werewolf Therapeutics, Inc. announced that a poster describing interim first-in-human clinical results from initial monotherapy dose-escalation cohorts in the ongoing Phase 1/1b study of WTX-124 will be presented at the Society for Immunotherapy of Cancer's (SITC) 38th Annual Meeting, taking place November 1-5, 2023 in San Diego, California. This Phase 1/1b, multi-center, open-label clinical trial is designed to evaluate WTX-124 as a monotherapy and in combination with KEYTRUDA® (pembrolizumab) in patients with immunotherapy sensitive advanced or metastatic solid tumors who have failed standard of care, including prior checkpoint inhibitor therapy. As of June 22, 2023, 11 patients with relapsed/refractory solid tumors, including non-small cell lung cancer, cutaneous melanoma and renal cell carcinoma were treated with WTX-124 in three monotherapy dose escalation cohorts of 1, 3 and 6 mg administered intravenously every two weeks.

WTX-124 was well-tolerated with no dose limiting toxicities at doses up to 6mg. Pharmacokinetic data as of June 22, 2023, demonstrated WTX-124 sustained prodrug exposure in plasma with low levels of active IL-2. These results support the potential of WTX-124 to deliver a potent, wild-type IL-2 to the tumor microenvironment in patients with solid tumors with limited toxicities. Tumor growth over time was measured in mice bearing syngeneic tumors treated with either mWTX-330 (a chimeric IL-12 containing INDUKINE TM molecule) or WTX-124 (a human IL-2 containing INDUKINE molecule) using various techniques, including high-plex immunofluorescence, resulting in significant remodeling of immune cell populations found within the tumor tissue and simultaneously increased immune cell infiltration generating a potent activation of effector cells.

These results were further amplified in combination with PD-1 pathway inhibitors, highlighting the potential for INDUKINE TM treatments to improve the effects of checkpoint inhibition therapies. Human IL-21 receptor knock-in (hIL-21R KI) mice bearing syngeneic tumors were treated with WTX-712, an IL-21 INDUKINETM molecule, or half-life extended human IL-21 to monitor tumor growth and body weight over time via flow cytometry, tissue pharmacokinetics and high-plex immunofluorescence. WTX-712 exhibited activity with an expanded therapeutic window compared to half-life extended IL-21 in mouse syngeneic tumor models including complete regressions and protection against tumor growth upon rechallenge.

The ability of INDUKINE molecules to improve the engraftment and antitumor activity of adoptive cell therapy (ACT) products was evaluated using a pmel-1 transgenic mouse model and a human CD19 CAR-T cell model. The combination of pmel-1 ACT and INDUKINETM polypeptides enhanced antitumor activity and animal survival compared to either pmel-1 or INDUKINE treatment alone, including increased donor cell engraftment and persistence of long-term effector memory T cells in both the periphery and the tumor microenvironment. The potential benefits of full activation of IL-2 were evaluated to determine antitumor response in syngeneic tumor models of WTX-124 as compared to non-alpha forms of IL-2 designed to reduce dose limiting toxicities associated with current cytokine therapy.

Systemic administration of WTX-124 resulted in robust antitumor immunity and preferentially activated tumor-infiltrating immune cells as compared to a non-alpha IL-2 version of the INDUKINE demonstrating that the full activity of IL-2 contained in WTX-124 is required to activate potent antitumor responses. A pharmacokinetic model was developed to evaluate peripheral and tumor lymphocyte IL-2 receptor occupancy for tumor-activated IL-2 molecules such as WTX-124 as compared to non-alpha IL-2 molecules. WTX-124 was found to be more likely to improve the therapeutic index by maximizing receptor occupancy on tumor-infiltrating CD8+ T cells than comparable doses of non-alpha IL-2 molecules and substantially higher doses of the non-alpha IL-2 molecule were required to attain the same receptor occupancy.