Cellectar to present Phase 2 WM subset data at IWWM 2026

Cellectar Biosciences has announced it will present a subset analysis from its Phase 2 CLOVER WaM trial at the International Workshop for Waldenström Macroglobulinemia, taking place 14 to 16 October 2026 in Palm Springs, California. The data concern patients with Waldenström Macroglobulinemia who received iopofosine I 131 immediately after failing BTK inhibitor therapy, a population representing some of the most difficult-to-treat cases in the indication.

The subset analysis showed a major response rate of 79.2%, an overall response rate of 87.5%, and a duration of response exceeding 16 months. The cohort analysed had received at least two prior lines of treatment before being dosed with the company's phospholipid drug conjugate, or PDC, radiotherapy agent. Full safety and efficacy details will be disclosed in the poster presentation on 15 October.

Regulatory path

Cellectar is using the data to underpin a regulatory filing strategy that leans on iopofosine I 131's existing FDA Breakthrough Therapy Designation. Chief operating officer Jarrod Longcor said the company remains on track to begin dosing patients in a confirmatory Phase 3 trial in early 2027 and to submit a New Drug Application for accelerated approval in the first half of 2027. "Given iopofosine I 131 has Breakthrough Therapy Designation, we expect a six-month review with a potential approval by the end of 2027," he said.

That timeline is ambitious but not implausible under the accelerated approval pathway. The FDA's accelerated approval mechanism allows approval on the basis of a surrogate endpoint, such as response rate, with confirmatory trial data required post-approval. Breakthrough Therapy Designation also entitles sponsors to more intensive FDA guidance during development, which can compress review timelines. A potential approval decision in late 2027 would depend on the NDA submission landing in the first half of the year as planned.

Market context

Waldenström Macroglobulinemia is a rare B-cell lymphoma with a relatively small but clearly defined patient population. BTK inhibitors, principally ibrutinib and zanubrutinib, are widely used in earlier lines of therapy, meaning patients who progress on or become resistant to these agents represent a growing and underserved segment. No therapy has yet been specifically approved for the BTKi-refractory WM population, leaving an opening that Cellectar is explicitly targeting.

Iopofosine I 131 is a radiopharmaceutical, a class that has attracted significant industry and investor interest since the approval of Novartis's lutetium-177-DOTATATE and lutetium-177-PSMA-617 established the commercial viability of targeted radioligand therapy. Competition in radioligand therapeutics is intensifying, with several large-cap pharmaceutical companies now holding programmes in the space. Cellectar's PDC delivery platform is differentiated from PSMA- or SSTR-targeting approaches by its phospholipid mechanism, though its relative clinical and commercial standing will only become clearer once Phase 3 data and comparative datasets emerge.

Cellectar also holds six Orphan Drug Designations, four Rare Pediatric Drug Designations, and two Fast Track Designations across multiple indications, and the EMA has granted iopofosine I 131 PRIME designation. The company is also pursuing parallel programmes in multiple myeloma, CNS lymphoma, and paediatric high-grade glioma, broadening the potential addressable market for the PDC platform beyond WM alone.