MRNA

SEC source: 0001127602-20-002079 · form4.xml · nonDerivative · entry 1

Bancel Stephane · CIK 0001443340 · Director · Chief Executive Officer

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 784,282

F1 · kind: This sale was effected pursuant to a Rule 10b5-1 trading plan adopted on 12/28/2018.

F2 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $20.56 to $21.29. Full information regarding the number of shares sold at each separate price can be furnished to the SEC staff upon request.

F3 · ownership.nature: These shares are owned directly by a trust for the benefit of Mr. Bancel's children and of which the trustee is an independent institution. The reporting person disclaims Section 16 beneficial ownership of these securities, and this report shall not be deemed an admission that the reporting person is the beneficial owner of such securities for Section 16 or any other purpose.

SEC source: 0001127602-20-001926 · form4.xml · nonDerivative · entry 1

Bancel Stephane · CIK 0001443340 · Director · Chief Executive Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 6,757,511

F1 · kind: The reported disposition was effected pursuant to a Rule 10b5-1 trading plan.

F2 · price: The reported disposition represents a bona fide charitable gift made by the reporting person.

SEC source: 0000899243-20-001179 · doc4.xml · nonDerivative · entry 2

KANIA EDWIN M JR · CIK 0001255927 · 10% owner

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 23,847

F2 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $19.90 to $20.155, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range.

SEC source: 0001127602-20-001577 · form4.xml · nonDerivative · entry 1

Hoge Stephen · CIK 0001760669 · President

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 2,086,530

F1 · kind: This sale was effected pursuant to a Rule 10b5-1 trading plan.

F2 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $18.68 to $19.42. Full information regarding the number of shares sold at each separate price can be furnished to the SEC staff upon request.

SEC source: 0001127602-20-001573 · form4.xml · nonDerivative · entry 4

Bancel Stephane · CIK 0001443340 · Director · Chief Executive Officer

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 9,244,695

F8 · kind: This sale was effected pursuant to a Rule 10b5-1 trading plan.

F9 · ownership.nature: These shares are owned directly by Boston Biotech Ventures, LLC ("Boston Biotech"). The reporting person is the majority equity unit holder and the sole managing member of Boston Biotech. The reporting person disclaims Section 16 beneficial ownership of these securities, except to the extent of his pecuniary interest therein, if any, and this report shall not be deemed an admission that the reporting person is the beneficial owner of such securities for Section 16 or any other purpose.

SEC source: 0001127602-20-001573 · form4.xml · nonDerivative · entry 3

Bancel Stephane · CIK 0001443340 · Director · Chief Executive Officer

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 7,969,328

F6 · kind: This sale was effected pursuant to a Rule 10b5-1 trading plan.

F7 · ownership.nature: These shares are owned directly by OCHA LLC ("OCHA"). The reporting person is the majority equity unit holder and the sole managing member of OCHA. The Reporting Person disclaims Section 16 beneficial ownership of these securities, except to the extent of his pecuniary interest therein, if any, and this report shall not be deemed an admission that the reporting person is the beneficial owner of such securities for Section 16 or any other purpose.

SEC source: 0001127602-20-001573 · form4.xml · nonDerivative · entry 2

Bancel Stephane · CIK 0001443340 · Director · Chief Executive Officer

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 795,328

F4 · kind: This sale was effected pursuant to a Rule 10b5-1 trading plan adopted on 12/28/2018.

F5 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $20.10 to $20.87. Full information regarding the number of shares sold at each separate price can be furnished to the SEC staff upon request.

F3 · ownership.nature: These shares are owned directly by a trust for the benefit of Mr. Bancel's children and of which the trustee is an independent institution. The reporting person disclaims Section 16 beneficial ownership of these securities, and this report shall not be deemed an admission that the reporting person is the beneficial owner of such securities for Section 16 or any other purpose.

SEC source: 0001127602-20-001573 · form4.xml · nonDerivative · entry 1

Bancel Stephane · CIK 0001443340 · Director · Chief Executive Officer

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 798,728

F1 · kind: This sale was affected pursuant to a Rule 10b5-1 trading plan adopted on 12/28/2018.

F2 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $19.08 to $20.04. Full information regarding the number of shares sold at each separate price can be furnished to the SEC staff upon request.

F3 · ownership.nature: These shares are owned directly by a trust for the benefit of Mr. Bancel's children and of which the trustee is an independent institution. The reporting person disclaims Section 16 beneficial ownership of these securities, and this report shall not be deemed an admission that the reporting person is the beneficial owner of such securities for Section 16 or any other purpose.

SEC source: 0000899243-20-001179 · doc4.xml · nonDerivative · entry 1

KANIA EDWIN M JR · CIK 0001255927 · 10% owner

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 141,472

F1 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $20.00 to $20.745, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range.

