SinoMab BioScience Limited — Share Issue/Capital Change 2026

Mar 24, 2026

Hong Kong Exchanges and Clearing Limited and The Stock Exchange of Hong Kong Limited take no responsibility for the contents of this announcement, make no representation as to its accuracy or completeness and expressly disclaim any liability whatsoever for any loss howsoever arising from or in reliance upon the whole or any part of the contents of this announcement.

SINOMAB

SinoMab BioScience Limited

中國抗體製藥有限公司

(Incorporated in Hong Kong with limited liability)

(Stock code: 3681)

GRANT OF SHARE OPTIONS

This announcement is made pursuant to Rules 17.06A of the Rules Governing the Listing of Securities on The Stock Exchange of Hong Kong Limited (the "Listing Rules").

The board (the "Board") of directors (the "Director(s)") of SinoMab BioScience Limited (the "Company", together with its subsidiaries as the "Group") hereby announces that on 24 March 2026, the Company granted 11,574,840 share options (the "Share Options") to 2 eligible persons (collectively, the "Grantees"), under its share option scheme adopted at the extraordinary general meeting held on 26 October 2022 and was subsequently amended at the annual general meeting held on 14 June 2024 (the "2022 Share Option Scheme") (the "Grant"). The Share Options entitle the Grantees to subscribe for a total of 11,574,840 new shares of the Company, subject to acceptance of the Grantees.

Details of the Grant are set out below:

Date of Grant
24 March 2026 (the "Grant Date")

Grantees and categories
Two employees (including 1 senior management)

Number of Share Options granted
11,574,840 Share Options. Each Share Option shall entitle the holder thereof to subscribe for one (1) Share.

Exercise price of Share Options granted
HK$1.940 per Share, which is the highest of:

(i) Closing price of the Shares on the date of Grant
HK$1.940 per Share

(ii) Average closing price of the Shares for the five consecutive trading days prior to the date of Grant
HK$1.736 per Share

---

• 2 -

Exercisable period of Share Options

The Share Options being granted to the senior management are exercisable for a period of 9 years commencing from 25 March 2027 to 24 March 2036

The Share Options being granted to the other employee are exercisable for a period of 8 years commencing from 25 March 2028 to 24 March 2036

Vesting Schedule of Share Options

The Share Options being granted to the senior management shall be vested as follows:

• 25% shall vest on 25 March 2027;
• 25% shall vest on 25 March 2028;
• 25% shall vest on 25 March 2029; and
• 25% shall vest on 25 March 2030.

The Share Options being granted to the other employee shall be vested as follows:

• 25% shall vest on 25 March 2028;
• 25% shall vest on 25 March 2029;
• 25% shall vest on 25 March 2030; and
• 25% shall vest on 25 March 2031.

Performance Target

The number of Options granted to the Grantees is based on the positions, job tenure and performance evaluation results of the Grantees. The Group has in place a performance evaluation mechanism for its employees to comprehensively evaluate their performance and contribution to the Group. Based on their performance evaluation results, the Grantees receive different levels of rating which may affect the vesting period and the number of Options to be vested of each individual Grantee. In any event, the earliest vesting date shall not be before 25 March 2027.

Clawback Mechanism

No clawback mechanism is stipulated in the Grant.

The remuneration committee of the Company is of the view that clawback mechanism is not necessary as the scheme rules of the 2022 Share Option Scheme already provided the lapse and cancellation of options in different scenarios and provided enough protection to the Company's interests.

Financial Assistance

No arrangement was made by Company or any of its subsidiaries to provide financial assistance to the Grantee to facilitate the purchase of Shares under the 2022 Share Option Scheme.

---

Number of Shares available 40,952,409
for future grant under
scheme mandate

Number of Shares available 0
for future grant under
service provider
sublimit (Note)

Note: service provider sublimit is within the scheme mandate.

To the best knowledge, information and belief of the Directors, as of the date of this announcement, none of the Grantees (i) is a chief executive or substantial shareholder of the Company, or any of their respective associates (as defined under the Listing Rules); (ii) is a participant with options granted and to be granted exceeding the 1% individual limit (as defined under the Listing Rules); or (iii) is a related entity participant or service provider (as defined under the Listing Rules) of the Company.

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

Hong Kong, 24 March 2026

As at the date of this announcement, the executive director of the Company is Dr. Shui On LEUNG, the non-executive directors of the Company are Dr. Haigang CHEN, Mr. Xun DONG, Ms. Xiaosu WANG and Dr. Jianmin ZHANG and the independent non-executive directors of the Company are Mr. George William Hunter CAUTHERLEY, Mr. Ping Cho Terence HON, Dr. Chi Ming LEE, Ms. Chi Sau Giselle LEE and Mr. Nan SHEN.

• 3 -