SCHEDULE 13D/A 0001711933 XXXXXXXX LIVE 1 Common Stock, par value $0.001 per share 01/09/2025 false 0001503274 74766Q101 Quanterix Corp

900 Middlesex Turnpike Billerica MA 01821

Patrick O'Malley (858) 677-1400 DLA Piper LLP (US) 4365 Executive Drive, Suite 1100 San Diego CA 92121 0001711933 N Akoya Biosciences, Inc. a OO Y DE 0.00 0.00 0.00 0.00 0.00 N 0 CO Common Stock, par value $0.001 per share Quanterix Corp 900 Middlesex Turnpike Billerica MA 01821 This Amendment No. 1 ("Amendment No. 1") amends and supplements the Schedule 13D filed on January 16, 2025 (the "Schedule 13D"). Except as specifically amended by this Amendment No. 1, the Schedule 13D remains in full force and effect. Capitalized terms used but not otherwise defined herein shall have the respective meanings previously ascribed to them in the Schedule 13D. Termination of the Voting Agreement On April 28, 2025, Akoya Biosciences, Inc., a Delaware corporation(the "Reporting Person" or "Akoya"), entered into an Amended and Restated Agreement and Plan of Merger (the "A&R Merger Agreement"), with Quanterix Corporation, a Delaware corporation ("Quanterix"), and Wellfleet Merger Sub, Inc., a Delaware corporation and wholly owned subsidiary of Quanterix ("Merger Sub"), pursuant to which, subject to the terms and conditions set forth therein, Merger Sub will merge with and into Akoya (the "Merger"), with Akoya surviving such Merger as a wholly owned subsidiary of Quanterix. The A&R Merger Agreement amends and restates in its entirety the Agreement and Plan of Merger, dated as of January 9, 2025, by and among Quanterix, Merger Sub and Akoya (the "Original Merger Agreement"). In connection with the entry into the Original Merger Agreement and as previously announced, Akoya had entered into a Voting and Support Agreement dated as of January 9, 2025 (the "Voting Agreement") with certain of Quanterix's stockholders, including the directors and executive officers of Quanterix. As a result of the entry into the A&R Merger Agreement, the Voting Agreement was terminated pursuant to its terms. The foregoing description of the A&R Merger Agreement is qualified in its entirety by reference to the full text of such agreement, a copy of which is filed hereto as Exhibit 99.2. The information contained in Item 3 of this Schedule 13D is incorporated by reference herein. Beneficial ownership of shares of Common Stock by the Reporting Person was reported in the Schedule 13D solely because the Reporting Person could have been deemed to have beneficial ownership of 2,955,532 shares of Common Stock as a result of certain provisions contained in the Voting Agreement. The Voting Agreement terminated by its terms on April 28, 2025, and the Reporting Person does not currently beneficially own any shares of Common Stock. To the knowledge of the Reporting Person, none of the persons named in Schedule A to the Schedule 13D beneficially owns any shares of Common Stock. The Reporting Person has not effected any transaction in Common Stock during the past sixty days and, to the knowledge of the Reporting Person, none of the persons listed on Schedule A have effected any such transaction. Not applicable. April 28, 2025 The information contained in Item 3 of this Schedule 13D is incorporated by reference herein. 99.1 Schedule A 99.2 Amended and Restated Agreement and Plan of Merger, dated as of April 28, 2025, by and among Quanterix Corporation, Wellfleet Merger Sub, Inc. and Akoya Biosciences, Inc. (incorporated by reference to Exhibit 2.1 of the Current Report on Form 8-K filed with the SEC on April 29, 2025 by Akoya Biosciences, Inc.) Akoya Biosciences, Inc. /s/ Brian McKelligon 04/30/2025