SEC source: 0001127602-20-001119 · form4.xml · nonDerivative · entry 3

Bancel Stephane · CIK 0001443340 · Director · Chief Executive Officer

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 806,374

F5 · kind: This sale was effected pursuant to a Rule 10b5-1 trading plan adopted on 12/28/2018.

F6 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $18.79 and $19.31. Full information regarding the number of shares sold at each separate price can be furnished to the SEC staff upon request.

F7 · ownership.nature: These shares are owned directly by a trust for the benefit of Mr. Bancel's children and of which the trustee is an independent institution. The reporting person disclaims Section 16 beneficial ownership of these securities, and this report shall not be deemed an admission that the reporting person is the beneficial owner of such securities for Section 16 or any other purpose.

SEC source: 0001127602-20-001119 · form4.xml · nonDerivative · entry 2

Bancel Stephane · CIK 0001443340 · Director · Chief Executive Officer

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 9,247,413

F3 · kind: This sale was effected pursuant to a Rule 10b5-1 trading plan.

F4 · ownership.nature: These shares are owned directly by Boston Biotech Ventures, LLC ("Boston Biotech"). The reporting person is the majority equity unit holder and the sole managing member of Boston Biotech. The reporting person disclaims Section 16 beneficial ownership of these securities, except to the extent of his pecuniary interest therein, if any, and this report shall not be deemed an admission that the reporting person is the beneficial owner of such securities for Section 16 or any other purpose.

SEC source: 0001127602-20-001119 · form4.xml · nonDerivative · entry 1

Bancel Stephane · CIK 0001443340 · Director · Chief Executive Officer

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 7,972,046

F1 · kind: This sale was effected pursuant to a Rule 10b5-1 trading plan.

F2 · ownership.nature: These shares are owned directly by OCHA LLC ("OCHA"). The reporting person is the majority equity unit holder and the sole managing member of OCHA. The Reporting Person disclaims Section 16 beneficial ownership of these securities, except to the extent of his pecuniary interest therein, if any, and this report shall not be deemed an admission that the reporting person is the beneficial owner of such securities for Section 16 or any other purpose.

SEC source: 0001127602-20-000607 · form4.xml · nonDerivative · entry 1

Bancel Stephane · CIK 0001443340 · Director · Chief Executive Officer

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 817,420

F1 · kind: This sale was effected pursuant to a Rule 10b5-1 trading plan adopted on 12/28/2018.

F2 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $19.26 to $19.96. Full information regarding the number of shares sold at each separate price can be furnished to the SEC staff upon request.

F3 · ownership.nature: These shares are owned directly by a trust for the benefit of Mr. Bancel's children and of which the trustee is an independent institution. The reporting person disclaims Section 16 beneficial ownership of these securities, and this report shall not be deemed an admission that the reporting person is the beneficial owner of such securities for Section 16 or any other purpose.

SEC source: 0001127602-19-035757 · form4.xml · nonDerivative · entry 1

Bancel Stephane · CIK 0001443340 · Director · Chief Executive Officer

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 828,466

F1 · kind: This sale was effected pursuant to a Rule 10b5-1 trading plan adopted on 12/28/2018.

F2 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $19.20 to $19.96. Full information regarding the number of shares sold at each separate price can be furnished to the SEC staff upon request.

F3 · ownership.nature: These shares are owned directly by a trust for the benefit of Mr. Bancel's children and of which the trustee is an independent institution. The reporting person disclaims Section 16 beneficial ownership of these securities, and this report shall not be deemed an admission that the reporting person is the beneficial owner of such securities for Section 16 or any other purpose.

SEC source: 0001127602-19-035076 · form4.xml · nonDerivative · entry 1

Bancel Stephane · CIK 0001443340 · Director · Chief Executive Officer

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 839,512

F1 · kind: This sale was affected pursuant to a Rule 10b5-1 trading plan adopted on 12/28/2018.

F2 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $18.35 to $18.70. Full information regarding the number of shares sold at each separate price can be furnished to the SEC staff upon request.

F3 · ownership.nature: These shares are owned directly by a trust for the benefit of Mr. Bancel's children and of which the trustee is an independent institution. The reporting person disclaims Section 16 beneficial ownership of these securities, and this report shall not be deemed an admission that the reporting person is the beneficial owner of such securities for Section 16 or any other purpose.

SEC source: 0001127602-19-035092 · form4.xml · nonDerivative · entry 1

Zaks Tal Zvi · CIK 0001690927 · Chief Medical Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 104,770

F1 · kind: This sale was effected pursuant to a Rule 10b5-1 trading plan.

