BIOCYTOGEN-B - VOLUNTARY ANNOUNCEMENT BIOCYTOGEN AND SIHUAN PHARMACEUTICAL ANNOUNCE STRATEGIC PARTNERSHIP TO ADVANCE INNOVATIVE DRUG DEVELOPMENT IN WEIGHT MANAGEMENT AND MULTIPLE THERAPEUTIC AREAS

BIOCYTOGEN PHARMACEUTICALS (BEIJING) CO., LTD.百奧賽圖（北京）醫藥科技股份有限公司

(A joint stock company incorporated in the People's Republic of China with limited liability)

(Stock Code: 2315)

VOLUNTARY ANNOUNCEMENT

BIOCYTOGEN AND SIHUAN PHARMACEUTICAL ANNOUNCE

STRATEGIC PARTNERSHIP TO ADVANCE INNOVATIVE DRUG

DEVELOPMENT IN WEIGHT MANAGEMENT AND

MULTIPLE THERAPEUTIC AREAS

This announcement is made by Biocytogen Pharmaceuticals (Beijing) Co., Ltd. (the "Company" or "Biocytogen") to provide its shareholders and potential investors with information in relation to the latest development of the Company.

The board (the "Board") of directors (the "Director(s)") of the Company is pleased to announce a strategic partnership with Sihuan Pharmaceutical Holdings Group Ltd. ("Sihuan Pharmaceutical", stock code: 0460).

Under the agreement, both parties will rely on Biocytogen's leading fully human antibody discovery platform, combined with Sihuan Pharmaceutical's extensive capabilities in drug development, manufacturing, and commercialization, to carry out cooperation and exchanges around the research and development ("R&D") of innovative drugs across multiple disease areas, including weight loss, leveraging complementary strengths to drive synergies and establish a long-term strategic and stable partnership.

Sihuan Pharmaceutical highly values the strength of Biocytogen's technology platforms. In this collaboration, Biocytogen will leverage its integrated platforms, including proprietary targethumanized mouse models and in vivo efficacy systems, as well as its AI-driven antibody discovery platform built on real human antibody sequences, to support the development of novel antibody therapeutics. By combining the complementary strengths of both parties, the partnership aims to accelerate the advancement of promising molecules toward clinical and commercial success.

Dr. Shen Yuelei, chairman of the Board and chief executive officer of Biocytogen, said: "We are pleased to establish this strategic partnership with Sihuan Pharmaceutical. Sihuan Pharmaceutical has a solid industrial foundation and rich experience in drug development, manufacturing, and commercialization. Relying on our proprietary fully human antibody discovery platform, Biocytogen has formed a systematic layout in various innovative therapeutic fields such as bispecific/multispecific antibodies, ADCs, VHH antibodies, and TCR, providing source innovation support for global R&D of innovative drugs. This partnership will help both parties expand broader cooperation space across multiple disease areas and further reflects the high recognition of industry partners for the strength of Biocytogen's technology platforms."

Information about Sihuan Pharmaceutical

Founded in 2001 and listed on the Main Board of The Stock Exchange of Hong Kong Limited in 2010, Sihuan Pharmaceutical is an international medical aesthetic and pharmaceutical company led by innovation, with an independent and leading research and development technology platform, a rich global product pipeline, strong product registration capability, a full dosage form production platform with high efficiency and low cost and a mature and excellent sales system. Adhering to the overall strategic goal for the "full promotion of a two-wheel drive strategy of its medical aesthetics and biopharmaceutical businesses", Sihuan Pharmaceutical endeavors to build itself into a leading medical aesthetics and biopharmaceutical company in China.

To the best knowledge and belief of the Directors, as of the date of this announcement, each of Sihuan Pharmaceutical and its ultimate beneficial owner(s) is independent of, and not connected with, the Company and its connected persons (as defined in the Rules Governing the Listing of Securities on The Stock Exchange of Hong Kong Limited (the "Listing Rules")). The transactions contemplated under the Agreement do not constitute any notifiable transactions or connected transactions of the Company under the Listing Rules.

Shareholders and potential investors of the Company are advised to exercise caution when dealing in the shares of the Company.

By order of the Board

Biocytogen Pharmaceuticals (Beijing) Co., Ltd. Shen Yuelei

Chairman of the Board, Chief Executive Officer and

Executive Director

Hong Kong, April 1, 2026