X0306 4 2017-12-11 0 0001503274 Quanterix Corp QTRX 0001219039 CRANDELL KEITH 8755 WEST HIGGINS ROAD, SUITE 1025 CHICAGO IL 60631 1 0 1 0 Common Stock 2017-12-11 4 C 0 398257 A 398257 I Held by ARCH Venture Fund VI, L.P. Common Stock 2017-12-11 4 C 0 1045426 A 1443683 I Held by ARCH Venture Fund VI, L.P. Common Stock 2017-12-11 4 C 0 477042 A 1920725 I Held by ARCH Venture Fund VI, L.P. Common Stock 2017-12-11 4 C 0 109769 A 2030494 I Held by ARCH Venture Fund VI, L.P. Common Stock 2017-12-11 4 C 0 381507 A 2412001 I Held by ARCH Venture Fund VI, L.P. Common Stock 2017-12-11 4 C 0 1271684 A 1271684 I Held by ARCH Venture Fund VIII Overage, L.P. Common Stock 2017-12-11 4 P 0 266000 15.00 A 1537684 I Held by ARCH Venture Fund VIII Overage, L.P. Series A-1 Preferred Stock 2017-12-11 4 C 0 1280000 D Common Stock 398257 0 I Held by ARCH Venture Fund VI, L.P. Series A-2 Preferred Stock 2017-12-11 4 C 0 3360000 D Common Stock 1045426 0 I Held by ARCH Venture Fund VI, L.P. Series B Preferred Stock 2017-12-11 4 C 0 1533214 D Common Stock 477042 0 I Held by ARCH Venture Fund VI, L.P. Warrant to Purchase Series C Preferred Stock (right to buy) 3.3299 2017-11-27 4 X 0 18450 D 2012-03-01 2017-11-30 Series C Preferred Stock 18450 14761 I Held by ARCH Venture Fund VI, L.P. Series C Preferred Stock 2017-11-27 4 X 0 18450 A Common Stock 5740 363869 I Held by ARCH Venture Fund VI, L.P. Series C Preferred Stock 2017-11-27 4 S 0 14350 4.2815 D Common Stock 4464 349519 I Held by ARCH Venture Fund VI, L.P. Warrant to Purchase Series C Preferred Stock (right to buy) 3.3299 2017-11-27 4 X 0 11993 D 2012-07-30 2017-11-30 Series C Preferred Stock 11993 2768 I Held by ARCH Venture Fund VI, L.P. Series C Preferred Stock 2017-11-27 4 X 0 11993 A Common Stock 3731 361512 I Held by ARCH Venture Fund VI, L.P. Series C Preferred Stock 2017-11-27 4 S 0 9328 4.2815 D Common Stock 2902 352184 I Held by ARCH Venture Fund VI, L.P. Warrant to Purchase Series C Preferred Stock (right to buy) 3.3299 2017-11-27 4 X 0 2768 D 2012-11-05 2017-11-30 Series C Preferred Stock 2768 0 I Held by ARCH Venture Fund VI, L.P. Series C Preferred Stock 2017-11-27 4 X 0 2768 A Common Stock 861 354952 I Held by ARCH Venture Fund VI, L.P. Series C Preferred Stock 2017-11-27 4 S 0 2152 4.2815 D Common Stock 669 352800 I Held by ARCH Venture Fund VI, L.P. Series C Preferred Stock 2017-12-11 4 C 0 352800 D Common Stock 109769 0 I Held by ARCH Venture Fund VI, L.P. Series D Preferred Stock 2017-12-11 4 C 0 1226158 D Common Stock 381507 0 I Held by ARCH Venture Fund VI, L.P. Series D Preferred Stock 2017-12-11 4 C 0 4087193 D Common Stock 1271684 0 I Held by ARCH Venture Fund VIII Overage, L.P. The shares of preferred stock automatically converted into common stock immediately prior to the closing of the Issuer's initial public offering using a calculation defined in the Issuer's Restated Certificate of Incorporation, as amended, based on the initial purchase price and the conversion rate in effect at the time of conversion. The shares of preferred stock automatically converted on a 1-for-3.214 basis and such conversion rate is reflected in the amount of common stock underlying the security. The shares are held of record by ARCH Venture Fund VI, L.P. ("ARCH Fund VI"). The sole general partner of ARCH Fund VI is ARCH Venture Partners VI, L.P. ("ARCH Partners VI"), which may be deemed to beneficially own the shares held by ARCH Fund VI. The sole general partner of ARCH Partners VI is ARCH Venture Partners VI, LLC ("ARCH VI LLC"), which may be deemed to beneficially own the shares held by ARCH Fund VI. ARCH Partners VI and ARCH VI LLC disclaim beneficial ownership of such shares, except to the extent of any pecuniary interest therein. As a managing director of ARCH VI LLC, the Reporting Person may be deemed to beneficially own the shares held by ARCH Fund VI. The Reporting Person disclaims beneficial ownership of such shares, except to the extent of any pecuniary interest therein. The shares are held of record by ARCH Venture Fund VIII Overage, L.P. ("ARCH Fund Overage"). The sole general partner of ARCH Fund Overage is ARCH Venture Partners VIII, LLC ("ARCH VIII LLC"), which may be deemed to beneficially own the shares held by ARCH Fund Overage. ARCH VIII LLC disclaims beneficial ownership of such shares, except to the extent of any pecuniary interest therein. As a managing director of ARCH VIII LLC, the Reporting Person may be deemed to beneficially own the shares held by ARCH Fund Overage. The Reporting Person disclaims beneficial ownership of such shares, except to the extent of any pecuniary interest therein. Reflects shares purchased in the Issuer's initial public offering. These shares were convertible into the Issuer's common stock in accordance with the Issuer's Restated Certificate of Incorporation, as amended, at any time after the issuance of such shares, at the holder's election. Not applicable. This transaction, which occurred prior to the Issuer's initial public offering of Common Stock, is being reported as required by Rule 16a-2(a) under the Securities Exchange Act of 1934, as amended. These warrants to purchase Series C preferred stock were exercised on a cashless basis for shares of Series C preferred stock, resulting in the Issuer's withholding of 14,350 shares of Series C preferred stock to pay the exercise price and issuing to the reporting person the remaining 4,100 shares of Series C preferred stock. The Issuer's withholding of Series C preferred stock was at a price per share of Series C preferred stock of $4.2815, which is equal to approximately $13.76 per share on an as-converted-to-common stock basis. These warrants to purchase Series C preferred stock were exercised on a cashless basis for shares of Series C preferred stock, resulting in the Issuer's withholding of 9,328 shares of Series C preferred stock to pay the exercise price and issuing to the reporting person the remaining 2,665 shares of Series C preferred stock. The Issuer's withholding of Series C preferred stock was at a price per share of Series C preferred stock of $4.2815, which is equal to approximately $13.76 per share on an as-converted-to-common stock basis. These warrants to purchase Series C preferred stock were exercised on a cashless basis for shares of Series C preferred stock, resulting in the Issuer's withholding of 2,152 shares of Series C preferred stock to pay the exercise price and issuing to the reporting person the remaining 616 shares of Series C preferred stock. The Issuer's withholding of Series C preferred stock was at a price per share of Series C preferred stock of $4.2815, which is equal to approximately $13.76 per share on an as-converted-to-common stock basis. /s/ Brian Keane, as Attorney-in-Fact for Keith L. Crandell 2017-12-11