On October 15, 2026 Cellectar Biosciences, Inc. (NASDAQ: CLRB), a late-stage clinical biopharmaceutical company focused on the discovery and development of drugs for the treatment of cancer, reported that efficacy results from a subset of patients treated with iopofosine I 131 immediately post-Bruton Tyrosine Kinase inhibitor (BTKi) therapy in the company’s Phase 2b CLOVER WaM clinical trial of iopofosine I 131 to treat relapsed or refractory (r/r) Waldenström macroglobulinemia (WM) were presented today at the International Workshop for Waldenström Macroglobulinemia (IWWM) taking place October 14 to October 16, 2026, in Palm Springs, California.

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The poster highlighted data from a subgroup (n=24) of patients treated with a BTKi immediately prior to iopofosine I 131 from the CLOVER WaM trial in WM. This subgroup analysis is derived from the CLOVER WaM clinical trial 12-month follow-up data set previously reported.

"These compelling data further strengthen the growing body of evidence supporting the potential of iopofosine I 131 to address a critical unmet need and offers something WM patients rarely get after BTK inhibitors: deep, durable responses from a short, fixed course of treatment. Because its targeted radiation works independently of the BTK pathway and other pathways currently targeted or attempting to be targeted, we believe it has the potential to remain effective as patients become refractory to today’s targeted therapies, and those still to come," said Jarrod Longcor, chief operating officer of Cellectar Biosciences. "Patients in the immediate post-BTKi setting often face limited treatment options and increasingly refractory disease, making the robust response rates, durable clinical benefit, and favorable tolerability profile observed in this analysis especially encouraging. With Breakthrough Therapy Designation, a mature and expanding CLOVER WaM dataset, and plans underway to dose patients in our confirmatory clinical trial in early 2027, we believe iopofosine I 131 is well positioned to become a meaningful new treatment option for these patients, and we remain focused on advancing the program toward potential regulatory approval."

Summary of Results in Subgroup Immediately post-BTKi treatment (n=24)
The patients included in this subset analysis were enrolled in the CLOVER WaM clinical trial and were treated with iopofosine I 131 immediately after receiving a regimen containing BTKi. Seventy-five percent were BTKi refractory and more than 54% had received multiple BTKi therapies. Patients had a median of three prior lines of therapy (range 2-7) with 17% being TP53 mutated and 29% being MYD88 wild type, both of which confer greater resistance and rapid progression. Key findings included:

Overall Response Rate (ORR): 87.5%
Major Response Rate (MRR): 79.2%
Median Duration of Response (DoR): 16.0 months
Treatment Free Survival (TFS): 19.1 months
Clinical Benefit Rate (CBR): 100%
Safety: Treatment emergent adverse events (TEAE) occurred in less than 10% of patients, with the only Grade 3 or higher TEAE being cytopenias
Cellectar is advancing plans to dose the first patients in the confirmatory Phase 3 randomized clinical trial in a post-first line, post-BTKi population. The registration-directed trial is expected to evaluate progression-free survival (PFS) as the primary endpoint, consistent with regulatory guidance.

The company is also preparing to submit a New Drug Application for accelerated approval with the U.S. Food and Drug Administration (FDA) in the first half of 2027, supported by the strength and maturity of the CLOVER WaM dataset.

About Accelerated Approval and Confirmatory Study Initiation
The CLOVER WaM dataset incorporates key elements aligned with regulatory expectations for accelerated approval as requested by the FDA, including:

Use of surrogate endpoints (MRR supported by DoR) reasonably likely to predict clinical benefit
Demonstration of durable responses in a high unmet need population
Completion of ≥12-month follow-up across all patients

(Press release, Cellectar Biosciences, OCT 15, 2026, View Source [SID1234673483])