On January 8, 2024 Cellectar Biosciences, Inc. (NASDAQ: CLRB), a late-stage clinical biopharmaceutical company focused on the discovery, development and commercialization of drugs for the treatment of cancer, reported data from its CLOVER WaM pivotal study, evaluating iopofosine I 131, a potential first-in-class, targeted radiotherapy candidate for the treatment of relapsed/refractory Waldenstrom’s macroglobulinemia (WM) patients that have received at least two prior lines of therapy, including Bruton tyrosine kinase inhibitors (BTKi) (Press release, Cellectar Biosciences, JAN 8, 2024, View Source [SID1234639149]). CLOVER WaM is the largest study to date in relapsed or refractory WM patients post-BTKi therapy and represents the most refractory population ever tested in clinical studies based upon a review of published literature.

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The CLOVER WaM study met its primary endpoint with a major response rate (MRR) of 61% (95% confidence interval [44.50%, 75.80%, two-sided p value < 0.0001]). The overall response rate (ORR) in evaluable patients was 75.6%, and 100% of patients experienced disease control. Responses were durable, with median duration of response not reached and 76% of patients remaining progression free at a median follow-up of eight months. These outcomes exceed real world data, which demonstrate a 4-12% MRR and a duration of response of approximately six months or less despite continuous treatment in a patient population that is less pretreated and less refractory to multiple classes of drugs. Notably, iopofosine monotherapy achieved an 8% stringent complete remission (sCR) in this highly refractory WM population.

"There is a critical need for new therapies with novel mechanisms of action to treat WM. There are no approved treatments for patients post BTKi therapy, where currently the expected response rate to salvage treatments is approximately 10%, and the expected duration of response in those patients is less than six months," said Sikander Ailawadhi, M.D., professor of medicine at Mayo Clinic, and lead investigator in the CLOVER WaM study. "The results from this pivotal study utilizing just four doses of iopofosine monotherapy in heavily pretreated patients are very compelling, demonstrating deep and durable remissions. The combination of the safety profile and deep durable responses with a high proportion of patients remaining treatment free is impressive."

CLOVER WaM is a single-arm registration study with a target enrollment of 50 patients. The study is fully enrolled and topline safety data is being reported on 45 patients meeting criteria for modified intent to treat (mITT) with a data cut-off date of January 3, 2024. Topline efficacy evaluable population (41) is defined as patients who have received a total administered dose of greater than 60 mCi and had follow up of at least 60 days post last dose. Among mITT patients, median age was 71 years, median IgM level prior to treatment with iopofosine was 2,185, 90% were refractory to either a BTKi (18/36 50%) or anti-CD20 therapy (18/41 40%), with 26.7% multiclass refractory, and 80% of patients were previously treated with a BTKi therapy.

Newton Guerin, International Waldenstrom’s Macroglobulinemia Foundation (IWMF) president and CEO, said, "These inspiring topline data represent important and exciting news for the entirety of the WM community battling this challenging disease. WM patients need new, clinically meaningful treatment modalities and currently, there are limited options for patients who have received prior BTKi therapy. Iopofosine’s product profile is notable because of its novel mechanism of action, fixed four-dose course of treatment completed within 75 days and the promise of an enhanced quality of life for patients, including a prolonged treatment-free interval."

Iopofosine I 131 was well tolerated and its toxicity profile was consistent with the Company’s previously reported safety data. There were no treatment-related adverse events (TRAEs) leading to discontinuation. The rates of Grade 3 or greater TRAEs observed in more than 10% of patients included thrombocytopenia (55%), neutropenia (37%), and anemia (26%). All patients recovered from cytopenias with no reported aplastic sequalae. Importantly, there were no clinically significant bleeding events, and the rate of febrile neutropenia was 2%. There were no treatment related deaths in the study.

"We are most grateful to the patients and their families, participating study sites, their staff and our dedicated employees for the successful completion of this study. Their respective contributions may provide a meaningful new treatment option for patients where there currently are no approved therapies," said James Caruso, president and CEO of Cellectar. "Iopofosine’s high major response rate and achievement of the study’s primary endpoint in highly refractory, Waldenstrom’s macroglobulinemia patients exhibits its potentially practice-changing clinical profile. We believe the currently impressive response rates and the duration of responses will continue to improve as the data matures. We plan to include these outcomes in our NDA submission and will be requesting an accelerated approval based upon our WM Fast Track Designation."

Conference Call & Webcast Details

Cellectar management will host a conference call for investors today, January 8, 2024, beginning at 8:00 am ET / 5:00 am PT. Dial-in: 1-888-886-7786. Webcast Link: Click HERE