STARR KEVIN P

SEC source: 0001562180-20-004431 · primarydocument.xml · derivative · entry 1

STARR KEVIN P · CIK 0001192603 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 10,000

Underlying: Common Stock · 10,000 shares

Expires 2030-06-09

F1 · derivative.exercise_date: The stock option award was issued pursuant to the Sage Therapeutics, Inc. 2014 Stock Option and Incentive Plan in accordance with the terms of the Amended and Restated Non-Employee Director Compensation Policy. The option will vest in full upon the earlier to occur of June 9, 2021 or the day immediately prior to the 2021 Annual Meeting of Sage's stockholders, subject to continued service as a director on such date.

SEC source: 0000899243-20-015874 · doc4.xml · derivative · 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: 0

Underlying: Common Stock · 2,132,867 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.

F2 · derivative.exercise_price: The Series A Preferred Stock converted into Common Stock on a 7.15-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock was convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Series A Preferred Stock had no expiration date.

F2 · derivative.exercise_date: The Series A Preferred Stock converted into Common Stock on a 7.15-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock was convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Series A Preferred Stock had no expiration date.

F2 · derivative.expiration_date: The Series A Preferred Stock converted into Common Stock on a 7.15-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock was convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Series A Preferred Stock had no expiration date.

F6 · ownership.nature: These shares are directly held by Third Rock Ventures IV.

F7 · 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 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 or he is the beneficial owner of such shares.

F8 · ownership.nature: Each of 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: 0000899243-20-015874 · doc4.xml · derivative · 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

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 · 5,559,440 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.

F2 · derivative.exercise_price: The Series A Preferred Stock converted into Common Stock on a 7.15-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock was convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Series A Preferred Stock had no expiration date.

F2 · derivative.exercise_date: The Series A Preferred Stock converted into Common Stock on a 7.15-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock was convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Series A Preferred Stock had no expiration date.

F2 · derivative.expiration_date: The Series A Preferred Stock converted into Common Stock on a 7.15-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock was convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Series A Preferred Stock had no expiration date.

F3 · ownership.direct: These shares are directly held by TRV III.

F4 · 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 TRV GP III, TRV GP III LLC, Levin, Starr and Tepper 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.

F8 · ownership.direct: Each of 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: 0000899243-20-015874 · 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

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: 2,132,867

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.

F5 · shares: Represents the total number of shares of Common Stock received by Third Rock Ventures IV, L.P. ("TRV IV") upon conversion of the preferred stock of the Issuer in connection with the closing of the Issuer's initial public offering.

F2 · price: The Series A Preferred Stock converted into Common Stock on a 7.15-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock was convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Series A Preferred Stock had no expiration date.

F6 · ownership.nature: These shares are directly held by Third Rock Ventures IV.

F7 · 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 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 or he is the beneficial owner of such shares.

F8 · ownership.nature: Each of 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: 0000899243-20-015874 · 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

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: 5,839,160

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 · shares: Represents the total number of shares of Common Stock received by Third Rock Ventures III, L.P. ("TRV III") upon conversion of the preferred stock of the Issuer in connection with the closing of the Issuer's initial public offering.

F2 · price: The Series A Preferred Stock converted into Common Stock on a 7.15-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock was convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Series A Preferred Stock had no expiration date.

F3 · ownership.direct: These shares are directly held by TRV III.

F4 · 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 TRV GP III, TRV GP III LLC, Levin, Starr and Tepper 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.

F8 · ownership.direct: Each of 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: 0000899243-20-004930 · 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

Third Rock Ventures II, L.P. · CIK 0001488495 · 10% owner

Third Rock Ventures GP II, L.P. · CIK 0001614061 · 10% owner

TRV GP II, LLC · CIK 0001614073 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

STARR KEVIN P · CIK 0001192603 · 10% owner

TEPPER ROBERT I · CIK 0001192595 · 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 · 1,909,317 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.

F2 · derivative.exercise_price: The Series A Preferred Stock, Series B Preferred Stock and Series C Preferred Stock converted into Common Stock on a one-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock, Series B Preferred Stock and Series C Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Preferred Stock had no expiration date.

F2 · derivative.exercise_date: The Series A Preferred Stock, Series B Preferred Stock and Series C Preferred Stock converted into Common Stock on a one-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock, Series B Preferred Stock and Series C Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Preferred Stock had no expiration date.

F2 · derivative.expiration_date: The Series A Preferred Stock, Series B Preferred Stock and Series C Preferred Stock converted into Common Stock on a one-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock, Series B Preferred Stock and Series C Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Preferred Stock had no expiration date.

F5 · ownership.direct: These shares are directly held by TRV II. The general partner of TRV II is Third Rock Ventures GP II, L.P. ("TRV GP II"). The general partner of TRV GP II is TRV GP II, LLC ("TRV GP II LLC"). The individual managers of TRV GP II LLC are Levin, Starr and Tepper. Each of TRV GP II, TRV GP II LLC, Levin, Starr and Tepper 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.

SEC source: 0000899243-20-004930 · 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

Third Rock Ventures II, L.P. · CIK 0001488495 · 10% owner

Third Rock Ventures GP II, L.P. · CIK 0001614061 · 10% owner

TRV GP II, LLC · CIK 0001614073 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

STARR KEVIN P · CIK 0001192603 · 10% owner

TEPPER ROBERT I · CIK 0001192595 · 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 · 49,879 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.

F2 · derivative.exercise_price: The Series A Preferred Stock, Series B Preferred Stock and Series C Preferred Stock converted into Common Stock on a one-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock, Series B Preferred Stock and Series C Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Preferred Stock had no expiration date.

F2 · derivative.exercise_date: The Series A Preferred Stock, Series B Preferred Stock and Series C Preferred Stock converted into Common Stock on a one-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock, Series B Preferred Stock and Series C Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Preferred Stock had no expiration date.

F2 · derivative.expiration_date: The Series A Preferred Stock, Series B Preferred Stock and Series C Preferred Stock converted into Common Stock on a one-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock, Series B Preferred Stock and Series C Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Preferred Stock had no expiration date.

F3 · ownership.direct: These shares are directly held by 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 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.

SEC source: 0000899243-20-004930 · doc4.xml · derivative · 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

Third Rock Ventures II, L.P. · CIK 0001488495 · 10% owner

Third Rock Ventures GP II, L.P. · CIK 0001614061 · 10% owner

TRV GP II, LLC · CIK 0001614073 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

STARR KEVIN P · CIK 0001192603 · 10% owner

TEPPER ROBERT I · CIK 0001192595 · 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 · 342,505 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.

F2 · derivative.exercise_price: The Series A Preferred Stock, Series B Preferred Stock and Series C Preferred Stock converted into Common Stock on a one-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock, Series B Preferred Stock and Series C Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Preferred Stock had no expiration date.

F2 · derivative.exercise_date: The Series A Preferred Stock, Series B Preferred Stock and Series C Preferred Stock converted into Common Stock on a one-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock, Series B Preferred Stock and Series C Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Preferred Stock had no expiration date.

