SinoMab BioScience Limited — Capital/Financing Update 2020

Jun 8, 2020

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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 – UPDATES REGARDING RECENT BUSINESS DEVELOPMENTS

SINOMAB ANNOUNCES CLINICAL RESULTS ON SM03 DELIVERED BY ORAL PRESENTATION AT THE EUROPEAN LEAGUE AGAINST RHEUMATISM (EULAR) 2020 CONGRESS

On 5 June 2020, SinoMab BioScience Limited (中國抗體製藥有限公司) (“ SinoMab ” or the “ Company ”), a biopharmaceutical company focused on developing and commercializing innovative drugs for the treatment of immunological disorders and other debilitating diseases, announced the first presentation of clinical results of SM03 for its Phase II clinical report of SM03 for rheumatoid arthritis (“ RA ”) titled “Efficacy and safety of SM03, a Recombinant Anti-human CD22 Monoclonal Antibody in Chinese Patients with Rheumatoid Arthritis: A Phase II randomized, double-blind, multi-dose, placebo-controlled study” (the “ Abstract ”). The data included clinical results from a randomized study to evaluate the efficiency and safety of SM03 compared to placebo in patients with moderate-to-severe active RA, were reported as an oral presentation by Professor Zhang Fengchun (張奉春教授), the leading principal investigator of the Phase II clinical study of SM03, at the European League Against Rheumatism (EULAR) 2020 Congress (the “ Congress* ”).

Major Responses in RA Patients treated with SM03

Abstract Number: OP0210

In this 24-week Phase II randomized, double-blind, multi-dose, placebo-controlled study, 156 patients were randomized with a ratio of 1:1:1 to receive 3,600 mg cumulative dose of SM03 (high dose (“ HD ”) group, 600 mg per infusion for 6 doses in 24 weeks), 2,400 mg cumulative dose of SM03 (low dose (“ LD ”) group, 600 mg per infusion for 4 doses in 24 weeks) and placebo (control group). All patients remained on background treatment of methotrexate (“ MTX ”). Efficacy and safety were assessed periodically according to protocol and requirement of industry guidance. The primary efficacy end point was the American College of Rheumatology (“ ACR ”) 20% improvement criteria (ACR20) response rate at week 24. Safety and tolerance profile were also assessed.

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Results of Phase II clinical study

ACR20 response rates at 24-week were significantly higher for HD (65.3%, p=0.002) and LD group (56.9%, p=0.024) than placebo (34.0%), difference between two groups of patients is considered statistically significant when p value is lower than 0.05), while the percentage refer the the proportion of the responders, who achieved clinical response at 24-week, among those randomized at the baseline. Numerically, there were more ACR responders in HD than in LD, despite no statistically significant difference was observed. We did not observe significant difference in any adverse event (“ AE ”) among HD (35.3%), LD (51.9%) and placebo (34.6%). The percentages refer to the proportion of cases who have experienced at least one adverse event during 24 weeks among those randomized at the baseline. In groups HD and LD, 13 (12.6%) patients reported treatment-related infection, and 5 (6.8%) patients dosed with SM03 were positive in an anti-drug antibodies analysis. The respective percentages refer to the proportion of cases with any treatment-emergent infections or tested positive for serum anti-drug antibody reactions among those randomized at the baseline. Chinese patients with active RA, SM03 in combination with methotrexate, demonstrated a good safety and tolerance, throughout 24 weeks of treatment, especially in terms of infusion-related reactions and treatment-related infections. No patient reported severe treatment-emergent infections or any malignancies, during the study.

Conclusion of Phase II clinical study

In Chinese patients with active RA, both 2,400 mg and 3,600 mg cumulative dose of SM03, in combination with MTX were efficacious and well tolerated throughout the 24 weeks of treatment. Moreover, SM03 has demonstrated a good safety profile, especially in terms of treatment-related infection, malignancy and immunogenicity.

To the best of the Company’s knowledge, this is the first randomized controlled trial on the use of anti-CD22 antibodies for the treatment of RA disclosed to the scientific community, and the directors of the Company believe that this is one of the main reasons that the Abstract has been accepted for an oral presentation at the Congress, representing an international recognition on the importance of the Company’s findings. To the best of the Company’s knowledge, the Company is one of the few Chinese biotechnology companies which have been invited for delivering oral presentations at the Congress.

The Company’s flagship product, SM03, is a potential global first-in-target monoclonal antibody for the treatment of RA and potentially for the treatment of other immunological diseases, which is in Phase III clinical trials in China and expected to be commercialized by the end of 2021.

The Company may not be able to ultimately develop and market SM03 successfully. Shareholders of the Company and potential investors are advised to exercise caution when dealing in the shares of the Company.

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

Hong Kong, 8 June 2020

As at the date of this announcement, the executive directors of the Company are Dr. Shui On LEUNG and Mr. Jing QIANG, the non-executive directors of the Company are Ms. Wenyi LIU, Dr. Haigang CHEN, Mr. Senlin LIU, Mr. Huiyuan MA and Mr. Xun DONG, and the independent non-executive directors of the Company are Mr. Dylan Carlo TINKER, Mr. Michael James Connolly HOGAN, Mr. Ping Cho Terence HON and Mr. George William Hunter CAUTHERLEY.

• For identification purpose only

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