HENLIUS - VOLUNTARY ANNOUNCEMENT - THE FIRST PATIENT HAS BEEN DOSED IN A PHASE 1 CLINICAL

STUDY OF HLX48 FOR INJECTION (AN ANTIBODY-DRUG CONJUGATE TARGETING EGFR AND C-MET) FOR THE TREATMENT OF ADVANCED/ METASTATIC SOLID TUMORS IN CHINESE MAINLAND

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 FIRST PATIENT HAS BEEN DOSED IN A PHASE 1 CLINICAL STUDY OF HLX48 FOR INJECTION (AN ANTIBODY-DRUG CONJUGATE TARGETING EGFR AND C-MET) FOR THE TREATMENT OF ADVANCED/

METASTATIC SOLID TUMORS IN CHINESE MAINLAND

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 development of the Company.

The board of directors of the Company (the "Board") is pleased to announce that, recently, the first patient has been dosed in the phase 1 clinical study of HLX48 for injection (an antibody-drug conjugate targeting EGFR and c-MET) ("HLX48") for the treatment of advanced/metastatic solid tumors in Chinese Mainland (excluding Hong Kong, Macau and Taiwan regions). The Company intends to further commence the relevant clinical trial in Australia upon fulfilment of the requisite conditions.

B. CLINICAL TRIAL DESIGN AND OBJECTIVES

This study is an open-label, dose-escalation, first-in-human phase 1 clinical study evaluating the safety, tolerability, pharmacokinetic (PK) profiles, and preliminary efficacy of HLX48 in subjects with advanced/metastatic solid tumors. The study includes six dose cohorts ranging from 1.5mg/kg to 15mg/kg. Eligible subjects will receive intravenous (IV) infusions of HLX48 monotherapy at specified dose levels administered once every three weeks (Q3W). Following the completion of dosing and a 21-day safety observation period for all subjects in a given cohort, the Safety Review Committee (SRC) will evaluate the data to determine whether to initiate the next dose level. The primary endpoints aim to evaluate the incidence of dose-limiting toxicity (DLT) to determine the maximum tolerated dose (MTD) of HLX48 monotherapy. Secondary endpoints include safety indicators such as adverse events, PK parameters, and immunogenicity, as well as efficacy indicators including objective response rate (ORR), progression-free survival (PFS), and overall survival (OS).

C. ABOUT HLX48

HLX48 is a bispecific antibody-drug conjugate (ADC) independently developed by the Company targeting both c-MET and EGFR, planned for the treatment of advanced/metastatic solid tumors. The antibody of HLX48 binds to tumor cells expressing c-MET/EGFR and induces receptor-mediated endocytosis into the tumor cells, releasing cytotoxic payloads that cause DNA damage and cell death, while also killing adjacent tumor cells through the bystander effect of the payloads. In addition, the variable region of the HLX48 antibody specifically binds to tumor cells expressing c-MET/EGFR, blocking the binding of ligands Epidermal Growth Factor (EGF)/Hepatocyte Growth Factor (HGF) to their respective receptors, thereby inhibiting the activation of downstream signaling pathways, and exerting antibody-dependent cell-mediated cytotoxicity (ADCC) through the Fragment crystallizable (Fc) region. Therefore, HLX48 is expected to exert synergistic effects through both targeted therapy and immune modulation, thereby inhibiting tumor growth with a favorable safety profile. Preclinical studies have demonstrated that HLX48 exhibits good anti-tumor efficacy and safety, and is expected to provide clinical benefits. In May 2026, the phase 1 clinical trial application of HLX48 for the treatment of advanced/metastatic solid tumors received approval from the relevant Human Research Ethics Committee and acknowledged by the Therapeutic Goods Administration (TGA) of Australia, and was approved by the National Medical Products Administration (NMPA), respectively.

D. MARKET CONDITION

As of the date of this announcement, no bispecific ADC targeting both EGFR and c-MET has been approved for marketing globally.

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 HLX48. 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, 30 June 2026