Abstract Text: T cell factor-1 (TCF1) is a key transcription factor associated with stem-like CD8+ T cells, and tumor-infiltrating Tcf1+CD8+ T cells have been implicated in proliferative anti-tumor efficacy of the anti-programmed cell death protein-1 (𝛼-PD-1) targeted immunotherapy. Here, we screened gut microbial metabolites and identified a unique metabolite that promotes stem-like T cells. The metabolite increased the level of central memory CD8+ T cells (CD44hiCD62Lhi) and promoted a subset of Tcf1+CD8+ T cells in vitro. To improve the pharmacokinetics of the metabolite and prolong its in vivo circulation, we have developed a long-acting “prodrug 201” and engineered it into an orally available formulation. Orally administered prodrug 201 improved the anti-tumor efficacy of 𝛼-PD-1 therapy, exerting potent antitumor efficacy in multiple tumor models including CT26 colon carcinoma and B16F10 melanoma. Tumor microenvironment analysis revealed that the prodrug 201 combined with 𝛼-PD-1 therapy significantly increased the levels of T cells in tumor and lymph nodes as well as the ratio of M1 to M2 macrophages. These findings revealed that the gut microbial metabolites as a source of unique modulators of CD8 T cells. Further studies are underway to delineate the mechanism of interaction for prodrug 201-mediated induction of Tcf1+CD8+ T cells.
