ASH 2025: Cellectis Presents Development Plan to Further Enhance High Response Rate Observed for Eti-cel in r/r NHL

Eti-cel showed an 88% ORR and 63% CR (n=8) at current dose level in r/r NHL after >2 prior lines of therapy

In vivo data suggest IL-2 may further enhance response rates and optimize eti-cel expansion and persistence

IL-2 cohort enrollment to start in Q1 2026; full Phase 1 dataset expected in 2026

New York, NY - December 8, 2025 - 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, announced the presentation of encouraging updated data of patients treated in the Phase 1 NATHALI-01 clinical trial with eti-cel, at the 67th Annual Meeting of the American Society of Hematology (ASH) in Orlando, FL.

Eti-cel product candidate is the first allogeneic dual CAR-T targeting CD20 and CD22 simultaneously, being developed in Phase 1 of the NATHALI-01 clinical trial, for patients with relapsed/refractory non-Hodgkin lymphoma (r/r NHL), following at least two lines of therapy.

Cellectis presented preliminary results on eti-cel, which demonstrated an encouraging overall response rate (ORR) of 88% and a complete response (CR) rate of 63% (n=8) at the current dose level.

Additional in vivo data presented suggest that exogenous low dose Interleukin-2 (IL-2) support can significantly enhance the expansion and persistence of CAR-T cells to boost CAR-T efficacy without exacerbating toxicity.

"Cellectis believes that, with the addition of low dose IL-2 support, it is possible to further deepen the already high response rates seen with eti-cel in these patients who have relapsed following multiple prior lines of therapy including, in most cases, a CD19 CAR-T" said Adrian Kilcoyne, MD, MPH, MBA, Chief Medical Officer at Cellectis. "The trial will now investigate any potential impact of low dose IL-2 support in these difficult to treat patients. We look forward to sharing the full Phase 1 dataset expected in 2026."

Next Steps

Overall, these preliminary data underscore the potential of this innovative approach to transform outcomes for r/r NHL patients. The Company will now investigate the potential impact of low dose IL-2 support and will start recruitment of patients in the IL-2 support cohort in Q1 2026. Cellectis expects to present the full Phase 1 dataset in 2026.

The poster presentation will be available on Cellectis' website.