Lymphotoxin beta receptor agonist binding proteins

Description

LYMPHOTOXIN BETA RECEPTOR AGONIST BINDING PROTEINS

[0001] The benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No.63 / 472,565, filed June 12, 2023, is hereby claimed, and the disclosure thereof is hereby incorporated by reference herein. FIELD

[0002] The field of this invention relates to compositions and methods related to lymphotoxin beta receptor (“LTβR” or “LTBR”) binding proteins. BACKGROUND OF VARIOUS EMBODIMENTS

[0003] Cancer immunotherapy enhances cancer patient survival by inducing or boosting an effective anti-tumor immune response in the patient. Immune checkpoint inhibition is one form of immunotherapy that has changed the treatment landscape for many tumors. This therapy works by blocking the immunosuppressive signals of immune checkpoint proteins, such as cytotoxic T lymphocyte antigen 4 (CTLA-4), programmed cell death protein 1 (PD-1), and programmed cell death ligand 1 (PD-L1), that mediate tumor immune evasion. Blockade of this immunosuppressive signaling restores and / or enhances the body’s natural anti-tumor response to facilitate tumor eradication. While this form of immunotherapy has generated durable responses in many patients, it fails to generate therapeutic response in many others. In particular, patients with “cold tumors”, i.e., tumors characterized by a lack of infiltrating T cells and the presence of other immunosuppressive cells, are typically resistant to immune checkpoint inhibitor therapy. Accordingly, there is a need in the art for an anti-cancer therapy that can induce T cell infiltration into the tumor microenvironment to inflame such cold tumors and overcome this resistance thereby rendering the tumor amenable to immunotherapy. SUMMARY OF VARIOUS EMBODIMENTS

[0004] A first aspect of the present disclosure is directed to an agonist lymphotoxin β receptor (LTβR) binding protein. The agonist LTβR binding protein of the disclosure binds one or more amino acid residues of human LTβR cysteine-rich domain 4 (CRD4) comprising amino acid residues 169-211 of SEQ ID NO: 1 and (a) does not inhibit LIGHT binding to LTβR or (b) does not inhibit LTα1β2 binding to LTβR.

[0005] Another aspect of the present disclosure is directed to a bispecific agonist LTβR binding protein. This bispecific binding protein comprises a LTβR binding domain, where the LTβR binding domain binds one or more amino acid residues of human LTβR CRD4 comprising amino acid residues 169- 211 of SEQ ID NO: 1; and a tumor-associated antigen binding domain. This bispecific binding protein agonizes LTβR activity, and (a) does not inhibit LIGHT binding to LTβR or (b) does not inhibit LTα1β2 binding to LTβR.

[0006] Other aspects of the present disclosure are directed to polynucleotides encoding the agonist LTβR binding proteins and bispecific LTβR binding proteins of the disclosure; vectors comprising these polynucleotides; and host cells comprising these vectors.

[0007] Additional aspects of the present disclosure are directed to pharmaceutical compositions comprising an agonist LTβR binding protein, a bispecific agonist LTβR binding protein, or a polynucleotide or vector encoding the same as described herein.

[0008] Another aspect of the disclosure is directed to methods of treating cancer in a subject that involve administering, to the subject having cancer, an agonist LTβR binding protein. The agonist LTβR binding protein used in these methods binds one or more amino acid residues of human LTβR cysteine-rich domain 4 (CRD4) comprising amino acid residues 169-211 of SEQ ID NO: 1 and (a) does not inhibit LIGHT binding to LTβR or (b) does not inhibit LTα1β2 binding to LTβR

[0009] Another aspect of the disclosure is directed to methods of treating cancer in a subject that involve administering, to the subject having cancer, a bispecific agonist LTβR binding protein. This bispecific agonist LTβR binding protein comprises a LTβR binding domain and a tumor-associated antigen binding domain. This LTβR binding domain binds one or more amino acid residues of human LTβR cysteine-rich domain (CRD4) comprising amino acid residues 169-211 of SEQ ID NO: 1. The bispecific LTβR binding protein further comprises a tumor-associated antigen binding domain. The bispecific LTβR binding protein agonizes LTβR activity and (a) does not inhibit LIGHT binding to LTβR or (b) does not inhibit LT1α2β binding to LTβR.

[0010] The potential utility of LTβR agonism as an anti-tumor therapy was suggested more than 20 years ago (see e.g., Browning et al., “Signaling through the Lymphotoxin β Receptor Induces the Death of Some Adenocarcinoma Tumor Lines,” J. Exp. Med. 183:867 (1996)). Despite this, only one LTβR antibody has progressed to a Phase I clinical trial, and that trial ended prematurely. LTβR is ubiquitously expressed on various cells throughout the body and plays a critical role in the formation and maintenance of lymphoid organs and various immune cell populations. Thus, for an LTβR antibody to be therapeutically effective and safe, it must selectively activate LTβR signaling in the tumor microenvironment without disrupting normal LTβR signaling outside of the tumor microenvironment. While targeting agonism to the tumor environment can be achieved using a bispecific modality that provides cross-linking specific LTβR activation; if not properly designed, the cross-linking dependent agonist will act as an antagonist when bound to LTβR in a target-independent manner. Given the importance of LTβR in the maintenance of immune functions, antagonizing its activity presents serious safety concerns.

[0011] The agonist LTβR binding proteins disclosed herein overcome this problem by exerting agonist activity in a cross-linking target-dependent manner without antagonizing normal LTβR signaling activity. This was achieved by specifically selecting for and engineering LTβR binding proteins that agonize LTβR in a cross-linking specific manner when bound to the cysteine rich domain 4 (CRD4) of LTβR without blocking endogenous LTβR ligand (i.e., LIGHT or LTα1β2) binding and signaling activity.BRIEF DESCRIPTION OF THE FIGURES

[0012] FIGs. 1A–1B show tumor associated antigen (TAA)-targeted LTβR agonism increases lymphocyte infiltration in the human EpCAM-expressing B16F10 melanoma tumor model. As shown in the graph of FIG.1A, the total number of T cells (CD3+T cells) infiltrating the tumor tissue increased at the 3 mg / kg dose of the human EpCAM x murine LTβR bispecific antibody relative to administration of an isotype control antibody. As shown in the graph of FIG.1B, the total number of B cells (CD19+B cells) infiltrating the tumor tissue increased with increasing doses (0.3, 3, and 30 mg / kg) of the huEpCAM x muLTβR BsAb relative to administration of an isotype control antibody.

[0013] FIG. 2 shows tumor associated antigen (TAA)-targeted LTβR agonism induces HEV formation in the human EpCAM-expressing B16F10 melanoma tumor model. FIG. 2 shows the immunohistochemical analysis of HEV formation in tumor tissue following isotype control treatment (top image) and 3mg / kg of huEpCAM-muLTβR bispecific antibody treatment (bottom image) as described in Example 1 herein.

[0014] FIG. 3 shows tumor associated antigen (TAA)-targeted LTβR agonism increased T cell infiltration in a human KPC pancreatic tumor model. The graph of FIG.3 shows T cells counts per gram of tumor tissue increased following administration of two different tool huLRRC15 x muLTβR BsAb to mice bearing a KPC M5 tumor. The huLRRC15 x muLTβR BsAb was administered twice a week for 3 doses before tumors were assessed with flow cytometry. One-way ANOVA with Dunnett’s multiple comparison test showed no significant difference against isotype, but treatments do show an upwards trend of T cell infiltration. Mean and SEM are represented in the graph.

[0015] FIG. 4 shows tumor associated antigen (TAA)-targeted LTβR agonism inhibited tumor growth in a human KPC pancreatic tumor model. The graph of FIG.4 shows mean tumor volume of KPC M5 pancreatic tumor model treated with PD-1 antibody, huLRRC15 x muLTβR BsAb, or the combination of these antibodies. huLRRC15 x muLTβR BsAb monotherapy (▼) produced a greater effect than PD-1 monotherapy (■). The combination of huLRRC15 x muLTβR BsAb and PD-1 Ab did show greater TGI, but the difference between the two treatment groups was not statistically significant. Two-way ANOVA with Tukey’s multiple comparison test demonstrated significance against isotype for huLRRC15 x muLTbR BsAb and huLRRC15 x muLTbR BsAb + PD-1 Ab (p<0.0001). N=10, Mean and SEM are represented in the graph.

[0016] FIG.5 contains Tables A and B summarizing characterization data of the LTβR antibodies identified in the first round of hybridoma screening. Table A contains functional potency values (EC50) and binding data, i.e., LTβR antibody binding to TNRFSF1 and TNRFSF2, mouse LTβR, and cynomolgus LTβR. Data is presented as GeoMean fold over mock transfected cells. Table A also shows the percent inhibition of human LIGHT or human LTα1β2 ligand binding to human LTβR in the presence of the indicated LTβR antibody as assessed using the single-point FACS bead-based receptor-ligand assay asdescribed in Example 4.6. Table B shows LTβR antibody binding affinity measurements (ka, kd, and KD) to human and cynomolgus LTβR.

[0017] FIG. 6 identifies the regions of the LTβR extracellular domain (ECD) (SEQ ID NO: 4) involved in the binding interaction with LTβR antibody, LIBC No.218990 (Bio. Reg. No.19320 / Well ID 30H1), as determined by hydrogen-deuterium exchange (HDX) mass spectrometry (MS) (see Example 6.1.1). Shown are deuterium uptake graphs of peptides corresponding to residues 56-64 and 81-101 of the LTβR extracellular domain (ECD) alone or in complex with the antibody. Protection from deuterium exchange in the complex derived peptides relative to non-complexed peptides indicates that one or more residues within these regions, i.e., residues 57-64 and 82-101, of the LTβR ECD are involved in the binding interaction (note that the N-terminal residues of a peptide does not have an amide hydrogen for measure and is therefore excluded in reporting epitope regions).

[0018] FIG. 7 identifies the regions of the LTβR ECD (SEQ ID NO: 4) involved in the binding interaction with LTβR antibody, LIBC No.218944 (Bio. Reg No.19321 / Well ID 31A3), as determined by HDX MS (see Example 6.1.1). Shown are deuterium uptake graphs of peptides corresponding to residues 3–9, 20–29, and 38–47 of the LTβR ECD alone or in complex with the antibody. Protection from deuterium exchange in the complex derived peptides relative to non-complexed peptides indicates that one or more residues within these regions, i.e., residues 4-9, 21-29, and 39-47, of the LTβR ECD are involved in the binding interaction (note that the N-terminal residues of a peptide does not have an amide hydrogen for measure and is therefore excluded in reporting epitope regions).

[0019] FIG. 8 identifies the regions of the LTβR ECD (SEQ ID NO: 4) involved in the binding interaction with LTβR antibody, LIBC No.219058 (Bio. Reg. No.19324 / Well ID 36G2), as determined by HDX MS (see Example 6.1.1). Shown are deuterium uptake graphs of peptides corresponding to residues 56-64 and 81-101 of the LTβR ECD alone or in complex with the antibody. Protection from deuterium exchange in the complex derived peptides relative to non-complexed peptides indicates that one or more residues within these regions, i.e., residues 57-64 and 82-101, of the LTβR ECD are involved in the binding interaction (note that the N-terminal residues of a peptide does not have an amide hydrogen for measure and is therefore excluded in reporting epitope regions).

[0020] FIG. 9 identifies the regions of the LTβR ECD (SEQ ID NO: 4) involved in the binding interaction with LTβR antibody, LIBC No. 219081 (Bio Reg. No. 19325 / Well ID 41B2), as determined by HDX MS (see Example 6.1.1). Shown are deuterium uptake graphs of peptides corresponding to residues 167–179 of the LTβR ECD alone or in complex with the antibody. Protection from deuterium exchange in the complex derived peptides relative to non-complexed peptides indicates that one or more residues within these regions, i.e., residue 168-179, of the LTβR ECD are involved in the binding interaction (note that the N-terminal residues of a peptide does not have an amide hydrogen for measure and is therefore excluded in reporting epitope regions).

[0021] FIG.10 identifies the regions of the LTβR ECD (SEQ ID NO: 4) involved in the binding interaction with LTβR antibody, LIBC No.219097 (Bio. Reg. No.19326 / Well ID 43D9), as determinedby HDX MS (see Example 6.1.1). Shown are deuterium uptake graphs of peptides corresponding to residues 38–42, 37–47, 56–64, and 65–70 of the LTβR ECD alone or in complex with the antibody. Protection from deuterium exchange in the complex derived peptides relative to non-complexed peptides indicates that one or more residues within these regions, i.e., residues 39–42 and 57–70, of the LTβR ECD are involved in the binding interaction (note that the N-terminal residues of a peptide does not have an amide hydrogen for measure and is therefore excluded in reporting epitope regions).

[0022] FIG. 11 identifies the regions of the LTβR ECD (SEQ ID NO: 4) involved in the binding interaction with LTβR antibody, LIBC No.218979 (Bio. Reg. No.19319 / Well ID 23E9), as determined by HDX MS (see Example 6.1.2). Shown are deuterium uptake graphs of peptides corresponding to residues 154–166, 167–177, 167–181, and 178–193 of the LTβR ECD alone or in complex with the antibody. Protection from deuterium exchange in the complex derived peptides relative to non-complexed peptides indicates that one or more residues within these regions, i.e., residues 168-178, of the LTβR ECD are involved in the binding interaction (note that the N-terminal residues of a peptide does not have an amide hydrogen for measure and is therefore excluded in reporting epitope regions).

[0023] FIG.12 identifies the regions of the LTβR ECD (SEQ ID NO: 4) involved in the binding interaction with LTβR antibody, LIBC No.219051 (Bio. Reg. No.19323 / Well ID 35F5), as determined by HDX MS (see Example 6.1.2). Shown are deuterium uptake graphs of peptides corresponding to residues 1–9, 1–20 (unglycosylated and glycosylated), 10–20, and 19–28 of the LTβR ECD alone or in complex with the antibody. Protection from deuterium exchange in the complex derived peptides relative to non-complexed peptides indicates that one or more residues within regions 1–19 of the LTβR ECD are involved in the binding interaction (note that Q1 has been converted to pyro-Q, which contains a measurable amide hydrogen).

[0024] FIG.13 identifies the variable heavy (VH) and variable light (VL) domain regions of LIBC No. 218990 (19320 / 30H1) involved in the binding interaction with LTβR. Shown are deuterium uptake graphs of VH and VL domain peptides alone or when bound to LTβR. Protection from deuterium exchange in the complexed peptides relative to non-complexed peptides indicates that one or more CDR residues within these regions of the antibody are involved in the binding interaction. The regions including these one or more residues are boxed in the shown VH and VL sequences and the three CDR regions of each variable domain are underlined.

[0025] FIGs.14A–14B identify the variable heavy (VH) and variable light (VL) domain regions of LIBC No. 218944 (19321 / 31A3) involved in the binding interaction with LTβR. Shown are deuterium uptake graphs of VH (FIG. 14A) and VL (FIG. 14B) domain peptides alone or when bound to LTβR. Protection from deuterium exchange in the complexed peptides relative to non-complexed peptides indicates that one or more CDR residues within these regions of the antibody are involved in the binding interaction. The regions including these one or more residues are boxed in the shown VH (FIG.14A) and VL (FIG.14B) sequences and the three CDR regions of each variable domain are underlined.

[0026] FIG.15 identifies the variable heavy (VH) and variable light (VL) domain regions of LIBC No. 219058 (19324 / 36G2) involved in the binding interaction with LTβR. Shown are deuterium uptake graphs of VH and VL domain peptides alone or when bound to LTβR. Protection from deuterium exchange in the complexed peptides relative to non-complexed peptides indicates that one or more CDR residues within these regions of the antibody are involved in the binding interaction. The regions including these one or more residues are boxed in the shown VH and VL sequences and the three CDR regions of each variable domain are underlined.

[0027] FIGs.16A–16B identify the variable heavy (VH) and variable light (VL) domain regions of LIBC No. 219081 (19325 / 41B2) involved in the binding interaction with LTβR. Shown are deuterium uptake graphs of VH (FIG. 16A) and VL (FIG. 16B) domain peptides alone or when bound to LTβR. Protection from deuterium exchange in the complexed peptides relative to non-complexed peptides indicates that one or more CDR residues within these regions of the antibody are involved in the binding interaction. The regions including these one or more residues are boxed in the shown VH (FIG.16A) and VL (FIG.16B) sequences and the three CDR regions of each variable domain are underlined.

[0028] FIGs.17A–17B identify the variable heavy (VH) and variable light (VL) domain regions of LIBC No. 219097 (19326 / 43D9) involved in the binding interaction with LTβR. Shown are deuterium uptake graphs of VH (FIG. 17A) and VL (FIG. 17B) domain peptides alone or when bound to LTβR. Protection from deuterium exchange in the complexed peptides relative to non-complexed peptides indicates that one or more CDR residues within these regions of the antibody are involved in the binding interaction. The regions including these one or more residues are boxed in the shown VH (FIG.17A) and VL (FIG.17B) sequences and the three CDR regions of each variable domain are underlined.

[0029] FIGs.18A–18B identify the variable heavy (VH) and variable light (VL) domain regions of LIBC No.218979 (Bio. Reg. No.19319 / Well ID 23E9) involved in the binding interaction with LTβR. Shown are deuterium uptake graphs of VH (FIG.18A) and VL (FIG.18B) domain peptides alone or when bound to LTβR. Protection from deuterium exchange in the complexed peptides relative to non-complexed peptides indicates that one or more CDR residues within these regions of the antibody are involved in the binding interaction. The regions including these one or more residues are boxed in the shown VH (FIG. 18A) and VL (FIG.18B) sequences and the three CDR regions of each variable domain are underlined.

[0030] FIGs.19A–19B identify the variable heavy (VH) and variable light (VL) domain regions of LIBC No.219051 (Bio. Reg. No.19323 / Well ID 35F5) involved in the binding interaction with LTβR. Shown are deuterium uptake graphs of VH (FIG.19A) and VL (FIG.19B) domain peptides alone or when bound to LTβR. Protection from deuterium exchange in the complexed peptides relative to non-complexed peptides indicates that one or more CDR residues within these regions of the antibody are involved in the binding interaction. The regions including these one or more residues are boxed in the shown VH (FIG. 19A) and VL (FIG.19B) sequences and the three CDR regions of each variable domain are underlined.

[0031] FIG. 20 is a graph showing potency of huLTβR x huCLDN6 bispecific antibodies (PUR149204-4, PUR149205-4, PUR149212-5, and PUR149213-4). Potency was measured by IL-8 releasefrom LTβR expressing human melanoma cells co-cultured with CLDN6 expressing hamster ovarian cells (CHOs) in the presence of an increasing concentration of the indicated huLTβR x huCLDN6 bispecific antibody. The “signal” of the y-axis represents relative IL-8 release calculated by the ratio of signal at 665 nm to signal at 615 nm.

[0032] FIG. 21 is a graph showing potency of huLTβR x huCLDN18.2 bispecific antibodies (PUR149206-4, PUR149214-4, and PUR149215-4). Potency was measured by IL-8 release from LTβR expressing human melanoma cells co-cultured with CLDN18.2 expressing CHO cells in the presence of an increasing concentration of the indicated huLTβR x huCLDN18.2 bispecific antibody. The “signal” of the y-axis represents relative IL-8 release calculated by the ratio of signal at 665 nm to signal at 615 nm.

[0033] FIG. 22 is a graph showing potency of huLTβR x huMUC17 bispecific antibodies (PUR149211-4, PUR149218-4, and PUR149219-4). Potency was as measured by IL-8 release from LTβR expressing human melanoma cells co-cultured with MUC17 expressing CHO cells in the presence of an increasing concentration of the indicated huLTβR x huMUC17 bispecific antibody. The “signal” of the y- axis represents relative IL-8 release calculated by the ratio of signal at 665 nm to signal at 615 nm.

[0034] FIG.23 is a graph showing potency of huLTβR x huLRRC15 bispecific antibodies (44245- 5, 45147-3, and 52208-3). Potency was as measured by IL-8 release from LTβR expressing human melanoma cells co-cultured with LRRC15 expressing Saos-2 cells in the presence of an increasing concentration of the huLTβR x huLRRC15 bispecific antibody. The “signal” of the y-axis represents relative IL-8 release calculated by the ratio of signal at 665 nm to signal at 615 nm.

[0035] FIGs.24A-24C are graphs showing LIGHT (FIG.24A) and LTα1β2 (FIG.24B) inhibition in the presence of increasing concentrations of various LTβR antibodies described herein. FIG. 24C is a graph showing anti-LTβR antibody binding to LTβR expressed by HEK293 cells to confirm that non-ligand blocking activity was not due to non-receptor binding by the tested antibody.

[0036] FIGs.25A-25C are graphs showing LIGHT (FIG.25A) and LTα1β2 (FIG.25B) inhibition in the presence of increasing concentrations of various LTβR-LRRC15 bispecific as described herein. FIG. 25C is a graph showing LTβR-LRRC15 bispecific antibody binding to LTβR expressed by HEK293 cells to confirm that non-ligand blocking activity was not due to non-receptor binding by the tested bispecific antibody.

[0037] FIGs.26A-26C are graphs showing LTα1β2 (FIG.26A) and LIGHT (FIG.26B) inhibition in the presence of increasing concentrations of the indicated LTβR-LRRC15 bispecific antibody (52208) as described herein. FIG. 26C is a graph showing LTβR-LRRC15 bispecific antibody binding to LTβR expressed by HEK293 cells to confirm that non-ligand blocking activity was not due to non-receptor binding by the tested bispecific antibody.

[0038] FIG. 27 provides a table summarizing the additional agonist LTβR CRD4 binding, non- ligand blocking antibodies identified in the rescreening of XenoMouse®hybridoma pools. Non-ligand blocking activity of the antibodies was assessed using the cell-based assay described in Example 9.3 and Caterra assay as described in Example 9.4.DETAILED DESCRIPTION OF THE VARIOUS EMBODIMENTS

[0039] The present disclosure is directed to protein molecules that bind to and agonize the lymphotoxin-beta receptor (LTβR). The present disclosure provides agonist LTβR binding proteins that bind one or more amino acid residues of human LTβR cysteine-rich domain 4 (CRD4) comprising amino acid residues 169-211 of SEQ ID NO: 1 and (a) do not inhibit LIGHT binding to LTβR or (b) do not inhibit LTα1β2 binding to LTβR. The present disclosure also provides bispecific agonist LTβR binding proteins comprising an LTβR binding domain that binds one or more amino acid residues of human LTβR CRD4 and (a) does not inhibit LIGHT binding to LTβR or (b) does not inhibit LT1α2β binding to LTβR, and a tumor-associated antigen binding domain.

[0040] The present disclosure is further directed to methods of treating cancer is a human subject. These methods comprise administering an agonist LTβR binding protein, e.g., and agonist LTβR antibody or a bispecific agonist LTβR binding protein as described herein, to a subject having cancer to induce or enhance an anti-tumor immune response in the subject. As demonstrated herein, LTβR agonism within the tumor microenvironment induces high endothelial venule formation to enhance immune cell infiltration into the tumor microenvironment. This LTβR-mediated anti-tumor immune response is sufficient to reduce tumor growth.

[0041] The present disclosure further provides compositions, kits, and methods relating to agonist LTβR binding proteins that bind to human LTβR. Also provided are nucleic acid molecules comprising a sequence of polynucleotides that encode all or a portion of the agonist LTβR binding proteins disclosed herein. The present disclosure further provides vectors and plasmids comprising such nucleic acids, and cells or cell lines comprising such nucleic acids and / or vectors and plasmids. The provided methods further include, for example, methods of making, identifying, and isolating agonist LTβR binding proteins, and methods for administering, to a human subject, an agonist LTβR binding protein of the disclosure.

[0042] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as disclosed.

[0043] Unless otherwise defined herein, scientific and technical terms used in connection with the present disclosure shall have the meanings that are commonly understood by those of ordinary skill in the art. Generally, nomenclatures used in connection with, and techniques of, cell and tissue culture, molecular biology, immunology, microbiology, genetics and protein and nucleic acid chemistry and hybridization described herein are those well-known and commonly used in the art. The methods and techniques of the present disclosure are generally performed according to conventional methods well known in the art and as described in various general and more specific references that are cited and discussed throughout the present specification unless otherwise indicated. See, e.g., Sambrook et al. Molecular Cloning: A Laboratory Manual, 2d ed., Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y. (1989) and Ausubel et al., Current Protocols in Molecular Biology, Greene Publishing Associates (1992), and Harlow and Lane Antibodies: A Laboratory Manual Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y. (1990),which are incorporated herein by reference. Enzymatic reactions and purification techniques are performed according to manufacturer’s specifications, as commonly accomplished in the art or as described herein. The terminology used in connection with, and the laboratory procedures and techniques of, analytical chemistry, synthetic organic chemistry, and medicinal and pharmaceutical chemistry described herein are those well-known and commonly used in the art.

[0044] In this disclosure, the use of the singular terms include pluralities and plural terms shall include the singular unless specifically stated otherwise. As used herein, the singular forms “a”, “an”, and “the”' include both singular and plural referents unless the context clearly dictates otherwise.

[0045] In this disclosure, the use of the term “including”, as well as other forms, such as “includes” and “included”, is not limiting. Also, terms such as “element” or “component” encompass both elements and components comprising one unit and elements and components that comprise more than one subunit unless specifically stated otherwise. Also, the use of the term “portion” can include part of a moiety or the entire moiety.

[0046] The recitation of numerical ranges by endpoints includes all numbers and fractions subsumed within the respective ranges, as well as the recited endpoints.

[0047] The term “about” as used herein when referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, is meant to encompass variations of ±10% or less, preferably ±1–5% or less from the specified value, insofar such variations are appropriate to perform in the disclosed embodiment. It is to be understood that the value to which the modifier “about” refers is itself also specifically, and preferably, disclosed.

[0048] Polynucleotide and polypeptide sequences are indicated using standard one- or three-letter abbreviations. Unless otherwise indicated, polypeptide sequences have their amino termini at the left and their carboxy termini at the right. Single-stranded nucleic acid sequences and the top strand of double- stranded nucleic acid sequences, have their 5’ termini at the left and their 3’ termini at the right. A particular section of a polypeptide can be designated by amino acid residue number such as amino acids 1 to 50, or by the actual residue at that site such as, e.g., asparagine to proline. A particular polypeptide or polynucleotide sequence also can be described by explaining how it differs from a reference sequence.

[0049] The following terms, unless otherwise indicated, shall be understood to have the following meanings:

[0050] “Sequence identity” refers to the relationship between two or more amino acid (polypeptide or protein) sequences or two or more nucleic acid (polynucleotide) sequences, as determined by comparing the sequences. The identity between two sequences is preferably defined by assessing their identity across the whole length of the sequence as identified herein.

[0051] When comparing the identity of two or more nucleotide or amino acid sequences, the percentage of sequence identity between a first sequence and a second sequence may be calculated using methods known by a person skilled in the art, e.g., by dividing the number of residues in the first sequence that are identical to the residues at the corresponding positions in the second sequence by the total numberof residues in the first sequence and multiplying by 100% or by using a known computer algorithm for sequence alignment such as NCBI Blast, e.g., BLASTN and BLASTP (Altschul, S. F. et al, J. Mol. Biol. 215:403-410 (1990), the GCG program package (Devereux, J., et al, Nucleic Acids Research 12 (1): 387 (1984)), BestFit, FASTA, and EMBOSS Needle (Madeira, F., et al, Nucleic Acids Research 47(W1): W636- W641 (2019)).

[0052] “Binding affinity” generally refers to the strength of the sum total of non-covalent interactions between a single binding site of a molecule (e.g., a LTβR binding protein as describe herein) and its binding partner (e.g., human LTβR). Unless indicated otherwise, as used herein, “binding affinity” refers to intrinsic binding affinity which reflects a 1:1 interaction between members of a binding pair (e.g., LTβR binding protein and LTβR). The affinity of a molecule X for its partner Y can generally be represented by the dissociation constant (KD). Affinity can be measured and / or expressed in a number of ways known in the art, including, but not limited to, equilibrium dissociation constant (KD) and equilibrium association constant (KA). The KDis calculated from the quotient of koff / kon, whereas KAis calculated from the quotient of kon / koff. konrefers to the association rate constant of, e.g., an antibody to an antigen, and koffrefers to the dissociation of, e.g., an antibody from an antigen. Binding affinity can be determined using a variety of techniques as described herein and as known in the art, for example but not limited to, equilibrium methods, e.g., enzyme-linked immunosorbent assay (ELISA), KinExA (see, e.g., Rathanaswami et al. Analytical Biochemistry, 373:52-60 (2008), which is hereby incorporated by reference in its entirety), and radioimmunoassay (RIA); a surface plasmon resonance assay; or other kinetics-based assay (e.g., BIACORE®analysis or Octet® analysis (forteBIO)). Affinity can also be determined using other methods such as indirect binding assays, competitive binding assays, fluorescence resonance energy transfer (FRET), gel electrophoresis, and chromatography (e.g., gel filtration). These and other methods may utilize a label on one or more of the components being examined and / or employ a variety of detection methods including but not limited to chromogenic, fluorescent, luminescent, or isotopic labels. A detailed description of binding affinities and kinetics can be found in Paul, W. E., ed., Fundamental Immunology, 4th Ed., Lippincott-Raven, Philadelphia (1999), which focuses on antibody-immunogen interactions.

[0053] The term “binding protein” as used herein refers to any one of many forms of binding proteins known in the art. In exemplary aspects, binding proteins of the present disclosure encompass (i) full-length immunoglobulin molecules, i.e., antibodies, (ii) epitope binding fragments of antibodies, and (iii) antibody derivatives, e.g. multi-specific antibodies.

[0054] As used herein, the term “antibody” refers to a protein having a conventional immunoglobulin format, comprising heavy and light chains, and comprising variable and constant regions. For example, an antibody may be an IgG which is a “Y-shaped” structure of two identical pairs of polypeptide chains, each pair having one “light” (typically having a molecular weight of about 25 kDa) and one “heavy” chain (typically having a molecular weight of about 50-70 kDa). An antibody has a variable region and a constant region. In IgG formats, the variable region is generally about 100-110 or more aminoacids, comprises three complementarity determining regions (CDRs) and is primarily responsible for antigen recognition.

[0055] The general structure and properties of CDRs of antibodies have been described in the art. Briefly, in an antibody scaffold, the CDRs are embedded within a framework in the heavy and light chain variable region where they constitute the regions largely responsible for antigen binding and recognition. A variable region typically comprises at least three heavy or light chain CDRs (Kabat et al., 1991, Sequences of Proteins of Immunological Interest, Public Health Service N.I.H., Bethesda, Md.; see also Chothia and Lesk, 1987, J. Mol. Biol. 196:901-917; Chothia et al., 1989, Nature 342: 877-883), within a framework region (designated framework regions 1-4, FR1, FR2, FR3, and FR4, by Kabat et al., 1991; see also Chothia and Lesk, 1987, supra).

[0056] Antibodies can comprise any constant region known in the art. Human light chains are classified as kappa and lambda light chains. Heavy chains are classified as mu, delta, gamma, alpha, or epsilon, and define the antibody's isotype as IgM, IgD, IgG, IgA, and IgE, respectively. In the present invention, antibodies are of the IgG isotype. IgG has several subclasses, including, but not limited to IgG1, IgG2, IgG3, and IgG4. The light chain constant region can be, for example, a kappa- or lambda-type light chain constant region, e.g., a human kappa- or lambda-type light chain constant region

[0057] An “epitope binding fragment” of an antibody encompasses any polypeptide fragment, region, portion, or domain of a full-length antibody that exhibits the same or substantially similar binding properties of the full-length antibody and can be obtained, for example, by protease cleavage of an intact parental antibody.

[0058] An “antibody derivative” is a protein or polypeptide that contains at least one epitope binding domain of an antibody and is typically formed using recombinant techniques or via chemical modification of a parent antibody or portion thereof. An antibody derivative comprises an amino acid sequence that is substantially similar to the amino acid sequence of one or more parental antibodies or relevant portions thereof. Exemplary antibody derivatives of the present disclosure include multispecific binding proteins, e.g., a bispecific binding protein.

[0059] The term “epitope” as used herein refers to the site or portion of a protein to which an antibody binds. An epitope can be composed of either or both contiguous amino acid residues or discontiguous amino acid residues that form a conformational spatial unit. For a discontiguous epitope, amino acids from differing portions of the linear sequence of the antigen come in close proximity in 3- dimensional space through the folding of the protein molecule. The epitope to which a LTβR binding protein binds can be determined by hydrogen / deuterium exchange coupled with mass spectrometry as described herein.

[0060] The term “paratope” as used herein refers to the portion of a binding protein, e.g., an antibody, that binds to the epitope of a protein target. A paratope can be linear in nature or can be discontinuous, formed by a spatial relationship between non-contiguous amino acid residues of an antibody rather than a linear series of amino acids. As referred to herein, “light chain paratope amino acid residues”,“heavy chain paratope amino acid residues”, or “paratope interface residues” refer to antibody light chain and / or heavy chain residues involved in the binding interaction with the protein target. The paratope may comprise amino acid residues of a single heavy chain CDR, e.g., heavy chain CDR3, or a combination of amino acid residues from the heavy chain CDRs (HCDR1, CDR2, HCDR3) and light chain CDRs (LCDR1, LCDR2, and LCDR3). As demonstrated herein, a paratope does not require all amino acid residues of a CDR and does not require amino acid residues from all six CDRs. LTβR Binding Proteins

[0061] The disclosure herein encompasses agonist lymphotoxin beta receptor (LTβR) binding proteins. LTβR, also known as tumor necrosis factor (TNF) receptor superfamily member 3 and tumor necrosis factor receptor type III (TNFR-III), is a member of the TNF family that is expressed on most cell types, including fibroblasts, epithelial cells, monocytes, dendritic cells, and cells of the myeloid lineage. LTβR is not expressed by T or B lymphocytes. LTβR is a receptor for two TNF family cytokine ligands. The first of these LTβR ligands is a heterotrimer of lymphotoxin α and lymphotoxin β subunits known as LTα1β2. The second ligand of LTβR is a homotrimer of LIGHT (Tumor necrosis factor ligand superfamily member 14 (TNFSF14)). LTα1β2 and LIGHT binding to LTβR initiates a signal transduction pathway that involves primarily the NFκB pathway. LTβR signaling is involved in lymph node (LN) organogenesis during development and the maintenance of lymphoid organs and various immune cells, including neutrophils, natural killer (NK) cells and invariant natural killer T (iNKT) cells in adulthood. LTβR also plays a critical role in the formation of LN-like cell clusters known as tertiary lymphoid structures (TLS) in non-lymph organs and the induction of genes critical for T cell migration across the endothelium, both of which are key to facilitating an effective anti-tumor response.

[0062] Human LTβR is a 61 kDa transmembrane protein having an amino acid sequence of SEQ ID NO: 1 (isoform 1) or SEQ ID NO: 2 (isoform 2) as shown below. The LTβR binding proteins as described herein bind to human LTβR. In one embodiment, the LTβR binding proteins of the present disclosure bind to one or more epitopes within the extracellular domain of human LTβR (comprising amino acid residues 31-227 of SEQ ID NO: 1), which contains four cysteine-rich domains (i.e., CRD1–CRD4).

