Sec Form 3 Filing - ARCH Venture Partners X, LLC @ Erasca, Inc. - 2021-07-15

FORM 3 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person ARCH Venture Partners X, LLC 2. Issuer Name and Ticker or Trading Symbol Erasca, Inc. [ ERAS] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 8755 W. HIGGINS ROAD, SUITE 1025, 3. Date of Earliest Transaction (MM/DD/YY) 07/15/2021 (Street) CHICAGO, IL60631 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Series A Preferred Stock $ 0 ( 1 ) ( 1 ) Common Stock 1,750,000 I By ARCH Venture Fund X, L.P. ( 2 ) ( 3 ) Series A Preferred Stock $ 0 ( 1 ) ( 1 ) Common Stock 1,750,000 I By ARCH Venture Fund X Overage, L.P. ( 2 ) ( 3 ) Series B-1 Preferred Stock $ 0 ( 4 ) ( 4 ) Common Stock 2,833,333 I By ARCH Venture Fund X, L.P. ( 2 ) ( 3 ) Series B-2 Preferred Stock $ 0 ( 4 ) ( 4 ) Common Stock 944,444 I By ARCH Venture Fund X Overage, L.P. ( 2 ) ( 3 ) Series B-1 Preferred Stock $ 0 ( 4 ) ( 4 ) Common Stock 2,833,333 I By ARCH Venture Fund X Overage, L.P. ( 2 ) Series B-2 Preferred Stock $ 0 ( 4 ) ( 4 ) Common Stock 944,444 I By ARCH Venture Fund X Overage, L.P. ( 2 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other ARCH Venture Partners X, LLC 8755 W. HIGGINS ROAD, SUITE 1025 CHICAGO, IL60631 X ARCH Venture Fund X, L.P. 8755 W. HIGGINS ROAD, SUITE 1025 CHICAGO, IL60631 X ARCH Venture Fund X Overage, L.P. 8755 W. HIGGINS ROAD, SUITE 1025 CHICAGO, IL60631 X ARCH Venture Partners X, L.P. 8755 W. HIGGINS ROAD, SUITE 1025 CHICAGO 60631, IL X ARCH Venture Partners X Overage, L.P. 8755 W. HIGGINS ROAD, SUITE 1025 CHICAGO, IL60631 X NELSEN ROBERT 8755 W. HIGGINS ROAD, SUITE 1025 CHICAGO, IL60631 X CRANDELL KEITH 8755 W. HIGGINS ROAD, SUITE 1025 CHICAGO, IL60631 X Burow Kristina 8755 W. HIGGINS ROAD, SUITE 1025 CHICAGO, IL60631 X GILLIS STEVEN 8755 W. HIGGINS ROAD, SUITE 1025 CHICAGO, IL60631 X Signatures /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 07/15/2021 Signature of Reporting Person Date /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 07/15/2021 Signature of Reporting Person Date /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 07/15/2021 Signature of Reporting Person Date /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 07/15/2021 Signature of Reporting Person Date /s/ ARCH Venture Partners X, LLC, its General Partner, By: Mark McDonnell, attorney-in-fact 07/15/2021 Signature of Reporting Person Date /s/ Robert Nelsen, By: Mark McDonnell, attorney-in-fact 07/15/2021 Signature of Reporting Person Date /s/ Keith Crandell, By: Mark McDonnell, attorney-in-fact 07/15/2021 Signature of Reporting Person Date /s/ Kristina Burow, By: Mark McDonnell, attorney-in-fact 07/15/2021 Signature of Reporting Person Date /s/ Steven Gillis, By: Mark McDonnell, attorney-in-fact 07/15/2021 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The shares of Series A Preferred Stock are convertible, at any time, at the holder's election, to shares of the Issuer's common stock at a ratio of 1.2-for-1. In addition, effective immediately prior to the closing of the Issuer's initial public offering of its common stock, each share of Series A Preferred Stock will automatically convert to shares of the Issuer's common stock at a ratio of 1.2-for-1. The Series A Preferred Stock has no expiration date. ( 2 )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. ( 3 )(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. ( 4 )The shares of Series B Preferred Stock are convertible, at any time, at the holder's election, to shares of the Issuer's common stock at a ratio of 1.2-for-1. In addition, effective immediately prior to the closing of the Issuer's initial public offering of its common stock, each share of Series B Preferred Stock will automatically convert to shares of the Issuer's common stock at a ratio of 1.2-for-1. The Series B Preferred Stock has no expiration date.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

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