F2 · derivative.expiration_date: The Series A Preferred Stock, Series B Preferred Stock and Series C Preferred Stock converted into Common Stock on a one-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock, Series B Preferred Stock and Series C Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Preferred Stock had no expiration date.

F3 · ownership.direct: These shares are directly held by 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 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.

SEC source: 0000899243-20-004930 · doc4.xml · derivative · 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

Third Rock Ventures II, L.P. · CIK 0001488495 · 10% owner

Third Rock Ventures GP II, L.P. · CIK 0001614061 · 10% owner

TRV GP II, LLC · CIK 0001614073 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

STARR KEVIN P · CIK 0001192603 · 10% owner

TEPPER ROBERT I · CIK 0001192595 · 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 · 8,220,641 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.

F2 · derivative.exercise_price: The Series A Preferred Stock, Series B Preferred Stock and Series C Preferred Stock converted into Common Stock on a one-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock, Series B Preferred Stock and Series C Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Preferred Stock had no expiration date.

F2 · derivative.exercise_date: The Series A Preferred Stock, Series B Preferred Stock and Series C Preferred Stock converted into Common Stock on a one-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock, Series B Preferred Stock and Series C Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Preferred Stock had no expiration date.

F2 · derivative.expiration_date: The Series A Preferred Stock, Series B Preferred Stock and Series C Preferred Stock converted into Common Stock on a one-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock, Series B Preferred Stock and Series C Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Preferred Stock had no expiration date.

F3 · ownership.direct: These shares are directly held by 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 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.

SEC source: 0000899243-20-004930 · 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

Third Rock Ventures II, L.P. · CIK 0001488495 · 10% owner

Third Rock Ventures GP II, L.P. · CIK 0001614061 · 10% owner

TRV GP II, LLC · CIK 0001614073 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

STARR KEVIN P · CIK 0001192603 · 10% owner

TEPPER ROBERT I · CIK 0001192595 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 1,909,317

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 · shares: Represents the total number of shares of Common Stock received by Third Rock Ventures II, L.P. ("TRV II") upon conversion of the Series B Preferred Stock of the Issuer in connection with the closing of the Issuer's initial public offering.

F2 · price: The Series A Preferred Stock, Series B Preferred Stock and Series C Preferred Stock converted into Common Stock on a one-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock, Series B Preferred Stock and Series C Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Preferred Stock had no expiration date.

F3 · ownership.direct: These shares are directly held by 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 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.

SEC source: 0000899243-20-004930 · 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

Third Rock Ventures II, L.P. · CIK 0001488495 · 10% owner

Third Rock Ventures GP II, L.P. · CIK 0001614061 · 10% owner

TRV GP II, LLC · CIK 0001614073 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

STARR KEVIN P · CIK 0001192603 · 10% owner

TEPPER ROBERT I · CIK 0001192595 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 9,024,031

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 · shares: Represents the total number of shares of Common Stock received by Third Rock Ventures III, L.P. ("TRV III") upon conversion of the Series A Preferred Stock, Series B Preferred Stock and Series C Preferred Stock of the Issuer in connection with the closing of the Issuer's initial public offering.

F2 · price: The Series A Preferred Stock, Series B Preferred Stock and Series C Preferred Stock converted into Common Stock on a one-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock, Series B Preferred Stock and Series C Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Preferred Stock had no expiration date.

F3 · ownership.direct: These shares are directly held by 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 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.

SEC source: 0000899243-19-020026 · doc4.xml · derivative · 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

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 · 0 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: On July 22, 2019, the Series A Preferred Stock converted into Common Stock on a seven-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock was convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial pubic offering. The shares had no expiration date.

F2 · shares: As of the date of this filing, Third Rock Ventures IV, L.P. ("TRV IV") holds 2,261,904 shares of Common Stock issued upon conversion of 15,833,333 shares of Series A Preferred Stock. 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"). Abbie Celniker, Ph.D., Tepper, Alexis Borisy, Craig Muir and Cary Pfeffer, M.D. are the managing members of TRV IV LLC who collectively make voting and investment decisions with respect to shares held by TRV IV LP. Tepper disclaims beneficial ownership of the shares except to the extent of his pecuniary interest therein, if any, and this report shall not be deemed an admission that he is the beneficial owner of such shares.

F3 · derivative.exercise_date: On July 22, 2019, the Series A Preferred Stock converted into Common Stock on a seven-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock was convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial pubic offering. The shares had no expiration date.

F3 · derivative.expiration_date: On July 22, 2019, the Series A Preferred Stock converted into Common Stock on a seven-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock was convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial pubic offering. The shares had no expiration date.

F2 · derivative.underlying_shares: As of the date of this filing, Third Rock Ventures IV, L.P. ("TRV IV") holds 2,261,904 shares of Common Stock issued upon conversion of 15,833,333 shares of Series A Preferred Stock. 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"). Abbie Celniker, Ph.D., Tepper, Alexis Borisy, Craig Muir and Cary Pfeffer, M.D. are the managing members of TRV IV LLC who collectively make voting and investment decisions with respect to shares held by TRV IV LP. Tepper disclaims beneficial ownership of the shares except to the extent of his pecuniary interest therein, if any, and this report shall not be deemed an admission that he is the beneficial owner of such shares.

F1 · ownership.direct: The 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 LP"). The general partner of TRV GP III LP 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 LP, 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.

SEC source: 0000899243-19-020026 · doc4.xml · derivative · 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

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 · 5,595,238 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: On July 22, 2019, the Series A Preferred Stock converted into Common Stock on a seven-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock was convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial pubic offering. The shares had no expiration date.

F3 · derivative.exercise_date: On July 22, 2019, the Series A Preferred Stock converted into Common Stock on a seven-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock was convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial pubic offering. The shares had no expiration date.

F3 · derivative.expiration_date: On July 22, 2019, the Series A Preferred Stock converted into Common Stock on a seven-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock was convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial pubic offering. The shares had no expiration date.

F1 · ownership.direct: The 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 LP"). The general partner of TRV GP III LP 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 LP, 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.

SEC source: 0000899243-19-020026 · 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

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 5,962,202

F2 · balance_after: As of the date of this filing, Third Rock Ventures IV, L.P. ("TRV IV") holds 2,261,904 shares of Common Stock issued upon conversion of 15,833,333 shares of Series A Preferred Stock. 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"). Abbie Celniker, Ph.D., Tepper, Alexis Borisy, Craig Muir and Cary Pfeffer, M.D. are the managing members of TRV IV LLC who collectively make voting and investment decisions with respect to shares held by TRV IV LP. Tepper disclaims beneficial ownership of the shares except to the extent of his pecuniary interest therein, if any, and this report shall not be deemed an admission that he is the beneficial owner of such shares.

F1 · ownership.direct: The 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 LP"). The general partner of TRV GP III LP 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 LP, 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.

SEC source: 0000899243-19-020026 · 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

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 5,880,952

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 · price: On July 22, 2019, the Series A Preferred Stock converted into Common Stock on a seven-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock was convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial pubic offering. The shares had no expiration date.

