Cellectis Presents Epigenetic Editing Platform to Turn Genes Off Without Altering DNA at the ASGCT Annual Meeting

New York, NY - April 27, 2026 - 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 presents new research on a TALE-based epigenetic editing approach, that does not cut or permanently modify the DNA sequence, making it a potentially safer alternative for genome editing, at the American Society of Gene and Cell Therapy (ASGCT) annual meeting, that will be held on May 11-15, in Boston (MA).

The data will be presented in a poster:

Title: TALE-based epigenetic modulators show sustained knock-down of target genes in T-cells and HEPG2 via a high-throughput multiplex screening platform

Transcription activator-like effector-based epigenetic modulators (TALEM) are engineered fusion proteins consisting of a TALE DNA-binding domain with functional domains that mediate epigenetic modifications. These proteins can be precisely guided to a target location in the genome to switch genes on or off through a process known as epigenetic editing.

Unlike traditional gene editing tools, this approach does not induce DNA breaks and DNA sequence modifications, making it a potentially safer alternative for genome editing.

In this work, Cellectis developed a high-throughput screening system capable of rapidly assembling and testing hundreds of these TALEM, identifying which combinations are most effective at regulating a given gene.

The results:

This strategy was used for two distinct genes: one highly expressed in hepatocytes (active in liver cells) and another implicated in T-cell dysfunction and exhaustion, a key challenge in cancer immunotherapy. In both cases, the approach achieved >90% reduction in gene activity, which remained stable throughout the study.

"We are excited to present these results at ASGCT, which demonstrate Cellectis' ability to apply its gene editing platform into the emerging field of epigenetic editing" said Louisa Mayer, Ph.D., Scientist II and Supervisor - Innovation & Gene Editing at Cellectis. "This work shows our ability to design and identify highly potent epigenetic editors across different cell types, thereby enriching our gene‑editing toolbox."

The abstract is published on the ASGCT website. The poster will be available on Cellectis' website on the presentation day, Wednesday May 13, 2026 at 5 pm ET.