Abstract 1130: A phase 1 dose escalation study of GCC19CART - a novel CoupledCAR therapy for subjects with metastatic colorectal cancer

Abstract Background: Chimeric antigen receptor (CAR) T-cell therapy has shown remarkable clinical efficacy in hematologic malignancies but limited success in solid tumors. GCC19CART, the first clinical candidate from the CoupledCAR solid tumor platform, is designed to overcome the limitations of conventional CAR T-cells in solid tumor malignancies by pairing solid tumor CAR T-cells with CD19 targeting CAR T-cells to amplify proliferation and activation of the solid tumor CAR T component. GCC19CART targets guanylate cyclase-C (GCC) which is expressed in the metastatic lesions of 70%-80% of subjects with colorectal cancers. A Phase 1 investigator-initiated clinical trial is underway in China for patients with relapsed or refractory metastatic colorectal cancer who have received at least 2 prior lines of therapy. Based on a data cutoff on October 20, 2022 21 subjects have been enrolled in 2 dose escalation groups at 5 hospitals in China. Methods: Subjects are screened for GCC expression by immunohistochemistry. Eligible subjects undergo leukapheresis, a single dose of lymphodepleting chemotherapy (fludarabine 30mg/m2 and cyclophosphamide 300mg/m2) 3 days prior to infusion, and then administration of a single infusion of GCC19CART at one of two preassigned doses: 1 × 106 or 2 × 106 CAR T-cells/kg. Endpoints are safety and preliminary evidence of efficacy as determined by CT or PET/CT per RECIST 1.1 or PERCIST 1.0. All responses were confirmed by an independent third-party imaging contract research organization (CRO). Results: 13 subjects have been enrolled to dose level 1 (1 × 106 cells/kg) and 8 subjects have been enrolled to dose level 2 (2 × 106 cells/kg). The most common adverse events were cytokine release syndrome (CRS) in 21/21 subjects (Grade 1 19/21 (90.48%) or Grade 2 2/21 (9.52%)) and diarrhea in 21/21 subjects (Grade 1 6/21 (28.57%) Grade 2 5/21 (23.81%) Grade 3 9/21 (42.86%) or Grade 4 1/21 (4.76%)). Neurotoxicity was observed in 2/21 (9.52%) subjects at Grade 3 or 4 and resolved with corticosteroids. The combined overall response rate (ORR) for both dose levels was 28.6% (6/21). For dose level 1, the overall response rate (ORR) per RECIST 1.1 was 15.4% (2/13). Two subjects demonstrated a partial response (PR) while 3 additional subjects had partial metabolic response (PMR) on PET/CT with stable disease (SD) or progressive disease (PD) per RECIST 1.1. For dose level 2, The ORR per RECIST 1.1 was 50% (4/8). 4 subjects demonstrated a PR (3 at month 1, 1 at month 3 after being SD at month 1) and 2 additional subjects had PMR on PET/CT with SD per RECIST 1.1. Conclusions: preliminary data show that GCC19CART has meaningful dose dependent clinical activity and an acceptable safety profile in relapsed or refractory metastatic colorectal cancer. This trial is ongoing and updated data will be presented. A Phase 1 trial of GCC19CART in the US under a cleared IND is expected to enroll patients from mid-2022. Citation Format: Naifei Chen, Chengfei Pu, Lingling Zhao, Ning Li, Chang Wang, Yusheng Huang, Suxia Luo, Xun Li, Zhenzhou Yang, Jun Bie, Ruihong Zhu, Xi Huang, Haiyang Tang, Tingting Liang, Yizhuo Wang, Beibei Jia, Dongqi Chen, Zhao Wu, Yongping Song, Victor Lu, Lei Xiao, Jiuwei Cui. A phase 1 dose escalation study of GCC19CART - a novel CoupledCAR therapy for subjects with metastatic colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1130.