F2 · balance_after: As of the date of this filing, Third Rock Ventures IV, L.P. ("TRV IV") holds 2,261,904 shares of Common Stock issued upon conversion of 15,833,333 shares of Series A Preferred Stock. 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"). Abbie Celniker, Ph.D., Tepper, Alexis Borisy, Craig Muir and Cary Pfeffer, M.D. are the managing members of TRV IV LLC who collectively make voting and investment decisions with respect to shares held by TRV IV LP. Tepper disclaims beneficial ownership of the shares except to the extent of his pecuniary interest therein, if any, and this report shall not be deemed an admission that he is the beneficial owner of such shares.

F1 · ownership.direct: The 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 LP"). The general partner of TRV GP III LP 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 LP, 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.

SEC source: 0001562180-19-003388 · primarydocument.xml · derivative · entry 1

STARR KEVIN P · CIK 0001192603 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 10,000

Underlying: Common Stock · 10,000 shares

Expires 2029-06-05

F1 · derivative.exercise_date: The stock option award was issued pursuant to the Sage Therapeutics, Inc., 2014 Stock Option and Incentive Plan in accordance with the terms of the Amended and Restated Non-Employee Director Compensation Policy. The option will vest in full upon the earlier to occur of June 5, 2020 or the day immediately prior to the 2020 Annual Meeting of Sage's stockholders, subject to continued service as a director on such date.

SEC source: 0000899243-19-003668 · doc4.xml · nonDerivative · entry 1

STARR KEVIN P · CIK 0001192603 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 0

F1 · shares: On February 12, 2019, Third Rock Ventures II, L.P. ("TRV II") sold 37,362 shares of Common Stock of the Issuer in multiple transactions at prices ranging from $153.60 to $154.51, inclusive, at a weighted average price per share of $154.2096. 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). Following the reported transaction, TRV II held zero shares of Common Stock of the Issuer.

F1 · price: On February 12, 2019, Third Rock Ventures II, L.P. ("TRV II") sold 37,362 shares of Common Stock of the Issuer in multiple transactions at prices ranging from $153.60 to $154.51, inclusive, at a weighted average price per share of $154.2096. 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). Following the reported transaction, TRV II held zero shares of Common Stock of the Issuer.

F1 · balance_after: On February 12, 2019, Third Rock Ventures II, L.P. ("TRV II") sold 37,362 shares of Common Stock of the Issuer in multiple transactions at prices ranging from $153.60 to $154.51, inclusive, at a weighted average price per share of $154.2096. 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). Following the reported transaction, TRV II held zero shares of Common Stock of the Issuer.

F2 · ownership.nature: These shares are directly held by TRV II. The general partner of TRV II is Third Rock Ventures GP II, L.P. ("TRV GP II"). The general partner of TRV GP II is TRV GP II, LLC ("TRV GP II LLC"). The individual managers of TRV GP II LLC are Mark Levin, Kevin Starr ("Starr") and Dr. Robert Tepper. Due to an ethical wall between Mr. Starr and each of TRV II, TRV GP II and TRV GP II LLC that prevents (i) the sharing of information related to the Issuer between Mr. Starr and the foregoing funds and their respective representatives and (ii) participation in investment decisions with respect to the common stock of the Issuer held by TRV II, Starr 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.

SEC source: 0000899243-18-024777 · 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

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 6,391,176

F1 · kind: Pursuant to a Rule 10b5-1 trading plan adopted by Third Rock Ventures III, L.P. ("TRV III"), Third Rock Ventures GP III, L.P. ("TRV GP III") and TRV GP III, LLC ("TRV GP III LLC"), TRV III distributed on September 19, 2018, for no consideration, 1,500,000 shares of Common Stock of the Issuer (the "Shares") to its limited partners and to TRV GP III, the general partner of TRV III, representing each such partner's pro rata interest in such Shares. On the same date, TRV GP III distributed, for no consideration, the Shares it received in the distribution by TRV III 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: Pursuant to a Rule 10b5-1 trading plan adopted by Third Rock Ventures III, L.P. ("TRV III"), Third Rock Ventures GP III, L.P. ("TRV GP III") and TRV GP III, LLC ("TRV GP III LLC"), TRV III distributed on September 19, 2018, for no consideration, 1,500,000 shares of Common Stock of the Issuer (the "Shares") to its limited partners and to TRV GP III, the general partner of TRV III, representing each such partner's pro rata interest in such Shares. On the same date, TRV GP III distributed, for no consideration, the Shares it received in the distribution by TRV III 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 III. The general partner of TRV III is TRV GP III. The general partner of TRV GP III is 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.

SEC source: 0000899243-18-023708 · doc4.xml · nonDerivative · entry 1

THIRD ROCK VENTURES LP · CIK 0001408591 · 10% owner

Third Rock Ventures GP, L.P. · CIK 0001578976 · 10% owner

TRV GP, LLC · CIK 0001578973 · 10% owner

STARR KEVIN P · CIK 0001192603 · 10% owner

TEPPER ROBERT I · CIK 0001192595 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 2,981,437

F1 · kind: Pursuant to a Rule 10b5-1 trading plan adopted by Third Rock Ventures, L.P. ("TRV"), Third Rock Ventures GP, L.P. ("TRV GP") and TRV GP, LLC ("TRV GP LLC"), TRV distributed on August 30, 2018, for no consideration, 1,000,000 shares of Common Stock of the Issuer (the "Shares") to its limited partners and to TRV GP, the general partner of TRV, representing each such partner's pro rata interest in such Shares. On the same date, TRV GP distributed, for no consideration, the Shares it received in the distribution by TRV 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: Pursuant to a Rule 10b5-1 trading plan adopted by Third Rock Ventures, L.P. ("TRV"), Third Rock Ventures GP, L.P. ("TRV GP") and TRV GP, LLC ("TRV GP LLC"), TRV distributed on August 30, 2018, for no consideration, 1,000,000 shares of Common Stock of the Issuer (the "Shares") to its limited partners and to TRV GP, the general partner of TRV, representing each such partner's pro rata interest in such Shares. On the same date, TRV GP distributed, for no consideration, the Shares it received in the distribution by TRV 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. The general partner of TRV is TRV GP. The general partner of TRV GP is TRV GP LLC. The individual managers of TRV GP LLC are Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of TRV GP, TRV GP 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.

SEC source: 0000899243-18-023212 · doc4.xml · derivative · entry 2

THIRD ROCK VENTURES LP · CIK 0001408591 · 10% owner

Third Rock Ventures GP, L.P. · CIK 0001578976 · 10% owner

TRV GP, LLC · CIK 0001578973 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

STARR KEVIN P · CIK 0001192603 · 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 · 51,032 shares

Expires 2021-05-24

F2 · derivative.exercise_date: The warrant was fully exercisable upon grant.

