Abstract 4078: WTX-712, a conditionally active IL-21 INDUKINETM molecule, induces a strong anti-tumor phenotype through a differentiated mechanism

Abstract Despite great strides seen recently in the development of immunotherapies such as immune checkpoint inhibitors (ICI), many patients do not respond or acquire resistance, highlighting a need for alternative immunotherapies. As potent immunomodulators, cytokines have been explored as treatments for cancer, but their use has been limited due to toxicity and poor pharmacokinetics (PK). One of these key cytokines, interleukin 21 (IL-21), is a pluripotent cytokine that activates anti-tumor T cell responses, induces B cell activation, and promotes generation and maintenance of germinal centers and tertiary lymphoid structures. IL-21 acts on a broader range of cells and does not induce vascular leak syndrome compared to IL-2, another common-gamma chain family member. Half-life extended IL-21 (IL-21-HLE) drives robust anti-tumor activity in several syngeneic tumor mouse models. Of particular interest, IL-21-HLE showed superior anti-tumor activity compared to IL-2-HLE in the EMT-6 and Renca models, both of which are highly resistant to anti-PD-1/PD-L1 treatment. Although IL-21-HLE and IL-2-HLE induced a similar frequency of tumor infiltrating CD8+ T cells, IL-21-HLE treatment led to higher polyfunctionality in CD8+ T cells than IL-2-HLE treatment. Of note, IL-21-HLE induced greater amounts of effector cytokines, Granzyme B and perforin, than IL-2-HLE. Transcriptomic analysis revealed that IL-21 drives upregulation of a type I IFN signature in the tumor promoting an anti-tumorigenic microenvironment. Clinical activity of IL-21 has been hampered by poor PK and adverse events at dose levels associated with signs of efficacy. To overcome these limitations Werewolf Therapeutics has developed WTX-712, an IL-21 INDUKINETM molecule, which contains wild-type human IL-21, an inactivation domain, and a half-life extension domain tethered together by protease sensitive linkers. In preclinical studies with mouse syngeneic tumor models, WTX-712 is inactive in the periphery, and wild-type IL-21 is selectively released within the tumor, resulting in anti-tumor efficacy with an expanded therapeutic window compared to IL-21-HLE. Anti-tumor efficacy was linked to expansion and activation of tumor infiltrating CD8 T cells with increased polyfunctionality. We will show additional mechanistic data evaluating the effect of WTX-712 dosing on immune populations, including tumor spatial profiling using different models. Citation Format: Jenna M. Sullivan, Pamela A. Aderhold, Heather R. Brodkin, Celesztina Nagy-Domonkos, Kyriakos Economides, Daniel J. Hicklin, Nesreen Ismail, Yuka Lewis, Cynthia Seidel-Dugan, William M. Winston, Andres Salmeron. WTX-712, a conditionally active IL-21 INDUKINETM molecule, induces a strong anti-tumor phenotype through a differentiated mechanism abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 4078.