SRRK

SEC source: 0001104659-18-037312 · a4.xml · derivative · entry 9

SPRINGER TIMOTHY A · CIK 0001055624 · Director · 10% owner

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 522,556 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.

F1 · derivative.exercise_price: Each share of Preferred Stock automatically converted into Common Stock, for no payment or additional consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no payment or additional consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.exercise_date: Each share of Preferred Stock automatically converted into Common Stock, for no payment or additional consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.expiration_date: Each share of Preferred Stock automatically converted into Common Stock, for no payment or additional consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

SEC source: 0001104659-18-037312 · a4.xml · derivative · entry 8

SPRINGER TIMOTHY A · CIK 0001055624 · Director · 10% owner

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 350,287 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.

F1 · derivative.exercise_price: Each share of Preferred Stock automatically converted into Common Stock, for no payment or additional consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no payment or additional consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.exercise_date: Each share of Preferred Stock automatically converted into Common Stock, for no payment or additional consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.expiration_date: Each share of Preferred Stock automatically converted into Common Stock, for no payment or additional consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

SEC source: 0001104659-18-037312 · a4.xml · nonDerivative · entry 7

SPRINGER TIMOTHY A · CIK 0001055624 · Director · 10% owner

10b5-1 filing: Not disclosed

Ownership: Indirect · By TAS Partners, LLC

Disclosed balance after: 275,903

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

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no payment or additional consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F2 · ownership.nature: Timothy Springer is the Managing Member of TAS Partners, LLC.

SEC source: 0001104659-18-037312 · a4.xml · nonDerivative · entry 6

SPRINGER TIMOTHY A · CIK 0001055624 · Director · 10% owner

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 3,273,519

SEC source: 0001104659-18-037312 · a4.xml · nonDerivative · entry 5

SPRINGER TIMOTHY A · CIK 0001055624 · Director · 10% owner

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 3,202,091

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

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no payment or additional consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

SEC source: 0001104659-18-037312 · a4.xml · nonDerivative · entry 4

SPRINGER TIMOTHY A · CIK 0001055624 · Director · 10% owner

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 2,902,459

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

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no payment or additional consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

SEC source: 0001104659-18-037312 · a4.xml · nonDerivative · entry 3

SPRINGER TIMOTHY A · CIK 0001055624 · Director · 10% owner

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 2,168,651

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

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no payment or additional consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

SEC source: 0001104659-18-037312 · a4.xml · nonDerivative · entry 2

SPRINGER TIMOTHY A · CIK 0001055624 · Director · 10% owner

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 1,660,989

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

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no payment or additional consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

SEC source: 0001104659-18-037312 · a4.xml · nonDerivative · entry 1

SPRINGER TIMOTHY A · CIK 0001055624 · Director · 10% owner

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 1,138,433

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

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no payment or additional consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

SEC source: 0001104659-18-037313 · a4.xml · derivative · entry 3

Artal International S.C.A. · CIK 0001218180 · 10% owner

Invus Public Equities, L.P. · CIK 0001340097 · 10% owner

Invus Public Equities Advisors, LLC · CIK 0001340096 · 10% owner

Artal International Management S.A. · CIK 0001522131 · 10% owner

Artal Group S.A. · CIK 0001053906 · 10% owner

Westend S.A. · CIK 0001283968 · 10% owner

Stichting Administratiekantoor Westend · CIK 0001460840 · 10% owner

Minne Pascal · CIK 0001460839 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 1,946,040 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.

F1 · derivative.exercise_price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018.

F1 · kind: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018.

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018.

F1 · derivative.exercise_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018.

F1 · derivative.expiration_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018.

F3 · ownership.direct: These securities are directly held by Artal International S.C.A.