[0063] In one embodiment, the LTβR binding proteins described herein also bind to cynomolgus (cyno) LTβR. The amino acid sequence of cyno LTβR is provided below (SEQ ID NO: 3). In one embodiment, the LTβR binding proteins described herein do not bind to murine LTβR. In one embodiment, the LTβR binding proteins described herein bind to human LTβR and cynomolgus LTβR but do not bind to murine LTβR.

[0064] In accordance with the present disclosure, the LTβR binding proteins are agonist LTβR binding proteins, for example, an agonist LTβR antibody, an agonist LTβR epitope binding fragment of an antibody, or an agonist LTβR antibody derivative (e.g., an agonist LTβR bispecific binding protein). An “agonist LTβR binding protein” as used herein is an LTβR binding molecule that induces LTβR-mediated signaling either directly, by binding to the receptor, or indirectly, via binding to the receptor and inducing its higher order clustering at the cell surface, e.g., by use of cross-linking antibodies. Binding of a LTβR binding protein of the disclosure to LTβR induces NFκB signaling, gene expression associated with T cell migration across the endothelium, and / or TLS cluster formation. Assays for measuring LTβR activation and / or the induction of LTβR signaling by a binding protein of the present disclosure are known in the art and are described herein.

[0065] In one embodiment, LTβR agonism is measured by assaying interleukin-8 (IL8) release from LTβR expressing cells following incubation with an agonist LTβR binding protein as described in Example 7 herein. An increase in the level of cellular IL8 release in the presence of an LTβR binding protein of the present disclosure as compared to its absence is an indication that the LTβR binding protein functions as an agonist LTβR binding protein. In another embodiment, LTβR agonism is measured by assaying transactivation of endothelial cells. LTβR-mediated endothelial cell transactivation can be measured by assaying the endothelial cell expression of adhesion molecules, such as vascular cell adhesion protein 1 (VCAM1; also known as CD106) and / or intracellular adhesion molecule 1 (ICAM; also known as CD54), and / or the expression or secretion of inflammatory chemokines, such as, e.g., CCL5, CCL2, and CXCL10. An increase in endothelial cell VCAM or ICAM expression in the presence of an agonist LTβR bindingprotein as compared to in its absence is an indication that the LTβR binding protein functions as an agonist LTβR binding protein. Similarly, an increase in endothelial cell expression or secretion of CCL5, CCL2, and / or CXCL10 in the presence of an LTβR binding protein as compared to in its absence is an indication that the LTβR binding protein functions as an agonist LTβR binding protein.

[0066] In one embodiment, the agonist activity of an LTβR binding protein described herein induces at least a 10% increase in LTβR signaling activity, as measured by, e.g., IL8 release or endothelial cell transactivation, relative to LTβR signaling activity in the absence of the agonist LTβR binding protein. In one embodiment, the LTβR binding protein described herein increases LTβR signaling activity by at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95% relative to the level of LTβR signaling in the absence of the agonist LTβR binding protein. In one embodiment, the LTβR binding protein described herein increases LTβR signaling activity by at least 100% relative to the level of LTβR signaling in the absence of the agonist LTβR binding protein.

[0067] In one embodiment, the agonist activity of the LTβR binding proteins described herein is measured using one or more of the in vitro functional endpoints as described above and the activity is expressed as a half maximal effective concentration (EC50). In one embodiment, the EC50of the LTβR binding proteins described herein is within about 1 pM to about 500 pM, about 1 pM to about 250 pM, about 1 pM to about 200 pM, about 1 pM to about 150 pM, about 1 pM to about 125 pM, about 1 to about 100 pM, about 1 pM to about 90 pM about 1 to about 80 pM about 1 pM to about 70 pM, about 1 pM to about 60 pM, about 1 pM to about 50 pM, about 1 pM to about 40 pM, about 1 to about 30 pM, about 1 to 200 pM, about 10 to about 200 pM, about 20 pM to about 200 pM, about 30 pM to about 200, about 40 pM to about 200 pM, about 50 pM to about 200 pM, about 60 pM to about 200 pM. In one embodiment, the EC50of agonist LTβR binding protein mediated IL-8 release as described herein is about 10 pM to about 200 pM, about 20 pM to about 150 pM, or about 30 pM to about 140 pM.

[0068] In one embodiment, the LTβR binding proteins as described herein bind to and agonize human LTβR while allowing endogenous LTβR ligand binding to the receptor and resulting activity to occur. As described supra, LTβR binds at least two different endogenous ligands, i.e., LIGHT and LTα1β2. When an LTβR binding protein of the present disclosure is bound to its corresponding epitope of LTβR, at least one of LIGHT or LTα1β2 can also bind to LTβR to initiate endogenous ligand-mediated signaling activity. Thus, in one embodiment, binding of an LTβR binding protein described herein does not inhibit, prevent, or preclude LTα1β2 binding to LTβR. In one embodiment, binding of an LTβR binding protein described herein does not inhibit, prevent, or preclude LIGHT binding to LTβR. In a preferred embodiment, binding of an LTβR binding protein described herein does not inhibit, prevent, or preclude either LIGHT binding to LTβR or LTα1β2 binding to LTβR.

[0069] This functional feature of the agonist LTβR binding protein, referred to herein as “non- ligand blocking activity”, is a beneficial feature of the agonist LTβR binding proteins of the present disclosure because it maximizes safety upon administration of the binding protein to, e.g., a patient.Additionally, the LTβR binding proteins described herein preferentially agonize LTβR in a cross-linking dependent manner, i.e., the binding molecule must bind to LTβR and another protein (e.g., an Fc receptor or a targeting protein) to induce LTβR activation. These two features provide a superior molecule from a safety perspective. If the binding molecule binds LTβR in a non-crosslinking dependent manner, e.g., it only binds to LTβR, its binding will not agonize the receptor. In addition, because the LTβR binding protein binds LTβR in a manner that does not block endogenous ligand binding, its binding will also not unintentionally antagonize or block endogenous ligand mediated activity.

[0070] In one embodiment, non-ligand blocking activity of an agonist LTβR binding protein as described herein is characterized by the percent inhibition that its binding has on LIGHT and LTα1β2 binding to LTβR. In one embodiment, LTβR binding by a binding protein of the present disclosure results in negligible inhibition or blocking of LIGHT binding (≤20% inhibition) to LTβR or LTα1β2 binding (≤20% inhibition) to LTβR as measured by the cell based receptor-ligand assay described infra (see also Example 8). For example, LTβR binding by a binding protein as described herein inhibits ≤20% of LIGHT binding to LTβR, ≤20% LTα1β2 binding to LTβR, or ≤20% of LIGHT and LTα1β2 binding to LTβR as measured by the cell-based receptor-ligand assay described herein. In one embodiment, the LTβR binding protein as described herein inhibits <20%, <15%, <10%, <9%, <8%, <7%, <6%, <5%, <4%, <3%, <2%, or <1% of LIGHT binding to LTβR or LTα1β2 binding to LTβR. In one embodiment, LTβR binding by a binding protein as described herein inhibits <15% of LIGHT binding to LTβR or inhibits <15% of LTα1β2 binding to LTβR as measured by the cell-based receptor ligand assay described herein and exemplified in Example 8.2. In one embodiment, LTβR binding by a binding protein as described herein inhibits <15% of LIGHT binding to LTβR and inhibits <15% of LTα1β2 binding to LTβR as measured by the cell-based receptor ligand assay described herein and exemplified in Example 8.2. In one embodiment, LTβR binding by a binding protein described herein inhibits < 10% of LIGHT binding to LTβR or inhibits <10% LTα1β2 binding to LTβR as measured by the cell-based receptor ligand assay described herein. In one embodiment, LTβR binding by a binding protein described herein inhibits < 10% of LIGHT binding to LTβR and inhibits <10% LTα1β2 binding to LTβR as measured by the cell-based receptor ligand assay described herein. In one embodiment, LTβR binding by a binding protein described herein inhibits < 5% of LIGHT binding to LTβR or inhibits <5% LTα1β2 binding to LTβR as measured by the cell-based receptor ligand assay described herein. In one embodiment, LTβR binding by a binding protein described herein inhibits < 5% of LIGHT binding to LTβR and inhibits <5% LTα1β2 binding to LTβR as measured by the cell-based receptor ligand assay described herein. Preferably, LTβR binding by a binding protein described herein inhibits 0% of LIGHT binding to LTβR or inhibits 0% of LTα1β2 binding to LTβR as measured by the cell- based receptor ligand assay described herein. More preferably, LTβR binding by a binding protein described herein inhibits 0% of LIGHT binding to LTβR and inhibits 0% of LTα1β2 binding to LTβR as measured by the cell-based receptor ligand assay described herein. Exemplary LTβR binding proteins described herein that do not inhibit LIGHT binding to LTβR and do not inhibit LTα1β2 binding to LTβR(i.e., exhibit 0% inhibition of LIGHT and 0% inhibition of LTα1β2 binding to LTβR) include, without limitation, the agonist LTβR binding proteins that bind to the CRD4 domain of LTβR.

[0071] Alternatively, non-ligand blocking activity of an agonist LTβR binding protein as described herein is characterized by the percentage of endogenous LTβR ligand binding that occurs in the presence of bound agonist LTβR binding protein. In one embodiment, LTβR binding by a binding protein as described herein allows at least 80% of endogenous LTβR ligand (i.e., LIGHT or LTα1β2) binding to occur as measured by the cell-based receptor-ligand assay described herein (see Example 8.2). In one embodiment, LTβR binding by a binding protein as described herein allows at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% of LIGHT binding to LTβR or LTα1β2 binding to LTβR to occur. In one embodiment, LTβR binding by a binding protein as described herein allows at least 90% of LIGHT binding to LTβR to occur or at least 90% of LTα1β2 ligand binding to LTβR to occur as measured by the cell based receptor-ligand assay described herein and exemplified in Example 8. In one embodiment, LTβR binding by a binding protein as described herein allows at least 90% of LIGHT binding to LTβR to occur and at least 90% of LTα1β2 ligand binding to LTβR to occur as measured by the cell based receptor-ligand assay described herein and exemplified in Example 8. In one embodiment, LTβR binding by a binding protein as described herein allows at least 95% of LIGHT binding to LTβR to occur or at least 95% of LTα1β2 ligand binding to LTβR to occur as measured by the cell based receptor-ligand assay described herein and exemplified in Example 8. In one embodiment, LTβR binding by a binding protein as described herein allows at least 95% of LIGHT binding to LTβR to occur and at least 95% of LTα1β2 ligand binding to LTβR to occur as measured by the cell based receptor-ligand assay described herein and exemplified in Example 8. Preferably, LTβR binding by a binding protein as described herein allows 100% of LIGHT binding to LTβR occur or 100% of LTα1β2 ligand binding to LTβR to occur as measured by the cell based receptor-ligand based assay described in Example 8. More preferably, LTβR binding by a binding protein as described herein allows 100% of LIGHT binding to LTβR occur and 100% of LTα1β2 ligand binding to LTβR to occur as measured by the cell based receptor-ligand based assay described in Example 8. Exemplary agonist LTβR binding proteins described herein that allow 100% of LIGHT binding to LTβR and 100% LTα1β2 binding to LTβR are the agonist LTβR binding proteins that bind to the CRD4 domain of LTβR.

[0072] Non-ligand blocking activity of the agonist LTβR binding proteins described herein is measured and quantified using a cell-based receptor-ligand binding assay. This assay measures the percent inhibition of LIGHT and / or LTα1β2 binding to LTβR in the presence of the agonist LTβR binding protein of the disclosure (see Example 8). This cell-based receptor-ligand binding assay involves incubating LTβR expressing cells with cell culture media containing the agonist LTβR binding protein for 1 hour at 4°C to allow the agonist LTβR binding protein to bind LTβR expressed on the cells. Suitable LTβR expressing cells include any cell type that naturally expresses LTβR, e.g., endothelial cells, macrophages, natural killer cells, etc., as well as cells engineered to express LTβR, e.g., a cell line (such as CHO cells, HEK 293 cells,melanoma cells, etc.) transfected with a LTβR expression vector. The concentration of agonist LTβR binding protein in the cell culture media is at a concentration effective to saturate binding of all LTβR expressed by the LTβR expressing cells. For example, the concentration of agonist LTβR binding protein in the cell culture media is at a concentration of 5-30nM to saturate binding of all LTβR expressed by the LTβR expressing cells. The assay further involves interacting the LTβR expressing cells, after incubating with the agonist LTβR binding protein, with a detectable LIGHT ligand, a detectable LTα1β2 ligand, or both (i.e., detectable LIGHT and LTα1β2 ligands) under conditions effective for the ligands to bind to LTβR. LIGHT and LTα1β2 ligands are rendered detectable by directly coupling them to a detectable label, e.g., a fluorescent label or tag. Binding of the detectable LIGHT and / or LTα1β2 ligands to the LTβR expressing cells in the presence of the agonist LTβR binding protein is detected using suitable means (e.g., Fluorescence-activated cell sorting). A quantitative assessment of ligand binding inhibition is determined by comparing the level of LIGHT and / or LTα1β binding to LTβR in the presence of an agonist LTβR binding protein to the corresponding level of LIGHT and / or LTα1β binding to LTβR in the absence of the agonist LTβR binding protein. Agonist LTβR binding proteins that minimally inhibit (≤20% inhibition) or do not inhibit (0% inhibition) LIGHT or LTα1β2 ligand binding to LTβR are identified as suitable for use in the methods described herein. The binding of the detectable LIGHT and / or LTα1β2 ligands to LTβR expressing cells in the presence or absence of the LTβR binding protein is detected via FACs on a flow cytometry machine.

[0073] Exemplary agonist LTβR binding proteins described herein exhibit the desired functional properties (e.g., cyno and human LTβR binding and non-ligand blocking activity) as a result, in part, of the epitope of LTβR bound by the agonist LTβR binding protein. In one embodiment, the LTβR binding proteins as disclosed herein bind to an epitope of LTβR comprising one or more segments of a cysteine rich domain (CRD) of the extracellular domain, i.e., one or more residues of CRD1, CRD2, CRD3, or CRD4. The human LTβR extracellular domain is provided below as SEQ ID NO: 4. In one embodiment, the agonist LTβR binding protein of the present disclosure binds to an epitope comprising residues of CRD1 of LTβR. CRD1 of LTβR comprises residues 12–51 of SEQ ID NO: 4, which corresponds to residues 42-81 of the full-length LTβR of SEQ ID NO: 1. In one embodiment, the LTβR binding protein of the present disclosure binds to an epitope comprising residues of LTβR CRD2. LTβR CRD2 comprises residues 52–94 of SEQ ID NO: 4, which corresponds to residues 82-124 of the full-length LTβR of SEQ ID NO: 1. In one embodiment, the LTβR binding protein of the present disclosure binds to an epitope comprising residues of LTβR CRD3. LTβR CRD3 comprises residues 95–138 of SEQ ID NO: 4, which corresponds to residues 125-168 of the full-length LTβR of SEQ ID NO: 1. In one embodiment, the LTβR binding protein of the present disclosure binds to an epitope comprising residues of LTβR CRD4. LTβR CRD4 comprises residues 139–181 of SEQ ID NO: 4, which corresponds to residues 168–211 of the full-length LTβR amino acid sequence of SEQ ID NO: 1.

[0074] In one embodiment, an agonist LTβR binding protein of the present disclosure binds to an epitope that comprises residues of the extracellular CRD2 and CRD3 of human LTβR. In one embodiment, the agonist LTβR binding protein binds to an epitope within CRD2 comprising one or more residues at positions 56–64 of SEQ ID NO: 4 and binds to an epitope spanning CRD2 and CRD3 comprising one or more residues at positions 81–101 of SEQ ID NO: 4 as determined by hydrogen / deuterium exchange (HDX) mass spectrometry (MS). In one embodiment, the agonist LTβR binding protein binds to the aforementioned regions of CRD2 and CRD3 and does not bind to a region of LTβR outside of CRD2 and CRD3. In other words, in one embodiment, the agonist LTβR binding protein binds to regions of LTβR consisting of one or more residues within CRD2 and CRD3. Binding of an LTβR binding protein to the identified regions of LTβR agonizes receptor signaling while allowing endogenous LTβR ligand binding. Agonist LTβR binding proteins that bind this epitope also bind cyno LTβR. Exemplary agonist LTβR binding proteins having these properties are identified herein as LIBC219058 (19324) and LIBC218990 (19320).

[0075] In another embodiment, an agonist LTβR binding protein of the present disclosure binds to an epitope that comprises residues of the extracellular CRD1 of human LTβR. In one embodiment, the agonist LTβR binding protein described herein binds to an epitope within CRD1 comprising one or more residues at positions 3–9, 20–29, and / or 38–47 of SEQ ID NO: 4 as determined by HDX MS. In one embodiment, the agonist LTβR binding protein binds to the aforementioned regions of CRD1 and does not bind to a region of LTβR outside of CRD1. In other words, in one embodiment, the agonist LTβR binding protein binds to a region of LTβR consisting of residues within CRD1. Binding of an LTβR binding protein to this epitope of LTβR agonizes receptor signaling while allowing endogenous LIGHT ligand binding to LTβR and minimally inhibiting LTα1β2 ligand binding (≤20%). Agonist LTβR binding proteins that bind this epitope also bind cyno LTβR. An exemplary agonist LTβR binding protein having these properties is identified herein as LIBC218994 (19321).

[0076] In another embodiment, an agonist LTβR binding protein of the present disclosure binds to an epitope that comprises residues of the extracellular CRD1 of human LTβR. In one embodiment, the agonist LTβR binding protein described herein binds to an epitope within CRD1 comprising one or more residues at positions 1–19 of SEQ ID NO: 4 as determined by HDX MS. In one embodiment, the agonist LTβR binding protein binds to the aforementioned regions of CRD1 and does not bind to a region of LTβR outside of CRD1. In other words, in one embodiment, the agonist LTβR binding protein binds to a region of LTβR consisting of residues within CRD1. Binding of an LTβR binding protein to this epitope of LTβR agonizes receptor signaling and does not inhibit endogenous LIGHT binding to LTβR and does not inhibit endogenous LTα1β2 binding to LTβR. Agonist LTβR binding proteins that bind this epitope also bind cyno LTβR. An exemplary agonist LTβR binding protein having these properties is identified herein as LIBC219051 (19323).

[0077] In another embodiment, an agonist LTβR binding protein of the present disclosure binds to an epitope that comprises residues of the extracellular CRD4 of human LTβR. In one embodiment, the agonist LTβR binding protein described herein binds to an epitope within CRD4 comprising one or more residues at positions 168–179 of the extracellular domain of LTβR (SEQ ID NO: 4) (residues 197-209 of SEQ ID NO: 1) as determined by HDX MS. In one embodiment, the agonist LTβR binding protein binds to the aforementioned region of CRD4 and does not bind to a region of LTβR outside of CRD4. In other words, in one embodiment, the agonist LTβR binding protein binds to a region of LTβR consisting of residues within CRD4. Binding of an agonist LTβR binding protein to this epitope of LTβR agonizes receptor signaling and does not inhibit endogenous LIGHT binding to LTβR and does not inhibit endogenous LTα1β2 binding to LTβR. Agonist LTβR binding proteins that bind this epitope also bind cyno LTβR. Exemplary agonist LTβR binding protein having these properties are identified herein as LIBC219081 (19325) and LIBC218979 (19319).

[0078] LTβR binding proteins that have an identical or overlapping epitope with the exemplary agonist LTβR binding proteins disclosed herein will compete with each other for binding to LTβR. Thus, in one embodiment, an exemplary agonist LTβR binding protein of the disclosure competes for binding to CRD4 with LIBC219081 (19325) and / or LIBC218979 (19319). To “compete” or “be in competition with” means the LTβR binding protein competes for the same epitope or binding site on a target. Such competition can be determined by an assay in which a reference agonist LTβR binding protein, such as agonist LTβR binding proteins LIBC219081 (19325) and LIBC218979 (19319), prevents or inhibits specific binding of a test LTβR binding protein. An exemplary competitive binding assay that can be utilized to identify agonist LTβR binding proteins encompassed by the present disclosure that compete for binding to CRD4 of LTβR is described herein in Example 9.2. Usually, when a competing LTβR binding protein is present in excess, it will inhibit binding of a reference agonist LTβR binding protein to a common epitope by at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, or at least 75%. In some instances, binding of a reference agonist LTβR binding protein to LTβR is inhibited by at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or more. Exemplary agonist LTβR binding proteins of the present disclosure that compete for binding to the CRD4 domain of LTβR with the binding proteins identified herein as LIBC219081 (19325) and LIBC218979 (19319) are described herein (see Tables 2–4 and 6–8).

[0079] An agonist LTβR binding protein of the present disclosure is a protein that binds to and agonizes LTβR without blocking or inhibiting one or both endogenous LTβR ligands from binding LTβR. The LTβR binding proteins described herein comprise one or more amino acid binding domains that alone, or in combination, bind a region of LTβR and activate signaling activity of the receptor. Optionally, the agonist LTβR binding proteins further comprise a scaffold or framework portion that allows the one or more binding domains to adopt a conformation that promotes a binding interaction between the binding domain(s) and LTβR. Exemplary LTβR binding proteins include, without limitation, LTβR antibodies (i.e.,immunoglobulins), epitope binding fragments of an LTβR antibody, and LTβR antibody derivatives, each of which is described in more detail herein.

[0080] An agonist LTβR binding protein as disclosed herein binds to its corresponding epitope within the extracellular domain of LTβR. In one embodiment, an agonist LTβR binding protein of the present disclosure binds epitope residues within CRD4 of the extracellular domain of LTβR (i.e., residues 139–181 of SEQ ID NO: 4 (ECD); residues 169–211 of SEQ ID NO: 1 (full-length LTβR)) more frequently, more rapidly, with greater duration and / or with greater affinity or avidity than an alternative epitope. In one embodiment, the agonist LTβR binding proteins described herein bind to any 2, 3, 4, 5, 6, 7, 8, 9, 10 or more amino acid residues of the extracellular CRD4 domain of LTβR, in particular one or more residues of 168-179 of SEQ ID NO: 4 or one or more residues of 168–178 of SEQ ID NO: 4.

[0081] In accordance with the present disclosure, an agonist LTβR binding protein binds to LTβR with a tight binding affinity as determined by an equilibrium dissociation constant (KD) value of 10-7M or less. In one embodiment, an agonist LTβR binding protein of the present disclosure (e.g., an LTβR antibody, epitope-binding fragment, or antibody derivative) binds human LTβR with an equilibrium dissociation constant or KD(koff / kon) of less than 10-7M, less than 10-8M, less than 10-9M, less than 10-10M, or less than 10-11M less than 10-12M, or less than 10-13M (lower values indicating tighter binding affinity).

[0082] In one embodiment, agonist LTβR binding proteins of the disclosure (e.g., antibodies, epitope-binding fragments, and antibody derivatives) bind human LTβR with an equilibrium dissociation constant or KD(koff / kon) of between about 10-7M and about 10-11M, between about 10-7M and about 10-10M, between about 10-7M and about 10-9M, between about 10-7M and about 10-8M, between about 10-8M and about 10-9M, between about 10-9M and about 10-10M, between about 10-10M and about 10-11M, between about 10-11M and about 10-12M, between about 10-12M and about 10-13M. In any embodiment, agonist LTβR binding proteins of the disclosure specifically bind human LTβR with a KDof between about 10-8M and about 10-11M or between about 10-9M and about 10-10M.

[0083] In one embodiment, agonist LTβR binding proteins of the disclosure (e.g., antibodies, epitope-binding fragments, and antibody derivatives) specifically bind human LTβR with an equilibrium dissociation constant or KD(koff / kon) of between about 0.01 mM and about 10 nM, between about 0.01 nM and about 9 nM, between about 0.01 nM and about 8 nM, between about 0.01 nM and about 7 nM, between about 0.01 nM and about 6 nM, between about 0.01 nM and about 5 nM, between about 0.01 nM and about 4 nM, between about 0.01 nM and about 3 nM, between about 0.01 nM and about 2 nM, between about 0.01 nM and about 1 nM, between about 0.1 nM and about 10 nM, between about 0.1 nM and about 9 nM, between about 0.1 nM and about 8 nM, between about 0.1 nM and about 7 nM, between about 0.1 nM and about 6 nM, between about 0.1 nM and about 5 nM, between about 0.1 nM and about 4 nM, between about 0.1 nM and about 3 nM, between about 0.1 nM and about 2 nM, between about 0.1 nM and about 1 nM, or between about 0.01 nM and about 0.1 nM.

[0084] The agonist LTβR binding proteins of the disclosure that bind to human LTβR also bind to cynomolgus monkey (cyno) LTβR with the same or similar affinities. The amino acid sequence of cyno LTβR is provided herein as SEQ ID NO: 3. In exemplary aspects, the agonist LTβR binding proteins described herein bind to cynomolgus monkey LTβR with a KDof between about 10-7M and about 10-8M, between about 10-8M and about 10-9M, between about 10-9M and about 10-10M, between about 10-10M and about 10-11M, between about 10-11M and about 10-12M. In any embodiment, LTβR binding proteins of the disclosure specifically bind cyno LTβR with a KDof between about 10-8M and about 10-10M.

[0085] In one embodiment, agonist LTβR binding proteins of the disclosure (e.g., antibodies, epitope-binding fragments, and antibody derivatives) bind cynomolgus monkey (cyno) LTβR with an equilibrium dissociation constant or KD(koff / kon) of between about 0.1 nM and about 30 nM, between about 0.1 nM and about 20 nM, between about 0.1 nM and about 10 nM, between about 0.1 nM and about 9 nM, between about 0.1 nM and about 8 nM, between about 0.1 nM and about 7 nM, between about 0.1 nM and about 6 nM, between about 0.1 nM and about 5 nM, between about 0.1 nM and about 4 nM, between about 0.1 nM and about 3 nM, between about 0.1 nM and about 2 nM, or between about 0.1 nM and about 1 nM.

[0086] The agonist LTβR binding proteins of the present disclosure bind with high affinity to both human LTβR and cyno LTβR. For example, the KDof the agonist LTβR binding protein for human LTβR is within about 100-fold, about 50-fold, about 25-fold, about 10-fold, about 5-fold, or about 2-fold or less of the KD of the agonist LTβR binding protein for cyno LTβR. In one embodiment, the KD of the agonist LTβR binding protein for human LTβR is about 10-fold or less of the KDof the agonist LTβR binding protein for cyno LTβR.

[0087] The agonist LTβR binding proteins as disclosed herein bind to the LTβR extracellular domain with an affinity corresponding to a KDthat is at least ten-fold lower, such as at least 100-fold lower, for instance at least 1,000-fold lower, such as at least 10,000-fold lower, for instance at least 100,000-fold lower than its affinity for binding to a non-specific antigen (e.g., TNFR-I or TNFR-II, etc.). The amount with which the affinity is lower is dependent on the KDof the binding protein to LTβR, so that when the KDof the agonist LTβR binding protein is very low (that is, the binding protein is highly specific), then the amount with which the affinity for LTβR is lower than the affinity for a non-specific antigen may be at least 10,000-fold.

[0088] In one embodiment, the agonist LTβR binding protein of the present disclosure is an LTβR antibody , an epitope-binding fragment of an LTβR antibody (e.g., an LTβR binding Fab, Fab′, F(ab′)2), or an LTβR antibody derivative (e.g., LTβR scFv, minibody, diabody, or multi-specific binding protein) as described herein.

[0089] In one embodiment, an agonist LTβR binding protein of the present disclosure is an antibody as defined herein. The term “antibody” also includes antibodies comprising 1, 2, 3, 4, or 5 amino acid residue insertions or deletions at the N-terminus and / or C-terminus of the heavy and / or light chain that retain the same or similar binding and / or function as the antibodies comprising two heavy chains and two light chains not comprising these amino acid residue substitutions, insertions, or deletions.

[0090] The heavy and light chain variable regions (VHand VL, respectively) of an antibody and other binding molecules described herein (i.e., epitope-binding fragments of an antibody and antibody derivatives) are responsible for LTβR recognition and binding, while the heavy and light chain constant regions mediate the binding of the immunoglobulin to host tissues or factors, including various cells of the immune system (e.g., effector cells) and the first component (Clq) of the classical complement system. Within light and heavy chains, the variable (V) and constant regions (C) are joined by a “J” region of about 12 or more amino acids, with the heavy chain also including a “D” region of about 10 more amino acids (see generally, Fundamental Immunology Ch.7 (Paul, W., ed., 2nd ed. Raven Press, N.Y. (1989), which is hereby incorporated by reference in its entirety). The variable regions of each light / heavy chain pair form the antibody binding site such that an intact immunoglobulin has two binding sites.

[0091] The VH and VL regions of an LTβR antibody and other LTβR binding proteins as described herein are further subdivided into regions of hypervariability, termed “complementarity determining regions,” or “CDRs,” that are interspersed within regions of more conserved sequence, termed “framework regions” (FR). One or more residues within one or more variable region CDRs of the heavy and light chains form a binding domain that interacts with an antigen, e.g., LTβR. Exemplary VHand VLdomain sequences and VHand VLCDR sequences of LTβR antibodies and binding proteins of the present disclosure are described in more detail infra.

[0092] In one embodiment, an agonist LTβR binding protein of the present disclosure is an epitope- binding fragment of a LTβR antibody. As used herein, the terms “fragment”, “region”, “portion”, and “domain” are generally intended to be synonymous, unless the context of their use indicates otherwise. Fragments of antibodies (e.g., Fab and (Fab′)2fragments) that exhibit LTβR binding ability can be obtained, for example, by protease cleavage of an intact parental antibody. Alternatively, the epitope binding fragment of the LTβR antibody is an amino acid sequence that comprises a portion of the amino acid sequence of such parental antibody. Exemplary LTβR-binding fragments encompassed by the present disclosure include, without limitation, (i) Fab' or Fab fragments, which are monovalent fragments containing the VL, VH, CL and CH1 domains as described supra; (ii) F(ab')2fragments, which are bivalent fragments comprising two Fab fragments linked by a disulfide bridge at the hinge region; (iii) Fd fragments consisting essentially of the VH and CH1 domains; (iv) Fv fragments consisting essentially of a VL and VH domain; (v) single domain antibodies or dAb fragments (Ward et al. “Binding Activities Of A Repertoire Of Single Immunoglobulin Variable Domains Secreted From Escherichia coli ,” Nature 341 :544-546 (1989), which is hereby incorporated by reference in its entirety), which consist essentially of a VH or VL domain (or an epitope binding portion of the VH or VL) and are also called domain antibodies or nanobodies (Holt et al. “Domain Antibodies: Proteins For Therapy,” Trends Biotechnol. 21(11):484-490 (2003); Revets et al. “Nanobodies As Novel Agents For Cancer Therapy,” Expert Opin. Biol. Ther.5(1):111-124 (2005), which are hereby incorporated by reference in their entirety); and (vi) isolated complementarity determining regions (CDR).

[0093] An agonist LTβR epitope-binding fragment of the present disclosure may contain 1, 2, 3, 4, 5 or all 6 of the CDR domains of an LTβR antibody as disclosed herein. In one embodiment, an epitope- binding fragment of an LTβR antibody comprises, essentially consists of, or consists of 30 to 100 amino acid residues, or 50 to 150 amino acid residues, or 70 to 200 amino acid residues of the parental LTβR antibody. In one embodiment, the length of an epitope-binding fragment of an LTβR antibody is at least 40%, 50%, 60%, 70%, 80%, 90% or 95% of the length of the LTβR antibody. In one embodiment, an LTβR epitope-binding fragment of the present disclosure elicits the same or similar activity of the LTβR antibody from which the fragment is derived from. In one embodiment, agonist LTβR epitope-binding fragments and LTβR antibodies as described herein elicit detectable LTβR binding activity and induce LTβR signaling as disclosed herein.

[0094] Epitope-binding fragments of an LTβR antibody may be obtained using conventional techniques known to those of skill in the art. For example, agonist LTβR F(ab')2fragments may be generated by treating an agonist LTβR antibody with pepsin. The resulting LTβR F(ab')2fragment may be treated to reduce disulfide bridges to produce LTβR Fab' fragments. Agonist LTβR Fab fragments may be obtained by treating an agonist LTβR antibody with papain, and LTβR Fab' fragments may be obtained with pepsin digestion of an agonist LTβR antibody. An agonist LTβR Fab' fragment may be obtained by treating an agonist LTβR F(ab')2fragment with a reducing agent, such as dithiothreitol. LTβR-binding fragments may also be generated by expression of nucleic acids encoding such fragments in recombinant cells (see e.g., Evans et al. “Rapid Expression Of An Anti-Human C5 Chimeric Fab Utilizing A Vector That Replicates In COS And 293 Cells,” J. Immunol. Meth.184:123-38 (1995), which is hereby incorporated by reference in its entirety). For example, a chimeric gene encoding a portion of a LTβR F(ab')2fragment could include DNA sequences encoding the CH1 domain and hinge region of the heavy chain, followed by a translational stop codon to yield such a truncated antibody fragment molecule. Suitable fragments capable of binding to a desired epitope of LTβR may be readily screened for utility in the same manner as an antibody. LTβR antibodies and their epitope-binding fragments of the present disclosure are “isolated” so as to exist in a physical milieu distinct from that in which it was produced or would be naturally occurring.

[0095] In one embodiment, the agonist LTβR binding protein of the present disclosure is an antibody derivative. Agonist LTβR antibody derivatives include proteins or polypeptides that contain at least one epitope binding domain of an agonist LTβR antibody and are typically formed using recombinant techniques. Agonist LTβR antibody derivatives can also or alternatively be obtained through chemical modification of a parent LTβR antibody or portion thereof. An agonist LTβR antibody derivative comprises an amino acid sequence that is substantially similar to the amino acid sequence of such parental antibody or relevant portion of the parental antibody, for example, differing by less than 30%, less than 20%, less than 10%, or less than 5% from such parental LTβR antibody or relevant portion thereof, or by 10 amino acid residues, or by fewer than 10, 9, 8, 7, 6, 5, 4, 3 or 2 amino acid residues from such parental molecule or relevant portion thereof.

[0096] An exemplary agonist LTβR antibody derivative of the present disclosure is a single chain Fv (scFv). An agonist LTβR scFv is formed from the two domains of the Fv fragment, i.e., the VLregion and the VHregion, which may be encoded by separate genes. Such gene sequences or their encoding cDNA are joined, using recombinant methods, by a flexible linker (typically of about 10, 12, 15 or more amino acid residues) that enables them to be made as a single protein chain in which the VLand VHregions associate to form monovalent epitope-binding proteins (see e.g., Bird et al. “Single-Chain Antigen-Binding Proteins,” Science 242:423-426 (1988); and Huston et al. “Protein Engineering Of Antibody Binding Sites: Recovery Of Specific Activity In An Anti-Digoxin Single-Chain Fv Analogue Produced In Escherichia coli,” Proc. Natl. Acad. Sci. (U.S.A.) 85:5879-5883 (1988), which are hereby incorporated by reference in their entirety).

[0097] Another exemplary agonist LTβR antibody derivative of the present disclosure is a bispecific scFv. A bispecific LTβR scFv can be formed by employing a flexible linker that enables the VLand VHregions of different single polypeptide chains (each having different epitope binding specificities) to associate together.

