A Phase 2 Trial of Nab-paclitaxel in Combination With Anti-PD1 Therapy in Advanced Urothelial Cancer

Immune checkpoint inhibitor therapy and nab-paclitaxel have each shown efficacy in platinum-refractory advanced urothelial cancer. We conducted a single-arm phase 2 trial of the combination of nab-paclitaxel and pembrolizumab in platinum-refractory or cisplatin-ineligible advanced urothelial cancer (NCT03240016).

Eligible patients had RECIST 1.1 measurable and cisplatin-ineligible or platinum-refractory advanced urothelial cancer. Patients received nab-paclitaxel at starting dose of 125 mg/m² intravenously on days 1 and 8 and pembrolizumab 200 mg intravenously on day 1 in 21-day cycles until progression, intolerable toxicity, or death. Nab-paclitaxel was permitted to be discontinued after 6 cycles. The nab-paclitaxel starting dose was reduced to 100 mg/m² after planned interim analysis. Primary end point was overall response rate by RECIST 1.1. Secondary end points included safety/toxicity, duration of response, progression-free survival), and overall survival.

Between February 2018 and April 2021, 36 response-evaluable patients were enrolled. There was an equal split of platinum-refractory and cisplatin-ineligible patients. Confirmed overall response rate was 50.0% (18/36) including 3 complete and 15 partial responses; 31/36 patients experienced some tumor shrinkage. At a median follow-up of 19.7 months, median duration of response was 4.4 months (95% CI: 4.0-8.6), median progression-free survival 6.8 months (95% CI: 4.4-not reached), and median overall survival 18.2 months (95% CI: 10.6-not reached). Grade ≥3 adverse events occurred in 21/36 patients including fatigue (n=6) and anemia (n=4). Ten patients had immune-mediated adverse events.

The combination of nab-paclitaxel and pembrolizumab exhibited promising activity in advanced urothelial cancer and warrants further study in this population. After reduction in nab-paclitaxel starting dose, no unanticipated or unexpected toxicities emerged.