SinoMab BioScience Limited — Regulatory Filings 2023

Nov 27, 2023

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SinoMab BioScience Limited 中國抗體製藥有限公司

(Incorporated in Hong Kong with limited liability)

(Stock code: 3681)

VOLUNTARY ANNOUNCEMENT

FIRST COHORT OF THE HEALTHY SUBJECTS DOSED IN A PHASE I CLINICAL TRIAL OF SM17 IN CHINA

Reference is made to the announcements of SinoMab BioScience Limited (中國 抗 體製 藥 有 限 公司 ) (the ‘‘Company’’, together with its subsidiaries, the ‘‘Group’’) on 16 February 2022, 14 March 2022, 15 June 2022, 22 May 2023, 12 June 2023, 14 August 2023 and 11 September 2023 in relation to the latest research and development progress of one of the Group’s key products, SM17.

The board of directors (the ‘‘Board’’) of the Company is pleased to announce that, on 25 November 2023, the first cohort of healthy subjects has been successfully dosed in a phase I clinical trial of SM17 in China. As of the date of this announcement, no adverse event was observed. The phase I trial aims to establish safety, pharmacokinetics (PK) and immunogenicity profiles of SM17 in Chinese population, as well as to test the preliminary safety, efficacy and pharmacodynamic characteristic of SM17 in Atopic Dermatitis (‘‘AD’’) patients.

SM17 is a novel, First-in-Class (FIC), humanized, IgG4-k monoclonal antibody which is capable of modulating Type II allergic reaction by targeting the receptor of a critical ‘‘alarmin’’ molecule interleukin 25 (IL-25). SM17 could suppress Type 2 helper T (Th2) immune responses by binding to IL-25 receptor (also known as IL-17RB) on Type 2 Innate Lymphoid cells (ILC2s) and Th2 cells, to block a cascade of responses induced by IL-25 and suppress the release of the downstream Th2 cytokines such as IL-4, IL-5 and IL-13.

IL-25 is a critical cytokine classified as ‘‘alarmin’’, which has shown to be implicated in the pathogenesis of autoimmune and inflammatory skin diseases, such as AD. Patients with AD also have an increasing all-cause mortality rate and disease-specific mortality rate in the following diseases, which include infections, respiratory diseases, gastrointestinal diseases and oncologic diseases. Current approved therapies for AD, including biologics, can significantly improve eczema area and severity index and patient’s quality of life. However, there is still an unmet medical need for patients showing irresponsiveness to those approved therapies.

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A Phase I study for SM17 conducted in the US is near completion, with Last Subject Last Visit (LPLV) completed in September 2023, and the clinical study report is expected to be released by the first quarter of 2024. As of the date of this announcement, no drug-related serious adverse event has been reported, suggesting the product is well tolerated in human and shows a very good safety profile. The Company believes that therapies targeting upstream of the Th2 inflammatory cytokine pathway, such as IL-25 receptor, will have broad effects on skin inflammation, implicating a great potential for SM17 as a differentiating, safer and more effective products for the treatment of AD.

By Order of the Board SinoMab BioScience Limited Dr. Shui On LEUNG Executive Director, Chairman and Chief Executive Officer

Hong Kong, 27 November 2023

As at the date of this announcement, the executive director is Dr. Shui On LEUNG, the non-executive directors are Dr. Haigang CHEN, Mr. Xun DONG, Dr. Wenyi LIU, Mr. Lei SHI and Dr. Jianmin ZHANG, and the independent non-executive directors are Mr. George William Hunter CAUTHERLEY, Mr. Ping Cho Terence HON, Dr. Chi Ming LEE and Mr. Dylan Carlo TINKER.

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