Cellectar Biosciences (NASDAQ:CLRB) outlined regulatory plans for its lead radiotherapeutic candidate iopofosine I 131, provided updates across its pipeline, and reviewed full-year 2025 financial results during its fourth-quarter and full-year conference call held March 4, 2026.
Regulatory pathway for iopofosine in Waldenström’s macroglobulinemia
President and CEO James Caruso said 2025 was “productive and strategically meaningful,” highlighting progress for iopofosine I 131 in Waldenström’s macroglobulinemia (WM). Management said it ended the year with regulatory alignment in Europe following guidance from the European Medicines Agency’s Scientific Advice Working Party (SAWP). Based on that guidance, Cellectar said it remains on track to submit a conditional marketing authorisation (CMA) application in the third quarter of 2026, which could position iopofosine for potential approval and commercialization in Europe as early as 2027.
Confirmatory Phase III plans and the role of 12-month follow-up data
Chief Operating Officer Jarrod Longcor said interactions with regulators have provided “clear, actionable” paths in both the EU and the U.S. He said the company has now collected 12 months of follow-up on all patients, which he described as a key FDA request from November 2024 as part of the Accelerated Approval framework. Longcor said the company is analyzing a more mature CLOVER-WaM dataset and is encouraged that results continue to show “robust and durable clinical benefit over time” in a salvage treatment setting where he said there are no approved drugs.
Management also said new subgroup analyses—particularly within defined high-need segments—are “especially promising” and will be shared with regulators as part of ongoing discussions.
Longcor said Cellectar agreed with FDA feedback that a confirmatory study in a post-BTK inhibitor (BTKi)-treated patient population in the second-line setting is appropriate. He emphasized that moving to an earlier line more than doubles the potential addressable population in the U.S. compared with later-line use. Caruso added that CLOVER-WaM patients were, on average, treated in the fifth line, and said internal analyses indicate outcomes improve as treatment moves earlier.
During Q&A, management described how it expects the confirmatory trial to support the Accelerated Approval timeline. Longcor said FDA expects the confirmatory study to be initiated and enrolling at the time of NDA submission and still enrolling at the time of regulatory action. He said the company’s approach is to submit an NDA roughly “a month or two” after initiating the confirmatory study, after opening a handful of sites and enrolling “one or two” patients. He also noted that, under the Accelerated Approval process described on the call, FDA would not be reviewing confirmatory trial data at that point, but rather confirming the trial is underway and enrolling. Caruso summarized the timeline as potentially receiving FDA feedback on accelerated approval within “7 to 9 months” of trial initiation, assuming submission shortly after initiation and a six-month review clock.
Longcor said the confirmatory study’s primary endpoint will be progression-free survival (PFS), with response rates—including major response rate—as secondary endpoints. He also said the company would not be announcing data from the confirmatory study during enrollment due to concerns about bias in a comparative trial.
Market context and enrollment expectations
In discussing expectations for PFS in post-BTKi patients, Longcor referenced data from an Italian group led by Varettoni that evaluated outcomes in 78 post-BTKi patients receiving various salvage therapies. He said the median PFS was eight months in second-line patients, and that rituximab combination regimens were “sub 8 months.” Caruso said the confirmatory study is powered based on available literature and the company’s own durability and PFS experience in CLOVER-WaM.
On trial enrollment, Longcor said physician interest appears “extremely high,” including from investigators involved in CLOVER-WaM. Caruso added that the company has also seen strong interest among community-based physicians, pointing to iopofosine’s “ease of administration” and “four simple doses.”
European commercialization approach and distribution considerations
Asked about Europe, Longcor said Cellectar does not plan to commercialize iopofosine itself there and is in discussions with potential partners to handle commercialization. He also highlighted what he described as a distribution advantage: iopofosine’s 21-day shelf life at room temperature, compared with what he said is a 3- to 7-day shelf life for many radiotherapies. He said the company’s prior global CLOVER-WaM trial helped establish logistics to ship and supply the product globally.
Longcor estimated the total European WM market at about 10,000 patients, and said the second-line setting in Europe is “a bit over 12,000, approaching 13,000” patients, compared with “just a bit south of 12,000” in the U.S. He added that, under the European CMA, use would likely be later-line (third line or later) in post-BTKi patients because BTKi adoption in Europe remains more split between first and second line. He said the company would seek to shift toward second-line positioning in Europe after confirmatory data.
Pipeline progress: CLR 125 and CLR 225
Beyond iopofosine, management reviewed progress in its phospholipid drug conjugate (PDC)-based radiotherapeutic pipeline. Caruso said Cellectar initiated a Phase 1b dose-finding study of CLR 125 in triple-negative breast cancer (TNBC). He described CLR 125 as an iodine-125 Auger-emitting agent intended for highly precise tumor targeting. Longcor said the study is active at two sites, with additional sites expected to be added in the second quarter, and that it is evaluating three dosing regimens with a planned expansion arm once a recommended Phase 2 dose is selected. The company expects early interim data in mid-2026, and Longcor said it anticipates a “steady cadence” of results through 2026, including early interim dosimetry, safety, and preliminary efficacy data.
For CLR 225, Cellectar said it completed IND-enabling work and is ready to initiate a Phase 1 trial pending available funding and strategic alignment. Longcor said preclinical studies in pancreatic cancer models showed “compelling tumor inhibition” across multiple dose levels.
Caruso also said the company strengthened infrastructure for its alpha-emitting program through new supply partnerships with ITM Isotope Technologies Munich and Ionetix, aimed at securing commercial-scale access to actinium-225 and astatine-211 for future clinical development.
2025 financial results and cash runway
Chief Financial Officer Chad Kolean said Cellectar ended 2025 with $13.2 million in cash and cash equivalents, compared with $23.3 million at the end of 2024. He said the company raised $5.8 million in the fourth quarter and expects cash on hand to fund budgeted operations into the third quarter of 2026.
Kolean reported a full-year 2025 net loss of $21.8 million, or $8.35 per basic and diluted share, compared with a net loss of $44.6 million in 2024. He said other income was $1.1 million in 2025 versus $7.3 million in 2024, describing the change as largely driven by non-cash warrant accounting effects and noting that warrants issued in 2025 were classified as permanent equity upon issuance.
- Cash and cash equivalents (end of 2025): $13.2 million (vs. $23.3 million at end of 2024)
- Q4 2025 financing raised: $5.8 million
- Expected cash runway: into Q3 2026
- Full-year 2025 net loss: $21.8 million (or $8.35 per share)
Management closed the call by reiterating expectations for multiple milestones in 2026, including planned regulatory submissions, medical meeting presentations featuring at least 12-month follow-up from CLOVER-WaM, and interim updates from the CLR 125 study.
About Cellectar Biosciences (NASDAQ:CLRB)
Cellectar Biosciences, Inc is a clinical‐stage biopharmaceutical company focused on the development of targeted cancer therapies and imaging agents. The company’s proprietary phospholipid drug conjugate (PDC) technology platform is designed to selectively deliver therapeutic and diagnostic payloads to malignant cells while sparing healthy tissue. Through its PDC approach, Cellectar aims to improve the efficacy and safety profile of traditional treatments like chemotherapy and radiotherapy.
Its lead therapeutic candidate, CLR 131, is a radioisotope‐labeled PDC being evaluated in Phase II clinical trials for relapsed or refractory B‐cell malignancies, including multiple myeloma and non‐Hodgkin lymphoma.
