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 d

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.

(Incorporated in the Cayman Islands with limited liability)

VOLUNTARY CONVERSION TO DUAL-PRIMARY LISTING ON

THE MAIN BOARD OF THE STOCK EXCHANGE

OF HONG KONG LIMITED

Reference is made to

the announcement of Zai Lab Limited (the Company , together with its subsidiaries, the Group ) dated April 24, 2022, regarding the approval by the board of directors of the Company (the Board )

regarding a motion to pursue the voluntary conversion to dual-primary listing (the Primary Conversion ) on The Main Board of The Stock Exchange of Hong Kong Limited (the HK Stock Exchange ).

The Company has been primary listed on the Nasdaq Global Market since September 2017 and secondary listed on The Main Board of the HK Stock

Exchange since September 2020. Taking into account the substantial presence of the Group s business operations in Greater China, as well as the long-term business development and prospects of the Company

(including but not limited to further broadening the investor base in Greater China), the Company announced on April 24, 2022 that the Board approved a motion to pursue the Primary Conversion and authorized the Company s senior management to

proceed with the relevant preparatory work and undertake the necessary procedures to complete the Primary Conversion, a voluntary conversion of its secondary listing status to primary listing on the HK Stock Exchange, including removal of the stock

marker S from its stock short name on the date, expected to be on June 27, 2022, on which the Primary Conversion will become effective (the Primary Conversion Effective Date ).

The Company has applied to the HK Stock Exchange with regard to the Primary Conversion (the Primary Conversion Application ).

On May 31, 2022, the Company received an acknowledgement from the HK Stock Exchange in respect of the Primary Conversion Application (the Primary Conversion Exchange Acknowledgement ) issued pursuant to paragraph 3.24 of the

Guidance Letter HKEX-GL112-22. Upon the Primary Conversion Effective Date, the Company will be dual primary listed on the HK Stock Exchange and the Nasdaq Global Market.

With the Group s business operations having a substantial presence in Greater China, the Board expects that the Primary Conversion would

allow the Company to expand its investor base in the region. The Primary Conversion is expected to attract more potential investors to trade in the Company s securities on the HK Stock Exchange and thus broaden the shareholder base of the

Company and increase the trading volume of the Company s securities on the HK Stock Exchange. In addition, the Board expects that the Primary Conversion would enhance the liquidity and the profile of the Company s securities in the global

market. Accordingly, the Board is of the view that the Primary Conversion is in the interests of both the Company and its shareholders as a whole.

Upon the Primary Conversion Effective Date, it is expected that the Company will be able to comply with the Rules Governing the Listing of

Securities on The Stock Exchange of Hong Kong Limited (the HK Listing Rules ) applicable to a dual primary listed issuer, including the HK Listing Rules subject to the waivers and exemptions granted or applicable to the Company as

a secondary listed issuer on the HK Stock Exchange (the Existing Waivers ) which will/are expected to be withdrawn or will be no longer applicable upon the Primary Conversion Effective Date, unless otherwise separately waived or

exempted by the HK Stock Exchange. In preparation of the Primary Conversion and prior to the Primary Conversion Effective Date, the Company will make the necessary arrangements, including, among others, the following to enable it to comply with the

relevant HK Listing Rules applicable to a dual primary listed issuer:

The Company will also

ensure compliance with all the other relevant HK Listing Rules applicable to a dual-primary listed issuer, including the HK Listing Rules subject to the waivers and exemptions granted or applicable to the Company as a secondary listed issuer on the

HK Stock Exchange which will/are expected to be withdrawn or will be no longer applicable upon the Primary Conversion Effective Date, unless otherwise separately waived or exempted by the HK Stock Exchange.

The Company expects that the above arrangements will be completed on or prior to the Primary Conversion Effective Date in order for the Company

to comply with all the relevant HK Listing Rules applicable to the Company as a dual-primary listed issuer upon the Primary Conversion Effective Date. Accordingly, the Company currently does not expect any transitional measures to be put in place

before the Primary Conversion Effective Date and there is no matter regarding the potential impact on shareholders and potential investors in connection with any transitional measures of the Company that need to be brought to the attention of the

shareholders and potential investors of the Company.

In the event that the Company is unable to demonstrate full compliance with an

applicable HK Listing Rule (where no waiver has been granted by the HK Stock Exchange) upon the Primary Conversion Effective Date, the HK Stock Exchange may request the Company to delay the Primary Conversion Effective Date. In the event that the

Company failed to comply with the obligations as set out in the HK Listing Rules applicable to a dual-primary listed issuer following the Primary Conversion Effective Date, the Company would be in potential breach of the HK Listing Rules, and would

potentially be subject to, depending on the nature and seriousness of the possible breach and the circumstances and the manner in which the conduct is giving rise to such possible breach, disciplinary action by the HK Stock Exchange. The Company may

also be directed to carry out possible remedial and enhancement actions such as internal control review and Directors training on regulatory and legal topics including compliance with HK Listing Rules.

