDR1 sequences listed in Table 5, 7, 9, or 19. In some embodiments an anti-EPOR or an anti-CD131 antibody can comprise any one of VL-CDR1 sequences listed in Table 5, 7, 9, or 19, or a variant thereof. In some embodiments, a variant can comprise a conservatively modified or substituted amino acid sequence variant.

[0244] In some embodiments, a VL-CDR2 can comprise an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VL-CDR2 sequences listed in Table 5, 7, 9, or 19. In some embodiments, a VL-CDR2 can comprise an amino acid sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of VL-CDR2 sequences listed in Table 5, 7, 9, or 19. In some embodiments, a VL-CDR2 can comprise an amino acid sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of VL-CDR2 sequences listed in Table 5, 7, 9, or 19. In some embodiments, a VL-CDR2 can comprise any one of VL-CDR2 sequences listed in Table 5, 7, 9, or 19, or a variant thereof. In some embodiments, a VL-CDR2 can comprise an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 1839-2026, 2731-2859, 3533-3668, or 5300-5457. In some embodiments, a VL-CDR2 can comprise an amino acid sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of SEQ ID NOs: 1839-2026, 2731-2859, 3533-3668, or 5300-5457. In some embodiments, a VL-CDR2 can comprise an amino acid sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identityAttorney Docket No. 62379-707601or sequence similarity to any one of SEQ ID NOs: 1839-2026, 2731-2859, 3533-3668, or 5300-5457. In some embodiments, a VL-CDR2 can comprise an amino acid sequence of any one of SEQ ID NOs: 1839-2026, 2731-2859, 3533-3668, or 5300-5457, or a variant thereof. In some embodiments, an anti-EPOR or an anti-CD 131 antibody that binds to EPO receptor subunit, CD 131 subunit, or both subunits of a hetero-EPOR can comprise a VL-CDR2 sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VL-CDR2 sequences listed in Table 5, 7, 9, or 19. In some embodiments, an anti-EPOR or an anti-CD 131 antibody that binds to EPO receptor subunit, CD 131 subunit, or both subunits of a hetero-EPOR can comprise a VL-CDR2 sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of VL-CDR2 sequences listed in Table 5, 7, 9, or 19. In some embodiments, an anti-EPOR or an anti-CD 131 antibody that binds to EPO receptor subunit, CD 131 subunit, or both subunits of a hetero-EPOR can comprise a VL-CDR2 sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of VL-CDR2 sequences listed in Table 5, 7, 9, or 19. In some embodiments, an anti-EPOR or an anti-CD131 antibody that binds to EPO receptor subunit, CD 131 subunit, or both subunits of a hetero-EPOR can comprise any one of VL-CDR2 sequences listed in Table 5, 7, 9, or 19, or a variant thereof. In some embodiments, a variant can comprise a conservatively modified or substituted amino acid sequence variant.

[0245] In some embodiments, a VL-CDR3 can comprise an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VL-CDR3 sequences listed in Table 5, 7, 9, 14, 16, or 19. In some embodiments, a VL-CDR3 can comprise an amino acid sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of VL-CDR3 sequences listed in Table 5, 7, 9, 14, 16, or 19. In some embodiments, a VL-CDR3 can comprise an amino acid sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of VL-CDR3 sequences listed in Table 5, 7, 9, 14, 16, or 19. In some embodiments, a VL-CDR3 can comprise any one of VL-CDR3 sequences listed in Table 5, 7, 9, 14, 16, or 19, or a variant thereof. In some embodiments, a VL-CDR3 can comprise an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%,Attorney Docket No. 62379-70760196%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 2027-2214, 2680-2988, 3669-3804, 4502-4599, 4631-4667, or 5458-5615. In some embodiments, a VL- CDR3 can comprise an amino acid sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of SEQ ID NOs: 2027-2214, 2680-2988, 3669-3804, 4502-4599, 4631- 4667, or 5458-5615. In some embodiments, a VL-CDR3 can comprise an amino acid sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of SEQ ID NOs: 2027-2214, 2680-2988, 3669-3804, 4502-4599, 4631-4667, or 5458-5615. In some embodiments, a VL-CDR3 can comprise an amino acid sequence of any one of SEQ ID NOs: 2027-2214, 2680-2988, 3669-3804, 4502-4599, 4631-4667, or 5458-5615, or a variant thereof. In some embodiments, an anti-EPOR or an anti-CD131 antibody that binds to EPO receptor subunit, CD131 subunit, or both subunits of a hetero-EPOR can comprise a VL-CDR3 sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VL-CDR3 sequences listed in Table 5, 7, 9, 14, 16, or 19. In some embodiments, an anti-EPOR or an anti-CD131 antibody that binds to EPO receptor subunit, CD 131 subunit, or both subunits of a hetero-EPOR can comprise a VL-CDR3 sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of VL-CDR3 sequences listed in Table 5, 7, 9, 14, 16, or 19. In some embodiments, an anti-EPOR or an anti-CD 131 antibody that binds to EPO receptor subunit, CD 131 subunit, or both subunits of a hetero- EPORcan comprise a VL-CDR3 sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of VL-CDR3 sequences listed in Table 5, 7, 9, 14, 16, or 19. In some embodiments an anti-EPOR or an anti-CD 131 antibody that binds to EPO receptor subunit, CD 131 subunit, or both subunits of a hetero-EPOR can comprise any one of VL-CDR3 sequences listed in Table 5, 7, 9, 14, 16, or 19, or a variant thereof. In some embodiments, a variant can comprise a conservatively modified or substituted amino acid sequence variant.

[0246] In some embodiments, an anti-EPOR, anti-CD 131, or anti -EPO antibody can comprise a VL-CDR1 sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VL-CDR1 sequences listed in Table 5, 7, 9, or 19, a VL-CDR2 sequence with at least about 100%,Attorney Docket No. 62379-70760199.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VL-CDR2 sequences listed in Table 5, 7, 9, or 19, and a VL-CDR3 sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VL-CDR3 sequences listed in Table 5, 7, 9, 14, 16, or 19. In some embodiments an anti-EPOR antibody or an anti-CD131 antibody can comprise any one of VL-CDR1 sequences listed in Table 5, 7, 9, or 19, or a variant thereof, VL-CDR2 sequences listed in Table 5, 7, 9, or 19, or a variant thereof, and VL-CDR3 sequences listed in Table 5, 7, 9, 14, 16, or 19, or a variant thereof. In some embodiments, a variant can comprise a conservatively modified or substituted amino acid sequence variant.

[0247] In some embodiments, an anti-EPOR, anti-CD131, or anti-EPO antibody can comprise a VL-CDR1 comprising an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 1651-1838, 2602-2730, 3397-3532, or 5142- 5299, a VL-CDR2 comprising an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 1839-2026, 2731-2859, 3533-3668, or 5300-5457, and a VL-CDR3 comprising an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 2027-2214, 2680-2988, 3669-3804, 4502-4599, 4631-4667, or 5458-5615.

[0248] In some embodiments, an anti-EPOR, anti-CD131, or anti-EPO antibody can comprise a VL- CDR1 comprising an amino acid sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of SEQ ID NOs: 1651-1838, 2602-2730, 3397-3532, or 5142-5299, a VL- CDR2 comprising an amino acid sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of SEQ ID NOs: 1839-2026, 2731-2859, 3533-3668, or 5300-5457, and a VL-CDR3 comprising an amino acid sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequenceAttorney Docket No. 62379-707601identity or sequence similarity to any one of SEQ ID NOs: 2027-2214, 2680-2988, 3669-3804, 4502-4599, 4631-4667, or 5458-5615.

[0249] In some embodiments, an anti-EPOR, anti-CD131, or anti-EPO antibody can comprise a VL-CDR1 comprising an amino acid sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of SEQ ID NOs: 1651-1838, 2602-2730, 3397-3532, or 5142-5299, a VL-CDR2 comprising an amino acid sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of SEQ ID NOs: 1839-2026, 2731-2859, 3533-3668, or 5300-5457, and a VL-CDR3 comprising an amino acid sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of SEQ ID NOs: 2027-2214, 2680-2988, 3669-3804, 4502-4599, 4631-4667, or 5458-5615.

[0250] In some embodiments, an anti-EPOR, anti-CD131, or anti-EPO antibody can comprise a VL-CDR1 comprising an amino acid sequence of any one of SEQ ID NOs: 1651-1838, 2602-2730, 3397-3532, or 5142-5299, or a variant thereof, a VL-CDR2 comprising an amino acid sequence of any one of SEQ ID NOs: 1839-2026, 2731-2859, 3533-3668, or 5300-5457, or a variant thereof, and aVL-CDR3 comprising an amino acid sequence of any one of SEQ ID NOs: 2027-2214, 2680-2988, 3669-3804, 4502-4599, 4631-4667, or 5458-5615, or a variant thereof. In some embodiments, a variant can comprise a conservatively modified or substituted amino acid sequence variant.

[0251] In some embodiments, an anti-EPOR, anti-CD131, or anti-EPO antibody can comprise a VH-CDR1 sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VH-CDR1 sequences listed in Table 5, 7, 9, or 18, a VH-CDR2 sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VH-CDR2 sequences listed in Table 5, 7, 9, or 18, a VH-CDR3 sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VH-CDR3 sequences listed in Table 5, 7, 9, 14, 16, or 18, a VL-CDR1 sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VL-CDR1 sequences listed in Table 5, 7, 9, or 19, a VL-CDR2 sequence with atAttorney Docket No. 62379-707601least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VL-CDR2 sequences listed in Table 5, 7, 9, or 19, and a VL-CDR3 sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VL-CDR3 sequences listed in Table 5, 7, 9, 14, 16, or 19. In some embodiments, an anti-EPOR, anti-CD131, or anti-EPO antibody can comprise any one of VH-CDR1 sequences listed in Table 5, 7, 9, or 18, or a variant thereof, VH-CDR2 sequences listed in Table 5, 7, 9, or 18, or a variant thereof, VH-CDR3, VL-CDR1 sequences listed in Table 5, 7, 9, or 19, or a variant thereof, VL-CDR2 sequences listed in Table 5, 7, 9, or 19, or a variant thereof, and VL-CDR3 sequences listed in Table 5, 7, 9, 14, 16, or 19, or a variant thereof. In some embodiments, a variant can comprise a conservatively modified or substituted amino acid sequence variant.

[0252] In some embodiments, an anti-EPOR, anti-CD131, or anti-EPO antibody can comprise a VH-CDR1 comprising an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 1087-1274, 2215-2343, 2989-3124, or 4668-4825, a VH-CDR2 comprising an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 1275-1462, 2344-2472, 3125-3260, or 4826-4983, a VH-CDR3 comprising an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 1463-1650, 2473-2601, 3261-3396, 4404-4501, 4600-4630, or 4984-5141, a VL-CDR1 comprising an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 1651-1838, 2602-2730, 3397-3532, or 5142-5299, a VL-CDR2 comprising an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 1839-2026, 2731-2859, 3533-3668, or 5300-5457, and a VL-CDR3 comprising an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 2027-2214, 2680-2988, 3669-3804, 4502-4599, 4631-4667, or 5458-5615.Attorney Docket No. 62379-707601

[0253] In some embodiments, an anti-EPOR, anti-CD131, or anti-EPO antibody can comprise a VH-CDR1 comprising an amino acid sequence with at most about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at most about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 1087-1274, 2215-2343, 2989-3124, or 4668-4825, a VH-CDR2 comprising an amino acid sequence with at most about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at most about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 1275-1462, 2344-2472, 3125-3260, or 4826-4983, a VH-CDR3 comprising an amino acid sequence with at most about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at most about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 1463-1650, 2473-2601, 3261-3396, 4404-4501, 4600-4630, or 4984-5141, a VL-CDR1 comprising an amino acid sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of SEQ ID NOs: 1651-1838, 2602-2730, 3397-3532, or 5142-5299, a VL-CDR2 comprising an amino acid sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of SEQ ID NOs: 1839-2026, 2731-2859, 3533-3668, or 5300-5457, and a VL-CDR3 comprising an amino acid sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of SEQ ID NOs: 2027-2214, 2680-2988, 3669-3804, 4502-4599, 4631-4667, or 5458-5615.

[0254] In some embodiments, an anti-EPOR, anti-CD131, or anti-EPO antibody can comprise a VH-CDR1 comprising an amino acid sequence with about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 1087-1274, 2215-2343, 2989-3124, or 4668-4825, a VH-CDR2 comprising an amino acid sequence with about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 1275-1462, 2344-2472, 3125-3260, or 4826-4983, a VH-CDR3 comprising an amino acid sequence with about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 1463-1650, 2473-2601, 3261-3396, 4404-4501, 4600-4630, orAttorney Docket No. 62379-7076014984-5141, a VL-CDR1 comprising an amino acid sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of SEQ ID NOs: 1651-1838, 2602-2730, 3397-3532, or 5142-5299, a VL-CDR2 comprising an amino acid sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of SEQ ID NOs: 1839-2026, 2731-2859, 3533-3668, or 5300-5457, and a VL-CDR3 comprising an amino acid sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%;84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of SEQ ID NOs: 2027-2214, 2680-2988, 3669-3804, 4502-4599, 4631-4667, or 5458-5615.