F2 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $18.33 to $19.01. Full information regarding the number of shares sold at each separate price can be furnished to the SEC staff upon request.

SEC source: 0000899243-19-028975 · doc4.xml · nonDerivative · entry 9

Flagship Ventures Fund IV General Partner LLC · CIK 0001508051 · Director · 10% owner

Flagship Ventures Fund IV, L.P. · CIK 0001503559 · 10% owner

Flagship Ventures Fund IV-Rx, L.P. · CIK 0001590973 · 10% owner

AFEYAN NOUBAR · CIK 0001222012 · Director · 10% owner

KANIA EDWIN M JR · CIK 0001255927 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 8,190,766

F7 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $18.65 to $18.74, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range.

F3 · ownership.nature: Shares held by Flagship Fund IV-Rx. Flagship Fund IV GP is the general partner of Flagship Fund IV-Rx. While Mr. Kania is retired from Pioneering he continues to serve as a manager of the Flagship Fund IV GP. Each of the reporting persons except for Flagship Fund IV-Rx disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.

SEC source: 0000899243-19-028975 · doc4.xml · nonDerivative · entry 8

Flagship Ventures Fund IV General Partner LLC · CIK 0001508051 · Director · 10% owner

Flagship Ventures Fund IV, L.P. · CIK 0001503559 · 10% owner

Flagship Ventures Fund IV-Rx, L.P. · CIK 0001590973 · 10% owner

AFEYAN NOUBAR · CIK 0001222012 · Director · 10% owner

KANIA EDWIN M JR · CIK 0001255927 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 31,216,399

F7 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $18.65 to $18.74, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range.

F2 · ownership.nature: Shares held by Flagship Fund IV. Flagship Fund IV GP is the general partner of Flagship Fund IV. Noubar B. Afeyan, Ph.D. and Edwin M. Kania, Jr. are the managers of Flagship Fund IV GP. While Mr. Kania is retired from Flagship Pioneering, Inc. ("Pioneering"), he continues to serve as a manager of Flagship Fund IV GP. Each of the reporting persons except for Flagship Fund IV disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.

SEC source: 0000899243-19-028978 · doc4.xml · nonDerivative · entry 1

KANIA EDWIN M JR · CIK 0001255927 · 10% owner

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 498,847

F1 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $18.75 to $18.96, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range.

SEC source: 0001127602-19-034834 · form4.xml · derivative · entry 2

Nader Francois · CIK 0001365343 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 17,889

Underlying: Common Stock · 17,889 shares

Expires 2029-12-10

F2 · derivative.exercise_date: This option will become fully vested and exercisable on the earlier of June 27, 2020, or the next Annual Meeting of Stockholders, subject to the recipient's continued service.

SEC source: 0001127602-19-034834 · form4.xml · derivative · entry 1

Nader Francois · CIK 0001365343 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 39,720

Underlying: Common Stock · 39,720 shares

Expires 2029-12-10

F1 · derivative.exercise_date: This option will be fully vested and exercisable on December 10, 2020.

SEC source: 0000899243-19-028975 · doc4.xml · nonDerivative · entry 7

Flagship Ventures Fund IV General Partner LLC · CIK 0001508051 · Director · 10% owner

Flagship Ventures Fund IV, L.P. · CIK 0001503559 · 10% owner

Flagship Ventures Fund IV-Rx, L.P. · CIK 0001590973 · 10% owner

AFEYAN NOUBAR · CIK 0001222012 · Director · 10% owner

KANIA EDWIN M JR · CIK 0001255927 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 8,229,132

F6 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $18.95 to $19.00, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range.

F3 · ownership.nature: Shares held by Flagship Fund IV-Rx. Flagship Fund IV GP is the general partner of Flagship Fund IV-Rx. While Mr. Kania is retired from Pioneering he continues to serve as a manager of the Flagship Fund IV GP. Each of the reporting persons except for Flagship Fund IV-Rx disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.

SEC source: 0000899243-19-028975 · doc4.xml · nonDerivative · entry 6

Flagship Ventures Fund IV General Partner LLC · CIK 0001508051 · Director · 10% owner

Flagship Ventures Fund IV, L.P. · CIK 0001503559 · 10% owner

Flagship Ventures Fund IV-Rx, L.P. · CIK 0001590973 · 10% owner

AFEYAN NOUBAR · CIK 0001222012 · Director · 10% owner

KANIA EDWIN M JR · CIK 0001255927 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 31,416,334

F6 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $18.95 to $19.00, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range.

F2 · ownership.nature: Shares held by Flagship Fund IV. Flagship Fund IV GP is the general partner of Flagship Fund IV. Noubar B. Afeyan, Ph.D. and Edwin M. Kania, Jr. are the managers of Flagship Fund IV GP. While Mr. Kania is retired from Flagship Pioneering, Inc. ("Pioneering"), he continues to serve as a manager of Flagship Fund IV GP. Each of the reporting persons except for Flagship Fund IV disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.

