BACKGROUND:Claudin18.2 is a promising therapeutic target expressed in various solid tumors, particularly gastric cancer. IBI389 is a novel anti-Claudin18.2 × CD3 bispecific antibody designed to engage T cells by binding CD3 and Claudin18.2, thereby induce immune synapse formation. Herein, we report preliminary results from a phase I study to evaluate safety and efficacy of IBI389 in patients with advanced solid tumors.
METHODS:Eligible patients with advanced solid tumors refractory to standard treatments were enrolled. The dose escalation of IBI389 monotherapy used intra-patient dose escalation with accelerated titration (0.003/0.01/0.03/0.1/0.3/1 µg/kg Q2W) and the classical 3 + 3 design (3/5/10/30/100/300/600 µg/kg Q3W). Selected dose levels were expanded in patients with advanced gastric/gastroesophageal junction cancer (GC/GEJC) and pancreatic ductal adenocarcinoma. The primary objective was safety. Secondary objective was efficacy assessed by investigator per RECIST v1.1 including objective response rate (ORR) and disease control rate (DCR).
RESULTS:A total of 121 patients with solid tumors were enrolled, comprising 23 gastric cancer, 14 gastroesophageal junction cancer, 73 pancreatic adenocarcinoma, and 11 other gastrointestinal solid tumors. No dose-limiting toxicity (DLT) was observed during escalation, and the maximum tolerated dose was not reached. Treatment-related adverse events (TRAEs) occurred in 120 patients (99.2%), with the most common grade ≥ 3 TRAE being gamma-glutamyltransferase increased (21.5%) and lymphocytopenia (14.0%) and other grade ≥ 3 TRAEs were ≤ 5%. Cytokine release syndrome (CRS) related adverse events occurred in 72 patients (59.5%), all grades 1-2 except one grade 3 event. No neurotoxicity or treatment-related deaths were observed. Among 37 patients with GC/GEJC, 27 of them expressing Claudin18.2 at levels of 2 + or 3 + ≥ 10%. In this subgroup, the ORR was 22.2% (6/27; 95% CI, 8.6-42.3) and DCR was 74.1% (20/27; 95% CI, 53.7-88.9). Median progression-free survival (PFS) was 4.3 months (95% CI, 2.7-7.2), and median overall survival (OS) was 10.3 months (95% CI, 6.6-not calculable). IBI389 exhibited dose-proportional exposure, with a terminal half-life (t1/2) ranging from 86.3 to 175.8 h.
CONCLUSIONS:IBI389 showed manageable safety profiles in patients with advanced solid tumors and preliminary efficacy in Claudin18.2-positive patients with GC/GEJC.
CLINICALTRIALS:gov . NCT05164458 (December 20, 2021).