Allurion Technologies Inc美股招股说明书(2025-11-12版)

ALLURION TECHNOLOGIES, INC. Up to 56,548,268 Shares of Common Stock This prospectus supplement no. 29 (this “Prospectus Supplement”) amends and supplements the prospectus dated December15, 2023 (as supplementedor amended from time to time, the “Prospectus”) which forms part of our Registration Statement on FormS-1/A(Registration StatementNo.333-274564).This Prospectus Supplement is being filed to update and supplement the information included or incorporated by reference in theProspectus with the information contained in our Current Report on Form8-K,filed with the Securities and Exchange Commission (the “SEC”) onNovember12, 2025 (the“8-K”).Accordingly, we have attached the8-Kto this Prospectus Supplement. This Prospectus Supplement updates and supplements the information in the Prospectus and is not complete without, and may not be delivered orutilized except in combination with, the Prospectus, including any amendments or supplements thereto. This Prospectus Supplement should be read inconjunction with the Prospectus, and if there is any inconsistency between the information in the Prospectus and this Prospectus Supplement, you shouldrely on this Prospectus Supplement. Our common stock is listed on The New York Stock Exchange (“NYSE”) under the symbol “ALUR” and our public warrants are listed on the NYSEunder the symbol “ALUR.WS”. On November11, 2025, the last quoted sale price for shares of our common stock as reported on the NYSE was $1.49per share, and the last quoted sale price for our public warrants as reported on the NYSE was $0.0250 per warrant. We are an “emerging growth company” under applicable federal securities laws and will be subject to reduced public company reportingrequirements. Investing in our securities involves a high degree of risk. Before buying any securities, you should carefully read thediscussion of the risks of investing in our securities in “Risk Factors” beginning on page 26 of the Prospectus. Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of the securities to beissued under the Prospectus or determined if the Prospectus is truthful or complete. Any representation to the contrary is a criminal offense. The date of this Prospectus Supplement is November12, 2025. UNITED STATESSECURITIES AND EXCHANGE COMMISSIONWashington, D.C. 20549 CURRENT REPORTPursuant to Section13 OR 15(d)of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November6, 2025 ALLURION TECHNOLOGIES, INC. (Exact name of registrant as specified in its charter) 001-41767(CommissionFile Number) 92-2182207(IRS EmployerIdentification No.) Check the appropriate box below if the Form8-Kfiling is intended to simultaneously satisfy the filing obligation of the registrant under any of the ☐Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)☐Soliciting material pursuant to Rule14a-12under the Exchange Act (17 CFR240.14a-12)☐Pre-commencementcommunications pursuant to Rule14d-2(b)under the Exchange Act (17 CFR240.14d-2(b))☐Pre-commencementcommunications pursuant to Rule13e-4(c)under the Exchange Act (17 CFR240.13e-4(c)) Securities registered pursuant to Section12(b) of the Act: Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of thischapter) or Rule12b-2of the Securities Exchange Act of 1934(§240.12b-2of this chapter). If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with anynew or revised financial accounting standards provided pursuant to Section13(a) of the Exchange Act.☐ Item 1.01Entry into a Material Definitive Agreement Securities Purchase Agreement On November11, 2025, Allurion Technologies, Inc. (the “Company” or “Allurion”) entered into a securities purchase agreement (the “SecuritiesPurchase Agreement”) with certain accredited investors named therein (the “Purchasers”), pursuant to which the Company agreed to issue and sell2,994,012 shares (the “Private Placement Shares”) of the Company’s common stock, par value $0.0001 per share (the “Common Stock”) andaccompanying common warrants to purchase up to 2,994,012 shares of Common Stock (the “Private Placement Warrants,” and together with the PrivatePlacement Shares, the “Private Placement Securities”), for an aggregate purchase price of approximately $5million at a purchase price of $1.67 perPrivate Placement Share and accompanying Private Placement Warrant (the “Private Placement”). The Securities Purchase Agreement contains customary representations, warranties and agreements by the Company, customary conditions to closing,certain obligations of the parties, and indemnification provisions. The Company is required to use its reasonable best efforts to hold a meeting ofstockholders no later than January31, 2026 for the purpose of, among