Background: Avelumab 1L maintenance is recommended as standard of care by international treatment guidelines for pts with aUC that has not progressed with 1L platinum-based chemotherapy, based on level 1 evidence from the phase 3 JAVELIN Bladder 100 trial (NCT02603432). In the trial, avelumab 1L maintenance + best supportive care (BSC) significantly prolonged overall survival (OS) and progression-free survival (PFS) vs BSC alone (median OS, 23.8 vs 15.0 mo; HR, 0.76 [95% CI, 0.63-0.91]; 2-sided p=0.0036). The long-term safety of avelumab 1L maintenance was also demonstrated. It is estimated that 25% of the world’s population will have BMI ≥30 by 2035, and high BMI is a risk factor for bladder cancer. We report post hoc analyses of long-term outcomes from JAVELIN Bladder 100 in pts with high BMI (≥30) at baseline. Methods: Eligible pts with unresectable locally advanced or metastatic UC without progression after 4-6 cycles of 1L platinum-based chemotherapy were randomized 1:1 to receive avelumab 10 mg/kg every 2 wk + BSC (n=350) or BSC alone (n=350). The primary endpoint was OS; secondary endpoints included PFS and safety. Results: At data cutoff (June 4, 2021), median follow-up was ≥38 mo in both arms. In the avelumab + BSC and BSC alone arms, 67 and 55 pts had high BMI at baseline, respectively. In these pts, median OS was 20.8 mo (95% CI, 16.9-34.4) with avelumab + BSC vs 12.7 mo (95% CI, 8.1-26.6) with BSC alone (HR, 0.77 [95% CI, 0.49-1.21]); 2-y OS rates were 47.8% vs 37.6%, respectively. Median PFS by investigator was 5.6 mo (95% CI, 3.7-7.5) with avelumab + BSC vs 2.1 mo (95% CI, 1.9-4.0) with BSC alone (HR, 0.64 [95% CI, 0.42-0.97]); 2-y PFS rates were 23.5% vs 11.3%, respectively. Long-term safety in pts with high BMI was generally consistent with the overall safety population (Table). Conclusions: This exploratory analysis shows the long-term efficacy and tolerability of avelumab 1L maintenance in pts with high BMI in JAVELIN Bladder 100, with no new safety concerns identified. These results further support the use of avelumab 1L maintenance as standard of care in pts with aUC who are progression free after 1L platinum-based chemotherapy, including pts with high BMI. Clinical trial information: NCT02603432.

TEAE, treatment-emergent adverse event; TRAE, treatment-related adverse event. *Attributed to immune-mediated nephritis by the investigator.