FATE

SEC source: 0001209191-20-000242 · doc4.xml · nonDerivative · entry 1

Shoemaker Daniel D · CIK 0001586892 · Chief Scientific Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 148,791

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

F1 · kind: This transaction was effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on September 20, 2018 and modified on December 10, 2018.

SEC source: 0001209191-19-061760 · doc4.xml · derivative · entry 6

Wolchko J Scott · CIK 0001586893 · Director · President and CEO

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 139,600

Underlying: Common Stock · 25,000 shares

Expires 2026-01-11

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

F1 · kind: This transaction was effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on July 19, 2019.

F5 · price: Not applicable.

F4 · derivative.exercise_date: The shares subject to this option vested and became exercisable in 48 equal monthly installments beginning on January 1, 2016 such that this option was fully exercisable on December 1, 2019.

SEC source: 0001209191-19-061760 · doc4.xml · nonDerivative · entry 4

Wolchko J Scott · CIK 0001586893 · Director · President and CEO

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 353,969

F1 · kind: This transaction was effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on July 19, 2019.

F3 · price: Represents the weighted average sale price of the shares sold ranging from $20.00 to $20.38 per share. The Reporting Person will provide, upon request by the Commission staff, the Issuer, or a security holder of the Issuer, full information regarding the number of shares sold at each price.

SEC source: 0001209191-19-061760 · doc4.xml · nonDerivative · entry 3

Wolchko J Scott · CIK 0001586893 · Director · President and CEO

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 378,969

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

F1 · kind: This transaction was effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on July 19, 2019.

SEC source: 0001209191-19-061760 · doc4.xml · derivative · entry 5

Wolchko J Scott · CIK 0001586893 · Director · President and CEO

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 164,600

Underlying: Common Stock · 25,000 shares

Expires 2026-01-11

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

F1 · kind: This transaction was effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on July 19, 2019.

F5 · price: Not applicable.

F4 · derivative.exercise_date: The shares subject to this option vested and became exercisable in 48 equal monthly installments beginning on January 1, 2016 such that this option was fully exercisable on December 1, 2019.

SEC source: 0001209191-19-061760 · doc4.xml · nonDerivative · entry 2

Wolchko J Scott · CIK 0001586893 · Director · President and CEO

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 353,969

F1 · kind: This transaction was effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on July 19, 2019.

F2 · price: Represents the weighted average sale price of the shares sold ranging from $20.00 to $20.71 per share. The Reporting Person will provide, upon request by the Commission staff, the Issuer, or a security holder of the Issuer, full information regarding the number of shares sold at each price.

SEC source: 0001209191-19-061760 · doc4.xml · nonDerivative · entry 1

Wolchko J Scott · CIK 0001586893 · Director · President and CEO

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 378,969

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

F1 · kind: This transaction was effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on July 19, 2019.

SEC source: 0001209191-19-053280 · doc4.xml · nonDerivative · entry 1

Wolchko J Scott · CIK 0001586893 · Director · President and CEO

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 353,969

F1 · shares: Required number of shares sold by the reporting person to cover tax withholding obligations in connection with the vesting of 43,125 shares of Common Stock underlying restricted stock units ("RSUs") granted to the reporting person on October 15, 2015. This sale was made pursuant to an irrevocable election on December 22, 2018 by the reporting person to satisfy tax withholding obligations through a "sell to cover" transaction and does not represent a discretionary trade by the reporting person.

F2 · price: The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $13.94 to $14.695 per share. 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 range set forth in this footnote.

F3 · balance_after: All remaining shares of Common Stock held by the reporting person are subject to the terms of a lock-up agreement with Jefferies LLC and Citigroup Global Markets Inc. (the "Representatives"), as representatives of the underwriters in the Company's public offering pursuant to a prospectus supplement dated September 11, 2019, pursuant to which the reporting person agreed, without the prior written consent of the Representatives, and subject to limited exceptions, not to sell, offer to sell, contract to sell or lend, effect any short sale, pledge, hypothecate or grant any security interest in, or otherwise transfer or dispose of, any shares of Common Stock, either directly or indirectly.

SEC source: 0001209191-19-053277 · doc4.xml · nonDerivative · entry 1

Valamehr Bahram · CIK 0001748177 · Chief Development Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 66,758

F1 · shares: Required number of shares sold by the reporting person to cover tax withholding obligations in connection with the vesting of 17,500 shares of Common Stock underlying restricted stock units ("RSUs") granted to the reporting person on October 15, 2015. This sale was made pursuant to an irrevocable election on December 18, 2018 by the reporting person to satisfy tax withholding obligations through a "sell to cover" transaction and does not represent a discretionary trade by the reporting person.

