Cellectis, a clinical-stage biotechnology company specializing in gene-editing platforms, unveiled significant advances in non-viral gene editing technology at the American Society of Gene and Cell Therapy (ASGCT) annual meeting in New Orleans, May 13-17, 2025. The company presented two research posters demonstrating innovations in TALEN-mediated transgene insertion and TALE base editing that could transform cellular and gene therapy development.
Non-Viral TALEN Technology Addresses Manufacturing Challenges
The first research presentation focused on TALEN-mediated non-viral transgene insertion, a technology designed to overcome limitations of traditional viral delivery methods. Current gene therapy approaches often rely on lentiviral or adeno-associated virus (AAV) systems, which face manufacturing constraints, potential genomic toxicities, and limited payload capacity.
Cellectis' research demonstrates that TALEN-mediated gene editing combined with non-viral templates, including linear and circular single-stranded DNA (ssDNA), achieves highly efficient gene insertion in T-cells and hematopoietic stem and progenitor cells (HSPCs). The approach promotes cell viability while maintaining insertion specificity.
Transcriptomic analysis and in vivo data revealed that circular ssDNA-mediated cell engineering provides superior maintenance of HSPC fitness compared to traditional viral donor template-mediated transgene delivery. This finding suggests the technology could enable more stable and safer gene editing outcomes.
"The implementation of these gene-editing techniques holds significant potential for the development of next-generation therapies, aiming to provide alternative efficient, and safe therapeutic options for patients with cancer, autoimmune diseases, monogenic disorders, and various other conditions," said Beatriz Aranda Orgilles, Ph.D., Associate Director of IO and business development analyst at Cellectis.
TALE Base Editors Deliver Precise C-to-T Editing
The second research presentation highlighted advances in TALE base editors (TALEB), which represent a novel approach to precise genetic modification. TALEB are fusion proteins combining a transcription activator-like effector domain (TALE), split-DddA deaminase halves, and a uracil glycosylase inhibitor (UGI). Unlike traditional gene editing methods, TALEB converts cytosine to thymine in double-stranded DNA without creating DNA strand breaks.
Cellectis developed a comprehensive method to characterize the efficiency of C-to-T conversion and examined factors influencing TALEB activity. The research utilized highly precise knock-in of single-stranded oligodeoxynucleotides (ssODN) in primary T cells to assess how target sequence composition and spacer variations affect editing efficiency.
Research findings demonstrated that TALEB enables efficient C-to-T conversion, with variations in target sequences and surrounding bases affecting editing efficiency. The company showed that educated selection of TALEB architecture allows precise control over editing outcomes.
Importantly, off-target editing assessments revealed no detectable editing in primary cells at previously described off-target sites, highlighting the specificity of TALEB for therapeutic applications. This specificity profile represents a significant advantage for clinical translation.
"It is inspiring to see the advancement of Cellectis' TALE technology into a new tool that is available in our gene editing toolbox. Our ability to understand and fine-tune the editing capacity of TALE base editors has equipped us with another efficient and specific approach that can be used to support novel gene editing and gene therapy applications," said Louisa Mayer, Ph.D., Scientist II and Supervisor of Innovation & Gene Editing at Cellectis.
Expanding Therapeutic Applications
These technological advances position Cellectis to address a broader range of therapeutic targets and disease indications. The non-viral approach could particularly benefit applications requiring large transgene payloads or where viral vector immunogenicity poses concerns. The precise base editing capabilities of TALEB open possibilities for correcting point mutations underlying genetic diseases.
Cellectis operates as one of the few end-to-end gene editing companies with in-house manufacturing capabilities, controlling the entire cell and gene therapy value chain. The company's allogeneic approach to CAR-T immunotherapies in oncology pioneers off-the-shelf, ready-to-use gene-edited CAR-T cells for cancer treatment.
The research abstracts are available on the ASGCT website, with full posters accessible on Cellectis' website beginning the first day of the conference. These presentations underscore the company's commitment to advancing gene editing technologies that could transform treatment options for patients with previously intractable diseases.
