SKB BIO-B - VOLUNTARY ANNOUNCEMENT INVESTIGATIONAL NEW DRUG APPROVAL FOR SKB103 BY THE NATIONAL MEDICAL PRODUCTS ADMINISTRATION

Sichuan Kelun-Biotech Biopharmaceutical Co., Ltd.

四川科倫博泰生物醫藥股份有限公司

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

(Stock Code: 6990)

VOLUNTARY ANNOUNCEMENT

INVESTIGATIONAL NEW DRUG APPROVAL FOR SKB103 BY THE

NATIONAL MEDICAL PRODUCTS ADMINISTRATION

The board (the "Board") of directors ("Directors") of Sichuan Kelun-Biotech Biopharmaceutical Co., Ltd. (the "Company") is pleased to announce that the Investigational New Drug (IND) application for SKB103, its self-developed novel bispecific antibodydrug conjugate (bsADC) with combined Tumor-Associated Antigen-targeting and Immuno- Oncology mechanisms (TAA-programmed cell death ligand 1 (PD-L1)), has been approved by the Center for Drug Evaluation (CDE) of the National Medical Products Administration (NMPA) of China for the treatment of advanced solid tumors. The approval marks SKB103 as the Company's first TAA-PD-L1 bsADC candidate and its second bsADC program for tumor therapy to enter the clinical stage, following SKB571.

As one of the industry leaders in the ADC field, the Company has established a solid competitive advantage. Currently, the Company's self-developed trophoblast cell-surface antigen 2 (TROP2)-directed ADC and human epidermal growth factor receptor 2 (HER2)directed ADC have been approved for marketing, demonstrating significant clinical efficacy and competitive differentiation. Focusing on advances in oncology therapeutics, the Company continues to expand its innovative layout by building a diversified pipeline covering cuttingedge therapies such as radionuclide drug conjugate (RDC) and bsADC and fully driving breakthroughs and innovations in existing cancer treatment paradigms.

About SKB103

SKB103 is a potential best-in-class novel TAA-PD-L1 bsADC developed using the Company's proprietary OptiDC™ platform. Designed as a single molecule, SKB103 is expected to realize targeted delivery of cytotoxic payloads to tumors and modulation of tumor immune microenvironment simultaneously. In preclinical studies, SKB103 demonstrated outstanding anti-tumor activity and a favorable safety profile. The therapeutic potential of SKB103 will support its subsequent clinical development.

RISK WARNING

SKB103 MAY NOT ULTIMATELY BE SUCCESSFULLY DEVELOPED AND COMMERCIALIZED. THE COMPANY'S SHAREHOLDERS AND POTENTIAL INVESTORS ARE REMINDED TO EXERCISE CAUTION WHEN DEALING IN THE SECURITIES OF THE COMPANY.

By order of the Board

Sichuan Kelun-Biotech Biopharmaceutical Co., Ltd. LIU Gexin

Chairman of the Board and Non-executive Director

Hong Kong, March 24, 2026