SEC source: 0001127602-19-034852 · form4.xml · nonDerivative · entry 1

Bancel Stephane · CIK 0001443340 · Director · Chief Executive Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 6,762,500

F1 · kind: Represents the receipt of shares by the reporting person pursuant to pro rata distributions-in-kind, without consideration, of shares of the company's common stock effected on December 9, 2019 by Flagship Ventures Fund IV, L.P. ("Flagship Fund IV") to the partners of Flagship Fund IV and by its general partner, Flagship Ventures Fund IV General Partner, LLC. The aforementioned distributions were made in accordance with the exemptions afforded by Rule 16a-13 and Rule 16a-9 of the Securities Exchange Act of 1934, as amended.

SEC source: 0000899243-19-028975 · doc4.xml · nonDerivative · entry 5

Flagship Ventures Fund IV General Partner LLC · CIK 0001508051 · Director · 10% owner

Flagship Ventures Fund IV, L.P. · CIK 0001503559 · 10% owner

Flagship Ventures Fund IV-Rx, L.P. · CIK 0001590973 · 10% owner

AFEYAN NOUBAR · CIK 0001222012 · Director · 10% owner

KANIA EDWIN M JR · CIK 0001255927 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 8,233,224

F5 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $18.90 to $19.115, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range.

F3 · ownership.nature: Shares held by Flagship Fund IV-Rx. Flagship Fund IV GP is the general partner of Flagship Fund IV-Rx. While Mr. Kania is retired from Pioneering he continues to serve as a manager of the Flagship Fund IV GP. Each of the reporting persons except for Flagship Fund IV-Rx disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.

SEC source: 0000899243-19-028975 · doc4.xml · nonDerivative · entry 4

Flagship Ventures Fund IV General Partner LLC · CIK 0001508051 · Director · 10% owner

Flagship Ventures Fund IV, L.P. · CIK 0001503559 · 10% owner

Flagship Ventures Fund IV-Rx, L.P. · CIK 0001590973 · 10% owner

AFEYAN NOUBAR · CIK 0001222012 · Director · 10% owner

KANIA EDWIN M JR · CIK 0001255927 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 31,437,659

F5 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $18.90 to $19.115, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range.

F2 · ownership.nature: Shares held by Flagship Fund IV. Flagship Fund IV GP is the general partner of Flagship Fund IV. Noubar B. Afeyan, Ph.D. and Edwin M. Kania, Jr. are the managers of Flagship Fund IV GP. While Mr. Kania is retired from Flagship Pioneering, Inc. ("Pioneering"), he continues to serve as a manager of Flagship Fund IV GP. Each of the reporting persons except for Flagship Fund IV disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.

SEC source: 0000899243-19-028975 · doc4.xml · nonDerivative · entry 3

Flagship Ventures Fund IV General Partner LLC · CIK 0001508051 · Director · 10% owner

Flagship Ventures Fund IV, L.P. · CIK 0001503559 · 10% owner

Flagship Ventures Fund IV-Rx, L.P. · CIK 0001590973 · 10% owner

AFEYAN NOUBAR · CIK 0001222012 · Director · 10% owner

KANIA EDWIN M JR · CIK 0001255927 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 0

F1 · kind: On December 9, 2019, Flagship Ventures Fund IV, L.P. ("Flagship Fund IV") and Flagship Ventures Fund IV-Rx, L.P. ("Flagship Fund IV-Rx") distributed to its limited partners and sole general partner, Flagship Ventures Fund IV General Partner, LLC ("Flagship Fund IV GP"), pro rata and without consideration, 6,292,342 shares and 1,207,658 shares, respectively, of the Issuer's common stock. Flagship Fund IV GP, in turn, distributed to its members, pro rata and without consideration, the 1,494,155 shares and 241,565 shares it received from Flagship Fund IV and Flagship Fund IV-Rx, respectively. Noubar B. Afeyan, Ph.D. and Edwin M. Kania, Jr., each a manager of Flagship Fund IV GP, each received 598,847 shares through Flagship Fund IV GP's distribution. The aforementioned distributions were made in accordance with the exemptions afforded by Rule 16a-13 and Rule 16a-9 of the Securities Exchange Act of 1934, as amended.

