FLORHAM PARK, N.J. — May 5, 2026 — Leads & Copy — Cellectar Biosciences, Inc. (NASDAQ: CLRB) has announced updated and mature 12-month follow-up data from its Phase 2b CLOVER WaM clinical trial, evaluating iopofosine I 131 in patients with relapsed or refractory (r/r) Waldenström macroglobulinemia (WM). The data includes a minimum of 12 months of follow-up for all enrolled patients, as requested by the U.S. Food and Drug Administration (FDA). The durability data presented here, further strengthen the previously reported efficacy results.
The company also reported subset analyses from CLOVER WaM, which showed iopofosine I 131 demonstrated efficacy in both BTKi-exposed and BTKi-refractory patients. The company plans to initiate its confirmatory study in the fourth quarter of this year.
According to Jarrod Longcor, chief operating officer of Cellectar Biosciences, the depth, durability, and consistency of responses observed across both the total population and BTKi-treated subsets highlight iopofosine’s potential as a meaningful new treatment option in WM. With the completion of at least 12-month follow-up on all patients, the company believes this dataset meets key regulatory expectations for an accelerated approval submission and positions it well as it advances toward initiating its confirmatory study.
Patients enrolled in the CLOVER WaM clinical trial had a median of four prior lines of therapy (range 2-15), with refractory rates running from 77% in Bruton tyrosine kinase inhibitors (BTKi)-exposed patients to 60% in chemotherapy-exposed patients and 58% in patients exposed to both BTKi and rituximab.
Updated 12-month data demonstrated high response rates and sustained durability, supporting its accelerated regulatory pathway and potential role as a differentiated treatment option. Summary of Efficacy Results in per Protocol Study Population (n=55): Overall Response Rate (ORR): 83.6%; Major Response Rate (MRR): 61.8%; Median Duration of Response (DoR): 17.8 months; Median Progression-Free Survival (PFS): 13.5 months; Very Good Partial Response/Complete Response Rate (VGPR/CR): 14.5%; Disease Control Rate (DCR): 98.2%
During the follow-up period, responses deepened and remained durable, underscoring the strength of the data, especially considering that treatment with iopofosine I 131 is a fixed-dosed regimen containing four ~30-minute infusions.
According to James Caruso, president and chief executive officer, the mature 12-month follow-up data, as required by the FDA, further strengthen the clinical profile of iopofosine I 131. He added that the durability of response continues to improve over time, and the consistency of activity in post-BTKi patients reinforces the potential of iopofosine to address a critical unmet need in the second line setting and beyond. The company plans to initiate its confirmatory study in the fourth quarter of this year.
Iopofosine I 131 continues to demonstrate a predictable and manageable safety profile. Adverse events were transient and unlike other therapies approved for WM there were no significant bleeding events and low rates of infection (<10%). Cytopenias were the most common treatment-emergent adverse events. Non-hematologic toxicities were primarily low grade (Grade <2).
Iopofosine I 131 demonstrated strong and consistent efficacy in both BTKi-exposed and BTKi-refractory patients. Summary of Efficacy Results in BTKi-Exposed Patients (n=39): MRR: 64.1%; Median DoR: 18.2 months; Median PFS: 15.9 months. Summary of Efficacy Results in BTKi-Refractory Patients (n=33): MRR: 63.6%; Median DoR: 18.2 months; Median PFS: 14.8 months.
These results demonstrate durability and depth of response comparable to, or exceeding, the overall study population, reinforcing the consistency of iopofosine’s activity across treatment-resistant subgroups.
Efficacy and safety results from r/r WM patients treated with iopofosine I 131 immediately following BTKi therapy have been accepted for presentation at the upcoming American Society of Clinical Oncology (ASCO) Annual Meeting taking place from May 29-June 2, 2026 in Chicago, Illinois. The company also plans to present the full data sets at upcoming medical congresses or scientific meetings.
The CLOVER WaM dataset incorporates key elements aligned with regulatory expectations for accelerated approval, including: use of surrogate endpoints (MRR supported by DoR); demonstration of durable responses in a high unmet need population; and completion of ≥12-month follow-up across all patients, as requested by the FDA.
Cellectar is advancing plans to initiate a confirmatory randomized study in a post-first line, post-BTKi population to evaluate progression-free survival (PFS) as the primary endpoint.
Waldenstrom’s Macroglobulinemia (WM) is a B-cell malignancy characterized by bone marrow infiltration with clonal lymphoplasmacytic cells that produce a monoclonal immunoglobulin M (IgM) that remains incurable with available treatments. Approximately 11,500 patients require treatment in the relapsed or refractory setting and there are an estimated 4,700 patients requiring third line or greater therapy. There are no FDA- approved treatment options for patients progressing on BTKi therapy. BTKi therapies do not demonstrate complete response rates and require continuous treatment.
Cellectar Biosciences is a late-stage clinical biopharmaceutical company focused on the discovery and development of proprietary drugs for the treatment of cancer, independently and through research and development collaborations. The company’s core objective is to leverage its proprietary Phospholipid Drug Conjugate™ (PDC) delivery platform to develop the next-generation of cancer cell-targeting treatments.
The company’s product pipeline includes iopofosine I 131, which is a PDC designed to provide targeted delivery of iodine-131 (radioisotope). Iopofosine I 131 has been tested in Phase 2b trials as a treatment for relapsed or refractory Waldenström Macroglobulinemia (WM), in relapsed or refractory multiple myeloma (MM) and central nervous system (CNS) lymphoma. The FDA has granted iopofosine I 131 Breakthrough, six Orphan Drug, four Rare Pediatric Drug and two Fast Track Designations for various cancer indications, and the EMA has granted iopofosine I 131 PRIority MEdicines (PRIME) designation.
Cellectar is also developing CLR 121125 (CLR 125), an iodine-125 Auger-emitting program targeted for solid tumors, and CLR 121225 (CLR 225), an actinium-225 based program targeting solid tumors.
Source: Cellectar Biosciences, Inc.
