VOLUNTARY ANNOUNCEMENT - CRB-701 (SYS6002) RECEIVES U.S. FDA CLEARANCE FOR THE REGISTRATIONAL TRIAL FOR THE SECOND-LINE TREATMENT OF OROPHARYNGEAL CANCER

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 CRB-701 (SYS6002) RECEIVES U.S. FDA CLEARANCE FOR THE REGIS TRATIONAL TRIAL FOR THE SECOND-LINE TREATMENT OF OROPHARYNGEAL CANCE R The Board of Directors (the ‘‘Board ’’) of CSPC Pharmaceutical Group Limited (the ‘‘Company ’’, together with its subsidiaries, the ‘‘Group ’’) is pleased to announce that CRB-701 (SYS6002) (the ‘‘Product ’’), developed by Corbus Pharmaceuticals, Inc. ( ‘‘Corbus ’’) under a licence granted by the Group, has obtained clearance from the U.S. Food and Drug Adm inistration ( ‘‘FDA’’) to initiate the registrational trial (study code: TEMPO-1) for the second- line (2L) treatment of oropharyngeal squamous cell carcinoma (OPSCC). The Product is a next-generation antibody drug conjugate (A DC). Nectin-4 is a clinically validated tumour-associated antigen that is clearly expressed in uro thelial cancer, and is also highly expressed in various tumours such as cervical cancer and head and neck squ amous cell carcinoma ( ‘‘HNSCC ’’). Previously, the U.S. FDA granted two Fast Track designation s to the Product for the treatment of HNSCC and cervical cancer, respectively. TEMPO-1 is a randomised controlled study. The study aims to e valuate the efficacy and safety of the Product compared to the investigator ’s choice of monotherapy (capecitabine, cetuximab, or docet axel). Its two primary endpoints are objective response rate (ORR) to support a potential accelerated approval and overall survival (OS) to support a potential full approv al. Corbus expects to initiate patient enrolment in TEMPO-1 in the third quarter of 2026. – 1 – The U.S. FDA ’s clearance to initiate this registrational trial is suppor ted by data derived from the ongoing Phase I/II clinical trial of the Product conducted b y Corbus, which were recently presented at the 2026 American Society of Clinical Oncology (ASCO) Annua l Meeting. Currently, patient follow-up for the study is still ongoing. By order of the Board CSPC Pharmaceutical Group Limited CAI Dong Chen Chairman Hong Kong, 29 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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