F1 · ownership.direct: These securities are directly held by Third Rock Ventures, L.P. ("TRV"). The general partner of TRV is Third Rock Ventures GP, L.P. ("TRV GP"). The general partner of TRV GP is TRV GP, LLC ("TRV GP LLC"). The individual managers of TRV GP LLC are Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of TRV GP, TRV GP 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

SEC source: 0000899243-18-023212 · doc4.xml · nonDerivative · entry 1

THIRD ROCK VENTURES LP · CIK 0001408591 · 10% owner

Third Rock Ventures GP, L.P. · CIK 0001578976 · 10% owner

TRV GP, LLC · CIK 0001578973 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

STARR KEVIN P · CIK 0001192603 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 3,034,083

F1 · ownership.direct: These securities are directly held by Third Rock Ventures, L.P. ("TRV"). The general partner of TRV is Third Rock Ventures GP, L.P. ("TRV GP"). The general partner of TRV GP is TRV GP, LLC ("TRV GP LLC"). The individual managers of TRV GP LLC are Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of TRV GP, TRV GP 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

SEC source: 0000899243-18-020534 · doc4.xml · derivative · entry 8

THIRD ROCK VENTURES LP · CIK 0001408591 · 10% owner

Third Rock Ventures GP, L.P. · CIK 0001578976 · 10% owner

TRV GP, LLC · CIK 0001578973 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

STARR KEVIN P · CIK 0001192603 · 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 · 90,840 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 July 23, 2018, the Series A, Series B, Series D, Series E-1 and Series F Preferred Stock converted into Common Stock on a 11.009-for-one basis, and the Series E Preferred Stock converted into Common Stock on a 8.56256-for-one basis, upon the closing of the Issuer's initial public offering without payment of consideration. The Series A, Series B, Series C, Series E, Series E-1 and Series F Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial pubic offering. The shares had no expiration date.

F1 · derivative.exercise_date: On July 23, 2018, the Series A, Series B, Series D, Series E-1 and Series F Preferred Stock converted into Common Stock on a 11.009-for-one basis, and the Series E Preferred Stock converted into Common Stock on a 8.56256-for-one basis, upon the closing of the Issuer's initial public offering without payment of consideration. The Series A, Series B, Series C, Series E, Series E-1 and Series F Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial pubic offering. The shares had no expiration date.

F1 · derivative.expiration_date: On July 23, 2018, the Series A, Series B, Series D, Series E-1 and Series F Preferred Stock converted into Common Stock on a 11.009-for-one basis, and the Series E Preferred Stock converted into Common Stock on a 8.56256-for-one basis, upon the closing of the Issuer's initial public offering without payment of consideration. The Series A, Series B, Series C, Series E, Series E-1 and Series F Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial pubic offering. The shares had no expiration date.

F2 · ownership.direct: These securities are directly held by Third Rock Ventures, L.P. ("TRV"). The general partner of TRV is Third Rock Ventures GP, L.P. ("TRV GP"). The general partner of TRV GP is TRV GP, LLC ("TRV GP LLC"). The individual managers of TRV GP LLC are Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of TRV GP, TRV GP 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

SEC source: 0000899243-18-020534 · doc4.xml · derivative · entry 7

THIRD ROCK VENTURES LP · CIK 0001408591 · 10% owner

Third Rock Ventures GP, L.P. · CIK 0001578976 · 10% owner

TRV GP, LLC · CIK 0001578973 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

STARR KEVIN P · CIK 0001192603 · 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 · 282,308 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 July 23, 2018, the Series A, Series B, Series D, Series E-1 and Series F Preferred Stock converted into Common Stock on a 11.009-for-one basis, and the Series E Preferred Stock converted into Common Stock on a 8.56256-for-one basis, upon the closing of the Issuer's initial public offering without payment of consideration. The Series A, Series B, Series C, Series E, Series E-1 and Series F Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial pubic offering. The shares had no expiration date.

F1 · derivative.exercise_date: On July 23, 2018, the Series A, Series B, Series D, Series E-1 and Series F Preferred Stock converted into Common Stock on a 11.009-for-one basis, and the Series E Preferred Stock converted into Common Stock on a 8.56256-for-one basis, upon the closing of the Issuer's initial public offering without payment of consideration. The Series A, Series B, Series C, Series E, Series E-1 and Series F Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial pubic offering. The shares had no expiration date.

F1 · derivative.expiration_date: On July 23, 2018, the Series A, Series B, Series D, Series E-1 and Series F Preferred Stock converted into Common Stock on a 11.009-for-one basis, and the Series E Preferred Stock converted into Common Stock on a 8.56256-for-one basis, upon the closing of the Issuer's initial public offering without payment of consideration. The Series A, Series B, Series C, Series E, Series E-1 and Series F Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial pubic offering. The shares had no expiration date.

F2 · ownership.direct: These securities are directly held by Third Rock Ventures, L.P. ("TRV"). The general partner of TRV is Third Rock Ventures GP, L.P. ("TRV GP"). The general partner of TRV GP is TRV GP, LLC ("TRV GP LLC"). The individual managers of TRV GP LLC are Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of TRV GP, TRV GP 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

SEC source: 0000899243-18-020534 · doc4.xml · derivative · entry 6

THIRD ROCK VENTURES LP · CIK 0001408591 · 10% owner

Third Rock Ventures GP, L.P. · CIK 0001578976 · 10% owner

TRV GP, LLC · CIK 0001578973 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

STARR KEVIN P · CIK 0001192603 · 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 · 266,934 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 July 23, 2018, the Series A, Series B, Series D, Series E-1 and Series F Preferred Stock converted into Common Stock on a 11.009-for-one basis, and the Series E Preferred Stock converted into Common Stock on a 8.56256-for-one basis, upon the closing of the Issuer's initial public offering without payment of consideration. The Series A, Series B, Series C, Series E, Series E-1 and Series F Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial pubic offering. The shares had no expiration date.

F1 · derivative.exercise_date: On July 23, 2018, the Series A, Series B, Series D, Series E-1 and Series F Preferred Stock converted into Common Stock on a 11.009-for-one basis, and the Series E Preferred Stock converted into Common Stock on a 8.56256-for-one basis, upon the closing of the Issuer's initial public offering without payment of consideration. The Series A, Series B, Series C, Series E, Series E-1 and Series F Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial pubic offering. The shares had no expiration date.

F1 · derivative.expiration_date: On July 23, 2018, the Series A, Series B, Series D, Series E-1 and Series F Preferred Stock converted into Common Stock on a 11.009-for-one basis, and the Series E Preferred Stock converted into Common Stock on a 8.56256-for-one basis, upon the closing of the Issuer's initial public offering without payment of consideration. The Series A, Series B, Series C, Series E, Series E-1 and Series F Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial pubic offering. The shares had no expiration date.

F2 · ownership.direct: These securities are directly held by Third Rock Ventures, L.P. ("TRV"). The general partner of TRV is Third Rock Ventures GP, L.P. ("TRV GP"). The general partner of TRV GP is TRV GP, LLC ("TRV GP LLC"). The individual managers of TRV GP LLC are Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of TRV GP, TRV GP 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

SEC source: 0000899243-18-020534 · doc4.xml · derivative · entry 5

THIRD ROCK VENTURES LP · CIK 0001408591 · 10% owner

Third Rock Ventures GP, L.P. · CIK 0001578976 · 10% owner

TRV GP, LLC · CIK 0001578973 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

STARR KEVIN P · CIK 0001192603 · 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 · 98,683 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 July 23, 2018, the Series A, Series B, Series D, Series E-1 and Series F Preferred Stock converted into Common Stock on a 11.009-for-one basis, and the Series E Preferred Stock converted into Common Stock on a 8.56256-for-one basis, upon the closing of the Issuer's initial public offering without payment of consideration. The Series A, Series B, Series C, Series E, Series E-1 and Series F Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial pubic offering. The shares had no expiration date.

