VOLUNTARY ANNOUNCEMENT - PHASE III CLINICAL STUDY OF ANBENITAMAB (KN026) IN COMBINATION WITH DOCETAXEL (ALBUMIN-BOUND) (HB1801) FOR NEOADJUVANT TREATMENT OF HER2+ 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 (ALBUMIN-BOUND) (HB1801) FOR NEOADJUVANT TREATMENT OF HER2+ BREAST CANCER MEETS PRIMARY ENDPOINT The Board of Directors (the ‘‘Board ’’) of CSPC Pharmaceutical Group Limited (the ‘‘Company ’’, together with its subsidiaries, the ‘‘Group ’’) is pleased to announce that Anbenitamab Injection (‘‘KN026 ’’), co-developed by the Company ’s subsidiary Shanghai JMT-BIO Technology Co., Ltd. (‘‘JMT-BIO ’’) and Jiangsu Alphamab Oncology Co., Ltd. ( ‘‘Alphamab ’’), in combination with Docetaxel for Injection (Albumin-bound) ( ‘‘HB1801 ’’) independently developed by the Group, has met the pre-specified primary endpoint of total pathological c omplete response ( ‘‘tpCR ’’) in a Phase III clinical study (Study Protocol No.: KN026 –004) for the neoadjuvant treatment of HER2-positive early or locally advanced breast cancer, and the results are highl y statistically and clinically significant. Breast cancer is the second most common malignancy among wom en in China, of which the HER2- positive subtype accounts for approximately 20%~30%. In Ch ina, about 75% of breast cancer patients are in the early or locally advanced stage at the time of initi al diagnosis. Surgery combined with neoadjuvant and/or adjuvant therapy is the core means to ach ieve a radical cure for early or locally advanced breast cancer. Studies have shown that patients wh o achieve tpCR after neoadjuvant therapy have significantly improved event-free survival (EFS) and overall survival (OS), particularly in HER2- positive breast cancer. Despite this, after receiving the s tandard neoadjuvant treatment regimen- trastuzumab combined with pertuzumab and chemotherapy (TH P/TCbHP) —only about half of the patients with early or locally advanced HER2-positive brea st cancer can achieve tpCR. In addition, beyond improving tpCR, neoadjuvant therapy also aims to fac ilitate earlier and more timely surgical intervention. Therefore, there is still a clinical need to e xplore better neoadjuvant treatment regimens that can allow for earlier surgery. – 1 – Neo-Healer (KN026 –004) is a randomised, controlled, open-label, multicenter Phase III clinical study, planning to enroll approximately 520 patients with early or locally advanced HER2-positive breast cancer, randomly assigned at a 1:1 ratio, aiming to compare t he efficacy and safety of KN026 combined with HB1801± carboplatin versus trastuzumab comb ined with pertuzumab and docetaxel± carboplatin as neoadjuvant therapy for early and locally ad vanced HER2-positive breast cancer. Its primary study endpoint is tpCR assessed by a Blinded Indepen dent Review Committee (BIRC). The study results showed that compared with the existing standa rd treatment, KN026 combined with HB1801± carboplatin significantly improved the tpCR of pat ients. The detailed data of this study will be announced at an international academic conference in the near future. About Anbenitamab Injection (KN026) Anbenitamab Injection is a HER2 bispecific antibody. Its Ne w Drug Application (NDA) for the second- line and above treatment of HER2-positive advanced gastric cancer was accepted by the National Medical Products Administration (NMPA) in September 2025. Currently, multiple registrational clinical studies of Anbenitamab for indications such as first-line t reatment of HER2-positive gastric cancer/ gastroesophageal junction cancer, first-line treatment o f HER2-positive breast cancer, and neoadjuvant and adjuvant treatment of HER2-positive breast cancer are o ngoing. Anbenitamab has been granted Orphan Drug Designation by the U.S. Food and Drug Administra tion (FDA) for the treatment of HER2- positive or HER2-low expressing gastric cancer; it has also been granted Breakthrough Therapy Designation by the National Medical Products Administrati on (NMPA) for the treatment of HER2- positive gastric cancer (including gastroesophageal junc tion cancer) after failure of first-line standard treatment. In August 2021, JMT-BIO reached a licensing agreement with A lphamab and obtained the exclusive development and commercialisation rights for KN026 in brea st cancer and gastric cancer indications in Chinese Mainland (excluding Hong Kong, Macao and Taiwan reg ions). About Docetaxel for Injection (Albumin-bound) Docetaxel for Injection (Albumin-bound) is one of the repre sentative drugs independently developed by the Group ’s nanomedicine technology platform. Currently, multiple m odified drugs developed based on this technology platform have been approved for launch, inc luding mitoxantrone liposome, irinotecan liposome and paclitaxel (albumin-bound). Docetaxel is a pa clitaxel analogue that is currently widely used in clinical practice both domestically and overseas fo r the monotherapy or combination therapy of multiple solid tumors such as breast cancer, non-small cell lung cancer, gastric cancer and pancreatic cancer. However, docetaxel has high hydrophobicity, and cu rrent formulations need to use polysorbate 80 ( ‘‘Tween-80 ’’) and ethanol as solvents, leading to many limitations in cli nical application: it is easy to cause severe allergic reactions, can only be administere d at low concentration and low drip rate; the product has poor compatibility and stability, requiring th e use of infusion devices without polyvinyl chloride (PVC) material and making clinical use inconvenie nt. HB1801 encapsulates docetaxel in human serum albumin. Because it does not contain Tween-80 an d ethanol, it has the following advantages compared with docetaxel injection: (1) Safety: no hypersensitivity reactions occur, and no hormone pretreatment is required. It can be administered ra pidly at high concentration, with higher safety and patient compliance; (2) Efficacy: it has signifi cant effects in multiple preclinical tumor models, and can be administered at a larger dose clinically, further improving efficacy. – 2 – Results of multiple early clinical studies at different sta ges showed that HB1801 demonstrated better anti-tumor efficacy and safety than docetaxel injection, a chieving the goal of reducing toxicity and increasing efficacy. Currently, HB1801 has entered the piv otal registrational Phase III clinical trial stage in indications such as breast cancer and gastric cance r. By order of the Board CSPC Pharmaceutical Group Limited CAI Dong Chen Chairman Hong Kong, 31 March 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, Mr. WANG Huaiy u, Dr. LI Chunlei, Dr. YAO Bing, Mr. CAI Xin, Mr. CHEN Weiping, Mr. QU Zhiyong and Mr. ZHANG Yiw ei as Executive Directors; and Mr. WANG Bo, Mr. CHEN Chuan, Prof. WANG Hongguang, Mr. AU Chun Kwok Alan, Mr. LAW Cheuk Kin Stephen and Ms. LI Quan as Independent Non-executive Dir ectors. – 3 –

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