On July 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 the publication of results from a Phase 1 dose-escalation study evaluating iopofosine I 131 in combination with low-dose dexamethasone in 31 patients with heavily pretreated relapsed/refractory multiple myeloma (r/r MM). The manuscript, titled "A Phase I Trial of Iopofosine I 131 and Dexamethasone in Patients with Relapsed/Refractory Multiple Myeloma," was published in the peer-reviewed journal, Cancers.
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"Iopofosine I 131 represents a differentiated therapeutic approach for patients with relapsed or refractory multiple myeloma who have limited remaining treatment options," said Sikander Ailawadhi, M.D., professor of medicine, division of hematology/oncology, Mayo Clinic, Jacksonville, Florida and lead author of the publication. "The study demonstrated manageable toxicity with adverse events being essentially limited to cytopenias, encouraging disease control, and evidence of antitumor activity in a heavily pretreated population, supporting the potential of this novel targeted radiotherapeutic in these most fragile patients. The predictability and recovery of the cytopenias support its potential for repeat dosing strategies in future clinical development."
Highlights of the Data:
The study evaluated both single-dose and fractionated-dose regimens of iopofosine I 131 in 31 heavily pretreated r/r MM patients, many of whom had exhausted available treatment options.
Among 26 efficacy-evaluable patients:
Clinical activity appeared more pronounced in patients receiving higher total administered doses
84.6% achieved stable disease or better following treatment
30% overall response rate observed among evaluable patients (n=10) receiving at least 60 mCi of iopofosine I 131
The overall response rate was 15.4%, with four patients achieving partial responses
Investigators reported a favorable and manageable safety profile, with adverse events primarily consisting of predictable and reversible hematologic toxicities
No new safety signals were identified, and non-hematologic adverse events were generally low grade
"Publication of these data in Cancers further validate the potential of iopofosine as a differentiated targeted radiopharmaceutical and underscore the promise of our phospholipid drug conjugate platform as a novel targeted radiotherapeutic platform," said Jarrod Longcor, Cellectar’s chief operating officer and co-author of the publication. "Importantly, the mechanism of action is not dependent on a single target or mutation, creating the opportunity to address a broad range of B-cell-mediated malignancies. We believe iopofosine has the potential to serve patients across multiple indications, including Waldenström macroglobulinemia, multiple myeloma, diffuse large B-cell lymphoma and other difficult-to-treat hematologic cancers where new therapeutic options remain urgently needed."
The authors further noted that iopofosine’s limited impact on renal and hepatic function, coupled with its predictable and manageable safety profile, may make it particularly attractive for older, frail, or heavily pretreated patients who may not be candidates for more intensive therapies. The study also demonstrated recovery of treatment-related cytopenias over time, supporting the potential for repeat dosing strategies in future clinical development.
The full article can be accessed here.
About the Phase 1 Study
The Phase 1 dose escalation and safety study was conducted as an open-label, multi-center trial, which enrolled 31 patients with relapsed or refractory multiple myeloma who had received a median of four prior lines of therapy. Patients received either a single dose or fractionated doses of iopofosine I 131 plus low-dose dexamethasone. The study established 31.25 mCi/m² as the maximum tolerated single dose and identified 20 mCi/m² administered twice, one week apart, as the highest evaluated fractionated dose regimen. The authors recommended a fractionated Phase 2 regimen of 15 mCi/m² administered on days 1 and 7 in combination with weekly low-dose dexamethasone.
(Press release, Cellectar Biosciences, JUL 15, 2026, View Source [SID1234669227])