Florham Park, N.J., April 21, 2026

Cellectar Biosciences, Inc. announced that a subset analysis from its CLOVER WaM clinical trial has been accepted for presentation at the American Society of Clinical Oncology (ASCO) Annual Meeting 2026, highlighting promising outcomes for patients with relapsed or refractory Waldenström macroglobulinemia (WM). The data focuses on patients treated with iopofosine I 131 following BTK inhibitor therapy, an area with significant unmet medical need.

Encouraging Clinical Efficacy in Hard-to-Treat Patients

The accepted abstract will present efficacy and safety results from a subgroup of WM patients who have progressed after BTK inhibitor treatment, a population with no approved FDA therapies and limited treatment options. According to the company, iopofosine I 131 demonstrated encouraging safety and clinical activity, suggesting its potential as a differentiated therapeutic option in later-line settings.

The findings are particularly significant as over 60% of WM treatments are currently salvage therapies, which often provide limited and short-term benefits. The ability of iopofosine to deliver targeted radiotherapeutic action could offer deeper and more durable responses, especially for heavily pretreated patients. The data will be presented as a poster during the ASCO meeting scheduled from May 29 to June 2, 2026, in Chicago.

Addressing a Significant Unmet Need in Waldenström Macroglobulinemia

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IWaldenström macroglobulinemia is a rare and incurable B-cell malignancy characterized by the accumulation of lymphoplasmacytic cells in the bone marrow and excessive production of monoclonal IgM protein. Despite advancements in therapy, patients progressing after BTK inhibitors lack FDA-approved options, leaving a critical treatment gap.

Epidemiological data indicate that approximately 26,000 patients in the U.S. are living with WM, with 1,500–1,900 new cases diagnosed annually. A significant portion of these patients eventually enter the relapsed or refractory stage, where treatment options become increasingly limited. Notably, around 1,000 patients exhaust all available therapies by the third line, emphasizing the urgent need for innovative and effective treatments.

Innovative Targeted Radiotherapy Platform Driving Pipeline Growth

Cellectar’s lead candidate, iopofosine I 131, is based on its proprietary Phospholipid Drug Conjugate™ (PDC) platform, designed to selectively target cancer cells while minimizing off-target toxicity. This targeted delivery mechanism enables the precise administration of iodine-131, enhancing therapeutic impact while improving safety profiles.

The therapy has already demonstrated potential across multiple indications, including multiple myeloma and central nervous system lymphoma, and has received multiple regulatory designations such as Breakthrough Therapy, Orphan Drug, Rare Pediatric Drug, and Fast Track from the FDA, along with PRIME designation from the EMA. These recognitions underscore the strong clinical promise and regulatory momentum behind the program.

Beyond iopofosine, the company is advancing a broader oncology pipeline, including CLR 125 (iodine-125-based therapy) and CLR 225 (actinium-225-based program), targeting solid tumors such as triple-negative breast cancer, lung cancer, and pancreatic cancer, further reinforcing its position in next-generation targeted radiopharmaceuticals.

Clinical and Business Implications

The acceptance of this data at ASCO 2026 represents a key milestone for Cellectar Biosciences, enhancing its visibility within the oncology community and supporting future regulatory and commercialization strategies. If successful in later-stage trials, iopofosine I 131 could redefine treatment paradigms for WM patients who currently face limited and ineffective therapeutic options.The development also strengthens the company’s competitive positioning in the radiopharmaceutical oncology space, an area witnessing rapid innovation and investment, and highlights its commitment to addressing high unmet needs in rare cancers.

Source: Cellectar Biosciences press release