Third Rock Ventures IV, L.P.

SEC source: 0001193125-25-266981 · ownership.xml · nonDerivative · entry 1

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

Third Rock Ventures V, L.P. · CIK 0001778071 · 10% owner

Third Rock Ventures GP V, LP · CIK 0001977498 · 10% owner

TRV GP V, LLC · CIK 0001990717 · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 4,473,958

F1 · kind: On November 4, 2025, Third Rock Ventures IV, L.P. ("TRV IV ") distributed, for no consideration, 1,600,000 shares of Common Stock of the Issuer (the "Shares") to its limited partners and to Third Rock Ventures GP IV, L.P. ("TRV GP IV "), the general partner of TRV IV, representing each such partner's pro rata interest in such Shares. On the same date, TRV GP IV distributed, for no consideration, the Shares it received in the distribution by TRV IV to its partners, representing each such partner's pro rata interest in such Shares. All of the aforementioned distributions were made in accordance with the exemptions afforded by Rules 16a-13 and 16a-9 of the Securities Exchange Act of 1934, as amended.

F1 · price: On November 4, 2025, Third Rock Ventures IV, L.P. ("TRV IV ") distributed, for no consideration, 1,600,000 shares of Common Stock of the Issuer (the "Shares") to its limited partners and to Third Rock Ventures GP IV, L.P. ("TRV GP IV "), the general partner of TRV IV, representing each such partner's pro rata interest in such Shares. On the same date, TRV GP IV distributed, for no consideration, the Shares it received in the distribution by TRV IV to its partners, representing each such partner's pro rata interest in such Shares. All of the aforementioned distributions were made in accordance with the exemptions afforded by Rules 16a-13 and 16a-9 of the Securities Exchange Act of 1934, as amended.

F2 · ownership.direct: The shares are held directly by TRV IV. The general partner of TRV IV is TRV GP IV. The general partner of TRV GP IV is TRV GP IV LLC. Each of TRV GP IV, and TRV GP IV LLC, disclaims beneficial ownership of these shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

F4 · ownership.direct: Each of Reporting Persons disclaims the existence of a Section 13(d) "group" as between the TRV IV related parties and the TRV V related parties and this report shall not be deemed an admission that any of such parties is or may be part of such a group with any of the other parties.

SEC source: 0001193125-25-251606 · ownership.xml · nonDerivative · entry 1

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 13,386,574

F1 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $10.00 to $10.65, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (1).

F2 · ownership.direct: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of TRV GP IV and TRV GP IV LLC disclaims beneficial ownership of the shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

SEC source: 0001193125-25-223227 · ownership.xml · nonDerivative · entry 1

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 13,863,975

F1 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $8.00 to $8.165, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (1).

F2 · ownership.direct: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of TRV GP IV and TRV GP IV LLC disclaims beneficial ownership of the shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

SEC source: 0001193125-25-206453 · ownership.xml · nonDerivative · entry 1

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 14,363,975

F1 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $7.00 to $7.19, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (1).

F2 · ownership.direct: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of TRV GP IV and TRV GP IV LLC disclaims beneficial ownership of the shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

SEC source: 0001193125-25-199177 · ownership.xml · nonDerivative · entry 2

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 14,727,516

F2 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $7.00 to $7.14, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (2).

F1 · ownership.direct: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of TRV GP IV and TRV GP IV LLC disclaims beneficial ownership of the shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

SEC source: 0001193125-25-199177 · ownership.xml · nonDerivative · entry 1

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 14,813,975

F1 · ownership.direct: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of TRV GP IV and TRV GP IV LLC disclaims beneficial ownership of the shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

SEC source: 0000950170-25-111457 · ownership.xml · nonDerivative · entry 1

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 15,456,881

F1 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $7.00 to $7.05, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (1).

F2 · ownership.direct: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of TRV GP IV and TRV GP IV LLC disclaims beneficial ownership of the shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

SEC source: 0000950170-25-110662 · ownership.xml · nonDerivative · entry 1

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 15,759,075

F1 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $7.00 to $7.12, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (1).

F2 · ownership.direct: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of TRV GP IV and TRV GP IV LLC disclaims beneficial ownership of the shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

SEC source: 0000950170-25-013760 · ownership.xml · derivative · entry 5

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

Third Rock Ventures V, L.P. · CIK 0001778071 · 10% owner

Third Rock Ventures GP V, LP · CIK 0001977498 · 10% owner

TRV GP V, LLC · CIK 0001990717 · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Indirect · See Footnotes

Disclosed balance after: 0

Underlying: Common Stock · 950,800 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 the closing of the Issuer's initial public offering, each share of Series A Preferred Stock and Series D-1 Preferred Stock (collectively, the "Preferred Stock") automatically converted into Common Stock on a one-for-0.1037 basis without payment of consideration. The Preferred Stock had no expiration date.

F1 · kind: Upon the closing of the Issuer's initial public offering, each share of Series A Preferred Stock and Series D-1 Preferred Stock (collectively, the "Preferred Stock") automatically converted into Common Stock on a one-for-0.1037 basis without payment of consideration. The Preferred Stock had no expiration date.

F1 · derivative.exercise_date: Upon the closing of the Issuer's initial public offering, each share of Series A Preferred Stock and Series D-1 Preferred Stock (collectively, the "Preferred Stock") automatically converted into Common Stock on a one-for-0.1037 basis without payment of consideration. The Preferred Stock had no expiration date.

