BEAM

SEC source: 0000899243-20-003931 · doc4.xml · derivative · entry 6

Burow Kristina · CIK 0001569248 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnote

Disclosed balance after: 0

Underlying: Common Stock · 2,750,335 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: 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.

F1 · kind: 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.

F1 · price: 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.

F1 · derivative.exercise_date: 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.

F1 · derivative.expiration_date: 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.

F3 · ownership.nature: The 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 Overage GPLP. The Reporting Person has an interest in the Overage GPLP and the GPLLC but does not have voting or investment control over the shares held by ARCH Overage. The Reporting Person disclaims ownership of such shares, except to the extent of her pecuniary interest therein.

SEC source: 0000899243-20-003931 · doc4.xml · derivative · entry 5

Burow Kristina · CIK 0001569248 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnote

Disclosed balance after: 0

Underlying: Common Stock · 2,750,336 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: 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.

F1 · kind: 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.

F1 · price: 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.

F1 · derivative.exercise_date: 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.

F1 · derivative.expiration_date: 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.

F2 · ownership.nature: The shares are 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 GPLP. The Reporting Person has an interest in the GPLP and the GPLLC but does not have voting or investment control over the shares held by ARCH IX. The Reporting Person disclaims ownership of such shares, except to the extent of her pecuniary interest therein.

SEC source: 0000899243-20-003931 · doc4.xml · derivative · entry 4

Burow Kristina · CIK 0001569248 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnote

Disclosed balance after: 0

Underlying: Common Stock · 1,338,000 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: 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.

F1 · kind: 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.

F1 · price: 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.

F1 · derivative.exercise_date: 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.

F1 · derivative.expiration_date: 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.

F3 · ownership.nature: The 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 Overage GPLP. The Reporting Person has an interest in the Overage GPLP and the GPLLC but does not have voting or investment control over the shares held by ARCH Overage. The Reporting Person disclaims ownership of such shares, except to the extent of her pecuniary interest therein.

SEC source: 0000899243-20-003931 · doc4.xml · derivative · entry 3

Burow Kristina · CIK 0001569248 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnote

Disclosed balance after: 0

Underlying: Common Stock · 1,338,000 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: 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.

F1 · kind: 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.

F1 · price: 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.

F1 · derivative.exercise_date: 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.

F1 · derivative.expiration_date: 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.

F2 · ownership.nature: The shares are 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 GPLP. The Reporting Person has an interest in the GPLP and the GPLLC but does not have voting or investment control over the shares held by ARCH IX. The Reporting Person disclaims ownership of such shares, except to the extent of her pecuniary interest therein.

SEC source: 0000899243-20-003931 · doc4.xml · nonDerivative · entry 2

Burow Kristina · CIK 0001569248 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnote

Disclosed balance after: 4,121,519

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · kind: 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.

F1 · price: 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.

F3 · ownership.nature: The 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 Overage GPLP. The Reporting Person has an interest in the Overage GPLP and the GPLLC but does not have voting or investment control over the shares held by ARCH Overage. The Reporting Person disclaims ownership of such shares, except to the extent of her pecuniary interest therein.

SEC source: 0000899243-20-003931 · doc4.xml · nonDerivative · entry 1

Burow Kristina · CIK 0001569248 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnote

Disclosed balance after: 4,121,520

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · kind: 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.

F1 · price: 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.

F2 · ownership.nature: The shares are 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 GPLP. The Reporting Person has an interest in the GPLP and the GPLLC but does not have voting or investment control over the shares held by ARCH IX. The Reporting Person disclaims ownership of such shares, except to the extent of her pecuniary interest therein.

SEC source: 0000899243-20-003930 · doc4.xml · derivative · entry 8

ARCH Venture Partners IX, LLC · CIK 0001723174 · 10% owner

ARCH Venture Partners IX, L.P. · CIK 0001723173 · 10% owner

ARCH Venture Partners IX Overage, L.P. · CIK 0001723172 · 10% owner

ARCH Venture Fund IX, L.P. · CIK 0001666306 · 10% owner

ARCH Venture Fund IX Overage, L.P. · CIK 0001666307 · 10% owner

CRANDELL KEITH · CIK 0001219039 · 10% owner

BYBEE CLINTON · CIK 0001219043 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnote

Disclosed balance after: 0

Underlying: Common Stock · 33,184 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: 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.