[0255] In some embodiments, an anti-EPOR, anti-CD131, or anti-EPO antibody can comprise a VH-CDR1 comprising an amino acid sequence of any one of SEQ ID NOs: 1087-1274, 2215-2343, 2989-3124, or 4668-4825, or a variant thereof, a VH-CDR2 comprising an amino acid sequence of any one of SEQ ID NOs: 1275-1462, 2344-2472, 3125-3260, or 4826-4983, or a variant thereof, a VH-CDR3 comprising an amino acid sequence of any one of SEQ ID NOs: 1463-1650, 2473-2601, 3261-3396, 4404-4501, 4600-4630, or 4984-5141, or a variant thereof, a VL-CDR1 comprising an amino acid sequence of any one of SEQ ID NOs: 1651-1838, 2602-2730, 3397-3532, or 5142-5299, or a variant thereof, a VL-CDR2 comprising an amino acid sequence of any one of SEQ ID NOs: 1839-2026, 2731-2859, 3533-3668, or 5300-5457, or a variant thereof, and a VL-CDR3 comprising an amino acid sequence of any one of SEQ ID NOs: 2027-2214, 2680-2988, 3669-3804, 4502-4599, 4631-4667, or 5458-5615, or a variant thereof. In some embodiments, a variant can comprise a conservatively modified or substituted amino acid sequence variant.

[0256] In some embodiments, an anti-EPOR antibody, anti-CD131 antibody, or anti-EPO antibody can comprise a VH sequence and a kappa chain variable regions (VK) sequence. In some embodiments, an anti-EPOR antibody, anti-CD131 antibody, or anti-EPO antibody can comprise a VH sequence and a lamda chain variable region. In some embodiments, an anti-EPOR antibody, anti-CD131 antibody, or anti-EPO antibody can comprise a VH sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VH sequences listed in Table 1-1, 10, or 11. In some embodiments, an anti-EPOR antibody, anti-CD131 antibody, or anti-EPO antibody can comprise a VH sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of VH sequences listed in Table 1-1, 10, or 11. In some embodiments, an anti-EPOR antibody, anti -CD 131Attorney Docket No. 62379-707601antibody, or anti-EPO antibody can comprise a VH sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of VH sequences listed in Table 1-1, 10, or 11. In some embodiments, an anti -EPOR antibody, anti-CD131 antibody, or anti-EPO antibody can comprise any one of VH sequences listed in Table 1-1, 10, or 11, or a variant thereof. In some embodiments, a variant can comprise a conservatively modified or substituted amino acid sequence variant.

[0257] In some embodiments, an anti-EPOR, anti-CD131, or anti-EPO antibody can comprise a VH sequence of any one of SEQ ID NOs: 1, 1053-1069, or 3805-3809, or a variant thereof. In some embodiments, a variant can comprise a conservatively modified or substituted amino acid sequence variant. For example, an anti-EPOR antibody or an anti-CD131 antibody can comprise a VH sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 1, 1053-1069, or 3805-3809. In some embodiments, an anti-EPOR, anti-CD131, or anti-EPO antibody can comprise a VH sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of SEQ ID NOs: 1, 1053-1069, or 3805-3809. In some embodiments, an anti-EPOR, anti-CD131, or anti-EPO antibody can comprise a VH sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of SEQ ID NOs: 1, 1053-1069, or 3805-3809.

[0258] In some embodiments, an anti-EPOR, anti-CD131, or anti-EPO antibody can comprise a VH-CDR1 amino acid sequence derived from a VH set forth in any one of SEQ ID NOs: 1, 1053-1069, or 3805-3809, a VH-CDR2 amino acid sequence derived from a VH set forth in any one of SEQ ID NOs: 1, 1053-1069, or 3805-3809, and a VH-CDR3 amino acid sequence derived from a VH set forth in any one of SEQ ID NOs: 1, 1053-1069, or 3805-3809. In some embodiments, VH-CDR1, VH-CDR2, and / or VH-CDR3 can be defined according to Kabat, Chothia, IMGT, AbM, or Contact.

[0259] In some embodiments, an anti-EPOR antibody, anti-CD131 antibody, or anti-EPO antibody can comprise a VK sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VK sequences listed in Table 1-1, 10, or 11. In some embodiments, an anti-EPOR antibody, anti-CD131 antibody, or anti-EPO antibody can comprise a VK sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or atAttorney Docket No. 62379-707601most about 99.5% sequence identity or sequence similarity to any one of VK sequences listed in Table 1-1, 10, or 11. In some embodiments, an anti-EPOR antibody, anti-CD 131 antibody, or anti-EPO antibody can comprise a VK sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of VK sequences listed in Table 1-1, 10, or 11. In some embodiments, an anti-EPOR antibody, anti-CD 131 antibody, or anti-EPO antibody can comprise any one of VK sequences listed in Table 1-1, 10, or 11, or a variant thereof. In some embodiments, a variant can comprise a conservatively modified or substituted amino acid sequence variant.

[0260] In some embodiments, an anti-EPOR antibody, anti-CD 131 antibody, or anti-EPO antibody can comprise a VK sequence of any one of SEQ ID NOs: 2, 1070-1086, or 3810-3814, or a variant thereof. In some embodiments, a variant can comprise a conservatively modified or substituted amino acid sequence variant. For example, an anti-EPOR antibody, anti-CD 131 antibody, or anti-EPO antibody can comprise a VK sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 2, 1070-1086, or 3810-3814. In some embodiments, an anti-EPOR antibody, anti-CD131 antibody, or anti-EPO antibody can comprise a VK sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of SEQ ID NOs: 2, 1070-1086, or 3810-3814. In some embodiments, an anti-EPOR antibody, anti-CD 131 antibody, or anti-EPO antibody can comprise a VK sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of SEQ ID NOs: 2, 1070-1086, or 3810-3814.

[0261] In some embodiments, an anti-EPOR, anti-CD 131, or anti-EPO antibody can comprise a VL-CDR1 amino acid sequence derived from a VL set forth in any one of SEQ ID NOs: 2, 1070-1086, or 3810-3814, a VL-CDR2 amino acid sequence derived from a VL set forth in any one of SEQ ID NOs: 2, 1070-1086, or 3810-3814, and a VL-CDR3 amino acid sequence derived from a VL set forth in any one of SEQ ID NOs: 2, 1070-1086, or 3810-3814. In some embodiments, VL-CDR1, VL-CDR2, and / or VL-CDR3 can be defined according to Kabat, Chothia, IMGT, AbM, or Contact.

[0262] In some embodiments, an anti-EPOR antibody, anti-CD 131 antibody, or anti-EPO antibody can comprise a VH sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VH sequences listed in Table 1-1, 10, or 11 and a VK sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%,Attorney Docket No. 62379-707601or at least about 20% sequence identity or sequence similarity to any one of VH sequences listed in Table 1-1, 10, or 11. In some embodiments, an anti-EPOR antibody, anti-CD131 antibody, or anti-EPO antibody can comprise a VH sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of VH sequences listed in Table 1-1, 10, or 11 and a VK sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of VH sequences listed in Table 1-1, 10, or 11. In some embodiments, an anti-EPOR antibody, anti-CD131 antibody, or anti-EPO antibody can comprise a VH sequence with a about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of VH sequences listed in Table 1-1, 10, or 11 and a VK sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of VH sequences listed in Table 1-1, 10, or 11. In some embodiments, an anti-EPOR antibody, anti-CD131 antibody, or anti-EPO antibody can comprise any one of VH sequences listed in Table 1-1, 10, or 11, or a variant thereof and any one of VK sequences listed in Table 1-1, 10, or 11, or a variant thereof. In some embodiments, a variant can comprise a conservatively modified or substituted amino acid sequence variant.

[0263] In some embodiments, an anti-EPOR, anti-CD131, or anti-EPO antibody can comprise a VH sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 1, 1053-1069, or 3805-3809 and a VK sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 2, 1070-1086, or 3810-3814. In some embodiments, an anti-EPOR, anti-CD131, or anti-EPO antibody can comprise a VH sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of SEQ ID NOs: 1, 1053-1069, or 3805-3809 and a VK sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of SEQ ID NOs: 2, 1070-1086, or 3810-3814. In some embodiments, an anti-EPOR, anti-CD131, or anti-EPO antibody can comprise a VH sequence with aAttorney Docket No. 62379-707601about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of SEQ ID NOs: 1, 1053-1069, or 3805-3809 and a VK sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of SEQ ID NOs: 2, 1070-1086, or 3810-3814. In some embodiments, an anti-EPOR, anti-CD131, or anti-EPO antibody can comprise a VH sequence of any one of SEQ ID NOs: 1, 1053-1069, or 3805-3809, or a variant thereof and a VK sequence of any one of SEQ ID NOs: 2, 1070-1086, or 3810-3814, or a variant thereof. In some embodiments, a variant can comprise a conservatively modified or substituted amino acid sequence variant.

[0264] In some embodiments, an anti-EPOR, anti-CD131, or anti-EPO antibody can comprise a VH-CDR1 amino acid sequence derived from a VH set forth in any one of SEQ ID NOs: 1, 1053-1069, or 3805-3809, a VH-CDR2 amino acid sequence derived from a VH set forth in any one of SEQ ID NOs: 1, 1053-1069, or 3805-3809, a VH-CDR3 amino acid sequence derived from a VH set forth in any one of SEQ ID NOs: 1, 1053-1069, or 3805-3809, a VL-CDR1 amino acid sequence derived from a VL set forth in any one of SEQ ID NOs: 2, 1070-1086, or 3810-3814, a VL-CDR2 amino acid sequence derived from a VL set forth in any one of SEQ ID NOs: 2, 1070-1086, or 3810-3814, and a VL-CDR3 amino acid sequence derived from a VL set forth in any one of SEQ ID NOs: 2, 1070-1086, or 3810-3814. In some embodiments, VH-CDR1, VH-CDR2, VH-CDR3 VL-CDR1, VL-CDR2, and / or VL-CDR3 can be defined according to Kabat, Chothia, IMGT, AbM, or Contact.

[0265] In some embodiments, a VH-CDR3 can comprise an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VH-CDR3 sequences listed in Table 12. In some embodiments, a VH-CDR3 can comprise an amino acid sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of VH-CDR3 sequences listed in Table 12. In some embodiments, a VH-CDR3 can comprise an amino acid sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of VH- CDR3 sequences listed in Table 12. In some embodiments, a VH-CDR3 can comprise any one of VH- CDR3 sequences listed in Table 12, or a variant thereof. In some embodiments, a VH-CDR3 can comprise an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequenceAttorney Docket No. 62379-707601similarity to any one of SEQ ID NOs: 3815-3819. In some embodiments, a VH-CDR3 can comprise an amino acid sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of SEQ ID NOs: 3815-3819. In some embodiments, a VH-CDR3 can comprise an amino acid sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of SEQ ID NOs: 3815-3819. In some embodiments, a VH-CDR3 can comprise an amino acid sequence of any one of SEQ ID NOs: 3815-3819, or a variant thereof. In some embodiments, an anti-EPOR or an anti-CD131 antibody that binds to EPO receptor subunit, CD 131 subunit, or both subunits of a hetero-EPOR can comprise a VH-CDR3 sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VH-CDR3 sequences listed in Table 12. In some embodiments, an anti-EPOR or an anti-CD131 antibody that binds to EPO receptor subunit, CD131 subunit, or both subunits of a hetero-EPOR can comprise a VH-CDR3 sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of VH-CDR3 sequences listed in Table 12. In some embodiments, an anti-EPOR or an anti-CD131 antibody that binds to EPO receptor subunit, CD131 subunit, or both subunits of a hetero-EPOR can comprise a VH-CDR3 sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of VH-CDR3 sequences listed in Table 12. In some embodiments, an anti-EPOR or an anti-CD131 antibody that binds to EPO receptor subunit, CD 131 subunit, or both subunits of a hetero-EPOR can comprise any one of VH-CDR3 sequences listed in Table 12, or a variant thereof. In some embodiments, a variant can comprise a conservatively modified or substituted amino acid sequence variant.

[0266] In some embodiments, a VL-CDR3 can comprise an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VL-CDR3 sequences listed in Table 12. In some embodiments, a VL-CDR3 can comprise an amino acid sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of VL-CDR3 sequences listed in Table 12. In some embodiments, a VL-CDR3 can comprise an amino acid sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%;Attorney Docket No. 62379-70760189%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of VL- CDR3 sequences listed in Table 12. In some embodiments, a VL-CDR3 can comprise any one of VL- CDR3 sequences listed in Table 12, or a variant thereof. In some embodiments, a VL-CDR3 can comprise an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of SEQ ID NOs: 3820-3823. In some embodiments, a VL-CDR3 can comprise an amino acid sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of SEQ ID NOs: 3820-3823. In some embodiments, a VL-CDR3 can comprise an amino acid sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of SEQ ID NOs: 3820-3823. In some embodiments, a VL-CDR3 can comprise an amino acid sequence of any one of SEQ ID NOs: 3820-3823, or a variant thereof. In some embodiments, an anti-EPOR or an anti-CD131 antibody that binds to EPO receptor subunit, CD 131 subunit, or both subunits of a hetero-EPOR can comprise a VL-CDR3 sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or at least about 20% sequence identity or sequence similarity to any one of VL-CDR3 sequences listed in Table 12. In some embodiments, an anti-EPOR or an anti-CD131 antibody that binds to EPO receptor subunit, CD 131 subunit, or both subunits of a hetero-EPOR can comprise a VL-CDR3 sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to any one of VL-CDR3 sequences listed in Table 12. In some embodiments, an anti-EPOR or an anti-CD131 antibody that binds to EPO receptor subunit, CD131 subunit, or both subunits of a hetero-EPOR can comprise a VL-CDR3 sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to any one of VL-CDR3 sequences listed in Table 12. In some embodiments, an anti-EPOR or an anti-CD131 antibody that binds to EPO receptor subunit, CD 131 subunit, or both subunits of a hetero-EPOR can comprise any one of VL-CDR3 sequences listed in Table 12, or a variant thereof. In some embodiments, a variant can comprise a conservatively modified or substituted amino acid sequence variant.

