SCHEDULE 13G 0001555119 XXXXXXXX LIVE Common Stock, par value $0.001 09/30/2025 0001503274 Quanterix Corp 74766Q101 1900 Middlesex Turnpike Billerica MA 01821 Rule 13d-1(c) Telegraph Hill Partners III, L.P. b DE 0.00 2504648.00 0.00 2504648.00 2504648.00 N 5.4 PN Row 6, 8, 9 and 11: Includes (i) 2,258,408 shares of common stock held by Telegraph Hill Partners III, L.P. and (ii) 246,240 shares of common stock held by THP III Affiliates Fund, LLC. Row 11: Consists of 46,710,797 shares of Common Stock of the Issuer outstanding on November 4, 2025, based on information publicly disclosed by the Issuer. THP III Affiliates Fund, LLC b DE 0.00 2504648.00 0.00 2504648.00 2504648.00 N 5.4 PN Row 6, 8, 9 and 11: Includes (i) 2,258,408 shares of common stock held by Telegraph Hill Partners III, L.P. and (ii) 246,240 shares of common stock held by THP III Affiliates Fund, LLC. Row 11: Consists of 46,710,797 shares of Common Stock of the Issuer outstanding on November 4, 2025, based on information publicly disclosed by the Issuer. Telegraph Hill Partners III Investment Management, LLC b DE 0.00 2504648.00 0.00 2504648.00 2504648.00 N 5.4 PN Row 6, 8, 9 and 11: Includes (i) 2,258,408 shares of common stock held by Telegraph Hill Partners III, L.P. and (ii) 246,240 shares of common stock held by THP III Affiliates Fund, LLC. Row 11: Consists of 46,710,797 shares of Common Stock of the Issuer outstanding on November 4, 2025, based on information publicly disclosed by the Issuer. Telegraph Hill Partners Management Company, LLC b DE 0.00 2504648.00 0.00 2504648.00 2504648.00 N 5.4 PN Row 6, 8, 9 and 11: Includes (i) 2,258,408 shares of common stock held by Telegraph Hill Partners III, L.P. and (ii) 246,240 shares of common stock held by THP III Affiliates Fund, LLC. Row 11: Consists of 46,710,797 shares of Common Stock of the Issuer outstanding on November 4, 2025, based on information publicly disclosed by the Issuer. Quanterix Corp 1900 Middlesex Turnpike Billerica, MA, 01821 This Statement is filed on behalf of each of the following persons (collectively, the "Reporting Persons"): (i) Telegraph Hill Partners III, L.P. (ii) THP III Affiliates Fund, LLC (iii) Telegraph Hill Partners III Investment Management, LLC (iv) Telegraph Hill Partners Management Company, LLC The address of the principal business and principal office of each of the Reporting Persons is 300 Montgomery Street, Suite 1130, San Francisco, California 94104. (i) Telegraph Hill Partners III, L.P. is a Delaware limited partnership. (ii) THP III Affiliates Fund, LLC is a Delaware limited liability company. (iii) Telegraph Hill Partners III Investment Management, LLC is a Delaware limited liability company. (iv) Telegraph Hill Partners Management Company, LLC is a Delaware limited liability company. Y Telegraph Hill Partners III, L.P. 2,258,408 shares of common stock are held of record by Telegraph Hill Partners III, L.P. ("THP III"). Telegraph Hill Partners III Investment Management, LLC ("THP IM") is the general partner of THP III. Telegraph Hill Partners Management Company, LLC ("THPMC") is the manager of THP IM. THP III Affiliates Fund, LLC 246,240 shares of common stock are held of record by THP III Affiliates Fund, LLC ("THP III AFF"). THP IM is the manager of THP III AFF. THPMC is the manager of THP IM. The information required by Item 4(b) is set forth in Rows (5)-(9) and (11) of the cover page for each Reporting Person hereto and is incorporated herein by reference for each Reporting Person. The information required by Item 4(c) is set forth in Rows (5)-(9) and (11) of the cover page for each Reporting Person hereto and is incorporated herein by reference for each Reporting Person. The information required by Item 4(c) is set forth in Rows (5)-(9) and (11) of the cover page for each Reporting Person hereto and is incorporated herein by reference for each Reporting Person. The information required by Item 4(c) is set forth in Rows (5)-(9) and (11) of the cover page for each Reporting Person hereto and is incorporated herein by reference for each Reporting Person. The information required by Item 4(c) is set forth in Rows (5)-(9) and (11) of the cover page for each Reporting Person hereto and is incorporated herein by reference for each Reporting Person. Y Y Y Y Y N By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11. Telegraph Hill Partners III, L.P. /s/ Rob Hart 11/17/2025 THP III Affiliates Fund, LLC /s/ Rob Hart 11/17/2025 Telegraph Hill Partners III Investment Management, LLC /s/ Rob Hart 11/17/2025 Telegraph Hill Partners Management Company, LLC /s/ Rob Hart 11/17/2025