Rapid Micro Biosystems Inc-A美股招股说明书(2026-05-19版)

71,607 Shares of ClassA Common Stock Series A Warrants to Purchase up to 71,607 Shares of ClassA Common Stock (or pre-funded warrants)Series B Warrants to Purchase up to 71,607 Shares of Class A Common Stock (or pre-funded warrants) We are offering 71,607 shares of our ClassA common stock, $0.01 par value per share, and accompanying SeriesAcommon stock warrants to purchase 71,607 shares of our ClassA common stock with an exercise price of $1.955 per share andaccompanying Series B common stock warrants to purchase 71,607 shares of our Class A common stock with an exercise priceof $2.34 per share, at a combined offering price of $1.955 per share, directly to certain of the Company’s directors and officers.This offering is being made without an underwriter or a placement agent and we are not paying underwriting discounts orcommissions, so the proceeds to us, before expenses, will be approximately $140,000. The ClassA common stock will be sold in combination with an accompanying SeriesA common stock warrant to purchase71,607 shares of ClassA common stock issued for each share of Class A common stock sold (or pre-funded warrants in lieuthereof) and Series B common stock warrant to purchase 71,607 shares of Class A common stock (or pre-funded warrants in lieuthereof). The shares of our ClassA common stock (or pre-funded warrants), SeriesA common stock warrants and Series B commonstock warrants are immediately separable and will be issued separately. The Series A common stock warrants are exercisable sixmonths from the date of issuance and will expire one year from the date of issuance. The SeriesB common stock warrants areexercisable six months from the date of issuance and will expire five years from the date of issuance. The SeriesA commonstock warrants will have an exercise price of $1.955 per share of our ClassA common stock, subject to adjustment as describedelsewhere in this prospectus supplement. The Series B common stock warrants will have an exercise price of $2.34 per share ofour Class A common stock, subject to adjustment as described elsewhere in this prospectus supplement. This offering isexpected to close on or about May 20, 2026, and is contingent and conditioned upon consummation of, the UnderwrittenOffering (as defined herein), as well as certain other customary closing conditions. In a concurrent underwritten registered direct offering, we entered into an underwriting agreement with TD Securities(USA) LLC and Lake Street Capital Markets LLC, as representatives of the several underwriters named therein relating to anunderwritten offering (the “Underwritten Offering”) of (i) 3,581,000 shares of our Class A common stock, and accompanyingSeries A warrants to purchase an aggregate of 3,581,000 shares of Class A common stock (or pre-funded warrants in lieuthereof) and Series B warrants to purchase an aggregate of 3,581,000 shares of Class A common stock (or pre-funded warrantsin lieu thereof), and, (ii) in lieu of Common Stock to certain investors, pre-funded warrants to purchase an aggregate of up to1,463,000 shares of Common Stock and accompanying Series A Common Warrants to purchase an aggregate of 1,463,000 sharesof Class A common stock (or pre-funded warrants in lieu thereof) at an exercise price of $1.955 per share and Series B CommonWarrants to purchase an aggregate of 1,463,000 shares of Class A common stock (or pre-funded warrants in lieu thereof) at anexercise price of $2.34 per share. The Underwritten Offering is expected to close on May 20, 2026, subject to customary closingconditions. Our ClassA common stock is listed on The Nasdaq Capital Market under the symbol “RPID.” On May 18, 2026, the lastreported sale price of our ClassA common stock on The Nasdaq Capital Market was $1.955 per share. There is no establishedpublic trading market for the pre-funded warrants, the SeriesA common stock warrants or the Series B common stock warrants,and we do not expect a market to develop. In addition, we do not intend to apply for a listing of the pre-funded warrants or theSeriesA common stock warrants or Series B common stock warrants on The Nasdaq Capital Market, any other nationalsecurities exchange or any other nationally recognized trading system. Investing in our securities involves a high degree of risk. See “Risk Factors” beginning on pageS-6of this prospectussupplement, in the accompanying prospectus and in the documents incorporated by reference into this prospectus supplement andthe accompanying prospectus. Neither the Securities and Exchange Commission nor any other regulatory body has approved or disapproved of these securitiesor passed on the adequacy or accuracy of this prospectus supplement or the accompanying prospectus. Any representation to thecontrary is a criminal offense. Prospectus Supplement dated May 18, 2026 TABLE OF CONTENTS PageABOUT THIS PROSPECTUS SUPPLEMENTS-iiMARKET, INDUSTRY AND OTHER DATAS-ivPROSPECTUS SUPPLEMENT SUMMARYS-1RISK FACTORSS-6CAUTIONARY STATEMEN