For the avoidance of doubt, notwithstanding the submission of the Primary Conversion

Application, or receipt of the Primary Conversion Exchange Acknowledgement, the Company will continue to be entitled to the Existing Waivers before the Primary Conversion Effective Date provided that it remains primary listed on the Nasdaq Global

Market, being a recognized stock exchange. Such Existing Waivers include, among others, the following specific waivers granted by the HK Stock Exchange, exemption and ruling granted by the Securities and Futures Commission of Hong Kong, on an

Details of the aforementioned Existing Waivers are set out in the Company s prospectus published on

September 17, 2020 in connection to its offering of shares for subscription by the public in Hong Kong. In the event of withdrawal of any of the aforementioned Existing Waivers upon the Primary Conversion Effective Date, the Company would fully

comply with such HK Listing Rules and provisions of the SFO and be considered a public company in Hong Kong for the purposes of the Takeovers Code.

In connection with the Primary Conversion, the Company has sought, subject to the approval of the HK

Stock Exchange, the following waivers from strict compliance with the relevant provisions of the HK Listing Rules:

Rule 19.25A of the HK Listing Rules provides that the annual accounts are required to conform with financial reporting standards acceptable to

the HK Stock Exchange, which are normally Hong Kong Financial Reporting Standards ( HKFRS ) or International Financial Reporting Standards ( IFRS ). Where the HK Stock Exchange allows annual accounts to be drawn up

otherwise than in conformity with HKFRS or IFRS, the annual accounts will be required to conform with financial reporting standards acceptable to the HK Stock Exchange. In such cases the HK Stock Exchange will normally require the annual accounts to

contain a reconciliation statement setting out the financial effect of the material differences (if any) from either HKFRS or IFRS.

2.1 to Paragraph 2 of Appendix 16 to the HK Listing Rules requires the Company to prepare its financial statements in the financial reports to be in conformity with: (a) HKFRS; (b) IFRS; or (c) China Accounting Standards for Business

Enterprises in the case of companies incorporated in China, subject to Note 2.6 to Paragraph 2 of Appendix 16 to the HK Listing Rules. Note 2.6 to Paragraph 2 of Appendix 16 to the HK Listing Rules provides that the HK Stock Exchange may allow the

annual financial statements of an overseas issuer to be drawn up otherwise than in conformity with financial reporting standards referred to in Note 2.1 to Paragraph 2 of Appendix 16 to the HK Listing Rules.

In the HK Stock Exchange s guidance letter GL111-22

( HKEX-GL111-22 ), the HK Stock Exchange has indicated that it has accepted that the financial statements and accountants reports of overseas issuers with, or seeking, a dual primary or

secondary listing in the U.S. and on the HK Stock Exchange can be prepared in conformity with U.S. GAAP. HKEX-GL111-22 further provides that, an overseas issuer adopting a body of financial reporting standards

other than HKFRS or IFRS for the preparation of its financial statements must include a reconciliation statement setting out the financial effect of any material differences between those financial statements and financial statements prepared

adopting HKFRS or IFRS in its accountants reports and annual/interim/quarterly reports.

As a company listed on Nasdaq, the Company prepares its financial statements in accordance

with U.S. GAAP which are audited under the standards of the United States Public Company Accounting Oversight Board for the purpose of the Company s filings with the U.S. Securities and Exchange Commission. U.S. GAAP is well recognized and

accepted by the international investment community, particularly among biotechnology companies, and significant progress has been made in the convergence between U.S. GAAP and IFRS. Additionally, we note that it might lead to confusion among the

Company s investors and shareholders if the Company was required to adopt different accounting standards for its disclosures in Hong Kong from those in the U.S.. Aligning the accountings standards used for disclosures in both markets will

alleviate any such confusion.

The Company has applied to the HK Stock Exchange for, subject to the grant of waiver by the HK Stock

Exchange, a waiver from strict compliance with the requirements of Rule 19.25A of, and Note 2.1 to paragraph 2 of Appendix 16 to, the HK Listing Rules subject to the following conditions:

Note (1) to Rule 17.03(9) of the HK Listing Rules states that the exercise price of an option must be at least

the higher of: (i) the closing price of the securities as stated in the HK Stock Exchange s daily quotations sheet on the date of grant, which must be a business day; and (ii) the average closing price of the securities as stated in

the HK Stock Exchange s daily quotations sheets for the five business days immediately preceding the date of grant. It is worth noting that the relevant requirement specifies the value of the exercise price but does not strictly limit the

currency at which grants are made.