F2 · price: The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $13.94 to $14.35 per share. 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 range set forth in this footnote.

F3 · balance_after: All remaining shares of Common Stock held by the reporting person are subject to the terms of a lock-up agreement with Jefferies LLC and Citigroup Global Markets Inc. (the "Representatives"), as representatives of the underwriters in the Company's public offering pursuant to a prospectus supplement dated September 11, 2019, pursuant to which the reporting person agreed, without the prior written consent of the Representatives, and subject to limited exceptions, not to sell, offer to sell, contract to sell or lend, effect any short sale, pledge, hypothecate or grant any security interest in, or otherwise transfer or dispose of, any shares of Common Stock, either directly or indirectly.

SEC source: 0001209191-19-053275 · doc4.xml · nonDerivative · entry 1

TAHL CINDY · CIK 0001655472 · General Counsel and Secretary

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 80,218

F1 · shares: Required number of shares sold by the reporting person to cover tax withholding obligations in connection with the vesting of 20,000 shares of Common Stock underlying restricted stock units ("RSUs") granted to the reporting person on October 15, 2015. This sale was made pursuant to an irrevocable election on December 18, 2018 by the reporting person to satisfy tax withholding obligations through a "sell to cover" transaction and does not represent a discretionary trade by the reporting person.

F2 · price: The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $13.94 to $14.58 per share. 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 range set forth in this footnote.

F3 · balance_after: All remaining shares of Common Stock held by the reporting person are subject to the terms of a lock-up agreement with Jefferies LLC and Citigroup Global Markets Inc. (the "Representatives"), as representatives of the underwriters in the Company's public offering pursuant to a prospectus supplement dated September 11, 2019, pursuant to which the reporting person agreed, without the prior written consent of the Representatives, and subject to limited exceptions, not to sell, offer to sell, contract to sell or lend, effect any short sale, pledge, hypothecate or grant any security interest in, or otherwise transfer or dispose of, any shares of Common Stock, either directly or indirectly.

SEC source: 0001209191-19-053272 · doc4.xml · nonDerivative · entry 1

Shoemaker Daniel D · CIK 0001586892 · Chief Scientific Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 123,791

F1 · shares: Required number of shares sold by the reporting person to cover tax withholding obligations in connection with the vesting of 33,000 shares of Common Stock underlying restricted stock units ("RSUs") granted to the reporting person on October 15, 2015. This sale was made pursuant to an irrevocable election on December 19, 2018 by the reporting person to satisfy tax withholding obligations through a "sell to cover" transaction and does not represent a discretionary trade by the reporting person.

F2 · price: The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $13.94 to $14.59 per share. 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 range set forth in this footnote.

F3 · balance_after: All remaining shares of Common Stock held by the reporting person are subject to the terms of a lock-up agreement with Jefferies LLC and Citigroup Global Markets Inc. (the "Representatives"), as representatives of the underwriters in the Company's public offering pursuant to a prospectus supplement dated September 11, 2019, pursuant to which the reporting person agreed, without the prior written consent of the Representatives, and subject to limited exceptions, not to sell, offer to sell, contract to sell or lend, effect any short sale, pledge, hypothecate or grant any security interest in, or otherwise transfer or dispose of, any shares of Common Stock, either directly or indirectly.

SEC source: 0001144204-19-044910 · tv529510_4.xml · nonDerivative · entry 1

Redmile Group, LLC · CIK 0001425738 · Director · 10% owner

Green Jeremy · CIK 0001650527 · Director · 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: 11,216,809

F1 · ownership.nature: These securities are directly owned by certain private investment vehicles and separately managed accounts managed by Redmile Group, LLC ("Redmile") and may be deemed beneficially owned by Redmile as investment manager of such private investment vehicles and separately managed accounts. The reported securities may also be deemed beneficially owned by Jeremy Green as the principal of Redmile. The Reporting Persons disclaim beneficial ownership of the reported securities except to the extent of their pecuniary interest therein, and this report shall not be deemed an admission that such Reporting Persons are the beneficial owners of the securities for purposes of Section 16 of the Securities Exchange Act of 1934, as amended, or for any other purpose.

