Flagship Ventures Fund IV-Rx, L.P.

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: 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: 0001104659-19-029735 · a4.xml · derivative · entry 25

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

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

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

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

Flagship Ventures 2007 General Partner LLC · CIK 0001508053 · 10% owner

Flagship Ventures Fund 2007, L.P. · CIK 0001508052 · 10% owner

Flagship Ventures Opportunities Fund I General Partner LLC · CIK 0001725004 · 10% owner

Flagship Ventures Opportunities Fund I, L.P. · CIK 0001677345 · 10% owner

AFEYAN NOUBAR · CIK 0001222012 · 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

Underlying: Common Stock · 486,023 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.

F8 · derivative.exercise_price: Each share of Series E Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F8 · price: Each share of Series E Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F8 · derivative.exercise_date: Each share of Series E Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F8 · derivative.expiration_date: Each share of Series E Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F9 · ownership.nature: Shares held by Flagship Ventures Opportunities Fund I, L.P. ("Flagship Opportunities I"). Flagship Ventures Opportunities Fund I General Partner LLC ("Flagship Opportunities GP") is the general partner of Flagship Opportunities I. Noubar B. Afeyan, Ph.D. serves as sole manager of Flagship Opportunities GP and may be deemed to possess sole voting and investment power with respect to all shares held by Flagship Opportunities I. Each of the reporting persons disclaims beneficial ownership of the shares except to the extent of his or its pecuniary interest therein.

SEC source: 0001104659-19-029735 · a4.xml · derivative · entry 24

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

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

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

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

Flagship Ventures 2007 General Partner LLC · CIK 0001508053 · 10% owner

Flagship Ventures Fund 2007, L.P. · CIK 0001508052 · 10% owner

Flagship Ventures Opportunities Fund I General Partner LLC · CIK 0001725004 · 10% owner

Flagship Ventures Opportunities Fund I, L.P. · CIK 0001677345 · 10% owner

AFEYAN NOUBAR · CIK 0001222012 · 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

Underlying: Common Stock · 48,602 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.

F8 · derivative.exercise_price: Each share of Series E Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F8 · price: Each share of Series E Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F8 · derivative.exercise_date: Each share of Series E Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F8 · derivative.expiration_date: Each share of Series E Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F6 · ownership.nature: Shares held by Flagship Ventures Fund IV-Rx, L.P. ("Flagship Fund IV-Rx"). Flagship Fund IV GP is the general partner of Flagship Fund IV-Rx. 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., he continues to serve as a manager of Flagship Fund IV GP. Each of these individuals and entities may be deemed to share voting and investment power with respect to all shares held by Flagship Fund IV-Rx. Each of the reporting persons disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.

SEC source: 0001104659-19-029735 · a4.xml · derivative · entry 23

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

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

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

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

Flagship Ventures 2007 General Partner LLC · CIK 0001508053 · 10% owner

Flagship Ventures Fund 2007, L.P. · CIK 0001508052 · 10% owner

Flagship Ventures Opportunities Fund I General Partner LLC · CIK 0001725004 · 10% owner

Flagship Ventures Opportunities Fund I, L.P. · CIK 0001677345 · 10% owner

AFEYAN NOUBAR · CIK 0001222012 · 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

Underlying: Common Stock · 194,409 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.

F8 · derivative.exercise_price: Each share of Series E Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F8 · price: Each share of Series E Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F8 · derivative.exercise_date: Each share of Series E Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F8 · derivative.expiration_date: Each share of Series E Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F4 · 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., he continues to serve as a manager of Flagship Fund IV GP. Each of these individuals and entities may be deemed to share voting and investment power with respect to all shares held by Flagship Fund IV. Each of the reporting persons disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.

SEC source: 0001104659-19-029735 · a4.xml · derivative · entry 22

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

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

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

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

Flagship Ventures 2007 General Partner LLC · CIK 0001508053 · 10% owner

Flagship Ventures Fund 2007, L.P. · CIK 0001508052 · 10% owner

Flagship Ventures Opportunities Fund I General Partner LLC · CIK 0001725004 · 10% owner

Flagship Ventures Opportunities Fund I, L.P. · CIK 0001677345 · 10% owner

AFEYAN NOUBAR · CIK 0001222012 · 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

Underlying: Common Stock · 82,324 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.

F7 · derivative.exercise_price: Each share of Series C Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F7 · price: Each share of Series C Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F7 · derivative.exercise_date: Each share of Series C Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F7 · derivative.expiration_date: Each share of Series C Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F6 · ownership.nature: Shares held by Flagship Ventures Fund IV-Rx, L.P. ("Flagship Fund IV-Rx"). Flagship Fund IV GP is the general partner of Flagship Fund IV-Rx. 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., he continues to serve as a manager of Flagship Fund IV GP. Each of these individuals and entities may be deemed to share voting and investment power with respect to all shares held by Flagship Fund IV-Rx. Each of the reporting persons disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.

SEC source: 0001104659-19-029735 · a4.xml · derivative · entry 21

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

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

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

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

Flagship Ventures 2007 General Partner LLC · CIK 0001508053 · 10% owner

Flagship Ventures Fund 2007, L.P. · CIK 0001508052 · 10% owner

Flagship Ventures Opportunities Fund I General Partner LLC · CIK 0001725004 · 10% owner

Flagship Ventures Opportunities Fund I, L.P. · CIK 0001677345 · 10% owner

AFEYAN NOUBAR · CIK 0001222012 · 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

Underlying: Common Stock · 335,457 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.

F7 · derivative.exercise_price: Each share of Series C Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F7 · price: Each share of Series C Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F7 · derivative.exercise_date: Each share of Series C Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F7 · derivative.expiration_date: Each share of Series C Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F4 · 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., he continues to serve as a manager of Flagship Fund IV GP. Each of these individuals and entities may be deemed to share voting and investment power with respect to all shares held by Flagship Fund IV. Each of the reporting persons disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.

SEC source: 0001104659-19-029735 · a4.xml · derivative · entry 20

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

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

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

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

Flagship Ventures 2007 General Partner LLC · CIK 0001508053 · 10% owner

Flagship Ventures Fund 2007, L.P. · CIK 0001508052 · 10% owner

Flagship Ventures Opportunities Fund I General Partner LLC · CIK 0001725004 · 10% owner

Flagship Ventures Opportunities Fund I, L.P. · CIK 0001677345 · 10% owner

AFEYAN NOUBAR · CIK 0001222012 · 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

Underlying: Common Stock · 120,795 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.

