FLORHAM PARK, N.J., July 15, 2026
Cellectar Biosciences announced the publication of results from its Phase 1 dose-escalation study evaluating iopofosine I 131 in combination with low-dose dexamethasone for patients with heavily pretreated relapsed/refractory multiple myeloma (r/r MM) in the peer-reviewed journal Cancers. The study demonstrated a favorable safety profile, encouraging disease control, and preliminary clinical activity, supporting continued development of the targeted radiotherapeutic across multiple B-cell malignancies.
Phase 1 Study Demonstrates Encouraging Clinical Activity
The open-label, multi-center Phase 1 study enrolled 31 heavily pretreated patients with relapsed/refractory multiple myeloma, many of whom had exhausted available treatment options. Among the 26 efficacy-evaluable patients, 84.6% achieved stable disease or better, while patients receiving higher cumulative doses showed stronger clinical activity. An overall response rate of 30% was observed among patients receiving at least 60 mCi of iopofosine I 131, with an overall study response rate of 15.4%, including four partial responses.
Favorable Safety Profile Supports Future Development
Investigators reported that treatment-related adverse events were primarily predictable and reversible hematologic toxicities, with no new safety signals identified. Non-hematologic adverse events were generally low grade, while recovery from treatment-related cytopenias supported the potential for repeat dosing strategies in future clinical development. The study established a maximum tolerated single dose of 31.25 mCi/m² and recommended a Phase 2 fractionated regimen of 15 mCi/m² administered on Days 1 and 7 in combination with weekly low-dose dexamethasone.
Advertisement
Publication Reinforces Broader Potential Across B-Cell Malignancies
Cellectar believes the publication further validates iopofosine I 131 as a differentiated targeted radiotherapeutic built on its proprietary Phospholipid Drug Conjugate (PDC) platform. Because the therapy is not dependent on a single molecular target or mutation, the company sees potential applications across multiple hematologic cancers, including Waldenström macroglobulinemia, multiple myeloma, diffuse large B-cell lymphoma, and other difficult-to-treat B-cell malignancies. The favorable safety profile, combined with limited renal and hepatic toxicity, may also make the therapy particularly suitable for older, frail, or heavily pretreated patients with limited treatment options.
Source: Cellectar Biosciences, press release
