The populations in clinical trials tend to be selected based on prior evidence of antiproliferative or anti-tumour responses and favourable pharmacodynamics and pharmacokinetics in preclinical studies and early-stage trials.22 For example, trials investigating the efficacy of anti-PD-L1 immune checkpoint inhibitors for ovarian cancer treatment have largely been restricted to evaluating patients with treatment-naïve advanced stage (stage III–IV) epithelial ovarian cancer, but have not been successful23–27 (table 1, online supplemental table 1). This evidence concerns the gene CD274 and ovarian carcinoma.