F1 · derivative.expiration_date: Upon the closing of the Issuer's initial public offering, each share of Series A Preferred Stock and Series D-1 Preferred Stock (collectively, the "Preferred Stock") automatically converted into Common Stock on a one-for-0.1037 basis without payment of consideration. The Preferred Stock had no expiration date.

F3 · ownership.nature: The shares are held directly by Third Rock Ventures V, L.P. ("TRV V"). The general partner of TRV V is Third Rock Ventures GP V, L.P. ("TRV GP V"). The general partner of TRV GP V is TRV GP V, LLC ("TRV GP V LLC"). Each of TRV GP V, and TRV GP V LLC, disclaims beneficial ownership of these shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

F4 · ownership.nature: Each of Reporting Persons disclaims the existence of a Section 13(d) "group" as between the TRV IV related parties and the TRV V related parties and this report shall not be deemed an admission that any of such parties is or may be part of such a group with any of the other parties.

SEC source: 0000950170-25-013760 · ownership.xml · derivative · entry 4

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

Third Rock Ventures V, L.P. · CIK 0001778071 · 10% owner

Third Rock Ventures GP V, LP · CIK 0001977498 · 10% owner

TRV GP V, LLC · CIK 0001990717 · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 1,008,786 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 the closing of the Issuer's initial public offering, each share of Series A Preferred Stock and Series D-1 Preferred Stock (collectively, the "Preferred Stock") automatically converted into Common Stock on a one-for-0.1037 basis without payment of consideration. The Preferred Stock had no expiration date.

F1 · kind: Upon the closing of the Issuer's initial public offering, each share of Series A Preferred Stock and Series D-1 Preferred Stock (collectively, the "Preferred Stock") automatically converted into Common Stock on a one-for-0.1037 basis without payment of consideration. The Preferred Stock had no expiration date.

F1 · derivative.exercise_date: Upon the closing of the Issuer's initial public offering, each share of Series A Preferred Stock and Series D-1 Preferred Stock (collectively, the "Preferred Stock") automatically converted into Common Stock on a one-for-0.1037 basis without payment of consideration. The Preferred Stock had no expiration date.

F1 · derivative.expiration_date: Upon the closing of the Issuer's initial public offering, each share of Series A Preferred Stock and Series D-1 Preferred Stock (collectively, the "Preferred Stock") automatically converted into Common Stock on a one-for-0.1037 basis without payment of consideration. The Preferred Stock had no expiration date.

F2 · ownership.direct: The shares are held directly by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of TRV GP IV, and TRV GP IV LLC, disclaims beneficial ownership of these shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

F4 · ownership.direct: Each of Reporting Persons disclaims the existence of a Section 13(d) "group" as between the TRV IV related parties and the TRV V related parties and this report shall not be deemed an admission that any of such parties is or may be part of such a group with any of the other parties.

SEC source: 0000950170-25-013760 · ownership.xml · derivative · entry 3

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

Third Rock Ventures V, L.P. · CIK 0001778071 · 10% owner

Third Rock Ventures GP V, LP · CIK 0001977498 · 10% owner

TRV GP V, LLC · CIK 0001990717 · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 4,754,002 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 the closing of the Issuer's initial public offering, each share of Series A Preferred Stock and Series D-1 Preferred Stock (collectively, the "Preferred Stock") automatically converted into Common Stock on a one-for-0.1037 basis without payment of consideration. The Preferred Stock had no expiration date.

F1 · kind: Upon the closing of the Issuer's initial public offering, each share of Series A Preferred Stock and Series D-1 Preferred Stock (collectively, the "Preferred Stock") automatically converted into Common Stock on a one-for-0.1037 basis without payment of consideration. The Preferred Stock had no expiration date.

F1 · derivative.exercise_date: Upon the closing of the Issuer's initial public offering, each share of Series A Preferred Stock and Series D-1 Preferred Stock (collectively, the "Preferred Stock") automatically converted into Common Stock on a one-for-0.1037 basis without payment of consideration. The Preferred Stock had no expiration date.

F1 · derivative.expiration_date: Upon the closing of the Issuer's initial public offering, each share of Series A Preferred Stock and Series D-1 Preferred Stock (collectively, the "Preferred Stock") automatically converted into Common Stock on a one-for-0.1037 basis without payment of consideration. The Preferred Stock had no expiration date.

F2 · ownership.direct: The shares are held directly by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of TRV GP IV, and TRV GP IV LLC, disclaims beneficial ownership of these shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

F4 · ownership.direct: Each of Reporting Persons disclaims the existence of a Section 13(d) "group" as between the TRV IV related parties and the TRV V related parties and this report shall not be deemed an admission that any of such parties is or may be part of such a group with any of the other parties.

SEC source: 0000950170-25-013760 · ownership.xml · nonDerivative · entry 2

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

Third Rock Ventures V, L.P. · CIK 0001778071 · 10% owner

Third Rock Ventures GP V, LP · CIK 0001977498 · 10% owner

TRV GP V, LLC · CIK 0001990717 · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Indirect · See Footnotes

Disclosed balance after: 950,800

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 the closing of the Issuer's initial public offering, each share of Series A Preferred Stock and Series D-1 Preferred Stock (collectively, the "Preferred Stock") automatically converted into Common Stock on a one-for-0.1037 basis without payment of consideration. The Preferred Stock had no expiration date.

