そーせいグループ（4565） – Notice Regarding Determination of Payment Amount and Other Matters of Issuance of New Shares Under Restricted Stock Unit (RSU) Plan

PRESS RELEASE Notice Regarding Determination of Payment Amount and Other Matters of Issuance of New Shares Under Restricted Stock Unit (RSU) Plan Tokyo, Japan and Cambridge, UK, 8 April 2022 – Sosei Group Corporation (“the Company”; TSE: 4565) today announces that the Company has determined the payment amount and other matters of issuance of new shares under the Restricted Stock Unit (“RSU”) Plan No. 8 as set forth below (“the Share Issuance”) as announced by the Company in Press Release “Notice of Issuance of New Shares Under Restricted Stock Unit (RSU) Plan” issued on 16 April 2020. 19 May 2022 207,030 shares of the Company’s common stock (1) Payment date (2) Type and number of shares to be issued (3) Payment amount (4) Total amount of payment (5) Allottees (6) Other details 1,427 Yen per share 295,431,810 Yen 7 Directors and Executive Officers of the Company 52 Directors of subsidiaries of the Company and employees of the Company and its subsidiaries The Securities Registration Statement relating to the Share Issuance has been filed in accordance with the Financial Instruments and Exchange Act. (Note) 1. The aforementioned payment amount per share has been determined by the Representative Executive Officer as at the closing price of the Company’s shares on the Tokyo Stock Exchange on the day immediately prior to the Date of Determination (7 April 2022). The payment amount per share is the market share price immediately preceding the Date of the Determination, so the Company considers it is not issuance of shares at a particularly favorable value. 2. The Company will deliver the aforementioned new shares to be issued to the Allottees in exchange for provision as contribution in kind of monetary compensation claims against the Company provided to the Allottees. 3. The Performance Period for the Share Issuance was from 1 April 2020 to 31 March 2022. 4. The number of shares to be issued under the Plan and other stock-based compensation plans of the Company including 6th RSU, under which the payment amount and other matters of issuance of new shares were determined on April 1, 2022, and 8th RSU will be 1.23 % of the total number of outstanding shares of the Company as of 31 March 2022. -ENDS- PRESS RELEASE About Sosei Heptares We are an international biopharmaceutical group focused on the discovery and early development of new medicines originating from our proprietary GPCR-targeted StaR® technology and structure-based drug design platform capabilities. We are advancing a broad and deep pipeline of novel medicines across multiple therapeutic areas, including neurology, immunology, gastroenterology, and inflammatory diseases. We have established partnerships with some of the world’s leading pharmaceutical companies and multiple emerging biotechnology companies, including AbbVie, AstraZeneca, Biohaven, Genentech (Roche), GSK, Neurocrine Biosciences, Novartis, Pfizer, Takeda and Verily. Sosei Heptares is headquartered in Tokyo, Japan with corporate and R&D facilities in Cambridge, UK. “Sosei Heptares” is the corporate brand and trademark of Sosei Group Corporation, which is listed on the Tokyo Stock Exchange (ticker: 4565). Sosei, Heptares, the logo and StaR® are trademarks of Sosei Group companies. For more information, please visit https://soseiheptares.com/ LinkedIn: @soseiheptaresco | Twitter: @soseiheptaresco | YouTube: @soseiheptaresco Enquiries: Sosei Heptares – Media and Investor Relations Hironoshin Nomura, CFO +81 (0)3 6679 2178 | Hironoshin.Nomura@SoseiHeptares.com Shinichiro Nishishita, VP Investor Relations, Head of Regulatory Disclosures +81 (0)3 5210 3399 | IR@SoseiHeptares.com MEDiSTRAVA Consulting (for International Media) Mark Swallow, David Dible, Eleanor Perkin +44 (0)203 928 6900| SoseiHeptares@medistrava.com Forward-looking statements This press release contains forward-looking statements, including statements about the discovery, development, and commercialization of products. Various risks may cause Sosei Group Corporation’s actual results to differ materially from those expressed or implied by the forward-looking statements, including: adverse results in clinical development programs; failure to obtain patent protection for inventions; commercial limitations imposed by patents owned or controlled by third parties; dependence upon strategic alliance partners to develop and commercialize products and services; difficulties or delays in obtaining regulatory approvals to market products and services resulting from development efforts; the requirement for substantial funding to conduct research and development and to expand commercialization activities; and product initiatives by competitors. As a result of these factors, prospective investors are cautioned not to rely on any forward-looking statements. We disclaim any intention or obligation to update or revise any forward-looking statements, whether as a result of new information, future events or otherwise.