STARR KEVIN P

SEC source: 0000899243-17-022949 · 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: 4,885,104

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 September 28, 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 September 28, 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: 0000899243-17-022635 · doc4.xml · nonDerivative · entry 1

STARR KEVIN P · CIK 0001192603 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 547,916

F1 · kind: On September 27, 2017, Third Rock Ventures II, L.P. ("TRV II") distributed for no consideration 545,000 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 September 27, 2017, Third Rock Ventures II, L.P. ("TRV II") distributed for no consideration 545,000 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: 0000899243-17-022638 · doc4.xml · nonDerivative · entry 2

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 6,885,104

F1 · ownership.nature: These shares are directly held by Third Rock Ventures II, L.P. ("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 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: 0000899243-17-022638 · 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: 7,285,104

F1 · ownership.nature: These shares are directly held by Third Rock Ventures II, L.P. ("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 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: 0000899243-17-021892 · doc4.xml · nonDerivative · entry 2

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 7,486,504

F2 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $42.20 to $42.45, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (2).

F1 · ownership.nature: These shares are directly held by Third Rock Ventures II, L.P. ("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 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: 0000899243-17-021892 · 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: 7,487,404

F1 · ownership.nature: These shares are directly held by Third Rock Ventures II, L.P. ("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 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: 0000899243-17-018549 · doc4.xml · nonDerivative · entry 1

STARR KEVIN P · CIK 0001192603 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 1,092,916

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 July 18, 2017, for no consideration, 800,000 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 July 18, 2017, for no consideration, 800,000 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: 0000899243-17-018238 · 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: 4,320,348

F1 · kind: Pursuant to a Rule 10b5-1 trading plan adopted by Third Rock Ventures, L.P. ("TRV"), TRV distributed on July 13, 2017, for no consideration, 850,000 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 July 13, 2017, for no consideration, 850,000 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: 0000899243-17-016554 · 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

TEPPER ROBERT I · CIK 0001192595 · 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: 2,475,191

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 June 14, 2017, for no consideration, 1,000,000 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 June 14, 2017, for no consideration, 1,000,000 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.direct: 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: 0000899243-17-016567 · doc4.xml · derivative · entry 1

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 11,000

Underlying: Common Stock · 11,000 shares

Expires 2027-06-13

F1 · derivative.exercise_date: The shares subject to this option shall vest and become exercisable in 12 equal monthly installments with the first installment on July 14, 2017, such that this option is fully exercisable on June 14, 2018. This option is subject to full acceleration of vesting with respect to all then-unvested shares upon the consummation of a Sale Event (as defined in the issuer's 2015 Stock Option and Incentive Plan).

SEC source: 0001562180-17-002242 · primarydocument.xml · derivative · entry 1

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 14,000

Underlying: Common Stock · 14,000 shares

Expires 2027-06-07

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 7, 2018 or the day immediately prior to the 2018 Annual Meeting of Sage's stockholders, subject to continued service as a director on such date.

SEC source: 0001553878-17-000035 · edgardoc.xml · derivative · entry 1

STARR KEVIN P · CIK 0001192603 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 11,250

Underlying: Common Stock · 11,250 shares

Expires 2027-06-01

SEC source: 0000899243-17-013908 · doc4.xml · nonDerivative · 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

TEPPER ROBERT I · CIK 0001192595 · 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: 3,475,191

F1 · kind: Reflects gifts by Mark Levin ("Levin"). The remaining shares are directly held by Levin.

F2 · 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 May 17, 2017, for no consideration, 1,000,000 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.

F3 · ownership.direct: 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 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: 0000899243-17-013908 · 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

TEPPER ROBERT I · CIK 0001192595 · 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: 163,996

F1 · shares: Reflects gifts by Mark Levin ("Levin"). The remaining shares are directly held by Levin.

F1 · ownership.direct: Reflects gifts by Mark Levin ("Levin"). The remaining shares are directly held by Levin.

SEC source: 0000899243-17-010312 · 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: 9,391,176

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 April 12, 2017, for no consideration, 920,000 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 April 12, 2017, for no consideration, 920,000 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: 0000899243-17-010309 · doc4.xml · nonDerivative · entry 1

STARR KEVIN P · CIK 0001192603 · 10% owner

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 31,419

SEC source: 0000899243-17-013908 · 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

TEPPER ROBERT I · CIK 0001192595 · 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: 165,704

F1 · shares: Reflects gifts by Mark Levin ("Levin"). The remaining shares are directly held by Levin.

F1 · ownership.direct: Reflects gifts by Mark Levin ("Levin"). The remaining shares are directly held by Levin.