[0267] In some embodiments, an anti-EPOR, anti-CD131, or anti -EPO antibody can comprise a VH-CDR1 amino acid sequence derived from a VH set forth in any one of SEQ ID NOs: 3805-3809, a VH-CDR2 amino acid sequence derived from a VH set forth in any one of SEQ ID NOs: 3805-3809, a VH-Attorney Docket No. 62379-707601CDR3 amino acid sequence set forth in any one of SEQ ID NOs: 3815-3819, a VL-CDR1 amino acid sequence derived from a VL set forth in any one of SEQ ID NOs: 3810-3814, a VL-CDR2 amino acid sequence derived from a VL set forth in any one of SEQ ID NOs: 3810-3814, and a VL-CDR3 amino acid sequence set forth in any one of SEQ ID NOs: 3820-3823. In some embodiments, VH-CDR1, VH-CDR2, VH-CDR3 VL-CDR1, VL-CDR2, and / or VL-CDR3 can be defined according to Kabat, Chothia, IMGT, AbM, or Contact.

[0268] In some aspects, an anti-EPOR antibody, anti-CD131 antibody, or an anti-EPO antibody can bind to EPOR or EPOwith an affinity of from about 1 pM to about 100 nM, from about 2.0 to about 5.1 nM, from about 45 nM to about 300 nM, or from about 2.0 to about 300 nM. In some embodiments, an anti-EPOR antibody, anti-CD131 antibody, or an anti-EPO antibody can bind with an affinity of at least about 300 nM, at least about 140 nM, at least about 100 nM, at least about 5.1 nm, at least about 3.8 nM, or at least about 2.4 nM. In some aspects, a binding affinity can be measured using any method known in the art. For example, a binding affinity can be measure using surface plasmon resonance (SPR;Biacore™, real time molecular interaction monitoring system for analysis of affinity and / or kinetics), KinExA™ Biosensor (system for measuring binding affinity KD), scintillation proximity assays, enzyme-linked immunosorbent assay (ELISA), ORIGEN immunoassay (IGEN), fluorescence quenching, fluorescence transfer, yeast display, or any combination thereof. In some embodiments, a binding affinity can be screened using a suitable bioassay.

[0269] In some embodiments, anti-EPO antibodies, anti-EPOR antibodies, or anti-CD131 antibodies described herein can have a binding affinity of less than about 600 nM, about 590 nM, about 580 nM, about 570 nM, about 560 nM, about 550 nM, about 540 nM, about 530 nM, about 520 nM, about 510 nM, about 500 nM, about 490 nM, about 480 nM, about 470 nM, about 460 nM, about 450 nM, about 440 nM, about 430 nM, about 420 nM, about 410 nM, about 400 nM, about 390 nM, about 380 nM, about 370 nM, about 360 nM, about 350 nM, about 340 nM, about 330 nM, about 320 nM, about 310 nM, about 300 nM, about 290 nM, about 280 nM, about 270 nM, about 260 nM, about 250 nM, about 240 nM, about 230 nM, about 220 nM, about 210 nM, about 200 nM, about 190 nM, about 180 nM, about 170 nM, about 160 nM, about 150 nM, about 140 nM, about 130 nM, about 120 nM, about 110 nM, about 100 nM, about 90 nM, about 80 nM, about 70 nM, about 50 nM, about 50 nM, about 49 nM, about 48 nM, about 47 nM, about 46 nM, about 45 nM, about 44 nM, about 43 nM, about 42 nM, about 41 nM, about 40 nM, about 39 nM, about 38 nM, about 37 nM, about 36 nM, about 35 nM, about 34 nM, about 33 nM, about 32 nM, about 31 nM, about 30 nM, about 29 nM, about 28 nM, about 27 nM, about 26 nM, about 25 nM, about 24 nM, about 23 nM, about 22 nM, about 21 nM, about 20 nM, about 19 nM, about 18 nM, about 17 nM, about 16 nM, about 15 nM, about 14 nM, about 13 nM, about 12 nM, about 11 nM, about 10 nM, about 9 nM, about 8 nM, about 7 nM, about 6 nM, about 5 nM, about 4 nM, about 3 nM, about 2 nM, about 1 nM, about 990 pM, about 980 pM, about 970 pM, about 960 pM, about 950 pM, about 940 pM, about 930 pM, about 920 pM, about 910 pM, about 900 pM, about 890 pM, about 880 pM, about 870 pM, about 860 pM, about 850 pM, about 840 pM, about 830 pM, about 820 pM, about 810 pM, about 800 pM, about 790 pM, about 780 pM, about 770 pM, about 760 pM, about 750 pM, about 740 pM, about 730 pM, about 720 pM, about 710 pM, about 700 pM, about 690 pM, about 680 pM, about 670 pM, about 660 pM, about 650 pM,Attorney Docket No. 62379-707601about 640 pM, about 630 pM, about 620 pM, about 610 pM, about 600 pM, about 590 pM, about 580 pM, about 570 pM, about 560 pM, about 550 pM, about 540 pM, about 530 pM, about 520 pM, about 510 pM, about 500 pM, about 490 pM, about 480 pM, about 470 pM, about 460 pM, about 450 pM, about 440 pM, about 430 pM, about 420 pM, about 410 pM, about 400 pM, about 390 pM, about 380 pM, about 370 pM, about 360 pM, about 350 pM, about 340 pM, about 330 pM, about 320 pM, about 310 pM, about 300 pM, about 290 pM, about 280 pM, about 270 pM, about 260 pM, about 250 pM, about 240 pM, about 230 pM, about 220 pM, about 210 pM, about 200 pM, about 190 pM, about 180 pM, about 170 pM, about 160 pM, or any integer therebetween. In some embodiments, anti-EPO antibodies, anti-EPOR antibodies, or anti-CD131 antibodies described herein can have a binding affinity of less than 150 pM, about 140 pM, about 130 pM, about 120 pM, about 110 pM, about 100 pM, about 95 pM, about 90 pM, about 85 pM, about 80 pM, about 75 pM, about 70 pM, about 65 pM, about 60 pM, about 55 pM, about 50 pM about 45 pM, about 40 pM, about 35 pM, about 30 pM, about 25 pM, about 20 pM, about 15 pM, about 10 pM, about 9 pM, about 8 pM, about 7 pM, about 6 pM, about 5 pM, about 4 pM, about 3 pM, about 2 pM, about 1 pM, about 0.9 pM, about 0.8 pM, about 0.7 pM, about 0.6 pM, about 0.5 pM, about 0.4 pM, about 0.3 pM, about 0.2 pM, about 0.1 pM, about 0.09 pM, about 0.08, about 0.07 pM, about 0.06 pM, about 0.05 pM, about 0.04 pM, about 0.03 pM, about 0.02 pM, about 0.01 pM, or any integer therebetween.

[0270] In some instances, anti-EPO antibodies, anti-EPOR antibodies, or anti-CD131 antibodies described herein can bind to EPO, EPOR, or CD131 from a subject other than human. For example, anti-EPO antibodies, anti-EPOR antibodies, or anti-CD131 antibodies described herein can bind to EPO, EPOR, or CD 131 from mouse or cynomolgus monkey. In some instances, optical density (OD) values can be used to describe antigen binding of anti-EPO antibodies, anti-EPOR antibodies, anti-CD131 antibodies described herein. For example, OD can be used to calculate the concentration of antigens or antigen binding in a sample for ELISA analysis. In some embodiments, anti-EPO antibodies, anti-EPOR antibodies, or anti-CD131 antibodies described herein can have OD450 value of from about 0.0150 to about 5.000, when analyzed by ELISA. In some embodiments, anti-EPO antibodies, anti-EPOR antibodies, anti-CD131 antibodies described herein can have OD450 value of from about 0.0150 to about 5.000 for human EPOR / CD131-Fc binding, when analyzed by ELISA. In some embodiments, anti-EPO antibodies, anti-EPOR antibodies, anti-CD131 antibodies described herein can have OD450 value of from about 0.400 to about 5.000 for mouse EPOR / CD131-Fc binding, when analyzed by ELISA. In some embodiments, anti-EPO antibodies, anti-EPOR antibodies, anti-CD131 antibodies described herein can have OD450 value of from about 0.050 to about 5.000 for cynomolgus monkey EPOR / CD131-Fc binding, when analyzed by ELISA. In some embodiments, anti-EPO antibodies, anti-EPOR antibodies, or anti-CD131 antibodies described herein can have OD450 value of from about 0.070 to about 5.000 for human EPOR-Fc binding, when analyzed by ELISA. In some embodiments, anti-EPO antibodies, anti-EPOR antibodies, or anti-CD131 antibodies described herein can have OD450 value of from about 0.060 to about 5.000 for human CD 131-Fc binding, when analyzed by ELISA. In some embodiments, anti-EPO antibodies, anti-EPOR antibodies, or anti-CD131 antibodies described herein can have OD450 value of from about 0.100 to about 5.000 for cynomolgus monkey EPOR-Fc binding, when analyzed by ELISA.Attorney Docket No. 62379-707601

[0271] In some instances, anti-EPO antibodies, anti -EPOR antibodies, or anti-CD131 antibodies described herein can have antagonistic effects. In some embodiments, anti-EPO antibodies described herein can bind EPOs and inhibit or block EPO / EPOR interaction. For example, anti-EPO antibodies can bind EPOs and inhibit EPOs from binding to homo-EPORs or hetero-EPORs. In some embodiments, anti-EPO antibodies, anti -EPOR antibodies, or anti-CD131 antibodies described herein can bind an EPOR subunit of homo-EPORs or hetero-EPORs and inhibit or block homo-EPOR complex formation, hetero-EPOR complex formation, EPO / homo-EPOR interaction, or EPO / hetero-EPOR interaction. For example, anti-EPO antibodies, anti -EPOR antibodies, or anti-CD131 antibodies described herein can bind an EPOR subunit and inhibit formation of homo-EPORs or hetero-EPORs. For example, anti-EPO antibodies, anti-EPOR antibodies, or anti-CD131 antibodies described herein can bind an EPOR subunit of homo-EPORs or hetero-EPORs and inhibit homo-EPORs or hetero-EPORs from binding to EPO. In some embodiments, anti-EPO antibodies, anti -EPOR antibodies, or anti-CD131 antibodies described herein can bind a CD 131 and inhibit or block hetero-EPOR complex formation or EPO / hetero-EPOR interaction. For example, anti-EPO antibodies, anti -EPOR antibodies, or anti-CD131 antibodies described herein can bind a CD 131 and inhibit formation of hetero-EPORs. For example, anti-EPO antibodies, anti -EPOR antibodies, or anti-CD131 antibodies described herein can bind a CD 131 subunit of hetero-EPORs and inhibit hetero-EPORs from binding to EPO. In some embodiments, preventing or inhibiting complex formation of a homo-EPOR or complex formation between an EPO protein and a homo-EPOR can lead to prevention or inhibition of homo-EPOR activation or function. In some embodiments, preventing or inhibiting complex formation of a hetero-EPOR or complex formation between an EPO protein and a hetero-EPOR can lead to prevention or inhibition of hetero-EPOR activation or function. In some embodiments, the level of prevention or inhibition is at least about 1%, 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 71%, at least about 72%, at least about 73%, at least about 74%, at least about 75%, at least about 80%, at least about 81%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or at least about 100%.

[0272] In some embodiments, anti-EPO antibodies, anti -EPOR antibodies, or anti-CD131 antibodies described herein can bind an EPO protein and inhibit or decrease the level of an activity of a homo-EPOR or a hetero-EPOR without affecting binding of the EPO protein to the homo-EPOR or the hetero-EPOR. In some embodiments, anti-EPO antibodies, anti -EPOR antibodies, or anti-CD131 antibodies described herein can bind to an EPO receptor subunit of a homo-EPOR or a hetero-EPOR and inhibit or decrease the level of an activity of the homo-EPOR or the hetero-EPOR without affecting the complex formation of the homo-EPOR or the hetero-EPOR, or complex formation between an EPO protein and the homo-EPOR or an EPO protein and the hetero-EPOR. In some embodiments, anti-EPO antibodies, anti-EPOR antibodies, or anti-CD131 antibodies described herein can bind a CD 131 subunit of a hetero-EPOR and inhibit orAttorney Docket No. 62379-707601decrease the level of an activity of the hetero-EPOR without affecting complex formation of the hetero-EPOR or binding of an EPO protein to the hetero-EPOR.

