VOLUNTARY ANNOUNCEMENT - PHASE IB/II CLINICAL TRIAL OF SYS6090 INJECTION FOR THE TREATMENT OF HEPATOCELLULAR CARCINOMA 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 IB/II CLINICAL TRIAL OF SYS6090 INJECTION FOR THE TREATMENT OF HEPATOCELLULAR CARCINOMA 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 the Phase Ib/II clinical trial (Study Protocol No.: SYS6090-007) of SYS6090 Injection (th e ‘‘Product ’’) developed by the Group, for the treatment of hepatocellular carcinoma has been offi cially initiated at the first centre in China. The Product, with a registration classification as a Class 1 therapeutic biological product, is a recombinant fully human anti-programmed cell death recept or 1 ( ‘‘PD-1 ’’) and interleukin-15 ( ‘‘IL- 15’’) fusion protein. It targets PD-1-positive tumour-infiltr ating immune cells through its left arm, to block the immunosuppressive function caused by the interac tion between PD-1 and programmed death ligand 1 (PD-L1); meanwhile, it binds to the IL-15 receptor t hrough its right arm to activate its downstream signalling pathways, further promoting the act ivation and proliferation of relevant immune cells. Pre-clinical study results showed that the Product s ignificantly inhibited tumour growth with favourable safety and tolerability, and demonstrated supe rior pharmacodynamic activity compared to other PD-1 monoclonal antibody drugs and IL-15 drugs. Previously, the Group received the Notice of Approval for Cl inical Trial of Drug issued by the National Medical Products Administration of the People ’s Republic of China for the Product in July 2026, and initiated the SYS6090-007 clinical trial following the app roval. The approved clinical trial is an open- label, multi-centre Phase Ib/II clinical study aimed at eva luating the safety, tolerability, and efficacy of the combination therapy of the Product in participants with hepatocellular carcinoma. – 1 – Based on the results of this study, the Group will subsequent ly continue to advance the Phase III clinical trial of the combination therapy of the Product in p articipants with hepatocellular carcinoma, to further verify the efficacy and safety of the Product. Curre ntly, the recruitment and screening of subjects for the SYS6090-007 study are actively underway. By order of the Board CSPC Pharmaceutical Group Limited CAI Dong Chen Chairman Hong Kong, 19 August 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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