X0306 4 2020-11-20 1 0001503274 Quanterix Corp QTRX 0001222135 ARCH VENTURE FUND VI LP 8755 WEST HIGGINS ROAD, SUITE 1025 CHICAGO IL 60631 0 0 1 0 0001617237 ARCH Venture Fund VIII Overage, L.P. 8755 WEST HIGGINS ROAD, SUITE 1025 CHICAGO IL 60631 0 0 1 0 0001274410 ARCH VENTURE PARTNERS VI LP 8755 WEST HIGGINS ROAD, SUITE 1025 CHICAGO IL 606031 0 0 1 0 0001274412 ARCH VENTURE PARTNERS VI LLC 8755 WEST HIGGINS ROAD, SUITE 1025 CHICAGO IL 606031 0 0 1 0 0001616165 ARCH Venture Partners VIII, LLC 8755 WEST HIGGINS ROAD, SUITE 1025 CHICAGO IL 606031 0 0 1 0 0001219043 BYBEE CLINTON C/O ARCH VENTURE PARTNERS IX, LLC 8755 W. HIGGINS ROAD, SUITE 1025 CHICAGO IL 60631 0 0 1 0 0001219042 NELSEN ROBERT 8755 W. HIGGINS ROAD, SUITE 1025 CHICAGO IL 60631 0 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 854 D Common Stock 2020-11-20 4 J 0 853 0 A 853 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 1888 D Common Stock 2020-11-24 4 J 0 1036 0 A 1889 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. As managing directors of GPLLC, each of Robert Nelsen and Clinton Bybee (the "ARCH Managing Directors"), may be deemed to beneficially own the shares held by ARCH VI. Each of GPLP, GPLLC and the ARCH Managing Directors disclaims beneficial ownership of the securities reported herein, except to the extent of their pecuniary interest therein, if any. 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 managing directors of ARCH VIII LLC, each of the ARCH Managing Directors may be deemed to beneficially own the shares held by ARCH Overage. Each of ARCH VIII LLC and the ARCH Managing Directors disclaims beneficial ownership of the securities reported herein, except to the extent of their pecuniary interest therein, if any. Change from indirect to direct ownership of shares previously reported as beneficially owned by the Reporting Person. Shares owned by Nelsen. Shares owned by Bybee. /s/ Mark McDonnell, as Attorney-in-Fact for ARCH Venture Fund VI, L.P. 2020-11-24 /s/ Mark McDonnell, as Attorney-in-Fact for ARCH Venture Fund VIII Overage, L.P. 2020-11-24 /s/ Mark McDonnell, as Attorney-in-Fact for ARCH Venture Partners VI, L.P. 2020-11-24 /s/ Mark McDonnell, as Attorney-in-Fact for ARCH Venture Partners VI, LLC 2020-11-24 /s/ Mark McDonnell, as Attorney-in-Fact for ARCH Venture Partners VIII, LLC 2020-11-24 /s/ Mark McDonnell, as Attorney-in-Fact for Clinton Bybee 2020-11-24 /s/ Mark McDonnell, as Attorney-in-Fact for Robert Nelsen 2020-11-24