RIBOLIFE-B - VOLUNTARY ANNOUNCEMENT - POSITIVE PHASE 2A STUDY RESULTS OF CORE PRODUCT

VORTOSIRAN FOR CAD

Suzhou Ribo Life Science Co., Ltd.

蘇州瑞博生物技術股份有限公司

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

(Stock Code: 6938)

VOLUNTARY ANNOUNCEMENT

POSITIVE PHASE 2A STUDY RESULTS OF CORE PRODUCT

VORTOSIRAN FOR CAD

This announcement is made by Suzhou Ribo Life Science Co., Ltd. (the "Company", together with its subsidiaries, the "Group") on a voluntary basis to provide shareholders of the Company (the "Shareholders") and potential investors with an update on the Group's research and development progress.

The board (the "Board") of directors (the "Directors") of the Company is pleased to announce that the Company presented the positive results from a Phase 2a study in Europe evaluating vortosiran (RBD4059), a small interfering RNA (siRNA) therapy targeting coagulation factor XI (FXI), in patients with chronic coronary artery disease (CAD) at the China Pharmaceutical Innovation Conference in Shanghai.

The randomized, double-blind, placebo-controlled study demonstrated that vortosiran in patients receiving standard-of-care aspirin treatment was generally well tolerated and achieved profound, dose-dependent, and long-lasting suppression of FXI activity. The trial enrolled patients with chronic CAD and previous myocardial infarction who were on aspirin therapy. Patients completing the high-dose vortosiran dosing regimen, at a maintenance dose of 400 mg, achieved a mean maximum reduction in FXI activity of 92%, which was sustained for several months following dosing. These data support dosing intervals of every three to six months across various indications. The degree of FXI inhibition is markedly greater than that estimated for ongoing small molecule programs, which are typically dosed once or twice daily and are currently in Phase 3 clinical development. Importantly, no treatment-related serious adverse events, major bleeding events, or clinically relevant non-major bleeding events were observed.

These findings represent the first clinical proof-of-concept globally for siRNA-mediated FXI suppression in patients with CAD, supporting the potential of vortosiran as a differentiated, long-acting antithrombotic therapy. By targeting FXI, vortosiran aims to reduce thrombotic risk while preserving hemostasis, potentially addressing a significant unmet need in cardiovascular disease.

Vortosiran is a GalNAc-conjugated siRNA candidate based on the proprietary RiboGalSTAR™ liver-targeting platform. By selectively suppressing FXI synthesis, vortosiran inhibits the intrinsic coagulation pathway and delivers potent antithrombotic activity. Compelling human genetic evidence indicates that individuals with naturally reduced FXI levels are protected against thrombotic disease without a corresponding increase in spontaneous bleeding risk. Consequently, FXI inhibition has emerged as a highly attractive therapeutic approach with the potential to combine effective thrombosis prevention with an improved safety profile relative to existing anticoagulant therapies.

Vortosiran may not ultimately be successfully developed and commercialized. Shareholders and potential investors are advised to exercise caution when dealing in the shares of the Company.

By Order of the Board

Suzhou Ribo Life Science Co., Ltd. LIANG Zicai

Chairman

Hong Kong, July 22, 2026

As of the date of this announcement, the executive Directors are Dr. LIANG Zicai, Dr. GAN Liming and Dr. ZHANG Hongyan, the non-executive Directors are Dr. QI Fei, Mr. LI Dongfang and Mr. LI Yuhui, and the independent non-executive Directors are Dr. YU Xuefeng, Mr. MA Chaosong and Mr. WANG Ruiping.