Allurion Technologies Inc美股招股说明书(2025-10-06版)

ALLURION TECHNOLOGIES, INC. Up to 56,548,268 Shares of Common Stock This prospectus supplement no. 28 (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”) onOctober3, 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 October2, 2025, the last quoted sale price for shares of our common stock as reported on the NYSE was $2.07 pershare, and the last quoted sale price for our public warrants as reported on the NYSE was $0.0297 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 the discussion of the risks ofinvesting in our securities in “Risk Factors” beginning on page 26 of the Prospectus. The date of this Prospectus Supplement is October3, 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): September 30, 2025 Allurion Technologies, Inc. (Exact name of Registrant as Specified in Its Charter) 001-41767(CommissionFile Number) (Former Name or Former Address, if Changed Since Last Report) Check the appropriate box below if the Form8-Kfiling is intended to simultaneously satisfy the filing obligation of the registrant under any of thefollowing provisions: ☐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). Emerging growth company☒ 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 5.02 Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangement of On September30, 2025, Milena Alberti-Perez, a ClassIII member of the board of directors (the “Board”) of Allurion Technologies, Inc. (the“Company”), notified the Company of her resignation from the Board and her role as the chairperson of the Audit Committee of the Board (the “AuditCommittee”), effective September30, 2025. Ms.Alberti-Perez’s resignation was not the result of any disagreement with management or the Board or onany matter relating to the Company’s operations, policies or practices. Ms.Alberti-Perez resigned to focus her time in the media sector, including a new position on the board of another public company in that sector. Suchresignation and resulting reduction in the size of the Board aligns with the Board’s determination that a smaller board will improve efficiency and reducedirector compensation costs. Effective upon Ms.Alberti-Perez’s resignation, the size of the Board will be reduced from nine to eight. The Board iscurrently evaluating which of its directors will replace Ms.Alberti-Perez as chairperson of the Audit Committee. SIGNATURES Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by theundersigned hereunto duly authorized. Date:October3, 2025