F3 · ownership.nature: The shares are held directly by Third Rock Ventures V, L.P. ("TRV V"). The general partner of TRV V is Third Rock Ventures GP V, L.P. ("TRV GP V"). The general partner of TRV GP V is TRV GP V, LLC ("TRV GP V LLC"). Each of TRV GP V, and TRV GP V LLC, disclaims beneficial ownership of these shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

F4 · ownership.nature: Each of Reporting Persons disclaims the existence of a Section 13(d) "group" as between the TRV IV related parties and the TRV V related parties and this report shall not be deemed an admission that any of such parties is or may be part of such a group with any of the other parties.

SEC source: 0000950170-25-013760 · ownership.xml · nonDerivative · entry 1

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

Third Rock Ventures V, L.P. · CIK 0001778071 · 10% owner

Third Rock Ventures GP V, LP · CIK 0001977498 · 10% owner

TRV GP V, LLC · CIK 0001990717 · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 6,073,958

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 the closing of the Issuer's initial public offering, each share of Series A Preferred Stock and Series D-1 Preferred Stock (collectively, the "Preferred Stock") automatically converted into Common Stock on a one-for-0.1037 basis without payment of consideration. The Preferred Stock had no expiration date.

F2 · ownership.direct: The shares are held directly by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of TRV GP IV, and TRV GP IV LLC, disclaims beneficial ownership of these shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

F4 · ownership.direct: Each of Reporting Persons disclaims the existence of a Section 13(d) "group" as between the TRV IV related parties and the TRV V related parties and this report shall not be deemed an admission that any of such parties is or may be part of such a group with any of the other parties.

SEC source: 0000950170-24-107330 · ownership.xml · nonDerivative · entry 1

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 16,859,075

F1 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $10.50 to $10.74, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (1).

F2 · ownership.direct: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of TRV GP IV and TRV GP IV LLC disclaims beneficial ownership of the shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

SEC source: 0000950170-24-104863 · ownership.xml · nonDerivative · entry 1

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 16,926,475

F1 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $11.54 to $11.76, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (1).

F2 · ownership.direct: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of TRV GP IV and TRV GP IV LLC disclaims beneficial ownership of the shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

SEC source: 0000950170-24-103661 · ownership.xml · nonDerivative · entry 1

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 17,001,475

F1 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $11.52 to $11.90, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (1).

F2 · ownership.direct: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of TRV GP IV and TRV GP IV LLC disclaims beneficial ownership of the shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

SEC source: 0000950170-24-101910 · ownership.xml · nonDerivative · entry 1

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 17,176,475

F1 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $11.53 to $11.64, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (1).

F2 · ownership.direct: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of TRV GP IV and TRV GP IV LLC disclaims beneficial ownership of the shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

SEC source: 0000950170-24-099253 · ownership.xml · nonDerivative · entry 2

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 17,201,475

F3 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $9.75 to $10.475, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (3).

F2 · ownership.direct: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of TRV GP IV and TRV GP IV LLC disclaims beneficial ownership of the shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

SEC source: 0000950170-24-099253 · ownership.xml · nonDerivative · entry 1

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 17,351,475

F1 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $9.75 to $9.95, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (1).

F2 · ownership.direct: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of TRV GP IV and TRV GP IV LLC disclaims beneficial ownership of the shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

SEC source: 0000950170-24-089474 · ownership.xml · nonDerivative · entry 3

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 17,486,475

F2 · ownership.direct: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of TRV GP IV and TRV GP IV LLC disclaims beneficial ownership of the shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

SEC source: 0000950170-24-089474 · ownership.xml · nonDerivative · entry 2

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 17,526,475

F3 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $9.84 to $10.21, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (3).

F2 · ownership.direct: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of TRV GP IV and TRV GP IV LLC disclaims beneficial ownership of the shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

SEC source: 0000950170-24-089474 · ownership.xml · nonDerivative · entry 1

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 17,626,475

F1 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $9.80 to $9.95, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (1).

F2 · ownership.direct: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of TRV GP IV and TRV GP IV LLC disclaims beneficial ownership of the shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

SEC source: 0000950170-24-087862 · ownership.xml · nonDerivative · entry 1

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 17,721,475

F1 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $9.75 to $10.07, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (1).

F2 · ownership.direct: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of TRV GP IV and TRV GP IV LLC disclaims beneficial ownership of the shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

SEC source: 0000950170-24-086894 · ownership.xml · nonDerivative · entry 2

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 17,771,475

F3 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $9.75 to $10.005, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (3).

F2 · ownership.direct: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of TRV GP IV and TRV GP IV LLC disclaims beneficial ownership of the shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

SEC source: 0000950170-24-086894 · ownership.xml · nonDerivative · entry 1

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 17,872,074

F1 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $9.78 to $10.025, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (1).

F2 · ownership.direct: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of TRV GP IV and TRV GP IV LLC disclaims beneficial ownership of the shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

SEC source: 0000950170-24-086051 · ownership.xml · nonDerivative · entry 2

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 18,072,074

F3 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $9.75 to $9.90, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (3).

F2 · ownership.direct: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of TRV GP IV and TRV GP IV LLC disclaims beneficial ownership of the shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

SEC source: 0000950170-24-086051 · ownership.xml · nonDerivative · entry 1

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 18,197,074

F1 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $9.75 to $9.91, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (1).

F2 · ownership.direct: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of TRV GP IV and TRV GP IV LLC disclaims beneficial ownership of the shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

SEC source: 0000950170-24-085256 · ownership.xml · nonDerivative · entry 1

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 18,459,814

F1 · ownership.direct: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of TRV GP IV and TRV GP IV LLC disclaims beneficial ownership of the shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

SEC source: 0000950170-24-084580 · ownership.xml · nonDerivative · entry 1

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 18,651,304

F1 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $9.75 to $10.00, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (1).