F7 · derivative.exercise_price: Each share of Series C Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F7 · price: Each share of Series C Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F7 · derivative.exercise_date: Each share of Series C Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F7 · derivative.expiration_date: Each share of Series C Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F1 · ownership.nature: Shares held by Flagship Ventures Fund 2007, L.P. ("Flagship Fund 2007"). Flagship Ventures 2007 General Partner LLC ("Fund 2007 GP") is the general partner of Flagship Fund 2007. Noubar B. Afeyan, Ph.D. and Edwin M. Kania, Jr. are the managers of Fund 2007 GP. While Mr. Kania is retired from Flagship Pioneering, Inc., he continues to serve as a manager of Flagship 2007 GP. Each of these individuals and entities may be deemed to share voting and investment power with respect to all shares held by Flagship Fund 2007. Each of the reporting persons disclaims beneficial ownership of the shares except to the extent of his or its pecuniary interest therein.

SEC source: 0001104659-19-029735 · a4.xml · derivative · entry 19

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

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

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

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

Flagship Ventures 2007 General Partner LLC · CIK 0001508053 · 10% owner

Flagship Ventures Fund 2007, L.P. · CIK 0001508052 · 10% owner

Flagship Ventures Opportunities Fund I General Partner LLC · CIK 0001725004 · 10% owner

Flagship Ventures Opportunities Fund I, L.P. · CIK 0001677345 · 10% owner

AFEYAN NOUBAR · CIK 0001222012 · 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

Underlying: Common Stock · 545,826 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_price: Each share of Series B Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F5 · price: Each share of Series B Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F5 · derivative.exercise_date: Each share of Series B Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F5 · derivative.expiration_date: Each share of Series B Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F6 · ownership.nature: Shares held by Flagship Ventures Fund IV-Rx, L.P. ("Flagship Fund IV-Rx"). Flagship Fund IV GP is the general partner of Flagship Fund IV-Rx. 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., he continues to serve as a manager of Flagship Fund IV GP. Each of these individuals and entities may be deemed to share voting and investment power with respect to all shares held by Flagship Fund IV-Rx. Each of the reporting persons disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.

SEC source: 0001104659-19-029735 · a4.xml · derivative · entry 18

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

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

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

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

Flagship Ventures 2007 General Partner LLC · CIK 0001508053 · 10% owner

Flagship Ventures Fund 2007, L.P. · CIK 0001508052 · 10% owner

Flagship Ventures Opportunities Fund I General Partner LLC · CIK 0001725004 · 10% owner

Flagship Ventures Opportunities Fund I, L.P. · CIK 0001677345 · 10% owner

AFEYAN NOUBAR · CIK 0001222012 · 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

Underlying: Common Stock · 503,840 shares

Expires not disclosed

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

F5 · derivative.exercise_price: Each share of Series B Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F5 · price: Each share of Series B Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F5 · derivative.exercise_date: Each share of Series B Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F5 · derivative.expiration_date: Each share of Series B Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F4 · 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., he continues to serve as a manager of Flagship Fund IV GP. Each of these individuals and entities may be deemed to share voting and investment power with respect to all shares held by Flagship Fund IV. Each of the reporting persons disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.

SEC source: 0001104659-19-029735 · a4.xml · derivative · entry 17

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

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

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

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

Flagship Ventures 2007 General Partner LLC · CIK 0001508053 · 10% owner

Flagship Ventures Fund 2007, L.P. · CIK 0001508052 · 10% owner

Flagship Ventures Opportunities Fund I General Partner LLC · CIK 0001725004 · 10% owner

Flagship Ventures Opportunities Fund I, L.P. · CIK 0001677345 · 10% owner

AFEYAN NOUBAR · CIK 0001222012 · 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

Underlying: Common Stock · 209,933 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_price: Each share of Series B Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F5 · price: Each share of Series B Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F5 · derivative.exercise_date: Each share of Series B Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F5 · derivative.expiration_date: Each share of Series B Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F1 · ownership.nature: Shares held by Flagship Ventures Fund 2007, L.P. ("Flagship Fund 2007"). Flagship Ventures 2007 General Partner LLC ("Fund 2007 GP") is the general partner of Flagship Fund 2007. Noubar B. Afeyan, Ph.D. and Edwin M. Kania, Jr. are the managers of Fund 2007 GP. While Mr. Kania is retired from Flagship Pioneering, Inc., he continues to serve as a manager of Flagship 2007 GP. Each of these individuals and entities may be deemed to share voting and investment power with respect to all shares held by Flagship Fund 2007. Each of the reporting persons disclaims beneficial ownership of the shares except to the extent of his or its pecuniary interest therein.

SEC source: 0001104659-19-029735 · a4.xml · derivative · entry 16

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

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

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

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

Flagship Ventures 2007 General Partner LLC · CIK 0001508053 · 10% owner

Flagship Ventures Fund 2007, L.P. · CIK 0001508052 · 10% owner

Flagship Ventures Opportunities Fund I General Partner LLC · CIK 0001725004 · 10% owner

Flagship Ventures Opportunities Fund I, L.P. · CIK 0001677345 · 10% owner

AFEYAN NOUBAR · CIK 0001222012 · 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

Underlying: Common Stock · 2,255,074 shares

Expires not disclosed

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

F3 · derivative.exercise_price: Each share of Series A Preferred Stock converted into shares of the Issuer's common stock, par value $0.0001 per share ("Common Stock") on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F3 · price: Each share of Series A Preferred Stock converted into shares of the Issuer's common stock, par value $0.0001 per share ("Common Stock") on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F3 · derivative.exercise_date: Each share of Series A Preferred Stock converted into shares of the Issuer's common stock, par value $0.0001 per share ("Common Stock") on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F3 · derivative.expiration_date: Each share of Series A Preferred Stock converted into shares of the Issuer's common stock, par value $0.0001 per share ("Common Stock") on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F4 · 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., he continues to serve as a manager of Flagship Fund IV GP. Each of these individuals and entities may be deemed to share voting and investment power with respect to all shares held by Flagship Fund IV. Each of the reporting persons disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.

