A novel 'Seed-and-Boost' immunotherapy drives potent TCR-T cell expansion, tumor infiltration, and durable tumor control

Background: While TCR-engineered T cell therapies show promise in solid tumors, long-term efficacy is limited by insufficient in vivo expansion and persistence. Current strategies also face significant challenges in manufacturing and clinical management. We present a novel strategy combining low-dose TCR-T cells (Seed) with a TCR-targeted cytokine biologic (Boost) to drive selective in vivo expansion, enhance tumor infiltration, and sustain tumor-specific responses. We demonstrate this by targeting WT1-positive solid tumors using WT1-specific TCR-T cells plus CUE-102, a clinically validated ImmunoSTAT™ fusion protein enabling controlled TCR engagement and delivery of IL-2 to WT1-specific T cells. Methods: We generated a highly specific dual HLA (HLA-A:02:01 and HLA-A:02:07) targeting TCR against the WT1 37-45 antigen. Preclinical characterization of this TCR, engineered into human primary T cells, included potency assessment against various WT1-positive cancer cell lines and testing for antigen cross-reactivity and HLA alloreactivity. WT1-specific TCR-T cells were combined with CUE-102 to assess specific TCR-T cell expansion, anti-tumor efficacy, tumor infiltration, and long-term efficacy both in vitro and in various xenograft models using WT1-expressing ovarian and pancreatic cell lines. Results: WT1-specific TCR-T cells demonstrated potent in vitro cytotoxicity against HLA-A*02:01 and HLA-A*02:07 WT1-positive cancer cell lines. In addition, we observed a favorable safety profile with no antigen cross-reactivity or HLA alloreactivity. In combination with CUE-102, we observed high potency and sustained anti-tumor cell efficacy at very low effector to target cell ratios and a vigorous selective in vivo expansion of WT1-specific TCR-T cells. In xenograft models of WT1-positive ovarian and pancreatic cancers, the combination therapy led to significantly higher numbers of circulating TCR-T cells, enhanced tumor infiltration, and robust tumor control even at very low TCR-T cell doses, compared to TCR-T cell monotherapy. Furthermore, in animals with higher tumor burden, the combined treatment resulted in sustained tumor regression and significantly extended survival. Conclusion: Our data demonstrate that boosting with CUE-102 triggers robust in vivo expansion and activation of engineered TCR-T cells seed, resulting in effective anti-tumor responses, T cell persistence, and prolonged survival without additional cell engineering. This approach offers a potentially transformative solution for long-term benefits in solid tumor patients and can address cell therapy manufacturing and clinical management challenges by enabling the infusion of fewer seed TCR-T cells, eliminating the need for systemic IL-2 administration, and potentially avoiding toxic conditioning regimens.