[0098] In another embodiment, the agonist LTβR antibody derivative of the present disclosure is a divalent or bivalent single chain variable fragment, engineered by linking two scFvs together either in tandem (i.e., tandem scFv), or such that they dimerize to form a diabody (Holliger et al. “‘Diabodies’ : Small Bivalent And Bispecific Antibody Fragments,” Proc. Natl. Acad. Sci. (U.S.A.) 90(14), 6444-8 (1993); which is hereby incorporated by reference in its entirety). In accordance with this embodiment, each scFv in the bivalent tandem scFv or diabody can be the same, i.e., recognize the same target epitope of LTβR or can be different, i.e., recognize and bind different target epitopes. In yet another embodiment, the agonist LTβR antibody derivative is a triabody, i.e., a trivalent single chain variable fragment, engineered by linking three scFvs together, either in tandem or in a trimer formation to form a triabody. In accordance with this embodiment, each scFv of the triabody can be the same, i.e., recognize the same target epitope, or can be different, i.e., recognize and bind different target epitopes. In another embodiment, the agonist LTβR antibody derivative is a tetrabody of four single chain variable fragments, where each of the scFv recognize the same or different target epitopes. In another embodiment, the agonist LTβR antibody derivative is a “linear antibody” which is an antibody comprising a pair of tandem Fd segments (VH-CH1- VH-CH1) which, together with complementary light chain polypeptides, form a pair of antigen binding regions (see Zapata et al. Protein Eng.8(10): 1057-1062 (1995), which is hereby incorporated by reference in its entirety). In another embodiment, the agonist LTβR antibody derivative is a minibody, comprising single-chain Fv regions coupled to the CH3 region (i.e., scFv-CH3). In another embodiment, the agonist LTβR antibody derivative is a modified domain antibody, e.g., a modified single VL or VH domain or two or more VH domains joined by a peptide linker (see, e.g., Ward et al., Nature, 341:544-546 (1989), which is hereby incorporated by reference in its entirety); a maxibody, i.e., two scFvs fused to Fc region (see, e.g., Fredericks et al., Protein Engineering, Design & Selection, 17:95-106 (2004) and Powers et al., J. Immunol. Methods, 251:123-135 (2001), which are hereby incorporated by reference in their entirety); or a peptibody(one or more peptides attached to an Fc region, see PCT Appl. Publ. No. WO00 / 024782 to Feige, which is hereby incorporated by reference in its entirety). In another embodiment, the agonist LTβR antibody derivative is an immunoglobulin fusion protein, which comprises an agonist LTβR binding domain (i.e., polypeptide comprising one or more heavy chain and / or light chain CDRs as described herein) coupled to a hinge region polypeptide and one or more immunoglobulin constant regions (see e.g., U.S. Patent Appl. Pub. No. 20030133939, which is hereby incorporated by reference in its entirety). Exemplary immunoglobulin fusion protein formats include, without limitation, an IgG-scFv, an IgG-Fab, 2scFv-IgG, 4scFv-IgG, VH-IgG, IgG-VH, and Fab-scFv-Fc.

[0099] Another exemplary agonist LTβR antibody derivative of the present disclosure is a multi- specific binding antibody, e.g., a bispecific or tri-specific binding protein. Multi-specific agonist LTβR binding proteins of the present disclosure comprise a first binding domain that binds to LTβR and is coupled to one or more additional binding domains, where each additional binding domain binds a target moiety that is not LTβR. An exemplary agonist LTβR multi-specific binding protein of the disclosure is a bispecific agonist LTβR binding protein that comprises an LTβR binding domain and a tumor-associated antigen binding domain. Exemplary LTβR binding domains of a bispecific agonist LTβR binding protein include the binding domains from any one of the LTβR antibodies disclosed herein. In one embodiment, the bispecific agonist LTβR binding protein comprises an LTβR binding domain that binds one or more amino acid residues of human LTβR cysteine-rich domain 4 (CRD4) comprising amino acid residues 169- 211 of SEQ ID NO: 1. This bispecific agonist binding protein does not inhibit LIGHT binding to LTβR and does not inhibit LT1α2β binding to LTβR.

[0100] In accordance with the present disclosure, the agonist LTβR binding protein is a human agonist LTβR binding protein. A human agonist LTβR binding protein comprises variable and constant regions or domains which correspond substantially to human germline immunoglobulin sequences known in the art, including, for example, those described by Kabat et al. (1991). The human agonist LTβR binding protein disclosed herein may include amino acid residues not encoded by human germline immunoglobulin sequences (e.g., mutations introduced by random or site-specific mutagenesis in vitro or by somatic mutation in vivo), for example in the CDRs, and, in particular, CDR3. The human agonist LTβR binding proteins of the present disclosure may have at least one, two, three, four, five, or more positions replaced with an amino acid residue that is not encoded by the human germline immunoglobulin sequence. The definition of human agonist binding proteins as used herein also contemplates fully human antibodies, which include non-artificially and / or non-genetically altered human sequences of antibodies as those can be derived by using technologies or systems known in the art, such as, for example, phage display technology or transgenic mouse technology, including but not limited to the XenoMouse®, which is a transgenic mouse capable of producing human antibodies.

[0101] In one embodiment, the agonist LTβR binding protein of the present disclosure is an IgG isotype. The choice of isotype typically will be guided by the desired effector functions, such as antibody- dependent cellular cytotoxicity (ADCC) induction. Exemplary IgG isotypes are IgG1, IgG2, IgG3, andIgG4. In one embodiment, the agonist LTβR binding protein of the present disclosure is an IgG1 isotype. In one embodiment, the agonist LTβR binding protein of the present disclosure is an IgG2 isotype.

[0102] In accordance with all aspects of the present disclosure, the binding domain of an exemplary agonist LTβR binding protein disclosed herein comprises one or more VH and VL CDRs that can be delineated using any one of the standard methods known in the art, including and without limitation, the Kabat numbering scheme (Kabat et al., Sequences of Proteins of Immunological Interest, 5thed., U.S. Dept. of Health and Human Services, NIH (1991)), Chothia numbering scheme (Chothia et al., J. Mol. Biol.196: 901-917 (1987) and Al-Lazikani et al., J. Mol. Biol. 273: 927-948 (1997), which are hereby incorporated by reference in their entirety), the Abhinandan numbering scheme (Abhinandan et al., Mol. Immunol.45: 3832-3839 (2008), which is hereby incorporated by reference in its entirety), the immunogenetic (IMGT) database numbering scheme (Giudicelli et al., Nucl. Acids Res. 34: D781–784 (2006) and Lefranc et al., Dev. Comp. Immunol.27: 55-77 (2003), which are hereby incorporated by reference in their entirety), the Aho numbering scheme (Honegger et al., J. Mol. Biol.309: 657-670 (2001), which is hereby incorporated by reference in its entirety), and the Contact numbering scheme (MacCallum et al., J. Mol. Biol.262732- 745 (1996), which is hereby incorporated by reference in its entirety). The residues of the VH and VL regions that comprise CDRs according to each system are provided in Table 1 below. Table 1. VH and VL CDR Residues According to Known Numbering Schemes

[0103] In one embodiment, an agonist LTβR binding protein of the present disclosure comprises a HCDR1, HCDR2, and HCDR3 of any one of the heavy chain variable region sequences as provided in Tables 4, 8, and 12, and a LCDR1, LCDR2, and LCDR3 of the corresponding light chain variable region as also provided in Tables 4, 8, and 12, where the CDRs are defined by the Kabat numbering scheme. In another embodiment, an agonist LTβR binding protein of the present disclosure comprises a HCDR1, HCDR2, and HCDR3 of any one of the heavy chain variable region sequences as provided in Tables 4, 8, and 12, and a LCDR1, LCDR2, and LCDR3 of the corresponding light chain variable region as also provided in Tables 4, 8, and 12, where the CDRs are defined by the Chothia numbering scheme. In one embodiment, an agonist LTβR binding protein of the present disclosure comprises a HCDR1, HCDR2, and HCDR3 of any one of the heavy chain variable region sequences as provided in Tables 4, 8, and 12, and a LCDR1, LCDR2, and LCDR3 of the corresponding light chain variable region as provided in Tables 4, 8, and 12, where the CDRs are defined by the AbM numbering scheme. In one embodiment, an agonist LTβRbinding protein of the present disclosure comprises a HCDR1, HCDR2, and HCDR3 of any one of the heavy chain variable region sequences as provided in Tables 4, 8, and 12, and a LCDR1, LCDR2, and LCDR3 of the corresponding light chain variable region as also provided in Tables 4, 8, and 12, where the CDRs are defined by the IMGT numbering scheme. In one embodiment, an agonist LTβR binding protein of the present disclosure comprises a HCDR1, HCDR2, and HCDR3 of any one of the heavy chain variable region sequences as provided in Tables 4, 8, and 12, and a LCDR1, LCDR2, and LCDR3 of the corresponding light chain variable region as also provided in Tables 4, 8, and 12, where the CDRs are defined by the Contact numbering scheme. In one embodiment, the agonist LTβR binding protein is an antibody. In one embodiment, the agonist LTβR binding protein is a bispecific antibody. LTβR Agonist Binding Proteins that Bind CRD4

[0104] In one embodiment, agonist LTβR binding proteins of the present disclosure bind to an epitope comprising residues of CRD4 of LTβR. CRD4 of LTβR span residues 139–181 of SEQ ID NO: 4 (LTβR ECD), which corresponds to residues 169–211 of SEQ ID NO: 1 (full-length LTβR). In one embodiment, the agonist LTβR binding protein described herein binds to an epitope comprising one or more CRD4 residues at positions 168–179 of the extracellular domain of LTβR (SEQ ID NO: 4) (residues 197- 209 of SEQ ID NO: 1) as determined by HDX MS. In one embodiment, the agonist LTβR binding proteins of the present disclosure bind to an epitope comprising residues of LTβR CRD4 and also binds to one or more residues outside of the CRD4. For example, in one embodiment, the agonist LTβR binding protein binds to an epitope comprising residues of CRD4 and residues of the adjacent CRD3 of LTβR. CRD3 of LTβR comprises residues 95–138 of SEQ ID NO: 4, which corresponds to residues 125-168 of the full- length LTβR of SEQ ID NO: 1.

[0105] In one embodiment, the agonist LTβR binding proteins of the present disclosure bind to an epitope of LTβR within CRD4 of LTβR and do not bind to a region of LTβR outside of the CRD4 as defined herein. In other words, in one embodiment, the agonist LTβR binding protein binds to an epitope consisting of residues within CRD4 of LTβR.

[0106] Binding of an agonist LTβR binding protein to CRD4 of LTβR agonizes receptor signaling and does not inhibit endogenous LTβR ligand (i.e., LIGHT or LTα1β2) binding to the receptor. In some embodiments, the agonist LTβR binding protein having these properties is an antibody. Exemplary agonist LTβR antibodies having these functional features are disclosed herein (see Tables 2–4 and 6–8). In some embodiments, the agonist LTβR binding protein having these properties is a bispecific binding protein. Exemplary agonist LTβR bispecific binding proteins having these functional features comprise a LTβR binding domain from the exemplary agonist LTβR antibodies disclosed herein.

[0107] In accordance with the present disclosure, agonist LTβR binding proteins having these functional properties, i.e., binding proteins that bind residues of CRD4 of LTβR and do not block LIGHT binding to LTβR or LTα1β2 binding to LTβR, are defined by their shared heavy chain variable region (VH) CDR structure. These agonist LTβR binding proteins can further be defined by their shared light chainvariable region (VL) CDR structure. This shared CDR structure, which is presented as consensus VHCDR and VLCDR sequences, was derived from the alignment of VH and VL domains of exemplary agonist LTβR binding proteins disclosed herein (Table 4), which (i) possess the above noted functional characteristics and (ii) comprise VHand VLamino acid sequences that have at least 90% sequence identity to the VHand VLamino acid sequences, respectively, of the LTβR binding proteins LIBC219081 and LIBC 218979.

[0108] Accordingly, in one embodiment, agonist LTβR binding proteins of the present disclosure that (i) bind residues of LTβR CRD4 and (ii) do not block LIGHT binding to LTβR and do not block LTα1β2 binding to LTβR comprise a shared VHCDR structure defined by the HCDR1 amino acid sequence of: X1YX3MX5(SEQ ID NO: 5), where X1is S or N; X3is G, D, or A; and X5is H or Y; the HCDR2 amino acid sequence of: X1IX3YDX6X7X8X9Y X11X12DSVKG (SEQ ID NO: 6), where X1 is A or V; X3 is W or R; X6is E or G; X7is S, R, or T; X8is N or K; X9is K, R, or Q; X11is H or Y; and X12is A or E; and the HCDR3 amino acid sequence of: X1RX3X4X5X6X7X8X9YYGX13X14V (SEQ ID NO: 7), where X1is D or E; X3is V, G, or I; X4is V, P, or A; X5is A, Y, or G; X6is R, A, G, or H; X7is P or G; X8is G, N, D, Y, A or H; X9is Y, T, or F; X13is L or M; and X14is D or A. In some embodiments, the agonist LTβR binding protein is an antibody. In some embodiments, the agonist LTβR binding protein is a bispecific binding protein.

[0109] Heavy chain CDR sequences of exemplary agonist LTβR binding proteins (e.g., antibodies or bispecific binding proteins) that bind CRD4 of LTβR, do not block LIGHT or LTα1β2 binding or activity, and comprises a HCDR1 of SEQ ID NO: 5, a HCDR2 of SEQ ID NO: 6, and a HCDR3 of SEQ ID NO: 7 are provided in Table 2 below. TABLE 2: Heavy Chain CDR Sequences of LTβR CRD4 Binders comprising 90% Sequence Identity to the Fv Domains of LIBC219081 and LIBC218979

[0110] In one embodiment, agonist LTβR binding proteins that (i) bind residues of LTβR CRD4, and (ii) do not block LIGHT binding to LTβR and do not block LTα1β2 binding to LTβR comprise a shared VLCDR structure defined by the LCDR1 amino acid sequence of: SGDX4LPX7X8YX10Y (SEQ ID NO: 62), where X4is A or T; X7is E, K, Q, D or N; X8is Q or H; and X10is A or T; the LCDR2 amino acid sequence of: KDNERPS (SEQ ID NO: 63); and the LCDR3 amino acid sequence of: QSX3DX5SX7X8YX10X11(SEQ ID NO: 64), where X3is A or T; X5is S, G, or N; X7is G or A; X8is T, S, or A; X10is V or M; and X11is I or V.

[0111] Light chain CDR sequences of exemplary agonist LTβR binding proteins that bind CRD4 of LTβR, do not block LIGHT or LTα1β2 binding or activity, and comprises a LCDR1 of SEQ ID NO: 62, a LCDR2 of SEQ ID NO: 63, and a LCDR3 of SEQ ID NO: 64 are provided in Table 3 below. TABLE 3: Light Chain CDRs of Exemplary LTβR CRD4 Binders Comprising 90% Sequence Identity to the Fv Domains of LIBC219081 and LIBC218979

[0112] In one embodiment, agonist LTβR binding proteins that bind residues of human LTβR CRD4 and (a) do not block LIGHT binding to LTβR and (b) do not block LTα1β2 binding to LTβR include those binding proteins possessing VH and VL amino acid sequences that have at least 80% sequence identity to the VH and VL amino acid sequences, respectively, of the LTβR binding protein LIBC219081 (SEQ ID NOs: 121 and 122, respectively). In one embodiment, agonist LTβR binding proteins that bind human LTβR CRD4 and (a) do not block LIGHT binding to LTβR and (b) do not block LTα1β2 binding to LTβR include those binding proteins possessing VH and VL amino acid sequences that have at least 80% sequence identity to the VH and VL amino acid sequences, respectively, of the LTβR binding protein LIBC218979 (SEQ ID NOs: 123 and 124, respectively). In one embodiment, agonist LTβR binding proteins that bind human LTβR CRD4 and (a) do not block LIGHT binding to LTβR and (b) do not block LTα1β2 binding to LTβR include those binding proteins possessing VH and VL amino acid sequences that have at least 80% sequence identity to the VH and VL amino acid sequences, respectively, of LTβR binding proteins LIBC219081 (SEQ ID NOs: 121 and 122, respectively) and LIBC218979 (SEQ ID NOs: 123 and 124, respectively).

[0113] In one embodiment, agonist LTβR binding proteins (e.g., antibodies or bispecific binding proteins) that bind human LTβR CRD4 and (a) do not block LIGHT binding to LTβR or (b) do not block LTα1β2 binding to LTβR include those binding proteins possessing VH and VL amino acid sequences that have at least 85% sequence identity to the VH and VL amino acid sequences, respectively, of the LTβR binding protein LIBC219081 (SEQ ID NOs: 121 and 122, respectively). In one embodiment, agonist LTβRbinding proteins that bind human LTβR CRD4 and (a) do not block LIGHT binding to LTβR and (b) do not block LTα1β2 binding to LTβR include those binding proteins possessing VH and VL amino acid sequences that have at least 85% sequence identity to the VH and VL amino acid sequences, respectively, of the LTβR binding protein LIBC218979 (SEQ ID NOs: 123 and 124, respectively). In one embodiment, agonist LTβR binding proteins that bind human LTβR CRD4 and (a) do not block LIGHT binding to LTβR and (b) do not block LTα1β2 binding to LTβR include those binding proteins possessing VH and VL amino acid sequences that have at least 85% sequence identity to the VH and VL amino acid sequences, respectively, of the LTβR binding proteins LIBC219081 (SEQ ID NOs: 121 and 122, respectively) and LIBC218979 (SEQ ID NOs: 123 and 124, respectively).

[0114] In one embodiment, agonist LTβR binding proteins (e.g., antibodies or bispecific binding proteins) that bind human LTβR CRD4 and (a) do not block LIGHT binding to LTβR and (b) do not block LTα1β2 binding to LTβR include those binding proteins possessing VH and VL amino acid sequences that have at least 90% sequence identity to the VH and VL amino acid sequences, respectively, of the LTβR binding proteins LIBC219081 and LIBC218979. Accordingly, in one embodiment, an agonist LTβR binding protein of the present disclosure comprises a VH amino acid sequence having at least 90% sequence identity to the amino acid sequence of SEQ ID NO: 121. In one embodiment, an agonist LTβR binding protein of the present disclosure comprises a VH amino acid sequence having at least 90% sequence identity to the amino acid sequence of SEQ ID NO: 123. In one embodiment, an agonist LTβR binding protein of the present disclosure comprises a VH amino acid sequence having at least 90% sequence identity to the amino acid sequence of SEQ ID NO: 121 and the amino acid sequence of SEQ ID NO: 123. Exemplary VH amino acid sequences having at least 90% sequence identity to the amino acid sequence of SEQ ID NO: 121 and SEQ ID NO: 123 are provided in Table 4 below.

[0115] In one embodiment, agonist LTβR binding proteins (e.g., antibodies or bispecific binding proteins) that bind human LTβR CRD4 and (a) do not block LIGHT binding to LTβR and (b) do not block LTα1β2 binding to LTβR include those binding proteins comprising a VH amino acid sequence having at least 90% sequence identity to the amino acid sequence of SEQ ID NO: 121. In one embodiment, an agonist LTβR binding protein of the present disclosure comprises a VH amino acid sequence having at least 90% sequence identity to the amino acid sequence of SEQ ID NO: 123. In one embodiment, an agonist LTβR binding protein of the present disclosure comprises a VH amino acid sequence having at least 90% sequence identity to the amino acid sequence of SEQ ID NO: 121 and the amino acid sequence of SEQ ID NO: 123. Exemplary VH amino acid sequences having at least 90% sequence identity to the amino acid sequence of SEQ ID NO: 121 and SEQ ID NO: 123 are provided in Table 4 below.

[0116] In one embodiment, agonist LTβR binding proteins (e.g., antibodies or bispecific binding proteins) that bind human LTβR CRD4 and (a) do not block LIGHT binding to LTβR and (b) do not block LTα1β2 binding to LTβR include those binding proteins comprising a VL amino acid sequence having at least 90% sequence identity to the amino acid sequence of SEQ ID NO: 122. In one embodiment, an agonist LTβR binding protein of the present disclosure comprises a VL amino acid sequence having at least 90%sequence identity to the amino acid sequence of SEQ ID NO: 124. In one embodiment, an agonist LTβR binding protein of the present disclosure comprises a VL amino acid sequence having at least 90% sequence identity to the amino acid sequence of SEQ ID NO: 122 and the amino acid sequence of SEQ ID NO: 124. Exemplary VL amino acid sequences having at least 90% sequence identity to the amino acid sequence of SEQ ID NO: 122 and SEQ ID NO: 124 are provided in Table 4 below.

[0117] In one embodiment, agonist LTβR binding proteins (e.g., antibodies or bispecific binding proteins) that bind human LTβR CRD4 and (a) do not block LIGHT binding to LTβR and (b) do not block LTα1β2 binding to LTβR comprise a VH amino acid sequence having at least 90% sequence identity to the amino acid sequence of SEQ ID NO: 121 and a VL amino acid sequence having at least 90% sequence identity to the amino acid sequence of SEQ ID NO: 122. In one embodiment, an agonist LTβR binding protein of the present disclosure comprises a VH amino acid sequence having at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 121 and a VL amino acid sequence having at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 122. In one embodiment, an agonist LTβR binding protein of the present disclosure comprises a VH amino acid sequence having at least 98% sequence identity to the amino acid sequence of SEQ ID NO: 121 and a VL amino acid sequence having at least 98% sequence identity to the amino acid sequence of SEQ ID NO: 122.

[0118] In one embodiment, agonist LTβR binding proteins (e.g., antibodies or bispecific binding proteins) that bind human LTβR CRD4 and (a) do not block LIGHT binding to LTβR and (b) do not block LTα1β2 binding to LTβR comprise a VH amino acid sequence having at least 90% sequence identity to the amino acid sequence of SEQ ID NO: 123 and a VL amino acid sequence having at least 90% sequence identity to the amino acid sequence of SEQ ID NO: 124. In one embodiment, an agonist LTβR binding protein of the present disclosure comprises a VH amino acid sequence having at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 123 and a VL amino acid sequence having at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 124. In one embodiment, an agonist LTβR binding protein of the present disclosure comprises a VH amino acid sequence having at least 98% sequence identity to the amino acid sequence of SEQ ID NO: 123 and a VL amino acid sequence having at least 98% sequence identity to the amino acid sequence of SEQ ID NO: 124.

[0119] In one embodiment, agonist LTβR binding proteins (e.g., antibodies or bispecific binding proteins) that bind human LTβR CRD4 and (a) do not block LIGHT binding to LTβR and (b) do not block LTα1β2 binding to LTβR comprise a VH amino acid sequence having at least 90% sequence identity to the amino acid sequence of SEQ ID NO: 121 and the amino acid sequence of SEQ ID NO: 123 and a VL amino acid sequence having at least 90% sequence identity to the amino acid sequence of SEQ ID NO: 122 and the amino acid sequence of SEQ ID NO: 124. In one embodiment, an agonist LTβR binding protein of the present disclosure comprises a VH amino acid sequence having at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 121 and the amino acid sequence of SEQ ID NO: 123 and a VL amino acid sequence having at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 122 and the amino acid sequence of SEQ ID NO: 124. In one embodiment, an agonist LTβR binding protein of thepresent disclosure comprises a VH amino acid sequence having at least 98% sequence identity to the amino acid sequence of SEQ ID NO: 121 and the amino acid sequence of SEQ ID NO: 123 and a VL amino acid sequence having at least 98% sequence identity to the amino acid sequence of SEQ ID NO: 122 and the amino acid sequence of SEQ ID NO: 124.

[0120] In one embodiment, agonist LTβR binding proteins (e.g., antibodies or bispecific binding proteins) that bind human LTβR CRD4 and (a) do not block LIGHT binding to LTβR and (b) do not block LTα1β2 binding to LTβR comprise a VH amino acid sequence having at least 90% sequence identity to the VH amino acid sequence of SEQ ID NO: 121 or SEQ ID NO: 123 and comprise the HCDR1 amino acid sequence of: X1YX3MX5(SEQ ID NO: 5), where X1is S or N; X3is G, D, or A; and X5is H or Y; the HCDR2 amino acid sequence of: X1IX3YDX6X7X8X9Y X11X12DSVKG (SEQ ID NO: 6), where X1is A or V; X3 is W or R; X6 is E or G; X7 is S, R, or T; X8 is N or K; X9 is K, R, or Q; X11 is H or Y; and X12 is A or E; and the HCDR3 amino acid sequence of: X1RX3X4X5X6X7X8X9YYGX13X14V (SEQ ID NO: 7), where X1is D or E; X3is V, G, or I; X4is V, P, or A; X5is A, Y, or G; X6is R, A, G, or H; X7is P or G; X8is G, N, D, Y, A or H; X9is Y, T, or F; X13is L or M; and X14is D or A. Exemplary VH amino acid sequences of agonist LTβR binding proteins comprising 90% sequence identity to the VH of amino acid sequence of SEQ ID NO: 121 or SEQ ID NO: 123 and comprising the HCDR sequences of SEQ ID NOs: 5, 6, and 7 are provided in Table 4 below.

[0121] These agonist LTβR binding proteins may further comprise a VL amino acid sequence having at least 90% sequence identity to the VL amino acid sequence of SEQ ID NO: 122 or SEQ ID NO: 124 and comprise the LCDR1 amino acid sequence of: SGDX4LPX7X8YX10Y (SEQ ID NO: 62), where X4is A or T; X7is E, K, Q, D or N; X8is Q or H; and X10is A or T; the LCDR2 amino acid sequence of: KDNERPS (SEQ ID NO: 63); and the LCDR3 amino acid sequence of: QSX3DX5SX7X8YX10X11(SEQ ID NO: 64), where X3is A or T; X5is S, G, or N; X7is G or A; X8is T, S, or A; X10is V or M; and X11is I, or V. Exemplary VL amino acid sequences of agonist LTβR binding proteins comprising 90% sequence identity to the VL of amino acid sequence of SEQ ID NO: 122 or SEQ ID NO: 124 and comprising the LCDR sequences of SEQ ID NOs: 62, 63, and 64 are provided in Table 4 below.

[0122] In one embodiment, an agonist LTβR binding protein (e.g., antibody or bispecific binding protein) that binds human LTβR CRD4 and (a) does not block LIGHT binding to LTβR and (b) does not block LTα1β2 binding to LTβR comprises a VH amino acid sequence of: QVQLVESGGGVVQPGRSLRLSCAASGFTFSX31YX33MX35WVRQAPGKGLEWVA X50IX52YDX55X56X57X58YX60X61DSVKGRFTISRDNSKNTLSLQMNSLRAEDTAVYYCARX99RX101X102X103X104X105X106X107YYGX111X112VWGQGTTVTVSS (SEQ ID NO: 119), where X31is S or N; X33is G or A; X35is H or Y; X50is A or V; X52is W or R; X55is E or G; X56is S, R, or T; X57is N or K; X58is K, R, or Q; X60is H or Y; X61is A or E; X99is D or E; X101is V, G, or I; X102is V, P, or A; X103is A, Y, or G; X104is R, A, G, or H; X106is G, N, D, Y, A, or H; X107is Y, T, or F; X111is L or M; and X112is D or A.

[0123] In one embodiment, an agonist LTβR binding protein (e.g., antibody or bispecific binding protein) that binds human LTβR CRD4 and (a) does not block LIGHT binding to LTβR and (b) does notblock LTα1β2 binding to LTβR comprises a VL amino acid sequence of: SYELTQPPSVSVSPRQTARITCSGDX26LPX29X30YX32YWYQQKPGQAPVLVIYKDNERPSGIPERFS GSSSGTTVTLTISGVQAEDEADYYCQSX90DX92SX94X95YX97X98FGGGTKLTVLG (SEQ ID NO: 120), where X26is A or T; X29is E, K, Q, D or N; X30is Q or H; X32is A or T; X90is A or T; X92is S, G, or N; X94is G or A; X95is T, S or A; X97is V or M; and X98is I or V.

[0124] In one embodiment, an agonist LTβR binding protein (e.g., antibody or bispecific binding protein) that binds human LTβR CRD4 and (a) does not block LIGHT binding to LTβR and (b) does not block LTα1β2 binding to LTβR comprises a VH, where the VH comprises an amino acid sequence of SEQ ID NO: 119 and shares at least 90% sequence identity to the VH amino acid sequence of SEQ ID NO: 121 and / or the VH amino acid sequence of SEQ ID NO: 123. The agonist LTβR binding protein further comprises a VL, where the VL comprises an amino acid sequence of SEQ ID NO: 120 and shares at least 90% sequence identity to the VL amino acid sequence of SEQ ID NO: 122 and / or the VL amino acid sequence of SEQ ID NO: 124.

[0125] In one embodiment, an agonist LTβR binding protein (e.g., antibody or bispecific binding protein) that binds human LTβR CRD4 and (a) does not block LIGHT binding to LTβR and (b) does not block LTα1β2 binding to LTβR comprises a VH, where the VH comprises an amino acid sequence of SEQ ID NO: 119 and shares at least 95% sequence identity to the VH amino acid sequence of SEQ ID NO: 121 and / or the VH amino acid sequence of SEQ ID NO: 123. The agonist LTβR binding protein further comprises a VL, where the VL comprises an amino acid sequence of SEQ ID NO: 120 and shares at least 95% sequence identity to the VL amino acid sequence of SEQ ID NO: 122 and / or the VL amino acid sequence of SEQ ID NO: 124.

[0126] In one embodiment, the agonist LTβR binding proteins of the present disclosure that bind human LTβR CRD4 and (a) do not block LIGHT binding to LTβR and (b) do not block LTα1β2 binding to LTβR comprise a variable light (VL) domain, a variable heavy (VH) domain, or a combination of VL and VH domain. VH and VL amino acid sequences of exemplary agonist LTβR binding proteins that share 90% sequence identity with the VH and VL amino acid sequences of LIBC219081 and LIBC218979 are provided in Table 4. In some embodiments, the VH domain of the agonist LTβR binding protein comprises any one of the VH amino acid sequences provided in Table 4, or an amino acid sequence that is at least 75%, at least 80%, at least 85%, at least 90%, or at least 95% identical to any one of the VH amino acid sequences listed in Table 4. In some embodiments, the VL domain of the agonist LTβR binding protein comprises any one of the VL amino acid sequences provided in Table 4 below, or an amino acid sequence that is at least 75%, at least 80%, at least 85%, at least 90%, at least 95% identical to any one of the VL amino acid sequences listed in Table 4. TABLE 4: VH and VL Sequences of LTβR CRD4 Binding Proteins Sharing 90% Sequence Identity

[0127] In one embodiment, the agonist LTβR binding protein (e.g., an agonist LTβR antibody or agonist LTβR bispecific binding protein) of the present disclosure binds to human LTβR CRD4, including one or more residues corresponding to residues 198-209 of SEQ ID NO: 1 (residues 168-179 of SEQ ID NO: 4), and (a) does not block LIGHT binding to LTβR and (b) does not block LTα1β2 binding to LTβR. This agonist LTβR binding protein comprises a VH, where the VH comprises a HCDR1 sequence comprising at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 8, a HCDR2 sequence comprising at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 9, and a HCDR3 sequence comprising at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 10. In one embodiment, the VH of this agonist LTβR binding protein comprises the HCDR1 sequence of SEQ ID NO: 5, the HCDR2 sequence of SEQ ID NO: 6, and the HCDR3 sequence of SEQ ID NO: 7. In one embodiment, the VH of this agonist LTβR binding protein comprises the HCDR1 sequence of SEQ ID NO: 8, the HCDR2 sequence of SEQ ID NO: 9, and the HCDR3 sequence of SEQ ID NO: 10.

[0128] In accordance with the preceding embodiment, this agonist LTβR binding protein of the present disclosure further comprises a VL, where the VL comprises a LCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 65, a LCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 66, and a LCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with thesequence SEQ ID NO: 67. In one embodiment, the VL comprises the LCDR1 sequence of SEQ ID NO: 62, the LCDR2 of SEQ ID NO: 63, and the LCDR3 sequence of SEQ ID NO: 64. In one embodiment, the VL comprises the LCDR1 sequence of SEQ ID NO: 65, the LCDR2 of SEQ ID NO: 66, and the LCDR3 sequence of SEQ ID NO: 67. An exemplary LTβR binding protein comprising a VH and VL of this embodiment includes, without limitation, the LTβR antibody identified herein as LIBC No.219081 (BR# 19325; 41B2).

[0129] In another embodiment, the agonist LTβR binding protein (e.g., an agonist LTβR antibody or agonist LTβR bispecific binding protein) of the present disclosure binds to human LTβR CRD4, including one or more residues corresponding to residues 197–209 of SEQ ID NO: 1) (i.e., residues 167- 179 of SEQ ID NO: 4), and (a) does not block LIGHT binding to LTβR and (b) does not block LTα1β2 binding to LTβR. This LTβR binding protein comprises a VH, where the VH comprises a HCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 11, a HCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 12, and a HCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 13. In one embodiment, the VH of this LTβR binding protein comprises the HCDR1 sequence of SEQ ID NO: 5, the HCDR2 sequence of SEQ ID NO: 6, and a HCDR3 sequence of SEQ ID NO: 7. In one embodiment, the VH of this LTβR binding protein comprises the HCDR1 sequence of SEQ ID NO: 11, the HCDR2 sequence of SEQ ID NO: 12, and the HCDR3 sequence of SEQ ID NO: 13.

[0130] In accordance with the preceding embodiment, this agonist LTβR binding protein of the present disclosure further comprises a VL, where the VL comprises a LCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 68, a LCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 69, and a LCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 70. In one embodiment, the VL comprises the LCDR1 sequence of SEQ ID NO: 62, the LCDR2 of SEQ ID NO: 63, and the LCDR3 sequence of SEQ ID NO: 64. In one embodiment, the VL comprises the LCDR1 sequence of SEQ ID NO: 68, the LCDR2 of SEQ ID NO: 69, and the LCDR3 sequence of SEQ ID NO: 70. An exemplary LTβR binding protein comprising a VH and VL of this embodiment includes, without limitation, the LTβR antibody identified herein as LIBC No. 218979 (BR#19319; 23E9).