SEC source: 0001104659-19-029735 · a4.xml · derivative · entry 15

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

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

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

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

Flagship Ventures 2007 General Partner LLC · CIK 0001508053 · 10% owner

Flagship Ventures Fund 2007, L.P. · CIK 0001508052 · 10% owner

Flagship Ventures Opportunities Fund I General Partner LLC · CIK 0001725004 · 10% owner

Flagship Ventures Opportunities Fund I, L.P. · CIK 0001677345 · 10% owner

AFEYAN NOUBAR · CIK 0001222012 · 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

Underlying: Common Stock · 751,691 shares

Expires not disclosed

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

F3 · derivative.exercise_price: Each share of Series A Preferred Stock converted into shares of the Issuer's common stock, par value $0.0001 per share ("Common Stock") on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F3 · price: Each share of Series A Preferred Stock converted into shares of the Issuer's common stock, par value $0.0001 per share ("Common Stock") on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F3 · derivative.exercise_date: Each share of Series A Preferred Stock converted into shares of the Issuer's common stock, par value $0.0001 per share ("Common Stock") on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F3 · derivative.expiration_date: Each share of Series A Preferred Stock converted into shares of the Issuer's common stock, par value $0.0001 per share ("Common Stock") on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F1 · ownership.nature: Shares held by Flagship Ventures Fund 2007, L.P. ("Flagship Fund 2007"). Flagship Ventures 2007 General Partner LLC ("Fund 2007 GP") is the general partner of Flagship Fund 2007. Noubar B. Afeyan, Ph.D. and Edwin M. Kania, Jr. are the managers of Fund 2007 GP. While Mr. Kania is retired from Flagship Pioneering, Inc., he continues to serve as a manager of Flagship 2007 GP. Each of these individuals and entities may be deemed to share voting and investment power with respect to all shares held by Flagship Fund 2007. Each of the reporting persons disclaims beneficial ownership of the shares except to the extent of his or its pecuniary interest therein.

SEC source: 0001104659-19-029735 · a4.xml · nonDerivative · entry 14

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

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

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

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

Flagship Ventures 2007 General Partner LLC · CIK 0001508053 · 10% owner

Flagship Ventures Fund 2007, L.P. · CIK 0001508052 · 10% owner

Flagship Ventures Opportunities Fund I General Partner LLC · CIK 0001725004 · 10% owner

Flagship Ventures Opportunities Fund I, L.P. · CIK 0001677345 · 10% owner

AFEYAN NOUBAR · CIK 0001222012 · 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: 986,023

F9 · ownership.nature: Shares held by Flagship Ventures Opportunities Fund I, L.P. ("Flagship Opportunities I"). Flagship Ventures Opportunities Fund I General Partner LLC ("Flagship Opportunities GP") is the general partner of Flagship Opportunities I. Noubar B. Afeyan, Ph.D. serves as sole manager of Flagship Opportunities GP and may be deemed to possess sole voting and investment power with respect to all shares held by Flagship Opportunities I. Each of the reporting persons disclaims beneficial ownership of the shares except to the extent of his or its pecuniary interest therein.

SEC source: 0001104659-19-029735 · a4.xml · nonDerivative · entry 13

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

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

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

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

Flagship Ventures 2007 General Partner LLC · CIK 0001508053 · 10% owner

Flagship Ventures Fund 2007, L.P. · CIK 0001508052 · 10% owner

Flagship Ventures Opportunities Fund I General Partner LLC · CIK 0001725004 · 10% owner

Flagship Ventures Opportunities Fund I, L.P. · CIK 0001677345 · 10% owner

AFEYAN NOUBAR · CIK 0001222012 · 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: 486,023

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.

F8 · price: Each share of Series E Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F9 · ownership.nature: Shares held by Flagship Ventures Opportunities Fund I, L.P. ("Flagship Opportunities I"). Flagship Ventures Opportunities Fund I General Partner LLC ("Flagship Opportunities GP") is the general partner of Flagship Opportunities I. Noubar B. Afeyan, Ph.D. serves as sole manager of Flagship Opportunities GP and may be deemed to possess sole voting and investment power with respect to all shares held by Flagship Opportunities I. Each of the reporting persons disclaims beneficial ownership of the shares except to the extent of his or its pecuniary interest therein.

SEC source: 0001104659-19-029735 · a4.xml · nonDerivative · entry 12

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

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

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

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

Flagship Ventures 2007 General Partner LLC · CIK 0001508053 · 10% owner

Flagship Ventures Fund 2007, L.P. · CIK 0001508052 · 10% owner

Flagship Ventures Opportunities Fund I General Partner LLC · CIK 0001725004 · 10% owner

Flagship Ventures Opportunities Fund I, L.P. · CIK 0001677345 · 10% owner

AFEYAN NOUBAR · CIK 0001222012 · 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: 676,752

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.

F8 · price: Each share of Series E Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F6 · ownership.nature: Shares held by Flagship Ventures Fund IV-Rx, L.P. ("Flagship Fund IV-Rx"). Flagship Fund IV GP is the general partner of Flagship Fund IV-Rx. 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., he continues to serve as a manager of Flagship Fund IV GP. Each of these individuals and entities may be deemed to share voting and investment power with respect to all shares held by Flagship Fund IV-Rx. Each of the reporting persons disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.

SEC source: 0001104659-19-029735 · a4.xml · nonDerivative · entry 11

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

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

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

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

Flagship Ventures 2007 General Partner LLC · CIK 0001508053 · 10% owner

Flagship Ventures Fund 2007, L.P. · CIK 0001508052 · 10% owner

Flagship Ventures Opportunities Fund I General Partner LLC · CIK 0001725004 · 10% owner

Flagship Ventures Opportunities Fund I, L.P. · CIK 0001677345 · 10% owner

AFEYAN NOUBAR · CIK 0001222012 · 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: 3,288,780

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

F8 · price: Each share of Series E Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F4 · 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., he continues to serve as a manager of Flagship Fund IV GP. Each of these individuals and entities may be deemed to share voting and investment power with respect to all shares held by Flagship Fund IV. Each of the reporting persons disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.

SEC source: 0001104659-19-029735 · a4.xml · nonDerivative · entry 10

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

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

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

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

Flagship Ventures 2007 General Partner LLC · CIK 0001508053 · 10% owner

Flagship Ventures Fund 2007, L.P. · CIK 0001508052 · 10% owner

Flagship Ventures Opportunities Fund I General Partner LLC · CIK 0001725004 · 10% owner

Flagship Ventures Opportunities Fund I, L.P. · CIK 0001677345 · 10% owner

AFEYAN NOUBAR · CIK 0001222012 · 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: 628,150

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.

F7 · price: Each share of Series C Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F6 · ownership.nature: Shares held by Flagship Ventures Fund IV-Rx, L.P. ("Flagship Fund IV-Rx"). Flagship Fund IV GP is the general partner of Flagship Fund IV-Rx. 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., he continues to serve as a manager of Flagship Fund IV GP. Each of these individuals and entities may be deemed to share voting and investment power with respect to all shares held by Flagship Fund IV-Rx. Each of the reporting persons disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.

SEC source: 0001104659-19-029735 · a4.xml · nonDerivative · entry 9

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

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

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

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

Flagship Ventures 2007 General Partner LLC · CIK 0001508053 · 10% owner

Flagship Ventures Fund 2007, L.P. · CIK 0001508052 · 10% owner

Flagship Ventures Opportunities Fund I General Partner LLC · CIK 0001725004 · 10% owner

Flagship Ventures Opportunities Fund I, L.P. · CIK 0001677345 · 10% owner

AFEYAN NOUBAR · CIK 0001222012 · 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: 3,094,371

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.