F2 · ownership.direct: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of TRV GP IV and TRV GP IV LLC disclaims beneficial ownership of the shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

SEC source: 0000950170-24-018198 · ownership.xml · nonDerivative · entry 1

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 19,201,475

F1 · ownership.direct: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of TRV GP IV and TRV GP IV LLC disclaims beneficial ownership of the shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

SEC source: 0000899243-23-004411 · doc4.xml · nonDerivative · entry 2

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 3,058,204

F3 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $0.801 to $0.893, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (3).

F2 · ownership.direct: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of TRV GP IV and TRV GP IV LLC disclaims beneficial ownership of the shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

SEC source: 0000899243-23-004411 · doc4.xml · nonDerivative · entry 1

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 4,558,204

F1 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $0.808 to $0.86, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (1).

F2 · ownership.direct: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of TRV GP IV and TRV GP IV LLC disclaims beneficial ownership of the shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

SEC source: 0000899243-21-034297 · doc4.xml · nonDerivative · entry 1

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 6,758,204

F1 · kind: On August 25, 2021, Third Rock Ventures IV, L.P. ("TRV IV") distributed for no consideration, 1,250,000 shares of Common Stock of the Issuer (the "Shares") to its limited partners and to Third Rock Ventures GP IV, L.P. ("TRV GP IV"), the general partner of TRV IV, representing each such partner's pro rata interest in such Shares. On the same date, TRV GP IV distributed, for no consideration, the Shares it received in the distribution by TRV IV to its partners, representing each such partner's pro rata interest in such Shares. All of the aforementioned distributions were made in accordance with the exemptions afforded by Rules 16a-13 and 16a-9 of the Securities Exchange Act of 1934, as amended.

F1 · price: On August 25, 2021, Third Rock Ventures IV, L.P. ("TRV IV") distributed for no consideration, 1,250,000 shares of Common Stock of the Issuer (the "Shares") to its limited partners and to Third Rock Ventures GP IV, L.P. ("TRV GP IV"), the general partner of TRV IV, representing each such partner's pro rata interest in such Shares. On the same date, TRV GP IV distributed, for no consideration, the Shares it received in the distribution by TRV IV to its partners, representing each such partner's pro rata interest in such Shares. All of the aforementioned distributions were made in accordance with the exemptions afforded by Rules 16a-13 and 16a-9 of the Securities Exchange Act of 1934, as amended.

F2 · ownership.direct: These shares are directly held by TRV IV. The general partner of TRV IV is TRV GP IV. The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of TRV GP IV and TRV GP IV LLC disclaims beneficial ownership of the shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it is the beneficial owner of such shares.

SEC source: 0000899243-21-002117 · doc4.xml · nonDerivative · entry 12

Third Rock Ventures III, L.P. · CIK 0001569705 · 10% owner

Third Rock Ventures GP III, L.P. · CIK 0001637300 · 10% owner

TRV GP III, LLC · CIK 0001637299 · 10% owner

STARR KEVIN P · CIK 0001192603 · 10% owner

TEPPER ROBERT I · CIK 0001192595 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 0

F12 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $41.00 to $41.46, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (12).

F13 · ownership.nature: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of the reporting persons, except for TRV IV, disclaims beneficial ownership of these shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it or he is the beneficial owner of such shares.

F14 · ownership.nature: Each of the reporting persons disclaims the existence of a Section 13(d) "group" as between the TRV III related parties and the TRV IV related parties and this report shall not be deemed an admission that any of such parties is or may be part of such a group with any of the other parties.

SEC source: 0000899243-21-002117 · doc4.xml · nonDerivative · entry 11

Third Rock Ventures III, L.P. · CIK 0001569705 · 10% owner

Third Rock Ventures GP III, L.P. · CIK 0001637300 · 10% owner

TRV GP III, LLC · CIK 0001637299 · 10% owner

STARR KEVIN P · CIK 0001192603 · 10% owner

TEPPER ROBERT I · CIK 0001192595 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 1,965,294

F11 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $44.03 to $44.98, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (11).

F13 · ownership.nature: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of the reporting persons, except for TRV IV, disclaims beneficial ownership of these shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it or he is the beneficial owner of such shares.

F14 · ownership.nature: Each of the reporting persons disclaims the existence of a Section 13(d) "group" as between the TRV III related parties and the TRV IV related parties and this report shall not be deemed an admission that any of such parties is or may be part of such a group with any of the other parties.

SEC source: 0000899243-21-002117 · doc4.xml · nonDerivative · entry 10

Third Rock Ventures III, L.P. · CIK 0001569705 · 10% owner

Third Rock Ventures GP III, L.P. · CIK 0001637300 · 10% owner

TRV GP III, LLC · CIK 0001637299 · 10% owner

STARR KEVIN P · CIK 0001192603 · 10% owner

TEPPER ROBERT I · CIK 0001192595 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 1,970,076

F10 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $43.04 to $44.00, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (10).

F13 · ownership.nature: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of the reporting persons, except for TRV IV, disclaims beneficial ownership of these shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it or he is the beneficial owner of such shares.

F14 · ownership.nature: Each of the reporting persons disclaims the existence of a Section 13(d) "group" as between the TRV III related parties and the TRV IV related parties and this report shall not be deemed an admission that any of such parties is or may be part of such a group with any of the other parties.

