HBM : VOLUNTARY ANNOUNCEMENT - DOSING OF FIRST PATIENT IN PHASE Ib/IIa CLINICAL STUDY OF NEXT-GENERATION ANTI-CTLA-4 ANTIBODY IN AUSTRALIA

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和鉑醫藥 控股 有 限公 司

HBM Holdings Limited

(incorporated in the Cayman Islands with limited liability)

(Stock Code: 02142)

VOLUNTARY ANNOUNCEMENT

DOSING OF FIRST PATIENT IN PHASE Ib/IIa CLINICAL STUDY OF

NEXT-GENERATIONANTI-CTLA-4 ANTIBODY IN AUSTRALIA

This announcement is made by HBM Holdings Limited (the "Company", together with its subsidiaries, the "Group") on a voluntary basis to inform the shareholders and potential investors of the Company about the latest business update.

The board of directors of the Company today announced the dosing of the first patient in part 2 of its phase I (the "phase Ib/IIa") clinical study of HBM4003 for Australian patients suffering from advanced melanoma, hepatocellular carcinoma (HCC), renal cell carcinoma (RCC) and other types of tumors (study no. 4003.1). This study will evaluate the safety, tolerability, PK/PD, and anti- tumor activity of HBM4003 as a single agent in multiple solid tumor types. The part 1 of phase I trial study results have been submitted to European Society of Medical Oncology (ESMO).

As the Company's next-generationanti-CTLA-4 antibody, HBM4003 is currently in an open label, multicenter global trial for patients with advanced solid tumors. The part 1 of phase I study was focused on dose escalation, and the phase Ib/IIa study is to proceed to dose expansion to further explore the anti-tumor activities of HBM4003 in multiple tumor types.

About HBM4003

HBM4003 is the fully human anti-CTLA-4 monoclonal heavy chain only antibody (HCAb) generated from Harbour Mice®. HBM4003 shows enhanced antibody-dependent cell cytotoxicity (ADCC) killing activity and is extremely specific to high CTLA-4 Treg cells in tumor tissues. The potent anti-tumor efficacy and differentiated pharmacokinetics with durable pharmacodynamic effect presents a favorable product profile. This novel and differentiated mechanism of action has the potential to improve efficacy while significantly reducing the toxicity of the drug.

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Cautionary Statement: We cannot guarantee that we will be able to develop, or ultimately market, HBM4003 successfully. Shareholders and potential investors of the Company are advised to exercise due care when dealing in the shares of the Company.

Company website: www.harbourbiomed.com

By order of the Board

HBM Holdings Limited

Dr. Jingsong Wang

Chairman and Executive Director

Hong Kong, May 11, 2021

As at the date of this announcement, the board of directors of the Company comprises Dr. Jingsong Wang and Dr. Mai-Jing Liao as executive Directors; Mr. Yu Min Qiu and Mr. Junfeng Wang as non-executive Directors; Dr. Robert Irwin Kamen, Dr. Xiaoping Ye and Ms. Weiwei Chen as independent non-executive Directors.

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