F7 · price: Each share of Series C Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F4 · 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., he continues to serve as a manager of Flagship Fund IV GP. Each of these individuals and entities may be deemed to share voting and investment power with respect to all shares held by Flagship Fund IV. Each of the reporting persons disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.

SEC source: 0001104659-19-029735 · a4.xml · nonDerivative · entry 8

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

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

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

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

Flagship Ventures 2007 General Partner LLC · CIK 0001508053 · 10% owner

Flagship Ventures Fund 2007, L.P. · CIK 0001508052 · 10% owner

Flagship Ventures Opportunities Fund I General Partner LLC · CIK 0001725004 · 10% owner

Flagship Ventures Opportunities Fund I, L.P. · CIK 0001677345 · 10% owner

AFEYAN NOUBAR · CIK 0001222012 · 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: 1,761,029

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.

F7 · price: Each share of Series C Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F1 · ownership.nature: Shares held by Flagship Ventures Fund 2007, L.P. ("Flagship Fund 2007"). Flagship Ventures 2007 General Partner LLC ("Fund 2007 GP") is the general partner of Flagship Fund 2007. Noubar B. Afeyan, Ph.D. and Edwin M. Kania, Jr. are the managers of Fund 2007 GP. While Mr. Kania is retired from Flagship Pioneering, Inc., he continues to serve as a manager of Flagship 2007 GP. Each of these individuals and entities may be deemed to share voting and investment power with respect to all shares held by Flagship Fund 2007. Each of the reporting persons disclaims beneficial ownership of the shares except to the extent of his or its pecuniary interest therein.

SEC source: 0001104659-19-029735 · a4.xml · nonDerivative · entry 7

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

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

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

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

Flagship Ventures 2007 General Partner LLC · CIK 0001508053 · 10% owner

Flagship Ventures Fund 2007, L.P. · CIK 0001508052 · 10% owner

Flagship Ventures Opportunities Fund I General Partner LLC · CIK 0001725004 · 10% owner

Flagship Ventures Opportunities Fund I, L.P. · CIK 0001677345 · 10% owner

AFEYAN NOUBAR · CIK 0001222012 · 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: 545,826

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 · price: Each share of Series B Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F6 · ownership.nature: Shares held by Flagship Ventures Fund IV-Rx, L.P. ("Flagship Fund IV-Rx"). Flagship Fund IV GP is the general partner of Flagship Fund IV-Rx. 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., he continues to serve as a manager of Flagship Fund IV GP. Each of these individuals and entities may be deemed to share voting and investment power with respect to all shares held by Flagship Fund IV-Rx. Each of the reporting persons disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.

SEC source: 0001104659-19-029735 · a4.xml · nonDerivative · entry 6

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

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

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

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

Flagship Ventures 2007 General Partner LLC · CIK 0001508053 · 10% owner

Flagship Ventures Fund 2007, L.P. · CIK 0001508052 · 10% owner

Flagship Ventures Opportunities Fund I General Partner LLC · CIK 0001725004 · 10% owner

Flagship Ventures Opportunities Fund I, L.P. · CIK 0001677345 · 10% owner

AFEYAN NOUBAR · CIK 0001222012 · 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: 2,758,914

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 · price: Each share of Series B Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F4 · 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., he continues to serve as a manager of Flagship Fund IV GP. Each of these individuals and entities may be deemed to share voting and investment power with respect to all shares held by Flagship Fund IV. Each of the reporting persons disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.

SEC source: 0001104659-19-029735 · a4.xml · nonDerivative · entry 5

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

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

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

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

Flagship Ventures 2007 General Partner LLC · CIK 0001508053 · 10% owner

Flagship Ventures Fund 2007, L.P. · CIK 0001508052 · 10% owner

Flagship Ventures Opportunities Fund I General Partner LLC · CIK 0001725004 · 10% owner

Flagship Ventures Opportunities Fund I, L.P. · CIK 0001677345 · 10% owner

AFEYAN NOUBAR · CIK 0001222012 · 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: 1,640,234

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 · price: Each share of Series B Preferred Stock converted into shares of the Issuer's Common Stock on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F1 · ownership.nature: Shares held by Flagship Ventures Fund 2007, L.P. ("Flagship Fund 2007"). Flagship Ventures 2007 General Partner LLC ("Fund 2007 GP") is the general partner of Flagship Fund 2007. Noubar B. Afeyan, Ph.D. and Edwin M. Kania, Jr. are the managers of Fund 2007 GP. While Mr. Kania is retired from Flagship Pioneering, Inc., he continues to serve as a manager of Flagship 2007 GP. Each of these individuals and entities may be deemed to share voting and investment power with respect to all shares held by Flagship Fund 2007. Each of the reporting persons disclaims beneficial ownership of the shares except to the extent of his or its pecuniary interest therein.

SEC source: 0001104659-19-029735 · a4.xml · nonDerivative · entry 4

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

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

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

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

Flagship Ventures 2007 General Partner LLC · CIK 0001508053 · 10% owner

Flagship Ventures Fund 2007, L.P. · CIK 0001508052 · 10% owner

Flagship Ventures Opportunities Fund I General Partner LLC · CIK 0001725004 · 10% owner

Flagship Ventures Opportunities Fund I, L.P. · CIK 0001677345 · 10% owner

AFEYAN NOUBAR · CIK 0001222012 · 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: 2,255,074

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

F3 · price: Each share of Series A Preferred Stock converted into shares of the Issuer's common stock, par value $0.0001 per share ("Common Stock") on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F4 · 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., he continues to serve as a manager of Flagship Fund IV GP. Each of these individuals and entities may be deemed to share voting and investment power with respect to all shares held by Flagship Fund IV. Each of the reporting persons disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.

SEC source: 0001104659-19-029735 · a4.xml · nonDerivative · entry 3

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

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

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

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

Flagship Ventures 2007 General Partner LLC · CIK 0001508053 · 10% owner

Flagship Ventures Fund 2007, L.P. · CIK 0001508052 · 10% owner

Flagship Ventures Opportunities Fund I General Partner LLC · CIK 0001725004 · 10% owner

Flagship Ventures Opportunities Fund I, L.P. · CIK 0001677345 · 10% owner

AFEYAN NOUBAR · CIK 0001222012 · 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: 1,430,301

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

F3 · price: Each share of Series A Preferred Stock converted into shares of the Issuer's common stock, par value $0.0001 per share ("Common Stock") on a one-for-1.842 basis upon the closing of the Issuer's initial public offering.

