Antengene Corporation Limited  ("Antengene", SEHK: 6996.HK), a leading innovative, commercial-stage global biotech company dedicated to discovering, developing and commercializing first-in-class and/or best-in-class medicines for autoimmune diseases, solid tumors and hematological malignancies indications, today announced that following review by the Center for Drug Evaluation (CDE) of China's National Medical Products Administration (NMPA), the company has received CDE endorsement to conduct the pivotal Phase III CLINCH-3 study of ATG-022, a Claudin 18.2 (CLDN18.2) antibody-drug conjugate (ADC), for the treatment of CLDN18.2+ advanced gastric or gastroesophageal junction adenocarcinoma. The study is expected to be initiated in China first and is planned as a multi-regional clinical trial (MRCT).

"Receiving CDE endorsement to conduct the pivotal Phase III CLINCH-3 study represents a defining milestone for Antengene." said Dr. Jay Mei, Founder, Chairman and Chief Executive Officer of Antengene. "This achievement underscores Antengene's fully integrated R&D capabilities, from the design and discovery of novel molecules to clinical translation and registrational development. The Breakthrough Therapy Designation previously granted by CDE provided an important basis for our regulatory discussions on this pivotal study and enabled efficient feedback from CDE. We are highly encouraged by the potential of ATG-022 to address the significant unmet medical needs of patients with CLDN18.2+ advanced gastric or gastroesophageal junction adenocarcinoma, and we look forward to working closely with investigators to advance this important study."

The CLINCH-3 study will be led by Prof. Lin Shen from Peking University Cancer Hospital as the principal investigator. This 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. As a pivotal registrational study, CLINCH-3 is intended to support a future marketing approval application for ATG-022 as monotherapy for the treatment of CLDN18.2+ advanced gastric or gastroesophageal junction adenocarcinoma. The primary endpoints of the study are progression-free survival as assessed by independent review committee (PFS by IRC) and overall survival (OS). Secondary endpoints include objective response rate (ORR), duration of response (DOR), disease control rate (DCR), safety, and other measures. The initiation of this pivotal study is supported by encouraging results from the Phase I/II CLINCH study, which showed that ATG-022, as monotherapy, demonstrated a differentiated efficacy and safety profile in patients with advanced gastric or gastroesophageal junction adenocarcinoma. As of December 25, 2025, among patients whose tumors had CLDN18.2 expression of IHC 2+ >20%, ATG-022 achieved ORRs of 46.7% and 40.0% at 1.8 mg/kg and 2.4 mg/kg, respectively, with corresponding DCRs of 86.7% and 90.0%. Median PFS (mPFS) was 6.97 months and 5.09 months, respectively, while median OS (mOS) was not yet reached in the 1.8 mg/kg cohort and was 14.72 months in the 2.4 mg/kg cohort. In the 1.8 mg/kg cohort, the incidence of Grade 3 or higher treatment-related adverse events (TRAEs) was 19.4%, highlighting a highly differentiated safety profile for an ADC. Together with its robust antitumor activity, encouraging survival outcomes and favorable tolerability, these data position ATG-022 as a potential best-in-disease therapy for gastric cancer or gastroesophageal junction adenocarcinoma.

"Advanced gastric and gastroesophageal junction adenocarcinoma remains one of the most difficult solid tumors to treat, and the challenge is particularly acute in the 3L setting, where current options, including chemotherapy, anti-angiogenic agents and immunotherapy, provide limited efficacy, low objective response rates and insufficient survival benefit," said Professor Lin Shen of Peking University Cancer Hospital, principal investigator of the CLINCH-3 study. "ATG-022 has shown a compelling clinical profile as monotherapy at 1.8 mg/kg, with strong anti-tumor activity, meaningful survival benefit and a favorable safety profile. The CDE endorsement to conduct this pivotal Phase III study represents an important step toward potentially transforming the treatment landscape for patients with CLDN18.2+ advanced gastric or gastroesophageal junction adenocarcinoma. I am pleased to lead CLINCH-3 and look forward to working with Antengene to bring this promising therapy to more patients."

Antengene will continue to advance a comprehensive clinical development strategy for ATG-022 across multiple settings, including its pivotal monotherapy study in advanced gastric or gastroesophageal junction adenocarcinoma, ongoing combination studies with anti-PD-1 therapy and chemotherapy in the 1L gastric cancer setting, and further exploration in other CLDN18.2+ solid tumors, including tumor types beyond the digestive system where encouraging efficacy signals with confirmed tumor responses,  have been observed. Through this strategy, the company aims to maximize the clinical potential of ATG-022 and bring innovative, impactful therapies to patients in China and around the world.