A Feasibility and Safety Study of a New CD19-Directed Fast CAR-T Therapy for Refractory and Relapsed B Cell Acute Lymphoblastic Leukemia

Introduction CD19-targeting chimeric antigen receptor (CAR) T cell therapy has demonstrated high success; however, its therapeutic potential can still be further improved. In addition, the high cost and lengthy process of CAR-T production limit its broad application. We have developed a new platform termed FasT (F) CAR-T with shortened manufacturing time to one day (plus 7 days of additional testing for regulatory requirements). Here we report results from a pre-clinical study of FasT (F) CAR-T (GC007F) and a phase Ⅰ clinical trial to assess the safety and feasibility of treating patients with CD19+ relapsed/refractory B-cell acute lymphoblastic leukemia (B-ALL). Methods In this study, a second generation of CD19-directed CAR-T was manufactured using the FasT CAR-T platform. Peripheral blood (PB) mononuclear cells were obtained by leukapheresis either from healthy donors for the pre-clinical study or from patients undergoing the clinical trial. T cells were separated and used for CAR-T generation. A xenograft mouse model was used to determine the efficacy of GC007F in vivo. Conventional (C) CAR-T derived from the same healthy donor were also made and tested in parallel for comparison. Between Feb. 2019 and July 2019, 10 adolescent and adult patients with CD19+ relapsed/refractory B-ALL were enrolled in a feasibility trial for CD19 FasT CAR-T (www.clinicaltrials.gov, NCT03825718). FasT CAR-T cells for all patients were successfully manufactured. All patients received a conditioning regimen of IV fludarabine (30mg/m2/d) and cyclophosphamide (250mg/m2/d) for 3 days followed by a single infusion of CAR-T cells. Six patients received a low-dose 6.5 (5.86-7.04) x104/kg of FasT CAR-T, 2 received a medium-dose 1 (1-1.16) x105/kg, and 1, a high-dose 1.56x105/kg. The primary end points of the study were to evaluate feasibility and toxicity, and the secondary end points included disease response and engraftment/persistence of infused FasT CAR-T cells. Results This preclinical study has demonstrated several significant improvements of CD19-directed F CAR-T over C CAR-T: 1) 5-30 fold superior expansion capability (p