SEC source: 0000899243-17-009646 · 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

TEPPER ROBERT I · CIK 0001192595 · 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: 4,475,191

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 April 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 April 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.direct: 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: 0000899243-17-009102 · 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: 7,687,754

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 30, 2017, for no consideration, 850,000 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 30, 2017, for no consideration, 850,000 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: 0000899243-17-008731 · 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

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: 5,170,348

F2 · price: This price is a weighted average price. These shares were sold in multiple transactions at prices ranging from $18.00 to $18.45, inclusive. Each of the reporting persons undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (2).

F1 · ownership.direct: These shares are directly held by Third Rock Ventures, 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: 0000899243-17-008731 · 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: 5,820,348

F1 · ownership.direct: These shares 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: 0000899243-17-007785 · 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: 6,820,348

F1 · kind: Pursuant to a Rule 10b5-1 trading plan adopted by Third Rock Ventures, L.P. ("TRV"), TRV distributed on March 15, 2017, for no consideration, 850,000 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 March 15, 2017, for no consideration, 850,000 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: 0000899243-17-006623 · doc4.xml · nonDerivative · entry 5

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

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

TEPPER ROBERT I · CIK 0001192595 · 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: 146,208

F6 · price: This price is a weighted average price. These shares were sold in multiple transactions at prices ranging from $28.50 to $28.975, inclusive.

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

SEC source: 0000899243-17-006623 · doc4.xml · nonDerivative · 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

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

TEPPER ROBERT I · CIK 0001192595 · 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: 157,108

F5 · price: This price is a weighted average price. These shares were sold in multiple transactions at prices ranging from $27.35 to $28.275, inclusive.

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

SEC source: 0000899243-17-006623 · doc4.xml · nonDerivative · 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

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

TEPPER ROBERT I · CIK 0001192595 · 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: 164,387

F3 · price: This price is a weighted average price. These shares were sold in multiple transactions at prices ranging from $26.35 to $27.30, inclusive. Levin 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 footnotes (3), (5) and (6) to this Form 4.

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

SEC source: 0000899243-17-006623 · 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

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

TEPPER ROBERT I · CIK 0001192595 · 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: 285,713

F2 · ownership.direct: These shares are directly held by Third Rock Ventures III, L.P. ("TRV III"). The general partner of TRV III is Third Rock Ventures GP III, L.P. ("TRV GP III"). The general partner of TRV GP III is TRV GP III, LLC ("TRV GP III LLC"). The individual managers of TRV GP III LLC are Levin, Starr and 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: 0000899243-17-006623 · 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

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

TEPPER ROBERT I · CIK 0001192595 · 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: 6,475,191

F1 · ownership.direct: These shares are directly held by Third Rock Ventures II, L.P. ("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 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: 0000899243-17-005572 · 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

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: 3,453,753

F1 · kind: Pursuant to a Rule 10b5-1 trading plan adopted by Third Rock Ventures II, L.P. ("TRV II"), TRV II distributed on February 27, 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 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: Pursuant to a Rule 10b5-1 trading plan adopted by Third Rock Ventures II, L.P. ("TRV II"), TRV II distributed on February 27, 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 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.direct: 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: 0000899243-17-003297 · 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

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: 4,453,753

F1 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $35.25 to $35.45, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (1).

F2 · ownership.direct: These shares are directly held by Third Rock Ventures II, L.P. ("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 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: 0000899243-17-002744 · 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

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

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 · 3,048,780 shares

Expires not disclosed

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

F3 · derivative.exercise_price: Each share of Series A Preferred Stock converted into Common Stock on a one-for-3.69 basis upon the closing of the Issuer's initial public offering without payment or consideration. Each share of 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 Preferred Stock had no expiration date.

F3 · derivative.exercise_date: Each share of Series A Preferred Stock converted into Common Stock on a one-for-3.69 basis upon the closing of the Issuer's initial public offering without payment or consideration. Each share of 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 Preferred Stock had no expiration date.

F3 · derivative.expiration_date: Each share of Series A Preferred Stock converted into Common Stock on a one-for-3.69 basis upon the closing of the Issuer's initial public offering without payment or consideration. Each share of 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 Preferred Stock had no expiration date.

F5 · 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 Levin, Starr and 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: 0000899243-17-002744 · 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

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

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 9,688,344 shares

Expires not disclosed

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

F3 · derivative.exercise_price: Each share of Series A Preferred Stock converted into Common Stock on a one-for-3.69 basis upon the closing of the Issuer's initial public offering without payment or consideration. Each share of 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 Preferred Stock had no expiration date.