[0273] In some embodiments, affinity maturation can be used with an antibody disclosed herein to obtain an anti-EPOR antibody, anti-CD131, or an anti -EPO antibody of a desired affinity. When an anti-EPOR antibody, anti-CD131, or anti -EPO antibody is obtained from an animal (e.g., a transgenic animal carrying a human antibody repertoire), the antibodies made in the transgenic animal can undergo affinity maturation. Alternatively, antibodies from a transgenic animal, or from other technologies (such as a display technology) can be affinity matured using chain shuffling approaches and / or mutation of the nucleic acids encoding VH and VL followed by screening and / or selecting for antibodies with greater affinity.

[0274] The most widely used methods for minimizing the immunogenicity of non-human antibodies while retaining specificity and affinity can involve grafting the CDRs of the non-human antibody onto human frameworks typically selected for their structural homology to the non-human framework (Jones et al., 1986, Nature 321:522-5; U. S. Pat. No. 5,225,539, both of which are hereby incorporated by reference in their entirety). The inclusion of some non-human residues at key positions in the framework can improve the affinity of the CDR grafted antibody (Bajorath et al., 1995, J Biol Chem 270:22081-4; Martin et al., 1991, Methods Enzymol. 203: 121-53; Al-Lazikani, 1997, J Mol Biol 273:927-48, all of which are hereby incorporated by reference in their entirety). Exemplary methods for humanization of antibodies by CDR grafting are disclosed, for example, in U. S. Pat. No. 6,180,370, which is hereby incorporated by reference in its entirety.

[0275] Improvements to the traditional CDR-grafting approaches can use various hybrid selection approaches, in which portions of the non-human antibody have been combined with libraries of complementary human antibody sequences in successive rounds of selection for antigen binding, in the course of which most of the non-human sequences are gradually replaced with human sequences. For example, in the chain-shuffling technique (Marks, et al., 1992, Biotechnology 10:779-83, which is hereby incorporated by reference in its entirety for all purposes) one chain of the non-human antibody can be combined with a naive human repertoire of the other chain on the rationale that the affinity of the non-human chain will be sufficient to constrain the selection of a human partner to the same epitope on the antigen. Selected human partners can then be used to guide selection of human counterparts for the remaining non-human chains.

[0276] Other methodologies can include chain replacement techniques where the non-human CDR3s were retained and only the remainder of the V-regions, including the frameworks and CDRs 1 and 2, were individually replaced in steps performed sequentially (e.g., U. S. Patent Application No. 20030166871; Rader, et al., Proc Natl Acad Sci USA 95:8910-15, 1998; Steinberger, et al., J. Biol. Chem. 275:36073-36078, 2000; Rader, et al., J. Biol. Chem. 275: 13668-13676, 2000, all of which are hereby incorporated by reference in their entirety for all purposes).

[0277] These technologies can be used to make antibodies suitable for use in non-human subjects by engineering the CDRs into framework regions of the subject species using analogous approaches to the CDR grafting methods used for making antibodies for use in humans.Attorney Docket No. 62379-707601

[0278] The disclosure encompasses pharmaceutically acceptable salts of anti-EPOR antibodies, anti-CD131 antibodies, or anti-EPO antibodies, including those with a positive net charge, those with a negative net charge, and those with no net charge, and including, without limitation, salts of anti-EPOR antibodies, anti-CD131 antibodies, or anti-EPO antibodies including fragments thereof as compounds, in pharmaceutical compositions, in their therapeutic and diagnostic uses, and in their production.

[0279] In some embodiments, anti-EPO antibodies, anti-EPOR antibodies, anti-CD131 antibodies described herein can have a half-life of from 1 minute to 1 hour in human plasma. In some embodiments, anti-EPO antibodies, anti-EPOR antibodies, anti-CD131 antibodies described herein can have a half-life of about 1 minute to 2 minutes, about 1 minute to about 4 minutes, about 1 minute to about 5 minutes, about 1 minute to about 10 minutes, about 1 minute to about 15 minutes, about 1 minute to about 20 minutes, about 1 minute to about 25 minutes, about 1 minute to about 30 minutes, about 1 minute to about 35 minutes, about 1 minute to about 40 minutes, about 1 minute to about 45 minutes, about 1 minute to about 50 minutes, about 1 minute to about 55 minutes, or about 1 minute to about 1 hour. In some embodiments, anti-EPO antibodies, anti-EPOR antibodies, anti-CD131 antibodies described herein can have a half-life of about 1 minute, about 2 minutes, about 3 minutes, about 4 minutes, about 5 minutes, about 10 minutes, about 15 minutes, about 20 minutes, about 25 minutes, about 30 minutes, about 35 minutes, about 40 minutes, about 45 minutes, about 50 minutes, about 55 minutes, or about 1 hour. In some embodiments, anti-EPO antibodies, anti-EPOR antibodies, anti-CD131 antibodies described herein can have a half-life of from 1 hour to 5 days in human plasma. In some embodiments, anti-EPO antibodies, anti-EPOR antibodies, anti-CD131 antibodies described herein can have a half-life about 1 hour to about 120 hours. In some embodiments, anti-EPO antibodies, anti-EPOR antibodies, anti-CD131 antibodies described herein can have a half-life about 1 hour to about 5 hours, about 1 hour to about 10 hours, about 1 hour to about 12 hours, about 1 hour to about 24 hours, about 1 hour to about 36 hours, about 1 hour to about 48 hours, about 1 hour to about 60 hours, about 1 hour to about 72 hours, about 1 hour to about 84 hours, about 1 hour to about 96 hours, about 1 hour to about 120 hours, about 5 hours to about 10 hours, about 5 hours to about 12 hours, about 5 hours to about 24 hours, about 5 hours to about 36 hours, about 5 hours to about 48 hours, about 5 hours to about 60 hours, about 5 hours to about 72 hours, about 5 hours to about 84 hours, about 5 hours to about 96 hours, about 5 hours to about 120 hours, about 10 hours to about 12 hours, about 10 hours to about 24 hours, about 10 hours to about 36 hours, about 10 hours to about 48 hours, about 10 hours to about 60 hours, about 10 hours to about 72 hours, about 10 hours to about 84 hours, about 10 hours to about 96 hours, about 10 hours to about 120 hours, about 12 hours to about 24 hours, about 12 hours to about 36 hours, about 12 hours to about 48 hours, about 12 hours to about 60 hours, about 12 hours to about 72 hours, about 12 hours to about 84 hours, about 12 hours to about 96 hours, about 12 hours to about 120 hours, about 24 hours to about 36 hours, about 24 hours to about 48 hours, about 24 hours to about 60 hours, about 24 hours to about 72 hours, about 24 hours to about 84 hours, about 24 hours to about 96 hours, about 24 hours to about 120 hours, about 36 hours to about 48 hours, about 36 hours to about 60 hours, about 36 hours to about 72 hours, about 36 hours to about 84 hours, about 36 hours to about 96 hours, about 36 hours to about 120 hours, about 48 hours to about 60 hours, about 48 hours to about 72 hours, about 48 hours to about 84 hours,Attorney Docket No. 62379-707601about 48 hours to about 96 hours, about 48 hours to about 120 hours, about 60 hours to about 72 hours, about 60 hours to about 84 hours, about 60 hours to about 96 hours, about 60 hours to about 120 hours, about 72 hours to about 84 hours, about 72 hours to about 96 hours, about 72 hours to about 120 hours, about 84 hours to about 96 hours, about 84 hours to about 120 hours, or about 96 hours to about 120 hours. In some embodiments, anti-EPO antibodies, anti-EPOR antibodies, anti-CD131 antibodies described herein can have a half-life about 1 hour, about 5 hours, about 10 hours, about 12 hours, about 24 hours, about 36 hours, about 48 hours, about 60 hours, about 72 hours, about 84 hours, about 96 hours, or about 120 hours. In some embodiments, anti-EPO antibodies, anti-EPOR antibodies, anti-CD131 antibodies described herein can have a half-life at least about 1 hour, about 5 hours, about 10 hours, about 12 hours, about 24 hours, about 36 hours, about 48 hours, about 60 hours, about 72 hours, about 84 hours, or about 96 hours. In some embodiments, anti-EPO antibodies, anti-EPOR antibodies, anti-CD131 antibodies described herein can have a half-life at most about 5 hours, about 10 hours, about 12 hours, about 24 hours, about 36 hours, about 48 hours, about 60 hours, about 72 hours, about 84 hours, about 96 hours, or about 120 hours. In some embodiments, anti-EPO antibodies, anti-EPOR antibodies, anti-CD131 antibodies described herein can have a half-life at least about 10 days, about 11 days, about 11 days, 12 days, 13 days, 14 days, 15 days, 16 days, 17 days, 18 days, 19 days, or 20 days. In some embodiments, anti-EPO antibodies, anti-EPOR antibodies, anti-CD131 antibodies described herein can have a half-life at about 10 days to about 11 days, about 10 to about 12 days, about 10 days to about 13 days, 10 days to about 14 days, about 10 days to about 15 days, about 10 days to about 16 days, about 10 days to about 17 days, about 10 days to about 18 days, about 10 days to about 19 days, or about 10 days to about 20 days. In some embodiments, anti-EPO antibodies, anti-EPOR antibodies, anti-CD131 antibodies described herein can have a half-life at about 14 days to about 17 days.

[0280] The disclosure also encompasses bispecific or multispecific antibodies that can have specificity for at least two antigens. For example, anti-EPO antibodies, anti-EPOR antibodies, anti-CD131 antibodies described herein can be generated as bispecific antibodies that can also bind another target. In some embodiments, anti-EPO antibodies, anti-EPOR antibodies, anti-CD131 antibodies described herein can be generated as bispecific antibodies that can also bind a cell surface marker associated with immune cells, a signaling molecule associated with immune cells, or an antigen associated with tumor. In some embodiments, bispecific antibodies described herein can enhance specificity and / or selectivity of anti-EPO, anti-EPOR, anti-CD131 antibodies described herein. For example, bispecific antibodies that can bind a cell surface marker of immune cells and any of EPO, homo-EPOR (e.g., EPOR homodimer comprising two EPORs), or hetero-EPOR (e.g., EPOR heterodimer comprising an EPOR and a CD131) can be used to target EPO, homo-EPOR, or hetero-EPOR in immune cells. For example, bispecific antibodies that can bind a signaling molecule of immune cells and any of EPO, homo-EPOR, or hetero-EPOR can be used to target EPO, homo-EPOR, or hetero-EPOR in immune cells. For example, bispecific antibodies that can bind an antigen associated with tumor and any of EPO, homo-EPOR, or hetero-EPOR can be used to target EPO, homo-EPOR, or hetero-EPOR in tumor or cancer cells.

[0281] In some embodiments, a bispecific antibody can bind (i) EPO, EPO receptor subunit of a homo-EPOR or a hetero-EPOR, CD 131 subunit of a hetero-EPOR, a homo-EPOR, a hetero EPOR; and (ii) a cellAttorney Docket No. 62379-707601surface marker associated with immune cells. Examples of cell surface markers associated with immune cells can include, but are not limited to, lymphocyte antigen 75 (DEC205), X-C motif chemokine receptor 1 (XCR1), or X-C motif chemokine ligand 1 (XCL1). In some embodiments, bispecific antibodies described herein can enhance specificity and / or selectivity of anti-EPO, anti-EPOR, anti-CD131 antibodies described herein for targeting immune cells. For example, bispecific antibodies that can bind a cell surface marker associated with immune cells and any of EPO, homo-EPOR, hetero-EPOR can be used to target EPO, homo-EPOR, or hetero-EPOR in immune cells. In some embodiments, bispecific antibodies described herein can specifically and / or selectively target EPO, homo-EPOR, or hetero-EPOR in immune cells and specifically and / or selectively increase or decrease homo-EPOR activity or hetero-EPOR activity described herein in immune cells. In some embodiments, immune cells can comprise macrophages, dendritic cells, T-cells, natural killer cells, or B cells.

[0282] In some embodiments, a bispecific antibody can bind (i) EPO, EPO receptor subunit of a homo-EPOR or a hetero-EPOR, CD 131 subunit of a hetero-EPOR, a homo-EPOR, a hetero EPOR; and (ii) a signaling molecule associated with immune cells. Examples of signaling molecules associated with immune cells can include, but are not limited to, Programmed Death Ligand 1 (PD-L1), T-cell immunoglobulin and mucin-domain containing 3 (Tim3), or Triggering receptor expressed on myeloid cells 2 (TREM2). In some embodiments, bispecific antibodies described herein can enhance specificity and / or selectivity of anti-EPO, anti-EPOR, or anti-CD131 antibodies described herein for targeting immune cells. For example, bispecific antibodies that can bind a signaling molecule associated with immune cells and any of EPO, homo-EPOR, or hetero-EPOR can be used to target EPO, homo-EPOR, or hetero-EPOR in immune cells and can have synergistic anti-cancer effect. In some embodiments, bispecific antibodies described herein can specifically and / or selectively target EPO, homo-EPOR, or hetero-EPOR in immune cells and specifically and / or selectively increase or decrease homo-EPOR activity or hetero-EPOR activity described herein in immune cells. For example, bispecific antibodies described herein can be used to specifically and / or selectively target EPO, homo-EPOR, or hetero-EPOR in immune cells and specifically and / or selectively increase hetero-EPOR activity to stimulate immune response in cancer. In some embodiments, immune cells can comprise macrophages, dendritic cells, T-cells, natural killer cells, or B cells.

