Cellectis

Report Publication Announcement • Sep 2, 2020

PRESS RELEASE

Cellectis to Participate in Upcoming Investor Conferences

September 2nd , 2020 – New York (N.Y.) – Cellectis (Euronext Growth: ALCLS - Nasdaq: CLLS), a clinical-stage biopharmaceutical company focused on developing immunotherapies based on gene-edited allogeneic CAR T-cells (UCART), will present at several upcoming investor conferences. Webcast information when available will be posted in the Investor Relations section of the Company's website at https://www.cellectis.com/en/investors/events-and-webcasts/

Citi Annual BioPharma Conference September 9, 2020 from 3:20 PM to 4:05 PM EDT André Choulika, Chairman & CEO, to participate in a panel on Innovation in Cell Therapy.

Wells Fargo Healthcare Conference Boston September 10, 2020 from 8:00 AM to 8:30 AM EDT André Choulika; Carrie Brownstein, CMO; Simon Harnest, VP, Corporate Strategy &

Baird's 2020 Global Healthcare Conference September 10, 2020 at 3:10 PM EDT Simon Harnest to participate in a firechat and a live Q&A.

Bank of America Healthcare Conference London September 17, 2020 from 4:55 AM to 5:45 AM EDT

André Choulika to provide a company presentation.

Finance to provide a company presentation.

About Cellectis

Cellectis is developing the first of its kind allogeneic approach for CAR-T immunotherapies in oncology, pioneering the concept of off-the-shelf and ready-to-use gene-edited CAR Tcells to treat cancer patients. As a clinical-stage biopharmaceutical company with over 20 years of expertise in gene editing, Cellectis is developing life-changing product candidates utilizing TALEN®, its gene editing technology, and PulseAgile, its pioneering electroporation system to harness the power of the immune system in order to target and eradicate cancer cells.

As part of its commitment to a cure, Cellectis remains dedicated to its goal of providing life-saving UCART product candidates to address unmet needs for multiple cancers including acute myeloid leukemia (AML), B-cell acute lymphoblastic leukemia (B-ALL) and multiple myeloma (MM).

Cellectis headquarters are in Paris, France, with additional locations in New York, New York and Raleigh, North Carolina. Cellectis is listed on the Nasdaq Global Market (ticker: CLLS) and on Euronext Growth (ticker: ALCLS). For more information, visit

www.cellectis.com.

Follow Cellectis on social media: @cellectis, LinkedIn and YouTube.

TALEN® is a registered trademark owned by Cellectis.

For further information, please contact:

Media contacts:

Jennifer Moore, VP of Communications, 917-580-1088, media@cellectis.com Caitlin Kasunich, KCSA Strategic Communications, 212-896-1241, ckasunich@kcsa.com

IR contact:

Simon Harnest, VP of Corporate Strategy and Finance, 646-385-9008, simon.harnest@cellectis.com