F3 · derivative.exercise_date: Each share of Series A Preferred Stock converted into Common Stock on a one-for-3.69 basis upon the closing of the Issuer's initial public offering without payment or consideration. Each share of 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 Preferred Stock had no expiration date.

F3 · derivative.expiration_date: Each share of Series A Preferred Stock converted into Common Stock on a one-for-3.69 basis upon the closing of the Issuer's initial public offering without payment or consideration. Each share of 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 Preferred Stock had no expiration date.

F4 · 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: 0000899243-17-002744 · 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

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

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 3,048,780

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

F3 · price: Each share of Series A Preferred Stock converted into Common Stock on a one-for-3.69 basis upon the closing of the Issuer's initial public offering without payment or consideration. Each share of 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 Preferred Stock had no expiration date.

F5 · 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 Levin, Starr and 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: 0000899243-17-002744 · 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

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

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 10,230,349

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 Series A Preferred Stock in connection with the closing of the Issuer's initial public offering.

F3 · price: Each share of Series A Preferred Stock converted into Common Stock on a one-for-3.69 basis upon the closing of the Issuer's initial public offering without payment or consideration. Each share of 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 Preferred Stock had no expiration date.

F4 · 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: 0000899243-17-001848 · doc4.xml · nonDerivative · entry 1

STARR KEVIN P · CIK 0001192603 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 1,892,916

F1 · kind: On January 23, 2017, Third Rock Ventures II, L.P. ("TRV II") distributed, 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 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 January 23, 2017, Third Rock Ventures II, L.P. ("TRV II") distributed, 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 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: 0000899243-16-036195 · 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: 10,311,176

F1 · kind: On December 19, 2016, Third Rock Ventures III, L.P. ("TRV III") distributed, for no consideration, 750,000 shares of Common Stock of the Issuer (the "Shares") to its limited partners and to Third Rock Ventures GP III, L.P. ("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: On December 19, 2016, Third Rock Ventures III, L.P. ("TRV III") distributed, for no consideration, 750,000 shares of Common Stock of the Issuer (the "Shares") to its limited partners and to Third Rock Ventures GP III, L.P. ("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 ("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: 0000899243-16-036208 · doc4.xml · nonDerivative · entry 1

STARR KEVIN P · CIK 0001192603 · 10% owner

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 0

SEC source: 0000899243-16-036056 · doc4.xml · nonDerivative · entry 1

STARR KEVIN P · CIK 0001192603 · 10% owner

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 82,544

F1 · price: The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $15.95 to $16.25, 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).

SEC source: 0000899243-16-035757 · doc4.xml · nonDerivative · entry 1

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

STARR KEVIN P · CIK 0001192603 · 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

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: 7,475,191

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 14, 2016, 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 14, 2016, 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.direct: 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: 0000899243-16-034695 · 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: 8,537,754

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 November 29, 2016, for no consideration, 850,000 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 November 29, 2016, for no consideration, 850,000 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: 0000899243-16-033679 · 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

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

TEPPER ROBERT I · CIK 0001192595 · 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: 1,285,713

F2 · ownership.direct: These shares are directly held by Third Rock Ventures III, L.P. ("TRV III"). The general partner of TRV III is Third Rock Ventures GP III, L.P. ("TRV GP III"). The general partner of TRV GP III is TRV GP III, LLC ("TRV GP III LLC"). The individual managers of TRV GP III LLC are Levin, Starr and 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: 0000899243-16-033679 · 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

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

TEPPER ROBERT I · CIK 0001192595 · 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: 9,475,191

F1 · ownership.direct: These shares are directly held by Third Rock Ventures II, L.P. ("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 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: 0000899243-16-033012 · 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: 7,670,348

F1 · kind: On November 7, 2016, Third Rock Ventures, L.P. ("TRV") distributed, 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: On November 7, 2016, Third Rock Ventures, L.P. ("TRV") distributed, 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: 0000899243-16-032856 · 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

TEPPER ROBERT I · CIK 0001192595 · 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: 10,475,191

F1 · kind: On November 3, 2016, Third Rock Ventures II, L.P. ("TRV II") distributed, for no consideration, 2,000,000 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 November 3, 2016, Third Rock Ventures II, L.P. ("TRV II") distributed, for no consideration, 2,000,000 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.direct: 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: 0000899243-16-028604 · doc4.xml · nonDerivative · entry 1

STARR KEVIN P · CIK 0001192603 · 10% owner

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 0

F1 · shares: Such shares were received as a distribution from Third Rock Ventures III, L.P. ("TRV III") on August 16, 2016 in a transaction exempt pursuant to Rule 16a-13 and Rule 16a-9.