Distinct global proteotypes for high-PD-L1 versus high-IDO1 expressing NSCLC could merit exploration in retrospective analysis of archival FFPE specimens from completed combination trials with disappointing or ambiguous outcomes, such as the recent ECHO-202/KEYNOTE-307 phase 3 trial of pembrolizumab and epacadostat in melanoma44. The gene discussed is IDO1; the disease is non-small cell lung carcinoma.