Since the listing of the Company s American Depositary Shares ( ADSs ) on Nasdaq

in September 2017, it has been the Company s practice to issue options exercisable into ordinary shares or ADSs (each of which represents one underlying ordinary share before March 30, 2022 or ten underlying ordinary shares on or after March

30, 2022) denominated in U.S. dollars under the Zai Lab Limited 2015 Omnibus Equity Incentive Plan ( 2015 Equity Incentive Plan ) and the Zai Lab Limited 2017 Equity Incentive Plan ( 2017 Equity Incentive Plan ),

with reference to a benchmark price on Nasdaq, which is not less than the closing price of the ADS as quoted on Nasdaq on the date of grant (or if no closing price was reported on that date, on the last trading date when such closing price was

Upon the Primary Conversion Effective Date, the Company will no longer grant options, stock appreciation rights, restricted and

unrestricted shares and share units, performance awards or other share awards under the 2015 Equity Incentive Plan and the 2017 Equity Incentive Plan and would grant options, share appreciation rights, restricted shares, restricted share units,

performance-based awards, unrestricted shares, dividend equivalent rights and cash-based awards under the new 2022 equity incentive plan (the 2022 Equity Incentive Plan ) if the 2022 Equity Incentive Plan is approved by the

shareholders at the AGM. Pursuant to the 2022 Equity Incentive Plan, the Company will grant options exercisable into ordinary shares or ADSs under the 2022 Equity Incentive Plan still denominated in U.S. dollars after the Primary Conversion

Effective Date. By definition, ADSs are denominated in U.S. dollars, and the exercise price for options with respect to ADSs will necessarily be presented in U.S. dollars. Subject to the waiver from strict compliance with Rule 19.25A of, and Note

2.1 to Paragraph 2 of Appendix 16 to, the HK Listing Rules described under the sub-section headed ADOPTION OF U.S. GAAP above, the Company will continue to prepare its accounts based on U.S. GAAP

after the Primary Conversion Effective Date in line with its established practice of granting options with exercise prices and share awards with grant values denominated in U.S. dollars and tied to the market price of its Nasdaq-traded ADSs.

In addition, the Company respectfully submits that it would be unduly burdensome for the

Company to grant options exercisable into ordinary shares or ADSs with exercise price denominated in Hong Kong dollars under the 2022 Equity Incentive Plan due to the following reasons:

On the bases that (a) the method for determining the exercise price of the options

based on the market price of ADSs substantially replicates the requirement in Note (1) to Rule 17.03(9) of the HK Listing Rules, (b) it has been the Company s practice to issue options in the form of ADSs or ordinary shares with an

exercise price denominated in U.S. dollars and with reference to ADS trading price on Nasdaq since September 2017, and that the Company will continue to prepare its accounts based on U.S. GAAP after the Primary Conversion Effective Date, and the

Company will grant options under the 2022 Equity Incentive Plan exercisable to ordinary shares or ADSs, with exercise prices based on the market price of its ADSs which are denominated in U.S. dollars after the Primary Conversion Effective Date if

the 2022 Equity Incentive Plan is approved by its shareholders at the AGM, (c) it would be unduly burdensome for the Company to grant options exercisable into ordinary shares or ADSs with exercise price denominated in Hong Kong dollars under

the new 2022 Equity Incentive Plan, and (d) the vast majority of the Company s trading volume for its securities is on Nasdaq since the Company s listing in September 2017 and that is expected to continue even after the Primary

Conversion Effective Date, the Company has applied for, subject to the grant of waiver by the HK Stock Exchange, a waiver from strict compliance with Note (1) to Rule 17.03(9) of the HK Listing Rules, such that the Company will be able to

determine the exercise price for grant of options exercisable to ordinary shares or ADSs under its 2022 Equity Incentive Plan based on the higher of:

Pursuant to Rules 3.28 and 8.17 of the HK Listing Rules, the company secretary must be an individual who, by virtue of their academic or

professional qualifications or relevant experience, is, in the opinion of the HK Stock Exchange, capable of discharging the functions of company secretary.

Pursuant to Note 1 to Rule 3.28 of the HK Listing Rules, the HK Stock Exchange considers the following academic or professional qualifications

Pursuant to Note 2 to Rule 3.28 of the HK Listing Rules, in assessing relevant

experience , the HK Stock Exchange will consider the individual s:

The Company will appoint Mr. F. Ty Edmondson and will appoint Ms. Nelly Au-Yeung as joint

company secretaries of the Company on or before the Primary Conversion Effective Date. Mr. Edmondson joined the Company as Chief Legal Officer in August 2020. Mr. Edmondson has served in various legal and compliance roles during his tenure

at Biogen Inc., a leading global biotech company where he has been from June 2014 through August 2020, including Senior Vice President, Chief Corporation Counsel and Assistant Secretary. During his time at Biogen, he also served as the Chief