F5 · ownership.direct: Mr. Pascal Minne is the sole member of the Board of Stichting Administratiekantoor Westend. Stichting Administratiekantoor Westend is the parent company of Westend S.A. Westend S.A. is the parent company of Artal Group S.A. Artal Group S.A. is the parent company of Artal International Management S.A., which is the managing partner of Artal International S.C.A. Artal International S.C.A. is the managing member of Invus Public Equities Advisors, LLC. Invus Public Equities Advisors, LLC is the general partner of Invus Public Equities, L.P.

F6 · ownership.direct: Each of the Reporting Persons (other than to the extent it directly holds securities reported herein) disclaims beneficial ownership of the securities held by the other Reporting Persons, except to the extent of such Reporting Person's pecuniary interest therein, and, pursuant to Rule 16a-1(a)(4) under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), each of the Reporting Persons (other than to the extent it directly holds securities reported herein) states that the inclusion of these securities in this report shall not be deemed an admission of beneficial ownership of all of the reported securities for purposes of Section 16 or for any other purpose.

SEC source: 0001104659-18-037313 · a4.xml · nonDerivative · entry 2

Artal International S.C.A. · CIK 0001218180 · 10% owner

Invus Public Equities, L.P. · CIK 0001340097 · 10% owner

Invus Public Equities Advisors, LLC · CIK 0001340096 · 10% owner

Artal International Management S.A. · CIK 0001522131 · 10% owner

Artal Group S.A. · CIK 0001053906 · 10% owner

Westend S.A. · CIK 0001283968 · 10% owner

Stichting Administratiekantoor Westend · CIK 0001460840 · 10% owner

Minne Pascal · CIK 0001460839 · 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: 450,000

F2 · kind: The shares reported as purchased on May 29, 2018 were purchased in the Issuer's initial public offering.

F4 · ownership.nature: These securities are directly held by Invus Public Equities, L.P.

F5 · ownership.nature: Mr. Pascal Minne is the sole member of the Board of Stichting Administratiekantoor Westend. Stichting Administratiekantoor Westend is the parent company of Westend S.A. Westend S.A. is the parent company of Artal Group S.A. Artal Group S.A. is the parent company of Artal International Management S.A., which is the managing partner of Artal International S.C.A. Artal International S.C.A. is the managing member of Invus Public Equities Advisors, LLC. Invus Public Equities Advisors, LLC is the general partner of Invus Public Equities, L.P.

F6 · ownership.nature: Each of the Reporting Persons (other than to the extent it directly holds securities reported herein) disclaims beneficial ownership of the securities held by the other Reporting Persons, except to the extent of such Reporting Person's pecuniary interest therein, and, pursuant to Rule 16a-1(a)(4) under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), each of the Reporting Persons (other than to the extent it directly holds securities reported herein) states that the inclusion of these securities in this report shall not be deemed an admission of beneficial ownership of all of the reported securities for purposes of Section 16 or for any other purpose.

SEC source: 0001104659-18-037313 · a4.xml · nonDerivative · entry 1

Artal International S.C.A. · CIK 0001218180 · 10% owner

Invus Public Equities, L.P. · CIK 0001340097 · 10% owner

Invus Public Equities Advisors, LLC · CIK 0001340096 · 10% owner

Artal International Management S.A. · CIK 0001522131 · 10% owner

Artal Group S.A. · CIK 0001053906 · 10% owner

Westend S.A. · CIK 0001283968 · 10% owner

Stichting Administratiekantoor Westend · CIK 0001460840 · 10% owner

Minne Pascal · CIK 0001460839 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 1,946,040

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

F1 · kind: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018.

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018.

F3 · ownership.direct: These securities are directly held by Artal International S.C.A.

F5 · ownership.direct: Mr. Pascal Minne is the sole member of the Board of Stichting Administratiekantoor Westend. Stichting Administratiekantoor Westend is the parent company of Westend S.A. Westend S.A. is the parent company of Artal Group S.A. Artal Group S.A. is the parent company of Artal International Management S.A., which is the managing partner of Artal International S.C.A. Artal International S.C.A. is the managing member of Invus Public Equities Advisors, LLC. Invus Public Equities Advisors, LLC is the general partner of Invus Public Equities, L.P.