F1 · kind: 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.

F1 · price: 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.

F1 · derivative.exercise_date: 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.

F1 · derivative.expiration_date: 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.

F3 · ownership.nature: 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.

SEC source: 0000899243-20-003930 · doc4.xml · derivative · entry 7

ARCH Venture Partners IX, LLC · CIK 0001723174 · 10% owner

ARCH Venture Partners IX, L.P. · CIK 0001723173 · 10% owner

ARCH Venture Partners IX Overage, L.P. · CIK 0001723172 · 10% owner

ARCH Venture Fund IX, L.P. · CIK 0001666306 · 10% owner

ARCH Venture Fund IX Overage, L.P. · CIK 0001666307 · 10% owner

CRANDELL KEITH · CIK 0001219039 · 10% owner

BYBEE CLINTON · CIK 0001219043 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnote

Disclosed balance after: 0

Underlying: Common Stock · 33,184 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: 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.

F1 · kind: 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.

F1 · price: 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.

F1 · derivative.exercise_date: 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.

F1 · derivative.expiration_date: 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.

F2 · ownership.nature: 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.

SEC source: 0000899243-20-003930 · doc4.xml · derivative · entry 6

ARCH Venture Partners IX, LLC · CIK 0001723174 · 10% owner

ARCH Venture Partners IX, L.P. · CIK 0001723173 · 10% owner

ARCH Venture Partners IX Overage, L.P. · CIK 0001723172 · 10% owner

ARCH Venture Fund IX, L.P. · CIK 0001666306 · 10% owner

ARCH Venture Fund IX Overage, L.P. · CIK 0001666307 · 10% owner

CRANDELL KEITH · CIK 0001219039 · 10% owner

BYBEE CLINTON · CIK 0001219043 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnote

Disclosed balance after: 0

Underlying: Common Stock · 2,750,335 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: 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.

F1 · kind: 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.

F1 · price: 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.

F1 · derivative.exercise_date: 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.

F1 · derivative.expiration_date: 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.

F3 · ownership.nature: 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.

SEC source: 0000899243-20-003930 · doc4.xml · derivative · entry 5

ARCH Venture Partners IX, LLC · CIK 0001723174 · 10% owner

ARCH Venture Partners IX, L.P. · CIK 0001723173 · 10% owner

ARCH Venture Partners IX Overage, L.P. · CIK 0001723172 · 10% owner

ARCH Venture Fund IX, L.P. · CIK 0001666306 · 10% owner

ARCH Venture Fund IX Overage, L.P. · CIK 0001666307 · 10% owner

CRANDELL KEITH · CIK 0001219039 · 10% owner

BYBEE CLINTON · CIK 0001219043 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnote

Disclosed balance after: 0

Underlying: Common Stock · 2,750,336 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: 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.

F1 · kind: 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.

F1 · price: 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.

F1 · derivative.exercise_date: 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.

F1 · derivative.expiration_date: 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.

F2 · ownership.nature: 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.

SEC source: 0000899243-20-003930 · doc4.xml · derivative · entry 4

ARCH Venture Partners IX, LLC · CIK 0001723174 · 10% owner

ARCH Venture Partners IX, L.P. · CIK 0001723173 · 10% owner

ARCH Venture Partners IX Overage, L.P. · CIK 0001723172 · 10% owner

ARCH Venture Fund IX, L.P. · CIK 0001666306 · 10% owner

ARCH Venture Fund IX Overage, L.P. · CIK 0001666307 · 10% owner

CRANDELL KEITH · CIK 0001219039 · 10% owner

BYBEE CLINTON · CIK 0001219043 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnote

Disclosed balance after: 0

Underlying: Common Stock · 1,338,000 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: 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.

F1 · kind: 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.

F1 · price: 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.

F1 · derivative.exercise_date: 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.

F1 · derivative.expiration_date: 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.

F3 · ownership.nature: 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.

