X0306 4 2020-11-20 0001503274 Quanterix Corp QTRX 0001219039 CRANDELL KEITH 8755 W. HIGGINS ROAD, SUITE 1025 CHICAGO IL 60631 1 0 1 0 Common Stock 2020-11-20 4 J 0 229006 0 D 2182995 I See Footnote Common Stock 2020-11-20 4 J 0 145994 0 D 1391690 I See Footnote Common Stock 2020-11-20 4 J 0 854 0 A 10925 D Common Stock 2020-11-24 4 J 0 277514 0 D 1905481 I See Footnote Common Stock 2020-11-24 4 J 0 176920 0 D 1214770 I See Footnote Common Stock 2020-11-24 4 J 0 1034 0 A 11959 D Distribution of Common Stock held by a limited partnership to its partners for no consideration. These shares are directly held by ARCH Venture Fund VI, L.P. ("ARCH VI"). ARCH Venture Partners VI, L.P. ("GPLP"), the sole general partner of ARCH VI, may be deemed to beneficially own the shares held by ARCH VI. ARCH Venture Partners VI, LLC ("GPLLC"), as the sole general partner of GPLP, may be deemed to beneficially own the shares held by ARCH VI. The Reporting Person is a managing director of the GPLLC and shares voting and investment control with respect to these shares. The Reporting Person may be deemed to beneficially own the shares held by ARCH VI. The Reporting Person disclaims beneficial ownership of the securities reported herein, except to the extent of his pecuniary interest therein, if any. These shares are directly held by ARCH Venture Fund VIII Overage, L.P. ("ARCH Overage"). ARCH Venture Partners VIII, LLC ("ARCH VIII LLC") the sole general partner of ARCH Overage, may be deemed to beneficially own the shares held by ARCH Overage. The Reporting Person is a managing director of the ARCH VIII LLC and shares voting and investment control with respect to these shares. The Reporting Person may be deemed to beneficially own the shares held by ARCH Overage. The Reporting Person disclaims beneficial ownership of the securities reported herein, except to the extent of his pecuniary interest therein, if any. Change from indirect to direct ownership of shares previously reported as beneficially owned by the Reporting Person. /s/ Mark McDonnell, as Attorney-in-Fact for Keith Crandell 2020-11-24