F1 · price: On December 9, 2019, Flagship Ventures Fund IV, L.P. ("Flagship Fund IV") and Flagship Ventures Fund IV-Rx, L.P. ("Flagship Fund IV-Rx") distributed to its limited partners and sole general partner, Flagship Ventures Fund IV General Partner, LLC ("Flagship Fund IV GP"), pro rata and without consideration, 6,292,342 shares and 1,207,658 shares, respectively, of the Issuer's common stock. Flagship Fund IV GP, in turn, distributed to its members, pro rata and without consideration, the 1,494,155 shares and 241,565 shares it received from Flagship Fund IV and Flagship Fund IV-Rx, respectively. Noubar B. Afeyan, Ph.D. and Edwin M. Kania, Jr., each a manager of Flagship Fund IV GP, each received 598,847 shares through Flagship Fund IV GP's distribution. The aforementioned distributions were made in accordance with the exemptions afforded by Rule 16a-13 and Rule 16a-9 of the Securities Exchange Act of 1934, as amended.

F4 · ownership.nature: Shares held by Flagship Fund IV GP. Noubar B. Afeyan, Ph.D. and Edwin M. Kania, Jr. are the managers of Flagship Fund IV GP. While Mr. Kania is retired from Pioneering, he continues to serve as a manager of Flagship Fund IV GP. Each of the reporting persons except for Flagship Fund IV GP disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.

SEC source: 0000899243-19-028975 · doc4.xml · nonDerivative · entry 2

Flagship Ventures Fund IV General Partner LLC · CIK 0001508051 · Director · 10% owner

Flagship Ventures Fund IV, L.P. · CIK 0001503559 · 10% owner

Flagship Ventures Fund IV-Rx, L.P. · CIK 0001590973 · 10% owner

AFEYAN NOUBAR · CIK 0001222012 · Director · 10% owner

KANIA EDWIN M JR · CIK 0001255927 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 8,260,938

F1 · kind: On December 9, 2019, Flagship Ventures Fund IV, L.P. ("Flagship Fund IV") and Flagship Ventures Fund IV-Rx, L.P. ("Flagship Fund IV-Rx") distributed to its limited partners and sole general partner, Flagship Ventures Fund IV General Partner, LLC ("Flagship Fund IV GP"), pro rata and without consideration, 6,292,342 shares and 1,207,658 shares, respectively, of the Issuer's common stock. Flagship Fund IV GP, in turn, distributed to its members, pro rata and without consideration, the 1,494,155 shares and 241,565 shares it received from Flagship Fund IV and Flagship Fund IV-Rx, respectively. Noubar B. Afeyan, Ph.D. and Edwin M. Kania, Jr., each a manager of Flagship Fund IV GP, each received 598,847 shares through Flagship Fund IV GP's distribution. The aforementioned distributions were made in accordance with the exemptions afforded by Rule 16a-13 and Rule 16a-9 of the Securities Exchange Act of 1934, as amended.

F1 · price: On December 9, 2019, Flagship Ventures Fund IV, L.P. ("Flagship Fund IV") and Flagship Ventures Fund IV-Rx, L.P. ("Flagship Fund IV-Rx") distributed to its limited partners and sole general partner, Flagship Ventures Fund IV General Partner, LLC ("Flagship Fund IV GP"), pro rata and without consideration, 6,292,342 shares and 1,207,658 shares, respectively, of the Issuer's common stock. Flagship Fund IV GP, in turn, distributed to its members, pro rata and without consideration, the 1,494,155 shares and 241,565 shares it received from Flagship Fund IV and Flagship Fund IV-Rx, respectively. Noubar B. Afeyan, Ph.D. and Edwin M. Kania, Jr., each a manager of Flagship Fund IV GP, each received 598,847 shares through Flagship Fund IV GP's distribution. The aforementioned distributions were made in accordance with the exemptions afforded by Rule 16a-13 and Rule 16a-9 of the Securities Exchange Act of 1934, as amended.

F3 · ownership.nature: Shares held by Flagship Fund IV-Rx. Flagship Fund IV GP is the general partner of Flagship Fund IV-Rx. While Mr. Kania is retired from Pioneering he continues to serve as a manager of the Flagship Fund IV GP. Each of the reporting persons except for Flagship Fund IV-Rx disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.

SEC source: 0000899243-19-028975 · doc4.xml · nonDerivative · entry 1

Flagship Ventures Fund IV General Partner LLC · CIK 0001508051 · Director · 10% owner

Flagship Ventures Fund IV, L.P. · CIK 0001503559 · 10% owner

Flagship Ventures Fund IV-Rx, L.P. · CIK 0001590973 · 10% owner

AFEYAN NOUBAR · CIK 0001222012 · Director · 10% owner

KANIA EDWIN M JR · CIK 0001255927 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 31,582,082