F1 · derivative.exercise_date: On July 23, 2018, the Series A, Series B, Series D, Series E-1 and Series F Preferred Stock converted into Common Stock on a 11.009-for-one basis, and the Series E Preferred Stock converted into Common Stock on a 8.56256-for-one basis, upon the closing of the Issuer's initial public offering without payment of consideration. The Series A, Series B, Series C, Series E, Series E-1 and Series F Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial pubic offering. The shares had no expiration date.

F1 · derivative.expiration_date: On July 23, 2018, the Series A, Series B, Series D, Series E-1 and Series F Preferred Stock converted into Common Stock on a 11.009-for-one basis, and the Series E Preferred Stock converted into Common Stock on a 8.56256-for-one basis, upon the closing of the Issuer's initial public offering without payment of consideration. The Series A, Series B, Series C, Series E, Series E-1 and Series F Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial pubic offering. The shares had no expiration date.

F2 · ownership.direct: These securities are directly held by Third Rock Ventures, L.P. ("TRV"). The general partner of TRV is Third Rock Ventures GP, L.P. ("TRV GP"). The general partner of TRV GP is TRV GP, LLC ("TRV GP LLC"). The individual managers of TRV GP LLC are Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of TRV GP, TRV GP 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

SEC source: 0000899243-18-020534 · doc4.xml · derivative · entry 4

THIRD ROCK VENTURES LP · CIK 0001408591 · 10% owner

Third Rock Ventures GP, L.P. · CIK 0001578976 · 10% owner

TRV GP, LLC · CIK 0001578973 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

STARR KEVIN P · CIK 0001192603 · 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 · 967,389 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 July 23, 2018, the Series A, Series B, Series D, Series E-1 and Series F Preferred Stock converted into Common Stock on a 11.009-for-one basis, and the Series E Preferred Stock converted into Common Stock on a 8.56256-for-one basis, upon the closing of the Issuer's initial public offering without payment of consideration. The Series A, Series B, Series C, Series E, Series E-1 and Series F Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial pubic offering. The shares had no expiration date.

F1 · derivative.exercise_date: On July 23, 2018, the Series A, Series B, Series D, Series E-1 and Series F Preferred Stock converted into Common Stock on a 11.009-for-one basis, and the Series E Preferred Stock converted into Common Stock on a 8.56256-for-one basis, upon the closing of the Issuer's initial public offering without payment of consideration. The Series A, Series B, Series C, Series E, Series E-1 and Series F Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial pubic offering. The shares had no expiration date.

F1 · derivative.expiration_date: On July 23, 2018, the Series A, Series B, Series D, Series E-1 and Series F Preferred Stock converted into Common Stock on a 11.009-for-one basis, and the Series E Preferred Stock converted into Common Stock on a 8.56256-for-one basis, upon the closing of the Issuer's initial public offering without payment of consideration. The Series A, Series B, Series C, Series E, Series E-1 and Series F Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial pubic offering. The shares had no expiration date.

F2 · ownership.direct: These securities are directly held by Third Rock Ventures, L.P. ("TRV"). The general partner of TRV is Third Rock Ventures GP, L.P. ("TRV GP"). The general partner of TRV GP is TRV GP, LLC ("TRV GP LLC"). The individual managers of TRV GP LLC are Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of TRV GP, TRV GP 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

SEC source: 0000899243-18-020534 · doc4.xml · derivative · entry 3

THIRD ROCK VENTURES LP · CIK 0001408591 · 10% owner

Third Rock Ventures GP, L.P. · CIK 0001578976 · 10% owner

TRV GP, LLC · CIK 0001578973 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

STARR KEVIN P · CIK 0001192603 · 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 · 999,180 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 July 23, 2018, the Series A, Series B, Series D, Series E-1 and Series F Preferred Stock converted into Common Stock on a 11.009-for-one basis, and the Series E Preferred Stock converted into Common Stock on a 8.56256-for-one basis, upon the closing of the Issuer's initial public offering without payment of consideration. The Series A, Series B, Series C, Series E, Series E-1 and Series F Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial pubic offering. The shares had no expiration date.

F1 · derivative.exercise_date: On July 23, 2018, the Series A, Series B, Series D, Series E-1 and Series F Preferred Stock converted into Common Stock on a 11.009-for-one basis, and the Series E Preferred Stock converted into Common Stock on a 8.56256-for-one basis, upon the closing of the Issuer's initial public offering without payment of consideration. The Series A, Series B, Series C, Series E, Series E-1 and Series F Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial pubic offering. The shares had no expiration date.

F1 · derivative.expiration_date: On July 23, 2018, the Series A, Series B, Series D, Series E-1 and Series F Preferred Stock converted into Common Stock on a 11.009-for-one basis, and the Series E Preferred Stock converted into Common Stock on a 8.56256-for-one basis, upon the closing of the Issuer's initial public offering without payment of consideration. The Series A, Series B, Series C, Series E, Series E-1 and Series F Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial pubic offering. The shares had no expiration date.

F2 · ownership.direct: These securities are directly held by Third Rock Ventures, L.P. ("TRV"). The general partner of TRV is Third Rock Ventures GP, L.P. ("TRV GP"). The general partner of TRV GP is TRV GP, LLC ("TRV GP LLC"). The individual managers of TRV GP LLC are Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of TRV GP, TRV GP 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

SEC source: 0000899243-18-020534 · doc4.xml · nonDerivative · entry 2

THIRD ROCK VENTURES LP · CIK 0001408591 · 10% owner

Third Rock Ventures GP, L.P. · CIK 0001578976 · 10% owner

TRV GP, LLC · CIK 0001578973 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

STARR KEVIN P · CIK 0001192603 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 2,983,051

F2 · ownership.direct: These securities are directly held by Third Rock Ventures, L.P. ("TRV"). The general partner of TRV is Third Rock Ventures GP, L.P. ("TRV GP"). The general partner of TRV GP is TRV GP, LLC ("TRV GP LLC"). The individual managers of TRV GP LLC are Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of TRV GP, TRV GP 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

SEC source: 0000899243-18-020534 · doc4.xml · nonDerivative · entry 1

THIRD ROCK VENTURES LP · CIK 0001408591 · 10% owner

Third Rock Ventures GP, L.P. · CIK 0001578976 · 10% owner

TRV GP, LLC · CIK 0001578973 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

STARR KEVIN P · CIK 0001192603 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 2,716,384

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 July 23, 2018, the Series A, Series B, Series D, Series E-1 and Series F Preferred Stock converted into Common Stock on a 11.009-for-one basis, and the Series E Preferred Stock converted into Common Stock on a 8.56256-for-one basis, upon the closing of the Issuer's initial public offering without payment of consideration. The Series A, Series B, Series C, Series E, Series E-1 and Series F Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial pubic offering. The shares had no expiration date.

