Cellectis Implements CLLS52 for the First Time in the Clinic with Sanofi’s Alemtuzumab

• Cellectis demonstrated that the addition of alemtuzumab to the lymphodepletion regimen was associated with prolonged lymphodepletion and significantly higher cell expansion and clinical activity

New York (NY) – April 24, 2023 – 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 it has implemented the use of alemtuzumab as a Cellectis Investigational Medicinal Product (IMP), coded as CLLS52, as part of the lymphodepletion regimen for UCART22 in the BALLI-01 clinical trial in relapsed/refractory B-cell ALL, for UCART123 in the AMELI-01 clinical trial in relapsed/refractory AML, and for UCART20x22 in the NatHaLi-01 clinical trial in relapsed/refractory B-cell NHL.

In May 2021, Cellectis entered into partnership and supply agreements with Sanofi regarding alemtuzumab. Under the agreements, Sanofi is supplying alemtuzumab to support Cellectis’ clinical trials and the parties agreed to enter into discussions to execute a commercial supply of alemtuzumab under pre-agreed financial conditions.

“As previously reported, the importance of alemtuzumab in the lymphodepletion regimen was demonstrated in our BALLI-01 and AMELI-01 studies, where the addition of this lymphodepletion agent to the fludarabine and cyclophosphamide regimen was associated with sustained lymphodepletion and significantly higher UCART cell expansion allowing for greater clinical activity. We believe these encouraging outcomes are a meaningful step forward to a safe, effective, and controllable therapeutic window for our allogeneic CAR T-cell product candidates” said Mark Frattini, M.D., Ph.D., Chief Medical Officer at Cellectis.

Cellectis is the inventor of the combination of CD52 knockout UCART cells with a lymphodepleting regimen containing an anti-CD52 antibody such as alemtuzumab. The CD52 knockout aims to render UCART product candidates resistant to alemtuzumab as part of the lymphodepleting regimen. Patients’ lymphodepleting regimens reduce host immune cells and should improve allogeneic CAR T-cell expansion and persistence. Cellectis’ UCART22, UCART123 and UCART20x22 product candidates have the CD52 gene inactivated by TALEN® gene editing technology.

To access Cellectis’ 2022 ASH data release and Live Webcast release announcing positive preliminary data from the BALLI-01 and AMELI-01 clinical studies, click here: https://cellectis.com/en/press/cellectis-announces-positive-preliminary-clinical-data-for-ucart22-in-all-and-ucart123-in-aml/