Introduction: CD19 targeted autologous CAR-T therapies have been approved for the treatment of r/r B-ALL and greatly improved outcome. However, some patients may not be eligible to receive autologous CAR-T. TruUCAR™ GC502 is an allogeneic, universal CAR-T product with CD19/CD7 dual directed CAR. Preclinical data of GC502 were reported at ASH 2021 (Abstract 148500). Here, we report early clinical results from a phase I open-label, non-randomized, prospective investigator initiate trial (IIT) of GC502 in r/r B-ALL patients.

Methods: GC502 is manufactured using leukopaks from HLA-unmatched healthy donors. It contains a 4-1BB based CD19/CD7 dual directing CAR, a T cell enhancer, and genetically disrupted TRAC and CD7 loci to avoid GvHD and fratricide.

Patients (pts) with r/r B-ALL were enrolled and treated with one of two different formulations (A or B) in escalating dose levels ranging from 1.0x107 (DL1) to 1.5x107 (DL2) cells/kg. Prior to infusion of GC502, pts received a Flu/Cy based lymphodepletion regimen. Adverse events, disease response and expansion kinetics were evaluated in this study.

Results: To date, 4 pts (15-34 yrs) were enrolled from Sep. 2021 to Jan. 2022. All patients were heavily pretreated, and had received either autologous or donor derived CD19 or CD19-CD22 targeted CAR-T therapy. Baseline marrow blast levels ranged from 19.5% to 92% (median 48.1%). 1 pt had extramedullary involvement.

At data cut-off (Jan. 28, 2022), all patients had received a single dose of GC502: 1 pt at DL 1 1.0x107cells/kg and 3 patients at DL 2 1.5x107cells/kg. At day 28 post CAR-T infusion, 2 out of 3 response evaluable patients had achieved CR/CRi; 1 pt achieved PR at month 1 and subsequently received HSCT on day 39.

TEAEs presented as Gr 3 febrile neutropenia (2/3), Gr 4 thrombocytopenia (1/3) and Gr 3 anemia (3/3). All TEAE resolved after treatment with SOC. Non-hematological TEAE presented as Gr≤3 γ-GT increase (3/3), Gr≤3 AST increase (2/3) and Gr≤3 ALT increase (3/3). CRS presented as Gr 2 in 2 patients with formulation B. 2 pts received formulation A and experienced Gr 3 CRS with a duration of 7 and 10 days respectively (CRS was graded according ASTCT Consensus Grading). CRS in all pts was manageable and resolved after treatment with Ruxolitinib, SOC and supportive care. No ICANS or aGvHD were observed. The pt treated in DL 1 did not show adequate GC502 cellular expansion. Peak expansions of GC502 in peripheral blood were observed between week 1-2 in DL 2. Median peak CAR copies were 149,945 copies/ug DNA (range 10,849-195,400).

Conclusions: TruUCAR™ GC502 demonstrated promising early results with a manageable safety profile. Robust CAR-T cell expansion was observed in DL2 at 1.5x107cells/kg in heavily pretreated r/r B-ALL patients, including those previously treated with CD19 CAR-T therapies. The study is ongoing and continues accruing patients.

Citation Format: Shiqi Li, Xinxin Wang, Zhongtao Yuan, Lin Liu, Yu Li, Jia Liu, Jiaping He, Zhimin Li, Wei Zhao, Jianning Ge, Yajin Ni, Lianjun Shen, Wei Cao, Xi Zhang, Martina Sersch, Sanbin Wang. Early results of a safety and efficacy study of allogeneic TruUCAR™ GC502 in patients with relapsed/refractory B-cell acute lymphoblastic leukemia (r/r B-ALL) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT196.