CSPC PHARMA - VOLUNTARY ANNOUNCEMENT - PHASE IB/II CLINICAL TRIAL OF SYS6090 INJECTION FOR THE TREATMENT OF HEPATOCELLULAR CARCINOMA OFFICIALLY INITIATED AT THE FIRST CENTRE IN CHINA

CSPC PHARMACEUTICAL GROUP LIMITED

石藥集團有限公司

(Incorporated in Hong Kong with limited liability)

(Stock Code: 1093)

VOLUNTARY ANNOUNCEMENT

PHASE IB/II CLINICAL TRIAL OF SYS6090 INJECTION

FOR THE TREATMENT OF HEPATOCELLULAR CARCINOMA

OFFICIALLY INITIATED AT THE FIRST CENTRE IN CHINA

The Board of Directors (the 'Board') of CSPC Pharmaceutical Group Limited (the 'Company', together with its subsidiaries, the 'Group') is pleased to announce that the Phase Ib/II clinical trial (Study Protocol No.: SYS6090-007) of SYS6090 Injection (the 'Product') developed by the Group, for the treatment of hepatocellular carcinoma has been officially initiated at the first centre in China.

The Product, with a registration classification as a Class 1 therapeutic biological product, is a recombinant fully human anti-programmed cell death receptor 1 ('PD-1') and interleukin-15 ('IL- 15') fusion protein. It targets PD-1-positive tumour-infiltrating immune cells through its left arm, to block the immunosuppressive function caused by the interaction between PD-1 and programmed death ligand 1 (PD-L1); meanwhile, it binds to the IL-15 receptor through its right arm to activate its downstream signalling pathways, further promoting the activation and proliferation of relevant immune cells. Pre-clinical study results showed that the Product significantly inhibited tumour growth with favourable safety and tolerability, and demonstrated superior pharmacodynamic activity compared to other PD-1 monoclonal antibody drugs and IL-15 drugs.

Previously, the Group received the Notice of Approval for Clinical Trial of Drug issued by the National Medical Products Administration of the People's Republic of China for the Product in July 2026, and initiated the SYS6090-007 clinical trial following the approval. The approved clinical trial is an openlabel, multi-centre Phase Ib/II clinical study aimed at evaluating the safety, tolerability, and efficacy of the combination therapy of the Product in participants with hepatocellular carcinoma.

Based on the results of this study, the Group will subsequently continue to advance the Phase III clinical trial of the combination therapy of the Product in participants with hepatocellular carcinoma, to further verify the efficacy and safety of the Product. Currently, the recruitment and screening of subjects for the SYS6090-007 study are actively underway.

By order of the Board

CSPC Pharmaceutical Group Limited CAI Dong Chen

Chairman

Hong Kong, 19 August 2026