SEC source: 0000899243-21-002117 · doc4.xml · nonDerivative · entry 9

Third Rock Ventures III, L.P. · CIK 0001569705 · 10% owner

Third Rock Ventures GP III, L.P. · CIK 0001637300 · 10% owner

TRV GP III, LLC · CIK 0001637299 · 10% owner

STARR KEVIN P · CIK 0001192603 · 10% owner

TEPPER ROBERT I · CIK 0001192595 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 1,972,867

F9 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $42.00 to $42.96, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (9).

F13 · ownership.nature: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of the reporting persons, except for TRV IV, disclaims beneficial ownership of these shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it or he is the beneficial owner of such shares.

F14 · ownership.nature: Each of the reporting persons disclaims the existence of a Section 13(d) "group" as between the TRV III related parties and the TRV IV related parties and this report shall not be deemed an admission that any of such parties is or may be part of such a group with any of the other parties.

SEC source: 0000899243-21-002117 · doc4.xml · nonDerivative · entry 8

Third Rock Ventures III, L.P. · CIK 0001569705 · 10% owner

Third Rock Ventures GP III, L.P. · CIK 0001637300 · 10% owner

TRV GP III, LLC · CIK 0001637299 · 10% owner

STARR KEVIN P · CIK 0001192603 · 10% owner

TEPPER ROBERT I · CIK 0001192595 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 2,000,517

F8 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $41.00 to $41.86, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (8).

F13 · ownership.nature: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of the reporting persons, except for TRV IV, disclaims beneficial ownership of these shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it or he is the beneficial owner of such shares.

F14 · ownership.nature: Each of the reporting persons disclaims the existence of a Section 13(d) "group" as between the TRV III related parties and the TRV IV related parties and this report shall not be deemed an admission that any of such parties is or may be part of such a group with any of the other parties.

SEC source: 0000899243-21-002117 · doc4.xml · nonDerivative · entry 7

Third Rock Ventures III, L.P. · CIK 0001569705 · 10% owner

Third Rock Ventures GP III, L.P. · CIK 0001637300 · 10% owner

TRV GP III, LLC · CIK 0001637299 · 10% owner

STARR KEVIN P · CIK 0001192603 · 10% owner

TEPPER ROBERT I · CIK 0001192595 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 2,006,147

F7 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $40.00 to $40.96, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (7).

F13 · ownership.nature: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV"). The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of the reporting persons, except for TRV IV, disclaims beneficial ownership of these shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it or he is the beneficial owner of such shares.

F14 · ownership.nature: Each of the reporting persons disclaims the existence of a Section 13(d) "group" as between the TRV III related parties and the TRV IV related parties and this report shall not be deemed an admission that any of such parties is or may be part of such a group with any of the other parties.

SEC source: 0000899243-21-002117 · doc4.xml · nonDerivative · entry 6

Third Rock Ventures III, L.P. · CIK 0001569705 · 10% owner

Third Rock Ventures GP III, L.P. · CIK 0001637300 · 10% owner

TRV GP III, LLC · CIK 0001637299 · 10% owner

STARR KEVIN P · CIK 0001192603 · 10% owner

TEPPER ROBERT I · CIK 0001192595 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 7,739,918

F6 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $44.03 to $44.98, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (6).

F1 · ownership.direct: These shares are directly held by Third Rock Ventures III, L.P. ("TRV III"). The general partner of TRV III is Third Rock Ventures GP III, L.P. ("TRV GP III"). The general partner of TRV GP III is TRV GP III, LLC ("TRV GP III LLC"). The individual managers of TRV GP III LLC are Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of TRV GP III, TRV GP III LLC, Levin, Starr and Tepper disclaims beneficial ownership of the shares except to the extent of its or his pecuniary interest therein, if any, and this report shall not be deemed an admission that it or he is the beneficial owner of such shares.

F14 · ownership.direct: Each of the reporting persons disclaims the existence of a Section 13(d) "group" as between the TRV III related parties and the TRV IV related parties and this report shall not be deemed an admission that any of such parties is or may be part of such a group with any of the other parties.

SEC source: 0000899243-21-002117 · doc4.xml · nonDerivative · entry 5

Third Rock Ventures III, L.P. · CIK 0001569705 · 10% owner

Third Rock Ventures GP III, L.P. · CIK 0001637300 · 10% owner

TRV GP III, LLC · CIK 0001637299 · 10% owner

STARR KEVIN P · CIK 0001192603 · 10% owner

TEPPER ROBERT I · CIK 0001192595 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 7,747,330

F5 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $43.04 to $44.00, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (5).

F1 · ownership.direct: These shares are directly held by Third Rock Ventures III, L.P. ("TRV III"). The general partner of TRV III is Third Rock Ventures GP III, L.P. ("TRV GP III"). The general partner of TRV GP III is TRV GP III, LLC ("TRV GP III LLC"). The individual managers of TRV GP III LLC are Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of TRV GP III, TRV GP III LLC, Levin, Starr and Tepper disclaims beneficial ownership of the shares except to the extent of its or his pecuniary interest therein, if any, and this report shall not be deemed an admission that it or he is the beneficial owner of such shares.

F14 · ownership.direct: Each of the reporting persons disclaims the existence of a Section 13(d) "group" as between the TRV III related parties and the TRV IV related parties and this report shall not be deemed an admission that any of such parties is or may be part of such a group with any of the other parties.

