Expansion cohorts included non-small cell lung cancer (NSCLC; checkpoint-inhibitor naïve, PD-L1 <1%) NSCLC (post checkpoint inhibitor), squamous cell carcinoma of the head and neck (SCCHN; checkpoint-inhibitor naïve), SCCHN (post checkpoint inhibitor), and urothelial cancer (UC) and melanoma (post checkpoint inhibitor). This evidence concerns the gene CD274 and head and neck squamous cell carcinoma.