HENLIUS - VOLUNTARY ANNOUNCEMENT -

THE INVESTIGATIONAL NEW DRUG APPLICATION FOR THE PHASE 1 CLINICAL TRIAL OF NIVOLUMAB BIOSIMILAR HLX18 (RECOMBINANT ANTI-PD-1 HUMANIZED MONOCLONAL ANTIBODY INJECTION) FOR THE TREATMENT OF MULTIPLE SOLID TUMORS WAS APPROVED BY THE NATIONAL MEDICAL PRODUCTS ADMINISTRATION

Shanghai Henlius Biotech, Inc.

上海復宏漢霖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: 2696)

VOLUNTARY ANNOUNCEMENT

THE INVESTIGATIONAL NEW DRUG APPLICATION

FOR THE PHASE 1 CLINICAL TRIAL OF NIVOLUMAB BIOSIMILAR HLX18 (RECOMBINANT ANTI-PD-1 HUMANIZED MONOCLONAL ANTIBODY INJECTION) FOR THE TREATMENT OF MULTIPLE SOLID TUMORS WAS APPROVED BY THE NATIONAL MEDICAL PRODUCTS

ADMINISTRATION

A. INTRODUCTION

This announcement is made by Shanghai Henlius Biotech, Inc. (the "Company") on a voluntary basis to inform the shareholders and potential investors of the Company about the latest business update of the Company.

The board of directors of the Company (the "Board") is pleased to announce that, recently, the investigational new drug application (IND) for the phase 1 clinical trial of nivolumab biosimilar HLX18 (recombinant anti-PD-1 humanized monoclonal antibody injection) ("HLX18") independently developed by the Company for the treatment of multiple solid tumors was approved by the National Medical Products Administration (NMPA).

B. ABOUT HLX18

HLX18 is a nivolumab biosimilar independently developed by the Company, and its potential indications include the indications of the original drug approved such as melanoma, non-small cell lung cancer, malignant pleural mesothelioma, renal cell carcinoma, classical Hodgkin lymphoma, squamous cell carcinoma of the head and neck, urothelial carcinoma, gastric cancer, gastroesophageal junction cancer or esophageal adenocarcinoma, esophageal cancer, colorectal cancer and hepatocellular carcinoma etc. Binding of the PD-1 ligands, PD-L1 and PD-L2, to the PD-1 receptor found on T cells, inhibits T-cell proliferation and cytokine production. Upregulation of PD-1 ligands occurs in some tumor cells and signaling through this pathway can contribute to inhibition of active T-cell immune surveillance of tumors. Nivolumab is a human immunoglobulin G4 (IgG4) monoclonal antibody (HuMAb) that binds to the PD-1 receptor and blocks its interaction with PD-L1 and PD-L2, releasing PD-1 pathway-mediated inhibition of the immune response, including the antitumor immune response. In December 2025, HLX18 was permitted to commence a phase 1 clinical trial for the treatment of multiple solid tumors in the United States.

C. MARKET CONDITION

According to the statistics released by IQVIA MIDASTM (IQVIA is a global provider of professional information and strategic consulting services in the pharmaceutical and healthcare industry), the sales volume of nivolumab worldwide for the year of 2025 was

approximately USD11.785 billion.

WARNING STATEMENT WITH REFERENCE TO THE REQUIREMENTS UNDER RULE 18A.05 OF THE RULES GOVERNING THE LISTING OF SECURITIES ON THE STOCK

EXCHANGE OF HONG KONG LIMITED: The Company cannot guarantee the successful development and commercialization of HLX18. Shareholders and potential investors of the Company are advised to exercise caution when dealing in the shares of the Company.

On behalf of the Board

Shanghai Henlius Biotech, Inc. Wenjie Zhang

Chairman

Hong Kong, 20 March 2026