X0508 4 2024-01-03 0 0001287098 MAXCYTE, INC. MXCT 0001874571 Masoud Maher C/O MAXCYTE, INC. 9713 KEY WEST AVENUE, SUITE 400 ROCKVILLE MD 20850 1 1 0 0 President and CEO 0 Employee Stock Option (right to buy) 4.42 2024-01-03 4 A 0 400000 0.00 A 2034-01-02 Common Stock 400000 400000 D This option grant was made pursuant to the terms of the letter agreement, dated as of December 11, 2023, by and between the Issuer and the reporting person, entered into in connection with his appointment as President and Chief Executive Officer of the Issuer, as set forth in a Current Report on Form 8-K filed by the Issuer on December 11, 2023. Of the shares underlying the option, 25% will vest on January 2, 2025 and the remaining 75% will vest in 36 equal monthly installments thereafter, in each case subject to the reporting person's continuous service with the Issuer at the applicable vesting date. /s/ Katie Kazem, Attorney-in-Fact 2024-01-04