Phase I study of CRISPR-engineered CAR-T cells with PD-1 inactivation in treating mesothelin-positive solid tumors.
Zhenguang Wang, Meixia Chen, Yan Zhang, Yang Liu, Qingming Yang, Jing Nie, Lianjun Shen, Pengfei Jiang, Jiaping He, Xun Ye, Wei Cao, Haoyi Wang, Weidong Han
Abstract
3038 Background: Our previous phase I study with MPTK-CAR-T (mesothelin-directed 28ζ CAR-T cells with PD-1 and TCR disruption by CRISPR-Cas9 system) demonstrated feasibility and safety of CRISPR-mediated PD-1 inactivation in CAR-T cells, and suggested the natural TCR is beneficial for the proliferation of CAR-T cells in solid tumors. Based on these observations, we initiated a pilot dose escalation study to investigate mesothelin-directed CAR-T cells with only PD-1 disruption by CRISPR (termed as GC008t) in patients with mesothelin-positive advanced solid tumors (NCT03747965). Methods: On the data cut-off date (Jan 20, 2020), nine patients (6 pancreatic cancers, 2 ovarian cancers, 1 colorectal cancer) were treated (5 received ≥12 numbers of therapy), three in cohort 1 (0.1-0.2×10 7 /kg), four in cohort 2 (0.5-1.0×10 7 /kg), two in cohort 3 (2.5-5×10 7 /kg). Eight of the 9 patients received lymphodepletion regimen of cyclophosphamide and nab-paclitaxel with or without gemcitabine. Four of the 9 patients received repeat infusions of GC008t per protocol. Results: Comparable proliferation capacity was observed in vitro between the MPTK-CAR-T and the GC008t products. The mean PD-1 surface expression in cell products was 0.5% (range, 0.2%-0.9%). GC008t infusions were well tolerated with no observed on-target/off-tumor toxicity, autoimmune activity. Only two patients in cohort 3 developed grade 1 CRS with fever and rash. Circulating GC008t expanded with a peak at day 7-14 and became undetectable by qPCR beyond 1 month. The mean peak levels of circulating CAR-T cells between GC008t and MPTK-CAR-T at similar dose level were not statistically significant. Failure of GC008t engraftment after repeat infusion was observed in 2 out of 4 patients. The best response of the 7 evaluable patients was stable disease in 4 and partial response in 2 patients (dosed ≥ 1×10 7 /kg) with PFS of 80 and 160 days. Conclusions: Phase I trial of GC008t further establishes that genetic inactivation of PD-1 in CAR-T cells by CRISPR is feasible and safe. The expansion and persistence of CAR-T cells with PD-1 disruption is not improved significantly even in the setting of natural TCR and lymphodepletion. Future endeavors are needed to improve the clinical efficacy of CAR-T therapy in the treatment of solid tumor. Clinical trial information: NCT03747965 .