Cellectar Biosciences reported that iopofosine I-131 achieved a 79.2% major response rate and median response duration of 16 months in 24 WM patients immediately after BTKi therapy, with 20% exceeding 30 months. The company plans to seek accelerated U.S. approval and start Phase 3 in 4Q26.
In a modified intent-to-treat analysis of 24 relapsed/refractory WM patients treated immediately after BTKi therapy, iopofosine I-131 achieved a 79.2% major response rate, 87.5% overall response rate and 100% clinical benefit rate. Median duration of response reached 16 months, with 20% of patients maintaining responses beyond 30 months.
The treatment was well-tolerated, with cytopenias as the only Grade 3 or higher adverse events reported. No new safety signals emerged, supporting a manageable toxicity profile in this heavily pretreated population.
Cellectar intends to initiate a confirmatory Phase 3 trial in fourth-quarter 2026 and pursue accelerated approval in the U.S. based on these results. The company aims to expand iopofosine I-131 into earlier treatment lines for WM if approved.