F6 · ownership.direct: Each of the Reporting Persons (other than to the extent it directly holds securities reported herein) disclaims beneficial ownership of the securities held by the other Reporting Persons, except to the extent of such Reporting Person's pecuniary interest therein, and, pursuant to Rule 16a-1(a)(4) under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), each of the Reporting Persons (other than to the extent it directly holds securities reported herein) states that the inclusion of these securities in this report shall not be deemed an admission of beneficial ownership of all of the reported securities for purposes of Section 16 or for any other purpose.

SEC source: 0001104659-18-037321 · a4.xml · derivative · entry 1

BUCKLER ALAN J. · CIK 0001740152 · Chief Scientific Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 15,838

Underlying: Common Stock` · 15,838 shares

Expires 2028-05-23

F1 · derivative.exercise_date: This option was granted on May 23, 2018 and following the closing of the Issuer's initial public offering on May 29, 2018, the vesting period for the stock option commenced and the stock option shall vest and become exercisable in 16 equal quarterly installments with the first quarterly amount to vest on August 29, 2018.

SEC source: 0001104659-18-037320 · a4.xml · derivative · entry 10

Burow Kristina · CIK 0001569248 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · By ARCH Venture Fund VIII, L.P.

Disclosed balance after: 0

Underlying: Common Stock · 293,813 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.

F1 · derivative.exercise_price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.exercise_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.expiration_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F2 · ownership.nature: The reportable securities are owned directly by ARCH Venture Fund VIII, L.P. ("ARCH Fund VIII"). The sole general partner of ARCH Fund VIII is ARCH Venture Partners VIII, L.P. ("ARCH Partners VIII"). ARCH Partners VIII may be deemed to share beneficial ownership over the securities held by ARCH Fund VIII. The sole general partner of ARCH Partners VIII is ARCH Venture Partners VIII, LLC ("ARCH VIII LLC"). ARCH VIII LLC may be deemed to share beneficial ownership over the securities held by ARCH Fund VIII. ARCH Partners VIII and ARCH VIII LLC disclaim beneficial ownership of such securities, except to the extent of any pecuniary interest therein.

F3 · ownership.nature: The managing directors of ARCH VIII LLC are Keith L. Crandell, Clinton Bybee and Robert Nelsen, and they may be deemed to beneficially own the shares held by ARCH Fund VIII. Messrs. Crandell, Bybee and Nelsen disclaim beneficial ownership of such shares, except to the extent of any pecuniary interest therein. The Reporting Person is a managing director of ARCH Partners VIII. The Reporting Person owns an interest in ARCH Partners VIII but does not have voting or investment control over the shares held by the fund, and disclaims beneficial ownership of such shares, except to the extent of any pecuniary interest therein.

SEC source: 0001104659-18-037320 · a4.xml · derivative · entry 9

Burow Kristina · CIK 0001569248 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · By ARCH Venture Fund VIII, L.P.

Disclosed balance after: 0

Underlying: Common Stock · 719,559 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.

F1 · derivative.exercise_price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.exercise_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.expiration_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F2 · ownership.nature: The reportable securities are owned directly by ARCH Venture Fund VIII, L.P. ("ARCH Fund VIII"). The sole general partner of ARCH Fund VIII is ARCH Venture Partners VIII, L.P. ("ARCH Partners VIII"). ARCH Partners VIII may be deemed to share beneficial ownership over the securities held by ARCH Fund VIII. The sole general partner of ARCH Partners VIII is ARCH Venture Partners VIII, LLC ("ARCH VIII LLC"). ARCH VIII LLC may be deemed to share beneficial ownership over the securities held by ARCH Fund VIII. ARCH Partners VIII and ARCH VIII LLC disclaim beneficial ownership of such securities, except to the extent of any pecuniary interest therein.