SEC source: 0000899243-21-002117 · doc4.xml · nonDerivative · entry 4

Third Rock Ventures III, L.P. · CIK 0001569705 · 10% owner

Third Rock Ventures GP III, L.P. · CIK 0001637300 · 10% owner

TRV GP III, LLC · CIK 0001637299 · 10% owner

STARR KEVIN P · CIK 0001192603 · 10% owner

TEPPER ROBERT I · CIK 0001192595 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 7,751,655

F4 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $42.00 to $42.96, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (4).

F1 · ownership.direct: These shares are directly held by Third Rock Ventures III, L.P. ("TRV III"). The general partner of TRV III is Third Rock Ventures GP III, L.P. ("TRV GP III"). The general partner of TRV GP III is TRV GP III, LLC ("TRV GP III LLC"). The individual managers of TRV GP III LLC are Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of TRV GP III, TRV GP III LLC, Levin, Starr and Tepper disclaims beneficial ownership of the shares except to the extent of its or his pecuniary interest therein, if any, and this report shall not be deemed an admission that it or he is the beneficial owner of such shares.

F14 · ownership.direct: Each of the reporting persons disclaims the existence of a Section 13(d) "group" as between the TRV III related parties and the TRV IV related parties and this report shall not be deemed an admission that any of such parties is or may be part of such a group with any of the other parties.

SEC source: 0000899243-21-002117 · doc4.xml · nonDerivative · entry 3

Third Rock Ventures III, L.P. · CIK 0001569705 · 10% owner

Third Rock Ventures GP III, L.P. · CIK 0001637300 · 10% owner

TRV GP III, LLC · CIK 0001637299 · 10% owner

STARR KEVIN P · CIK 0001192603 · 10% owner

TEPPER ROBERT I · CIK 0001192595 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 7,794,515

F3 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $41.00 to $41.86, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (3).

F1 · ownership.direct: These shares are directly held by Third Rock Ventures III, L.P. ("TRV III"). The general partner of TRV III is Third Rock Ventures GP III, L.P. ("TRV GP III"). The general partner of TRV GP III is TRV GP III, LLC ("TRV GP III LLC"). The individual managers of TRV GP III LLC are Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of TRV GP III, TRV GP III LLC, Levin, Starr and Tepper disclaims beneficial ownership of the shares except to the extent of its or his pecuniary interest therein, if any, and this report shall not be deemed an admission that it or he is the beneficial owner of such shares.

F14 · ownership.direct: Each of the reporting persons disclaims the existence of a Section 13(d) "group" as between the TRV III related parties and the TRV IV related parties and this report shall not be deemed an admission that any of such parties is or may be part of such a group with any of the other parties.

SEC source: 0000899243-21-002117 · doc4.xml · nonDerivative · entry 2

Third Rock Ventures III, L.P. · CIK 0001569705 · 10% owner

Third Rock Ventures GP III, L.P. · CIK 0001637300 · 10% owner

TRV GP III, LLC · CIK 0001637299 · 10% owner

STARR KEVIN P · CIK 0001192603 · 10% owner

TEPPER ROBERT I · CIK 0001192595 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 7,803,242

F2 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $40.00 to $40.96, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (2).

F1 · ownership.direct: These shares are directly held by Third Rock Ventures III, L.P. ("TRV III"). The general partner of TRV III is Third Rock Ventures GP III, L.P. ("TRV GP III"). The general partner of TRV GP III is TRV GP III, LLC ("TRV GP III LLC"). The individual managers of TRV GP III LLC are Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of TRV GP III, TRV GP III LLC, Levin, Starr and Tepper disclaims beneficial ownership of the shares except to the extent of its or his pecuniary interest therein, if any, and this report shall not be deemed an admission that it or he is the beneficial owner of such shares.

F14 · ownership.direct: Each of the reporting persons disclaims the existence of a Section 13(d) "group" as between the TRV III related parties and the TRV IV related parties and this report shall not be deemed an admission that any of such parties is or may be part of such a group with any of the other parties.

SEC source: 0000899243-21-002117 · doc4.xml · nonDerivative · entry 1

Third Rock Ventures III, L.P. · CIK 0001569705 · 10% owner

Third Rock Ventures GP III, L.P. · CIK 0001637300 · 10% owner

TRV GP III, LLC · CIK 0001637299 · 10% owner

STARR KEVIN P · CIK 0001192603 · 10% owner

TEPPER ROBERT I · CIK 0001192595 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 9,051,115

F1 · ownership.direct: These shares are directly held by Third Rock Ventures III, L.P. ("TRV III"). The general partner of TRV III is Third Rock Ventures GP III, L.P. ("TRV GP III"). The general partner of TRV GP III is TRV GP III, LLC ("TRV GP III LLC"). The individual managers of TRV GP III LLC are Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of TRV GP III, TRV GP III LLC, Levin, Starr and Tepper disclaims beneficial ownership of the shares except to the extent of its or his pecuniary interest therein, if any, and this report shall not be deemed an admission that it or he is the beneficial owner of such shares.

F14 · ownership.direct: Each of the reporting persons disclaims the existence of a Section 13(d) "group" as between the TRV III related parties and the TRV IV related parties and this report shall not be deemed an admission that any of such parties is or may be part of such a group with any of the other parties.

SEC source: 0000899243-20-019850 · doc4.xml · derivative · entry 8

Third Rock Ventures III, L.P. · CIK 0001569705 · 10% owner

Third Rock Ventures GP III, L.P. · CIK 0001637300 · 10% owner

TRV GP III, LLC · CIK 0001637299 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

STARR KEVIN P · CIK 0001192603 · 10% owner

TEPPER ROBERT I · CIK 0001192595 · 10% owner

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 0

Underlying: Common Stock · 17,427 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.