F1 · kind: On December 9, 2019, Flagship Ventures Fund IV, L.P. ("Flagship Fund IV") and Flagship Ventures Fund IV-Rx, L.P. ("Flagship Fund IV-Rx") distributed to its limited partners and sole general partner, Flagship Ventures Fund IV General Partner, LLC ("Flagship Fund IV GP"), pro rata and without consideration, 6,292,342 shares and 1,207,658 shares, respectively, of the Issuer's common stock. Flagship Fund IV GP, in turn, distributed to its members, pro rata and without consideration, the 1,494,155 shares and 241,565 shares it received from Flagship Fund IV and Flagship Fund IV-Rx, respectively. Noubar B. Afeyan, Ph.D. and Edwin M. Kania, Jr., each a manager of Flagship Fund IV GP, each received 598,847 shares through Flagship Fund IV GP's distribution. The aforementioned distributions were made in accordance with the exemptions afforded by Rule 16a-13 and Rule 16a-9 of the Securities Exchange Act of 1934, as amended.

F1 · price: On December 9, 2019, Flagship Ventures Fund IV, L.P. ("Flagship Fund IV") and Flagship Ventures Fund IV-Rx, L.P. ("Flagship Fund IV-Rx") distributed to its limited partners and sole general partner, Flagship Ventures Fund IV General Partner, LLC ("Flagship Fund IV GP"), pro rata and without consideration, 6,292,342 shares and 1,207,658 shares, respectively, of the Issuer's common stock. Flagship Fund IV GP, in turn, distributed to its members, pro rata and without consideration, the 1,494,155 shares and 241,565 shares it received from Flagship Fund IV and Flagship Fund IV-Rx, respectively. Noubar B. Afeyan, Ph.D. and Edwin M. Kania, Jr., each a manager of Flagship Fund IV GP, each received 598,847 shares through Flagship Fund IV GP's distribution. The aforementioned distributions were made in accordance with the exemptions afforded by Rule 16a-13 and Rule 16a-9 of the Securities Exchange Act of 1934, as amended.

F2 · ownership.nature: Shares held by Flagship Fund IV. Flagship Fund IV GP is the general partner of Flagship Fund IV. Noubar B. Afeyan, Ph.D. and Edwin M. Kania, Jr. are the managers of Flagship Fund IV GP. While Mr. Kania is retired from Flagship Pioneering, Inc. ("Pioneering"), he continues to serve as a manager of Flagship Fund IV GP. Each of the reporting persons except for Flagship Fund IV disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.

SEC source: 0001127602-19-034630 · form4.xml · derivative · entry 7

Kim Lorence H. · CIK 0001643746 · Chief Financial Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 229,358 shares

Expires not disclosed

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

F5 · derivative.exercise_date: These Restricted Stock Units are fully vested and settled in accordance with their terms.

F5 · derivative.expiration_date: These Restricted Stock Units are fully vested and settled in accordance with their terms.

SEC source: 0001127602-19-034630 · form4.xml · derivative · entry 6

Kim Lorence H. · CIK 0001643746 · Chief Financial Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 229,357 shares

Expires not disclosed

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

F5 · derivative.exercise_date: These Restricted Stock Units are fully vested and settled in accordance with their terms.

F5 · derivative.expiration_date: These Restricted Stock Units are fully vested and settled in accordance with their terms.

SEC source: 0001127602-19-034630 · form4.xml · nonDerivative · entry 5

Kim Lorence H. · CIK 0001643746 · Chief Financial Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 1,362,510

F1 · kind: This sale was effected pursuant to a Rule 10b5-1 trading plan adopted on 12/28/2018, and amended on September 17, 2019. The sale was made to generate proceeds to cover the tax liability incident to the delivery of restricted stock units.

F4 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $20.92 to $20.97. Full information regarding the number of shares sold at each separate price can be furnished to the SEC staff upon request.

SEC source: 0001127602-19-034630 · form4.xml · nonDerivative · entry 4

Kim Lorence H. · CIK 0001643746 · Chief Financial Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 1,363,816

F1 · kind: This sale was effected pursuant to a Rule 10b5-1 trading plan adopted on 12/28/2018, and amended on September 17, 2019. The sale was made to generate proceeds to cover the tax liability incident to the delivery of restricted stock units.

F3 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $19.87 to $20.86. Full information regarding the number of shares sold at each separate price can be furnished to the SEC staff upon request.

SEC source: 0001127602-19-034630 · form4.xml · nonDerivative · entry 3

Kim Lorence H. · CIK 0001643746 · Chief Financial Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 1,511,344

F1 · kind: This sale was effected pursuant to a Rule 10b5-1 trading plan adopted on 12/28/2018, and amended on September 17, 2019. The sale was made to generate proceeds to cover the tax liability incident to the delivery of restricted stock units.

F2 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $18.86 to $19.85. Full information regarding the number of shares sold at each separate price can be furnished to the SEC staff upon request.