F2 · ownership.nature: Michael Lee, a member of the board of directors of the Issuer and a managing director of Redmile, was elected to the board of the Issuer as a representative of Redmile. As a result, the Reporting Persons are directors by deputization for purposes of Section 16 of the Securities Exchange Act of 1934, as amended.

SEC source: 0000899243-19-020915 · doc4.xml · nonDerivative · entry 8

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 11,034

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F4 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $22.50 to $22.62, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (4) to this Form 4.

F7 · ownership.nature: The reportable securities are owned directly by PVPSFF V. PVM V is the general partner of PVPSFF V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Flint and McGuire are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVPSFF V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-19-020915 · doc4.xml · nonDerivative · entry 6

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 7,539

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F4 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $22.50 to $22.62, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (4) to this Form 4.

F6 · ownership.nature: The reportable securities are owned directly by PVPFF V. PVM V is the general partner of PVPFF V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Flint and McGuire are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVPFF V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-19-020915 · doc4.xml · nonDerivative · entry 4

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 21,438

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F4 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $22.50 to $22.62, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (4) to this Form 4.

F5 · ownership.nature: The reportable securities are owned directly by PVPE V. PVM V is the general partner of PVPE V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Flint and McGuire are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVPE V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-19-020915 · doc4.xml · nonDerivative · entry 2

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 1,099,772

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F4 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $22.50 to $22.62, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (4) to this Form 4.

F3 · ownership.nature: The reportable securities are owned directly by PVP V. Polaris Venture Management Co. V, L.L.C. ("PVM V") is the general partner of PVP V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Jonathan A. Flint ("Flint") and Terrance G. McGuire ("McGuire") are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVP V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-19-020915 · doc4.xml · nonDerivative · entry 7

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 11,333

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F2 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $22.50 to $22.77, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the United States Securities 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) to this Form 4.

F7 · ownership.nature: The reportable securities are owned directly by PVPSFF V. PVM V is the general partner of PVPSFF V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Flint and McGuire are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVPSFF V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-19-020915 · doc4.xml · nonDerivative · entry 5

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 7,743

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F2 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $22.50 to $22.77, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the United States Securities 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) to this Form 4.

F6 · ownership.nature: The reportable securities are owned directly by PVPFF V. PVM V is the general partner of PVPFF V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Flint and McGuire are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVPFF V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-19-020915 · doc4.xml · nonDerivative · entry 3

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 22,019

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F2 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $22.50 to $22.77, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the United States Securities 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) to this Form 4.

F5 · ownership.nature: The reportable securities are owned directly by PVPE V. PVM V is the general partner of PVPE V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Flint and McGuire are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVPE V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-19-020915 · doc4.xml · nonDerivative · entry 1

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 1,129,554

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F2 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $22.50 to $22.77, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the United States Securities 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) to this Form 4.

F3 · ownership.nature: The reportable securities are owned directly by PVP V. Polaris Venture Management Co. V, L.L.C. ("PVM V") is the general partner of PVP V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Jonathan A. Flint ("Flint") and Terrance G. McGuire ("McGuire") are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVP V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0001144204-19-037477 · tv526464_4.xml · derivative · entry 3

Redmile Group, LLC · CIK 0001425738 · Director · 10% owner

Green Jeremy · CIK 0001650527 · Director · 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 · 125,000 shares

Expires not disclosed

F1 · derivative.exercise_price: The Class A Convertible Preferred Stock is convertible into shares of the Issuer's common stock in accordance with the terms of the Issuer's Amended and Restated Certificate of Incorporation and Certificate of Designation of Preferences, Rights and Limitations of Class A Convertible Preferred Stock at any time and from time to time at the holder's election using a calculation based on the stated value of the shares and the conversion rate in effect at the time of conversion. The shares of Class A Convertible Preferred Stock will currently convert on a 1-for-5 basis and such conversion rate is reflected in the amount listed under Column 7.

F2 · derivative.exercise_price: The terms of the Class A Convertible Preferred Stock provide that the holder may not convert any shares of Class A Convertible Preferred Stock if, after giving effect to the attempted conversion, the holder and its affiliates would collectively beneficially own more than 9.99% of the number of shares of Common Stock outstanding after giving effect to such attempted conversion. The Class A Convertible Preferred Stock has no expiration date.

F7 · kind: Gift to a charitable foundation.

F1 · derivative.exercise_date: The Class A Convertible Preferred Stock is convertible into shares of the Issuer's common stock in accordance with the terms of the Issuer's Amended and Restated Certificate of Incorporation and Certificate of Designation of Preferences, Rights and Limitations of Class A Convertible Preferred Stock at any time and from time to time at the holder's election using a calculation based on the stated value of the shares and the conversion rate in effect at the time of conversion. The shares of Class A Convertible Preferred Stock will currently convert on a 1-for-5 basis and such conversion rate is reflected in the amount listed under Column 7.

