IDO1 and squamous cell carcinoma: Additionally, the trial “Nivolumab and BMS-986205 in Treating Patients With Stage II-IV Squamous Cell Cancer of the Head and Neck” (NCT03854032), enrollment (n = 45), which was terminated due to toxicity, aimed to evaluate the effectiveness of nivolumab in combination with the IDO1 inhibitor BMS-986205, along with therapeutic surgery, in treating advanced squamous cell cancer of the lip, oral cavity, and pharynx.