Cellectar Targets H1 2027 Filing, Delays EU Submission Nine Months

Cellectar Biosciences (NASDAQ:CLRB) plans a U.S. regulatory submission for its lead radiopharmaceutical in the first half of 2027, while deferring a European filing by roughly nine months to protect American pricing talks. The delay is deliberate. Management fears that setting a European price first could drag down the U.S. price under most-favored-nation pricing rules.

On its third-quarter earnings call, the company said it expects to dose the first patient in a confirmatory Phase III trial of Iopofosine I-131 for relapsed or refractory Waldenström's macroglobulinemia (WM) in the first quarter of 2027. Cellectar 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.

What does the confirmatory trial require?

Chief Operating Officer Jarrod Longcor said the Phase III study is intended to meet the FDA'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. Several sites should be active and initiated by the end of 2026, he said.

Asked how many patients must enroll before filing, Longcor said the FDA has not fixed a number and decides case by case. Based on consultant discussions, Cellectar is targeting enrollment of approximately 5% to 15% of the study at the time of regulatory action, rather than at submission. That range is the company's assessment, not a stated FDA requirement.

On Europe, Longcor said Cellectar plans to defer its conditional marketing authorization submission by approximately nine months. Management cited most-favored-nation pricing in the United States and the risk that a European price set first could affect U.S. pricing.

The takeaway: the company is sequencing its filings so the U.S. price anchors every other negotiation.

What did the CLOVER-WaM data show?

Management highlighted an analysis from the CLOVER-WaM study presented in October. Among patients treated with Iopofosine I-131 immediately after BTK inhibitor therapy:

• Overall response rate: 87.5%
• Major response rate: 79.2%
• Median duration of response: 16 months
• Clinical benefit rate: 100%

Longcor reported the figures. 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: updated 12-month CLOVER-WaM follow-up data, an analysis of response duration by prior lines of therapy, and the Phase III trial design.

What is the earlier-treatment strategy?

The company has initiated a separate Phase Ib dosimetry study expected to enroll 20 to 30 newly diagnosed and relapsed WM patients, with no specific prior-treatment requirement. The study will assess drug uptake in tissues and collect safety and efficacy data. Caruso said the first patient is expected around the first quarter of 2027.

Management does not expect the dosimetry study to materially compete for Phase III enrollment, citing broader patient eligibility and predominantly different sites. Longcor said a comparative, controlled trial would be the expected route for a frontline indication. Caruso suggested favorable Phase Ib data could help support consideration for earlier-line treatment in clinical guidelines.

How did the quarter look financially?

Cellectar ended September with approximately $24.6 million in cash and cash equivalents, up from $13.2 million at the end of 2025. CFO Chad Kolean said the cash runway extends into the second quarter of 2027 and covers planned operations, including Phase III initiation and a potential new drug application submission.

The company completed an oversubscribed financing in May: $35 million upfront plus $105 million in milestone-based capital, for a total of up to $140 million, Kolean said.

Quarterly spending:

• R&D expenses rose to $5.4 million from $2.5 million a year earlier, driven by Phase III startup costs and increased activity in the Phase Ib CLR 125 triple-negative breast cancer trial
• G&A expenses increased to $2.7 million from $2.3 million, mainly on higher professional fees and personnel costs
• Net loss widened to $8 million, or $0.46 per share, from $4.4 million, or $1.41 per share, a year earlier

The takeaway: spending has more than doubled on R&D, and the runway now stretches past the planned filing date.

What else is in the pipeline?

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 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 initial dosimetry and safety data remain on track for presentation later in 2026 at the San Antonio Breast Cancer Symposium.

Cellectar is a clinical-stage biopharmaceutical company developing targeted radiotherapeutics and oncology treatments. Its platform uses phospholipid ether compounds designed to accumulate preferentially in cancer cells while limiting exposure to healthy tissue. Its lead candidate, iopofosine I 131 (CLR 131), is a small-molecule radiopharmaceutical being studied for hematologic malignancies, including relapsed or refractory multiple myeloma and certain lymphomas.