LAUSR

While Interleukin-2 (IL-2) has produced remarkable clinical efficacy in a fraction of cancer patients, its clinical use is limited by its narrow therapeutic index due to systemic and pleotropic activation of both inflammatory and suppressive lymphocytes. Numerous approaches to improve the specificity and activity profile of IL-2 are being evaluated. Using Tentarix’s propriety Tentacles™ platform, which is based on fully human stabilized antibody VH domains, we generated TNRX-257, a novel multispecific biologic that effectively blocks LAG3 while simultaneously delivering IL2Rγ/β agonism to LAG3+ cells in a highly conditional manner. LAG3 expression is restricted to antigen-experienced and tumor-reactive immune cells with little expression on peripheral PBMC or immune cells in normal tissues. TNRX-257 was designed to combine LAG3 inhibition with an IL2R agonist moiety to activate and expand LAG3+ tumor-reactive T cells in tumor microenvironment while enhancing their effector function and anti-tumor immunity with minimal systemic toxicity. TNRX-257 blocks the interaction of LAG3 with MHC-II and enhances TCR signaling with similar potency as Relatlimab. TNRX-257 also selectively induces pSTAT5 on LAG3+ immune cells with little activity on LAG3- immune cells, including resting human PBMCs. Moreover, the lower level of pSTAT5 (Emax) induced by TNRX-257 than IL-2 indicates TNRX-257 mediates its activity as a partial agonist, a phenotype that preserves stemness. TNRX-257 induces higher and preferential activation of CD8+ T cells over CD4+ T cells due to higher expression of LAG3 on CD8+ T cells than CD4+ T cells, particularly within the tumor microenvironment. Unlike an undirected IL-15 agonist that induced total CD8+ T cell proliferation, TNRX-257 selectively induced proliferation of LAG3+ CD8+ T cells in a human melanoma TIL stimulation assay without expansion of Tregs. TNRX-257 treatment also preserved the stem-like CD8+ population compared to the undirected IL-15 agonist. TNRX-257 showed in vitro and in vivo molecular stability, as well as good pharmacokinetic (PK) and pharmacodynamic (PD) properties. TNRX-257 induced robust anti-tumor efficacy when tested in early and established tumor models using melanoma A375-CMV-pp65 or colorectal cancer HT-29 cells in humanized mice. In contrast, the corresponding untargeted IL2Rγ/β Tentacle had no efficacy. Together, these data show that TNRX-257 has drug-like properties and elicits strong anti-tumor efficacy, supporting its clinical development. Citation Format: Rajesh K. Sharma, Jianying Dong, Natasha Del Cid, Yasamine Ghorbanian, Christina Carnevale, Christen Buetz, Matthew Lundberg, Glenn Capodagli, Jayd Hannah, Gavin Hong, Pricilla Walters, Arlene Sereno, Falene Chai, Abby Lin, James Furney, Wendy Zhang, Craig Pigott, Paul Kang, Michael Gallo, Margaret Karow, Stephen Demarest. TNRX-257, a novel multifunctional biologic effectively blocks LAG3 and conditionally delivers IL2Rg/b agonism to LAG3+ cells for robust anti-tumor immunity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2956.