Abstract 2055: WTX-330 is a conditionally activated IL-12 prodrug that fundamentally reprograms tumor infiltrating CD8+ T cells and drives tumor regression
Authors: Nirschl Christopher J. , Alderhold Pam , Brodkin Heather R. , Dwyer Connor J. , Hicklin Daniel J. , Ismail Nesreen , Salmeron Andres , Seidel-Dugan Cynthia , Steiner Philipp , Steuert Zoe , Sullivan Jenna , Winston William M. 
Published: June 2022

Abstract
Immune checkpoint inhibition (ICI) has established immunotherapy as the first line of treatment in a subset of cancers. However, there are still many patients and cancer types where ICI is not effective, representing a significant unmet clinical need for novel immunotherapies to expand the clinical options for patients. Interleukin 12 (IL-12) is a pleiotropic cytokine that drives naïve T cells towards a TH1 phenotype, activates NK cells and cytotoxic T cells, and strongly induces the expression of IFNγ by multiple cell types, making it an attractive pro-inflammatory cytokine for cancer immunotherapy. However, despite its demonstrated clinical benefits, poor pharmacokinetic properties and dose-limiting toxicities after systemic administration have greatly limited the use of IL-12 in the clinic. WTX-330 is a novel IL-12 pro-drug that is designed to harness the dysregulated protease activity of tumors to selectively deliver fully active IL-12 to the tumor microenvironment (TME). WTX-330 consists of wild-type IL-12 tethered to a high affinity antibody blockade domain and a half-life extension (HLE) domain via tumor protease-sensitive linkers. Following systemic administration, WTX-330 circulates as an inactive prodrug that is unable to bind to IL-12 receptors in normal tissues. When WTX-330 enters the tumor however, proteases found in the TME cleave the protease-sensitive linkers, releasing fully active IL-12 selectively in the tumor. WTX-330 is highly efficacious in murine syngeneic tumor models, leading to complete, CD8+ T cell dependent tumor regressions when MC38 tumor bearing mice were treated with a murine surrogate of WTX-330. Importantly, while murine WTX-330 was well tolerated by the mice, equimolar amounts of wild-type IL-12 was not, highlighting the tumor selective activity of the INDUKINE™ protein. Murine WTX-330 treatment of either MC38 or EMT6 tumor bearing mice increased the frequency of tumor infiltrating polyfunctional CD8+ T cells and activated tumor infiltrating NK cells in both models. In the EMT6 model, Geospatial NanoString analysis revealed significantly more tumor penetration by CD8+ T cells following murine WTX-330 treatment at multiple timepoints and demonstrated that systemic dosing with the IL-12 INDUKINE™ molecule resulted in IL-12 signaling by the tumor infiltrating CD8+ T cells. Furthermore, murine WTX-330 treatment fundamentally reprogrammed the metabolic program of tumor infiltrating CD8+ T cells, increasing both glycolysis and mitochondrial biogenesis, while also increasing TCR signaling and degranulation. Finally, ex vivo incubation of WTX-330 with various primary human tumors led to the release of active IL-12, while WTX-330 was stable in human serum and healthy human primary cells from various tissues. Together, these data support continued development of this innovative IL-12 therapy into clinical testing.
Citation Format: Christopher J. Nirschl, Pam Alderhold, Heather R. Brodkin, Connor J. Dwyer, Daniel J. Hicklin, Nesreen Ismail, Andres Salmeron, Cynthia Seidel-Dugan, Philipp Steiner, Zoe Steuert, Jenna Sullivan, William M. Winston. WTX-330 is a conditionally activated IL-12 prodrug that fundamentally reprograms tumor infiltrating CD8+ T cells and drives tumor regression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2055.