VOLUNTARY ANNOUNCEMENT - USTEKINUMAB INJECTION RECEIVES MARKETING AUTHORISATION FROM 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 USTEKINUMAB INJECTION RECEIVES MARKETING AUTHORISATION FROM 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 Ustekinumab Injection (brand name: Enyike ( 恩益克®)) (the ‘‘Product ’’) developed by the Group has received marketing authorisation from the National Medical Products Administ ration of the People ’s Republic of China (‘‘NMPA ’’). The Product is a fully human IgG1 κmonoclonal antibody that binds with high affinity and speci ficity to the p40 protein subunit of human interleukins IL-12 and IL -23. IL-12 and IL-23 are naturally occurring cytokines involved in the inflammatory and immun e response processes of plaque psoriasis and Crohn ’s disease, playing a central role in their pathogenesis. Ust ekinumab disrupts the IL-12- and IL-23-mediated signaling and cytokine cascades by disrupt ing the interaction of these cytokines with the cell-surface receptor chain, IL-12R β1, thereby effectively alleviating disease symptoms, continuously improving the condition, and bringing long-t erm clinical benefits to patients. The originator drug of the Product, Stelara ® (Ustekinumab Injection), was approved for marketing in China in 2017 and has been approved for three indications in C hina, namely adult plaque psoriasis, paediatric plaque psoriasis and Crohn ’s disease. Since its launch, it has consistently remained am ong the mainstream drugs for the treatment of autoimmune diseas es in China, and its efficacy and safety have been widely recognised. The Product was developed as a Class 3.3 therapeutic biologi cal product and is a biosimilar to the originator drug, Stelara ®. It is indicated for the treatment of adult patients with mod erate to severe plaque psoriasis who have failed to respond to, or who have a c ontraindication to, or are intolerant to other systemic therapies including cyclosporine, methotr exate (MTX) or PUVA (psoralen and ultraviolet A), as well as paediatric patients and adolesce nts aged 6 years and above (weighing 60 kg to 100 kg) with moderate to severe plaque psoriasis who have a n inadequate response to or are intolerant to other systemic therapies or phototherapies. – 1 – The development of the Product followed relevant research g uidelines for biosimilars. Adhering to a stepwise approach, and on the basis of completing comprehen sive pharmaceutical and non-clinical comparative studies, ‘‘head-to-head ’’ clinical pharmacokinetic, efficacy and safety comparativ e trials were conducted against the originator drug, Stelara ®, confirming a high degree of similarity between the Product and Stelara ® in terms of quality, pharmacokinetics, efficacy and safety . The results of the aforementioned comparative clinical trials on efficacy an d safety have been published in the Journal of the American Academy of Dermatology , the official journal of the American Academy of Dermatolog y (AAD), which ranks first in the field of dermatology. The approval of the Product will further enrich the Group ’s product portfolio in the field of autoimmune diseases and is expected to bring more treatment options to patients. By order of the Board CSPC Pharmaceutical Group Limited CAI Dong Chen Chairman Hong Kong, 22 May 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. – 2 –

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