Cellectis’ R&D Day Highlights Lasme-cel’s Potential to Address Significant Unmet Need for Patients with r/r B-ALL

 ○ Efficacy: ORR of 68% with lasme-cel Process 2 (n=22), 83% at RP2D (n=12) and 100% in the target Phase 2 population (n=9)

○ Safety: in Phase 1 (n=40), lasme-cel was generally well-tolerated (including 1 case of grade 2 IEC-HS which resolved)

○ Durability: in patients who achieved MRD-negative CR/CRi, median OS was 14.8 months

○ In the target Phase 2 population, CR/CRi rate of 56% with ~80% of patients achieving MRD-negative status

○ In the target Phase 2 population, 100% patients became transplant eligible with 78% proceeding to transplant

○ Among 11 patients previously treated with all 3 targeted therapies (inotuzumab, blinatumomab, and CD19 CAR-T), 8 responded and 7 achieved MRD-negative status

○ BALLI-01 pivotal Phase 2 in r/r B-ALL initiated

○ Potential peak gross sales of up to ~$700 million across the U.S., EU4, UK

NEW YORK, Oct. 16, 2025 (GLOBE NEWSWIRE) -- Cellectis (the “Company”) (Euronext Growth: ALCLS - NASDAQ: CLLS), a clinical-stage biotechnology company using its pioneering gene editing platform to develop life-saving cell and gene therapies, today hosted an R&D Day providing promising clinical data from the Phase 1 BALLI-01 study of lasme-cel (UCART22) for transplant ineligible patients with relapsed/refractory B-cell acute lymphoblastic leukemia (r/r B-ALL) in the third line or beyond (3L+). The Company unveiled the design of the pivotal Phase 2, its planned registration path for lasme-cel's initial indication, as well as the commercial opportunity. The event also included panel discussions with global hematology experts on the potential of lasme-cel to address the significant unmet need for heavily pretreated patients.

“We are encouraged by the Phase 1 results of the BALLI-01 study in a population that had largely exhausted treatment options and faced a poor prognosis. The depth of response we observed, enabling a high percentage of patients in the study to proceed to transplant, with the potential for durable remission, is clinically meaningful. We are focused on rapidly advancing our pivotal Phase 2 program and bringing lasme¹-cel to patients with this significant unmet need,” said Adrian Kilcoyne, MD, MPH, MBA, Chief Medical Officer of Cellectis.