F3 · ownership.nature: The managing directors of ARCH VIII LLC are Keith L. Crandell, Clinton Bybee and Robert Nelsen, and they may be deemed to beneficially own the shares held by ARCH Fund VIII. Messrs. Crandell, Bybee and Nelsen disclaim beneficial ownership of such shares, except to the extent of any pecuniary interest therein. The Reporting Person is a managing director of ARCH Partners VIII. The Reporting Person owns an interest in ARCH Partners VIII but does not have voting or investment control over the shares held by the fund, and disclaims beneficial ownership of such shares, except to the extent of any pecuniary interest therein.

SEC source: 0001104659-18-037320 · a4.xml · derivative · entry 8

Burow Kristina · CIK 0001569248 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · By ARCH Venture Fund VIII, L.P.

Disclosed balance after: 0

Underlying: Common Stock · 551,807 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.

F1 · derivative.exercise_price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.exercise_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.expiration_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F2 · ownership.nature: The reportable securities are owned directly by ARCH Venture Fund VIII, L.P. ("ARCH Fund VIII"). The sole general partner of ARCH Fund VIII is ARCH Venture Partners VIII, L.P. ("ARCH Partners VIII"). ARCH Partners VIII may be deemed to share beneficial ownership over the securities held by ARCH Fund VIII. The sole general partner of ARCH Partners VIII is ARCH Venture Partners VIII, LLC ("ARCH VIII LLC"). ARCH VIII LLC may be deemed to share beneficial ownership over the securities held by ARCH Fund VIII. ARCH Partners VIII and ARCH VIII LLC disclaim beneficial ownership of such securities, except to the extent of any pecuniary interest therein.

F3 · ownership.nature: The managing directors of ARCH VIII LLC are Keith L. Crandell, Clinton Bybee and Robert Nelsen, and they may be deemed to beneficially own the shares held by ARCH Fund VIII. Messrs. Crandell, Bybee and Nelsen disclaim beneficial ownership of such shares, except to the extent of any pecuniary interest therein. The Reporting Person is a managing director of ARCH Partners VIII. The Reporting Person owns an interest in ARCH Partners VIII but does not have voting or investment control over the shares held by the fund, and disclaims beneficial ownership of such shares, except to the extent of any pecuniary interest therein.

SEC source: 0001104659-18-037320 · a4.xml · derivative · entry 7

Burow Kristina · CIK 0001569248 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · By ARCH Venture Fund VIII, L.P.

Disclosed balance after: 0

Underlying: Common Stock · 634,579 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.

F1 · derivative.exercise_price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.exercise_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.expiration_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F2 · ownership.nature: The reportable securities are owned directly by ARCH Venture Fund VIII, L.P. ("ARCH Fund VIII"). The sole general partner of ARCH Fund VIII is ARCH Venture Partners VIII, L.P. ("ARCH Partners VIII"). ARCH Partners VIII may be deemed to share beneficial ownership over the securities held by ARCH Fund VIII. The sole general partner of ARCH Partners VIII is ARCH Venture Partners VIII, LLC ("ARCH VIII LLC"). ARCH VIII LLC may be deemed to share beneficial ownership over the securities held by ARCH Fund VIII. ARCH Partners VIII and ARCH VIII LLC disclaim beneficial ownership of such securities, except to the extent of any pecuniary interest therein.

F3 · ownership.nature: The managing directors of ARCH VIII LLC are Keith L. Crandell, Clinton Bybee and Robert Nelsen, and they may be deemed to beneficially own the shares held by ARCH Fund VIII. Messrs. Crandell, Bybee and Nelsen disclaim beneficial ownership of such shares, except to the extent of any pecuniary interest therein. The Reporting Person is a managing director of ARCH Partners VIII. The Reporting Person owns an interest in ARCH Partners VIII but does not have voting or investment control over the shares held by the fund, and disclaims beneficial ownership of such shares, except to the extent of any pecuniary interest therein.