F1 · ownership.nature: Shares held by Flagship Ventures Fund 2007, L.P. ("Flagship Fund 2007"). Flagship Ventures 2007 General Partner LLC ("Fund 2007 GP") is the general partner of Flagship Fund 2007. Noubar B. Afeyan, Ph.D. and Edwin M. Kania, Jr. are the managers of Fund 2007 GP. While Mr. Kania is retired from Flagship Pioneering, Inc., he continues to serve as a manager of Flagship 2007 GP. Each of these individuals and entities may be deemed to share voting and investment power with respect to all shares held by Flagship Fund 2007. Each of the reporting persons disclaims beneficial ownership of the shares except to the extent of his or its pecuniary interest therein.

SEC source: 0000899243-18-030859 · doc4.xml · derivative · entry 18

AFEYAN NOUBAR · CIK 0001222012 · Director · 10% owner

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

Flagship Pioneering Inc. · CIK 0001400240 · 10% owner

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

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

Flagship Ventures Fund IV-Rx, L.P. · CIK 0001590973 · 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 · By: Flagship Ventures Fund IV-Rx, LP

Disclosed balance after: 0

Underlying: Common Stock · 21,496 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.

F8 · derivative.exercise_price: The Series D Preferred Stock converted into Common Stock based on an applicable conversion ratio of 0.45854 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series D Preferred Stock had no expiration date.

F8 · price: The Series D Preferred Stock converted into Common Stock based on an applicable conversion ratio of 0.45854 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series D Preferred Stock had no expiration date.

F8 · derivative.exercise_date: The Series D Preferred Stock converted into Common Stock based on an applicable conversion ratio of 0.45854 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series D Preferred Stock had no expiration date.

F8 · derivative.expiration_date: The Series D Preferred Stock converted into Common Stock based on an applicable conversion ratio of 0.45854 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series D Preferred Stock had no expiration date.

F2 · ownership.nature: Shares held by Flagship Ventures Fund IV-Rx, L.P. ("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: 0000899243-18-030859 · doc4.xml · derivative · entry 17

AFEYAN NOUBAR · CIK 0001222012 · Director · 10% owner

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

Flagship Pioneering Inc. · CIK 0001400240 · 10% owner

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

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

Flagship Ventures Fund IV-Rx, L.P. · CIK 0001590973 · 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 · By: Flagship Ventures Fund IV, LP

Disclosed balance after: 0

Underlying: Common Stock · 85,989 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.

F8 · derivative.exercise_price: The Series D Preferred Stock converted into Common Stock based on an applicable conversion ratio of 0.45854 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series D Preferred Stock had no expiration date.

F8 · price: The Series D Preferred Stock converted into Common Stock based on an applicable conversion ratio of 0.45854 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series D Preferred Stock had no expiration date.

F8 · derivative.exercise_date: The Series D Preferred Stock converted into Common Stock based on an applicable conversion ratio of 0.45854 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series D Preferred Stock had no expiration date.

F8 · derivative.expiration_date: The Series D Preferred Stock converted into Common Stock based on an applicable conversion ratio of 0.45854 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series D Preferred Stock had no expiration date.

F1 · ownership.nature: Shares held by Flagship Ventures Fund IV, L.P. ("Flagship Fund IV"). Flagship Ventures Fund IV General Partner LLC ("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: 0000899243-18-030859 · doc4.xml · derivative · entry 16

AFEYAN NOUBAR · CIK 0001222012 · Director · 10% owner

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

Flagship Pioneering Inc. · CIK 0001400240 · 10% owner

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

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

Flagship Ventures Fund IV-Rx, L.P. · CIK 0001590973 · 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 · By: Flagship Ventures Fund IV-Rx, LP

Disclosed balance after: 0

Underlying: Common Stock · 1,428,432 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.

F7 · derivative.exercise_price: The Series C Preferred Stock converted into Common Stock based on an applicable conversion ratio of 0.45853 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series C Preferred Stock had no expiration date.

F7 · price: The Series C Preferred Stock converted into Common Stock based on an applicable conversion ratio of 0.45853 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series C Preferred Stock had no expiration date.

F7 · derivative.exercise_date: The Series C Preferred Stock converted into Common Stock based on an applicable conversion ratio of 0.45853 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series C Preferred Stock had no expiration date.

F7 · derivative.expiration_date: The Series C Preferred Stock converted into Common Stock based on an applicable conversion ratio of 0.45853 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series C Preferred Stock had no expiration date.

F2 · ownership.nature: Shares held by Flagship Ventures Fund IV-Rx, L.P. ("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: 0000899243-18-030859 · doc4.xml · derivative · entry 15

AFEYAN NOUBAR · CIK 0001222012 · Director · 10% owner

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

Flagship Pioneering Inc. · CIK 0001400240 · 10% owner

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

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

Flagship Ventures Fund IV-Rx, L.P. · CIK 0001590973 · 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 · By: Flagship Ventures Fund IV, LP

Disclosed balance after: 0

Underlying: Common Stock · 5,713,739 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.

F7 · derivative.exercise_price: The Series C Preferred Stock converted into Common Stock based on an applicable conversion ratio of 0.45853 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series C Preferred Stock had no expiration date.

F7 · price: The Series C Preferred Stock converted into Common Stock based on an applicable conversion ratio of 0.45853 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series C Preferred Stock had no expiration date.

F7 · derivative.exercise_date: The Series C Preferred Stock converted into Common Stock based on an applicable conversion ratio of 0.45853 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series C Preferred Stock had no expiration date.

F7 · derivative.expiration_date: The Series C Preferred Stock converted into Common Stock based on an applicable conversion ratio of 0.45853 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series C Preferred Stock had no expiration date.

F1 · ownership.nature: Shares held by Flagship Ventures Fund IV, L.P. ("Flagship Fund IV"). Flagship Ventures Fund IV General Partner LLC ("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: 0000899243-18-030859 · doc4.xml · derivative · entry 14

AFEYAN NOUBAR · CIK 0001222012 · Director · 10% owner

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

Flagship Pioneering Inc. · CIK 0001400240 · 10% owner

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

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

Flagship Ventures Fund IV-Rx, L.P. · CIK 0001590973 · 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 · By: Flagship Ventures Fund IV-Rx, LP

Disclosed balance after: 0

Underlying: Common Stock · 6,195,632 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.

F6 · derivative.exercise_price: The Series B Preferred Stock converted into Common Stock based on an applicable conversion ratio of 0.45457 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series B Preferred Stock had no expiration date.

F6 · price: The Series B Preferred Stock converted into Common Stock based on an applicable conversion ratio of 0.45457 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series B Preferred Stock had no expiration date.

F6 · derivative.exercise_date: The Series B Preferred Stock converted into Common Stock based on an applicable conversion ratio of 0.45457 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series B Preferred Stock had no expiration date.