SEC source: 0000899243-20-003930 · doc4.xml · derivative · entry 3

ARCH Venture Partners IX, LLC · CIK 0001723174 · 10% owner

ARCH Venture Partners IX, L.P. · CIK 0001723173 · 10% owner

ARCH Venture Partners IX Overage, L.P. · CIK 0001723172 · 10% owner

ARCH Venture Fund IX, L.P. · CIK 0001666306 · 10% owner

ARCH Venture Fund IX Overage, L.P. · CIK 0001666307 · 10% owner

CRANDELL KEITH · CIK 0001219039 · 10% owner

BYBEE CLINTON · CIK 0001219043 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnote

Disclosed balance after: 0

Underlying: Common Stock · 1,338,000 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: 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.

F1 · kind: 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.

F1 · price: 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.

F1 · derivative.exercise_date: 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.

F1 · derivative.expiration_date: 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.

F2 · ownership.nature: 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.

SEC source: 0000899243-20-003930 · doc4.xml · nonDerivative · entry 2

ARCH Venture Partners IX, LLC · CIK 0001723174 · 10% owner

ARCH Venture Partners IX, L.P. · CIK 0001723173 · 10% owner

ARCH Venture Partners IX Overage, L.P. · CIK 0001723172 · 10% owner

ARCH Venture Fund IX, L.P. · CIK 0001666306 · 10% owner

ARCH Venture Fund IX Overage, L.P. · CIK 0001666307 · 10% owner

CRANDELL KEITH · CIK 0001219039 · 10% owner

BYBEE CLINTON · CIK 0001219043 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnote

Disclosed balance after: 4,121,519

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · kind: 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.

F1 · price: 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.

F3 · ownership.nature: 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.

SEC source: 0000899243-20-003930 · doc4.xml · nonDerivative · entry 1

ARCH Venture Partners IX, LLC · CIK 0001723174 · 10% owner

ARCH Venture Partners IX, L.P. · CIK 0001723173 · 10% owner

ARCH Venture Partners IX Overage, L.P. · CIK 0001723172 · 10% owner

ARCH Venture Fund IX, L.P. · CIK 0001666306 · 10% owner

ARCH Venture Fund IX Overage, L.P. · CIK 0001666307 · 10% owner

CRANDELL KEITH · CIK 0001219039 · 10% owner

BYBEE CLINTON · CIK 0001219043 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnote

Disclosed balance after: 4,121,520

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · kind: 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.

F1 · price: 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.

F2 · ownership.nature: 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.

SEC source: 0000315066-20-001331 · primary_doc.xml · derivative · entry 6

FMR LLC · CIK 0000315066 · 10% owner · See Remark 1

10b5-1 filing: Not disclosed

Ownership: Indirect · F-Prime Capital Partners Healthcare Fund V LP

Disclosed balance after: 0

Underlying: Common Stock · 2,189,820 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: On February 10, 2020, in connection with the completion of the issuer's initial public offering, each 4.4843 shares of Series A-1, A-2, and B Convertible Preferred Stock converted into 1 share of Common Stock.

F1 · price: On February 10, 2020, in connection with the completion of the issuer's initial public offering, each 4.4843 shares of Series A-1, A-2, and B Convertible Preferred Stock converted into 1 share of Common Stock.

F1 · derivative.exercise_date: On February 10, 2020, in connection with the completion of the issuer's initial public offering, each 4.4843 shares of Series A-1, A-2, and B Convertible Preferred Stock converted into 1 share of Common Stock.

F1 · derivative.expiration_date: On February 10, 2020, in connection with the completion of the issuer's initial public offering, each 4.4843 shares of Series A-1, A-2, and B Convertible Preferred Stock converted into 1 share of Common Stock.

SEC source: 0000315066-20-001331 · primary_doc.xml · derivative · entry 5

FMR LLC · CIK 0000315066 · 10% owner · See Remark 1

10b5-1 filing: Not disclosed

Ownership: Indirect · F-Prime Capital Partners Healthcare Fund V LP

Disclosed balance after: 0

Underlying: Common Stock · 4,715,723 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: On February 10, 2020, in connection with the completion of the issuer's initial public offering, each 4.4843 shares of Series A-1, A-2, and B Convertible Preferred Stock converted into 1 share of Common Stock.

F1 · price: On February 10, 2020, in connection with the completion of the issuer's initial public offering, each 4.4843 shares of Series A-1, A-2, and B Convertible Preferred Stock converted into 1 share of Common Stock.