SEC source: 0001127602-19-034630 · form4.xml · nonDerivative · entry 2

Kim Lorence H. · CIK 0001643746 · Chief Financial Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 1,601,042

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

SEC source: 0001127602-19-034630 · form4.xml · nonDerivative · entry 1

Kim Lorence H. · CIK 0001643746 · Chief Financial Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 1,371,684

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

SEC source: 0001127602-19-034618 · form4.xml · nonDerivative · entry 3

Bancel Stephane · CIK 0001443340 · Director · Chief Executive Officer

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 850,558

F1 · kind: This sale was effected pursuant to a Rule 10b5-1 trading plan adopted on 12/28/2018.

F5 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $20.93 to $20.97. Full information regarding the number of shares sold at each separate price can be furnished to the SEC staff upon request.

F3 · ownership.nature: These shares are owned directly by a trust for the benefit of Mr. Bancel's children and of which the trustee is an independent institution. The reporting person disclaims Section 16 beneficial ownership of these securities, and this report shall not be deemed an admission that the reporting person is the beneficial owner of such securities for Section 16 or any other purpose.

SEC source: 0001127602-19-034618 · form4.xml · nonDerivative · entry 2

Bancel Stephane · CIK 0001443340 · Director · Chief Executive Officer

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 850,758

F1 · kind: This sale was effected pursuant to a Rule 10b5-1 trading plan adopted on 12/28/2018.

F4 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $19.92 to 20.85. Full information regarding the number of shares sold at each separate price can be furnished to the SEC staff upon request.

F3 · ownership.nature: These shares are owned directly by a trust for the benefit of Mr. Bancel's children and of which the trustee is an independent institution. The reporting person disclaims Section 16 beneficial ownership of these securities, and this report shall not be deemed an admission that the reporting person is the beneficial owner of such securities for Section 16 or any other purpose.

SEC source: 0001127602-19-034618 · form4.xml · nonDerivative · entry 1

Bancel Stephane · CIK 0001443340 · Director · Chief Executive Officer

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 856,958

F1 · kind: This sale was effected pursuant to a Rule 10b5-1 trading plan adopted on 12/28/2018.

F2 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $18.88 to $19.87. Full information regarding the number of shares sold at each separate price can be furnished to the SEC staff upon request.

F3 · ownership.nature: These shares are owned directly by a trust for the benefit of Mr. Bancel's children and of which the trustee is an independent institution. The reporting person disclaims Section 16 beneficial ownership of these securities, and this report shall not be deemed an admission that the reporting person is the beneficial owner of such securities for Section 16 or any other purpose.

SEC source: 0001127602-19-034027 · form4.xml · nonDerivative · entry 1

Bancel Stephane · CIK 0001443340 · Director · Chief Executive Officer

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 861,604

F1 · kind: This sale was effected pursuant to a Rule 10b5-1 trading plan adopted on 12/28/2018.

F2 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $20.31 to $20.91. Full information regarding the number of shares sold at each separate price can be furnished to the SEC staff upon request.

F3 · ownership.nature: These shares are owned directly by a trust for the benefit of Mr. Bancel's children and of which the trustee is an independent institution. The reporting person disclaims Section 16 beneficial ownership of these securities, and this report shall not be deemed an admission that the reporting person is the beneficial owner of such securities for Section 16 or any other purpose.

SEC source: 0001127602-19-033671 · form4.xml · nonDerivative · entry 1

Bancel Stephane · CIK 0001443340 · Director · Chief Executive Officer

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 872,650

F1 · kind: This sale was effected pursuant to a Rule 10b5-1 trading plan adopted on 12/28/2018.

F2 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $20.00 to $20.71. Full information regarding the number of shares sold at each separate price can be furnished to the SEC staff upon request.

F3 · ownership.nature: These shares are owned directly by a trust for the benefit of Mr. Bancel's children and of which the trustee is an independent institution. The reporting person disclaims Section 16 beneficial ownership of these securities, and this report shall not be deemed an admission that the reporting person is the beneficial owner of such securities for Section 16 or any other purpose.

SEC source: 0001127602-19-033520 · form4.xml · derivative · entry 3

HUTT PETER BARTON · CIK 0001171527 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 502,752

Underlying: Common Stock · 200,000 shares

Expires 2022-03-27

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

F2 · derivative.exercise_date: This option is fully vested and exercisable.

SEC source: 0001127602-19-033520 · form4.xml · nonDerivative · entry 2

HUTT PETER BARTON · CIK 0001171527 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 3,924

F1 · price: The price reported in Column 4 is a weighted average price. The shares sold in multiple transactions at prices ranging from $20.00 to $20.34. Full information regarding the number of shares sold at each separate price can be furnished to the SEC staff upon request.