[0131] In another embodiment, the agonist LTβR binding protein (e.g., an agonist LTβR antibody or agonist LTβR bispecific binding protein) of the present disclosure that binds to human LTβR CRD4, and (a) does not block LIGHT binding to LTβR and (b) does not block LTα1β2 binding to LTβR comprises acombination of HCDR1, HCDR2, HCDR3, LCDR1, LCDR2, and LCDR3 amino acid sequences selected from: (i) SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 16, SEQ ID NO: 71, SEQ ID NO: 72, and SEQ ID NO: 73, respectively, (ii) SEQ ID NO: 17, SEQ ID NO: 18, SEQ ID NO: 19, SEQ ID NO: 74, SEQ ID NO: 75, and SEQ ID NO: 76, respectively; (iii) SEQ ID NO: 20, SEQ ID NO: 21, SEQ ID NO: 22, SEQ ID NO: 77, SEQ ID NO: 78, and SEQ ID NO: 79, respectively; (iv) SEQ ID NO: 23, SEQ ID NO: 24, SEQ ID NO: 25, SEQ ID NO: 80, SEQ ID NO: 81, and SEQ ID NO: 82, respectively; (v) SEQ ID NO: 26, SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 83, SEQ ID NO: 84, and SEQ ID NO: 85, respectively; (vi) SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 31, SEQ ID NO: 86, SEQ ID NO: 87, and SEQ ID NO: 88, respectively; (vii) SEQ ID NO: 32, SEQ ID NO: 33, SEQ ID NO: 34, SEQ ID NO: 89, SEQ ID NO: 90, and SEQ ID NO: 91, respectively; (viii) SEQ ID NO: 35, SEQ ID NO: 36, SEQ ID NO: 37, SEQ ID NO: 92, SEQ ID NO: 93, and SEQ ID NO: 94, respectively; (vix) SEQ ID NO: 38, SEQ ID NO: 39, SEQ ID NO: 40, SEQ ID NO: 95, SEQ ID NO: 96, and SEQ ID NO: 97, respectively; (x) SEQ ID NO: 41, SEQ ID NO: 42, SEQ ID NO: 43, SEQ ID NO:98, SEQ ID NO: 99, and SEQ ID NO: 100, respectively; (xi) SEQ ID NO: 44, SEQ ID NO: 45, SEQ ID NO: 46, SEQ ID NO: 101, SEQ ID NO: 102, and SEQ ID NO: 103, respectively; (xii) SEQ ID NO: 47, SEQ ID NO: 48 SEQ ID NO: 49, SEQ ID NO: 104, SEQ ID NO: 105, and SEQ ID NO: 106, respectively; (xiii) SEQ ID NO: 50, SEQ ID NO: 51, SEQ ID NO: 52, SEQ ID NO: 107, SEQ ID NO: 108, and SEQ ID NO: 109, respectively; (xiv) SEQ ID NO: 53, SEQ ID NO: 54, SEQ ID NO: 55, SEQ ID NO: 110, SEQ ID NO: 111, and SEQ ID NO: 112, respectively; (xv) SEQ ID NO: 56, SEQ ID NO: 57, SEQ ID NO: 58, SEQ ID NO: 113, SEQ ID NO: 114, and SEQ ID NO: 115, respectively; and (xvi) SEQ ID NO: 59, SEQ ID NO: 60, SEQ ID NO: 61, SEQ ID NO: 116, SEQ ID NO: 117, and SEQ ID NO: 118, respectively.

[0132] In another embodiment, the agonist LTβR binding protein (e.g., an agonist LTβR antibody or agonist LTβR bispecific binding protein) of the present disclosure that binds to human LTβR CRD4, and (a) does not block LIGHT binding to LTβR and (b) does not block LTα1β2 binding to LTβR comprises a VH amino acid sequence and a VL amino acid sequence selected from: a VH amino acid sequence of SEQ ID NO: 119 and a VL amino acid sequence of SEQ ID NO: 120; a VH amino acid sequence of SEQ ID NO: 121 and a VL amino acid sequence of SEQ ID NO: 122; a VH amino acid sequence of SEQ ID NO: 123 and a VL amino acid sequence of SEQ ID NO: 124; a VH amino acid sequence of SEQ ID NO: 125 and a VL amino acid sequence of SEQ ID NO: 126; a VH amino acid sequence of SEQ ID NO: 127 and a VL amino acid sequence of SEQ ID NO: 128; a VH amino acid sequence of SEQ ID NO: 129 and a VL amino acid sequence of SEQ ID NO: 130; a VH amino acid sequence of SEQ ID NO: 131 and a VL amino acid sequence of SEQ ID NO: 132; a VH amino acid sequence of SEQ ID NO: 133 and a VL amino acid sequence of SEQ ID NO: 134; a VH amino acid sequence of SEQ ID NO: 135 and a VL amino acid sequence of SEQ ID NO: 136; a VH amino acid sequence of SEQ ID NO: 137 and a VL amino acid sequence of SEQ ID NO: 138; a VH amino acid sequence of SEQ ID NO: 139 and a VL amino acid sequence of SEQ ID NO: 140; a VH amino acid sequence of SEQ ID NO: 141 and a VL amino acid sequence of SEQ ID NO: 142; a VH amino acid sequence of SEQ ID NO: 143 and a VL amino acid sequence of SEQ ID NO: 144; a VH aminoacid sequence of SEQ ID NO: 145 and a VL amino acid sequence of SEQ ID NO: 146; a VH amino acid sequence of SEQ ID NO: 147 and a VL amino acid sequence of SEQ ID NO: 148; a VH amino acid sequence of SEQ ID NO: 149 and a VL amino acid sequence of SEQ ID NO: 150; a VH amino acid sequence of SEQ ID NO: 151 and a VL amino acid sequence of SEQ ID NO: 152; a VH amino acid sequence of SEQ ID NO: 153 and a VL amino acid sequence of SEQ ID NO: 154; a VH amino acid sequence of SEQ ID NO: 155 and a VL amino acid sequence of SEQ ID NO: 156; and a VH amino acid sequence of SEQ ID NO: 157 and a VL amino acid sequence of SEQ ID NO: 158.

[0133] In another embodiment, the agonist LTβR binding protein (e.g., an agonist LTβR antibody or agonist LTβR bispecific binding protein) of the present disclosure that binds to human LTβR CRD4, and (a) does not block LIGHT binding to LTβR and (b) does not block LTα1β2 binding to LTβR comprises a VH region and / or VL region as described supra and further comprises one or more heavy chain constant regions coupled to the VH region and / or a light chain constant region coupled to the VL region. For example, in one embodiment, the LTβR binding protein is a Fab comprising a VH and first heavy chain constant domain (CH1) coupled to a VL and light chain constant region (CL). In another embodiment, the LTβR binding protein is a F(ab’)2 comprising both LTβR binding regions of a full antibody coupled by the hinge region, where each binding region comprises a VH-CH1 and VL-CL. In another embodiment, the LTβR binding protein is an antibody comprising full light chains (VL-CL) and full heavy chains (VH-CH1- CH2-CH3).

[0134] In another embodiment, the agonist LTβR binding protein (e.g., an agonist LTβR antibody or agonist LTβR bispecific binding protein) of the present disclosure that binds to human LTβR CRD4, and (a) does not block LIGHT binding to LTβR and (b) does not block LTα1β2 binding to LTβR comprise a human IgG1 heavy chain. In another embodiment, the agonist LTβR binding protein (e.g., an agonist LTβR antibody or agonist LTβR bispecific binding protein) of the present disclosure that binds to human LTβR CRD4, and (a) does not block LIGHT binding to LTβR and (b) does not block LTα1β2 binding to LTβR comprise a human IgG2 heavy chain. In one embodiment, the human IgG heavy chain is modified to prevent or reduce interaction with Fc gamma receptors. In one embodiment, the human IgG is a Stable Effector Functionless (SEFL) IgG (Liu et al., J Biol. Chem. 292(5):1876-1883), which is hereby incorporated by reference in its entirety). The amino acid sequences of exemplary light chain constant regions and heavy chain constant regions of the LTβR binding proteins of the present disclosure are provided in Table 5 below. Table 5: Exemplary LC and HC Constant Domain Regions

[0135] Exemplary amino acid sequences of LTβR antibodies of the present disclosure that bind to human LTβR CRD4, and (a) do not block LIGHT binding to LTβR and (b) do not block LTα1β2 binding to LTβR are provided in Table 9 herein.

[0136] In another embodiment, an agonist LTβR binding protein of the present disclosure (e.g., agonist LTβR antibody or agonist LTβR bispecific binding protein) competes with the LTβR binders LIBC219081 and LIBC218979 for binding to human LTβR CRD4, and (a) does not block LIGHT binding to LTβR and (b) does not block LTα1β2 binding to LTβR.

[0137] In accordance with the present disclosure, agonist LTβR binding proteins having these functional properties, i.e., compete with the LTβR binders LIBC219081 and LIBC218979 for binding to CRD4 of LTβR and do not block LIGHT or LTα1β2 binding to LTβR, are defined by their structurally similar VH and VL domains. This shared variable region structure, presented as consensus VH and VL CDR sequences as well as consensus VH and VL sequences, was derived from alignment of exemplary agonist LTβR binding proteins disclosed herein (see Tables 6, 7, and 8), which (i) possess these functional characteristics and (ii) comprise VH and VL amino acid sequences that share at least 90% sequence identity across their respective entire length, i.e. from N-terminus to C-terminus across the FR1, CDR1, FR2, CDR2, FR3, CDR3, and FR4.

[0138] Accordingly, in one embodiment, the agonist LTβR binding proteins (e.g., agonist LTβR antibodies or agonist LTβR bispecific binding proteins) of the present disclosure that bind to human LTβR CRD4, and (a) do not block LIGHT binding to LTβR and (b) do not block LTα1β2 binding to LTβR comprise a shared VH CDR structure defined by the HCDR1 amino acid sequence of: GX2YMH (SEQ ID NO: 159),where X2is Y or F; the HCDR2 amino acid sequence of: WINPNX6GGTNYAQKFQG (SEQ ID NO: 160), where X6is S, N, or R; and the HCDR3 amino acid sequence of: X1X2X3X4GX6X7X8YYGMDV (SEQ ID NO: 161), where X1is D or A; X2is R or D; X3is N, S, or A; X4is G or S; X6is V or W; X7is Y or absent; X8is Y or absent. Heavy chain CDR sequences of exemplary agonist LTβR binding proteins that bind to human LTβR CRD4, do not block LIGHT binding to LTβR, do not block LTα1β2 binding to LTβR, and comprise a HCDR1 of SEQ ID NO: 159, a HCDR2 of SEQ ID NO: 160, and a HCDR3 of SEQ ID NO: 161 are provided in Table 6 below.

[0139] In one embodiment, the agonist LTβR binding proteins of the present disclosure comprising the HCDRs 1–3 of SEQ ID NOs: 159-161, respectively, further comprise a shared VL CDR structure defined by the LCDR1 amino acid sequence of TGTX4SDVGSYNLVS (SEQ ID NO: 278), where X4is TN, or S; the LCDR2 amino acid sequence of EVX3X4RPS (SEQ ID NO: 279), where X3is T or S and X4is K or V; and the LCDR3 amino acid sequence of CSYX4X5SX7TX9V (SEQ ID NO: 280), where X4is A or V; X5is D or E; X7is S or K; X9is L or W. Light chain CDR sequences of exemplary agonist LTβR binding proteins that bind to human LTβR CRD4, do not block LIGHT binding to LTβR, do not block LTα1β2 binding to LTβR, and comprise a LCDR1 of SEQ ID NO: 278, a LCDR2 of SEQ ID NO: 279, and a LCDR3 of SEQ ID NO: 280 are provided in Table 7 below.

[0140] In one embodiment, the agonist LTβR binding proteins of the present disclosure comprising the HCDRs 1–3 of SEQ ID NOs. 159-161, respectively, further comprise a shared VL CDR structure defined by the LCDR1 amino acid sequence of SGDX4LPX7X8YX10Y (SEQ ID NO: 308), where X4is A or T; X7is Q, E, N, R, or K; X8is H or Q; X10is V, T, or A; the LCDR2 amino acid sequence of KDX3X4RPS (SEQ ID NO: 309) where X3 is N or S; X4 is D or E; and the LCDR3 amino acid sequence of QSADX5SGX8X9VV (SEQ ID NO: 310), where X5is I, N, or S; X8is S, A, I, or T; and X9is F or Y. Light chain CDR sequences of exemplary agonist LTβR binding proteins that bind to human LTβR CRD4, do not block LIGHT binding to LTβR, do not block LTα1β2 binding to LTβR, and comprise a LCDR1 of SEQ ID NO: 308, a LCDR2 of SEQ ID NO: 309, and a LCDR3 of SEQ ID NO: 310 are provided in Table 7 below. TABLE 6. Heavy Chain CDR Sequences of agonist LTβR binding proteins that bind human LTβR CRD4 and do not block LIGHT or LTα1β2 binding to LTβRTABLE 7. Light Chain CDR Sequences of agonist LTβR binding proteins that bind human LTβR CRD4 and do not block LIGHT or LTα1β2 binding to LTβR

[0141] In another embodiment, the agonist LTβR binding proteins (e.g., agonist LTβR antibodies or agonist LTβR bispecific binding proteins) of the present disclosure that bind to human LTβR CRD4, and (a) do not block LIGHT binding to LTβR and (b) do not block LTα1β2 binding to LTβR comprise a shared VH CDR structure defined by the HCDR1 amino acid sequence of: X1YGMH (SEQ ID NO: 195), whereX1is A or S; the HCDR2 amino acid sequence of: X1IWYDGNNKYYX12DSVKG (SEQ ID NO: 196), where X1is L or V, and X12is E or A; and the HCDR3 amino acid sequence of: DRITX5VRGVTNYGMDV (SEQ ID NO: 197), where X5is M or R. Heavy chain CDR sequences of exemplary agonist LTßR binding proteins that bind to human LTßR CRD4, do not block LIGHT binding to LTßR, do not block LTa1ß2 binding to LTßR, and comprise a HCDR1 of SEQ ID NO: 195, a HCDR2 of SEQ ID NO: 196, and a HCDR3 of SEQ ID NO: 197 are provided in Table 6 above.

[0142] In one embodiment, the agonist LTβR binding proteins of the present disclosure comprising the HCDRs 1–3 of SEQ ID NOs: 195-197, respectively, further comprise a shared VL CDR structure defined by the LCDR1 amino acid sequence of SGDX4LPX7X8YX10Y (SEQ ID NO: 308), where X4is A or T; X7is Q, E, N, R, or K; X8is H or Q; and X10is V, T, or A; the LCDR2 amino acid sequence of KDX3X4RPS (SEQ ID NO: 309), where X3 is N or S, and X4 is D or E; and the LCDR3 amino acid sequence of QSADX5SGX8X9VV (SEQ ID NO: 310), where X5is I, N, or S; X8is S, A, I, or T; X9is F or Y. Light chain variable region CDR sequences of exemplary agonist LTβR binding proteins that bind to human LTβR CRD4, do not block LIGHT binding to LTβR, do not block LTα1β2 binding to LTβR, and comprise the LCDR1 of SEQ ID NO: 308, the LCDR2 of SEQ ID NO: 309, and the LCDR3 of SEQ ID NO: 310 are provided in Table 7 above.

[0143] In another embodiment, agonist LTβR binding proteins (e.g., agonist LTβR antibodies or agonist LTβR bispecific binding proteins) that bind to human LTβR CRD4, and (a) do not block LIGHT binding to LTβR and (b) do not block LTα1β2 binding to LTβR comprise a shared VH CDR structure defined by the HCDR1 amino acid sequence of: SX2AMH (SEQ ID NO: 224),where X2is Y or F; the HCDR2 amino acid sequence of: VIWYX5X6X7NX9FYADSVKG (SEQ ID NO: 225), where X5is D, A, or N; X6is R or E; X7is N or S; X9is K or N; the HCDR3 amino acid sequence of: GDX3X4YX6YX8YGX11DX13(SEQ ID NO: 226), where X3is W or R; X4is N or D; X6is S, H, or Y; X8is Y, Q, or K; X11is M or V; X13is L or V. Heavy chain CDR sequences of exemplary agonist LTβR binding proteins that bind to human LTβR CRD4, do not block LIGHT binding to LTβR, do not block LTα1β2 binding to LTβR, and comprise a HCDR1 of SEQ ID NO: 224, a HCDR2 of SEQ ID NO: 225, and a HCDR3 of SEQ ID NO: 226 are provided in Table 6 above.

[0144] In one embodiment, the agonist LTβR binding proteins of the present disclosure comprising the HCDRs 1–3 of SEQ ID NOs. 224-226, respectively, further comprise a shared VL CDR structure defined by the LCDR1 amino acid sequence of TGX3X4SDVGSYNLVS (SEQ ID NO: 356), where X3is S or T; X4is N, S, or I; the LCDR2 amino acid sequence of: EVX3KRPS (SEQ ID NO: 357), where X3is T, N or S; and the LCDR3 amino acid sequence of: CSYAX5X6X7TYV (SEQ ID NO: 358), where X5is D or G; X6is T or S; X7is R, S, or K. Light chain variable region CDR sequences of exemplary agonist LTβR binding proteins that bind to human LTβR CRD4, do not block LIGHT binding to LTβR, do not block LTα1β2 binding to LTβR, and comprise a LCDR1 of SEQ ID NO: 356, a LCDR2 of SEQ ID NO: 357, and a LCDR3 of SEQ ID NO: 358 are provided in Table 7 above.

[0145] In one embodiment, the agonist LTβR binding proteins of the present disclosure (e.g., agonist LTβR antibodies or agonist LTβR bispecific binding proteins) that bind to human LTβR CRD4, and (a) do not block LIGHT binding to LTβR and (b) do not block LTα1β2 binding to LTβR comprise a variable light (VL) domain, a variable heavy (VH) domain, or a combination of VL and VH domain. In any embodiment, the VH domain of the agonist LTβR binding protein comprises any one of the VH amino acid sequences provided in Table 8 below, or an amino acid sequence that is at least 75%, at least 80%, at least 85%, at least 90%, or at least 95% identical to any one of the VH amino acid sequences listed in Table 8. In any embodiment, the VL domain of the agonist LTβR binding protein comprises any one of the VL amino acid sequences provided in Table 8 below, or an amino acid sequence that is at least 75%, at least 80%, at least 85%, at least 90%, at least 95% identical to any one of the VL amino acid sequences listed in Table 8.

[0146] Exemplary agonist LTβR binding proteins of the present disclosure (e.g., agonist LTβR antibodies or agonist LTβR bispecific binding proteins) that bind to human LTβR CRD4, and (a) do not block LIGHT binding to LTβR and (b) do not block LTα1β2 binding to LTβR comprises a combination of HCDR1, HCDR2, HCDR3, LCDR1, LCDR2, and LCDR3 amino acid sequences selected from: (i) SEQ ID NO: 159, SEQ ID NO: 160, SEQ ID NO: 161, SEQ ID NO: 278, SEQ ID NO: 279, and SEQ ID NO: 280, respectively; (ii) SEQ ID NO: 162, SEQ ID NO: 163, SEQ ID NO: 164, SEQ ID NO: 281, SEQ ID NO: 282, and SEQ ID NO: 283, respectively; (iii) SEQ ID NO: 165, SEQ ID NO: 166, SEQ ID NO: 167, SEQ ID NO: 284, SEQ ID NO: 285, and SEQ ID NO: 286, respectively; (iv) SEQ ID NO: 168, SEQ ID NO: 169, SEQ ID NO: 170, SEQ ID NO: 287, SEQ ID NO: 288, and SEQ ID NO: 289, respectively; (v) SEQ ID NO: 171, SEQ ID NO: 172, SEQ ID NO: 173, SEQ ID NO: 290, SEQ ID NO: 291, and SEQ ID NO: 292, respectively; (vi) SEQ ID NO: 174, SEQ ID NO: 175, SEQ ID NO: 176, SEQ ID NO: 293, SEQ ID NO: 294, and SEQ ID NO: 295, respectively; (vii) SEQ ID NO: 177, SEQ ID NO: 178, SEQ ID NO: 179, SEQ ID NO: 296, SEQ ID NO: 297, and SEQ ID NO: 298, respectively; (viii) SEQ ID NO: 180, SEQ ID NO: 181, SEQ ID NO: 182, SEQ ID NO: 302, SEQ ID NO: 303, and SEQ ID NO: 304, respectively; (ix) SEQ ID NO: 183, SEQ ID NO: 184, SEQ ID NO: 185, SEQ ID NO: 305, SEQ ID NO: 306, and SEQ ID NO: 307, respectively.

[0147] In one embodiment, agonist LTβR binding proteins (e.g., agonist LTβR antibodies or agonist LTβR bispecific binding proteins) bind to human LTβR CRD4, and (a) do not block LIGHT binding to LTβR and (b) do not block LTα1β2 binding to LTβR include those binding proteins that comprise HCDR1, HCDR2, and HCDR3 amino acid sequences of SEQ ID NOs: 159-161, respectively, and LCDR1, LCDR2, and LCDR3 amino acid sequences of SEQ ID NOs: 278-280, respectively. These agonist LTβR binding proteins further comprise a VH and VL amino acid sequence selected from: a VH amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VH amino acid sequence of SEQ ID NO: 401 and a VL amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VL amino acid sequence of SEQ ID NO: 402; a VH amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VH amino acid sequence of SEQ ID NO: 403and a VL amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VL amino acid sequence of SEQ ID NO: 404; a VH amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VH amino acid sequence of SEQ ID NO: 405 and a VL amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VL amino acid sequence of SEQ ID NO: 406; a VH amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VH amino acid sequence of SEQ ID NO: 407 and a VL amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VL amino acid sequence of SEQ ID NO: 408; a VH amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VH amino acid sequence of SEQ ID NO: 409 and a VL amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VL amino acid sequence of SEQ ID NO: 410; a VH amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VH amino acid sequence of SEQ ID NO: 411 and a VL amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VL amino acid sequence of SEQ ID NO: 412; a VH amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VH amino acid sequence of SEQ ID NO: 413 and a VL amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VL amino acid sequence of SEQ ID NO: 414; a VH amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VH amino acid sequence of SEQ ID NO: 415 and a VL amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VL amino acid sequence of SEQ ID NO: 416. VH and VL amino acid sequences described herein are provided in Table 8 below.

[0148] In one embodiment, exemplary agonist LTβR binding proteins of the present disclosure (e.g., agonist LTβR antibodies or agonist LTβR bispecific binding proteins) that bind to human LTβR CRD4, and (a) do not block LIGHT binding to LTβR and (b) do not block LTα1β2 binding to LTβR comprise a combination of HCDR1, HCDR2, HCDR3, LCDR1, LCDR2, and LCDR3 amino acid sequences selected from: (i) SEQ ID NO: 159, SEQ ID NO: 160, SEQ ID NO: 161, SEQ ID NO: 308, SEQ ID NO: 309, and SEQ ID NO: 310, respectively; (ii) SEQ ID NO: 189, SEQ ID NO: 190, SEQ ID NO: 191, SEQ ID NO: 314, SEQ ID NO: 315, and SEQ ID NO: 316, respectively; (iii) SEQ ID: 186, SEQ ID NO: 187, SEQ ID NO: 188, SEQ ID NO: 311, SEQ ID NO: 312, and SEQ ID NO: 313, respectively; (iv) SEQ ID NO: 192, SEQ ID NO: 193, SEQ ID NO: 194, SEQ ID NO: 317, SEQ ID NO: 318, and SEQ ID NO: 319, respectively.

[0149] In one embodiment, agonist LTβR binding proteins of the present disclosure (e.g., agonist LTβR antibodies or agonist LTβR bispecific binding proteins) that bind to human LTβR CRD4, and (a) do not block LIGHT binding to LTβR and (b) do not block LTα1β2 binding to LTβR include those binding proteins that comprise HCDR1, HCDR2, and HCDR3 amino acid sequences of SEQ ID NOs: 159-161, respectively, and LCDR1, LCDR2, and LCDR3 amino acid sequences of SEQ ID NOs: 308-310, respectively. These agonist LTβR binding proteins further comprise a VH and VL amino acid sequence selected from: a VH amino acid sequence having at least 90%, at least 95%, or at least 98% sequenceidentity to the VH amino acid sequence of SEQ ID NO: 417 and a VL amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VL amino acid sequence of SEQ ID NO: 418; a VH amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VH amino acid sequence of SEQ ID NO: 419 and a VL amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VL amino acid sequence of SEQ ID NO: 420; and a VH amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VH amino acid sequence of SEQ ID NO: 421 and a VL amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VL amino acid sequence of SEQ ID NO: 422. VH and VL amino acid sequences described herein are provided in Table 8 below.

[0150] In one embodiment, exemplary agonist LTβR binding proteins of the present disclosure (e.g., agonist LTβR antibodies or agonist LTβR bispecific binding proteins) that bind to human LTβR CRD4, and (a) do not block LIGHT binding to LTβR and (b) do not block LTα1β2 binding to LTβR comprise a combination of HCDR1, HCDR2, HCDR3, LCDR1, LCDR2, and LCDR3 amino acid sequences selected from: (i) SEQ ID NO: 195, SEQ ID NO: 196, SEQ ID NO: 197, SEQ ID NO: 308, SEQ ID NO: 309, and SEQ ID NO: 310; (ii) SEQ ID NO: 197, SEQ ID NO: 198, SEQ ID NO: 199, SEQ ID NO: 320, SEQ ID NO: 321, and SEQ ID NO: 322; (iii) SEQ ID NO: 200, SEQ ID NO: 201, SEQ ID NO: 202, SEQ ID NO: 323, SEQ ID NO: 324, and SEQ ID NO: 325, respectively; (iv) SEQ ID NO: 203, SEQ ID NO: 204, SEQ ID NO: 205, SEQ ID NO: 326, SEQ ID NO: 327, and SEQ ID NO: 328, respectively; (v) SEQ ID NO: 206, SEQ ID NO: 207, SEQ ID NO: 208, SEQ ID NO: 329, SEQ ID NO: 330, and SEQ ID NO: 331, respectively; (vi) SEQ ID NO: 209, SEQ ID NO: 210, SEQ ID NO: 211, SEQ ID NO: 332, SEQ ID NO: 333, and SEQ ID NO: 334, respectively; (vii) SEQ ID NO: 212, SEQ ID NO: 213, SEQ ID NO: 214, SEQ ID NO: 335, SEQ ID NO: 336, and SEQ ID NO: 337, respectively; (viii) SEQ ID NO: 215, SEQ ID NO: 216, SEQ ID NO: 217, SEQ ID NO: 338, SEQ ID NO: 339, and SEQ ID NO: 340, respectively; (ix) SEQ ID NO: 218, SEQ ID NO: 219, SEQ ID NO: 220, SEQ ID NO: 341, SEQ ID NO: 342, and SEQ ID NO: 343, respectively; (x) SEQ ID NO: 221, SEQ ID NO: 222, SEQ ID NO: 223, SEQ ID NO: 343, SEQ ID NO: 344, and SEQ ID NO: 345, respectively.

[0151] In one embodiment, agonist LTβR binding proteins of the present disclosure (e.g., agonist LTβR antibodies or agonist LTβR bispecific binding proteins) that bind to human LTβR CRD4, and (a) do not block LIGHT binding to LTβR and (b) do not block LTα1β2 binding to LTβR comprise HCDR1, HCDR2, and HCDR3 amino acid sequences of SEQ ID NOs: 195-197, respectively, and LCDR1, LCDR2, and LCDR3 amino acid sequences of SEQ ID NOs: 308-310, respectively. These agonist LTβR binding proteins further comprise a VH and VL amino acid sequence selected from: a VH amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VH amino acid sequence of SEQ ID NO: 423 and a VL amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VL amino acid sequence of SEQ ID NO: 424; a VH amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VH amino acid sequence of SEQ ID NO: 425 and a VL amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to theVL amino acid sequence of SEQ ID NO: 426; a VH amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VH amino acid sequence of SEQ ID NO: 427 and a VL amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VL amino acid sequence of SEQ ID NO: 428; a VH amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VH amino acid sequence of SEQ ID NO: 429 and a VL amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VL amino acid sequence of SEQ ID NO: 430; a VH amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VH amino acid sequence of SEQ ID NO: 431 and a VL amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VL amino acid sequence of SEQ ID NO: 432; a VH amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VH amino acid sequence of SEQ ID NO: 433 and a VL amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VL amino acid sequence of SEQ ID NO: 434; a VH amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VH amino acid sequence of SEQ ID NO: 435 and a VL amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VL amino acid sequence of SEQ ID NO: 436; a VH amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VH amino acid sequence of SEQ ID NO: 437 and a VL amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VL amino acid sequence of SEQ ID NO: 438; a VH amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VH amino acid sequence of SEQ ID NO: 439 and a VL amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VL amino acid sequence of SEQ ID NO: 440. VH and VL amino acid sequences described herein are provided in Table 8 below.

[0152] In one embodiment, exemplary agonist LTβR binding proteins of the present disclosure (e.g., agonist LTβR antibodies or agonist LTβR bispecific binding proteins) that bind to human LTβR CRD4, and (a) do not block LIGHT binding to LTβR and (b) do not block LTα1β2 binding to LTβR comprise a combination of HCDR1, HCDR2, HCDR3, LCDR1, LCDR2, and LCDR3 amino acid sequences selected from: (i) SEQ ID NO: 224, SEQ ID NO: 225, SEQ ID NO: 226, SEQ ID NO: 356, SEQ ID NO: 357, and SEQ ID NO: 358, respectively; (ii) SEQ ID NO: 227, SEQ ID NO: 228, SEQ ID NO: 229, SEQ ID NO: 359, SEQ ID NO: 360, and SEQ ID NO: 361, respectively; (iii) SEQ ID NO: 230, SEQ ID NO: 231, SEQ ID NO: 232, SEQ ID NO: 362, SEQ ID NO: 363, and SEQ ID NO: 364, respectively; (iv) SEQ ID NO: 233, SEQ ID NO: 234, SEQ ID NO: 235, SEQ ID NO: 365, SEQ ID NO: 366, and SEQ ID NO: 367, respectively; (v) SEQ ID NO: 236, SEQ ID NO: 237, SEQ ID NO: 238, SEQ ID NO: 368, SEQ ID NO: 369, and SEQ ID NO: 370, respectively; (vi) SEQ ID NO: 239, SEQ ID NO: 240, SEQ ID NO: 241, SEQ ID NO: 371, SEQ ID NO: 372, and SEQ ID NO: 373, respectively; (vii) SEQ ID NO: 242, SEQ ID NO: 243, SEQ ID NO: 244, SEQ ID NO: 374, SEQ ID NO: 375, and SEQ ID NO: 376, respectively; (viii) SEQ ID NO: 245, SEQ ID NO: 246, SEQ ID NO: 247, SEQ ID NO: 377, SEQ ID NO: 378, and SEQ ID NO: 379, respectively; (ix) SEQ ID NO: 248, SEQ ID NO: 249, SEQ ID NO: 250, SEQ ID NO: 380, SEQ ID NO: 381, and SEQ ID NO: 382, respectively; (x) SEQ ID NO: 251, SEQ ID NO: 252, SEQ ID NO: 253,SEQ ID NO: 383, SEQ ID NO: 384, and SEQ ID NO: 385, respectively; (xi) SEQ ID NO: 254, SEQ ID NO: 255, SEQ ID NO: 256, SEQ ID NO: 386, SEQ ID NO: 387, and SEQ ID NO: 388, respectively; (xii) SEQ ID NO: 180, SEQ ID NO: 181, SEQ ID NO: 182, SEQ ID NO: 302, SEQ ID NO: 303, and SEQ ID NO: 304, respectively; ; (xiii) SEQ ID NO: 183, SEQ ID NO: 184, SEQ ID NO: 185, SEQ ID NO: 305, SEQ ID NO: 306, and SEQ ID NO: 307, respectively; (xiv) SEQ ID NO: 257, SEQ ID NO: 258, SEQ ID NO: 259, SEQ ID NO: 389, SEQ ID NO: 390, and SEQ ID NO: 391, respectively.

[0153] In one embodiment, agonist LTβR binding proteins of the present disclosure (e.g., agonist LTβR antibodies or agonist LTβR bispecific binding proteins) that bind to human LTβR CRD4, and (a) do not block LIGHT binding to LTβR and (b) do not block LTα1β2 binding to LTβR comprise HCDR1, HCDR2, and HCDR3 amino acid sequences of SEQ ID NOs: 224-226, respectively, and LCDR1, LCDR2, and LCDR3 amino acid sequences of SEQ ID NOs: 356-358, respectively. These agonist LTβR binding proteins further comprise a VH and VL amino acid sequence selected from: a VH amino acid sequence having at least 90% sequence identity to the VH amino acid sequence of SEQ ID NO: 441 and a VL amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VL amino acid sequence of SEQ ID NO: 442; a VH amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VH amino acid sequence of SEQ ID NO: 443 and a VL amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VL amino acid sequence of SEQ ID NO: 444; a VH amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VH amino acid sequence of SEQ ID NO: 445 and a VL amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VL amino acid sequence of SEQ ID NO: 446; a VH amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VH amino acid sequence of SEQ ID NO: 447 and a VL amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VL amino acid sequence of SEQ ID NO: 448; a VH amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VH amino acid sequence of SEQ ID NO: 449 and a VL amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VL amino acid sequence of SEQ ID NO: 450; a VH amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VH amino acid sequence of SEQ ID NO: 451 and a VL amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VL amino acid sequence of SEQ ID NO: 452; a VH amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VH amino acid sequence of SEQ ID NO: 453 and a VL amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VL amino acid sequence of SEQ ID NO: 454; a VH amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VH amino acid sequence of SEQ ID NO: 455 and a VL amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VL amino acid sequence of SEQ ID NO: 456; a VH amino acid sequence having at least 90% sequence identity to the VH amino acid sequence of SEQ ID NO: 457 and a VL amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VL amino acid sequence of SEQ ID NO: 458; a VH amino acid sequence having at least 90%, at least95%, or at least 98% sequence identity to the VH amino acid sequence of SEQ ID NO: 459 and a VL amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VL amino acid sequence of SEQ ID NO: 460; a VH amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VH amino acid sequence of SEQ ID NO: 461 and a VL amino acid sequence having at least 90%, at least 95%, or at least 98% sequence identity to the VL amino acid sequence of SEQ ID NO: 462. VH and VL amino acid sequences described herein are provided in Table 8 below.