F1 · derivative.exercise_date: On February 10, 2020, in connection with the completion of the issuer's initial public offering, each 4.4843 shares of Series A-1, A-2, and B Convertible Preferred Stock converted into 1 share of Common Stock.

F1 · derivative.expiration_date: On February 10, 2020, in connection with the completion of the issuer's initial public offering, each 4.4843 shares of Series A-1, A-2, and B Convertible Preferred Stock converted into 1 share of Common Stock.

SEC source: 0000315066-20-001331 · primary_doc.xml · derivative · entry 4

FMR LLC · CIK 0000315066 · 10% owner · See Remark 1

10b5-1 filing: Not disclosed

Ownership: Indirect · F-Prime Capital Partners Healthcare Fund V LP

Disclosed balance after: 0

Underlying: Common Stock · 66,369 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: On February 10, 2020, in connection with the completion of the issuer's initial public offering, each 4.4843 shares of Series A-1, A-2, and B Convertible Preferred Stock converted into 1 share of Common Stock.

F1 · price: On February 10, 2020, in connection with the completion of the issuer's initial public offering, each 4.4843 shares of Series A-1, A-2, and B Convertible Preferred Stock converted into 1 share of Common Stock.

F1 · derivative.exercise_date: On February 10, 2020, in connection with the completion of the issuer's initial public offering, each 4.4843 shares of Series A-1, A-2, and B Convertible Preferred Stock converted into 1 share of Common Stock.

F1 · derivative.expiration_date: On February 10, 2020, in connection with the completion of the issuer's initial public offering, each 4.4843 shares of Series A-1, A-2, and B Convertible Preferred Stock converted into 1 share of Common Stock.

SEC source: 0000315066-20-001331 · primary_doc.xml · nonDerivative · entry 3

FMR LLC · CIK 0000315066 · 10% owner · See Remark 1

10b5-1 filing: Not disclosed

Ownership: Indirect · F-Prime Capital Partners Healthcare Fund V LP

Disclosed balance after: 6,971,912

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · price: On February 10, 2020, in connection with the completion of the issuer's initial public offering, each 4.4843 shares of Series A-1, A-2, and B Convertible Preferred Stock converted into 1 share of Common Stock.

SEC source: 0000315066-20-001331 · primary_doc.xml · nonDerivative · entry 2

FMR LLC · CIK 0000315066 · 10% owner · See Remark 1

10b5-1 filing: Not disclosed

Ownership: Indirect · F-Prime Capital Partners Healthcare Fund V LP

Disclosed balance after: 4,782,092

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · price: On February 10, 2020, in connection with the completion of the issuer's initial public offering, each 4.4843 shares of Series A-1, A-2, and B Convertible Preferred Stock converted into 1 share of Common Stock.

SEC source: 0000315066-20-001331 · primary_doc.xml · nonDerivative · entry 1

FMR LLC · CIK 0000315066 · 10% owner · See Remark 1

10b5-1 filing: Not disclosed

Ownership: Indirect · F-Prime Capital Partners Healthcare Fund V LP

Disclosed balance after: 66,369

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · price: On February 10, 2020, in connection with the completion of the issuer's initial public offering, each 4.4843 shares of Series A-1, A-2, and B Convertible Preferred Stock converted into 1 share of Common Stock.

SEC source: 0000899243-21-036823 · doc4a.xml · derivative · entry 2

Ciaramella Giuseppe · CIK 0001786322 · President & CSO

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 12,978

Underlying: Common Stock · 12,978 shares

Expires 2029-02-13

F1 · security: On February 11, 2020, the reporting person filed a Form 4 which inadvertently omitted certain options held by the reporting person on such date (the "Original Form 4").

F4 · derivative.exercise_date: On February 13, 2019, the reporting person was granted an option to purchase 25,957 shares of common stock of the Company. The option award vests (i) fifty percent (50%) upon the Company achieving a certain development milestone related to base editing applications, and (ii) fifty percent (50%) upon the achievement of a closing price hurdle following the Company's IPO (which closing price hurdle has been achieved). The portion of the award subject to satisfaction of the Price Condition is scheduled to vest in three equal installments on December 21, 2021, June 30, 2022 and December 31, 2022. Upon the closing of the IPO, vesting of the portion of the option award subject to condition (ii) was tied only to the passage of time and the market price of the Company's securities and thus, 50% of the option award became reportable. The Original Form 4 failed to report the portion of the option award that became reportable upon the closing of the Company's IPO.

