Cellectar Biosciences (NASDAQ:CLRB) is targeting a U.S. regulatory submission for its lead radiopharmaceutical in the first half of 2027, while delaying a European filing by approximately nine months to allow U.S. pricing discussions to advance.
On its third-quarter earnings call, management said the company expects to dose the first patient in a confirmatory Phase III trial of Iopofosine I-131 for relapsed or refractory Waldenström’s macroglobulinemia, or WM, in the first quarter of 2027. The company is seeking accelerated approval for patients who have received prior treatment, including exposure to BTK inhibitors.
President and CEO Jim Caruso said the drug could be approved and commercially available in the United States as early as late 2027 or early 2028. That timeline depends on regulatory review and the company’s execution of its clinical plans.
Confirmatory trial and regulatory plans
Chief Operating Officer Jarrod Longcor said the Phase III study is intended to meet the Food and Drug Administration’s expectation that a confirmatory trial be initiated when an accelerated approval application is submitted and underway at the time of regulatory action. Site activation is in progress, with several sites expected to be active and initiated by the end of 2026, he said.
Asked how many patients would need to enroll before the company files, Longcor said the FDA has not specified a fixed number and makes determinations case by case. Based on discussions with consultants, Cellectar is targeting enrollment of approximately 5% to 15% of the study at the time of regulatory action, rather than at submission, he said. That range is the company’s assessment, not a stated FDA requirement.
Longcor said Cellectar plans to defer its European conditional marketing authorization submission by approximately nine months. Management cited the introduction of most-favored-nation pricing in the United States and the risk that establishing a European price first could affect U.S. pricing.
Clinical data and earlier treatment study
Management highlighted an analysis from the CLOVER-WaM study presented in October. Among patients treated with Iopofosine I-131 immediately after BTK inhibitor therapy, the overall response rate was 87.5%, the major response rate was 79.2%, and the median duration of response was 16 months, Longcor said. The clinical benefit rate was 100%.
Caruso said that subgroup reflects the population to be evaluated in the confirmatory trial. Cellectar also plans three presentations at the American Society of Hematology annual meeting, including updated 12-month CLOVER-WaM follow-up data, an analysis of response duration by prior lines of therapy and the Phase III trial design.
The company has initiated a separate Phase Ib dosimetry study expected to enroll 20 to 30 newly diagnosed and relapsed WM patients, without a specific prior-treatment requirement. The study will assess drug uptake in tissues as well as collect safety and efficacy data. Caruso said the first patient is expected around the first quarter of 2027.
Management said it does not expect the dosimetry study to materially compete for Phase III enrollment, citing its broader patient eligibility and predominantly different sites. Longcor said a comparative, controlled trial would be the expected route for pursuing a frontline indication. Caruso also suggested that favorable Phase Ib data could help support consideration for earlier-line treatment in clinical guidelines.
Third-quarter finances
Cellectar ended September with approximately $24.6 million in cash and cash equivalents, up from $13.2 million at the end of 2025. Chief Financial Officer Chad Kolean said the company’s cash runway extends into the second quarter of 2027 and is sufficient for planned operations, including the Phase III initiation and a potential new drug application submission.
The company completed an oversubscribed financing in May consisting of $35 million upfront and $105 million in milestone-based capital, for a total of up to $140 million, Kolean said.
Research and development expenses rose to $5.4 million from $2.5 million a year earlier, primarily reflecting Phase III startup costs and increased activity in the Phase Ib CLR 125 trial in triple-negative breast cancer. General and administrative expenses increased to $2.7 million from $2.3 million, mainly because of higher professional fees and personnel costs.
The quarterly net loss widened to $8 million, or $0.46 per share, from $4.4 million, or $1.41 per share, a year earlier.
Additional pipeline programs
Outside WM, Longcor discussed a single patient with diffuse large B-cell lymphoma who remained in complete response for more than eight years after one administration of Iopofosine I-131. He noted that the case represented one patient’s experience.
Cellectar is also enrolling patients in a Phase Ib trial of CLR 125, an iodine-125 radiotherapeutic candidate for triple-negative breast cancer. Longcor said the company remains on track to present initial dosimetry and safety data later in 2026 at the San Antonio Breast Cancer Symposium.
About Cellectar Biosciences (NASDAQ:CLRB)
Cellectar Biosciences, Inc (NASDAQ: CLRB) is a clinical-stage biopharmaceutical company focused on developing targeted radiotherapeutics and oncology treatments. Its technology platform uses phospholipid ether compounds, which are designed to preferentially accumulate in cancer cells and other diseased tissues while limiting exposure to healthy tissue.
The company’s leading product candidate is iopofosine I 131, also known as CLR 131, a small-molecule radiopharmaceutical being studied for the treatment of hematologic malignancies, including relapsed or refractory multiple myeloma and certain types of lymphoma.
