144 0001874850 XXXXXXXX LIVE 0001287098 MAXCYTE, INC. 001-40674 9713 KEY WEST AVENUE, SUITE 400 ROCKVILLE MD 20850 301-517-5556 Johnston John Joseph Affiliate Common Stifel Nicolaus & Company Inc.

501 N. Broadway St. Louis MO 63102

12000 49320.00 105482558 12/26/2024 NASDAQ Common 07/18/2018 option exercise Issuer N 12000 12/26/2024 Cash N John Joseph Johnston

9713 KEY WEST AVENUE, SUITE 400 ROCKVILLE MD 20850

Common 09/26/2024 3000 11459.00 John Joseph Johnston

9713 KEY WEST AVENUE,, SUITE 400 ROCKVILLE MD 20850

Common 10/28/2024 3000 11166.00 John Joseph Johnston

9713 KEY WEST AVENUE,, SUITE 400 ROCKVILLE MD 20850

Common 12/06/2024 505 1868.00 John Joseph Johnston

9713 KEY WEST AVENUE,, SUITE 400 ROCKVILLE MD 20850

Common 12/09/2024 2495 9456.00 12/26/2024 12/19/2023 /s/ Dominick Iadicicco is a duly authorized representative of STIFEL, as attorney-in-fact for John Joseph Johnston