VOLUNTARY ANNOUNCEMENT - PIVOTAL PHASE II/III CLINICAL STUDY OF KN026 MET PRIMARY ENDPOINT OF PROGRESSION-FREE SURVIVAL (PFS) AT INTERIM ANALYSIS

Hong Kong Exchanges and Clearing Limited and The Stock Excha nge of Hong Kong Limited take no responsibility for the contents of this announcement, make no representation as to its accuracy or completeness and expressly disclaim any liability whatsoe ver for any loss howsoever arising from or in reliance upon the whole or any part of the contents of this ann ouncement. CSPC PHARMACEUTICAL GROUP LIMITED (Incorporated in Hong Kong with limited liability) (Stock Code: 1093) ʮ ̡ VOLUNTARY ANNOUNCEMENT PIVOTAL PHASE II/III CLINICAL STUDY OF KN026 MET PRIMARY ENDPOINT OF PROGRESSION-FREE SURVIVAL (P FS) AT INTERIM ANALYSIS The board of directors (the ‘‘Board ’’) of CSPC Pharmaceutical Group Limited (the ‘‘Company ’’, together with its subsidiaries, the ‘‘Group ’’) is pleased to announce that the pivotal Phase II/III clinic al study of KN026, a recombinant humanised anti-HER2 bispecif ic antibody injection co-developed by the Company ’s subsidiary, Shanghai JMT-Bio Technology Co., Ltd., and Ji angsu Alphamab Oncology Co., Ltd., for the treatment of patients with HER2-positive loca lly advanced, recurrent, or metastatic gastric or gastroesophageal junction adenocarcinoma who have rece ived and failed at least one prior systemic treatment (which must include trastuzumab in combination w ith chemotherapy) (KC-WISE), has met the pre-specified primary endpoint of progression-free su rvival (PFS) as evaluated by an Independent Data Monitoring Committee (IDMC), with both statistical si gnificance and clinical relevance. KN026 is a HER2 bispecific antibody that can simultaneously bind two non-overlapping epitopes of HER2, leading to HER2 signaling blockade, and has demonstra ted superior therapeutic efficacy compared to the combination of trastuzumab and pertuzumab t herapy. Multiple clinical studies at various stages showed that KN026 had favorable efficacy and safety profiles. Currently, a number of registration clinical trials are underway for indications such as breast cancer and gastric or gastroesophageal junction adenocarcinoma. In November 20 23, KN026 in combination with chemotherapy for the treatment of HER2-positive gastric or gastroesophageal junction adenocarcinoma after failure of the first-line standard treatment was gran ted Breakthrough Therapy Designation by the Center for Drug Evaluation (CDE) of the National Medical Pro ducts Administration (NMPA) of the People ’s Republic of China. – 1 – The KC-WISE (KN026-001) study is a randomised, multicenter , Phase II/III clinical study designed to evaluate the efficacy and safety of KN026 in combination wit h chemotherapy in subjects with HER2- positive locally advanced, recurrent, or metastatic gastr ic or gastroesophageal junction adenocarcinoma who have failed first-line standard treatment. In the Phase III stage of this study, subjects with HER2- positive gastric or gastroesophageal junction adenocarci noma who had previously received and failed at least first-line standard treatment were enrolled and rand omised 1:1 to receive either KN026 in combination with chemotherapy or placebo in combination wi th chemotherapy. The primary endpoints of this study were PFS as assessed by an Independent Review Co mmittee (IRC), and overall survival (OS). The main objective of this planned interim analysis wa s to evaluate the efficacy based on the IRC-assessed PFS. The interim analysis results indicated t hat compared to the current standard treatment, KN026 in combination with chemotherapy signifi cantly improved PFS, reduced the risk of disease progression or death, and demonstrated a trend towa rd an OS benefit. Detailed data from this study will be presented at an upcoming international academ ic conference. By order of the Board CSPC Pharmaceutical Group Limited CAI Dongchen Chairman Hong Kong, 30 April 2025 As at the date of this announcement, the Board comprises Mr. C AI Dongchen, Mr. ZHANG Cuilong, Mr. WANG Zhenguo, Mr. PAN Weidong, Mr. WANG Huaiyu, Dr. LI Chu nlei, Dr. YAO Bing, Mr. CAI Xin and Mr. CHEN Weiping as executive directors; and M r. WANG Bo, Mr. CHEN Chuan, Prof. WANG Hongguang, Mr. AU Chun Kwok Alan, Mr. LAW Cheuk Kin Stephen and Ms. LI Quan as independent non-executive directors. – 2 –

The release as fetched from its publisher. irasia.com ↗