[0154] In one embodiment, exemplary agonist LTβR binding proteins of the present disclosure (e.g., agonist LTβR antibodies or agonist LTβR bispecific binding proteins) that bind to human LTβR CRD4, and (a) do not block LIGHT binding to LTβR and (b) do not block LTα1β2 binding to LTβR comprise a combination of HCDR1, HCDR2, HCDR3, LCDR1, LCDR2, and LCDR3 amino acid sequences selected from (i) SEQ ID NO: 257, SEQ ID NO: 258, SEQ ID NO: 259, SEQ ID NO: 389, SEQ ID NO: 390, and SEQ ID NO: 391, respectively (1319279); (ii) SEQ ID NO: 260, SEQ ID NO: 261, SEQ ID NO: 262, SEQ ID NO: 347, SEQ ID NO: 348 and SEQ ID NO: 349, respectively (1318253); (iii) SEQ ID NO: 263, SEQ ID NO: 264, SEQ ID NO: 265, SEQ ID NO: 350, SEQ ID NO: 351, and SEQ ID NO: 352 (1318209), respectively; (iv) SEQ ID NO: 266, SEQ ID NO: 267, SEQ ID NO: 268, SEQ ID NO: 353, SEQ ID NO: 354, and SEQ ID NO: 355 (1318188), respectively; (v) SEQ ID NO: 269, SEQ ID NO: 270, SEQ ID NO: 271, SEQ ID NO: 392, SEQ ID NO: 393, and SEQ ID NO: 394 (1319569), respectively; (vi) SEQ ID NO: 272, SEQ ID NO: 273, SEQ ID NO: 274, SEQ ID NO: 395, SEQ ID NO: 396, and SEQ ID NO: 397 (1317105), respectively; (vii) SEQ ID NO: 275, SEQ ID NO: 276, SEQ ID NO: 277, SEQ ID NO: 398, SEQ ID NO: 399, and SEQ ID NO: 400 (1318198), respectively;

[0155] In another embodiment, LTβR binding proteins of the present disclosure (e.g., agonist LTβR antibodies or agonist LTβR bispecific binding proteins) that bind to human LTβR CRD4, and (a) do not block LIGHT binding to LTβR and (b) do not block LTα1β2 binding to LTβR comprise a VH amino acid sequence and a VL amino acid sequence selected from: a VH amino acid sequence of SEQ ID NO: 401 and a VL amino acid sequence of SEQ ID NO: 402; a VH amino acid sequence of SEQ ID NO: 403 and a VL amino acid sequence of SEQ ID NO: 404; a VH amino acid sequence of SEQ ID NO: 405 and a VL amino acid sequence of SEQ ID NO: 406; a VH amino acid sequence of SEQ ID NO: 407 and a VL amino acid sequence of SEQ ID NO: 408; a VH amino acid sequence of SEQ ID NO: 409 and a VL amino acid sequence of SEQ ID NO: 410; a VH amino acid sequence of SEQ ID NO: 411 and a VL amino acid sequence of SEQ ID NO: 412; a VH amino acid sequence of SEQ ID NO: 413 and a VL amino acid sequence of SEQ ID NO: 414; a VH amino acid sequence of SEQ ID NO: 415 and a VL amino acid sequence of SEQ ID NO: 416; a VH amino acid sequence of SEQ ID NO: 417 and a VL amino acid sequence of SEQ ID NO: 418; a VH amino acid sequence of SEQ ID NO: 419 and a VL amino acid sequence of SEQ ID NO: 420; a VH amino acid sequence of SEQ ID NO: 421 and a VL amino acid sequence of SEQ ID NO: 422; a VH amino acid sequence of SEQ ID NO: 423 and a VL amino acid sequence of SEQ ID NO: 424; a VH amino acid sequence of SEQ ID NO: 425 and a VL amino acid sequence of SEQ ID NO: 426; a VH amino acid sequence of SEQ ID NO: 427 and a VL amino acid sequence of SEQ ID NO: 428; a VH amino acid sequence of SEQID NO: 429 and a VL amino acid sequence of SEQ ID NO: 430; a VH amino acid sequence of SEQ ID NO: 431 and a VL amino acid sequence of SEQ ID NO: 432; a VH amino acid sequence of SEQ ID NO: 433 and a VL amino acid sequence of SEQ ID NO: 434; a VH amino acid sequence of SEQ ID NO: 435 and a VL amino acid sequence of SEQ ID NO: 436; a VH amino acid sequence of SEQ ID NO: 437 and a VL amino acid sequence of SEQ ID NO: 438; a VH amino acid sequence of SEQ ID NO: 439 and a VL amino acid sequence of SEQ ID NO: 440; a VH amino acid sequence of SEQ ID NO: 441 and a VL amino acid sequence of SEQ ID NO: 442; a VH amino acid sequence of SEQ ID NO: 443 and a VL amino acid sequence of SEQ ID NO: 444; a VH amino acid sequence of SEQ ID NO: 445 and a VL amino acid sequence of SEQ ID NO: 446; a VH amino acid sequence of SEQ ID NO: 447 and a VL amino acid sequence of SEQ ID NO: 448; a VH amino acid sequence of SEQ ID NO: 449 and a VL amino acid sequence of SEQ ID NO: 450; a VH amino acid sequence of SEQ ID NO: 451 and a VL amino acid sequence of SEQ ID NO: 452; a VH amino acid sequence of SEQ ID NO: 453 and a VL amino acid sequence of SEQ ID NO: 454; a VH amino acid sequence of SEQ ID NO: 455 and a VL amino acid sequence of SEQ ID NO: 456; a VH amino acid sequence of SEQ ID NO: 457 and a VL amino acid sequence of SEQ ID NO: 458; a VH amino acid sequence of SEQ ID NO: 459 and a VL amino acid sequence of SEQ ID NO: 460; a VH amino acid sequence of SEQ ID NO: 461 and a VL amino acid sequence of SEQ ID NO: 462; a VH amino acid sequence of SEQ ID NO: 463 and a VL amino acid sequence of SEQ ID NO: 464; a VH amino acid sequence of SEQ ID NO: 465 and a VL amino acid sequence of SEQ ID NO: 466; a VH amino acid sequence of SEQ ID NO: 467 and a VL amino acid sequence of SEQ ID NO: 468; a VH amino acid sequence of SEQ ID NO: 469 and a VL amino acid sequence of SEQ ID NO: 470; a VH amino acid sequence of SEQ ID NO: 471 and a VL amino acid sequence of SEQ ID NO: 472; and a VH amino acid sequence of SEQ ID NO: 473 and a VL amino acid sequence of SEQ ID NO: 474. VH and VL amino acid sequences described herein are provided in Table 8 below. Table 8: VH and VL amino acid sequences of LTβR binding proteins that compete for binding to CRD4 of LTβR with the LTβR binders LIBC219081 and LIBC218979 and do not block LIGHT or LTα1β2 binding

[0156] In another embodiment, the agonist LTβR binding protein (e.g., an agonist LTβR antibody or agonist LTβR bispecific binding protein) of the present disclosure that binds to human LTβR CRD4, and (a) does not block LIGHT binding to LTβR and (b) does not block LTα1β2 binding to LTβR comprises a VH region and / or VL region as described supra and further comprises one or more heavy chain constant regions coupled to the VH region and / or a light chain constant region coupled to the VL region. For example, in one embodiment, the LTβR binding protein is a Fab comprising a VH and first heavy chain constant domain (CH1) coupled to a VL and light chain constant region (CL). In another embodiment, the LTβR binding protein is a F(ab’)2 comprising both LTβR binding regions of a full antibody coupled by the hinge region, where each binding region comprises a VH-CH1 and VL-CL. In another embodiment, the LTβR binding protein is an antibody comprising full light chains (VL-CL) and full heavy chains (VH-CH1- CH2-CH3). Exemplary amino acid sequences of LTβR antibodies of the present disclosure that bind to human LTβR CRD4, and (a) do not block LIGHT binding to LTβR and (b) do not block LTα1β2 binding to LTβR are provided in Table 9 below. Table 9. Antibody HC and LC Sequences of LTβR CRD4 Binding AntibodiesLTβR Agonist Binding Proteins that Bind CRD1, CRD2, and / or CRD3

[0157] In accordance with all aspects of the present disclosure, an agonist LTβR binding protein as described herein, comprises one or more binding domains that bind to and agonize LTβR activity. In one embodiment, this binding domain comprises a heavy chain variable region (VH) or fragment thereof, where the VH comprises one or more complementarity determining regions (i.e., HCDR1, HCDR2, and / or HCDR3), or portions thereof, that bind to LTβR. In one embodiment, this VH comprises a HCDR1 amino acid sequence of any one of SEQ ID NOs: 475-498,740-742, or a modified sequence thereof, wherein said modified sequence contains 1, 2, or 3 amino acid residue modifications as compared to any one of SEQ ID NOs: 475-498 and 740-742. In one embodiment, the VH comprises a HCDR2 amino acid sequence of any one of SEQ ID NOs: 499-528, 743, or a modified sequence thereof, wherein said modified sequence contains 1, 2, or 3 amino acid residue modifications as compared to any one of SEQ ID NOs: 499-528 and 743. In one embodiment, the VH comprises a HCDR3 amino acid sequence of any one of SEQ ID NOs: 529-558, 744-746, or a modified sequence thereof, wherein said modified sequence contains 1, 2, or 3 amino acid residue modifications as compared to any one of SEQ ID NOs: 529-558 and 744-746. The heavy chain CDR sequences of exemplary agonist LTβR binding proteins described herein are provided in Table 10 below.

[0158] As described in the Examples herein, paratope mapping studies of several LTβR antibodies disclosed herein showed that, in some cases, binding of a particular LTβR antibody to LTβR did not involve or require all three heavy chain CDR regions of the antibody and / or did not involve all residues of one or more heavy chain CDRs. Heavy chain CDRs shown not to be involved in the LTβR antibody binding interaction are indicated with an asterisk in Table 10 below. Residues of heavy chain CDR regions shown not to be involved in or required for the LTβR antibody binding interaction as identified by paratope mapping or mutational analysis are identified as variable residue (X). The identity of X residues within the sequences of Table 10 is provided in Tables 18-25 herein. Table 10. Heavy Chain CDR Sequences of LTβR Binding Proteins

[0159] In one embodiment, the agonist LTβR binding protein of the present disclosure comprises a light chain variable region (VL), where the VL comprises one or more complementarity determining regions (i.e., LCDR1, LCDR2, and / or LCDR3), or portions thereof, that alone or together with the VH CDRs bind to LTβR. In one embodiment, the VL comprises a LCDR1 amino acid sequence of any one of SEQ ID NOs: 559-589 or a modified sequence thereof, wherein said modified sequence contains 1, 2, or 3 amino acid residue modifications as compared to any one of SEQ ID NOs: 559-589. In one embodiment, the VL comprises a LCDR2 amino acid sequence of any one of SEQ ID NOs: 590-618 or a modified sequence thereof, wherein said modified sequence contains 1, 2, or 3 amino acid residue modifications as compared to any one of SEQ ID NOs: 590-618. In one embodiment, the VL comprises a LCDR3 amino acid sequence of any one of SEQ ID NOs: 619-643 or a modified sequence thereof, wherein said modified sequence contains 1, 2, or 3 amino acid residue modifications as compared to any one of SEQ ID NOs: 619-643. The light chain CDR sequences of exemplary agonist LTβR binding proteins described herein are provided in Table 11 below.

[0160] As described in the Examples herein, paratope mapping studies of several LTβR antibodies disclosed herein showed that, in some cases, binding of a particular LTβR antibody to LTβR did not involve or require all three light chain CDR regions of the antibody and / or did not involve all residues of one or more light chain CDRs. Light chain CDRs shown not to be involved in the LTβR antibody binding interaction are indicated with an asterisk in Table 11 below. Residues of light chain CDR regions shown not to be involved in or required for the LTβR antibody binding interaction as identified by paratope mapping or mutational analysis are identified as variable residue (X). The identity of X residues within the sequences of Table 11 is provided in Tables 18-25 herein. Table 11. Light Chain CDR Sequences of LTβR Binding Proteins

[0161] In one embodiment, the agonist LTβR binding protein of the present disclosure binds to CRD2 and CRD3 of human LTβR, including one or more residues corresponding to residues 56-64 and 81- 101 of SEQ ID NO: 4 (corresponding to residues 86-94 and 111-131 of SEQ ID NO: 1), and permitsendogenous LTβR ligand binding activity as defined herein. This agonist LTβR binding protein comprises a variable heavy domain (VH) comprising a HCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 501, and a HCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 531. Optionally, this VH further comprises a HCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 475. In one embodiment, the VH of this LTβR binding protein comprises the HCDR2 sequence of SEQ ID NO: 499 and the HCDR3 sequence of SEQ ID NO: 529; or as further defined by the HCDR2 sequence of SEQ ID NO: 500 and the HCDR3 sequence of SEQ ID NO: 530. In one embodiment, the VH of this LTβR binding protein comprises the HCDR2 sequence of SEQ ID NO: 501 and the HCDR3 sequence of SEQ ID NO: 531. Optionally, the VH of this exemplary agonist LTβR binding protein further comprises the HCDR1 of SEQ ID NO: 475.

[0162] In accordance with the preceding embodiment, this agonist LTβR binding protein optionally further comprises a VL, where the VL comprises a LCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 561, and a LCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 619. Optionally, the VL further comprises an LCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 590. In one embodiment, the VL comprises the LCDR1 sequence of SEQ ID NO: 559 and the LCDR3 sequence of SEQ ID NO: 619; or as further defined by the LCDR1 sequence of SEQ ID NO: 560 and the LCDR3 sequence of SEQ ID NO: 619; or as further defined by the LCDR1 sequence of SEQ ID NO: 560 and the LCDR3 sequence of SEQ ID NO: 619. Optionally, the VL further comprises an LCDR2 of SEQ ID NO: 590. An exemplary agonist LTβR binding protein comprising a VH and VL of this embodiment includes, without limitation, the LTβR antibody identified herein as LIBC No.218990 (19320; 30H1).

[0163] In another embodiment, the agonist LTβR binding protein of the present disclosure is a binding protein that binds to the CRD1 of LTβR, including one or more residues corresponding to residues 3-9, 20-29, and 38-47 of SEQ ID NO: 4 (corresponding to residues 33-39, 50-59, and 68-77 of SEQ ID NO: 1). In one embodiment, this LTβR binding protein does not block or inhibit endogenous LIGHT binding to LTβR to occur and at least or about 80% of endogenous LTα1β2 binding to LTβR to occur. This LTβR binding protein comprises a VH, where the VH comprises HCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 478, a HCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 504, and a HCDR3 sequence that shares at least 80%, at least 85%, at least90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 534. In one embodiment, the VH of this LTβR binding protein comprises the HCDR1 sequence of SEQ ID NO: 476, the HCDR2 sequence of SEQ ID NO: 502, and the HCDR3 sequence of SEQ ID NO: 532; or as further defined by the HCDR1 sequence of SEQ ID NO: 477, the HCDR2 sequence of SEQ ID NO: 503, and the HCDR3 sequence of SEQ ID NO: 533; or as further defined by the HCDR1 sequence of SEQ ID NO: 478, the HCDR2 sequence of SEQ ID NO: 504, and the HCDR3 sequence of SEQ ID NO: 534.

[0164] In accordance with the preceding embodiment, this agonist LTβR binding protein of the present disclosure optionally further comprises a VL, where the VL comprises a LCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 564, a LCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 593, and a LCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 622. In one embodiment, the VL comprises the LCDR1 sequence of SEQ ID NO: 562, the LCDR2 of SEQ ID NO: 591, and the LCDR3 sequence of SEQ ID NO: 620; or as further defined by the LCDR1 sequence of SEQ ID NO: 563, the LCDR2 of SEQ ID NO: 592, and the LCDR3 sequence of SEQ ID NO: 621; or as further defined by the LCDR1 sequence of SEQ ID NO: 564, the LCDR2 of SEQ ID NO: 593, and the LCDR3 sequence of SEQ ID NO: 622. An exemplary agonist LTβR binding protein comprising a VH and VL of this embodiment includes, without limitation, the LTβR antibody identified herein as LIBC No.218994 (19321; 31A3)

[0165] In another embodiment, the agonist LTβR binding protein of the present disclosure binds to CRD2 and CRD3 of human LTβR, including one or more residues corresponding to residues 56-64 and 81- 101 of SEQ ID NO: 4 (corresponding to residues 86-94 and 111-131 of SEQ ID NO: 1). In one embodiment, this agonist LTβR binding protein does not block endogenous LIGHT or LTα1β2 binding to LTβR at concentrations of < 8nM as measured by the cell based receptor-ligand assay described herein (see e.g., Example 8.2). This LTβR binding protein comprises a VH, where the VH comprises HCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 479, a HCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 507, and a HCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 537. In one embodiment, the VH of this LTβR binding protein comprises the HCDR1 sequence of SEQ ID NO: 479, a HCDR2 sequence of SEQ ID NO: 505, and a HCDR3 sequence of SEQ ID NO: 535; or as further defined by the HCDR1 sequence of SEQ ID NO: 479, a HCDR2 sequence of SEQ ID NO: 506, and a HCDR3 sequence of SEQ ID NO: 536; or as further definedby the HCDR1 sequence of SEQ ID NO: 479, a HCDR2 sequence of SEQ ID NO: 507, and a HCDR3 sequence of SEQ ID NO: 537.

[0166] In accordance with the preceding embodiment, this agonist LTβR binding protein of the present disclosure optionally further comprises a VL, where the VL comprises a LCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 596. Optionally, the VL comprises a LCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 565, and optionally comprises an LCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 623. In one embodiment, the VL comprises the LCDR2 of SEQ ID NO: 594, or as further defined by the LCDR2 of SEQ ID NO: 595, or as further defined by the LCDR2 of SEQ ID NO: 596. Optionally, the VL comprises the LCDR1 sequence of SEQ ID NO: 565, the LCDR2 of SEQ ID NO: 596, and the LCDR3 sequence of SEQ ID NO: 623. An exemplary agonist LTβR binding protein comprising a VH and VL of this embodiment includes, without limitation, the LTβR antibody identified herein as LIBC No.219058 (19324; 36G2).

[0167] In another embodiment, the agonist LTβR binding protein of the present disclosure is a binding protein that binds to LTβR and does not block or inhibit LIGHT binding to LTβR to occur. This agonist LTβR binding protein comprises a VH, where the VH comprises a HCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 480, a HCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 508, and a HCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 538. In one embodiment, the VH comprises the HCDR1 sequence of SEQ ID NO: 408, the HCDR2 of SEQ ID NO: 508, and the HCDR3 sequence of SEQ ID NO: 538.

[0168] In accordance with the preceding embodiment, this agonist LTβR binding protein of the present disclosure optionally further comprises a VL, where the VL comprises a LCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 567, a LCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 600, and a LCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 625. In one embodiment, the VL comprises the LCDR1 sequence of SEQ ID NO: 567, the LCDR2 of SEQ ID NO: 600, and the LCDR3 sequence of SEQ ID NO: 625. An exemplary agonist LTβR binding protein comprising a VH and VL of this embodiment includes, without limitation, the LTβR antibody identified herein as LIBC No.219037 (19322; 34D1).

[0169] In another embodiment, the agonist LTβR binding protein of the present disclosure is a binding protein that binds to LTβR and does not block or inhibit LIGHT binding to LTβR as defined herein. In one embodiment, this agonist LTβR binding protein and does not block or inhibit LIGHT binding to LTβR. This LTβR binding protein comprises a VH, where the VH comprises a HCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 4812, a HCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 509, and a HCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 539. In one embodiment, the VH comprises the HCDR1 sequence of SEQ ID NO: 481, the HCDR2 of SEQ ID NO: 509, and the HCDR3 sequence of SEQ ID NO: 539 or as further defined by the HCDR1 sequence of SEQ ID NO: 481, the HCDR2 of SEQ ID NO: 509, and the HCDR3 sequence of SEQ ID NO: 540; or as further defined by the HCDR1 sequence of SEQ ID NO: 481, the HCDR2 of SEQ ID NO: 509, and the HCDR3 sequence of SEQ ID NO: 541.

[0170] In accordance with the preceding embodiment, this agonist LTβR binding protein of the present disclosure optionally further comprises a VL, where the VL comprises a LCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 570, a LCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 601, and a LCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 626. In one embodiment, the VL comprises the LCDR1 sequence of SEQ ID NO: 568, the LCDR2 of SEQ ID NO: 601, and the LCDR3 sequence of SEQ ID NO: 626; or as further defined by the LCDR1 sequence of SEQ ID NO: 569, the LCDR2 of SEQ ID NO: 601, and the LCDR3 sequence of SEQ ID NO: 626; or as further defined by the LCDR1 sequence of SEQ ID NO: 570, the LCDR2 of SEQ ID NO: 601, and the LCDR3 sequence of SEQ ID NO: 626; or as further defined by the LCDR1 sequence of SEQ ID NO: 571, the LCDR2 of SEQ ID NO: 602, and the LCDR3 sequence of SEQ ID NO: 627. An exemplary agonist LTβR binding protein comprising a VH and VL of this embodiment includes, without limitation, the LTβR antibody identified herein as LIBC No.219098 (19327; 44B1).

[0171] In another embodiment, the agonist LTβR binding protein of the present disclosure (e.g., agonist LTβR antibody or agonist LTβR bispecific binding protein) binds to human LTβR CRD1 including one or more residues corresponding to residues 1-19 of SEQ ID NO: 4 (corresponding to residues 31-49 of SEQ ID NO: 1). This agonist LTβR binding protein does not block LIGHT binding to LTβR and does not block LTα1β2 binding to LTβR. This agonist LTβR binding protein comprises a VH, where the VH comprises a HCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 483,a HCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 513, and a HCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 543. In one embodiment, the VH comprises the HCDR1 sequence of SEQ ID NO: 483, the HCDR2 of SEQ ID NO: 511, and the HCDR3 sequence of SEQ ID NO: 543; or as further defined the HCDR1 sequence of SEQ ID NO: 483, the HCDR2 of SEQ ID NO: 512, and the HCDR3 sequence of SEQ ID NO: 543; or as further defined the HCDR1 sequence of SEQ ID NO: 483, the HCDR2 of SEQ ID NO: 513, and the HCDR3 sequence of SEQ ID NO: 543.

[0172] In accordance with the preceding embodiment, the agonist LTβR binding protein of the present disclosure optionally further comprises a VL, where the VL comprises a LCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 574, a LCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 603, and a LCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 628. In one embodiment, the VL comprises the LCDR1 sequence of SEQ ID NO: 57217, the LCDR2 of SEQ ID NO: 603, and the LCDR3 sequence of SEQ ID NO: 628; or as further defined by the LCDR1 sequence of SEQ ID NO: 573, the LCDR2 of SEQ ID NO: 603, and the LCDR3 sequence of SEQ ID NO: 628; or as further defined by the LCDR1 sequence of SEQ ID NO: 574, the LCDR2 of SEQ ID NO: 603, and the LCDR3 sequence of SEQ ID NO: 628. An exemplary agonist LTβR binding protein comprising a VH and VL of this embodiment includes, without limitation, the LTβR antibody identified herein as LIBC No.219051 (19323; 35F5).

[0173] In another embodiment, the LTβR binding protein of the present disclosure is an antibody- based molecule that binds to LTβR CRD1 and CRD2, including one or more residues corresponding to residues 38-42 and 56-70 of SEQ ID NO: 4. This LTβR antibody-based molecule comprises a VH, where the VH comprises a HCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 742, and a HCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 746. Optionally, the VH of this LTβR binding protein further comprises a HCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 743. In any embodiment, the VH of this LTβR binding protein comprises the HCDR1 sequence of SEQ ID NO: 740 and the HCDR3 sequence of SEQ ID NO: 744; or as further defined by the HCDR1 sequence of SEQ ID NO: 741 and the HCDR3 sequence of SEQ ID NO: 745; or as further defined by the HCDR1 sequence of SEQ ID NO: 742 and the HCDR3 sequence of SEQ ID NO:746. Optionally, the VH of this exemplary LTβR binding protein further comprises the HCDR2 of SEQ ID NO: 743.

[0174] In accordance with the preceding embodiment, this LTβR antibody-based molecule of the present disclosure optionally further comprises a VL, where the VL comprises a LCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 566, a LCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 599. Optionally, the VL further comprises a LCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 624. In any embodiment, the VL comprises the LCDR1 sequence of SEQ ID NO: 566 and the LCDR2 of SEQ ID NO: 597; or as further defined by the LCDR1 sequence of SEQ ID NO: 566 and the LCDR2 of SEQ ID NO: 598; or as further defined by the LCDR1 sequence of SEQ ID NO: 566 and the LCDR2 of SEQ ID NO: 599. Optionally, the VL further comprises a LCDR3 of SEQ ID NO: 624. An exemplary LTβR antibody-based molecule comprising a VH and VL of this embodiment includes, without limitation, the LTβR antibody identified herein as LIBC No.219097 (19326; 43D9).

[0175] In another embodiment, the agonist LTβR binding protein comprises a VH, where the VH comprises a HCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 484, a HCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 514, and a HCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 544. In one embodiment, the VH comprises the HCDR1 sequence of SEQ ID NO: 484, the HCDR2 of SEQ ID NO: 514, and the HCDR3 sequence of SEQ ID NO: 544. This agonist LTβR binding protein further comprises a VL, where the VL comprises a LCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 575, a LCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 604, and a LCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 629. In one embodiment, the VL comprises the LCDR1 sequence of SEQ ID NO: 575, the LCDR2 of SEQ ID NO: 604, and the LCDR3 sequence of SEQ ID NO: 629. An exemplary agonist LTβR binding protein comprising a VH and VL of this embodiment includes, without limitation, the LTβR antibody identified herein as LIBC No.218989.

[0176] In another embodiment, the agonist LTβR binding protein comprises a VH, where the VH comprises a HCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 485,a HCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 515, and a HCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 545. In one embodiment, the VH comprises the HCDR1 sequence of SEQ ID NO: 485, the HCDR2 of SEQ ID NO: 515, and the HCDR3 sequence of SEQ ID NO: 545. This agonist LTβR binding protein of the present disclosure further comprises a VL, where the VL comprises a LCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 576, a LCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 605, and a LCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 630. In one embodiment, the VL comprises the LCDR1 sequence of SEQ ID NO: 576, the LCDR2 of SEQ ID NO: 605, and the LCDR3 sequence of SEQ ID NO: 630. An exemplary agonist LTβR binding protein comprising a VH and VL of this embodiment includes, without limitation, the LTβR antibody identified herein as LIBC No.218967.

[0177] In another embodiment, the agonist LTβR binding protein of the present disclosure comprises a VH, where the VH comprises a HCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 486, a HCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 516, and a HCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 546. In one embodiment, the VH comprises the HCDR1 sequence of SEQ ID NO: 486, the HCDR2 of SEQ ID NO: 516, and the HCDR3 sequence of SEQ ID NO: 546. This agonist LTβR binding protein of the present disclosure optionally further comprises a VL, where the VL comprises a LCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 577, a LCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 606, and a LCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 631. In one embodiment, the VL comprises the LCDR1 sequence of SEQ ID NO: 577, the LCDR2 of SEQ ID NO: 6068, and the LCDR3 sequence of SEQ ID NO: 631. An exemplary agonist LTβR binding protein comprising a VH and VL of this embodiment includes, without limitation, the LTβR antibody identified herein as LIBC No.218981.

[0178] In another embodiment, the agonist LTβR binding protein of the present disclosure comprises a VH, where the VH comprises a HCDR1 sequence that shares at least 80%, at least 85%, at least90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 487, a HCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 517, and a HCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 547. In one embodiment, the VH comprises the HCDR1 sequence of SEQ ID NO: 487, the HCDR2 of SEQ ID NO: 517 and the HCDR3 sequence of SEQ ID NO: 547. This agonist LTβR binding protein of the present disclosure further comprises a VL, where the VL comprises a LCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 578, a LCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 607, and a LCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 632. In one embodiment, the VL comprises the LCDR1 sequence of SEQ ID NO: 578, the LCDR2 of SEQ ID NO: 607, and the LCDR3 sequence of SEQ ID NO: 632. An exemplary agonist LTβR binding protein comprising a VH and VL of this embodiment includes, without limitation, the LTβR antibody identified herein as LIBC No.218995.

[0179] In another embodiment, the agonist LTβR binding protein of the present disclosure comprises a VH, where the VH comprises a HCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 488, a HCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 518, and a HCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 548. In one embodiment, the VH comprises the HCDR1 sequence of SEQ ID NO: 488, the HCDR2 of SEQ ID NO: 518, and the HCDR3 sequence of SEQ ID NO: 548. This agonist LTβR binding protein of the present disclosure optionally further comprises a VL, where the VL comprises a LCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 579, a LCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 608, and a LCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 633. In one embodiment, the VL comprises the LCDR1 sequence of SEQ ID NO: 579, the LCDR2 of SEQ ID NO: 608, and the LCDR3 sequence of SEQ ID NO: 633. An exemplary agonist LTβR binding protein comprising a VH and VL of this embodiment includes, without limitation, the LTβR antibody identified herein as LIBC No.218996.

[0180] In another embodiment, the agonist LTβR binding protein of the present disclosure comprises a VH, where the VH comprises a HCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 489, a HCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 519, and a HCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 549. In one embodiment, the VH comprises the HCDR1 sequence of SEQ ID NO: 489, the HCDR2 of SEQ ID NO: 519, and the HCDR3 sequence of SEQ ID NO: 549. This agonist LTβR binding protein of the present disclosure optionally further comprises a VL, where the VL comprises a LCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 580, a LCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 609, and a LCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 634. In one embodiment, the VL comprises the LCDR1 sequence of SEQ ID NO: 580, the LCDR2 of SEQ ID NO: 609, and the LCDR3 sequence of SEQ ID NO: 634. An exemplary agonist LTβR binding protein comprising a VH and VL of this embodiment includes, without limitation, the LTβR antibody identified herein as LIBC No.218998.

[0181] In another embodiment, the agonist LTβR binding protein of the present disclosure comprises a VH, where the VH comprises a HCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 490, a HCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 520, and a HCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 550. In one embodiment, the VH comprises the HCDR1 sequence of SEQ ID NO: 490, the HCDR2 of SEQ ID NO: 520, and the HCDR3 sequence of SEQ ID NO: 550. This agonist LTβR binding protein of the present disclosure optionally further comprises a VL, where the VL comprises a LCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 581, a LCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 610, and a LCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 635. In one embodiment, the VL comprises the LCDR1 sequence of SEQ ID NO: 581, the LCDR2 of SEQ ID NO: 610, and the LCDR3 sequence of SEQ ID NO: 635. Anexemplary agonist LTβR binding protein comprising a VH and VL of this embodiment includes, without limitation, the LTβR antibody identified herein as LIBC No.219083.

[0182] In another embodiment, the agonist LTβR binding protein of the present disclosure comprises a VH, where the VH comprises a HCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 491, a HCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 521, and a HCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 551. In one embodiment, the VH comprises the HCDR1 sequence of SEQ ID NO: 491, the HCDR2 of SEQ ID NO: 521, and the HCDR3 sequence of SEQ ID NO: 551. This agonist LTβR binding protein of the present disclosure optionally further comprises a VL, where the VL comprises a LCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 582, a LCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 611, and a LCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 636. In one embodiment, the VL comprises the LCDR1 sequence of SEQ ID NO: 582, the LCDR2 of SEQ ID NO: 611, and the LCDR3 sequence of SEQ ID NO: 636. An exemplary agonist LTβR binding protein comprising a VH and VL of this embodiment includes, without limitation, the LTβR antibody identified herein as LIBC No.219092.

[0183] In another embodiment, the agonist LTβR binding protein of the present disclosure is a binding protein that binds to LTβR and permits endogenous LTβR ligand binding activity as defined herein. This LTβR binding protein comprises a VH, where the VH comprises a HCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 492, a HCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 522, and a HCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 552. In one embodiment, the VH comprises the HCDR1 sequence of SEQ ID NO: 492, the HCDR2 of SEQ ID NO: 522, and the HCDR3 sequence of SEQ ID NO: 552. In one embodiment, the HCDR2 of SEQ ID NO: 522 is modified to substitute the cysteine residues at positions 4 and 8 in SEQ ID NO: 522. In one embodiment, the HCDR2 of this LTβR binding protein comprises an HCDR2 of SEQ ID NO: 523. This agonist LTβR binding protein of the present disclosure optionally further comprises a VL, where the VL comprises a LCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 583, a LCDR2 sequence that shares at least 80%, at least 85%, at least 90%, atleast 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 612, and a LCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 637. In one embodiment, the VL comprises the LCDR1 sequence of SEQ ID NO: 583, the LCDR2 of SEQ ID NO: 612, and the LCDR3 sequence of SEQ ID NO: 637. An exemplary agonist LTβR binding protein comprising a VH and VL of this embodiment includes, without limitation, the LTβR antibody identified herein as LIBC No.219023.

[0184] In another embodiment, the agonist LTβR binding protein of the present disclosure comprises a VH, where the VH comprises a HCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 494, a HCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 524, and a HCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 554. In one embodiment, the VH comprises the HCDR1 sequence of SEQ ID NO: 494, the HCDR2 of SEQ ID NO: 524, and the HCDR3 sequence of SEQ ID NO: 554. This agonist LTβR binding protein of the present disclosure optionally further comprises a VL, where the VL comprises a LCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 585, a LCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 614, and a LCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 639. In one embodiment, the VL comprises the LCDR1 sequence of SEQ ID NO: 585, the LCDR2 of SEQ ID NO: 614, and the LCDR3 sequence of SEQ ID NO: 639. An exemplary agonist LTβR binding protein comprising a VH and VL of this embodiment includes, without limitation, the LTβR antibody identified herein as LIBC No.219095.

[0185] In another embodiment, the agonist LTβR binding protein of the present disclosure comprises a VH, where the VH comprises a HCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 495, a HCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 525, and a HCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 555. In one embodiment, the VH comprises the HCDR1 sequence of SEQ ID NO: 495, the HCDR2 of SEQ ID NO: 525, and the HCDR3 sequence of SEQ ID NO: 555. This agonist LTβR binding protein of the present disclosure optionally further comprises a VL, where the VL comprises a LCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or atleast 99% sequence identity with the sequence of SEQ ID NO: 586, a LCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 615, and a LCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 640. In one embodiment, the VL comprises the LCDR1 sequence of SEQ ID NO: 586, the LCDR2 of SEQ ID NO: 615, and the LCDR3 sequence of SEQ ID NO: 640. An exemplary agonist LTβR binding protein comprising a VH and VL of this embodiment includes, without limitation, the LTβR antibody identified herein as LIBC No.219102.

[0186] In another embodiment, the agonist LTβR binding protein of the present disclosure comprises a VH, where the VH comprises a HCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 496, a HCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 526, and a HCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 556. In one embodiment, the VH comprises the HCDR1 sequence of SEQ ID NO: 496, the HCDR2 of SEQ ID NO: 526, and the HCDR3 sequence of SEQ ID NO: 556. This agonist LTβR binding protein of the present disclosure optionally further comprises a VL, where the VL comprises a LCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 587, a LCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 616, and a LCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 641. In one embodiment, the VL comprises the LCDR1 sequence of SEQ ID NO: 587, the LCDR2 of SEQ ID NO: 616, and the LCDR3 sequence of SEQ ID NO: 641. An exemplary agonist LTβR binding protein comprising a VH and VL of this embodiment includes, without limitation, the LTβR antibody identified herein as LIBC No.218973.

[0187] In another embodiment, the agonist LTβR binding protein of the present disclosure comprises a VH, where the VH comprises a HCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 497, a HCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 527, and a HCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 557. In one embodiment, the VH comprises the HCDR1 sequence of SEQ ID NO: 497, the HCDR2 of SEQ ID NO: 527, and the HCDR3 sequence of SEQ ID NO: 557. This agonist LTβR binding protein of the present disclosure optionally further comprises a VL, where the VL comprises a LCDR1 sequence thatshares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 588, a LCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 617, and a LCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 642. In one embodiment, the VL comprises the LCDR1 sequence of SEQ ID NO: 588, the LCDR2 of SEQ ID NO: 617, and the LCDR3 sequence of SEQ ID NO: 642. An exemplary agonist LTβR binding protein comprising a VH and VL of this embodiment includes, without limitation, the LTβR antibody identified herein as LIBC No.219044.

[0188] In another embodiment, the agonist LTβR binding protein of the present disclosure comprises a VH, where the VH comprises a HCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 498, a HCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 528, and a HCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 558. In one embodiment, the VH comprises the HCDR1 sequence of SEQ ID NO: 498, the HCDR2 of SEQ ID NO: 528, and the HCDR3 sequence of SEQ ID NO: 558. This agonist LTβR binding protein of the present disclosure optionally further comprises a VL, where the VL comprises a LCDR1 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 589, a LCDR2 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence of SEQ ID NO: 618, and a LCDR3 sequence that shares at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% sequence identity with the sequence SEQ ID NO: 643. In one embodiment, the VL comprises the LCDR1 sequence of SEQ ID NO: 589, the LCDR2 of SEQ ID NO: 618, and the LCDR3 sequence of SEQ ID NO: 643. An exemplary agonist LTβR binding protein comprising a VH and VL of this embodiment includes, without limitation, the LTβR antibody identified herein as LIBC No.218997.

