Dual blockade of CTLA-4 or PD-1/PD-L1 combined with IDO inhibition proved to be highly effective in enhancing the TME-infiltration with CD8+ T cells [139]; however, a phase II l trial, Check-Mate 9UT (NCT03519256), designed to assess the anti-tumor efficacy of an oral IDO inhibitor, BMS-986205, in combination with nivolumab in patients with high-risk BCG-unresponsive NMIBC, was discontinued due to poor enrollment [140]. Here, IDO1 is linked to neoplasm.