[0283] In some embodiments, a bispecific antibody can bind (i) EPO, EPO receptor subunit of a homo-EPOR or a hetero-EPOR, CD 131 subunit of a hetero-EPOR, a homo-EPOR, a hetero EPOR; and (ii) a tumor marker or an antigen associated with tumor. Examples of tumor markers or antigens associated with tumor can include, but are not limited to, PD1, HER2, CEA, CEACAM5, CD19, CD20, CD22, prostate specific antigen (PSA), CD123, CLL-1, B cell maturation antigen, CD138, CD133 (PROM1), CD44, ALDH1A1, CD34, CD24, EpCAM (ESA), CD117 (KIT), CD90 (THY1), CD166 (ALCAM), PDXL-1, PTCH, CD87 (PLAUR), SSEA-1, EGFR, SP, ALDH, CD49, CD326, LGR5, ALDH1A, LETM1, NANOG, POU5F1, SALL4, SOX2, LINGO2, AFP, NOTCH1, NOTCH2, NOTCH3, CTNNBL1, CD29, CD25, CD61, PROCR, TSPAN8, BMI1, FOXO1, FOXO3, FOXO4, CD15 (FUT4), CHL1, KLF4, NES, TACSTD2, TGM2, CD36, IL1RAP, GLI2, TET2, DNMT3A, KRAS, LDHB, LDHC, LDHD, NPM1, CD33, CD49f, CD 171, ABCG2, FZD, CXCR4, OCT4, ALDH, E-cadherin,Attorney Docket No. 62379-707601CD200, ABCB5, vimentin, CD146, CD31, CD144, or CD201 (PROCR). In some embodiments, bispecific antibodies described herein can enhance specificity and / or selectivity of anti-EPO, anti-EPOR, or anti-CD131 antibodies described herein for targeting tumors. For example, bispecific antibodies that can bind a tumor-associated antigen and any of EPO, homo-EPOR, or hetero-EPOR can be used to target EPO, homo-EPOR, or hetero-EPOR in cancer or tumor cells. In some embodiments, tumor-associated antigens can be on cancer or tumor cells (e.g., on cell membrane) or secreted by cancer or tumor cells. In some embodiments, bispecific antibodies described herein can specifically and / or selectively target EPO, homo-EPOR, or hetero-EPOR in cancer or tumor cells and specifically and / or selectively increase or decrease homo-EPOR activity or hetero-EPOR activity described herein in cancer or tumor cells.

[0284] In some aspects, provided herein is a bispecific antibody that can bind a first target and a second target. In some embodiments, a bispecific antibody can comprise a first antigen-binding domain and a second antigen-binding domain. In some embodiments, the first or the second antigen-binding domain can comprise a VH comprising a VH-CDR1 sequence, a VH-CDR2 sequence, and a VH-CDR3 sequence; and a VL comprising a VL-CDR1 sequence, a VL-CDR2 sequence, and a VL-CDR3 sequence; a VH and a VK; or a VH and a lambda chain variable regions. In some embodiments, the first or the second antigen-binding domain can comprise a Fab, a Fab’, a (Fab’)2, a variable fragment (Fv), a single chain variable fragment (scFv), a scFv-Fc, a Fab-Fc, a VHH, a non-antibody scaffold, or a combination thereof. In some embodiments, a bispecific antibody can further comprise a linker, e.g., a peptide linker described herein. For example, a bispecific antibody can comprise (i) a heavy chain and a light chain of an anti-EPO antibody, an anti-EPOR antibody, or an anti-CD131 antibody, (ii) a VHH or a nanobody of a second antibody, and optionally (iii) a peptide linker described herein. In some embodiments, a bispecific antibody can comprise (i) a heavy chain and a light chain of an anti-EPO antibody, an anti-EPOR antibody, or an anti-CD131 antibody, (ii) a VHH or a nanobody that can bind to an immune checkpoint protein, and optionally (iii) a peptide linker described herein. In some embodiments, an immune checkpoint protein can comprise PD-1, PD-L1, or CTLA-4. In some embodiments, a bispecific antibody can comprise (i) a heavy chain and a light chain of an anti-EPO antibody, an anti-EPOR antibody, or an anti-CD131 antibody, (ii) an anti-PD-Ll nanobody comprising an amino sequence of SEQ ID NO: 5992 or a variant thereof, and optionally (iii) a peptide linker comprising (GGGGS)3(SEQ ID NO: 79) or (GGGGS)4 (SEQ ID NO: 80). In some embodiments, a variant can comprise a conservatively modified or substituted amino acid sequence variant. In some embodiments, a bispecific antibody described herein can bind to (i) EPO, homo-EPOR, or hetero-EPOR and (ii) an immune checkpoint protein (e.g., PD-1, PD-L1, or CTLA-4, etc.). In some embodiments, binding of the bispecific antibody to an immune checkpoint protein can inhibit immune tolerance.

[0285] KN035 nanobody sequence (SEQ ID NO: 5992):QVQLQESGGGLVQPGGSLRLSCAASGKMSSRRCMAWFRQAPGKERERVAKLLTTSGSTYLADS VKGRFTISQNNAKSTVYLQMNSLKPEDTAMYYCAADSFEDPTCTLVTSSGAFQYWGQGTQVTV SS

[0286] In some embodiments, a bispecific antibody can comprise a heavy chain of an anti-EPO antibody, an anti-EPOR antibody, or an anti-CD131 antibody comprising an amino acid sequence with atAttorney Docket No. 62379-707601least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%;30%, 25%, or at least about 20% sequence identity or sequence similarity to SEQ ID NO: 1, 3, 147-334, 523-651, 781-916, 1053-1069, 3805-3809, 3824-3921, 4020-4050, 4088-4245, or 5616-5803. In some embodiments, a bispecific antibody can comprise a heavy chain of an anti-EPO antibody, an anti-EPOR antibody, or an anti-CD131 antibody comprising an amino acid sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to SEQ ID NO: 1, 3, 147-334, 523-651, 781-916, 1053- 1069, 3805-3809, 3824-3921, 4020-4050, 4088-4245, or 5616-5803. In some embodiments, a bispecific antibody can comprise a heavy chain of an anti-EPO antibody, an anti-EPOR antibody, or an anti-CD131 antibody comprising an amino acid sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to SEQ ID NO: 1, 3, 147-334, 523-651, 781-916, 1053-1069, 3805-3809, 3824-3921, 4020-4050, 4088-4245, or 5616-5803. In some embodiments, abispecific antibody can comprise a heavy chain of an anti-EPO antibody, an anti-EPOR antibody, or an anti-CD131 antibody comprising an amino acid sequence of SEQ ID NO: 1, 3, 147-334, 523-651, 781-916, 1053-1069, 3805-3809, 3824-3921, 4020-4050, 4088-4245, or 5616-5803, or a variant thereof. In some embodiments, a variant can comprise a conservatively modified or substituted amino acid sequence variant.

[0287] In some embodiments, a bispecific antibody can comprise a light chain of an anti-EPO antibody, an anti-EPOR antibody, or an anti-CD131 antibody comprising an amino acid sequence with at least about 100%, 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, 99.4%, 99.3%, 99.2%, 99.1%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%;30%, 25%, or at least about 20% sequence identity or sequence similarity to SEQ ID NO: 2, 4, 335-522, 652-780, 917-1052, 1070-1086, 3810-3814, 3922-4019, 4051-4087, 4246-4403, or 5804-5991. In some embodiments, a bispecific antibody can comprise a light chain of an anti-EPO antibody, an anti-EPOR antibody, or an anti-CD131 antibody comprising an amino acid sequence with at most about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or at most about 99.5% sequence identity or sequence similarity to SEQ ID NO: 2, 4, 335-522, 652-780, 917-1052, 1070- 1086, 3810-3814, 3922-4019, 4051-4087, 4246-4403, or 5804-5991. In some embodiments, a bispecific antibody can comprise a light chain of an anti-EPO antibody, an anti-EPOR antibody, or an anti-CD131 antibody comprising an amino acid sequence with about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or about 100% sequence identity or sequence similarity to SEQ ID NO: 2, 4, 335-522, 652-780, 917-1052, 1070- 1086, 3810-3814, 3922-4019, 4051-4087, 4246-4403, or 5804-5991. In some embodiments, abispecificAttorney Docket No. 62379-707601antibody can comprise a light chain of an anti-EPO antibody, an anti-EPOR antibody, or an anti-CD131 antibody comprising an amino acid sequence of SEQ ID NO: 2, 4, 335-522, 652-780, 917-1052, 1070- 1086, 3810-3814, 3922-4019, 4051-4087, 4246-4403, or 5804-5991, or a variant thereof In some embodiments, a variant can comprise a conservatively modified or substituted amino acid sequence variant.

[0288] The disclosure also encompasses a composition comprising a combination or a population of antibodies or functional fragments thereof described herein. For example, a composition can comprise one, two, three, four, five, six, seven, eight, nine, ten, or more different antibodies or functional fragments thereof. In one embodiment, a composition can comprise one antibody or a functional fragment thereof described herein. In another embodiment, a composition can comprise a combination or a population of antibodies or functional fragments comprising two different antibodies or functional fragments thereof. In another embodiment, a composition can comprise a combination or a population of antibodies or functional fragments thereof comprising three different antibodies or functional fragments thereof. In yet another embodiment, a composition can comprise a combination or a population of antibodies or functional fragments thereof comprising four, five, six, seven, eight, nine, ten, or more than ten different antibodies or functional fragments thereof. In some embodiments, each of the one, two, three, four, five, six, seven, eight, nine, ten, or more different antibodies or functional fragments thereof can bind to the same target (e.g., an EPO protein, an EPO receptor subunit, or a CD 131 subunit, etc.). In some embodiments, each of the one, two, three, four, five, six, seven, eight, nine, ten, or more different antibodies or functional fragments thereof can bind to a different part of the same target (e.g., an EPO protein, an EPO receptor subunit, or a CD 131 subunit, etc.). In some embodiments, each of the one, two, three, four, five, six, seven, eight, nine, ten, or more different antibodies or functional fragments thereof can bind to a different target (e.g., an EPO protein, an EPO receptor subunit, a CD 131 subunit, or a combination thereof). In some embodiments, at least two of the one, two, three, four, five, six, seven, eight, nine, ten, or more different antibodies or functional fragments thereof can bind to the same target (e.g., an EPO protein, an EPO receptor subunit, or a CD 131 subunit, etc.) and at least two of the one, two, three, four, five, six, seven, eight, nine, ten, or more different antibodies or functional fragments thereof can bind to a different target (e.g., an EPO protein, an EPO receptor subunit, a CD 131 subunit, or a combination thereof). In some embodiments, at least two of the one, two, three, four, five, six, seven, eight, nine, ten, or more different antibodies or functional fragments thereof can bind to the same target (e.g., an EPO protein, an EPO receptor subunit, or a CD 131 subunit, etc.), wherein each of the at least two of the one, two, three, four, five, six, seven, eight, nine, ten, or more different antibodies or functional fragments thereof can bind to a different part of the same target, and at least two of the one, two, three, four, five, six, seven, eight, nine, ten, or more different antibodies or functional fragments thereof can bind to a different target (e.g., an EPO protein, an EPO receptor subunit, a CD 131 subunit, or a combination thereof).Modifications of Antibodies

[0289] Antibodies described herein can have one or more modifications that can enhance their activity, binding, specificity, selectivity, or another feature. In some aspects, an anti-EPOR antibody, and / or anAttorney Docket No. 62379-707601anti-CD131 antibody, and / or an anti-EPO antibody, and / or an engineered EPO can include a moiety that extends a half-life (T1 / 2) or / and the duration of action of the antibody. In some embodiments, the moiety can extend the circulation T1 / 2, blood T1 / 2, plasma T1 / 2, serum T1 / 2, terminal T1 / 2, biological T1 / 2, elimination T1 / 2 or functional T1 / 2, or any combination thereof, of the antibody. In some embodiments, an Fc portion of an antibody described herein can be modified to extend half-life of the antibody.

[0290] In one aspect, an anti-EPOR antibody and / or anti-CD131 antibody and / or an anti-EPO antibody and / or an engineered EPO may be modified by a single moiety. In another aspect, an anti-EPOR antibody and / or an anti-CD131 antibody and / or an anti-EPO antibody and / or an engineered EPO may be modified by two or more substantially similar or identical moieties or two or more moieties of the same type. In some embodiments, an anti-EPOR antibody and / or an anti-CD131 antibody and / or an anti-EPO antibody and / or an engineered EPO may include two or more moieties of different types, or two or more different types of moieties. In some embodiments, two or more anti-EPOR antibodies and / or anti-CD131 antibodies and / or anti-EPO antibodies and / or engineered EPOs can also be attached to one moiety. In some embodiments, the attachment between the anti-EPOR antibody and / or anti-CD131 antibody and / or anti-EPO antibody and / or engineered EPO and the moiety can be covalent or noncovalent.

[0291] In some aspects, a polypeptide moiety can be recombinantly fused to the N-terminus or the C-terminus of the heavy chain or the light chain of an anti-EPOR antibody and / or an anti-CD131 antibody and / or an anti-EPO antibody and / or an engineered EPO, optionally via a linker. In some embodiments, the linker may comprise about 4-30 amino acid residues. For example, the linker may comprise from about 6 or 8 amino acid residues to about 20 amino acid residues, or from about 6 or 8 amino acid residues to about 15 amino acid residues.

