Cellectis to Present Data on TALE-Base Editors and Non-Viral Gene Therapy at the ESGCT 31st Annual Congress

New York, NY - October 22, 2024 - 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 today that they will be showcasing pre-clinical data that permit the design of an efficient and specific TALE base editors (TALEB) as well as a process to enhance the efficacy of non-viral gene insertion in hematopoietic stem and progenitor cells (HSPCs) at the European Society of Cell and Gene Therapy 31st annual congress, that will take place on October 22-25, 2024, in Roma, Italy.

The data will be presented in two posters:

Controlling C-to-T editing with TALE base editors

Presenter: Alexandre Juillerat, Ph.D., Vice-President Gene Editing & NY Lab Head at Cellectis

Date/Time: Thursday, October 24 from 2:00pm to 3:30pm CET

Poster number: P0666

TALE base editors (TALEB) are fusions of a transcription activator-like effector domain (TALE), split-DddA deaminase halves, and an uracil glycosylase inhibitor (UGI). The C-to-T class of TALEB edits double strand DNA by converting a cytosine (C) to a thymine (T) via the formation of an uracil intermediate.

Cellectis recently developed a strategy that allows the comprehensive characterization of C-to-T conversion efficiencies within the editing window. This method also takes advantage of a highly precise and efficient TALEN®-mediated ssODN knock-in in primary T cells to assess how target composition and spacer variations affect TALEB activity/efficiency.

The datasets obtained in this study enhanced our understanding of TALEB and permitted the design of efficient and specific tools that could be compatible with the potential development of therapeutic applications.

Circular Single-Stranded DNA Enables Efficient TALEN-Mediated Gene Insertion in Long Term HSC

Presenter: Julien Valton, Ph.D., Vice-President Gene Therapy at Cellectis

Date/Time: Thursday, October 24 from 2:00pm to 3:30pm CET

Poster number: P0585

Non-viral alternatives such as linear single-stranded DNA (LssDNA) and circular single-stranded DNA (CssDNA) are emerging as promising options to vectorized DNA donor template for nuclease-mediated gene insertion in hematopoietic stem and progenitor cells (HSPCs) used for gene therapy applications.

Capitalizing on its TALEN® technology, Cellectis has devised a gene editing process that incorporates non-viral DNA donor template delivery (LssDNA or CssDNA) to enhance gene insertion in HSPCs.

The circularization of ssDNA increases gene insertion rates in long term HSCs and has the potential to enhance their engraftment capacity in preclinical murine model, thereby to facilitate the advancement of next-generation cell therapies. This research marks a crucial step towards enhancing the efficacy of non-viral gene therapy.

The posters will be published on Cellectis' website after the presentations.