Summary Background Patients with metastatic urothelial carcinoma have limited treatment options after failure of platinum-based chemotherapy. This multicenter, single-arm phase 2 trial evaluated atezolizumab, an engineered humanized IgG1 monoclonal antibody that binds selectively to programmed death–ligand 1 (PD-L1), in this population. Methods Three hundred and ten patients received atezolizumab (1200 mg, every 3 weeks). PD-L1 expression on tumor-infiltrating immune cells (IC) was prospectively assessed by immunohistochemistry. The co-primary endpoints were the objective response rate by RECIST v1.1 and immune modified RECIST. A hierarchical testing procedure was used to test whether the objective response rate was significantly higher than the historical control of 10% at alpha level of 0·05. Exploratory analyses included assessing the association between The Cancer Genome Atlas (TCGA) molecular subtypes, CD8+ T cell infiltration, mutation load, and clinical outcomes. Findings By independent review, objective response rates were 26% (95% CI 18 to 36) in the IC2/3 group, 18% (95% CI 13 to 24) in the IC1/2/3 group and 15% (95% CI 11 to 19) in all patients. With a median follow-up of 11·7 months, ongoing responses were observed in 84% of responders. The median duration of response was not reached (range 2·0*, 13·7* months, *censored). The median overall survival was 11·4 months (95% CI 9·0 to not estimable) in the IC2/3 group, 8·8 months (95% CI 7·1 to 10·6) in the IC1/2/3, and 7·9 months (95% CI 6·6 to 9·3) in all patients. Grade 3–4 related treatment-related adverse events occurred in 16% and grade 3–4 immune-mediated adverse events occurred in 5% of treated patients. Exploratory analyses showed TCGA subtypes and mutation load to be independently predictive for response to atezolizumab. Interpretation Atezolizumab demonstrated durable activity and good tolerability in this population. PD-L1 expression on immune cells was associated with response. This is the first report to show the association of TCGA subtypes with response to immune checkpoint inhibition and demonstrate the importance of mutation load as a biomarker of response to this class of agents in advanced urothelial carcinoma. Funding F. Hoffmann-La Roche Ltd.

Summary Background First-line chemotherapy for patients with cisplatin-ineligible locally-advanced or metastatic urothelial carcinoma (mUC) is associated with short response duration, poor survival, and high toxicity. This multicenter, 2-cohort phase 2 study evaluated atezolizumab (anti–programmed death-ligand 1 [PD-L1]) as treatment for mUC in this setting, as well as in later lines. Methods In a cohort of previously untreated patients who were cisplatin ineligible, atezolizumab was given 1200 mg every 3 weeks until progression. The primary endpoint was independently confirmed objective response rate per Response Evaluation Criteria In Solid Tumors v1.1 (central review), evaluated in pre-specified subgroups based on PD-L1 expression and in all patients. Secondary endpoints included response duration, progression-free survival, overall survival, and safety. Exploratory analyses included biomarker correlates of response and survival. This study is registered with ClinicalTrials.gov, number NCT02108652. Findings Of 119 patients who received atezolizumab in the first-line setting, 83 (70%) had baseline renal impairment, and 24 (20%) had Eastern Cooperative Oncology Group performance status 2. At 17·2 months’ median follow-up, the objective response rate was 23% (95% CI 16–31), the complete response rate was 9%, and 19 of 27 responses were ongoing. Median response duration was not reached. Responses occurred across all PD-L1 and poor prognostic factor subgroups. Median progression-free survival was 2·7 months. Median overall survival was 15·9 months. Tumour mutation load was associated with response. Treatment-related adverse events ≥10% were fatigue, diarrhoea, and pruritus. One treatment-related death (sepsis) occurred. Nine patients (8%) had an adverse event leading to treatment discontinuation. Immune-mediated events occurred in 14 (12%) patients. Interpretation Atezolizumab demonstrated encouraging durable response rates, survival, and tolerability, supporting its therapeutic use in untreated mUC. Funding F. Hoffmann-La Roche Ltd./Genentech, Inc., a member of the Roche Group.

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F Hoffmann-La Roche, Genentech.