Cellectis Presents Research Data on a Novel Immune-Evasive Universal CAR T-cell at ASGCT

New York, NY – May 16, 2022 - 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 will present its first research data on the development of a novel universal CAR T-cell with immune-evasive properties using TALEN®-gene editing, at the American Society of Cell and Gene Therapy Annual Meeting (ASGCT) being held on May 16-19, 2022. This novel immune-evasive CAR T-cell scaffold evades NK (Natural Killer) cell and alloresponsive T-cell attacks and imparts efficient antitumor activity in vitro and in vivo . Cellectis’ novel immune-evasive CAR T-cell (ΔTRACCARΔB2MHLAE), was developed using a combination of TALEN®-mediated gene editing and adeno-associated virus (AAV) dependent gene insertion. ΔTRACCARΔB2MHLAE is devoid of TCRαβ and human leukocyte antigen (HLA) Class I expression and endowed with an engineered surface-exposed HLA-E. These three features could enable CAR T-cells to prevent graft versus host (GvH) reaction and evade the cytolytic activities from alloresponsive T-cells and NK cells. « Universal CAR T-cell therapies are poised to revolutionize cancer treatment and to improve patient outcomes. Realizing these advantages in an allogeneic setting requires universal CAR T cells that can kill target tumor cells, avoid depletion by the host immune system, and proliferate without attacking host tissues. Cellectis’ research suggested that ΔTRACCARΔB2MHLAE T-cells evade NK cell and alloresponsive T-cell attacks and showed prolonged antitumor activity in the presence of cytotoxic levels of NK cells. This new cellular scaffold could enable the broad use of universal CAR T-cells in allogeneic settings and holds great promise for clinical applications. » said Julien Valton, Ph.D., Vice President Gene Therapy at Cellectis. Research data showed that: ΔTRACCARΔB2MHLAE overcame alloresponsive T-cell and NK cells attacks. The immune-evasive property of ΔTRACCARΔB2MHLAE was similar toward NK cells from healthy donors, acute myeloid leukemia (AML) patients and acute lymphocytic leukemia (ALL) patients. ΔTRACCARΔB2MHLAE T-cells exhibit prolonged antitumor activity in the presence of cytotoxic levels of NK cells. Title: Endowing Universal CAR T-cell with Immune-Evasive Properties Using TALEN® -Gene Editing Session Date: May 16, 2022 Presentation Time: 3:45pm - 4:00pm ET Location: Walter E. Washington Convention Center Session title: Cell-Based Cancer Immunotherapies I Room: 207 Final abstract number: 99 The research data will be presented today in an oral presentation. The abstract can be accessed on the ASGCT website , and the oral presentation will be posted on Cellectis’ website during the conference.

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