X0306 4 2021-07-20 1 0001761918 Erasca, Inc. ERAS 0001769012 ARCH Venture Partners X, LLC 8755 W. HIGGINS ROAD, SUITE 1025 CHICAGO IL 60631 0 0 1 0 0001757011 ARCH Venture Fund X, L.P. 8755 W. HIGGINS ROAD, SUITE 1025 CHICAGO IL 60631 0 0 1 0 0001757017 ARCH Venture Fund X Overage, L.P. 8755 W. HIGGINS ROAD, SUITE 1025 CHICAGO IL 60631 0 0 1 0 0001782583 ARCH Venture Partners X, L.P. 8755 W. HIGGINS ROAD, SUITE 1025 CHICAGO 60631 IL 0 0 1 0 0001768905 ARCH Venture Partners X Overage, L.P. 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 0001219039 CRANDELL KEITH 8755 W. HIGGINS ROAD, SUITE 1025 CHICAGO IL 60631 0 0 1 0 0001569248 Burow Kristina 8755 W. HIGGINS ROAD, SUITE 1025 CHICAGO IL 60631 0 0 1 0 0001229592 GILLIS STEVEN 8755 W. HIGGINS ROAD, SUITE 1025 CHICAGO IL 60631 0 0 1 0 Common Stock 2021-07-20 4 C 0 5527777 A 5527777 I By ARCH Venture Fund X, L.P. Common Stock 2021-07-20 4 C 0 5527777 A 5527777 I By ARCH Venture Fund X Overage, L.P. Series A Preferred Stock 0.00 2021-07-20 4 C 0 2100000 D Common Stock 1750000 0 I By ARCH Venture Fund X, L.P. Series A Preferred Stock 0.00 2021-07-20 4 C 0 2100000 D Common Stock 1750000 0 I By ARCH Venture Fund X Overage, L.P. Series B-1 Preferred Stock 0.00 2021-07-20 4 C 0 3400000 D Common Stock 2833333 0 I By ARCH Venture Fund X, L.P. Series B-2 Preferred Stock 0.00 2021-07-20 4 C 0 1133333 D Common Stock 944444 0 I By ARCH Venture Fund X, L.P. Series B-1 Preferred Stock 0.00 2021-07-20 4 C 0 3400000 D Common Stock 2833333 0 I By ARCH Venture Fund X Overage, L.P. Series B-2 Preferred Stock 0.00 2021-07-20 4 C 0 1133333 D Common Stock 944444 0 I By ARCH Venture Fund X Overage, L.P. The shares of the Issuer's Series A and Series B Preferred Stock automatically converted into shares of the Issuer's Common Stock, for no additional consideration, at a ratio of 1.2-for-1 share, immediately prior to the consummation of the Issuer's initial public offering. ARCH Venture Partners X, L.P. (AVP X LP) is the sole general partner of ARCH Venture Fund X, L.P. (ARCH X). ARCH Venture Partners X Overage, L.P. (AVP X Overage LP) is the sole general partner of ARCH Venture Fund X Overage, L.P. (ARCH X Overage). ARCH Venture Partners X, LLC (AVP X LLC) is the sole general partner of each of AVP X LP and AVP X Overage LP. Keith Crandell, Kristina Burow, Steven Gillis, and Robert Nelsen comprise the investment committee of AVP X LLC (the AVP X Committee Members). AVP X LP and AVP X Overage LP may be deemed to beneficially own the shares held by ARCH X and ARCH X Overage, respectively, AVP X LLC may be deemed to beneficially own the shares held by ARCH X and ARCH X Overage, and each of the AVP X Committee Members may be deemed to share the power to direct the disposition and vote of the shares held by ARCH X and ARCH X Overage. (Continued from Footnote 2) AVP X LP, AVP X Overage LP, AVP X LLC, and the AVP X Committee Members each disclaim beneficial ownership except to any pecuniary interest therein. /s/ ARCH Venture Fund X, L.P., By: ARCH Venture Partners X, L.P., its General Partner, By: ARCH Venture Partners X, LLC, its General Partner, By: Mark McDonnell, attorney-in-fact 2021-07-20 /s/ ARCH Venture Fund X Overage, L.P., By: ARCH Venture Partners X Overage, L.P., its General Partner, By: ARCH Venture Partners X, LLC, its General Partner, By: Mark McDonnell, attorney-in-fact 2021-07-20 /s/ ARCH Venture Partners X, L.P., its General Partner, By: ARCH Venture Partners X, LLC, its General Partner, By: Mark McDonnell, attorney-in-fact 2021-07-20 /s/ ARCH Venture Partners X Overage, L.P., its General Partner, By: ARCH Venture Partners X, LLC, its General Partner, By: Mark McDonnell, attorney-in-fact 2021-07-20 /s/ ARCH Venture Partners X, LLC, its General Partner, By: Mark McDonnell, attorney-in-fact 2021-07-20 /s/ Robert Nelsen, By: Mark McDonnell, attorney-in-fact 2021-07-20 /s/ Keith Crandell, By: Mark McDonnell, attorney-in-fact 2021-07-20 /s/ Kristina Burow, By: Mark McDonnell, attorney-in-fact 2021-07-20 /s/ Steven Gillis, By: Mark McDonnell, attorney-in-fact 2021-07-20