Youngren Bryce

SEC source: 0000899243-19-020425 · doc4.xml · nonDerivative · entry 12

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 13,788

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") on June 14, 2019.

F6 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $28.50 to $29.28, 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 (6) to this Form 4.

F8 · 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: 0000899243-19-020425 · doc4.xml · nonDerivative · entry 8

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 39,231

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") on June 14, 2019.

F6 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $28.50 to $29.28, 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 (6) to this Form 4.

F7 · 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: 0000899243-19-020425 · doc4.xml · nonDerivative · entry 4

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 2,013,172

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") on June 14, 2019.

F6 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $28.50 to $29.28, 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 (6) 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: 0000899243-19-020425 · doc4.xml · nonDerivative · entry 15

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 20,356

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") on June 14, 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 $29.50 to $29.80, 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.

F9 · 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: 0000899243-19-020425 · doc4.xml · nonDerivative · entry 14

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 20,601

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") on June 14, 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 $28.50 to $29.49, 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.

F9 · 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: 0000899243-19-020425 · doc4.xml · nonDerivative · entry 11

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 13,929

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") on June 14, 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 $29.50 to $29.80, 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.

F8 · 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: 0000899243-19-020425 · doc4.xml · nonDerivative · entry 10

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 14,097

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") on June 14, 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 $28.50 to $29.49, 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.

F8 · 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: 0000899243-19-020425 · doc4.xml · nonDerivative · entry 7

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 39,633

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") on June 14, 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 $29.50 to $29.80, 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.

F7 · 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: 0000899243-19-020425 · doc4.xml · nonDerivative · entry 6

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 40,111

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") on June 14, 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 $28.50 to $29.49, 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 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: 0000899243-19-020425 · doc4.xml · nonDerivative · entry 3

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 2,033,793

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") on June 14, 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 $29.50 to $29.80, 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 · 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: 0000899243-19-020425 · doc4.xml · nonDerivative · entry 2

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 2,058,312

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") on June 14, 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 $28.50 to $29.49, 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: 0000899243-19-020425 · doc4.xml · nonDerivative · entry 13

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 20,989

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") on June 14, 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 $28.545 to $28.61, 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 (2) to this Form 4.

F9 · 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: 0000899243-19-020425 · doc4.xml · nonDerivative · entry 9

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 14,362

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") on June 14, 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 $28.545 to $28.61, 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 (2) to this Form 4.

F8 · 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: 0000899243-19-020425 · doc4.xml · nonDerivative · entry 5

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 40,866

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") on June 14, 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 $28.545 to $28.61, 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 (2) to this Form 4.

F7 · 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: 0000899243-19-020425 · doc4.xml · nonDerivative · entry 1

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 2,097,054

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") on June 14, 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 $28.545 to $28.61, 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 (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: 0000899243-19-020032 · doc4.xml · nonDerivative · entry 8

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 21,000

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") on June 14, 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 $28.50 to $28.55, 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: 0000899243-19-020032 · doc4.xml · nonDerivative · entry 6

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 14,369

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") on June 14, 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 $28.50 to $28.55, 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: 0000899243-19-020032 · doc4.xml · nonDerivative · entry 4

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 40,887

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") on June 14, 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 $28.50 to $28.55, 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: 0000899243-19-020032 · doc4.xml · nonDerivative · entry 2

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 2,098,115

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") on June 14, 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 $28.50 to $28.55, 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: 0000899243-19-020032 · doc4.xml · nonDerivative · entry 7

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 21,029

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") on June 14, 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 $27.28 to $28.15, 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 (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: 0000899243-19-020032 · doc4.xml · nonDerivative · entry 5

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 14,388

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") on June 14, 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 $27.28 to $28.15, 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 (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: 0000899243-19-020032 · doc4.xml · nonDerivative · entry 3

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 40,943

F2 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $27.28 to $28.15, 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 (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: 0000899243-19-020032 · doc4.xml · nonDerivative · entry 1

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 2,100,982

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") on June 14, 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 $27.28 to $28.15, 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 (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: 0000899243-19-019787 · doc4.xml · nonDerivative · entry 12

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 21,331

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") on June 14, 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 $27.13 to $27.71, 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.

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: 0000899243-19-019787 · doc4.xml · nonDerivative · entry 9

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 14,595

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") on June 14, 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 $27.13 to $27.71, 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.

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: 0000899243-19-019787 · doc4.xml · nonDerivative · entry 6

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 41,532

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") on June 14, 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 $27.13 to $27.71, 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.

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: 0000899243-19-019787 · doc4.xml · nonDerivative · entry 3

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 2,131,187

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") on June 14, 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 $27.13 to $27.71, 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 · 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: 0000899243-19-020739 · doc4a.xml · nonDerivative · entry 12

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 21,331

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") on June 14, 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 $27.13 to $27.71, 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.

