CD274 and neoplasm: A non-randomized, open-label, phase Ib trial, the KEYNOTE-028 (NCT02054806), firstly investigated the anti-tumor efficacy of pembrolizumab in 25 PD-L1 positive malignant non-responder mesothelioma patients receiving 10 mg/kg of pembrolizumab every two weeks for up to two years or until progression or toxicity.