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Genscript Biotech Corporation

(Incorporated in the Cayman Islands with limited liability)

(Stock code: 1548)

VOLUNTARY ANNOUNCEMENT LEGEND ANNOUNCES PRELIMINARY SALES FOR CARVYKTI® FOR THE QUARTER ENDED 30 JUNE 2026

This is a voluntary announcement made by Genscript Biotech Corporation (the "Company").

Reference is made to the announcement of the Company dated 14 April 2026 in relation to the preliminary sales of CARVYKTI® for the quarter ended 31 March 2026.

The board of directors (the "Board") of the Company is pleased to announce that Legend Biotech Corporation ("Legend"), an associate of the Company, whose shares are listed by way of American Depositary Shares on the Nasdaq Global Select Market in the United States ("U.S."), has filed a Form 6-K with the United States Securities and Exchange Commission (the "SEC") on 15 July 2026 (New York time) (after trading hours on 15 July 2026 in Hong Kong) and announced that CARVYKTI® generated approximately US$657 million in net trade sales during the quarter ended 30 June 2026. This is pursuant to the Collaboration and License Agreement dated 21 December 2017 between Legend and Janssen Biotech, Inc. ("Janssen"). The net trade sales figure is based on information provided to Legend by Janssen, and neither Legend nor the Company have independently verified the accuracy of such sales figure. For details, please refer to the full Form 6-K as published on the SEC's website available at https://www.sec.gov/Archives/edgar/data/1801198/000117184326004649/0001171843-26-004649-index.html.

Cautionary Note Regarding Forward-Looking Statements

Statements in this announcement about future expectations, plans, and prospects, as well as any other statements regarding matters that are not historical facts, constitute "forward-looking statements" within the meaning of The Private Securities Litigation Reform Act of 1995. These statements include, but are not limited to, statements relating to CARVYKTI®, including Legend's expectations for net trade sales and resulting gross profit of CARVYKTI®. The words "anticipate," "believe," "continue," "could," "estimate," "expect," "intend," "may," "plan," "potential," "predict," "project," "should," "target," "will," "would" and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. Actual results may differ materially from those indicated by such forward-looking statements as a result of various important factors. Legend's expectations could be affected by, among other things, uncertainties involved in the development of new pharmaceutical products; unexpected clinical trial results, including as a result of additional analysis of existing clinical data or unexpected new clinical data; unexpected regulatory actions or delays, including

requests for additional safety and/or efficacy data or analysis of data, or government regulation generally; unexpected delays as a result of actions undertaken, or failures to act, by Legend's third party partners; uncertainties arising from challenges to Legend's patent or other proprietary intellectual property protection, including the uncertainties involved in the U.S. litigation process; competition in general; government, industry, and general public pricing and other political pressures; as well as the other factors discussed in the "Risk Factors" section of the Legend's Annual Report on Form 20-F filed with the Securities and Exchange Commission on 10 March 2026. Should one or more of these risks or uncertainties materialize, or should underlying assumptions prove incorrect, actual results may vary materially from those described in this announcement as anticipated, believed, estimated or expected. Any forward-looking statements contained in this announcement speak only as of the date of this announcement. The Company specifically disclaims any obligation to update any forward-looking statement, whether as a result of new information, future events or otherwise.

This announcement has been issued in the English language with a separate Chinese language translation. If there is any inconsistency or ambiguity between the English version and the Chinese version, the English version shall prevail.

Shareholders and potential investors of the Company are advised to pay attention to investment risks and exercise caution when they deal or contemplate dealing in the securities of the Company.

By order of the Board

Genscript Biotech Corporation

Robin Meng

Chairman and Executive Director

Hong Kong, 15 July 2026

As at the date of this announcement, the executive Directors are Mr. Jiange Meng ("Mr. Robin Meng"), Dr. Fangliang Zhang ("Dr. Frank Zhang"), Dr. Li Zhu and Ms. Ye Wang ("Ms. Sally Wang"); and the independent non-executive Directors are Dr. Alphonse Galdes, Mr. Yiu Leung Andy Cheung ("Mr. Andy Cheung"), Mr. Jiuan Pan ("Mr. Ethan Pan"), Dr. John Quelch, Dr. Ross Grossman and Dr. Chenyang Shi ("Dr. Victor Shi").

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