F6 · derivative.expiration_date: The Series B Preferred Stock converted into Common Stock based on an applicable conversion ratio of 0.45457 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series B Preferred Stock had no expiration date.

F2 · ownership.nature: Shares held by Flagship Ventures Fund IV-Rx, L.P. ("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: 0000899243-18-030859 · doc4.xml · derivative · entry 13

AFEYAN NOUBAR · CIK 0001222012 · Director · 10% owner

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

Flagship Pioneering Inc. · CIK 0001400240 · 10% owner

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

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

Flagship Ventures Fund IV-Rx, L.P. · CIK 0001590973 · 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 · By: Flagship Ventures Fund IV, LP

Disclosed balance after: 0

Underlying: Common Stock · 24,782,551 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.

F6 · derivative.exercise_price: The Series B Preferred Stock converted into Common Stock based on an applicable conversion ratio of 0.45457 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series B Preferred Stock had no expiration date.

F6 · price: The Series B Preferred Stock converted into Common Stock based on an applicable conversion ratio of 0.45457 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series B Preferred Stock had no expiration date.

F6 · derivative.exercise_date: The Series B Preferred Stock converted into Common Stock based on an applicable conversion ratio of 0.45457 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series B Preferred Stock had no expiration date.

F6 · derivative.expiration_date: The Series B Preferred Stock converted into Common Stock based on an applicable conversion ratio of 0.45457 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series B Preferred Stock had no expiration date.

F1 · ownership.nature: Shares held by Flagship Ventures Fund IV, L.P. ("Flagship Fund IV"). Flagship Ventures Fund IV General Partner LLC ("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: 0000899243-18-030859 · doc4.xml · derivative · entry 12

AFEYAN NOUBAR · CIK 0001222012 · Director · 10% owner

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

Flagship Pioneering Inc. · CIK 0001400240 · 10% owner

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

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

Flagship Ventures Fund IV-Rx, L.P. · CIK 0001590973 · 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 · By: Flagship Ventures Fund IV-Rx, LP

Disclosed balance after: 0

Underlying: Common Stock · 1,823,036 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_price: The Series A Preferred Stock converted into shares of the Issuer's common stock, $0.0001 par value per share ("Common Stock") based on an applicable conversion ratio of 0.45576 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series A Preferred Stock had no expiration date.

F5 · price: The Series A Preferred Stock converted into shares of the Issuer's common stock, $0.0001 par value per share ("Common Stock") based on an applicable conversion ratio of 0.45576 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series A Preferred Stock had no expiration date.

F5 · derivative.exercise_date: The Series A Preferred Stock converted into shares of the Issuer's common stock, $0.0001 par value per share ("Common Stock") based on an applicable conversion ratio of 0.45576 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series A Preferred Stock had no expiration date.

F5 · derivative.expiration_date: The Series A Preferred Stock converted into shares of the Issuer's common stock, $0.0001 par value per share ("Common Stock") based on an applicable conversion ratio of 0.45576 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series A Preferred Stock had no expiration date.

F2 · ownership.nature: Shares held by Flagship Ventures Fund IV-Rx, L.P. ("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: 0000899243-18-030859 · doc4.xml · derivative · entry 11

AFEYAN NOUBAR · CIK 0001222012 · Director · 10% owner

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

Flagship Pioneering Inc. · CIK 0001400240 · 10% owner

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

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

Flagship Ventures Fund IV-Rx, L.P. · CIK 0001590973 · 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 · By: Flagship Ventures Fund IV, LP

Disclosed balance after: 0

Underlying: Common Stock · 7,292,145 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_price: The Series A Preferred Stock converted into shares of the Issuer's common stock, $0.0001 par value per share ("Common Stock") based on an applicable conversion ratio of 0.45576 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series A Preferred Stock had no expiration date.

F5 · price: The Series A Preferred Stock converted into shares of the Issuer's common stock, $0.0001 par value per share ("Common Stock") based on an applicable conversion ratio of 0.45576 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series A Preferred Stock had no expiration date.

F5 · derivative.exercise_date: The Series A Preferred Stock converted into shares of the Issuer's common stock, $0.0001 par value per share ("Common Stock") based on an applicable conversion ratio of 0.45576 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series A Preferred Stock had no expiration date.

F5 · derivative.expiration_date: The Series A Preferred Stock converted into shares of the Issuer's common stock, $0.0001 par value per share ("Common Stock") based on an applicable conversion ratio of 0.45576 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series A Preferred Stock had no expiration date.

F1 · ownership.nature: Shares held by Flagship Ventures Fund IV, L.P. ("Flagship Fund IV"). Flagship Ventures Fund IV General Partner LLC ("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: 0000899243-18-030859 · doc4.xml · nonDerivative · entry 8

AFEYAN NOUBAR · CIK 0001222012 · Director · 10% owner

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

Flagship Pioneering Inc. · CIK 0001400240 · 10% owner

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

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

Flagship Ventures Fund IV-Rx, L.P. · CIK 0001590973 · 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 · By: Flagship Ventures Fund IV-Rx, LP

Disclosed balance after: 9,468,596

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.

F8 · price: The Series D Preferred Stock converted into Common Stock based on an applicable conversion ratio of 0.45854 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series D Preferred Stock had no expiration date.

F2 · ownership.nature: Shares held by Flagship Ventures Fund IV-Rx, L.P. ("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: 0000899243-18-030859 · doc4.xml · nonDerivative · entry 7

AFEYAN NOUBAR · CIK 0001222012 · Director · 10% owner

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

Flagship Pioneering Inc. · CIK 0001400240 · 10% owner

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

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

Flagship Ventures Fund IV-Rx, L.P. · CIK 0001590973 · 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 · By: Flagship Ventures Fund IV, LP

Disclosed balance after: 37,874,424

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.

F8 · price: The Series D Preferred Stock converted into Common Stock based on an applicable conversion ratio of 0.45854 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series D Preferred Stock had no expiration date.

F1 · ownership.nature: Shares held by Flagship Ventures Fund IV, L.P. ("Flagship Fund IV"). Flagship Ventures Fund IV General Partner LLC ("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: 0000899243-18-030859 · doc4.xml · nonDerivative · entry 6

AFEYAN NOUBAR · CIK 0001222012 · Director · 10% owner

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

Flagship Pioneering Inc. · CIK 0001400240 · 10% owner

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

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

Flagship Ventures Fund IV-Rx, L.P. · CIK 0001590973 · 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 · By: Flagship Ventures Fund IV-Rx, LP

Disclosed balance after: 9,447,100

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.

F7 · price: The Series C Preferred Stock converted into Common Stock based on an applicable conversion ratio of 0.45853 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series C Preferred Stock had no expiration date.

