Based on analogous studies with other checkpoint inhibitors that have shown a relationship between tumor pathway expression [e.g., PD-(L)1] and clinical response to pembrolizumab (23), nivolumab (24), and atezolizumab (25), baseline assessments for tumor CD200R1 and CD200 expressions were performed to evaluate potential correlates with efficacy. This evidence concerns the gene CD274 and neoplasm.