X0609 4 2026-09-09 1 0001828185 Barinthus Biotherapeutics plc. BRNS 0002027157 Hooftman Leon false C/O BARINTHUS BIOTHERAPEUTICS PLC 20400 CENTURY BOULEVARD GERMANTOWN MD 20874 0 1 0 0 Chief Medical Officer 0 Ordinary Shares 2026-09-09 4 A 0 361530 A 361530 D Ordinary Shares 2026-09-09 4 D 0 361530 D 0 D Share Option (Right to Buy) 2.00 2026-09-09 4 D 0 195166 0.00 D 2034-06-03 Ordinary Shares 195166 0 D Share Option (Right to Buy) 1.00 2026-09-09 4 D 0 140000 0.00 D 2035-02-03 Ordinary Shares 140000 0 D The Ordinary Shares may be represented by American Depositary Shares ("ADSs" and together with the Ordinary Shares, the "Shares"), each of which currently represents one Ordinary Share. This Form 4 reports securities transacted in connection with the Agreement and Plan of Merger, dated September 29, 2025, as amended (the "Merger Agreement") by and among the Issuer, Beacon Topco, Inc. ("Topco"), a Delaware corporation and a direct wholly owned subsidiary of the Issuer, Cdog Merger Sub, Inc., a Delaware corporation and a direct wholly owned subsidiary of Topco, and Clywedog Therapeutics, Inc., a Delaware corporation. On September 9, 2026 (the "Effective Time"), in connection with the effectiveness of the scheme of arrangement under Part 26 of the United Kingdom Companies Act 2006 (the "Scheme") contemplated by the Merger Agreement, Topco acquired the entire issued share capital of the Issuer, resulting in the Issuer becoming a direct wholly owned subsidiary of Topco. Represents restricted share units ("RSUs") previously granted to the Reporting Person, vesting of which was subject to completion of the transactions contemplated by the Merger Agreement. Each RSU represented the contingent right to receive one Share of the Issuer. At the Effective time, each RSU, whether or not then vested, was automatically released in consideration of the assumption of such RSU by Topco and converted into an RSU relating to the common stock, $0.0001 par value per share, of Topco (the "Topco Common Stock"). Pursuant to the Merger Agreement, at the Effective Time, each option to acquire Shares under the Issuer's equity plans that was outstanding as of immediately prior to the Effective Time ceased to represent a right to acquire Shares of the Issuer, and was converted into an option to acquire shares of Topco Common Stock and assumed by Topco on the same terms and conditions (including applicable vesting and exercisability conditions) as were applicable to such option immediately prior to the Effective Time. /s/ William Enright, Attorney-in-Fact 2026-09-09