F2 · ownership.nature: Shares held by Flagship Ventures Fund IV-Rx, L.P. ("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: 0000899243-18-030859 · doc4.xml · nonDerivative · entry 5

AFEYAN NOUBAR · CIK 0001222012 · Director · 10% owner

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

Flagship Pioneering Inc. · CIK 0001400240 · 10% owner

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

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

Flagship Ventures Fund IV-Rx, L.P. · CIK 0001590973 · 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 · By: Flagship Ventures Fund IV, LP

Disclosed balance after: 37,788,435

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.

F7 · price: The Series C Preferred Stock converted into Common Stock based on an applicable conversion ratio of 0.45853 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series C Preferred Stock had no expiration date.

F1 · ownership.nature: Shares held by Flagship Ventures Fund IV, L.P. ("Flagship Fund IV"). Flagship Ventures Fund IV General Partner LLC ("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: 0000899243-18-030859 · doc4.xml · nonDerivative · entry 4

AFEYAN NOUBAR · CIK 0001222012 · Director · 10% owner

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

Flagship Pioneering Inc. · CIK 0001400240 · 10% owner

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

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

Flagship Ventures Fund IV-Rx, L.P. · CIK 0001590973 · 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 · By: Flagship Ventures Fund IV-Rx, LP

Disclosed balance after: 8,018,668

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.

F6 · price: The Series B Preferred Stock converted into Common Stock based on an applicable conversion ratio of 0.45457 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series B Preferred Stock had no expiration date.

F2 · ownership.nature: Shares held by Flagship Ventures Fund IV-Rx, L.P. ("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: 0000899243-18-030859 · doc4.xml · nonDerivative · entry 3

AFEYAN NOUBAR · CIK 0001222012 · Director · 10% owner

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

Flagship Pioneering Inc. · CIK 0001400240 · 10% owner

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

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

Flagship Ventures Fund IV-Rx, L.P. · CIK 0001590973 · 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 · By: Flagship Ventures Fund IV, LP

Disclosed balance after: 32,074,696

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.

F6 · price: The Series B Preferred Stock converted into Common Stock based on an applicable conversion ratio of 0.45457 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series B Preferred Stock had no expiration date.

F1 · ownership.nature: Shares held by Flagship Ventures Fund IV, L.P. ("Flagship Fund IV"). Flagship Ventures Fund IV General Partner LLC ("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: 0000899243-18-030859 · doc4.xml · nonDerivative · entry 2

AFEYAN NOUBAR · CIK 0001222012 · Director · 10% owner

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

Flagship Pioneering Inc. · CIK 0001400240 · 10% owner

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

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

Flagship Ventures Fund IV-Rx, L.P. · CIK 0001590973 · 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 · By: Flagship Ventures Fund IV-Rx, LP

Disclosed balance after: 1,823,036

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 · price: The Series A Preferred Stock converted into shares of the Issuer's common stock, $0.0001 par value per share ("Common Stock") based on an applicable conversion ratio of 0.45576 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series A Preferred Stock had no expiration date.

F2 · ownership.nature: Shares held by Flagship Ventures Fund IV-Rx, L.P. ("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: 0000899243-18-030859 · doc4.xml · nonDerivative · entry 1

AFEYAN NOUBAR · CIK 0001222012 · Director · 10% owner

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

Flagship Pioneering Inc. · CIK 0001400240 · 10% owner

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

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

Flagship Ventures Fund IV-Rx, L.P. · CIK 0001590973 · 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 · By: Flagship Ventures Fund IV, LP

Disclosed balance after: 7,292,145

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 · price: The Series A Preferred Stock converted into shares of the Issuer's common stock, $0.0001 par value per share ("Common Stock") based on an applicable conversion ratio of 0.45576 upon the closing of the Issuer's initial public offering on December 11, 2018. The Series A Preferred Stock had no expiration date.

F1 · ownership.nature: Shares held by Flagship Ventures Fund IV, L.P. ("Flagship Fund IV"). Flagship Ventures Fund IV General Partner LLC ("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: 0001104659-18-046534 · a4.xml · derivative · entry 21

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

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

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

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

Flagship Ventures Fund V, L.P. · CIK 0001627639 · 10% owner

Flagship V VentureLabs Rx Fund, L.P. · CIK 0001724939 · 10% owner

Flagship Ventures Opportunities Fund I, L.P. · CIK 0001677345 · 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

Underlying: Common Stock · 781,860 shares

Expires not disclosed

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

F2 · derivative.exercise_price: The preferred stock is convertible into the Issuer's common stock on a one-for-one basis at the holder's election and has no expiration date. The preferred stock automatically convert into common stock upon the closing of the Issuer's initial public offering held on July 20, 2018.

F2 · price: The preferred stock is convertible into the Issuer's common stock on a one-for-one basis at the holder's election and has no expiration date. The preferred stock automatically convert into common stock upon the closing of the Issuer's initial public offering held on July 20, 2018.

F2 · derivative.exercise_date: The preferred stock is convertible into the Issuer's common stock on a one-for-one basis at the holder's election and has no expiration date. The preferred stock automatically convert into common stock upon the closing of the Issuer's initial public offering held on July 20, 2018.

F2 · derivative.expiration_date: The preferred stock is convertible into the Issuer's common stock on a one-for-one basis at the holder's election and has no expiration date. The preferred stock automatically convert into common stock upon the closing of the Issuer's initial public offering held on July 20, 2018.

F7 · ownership.nature: Shares held by Flagship Ventures Opportunities Fund I, L.P. ("Flagship Opportunities Fund I"). Flagship Ventures Opportunities Fund I General Partner LLC ("Flagship Opportunities GP") is the general partner of Flagship Opportunities I. Noubar B. Afeyan, Ph.D. is the sole manager of Flagship Opportunities GP and may be deemed to possess sole voting and investment power with respect to all shares held by Flagship Opportunities I. Each of the filing persons disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.

SEC source: 0001104659-18-046534 · a4.xml · derivative · entry 20

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

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

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

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

Flagship Ventures Fund V, L.P. · CIK 0001627639 · 10% owner

Flagship V VentureLabs Rx Fund, L.P. · CIK 0001724939 · 10% owner

Flagship Ventures Opportunities Fund I, L.P. · CIK 0001677345 · 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

Underlying: Common Stock · 195,466 shares

Expires not disclosed

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

F2 · derivative.exercise_price: The preferred stock is convertible into the Issuer's common stock on a one-for-one basis at the holder's election and has no expiration date. The preferred stock automatically convert into common stock upon the closing of the Issuer's initial public offering held on July 20, 2018.

F2 · price: The preferred stock is convertible into the Issuer's common stock on a one-for-one basis at the holder's election and has no expiration date. The preferred stock automatically convert into common stock upon the closing of the Issuer's initial public offering held on July 20, 2018.

