ANTENGENE-B - VOLUNTARY ANNOUNCEMENT

CHINA IND APPROVAL FOR PIVOTAL PHASE III CLINCH-3 STUDY OF ATG-022 IN CLDN18.2+ ADVANCED GASTRIC/GEJ CANCER

Antengene Corporation Limited

德琪醫藥有限公司

(Incorporated in the Cayman Islands with limited liability)

(Stock Code: 6996)

VOLUNTARY ANNOUNCEMENT

CHINA IND APPROVAL FOR PIVOTAL PHASE III CLINCH-3 STUDY OF

ATG-022 IN CLDN18.2+ ADVANCED GASTRIC/GEJ CANCER

This announcement is made by Antengene Corporation Limited (the "Company", together with its subsidiaries, the "Group") on a voluntary basis to inform the shareholders and potential investors of the Company about the latest business updates of the Group. The board of directors of the Company (the "Board") is pleased to announce 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 (GEJ) adenocarcinoma. The study is expected to be initiated in China first and is planned as a multi-regional clinical trial (MRCT).

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 Group cannot guarantee that ATG-022 will ultimately be successfully developed and marketed. Shareholders and potential investors of the Company are advised to exercise caution when dealing in the shares of the Company.

By the order of the Board

Antengene Corporation Limited Dr. Jay Mei

Chairman

Hong Kong, May 28, 2026