F2 · ownership.direct: These securities are directly held by Third Rock Ventures, L.P. ("TRV"). The general partner of TRV is Third Rock Ventures GP, L.P. ("TRV GP"). The general partner of TRV GP is TRV GP, LLC ("TRV GP LLC"). The individual managers of TRV GP LLC are Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of TRV GP, TRV GP 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

SEC source: 0001104659-18-043853 · a4.xml · derivative · 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

LEVIN MARK J · CIK 0001180428 · 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 · 341,637 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.

F2 · derivative.exercise_price: All series of Preferred Stock automatically converted into the Issuer's Common Stock on a 5-for-1 basis upon the closing of the Issuer's initial public offering on June 29, 2018 and had no expiration date.

F2 · price: All series of Preferred Stock automatically converted into the Issuer's Common Stock on a 5-for-1 basis upon the closing of the Issuer's initial public offering on June 29, 2018 and had no expiration date.

F2 · derivative.exercise_date: All series of Preferred Stock automatically converted into the Issuer's Common Stock on a 5-for-1 basis upon the closing of the Issuer's initial public offering on June 29, 2018 and had no expiration date.

F2 · derivative.expiration_date: All series of Preferred Stock automatically converted into the Issuer's Common Stock on a 5-for-1 basis upon the closing of the Issuer's initial public offering on June 29, 2018 and had no expiration date.

F4 · ownership.direct: These shares are directly held by 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.

SEC source: 0001104659-18-043853 · a4.xml · derivative · 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

LEVIN MARK J · CIK 0001180428 · 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 · 8,999,999 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.

F2 · derivative.exercise_price: All series of Preferred Stock automatically converted into the Issuer's Common Stock on a 5-for-1 basis upon the closing of the Issuer's initial public offering on June 29, 2018 and had no expiration date.

F2 · price: All series of Preferred Stock automatically converted into the Issuer's Common Stock on a 5-for-1 basis upon the closing of the Issuer's initial public offering on June 29, 2018 and had no expiration date.

F2 · derivative.exercise_date: All series of Preferred Stock automatically converted into the Issuer's Common Stock on a 5-for-1 basis upon the closing of the Issuer's initial public offering on June 29, 2018 and had no expiration date.

F2 · derivative.expiration_date: All series of Preferred Stock automatically converted into the Issuer's Common Stock on a 5-for-1 basis upon the closing of the Issuer's initial public offering on June 29, 2018 and had no expiration date.

F4 · ownership.direct: These shares are directly held by 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.

SEC source: 0001104659-18-043853 · a4.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

LEVIN MARK J · CIK 0001180428 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 9,741,636

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 · shares: Represents the total number of shares of Common Stock received by TRV III upon the conversion of the Issuer's Series B Preferred Stock in connection with the closing of the Issuer's initial public offering.

F2 · price: All series of Preferred Stock automatically converted into the Issuer's Common Stock on a 5-for-1 basis upon the closing of the Issuer's initial public offering on June 29, 2018 and had no expiration date.

F4 · ownership.direct: These shares are directly held by 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.

SEC source: 0001104659-18-043853 · a4.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

LEVIN MARK J · CIK 0001180428 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 9,399,999

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 · shares: Represents the total number of shares of Common Stock received by Third Rock Ventures III, L.P. ("TRV III") upon the conversion of the Issuer's Series A Preferred Stock in connection with the closing of the Issuer's initial public offering.

F2 · price: All series of Preferred Stock automatically converted into the Issuer's Common Stock on a 5-for-1 basis upon the closing of the Issuer's initial public offering on June 29, 2018 and had no expiration date.

F4 · ownership.direct: These shares are directly held by 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.

SEC source: 0000899243-18-017587 · 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

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 7,891,176

F1 · kind: Pursuant to a Rule 10b5-1 trading plan adopted by Third Rock Ventures III, L.P. ("TRV III"), Third Rock Ventures GP III, L.P. ("TRV GP III") and TRV GP III, LLC ("TRV GP III LLC"), TRV III distributed on June 20, 2018, for no consideration, 1,500,000 shares of Common Stock of the Issuer (the "Shares") to its limited partners and to TRV GP III, the general partner of TRV III, representing each such partner's pro rata interest in such Shares. On the same date, TRV GP III distributed, for no consideration, the Shares it received in the distribution by TRV III 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: Pursuant to a Rule 10b5-1 trading plan adopted by Third Rock Ventures III, L.P. ("TRV III"), Third Rock Ventures GP III, L.P. ("TRV GP III") and TRV GP III, LLC ("TRV GP III LLC"), TRV III distributed on June 20, 2018, for no consideration, 1,500,000 shares of Common Stock of the Issuer (the "Shares") to its limited partners and to TRV GP III, the general partner of TRV III, representing each such partner's pro rata interest in such Shares. On the same date, TRV GP III distributed, for no consideration, the Shares it received in the distribution by TRV III 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 III. The general partner of TRV III is TRV GP III. The general partner of TRV GP III is 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.

SEC source: 0001562180-18-002933 · primarydocument.xml · derivative · entry 1

STARR KEVIN P · CIK 0001192603 · Director · 10% owner

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 10,000

Underlying: Common Stock · 10,000 shares

Expires 2028-06-06

F1 · derivative.exercise_date: The stock option award was issued pursuant to the Sage Therapeutics, Inc., 2014 Stock Option and Incentive Plan. The option will vest in full upon the earlier to occur of June 6, 2019 or the day immediately prior to the 2019 Annual Meeting of Sage's stockholders, subject to continued service as a director on such date.

SEC source: 0000899243-18-010410 · doc4.xml · nonDerivative · entry 2

STARR KEVIN P · CIK 0001192603 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 302,817

SEC source: 0000899243-18-010410 · doc4.xml · nonDerivative · entry 1

STARR KEVIN P · CIK 0001192603 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 326,817

SEC source: 0000899243-18-006628 · doc4.xml · nonDerivative · entry 1

STARR KEVIN P · CIK 0001192603 · Director · 10% owner

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 885,104

F1 · kind: Pursuant to a Rule 10b5-1 trading plan adopted by Third Rock Ventures II, L.P. ("TRV II"), Third Rock Ventures GP II, L.P. ("TRV GP II") and TRV GP II, LLC ("TRV GP II LLC"), TRV II distributed on March 7, 2018, for no consideration, 2,000,000 shares of Common Stock of the Issuer (the "Shares") to its limited partners and to TRV GP II, the general partner of TRV II, representing each such partner's pro rata interest in such Shares. On the same date, TRV GP II distributed, for no consideration, the Shares it received in the distribution by TRV II 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: Pursuant to a Rule 10b5-1 trading plan adopted by Third Rock Ventures II, L.P. ("TRV II"), Third Rock Ventures GP II, L.P. ("TRV GP II") and TRV GP II, LLC ("TRV GP II LLC"), TRV II distributed on March 7, 2018, for no consideration, 2,000,000 shares of Common Stock of the Issuer (the "Shares") to its limited partners and to TRV GP II, the general partner of TRV II, representing each such partner's pro rata interest in such Shares. On the same date, TRV GP II distributed, for no consideration, the Shares it received in the distribution by TRV II 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.nature: These shares are directly held by TRV II. The general partner of TRV II is TRV GP II. The general partner of TRV GP II is TRV GP II LLC. The individual managers of TRV GP II LLC are Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of TRV GP II, TRV GP II 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.

