Abstract 963: Evolved therapies specifically activate and expand endogenous γ;γ; T cells to remove the barriers to broadly effective immunotherapies

Abstract Live bacterial therapeutics have the potential to generate transformative outcomes for cancer patients. CAR-T cells are a synthetic attempt to combine B and T cell biology to maximize targeted killing and deliver abundant and active cells to overcome the limitations of endogenous immune cells. Although these therapies have provided some immunotherapy success, they are limited by practical challenges such as an inability to manufacture sufficient material, extreme cost, an inability to re-dose, and severe acute toxicities. In contrast, 𝛄;; T cells have emerged as an exciting alternative to CAR-T. Because they have evolved to fill a unique niche at the interface of the innate and adaptive immune system they may be a solution to the limitations of CAR-T. Where CAR-T cells carry the risk of GvHD, 𝛄;; T cells are MHC-independent, and possess multiple checkpoints that prevent killing healthy cells. The tumor microenvironment prevents CAR-T penetration, but resident 𝛄;; T cells exist within every tissue, awaiting activation and expansion. 𝛄;; T cell dominance of immunotherapy has so far been prevented by our inability to durably or repeatedly expand endogenous cells. Our solution to these limitations is to exploit the natural properties of Listeria monocytogenes to induce the proliferation and durable activation of endogenous 𝛄;; T cells. Our pre-clinical in vitro and in vivo data, combined with results from previous clinical studies show that Listeria expanded endogenous 𝛄;δ; T cell populations to >1x109 cells, orders of magnitude more than other approaches. Furthermore, Listeria-activated 𝛄;; T cells are uniquely cytotoxic, durable, and safe. They eliminate cancer cell lines in vitro at E:T ratios of ∼1, whereas antibody and cell therapies require E:T ratios >10. They down-regulate exhaustion markers and remain active for multiple rounds of cell killing, and they express 5-fold less IL-6, the primary indicator of CRS toxicity. Listeria-activated 𝛄;; T cells are more abundant, cytotoxic, durable, and less toxic than CAR-T, and they can be re-dosed for persistent efficacy. To improve on the safety profile of previous Listeria-based therapeutics, we have generated a quadruple attenuated strain (QUAIL) that cannot grow extracellularly. Our in vitro and in vivo data show that QUAIL cannot grow in human serum or on stents or indwelling ports, where previous therapeutic strains thrived, and cannot persist in RAG1 -/- mice that lack T and B cells, all while maintaining the 𝛄;δ; T cell activation and expansion that was observed in cancer patients. QUAIL will enter the clinic in multiple myeloma in 2025, and we believe that this novel therapy will generate meaningful and lasting cancer remission where current cell therapies have provided a glimpse of what’s possible. Citation Format: Jonathan W. Kotula, Ed Lemmens, Rafael Rivera-Lugo, Ying Feng, Daniel A. Portnoy. Evolved therapies specifically activate and expand endogenous γ;γ; T cells to remove the barriers to broadly effective immunotherapies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 963.