F2 · derivative.exercise_date: The terms of the Class A Convertible Preferred Stock provide that the holder may not convert any shares of Class A Convertible Preferred Stock if, after giving effect to the attempted conversion, the holder and its affiliates would collectively beneficially own more than 9.99% of the number of shares of Common Stock outstanding after giving effect to such attempted conversion. The Class A Convertible Preferred Stock has no expiration date.

F1 · derivative.expiration_date: The Class A Convertible Preferred Stock is convertible into shares of the Issuer's common stock in accordance with the terms of the Issuer's Amended and Restated Certificate of Incorporation and Certificate of Designation of Preferences, Rights and Limitations of Class A Convertible Preferred Stock at any time and from time to time at the holder's election using a calculation based on the stated value of the shares and the conversion rate in effect at the time of conversion. The shares of Class A Convertible Preferred Stock will currently convert on a 1-for-5 basis and such conversion rate is reflected in the amount listed under Column 7.

F2 · derivative.expiration_date: The terms of the Class A Convertible Preferred Stock provide that the holder may not convert any shares of Class A Convertible Preferred Stock if, after giving effect to the attempted conversion, the holder and its affiliates would collectively beneficially own more than 9.99% of the number of shares of Common Stock outstanding after giving effect to such attempted conversion. The Class A Convertible Preferred Stock has no expiration date.

F5 · ownership.direct: Michael Lee, a member of the board of directors of the Issuer and a managing director of Redmile, was elected to the board of the Issuer as a representative of Redmile. As a result, the Reporting Persons are directors by deputization for purposes of Section 16 of the Securities Exchange Act of 1934, as amended.

F6 · ownership.direct: These securities are directly owned by Jeremy Green. Redmile disclaims beneficial ownership of the reported securities except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that Redmile is the beneficial owner of the securities for purposes of Section 16 of the Securities Exchange Act of 1934, as amended, or for any other purpose.

SEC source: 0001144204-19-037477 · tv526464_4.xml · derivative · entry 2

Redmile Group, LLC · CIK 0001425738 · Director · 10% owner

Green Jeremy · CIK 0001650527 · Director · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 25,000

Underlying: Common Stock · 125,000 shares

Expires not disclosed

F1 · derivative.exercise_price: The Class A Convertible Preferred Stock is convertible into shares of the Issuer's common stock in accordance with the terms of the Issuer's Amended and Restated Certificate of Incorporation and Certificate of Designation of Preferences, Rights and Limitations of Class A Convertible Preferred Stock at any time and from time to time at the holder's election using a calculation based on the stated value of the shares and the conversion rate in effect at the time of conversion. The shares of Class A Convertible Preferred Stock will currently convert on a 1-for-5 basis and such conversion rate is reflected in the amount listed under Column 7.

F2 · derivative.exercise_price: The terms of the Class A Convertible Preferred Stock provide that the holder may not convert any shares of Class A Convertible Preferred Stock if, after giving effect to the attempted conversion, the holder and its affiliates would collectively beneficially own more than 9.99% of the number of shares of Common Stock outstanding after giving effect to such attempted conversion. The Class A Convertible Preferred Stock has no expiration date.

F3 · kind: Distribution from a private investment vehicle managed by Redmile Group, LLC ("Redmile") to an affiliate of Redmile that is a shareholder of of such private investment vehicle to Jeremy Green, who is a member of such affiliate.

F3 · price: Distribution from a private investment vehicle managed by Redmile Group, LLC ("Redmile") to an affiliate of Redmile that is a shareholder of of such private investment vehicle to Jeremy Green, who is a member of such affiliate.

F1 · derivative.exercise_date: The Class A Convertible Preferred Stock is convertible into shares of the Issuer's common stock in accordance with the terms of the Issuer's Amended and Restated Certificate of Incorporation and Certificate of Designation of Preferences, Rights and Limitations of Class A Convertible Preferred Stock at any time and from time to time at the holder's election using a calculation based on the stated value of the shares and the conversion rate in effect at the time of conversion. The shares of Class A Convertible Preferred Stock will currently convert on a 1-for-5 basis and such conversion rate is reflected in the amount listed under Column 7.