[0189] Suitable amino acid modifications to the heavy chain CDR sequences and / or the light chain CDR sequences of the LTβR binding protein disclosed herein include, for example, conservative substitutions or functionally equivalent amino acid residue substitutions that result in variant CDR sequences having similar or enhanced binding characteristics to those of the CDR sequences described above. Encompassed by the present disclosure are CDRs of Tables 2, 3, 6, 7, 9 and 10 containing 1, 2, 3, 4, 5, or more amino acid substitutions (depending on the length of the CDR) that maintain or enhance LTβR binding of the antibody. The resulting modified CDRs are at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95% similar in sequence to the CDRs as provided in Tables 2, 3, 6, 7, 9 and 10.

[0190] Suitable amino acid modifications to the heavy chain and light chain CDR sequences disclosed herein include, for example, conservative substitutions or functionally equivalent amino acid residue substitutions that result in variant CDR sequences having similar or enhanced binding characteristics to those of the CDR sequences disclosed herein. Conservative substitutions are those that take place within a family of amino acids that are related in their side chains. Genetically encoded amino acids can be divided into four families: (1) acidic (aspartate, glutamate); (2) basic (lysine, arginine, histidine); (3) nonpolar (alanine, valine, leucine, isoleucine, proline, phenylalanine, methionine, tryptophan); and (4) uncharged polar (glycine, asparagine, glutamine, cysteine, serine, threonine, tyrosine). Phenylalanine, tryptophan, and tyrosine are sometimes classified jointly as aromatic amino acids. Alternatively, the amino acid repertoire can be grouped as (1) acidic (aspartate, glutamate); (2) basic (lysine, arginine histidine), (3) aliphatic (glycine, alanine, valine, leucine, isoleucine, serine, threonine), with serine and threonine optionally grouped separately as aliphatic-hydroxyl; (4) aromatic (phenylalanine, tyrosine, tryptophan); (5) amide (asparagine, glutamine); and (6) sulfur-containing (cysteine and methionine) (Stryer (ed.), Biochemistry, 2nd ed, WH Freeman and Co., 1981, which is hereby incorporated by reference in its entirety). Non- conservative substitutions can also be made to the heavy chain CDR sequences and the light chain CDR sequences disclosed herein. Non-conservative substitutions involve substituting one or more amino acid residues of the CDR with one or more amino acid residues from a different class of amino acids to improve or enhance the binding properties of CDR. The amino acid sequences of the heavy chain variable region CDRs and / or the light chain variable region CDRs disclosed herein may further comprise one or more internal neutral amino acid insertions or deletions that maintain or enhance LTβR binding.

[0191] The LTβR binding proteins that bind LTβR as described herein may comprise a variable light (VL) chain, a variable heavy (VH) chain, or a combination of VL and VH chains. In one embodiment, the VH chain of the LTβR binding protein comprises any one of the VH amino acid sequences provided in Table 12 below, or an amino acid sequence that is at least 75%, at least 80%, at least 85%, at least 90%, or at least 95% identical to any one of the VH amino acid sequences listed in Table 12. In one embodiment, the VL chain of the LTβR binding protein comprises any one of the VL amino acid sequences provided in Table 12 below, or an amino acid sequence that is at least 75%, at least 80%, at least 85%, at least 90%, at least 95% identical to any one of the VL amino acid sequences listed in Table 12.

[0192] In one embodiment, an agonist LTβR binding protein of the present disclosure binds to and agonizes human LTβR (SEQ ID NO: 1) while allowing endogenous LTβR ligand binding and activity (i.e., LIGHT or LTα1β2 binding) as described herein, and comprises a heavy chain variable domain having at least 85%, at least 90%, or at least 95% sequence identity to any one of the VH domain amino acid sequences set forth in Table 12. In one embodiment, an agonist LTβR binding protein of the present disclosure binds to and agonizes human LTβR (SEQ ID NO: 1) while allowing endogenous LTβR ligand binding and activity (i.e., LIGHT or LTα1β2 binding) as described herein, and comprises a light chain variable domain having at least 85%, at least 90%, or at least 95% sequence identity to any one of the VL domain amino acid sequences set forth in Table 12. In one embodiment, the agonist LTβR binding protein of the presentdisclosure binds to and agonizes human LTβR (SEQ ID NO: 1) while allowing endogenous LTβR ligand binding and activity (i.e., LIGHT or LTα1β2 binding) as described herein, and comprises a heavy chain variable domain having at least 85%, at least 90%, or at least 95% sequence identity to any one of the VH domain amino acid sequences set forth in Table 12, and a light chain variable domain having at least 85%, at least 90%, or at least 95% sequence identity to the corresponding VL domain amino acid sequence as set forth in Table 12. TABLE 12. LTβR Binding Protein VH and VL Amino Acid Sequences

[0193] In one embodiment, an agonist LTβR binding protein of the present disclosure binds to and agonizes human and cyno LTβR. This agonist LTβR binding protein binds CRD2 and CRD3 of human LTβR at an epitope comprising or consisting of one or more residues at positions 56-64 and 81-101 of SEQ ID NO: 4 (corresponding to residues 86-94 and 111-131 of SEQ ID NO: 1). This agonist LTβR binding protein comprises a heavy chain variable domain having at least 80%, at least 85%, at least 90%, or at least 95% sequence identity to the VH domain amino acid sequence of SEQ ID NO: 644 and a light chain variable domain having at least 80%, at least 85%, at least 90%, or at least 95% sequence identity to the VL domain amino acid sequence of SEQ ID NO: 645. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence that is at least 95% identical to SEQ ID NO: 644 and a VL amino acid sequence that is at least 95% identical to SEQ ID NO: 645. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence of SEQ ID NO: 644 and a VL amino acid sequence of SEQ ID NO: 645 (30H1 / 19320).

[0194] In one embodiment, an agonist LTβR binding protein of the present disclosure binds to and agonizes human and cyno LTβR. This agonist LTβR binding protein binds CRD1 of human LTβR at an epitope comprising or consisting of one or more residues at positions 3-9, 12-29, and 38-47 of SEQ ID NO: 4 (corresponding to residues 33-39, 50-59, and 68-77 of SEQ ID NO: 1). This agonist LTβR binding protein allows 100% of LIGHT and / or at least or about 80% of LTα1β2 binding to LTβR to occur and comprises a heavy chain variable domain having at least 80%, at least 85%, at least 90%, or at least 95% sequence identity to the VH domain amino acid sequence of SEQ ID NO: 646. This LTβR binding protein further comprises a light chain variable domain having at least 80%, at least 85%, at least 90%, or at least 95% sequence identity to the VL domain amino acid sequence of SEQ ID NO: 647. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence that is at least 95% identical to SEQ ID NO: 646 and a VL amino acid sequence that is at least 95% identical to SEQ ID NO: 647. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence of SEQ ID NO: 646 and a VL amino acid sequence of SEQ ID NO: 647 (19321).

[0195] In one embodiment, an agonist LTβR binding protein of the present disclosure binds to and agonizes human and cyno LTβR. This agonist LTβR binding protein binds to CRD2 and CRD3 of human LTβR at an epitope comprising or consisting of one or more residues at positions 56-64 and 81-101 of SEQ ID NO: 4 (corresponding to residues 86-94 and 111-131 of SEQ ID NO: 1). This agonist LTβR binding protein does not inhibit LIGHT and LTα1β2 binding to LTβR at concentrations of <8 nM in the cell based receptor-ligand assay as described herein. This LTβR binding protein and comprises a heavy chain variable domain having at least 80%, at least 85%, at least 90%, or at least 95% sequence identity to the VH domainamino acid sequence of SEQ ID NO: 648 and a light chain variable domain having at least 80%, at least 85%, at least 90%, or at least 95% sequence identity to the VL domain amino acid sequence of SEQ ID NO: 649. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence that is at least 95% identical to SEQ ID NO: 648 and a VL amino acid sequence that is at least 95% identical to SEQ ID NO: 649. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence of SEQ ID NO: 648 and a VL amino acid sequence of SEQ ID NO: 649 (19324).

[0196] In one embodiment, an agonist LTβR binding protein of the present disclosure binds to and agonizes human and cyno LTβR. This LTβR binding protein binds to CRD1 and CRD2 of human LTβR at an epitope comprising or consisting of one or more residues at positions 38-42, 56-65, and 65-70 of SEQ ID NO: 4. This agonist LTβR binding protein comprises a heavy chain variable domain having at least 80%, at least 85%, at least 90%, or at least 95% sequence identity to the VH domain amino acid sequence of SEQ ID NO: 650 and a light chain variable domain having at least 80%, at least 85%, at least 90%, or at least 95% sequence identity to the VL domain amino acid sequence of SEQ ID NO: 651. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence that is at least 95% identical to SEQ ID NO: 650 and a VL amino acid sequence that is at least 95% identical to SEQ ID NO: 651. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence of SEQ ID NO: 650 and a VL amino acid sequence of SEQ ID NO: 651.

[0197] In one embodiment, an agonist LTβR binding protein of the present disclosure binds to and agonizes human and cyno LTβR, and does not inhibit endogenous LIGHT binding to LTβR. This agonist LTßR binding protein comprises a heavy chain variable domain having at least 80%, at least 85%, at least 90%, or at least 95% sequence identity to the VH domain amino acid sequence of SEQ ID NO: 652 and a light chain variable domain having at least 80%, at least 85%, at least 90%, or at least 95% sequence identity to the VL domain amino acid sequence of SEQ ID NO: 653. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence that is at least 95% identical to SEQ ID NO: 652 and a VL amino acid sequence that is at least 95% identical to SEQ ID NO: 653. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence of SEQ ID NO: 652 and a VL amino acid sequence of SEQ ID NO: 653 (19322).

[0198] In one embodiment, an agonist LTβR binding protein of the present disclosure binds to and agonizes human and cyno LTβR, and does not inhibit endogenous LIGHT binding to LTβR. This agonist LTβR binding protein comprises a VH amino acid sequence that is at least 80%, at least 85%, or at least 90% identical to SEQ ID NO: 654 and a VL amino acid sequence that is at least 80%, at least 85%, or at least 90% identical to SEQ ID NO: 655 or SEQ ID NO: 657. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence that is at least 95% identical to SEQ ID NO: 654 and a VL amino acid sequence that is at least 95% identical to SEQ ID NO: 657. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence of SEQ ID NO: 654 and a VL amino acid sequence of SEQ ID NO: 657 (19327).

[0199] In one embodiment, an LTβR binding protein of the present disclosure binds to and agonizes human and cyno LTβR, and does not inhibit LTα1β2 binding to LTβR and does not inhibit LIGHT binding to LTβR to occur. This agonist LTβR binding protein comprises a heavy chain variable domain having at least 80%, at least 85%, at least 90%, or at least 95% sequence identity to the VH domain amino acid sequence of SEQ ID NO: 658 and a light chain variable domain having at least 85%, at least 90%, or at least 95% sequence identity to the VL domain amino acid sequence of SEQ ID NO: 659. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence that is at least 95% identical to SEQ ID NO: 658 and a VL amino acid sequence that is at least 95% identical to SEQ ID NO: 659. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence of SEQ ID NO: 658 and a VL amino acid sequence of SEQ ID NO: 659. (35F5 / 19323)

[0200] In one embodiment, the agonist LTβR binding protein of the present disclosure binds to and agonizes human and cyno LTβR and comprises a VH amino acid sequence that is at least 80%, at least 85%, or at least 90% identical to SEQ ID NO: 660 and a VL amino acid sequence that is at least 80%, at least 85%, or at least 90% identical to SEQ ID NO: 661. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence that is at least 95% identical to SEQ ID NO: 660 and a VL amino acid sequence that is at least 95% identical to SEQ ID NO: 661. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence of SEQ ID NO: 660 and a VL amino acid sequence of SEQ ID NO: 661.

[0201] In one embodiment, the agonist LTβR binding protein of the present disclosure binds to and agonizes human and cyno LTβR and comprises a VH amino acid sequence that is at least 80%, at least 85%, or at least 90% identical to SEQ ID NO: 662 and a VL amino acid sequence that is at least 80%, at least 85%, or at least 90% identical to SEQ ID NO: 663. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence that is at least 95% identical to SEQ ID NO: 662 and a VL amino acid sequence that is at least 95% identical to SEQ ID NO: 663. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence of SEQ ID NO: 662 and a VL amino acid sequence of SEQ ID NO: 663.

[0202] In one embodiment, the agonist LTβR binding protein of the present disclosure is an agonist binding protein that binds to LTβR and comprises a VH amino acid sequence that is at least 80%, at least 85%, or at least 90% identical to SEQ ID NO: 664 and a VL amino acid sequence that is at least 80%, at least 85%, or at least 90% identical to SEQ ID NO: 665. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence that is at least 95% identical to SEQ ID NO: 664 and a VL amino acid sequence that is at least 95% identical to SEQ ID NO: 665. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence of SEQ ID NO: 664 and a VL amino acid sequence of SEQ ID NO: 665.

[0203] In one embodiment, the agonist LTβR binding protein of the present disclosure is an agonist binding protein that binds to LTβR and comprises a VH amino acid sequence that is at least 80%, at least 85%, or at least 90% identical to SEQ ID NO: 666 and a VL amino acid sequence that is at least 80%, atleast 85%, or at least 90% identical to SEQ ID NO: 667. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence that is at least 95% identical to SEQ ID NO: 666 and a VL amino acid sequence that is at least 95% identical to SEQ ID NO: 667. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence of SEQ ID NO: 666 and a VL amino acid sequence of SEQ ID NO: 667.

[0204] In one embodiment, the agonist LTβR binding protein of the present disclosure is an agonist binding protein that binds to LTβR and comprises a VH amino acid sequence that is at least 80%, at least 85%, or at least 90% identical to SEQ ID NO: 668 and a VL amino acid sequence that is at least 80%, at least 85%, or at least 90% identical to SEQ ID NO: 669. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence that is at least 95% identical to SEQ ID NO: 668 and a VL amino acid sequence that is at least 95% identical to SEQ ID NO: 669. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence of SEQ ID NO: 668 and a VL amino acid sequence of SEQ ID NO: 669.

[0205] In one embodiment, the agonist LTβR binding protein of the present disclosure is an agonist binding protein that binds to LTβR and comprises a VH amino acid sequence that is at least 80%, at least 85%, or at least 90% identical to SEQ ID NO: 670 and a VL amino acid sequence that is at least 80%, at least 85%, or at least 90% identical to SEQ ID NO: 671. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence that is at least 95% identical to SEQ ID NO: 670 and a VL amino acid sequence that is at least 95% identical to SEQ ID NO: 671. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence of SEQ ID NO: 670 and a VL amino acid sequence of SEQ ID NO: 671.

[0206] In one embodiment, the agonist LTβR binding protein of the present disclosure is an agonist binding protein that binds to LTβR and comprises a VH amino acid sequence that is at least 80%, at least 85%, or at least 90% identical to SEQ ID NO: 672 and a VL amino acid sequence that is at least 80%, at least 85%, or at least 90% identical to SEQ ID NO: 673. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence that is at least 95% identical to SEQ ID NO: 672 and a VL amino acid sequence that is at least 95% identical to SEQ ID NO: 673. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence of SEQ ID NO: 672 and a VL amino acid sequence of SEQ ID NO: 673.

[0207] In one embodiment, the agonist LTβR binding protein of the present disclosure is an agonist binding protein that binds to LTβR and comprises a VH amino acid sequence that is at least 80%, at least 85%, or at least 90% identical to SEQ ID NO: 674 and a VL amino acid sequence that is at least 80%, at least 85%, or at least 90% identical to SEQ ID NO: 675. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence that is at least 95% identical to SEQ ID NO: 674 and a VL amino acid sequence that is at least 95% identical to SEQ ID NO: 675. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence of SEQ ID NO: 674 and a VL amino acid sequence of SEQ ID NO: 675.

[0208] In one embodiment, the agonist LTβR binding protein of the present disclosure is an agonist binding protein that binds to LTβR and comprises a VH amino acid sequence that is at least 80%, at least 85%, or at least 90% identical to SEQ ID NO: 676 and a VL amino acid sequence that is at least 80%, at least 85%, or at least 90% identical to SEQ ID NO: 677. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence that is at least 95% identical to SEQ ID NO: 676 and a VL amino acid sequence that is at least 95% identical to SEQ ID NO: 677. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence of SEQ ID NO: 676 and a VL amino acid sequence of SEQ ID NO: 677.

[0209] In one embodiment, the agonist LTβR binding protein of the present disclosure is an agonist binding protein that binds to LTβR and comprises a VH amino acid sequence that is at least 80%, at least 85%, or at least 90% identical to SEQ ID NO: 678 and a VL amino acid sequence that is at least 80%, at least 85%, or at least 90% identical to SEQ ID NO: 679. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence that is at least 95% identical to SEQ ID NO: 678 and a VL amino acid sequence that is at least 95% identical to SEQ ID NO: 679. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence of SEQ ID NO: 678 and a VL amino acid sequence of SEQ ID NO: 679.

[0210] In one embodiment, the agonist LTβR binding protein of the present disclosure is an agonist binding protein that binds to LTβR and comprises a VH amino acid sequence that is at least 80%, at least 85%, or at least 90% identical to SEQ ID NO: 680 and a VL amino acid sequence that is at least 80%, at least 85%, or at least 90% identical to SEQ ID NO: 681. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence that is at least 95% identical to SEQ ID NO: 680 and a VL amino acid sequence that is at least 95% identical to SEQ ID NO: 681. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence of SEQ ID NO: 680 and a VL amino acid sequence of SEQ ID NO: 681.

[0211] In one embodiment, the agonist LTβR binding protein of the present disclosure is an agonist binding protein that binds to LTβR and comprises a VH amino acid sequence that is at least 80%, at least 85%, or at least 90% identical to SEQ ID NO: 682 and a VL amino acid sequence that is at least 80%, at least 85%, or at least 90% identical to SEQ ID NO: 683 or SEQ ID NO: 685. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence that is at least 95% identical to SEQ ID NO: 682 and a VL amino acid sequence that is at least 95% identical to SEQ ID NO: 683 or SEQ ID NO: 685. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence of SEQ ID NO: 682 and a VL amino acid sequence of SEQ ID NO: 683 or SEQ ID NO: 685.

[0212] In one embodiment, the agonist LTβR binding protein of the present disclosure is an agonist binding protein that binds to LTβR and comprises a VH amino acid sequence that is at least 80%, at least 85%, or at least 90% identical to SEQ ID NO: 686 and a VL amino acid sequence that is at least 80%, at least 85%, or at least 90% identical to SEQ ID NO: 687. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence that is at least 95% identical to SEQ ID NO: 686 and a VLamino acid sequence that is at least 95% identical to SEQ ID NO: 687. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence of SEQ ID NO: 686 and a VL amino acid sequence of SEQ ID NO: 687.

[0213] In one embodiment, the agonist LTβR binding protein of the present disclosure is an agonist binding protein that binds to LTβR and comprises a VH amino acid sequence that is at least 80%, at least 85%, or at least 90% identical to SEQ ID NO: 688 and a VL amino acid sequence that is at least 80%, at least 85%, or at least 90% identical to SEQ ID NO: 689. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence that is at least 95% identical to SEQ ID NO: 688 and a VL amino acid sequence that is at least 95% identical to SEQ ID NO: 689. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence of SEQ ID NO: 688 and a VL amino acid sequence of SEQ ID NO: 689.

[0214] In one embodiment, the agonist LTβR binding protein of the present disclosure is an agonist binding protein that binds to LTβR and comprises a VH amino acid sequence that is at least 80%, at least 85%, or at least 90% identical to SEQ ID NO: 690 and a VL amino acid sequence that is at least 80%, at least 85%, or at least 90% identical to SEQ ID NO: 691. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence that is at least 95% identical to SEQ ID NO: 690 and a VL amino acid sequence that is at least 95% identical to SEQ ID NO: 691. In one embodiment, the agonist LTβR binding protein comprises a VH amino acid sequence of SEQ ID NO: 690 and a VL amino acid sequence of SEQ ID NO: 691.

[0215] In one embodiment, the agonist LTβR binding protein of the present disclosure comprises a VH region and / or VL region as described supra and further comprises one or more heavy chain constant regions coupled to the VH region and / or a light chain constant region coupled to the VL region. For example, in one embodiment, the agonist LTβR binding protein is a Fab comprising a VH and first heavy chain constant domain (CH1) coupled to a VL and light chain constant region (CL). In another embodiment, the agonist LTβR binding protein is a F(ab’)2 comprising both LTβR binding regions of a full antibody coupled by the hinge region, where each binding region comprises a VH-CH1 and VL-CL. The complete heavy chain and light chain amino acid sequences of exemplary agonist LTβR antibodies of the present disclosure are provided herein in Table 13. Table 13. Full-length Amino Acid Sequences of LTβR Antibodies01 RGLEWLGRTYYRSKWYSDYALSVKSRATINPDTSENQFSLQLNSMulti-Specific LTβR Binding Molecules

[0216] In another aspect of the present disclosure the agonist LTβR binding protein is a multi- specific agonist LTβR binding protein. In accordance with this aspect of the disclosure, the multi-specific agonist LTβR binding protein comprises a first binding domain that binds to human LTβR (SEQ ID NO: 1), and a second binding domain that binds a non-LTβR protein target (i.e., a protein other than LTβR), where the multi-specific binding protein agonizes LTβR activity and (a) does not inhibit LIGHT binding to LTßR and (b) does not inhibit LT1α2β binding to LTβR. The second binding domain of an exemplary LTβR multi-specific binding protein as described herein, binds to a non-LTβR protein target. In one embodiment, the second binding domain of the LTβR multi-specific binding protein binds to a protein or antigen preferentially expressed by a tumor cell or other cells of the tumor microenvironment (TME).

[0217] In one embodiment, the multi-specific agonist LTβR binding protein is monovalent for each of the protein targets bound by the first and second binding domains multi-specific binding protein. In one embodiment, the multi-specific agonist LTβR binding protein is monovalent for the LTβR ligand binding domain and bivalent for the non-LTβR binding domain.

[0218] In one embodiment, the multi-specific agonist LTβR binding protein of the present disclosure further comprises one or more additional binding domains. In one embodiment, the multi- specific agonist LTβR binding protein described herein comprises a third binding domain, where the third binding domain binds the same protein target as the first or second binding domain to form a bi-specific binding protein that is bivalent for one of the protein targets bound by the bi-specific binding protein. In another embodiment, the third binding domain binds a different protein target than the first and second binding domains, thereby forming a monovalent trispecific binding protein. In one embodiment, the multi- specific agonist LTβR binding protein can further comprise a fourth binding domain, where the fourth binding domain binds to the same protein target as the first, second, or third binding domain.

[0219] In accordance with this aspect of the present disclosure the multi-specific agonist LTβR binding protein can assume any multi-specific binding protein format known in the art. For example, in one embodiment, the multi-specific agonist LTβR binding protein is an agonist LTβR bispecific binding protein or a trispecific agonist LTβR binding protein. In one embodiment, the first, second, and / or third binding domain of the multi-specific agonist LTβR binding domain is a Fab. Alternatively, the first, second, and / or third binding domain of a multi-specific agonist LTβR binding domain is a scFv. In one embodiment, the first binding domain is a Fab, the second binding domain is a scFv, and an optionally present third binding domain is a Fab or scFv. In one embodiment, the second binding domain is a Fab, the first binding domain is a scFv, and an optionally present third binding domain is a Fab or scFv. In one embodiment, both the first and second binding domains are Fabs, and the optionally present third binding domain is aFab or scFv. In one embodiment, both the first and second binding domains are scFvs, and the optionally present third binding domain is a Fab or scFv.

[0220] In one embodiment of the present disclosure the multi-specific agonist LTβR binding protein is a bispecific agonist LTβR binding protein. A “bispecific binding protein” as referred to herein is a binding protein that binds to two different antigens at the same time. Bispecific agonist LTβR binding proteins of the present disclosure encompass any bispecific molecular format known in the art (see e.g., Spiess et al., Mol. Immunol. 67(2): 95-106 (2015), which is hereby incorporated by reference in its entirety). These molecule formats include IgG-like formats which retain the traditional monoclonal antibody structure with two Fab arms and one Fc region, IgG formats containing an appended additional antigen binding moiety, bispecific binding protein fragments, bispecific fusions proteins, and combinations thereof.

[0221] In one embodiment, the first and / or second binding domain of the bispecific agonist LTβR binding protein is a Fab. Alternatively, the first and / or second binding domain of the bispecific agonist LTβR binding protein is a scFv. In one embodiment, the first binding domain is a Fab and the second binding domain is a scFv. In one embodiment, the second binding domain is a Fab and the first binding domain is a scFv. In one embodiment, both the first and second binding domains are Fabs. In one embodiment, both the first and second binding domains are scFvs.

[0222] In one embodiment, the bispecific agonist LTβR binding protein of the present disclosure is a full-length bispecific IgG or comprises an IgG-like structure. In one embodiment, the bispecific agonist LTβR binding protein is a hetero-IgG that is monovalent for each target protein bound by the bispecific binding protein. Exemplary hetero-IgG bispecific formats comprising Fc domains engineered to enhance heterodimer formation are well known in the art and are suitable formats for the bispecific agonist LTβR binding protein of the present disclosure. These hetero-IgG formats include, without limitation, knob-into- holes format (see e.g., Ridgway et al., “‘Knobs-into-holes’ engineering of antibody CH3 domains for heavy chain heterodimerization,” Protein Eng. 9:617–621 (1996) and Atwell et al., “Stable heterodimers from remodeling the domain interface of a homodimer using a phage display library,” J. Mol. Biol. 270:26–35 (1997), which are hereby incorporated by reference in their entirety), DuoBody format (see e.g., Labrijn et al., “Efficient generation of stable bispecific IgG1 by controlled Fab-arm exchange,” Proc. Natl. Acad. Sci. U.S.A., 110: 5145-5150 (2013), which is hereby incorporated by reference in its entirety); Azymetric format (see e.g., Von Kreudenstein et al., “Improving biophysical properties of a bispecific antibody scaffold to aid developability: quality by molecular design,” mAbs 5:646-654 (2013), which is hereby incorporated by reference in its entirety); charged Fc pairs (see e.g., Gunasekaran et al., “Enhancing antibody Fc heterodimer formation through electrostatic steering effects: applications to bispecific molecules and monovalent IgG,” J. Biol. Chem., 285: 19637-46 (2010) and Strop et al., “Generating bispecific human IgG1 and IgG2 antibodies from any antibody pair,” J. Mol. Biol., 420:204-219 (2012) which are hereby incorporated by reference in their entirety); mAb-Fv (see e.g., Close et al., “A novel bispecific antibody format enables simultaneous bivalent and monovalent co-engagement of distinct target antigens,” mAbs 3: 546-557 (2011), which is hereby incorporated by reference in its entirety); strand-exchange engineered domain (SEED)C(H)3 heterodimer format (see e.g., Davis et al., “SEEDbodies: fusion proteins based on strand-exchange engineered domain (SEED) CH3 heterodimers in an Fc analogue platform for asymmetric binders or immunofusions and bispecific antibodies,” Protein Eng. Des. Sel. 23:195-202 (2010), which is hereby incorporated by reference in its entirety); and differential Protein A affinity (see e.g., U.S. Patent No. 8,586,713 to Davis et al., which is hereby incorporated by referenced in its entirety).

[0223] In one embodiment, the bispecific agonist LTβR binding protein of the present disclosure is a construct comprising one or more binding protein fragments. Suitable LTβR bispecific binding protein fragments constructs of the present disclosure include, without limitation, nanobodies comprising two single variable (VHH) domains connected via a peptide linker (Els Conrath et al., “Camel single-domain antibodies as modular building units in bispecific and bivalent antibody constructs,” J. Biol. Chem. 276:7346–50 (2001), which is hereby incorporated by reference in its entirety), and diabodies comprising two scFv fragments coupled together (Holliger et al., “‘Diabodies’: small bivalent and bispecific antibody fragments,” Proc. Natl. Acad. Sci. U.S.A., 90: 6444-6448 (1993), which is hereby incorporated by reference in its entirety). Suitable diabody LTβR bispecific constructs include, without limitation, single chain diabodies (see e.g., Alt et al., “Novel tetravalent and bispecific IgG-like antibody molecules combining single-chain diabodies with the immunoglobulin gamma1 Fc or CH3 region,” FEBS Lett.454: 90-94 (1999), which is hereby incorporated by reference in its entirety), dual-affinity re-targeting diabodies (DART) (see e.g., Johnson et al., “Effector cell recruitment with novel Fv-based dual-affinity re-targeting protein leads to potent tumor cytolysis and in vivo B-cell depletion,” J. Mol. Biol.399: 436-449 (2010), which is hereby incorporated by reference in its entirety), tandem diabodies, and tetravalent tandem diabodies (TandAb) comprising two pairs of VL and VH domains connected in a single polypeptide chain (see e.g., Arndt et al., “A bispecific diabody that mediates natural killer cell cytotoxicity against xenotransplanted human Hodgkin's tumors,” Blood 94: 2562-2568 (1999), which is hereby incorporated by reference in its entirety). Suitable LTβR bispecific constructs also include scFv fragments or diabodies coupled to an Fc portion (e.g., minibodies, Diabody-CH3, scDiabody-CH3, scFv-CH3, minibodies) or fused to one or more other moieties to extend half-life (e.g., fusion to serum albumin or albumin binding proteins).

[0224] In one embodiment, the bispecific agonist LTβR binding protein of the present disclosure is a monospecific IgG antibody (e.g., containing the first or second binding domain of the bispecific antibody) engineered for bispecificity with the coupling of an additional binding domain (e.g., the second or first binding domain, respectively) comprising, e.g., a VHH, scFv, 2scFv, Fv, Fab, or antibody mimetic binding domain to either the amino or carboxy termini of either the light or heavy chain(s) of the antibody. Exemplary engineered bispecific binding proteins include, without limitation dual variable domain (DVD)- IgG, 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, IgG-scFab, 2scFv-IgG, IgG-2scFv, scFv4-Ig (see e.g., Spiess et al., “Alternative molecular formats and therapeutic applications for bispecific antibodies,” Mol. Immunol.67(2): 95-106 (2015), which is hereby incorporated by reference in its entirety).

[0225] In one embodiment, the multi-specific agonist LTβR binding protein of the present disclosure is a bispecific agonist LTβR binding protein. This bispecific agonist LTβR binding protein comprises a (i) LTβR binding domain, where the LTβR binding domain binds one or more amino acid residues of human LTβR CRD4 comprising amino acid residues 169-211 of SEQ ID NO: 1, and (ii) a tumor associated antigen binding domain. This bispecific LTβR binding protein agonizes LTβR activity and (a) does not inhibit LIGHT to LTβR and (b) does not inhibit LT1α2β binding to LTβR.

[0226] Exemplary LTβR binding domains, i.e., HCDRs and LCDRs, and VH and VL domains, that bind CRD4 of human LTβR are described supra, and include, without limitation the binding domains of LIBC219081 and LIBC218979 as well as binding domains of the LTβR binding proteins provided in Tables 2–4 and 6–8. In particular, suitable first binding domains of the bispecific agonist LTβR binding protein as described herein may comprise a heavy chain variable domain (VH) or fragment thereof comprising one or more of the HCDR1, HCDR2, and / or HCDR3 or portions thereof as set forth in a single row of Table 2 or Table 6. In one embodiment, the first binding domain of the bispecific agonist LTβR binding protein comprises all three of the HCDR1, HCDR2, and HCDR3 or portions thereof as set forth in a single row of Table 2 or Table 6. In one embodiment, the first binding domain of the bispecific agonist LTβR binding protein comprises a light chain variable domain (VL) or fragment thereof comprising one or more of the LCDR1, LCDR2, and / or LCDR3 or portions thereof as set forth in a single row in Table 3 or Table 7. In one embodiment, the first binding domain of the bispecific agonist LTβR binding protein comprises all three of the LCDR1, LCDR2, and LCDR3 or portions thereof as set forth in a single row of Table 3 or Table 7. In one embodiment, the first binding domain of the bispecific agonist LTβR binding protein as described herein comprises a VH or fragment thereof comprising one or more of the HCDR1, HCDR2, and / or HCDR3 or portions thereof as set forth in a single row of Table 2 or Table 6 and a VL or fragment thereof comprising one or more of the LCDR1, LCDR2, and / or LCDR3 or portions thereof of a corresponding binding molecule as set forth in a single row of Table 3 or Table 7. In one embodiment, the first binding domain of the bispecific agonist LTβR binding protein as described herein comprises a VH or fragment thereof comprising all three of the HCDR1, HCDR2, and HCDR3 or portions thereof as set forth in a single row of Table 2 or Table 6 and a VL or fragment thereof comprising all three of the LCDR1, LCDR2, and LCDR3 or portions of a corresponding binding molecule as set forth in a single row of Table 3 or Table 7. This bispecific agonist LTβR binding protein (a) does not inhibit LIGHT binding to LTβR and (b) does not inhibit LT1α2β binding to LTβR.

[0227] In one embodiment, the first binding domain of a bispecific agonist LTβR binding protein that binds CRD4 of human LTβR comprises a heavy chain variable domain (VH), a light chain variable domain (VL), or a combination of VH and VL domains. In one embodiment, the VH domain of the first binding domain of the bispecific agonist LTβR binding protein comprises any one of the VH amino acid sequences provided in Table 4 or Table 8, or an amino acid sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95% identical to any one of the VH amino acid sequences listed in Table 4 or Table 8. In one embodiment, the VL domain of the first bindingdomain of the bispecific agonist LTβR binding protein comprises any one of the VL amino acid sequences provided in Table 4 or Table 8, or an amino acid sequence that is at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95% identical to any one of the VL amino acid sequences listed in Table 4 or Table 8. This bispecific agonist LTβR binding protein (a) does not inhibit LIGHT binding to LTβR and (b) does not inhibit LT1α2β binding to LTβR.

[0228] In one embodiment, the first binding domain of a bispecific agonist LTβR binding protein that binds CRD4 of human LTβR comprises a heavy chain variable domain having at least 85%, at least 90%, at least 95%, or 100% sequence identity to any one of the VH domain amino acid sequences set forth in Table 4 or Table 8, and a light chain variable domain having at least 85%, at least 90%, at least 95%, or 100% sequence identity to the corresponding VL domain amino acid sequence as set forth in Table 4 or Table 8. This bispecific agonist LTβR binding protein (a) does not inhibit LIGHT binding to LTβR and (b) does not inhibit LT1α2β binding to LTβR.

[0229] In one embodiment, the LTβR binding domain of the bispecific agonist LTβR binding protein that binds to CRD4 of human LTβR comprises a VH comprising the HCDR1 amino acid sequence of: X1YX3MX5(SEQ ID NO: 5), where X1is S or N; X3is G, D, or A; and X5is H or Y; the HCDR2 amino acid sequence of: X1IX3YDX6X7X8X9Y X11X12DSVKG (SEQ ID NO: 6), where X1is A or V; X3is W or R; X6is E or G; X7is S, R, or T; X8is N or K; X9is K, R, or Q; X11is H or Y; and X12is A or E; and the HCDR3 amino acid sequence of: X1RX3X4X5X6 X7X8X9YYGX13X14V (SEQ ID NO: 7), where X1 is D or E; X3is V, G, or I; X4is V, P, or A; X5is A, Y, or G; X6is R, A, G, or H; X7is P or G; X8is G, N, D, Y, A or H; X9is Y, T, or F; X13is L or M; and X14is D or A. This bispecific agonist LTβR binding protein (a) does not inhibit LIGHT binding to LTβR and (b) does not inhibit LT1α2β binding to LTβR.