F6 · derivative.exercise_price: Each share of Series B Preferred Stock automatically converted into shares of the Issuer's common stock, par value $0.001 per share ("Common Stock") on a 1-for-3.55092 basis upon the closing of the Issuer's initial public offering on July 20, 2020 and had no expiration date.

F6 · price: Each share of Series B Preferred Stock automatically converted into shares of the Issuer's common stock, par value $0.001 per share ("Common Stock") on a 1-for-3.55092 basis upon the closing of the Issuer's initial public offering on July 20, 2020 and had no expiration date.

F6 · derivative.exercise_date: Each share of Series B Preferred Stock automatically converted into shares of the Issuer's common stock, par value $0.001 per share ("Common Stock") on a 1-for-3.55092 basis upon the closing of the Issuer's initial public offering on July 20, 2020 and had no expiration date.

F6 · derivative.expiration_date: Each share of Series B Preferred Stock automatically converted into shares of the Issuer's common stock, par value $0.001 per share ("Common Stock") on a 1-for-3.55092 basis upon the closing of the Issuer's initial public offering on July 20, 2020 and had no expiration date.

F4 · ownership.nature: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV").

F5 · ownership.nature: The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of the reporting persons, except for TRV IV, disclaims beneficial ownership of these shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it or he is the beneficial owner of such shares.

F6 · ownership.nature: Each share of Series B Preferred Stock automatically converted into shares of the Issuer's common stock, par value $0.001 per share ("Common Stock") on a 1-for-3.55092 basis upon the closing of the Issuer's initial public offering on July 20, 2020 and had no expiration date.

F7 · ownership.nature: Each of the reporting persons disclaims the existence of a Section 13(d) "group" as between the TRV III related parties and the TRV IV related parties and this report shall not be deemed an admission that any of such parties is or may be part of such a group with any of the other parties.

SEC source: 0000899243-20-019850 · doc4.xml · derivative · entry 7

Third Rock Ventures III, L.P. · CIK 0001569705 · 10% owner

Third Rock Ventures GP III, L.P. · CIK 0001637300 · 10% owner

TRV GP III, LLC · CIK 0001637299 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

STARR KEVIN P · CIK 0001192603 · 10% owner

TEPPER ROBERT I · CIK 0001192595 · 10% owner

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 17,427 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.

F6 · derivative.exercise_price: Each share of Series B Preferred Stock automatically converted into shares of the Issuer's common stock, par value $0.001 per share ("Common Stock") on a 1-for-3.55092 basis upon the closing of the Issuer's initial public offering on July 20, 2020 and had no expiration date.

F6 · price: Each share of Series B Preferred Stock automatically converted into shares of the Issuer's common stock, par value $0.001 per share ("Common Stock") on a 1-for-3.55092 basis upon the closing of the Issuer's initial public offering on July 20, 2020 and had no expiration date.

F6 · derivative.exercise_date: Each share of Series B Preferred Stock automatically converted into shares of the Issuer's common stock, par value $0.001 per share ("Common Stock") on a 1-for-3.55092 basis upon the closing of the Issuer's initial public offering on July 20, 2020 and had no expiration date.

F6 · derivative.expiration_date: Each share of Series B Preferred Stock automatically converted into shares of the Issuer's common stock, par value $0.001 per share ("Common Stock") on a 1-for-3.55092 basis upon the closing of the Issuer's initial public offering on July 20, 2020 and had no expiration date.

F1 · ownership.direct: These shares are directly held by Third Rock Ventures III, L.P. ("TRV III").

F2 · ownership.direct: The general partner of TRV III is Third Rock Ventures GP III, L.P. ("TRV GP III"). The general partner of TRV GP III is TRV GP III, LLC ("TRV GP III LLC"). The individual managers of TRV GP III LLC are Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of the reporting persons, except for TRV III, disclaims beneficial ownership of these shares except to the extent of its or his pecuniary interest therein, if any, and this report shall not be deemed an admission that it or he is the beneficial owner of such shares.

F6 · ownership.direct: Each share of Series B Preferred Stock automatically converted into shares of the Issuer's common stock, par value $0.001 per share ("Common Stock") on a 1-for-3.55092 basis upon the closing of the Issuer's initial public offering on July 20, 2020 and had no expiration date.

F7 · ownership.direct: Each of the reporting persons disclaims the existence of a Section 13(d) "group" as between the TRV III related parties and the TRV IV related parties and this report shall not be deemed an admission that any of such parties is or may be part of such a group with any of the other parties.

SEC source: 0000899243-20-019850 · doc4.xml · derivative · entry 6

Third Rock Ventures III, L.P. · CIK 0001569705 · 10% owner

Third Rock Ventures GP III, L.P. · CIK 0001637300 · 10% owner

TRV GP III, LLC · CIK 0001637299 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

STARR KEVIN P · CIK 0001192603 · 10% owner

TEPPER ROBERT I · CIK 0001192595 · 10% owner

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 0

Underlying: Common Stock · 2,793,770 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.

F3 · derivative.exercise_price: Each share of Series A Preferred Stock automatically converted into shares of the Issuer's common stock, par value $0.001 per share ("Common Stock") on a 1-for-3.55092 basis upon the closing of the Issuer's initial public offering on July 20, 2020 and had no expiration date.

