X0306 4 2020-02-10 0 0001745999 Beam Therapeutics Inc. BEAM 0001723174 ARCH Venture Partners IX, LLC 8755 W. HIGGINS ROAD SUITE 1025 CHICAGO IL 60631 0 0 1 0 0001723173 ARCH Venture Partners IX, L.P. 8755 W. HIGGINS ROAD SUITE 1025 CHICAGO IL 60631 0 0 1 0 0001723172 ARCH Venture Partners IX Overage, L.P. 8755 W. HIGGINS ROAD SUITE 1025 CHICAGO IL 60631 0 0 1 0 0001666306 ARCH Venture Fund IX, L.P. 8755 W. HIGGINS ROAD SUITE 1025 CHICAGO IL 60631 0 0 1 0 0001666307 ARCH Venture Fund IX Overage, L.P. 8755 W. HIGGINS ROAD SUITE 1025 CHICAGO IL 60631 0 0 1 0 0001219039 CRANDELL KEITH C/O ARCH VENTURE PARTNERS IX, LLC 8755 W. HIGGINS ROAD SUITE 1025 CHICAGO IL 60631 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 Common Stock 2020-02-10 4 C 0 4121520 A 4121520 I See footnote Common Stock 2020-02-10 4 C 0 4121519 A 4121519 I See footnote Series A-1 Preferred Stock 2020-02-10 4 C 0 1338000 D Common Stock 1338000 0 I See footnote Series A-1 Preferred Stock 2020-02-10 4 C 0 1338000 D Common Stock 1338000 0 I See footnote Series A-2 Preferred Stock 2020-02-10 4 C 0 2750336 D Common Stock 2750336 0 I See footnote Series A-2 Preferred Stock 2020-02-10 4 C 0 2750335 D Common Stock 2750335 0 I See footnote Series B Preferred Stock 2020-02-10 4 C 0 33184 D Common Stock 33184 0 I See footnote Series B Preferred Stock 2020-02-10 4 C 0 33184 D Common Stock 33184 0 I See footnote Upon closing of the Issuer's initial public offering, each share of Series A-1 Preferred Stock, Series A-2 Preferred Stock, and Series B Preferred Stock automatically converted into shares of Common Stock without payment or further consideration. There was no expiration date for the Series A-1 Preferred Stock, Series A-2 Preferred Stock, or Series B Preferred Stock. These shares are directly held by ARCH Venture Fund IX, L.P. ("ARCH IX"). ARCH Venture Partners IX, L.P. ("GPLP"), as the sole general partner of ARCH IX, may be deemed to beneficially own the shares held by ARCH IX. ARCH Venture Partners IX, LLC ("GPLLC"), as the sole general partner of GPLP, may be deemed to beneficially own the shares held by ARCH IX. As managing directors of GPLLC, each of Keith Crandell and Clinton Bybee (the "ARCH Managing Directors"), may be deemed to beneficially own the shares held by ARCH IX. 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. These shares are directly held by ARCH Venture Fund IX Overage, L.P. ("ARCH Overage"). ARCH Venture Partners IX Overage, L.P. ("Overage GPLP"), as the sole general partner of ARCH Overage, may be deemed to beneficially own the shares held by ARCH Overage. GPLLC, as the sole general partner of Overage GPLP, may be deemed to beneficially own the shares held by ARCH Overage. As managing directors of GPLLC, each of the ARCH Managing Directors may be deemed to beneficially own the shares held by ARCH Overage. Each of Overage 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. By: ARCH Venture Partners IX, LLC, By: /s/ Mark McDonnell, as Attorney-in-Fact for Robert Nelsen, Managing Director 2020-02-11 By: ARCH Venture Partners IX, L.P., By: ARCH Venture Partners IX, LLC, its General Partner, By: /s/ Mark McDonnell, as Attorney-in-Fact for Keith Crandell, Managing Director 2020-02-11 By: ARCH Venture Partners IX Overage, L.P., By: ARCH Venture Partners IX, LLC, its General Partner, By: /s/ Mark McDonnell, as Attorney-in-Fact for Keith Crandell, Managing Director 2020-02-11 By: ARCH Venture Fund IX, L.P., By: ARCH Venture Partners IX, L.P., its General Partner, By: ARCH Venture Partners IX, LLC, its General Partner, By: /s/ Mark McDonnell, as Attorney-in-Fact for Keith Crandell, Managing Director 2020-02-11 By: ARCH Venture Fund IX Overage, L.P., By: ARCH Venture Partners IX Overage, L.P., its General Partner, By: ARCH Venture Partners IX, LLC, its General Partner, By: /s/ Mark McDonnell, as Attorney-in-Fact for Keith Crandell, Managing Director 2020-02-11 By: Keith Crandell, Managing Director, By: /s/ Mark McDonnell, as Attorney-in-Fact 2020-02-11 By: Clinton Bybee, Managing Director, By: /s/ Mark McDonnell, as Attorney-in-Fact 2020-02-11