Zai Lab Limited — Board/Management Information 2026

May 22, 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.

Zai Lab Limited

再鼎醫藥有限公司*

(Incorporated in the Cayman Islands with limited liability)

(Stock Code: 9688)

OVERSEAS REGULATORY ANNOUNCEMENT - FORM 8-K

This announcement is made by Zai Lab Limited (the "Company") pursuant to Rule 13.10B of the Rules Governing the Listing of Securities on The Stock Exchange of Hong Kong Limited.

On May 21, 2026 (U.S. Eastern Time)/May 22, 2026 (Shanghai and Hong Kong Time), the Company filed a Form 8-K with the U.S. Securities and Exchanges Commission (the "SEC") with respect to the determination of the board of directors of the Company (the "Board") that Mr. Josh Smiley will cease serving as President and Chief Operating Officer of the Company, effective as of May 18, 2026, and his last day of employment with the Company will be May 22, 2026. For more details, please refer to the attached for the Form 8-K which has been published on the website of the SEC at www.sec.gov and the website of the Company at www.zailaboratory.com.

By order of the Board

Zai Lab Limited

Samantha Du

Director, Chairperson and Chief Executive Officer

Hong Kong, May 22, 2026

As at the date of this announcement, the board of directors of the Company comprises Dr. Samantha Du and Mr. Leon O. Moulder, Jr. as directors, and Dr. John Diekman, Dr. Richard Gaynor, Ms. Nisa Leung, Mr. William Lis, Mr. Scott W. Morrison, Mr. Michel Vounatsos and Mr. Peter Wirth as independent directors.

• For identification only

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UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): May 18, 2026

ZAI LAB LIMITED

(Exact name of registrant as specified in its charter)

| Cayman Islands
(State or other jurisdiction of incorporation) | 001-38205
(Commission File Number) | 98-1144595
(I.R.S. Employer Identification No.) |
| --- | --- | --- |
| 899 Halei Road
Building B, Pudong
Shanehai China
314 Main Street
4th Floor, Suite 100
Cambridge, MA, USA
(Address of principal executive offices) | | 201203
02142
(Zip Code) |

+86 21 6163 2588

+1 857 706 2604

(Registrant’s Telephone Number, Including Area Code)

Not Applicable

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)
☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)
☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))
☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class	Trading Symbol(s)	Name of each exchange on which registered
American Depositary Shares, each representing 10 Ordinary Shares, par value $0.000006 per share	ZLAB	The Nasdaq Global Market
Ordinary Shares, par value $0.000006 per share*	9688	The Stock Exchange of Hong Kong Limited

• Included in connection with the registration of the American Depositary Shares with the Securities and Exchange Commission. The ordinary shares are not registered or listed for trading in the United States but are listed for trading on The Stock Exchange of Hong Kong Limited

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

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Item 5.02 Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers.

On May 18, 2026, the Board of Directors of Zai Lab Limited (the "Company") determined that Mr. Josh Smiley will cease serving as President and Chief Operating Officer of the Company, effective as of May 18, 2026, and his last day of employment with the Company will be May 22, 2026. The responsibilities previously associated with such positions have been assumed by Samantha Du, the Company's Board Chair, Founder and Chief Executive Officer, and other members of the Company's management team.

Mr. Smiley will receive severance pursuant to his existing employment agreement, subject to his execution of a customary release.

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SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

ZAI LAB LIMITED

By: /s/ F. Ty Edmondson

Name: F. Ty Edmondson

Title: Chief Legal Officer and Corporate Secretary

Date: May 21, 2026