Core Insights - Cellectis announced the strong potential of circular single-stranded DNA (CssDNA) as a universal, efficient non-viral template for gene therapy, which will be presented at the ESGCT annual congress in Sevilla, Spain from October 7-10, 2025 [1][3] Group 1: CssDNA and Gene Therapy - The company developed an editing process using kilobase-long CssDNA donor templates to expand the scope of gene therapy beyond gene corrections [3] - Research data indicate that CssDNA editing achieved high gene insertion frequency in viable hematopoietic stem and progenitor cells (HSPCs), showing a higher propensity to engraft and maintain gene edits compared to adeno-associated viruses (AAV)-edited HSPCs [8] Group 2: TALE Base Editors (TALEB) - Cellectis presented a comprehensive analysis of TALE base editors (TALEB) at the ESGCT congress, focusing on their off-target effects in the nuclear genome [5][7] - TALEB can directly edit double-strand DNA without the need for DNA breaks, converting cytosine (C) to thymine (T) through an uracil (U) intermediate, which is significant for therapeutic applications [6] Group 3: Safety and Off-Target Effects - The study found no evidence of biases towards off-site C-to-T editing at sites flanked by CTCF binding sites, supporting the safe development of TALEB in therapeutic cell engineering [9] - Cellectis combined advanced bioinformatic predictions with experimental approaches to evaluate the safety of TALEB, focusing on potential off-target effects in primary T cells [7] Group 4: Company Overview - Cellectis is a clinical-stage biotechnology company focused on developing life-saving cell and gene therapies using its gene-editing platform, with a unique allogeneic approach for CAR T immunotherapies [10] - The company controls the entire cell and gene therapy value chain from start to finish, with headquarters in Paris and additional locations in New York and Raleigh, NC [11]

Core Insights - Cellectis is presenting research data on TALEN®-mediated non-viral transgene insertion and advancements in genetic editing using TALE base editors at the ASGCT annual meeting in May 2025 [1][13] - The company aims to develop life-saving cell and gene therapies through its innovative gene-editing platform [1][14] Group 1: TALEN®-Mediated Non-Viral Transgene Insertion - Cellectis combines TALEN®-mediated gene editing with non-viral delivery methods to enhance cellular and gene therapies, focusing on gene insertion efficacy and cellular health using single-stranded DNA (ssDNA) [3][4] - This approach addresses challenges associated with traditional viral methods, such as manufacturing constraints and potential genomic toxicities [4][10] - The research indicates that TALEN®-mediated gene editing with non-viral templates can achieve high efficiency in gene insertion in T-cells and hematopoietic stem and progenitor cells (HSPCs) [10] Group 2: TALE Base Editors (TALEB) - TALEB technology allows for high-fidelity C-to-T editing of double-stranded DNA without DNA strand nicking, enhancing the precision of gene editing [7][11] - Cellectis has developed methods to characterize TALEB efficiency and assess factors influencing its activity, including target sequence composition [8][11] - The research shows that TALEB can achieve efficient C-to-T conversion while maintaining specificity, with no detectable off-target editing in primary cells [11][12] Group 3: Future Implications - The advancements in TALEN® and TALEB technologies are expected to provide alternative, efficient, and safe therapeutic options for patients with various diseases, including cancer and autoimmune disorders [6][10] - Cellectis' innovative gene-editing tools are positioned to support novel gene therapy applications, enhancing the control and efficiency of gene editing processes [12][13]