Preliminary Data from Servier and Pfizer’s UCART19 Product Candidate Shows High Complete Remission Rate Across Two Phase I Adult and Pediatric Acute Lymphoblastic Leukemia Trials

12 December 2017 – Servier, Pfizer Inc. (NYSE: PFE) and Cellectis (Euronext Growth: ALCLS - Nasdaq: CLLS) presented at the 59th American Society of Hematology (ASH) Annual Meeting and Exposition in Atlanta preliminary results from two phase 1 studies of UCART19, an investigational allogeneic anti-CD19 CAR T-cell product, in adult and pediatric patients with relapsed or refractory (R/R) CD19-positive B-cell acute lymphoblastic leukemia (B-ALL). These first-in-human data demonstrated the safety and tolerability of UCART19, resulting in an 83% complete remission rate across the adult and pediatric patient population.

Results from the CALM (UCART19 in Advanced Lymphoid Malignancies) Trial

The CALM study (UCART19 in Advanced Lymphoid Malignancies) is an open label, dose-escalation study designed to evaluate the safety, tolerability and anti-leukemic activity of UCART19 in adult patients with R/R B-ALL. Five out seven patients treated achieved molecular remission at Day 28 post UCAR19. Molecular remission is defined by negative minimal residual disease (MRD). MRD is a measurement of the number of residual leukemic cells that remain after treatment.

“These early results for UCART19 are very encouraging both in terms of manageable safety and the impressive complete molecular remission rate in these hard-to-treat adult patients with R/R B-ALL,” said Reuben Benjamin, Principal Investigator of the CALM Study and Consultant Hematologist at King’s College Hospital, United Kingdom. “This first cohort explored a lower dose of UCART19 that is approximately one tenth of that used in most autologous CAR-T trials. These results support additional evaluation of UCART19 at varying doses.”

Only one Grade 1 cutaneous acute graft versus host disease (GvHD) occurred. No severe neurotoxicity was observed. Cytokine release syndromes (CRS) were mild and manageable except in one patient treated with UCART19 at the first dose level, who developed CRS Grade 4 and neutropenic sepsis leading to death at Day 15.

Results from the PALL (Pediatric Acute Lymphoblastic Leukemia) Trial

The PALL (Pediatric Acute Lymphoblastic Leukemia) study is a phase 1, open label study designed to evaluate the safety and ability of UCART19 to induce molecular remission defined by MRD negativity at Day 28 to enable allogeneic stem cell transplantation in pediatric patients with high-risk R/R B-ALL. Results showed all five children achieved MRD negativity, enabling them to proceed to allogeneic stem cell transplant. Only one Grade 1 cutaneous acute GvHD occurred. No severe neurotoxicity was observed. Cytokine release syndromes were mild in the majority of cases and were all manageable.

Servier is the sponsor of both studies that are active in Europe and the United States.

“We are proud to present the first clinical trial data with UCART19 in patients with heavily pretreated R/R ALL,” said Patrick Therasse, MD, PhD, Head of Research and Development-Oncology for Servier. “We believe this innovative, allogeneic CAR T-cell approach could be disruptive to the patient community.”

About UCART19

UCART19 is an allogeneic CAR T-cell product candidate being developed for treatment of CD19-expressing hematological malignancies, gene edited with TALEN®. UCART19 is initially being developed in adult and pediatric ALL and is currently in Phase I. UCART19 has the potential to overcome the limitation of the current autologous approach by providing an allogeneic, frozen, “off-the-shelf” T cell based medicinal product.

In November 2015, Servier acquired the exclusive rights to UCART19 from Cellectis. Following further agreements, Servier and Pfizer began collaborating on a joint clinical development program for this cancer immunotherapy. Pfizer has been granted exclusive rights by Servier to develop and commercialize UCART19 in the United States, while Servier retains exclusive rights for all other countries.