[0292] In some aspects, a protracting moiety can be human serum albumin (HSA) or a portion thereof (e.g., domain III) that binds to the neonatal Fc receptor (FcRn). The HSA or FcRn-binding portion thereof can optionally have one or more mutations that confer a beneficial property or effect. In some embodiments, the HSA or FcRn-binding portion thereof can comprise one or more mutations that can enhance pH-dependent HSA binding to FcRn or / and increase HSA half-life, such as K573P or / and E505G / V547A. In some embodiments, a protracting moiety can be an unstructured polypeptide.

[0293] In some aspects, a protracting moiety can be a carboxy-terminal peptide (CTP) derived from the P-subunit of human chorionic gonadotropin (hCG). In the human body, the fourth, fifth, seventh and eight serine residues of the 34-aa CTP of hCG- typically are attached to O-glycans terminating with a sialic acid residue.

[0294] In some aspects, a protracting moiety can be 1, 2, 3, 4, 5, or more moieties of a synthetic polymer. In some embodiments, the synthetic polymer can be biodegradable or non-biodegradable. Biodegradable polymers useful as protracting moieties can include, but are not limited to, poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) and poly[oligo(ethylene glycol) methyl ether methacrylate] (POEGMA). Non-biodegradable polymers useful as protracting moieties include without limitation polyethylene glycol)(PEG), polyglycerol, poly(N-(2-hydroxypropyl)methacrylamide) (PHPMA), polyoxazolines and poly(N-vinylpyrrolidone) (PVP). In some embodiments, a syntheticAttorney Docket No. 62379-707601polymer can be polyethylene glycol (PEG). PEGylation can be done by chemical or enzymatic, sitespecific coupling or by random coupling.

[0295] In some embodiments, the individual mass (e.g, average molecular weight), or the total mass, of the one or more synthetic polymer moieties can be about 10-50 kDa, about 10-20 kDa, about 20-30 kDa, about 30-40 kDa, or kDa 40-50 kDa. In some embodiments, the individual mass (e.g., average molecular weight), or the total mass, of the one or more synthetic polymer moieties can be about 10 kDa, about 20 kDa, about 30 kDa, about 40 kDa, or 50 kDa. In some embodiments, the individual mass (e.g., average MW), or the total mass, of the one or more synthetic polymer moieties can be greater than about 50 kDa, such as about 50-100 kDa, about 50-60 kDa, about 60-70 kDa, about 70-80 kDa, about 80-90 kDa, or about 90-100 kDa. In some embodiments, the individual mass (e.g., average molecular weight), or the total mass, of the one or more synthetic polymer moieties can be about 60 kDa, about 70 kDa, about 80 kDa, about 90 kDa, or about 100 kDa. In some embodiments, the mass (e.g., average MW) of an individual synthetic polymer moiety can be less than about 10 kDa, such as about 1-5 kDa, about 5-10 kDa, or about 5 kDa. In some embodiments, the individual mass (e.g., average MW), or the total mass, of the one or more synthetic polymer (e.g, PEG) moieties can be about 20 kDa or about 40 kDa.

[0296] In some aspects, modified antibodies can comprise a human modified antibody. In some aspects, also provided herein are amino acid sequence variants of modified antibodies which can be prepared by introducing appropriate nucleotide changes into the DNA sequence of modified antibodies, or by synthesis of the desired modified antibody polypeptides. In some embodiments, such variants can include, for example, a deletion, an insertion, or a substitution of one or more residues within the amino acid sequence of an antibody. In some embodiments, any combinations of deletion, insertion, and substitution can be made to generate an antibody that can have desired antigen-binding characteristics. The amino acid changes of a modified antibody can also alter post-translational processes of the modified antibody, including, but are not limited to, changing the number or position of glycosylation sites. In some embodiments, alanine scanning mutagenesis can be used to identify one or more residues or regions of a modified antibody that may be preferred locations for mutagenesis. In some embodiments, a residue or a group of target residues can be identified (e.g., charged residues such as Arg, Asp, His, Lys, and Glu) and replaced by a neutral or negatively charged amino acid (e.g., alanine or polyalanine) to affect an interaction of the amino acids with the surrounding aqueous environment in or outside a cell. In some embodiments, one or more domains demonstrating functional sensitivity to amino acid substitutions can be refined by introducing further amino acid substitution or other substitutions. In some embodiments, amino acid substitutions can include one or more conservative amino acid replacements in non-functional regions of a modified antibody.

[0297] In some embodiments, anti-EPO antibodies, anti-EPOR antibodies, or anti-CD131 antibodies described herein can comprise an amino acid sequence with one or more insertions, deletions, and / or substitutions relative to any one of SEQ ID NOs: 1-4, 147-1086, 3805-3814, 3824-4403, or 5616-5991. For example, anti-EPO antibodies, anti-EPOR antibodies, or anti-CD131 antibodies described herein can comprise an amino acid sequence with at least 1, at least 2, at least 3, at least 4, at least 5, at least 6, at least 7, at least 8, at least 9, at least 10, at least 11, at least 12, at least 13, at least 14, at least 15, at leastAttorney Docket No. 62379-70760116, at least 17, at least 18, at least 19, at least 20, at least 25, or at least 30 amino acid insertions, deletions, and / or substitutions relative to any one of SEQ ID NOs: 1-4, 147-1086, 3805-3814, 3824-4403, or 5616-5991. In some embodiments, anti-EPO antibodies, anti -EPOR antibodies, or anti -CD 131 antibodies described herein can comprise an amino acid sequence with at most 1, at most 2, at most 3, at most 4, at most 5, at most 6, at most 7, at most 8, at most 9, at most 10, at most 11, at most 12, at most 13, at most 14, at most 15, at most 16, at most 17, at most 18, at most 19, at most 20, at most 25, at most 30, at most 35, at most 40, at most 45, or at most 50 amino acid insertions, deletions, and / or substitutions relative to any one of SEQ ID NOs: 1-4, 147-1086, 3805-3814, 3824-4403, or 5616-5991. In some embodiments, anti-EPO antibodies, anti -EPOR antibodies, or anti-CD131 antibodies described herein can comprise 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, 45, or 50 amino acid insertions, deletions, and / or substitutions relative to any one of SEQ ID NOs: 1-4, 147-1086, 3805-3814, 3824-4403, or 5616-5991. In some embodiments, the one or more insertions, deletions, and / or substitutions can be at the N-terminus, the C-terminus, within the amino acid sequence, or a combination thereof. In some embodiments, the one or more insertions, deletions, and / or substitutions can be contiguous, noncontiguous, or a combination thereof.

[0298] In some embodiments, the one or more amino acid substitutions described herein can comprise a conservative amino acid substitution. For example, anti-EPO antibodies, anti-EPOR antibodies, or anti-CD131 antibodies described herein can comprise one or more conservative amino acid substitutions. In some embodiments, anti-EPO antibodies, anti-EPOR antibodies, or anti-CD131 antibodies described herein can comprise an amino acid sequence with at least 1, at least 2, at least 3, at least 4, at least 5, at least 6, at least 7, at least 8, at least 9, at least 10, at least 11, at least 12, at least 13, at least 14, at least 15, at least 16, at least 17, at least 18, at least 19, at least 20, at least 25, or at least 30 conservative amino acid substitutions relative to any one of SEQ ID NOs: 1-4, 147-1086, 3805-3814, 3824-4403, or 5616-5991. In some embodiments, anti-EPO antibodies, anti-EPOR antibodies, or anti-CD131 antibodies described herein can comprise an amino acid sequence with at most 1, at most 2, at most 3, at most 4, at most 5, at most 6, at most 7, at most 8, at most 9, at most 10, at most 11, at most 12, at most 13, at most 14, at most 15, at most 16, at most 17, at most 18, at most 19, at most 20, at most 25, at most 30, at most 35, at most 40, at most 45, or at most 50 conservative amino acid substitutions relative to any one of SEQ ID NOs: 1- 4, 147-1086, 3805-3814, 3824-4403, or 5616-5991. In some embodiments, anti-EPO antibodies, anti-EPOR antibodies, or anti-CD131 antibodies described herein can comprise 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, 45, or 50 conservative amino acid substitutions relative to any one of SEQ ID NOs: 1-4, 147-1086, 3805-3814, 3824-4403, or 5616-5991.

[0299] In some aspects, modifications of antibodies described herein can be covalent modifications. In some embodiments, covalent modifications can be introduced by reacting one or more targeted amino acid residues of an antibody or functional fragment thereof with an organic derivatizing agent that can be capable of reacting with selected side chains or the N- or C-terminal residues. In some embodiments, covalent modifications can be introduced by altering the native glycosylation pattern of an antibody. For example, one or more carbohydrate moieties can be deleted from an antibody. For example, one or more glycosylation sites that are not present in an antibody can be added. In some embodiments, addition ofAttorney Docket No. 62379-707601glycosylation sites to an antibody can be accomplished by altering the amino acid sequence such that it contains one or more N-linked glycosylation sites. In some embodiments, addition of glycosylation sites to an antibody can be accomplished by adding or substituting one or more serine or threonine residues of an antibody (for O-linked glycosylation sites). In some embodiments, a number of carbohydrate moieties on an antibody can be increased by chemical or enzymatic coupling of glycosides to the antibody. In some embodiments, carbohydrate moieties present on an antibody can be removed chemically or enzymatically. In some embodiments, one or more of non-proteinaceous polymers (e.g, polyethylene glycol, polypropylene glycol, or polyoxyalkylenes) can be covalently added to an antibody.

[0300] In some embodiments, antibodies described herein can be attached at their C-terminal end to all, or part, of an immunoglobulin heavy chain derived from any antibody isotype, e.g., IgG, IgA, IgE, IgD, or IgM, or any of the isotype sub-classes, e.g., IgGl, IgG2b, IgG2a, IgG3, or IgG4. In some embodiments, antibodies, or functional fragments thereof may be glycosylated. In some embodiments, glycosylation at a variable domain framework residue can alter the binding interaction of the antibody with antigen. In some embodiments, antibodies, or functional fragments thereof may be modified by adding polyethylene glycol (PEG). In some embodiments, addition of PEG can lead to one or more of improved circulation time, improved solubility, improved resistance to proteolysis, reduced antigenicity and immunogenicity, improved bioavailability, reduced toxicity, improved stability, and / or easier formulation. In some embodiments, antibodies, or functional fragments thereof can be conjugated to, or recombinantly engineered with, an affinity tag (e.g., a purification tag).Engineered EPO Receptor Fusion Molecules or EPO Traps

[0301] The disclosure also encompasses engineered EPORs comprising extracellular domain (ECD) of EPOR. The ECD of EPOR comprises 2 domains, D 1 and D2, and these two domains are required for EPO binding. In some embodiments, Fc fusion protein of ECD EPOR-Fc can bind to EPO. In some embodiments, Fc fusion protein of ECD EPOR-Fc can block EPOR activation. In some embodiments, Fc fusion protein of ECD EPOR-Fc can comprise a mutation. For example, Fc fusion protein of ECD EPOR-Fc can comprise a mutation at amino acid residue F93. In some embodiments, Fc fusion protein of ECD EPOR-Fc can comprise F93A mutation. In some embodiments, Fc fusion protein of ECD EPOR-Fc comprising F93A mutation may not bind EPO. For example, a monomeric EPOR ECD comprising F93A mutation or a dimeric EPOR-Fc comprising F93A mutation may not bind EPO.

[0302] The disclosure also encompasses engineered hetero-EPORs comprising extra cellular domain (ECD) of CD 131. The ECD of CD131 comprises 4 domains, DI, D2, D3, and D4. DI and D2 domains are responsible for dimerization distal to the cell membrane. Without wishing to be bound by theory, D3 and D4 domains can be the regions interacting with EPOR to form a hetero-EPOR. In some embodiments, knobs-in-holes technology can be used to generate heterodimeric Fc fusion proteins with EPOR ECD and CD131 ECD. Non-limiting examples of designs of heterodimeric Fc fusion proteins with EPOR ECD and CD131 ECD are shown in Table 1-2 and the sequences are shown in FIGs. 39A-39D. In some embodiments, EPO binding may require D3 and D4 domains of CD 131. For example, the monomeric or dimeric EPOR with the F93A substitution may not bind EPO, however, a hetero-EPOR of a monomeric EPOR with the F93A mutation and a CD 131 monomer binds EPO. It seems that EPO bindingAttorney Docket No. 62379-707601to the hetero-EPOR is specific to CD131 subunit. In some embodiments, heterodimeric EPOR(F93A) / CD131-Fc may be used to specifically block hetero-EPORs but not homo-EPORs. In some embodiments, the EPOR ECD and CD 131 ECD lack the signal sequence of the polypeptide.Table 1-2. Design of Heterodimeric EPOR / CD131-Fc Fusion ProteinsEPOR Arm (holes) CD131 Arm (knobs)hEPOR ECDhCD131 ECDhCD131 D3D4hCD131 D4hEPOR ECD (F93A)RNAi and Small Molecules

[0303] RNAi and small molecules that reduce expression or activity of EPO, EPOR, and / or CD 131 can be used to overcome tumor suppressive microenvironments in certain tumors. RNAi includes, for example, siRNA, miRNA, antisense RNA, IncRNA, etc.

