First Patient Dosed in Pivotal Phase III CLINCH-3 Study of ATG-022

Antengene Corporation Limited ("Antengene", SEHK: 6996.HK), a leading innovative, commercial-stage global biotech company, has announced the dosing of the first patient in China in the pivotal Phase III CLINCH-3 study of ATG-022. ATG-022 is a CLDN18.2 antibody-drug conjugate (ADC) being evaluated for the treatment of CLDN18.2+ advanced gastric or gastroesophageal junction adenocarcinoma.

This study, initiated in China with the first patient dosed and planned for expansion into a multi-regional clinical trial (MRCT), is intended to generate robust clinical evidence to support a future marketing approval application for ATG-022 as monotherapy for CLDN18.2+ advanced gastric or gastroesophageal junction adenocarcinoma. The CLINCH-3 study is led by Professor Lin Shen from Peking University Cancer Hospital as the principal investigator.

The CLINCH-3 study is a randomized, controlled, open-label, multicenter Phase III clinical study designed to evaluate the efficacy and safety of ATG-022 versus treatment of investigator's choice in patients with CLDN18.2+ advanced gastric or gastroesophageal junction adenocarcinoma. The study builds on encouraging results from the Phase I/II CLINCH studies, which showed that ATG-022, as monotherapy, demonstrated a differentiated robust efficacy and well-tolerated safety profile in patients with advanced gastric or gastroesophageal junction adenocarcinoma.

As of June 26, 2026, among patients with moderate to high CLDN18.2 expression (IHC 2+ ≥ 20%), in the 1.8 mg/kg dose cohort, the recommended phase 2 dose (RP2D), the objective response rate (ORR) was 46.7% (14/30) with a confirmed ORR of 40% (12/30), the disease control rate (DCR) was 86.7% (26/30), and the median overall survival (mOS) had not yet been reached after a median follow-up of 14.03 months. Among patients with low/ultra-low CLDN18.2 expression treated at the efficacious dose range of 1.8-2.4 mg/kg, the ORR was 28.6% (6/21) and the DCR was 52.4% (11/21). In addition, multiple patients achieved complete responses (CR).

The incidence of Grade ≥3 treatment-related adverse events (TRAEs) in the 1.8 mg/kg dose cohort increased slightly from 19.4% to 21.0%, with only 9.7% of patients experiencing dose reduction due to TRAEs. Despite more than six additional months of treatment exposure and follow-up, the incidence of Grade ≥3 TRAEs remained broadly stable in the 1.8 mg/kg dose cohort.

Antengene's pipeline includes a range of investigational candidates, including ATG-022 (CLDN18.2 ADC), ATG-037 (oral CD73 inhibitor), ATG-101 (PD-L1 x 4-1BB bispecific antibody), ATG-125 (B7-H3 × PD-L1 bispecific ADC), ATG-207 (αCD3-TGF-β bifunctional fusion protein), and T cell engager (TCE) programs developed using Antengene's proprietary AnTenGager® platform. The AnTenGager® platform features "2+1" bivalent binding for low expressing targets, steric hindrance masking, and proprietary CD3 sequences with fast on/off kinetics to minimize cytokine release syndrome (CRS) and enhance efficacy.

The company aims to maximize the clinical potential of ATG-022 and bring innovative, impactful therapies to patients in China and around the world. The CLINCH-3 study is part of Antengene's strategy to advance the three complementary clinical development pathways planned for ATG-022, with the CLINCH-2 study evaluating ATG-022 in 1L in combination with standard-of-care chemotherapy and anti-PD-1 therapy, targeting the broadest CLDN18.2-positive population starting from IHC 1+ ≥ 1%.