[0230] In one embodiment, the LTβR binding domain of the bispecific agonist LTβR binding protein that binds to CRD4 of human LTβR further comprises a VL comprising the LCDR1 amino acid sequence of: SGDX4LPX7X8YX10Y (SEQ ID NO: 62), where X4is A or T; X7is E, K, Q, D or N; X8is Q or H; and X10is A or T; the LCDR2 amino acid sequence of: KDNERPS (SEQ ID NO: 63); and the LCDR3 amino acid sequence of: QSX3DX5SX7X8YX10X11(SEQ ID NO: 64), where X3is A or T; X5is S, G, or N; X7is G or A; X8is T, S, or A; X10is V or M; and X11is I or V. This bispecific agonist LTβR binding protein (a) does not inhibit LIGHT binding to LTβR and (b) does not inhibit LT1α2β binding to LTβR.

[0231] In one embodiment, the LTβR binding domain of the bispecific agonist LTβR binding protein that binds to CRD4 of human LTβR comprises a VH amino acid sequence having at least 90% sequence identity to the amino acid sequence of SEQ ID NO: 121. In one embodiment, an LTβR binding domain comprises a VH amino acid sequence having at least 90% sequence identity to the amino acid sequence of SEQ ID NO: 123. In one embodiment, an LTβR binding domain comprises a VH amino acid sequence having at least 90% sequence identity to the amino acid sequence of SEQ ID NO: 121 and the amino acid sequence of SEQ ID NO: 123. Exemplary VH amino acid sequences having at least 90% sequence identity to the amino acid sequence of SEQ ID NO: 121 and SEQ ID NO: 123 are provided inTable 4 supra. This bispecific agonist LTβR binding protein (a) does not inhibit LIGHT binding to LTβR and (b) does not inhibit LT1α2β binding to LTβR.

[0232] In one embodiment, the LTβR binding domain of the bispecific agonist LTβR binding protein that binds to CRD4 of human LTβR comprises a VL amino acid sequence having at least 90% sequence identity to the amino acid sequence of SEQ ID NO: 122. In one embodiment, the LTβR binding domain comprises a VL amino acid sequence having at least 90% sequence identity to the amino acid sequence of SEQ ID NO: 124. In one embodiment, the LTβR binding domain comprises a VL amino acid sequence having at least 90% sequence identity to the amino acid sequence of SEQ ID NO: 122 and the amino acid sequence of SEQ ID NO: 124. Exemplary VL amino acid sequences having at least 90% sequence identity to the amino acid sequence of SEQ ID NO: 122 and SEQ ID NO: 124 are provided in Table 4 supra. This bispecific agonist LTβR binding protein (a) does not inhibit LIGHT binding to LTβR and (b) does not inhibit LT1α2β binding to LTβR.

[0233] In one embodiment, the LTβR binding domain of the bispecific agonist LTβR binding protein that binds to CRD4 of human LTβR comprises a VH amino acid sequence having at least 90% sequence identity to the amino acid sequence of SEQ ID NO: 121 and a VL amino acid sequence having at least 90% sequence identity to the amino acid sequence of SEQ ID NO: 122. In one embodiment, the LTβR binding domain comprises a VH amino acid sequence having at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 121 and a VL amino acid sequence having at least 95% sequence identity to the amino acid sequence of SEQ ID NO: 122. In one embodiment, an LTβR binding domain comprises a VH amino acid sequence having at least 98% sequence identity to the amino acid sequence of SEQ ID NO: 121 and a VL amino acid sequence having at least 98% sequence identity to the amino acid sequence of SEQ ID NO: 122. This bispecific agonist LTβR binding protein (a) does not inhibit LIGHT binding to LTβR and (b) does not inhibit LT1α2β binding to LTβR.

[0234] In one embodiment, the LTβR binding domain of the bispecific agonist LTβR binding protein comprises a VH amino acid sequence having at least 90% sequence identity to SEQ ID NO: 123 and a HCDR1 amino acid sequence of SEQ ID NO: 5 (X1YX3MX5), a HCDR2 amino acid sequence of SEQ ID NO: 6 (X1IX3YDX6X7X8X9YX11X12DSVKG), and a HCDR3 amino acid sequence of SEQ ID NO: 7 (X1RX3X4X5X6X7X8X9YYGX13X14V). In one embodiment, this LTβR binding domain further comprises a VL amino acid sequence having at least 90% sequence identity to SEQ ID NO: 124 and a LCDR1 amino acid sequence of SEQ ID NO: 62 (SGDX4LPX7X8YX10Y), a LCDR2 amino acid sequence of SEQ ID NO: 63 (KDX3ERPS), and a LCDR3 amino acid sequence of SEQ ID NO: 64 (QSX3DX5SX7X8YX10X11). This bispecific agonist LTβR binding protein (a) does not inhibit LIGHT binding to LTβR and (b) does not inhibit LT1α2β binding to LTβR.

[0235] In one embodiment, the LTβR binding domain of the bispecific agonist LTβR binding protein comprises a VH, which comprises the HCDR1, HCDR2, and HCDR3 of amino acid sequences of SEQ ID NO: 11-13, respectively, and a VL comprising the LCDR1, LCDR2, and LCDR3 amino acidsequences of SEQ ID NO: 68-70, respectively. In one embodiment, the LTβR binding domain comprises a VH comprising the HCDR1, HCDR2, and HCDR3 of amino acid sequences of SEQ ID NO: 8-10, respectively, and a VL comprising the LCDR1, LCDR2, and LCDR3 amino acid sequences of SEQ ID NO: 65-67, respectively. This bispecific agonist LTβR binding protein (a) does not inhibit LIGHT binding to LTβR and (b) does not inhibit LT1α2β binding to LTβR.

[0236] In one embodiment, the LTβR binding domain of the bispecific agonist LTβR binding protein competes for binding to LTβR with the exemplary LTβR binders of LIBC219081 and LIBC218979. In one embodiment, this first binding domain comprises HCDR1, HCDR2, HCDR3, LCDR1, LCDR2, and LCDR3 amino acid sequences selected from (i) SEQ ID NO: 159, SEQ ID NO: 160, SEQ ID NO: 161, SEQ ID NO: 278, SEQ ID NO: 279, and SEQ ID NO: 280; (ii) SEQ ID NO: 159, SEQ ID NO: 160, SEQ ID NO: 161, SEQ ID NO: 299, SEQ ID NO: 300, and SEQ ID NO: 301; (iii) SEQ ID NO: 159, SEQ ID NO: 160, SEQ ID NO: 161, SEQ ID NO: 308, SEQ ID NO: 309, and SEQ ID NO: 310; (iv) SEQ ID NO: 195, SEQ ID NO: 196, SEQ ID NO: 197, SEQ ID NO: 308, SEQ ID NO: 309, and SEQ ID NO: 310; (v) SEQ ID NO: 224, SEQ ID NO: 225, SEQ ID NO: 226, SEQ ID NO: 356, SEQ ID NO: 357, and SEQ ID NO: 358. Bispecific agonist LTβR binding proteins comprising a first binding domain with the aforementioned heavy chain and light chain CDRs does not inhibit LIGHT binding to LTβR and does not inhibit LT1α2β binding to LTβR.

[0237] In one embodiment, the LTβR binding domain of the bispecific agonist LTβR binding protein binds human LTβR CRD1 and comprises a heavy chain variable domain having at least 85%, at least 90%, or at least 95% sequence identity to the VH domain amino acid sequence of SEQ ID NO: 646 and a light chain variable domain having at least 85%, at least 90%, or at least 95% sequence identity to the VL domain amino acid sequence of SEQ ID NO: 647. This bispecific LTβR binding protein does not inhibit endogenous LIGHT binding to LTβR and allows 80% of endogenous LTα1β2 binding to LTβR to occur.

[0238] In one embodiment, the LTβR binding domain of the bispecific agonist LTβR binding protein binds to human LTβR, and comprises a heavy chain variable domain having at least 85%, at least 90%, or at least 95% sequence identity to the VH domain amino acid sequence of SEQ ID NO: 652 and a light chain variable domain having at least 85%, at least 90%, or at least 95% sequence identity to the VL domain amino acid sequence of SEQ ID NO: 653. This bispecific LTβR binding protein does not inhibit endogenous LIGHT binding to LTβR.

[0239] In one embodiment, the LTβR binding domain of the bispecific agonist LTβR binding protein binds to human LTβR, and comprises a heavy chain variable domain having at least 85%, at least 90%, or at least 95% sequence identity to the VH domain amino acid sequence of SEQ ID NO: 654 and a light chain variable domain having at least 85%, at least 90%, or at least 95% sequence identity to the VL domain amino acid sequence of SEQ ID NO: 655. This bispecific LTβR binding protein does not inhibit endogenous LIGHT binding to LTβR

[0240] In one embodiment, the LTβR binding domain of the bispecific agonist LTβR binding protein binds to human LTβR CRD1, and comprises a heavy chain variable domain having at least 85%, atleast 90%, or at least 95% sequence identity to the VH domain amino acid sequence of SEQ ID NO: 658 and a light chain variable domain having at least 85%, at least 90%, or at least 95% sequence identity to the VL domain amino acid sequence of SEQ ID NO: 659. This bispecific LTβR binding protein does not inhibit endogenous LIGHT binding to LTßR and does not inhibit LTα1β2 binding to LTβR

[0241] In one embodiment, the LTβR binding domain of the bispecific agonist LTβR binding protein binds to human LTβR CRD2 and CRD3 and comprises a heavy chain variable domain having at least 85%, at least 90%, or at least 95% sequence identity to the VH domain amino acid sequence of SEQ ID NO: 648 and a light chain variable domain having at least 85%, at least 90%, or at least 95% sequence identity to the VL domain amino acid sequence of SEQ ID NO: 649. This LTβR binding protein does not inhibit LIGHT and LTα1β2 binding to LTβR at concentrations <8 nM in the cell based receptor-ligand assay as described herein.

[0242] In one embodiment, the LTβR binding domain of the bispecific agonist LTβR binding protein binds to human LTβR CRD2 and CRD3 and comprises a heavy chain variable domain having at least 85%, at least 90%, or at least 95% sequence identity to the VH domain amino acid sequence of SEQ ID NO: 644 and a light chain variable domain having at least 85%, at least 90%, or at least 95% sequence identity to the VL domain amino acid sequence of SEQ ID NO: 645.

[0243] In one embodiment, the tumor-associated binding domain of the bispecific agonist LTβR binding protein binds to a tumor-associated antigen (TAA). In one embodiment, the TAA is solid tumor TAA. Suitable TAAs are known in the art and include, without limitation, alpha-fetoprotein (AFP), CD44v6, carbonic anhydrase IX (CAIX), carcinoembryonic antigen (CEA), CD133, hepatocyte growth factor receptor (c-MET), claudin 18.2 (CLDN18.2), claudin 6 (CLDN6), leucine-rich repeat containing protein 15 (LRRC15), epidermal growth factor receptor (EGFR), type III variant epidermal growth factor receptor (EGFRvIII), erythropoietin producing hepatocellular carcinoma A2 (EphA2), epithelial cell adhesion molecule (EpCAM), fetal acetylcholine receptor, folate receptor alpha (FRα), ganglioside GD2 (GD2), glypican-3 (GPC3), guanylyl cyclase C (GUCY2C), human epidermal growth factor receptor 1 (HER1), human epidermal growth factor receptor 2 (ERBB2 / HER2), intercellular adhesion molecule 1 (ICAM-1), interleukin 13 receptor α2 (IL13Rα2), interleukin 11 receptor α (IL11Rα), Kirsten rat sarcoma viral oncogene homolog (KRAS), KRAS G12D, L1-cell adhesion molecule (L1CAM), MAGE, MET, mucin 1 (MUC1), mucin 16 (MUC16), mucin 17 (MUC17), natural killer group 2 member D (NKG2D), NYESO-1, prostate stem cell antigen (PSCA), Wilms tumor 1 (WT-1), galectin 9 (Gal9), program cell death 1 ligand 1 (PD-L1), trophoblast glycoprotein (5T4 oncofetal antigen), folate receptor alpha (FOLR1), and tumor-associated calcium signal transducer 2 (TROP2).

[0244] Binding proteins capable of binding these TAAs are described in the Examples and readily known in the art. Any of these known binding proteins or a TAA binding domain derived therefrom can readily be utilized as the TAA binding domain of the bispecific agonist LTβR binding protein described herein. For example, and without limitation the TAA binding domain may comprise the CLDN6 binding domain, the CLDN18.2 binding domain, the LRRC15 binding domain, or the MUC17 binding domaindescribed in Example 7 herein. Other suitable TAA binding domains include, without limitation, an anti- alpha-fetoprotein (AFP) antibody or binding domain thereof (see e.g., U.S. Patent No.8,268,312 to Hansen et al., which is hereby incorporated by reference in its entirety); an anti-CD44v6 antibody or binding domain thereof (see e.g., U.S. Patent No.6,972,324 to Adolf et al., which is hereby incorporated by reference in its entirety); an anti-carbonic anhydrase IX (CAIX) antibody or binding domain thereof (see e.g., WO2011139375 to Renner and U.S. Patent No.10,487,153 to Lenferink, which are hereby incorporate by reference in their entirety); an anti-carcinoembryonic antigen (CEA) antibody or binding domain thereof (see e.g., U.S. Patent Appl. Publ. No. 20160075795 to Mossner et al., which is hereby incorporated by reference in its entirety); an anti-CD133 antibody or binding domain thereof (see e.g., U.S. Patent No.11, 098,109 to Vallera and U.S. Patent Appl. Publ. No. 20200354468 to Pfister et al., which are hereby incorporate by reference in their entirety); an anti-hepatocyte growth factor receptor (c-MET) antibody or binding domain thereof (see e.g., U.S. Patent No.9,458,245 to Harms et al., and U.S. Patent No.9,068,011 to Neijssen et al., which are hereby incorporate by reference in their entirety); an anti-claudin 18.2 antibody or binding domain thereof (see e.g., U.S. Patent App. Publ. No.20200055932 to Dahlhoff et al., and U.S. Patent No. 10,421,817 to Hu et al., which are hereby incorporate by reference in their entirety); an anti- claudin 6 antibody or binding domain thereof (see e.g., U.S. Patent No. 11,248,046 to Chambers et al., which is hereby incorporated by reference in its entirety); an anti-epidermal growth factor receptor (EGFR) antibody or binding domain thereof (see e.g., U.S. Patent No.9,695,242 to Chiu et al., and U.S. Patent No. 9,458,236 to van de Winkel et al., which are hereby incorporate by reference in their entirety); an anti-type III variant epidermal growth factor receptor (EGFRvIII) antibody or binding domain thereof (see e.g., U.S. Patent No.10,738,124 to Kirschner et al., and U.S. Patent No. 10,273,309 to Ellwanger et al., which are hereby incorporate by reference in their entirety); an anti-erythropoietin producing hepatocellular carcinoma A2 (EphA2) antibody or binding domain thereof (see e.g., U.S. Patent No.9,676,864 to Bouchard et al., and U.S. Patent No. 10,406,225 to Zhou and Marks, which are hereby incorporate by reference in their entirety); an anti-epithelial cell adhesion molecule (EpCAM) antibody or binding domain thereof (see e.g., U.S. Patent No.8,637,017 to Gunnarsson et al., and U.S. Patent No.9,790,274 to Harvey et al., which are hereby incorporate by reference in their entirety); an anti-fetal acetylcholine receptor antibody or binding domain thereof (see e.g., WO2013011030 to Martinez-Martinez which is hereby incorporated by reference in its entirety); anti-folate receptor alpha (FRα) binding domain (see e.g., U.S. Patent No. 8,475,795 to O’Shannessy, which is hereby incorporated by reference in its entirety); an anti-ganglioside GD2 (GD2) antibody or binding domain thereof (see e.g., U.S. Patent App. Publ. No.20210189000 to Scholz et al., and U.S. Patent App. Publ. No. 20210179732 to Leusen et al., which are hereby incorporate by reference in their entirety); an anti-glypican-3 (GPC3) antibody or binding domain thereof (see e.g., U.S. Patent No. 9,217,033 to Terrett et al., which is hereby incorporated by reference in its entirety); an anti-guanylyl cyclase C (GUCY2C) antibody or binding domain thereof (see e.g., U.S. Patent Appl. Publ. No.20200010566 to Chang et al., which is hereby incorporated by reference in its entirety); an anti-human epidermal growth factor receptor 1 (HER1) antibody or binding domain thereof (see e.g., U.S. Patent Appl. Publ. No.20180100022 to Bossenmaier et al., which is hereby incorporated by reference in its entirety); an anti- human epidermal growth factor receptor 2 (ERBB2 / HER2) antibody or binding domain thereof (see e.g., U.S. Patent No. 11,046,771 to Goeij et al. and U.S. Patent No. 8,722,362 to Alper, which are hereby incorporate by reference in their entirety); an anti-intercellular adhesion molecule 1 (ICAM-1) antibody or binding domain thereof (see e.g., U.S. Patent Appl. Publ. No.20160280788 Hansson et al., and U.S. Patent No. 8,623,369 to Abulrob et al., which are hereby incorporate by reference in their entirety); an anti- interleukin 13 receptor α2 (IL13Rα2) antibody or binding domain thereof (see e.g., U.S. Patent Appl. Publ. No.20200181227 to Balyasnikova et al., which is hereby incorporated by reference in its entirety); an anti- interleukin 11 receptor α (IL11Rα) antibody or binding domain thereof (see e.g., U.S. Patent No.9,340,618 to Edwards et al., which is hereby incorporated by reference in its entirety); an anti-Kirsten rat sarcoma viral oncogene homolog (KRAS) antibody or binding domain thereof (see e.g., U.S. Patent No.11,174,314 to Zhou et al., which is hereby incorporated by reference in its entirety); an anti-L1-cell adhesion molecule (L1CAM) antibody or binding domain thereof (see e.g., U.S. Patent Appl. Publ. No.20220033494 to Hong et al., which is hereby incorporated by reference in its entirety); an anti-MAGE antibody or binding domain thereof (see e.g., U.S. Patent No.8,987,423 to Bergeron et al., and U.S. Patent Appl. Publ. No.20140093514 to Esslinger et al., which are hereby incorporated by reference in their entirety); an anti-hepatocyte growth factor receptor (HGF receptor / MET) antibody or binding domain thereof (see e.g., U.S. Patent No. 8,609,090 to Burgess et al., and U.S. Patent No.8,545,839 to Goetsch et al., which are hereby incorporated by reference in their entirety); an anti-mucin 1 (MUC1) antibody or binding domain thereof (see e.g., U.S. Patent No. 7,183,388 to Denardo et al., and U.S. Patent No.8,951,526 to Yonezawa, which are hereby incorporated by reference in their entirety); an anti-mucin 16 (MUC16) antibody or binding domain thereof (see e.g., U.S. Patent No. 10,941,208 to Haber et al., which is hereby incorporated by reference in its entirety); an anti-mucin 17 (MUC17) antibody or binding domain thereof (see e.g., U.S. Patent Appl. Publ. No.20210130465 to Raum et al., which is hereby incorporated by reference in its entirety) an anti-natural killer group 2 member D (NKG2D) antibody or binding domain thereof (see e.g., U.S. Patent No. 10,526,409 to Urso et al., which is hereby incorporated by reference in its entirety); an anti-cancer / testis antigen 1 (CT6.1) antibody or binding domain thereof (see e.g., U.S. Patent Appl. Publ. No.20190382504, which is hereby incorporated by reference in its entirety); an anti-prostate stem cell antigen (PSCA) antibody or binding domain thereof (see e.g., U.S. Patent No.8,013,128 to Gudas et al., which is hereby incorporated by reference in its entirety); an anti-Wilms tumor 1 (WT-1) antibody or binding domain thereof (see e.g., U.S. Patent No. 11,192,957 to Benz et al., which is hereby incorporated by reference in its entirety); an anti-galectin 9 (Gal9) antibody or binding domain thereof (see e.g., U.S. Patent No.10,344,091 to Koide et al., which is hereby incorporated by reference in its entirety); an anti-program cell death 1 ligand 1 (PD-L1) antibody or binding domain thereof (see e.g., U.S. Patent No.9,988,452 to Freeman et al., which is hereby incorporated by reference in its entirety); an anti-trophoblast glycoprotein (5T4 oncofetal antigen) antibody or binding domain thereof (see e.g., U.S. Patent No.8,044,178 to Boghaert et al., which is hereby incorporated by reference in its entirety); an anti-folate receptor alpha (FOLR1) antibody or binding domainthereof (see e.g., U.S. Patent No.9,207,238 to Ando et al., which is hereby incorporated by reference in its entirety); and anti-tumor-associated calcium signal transducer 2 (trophoblast cell surface antigen 2; TROP2) antibody or binding domain thereof (see e.g., U.S. Patent No.11,192,954 to Tang et al., which is hereby incorporated by reference in its entirety).

[0245] In another embodiment, the tumor-associated antigen binding domain of the bispecific LTβR binding protein binds to a stromal associated antigen (SAA) of the tumor microenvironment (TME). Suitable SAAs include, without limitation, fibronectin (FN1), matrix metalloproteinase-2 (MMP2), platelet derived growth factor receptor-β (PDGFRβ), dickkopf-related protein 3 (DKK3), platelet-derived growth factor subunit B (PDGFB), NUAK family SNF1-like kinase 1 (NUAK1), fibroblast growth factor (FGF1), PDZ and LIM domain protein 4 (PDLIM4), gremlin 1(Grem1), and periostin (POSTN).

[0246] Binding proteins capable of binding these SAAs are readily known in the art and can readily be utilized as the second binding domain of the LTβR bispecific binding protein described herein. For example, and without limitation, the second binding domain may comprise an anti-fibronectin antibody or binding domain thereof (see e.g., U.S. Patent Appl. Publ. No.20100248262 to Kato et al., which is hereby incorporated by reference in its entirety), an anti-matrix metalloproteinase-2 antibody or binding domain thereof (see e.g., U.S. Patent No. 8,013,125 to Devy which is hereby incorporated by reference in its entirety), an anti-platelet derived growth factor receptor-β (PDGFRβ) antibody or binding domain thereof (see e.g., U.S. Patent No. 7,740,850 to Zhu et al., which is hereby incorporated by reference in its entirety), an anti-dickkopf-related protein 3 antibody or binding domain thereof (see e.g., U.S. Patent Appl. Publ. No.20210340232 to Hwang et al., which is hereby incorporated by reference in its entirety), an anti- platelet-derived growth factor subunit B antibody or binding domain thereof (see e.g., U.S. Patent No. 9,428,577 to Arch et al., which is hereby incorporated by reference in its entirety), an anti-NUAK family SNF1-like kinase 1 (NUAK1) antibody or binding domain thereof, an anti-fibroblast growth factor antibody or binding domain thereof (see e.g., U.S. Patent No. 8,410,250 to Ashkenazi et al., and U.S. Patent No. 8,481,168 to Weng et al., which are hereby incorporated by reference in their entirety), an anti-PDZ and LIM domain protein 4 (PDLIM4) antibody or binding domain thereof, an anti-gremlin 1 antibody or binding domain thereof (see e.g., U.S. Patent Appl. Publ. No. 20180057580 to Chalothorn et al., and U.S. Patent Appl. Publ. No.20210163586 to Dedi et al., which are hereby incorporated by reference in their entirety, and an anti-periostin antibody or binding domain thereof (see e.g., U.S. Patent No.8,372,957 to Taniyama et al., which is hereby incorporated by reference in its entirety).

[0247] In one embodiment, the multi-specific LTβR binding protein of the present disclosure is a bispecific LTβR binding protein that is monovalent for LTβR binding. For the LTβR binding domains described herein, it has been discovered that bispecific molecules comprising these LTβR binding domains in monovalent form (but not bivalent form) exhibit cross-linking dependent LTβR agonism. In other words, bispecific molecules comprising monovalent LTβR binding domains require binding of both the first and second binding domains to induce LTβR receptor clustering and achieve LTβR agonism. This bispecific construct, having monovalency for LTβR, is particularly beneficial for targeting LTβR agonism to aparticular tissue, such as the tumor microenvironment, because activity is dependent on binding of the first and second binding domains. Additionally, the LTβR binders disclosed herein were specifically screened and selected based on their binding to LTβR at a region, e.g., CRD4, that that does not inhibit endogenous LTβR ligand binding and signaling. Together these features of the LTβR binding proteins disclosed herein ensure that if a LTβR bispecific binding protein binds to LTβR outside of the targeted tumor microenvironment, (i) binding will not induce off-target LTβR signaling in the absence of the second binding domain binding to its target, and (ii) such binding will not block endogenous LTβR ligand (i.e., LIGHT and LTα1β2) signaling in the off-target tissue. These design features provide LTβR binding proteins having superior safety and efficacy properties relative to previously described LTβR binding proteins. Derivatives, Variants, and Mimetics

[0248] In one embodiment, the LTβR binding proteins described herein comprise one or more amino acid modifications in the heavy chain constant regions that improve half-life / stability or render the antibody more suitable for expression / manufacturability. In one embodiment, the LTβR binding protein is designed to prevent or reduce interaction with Fc receptors. In exemplary instances, the binding protein is a Stable Effector Functionless (SEFL) binding protein comprising a constant region that lacks the ability to interact with Fcγ receptors. The amino acid mutations and methods of making SEFL antibodies are known in the art, see, e.g., Liu et al., J. Biol. Chem.292: 1876-1883 (2016); and Jacobsen et al., J. Biol. Chem.292: 1865-1875 (2017), which are hereby incorporated by reference in their entirety. In exemplary aspects, an LTβR binding protein described herein is modified to comprise one or more of the following mutations, numbered according to the EU system: L242C, A287C, R292C, N297G, V302C, L306C, and / or K334C. In exemplary aspects, an LTβR binding protein described herein comprises an N297G substitution to form a SEFL binding protein. In exemplary aspects, an LTβR binding protein described herein comprises A287C, N297G, and L306C substitutions to form a SEFL binding protein. In other exemplary aspects, the LTβR binding protein comprises R292C, N297G, and V302C substitutions to form a SEFL2-2 antibody based molecule.

[0249] In one embodiment, the agonist LTβR binding proteins as described herein may comprise other half-life extension (HLE) modifications. In one embodiment, the HLE modification occurs in the heavy chain constant region and comprises one or more of the following amino acid substitutions, numbered according to the EU system: M252Y, S254T, and T256E. In exemplary instances, the LTβR binding proteins comprise one or two of M252Y, S254T, and T256E substitutions. In exemplary instances, the LTβR binding proteins of the present disclosure comprise all three of M252Y, S254T, and T256E. In one embodiment, the HLE modification occurs in the heavy chain constant region and comprises one or more of the following substitutions, numbered according to the EU system: L309D, Q311H, and N434S. In exemplary instances, the LTβR binding proteins of the present disclosure comprise one, two or all three of the L309D, Q311H, and N434S substitutions. In exemplary instances, the LTβR binding proteins compriseall three of L309D, Q311H, and N434S substitutions. In one embodiment, the LTβR binding proteins disclosed herein comprise SEFL or SEFL2-2 modifications in combination with any of the herein described HLE modifications.

[0250] In certain embodiments, variants of the agonist LTβR binding protein include glycosylation variants wherein the number and / or type of glycosylation site has been altered compared to the amino acid sequences of a parent polypeptide. In certain embodiments, variants comprise a greater or a lesser number of N-linked glycosylation sites than the native protein. Alternatively, substitutions which eliminate this sequence will remove an existing N-linked carbohydrate chain. Also provided is a rearrangement of N- linked carbohydrate chains wherein one or more N-linked glycosylation sites (typically those that are naturally occurring) are eliminated and one or more new N-linked sites are created. Additional binding protein variants include cysteine variants wherein one or more cysteine residues are deleted from or substituted for another amino acid (e.g., serine) as compared to the parent amino acid sequence. Cysteine variants may be useful when antibodies must be refolded into a biologically active conformation such as after the isolation of insoluble inclusion bodies. Cysteine variants generally have fewer cysteine residues than the native protein, and typically have an even number to minimize interactions resulting from unpaired cysteines.

[0251] In one embodiment, the agonist LTβR binding proteins disclosed herein (e.g., agonist LTβR antibodies and bispecific agonist LTβR binding proteins) include post translationally modified variants. For example, in one embodiment the agonist LTβR binding proteins comprising a heavy chain, have the C- terminal lysine residue deleted.

[0252] Other desired amino acid substitutions (whether conservative or non-conservative) and deletions can be determined by those skilled in the art at the time such substitution or deletion is desired. In certain embodiments, amino acid substitutions can be used, for example, to identify important residues of a binding protein associated with function, to increase or decrease the affinity of the antibodies to the target of interest described herein, reduce susceptibility to proteolysis, reduce susceptibility to oxidation, alter binding affinity for forming protein complexes, and / or confer or modify other physiochemical or functional properties on such polypeptides. According to certain embodiments, single or multiple amino acid substitutions (in certain embodiments, conservative amino acid substitutions) may be made in the naturally-occurring sequence (in certain embodiments, in the portion of the polypeptide outside the domain(s) forming intermolecular contacts). In certain embodiments, a conservative amino acid substitution typically may not substantially change the structural characteristics of the parent sequence (e.g., a replacement amino acid should not tend to break a helix that occurs in the parent sequence or disrupt other types of secondary structure that characterizes the parent sequence). Examples of art-recognized polypeptide secondary and tertiary structures are described in Proteins, Structures and Molecular Principles (Creighton, Ed., W. H. Freeman and Company, New York (1984)); Introduction to Protein Structure (C. Branden and J. Tooze, eds., Garland Publishing, New York, N.Y. (1991)); and Thornton et al. Nature 354:105 (1991), which are each incorporated herein by reference.Nucleic Acid Molecules Encoding LTβR Binding Proteins

[0253] The present disclosure further provides nucleic acid molecules comprising a nucleotide sequence encoding an agonist LTβR binding protein of the present disclosure. A “nucleic acid molecule” as used herein encompasses polynucleotides and oligonucleotides and generally refers to a polymer of DNA or RNA, or modified forms thereof, which can be single-stranded or double-stranded, synthesized or obtained (e.g., isolated and / or purified) from natural sources, which can contain natural, non-natural or altered nucleotides, and which can contain a natural, non-natural or altered inter-nucleotide linkage, such as a phosphoroamidate linkage or a phosphorothioate linkage, instead of the phosphodiester found between the nucleotides of an unmodified oligonucleotide. The nucleic acid molecule can comprise any nucleotide sequence which encodes any of the agonist LTβR binding proteins of the present disclosure. In some embodiments, the nucleic acid does not comprise any insertions, deletions, inversions, and / or substitutions. In other embodiments, the nucleic acid comprises one or more insertions, deletions, inversions, and / or substitutions.

[0254] In some aspects, the nucleic acid molecules of the present disclosure are recombinant. As used herein, the term “recombinant” refers to molecules that are constructed outside living cells by joining natural or synthetic nucleic acid segments using laboratory methods to form nucleic acid molecules that are not otherwise found in nature.

[0255] The nucleic acid molecules of the present disclosure in some aspects are constructed based on chemical synthesis and / or enzymatic ligation reactions using procedures known in the art. See, for example, Sambrook et al., Molecular Cloning: A Laboratory Manual. 3rd ed., Cold Spring Harbor Press, Cold Spring Harbor, NY 2001; and Ausubel et al., Current Protocols in Molecular Biology, Greene Publishing Associates and John Wiley & Sons, NY, 1994. For example, a nucleic acid molecule can be chemically synthesized using naturally occurring nucleotides or variously modified nucleotides designed to increase the biological stability of the molecules or to increase the physical stability of the duplex formed upon hybridization (e.g., phosphorothioate derivatives and acridine substituted nucleotides). Examples of modified nucleotides that can be used to generate the nucleic acids include, but are not limited to, 5- fluorouracil, 5-bromouracil, 5-chIorouracil, 5-iodouracil, hypoxanthine, xanthine, 4-acetylcytosine, 5- (carboxyhydroxymethyl) uracil, 5-carboxymethylaminomethyl-2-thiouridme, 5- carboxymethylaminomethyluracil, dihydrouracil, beta-D-galactosylqueosine, inosine, N6- isopentenyladenine, 1-methylguanine, 1-methylinosine, 2,2-dimethylguanine, 2-methyladenine, 2- methylguanine, 3-methylcytosine, 5-methylcytosine, N -substituted adenine, 7-methylguanine, 5- methylammomethyluracil, 5- methoxyaminomethyl-2-thiouracil, beta-D-mannosylqueosine, 5'- methoxycarboxymethyluracil, 5-methoxyuracil, 2-methylthio-N6-isopentenyladenine, uracil- 5-oxyacetic acid (v), wybutoxosine, pseudouratil, queosine, 2-thiocytosine, 5-methyl-2- thiouracil, 2-thiouracil, 4- thiouracil, 5-methyluracil, uracil-5-oxyacetic acid methylester, 3- (3-amino-3-N-2-carboxypropyl) uracil, and 2,6-diaminopurine.

[0256] In one embodiment, the nucleic acid molecule comprises one or more polynucleotides that encode all or part of an agonist LTβR binding protein, for example, one or both chains of a binding protein as disclosed herein. The polynucleotide can be any length as appropriate for the desired use or function, and can be operably coupled to one or more additional sequences, for example, regulatory sequences, and / or be part of a larger nucleic acid molecule, for example, a vector. A polynucleotide is “operably coupled” or “operably linked” to a regulatory sequence if the regulatory sequence affects the expression (e.g., the level, timing, or location of expression) of the polynucleotide sequence. The polynucleotide molecule can be single-stranded or double-stranded and can comprise RNA and / or DNA nucleotides, and artificial variants thereof (e.g., peptide nucleic acids).

[0257] In one embodiment, a polynucleotide of the present disclosure encodes an agonist LTβR binding protein disclosed supra and comprises a sequence encoding any one, any two, any three, any four, any five, or any six of the CDRs described supra, including the heavy chain CDRs provided in Tables 2, 6, and 10, and the light chain CDRs provided in Tables 3, 7 and 11.

