Afatinib exerts an inhibitory effect on T cell-mediated cytotoxicity.

Adoptive T cell therapy has shown significant efficacy in cancer treatment, especially in hematologic malignancies, and is increasingly being explored for solid cancers. Combining T cell therapy with conventional treatments holds promise for enhancing therapeutic effects. In this study, we conducted an in vitro inhibitor screening to evaluate the effects of various inhibitors on T cell-mediated cytotoxic activity against cancer cells. Among the candidates, we identified afatinib as an immunosuppressive agent that attenuates T cell cytotoxic activity by reducing interferon-γ (IFN-γ) secretion and suppressing T cell activation. Notably, this IFN-γ reduction was independent of T cell proliferation. RNA-seq analysis revealed that afatinib downregulated the T cell receptor (TCR) pathway signature. RT-qPCR demonstrated a dose-dependent suppression of IFNG mRNA expression in afatinib-treated T cells. Furthermore, afatinib impaired tumor rejection in an immunological memory mouse model that had been previously cured by anti-PD-L1 therapy, suggesting that afatinib may inhibit the function of effector memory T cells. Collectively, our findings highlight afatinib's potential to impair T cell effector functions, indicating that strategic consideration is essential when combining epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs), including afatinib, with adoptive T cell therapies.