F9 · 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: 0000899243-19-020739 · doc4a.xml · nonDerivative · entry 9

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 14,595

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") on June 14, 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 $27.13 to $27.71, 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.

F8 · 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: 0000899243-19-020739 · doc4a.xml · nonDerivative · entry 6

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 41,532

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") on June 14, 2019.

F7 · shares: The number of shares reported in Column 4 of the original Form 4 was incorrect due to a scrivener's error.

F5 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $27.13 to $27.71, 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.

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: 0000899243-19-020739 · doc4a.xml · nonDerivative · entry 3

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 2,131,187

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") on June 14, 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 $27.13 to $27.71, 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 · 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: 0000899243-19-019787 · doc4.xml · nonDerivative · entry 11

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 21,599

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") on June 14, 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 $27.4 to $28.235, 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.

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: 0000899243-19-019787 · doc4.xml · nonDerivative · entry 8

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 14,778

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") on June 14, 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 $27.4 to $28.235, 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 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: 0000899243-19-019787 · doc4.xml · nonDerivative · entry 5

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 42,054

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") on June 14, 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 $27.4 to $28.235, 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 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: 0000899243-19-019787 · doc4.xml · nonDerivative · entry 2

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 2,157,965

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") on June 14, 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 $27.4 to $28.235, 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: 0000899243-19-020739 · doc4a.xml · nonDerivative · entry 11

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 21,599

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") on June 14, 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 $27.4 to $28.235, 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.

F9 · 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: 0000899243-19-020739 · doc4a.xml · nonDerivative · entry 8

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 14,778

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") on June 14, 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 $27.4 to $28.235, 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.

F8 · 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: 0000899243-19-020739 · doc4a.xml · nonDerivative · entry 5

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 42,054

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") on June 14, 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 $27.4 to $28.235, 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 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: 0000899243-19-020739 · doc4a.xml · nonDerivative · entry 2

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 2,157,965

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") on June 14, 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 $27.4 to $28.235, 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: 0000899243-19-019787 · doc4.xml · nonDerivative · entry 10

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 21,801

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") on June 14, 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 $27.335 to $28.185, 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 (2) to this Form 4.

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: 0000899243-19-019787 · doc4.xml · nonDerivative · entry 7

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 14,917

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") on June 14, 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 $27.335 to $28.185, 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 (2) to this Form 4.

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: 0000899243-19-019787 · doc4.xml · nonDerivative · entry 4

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 42,448

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") on June 14, 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 $27.335 to $28.185, 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 (2) to this Form 4.

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: 0000899243-19-019787 · doc4.xml · nonDerivative · entry 1

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 2,178,192

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") on June 14, 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 $27.335 to $28.185, 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 (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: 0000899243-19-020739 · doc4a.xml · nonDerivative · entry 10

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 21,801

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") on June 14, 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 $27.335 to $28.185, 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 (2) to this Form 4.

F9 · 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: 0000899243-19-020739 · doc4a.xml · nonDerivative · entry 7

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 14,917

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") on June 14, 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 $27.335 to $28.185, 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 (2) to this Form 4.

F8 · 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: 0000899243-19-020739 · doc4a.xml · nonDerivative · entry 4

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 42,448

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") on June 14, 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 $27.335 to $28.185, 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 (2) to this Form 4.

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: 0000899243-19-020739 · doc4a.xml · nonDerivative · entry 1

Youngren Bryce · CIK 0001489625 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 2,178,192

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") on June 14, 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 $27.335 to $28.185, 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 (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: 0001209191-19-039158 · doc4.xml · derivative · entry 1

Youngren Bryce · CIK 0001489625 · Director · 10% owner

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 6,353

Underlying: Common Stock · 6,353 shares

Expires not disclosed

F1 · derivative.exercise_price: Each restricted stock unit ("RSU") represents a contingent right to receive one share of common stock of the Issuer, or at the election of the Issuer, its cash equivalent.

F2 · derivative.exercise_date: The RSUs shall vest in full on the one-year anniversary of the date of grant, provided that the Reporting Person remains a director of the Issuer on such vesting date.

F2 · derivative.expiration_date: The RSUs shall vest in full on the one-year anniversary of the date of grant, provided that the Reporting Person remains a director of the Issuer on such vesting date.

SEC source: 0000899243-19-016465 · doc4.xml · nonDerivative · entry 4

Youngren Bryce · CIK 0001489625 · Director · 10% owner

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 21,994

F1 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $25.08 to $25.92, 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 (1) to this Form 4.

F5 · ownership.nature: The reportable securities are owned directly by Polaris Venture Partners Special Founders' Fund V, L.P. ("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: 0000899243-19-016465 · doc4.xml · nonDerivative · entry 3

Youngren Bryce · CIK 0001489625 · Director · 10% owner

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 15,049

F1 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $25.08 to $25.92, 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 (1) to this Form 4.

F4 · ownership.nature: The reportable securities are owned directly by Polaris Venture Partners Founders' Fund V, L.P. ("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.