Shanghai – September 20, 2026 -- Antengene Corporation Limited (SEHK: 6996.HK) has dosed the first patient in China in its pivotal Phase III CLINCH-3 study evaluating ATG-022, a CLDN18.2 antibody-drug conjugate, as monotherapy for CLDN18.2-positive advanced gastric or gastroesophageal junction adenocarcinoma.
Breakthrough Therapy Designation accelerated the trial's launch
China's National Medical Products Administration granted ATG-022 Breakthrough Therapy Designation, which the company says streamlined regulatory communications and enabled the rapid start of CLINCH-3. The randomized, controlled, open-label multicenter study is initiated in China and planned for expansion into a multi-regional clinical trial, with Professor Lin Shen of Peking University Cancer Hospital serving as principal investigator. The study compares ATG-022 against treatment of investigator's choice, targeting a future marketing approval application.
Phase I/II data show 46.7% response rate at the recommended dose
As of a June 26, 2026 data cutoff, among patients with moderate-to-high CLDN18.2 expression (IHC 2+ ≥20%) treated at the 1.8 mg/kg recommended Phase 2 dose, ATG-022 produced an objective response rate of 46.7% (14/30), a confirmed ORR of 40% (12/30) and a disease control rate of 86.7% (26/30). Median overall survival had not been reached after a median follow-up of 14.03 months. Among patients with low or ultra-low CLDN18.2 expression treated at 1.8-2.4 mg/kg, ORR reached 28.6% (6/21) and DCR was 52.4% (11/21), with multiple complete responses recorded across cohorts.
Safety profile remains stable after extended follow-up
Compared with a December 25, 2025 cutoff, the incidence of Grade 3 or higher treatment-related adverse events in the 1.8 mg/kg cohort rose only slightly, from 19.4% to 21.0%, with just 9.7% of patients requiring dose reduction due to TRAEs. Antengene said the rate remained broadly stable despite more than six additional months of treatment exposure and follow-up.
Three parallel trials aim to expand ATG-022's addressable market
Beyond CLINCH-3, which targets third-line-plus monotherapy use in patients with IHC 2+ ≥20% expression, Antengene is running CLINCH-2 to test ATG-022 in first-line combination with chemotherapy and anti-PD-1 therapy across a broader CLDN18.2-positive population starting from IHC 1+ ≥1%. A separate CLINCH basket trial is testing the ADC in non-gastric CLDN18.2-positive solid tumors, where the company reports encouraging early efficacy signals.