Abstract
Background: Chimeric antigen receptor (CAR) T cells have revolutionized care for lymphoid malignancies but continue to present challenges with safety and accessibility. Alternative antiCD19 CAR constructs may improve toxicity and efficacy, and on-site manufacturing may decrease vein-to-vein time, improving cost-effectiveness and patient access. We hypothesized that CAR T cells with a fully human antiCD19 (huCD19) scFv would have a favorable safety and toxicity profile. We report results of a phase 1 clinical trial using this CAR T-cell product.
Methods: Patients aged ≥18-years with relapsed/refractory (R/R) CD19+ B-cell malignancies who failed ≥ 2 lines of therapy were enrolled. Non-Hodgkin lymphoma (NHL) patients were enrolled in group A and B-cell acute lymphoblastic leukemia (ALL) patients in group B. B-ALL patients received split dosing of the CAR-T with 40% on day 1 and 60% on day 7 based on previous literature. Bridging therapy was permitted but not required. Autologous T-cells were transduced using a lentiviral vector (Lentigen Technology, Inc, LTG2741) encoding the fully human antiCD19 binding motif, CD8 linker and transmembrane region and 4-1BB/CD3z domains. GMP-compliant manufacturing was done using CliniMACS Prodigy in 8-day cultures. Dose escalation was conducted according to a 3+3 design with three dose levels (0.5, 1 and 2 x106 CAR-T cells/kg). Patients received lymphodepletion with cyclophosphamide 60mg/kg on day -6 and fludarabine 25mg/m2/day on days -5 to -3. After confirmation of successful manufacturing in early patients, patients on dose level 3 were permitted to start lymphodepleting therapy during cell manufacturing to receive infusion without cryopreservation. Primary objective was to determine safety of treatment and establish the recommended phase II dose. Secondary objectives included describing overall response, duration of response, overall and progression free survival. Exploratory endpoints included CAR-T cell production efficiency and in vivo persistence after infusion.
Results: 22 patients were enrolled while 15 (4 female, 11 male) received the study CART cells. Median age was 62 (40-77). NHL diagnoses included mantle cell lymphoma (MCL) (n=4), chronic lymphocytic leukemia (CLL) (n=3), splenic marginal zone lymphoma/Waldenstrom macroglobulinemia (SMZL/WM) (n=3) diffuse large B-cell lymphoma (DLBCL) (n=2) and follicular lymphoma (FL) (n=1), with a median of 4 (range 2-12) prior lines of therapies. Two patients with B-cell ALL were enrolled in group B at dose level 1, further dose expansion was not done due to poor accrual. Nine patients received bridging therapy with chemotherapy and/or radiation, only 3 had partial response to bridging. The median apheresis to infusion time was 23 days (range 23-37) at dose level 1 and 2, and 11 days (range 8-22) at dose level 3. Three products were infused fresh.
CAR-T cell product manufacturing was successful in all patients. Median transduction rate was 47.35% (27-57), median fold expansion was 18.7 (4.5-34.6). CAR-T expansion based on vector sequence peaked between 14-21 days. The longest persistence was 24 months in 2 patients and median persistence was 3 months (0.5-24).
Cytokine release syndrome (CRS) severity was noted as grade 1 (n=1), grade 2 (n=7) and grade 3 (n=1). Grade 2 CRS was treated with tocilizumab and grade 3 CRS with tocilizumab and anakinra. Immune effector cell-associated neurotoxicity syndrome (ICANS) grade 1-2 occurred in 6 patients, treated with steroids (n=6) and anakinra (n=3). No grade 3 or higher ICANS was observed. No treatment-related mortality occurred.
At last follow up, 7(47%) patients had disease response and 5(33%) patients were in complete remission (CR). After a median follow-up of 21 months (range 2-50 months), in group A, 5 patients (39%) relapsed, 1 was not evaluable due to death at 2 months post CAR-T, while in group B, both patients relapsed. Five patients died during study period, three from relapse, one from previously undiagnosed concomitant Hodgkin lymphoma and one from an uncertain neurodegenerative disease not related to ICANS.
Conclusion: AntiCD19 CAR T cells with a fully human antigen recognition domain have acceptable safety and clinical activity against R/R B cell malignancies. Point of care manufacture and fresh infusion result in rapid access to this therapy. This novel construct and manufacturing process represent a platform for future development of innovative cellular therapies.