SEC source: 0000899243-18-004571 · doc4.xml · nonDerivative · entry 1

STARR KEVIN P · CIK 0001192603 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 37,362

F1 · kind: On February 16, 2018, Third Rock Ventures II, L.P. ("TRV II") distributed for no consideration 510,554 shares of Common Stock of the Issuer (the "Shares") to its limited partners and to Third Rock Ventures GP II, L.P. ("TRV GP II"), the general partner of TRV II, representing each such partner's pro rata interest in such Shares. On the same date, TRV GP II distributed, for no consideration, the Shares it received in the distribution by TRV II 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 February 16, 2018, Third Rock Ventures II, L.P. ("TRV II") distributed for no consideration 510,554 shares of Common Stock of the Issuer (the "Shares") to its limited partners and to Third Rock Ventures GP II, L.P. ("TRV GP II"), the general partner of TRV II, representing each such partner's pro rata interest in such Shares. On the same date, TRV GP II distributed, for no consideration, the Shares it received in the distribution by TRV II 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.nature: These shares are directly held by TRV II. The general partner of TRV II is TRV GP II. The general partner of TRV GP II is TRV GP II, LLC ("TRV GP II LLC"). The individual managers of TRV GP II LLC are Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of TRV GP II, TRV GP II 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.

SEC source: 0000899243-18-000583 · doc4.xml · nonDerivative · entry 1

STARR KEVIN P · CIK 0001192603 · Director · 10% owner

10b5-1 filing: Not disclosed

Ownership: Indirect · See footnote

Disclosed balance after: 680,272

F1 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $42.00 to $42.15, 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.nature: 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.

SEC source: 0000899243-17-028252 · doc4.xml · nonDerivative · entry 1

STARR KEVIN P · CIK 0001192603 · Director · 10% owner

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 2,885,104

F1 · kind: Pursuant to a Rule 10b5-1 trading plan adopted by Third Rock Ventures II, L.P. ("TRV II"), Third Rock Ventures GP II, L.P. ("TRV GP II") and TRV GP II, LLC ("TRV GP II LLC"), TRV II distributed on December 6, 2017, for no consideration, 2,000,000 shares of Common Stock of the Issuer (the "Shares") to its limited partners and to TRV GP II, the general partner of TRV II, representing each such partner's pro rata interest in such Shares. On the same date, TRV GP II distributed, for no consideration, the Shares it received in the distribution by TRV II 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: Pursuant to a Rule 10b5-1 trading plan adopted by Third Rock Ventures II, L.P. ("TRV II"), Third Rock Ventures GP II, L.P. ("TRV GP II") and TRV GP II, LLC ("TRV GP II LLC"), TRV II distributed on December 6, 2017, for no consideration, 2,000,000 shares of Common Stock of the Issuer (the "Shares") to its limited partners and to TRV GP II, the general partner of TRV II, representing each such partner's pro rata interest in such Shares. On the same date, TRV GP II distributed, for no consideration, the Shares it received in the distribution by TRV II 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.nature: These shares are directly held by TRV II. The general partner of TRV II is TRV GP II. The general partner of TRV GP II is TRV GP II LLC. The individual managers of TRV GP II LLC are Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of TRV GP II, TRV GP II 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.

SEC source: 0000899243-17-025425 · doc4.xml · derivative · entry 4

Third Rock Ventures II, L.P. · CIK 0001488495 · 10% owner

Third Rock Ventures GP II, L.P. · CIK 0001614061 · 10% owner

TRV GP II, LLC · CIK 0001614073 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

STARR KEVIN P · CIK 0001192603 · 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 · 1,109,159 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.

F2 · derivative.exercise_price: The Series A Preferred Stock and Series B Preferred Stock converted into Common Stock on a 4.174-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock and Series B Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Preferred Stock had no expiration date.

F2 · derivative.exercise_date: The Series A Preferred Stock and Series B Preferred Stock converted into Common Stock on a 4.174-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock and Series B Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Preferred Stock had no expiration date.

F2 · derivative.expiration_date: The Series A Preferred Stock and Series B Preferred Stock converted into Common Stock on a 4.174-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock and Series B Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Preferred Stock had no expiration date.

F3 · ownership.direct: These shares are directly held by TRV II. The general partner of TRV II is Third Rock Ventures GP II, L.P. ("TRV GP II"). The general partner of TRV GP II is TRV GP II, LLC ("TRV GP II LLC"). The individual managers of TRV GP II LLC are Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of TRV GP II, TRV GP II LLC, Levin, Starr and Tepper 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.

SEC source: 0000899243-17-025425 · doc4.xml · derivative · entry 3

Third Rock Ventures II, L.P. · CIK 0001488495 · 10% owner

Third Rock Ventures GP II, L.P. · CIK 0001614061 · 10% owner

TRV GP II, LLC · CIK 0001614073 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

STARR KEVIN P · CIK 0001192603 · 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 · 1,466,805 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.

F2 · derivative.exercise_price: The Series A Preferred Stock and Series B Preferred Stock converted into Common Stock on a 4.174-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock and Series B Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Preferred Stock had no expiration date.

F2 · derivative.exercise_date: The Series A Preferred Stock and Series B Preferred Stock converted into Common Stock on a 4.174-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock and Series B Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Preferred Stock had no expiration date.

F2 · derivative.expiration_date: The Series A Preferred Stock and Series B Preferred Stock converted into Common Stock on a 4.174-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock and Series B Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Preferred Stock had no expiration date.

F3 · ownership.direct: These shares are directly held by TRV II. The general partner of TRV II is Third Rock Ventures GP II, L.P. ("TRV GP II"). The general partner of TRV GP II is TRV GP II, LLC ("TRV GP II LLC"). The individual managers of TRV GP II LLC are Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of TRV GP II, TRV GP II LLC, Levin, Starr and Tepper 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.

SEC source: 0000899243-17-025425 · doc4.xml · nonDerivative · entry 2

Third Rock Ventures II, L.P. · CIK 0001488495 · 10% owner

Third Rock Ventures GP II, L.P. · CIK 0001614061 · 10% owner

TRV GP II, LLC · CIK 0001614073 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

STARR KEVIN P · CIK 0001192603 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 2,790,964

F4 · kind: Represents shares of Common Stock purchased by TRV II in the Issuer's initial public offering.

F3 · ownership.direct: These shares are directly held by TRV II. The general partner of TRV II is Third Rock Ventures GP II, L.P. ("TRV GP II"). The general partner of TRV GP II is TRV GP II, LLC ("TRV GP II LLC"). The individual managers of TRV GP II LLC are Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of TRV GP II, TRV GP II LLC, Levin, Starr and Tepper 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.

SEC source: 0000899243-17-025425 · doc4.xml · nonDerivative · entry 1

Third Rock Ventures II, L.P. · CIK 0001488495 · 10% owner

Third Rock Ventures GP II, L.P. · CIK 0001614061 · 10% owner

TRV GP II, LLC · CIK 0001614073 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

STARR KEVIN P · CIK 0001192603 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 2,575,964

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 · shares: Represents the total number of shares of Common Stock received by Third Rock Ventures II, L.P. ("TRV II") upon conversion of the Series A Preferred Stock and Series B Preferred Stock of the Issuer in connection with the closing of the Issuer's initial public offering.

