First in Human Administration of UCART123 in Cellectis’ AML Phase I Clinical Trial at Weill Cornell Medicine, NewYork-Presbyterian Hospital

NEW YORK–(BUSINESS WIRE)– Regulatory News:

Cellectis
(Alternext: ALCLS; Nasdaq: CLLS), a clinical-stage biopharmaceutical
company focused on developing immunotherapies based on gene-edited CAR
T-cells (UCART), announced today the first administration in the Phase I
clinical study in Acute Myeloid Leukemia (AML) for its investigational
product UCART123, one of the Company’s wholly-controlled TALEN®
gene-edited product candidates. This marks the first allogeneic,
“off-the-shelf” gene-edited CAR T-cell product candidate targeting CD123
to be investigated in clinical trials.

This clinical research in AML is led by Principal Investigator Dr. Gail
J. Roboz, Professor of Medicine at Weill Cornell Medicine and Director
of the Clinical and Translational Leukemia Programs at Weill Cornell
Medicine and NewYork-Presbyterian Hospital.

The clinical trial will investigate the safety and efficacy of UCART123
in patients with AML. AML is a devastating clonal hematopoietic stem
cell neoplasm which is characterized by uncontrolled proliferation and
accumulation of leukemic blasts in bone marrow, peripheral blood and,
occasionally, in other tissues. These cells disrupt normal hematopoiesis
and rapidly cause bone marrow failure. In the U.S., there are an
estimated 19,950 new AML cases per year, with 10,430 estimated deaths
per year. While complete response rates can be as high as 80 percent in
younger patients who undergo initial induction cytotoxic chemotherapy,
the majority of AML patients relapse and die from the disease. AML
patients with high-risk genetic features have an especially urgent unmet
medical need, as their outcomes are dismal with all existing treatment
modalities, including allogeneic stem cell transplantation.

“After being granted rapid approval from Regulatory Authorities and
Institutional Review Boards to initiate UCART123 studies, the enrollment
and treatment of the first patient represents a major milestone for
Cellectis, and we are eager to hit the ground running with the
recruitment of our first patient for our second UCART123 Phase I study
in BPDCN soon,” said Dr. Loan Hoang-Sayag, Cellectis Chief Medical
Officer. “This first program targeting CD123 will be a paradigm shift
for our Company, as it will provide a wealth of valuable additional
knowledge and data to drive our gene-edited allogeneic CAR T-cell
platform.”

“We are excited to be enrolling our first patient with UCART123 and are
hopeful that this novel immunotherapy modality will prove to be a
significant and effective weapon against AML,” said Dr. Roboz.

The clinical trial is part of a strategic translational research
alliance that was formed between Cellectis and Weill Cornell Medicine in
2015. Dr. Monica Guzman, an associate professor of pharmacology in
medicine at Weill Cornell Medicine, is co-principal investigator whose
work focuses on preclinical and early-stage testing to optimize the
development of stem cell-targeted cancer drugs.

About Cellectis

Cellectis is a clinical-stage biopharmaceutical company focused on
developing a new generation of cancer immunotherapies based on
gene-edited T-cells (UCART). By capitalizing on its 17 years of
expertise in gene editing – built on its flagship TALEN® technology and
pioneering electroporation system PulseAgile – Cellectis uses the power
of the immune system to target and eradicate cancer cells.

Using its life-science-focused, pioneering genome engineering
technologies, Cellectis’ goal is to create innovative products in
multiple fields and with various target markets.

Cellectis is listed on the Nasdaq market (ticker: CLLS) and on the NYSE
Alternext market (ticker: ALCLS). To find out more about us, visit our
website: www.cellectis.com

Talking about gene editing? We do it. TALEN® is a registered trademark
owned by the Cellectis Group.

Disclaimer

This press release contains “forward-looking” statements that are based
on our management’s current expectations and assumptions and on
information currently available to management. Forward-looking
statements involve known and unknown risks, uncertainties and other
factors that may cause our actual results, performance or achievements
to be materially different from any future results, performance or
achievements expressed or implied by the forward-looking statements. The
risks and uncertainties include, but are not limited to, the risk that
the preliminary results from our product candidates will not continue or
be repeated, the risk of not maintaining regulatory approval to pursue
UCART123 clinical trials, the risk of not obtaining regulatory approvals
to commence clinical studies on UCART123 in other countries or on other
UCART product candidates, the risk that any one or more of our product
candidates will not be successfully developed and commercialized.
Further information on the risks factors that may affect company
business and financial performance, is included in filings Cellectis
makes with the Security Exchange Commission from time to time and its
financial reports. Except as required by law, we assume no obligation to
update these forward-looking statements publicly, or to update the
reasons actual results could differ materially from those anticipated in
the forward-looking statements, even if new information becomes
available in the future.

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