Background: Immune checkpoint inhibitors, including nivo (anti–PD-1), have demonstrated favorable tolerability and efficacy profiles, ushering in a new treatment (tx) paradigm for advanced bladder cancer (advBC). However, an unmet need exists for new effective tx options in earlier stages of disease, specifically for patients (pts) with BCG-unresponsive, high-risk NMIBC. Increased IDO and PD-L1 expression in NMIBC tumors (Inman, et al. Cancer 2007; Hudolin, et al. Anticancer Res 2017), support the combination of anti–PD-1 and IDO1 inhibition in NMIBC. BMS-986205, a selective, potent, once-daily IDO1 inhibitor that works early in the IDO1 pathway, has demonstrated clinical activity in combination with nivo in pts with immunotherapy-naive advBC who received ≥ 1 prior line of therapy (objective response rate, 37%; Tabernero, et al. J Clin Oncol 2018;36(suppl) [abstr 4512]). These findings provide a rationale for investigation of nivo + BMS-986205 ± intravesical BCG therapy in BCG-unresponsive high-risk NMIBC. Here we describe a phase 2, randomized, open-label study assessing the safety and efficacy of nivo ± BMS-986205 ± intravesical BCG in pts with BCG-unresponsive, high-risk NMIBC. Methods: Pts aged ≥ 18 years with BCG-unresponsive (per February 2018 FDA guidance), high-risk NMIBC, defined as carcinoma-in-situ (CIS) with or without papillary component, any T1, or Ta high-grade lesions, will be enrolled. Pts must have urothelial carcinoma as the predominant histological component (>50%). Key exclusion criteria include locally advanced or metastatic BC, upper urinary tract disease within 2 years, prostatic urethral disease within 1 year, and prior immunotherapy. Using a novel adaptive-type design, pts will be randomized to 1 of 4 tx arms with nivo ± BMS-986205 ± BCG. Primary endpoints include proportion of pts with CIS with complete response (CR), duration of CR in pts with CIS, and event-free survival for all pts without CIS. Secondary endpoints are progression-free survival and safety. This global study in 13 countries is underway, with a target enrollment of 436 pts. (Clinical trial information: NCT03519256