VOLUNTARY ANNOUNCEMENT - PHASE III CLINICAL TRIAL OF SYS6043 FOR THE TREATMENT OF PLATINUM-RESISTANT ADVANCED OVARIAN CANCER, PRIMARY PERITONEAL CANCER, AND FALLOPIAN TUBE CANCER OFFICIALLY INITIATED AT THE FIRST CENTRE IN CHINA

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 PHASE III CLINICAL TRIAL OF SYS6043 FOR THE TREATMENT OF PLATINUM-RESISTANT ADVANCED OVARIAN CANCER, PRIMARY PERITONEAL CANCER, AND FALLOPIAN TUBE CANCER OFFICIALLY INITIATED AT THE FIRST CENTRE IN CHINA The Board of Directors (the ‘‘Board ’’) of CSPC Pharmaceutical Group Limited (the ‘‘Company ’’, together with its subsidiaries, the ‘‘Group ’’), is pleased to announce that a randomised, multicenter, open-label Phase III clinical trial evaluating SYS6043 (B7 -H3-ADC) (the ‘‘Product ’’) developed by the Group versus investigator ’s choice of chemotherapy for the treatment of participants w ith platinum- resistant advanced ovarian cancer, primary peritoneal can cer, and fallopian tube cancer has officially been initiated at the clinical first centre in China. The Product is an antibody-drug conjugate (ADC) targeting B 7-H3 developed by the Group. The antibody component can specifically bind to B7-H3 expresse d on the surface of tumour cells and be internalised into the cells. The linker-drug, comprising a tetrapeptide linker conjugated to a topoisomerase I inhibitor, can be specifically cleaved by p roteases to release a small-molecule toxin that kills tumour cells and exerts a bystander effect to non- specifically kill surrounding tumour cells. Unlike antibodies with conventional wild-type fragment cr ystallisable (Fc) regions, the Product can reduce lymphocyte uptake and mitigate the risk of off-targe t toxicity, thereby enhancing treatment safety. In July 2026, the Group received the Notice of Approval for Cl inical Trial of Drug from the National Medical Products Administration of the People ’s Republic of China. Following approval, the Group initiated a randomised, multicentre, open-label, active- controlled Phase III clinical trial evaluating the Product versus investigator ’s choice of chemotherapy for participants with platinum-re sistant advanced ovarian cancer, primary peritoneal cancer, and fallopian t ube cancer. – 1 – This Phase III clinical trial aims to evaluate the clinical e fficacy and safety of the Product compared with investigator ’s choice of chemotherapy regimens in the treatment of partic ipants with platinum- resistant advanced ovarian cancer, primary peritoneal can cer, and fallopian tube cancer. Currently, subject recruitment and screening are actively underway. By Order of the Board CSPC Pharmaceutical Group Limited CAI Dong Chen Chairman Hong Kong, 16 July 2026 As at the date of this announcement, the Board comprises Mr. C AI Dong Chen, Dr. CAI Lei, Mr. WEI Qingjie, Mr. ZHANG Cuilong, Mr. WANG Zhenguo, Dr. LI Chunlei , Dr. YAO Bing, Mr. CAI Xin, Mr. CHEN Weiping, Mr. QU Zhiyong and Mr. ZHANG Yiwei as Executive Directors; and Mr. WANG Bo, Mr. CHEN Chuan, Prof. WANG Hongguang, Mr. AU Chun Kwok Alan, M r. LAW Cheuk Kin Stephen and Ms. LI Quan as Independent Non-executive Directors. – 2 –

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