F3 · price: Each share of Series A Preferred Stock automatically converted into shares of the Issuer's common stock, par value $0.001 per share ("Common Stock") on a 1-for-3.55092 basis upon the closing of the Issuer's initial public offering on July 20, 2020 and had no expiration date.

F3 · derivative.exercise_date: Each share of Series A Preferred Stock automatically converted into shares of the Issuer's common stock, par value $0.001 per share ("Common Stock") on a 1-for-3.55092 basis upon the closing of the Issuer's initial public offering on July 20, 2020 and had no expiration date.

F3 · derivative.expiration_date: Each share of Series A Preferred Stock automatically converted into shares of the Issuer's common stock, par value $0.001 per share ("Common Stock") on a 1-for-3.55092 basis upon the closing of the Issuer's initial public offering on July 20, 2020 and had no expiration date.

F3 · ownership.nature: Each share of Series A Preferred Stock automatically converted into shares of the Issuer's common stock, par value $0.001 per share ("Common Stock") on a 1-for-3.55092 basis upon the closing of the Issuer's initial public offering on July 20, 2020 and had no expiration date.

F4 · ownership.nature: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV").

F5 · ownership.nature: The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of the reporting persons, except for TRV IV, disclaims beneficial ownership of these shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it or he is the beneficial owner of such shares.

F7 · ownership.nature: Each of the reporting persons disclaims the existence of a Section 13(d) "group" as between the TRV III related parties and the TRV IV related parties and this report shall not be deemed an admission that any of such parties is or may be part of such a group with any of the other parties.

SEC source: 0000899243-20-019850 · doc4.xml · derivative · entry 5

Third Rock Ventures III, L.P. · CIK 0001569705 · 10% owner

Third Rock Ventures GP III, L.P. · CIK 0001637300 · 10% owner

TRV GP III, LLC · CIK 0001637299 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

STARR KEVIN P · CIK 0001192603 · 10% owner

TEPPER ROBERT I · CIK 0001192595 · 10% owner

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 9,970,454 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.

F3 · derivative.exercise_price: Each share of Series A Preferred Stock automatically converted into shares of the Issuer's common stock, par value $0.001 per share ("Common Stock") on a 1-for-3.55092 basis upon the closing of the Issuer's initial public offering on July 20, 2020 and had no expiration date.

F3 · price: Each share of Series A Preferred Stock automatically converted into shares of the Issuer's common stock, par value $0.001 per share ("Common Stock") on a 1-for-3.55092 basis upon the closing of the Issuer's initial public offering on July 20, 2020 and had no expiration date.

F3 · derivative.exercise_date: Each share of Series A Preferred Stock automatically converted into shares of the Issuer's common stock, par value $0.001 per share ("Common Stock") on a 1-for-3.55092 basis upon the closing of the Issuer's initial public offering on July 20, 2020 and had no expiration date.

F3 · derivative.expiration_date: Each share of Series A Preferred Stock automatically converted into shares of the Issuer's common stock, par value $0.001 per share ("Common Stock") on a 1-for-3.55092 basis upon the closing of the Issuer's initial public offering on July 20, 2020 and had no expiration date.

F1 · ownership.direct: These shares are directly held by Third Rock Ventures III, L.P. ("TRV III").

F2 · ownership.direct: The general partner of TRV III is Third Rock Ventures GP III, L.P. ("TRV GP III"). The general partner of TRV GP III is TRV GP III, LLC ("TRV GP III LLC"). The individual managers of TRV GP III LLC are Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of the reporting persons, except for TRV III, disclaims beneficial ownership of these shares except to the extent of its or his pecuniary interest therein, if any, and this report shall not be deemed an admission that it or he is the beneficial owner of such shares.

F3 · ownership.direct: Each share of Series A Preferred Stock automatically converted into shares of the Issuer's common stock, par value $0.001 per share ("Common Stock") on a 1-for-3.55092 basis upon the closing of the Issuer's initial public offering on July 20, 2020 and had no expiration date.

F7 · ownership.direct: Each of the reporting persons disclaims the existence of a Section 13(d) "group" as between the TRV III related parties and the TRV IV related parties and this report shall not be deemed an admission that any of such parties is or may be part of such a group with any of the other parties.

SEC source: 0000899243-20-019850 · doc4.xml · nonDerivative · entry 4

Third Rock Ventures III, L.P. · CIK 0001569705 · 10% owner

Third Rock Ventures GP III, L.P. · CIK 0001637300 · 10% owner

TRV GP III, LLC · CIK 0001637299 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

STARR KEVIN P · CIK 0001192603 · 10% owner

TEPPER ROBERT I · CIK 0001192595 · 10% owner

Third Rock Ventures IV, L.P. · CIK 0001688327 · 10% owner

Third Rock Ventures GP IV, L.P. · CIK 0001688326 · 10% owner

TRV GP IV, LLC · CIK 0001688325 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 2,811,197

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.

F4 · ownership.nature: These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV").

F5 · ownership.nature: The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of the reporting persons, except for TRV IV, disclaims beneficial ownership of these shares except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that it or he is the beneficial owner of such shares.

F6 · ownership.nature: Each share of Series B Preferred Stock automatically converted into shares of the Issuer's common stock, par value $0.001 per share ("Common Stock") on a 1-for-3.55092 basis upon the closing of the Issuer's initial public offering on July 20, 2020 and had no expiration date.

F7 · ownership.nature: Each of the reporting persons disclaims the existence of a Section 13(d) "group" as between the TRV III related parties and the TRV IV related parties and this report shall not be deemed an admission that any of such parties is or may be part of such a group with any of the other parties.