SEC source: 0001104659-18-037320 · a4.xml · derivative · entry 6

Burow Kristina · CIK 0001569248 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · By ARCH Venture Fund VIII, L.P.

Disclosed balance after: 0

Underlying: Common Stock · 437,859 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.

F1 · derivative.exercise_price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.exercise_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.expiration_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F2 · ownership.nature: The reportable securities are owned directly by ARCH Venture Fund VIII, L.P. ("ARCH Fund VIII"). The sole general partner of ARCH Fund VIII is ARCH Venture Partners VIII, L.P. ("ARCH Partners VIII"). ARCH Partners VIII may be deemed to share beneficial ownership over the securities held by ARCH Fund VIII. The sole general partner of ARCH Partners VIII is ARCH Venture Partners VIII, LLC ("ARCH VIII LLC"). ARCH VIII LLC may be deemed to share beneficial ownership over the securities held by ARCH Fund VIII. ARCH Partners VIII and ARCH VIII LLC disclaim beneficial ownership of such securities, except to the extent of any pecuniary interest therein.

F3 · ownership.nature: The managing directors of ARCH VIII LLC are Keith L. Crandell, Clinton Bybee and Robert Nelsen, and they may be deemed to beneficially own the shares held by ARCH Fund VIII. Messrs. Crandell, Bybee and Nelsen disclaim beneficial ownership of such shares, except to the extent of any pecuniary interest therein. The Reporting Person is a managing director of ARCH Partners VIII. The Reporting Person owns an interest in ARCH Partners VIII but does not have voting or investment control over the shares held by the fund, and disclaims beneficial ownership of such shares, except to the extent of any pecuniary interest therein.

SEC source: 0001104659-18-037320 · a4.xml · nonDerivative · entry 5

Burow Kristina · CIK 0001569248 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · By ARCH Venture Fund VIII, L.P.

Disclosed balance after: 2,637,617

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

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F2 · ownership.nature: The reportable securities are owned directly by ARCH Venture Fund VIII, L.P. ("ARCH Fund VIII"). The sole general partner of ARCH Fund VIII is ARCH Venture Partners VIII, L.P. ("ARCH Partners VIII"). ARCH Partners VIII may be deemed to share beneficial ownership over the securities held by ARCH Fund VIII. The sole general partner of ARCH Partners VIII is ARCH Venture Partners VIII, LLC ("ARCH VIII LLC"). ARCH VIII LLC may be deemed to share beneficial ownership over the securities held by ARCH Fund VIII. ARCH Partners VIII and ARCH VIII LLC disclaim beneficial ownership of such securities, except to the extent of any pecuniary interest therein.

F3 · ownership.nature: The managing directors of ARCH VIII LLC are Keith L. Crandell, Clinton Bybee and Robert Nelsen, and they may be deemed to beneficially own the shares held by ARCH Fund VIII. Messrs. Crandell, Bybee and Nelsen disclaim beneficial ownership of such shares, except to the extent of any pecuniary interest therein. The Reporting Person is a managing director of ARCH Partners VIII. The Reporting Person owns an interest in ARCH Partners VIII but does not have voting or investment control over the shares held by the fund, and disclaims beneficial ownership of such shares, except to the extent of any pecuniary interest therein.

SEC source: 0001104659-18-037320 · a4.xml · nonDerivative · entry 4

Burow Kristina · CIK 0001569248 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · By ARCH Venture Fund VIII, L.P.

Disclosed balance after: 2,343,804

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

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F2 · ownership.nature: The reportable securities are owned directly by ARCH Venture Fund VIII, L.P. ("ARCH Fund VIII"). The sole general partner of ARCH Fund VIII is ARCH Venture Partners VIII, L.P. ("ARCH Partners VIII"). ARCH Partners VIII may be deemed to share beneficial ownership over the securities held by ARCH Fund VIII. The sole general partner of ARCH Partners VIII is ARCH Venture Partners VIII, LLC ("ARCH VIII LLC"). ARCH VIII LLC may be deemed to share beneficial ownership over the securities held by ARCH Fund VIII. ARCH Partners VIII and ARCH VIII LLC disclaim beneficial ownership of such securities, except to the extent of any pecuniary interest therein.

