Maintenance avelumab + best supportive care (BSC) versus BSC alone after platinum-based first-line (1L) chemotherapy in advanced urothelial carcinoma (UC): JAVELIN Bladder 100 phase III interim analysis.

LBA1 Background: Platinum-based chemotherapy is an active 1L regimen for advanced UC; however, progression-free survival (PFS) and overall survival (OS) are generally short because of chemotherapy resistance. This randomized, phase 3 trial (JAVELIN Bladder 100; NCT02603432) evaluated avelumab (anti–PD-L1) as maintenance therapy following response or stable disease with 1L platinum-based chemotherapy in patients with advanced UC. Methods: Eligible patients with unresectable locally advanced or metastatic UC without disease progression after 4-6 cycles of gemcitabine with either cisplatin or carboplatin were randomized 1:1 to receive maintenance avelumab (10 mg/kg IV every 2 weeks) + best supportive care (BSC) or BSC alone, stratified by best response to 1L chemotherapy (complete/partial response vs stable disease) and by visceral vs nonvisceral disease when initiating 1L chemotherapy. The primary endpoint was OS, assessed from randomization in 2 primary populations: all randomized patients and patients with PD-L1+ tumors (Ventana SP263 assay). Secondary endpoints included PFS, objective response, and safety. Results: 700 patients were randomly assigned to maintenance avelumab + BSC (n=350) or BSC alone (n=350) and were followed for a median of 19.6 and 19.2 months, respectively. Overall, 358 (51%) had PD-L1+ tumors. Avelumab + BSC significantly prolonged OS vs BSC alone in all randomized patients (hazard ratio [HR] 0.69; 95% CI 0.56, 0.86; 1-sided p=0.0005); median OS with avelumab + BSC vs BSC alone was 21.4 vs 14.3 months, respectively. Avelumab + BSC also significantly prolonged OS vs BSC alone in patients with PD-L1+ tumors (HR 0.56; 95% CI 0.40, 0.79; 1-sided p=0.0003); median OS was not reached vs 17.1 months, respectively. An OS benefit was also observed across all prespecified subgroups. The HR for PFS based on blinded independent central review with avelumab + BSC vs BSC alone was 0.62 (95% CI 0.52, 0.75) in all randomized patients and 0.56 (95% CI 0.43, 0.73) in patients with PD-L1+ tumors. In treated patients in the avelumab + BSC (n=344) vs BSC alone (n=345) arms, respectively, all-causality adverse events (AEs) were reported at any grade in 98.0% vs 77.7% and at grade ≥3 in 47.4% vs 25.2%, and the most frequent grade ≥3 AEs were urinary tract infection (4.4% vs 2.6%), anemia (3.8% vs 2.9%), hematuria (1.7% vs 1.4%), fatigue (1.7% vs 0.6%), and back pain (1.2% vs 2.3%). Conclusions: JAVELIN Bladder 100 met its primary objective, demonstrating significantly prolonged OS with 1L maintenance avelumab + BSC vs BSC alone in advanced UC in all randomized patients and patients with PD-L1+ tumors. Efficacy benefits were seen across all prespecified subgroups, and the safety profile of avelumab was consistent with previous studies of monotherapy. Clinical trial information: NCT02603432 .