Material Agreement (Form 8-K)

Underwriting Agreement

On May 18, 2026, Rapid Micro Biosystems, Inc. (the "Company") entered into an underwriting agreement (the "Underwriting Agreement") with TD Securities (USA) LLC and Lake Street Capital Markets LLC, as representatives of the several underwriters named therein (the "Underwriters") relating to an underwritten offering (the "Offering") of (i) 3,581,000 shares (the "Shares") of the Company's Class A common stock, $0.01 par value per share (the "Common Stock") and accompanying Series A warrants ("Series A Common Stock Warrants") to purchase an aggregate of 3,581,000 shares of Class A common stock (or pre-funded warrants in lieu thereof) and Series B warrants ("Series B Common Stock Warrants") to purchase an aggregate of 3,581,000 shares of Class A common stock (or pre-funded warrants in lieu thereof), and, (ii) in lieu of Common Stock to certain investors, pre-funded warrants to purchase an aggregate of up to 1,463,000 shares of Common Stock (the "Pre-Funded Warrants" and together with the Series A Common Stock Warrants, and Series B Common Stock Warrants, the "Warrants" and the shares of Common Stock issuable upon exercise of the warrants, the "Warrant Shares") and accompanying Series A Common Stock Warrants to purchase an aggregate of 1,463,000 shares of Class A common stock (or pre-funded warrants in lieu thereof) at an exercise price of $1.955 per share and Series B Common Stock Warrants to purchase an aggregate of 1,463,000 shares of Class A common stock (or pre-funded warrants in lieu thereof) at an exercise price of $2.340 per share. Each Share was offered and sold together with an accompanying Series A Common Stock Warrant and a Series B Common Stock Warrant at a combined offering price of $1.955, and each Pre-Funded Warrant was offered and sold together with an accompanying Series A Common Stock Warrant and a Series B Common Stock Warrant at a combined offering price of $1.945, which is equal to the combined offering price per share of Common Stock and accompanying Series A Common Stock Warrant and Series B Common Stock Warrant less the $0.01 exercise price of each Pre-Funded Warrant. The Offering is expected to close on May 20, 2026, subject to customary closing conditions.

Each Pre-Funded Warrant has an initial exercise price per share of $0.01, subject to certain adjustments. The Pre-Funded Warrants are exercisable immediately and may be exercised at any time until all of the Pre-Funded Warrants are exercised in full. Each Series A Common Stock Warrant has an initial exercise price per share of $1.955, subject to certain adjustments and each Series B Common Stock Warrant has an initial exercise price per share of $2.340, subject to certain adjustments. The Series A Common Stock Warrants are exercisable 6 months from the date of issuance and will expire one year from the date of issuance. The Series B Common Stock Warrants are exercisable 6 months from the date of issuance and will expire five years from the date of issuance.

Under the Warrants, the Company may not effect the exercise of any Warrant, and a holder will not be entitled to exercise any portion of any Warrant (i) if immediately prior to the exercise, holder (together with its affiliates), beneficially own an aggregate number of shares of Common Stock greater than 4.5% or 4.99% or 9.99%, as applicable (the "Maximum Percentage") of the total number of issued and outstanding shares of Common Stock of the Company without taking into account any Warrant Shares, or (ii) to the extent that immediately following the exercise, the holder (together with its affiliates) would beneficially own in excess of the Maximum Percentage of the number of shares of Common Stock outstanding immediately after giving effect to the issuance of such shares of Common Stock, which such percentage may be changed at the holder's election to a higher or lower percentage not in excess of 19.99% upon 61 days' notice to the Company.

The Series A Common Stock Warrants include certain rights upon "fundamental transactions" as described therein, including the right of the holders thereof to receive, upon exercise of the Series A Common Stock Warrants following such fundamental transaction, the same amount and kind of securities, cash or property as the holder would have been entitled to receive upon the occurrence of such fundamental transaction if it had been, immediately prior to such fundamental transaction, the holder of the number of Warrant Shares issuable upon exercise of the Series A Common Stock Warrants.

The Series A Common Stock Warrants also contain a forced exercise provision granting the Company the right, upon the satisfaction of specified conditions, to require holders to exercise all or any portion of their Series A Common Stock Warrants.

The Series B Common Stock Warrants include certain rights upon "fundamental transactions" as described therein, including the right of the holders thereof to receive from the Company or a successor entity the same type or form of consideration (and in the same proportion) that is being offered and paid to the holders of Common Stock in such fundamental transaction in the amount of the Black Scholes Value (as described in such Series A Common Stock Warrants) of the unexercised portion of the applicable Series B Common Stock Warrants on the date of the consummation of such fundamental transaction.

The Series B Common Stock Warrants also include a participation rights whereby for a period of twelve months from the original issue date, holders of the Series B Common Stock Warrants have the right to participate in future issuances of the Company's Class A common stock or Common Stock equivalents on pro rata basis, up to an aggregate of 25% of such offering, subject to certain conditions.