F2 · derivative.exercise_date: The preferred stock is convertible into the Issuer's common stock on a one-for-one basis at the holder's election and has no expiration date. The preferred stock automatically convert into common stock upon the closing of the Issuer's initial public offering held on July 20, 2018.

F2 · derivative.expiration_date: The preferred stock is convertible into the Issuer's common stock on a one-for-one basis at the holder's election and has no expiration date. The preferred stock automatically convert into common stock upon the closing of the Issuer's initial public offering held on July 20, 2018.

F6 · ownership.nature: Shares held by Flagship V VentureLabs Rx Fund, L.P. ("VentureLabs Rx V"). Flagship Fund V GP is the general partner of VentureLabs Rx V. Noubar B. Afeyan, Ph.D. is the sole manager of Flagship Fund V GP and may be deemed to possess sole voting and investment power with respect to all shares held by VentureLabs Rx V. Each of the filing persons disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.

SEC source: 0001104659-18-046534 · a4.xml · derivative · entry 19

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

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

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

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

Flagship Ventures Fund V, L.P. · CIK 0001627639 · 10% owner

Flagship V VentureLabs Rx Fund, L.P. · CIK 0001724939 · 10% owner

Flagship Ventures Opportunities Fund I, L.P. · CIK 0001677345 · 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

Underlying: Common Stock · 195,466 shares

Expires not disclosed

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

F2 · derivative.exercise_price: The preferred stock is convertible into the Issuer's common stock on a one-for-one basis at the holder's election and has no expiration date. The preferred stock automatically convert into common stock upon the closing of the Issuer's initial public offering held on July 20, 2018.

F2 · price: The preferred stock is convertible into the Issuer's common stock on a one-for-one basis at the holder's election and has no expiration date. The preferred stock automatically convert into common stock upon the closing of the Issuer's initial public offering held on July 20, 2018.

F2 · derivative.exercise_date: The preferred stock is convertible into the Issuer's common stock on a one-for-one basis at the holder's election and has no expiration date. The preferred stock automatically convert into common stock upon the closing of the Issuer's initial public offering held on July 20, 2018.

F2 · derivative.expiration_date: The preferred stock is convertible into the Issuer's common stock on a one-for-one basis at the holder's election and has no expiration date. The preferred stock automatically convert into common stock upon the closing of the Issuer's initial public offering held on July 20, 2018.

F5 · ownership.nature: Shares held by Flagship Ventures Fund V, L.P. ("Flagship Fund V"). Flagship Ventures Fund V General Partner LLC ("Flagship Fund V GP") is the general partner of Flagship Fund V. Noubar B. Afeyan, Ph.D. is the sole manager of Flagship Fund V GP and may be deemed to possess sole voting and investment power with respect to all shares held by Flagship Fund V. Each of the filing persons disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.

SEC source: 0001104659-18-046534 · a4.xml · derivative · entry 18

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

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

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

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

Flagship Ventures Fund V, L.P. · CIK 0001627639 · 10% owner

Flagship V VentureLabs Rx Fund, L.P. · CIK 0001724939 · 10% owner

Flagship Ventures Opportunities Fund I, L.P. · CIK 0001677345 · 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

Underlying: Common Stock · 1,781,843 shares

Expires not disclosed

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

F2 · derivative.exercise_price: The preferred stock is convertible into the Issuer's common stock on a one-for-one basis at the holder's election and has no expiration date. The preferred stock automatically convert into common stock upon the closing of the Issuer's initial public offering held on July 20, 2018.

F2 · price: The preferred stock is convertible into the Issuer's common stock on a one-for-one basis at the holder's election and has no expiration date. The preferred stock automatically convert into common stock upon the closing of the Issuer's initial public offering held on July 20, 2018.

F2 · derivative.exercise_date: The preferred stock is convertible into the Issuer's common stock on a one-for-one basis at the holder's election and has no expiration date. The preferred stock automatically convert into common stock upon the closing of the Issuer's initial public offering held on July 20, 2018.

F2 · derivative.expiration_date: The preferred stock is convertible into the Issuer's common stock on a one-for-one basis at the holder's election and has no expiration date. The preferred stock automatically convert into common stock upon the closing of the Issuer's initial public offering held on July 20, 2018.

F7 · ownership.nature: Shares held by Flagship Ventures Opportunities Fund I, L.P. ("Flagship Opportunities Fund I"). Flagship Ventures Opportunities Fund I General Partner LLC ("Flagship Opportunities GP") is the general partner of Flagship Opportunities I. Noubar B. Afeyan, Ph.D. is the sole manager of Flagship Opportunities GP and may be deemed to possess sole voting and investment power with respect to all shares held by Flagship Opportunities I. Each of the filing persons disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.

SEC source: 0001104659-18-046534 · a4.xml · derivative · entry 17

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

Flagship VentureLabs IV, LLC · CIK 0001642578 · 10% owner

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

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

Flagship Ventures Fund V, L.P. · CIK 0001627639 · 10% owner

Flagship V VentureLabs Rx Fund, L.P. · CIK 0001724939 · 10% owner

Flagship Ventures Opportunities Fund I, L.P. · CIK 0001677345 · 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

Underlying: Common Stock · 593,948 shares

Expires not disclosed

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

F2 · derivative.exercise_price: The preferred stock is convertible into the Issuer's common stock on a one-for-one basis at the holder's election and has no expiration date. The preferred stock automatically convert into common stock upon the closing of the Issuer's initial public offering held on July 20, 2018.

F2 · price: The preferred stock is convertible into the Issuer's common stock on a one-for-one basis at the holder's election and has no expiration date. The preferred stock automatically convert into common stock upon the closing of the Issuer's initial public offering held on July 20, 2018.

F2 · derivative.exercise_date: The preferred stock is convertible into the Issuer's common stock on a one-for-one basis at the holder's election and has no expiration date. The preferred stock automatically convert into common stock upon the closing of the Issuer's initial public offering held on July 20, 2018.

F2 · derivative.expiration_date: The preferred stock is convertible into the Issuer's common stock on a one-for-one basis at the holder's election and has no expiration date. The preferred stock automatically convert into common stock upon the closing of the Issuer's initial public offering held on July 20, 2018.

F6 · ownership.nature: Shares held by Flagship V VentureLabs Rx Fund, L.P. ("VentureLabs Rx V"). Flagship Fund V GP is the general partner of VentureLabs Rx V. Noubar B. Afeyan, Ph.D. is the sole manager of Flagship Fund V GP and may be deemed to possess sole voting and investment power with respect to all shares held by VentureLabs Rx V. Each of the filing persons disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.