SEC source: 0000899243-21-036823 · doc4a.xml · derivative · entry 1

Ciaramella Giuseppe · CIK 0001786322 · President & CSO

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 23,317

Underlying: Common Stock · 27,317 shares

Expires 2028-05-08

F1 · security: On February 11, 2020, the reporting person filed a Form 4 which inadvertently omitted certain options held by the reporting person on such date (the "Original Form 4").

F2 · derivative.exercise_date: On May 8, 2018, the reporting person was granted an option to purchase 54,635 shares of common stock of Beam Therapeutics Inc. (the "Company"). The option award vests (i) fifty percent (50%) upon the Company achieving a certain development milestone related to base editing applications, and (ii) fifty percent (50%) upon the achievement of a closing price hurdle following the Company's initial public offering ("IPO") (which closing price hurdle has been achieved) (the "Price Condition"). The portion of the award subject to satisfaction of the Price Condition is scheduled to vest in three equal installments on December 21, 2021, June 30, 2022 and December 31, 2022. Upon the closing of the IPO, vesting of the portion of the option award subject to condition (ii) was tied only to the passage of time and the market price of the Company's securities and thus, 50% of the option award became reportable.

F3 · derivative.exercise_date: (Continued from Footnote 2) The Original Form 4 failed to report the portion of the option award that became reportable upon the closing of the Company's IPO.

SEC source: 0000899243-21-036822 · doc4a.xml · derivative · entry 2

Evans John M. · CIK 0001786304 · Director · CEO

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 53,964

Underlying: Common Stock · 53,964 shares

Expires 2029-02-13

F1 · security: On August 17, 2020, the reporting person filed a Form 4 which inadvertently omitted certain options held by the reporting person on such date (the "Original Form 4").

F4 · derivative.exercise_date: On February 13, 2019, the reporting person was granted an option to purchase 107,929 shares of common stock of the Company. The option award vests (i) fifty percent (50%) upon the Company achieving a certain development milestone related to base editing applications, and (ii) fifty percent (50%) upon the achievement of a closing price hurdle following the Company's IPO (which closing price hurdle has been achieved). The portion of the award subject to satisfaction of the Price Condition is scheduled to vest in three equal installments on December 21, 2021, June 30, 2022 and December 31, 2022. Upon the closing of the IPO, vesting of the portion of the option award subject to condition (ii) was tied only to the passage of time and the market price of the Company's securities and thus, 50% of the option award became reportable. The Original Form 4 failed to report the portion of the option award that became reportable upon the closing of the Company's IPO.

SEC source: 0000899243-21-036822 · doc4a.xml · derivative · entry 1

Evans John M. · CIK 0001786304 · Director · CEO

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 99,336

Underlying: Common Stock · 99,336 shares

Expires 2028-05-08

F1 · security: On August 17, 2020, the reporting person filed a Form 4 which inadvertently omitted certain options held by the reporting person on such date (the "Original Form 4").

F2 · derivative.exercise_date: On May 8, 2018, the reporting person was granted an option to purchase 198,672 shares of common stock of Beam Therapeutics Inc. (the "Company"). The option award vests (i) fifty percent (50%) upon the Company achieving a certain development milestone related to base editing applications, and (ii) fifty percent (50%) upon the achievement of a closing price hurdle following the Company's initial public offering ("IPO") (which closing price hurdle has been achieved) (the "Price Condition"). The portion of the award subject to satisfaction of the Price Condition is scheduled to vest in three equal installments on December 21, 2021, June 30, 2022 and December 31, 2022. Upon the closing of the IPO, vesting of the portion of the option award subject to condition (ii) was tied only to the passage of time and the market price of the Company's securities and thus, 50% of the option award became reportable.

F3 · derivative.exercise_date: (Continued from Footnote 2) The Original Form 4 failed to report the portion of the option award that became reportable upon the closing of the Company's IPO.