Abstract 1716: WTX-330, a conditionally activated IL-12 INDUKINE, releases IL-12 selectively in the tumor microenvironment to activate anti-tumor immune responses and induce regressions in mouse tumor models
Authors: Steiner Philipp , Brodkin Heather , Hicklin Dan , Ismail Nesreen , Morris Kristin , Nirschl Christopher , Salmeron Andres , Seidel-Dugan Cindy , Steuert Zoe , Sullivan Jenna , Winston William 
Published: July 2021

Abstract
Systemic therapy with proinflammatory immune modulators is a promising approach to treat cancer by activating innate and adaptive anti-tumor immunity. However, dose-limiting toxicities such as inflammation, cytokine release syndrome, and tissue damage rendered the strategy impractical for cytokines such as the cytotoxic T and NK cell activating interleukin 12 (IL-12). WTX-330 is a novel systemically delivered therapy with targeted intra-tumoral activation to deliver wild-type IL-12 in the tumor microenvironment identified using the Predator™ discovery platform. WTX-330 is a member of a class of inducible polypeptides (INDUKINE™ therapies) designed to be an inactive IL-12 pro-drug with a half-life extension (HLE) domain to support infrequent systemic administration. The INDUKINE™ polypeptide is kept inactive in the periphery via high affinity antibody blockade tethered to IL-12 via a tumor protease-sensitive linker. Cleavage of the same linker also removes the HLE domain producing a PK profile similar to wild-type IL-12. WTX-330 was selected as a lead molecule due to its beneficial in vitro profile. The mouse MC38 syngeneic tumor model was used to demonstrate strong anti-tumor activity of lead mouse INDUKINE™ polypeptides. Intraperitoneal (i.p.) administration of mouse WTX-330 led to complete regression of all MC38 tumors at dose levels which only moderately induced systemic IFNγ and were well tolerated by the mice. Similar efficacy was observed in CT26, B16F10, and EMT-6 syngeneic models. Importantly, wild-type IL-12, while active in mouse tumor models, was not tolerated by the mice after i.p. injection at equimolar amounts compared to the IL-12 INDUKINE™ polypeptide. Mouse WTX-330 strongly activated NK and CD8+ cell responses and induced APC and effector cell markers in MC38 tumors supporting a mechanism of action as described for wild-type IL-12. In non-human primates, WTX-330 was well tolerated at exposure levels which vastly exceeded the levels needed for efficacy in mice. In addition, plasma levels of free IL-12 after dosing with WTX-330 were very low compared to tolerated levels after treatment with wild-type IL-12. Ex vivo incubation of WTX-330 with numerous primary human tumors led to the rapid release of IL-12, while WTX-330 proved to be stable in human serum and normal tissues. Pharmacological and translational data obtained so far clearly support continued preclinical development with the goal of moving this innovative and differentiated engineered IL-12 therapy into human clinical testing.
Citation Format: Philipp Steiner, Heather Brodkin, Dan Hicklin, Nesreen Ismail, Kristin Morris, Christopher Nirschl, Andres Salmeron, Cindy Seidel-Dugan, Zoe Steuert, Jenna Sullivan, William Winston. WTX-330, a conditionally activated IL-12 INDUKINE, releases IL-12 selectively in the tumor microenvironment to activate anti-tumor immune responses and induce regressions in mouse tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1716.