SEC source: 0001127602-19-033520 · form4.xml · nonDerivative · entry 1

HUTT PETER BARTON · CIK 0001171527 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 203,924

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

SEC source: 0001127602-19-033233 · form4.xml · nonDerivative · entry 2

Bancel Stephane · CIK 0001443340 · Director · Chief Executive Officer

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 883,696

F1 · kind: This sale was effected pursuant to a Rule 10b5-1 trading plan adopted on 12/28/2018.

F4 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $19.37 to $19.43. Full information regarding the number of shares sold at each separate price can be furnished to the SEC staff upon request.

F3 · ownership.nature: These shares are owned directly by a trust for the benefit of Mr. Bancel's children and of which the trustee is an independent institution. The reporting person disclaims Section 16 beneficial ownership of these securities, and this report shall not be deemed an admission that the reporting person is the beneficial owner of such securities for Section 16 or any other purpose.

SEC source: 0001127602-19-033233 · form4.xml · nonDerivative · entry 1

Bancel Stephane · CIK 0001443340 · Director · Chief Executive Officer

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 884,032

F1 · kind: This sale was effected pursuant to a Rule 10b5-1 trading plan adopted on 12/28/2018.

F2 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $18.36 to $19.36. Full information regarding the number of shares sold at each separate price can be furnished to the SEC staff upon request.

F3 · ownership.nature: These shares are owned directly by a trust for the benefit of Mr. Bancel's children and of which the trustee is an independent institution. The reporting person disclaims Section 16 beneficial ownership of these securities, and this report shall not be deemed an admission that the reporting person is the beneficial owner of such securities for Section 16 or any other purpose.

SEC source: 0001127602-19-032406 · form4.xml · nonDerivative · entry 1

Bancel Stephane · CIK 0001443340 · Director · Chief Executive Officer

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 894,742

F1 · kind: This sale was effected pursuant to a Rule 10b5-1 trading plan adopted on 12/28/2018.

F2 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $17.19 to $17.50. Full information regarding the number of shares sold at each separate price can be furnished to the SEC staff upon request.

F3 · ownership.nature: These shares are owned directly by a trust for the benefit of Mr. Bancel's children and of which the trustee is an independent institution. The reporting person disclaims Section 16 beneficial ownership of these securities, and this report shall not be deemed an admission that the reporting person is the beneficial owner of such securities for Section 16 or any other purpose.

SEC source: 0001127602-19-031912 · form4.xml · nonDerivative · entry 2

Bancel Stephane · CIK 0001443340 · Director · Chief Executive Officer

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 905,788

F1 · kind: This sale was effected pursuant to a Rule 10b5-1 trading plan adopted on 12/28/2018.

F4 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $16.56 to $16.81. Full information regarding the number of shares sold at each separate price can be furnished to the SEC staff upon request.

F3 · ownership.nature: These shares are owned directly by a trust for the benefit of Mr. Bancel's children and of which the trustee is an independent institution. The reporting person disclaims Section 16 beneficial ownership of these securities, and this report shall not be deemed an admission that the reporting person is the beneficial owner of such securities for Section 16 or any other purpose.

SEC source: 0001127602-19-031912 · form4.xml · nonDerivative · entry 1

Bancel Stephane · CIK 0001443340 · Director · Chief Executive Officer

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnote

Disclosed balance after: 910,288

F1 · kind: This sale was effected pursuant to a Rule 10b5-1 trading plan adopted on 12/28/2018.

F2 · price: The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $15.62 to $15.72. Full information regarding the number of shares sold at each separate price can be furnished to the SEC staff upon request.

F3 · ownership.nature: These shares are owned directly by a trust for the benefit of Mr. Bancel's children and of which the trustee is an independent institution. The reporting person disclaims Section 16 beneficial ownership of these securities, and this report shall not be deemed an admission that the reporting person is the beneficial owner of such securities for Section 16 or any other purpose.

SEC source: 0001127602-19-029070 · form4.xml · nonDerivative · entry 1

Kim Lorence H. · CIK 0001643746 · Chief Financial Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 1,142,327

F1 · price: The reported disposition represents a bona fide charitable gift made by the reporting person.

F2 · balance_after: Of the shares reported in this column, (i) 40,954 shares are subject to a restricted stock grant dated August 10, 2016, which vests as follows: 25% of the Shares to vest on the first anniversary of the vest start date of April 9, 2015, and the remainder vests in 12 quarterly installments and (ii) 273,027 shares are subject to a restricted stock grant dated August 10, 2016, which vests as follows: 25% of the Shares to vest on the first anniversary of the vest start date of November 18, 2015, and the remainder vests in 12 quarterly installments.