VOLUNTARY ANNOUNCEMENT - PHASE III CLINICAL STUDY OF ANBENITAMAB (KN026) IN COMBINATION WITH DOCETAXEL FOR INJECTION (ALBUMIN-BOUND) (HB1801) FOR FIRST-LINE TREATMENT OF HER2-POSITIVE ADVANCED BREAST CANCER MEETS PRIMARY ENDPOINT

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 STUDY OF ANBENITAMAB (KN026) IN COMBINAT ION WITH DOCETAXEL FOR INJECTION (ALBUMIN-BOUND) (HB1801) FOR FIRST-LINE TRE ATMENT OF HER2-POSITIVE ADVANCED BREAST CANCER MEETS PRIMARY ENDP OINT 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 III clinical study (Study Protocol No.: KN026-003) of Anbenitamab ( ‘‘KN026 ’’), co-developed by Shanghai JMT-BIO Technology Co., Ltd. ( ‘‘JMT-BIO ’’), a subsidiary of the Company, and Jiangsu Alphamab Oncolog y Co., Ltd., in combination with the Group ’s self-developed Docetaxel for Injection (Albumin-bound) (‘‘HB1801 ’’) for the first-line treatment of HER2-positive advanced br east cancer has successfully met the pre-specified primary endpoint of progression-free su rvival ( ‘‘PFS’’) as assessed by the Independent Data Monitoring Committee (the ‘‘IDMC ’’), yielding results that are both statistically significan t and clinically meaningful, with a favourable safety profile. Breast cancer is the second most common malignancy among wom en in China, of which the HER2- positive subtype accounts for approximately 20% to 30%. In C hina, approximately 20% of patients with breast cancer are already at an advanced stage upon initial d iagnosis, and approximately 10% of patients with HER2-positive early breast cancer experienc e disease recurrence within 3 years after radical surgery. Trastuzumab in combination with pertuzum ab and docetaxel (the ‘‘THP regimen ’’) currently remains the preferred first-line treatment for H ER2-positive advanced breast cancer both domestically and overseas. Although this treatment regime n has significantly prolonged the PFS of these patients, approximately 50% of patients still experi ence disease progression within 2 years, representing an urgent unmet clinical need. Healer (KN026 –003) is a randomised, controlled, open-label, multicenter Phase III clinical study. It plans to enrol approximately 880 patients with HER2-positi ve advanced breast cancer, randomly assigned at a 1:1 ratio. The study aims to compare the efficac y and safety of KN026 in combination with HB1801 versus the THP regimen for the first-line treatm ent of HER2-positive advanced breast cancer. The primary endpoint is PFS as assessed by the Blinde d Independent Review Committee (BIRC). As evaluated by the IDMC, KN026 in combination with H B1801 significantly prolonged – 1 – patients ’ PFS and reduced the risk of disease progression or death comp ared with the THP regimen, with a trend toward an overall survival (OS) benefit. Detail ed data from this study will be presented at an upcoming international academic conference. About Ennituo ( 恩尼妥®) (Anbenitamab Injection) Anbenitamab Injection is a HER2 bispecific antibody. On 28 M ay 2026, the National Medical Products Administration (the ‘‘NMPA ’’) of the People ’s Republic of China approved its marketing authorisation through the priority review and approval process, for use in combination with chemotherapy for the treatment of adult patients with locally advanced or metast atic HER2-positive gastric or gastroesophageal junction adenocarcinoma who have receiv ed one prior treatment regimen containing trastuzumab. The Phase III clinical study of Anbenitamab In jection for the neoadjuvant treatment of HER2-positive breast cancer has also met its primary endpoi nt, and a New Drug Application (NDA) will be submitted in the near future. In addition, multiple c linical studies of Anbenitamab Injection, including the adjuvant treatment of HER2-positive breast c ancer and the first-line treatment of HER2- positive gastric cancer, are ongoing. Anbenitamab Injecti on has been granted Orphan Drug Designation by the U.S. Food and Drug Administration (FDA) for the treatm ent of HER2-expressing gastric cancer, and has also received Breakthrough Therapy Designation fro m the NMPA for the treatment of HER2- positive gastric cancer that has failed first-line standar d treatment. About Docetaxel for Injection (Albumin-bound) (HB1801) Docetaxel for Injection (Albumin-bound) (HB1801) is one of the representative drugs independently developed by the Group ’s nanomedicine technology platform. HB1801 encapsulates d ocetaxel in human serum albumin. As it does not contain polysorbate 80 (Tween- 80) and ethanol, it offers the following advantages over docetaxel injection: (1) Safety: it causes no allergic reactions and requires no steroid premedication; it can be administered rapidly at high conce ntration, enhancing the safety profile and patient compliance; (2) Efficacy: preclinical and clinica l studies have demonstrated significant anti- tumour activity, allowing for higher doses in clinical prac tice to further improve efficacy. Currently, HB1801 has entered Phase III clinical study stages in indica tions including breast cancer and gastric cancer. By Order of the Board CSPC Pharmaceutical Group Limited CAI Dong Chen Chairman Hong Kong, 10 June 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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