F3 · ownership.nature: The managing directors of ARCH VIII LLC are Keith L. Crandell, Clinton Bybee and Robert Nelsen, and they may be deemed to beneficially own the shares held by ARCH Fund VIII. Messrs. Crandell, Bybee and Nelsen disclaim beneficial ownership of such shares, except to the extent of any pecuniary interest therein. The Reporting Person is a managing director of ARCH Partners VIII. The Reporting Person owns an interest in ARCH Partners VIII but does not have voting or investment control over the shares held by the fund, and disclaims beneficial ownership of such shares, except to the extent of any pecuniary interest therein.

SEC source: 0001104659-18-037320 · a4.xml · nonDerivative · entry 3

Burow Kristina · CIK 0001569248 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · By ARCH Venture Fund VIII, L.P.

Disclosed balance after: 1,624,245

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

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F2 · ownership.nature: The reportable securities are owned directly by ARCH Venture Fund VIII, L.P. ("ARCH Fund VIII"). The sole general partner of ARCH Fund VIII is ARCH Venture Partners VIII, L.P. ("ARCH Partners VIII"). ARCH Partners VIII may be deemed to share beneficial ownership over the securities held by ARCH Fund VIII. The sole general partner of ARCH Partners VIII is ARCH Venture Partners VIII, LLC ("ARCH VIII LLC"). ARCH VIII LLC may be deemed to share beneficial ownership over the securities held by ARCH Fund VIII. ARCH Partners VIII and ARCH VIII LLC disclaim beneficial ownership of such securities, except to the extent of any pecuniary interest therein.

F3 · ownership.nature: The managing directors of ARCH VIII LLC are Keith L. Crandell, Clinton Bybee and Robert Nelsen, and they may be deemed to beneficially own the shares held by ARCH Fund VIII. Messrs. Crandell, Bybee and Nelsen disclaim beneficial ownership of such shares, except to the extent of any pecuniary interest therein. The Reporting Person is a managing director of ARCH Partners VIII. The Reporting Person owns an interest in ARCH Partners VIII but does not have voting or investment control over the shares held by the fund, and disclaims beneficial ownership of such shares, except to the extent of any pecuniary interest therein.

SEC source: 0001104659-18-037320 · a4.xml · nonDerivative · entry 2

Burow Kristina · CIK 0001569248 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · By ARCH Venture Fund VIII, L.P.

Disclosed balance after: 1,072,438

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

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F2 · ownership.nature: The reportable securities are owned directly by ARCH Venture Fund VIII, L.P. ("ARCH Fund VIII"). The sole general partner of ARCH Fund VIII is ARCH Venture Partners VIII, L.P. ("ARCH Partners VIII"). ARCH Partners VIII may be deemed to share beneficial ownership over the securities held by ARCH Fund VIII. The sole general partner of ARCH Partners VIII is ARCH Venture Partners VIII, LLC ("ARCH VIII LLC"). ARCH VIII LLC may be deemed to share beneficial ownership over the securities held by ARCH Fund VIII. ARCH Partners VIII and ARCH VIII LLC disclaim beneficial ownership of such securities, except to the extent of any pecuniary interest therein.

F3 · ownership.nature: The managing directors of ARCH VIII LLC are Keith L. Crandell, Clinton Bybee and Robert Nelsen, and they may be deemed to beneficially own the shares held by ARCH Fund VIII. Messrs. Crandell, Bybee and Nelsen disclaim beneficial ownership of such shares, except to the extent of any pecuniary interest therein. The Reporting Person is a managing director of ARCH Partners VIII. The Reporting Person owns an interest in ARCH Partners VIII but does not have voting or investment control over the shares held by the fund, and disclaims beneficial ownership of such shares, except to the extent of any pecuniary interest therein.

