IDO1 and cancer: While current preclinical research has focused primarily on these clinically established ICIs, which have broad clinical relevance across many cancer types, the emergence of novel targets such as lymphocyte activation gene-3, T cell immunoglobulin and ITIM domain (TIGIT), T cell immunoglobulin and mucin-domain containing-3 (TIM-3), and indoleamine 2,3-dioxygenase (IDO) calls for further investigation to evaluate their potential synergy with TRT [5].