SCRI-CAR19

This study reports outcomes of PLAT-02, a phase 2 trial of SCRI-CAR19, a second-generation CAR T-cell product with FMC63 scFv and 41BB costimulation, in pediatric and young adult patients with B-cell acute lymphoblastic leukemia; and PLAT-03, a companion study evaluating exogenous CD19 antigen stimulation with serial infusions of T cells expressing truncated CD19, T-cell antigen presenting cells (T-APCs). The efficacy cohort of PLAT-02 (n=72 patients, median age 12.5 years) received fludarabine/cyclophosphamide lymphodepletion followed by a dose of 1X106 CAR+ T cells/kg...Further exploration of serial artificial CD19 antigen exposure is warranted based on these pilot results. PLAT-02 (NCT02028455) and PLAT-03 (NCT03186118).

The primary efficacy cohort was defined as those who received fludarabine/cyclophosphamide (flu/cy) LD and were infused with CAR19. However, subjects were not randomized to receive T-APCs and those enrolled on PLAT-03 were more heavily treated and more likely to have received a prior HCT. Further exploration of T-APCs is warranted to define and evaluate their impact on persistence and durable responses.

We tested the modified manufacturing process and resulting product, designated SCRI-CAR19v2, in a cohort of 21 subjects on the phase 2 arm of the trial. Here, we describe the unanticipated enhancement in product performance resulting in prolonged persistence and B-cell aplasia, and improved leukemia-free survival with SCRI-CAR19v2 as compared to SCRI-CAR19v1.