Zai Lab Limited — Capital/Financing Update 2021

Jan 6, 2021

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.

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**Zai Lab Limited 再鼎醫藥有限公司 ***

(Incorporated in the Cayman Islands with limited liability)

(Stock Code: 9688)

INSIDE INFORMATION ANNOUNCEMENT OVERSEAS REGULATORY ANNOUNCEMENT STRATEGIC COLLABORATION WITH ARGENX AND

ISSUE OF SUBSCRIPTION SHARES TO ARGENX

This announcement is made by Zai Lab Limited (the “ Company ” or “ Zai Lab ”, together with its subsidiaries, the “ Group ”) pursuant to Rule 13.10B and Rule 13.09 of the Rules (“ Listing Rules ”) Governing the Listing of Securities on The Stock Exchange of Hong Kong Limited (the “ Hong Kong Stock Exchange ”) and the Inside Information Provisions (as defined in the Listing Rules) under Part XIVA of the Securities and Futures Ordinance (Chapter 571, Laws of Hong Kong) (the “ SFO ”).

On January 7, 2021 (Hong Kong time) (before trading hours), Zai Auto Immune (Hong Kong) Limited, a wholly-owned subsidiary of the Company (“ Zai Auto Immune ”) entered into a collaboration and license agreement (the “ Collaboration Agreement ”) with argenx BV (“ Argenx ”) pursuant to which Zai Auto Immune received an exclusive license to develop and commercialize products containing Argenx’s proprietary antibody fragment, known as efgartigimod, in mainland China, Hong Kong, Macau and Taiwan (the “ Collaboration ”).

On the same date, as partial consideration for the exclusive license granted by Argenx to Zai Auto Immune in connection with the Collaboration, the Company entered into a share issuance agreement (the “ Share Issuance Agreement ”) with Argenx pursuant to which the Company has agreed to issue 568,182 ordinary shares of the Company (the “ Subscription Shares ”) to Argenx.

The transaction for the issuance of shares to Argenx under the Share Issuance Agreement has been approved by the boards of directors of both companies and is expected to close in January 2021, subject to approval by the Listing Committee of the Hong Kong Stock Exchange for the listing of, and permission to deal in, the Subscription Shares on the Hong Kong Stock Exchange, and satisfaction of other customary closing conditions (the “ Closing ”).

An application will be made by the Company to the Hong Kong Stock Exchange for the listing of, and permission to deal in, the Subscription Shares on the Hong Kong Stock Exchange.

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On January 7, 2021 (Hong Kong time) (before trading hours), the Company entered into the Collaboration Agreement with Argenx in relation to the Collaboration. As partial consideration for the exclusive license granted by Argenx to Zai Auto Immune in connection with the Collaboration, the Company has agreed to issue the Subscription Shares to Argenx pursuant to the Share Issuance Agreement.

The principal terms of the Collaboration are further summarized below.

Collaboration

On January 7, 2021 (Hong Kong time), Zai Auto Immune entered into the Collaboration Agreement with Argenx, pursuant to which Zai Auto Immune received an exclusive license under relevant patents and know-how to develop and commercialize Argenx’s proprietary antibody fragment, efgartigimod (the “ Licensed Compound ”) and biopharmaceutical products containing the Licensed Compound (the “ Licensed Products ”) in mainland China, Hong Kong, Macau and Taiwan (the “ Territory ”). Under the Collaboration Agreement, Zai Auto Immune may participate in Argenx’s global phase 3 trials for Licensed Products by enrolling patients in the Territory.

Pursuant to the Collaboration Agreement, Zai Auto Immune will be responsible for the development of the Licensed Compound and Licensed Products in the Territory in accordance with a development plan to support the regulatory approval of the Licensed Product in the Territory.

For each Licensed Product that is approved in the Territory, Zai Auto Immune will have the right to commercialize such Licensed Product in the Territory, during which Argenx is eligible to receive tiered royalties (mid-teen to low-twenties on a percentage basis and subject to customary reductions) based on annual net sales of all Licensed Products in the Territory. Zai Auto Immune’s royalty obligations will continue on a jurisdiction-by-jurisdiction and Licensed Product-by-Licensed Product basis until the last to occur of (i) expiration of the last valid claim of a licensed patent that covers such Licensed Product in such jurisdiction, (ii) expiration of regulatory exclusivity in such jurisdiction for such Licensed Product and (iii) twelve years from the first commercial sale of such Licensed Product in such jurisdiction.