F2 · derivative.exercise_date: The terms of the Class A Convertible Preferred Stock provide that the holder may not convert any shares of Class A Convertible Preferred Stock if, after giving effect to the attempted conversion, the holder and its affiliates would collectively beneficially own more than 9.99% of the number of shares of Common Stock outstanding after giving effect to such attempted conversion. The Class A Convertible Preferred Stock has no expiration date.

F1 · derivative.expiration_date: The Class A Convertible Preferred Stock is convertible into shares of the Issuer's common stock in accordance with the terms of the Issuer's Amended and Restated Certificate of Incorporation and Certificate of Designation of Preferences, Rights and Limitations of Class A Convertible Preferred Stock at any time and from time to time at the holder's election using a calculation based on the stated value of the shares and the conversion rate in effect at the time of conversion. The shares of Class A Convertible Preferred Stock will currently convert on a 1-for-5 basis and such conversion rate is reflected in the amount listed under Column 7.

F2 · derivative.expiration_date: The terms of the Class A Convertible Preferred Stock provide that the holder may not convert any shares of Class A Convertible Preferred Stock if, after giving effect to the attempted conversion, the holder and its affiliates would collectively beneficially own more than 9.99% of the number of shares of Common Stock outstanding after giving effect to such attempted conversion. The Class A Convertible Preferred Stock has no expiration date.

F5 · ownership.direct: Michael Lee, a member of the board of directors of the Issuer and a managing director of Redmile, was elected to the board of the Issuer as a representative of Redmile. As a result, the Reporting Persons are directors by deputization for purposes of Section 16 of the Securities Exchange Act of 1934, as amended.

F6 · ownership.direct: These securities are directly owned by Jeremy Green. Redmile disclaims beneficial ownership of the reported securities except to the extent of its pecuniary interest therein, if any, and this report shall not be deemed an admission that Redmile is the beneficial owner of the securities for purposes of Section 16 of the Securities Exchange Act of 1934, as amended, or for any other purpose.

SEC source: 0001144204-19-037477 · tv526464_4.xml · derivative · entry 1

Redmile Group, LLC · CIK 0001425738 · Director · 10% owner

Green Jeremy · CIK 0001650527 · Director · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 2,794,549

Underlying: Common Stock · 125,000 shares

Expires not disclosed

F1 · derivative.exercise_price: The Class A Convertible Preferred Stock is convertible into shares of the Issuer's common stock in accordance with the terms of the Issuer's Amended and Restated Certificate of Incorporation and Certificate of Designation of Preferences, Rights and Limitations of Class A Convertible Preferred Stock at any time and from time to time at the holder's election using a calculation based on the stated value of the shares and the conversion rate in effect at the time of conversion. The shares of Class A Convertible Preferred Stock will currently convert on a 1-for-5 basis and such conversion rate is reflected in the amount listed under Column 7.

F2 · derivative.exercise_price: The terms of the Class A Convertible Preferred Stock provide that the holder may not convert any shares of Class A Convertible Preferred Stock if, after giving effect to the attempted conversion, the holder and its affiliates would collectively beneficially own more than 9.99% of the number of shares of Common Stock outstanding after giving effect to such attempted conversion. The Class A Convertible Preferred Stock has no expiration date.

F3 · kind: Distribution from a private investment vehicle managed by Redmile Group, LLC ("Redmile") to an affiliate of Redmile that is a shareholder of of such private investment vehicle to Jeremy Green, who is a member of such affiliate.

F3 · price: Distribution from a private investment vehicle managed by Redmile Group, LLC ("Redmile") to an affiliate of Redmile that is a shareholder of of such private investment vehicle to Jeremy Green, who is a member of such affiliate.

F1 · derivative.exercise_date: The Class A Convertible Preferred Stock is convertible into shares of the Issuer's common stock in accordance with the terms of the Issuer's Amended and Restated Certificate of Incorporation and Certificate of Designation of Preferences, Rights and Limitations of Class A Convertible Preferred Stock at any time and from time to time at the holder's election using a calculation based on the stated value of the shares and the conversion rate in effect at the time of conversion. The shares of Class A Convertible Preferred Stock will currently convert on a 1-for-5 basis and such conversion rate is reflected in the amount listed under Column 7.

F2 · derivative.exercise_date: The terms of the Class A Convertible Preferred Stock provide that the holder may not convert any shares of Class A Convertible Preferred Stock if, after giving effect to the attempted conversion, the holder and its affiliates would collectively beneficially own more than 9.99% of the number of shares of Common Stock outstanding after giving effect to such attempted conversion. The Class A Convertible Preferred Stock has no expiration date.

