X0508 4 2024-01-30 0 0000907654 ARCA biopharma, Inc. ABIO 0001113661 MITCHELL DANIEL J 10170 CHURCH RANCH WAY SUITE 100 WESTMINSTER CO 80021 1 0 0 0 0 Common Stock 611 D Stock Option (right to buy) 1.64 2024-01-30 4 A 0 6000 0.00 A 2034-01-30 Common Stock 6000 6000 D Grant to the Reporting Person of a stock option under the 2020 Equity Incentive Plan, vesting in 12 equal monthly installments beginning as of January 30, 2024, subject to the Reporting Person continuing to provide Continuous Service (as defined in the 2020 Equity Incentive Plan) through such date. If the Reporting Person's service as a director of the Issuer terminates in connection with or at any time following a change in control (for whatever reason), then any unexpired options that remain unvested shall become fully vested. /s/ C. Jeffrey Dekker, Attorney-in-Fact 2024-01-31