VOLUNTARY ANNOUNCEMENT - NEW DRUG APPLICATION FOR TRASTUZUMAB ENVEDOTIN INJECTION ACCEPTED BY THE NMPA

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 NEW DRUG APPLICATION FOR TRASTUZUMAB ENVEDOTIN INJECTION ACCEPTED BY THE NMPA 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 new drug application for Trastuzumab Envedotin Injection (the ‘‘Product ’’) developed by the Group has been accepted by the National Medical Products Administration (the ‘‘NMPA ’’) of the People ’s Republic of China. The Product has been filed as a Class 1 therapeutic biological pr oduct, and its indication is for the treatment of unresectable or metastatic HER2-positive breast cancer in adult patients who have received one or more prior anti-HER2 therapies. Trastuzumab Envedotin Injection is a HER2-targeted antibo dy-drug conjugate (ADC). The Product binds to the HER2 receptors on HER2-positive tumour cells an d induces internalisation, followed by lysosomal hydrolysis to release MMAE, thereby inhibiting t ubulin polymerisation during the tumour cell division cycle, ultimately inducing tumour cell apopt osis and exerting anti-tumour effects. The new drug application for the Product is primarily based o n a pivotal Phase III clinical trial, which enrolled patients with unresectable or metastatic HER2-po sitive breast cancer who had previously received at least trastuzumab and taxane. The results demon strated that, compared with T-DM1, the Product significantly prolonged progression-free surviv al (PFS) in the second-line and beyond treatment of HER2-positive advanced breast cancer, with a s tatistically significant and clinically meaningful benefit. Results from other secondary endpoint s and subgroup analyses consistently demonstrated that the Product had superior anti-tumour eff icacy compared with T-DM1. Meanwhile, the Product demonstrated favourable safety and tolerabili ty profiles. – 1 – Based on its advantages in efficacy and safety, the Product h as favourable clinical application value and is expected to bring benefits to a greater number of patie nts. By Order of the Board CSPC Pharmaceutical Group Limited CAI Dong Chen Chairman Hong Kong, 17 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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