CD274 and neoplasm: Similarly, Powles et al. in a phase I escalation and expansion study investigated the safety and activity of single-agent atezolizumab at a dose of 15 mg/kg of body weight every 3 weeks in 205 heavily pretreated patients with urothelial carcinoma (UC) which were stratified by the percentage of PD-L1-positive immune cells in the tumor microenvironment by immunohistochemistry (IHC) defined by IHC 0 (< 1%), IHC 1 (≥ 1% but < 5%), and IHC 2/3 (≥ 5%) [37].