F1 · derivative.expiration_date: The Class A Convertible Preferred Stock is convertible into shares of the Issuer's common stock in accordance with the terms of the Issuer's Amended and Restated Certificate of Incorporation and Certificate of Designation of Preferences, Rights and Limitations of Class A Convertible Preferred Stock at any time and from time to time at the holder's election using a calculation based on the stated value of the shares and the conversion rate in effect at the time of conversion. The shares of Class A Convertible Preferred Stock will currently convert on a 1-for-5 basis and such conversion rate is reflected in the amount listed under Column 7.

F2 · derivative.expiration_date: The terms of the Class A Convertible Preferred Stock provide that the holder may not convert any shares of Class A Convertible Preferred Stock if, after giving effect to the attempted conversion, the holder and its affiliates would collectively beneficially own more than 9.99% of the number of shares of Common Stock outstanding after giving effect to such attempted conversion. The Class A Convertible Preferred Stock has no expiration date.

F4 · ownership.nature: These securities are directly owned by certain private investment vehicles and separately managed accounts managed by Redmile and may be deemed beneficially owned by Redmile as investment manager of such private investment vehicles and separately managed accounts. The reported securities may also be deemed beneficially owned by Jeremy Green as the principal of Redmile. The Reporting Persons disclaim beneficial ownership of the reported securities except to the extent of their pecuniary interest therein, and this report shall not be deemed an admission that such Reporting Persons are the beneficial owners of the securities for purposes of Section 16 of the Securities Exchange Act of 1934, as amended, or for any other purpose.

F5 · ownership.nature: Michael Lee, a member of the board of directors of the Issuer and a managing director of Redmile, was elected to the board of the Issuer as a representative of Redmile. As a result, the Reporting Persons are directors by deputization for purposes of Section 16 of the Securities Exchange Act of 1934, as amended.

SEC source: 0000899243-19-020605 · doc4.xml · nonDerivative · entry 12

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 11,635

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F4 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $22.50 to $22.55, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (4) to this Form 4.

F7 · ownership.nature: The reportable securities are owned directly by PVPSFF V. PVM V is the general partner of PVPSFF V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Flint and McGuire are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVPSFF V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-19-020605 · doc4.xml · nonDerivative · entry 9

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 7,949

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F4 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $22.50 to $22.55, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (4) to this Form 4.

F6 · ownership.nature: The reportable securities are owned directly by PVPFF V. PVM V is the general partner of PVPFF V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Flint and McGuire are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVPFF V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-19-020605 · doc4.xml · nonDerivative · entry 6

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 22,605

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F4 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $22.50 to $22.55, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (4) to this Form 4.

F5 · ownership.nature: The reportable securities are owned directly by PVPE V. PVM V is the general partner of PVPE V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Flint and McGuire are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVPE V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-19-020605 · doc4.xml · nonDerivative · entry 3

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 1,159,599

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F4 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $22.50 to $22.55, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (4) to this Form 4.

F3 · ownership.nature: The reportable securities are owned directly by PVP V. Polaris Venture Management Co. V, L.L.C. ("PVM V") is the general partner of PVP V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Jonathan A. Flint ("Flint") and Terrance G. McGuire ("McGuire") are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVP V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-19-020605 · doc4.xml · nonDerivative · entry 11

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 12,508

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F7 · ownership.nature: The reportable securities are owned directly by PVPSFF V. PVM V is the general partner of PVPSFF V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Flint and McGuire are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVPSFF V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-19-020605 · doc4.xml · nonDerivative · entry 8

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 8,545

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F6 · ownership.nature: The reportable securities are owned directly by PVPFF V. PVM V is the general partner of PVPFF V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Flint and McGuire are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVPFF V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-19-020605 · doc4.xml · nonDerivative · entry 5

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 24,301

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F5 · ownership.nature: The reportable securities are owned directly by PVPE V. PVM V is the general partner of PVPE V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Flint and McGuire are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVPE V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-19-020605 · doc4.xml · nonDerivative · entry 2

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 1,246,609

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F3 · ownership.nature: The reportable securities are owned directly by PVP V. Polaris Venture Management Co. V, L.L.C. ("PVM V") is the general partner of PVP V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Jonathan A. Flint ("Flint") and Terrance G. McGuire ("McGuire") are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVP V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-19-020605 · doc4.xml · nonDerivative · entry 10

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 12,511

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F2 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $22.50 to $22.52, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the United States Securities 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) to this Form 4.

