Cellectis to Present Preliminary Results of NATHALI_01 and Updated Results of the BALLI_01 Phases I Trials at the American Society of Hematology (ASH) 65th Annual Meeting

New York, NY – November 2, 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 today that preliminary results of the Phase I NATHALI-01 clinical trial evaluating UCART20x22  in patients with relapsed or refractory non-Hodgkin lymphoma (r/r NHL) and updated results of the Phase I BALLI-01 clinical trial evaluating UCART22 in patients with relapsed or refractory CD22+ B-cell acute lymphoblastic leukemia, (r/r B-ALL) will be presented at the American Society of Hematology 65^th Annual Meeting (ASH 2023), that will take place on December 9-12, 2023 in San Diego (CA) and online.

These data will be presented in two poster sessions:

Poster Presentation (P2110)

Title: Preliminary Results of Nathali-01: A First-in-Human Phase I/IIa Study of UCART20x22, a Dual Allogeneic CAR-T Cell Product Targeting CD20 and CD22, in Relapsed or Refractory (R/R) Non-Hodgkin Lymphoma (NHL)

Session Name: 704. Cellular Immunotherapies: Early Phase and Investigational Therapies: Poster I

Presenter: Dr. Jeremy Abramson (Massachusetts General Hospital Cancer Center)

Date/Time: Saturday, December 9, 2023 at 5:30 - 7:30 PM PT at San Diego Convention Center, Halls G-H

The poster presentation highlights the following data:

• as of July 1, 2023, 3 patients were enrolled and treated at dose level 1 (50 million cells) with product manufactured in-house by Cellectis. Cytokine release syndrome (CRS) Grade 1 or 2 occurred in all patients, and all CRS resolved with treatment.
• No immune effector cell associated neurotoxicity (ICANS) or graft versus host disease (GvHD) was observed. There were no UCART20x22 dose limiting toxicities (DLTs), and there was 1 DLT in connection with CLLS52 (alemtuzumab).
• All patients responded at Day 28, with 1 partial metabolic response and 2 complete metabolic responses in patients who had failed prior autologous CD19 CAR T-cell therapies.
• UCART20x22 expansion correlated with increases in serum cytokine and inflammatory marker levels as well as with CRS.
• These initial data support the continued clinical trial evaluating UCART20x22 in R/R NHL.

Poster Presentation (P4847)

Title: Updated Results of the Phase I BALLI-01 Trial of UCART22 Process 2 (P2), an Anti-CD22 Allogeneic CAR-T Cell Product Manufactured By Cellectis Biologics, in Patients with Relapsed or Refractory (R/R) CD22+ B-Cell Acute Lymphoblastic Leukemia (B-ALL)

Session Name: 704. Cellular Immunotherapies: Early Phase and Investigational Therapies: Poster III

Presenter: Dr. Nitin Jain (University of Texas MD Anderson Cancer Center)

Date/Time: Monday, December 11, 2023 at 6:00 - 8:00 PM PT at San Diego Convention Center, Halls G-H

The poster presentation highlights the following data:

• in vitro comparability studies suggested that UCART22 Process 2 (P2) (manufactured in-house by Cellectis) is more potent than UCART22 Process 1 (P1) (manufactured by an external CDMO), and as of July 1, 2023, 3 patients were enrolled into the first UCART22 P2 cohort at dose level 2 (1 million cells/kg).
• UCART22 P2 was administered after fludarabine, cyclophosphamide, and alemtuzumab (FCA) lymphodepletion regimen and was well tolerated. No DLTs or ICANS was observed, and the CRS observed was Grade 1 or 2.
• There was a higher preliminary response rate (67%) at dose level 2 (1 million cells/kg) with UCART22 P2 (manufactured in-house by Cellectis) compared to 50% at dose level 3 (5 million cells/kg) with UCART22 P1 (manufactured by an external CDMO).
• UCART22 expansion was observed in the responding patients and correlated with increases in serum cytokines and inflammatory markers.
• The study continues to enroll patients at dose level 2i (2.5 million cells/kg) with UCART22 P2.