Cellectar Biosciences, Inc. (CLRB) Earnings

Management highlights

### Clinical Development Progress for Lead Asset Iopopocene I131 - Reported positive 12-month follow-up data from the Phase IIb Clover-WAM study for Iopopocene I131 in relapsed/refractory Waldenstrom's macroglobulemia (WM), a rare lymphoma with 60,000-80,000 patients in the U.S. and EU, and an urgent unmet need for patients progressing after BTKI inhibitor therapy who have no approved post-BTKI treatment options. - The study enrolled 55 heavily pretreated patients (median 4 prior lines of therapy, with 77% BTKI-refractory, 60% chemotherapy-exposed, 58% dual BTKI/rituximab refractory). The therapy met all primary and secondary endpoints: overall response rate of 83.6%, major response rate of 61.8%, median duration of response of 17.8 months, median progression-free survival of 13.5 months, and disease control rate of 98.2%. Over 30% of responders maintained responses beyond 36 months, with consistent efficacy in BTKI-exposed and BTKI-refractory patients, and a manageable safety profile. - The post-BTKI subgroup analysis from Clover-WAM has been selected for presentation at the upcoming ASCO conference. With the full 12-month data set complete, the company is advancing plans to file for FDA accelerated approval and initiate a randomized Phase III confirmatory trial. ### Pipeline Progress - The first patient has been dosed in the Phase Ib trial of CLR125, an alpha-emitting radioconjugate for relapsed/refractory triple-negative breast cancer (TNBC), an aggressive subtype with limited treatment options. - The open-label, dose-finding Phase Ib trial will test 3 dose regimens of CLR125, enroll ~15 patients per arm plus a 15-patient expansion arm for the recommended Phase 2 dose, and evaluate safety, tolerability, and preliminary efficacy. Initial data insights are expected later in 2026. ### Financial Highlights - The company completed an oversubscribed post-quarter financing of up to $140 million, consisting of an upfront $35 million and up to $105 million in milestone-based tranches ($35 million per milestone tied to Phase III initiation, NDA acceptance, and FDA approval, respectively). This financing materially strengthens the balance sheet and provides sufficient capital to advance Iopopocene through the Phase III trial and potential commercialization, while continuing CLR125 development.

Guidance

- The Phase III confirmatory trial for Iopopocene I131 in WM is expected to initiate in late Q4 2026. - The company expects current cash resources (after the financing) to fund all planned operations through Q2 2027. - After the Phase III trial is initiated and enrolling patients (expected 2-3 months after trial initiation in late 2026), the company plans to submit the NDA for Iopopocene under the FDA accelerated approval pathway. Thanks to the granted breakthrough therapy designation, FDA will review the submission within a 6-month window, putting potential approval on track for the second half of 2027. - Preliminary data from the CLR125 Phase Ib trial in TNBC is expected to be released later in 2026.

Segment performance

Selectar Biosciences is a clinical-stage biotech company focused on radiopharmaceutical development, with no commercial product segments generating revenue as of Q1 2026. All expenses are allocated to corporate and research and development operations. For Q1 2026: research and development expenses were $3 million (down from $3.4 million in Q1 2025), general and administrative expenses were $2.8 million (down from $3 million in Q1 2025), and net loss was $5.7 million ($1.33 per share), compared to a $6.6 million net loss ($4.30 per share) in Q1 2025. The company ended Q1 2026 with $8.3 million in cash and cash equivalents (excluding the post-quarter financing), compared to $13.2 million at the end of 2025.

Risks & headwinds

Forward-looking statements (including clinical trial initiation and outcome, regulatory submission timelines, approval expectations, and cash runway forecasts) are subject to material risks and uncertainties that could cause actual results to differ materially. Key risks include: potential delays in clinical trial enrollment, unexpected safety or efficacy issues that could alter trial designs or regulatory requirements, failure to achieve development milestones needed to access the full $105 million in milestone financing, failure to meet FDA regulatory requirements for accelerated approval or full approval, and the inherent uncertainty of clinical drug development. The company has no obligation to update forward-looking statements after the date of the call.

Analyst Q&A

• Q: For BTKI-exposed patients in the Clover-WAM study, how many transitioned directly from BTKI to Iopopocene, and what were the most common prior therapies for patients who received other treatments between BTKI and study entry? /

  A: Over 50% of study patients came directly off BTKI therapy immediately before receiving Iopopocene. The next most common immediate prior therapy was rituximab, either as monotherapy or in combination with chemotherapy. This matches the study's focus on the immediate post-BTKI patient population, which has the highest unmet need.

• Q: What is the comparator arm for the Phase III confirmatory trial, and what is the expected range of progression-free survival (PFS) for the control arm? /

  A: The company aligned with the FDA to use rituximab, cyclophosphamide, dexamethasone (RCD) as the comparator, which is a common salvage therapy for post-BTKI WM patients. Published literature shows that median PFS for BTKI-refractory post-BTKI patients receiving RCD combination salvage therapy ranges from 5.8 to 8.1 months, with 5.8 months being the expected PFS for the heavily BTKI-refractory population that will enroll in the trial. For comparison, Iopopocene achieved over 15 months of PFS in this same patient population in the Phase II Clover-WAM study.

• Q: How did you power the Phase III trial, and what is the expected timing for NDA submission and potential approval? /

  A: The trial was powered assuming 8 months of PFS for the comparator arm and 12 months of PFS for Iopopocene, which means it is over-powered for the expected larger gap in PFS (around 6 months for RCD vs 15 months for Iopopocene), increasing the likelihood of a positive outcome. NDA submission is planned 2-3 months after Phase III initiation (expected to be early 2027). With breakthrough therapy designation, FDA has 6 months to review the submission, putting potential approval in the second half of 2027.