VOLUNTARY ANNOUNCEMENT - PHASE II CLINICAL TRIAL OF SYH2085 TABLETS FOR THE TREATMENT OF UNCOMPLICATED INFLUENZA IN ADULTS OFFICIALLY INITIATED 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 II CLINICAL TRIAL OF SYH2085 TABLETS FOR THE TREATMENT OF UNCOMPLICATED INFLUENZA IN ADULTS OFFICIALLY INITIATED 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 the Phase II clinical trial of SYH2085 tablets (the ‘‘Product ’’) developed by the Group for the treatment of uncomplicated influenza in adults has been officially initiated at the fir st centre in China. The Product is a small molecule inhibitor targeting the PA su bunit of influenza virus RNA polymerase and is registered as a Class 1 chemical drug. The Product is co nverted in vivo into its main active metabolite, SYH2085A-01207, which selectively inhibits t he endonuclease activity of the viral polymerase PA subunit, thereby suppressing the replicatio n of the influenza virus. Previously, the Group obtained the Notice of Approval for Cl inical Trial of Drug for the Product issued by the National Medical Products Administration of the Peop le’s Republic of China in December 2025. Following the approval, the Group initiated the Phase I clin ical trial to evaluate the safety, tolerability and pharmacokinetic profiles of the Product in healthy Chin ese participants. Currently, the Phase I trial data have preliminarily verified its safety, as well as its p harmacokinetic and pharmacodynamic profiles in humans, and also demonstrated that a single oral administ ration of the Product exhibited a favorable safety profile, good compliance and a low risk of developing drug resistance. – 1 – The clinical trial of the Product initiated on this occasion is a multi-centre, randomised, double-blind, placebo-controlled Phase II clinical trial designed to eva luate the efficacy and safety of the Product in Chinese adult participants with uncomplicated influenza. At present, the recruitment and screening of participants for this trial are actively underway. By order of the Board CSPC Pharmaceutical Group Limited CAI Dong Chen Chairman Hong Kong, 7 September 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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