In partial consideration of the license granted to Zai Auto Immune, a $75 million upfront payment will be made to Argenx through the issuance by the Company of 568,182 Subscription Shares calculated at a price of US$132.00 per share. In addition, Zai Auto Immune will make a guaranteed non-creditable, non-refundable development cost-sharing payment of $75 million to Argenx and a cash payment of $25 million upon the first regulatory approval of a Licensed Product by the U.S. Food and Drug Administration for Myasthenia Gravis.

The Collaboration Agreement contains customary representations, warranties and covenants by the parties. Unless terminated earlier pursuant to its terms, the agreement will continue in effect on a jurisdiction-by-jurisdiction and Licensed Product-by-Licensed Product basis until expiration of the royalty term for such Licensed Product in such jurisdiction. The Collaboration Agreement may be terminated by either party upon the other party’s uncured material breach, bankruptcy, insolvency or similar event. In addition, Zai Auto Immune may terminate the Collaboration Agreement for any or no reason upon 180 days’ prior written notice of Argenx. If Zai Auto Immune or any of its

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affiliates or sublicensees challenges a patent licensed by Argenx under the Collaboration Agreement as invalid, unenforceable or otherwise not patentable, Argenx will have the right to immediately terminate the Collaboration Agreement, subject to certain exceptions. In addition, if a force majeure event is specific to Zai Auto Immune and persists for a specified period of time, Argenx will have the right to terminate the Collaboration Agreement upon notice to Zai Auto Immune.

In connection with the Collaboration Agreement, on January 7, 2021 (Hong Kong time), the Company entered into the Share Issuance Agreement with Argenx pursuant to which the Company will issue and deliver to Argenx the Subscription Shares consisting of 568,182 ordinary shares of the Company, par value US$0.00006 per share, in full satisfaction of the $75 million upfront payment under the Collaboration Agreement.

The issuance of the Subscription Shares pursuant to the Share Issuance Agreement will be made in reliance upon Regulation S under the Securities Act of 1933, as amended (the “ Securities Act ”) to Argenx, a non-U.S. person and will be restricted securities under the Securities Act. An application will be made by the Company to the Hong Kong Stock Exchange for the listing of, and permission to deal in, the Subscription Shares on the Hong Kong Stock Exchange.

About Zai Lab

Zai Lab (NASDAQ:ZLAB; HKEX: 9688) is an innovative commercial-stage biopharmaceutical company focused on bringing transformative medicines for cancer and infectious and autoimmune diseases to patients in China and around the world. Zai Lab aims to address significant unmet medical needs in large, fast-growing segments of the pharmaceutical market. To that end, Zai Lab’s experienced team has secured partnerships with leading global biopharmaceutical companies in order to generate a broad pipeline of innovative marketed products and drug candidates. Zai Lab also built an in-house team with strong drug discovery and translational research capabilities and are establishing a pipeline of proprietary drug candidates with global rights. Zai Lab’s vision is to become a leading global biopharmaceutical company, discovering, developing, manufacturing and commercializing our portfolio in order to impact human health worldwide.

About Argenx

Argenx is a global immunology company committed to improving the lives of people suffering from severe autoimmune diseases and cancer. Partnering with leading academic researchers through its Immunology Innovation Program (IIP), Argenx aims to translate immunology breakthroughs into a world-class portfolio of novel antibody-based medicines. Argenx is evaluating efgartigimod in multiple serious autoimmune diseases, and cusatuzumab in hematological cancers in collaboration with Janssen. Argenx is also advancing several earlier stage experimental medicines within its therapeutic franchises. Argenx has offices in Belgium, the United States, and Japan.

The Company has filed a Form 8-K on January 7, 2021 (Hong Kong time) with the Securities and Exchange Commission of the United States (the “ SEC ”) to report the Collaboration. Full report of the Form 8-K is available on the Company’s website at http://www.zailaboratory.com/in5/info.aspx and on the website of the SEC.

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WARNING

The Company cannot guarantee that it will be able to ultimately market the Licensed Product successfully. The Closing of the Share Issuance Agreement is subject to the fulfilment of the conditions therein. If any of the conditions are not satisfied, the transactions contemplated by the Share Issuance Agreement will not proceed. Shareholders and potential investors of the Company are therefore advised to exercise caution when dealing in the shares of the Company.

By order of the Board Zai Lab Limited Samantha Du Director, Chairperson and Chief Executive Officer

Hong Kong, January 7, 2021

As at the date of this announcement, the board of directors of the Company comprises Dr. Samantha Du and Mr. Tao Fu as the directors, and Dr. Kai-Xian Chen, Dr. John Diekman, Ms. Nisa Leung, Mr. William Lis, Mr. Leon O. Moulder, Jr. and Mr. Peter Wirth as the independent directors.

• For identification only

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