[0304] RNA interference is a method of post-transcriptional gene regulation that is conserved throughout many eukaryotic organisms. RNAi can be induced by short (i.e., <30 nucleotide) double stranded RNA (“dsRNA”) molecules which are present in the cell. These short dsRNA molecules, called “short interfering RNA” or “siRNA,” cause the destruction of target RNAs which share sequence homology with the siRNA. It is believed that the siRNA and the targeted RNA bind to an “RNA-induced silencing complex” or “RISC,” which cleaves the targeted RNA. The siRNA can be recycled much like a multiple-turnover enzyme, with a single siRNA molecule capable of inducing cleavage of approximately 1000 target RNA molecules.

[0305] In an aspect, the disclosure relates to regulatory RNAs for inhibiting the expression of EPO (erythropoietin), EPOR (erythropoietin receptor) and / or CD 131.

[0306] Regulatory RNAs (e.g., siRNAs) described herein can target EPO mRNA to reduce the half-life and / or function of the EPO mRNA. Regulatory RNAs (e.g., siRNAs) can target exons and UTRs of the EPO mRNA. The cDNA sequence of human EPO (NCBI Reference Sequence: NM_000799.4) is:1 cctttcccag atagcacgct ccgccagtcc caagggtgcg caaccggctg cactcccctc 61 ccgcgaccca gggcccggga gcagccccca tgacccacac gcacgtctgc agcagccccg 121 ctcacgcccc ggcgagcctc aacccaggcg tcctgcccct gctctgaccc cgggtggccc 181 ctacccctgg cgacccctca cgcacacagc ctctccccca cccccacccg cgcacgcaca 241 catgcagata acagccccga cccccggcca gagccgcaga gtccctgggc caccccggcc 301 gctcgctgcg ctgcgccgca ccgcgctgtc ctcccggagc cggaccgggg ccaccgcgcc 361 cgctctgctc cgacaccgcg ccccctggac agccgccctc tcctccaggc ccgtggggct 421 ggccctgcac cgccgagctt cccgggatga gggcccccgg tgtggtcacc cggcgcgccc 481 caggtcgctg agggaccccg gccaggcgcg gagatggggg tgcacgaatg tcctgcctgg 541 ctgtggcttc tcctgtccct gctgtcgctc cctctgggcc tcccagtcct gggcgcccca 601 ccacgcctca tctgtgacag ccgagtcctg gagaggtacc tcttggaggc caaggaggcc 661 gagaatatca cgacgggctg tgctgaacac tgcagcttga atgagaatat cactgtccca 721 gacaccaaag ttaatttcta tgcctggaag aggatggagg tcgggcagca ggccgtagaa 781 gtctggcagg gcctggccct gctgtcggaa gctgtcctgc ggggccaggc cctgttggtc 841 aactcttccc agccgtggga gcccctgcag ctgcatgtgg ataaagccgt cagtggcctt 901 cgcagcctca ccactctgct tcgggctctg ggagcccaga aggaagccat ctcccctcca 961 gatgcggcct cagctgctcc actccgaaca atcactgctg acactttccg caaactcttc 1021 cgagtctact ccaatttcct ccggggaaag ctgaagctgt acacagggga ggcctgcagg 1081 acaggggaca gatgaccagg tgtgtccacc tgggcatatc caccacctcc ctcaccaacaAttorney Docket No. 62379-7076011141 ttgcttgtgc cacaccctcc cccgccactc ctgaaccccg tcgaggggct ctcagctcag 1201 cgccagcctg tcccatggac actccagtgc cagcaatgac atctcagggg ccagaggaac 1261 tgtccagaga gcaactctga gatctaagga tgtcacaggg ccaacttgag ggcccagagc 1321 aggaagcatt cagagagcag ctttaaactc agggacagag ccatgctggg aagacgcctg 1381 agctcactcg gcaccctgca aaatttgatg ccaggacacg ctttggaggc gatttacctg 1441 ttttcgcacc taccatcagg gacaggatga cctggataac ttaggtggca agctgtgact 1501 tctccaggtc tcacgggcat gggcactccc ttggtggcaa gagccccctt gacaccgggg 1561 tggtgggaac catgaagaca ggatgggggc tggcctctgg ctctcatggg gtccaagttt 1621 tgtgtattct tcaacctcat tgacaagaac tgaaaccacc aa (SEQ ID NO: 5).

[0307] Exemplary nucleic acids encoding RNAi targeting mRNA encoding EPO include siRNA targeting the sequences (these sequences will have U instead of T in the mRNA):CTTGAATGAGAATATCACTGTCCCA (SEQ ID NO: 6) GCAGCTTGAATGAGAATATCACTGT (SEQ ID NO: 7) GCATGTGGATAAAGCCGTCAGTGGC (SEQ ID NO: 8) CCGAACAATCACTGCTGACACTTTC (SEQ ID NO: 9) CTTTCCGCAAACTCTTCCGAGTCTA (SEQ ID NO: 10) AAACTCTTCCGAGTCTACTCCAATT (SEQ ID NO: 11) GAGAGCAACTCTGAGATCTAAGGAT (SEQ ID NO: 12) AGAGCAACTCTGAGATCTAAGGATG (SEQ ID NO: 13) GAGCAACTCTGAGATCTAAGGATGT (SEQ ID NO: 14) CAGGAAGCATTCAGAGAGCAGCTTT (SEQ ID NO: 15) AGGAAGCATTCAGAGAGCAGCTTTA (SEQ ID NO: 16) GAAGCATTCAGAGAGCAGCTTTAAA (SEQ ID NO: 17) GAGAGCAGCTTTAAACTCAGGGACA (SEQ ID NO: 18) CAGGACACGCTTTGGAGGCGATTTA (SEQ ID NO: 19) CATCAGGGACAGGATGACCTGGATA (SEQ ID NO: 20) GGGACAGGATGACCTGGATAACTTA (SEQ ID NO: 21)

[0308] Regulatory RNAs (e.g., siRNAs) described herein can target EPOR mRNA to reduce the halflife and / or function of the EPOR mRNA. Regulatory RNAs (e.g., siRNAs) can target exons and UTRs of the EPORmRNA. The cDNA sequence ofhuman EPOR (NCBI Reference Sequence: NM_000121.4) is:1 ggtcagctgc gtccggcgga ggcagctgct gacccagctg tggactgtgc cgggggcggg 61 ggacggaggg gcaggagccc tgggctcccc gtggcggggg ctgtatcatg gaccacctcg 121 gggcgtccct ctggccccag gtcggctccc tttgtctcct gctcgctggg gccgcctggg 181 cgcccccgcc taacctcccg gaccccaagt tcgagagcaa agcggccttg ctggcggccc 241 gggggcccga agagcttctg tgcttcaccg agcggttgga ggacttggtg tgtttctggg 301 aggaagcggc gagcgctggg gtgggcccgg gcaactacag cttctcctac cagctcgagg 361 atgagccatg gaagctgtgt cgcctgcacc aggctcccac ggctcgtggt gcggtgcgct 421 tctggtgttc gctgcctaca gccgacacgt cgagcttcgt gcccctagag ttgcgcgtca 481 cagcagcctc cggcgctccg cgatatcacc gtgtcatcca catcaatgaa gtagtgctcc 541 tagacgcccc cgtggggctg gtggcgcggt tggctgacga gagcggccac gtagtgttgc 601 gctggctccc gccgcctgag acacccatga cgtctcacat ccgctacgag gtggacgtct 661 cggccggcaa cggcgcaggg agcgtacaga gggtggagat cctggagggc cgcaccgagt 721 gtgtgctgag caacctgcgg ggccggacgc gctacacctt cgccgtccgc gcgcgtatgg 781 ctgagccgag cttcggcggc ttctggagcg cctggtcgga gcctgtgtcg ctgctgacgc 841 ctagcgacct ggaccccctc atcctgacgc tctccctcat cctcgtggtc atcctggtgc 901 tgctgaccgt gctcgcgctg ctctcccacc gccgggctct gaagcagaag atctggcctg 961 gcatcccgag cccagagagc gagtttgaag gcctcttcac cacccacaag ggtaacttccAttorney Docket No. 62379-7076011021 agctgtggct gtaccagaat gatggctgcc tgtggtggag cccctgcacc cccttcacgg 1081 aggacccacc tgcttccctg gaagtcctct cagagcgctg ctgggggacg atgcaggcag 1141 tggagccggg gacagatgat gagggccccc tgctggagcc agtgggcagt gagcatgccc 1201 aggataccta tctggtgctg gacaaatggt tgctgccccg gaacccgccc agtgaggacc 1261 tcccagggcc tggtggcagt gtggacatag tggccatgga tgaaggctca gaagcatcct 1321 cctgctcatc tgctttggcc tcgaagccca gcccagaggg agcctctgct gccagctttg 1381 agtacactat cctggacccc agctcccagc tcttgcgtcc atggacactg tgccctgagc 1441 tgccccctac cccaccccac ctaaagtacc tgtaccttgt ggtatctgac tctggcatct 1501 caactgacta cagctcaggg gactcccagg gagcccaagg gggcttatcc gatggcccct 1561 actccaaccc ttatgagaac agccttatcc cagccgctga gcctctgccc cccagctatg 1621 tggcttgctc ttaggacacc aggctgcaga tgatcaggga tccaatatga ctcagagaac 1681 cagtgcagac tcaagactta tggaacaggg atggcgaggc ctctctcagg agcaggggca 1741 ttgctgattt tgtctgccca atccatcctg ctcaggaaac cacaaccttg cagtattttt 1801 aaatatgtat agtttttttt tgtatctata tatatatata cacatatgta tgtaagtttt 1861 tctaccatga tttctacaaa caccctttaa gtcccatctt cccctgggca taggccatag 1921 ggatagaagt taaagttctt gagcttattc agaagctgga tctgcaatct gaatgctact 1981 cataacataa caaaatagta tgttaaacag ctcttaaatc ttactggctt accacattaa 2041 atgatttctc tctcctaact cagctcaaat gggcagccat ccatgggatg agtcagaggt 2101 tcagactctt ccagtctgta gctctacctt ctcttagggt acttagatgg atcccctgtt 2161 ctacaaactg ccagtcagca agggaagaaa aagggcagca atgaccctca atgggccatt 2221 tgagggatct ggcctggaaa tgggcttcct ctcttcttct cacacctcac tggctggaaa 2281 cagtcacatg accccagtca catgaaaggc caggaaactt agtttagctg tacacccagg 2341 aagggcaaag ctgtttaagg gccactagct agtctctgcc actaataata ataaaagtaa 2401 ttctgaatca g (SEQ ID NO: 22).

[0309] Exemplary nucleic acids encoding RNAi targeting mRNA encoding EPOR include siRNA targeted at the following sequences (these sequence will be in the mRNA with U instead of T):CACCGAGCGGTTGGAGGACTTGGTG (SEQ ID NO: 23) CGAGGATGAGCCATGGAAGCTGTGT (SEQ ID NO: 24) ATGGAAGCTGTGTCGCCTGCACCAG (SEQ ID NO: 25) CACCAGGCTCCCACGGCTCGTGGTG (SEQ ID NO: 26) ATATCACCGTGTCATCCACATCAAT (SEQ ID NO: 27) ACATCAATGAAGTAGTGCTCCTAGA (SEQ ID NO: 28) ATCAATGAAGTAGTGCTCCTAGACG (SEQ ID NO: 29) CGTGGGGCTGGTGGCGCGGTTGGCT (SEQ ID NO: 30) CTGGAGGGCCGCACCGAGTGTGTGC (SEQ ID NO: 31) ACCACCCACAAGGGTAACTTCCAGC (SEQ ID NO: 32) CAGAATGATGGCTGCCTGTGGTGGA (SEQ ID NO: 33) AGCGCTGCTGGGGGACGATGCAGGC (SEQ ID NO: 34) GAGGGAGCCTCTGCTGCCAGCTTTG (SEQ ID NO: 35) CCTGTACCTTGTGGTATCTGACTCT (SEQ ID NO: 36) ATCTGACTCTGGCATCTCAACTGAC (SEQ ID NO: 37) TCTGGCATCTCAACTGACTACAGCT (SEQ ID NO: 38) CAGGGGACTCCCAGGGAGCCCAAGG (SEQ ID NO: 39) AGCCTCTGCCCCCCAGCTATGTGGC (SEQ ID NO: 40) CTCAAGACTTATGGAACAGGGATGG (SEQ ID NO: 41) CTTACTGGCTTACCACATTAAATGA (SEQ ID NO: 42)Attorney Docket No. 62379-707601

