Follow-up on Phase 1 Study of AT101, a Novel Anti-Cd19 Chimeric Antigen Receptor Cell Therapy (CAR-T) in Patients with Relapsed or Refractory (r/r) B-Cell Non-Hodgkin Lymphoma.

7035 Background: All the FDA-approved CD19 CAR-T products are based on FMC63 scFv, which binds to the membrane-distal region of CD19. We developed a novel anti-CD19 antibody clone (1218) binding to a membrane-proximal epitope of CD19 with fast on/off kinetics. AT101 is an autologous CAR-T cell transduced with a lentiviral vector encoding CAR comprised of a humanized scFv of 1218, 4-1BB costimulatory, and CD3zeta domain. Methods: In the phase 1 trial, patients (n=3 per dose level; up to n=18 in total) are treated with AT101 in 3 dose-escalation cohorts based on a standard 3 + 3 design. Each patient received a single intravenous dose of AT101 at dose level (DL) 1 (0.2 x 10 6 cells/kg), DL2 (1.0 x 10 6 cells/kg), or DL3 (5.0 x 10 6 cells/kg). The primary objective is to determine the safety, the maximum tolerated dose, and the recommended phase 2 dose of AT101. Key eligibility criteria include patients aged ≥19 with histologically confirmed relapsed or refractory B-cell non-Hodgkin lymphoma (NHL). Tumor responses were evaluated using Lugano 2014 criteria at 4 weeks before AT101 infusion as well as at 4 weeks and 3, 6, 9, 12, and 18 months after AT101 infusion. Results: From March 2022 to December 2022, fourteen patients were enrolled and 12 patients were treated, who were their median age of 62.5 years (range 39 to 84) and received a median of three prior lines of therapy (range 2-9). Their subtypes were as follows: diffuse large B cell lymphoma (DLBCL; n=7, 58.3%), follicular lymphoma (FL; n=3, 25.0%), mantle cell lymphoma (MCL; n=1, 8.3%), or marginal zone lymphoma (MZL; n=1, 8.3%)). The data collection cut-off date was January 31, 2024. Based on the best overall response up to three months, eleven patients responded with an overall response rate (ORR) of 91.7%, and a complete response (CR) was observed in nine patients (75%). Remarkably, in DL2 and DL3 groups, the CR was 100.0%. Among nine patients who achieved CR, seven patients have remained in CR during the median follow-up of 13.6 months (1.6-22.3 months). One patient experienced relapse and another one died from septic shock. The median duration of response (DOR), progression-free survival (PFS), overall survival (OS), and event-free survival (EFS) were 19.5, 17.2, 18.9 and 17.2 months, respectively. The median DOR, PFS, OS and EFS were not reached. Conclusions: In this first-in-human phase 1 trial, AT101 was tolerable with limited and manageable toxicities. In comparison to current FMC63 scFv-based CD19 CAR-T therapies, AT101 exhibited potent and more enduring efficacy with a remarkable suppression of relapse after CR. A phase 2 clinical trial is currently under-going for DLBCL patients. Clinical trial information: NCT05338931 .