F7 · ownership.nature: The reportable securities are owned directly by PVPSFF V. PVM V is the general partner of PVPSFF V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Flint and McGuire are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVPSFF V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-19-020605 · doc4.xml · nonDerivative · entry 7

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 8,548

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F6 · ownership.nature: The reportable securities are owned directly by PVPFF V. PVM V is the general partner of PVPFF V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Flint and McGuire are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVPFF V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-19-020605 · doc4.xml · nonDerivative · entry 4

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 24,307

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F5 · ownership.nature: The reportable securities are owned directly by PVPE V. PVM V is the general partner of PVPE V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Flint and McGuire are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVPE V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-19-020605 · doc4.xml · nonDerivative · entry 1

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 1,246,926

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F2 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $22.50 to $22.52, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the United States Securities 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) to this Form 4.

F3 · ownership.nature: The reportable securities are owned directly by PVP V. Polaris Venture Management Co. V, L.L.C. ("PVM V") is the general partner of PVP V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Jonathan A. Flint ("Flint") and Terrance G. McGuire ("McGuire") are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVP V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-19-020426 · doc4.xml · nonDerivative · entry 8

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 12,781

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F4 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $22.50 to $22.52, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the United States Securities Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (4) to this Form 4.

F7 · ownership.nature: The reportable securities are owned directly by PVPSFF V. PVM V is the general partner of PVPSFF V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Flint and McGuire are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVPSFF V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-19-020426 · doc4.xml · nonDerivative · entry 6

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 8,732

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F4 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $22.50 to $22.52, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the United States Securities Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (4) to this Form 4.

F6 · ownership.nature: The reportable securities are owned directly by PVPFF V. PVM V is the general partner of PVPFF V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Flint and McGuire are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVPFF V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-19-020426 · doc4.xml · nonDerivative · entry 4

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 24,830

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F4 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $22.50 to $22.52, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the United States Securities Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (4) to this Form 4.

F5 · ownership.nature: The reportable securities are owned directly by PVPE V. PVM V is the general partner of PVPE V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Flint and McGuire are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVPE V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-19-020426 · doc4.xml · nonDerivative · entry 2

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 1,273,778

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F4 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $22.50 to $22.52, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the United States Securities Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (4) to this Form 4.

F3 · ownership.nature: The reportable securities are owned directly by PVP V. Polaris Venture Management Co. V, L.L.C. ("PVM V") is the general partner of PVP V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Jonathan A. Flint ("Flint") and Terrance G. McGuire ("McGuire") are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVP V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-19-020426 · doc4.xml · nonDerivative · entry 7

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 12,973

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F2 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $22.50 to $22.56, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the United States Securities 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) to this Form 4.

F7 · ownership.nature: The reportable securities are owned directly by PVPSFF V. PVM V is the general partner of PVPSFF V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Flint and McGuire are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVPSFF V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-19-020426 · doc4.xml · nonDerivative · entry 5

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 8,864

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F2 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $22.50 to $22.56, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the United States Securities 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) to this Form 4.

F6 · ownership.nature: The reportable securities are owned directly by PVPFF V. PVM V is the general partner of PVPFF V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Flint and McGuire are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVPFF V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-19-020426 · doc4.xml · nonDerivative · entry 3

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 25,204

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F2 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $22.50 to $22.56, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the United States Securities 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) to this Form 4.

F5 · ownership.nature: The reportable securities are owned directly by PVPE V. PVM V is the general partner of PVPE V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Flint and McGuire are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVPE V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-19-020426 · doc4.xml · nonDerivative · entry 1

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 1,292,946

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F2 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $22.50 to $22.56, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the United States Securities 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) to this Form 4.

F3 · ownership.nature: The reportable securities are owned directly by PVP V. Polaris Venture Management Co. V, L.L.C. ("PVM V") is the general partner of PVP V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Jonathan A. Flint ("Flint") and Terrance G. McGuire ("McGuire") are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVP V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-19-020033 · doc4.xml · nonDerivative · entry 12

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 13,574

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F5 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $22.50 to $22.70, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (5) to this Form 4.

F3 · balance_after: In prior Form 4 filings, the shares reported in Column 5 were reported as an aggregate number of shares owned by all of the Polaris Funds. The format of the disclosure contained herein has been revised to show the number of securities beneficially owned by each of the Polaris Funds, on a fund by fund basis.

