CStone Pharmaceuticals — Director's Dealing 2025

Apr 9, 2025

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基石药业

CSTONE

PHARMACEUTICALS

CStone Pharmaceuticals

基石藥業

(Incorporated in the Cayman Islands with limited liability)

(Stock Code: 2616)

VOLUNTARY ANNOUNCEMENT FURTHER INCREASE IN SHAREHOLDING BY CEO AND EXECUTIVE DIRECTOR DR. JIANXIN YANG BY 560,000 SHARES, WITH ACCUMULATED PURCHASE TOTALLING 10,359,000 SHARES

This announcement is made by CStone Pharmaceuticals (the "Company" or "CStone" and together with its subsidiaries, the "Group") on a voluntary basis to inform its shareholders and potential investors in relation to the increase in shareholding in the Company (the "Shares") by Dr. Jianxin Yang ("Dr. Yang"), the chief executive officer (the "CEO"), president of research and development and an executive director of the Company.

The Company was informed by Dr. Yang that he has purchased a total of 560,000 Shares in the open market with his own funds on April 2 to 7, 2025 (the "Share Purchases"), with purchase price per Share ranging from HKD 2.26 to HKD 3.29. Since assuming the role as CEO in August 2022, Dr. Yang has purchased a total of 10,359,000 Shares in the open market with purchase price per Share ranging from HKD 0.82 to HKD 4.60. Following the Share Purchases, Dr. Yang's total shareholding interest in the Company was approximately $5.46\%$ of the total issued share capital of the Company as at the date of this announcement.

Dr. Yang informed the Company that he is confident with the Company's outlook, and the increase in his shareholding in the Company represents his belief in the Company's ability to maintain steady operations and to achieve rapid growth in a complex and volatile market environment, and the Share Purchases demonstrates his unfailing support towards the growth and development of the Company. Dr. Yang does not rule out the possibility of further increasing his shareholding in the Company as and when appropriate.

The board of directors of the Company (the "Board") is of the view that the increase in shareholding of the

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Company by its CEO, president of research and development and executive director signifies Dr. Yang’s long-term commitment to, and confidence towards, the future business prospects of the Company.

About CStone

CStone (HKEX: 2616), established in late 2015, is an innovation-driven biopharmaceutical company focused on the research and development of anti-cancer therapies. Dedicated to addressing patients’ unmet medical needs in China and globally, the Company has made significant strides since its inception. To date, the Company has successfully launched 4 innovative drugs and secured approvals for 16 new drug applications covering 9 indications. The Company’s pipeline is balanced by 16 promising candidates, featuring potentially first-in-class or best-in-class antibody-drug conjugates (ADCs), multispecific antibodies, immunotherapies and precision medicines. CStone also prides itself on a management team with comprehensive experiences and capabilities that span the entire drug development spectrum, from preclinical and translational research to clinical development, drug manufacturing, business development, and commercialization.

For more information about CStone, please visit: www.cstonepharma.com.

By Order of the Board

CStone Pharmaceuticals

Dr. Wei Li

Chairman

Suzhou, the People’s Republic of China, April 9, 2025

As at the date of this announcement, the board of directors of the Company comprises Dr. Wei Li as Chairman and non-executive director, Dr. Jianxin Yang as executive director, Mr. Kenneth Walton Hitchner III, Mr. Xianghong Lin and Mr. Edward Hu as non-executive directors, and Dr. Paul Herbert Chew, Mr. Ting Yuk Anthony Wu, Mr. Hongbin Sun and Ms. Yip Betty Ho as independent non-executive directors.

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