[0310] Regulatory RNAs (e.g., siRNAs) described herein can target CD131 mRNA to reduce the halflife and / or function of the CD 131 mRNA. Regulatory RNAs (e.g., siRNAs) can target exons and UTRs of the CD131 mRNA. The cDNA sequence of CD131 (NCBI Reference Sequence: NM_000395.3) is:1 actctgccta gaggctccag aagaagactg gtctctccca ccacacagag gcctggagga 61 ggcagaggcc aggagggaga ggtcccaaga gcctgtgaaa tgggtctggc ctggctccca 121 gctgggcagg aacacaggac ttcaggacac taaggaccct gtcatgccca tggccagcac 181 ccaccagtgc tggtgcctgc ctgtccagag ctgaccaggg agatggtgct ggcccagggg 241 ctgctctcca tggccctgct ggccctgtgc tgggagcgca gcctggcagg ggcagaagaa 301 accatcccgc tgcagaccct gcgctgctac aacgactaca ccagccacat cacctgcagg 361 tgggcagaca cccaggatgc ccagcggctc gtcaacgtga ccctcattcg ccgggtgaat 421 gaggacctcc tggagccagt gtcctgtgac ctcagtgatg acatgccctg gtcagcctgc 481 ccccatcccc gctgcgtgcc caggagatgt gtcattccct gccagagttt tgtcgtcact 541 gacgttgact acttctcatt ccaaccagac aggcctctgg gcacccggct caccgtcact 601 ctgacccagc atgtccagcc tcctgagccc agggacctgc agatcagcac cgaccaggac 661 cacttcctgc tgacctggag tgtggccctt gggagtcccc agagccactg gttgtcccca 721 ggggatctgg agtttgaggt ggtctacaag cggcttcagg actcttggga ggacgcagcc 781 atcctcctct ccaacacctc ccaggccacc ctggggccag agcacctcat gcccagcagc 841 acctacgtgg cccgagtacg gacccgcctg gccccaggtt ctcggctctc aggacgtccc 901 agcaagtgga gcccagaggt ttgctgggac tcccagccag gggatgaggc ccagccccag 961 aacctggagt gcttctttga cggggccgcc gtgctcagct gctcctggga ggtgaggaag 1021 gaggtggcca gctcggtctc ctttggccta ttctacaagc ccagcccaga tgcaggggag 1081 gaagagtgct ccccagtgct gagggagggg ctcggcagcc tccacaccag gcaccactgc 1141 cagattcccg tgcccgaccc cgcgacccac ggccaataca tcgtctctgt tcagccaagg 1201 agggcagaga aacacataaa gagctcagtg aacatccaga tggcccctcc atccctcaac 1261 gtgaccaagg atggagacag ctacagcctg cgctgggaaa caatgaaaat gcgatacgaa 1321 cacatagacc acacatttga gatccagtac aggaaagaca cggccacgtg gaaggacagc 1381 aagaccgaga ccctccagaa cgcccacagc atggccctgc cagccctgga gccctccacc 1441 aggtactggg ccagggtgag ggtcaggacc tcccgcaccg gctacaacgg gatctggagc 1501 gagtggagtg aggcgcgctc ctgggacacc gagtcggtgc tgcctatgtg ggtgctggcc 1561 ctcatcgtga tcttcctcac catcgctgtg ctcctggccc tccgcttctg tggcatctac 1621 gggtacaggc tgcgcagaaa gtgggaggag aagatcccca accccagcaa gagccacctg 1681 ttccagaacg ggagcgcaga gctttggccc ccaggcagca tgtcggcctt cactagcggg 1741 agtcccccac accaggggcc gtggggcagc cgcttccctg agctggaggg ggtgttccct 1801 gtaggattcg gggacagcga ggtgtcacct ctcaccatag aggaccccaa gcatgtctgt 1861 gatccaccat ctgggcctga cacgactcca gctgcctcag atctacccac agagcagccc 1921 cccagccccc agccaggccc gcctgccgcc tcccacacac ctgagaaaca ggcttccagc 1981 tttgacttca atgggcccta cctggggccg ccccacagcc gctccctacc tgacatcctg 2041 ggccagccgg agcccccaca ggagggtggg agccagaagt ccccacctcc agggtccctg 2101 gagtacctgt gtctgcctgc tggggggcag gtgcaactgg tccctctggc ccaggcgatg 2161 ggaccaggac aggccgtgga agtggagaga aggccgagcc agggggctgc agggagtccc 2221 tccctggagt ccgggggagg ccctgcccct cctgctcttg ggccaagggt gggaggacag 2281 gaccaaaagg acagccctgt ggctataccc atgagctctg gggacactga ggaccctgg...

Claims

1. Attorney Docket No. 62379-707601CLAIMS WHAT IS CLAIMED IS:

1. A method for treating or inhibiting cancer metastasis in a subject, comprising:administering a pharmaceutically effective amount of a composition that:i) inhibits or reduces binding of an erythropoietin (EPO) protein to an EPO receptor (EPOR) complex, wherein said EPO receptor complex comprises (a) at least two EPOR subunits or (b) at least one EPOR subunit and at least one CD 131 subunit;ii) inhibits or reduces formation of an EPO receptor (EPOR) complex, wherein said EPO receptor complex comprises (a) at least two EPOR subunits or (b) at least one EPOR subunit and at least one CD 131 subunit;iii) inhibits or reduces activation of an EPO receptor (EPOR) complex on a plurality of macrophages, wherein said EPO receptor complex comprises (a) at least two EPOR subunits or (b) at least one EPOR subunit and at least one CD 131 subunit;iv) reduces an amount of circulating EPO protein in said subject; and / orv) reduces an expression level of an EPO receptor (EPOR) complex on a plurality of macrophages, wherein said EPO receptor complex comprises (a) at least two EPOR subunits or (b) at least one EPOR subunit and at least one CD 131 subunit;thereby:a) treating the cancer metastasis;b) inhibiting formation of a pre-metastatic niche in a distant site that is different from a location of a primary tumor; orc) inhibiting a metastatic nodule growth.

2. The method of claim 1, wherein said EPO receptor complex is a homo-EPO receptor complex that comprises at least two EPOR subunits.

3. The method of claim 2, wherein said homo-EPO receptor complex comprises or consists of two EPOR subunits.

4. The method of claim 1, wherein said EPO receptor complex is a hetero-EPO receptor complex that comprises at least one EPOR subunit and at least one CD 131 subunit.

5. The method of claim 4, wherein said hetero-EPO receptor complex comprises or consists of an EPOR subunit and a CD 131 subunit.

6. The method of any one of the preceding claims, wherein said subject has an existing metastatic cancer.

7. The method of any one of claims 1-5, wherein said subject does not have an existing metastatic cancer.

8. The method of any one of the preceding claims, further comprising inhibiting or reducing exacerbating said primary tumor.

9. The method of any one of the preceding claims, further comprising increasing CD8+ T cell / regulatory T cell ratio.Attorney Docket No. 62379-70760110. The method of any one of the preceding claims, further comprising inhibiting development of regulatory T cells (Tregs).

11. The method of claim 9, wherein CD8+ T cells expresses Cluster of Differentiation 45 (CD45), CD3, CD8, Perforin, Interferon gamma (IFNy), Granzyme B, or tumor necrosis factor alpha (TNFa).

12. The method of claim 9 or 10, wherein Tregs express Cluster of Differentiation 4 (CD4), CD25, CD127, Forkhead Box P3 (FoxP3), CD39, protein tyrosine phosphatase receptor type C (CD45RA), Interleukin-2 (IL-2), or a Cytotoxic T-Lymphocyte Associated Protein 4 (CTLA-4).

13. The method of any one of the preceding claims, further comprising rendering said cancer metastasis sensitive to an immune checkpoint inhibitor.

14. The method of claim 13, wherein said immune checkpoint inhibitor comprises a Cytotoxic T- Lymphocyte Associated Protein 4 (CTLA-4) inhibitor, a Programmed Death 1 (PD-1) inhibitor, or a Programmed Death Ligand 1 (PD-L1) inhibitor.

15. The method of any one of the preceding claims, wherein said distant site is different from a location of said primary tumor or said distant site is a tissue that is distinct from a tissue where said primary tumor is located.

16. The method of any one of the preceding claims, wherein said distant site is located in liver.

17. The method of any one of the preceding claims, wherein said primary tumor is located in colon.

18. The method of any one of the preceding claims, wherein said primary tumor is located in breast.

19. The method of any one of the preceding claims, wherein said primary tumor is located in pancreas.

20. The method of any one of the preceding claims, wherein said primary tumor is located in ovary.

21. The method of any one of the preceding claims, wherein said composition comprises an antibody or a functional fragment thereof.

22. The method of any one of the preceding claims, wherein said antibody or said functional fragment thereof selectively binds to an EPO receptor subunit, a CD 131 subunit, or a combination thereof.

23. The method of any one of the preceding claims, wherein said composition comprises a compound or a salt thereof, wherein said compound is an inhibitor of hypoxia-inducible factor (HIF), IL-la, IL-ip, TNF-a, IL-6, estrogen receptors, phospholipase C-yl, or Cbl / p85 / Episin-l pathway.

24. The method of any one of the preceding claims, wherein said composition comprises a plurality of lipid nanoparticles (LNPs) comprising siRNA directed to hetero-EPO receptor on macrophages.

25. The method of any one of the preceding claims, wherein said composition comprises an engineered EPO receptor comprising an extracellular domain (ECD) of said EPO receptor subunit.

26. The method of any one of claims 21-25, wherein said composition further comprises a second antibody or a functional fragment thereof that selectively binds to an immune checkpoint protein.

27. The method of claim 26, wherein said immune checkpoint protein comprises PD-1, PD-L1, or CTLA- 4.

28. The method of claim 27, wherein said immune checkpoint protein is PD-1.

29. A method for treating or inhibiting cancer metastasis in a subject, the method comprising:administering a pharmaceutically effective amount of a composition that comprises (i) an antibody or a functional fragment thereof, or (ii) an engineered fusion protein or a functional fragment thereof,Attorney Docket No. 62379-707601wherein said antibody or said functional fragment thereof selectively binds to a first target and a second target,wherein the first target comprises an erythropoietin (EPO) protein, an EPO receptor subunit, a CD131 subunit, or a combination thereof,wherein the second target comprises an immune checkpoint protein, andwherein said antibody or said functional fragment thereof comprises a first antigen-binding domain and a second antigen-binding domain.

30. The method of claim 29, wherein said binding of said antibody or said functional fragment thereof to said first target inhibits or reduces (i) binding of an erythropoietin (EPO) protein to an EPO receptor (EPOR) complex, wherein said EPO receptor complex comprises (a) at least two EPOR subunits or (b) at least one EPOR subunit and at least one CD 131 subunit; (ii) formation of an EPO receptor (EPOR) complex, wherein said EPO receptor complex comprises (a) at least two EPOR subunits or (b) at least one EPOR subunit and at least one CD 131 subunit; (iii) activation of an EPO receptor (EPOR) complex on a plurality of macrophages, wherein said EPO receptor complex comprises (a) at least two EPOR subunits or (b) at least one EPOR subunit and at least one CD 131 subunit.

31. The method of claim 30, wherein said inhibiting or reducing (i) binding of an erythropoietin (EPO) protein to an EPO receptor (EPOR) complex, wherein said EPO receptor complex comprises (a) at least two EPOR subunits or (b) at least one EPOR subunit and at least one CD 131 subunit; or (ii) formation of an EPO receptor (EPOR) complex, wherein said EPO receptor complex comprises (a) at least two EPOR subunits or (b) at least one EPOR subunit and at least one CD 131 subunit inhibits immune tolerance.

32. The method of claim 29, wherein said binding of said antibody or said functional fragment thereof to said second target inhibits immune checkpoint.

33. The method of claim 32, wherein said inhibiting immune checkpoint inhibits immune tolerance.

34. The method of any one of claims 29-33, wherein said first antigen-binding domain comprises:a heavy chain variable region (VH) comprising a VH complementarity determining region 1 (VH- CDR1) sequence, a VH-CDR2 sequence, and a VH-CDR3 sequence; and a light chain variable region (VL) comprising a VL-CDR1 sequence, a VL-CDR2 sequence, and a VL-CDR3 sequence;a VH and a kappa chain variable regions (VK); ora VH and a lambda chain variable regions.

35. The method of any one of claims 29-34, wherein said first antigen-binding domain and / or said second antigen-binding domain comprises a Fab, a Fab’, a (Fab’)2, a variable fragment (Fv), a single chain variable fragment (scFv), a scFv-Fc, a Fab-Fc, a VHH, a non-antibody scaffold, or a combination thereof.

36. The method of claim 35, wherein said second antigen-binding domain comprises a VHH.

37. The method of any one of claims 29-36, wherein said immune checkpoint protein comprises PD-1, PD-L1, or CTLA-4.

38. The method of claim 37, wherein said immune checkpoint protein is PD-1.Attorney Docket No. 62379-70760139. The method of any one of claims 29-38, wherein said antibody or said functional fragment thereof is an IgG, an IgM, an IgE, an IgA, an IgD, is derived therefrom, or a combination thereof.

40. The method of any one of claims 29-39, wherein said antibody or said functional fragment thereof comprises a monoclonal antibody, a grafted antibody, a chimeric antibody, a human antibody, a humanized antibody, or a combination thereof.

41. The method of any one of claims 29-40, wherein said first antigen binding domain and / or said second antigen binding domain is isolated, recombinant, synthetic, or a combination thereof.

42. The method of any one of claims 29-41, wherein said antibody or a functional variant thereof further comprises a peptide linker.

43. The method of any one of claims 29-42, wherein said engineered fusion protein or said functional fragment thereof comprises an engineered EPO receptor comprising an extracellular domain (ECD) of said EPO receptor subunit.

44. The method of any one of claims 29-43, wherein said first target comprises an EPO receptor subunit, a CD 131 subunit, or a combination thereof.

45. The method of any one of claims 29-44, wherein said subject has an existing metastatic cancer.

46. The method of any one of claims 29-44, wherein said subject does not have an existing metastatic cancer.

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