A Phase 1 Dose Escalation and Expansion Trial of Third-Generation CD19-Directed CAR T-Cells Incorporating CD28 and Toll-like Receptor 2 (TLR2) Co-Stimulation for Relapsed or Refractory B-Cell Non-Hodgkin Lymphomas (ENABLE-1)

Introduction: Chimeric antigen receptor (CAR) T cells directed against CD19 and incorporating CD28 co-stimulation are standard care for relapsed or refractory (r/r) B-cell non-Hodgkin lymphomas (B-NHL), but are associated with immune effector cell-associated neurotoxicity syndrome (ICANS) in ≈50%, cytokine release syndrome (CRS) in ≈85%, and immune effector cell-associated hematotoxicity (ICAHT) in up to 60%, contributing to healthcare costs. The pathogenesis of ICANS and CRS involves CAR T-cell derived GM-CSF and IFN-γ, while T-cell derived IFN-γ has been implicated in late ICAHT.

Engagement of endogenous toll-like receptor 2 (TLR2) enhances T-cell expansion, modulates cytokines and promotes long-lived memory. In preclinical studies, incorporation of an intracellular TLR2 domain between intracellular CD28 and CD3ζ CAR domains lowered CAR T-cell GM-CSF and IFN-γ production without impairing cytotoxicity. We investigated clinical safety and efficacy of an autologous third generation CD19-directed CAR T-cell product (WZTL-002), which combines CD28 and TLR2 co-stimulatory domains.

Methods: We completed a first-in-human phase 1 dose escalation and expansion trial of WZTL-002 CAR T-cells (‘ENABLE-1’, NCT04049513) for adults with r/r B-NHL. Following a 3+3 dose escalation cohort (5×10⁴–1×10⁶ viable CAR⁺cells/kg recipient weight; n=21, ASH 2023 abstract 890), we implemented closed automated manufacture (Cocoon® Platform) and outpatient management during dose expansion at recommended phase 2 dose (RP2D) (0.5–1×10⁶ CAR⁺cells/kg, n=9). Eligible participants had radiologically assessable disease and no central nervous system B-NHL involvement. Bridging therapy was permitted between leukapheresis and lymphodepletion (fludarabine 30mg/m²/day & cyclophosphamide 500mg/m²/day ×3d); WZTL-002 CAR T-cells were given intravenously 2d later. Adverse events (AEs) were graded by CTCAE 5.0 except ICANS and CRS (American Society for Transplantation and Cellular Therapy grading) and late ICAHT (European Hematology Association/European Society for Blood and Marrow Transplantation consensus grading). Response assessment was by PET/CT at month 3 per Lugano 2014 criteria. Cellular kinetics were determined by digital PCR for CAR transgenes in blood mononuclear cells.

Results: Of 30 treated patients, median age was 58.5 years (range 22–72); 10 (33%) female; 22 (73%) European, 7 (23%) Māori and 1 (3%) Asian. Lymphomas were of large cell histology in 25 (83%). Participants had received a median 3 prior lines of therapy including autograft in 13 (43%) and allograft in 1 (3%). Product CAR⁺ cells were median 50% CD4⁺, 41% CD8⁺, 45% CD62L⁺. 26 (87%) received bridging therapy. Pre-lymphodepletion, 13% (43%) had metabolically active disease, 15 (50%) high-risk CAR-HEMATOTOX score and 16 (53%) intermediate or high risk EASIX-FC score. As of July 17 2024, all had reached primary follow-up (3 months after WZTL-002). Grade ≥3 AEs in ≥10% of recipients were: lymphopenia (100%), neutropenia (97%), hypogammaglobulinemia (53%), febrile neutropenia (50%), thrombocytopenia (40%), anemia (30%), and tumor pain (20%). A single episode of grade 1 ICANS occurred (3%) and resolved spontaneously. Grade 1 or 2 CRS occurred in 17 patients (57%) no grade ≥3 CRS events occurred; 9 (30%) received tocilizumab and 3 (10%) dexamethasone for CRS. No participant required intensive care within 28 days of WZTL-002. Grade 1-2 late ICAHT occurred in 6 patients (20%) and grade 3–4 in 4 (13%). 3 month complete response (CR) rate was 52% in the dose escalation cohort (n=21) and 56% in dose expansion (n=9). Among RP2D recipients, geo-mean peak WZTL-002 CAR T-cell level (C_max) was 29,515 transgenes/μg genomic DNA, reached at median day 11 (T_max), and CARs remained detectable at day 90 in 14 of 16 assessed (88%).

Conclusions: In this dose escalation and expansion phase 1 trial of third-generation CD19-directed CAR T-cells, we found low rates of ICANS, CRS, and late ICAHT, with complete response rates comparable to commercial second-generation products at this line of therapy. Addition of a TLR2 domain between CD28 and CD3ζ may lower CAR T-cell toxicity risk while maintaining efficacy. This safety profile could facilitate outpatient management, lower treatment costs and improve the patient experience of CAR T-cell therapy. A phase 2 trial of WZTL-002 as 2^nd or 3^rd line treatment for r/r LBCL has commenced (ENABLE-2, NCT06486051).