F8 · ownership.nature: The reportable securities are owned directly by PVPSFF V. PVM V is the general partner of PVPSFF V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Flint and McGuire are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVPSFF V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-19-020033 · doc4.xml · nonDerivative · entry 9

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 9,275

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F5 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $22.50 to $22.70, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (5) to this Form 4.

F3 · balance_after: In prior Form 4 filings, the shares reported in Column 5 were reported as an aggregate number of shares owned by all of the Polaris Funds. The format of the disclosure contained herein has been revised to show the number of securities beneficially owned by each of the Polaris Funds, on a fund by fund basis.

F7 · ownership.nature: The reportable securities are owned directly by PVPFF V. PVM V is the general partner of PVPFF V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Flint and McGuire are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVPFF V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-19-020033 · doc4.xml · nonDerivative · entry 6

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 26,371

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F5 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $22.50 to $22.70, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (5) to this Form 4.

F3 · balance_after: In prior Form 4 filings, the shares reported in Column 5 were reported as an aggregate number of shares owned by all of the Polaris Funds. The format of the disclosure contained herein has been revised to show the number of securities beneficially owned by each of the Polaris Funds, on a fund by fund basis.

F6 · ownership.nature: The reportable securities are owned directly by PVPE V. PVM V is the general partner of PVPE V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Flint and McGuire are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVPE V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-19-020033 · doc4.xml · nonDerivative · entry 3

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 1,352,800

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F5 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $22.50 to $22.70, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote (5) to this Form 4.

F3 · balance_after: In prior Form 4 filings, the shares reported in Column 5 were reported as an aggregate number of shares owned by all of the Polaris Funds. The format of the disclosure contained herein has been revised to show the number of securities beneficially owned by each of the Polaris Funds, on a fund by fund basis.

F4 · ownership.nature: The reportable securities are owned directly by PVP V. Polaris Venture Management Co. V, L.L.C. ("PVM V") is the general partner of PVP V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Jonathan A. Flint ("Flint") and Terrance G. McGuire ("McGuire") are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVP V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-19-020033 · doc4.xml · nonDerivative · entry 11

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 14,046

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F3 · balance_after: In prior Form 4 filings, the shares reported in Column 5 were reported as an aggregate number of shares owned by all of the Polaris Funds. The format of the disclosure contained herein has been revised to show the number of securities beneficially owned by each of the Polaris Funds, on a fund by fund basis.

F8 · ownership.nature: The reportable securities are owned directly by PVPSFF V. PVM V is the general partner of PVPSFF V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Flint and McGuire are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVPSFF V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-19-020033 · doc4.xml · nonDerivative · entry 8

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 9,598

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F3 · balance_after: In prior Form 4 filings, the shares reported in Column 5 were reported as an aggregate number of shares owned by all of the Polaris Funds. The format of the disclosure contained herein has been revised to show the number of securities beneficially owned by each of the Polaris Funds, on a fund by fund basis.

F7 · ownership.nature: The reportable securities are owned directly by PVPFF V. PVM V is the general partner of PVPFF V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Flint and McGuire are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVPFF V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0000899243-19-020033 · doc4.xml · nonDerivative · entry 5

Nashat Amir · CIK 0001575843 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 27,288

F1 · kind: The sale of these shares were effected pursuant to Rule 10b5-1 trading plans adopted by each of Polaris Venture Partners V, L.P. ("PVP V"), Polaris Venture Partners Entrepreneurs' Fund V, L.P. ("PVPE V"), Polaris Venture Partners Founders' Fund V, L.P. ("PVPFF V") and Polaris Venture Partners Special Founders' Fund V, L.P. ("PVPSFF V", together with PVP V, PVPE V, PVPFF V, the "Polaris Funds") on June 17, 2019.

F3 · balance_after: In prior Form 4 filings, the shares reported in Column 5 were reported as an aggregate number of shares owned by all of the Polaris Funds. The format of the disclosure contained herein has been revised to show the number of securities beneficially owned by each of the Polaris Funds, on a fund by fund basis.

F6 · ownership.nature: The reportable securities are owned directly by PVPE V. PVM V is the general partner of PVPE V. The Reporting Person, a member of the Issuer's Board of Directors, is a member of PVM V. Each of Flint and McGuire are the managing members of PVM V. Each of Flint, McGuire and the Reporting Person, in their respective capacities with respect to PVM V, may be deemed to have shared voting and dispositive power over the shares held by PVPE V. Each of PVM V, Flint, McGuire and the Reporting Person disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any one of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.