RAPID MICRO BIOSYSTEMS, INC.

(a)

None.

(b)

None.

(c)Director and Officer Trading Plans and Arrangements

On June 15, 2026, Robert Spignesi, President, Chief Executive Officer and Director, terminated a 10b5-1 trading plan that he entered into on March 17, 2026 (the “Prior Spignesi 10b5-1 Trading Plan”) intended to satisfy the affirmative defense of Rule 10b5-1(c) of the Exchange Act and provided for the potential exercise of expiring vested stock options and the associated sale of up to 398,230 shares of our Class A common stock.

On June 16, 2026, Robert Spignesi, President, Chief Executive Officer and Director, adopted a new 10b5-1 trading plan (the “Spignesi 10b5-1 Trading Plan”) intended to satisfy the affirmative defense of Rule 10b5-1(c) of the Exchange Act and providing for the potential exercise of expiring vested stock options and the associated sale of up to 396,828 shares of our Class A common stock. The Spignesi 10b5-1 Trading Plan will remain in effect until the earlier of (1)December 31, 2026, (2) the date on which all trades set forth in the Spignesi 10b5-1 Trading Plan have been executed, or (3) such time as the Spignesi 10b5-1 Trading Plan is otherwise terminated according to its terms.

None of our other directors or officers adopted, modified or terminated a Rule 10b5-1 trading arrangement, oradopted, modified orterminated a non-Rule 10b5-1 trading arrangement (as defined in Item 408(c) of Regulation S-K) during the quarter ended June 30, 2026.