[0258] In one embodiment, polynucleotide molecules of the present disclosure comprise a nucleotide sequence encoding a VH domain and a VL domain of an LTβR binding protein that binds to the CRD4 of LTβR. Accordingly, in one embodiment, the polynucleotide molecule comprises a nucleotide sequence encoding a VH and VL domain selected from: a VH amino acid sequence of SEQ ID NO: 119 and a VL amino acid sequence of SEQ ID NO: 120; a VH amino acid sequence of SEQ ID NO: 121 and a VL amino acid sequence of SEQ ID NO: 122; a VH amino acid sequence of SEQ ID NO: 123 and a VL amino acid sequence of SEQ ID NO: 124; a VH amino acid sequence of SEQ ID NO: 125 and a VL amino acid sequence of SEQ ID NO: 126; a VH amino acid sequence of SEQ ID NO: 127 and a VL amino acid sequence of SEQ ID NO: 128; a VH amino acid sequence of SEQ ID NO: 129 and a VL amino acid sequence of SEQ ID NO: 130; a VH amino acid sequence of SEQ ID NO: 131 and a VL amino acid sequence of SEQ ID NO: 132; a VH amino acid sequence of SEQ ID NO: 133 and a VL amino acid sequence of SEQ ID NO: 134; a VH amino acid sequence of SEQ ID NO: 135 and a VL amino acid sequence of SEQ ID NO: 136; a VH amino acid sequence of SEQ ID NO: 137 and a VL amino acid sequence of SEQ ID NO: 138; a VH amino acid sequence of SEQ ID NO: 139 and a VL amino acid sequence of SEQ ID NO: 140; a VH amino acid sequence of SEQ ID NO: 141 and a VL amino acid sequence of SEQ ID NO: 142; a VH amino acid sequence of SEQ ID NO: 143 and a VL amino acid sequence of SEQ ID NO: 144; a VH amino acid sequence of SEQ ID NO: 145 and a VL amino acid sequence of SEQ ID NO: 146; a VH amino acid sequence of SEQ ID NO: 147 and a VL amino acid sequence of SEQ ID NO: 148; a VH amino acid sequence of SEQ ID NO: 149 and a VL amino acid sequence of SEQ ID NO: 150; a VH amino acid sequence of SEQ ID NO: 151 and a VL amino acid sequence of SEQ ID NO: 152; a VH amino acid sequence of SEQ ID NO: 153 and a VL amino acid sequence of SEQ ID NO: 154; a VH amino acid sequence of SEQ ID NO: 155 and a VL amino acid sequence of SEQ ID NO: 156; and a VH amino acid sequence of SEQ ID NO: 157 and a VL amino acid sequence of SEQ ID NO: 158.

[0259] In one embodiment, the polynucleotide molecule of the present disclosure comprises a nucleotide sequence encoding a VH domain and a VL domain of an agonist LTβR binding protein that competes for binding to CRD4 of LTβR with the exemplary LTβR binders of LIBC219081 and LIBC218979. Accordingly, in one embodiment, the polynucleotide molecule comprises a nucleotide sequence encoding a VH and VL domain selected from: a VH amino acid sequence of SEQ ID NO: 401 and a VL amino acid sequence of SEQ ID NO: 402; a VH amino acid sequence of SEQ ID NO: 403 and a VL amino acid sequence of SEQ ID NO: 404; a VH amino acid sequence of SEQ ID NO: 405 and a VL amino acid sequence of SEQ ID NO: 406; a VH amino acid sequence of SEQ ID NO: 407 and a VL amino acid sequence of SEQ ID NO: 408; a VH amino acid sequence of SEQ ID NO: 409 and a VL amino acid sequence of SEQ ID NO: 410; a VH amino acid sequence of SEQ ID NO: 411 and a VL amino acid sequence of SEQ ID NO: 412; a VH amino acid sequence of SEQ ID NO: 413 and a VL amino acid sequence of SEQ ID NO: 414; a VH amino acid sequence of SEQ ID NO: 415 and a VL amino acid sequence of SEQ ID NO: 416; a VH amino acid sequence of SEQ ID NO: 417 and a VL amino acid sequence of SEQ ID NO: 418; a VH amino acid sequence of SEQ ID NO: 419 and a VL amino acid sequence of SEQ ID NO: 420; a VH amino acid sequence of SEQ ID NO: 421 and a VL amino acid sequence of SEQ ID NO: 422; a VH amino acid sequence of SEQ ID NO: 423 and a VL amino acid sequence of SEQ ID NO: 424; a VH amino acid sequence of SEQ ID NO: 425 and a VL amino acid sequence of SEQ ID NO: 426; a VH amino acid sequence of SEQ ID NO: 427 and a VL amino acid sequence of SEQ ID NO: 428; a VH amino acid sequence of SEQ ID NO: 429 and a VL amino acid sequence of SEQ ID NO: 430; a VH amino acid sequence of SEQ ID NO: 431 and a VL amino acid sequence of SEQ ID NO: 432; a VH amino acid sequence of SEQ ID NO: 433 and a VL amino acid sequence of SEQ ID NO: 434; a VH amino acid sequence of SEQ ID NO: 435 and a VL amino acid sequence of SEQ ID NO: 436; a VH amino acid sequence of SEQ ID NO: 437 and a VL amino acid sequence of SEQ ID NO: 438; a VH amino acid sequence of SEQ ID NO: 439 and a VL amino acid sequence of SEQ ID NO: 440; a VH amino acid sequence of SEQ ID NO: 441 and a VL amino acid sequence of SEQ ID NO: 442; a VH amino acid sequence of SEQ ID NO: 443 and a VL amino acid sequence of SEQ ID NO: 444; a VH amino acid sequence of SEQ ID NO: 445 and a VL amino acid sequence of SEQ ID NO: 446; a VH amino acid sequence of SEQ ID NO: 447 and a VL amino acid sequence of SEQ ID NO: 448; a VH amino acid sequence of SEQ ID NO: 449 and a VL amino acid sequence of SEQ ID NO: 450; a VH amino acid sequence of SEQ ID NO: 451 and a VL amino acid sequence of SEQ ID NO: 452; a VH amino acid sequence of SEQ ID NO: 453 and a VL amino acid sequence of SEQ ID NO: 454; a VH amino acid sequence of SEQ ID NO: 455 and a VL amino acid sequence of SEQ ID NO: 456; a VH amino acid sequence of SEQ ID NO: 457 and a VL amino acid sequence of SEQ ID NO: 458; a VH amino acid sequence of SEQ ID NO: 459 and a VL amino acid sequence of SEQ ID NO: 460; a VH amino acid sequence of SEQ ID NO: 461 and a VL amino acid sequence of SEQ ID NO: 462; a VH amino acid sequence of SEQ ID NO: 463 and a VL amino acid sequence of SEQ ID NO: 464; a VH amino acid sequence of SEQ ID NO: 465 and a VL amino acid sequence of SEQ ID NO: 466; a VH amino acid sequence of SEQ ID NO: 467 and a VL amino acid sequence of SEQ ID NO: 468; a VH amino acid sequence of SEQ ID NO: 469 and a VLamino acid sequence of SEQ ID NO: 470; a VH amino acid sequence of SEQ ID NO: 471 and a VL amino acid sequence of SEQ ID NO: 472; and a VH amino acid sequence of SEQ ID NO: 473 and a VL amino acid sequence of SEQ ID NO: 474.

[0260] In one embodiment, the polynucleotide molecule of the present disclosure comprises a nucleotide sequence encoding a VH domain and a VL domain of an agonist LTβR binding protein that binds human LTβR. Accordingly, in one embodiment, the polynucleotide comprises a nucleotide sequence encoding a VH and VL domain selected from: a VH amino acid sequence of SEQ ID NO: 644 and a VL amino acid sequence of SEQ ID NO: 645; a VH amino acid sequence of SEQ ID NO: 646 and a VL amino acid sequence of SEQ ID NO: 647; a VH amino acid sequence of SEQ ID NO: 648 and a VL amino acid sequence of SEQ ID NO: 649; a VH amino acid sequence of SEQ ID NO: 650 and a VL amino acid sequence of SEQ ID NO: 651; a VH amino acid sequence of SEQ ID NO: 652 and a VL amino acid sequence of SEQ ID NO: 653; a VH amino acid sequence of SEQ ID NO: 654 and a VL amino acid sequence of SEQ ID NO: 655; a VH amino acid sequence of SEQ ID NO: 656 and a VL amino acid sequence of SEQ ID NO: 657; a VH amino acid sequence of SEQ ID NO: 658 and a VL amino acid sequence of SEQ ID NO: 659; a VH amino acid sequence of SEQ ID NO: 660 and a VL amino acid sequence of SEQ ID NO: 661; a VH amino acid sequence of SEQ ID NO: 662 and a VL amino acid sequence of SEQ ID NO: 663; a VH amino acid sequence of SEQ ID NO: 664 and a VL amino acid sequence of SEQ ID NO: 665; a VH amino acid sequence of SEQ ID NO: 666 and a VL amino acid sequence of SEQ ID NO: 667; a VH amino acid sequence of SEQ ID NO: 668 and a VL amino acid sequence of SEQ ID NO: 669; a VH amino acid sequence of SEQ ID NO: 670 and a VL amino acid sequence of SEQ ID NO: 671; a VH amino acid sequence of SEQ ID NO: 672 and a VL amino acid sequence of SEQ ID NO: 673; a VH amino acid sequence of SEQ ID NO: 674 and a VL amino acid sequence of SEQ ID NO: 675; a VH amino acid sequence of SEQ ID NO: 676 and a VL amino acid sequence of SEQ ID NO: 677; a VH amino acid sequence of SEQ ID NO: 678 and a VL amino acid sequence of SEQ ID NO: 679; a VH amino acid sequence of SEQ ID NO: 680 and a VL amino acid sequence of SEQ ID NO:681; a VH amino acid sequence of SEQ ID NO: 682 and a VL amino acid sequence of SEQ ID NO: 683; a VH amino acid sequence of SEQ ID NO: 684 and a VL amino acid sequence of SEQ ID NO: 685; a VH amino acid sequence of SEQ ID NO: 686 and a VL amino acid sequence of SEQ ID NO: 687; a VH amino acid sequence of SEQ ID NO: 688 and a VL amino acid sequence of SEQ ID NO: 689; a VH amino acid sequence of SEQ ID NO: 690 and a VL amino acid sequence of SEQ ID NO: 691. Exemplary nucleic acid sequences encoding the VH and VL domains of the agonist LTβR binding proteins disclosed herein are provided in Table 14 below Table 14. Nucleic Acid Sequences of LTβR Binding Proteins

[0261] Changes can be introduced into the nucleic acid molecules disclosed herein by mutation, thereby leading to changes in the amino acid sequence of a polypeptide (e.g., the LTβR binding protein) that it encodes. Mutations can be introduced using any technique known in the art. In one embodiment, one or more particular amino acid residues are changed using, for example, a site-directed mutagenesis protocol. In another embodiment, one or more randomly selected residues is changed using, for example, a random mutagenesis protocol. Irrespective of how it is made, a mutant polypeptide can be expressed and screened for a desired property.

[0262] Mutations can be introduced into a nucleic acid molecule disclosed herein without significantly altering the biological activity of a polypeptide that it encodes. For example, one can make nucleotide substitutions leading to amino acid substitutions at non-essential amino acid residues. In one embodiment, a nucleotide sequence provided herein for one of the agonist LTβR binding proteins of the present disclosure is mutated such that it encodes an amino acid sequence comprising one or more deletions or substitutions of amino acid residues that are shown herein for the light chains and / or the heavy chains of the LTβR binding proteins of the present disclosure. In another embodiment, the mutagenesis inserts an amino acid adjacent to one or more amino acid residues shown herein for the light and / or heavy chains of the agonist LTβR binding proteins of the present disclosure. Alternatively, one or more mutations can be introduced into the nucleic acid molecules as disclosed herein that selectively changes the biological activity of the agonist LTβR binding protein that it encodes.

[0263] The nucleotide sequences of the agonist LTβR binding proteins of the present disclosure, encoding the corresponding amino acid sequences of the antibodies of the present disclosure, can be altered, for example, by random mutagenesis or by site-directed mutagenesis to create an altered polynucleotide comprising one or more particular nucleotide substitutions, deletions, or insertions as compared to the non- mutated polynucleotide. Examples of techniques for making such alterations are described in Walder et al., Gene 42:133 (1986); Bauer et al. Gene 37:73 (1985); Smith et al., 1981, Genetic Engineering: Principles and Methods, Plenum Press; and U.S. Patent Nos.4,518,584 and 4,737,462. These and other methods can be used to make, for example, derivatives of the LTβR binding proteins that have a desired property, forexample, increased affinity, avidity, or specificity for a desired target, increased activity or stability in vivo or in vitro, or reduced in vivo side-effects as compared to the underivatized antibody.

[0264] In another embodiment, the present disclosure provides vectors comprising a polynucleotide encoding an agonist LTβR binding protein as disclosed herein. A vector is a nucleic acid molecule used to introduce another nucleic acid into a cell. Examples of vectors include, but are not limited to, plasmids, viral vectors, non-episomal mammalian vectors and expression vectors, for example, recombinant expression vectors.

[0265] Vectors comprising a polynucleotide of the present disclosure can be prepared using standard recombinant DNA techniques described in, for example, Sambrook et al., Molecular Cloning: A Laboratory Manual.3rd ed., Cold Spring Harbor Press, Cold Spring Harbor, NY (2001); and Ausubel et al., Current Protocols in Molecular Biology, Greene Publishing Associates and John Wiley & Sons, NY (1994), which are hereby incorporated by reference in their entirety. Constructs of expression vectors, which are circular or linear, can be prepared to contain a replication system functional in a prokaryotic or eukaryotic host cell. Replication systems can be derived, e.g., from CoIEl, 2 μ plasmid, λ, SV40, bovine papilloma virus, and the like.

[0266] In one embodiment, the expression vector is a circular plasmid (see, e.g., Muthumani et al., “Optimized and Enhanced DNA Plasmid Vector Based In vivo Construction of a Neutralizing anti-HIV-1 Envelope Glycoprotein Fab,” Hum. Vaccin. Immunother. 9: 2253-2262 (2013), which is hereby incorporated by reference in its entirety). Plasmids can transform a target cell by integration into the cellular genome or exist extrachromosomally (e.g., autonomous replicating plasmid with an origin of replication). Exemplary plasmid vectors include, without limitation, pCEP4, pREP4, pVAX, pcDNA3.0, provax, or any other expression vector capable of expressing the heavy chain polypeptide and / or light chain polypeptide encoded by the recombinant nucleic acid sequence construct.

[0267] In another embodiment, the expression vector is a linear expression cassette (“LEC”). LECs are capable of being efficiently delivered to a subject via electroporation to express the heavy chain polypeptide and / or light chain polypeptide encoded by the recombinant nucleic acid sequence construct. The LEC may be any linear DNA devoid of a phosphate backbone. In one embodiment, the LEC does not contain any antibiotic resistance genes and / or a phosphate backbone. In another embodiment, the LEC does not contain other nucleic acid sequences unrelated to the desired gene expression.

[0268] The LEC may be derived from any plasmid capable of being linearized. The plasmid may be capable of expressing the heavy chain polypeptide and / or light chain polypeptide encoded by the recombinant nucleic acid sequence construct. Exemplary plasmids include, without limitation, pNP (Puerto Rico / 34), pM2 (New Caledonia / 99), WLV009, pVAX, pcDNA3.0, or provax, or any other expression vector capable of expressing the heavy chain polypeptide and / or light chain polypeptide encoded by the recombinant nucleic acid sequence construct.

[0269] In another embodiment, the expression vector is a viral vector. Suitable viral vectors that are capable of expressing full length antibodies or binding portions thereof include, for example, an adeno-associated virus (AAV) vector (see, e.g., Lewis et al., “Generation of Neutralizing Activity against Human Immunodeficiency Virus Type I in Serum by Antibody Gene Transfer,” J. Virol.76:8769-775 (2002); Fang et al., “An Antibody Delivery System for Regulated Expression of Therapeutic Levels of Monoclonal Antibodies In vivo,” Mol. Ther. 15(6): 1153-9 (2007); Buning et al, “Recent Developments in Adeno- associated Virus Vector Technology,” J. Gene Med.10:717-733 (2008), a lentivirus vector (see, e.g., Joseph et al., “Inhibition of In vivo HIV Infection in Humanized Mice by Gene Therapy of Human Hematopoietic Stem Cells with a Lentiviral Vector Encoding a Broadly Neutralizing anti-HIV Antibody,” J. Virol., 84: 6645-53 (2010); and Luo et al., “Engineering Human Hematopoietic Stem / Progenitor Cells to Produce a Broadly Neutralizing anti-HIV Antibody after In vivo Maturation to Human B Lymphocytes,” Blood 113: 1422-1431 (2009)), a retrovirus vector, a replication deficient adenovirus vector and a gutless adenovirus vector (see e.g., U.S. Pat. No. 5,872,005). Methods for generating and isolating adeno-associated viruses (AAVs) suitable for use as vectors are known in the art (see, e.g., Grieger & Samulski, “Adeno-associated Virus as a Gene Therapy Vector: Vector Development, Production and Clinical Applications,” Adv. Biochem. EnginBiotechnol.99: 119-145 (2005); Buning et al, “Recent Developments in Adeno-associated Virus Vector Technology,” J. Gene Med.10:717-733 (2008)).

[0270] The expression vector construct encoding the agonist LTβR binding protein as described herein can include the polynucleotide encoding a heavy chain polypeptide, a heavy chain variable region, or a fragment thereof. The heavy chain polypeptide can include a variable heavy chain (VH) region and / or at least one constant heavy chain (CH) region. The at least one constant heavy chain region can include a constant heavy chain region 1 (CH1), a constant heavy chain region 2 (CH2), and a constant heavy chain region 3 (CH3), and / or a hinge region. In some embodiments, the heavy chain polypeptide can include a VH region and a CH1 region. In other embodiments, the heavy chain polypeptide can include a VH region, a CH1 region, a hinge region, a CH2 region, and a CH3 region. The expression construct can also include a polynucleotide sequence encoding a light chain polypeptide, a light chain variable region, or a fragment thereof. The light chain polypeptide can include a variable light chain (VL) region and / or a constant light chain (CL) region.

[0271] In some aspects, the vector comprises one or more regulatory sequences. A “regulatory sequence” is a nucleic acid that affects the expression (e.g., the level, timing, or location of expression) of a nucleic acid to which it is operably linked. Exemplary regulatory sequences include transcription and translation initiation and termination codons, which are specific to the type of host (e.g., bacterium, fungus, plant, or animal) into which the vector is to be introduced, as appropriate and taking into consideration whether the vector is DNA- or RNA-based. Suitable regulatory sequences are selected on the basis of the host cells to be used for expression and are operably linked to the nucleic acid sequence to be expressed. Regulatory sequences include those that direct constitutive expression of a nucleotide sequence in many types of host cells (e.g., SV40 early gene enhancer, Rous sarcoma virus promoter and cytomegalovirus promoter), those that direct expression of the nucleotide sequence only in certain host cells (e.g., tissue- specific regulatory sequences), and those that direct inducible expression of a nucleotide sequence inresponse to particular treatment or condition (e.g., the metallothionein promoter in mammalian cells and the tet-responsive and / or streptomycin responsive promoter in both prokaryotic and eukaryotic systems (see e.g., Voss et al., Trends Biochem. Sci.11:287 (1986), Maniatis et al., Science 236:1237 (1987)). It will be appreciated by those skilled in the art that the design of the expression vector can depend on such factors as the choice of the host cell to be transformed, the level of expression of protein desired, etc. The expression vectors of the disclosure can be introduced into host cells to thereby produce proteins or peptides encoded by nucleic acids as described herein.

[0272] The expression construct can further encode a protease cleavage site. The protease cleavage site can be recognized by a protease or peptidase. The protease can be an endopeptidase or endoprotease, for example, but not limited to, furin, elastase, HtrA, calpain, trypsin, chymotrypsin, trypsin, and pepsin. In other embodiments, the protease can be a serine protease, a threonine protease, cysteine protease, aspartate protease, metalloprotease, glutamic acid protease, or any protease that cleaves an internal peptide bond (i.e., does not cleave the N-terminal or C-terminal peptide bond). The protease cleavage site can include one or more amino acid sequences that promote or increase the efficiency of cleavage.

[0273] The expression construct can further encode a linker sequence. The linker sequence can encode an amino acid sequence that spatially separates and / or links the one or more components of the expression construct (heavy chain and light chain components of the encoded antibody).

[0274] In one embodiment, a first expression vector construct encodes a heavy chain polypeptide that includes a VH and CH1, and a second expression vector construct encodes a light chain polypeptide that includes a VL and CL. An alternative arrangement includes a first vector encoding a heavy chain polypeptide ...

Claims

CLAIMS 1. An agonist Lymphotoxin β Receptor (LTβR) binding protein, wherein said binding protein binds an epitope comprising one or more residues of human LTβR cysteine-rich domain 4 (CRD4), wherein human LTβR CRD4 comprises amino acid residues 169-211 of SEQ ID NO: 1, and wherein said binding protein (a) does not inhibit LIGHT binding to LTβR or (b) does not inhibit LTα1β2 binding to LTβR.

2. The agonist LTβR binding protein of claim 1, wherein said binding protein (a) does not inhibit LIGHT binding to LTβR and (b) does not inhibit LTα1β2 binding to LTβR.

3. The agonist LTβR binding protein of claim 1, wherein the epitope comprises one or more residues of LTβR CRD4 at positions 197-209 of SEQ ID NO:

1.

4. The agonist LTβR binding protein of any one of claims 1–3, wherein inhibition of LIGHT and / or LTα1β2 binding to LTβR in the presence of the agonist LTβR binding protein is measured in a cell-based receptor-ligand binding assay, said assay comprising the steps of: incubating LTβR expressing cells with media containing the agonist LTβR binding protein for 1 hour; contacting the LTβR expressing cells, after said incubating, with a detectable LIGHT ligand, a detectable LTα1β2 ligand, or a combination thereof to allow the detectable ligands to bind to LTβR; detecting, after said contacting, the detectable LIGHT and / or LTα1β2 ligands bound to LTβR expressing cells in the presence of the LTβR binding protein; and identifying the agonist LTβR binding protein as not inhibiting LIGHT or LTα1β2 binding to LTβR based on said detecting.

5. The agonist LTβR binding protein of any one of claims 1–3, wherein said binding protein comprises: a heavy chain variable domain (VH) amino acid sequence having at least 90% sequence identity to SEQ ID NO: 121 or SEQ ID NO: 123 and a light chain variable domain (VL) amino acid sequence having at least 90% sequence identity to SEQ ID NO: 122 or SEQ ID NO:

124.

6. The agonist LTβR binding protein of any one of claims 1–3, wherein said binding protein comprises: a VH amino acid sequence having at least 90% sequence identity to SEQ ID NO: 121 and SEQ ID NO: 123, and a VL amino acid sequence having at least 90% sequence identity to SEQ ID NO: 122 and SEQ ID NO:124.

7. The agonist LTβR binding protein of any one of claims 1–3, wherein said binding protein comprises: a VH amino acid sequence having at least 95% sequence identity to SEQ ID NO: 121 and SEQ ID NO: 123, and a VL amino acid sequence having at least 95% sequence identity to SEQ ID NO: 122 and SEQ ID NO:

124.

8. The agonist LTβR binding protein of any one of claims 1–7, wherein said binding protein comprises: a VH comprising the HCDR1 amino acid sequence of X1YX3MX5(SEQ ID NO: 5), wherein X1is S or N; X3is G, D, or A; and X5is H or Y; the HCDR2 amino acid sequence of X1IX3YDX6X7X8X9Y X11X12DSVKG (SEQ ID NO: 6), wherein X1is A or V; X3is W or R; X6is E or G; X7is S, R, or T; X8is N or K; X9is K, R, or Q; X11is H or Y; and X12is A or E; and the HCDR3 amino acid sequence of X1RX3X4X5X6X7X8X9YYGX13X14V (SEQ ID NO: 7), wherein X1is D or E; X3is V, G, or I; X4is V, P, or A; X5is A, Y, or G; X6is R, A, G, or H; X7is P or G; X8is G, N, D, Y, A or H; X9is Y, T, or F; X13is L or M; and X14is D or A; a VL comprising the LCDR1 amino acid sequence of SGDX4LPX7X8YX10Y (SEQ ID NO: 62), wherein X4is A or T; X7is E, K, Q, D or N; X8is Q or H; and X10is A or T; the LCDR2 amino acid sequence of KDNERPS (SEQ ID NO: 63); and the LCDR3 amino acid sequence of QSX3DX5SX7X8YX10X11(SEQ ID NO: 64), wherein X3is A or T; X5is S, G, or N; X7is G or A; X8is T, S, or A; X10is V or M; and X11is I or V.

9. The agonist LTβR binding protein of any one of claims 1–8, wherein said binding protein comprises: a VH amino acid sequence having at least 90% sequence identity to SEQ ID NO: 121 and a HCDR1 amino acid sequence of SEQ ID NO: 5, a HCDR2 amino acid sequence of SEQ ID NO: 6, and a HCDR3 amino acid sequence of SEQ ID NO: 7; and a VL amino acid sequence having at least 90% sequence identity to SEQ ID NO: 122 and a LCDR1 amino acid sequence of SEQ ID NO: 62, a LCDR2 amino acid sequence of SEQ ID NO: 63, and a LCDR3 amino acid sequence of SEQ ID NO:

64.

10. The agonist LTβR binding protein of any one of claims 1–9, wherein said binding protein comprises: a VH comprising the HCDR1, HCDR2, and HCDR3 of amino acid sequences of SEQ ID NO: 11- 13, respectively, and a VL comprising the LCDR1, LCDR2, and LCDR3 amino acid sequences of SEQ ID NO: 68-70, respectively; or a VH comprising the HCDR1, HCDR2, and HCDR3 of amino acid sequences of SEQ ID NO: 8- 10, respectively, and a VL comprising the LCDR1, LCDR2, and LCDR3 amino acid sequences of SEQ ID NO: 65-67, respectively.

11. The agonist LTβR binding protein of any one of claims 1–10, wherein the binding protein is an antibody.

12. The agonist LTβR binding protein of any one of claims 1–10, wherein the binding protein is a bispecific binding protein.

13. A bispecific Lymphotoxin β Receptor (LTβR) binding protein, said binding protein comprising: an LTβR binding domain, wherein the LTβR binding domain binds an epitope comprising one or more residues of human LTβR cysteine-rich domain 4 (CRD4), wherein said LTβR CRD4 comprises amino acid residues 169-211 of SEQ ID NO: 1; and a tumor-associated antigen binding domain, wherein the bispecific binding protein agonizes LTβR activity, and (a) does not inhibit LIGHT binding to LTβR or (b) does not inhibit LT1α2β binding to LTβR.

14. The bispecific agonist LTβR binding protein of claim 13, wherein said binding protein (a) does not inhibit LIGHT binding to LTβR and (b) does not inhibit LTα1β2 binding to LTβR.

15. The bispecific agonist LTβR binding protein of claim 13, wherein the epitope comprises one or more residues of LTβR CRD4 at positions 197-209 of SEQ ID NO:

1.

16. The bispecific agonist LTβR binding protein of any one of claims 13–15, wherein inhibition of LIGHT and / or LTα1β2 binding to LTβR in the presence of the bispecific agonist LTβR binding protein is measured in a cell-based receptor-ligand binding assay, said assay comprising the steps of: incubating LTβR expressing cells with media containing the bispecific agonist LTβR binding protein for 1 hour; contacting the LTβR expressing cells, after said incubating, with a detectable LIGHT ligand, a detectable LTα1β2 ligand, or a combination thereof to allow the detectable ligands to bind to LTβR; detecting, after said contacting, the detectable LIGHT and / or LTα1β2 ligands bound to LTβR expressing cells in the presence of the bispecific agonist LTβR binding protein; and identifying the bispecific agonist LTβR binding protein as not inhibiting LIGHT or LTα1β2 binding to LTβR based on said detecting.

17. The bispecific agonist LTβR binding protein of claim 13, wherein the LTβR binding domain comprises: a VH amino acid sequence having at least 90% sequence identity to SEQ ID NO: 121 or SEQ ID NO: 123, and a VL amino acid sequence having at least 90% sequence identity to SEQ ID NO: 122 or SEQ ID NO: 124.

18. The bispecific agonist LTβR binding protein of claim 13, wherein the LTβR binding domain comprises: a VH amino acid sequence having at least 90% sequence identity to SEQ ID NO: 121 and SEQ ID NO: 123 and a VL amino acid sequence having at least 90% sequence identity to SEQ ID NO: 122 and SEQ ID NO:

124.

19. The bispecific agonist LTβR binding protein of claim 13, wherein the LTβR binding domain comprises: a VH amino acid sequence having at least 95% sequence identity to SEQ ID NO: 121 and SEQ ID NO: 123 and a VL amino acid sequence having at least 95% sequence identity to SEQ ID NO: 122 and SEQ ID NO: 124 20. The bispecific agonist LTβR binding protein of any one of claims 13–19, wherein the LTβR binding domain comprises: a VH comprising the HCDR1 amino acid sequence of X1YX3MX5(SEQ ID NO: 5), wherein X1is S or N; X3is G, D, or A; and X5is H or Y; the HCDR2 amino acid sequence of X1IX3YDX6X7X8X9Y X11X12DSVKG (SEQ ID NO: 6), wherein X1is A or V; X3is W or R; X6is E or G; X7is S, R, or T; X8is N or K; X9is K, R, or Q; X11is H or Y; and X12is A or E; and the HCDR3 amino acid sequence of X1RX3X4X5X6X7X8X9YYGX13X14V (SEQ ID NO: 7), wherein X1is D or E; X3is V, G, or I; X4is V, P, or A; X5is A, Y, or G; X6is R, A, G, or H; X7is P or G; X8is G, N, D, Y, A or H; X9is Y, T, or F; X13is L or M; and X14is D or A; a VL comprising the LCDR1 amino acid sequence of SGDX4LPX7X8YX10Y (SEQ ID NO: 62), wherein X4is A or T; X7is E, K, Q, D or N; X8is Q or H; and X10is A or T; the LCDR2 amino acid sequence of KDNERPS (SEQ ID NO: 63); and the LCDR3 amino acid sequence of QSX3DX5SX7X8YX10X11 (SEQ ID NO: 64), wherein X3 is A or T; X5 is S, G, or N; X7 is G or A; X8 is T, S, or A; X10is V or M; and X11is I or V.

21. The bispecific agonist LTβR binding protein of any one of claims 13–20, wherein said binding protein comprises: a VH amino acid sequence having at least 90% sequence identity to SEQ ID NO: 121 and a HCDR1 amino acid sequence of SEQ ID NO: 5, a HCDR2 amino acid sequence of SEQ ID NO: 6, and a HCDR3 amino acid sequence of SEQ ID NO: 7; and a VL amino acid sequence having at least 90% sequence identity to SEQ ID NO: 122 and a LCDR1 amino acid sequence of SEQ ID NO: 62, a LCDR2 amino acid sequence of SEQ ID NO: 63, and a LCDR3 amino acid sequence of SEQ ID NO:

64.

22. The bispecific agonist LTβR binding protein of claim 13, wherein the VH comprises the HCDR1, HCDR2, and HCDR3 of amino acid sequences of SEQ ID NO: 11-13, respectively, and the VL comprises the LCDR1, LCDR2, and LCDR3 amino acid sequences of SEQ ID NO: 68-70, respectively; orthe VH comprises the HCDR1, HCDR2, and HCDR3 of amino acid sequences of SEQ ID NO: 8- 10, respectively, and the VL comprises the LCDR1, LCDR2, and LCDR3 amino acid sequences of SEQ ID NO: 65-67, respectively.

23. The bispecific agonist LTβR binding protein of any one of claims 13–22, wherein the bispecific binding protein comprises only one LTβR binding domain.

24. The bispecific agonist LTβR binding protein of any one of claims 13–22, wherein the LTβR binding domain is a Fab.

25. The bispecific agonist LTβR binding protein of any one of claims 13–24, wherein binding protein comprises one tumor-associated antigen binding domain.

26. The bispecific agonist LTβR binding protein of claim 25, wherein the tumor-associated antigen binding domain is a Fab.

27. The bispecific agonist LTβR binding protein of any one of claims 13-24, wherein binding protein comprises two tumor-associated antigen binding domains.

28. The bispecific agonist LTβR binding protein of any one of claims 13–22, wherein the LTβR binding domain is a Fab and the tumor-associated antigen binding domain is a Fab.

29. The bispecific agonist LTβR binding protein of any one of claims 13–28, wherein the LTβR binding domain and the tumor-associated antigen binding domain are each coupled to an Fc portion.

30. The bispecific agonist LTβR binding protein of claim 29, wherein the Fc portion does not bind to an Fc-gamma receptor.

31. A polynucleotide encoding the agonist LTβR binding protein of any one of claims 1–12.

32. A vector comprising the polynucleotide of claim 31.

33. A host cell comprising the polynucleotide of claim 31 or the vector of claim 32.

34. One or more polynucleotides encoding the bispecific agonist LTβR binding protein of any one of claims 13–30.

35. A vector comprising the one or more polynucleotides of claim 34.

36. A host cell comprising the one or more polynucleotides of claim 34 or the vector of claim 35.

37. A pharmaceutical composition comprising:the agonist LTβR binding protein of any one of claims 1–12, the bispecific agonist LTβR binding protein of any one of claims 13–30, the one or more polynucleotides of claims 31 or 34, or the vector of claims 32 or 35, and a pharmaceutically acceptable carrier.

38. The agonist LTβR binding protein of any one of claims 1–12 for use as a medicament.

39. The agonist LTβR binding protein of any one of claims 1–12 for use in the treatment of cancer.

40. The agonist LTβR binding protein of any one of claims 1–12 for use in the manufacture of a medicament for the treatment of cancer 41. The bispecific agonist LTβR binding protein of any one of claims 13–30 for use as a medicament.

42. The bispecific agonist LTβR binding protein of any one of claims 13–30 for use in the treatment of cancer.

43. The bispecific agonist LTβR binding protein of any one of claims 13–30 for use in the manufacture of a medicament for the treatment of cancer.

44. A method of treating cancer in a subject, said method comprising: administering, to the subject having cancer, an agonist Lymphotoxin β Receptor (LTβR) binding protein, wherein said binding protein binds an epitope comprising one or more residues of human LTβR cysteine-rich domain 4 (CRD4), wherein human LTβR CRD4 comprises amino acid residues 169-211 of SEQ ID NO: 1, and wherein said binding protein (a) does not inhibit LIGHT binding to LTβR or (b) does not inhibit LTα1β2 binding to LTβR.

45. A method of treating cancer in a subject, said method comprising: administering, to the subject having cancer, a bispecific Lymphotoxin β Receptor (LTβR) binding protein, said binding protein comprising: an LTβR binding domain, wherein the LTβR binding domain binds an epitope comprising one or more amino acid residues of human LTβR cysteine-rich domain 4 (CRD4), wherein human LTβR CRD4 comprises amino acid residues 169-211 of SEQ ID NO: 1; and a tumor-associated antigen binding domain, wherein the bispecific binding protein agonizes LTβR activity, and (a) does not inhibit LIGHT binding to LTβR or (b) does not inhibit LT1α2β binding to LTβR.

46. The method of claim 44 or claim 45 further comprising: administering an immunomodulatory therapeutic in conjunction with said agonist LTβR binding protein or bispecific LTβR binding protein.

47. The method of claims 41 or 42, wherein the subject has a solid tumor selected from the group consisting of mesothelioma, a pancreatic tumor, an ovarian tumor, a lung tumor, an esophageal tumor, a gastric tumor, a hepatic tumor, a colorectal tumor, a cervical tumor, an endometrial tumor, a breast tumor, a renal tumor, a bladder tumor, a testicular tumor, a prostate tumor, a brain tumor, a bone tumor, and a head and neck tumor.

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