F2 · price: The Series A Preferred Stock and Series B Preferred Stock converted into Common Stock on a 4.174-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Preferred Stock and Series B Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Preferred Stock had no expiration date.

F3 · ownership.direct: These shares are directly held by TRV II. The general partner of TRV II is Third Rock Ventures GP II, L.P. ("TRV GP II"). The general partner of TRV GP II is TRV GP II, LLC ("TRV GP II LLC"). The individual managers of TRV GP II LLC are Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of TRV GP II, TRV GP II LLC, Levin, Starr and Tepper 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.

SEC source: 0000899243-17-024464 · doc4.xml · nonDerivative · entry 1

THIRD ROCK VENTURES LP · CIK 0001408591 · 10% owner

Third Rock Ventures GP, L.P. · CIK 0001578976 · 10% owner

TRV GP, LLC · CIK 0001578973 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

STARR KEVIN P · CIK 0001192603 · 10% owner

TEPPER ROBERT I · CIK 0001192595 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 3,320,348

F1 · kind: Pursuant to a Rule 10b5-1 trading plan adopted by Third Rock Ventures, L.P. ("TRV"), TRV distributed on October 18, 2017, for no consideration, 1,000,000 shares of Common Stock of the Issuer (the "Shares") to its limited partners and to Third Rock Ventures GP, L.P. ("TRV GP"), the general partner of TRV, representing each such partner's pro rata interest in such Shares. On the same date, TRV GP distributed, for no consideration, the Shares it received in the distribution by TRV 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: Pursuant to a Rule 10b5-1 trading plan adopted by Third Rock Ventures, L.P. ("TRV"), TRV distributed on October 18, 2017, for no consideration, 1,000,000 shares of Common Stock of the Issuer (the "Shares") to its limited partners and to Third Rock Ventures GP, L.P. ("TRV GP"), the general partner of TRV, representing each such partner's pro rata interest in such Shares. On the same date, TRV GP distributed, for no consideration, the Shares it received in the distribution by TRV 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. The general partner of TRV is TRV GP. The general partner of TRV GP is TRV GP, LLC ("TRV GP LLC"). The individual managers of TRV GP LLC are Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of TRV GP, TRV GP 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.

SEC source: 0000899243-17-024006 · doc4.xml · derivative · entry 3

THIRD ROCK VENTURES LP · CIK 0001408591 · 10% owner

Third Rock Ventures GP, L.P. · CIK 0001578976 · 10% owner

TRV GP, LLC · CIK 0001578973 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

STARR KEVIN P · CIK 0001192603 · 10% owner

TEPPER ROBERT I · CIK 0001192595 · 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 · 2,930,059 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.

F2 · derivative.exercise_price: The Series A Convertible Preferred Stock and Series A-1 Junior Preferred Stock converted into Common Stock on a 9.17-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Convertible Preferred Stock and Series A-1 Junior Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Preferred Stock had no expiration date.

F2 · derivative.exercise_date: The Series A Convertible Preferred Stock and Series A-1 Junior Preferred Stock converted into Common Stock on a 9.17-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Convertible Preferred Stock and Series A-1 Junior Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Preferred Stock had no expiration date.

F2 · derivative.expiration_date: The Series A Convertible Preferred Stock and Series A-1 Junior Preferred Stock converted into Common Stock on a 9.17-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Convertible Preferred Stock and Series A-1 Junior Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Preferred Stock had no expiration date.

F3 · ownership.direct: These shares are directly held by TRV. The general partner of TRV is Third Rock Ventures GP, L.P. ("TRV GP"). The general partner of TRV GP is TRV GP, LLC ("TRV GP LLC"). The individual managers of TRV GP LLC are Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of TRV GP, TRV GP LLC, Levin, Starr and Tepper 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.

SEC source: 0000899243-17-024006 · doc4.xml · derivative · entry 2

THIRD ROCK VENTURES LP · CIK 0001408591 · 10% owner

Third Rock Ventures GP, L.P. · CIK 0001578976 · 10% owner

TRV GP, LLC · CIK 0001578973 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

STARR KEVIN P · CIK 0001192603 · 10% owner

TEPPER ROBERT I · CIK 0001192595 · 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 · 1,033,751 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.

F2 · derivative.exercise_price: The Series A Convertible Preferred Stock and Series A-1 Junior Preferred Stock converted into Common Stock on a 9.17-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Convertible Preferred Stock and Series A-1 Junior Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Preferred Stock had no expiration date.

F2 · derivative.exercise_date: The Series A Convertible Preferred Stock and Series A-1 Junior Preferred Stock converted into Common Stock on a 9.17-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Convertible Preferred Stock and Series A-1 Junior Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Preferred Stock had no expiration date.

F2 · derivative.expiration_date: The Series A Convertible Preferred Stock and Series A-1 Junior Preferred Stock converted into Common Stock on a 9.17-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Convertible Preferred Stock and Series A-1 Junior Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Preferred Stock had no expiration date.

F3 · ownership.direct: These shares are directly held by TRV. The general partner of TRV is Third Rock Ventures GP, L.P. ("TRV GP"). The general partner of TRV GP is TRV GP, LLC ("TRV GP LLC"). The individual managers of TRV GP LLC are Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of TRV GP, TRV GP LLC, Levin, Starr and Tepper 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.

SEC source: 0000899243-17-024006 · doc4.xml · nonDerivative · entry 1

THIRD ROCK VENTURES LP · CIK 0001408591 · 10% owner

Third Rock Ventures GP, L.P. · CIK 0001578976 · 10% owner

TRV GP, LLC · CIK 0001578973 · 10% owner

LEVIN MARK J · CIK 0001180428 · 10% owner

STARR KEVIN P · CIK 0001192603 · 10% owner

TEPPER ROBERT I · CIK 0001192595 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 3,981,437

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 · shares: Represents the total number of shares of Common Stock received by Third Rock Ventures, L.P. ("TRV") upon conversion of the Series A Convertible Preferred Stock and Series A-1 Junior Preferred Stock of the Issuer in connection with the closing of the Issuer's initial public offering.

F2 · price: The Series A Convertible Preferred Stock and Series A-1 Junior Preferred Stock converted into Common Stock on a 9.17-for-one basis upon the closing of the Issuer's initial public offering without payment of consideration. The Series A Convertible Preferred Stock and Series A-1 Junior Preferred Stock were convertible at any time at the holder's election and automatically upon the closing of the Issuer's initial public offering. The Preferred Stock had no expiration date.

F3 · ownership.direct: These shares are directly held by TRV. The general partner of TRV is Third Rock Ventures GP, L.P. ("TRV GP"). The general partner of TRV GP is TRV GP, LLC ("TRV GP LLC"). The individual managers of TRV GP LLC are Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of TRV GP, TRV GP LLC, Levin, Starr and Tepper 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.

SEC source: 0000899243-17-023510 · doc4.xml · nonDerivative · entry 1

STARR KEVIN P · CIK 0001192603 · Director · 10% owner

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 70,763