SEC source: 0001104659-18-037320 · a4.xml · nonDerivative · entry 1

Burow Kristina · CIK 0001569248 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · By ARCH Venture Fund VIII, L.P.

Disclosed balance after: 437,859

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

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis at the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F2 · ownership.nature: The reportable securities are owned directly by ARCH Venture Fund VIII, L.P. ("ARCH Fund VIII"). The sole general partner of ARCH Fund VIII is ARCH Venture Partners VIII, L.P. ("ARCH Partners VIII"). ARCH Partners VIII may be deemed to share beneficial ownership over the securities held by ARCH Fund VIII. The sole general partner of ARCH Partners VIII is ARCH Venture Partners VIII, LLC ("ARCH VIII LLC"). ARCH VIII LLC may be deemed to share beneficial ownership over the securities held by ARCH Fund VIII. ARCH Partners VIII and ARCH VIII LLC disclaim beneficial ownership of such securities, except to the extent of any pecuniary interest therein.

F3 · ownership.nature: The managing directors of ARCH VIII LLC are Keith L. Crandell, Clinton Bybee and Robert Nelsen, and they may be deemed to beneficially own the shares held by ARCH Fund VIII. Messrs. Crandell, Bybee and Nelsen disclaim beneficial ownership of such shares, except to the extent of any pecuniary interest therein. The Reporting Person is a managing director of ARCH Partners VIII. The Reporting Person owns an interest in ARCH Partners VIII but does not have voting or investment control over the shares held by the fund, and disclaims beneficial ownership of such shares, except to the extent of any pecuniary interest therein.

SEC source: 0001104659-18-037319 · a4.xml · derivative · entry 26

Polaris Venture Management Co. VI, L.L.C. · CIK 0001665594 · 10% owner

Polaris Venture Partners VI, L.P. · CIK 0001493463 · 10% owner

Polaris Venture Partners Founders' Fund VI, L.P. · CIK 0001575691 · 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 · 16,542 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.

F1 · derivative.exercise_price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.exercise_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.expiration_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F4 · ownership.nature: The reportable securities are owned directly by Polaris Venture Partners Founders' Fund VI, L.P. ("PVPFF VI"). PVM VI is the general partner of PVPFF VI. PVM VI may be deemed to have sole voting and dispositive power with respect to the shares held by PVPFF VI and the Managing Members may each be deemed to have shared voting and dispositive power with respect to the shares held by PVPFF VI. Each of PVM VI and the Managing Members disclaims beneficial ownership of these securities and this report shall not be deemed an admission that PVM VI or any of the Managing Members is a beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0001104659-18-037319 · a4.xml · derivative · entry 25

Polaris Venture Management Co. VI, L.L.C. · CIK 0001665594 · 10% owner

Polaris Venture Partners VI, L.P. · CIK 0001493463 · 10% owner

Polaris Venture Partners Founders' Fund VI, L.P. · CIK 0001575691 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 0

Underlying: Common Stock · 283,090 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.

F1 · derivative.exercise_price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.exercise_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.expiration_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F2 · ownership.nature: The reportable securities are owned directly by Polaris Venture Partners VI, L.P. ("PVP VI"). Polaris Venture Management Co. VI, L.L.C. ("PVM VI") is the general partner of PVP VI. PVM VI is managed by its managing members, one of whom is Dr. Amir Nashat, a member of the Issuer's Board of Directors (collectively, the "Managing Members"). PVM VI may be deemed to have sole voting and dispositive power with respect to the shares held by PVP VI and the Managing Members may each be deemed to have shared voting and dispositive power with respect to the shares held by PVP VI.

F3 · ownership.nature: Each of PVM VI and the Managing Members disclaims beneficial ownership of these securities and this report shall not be deemed an admission that PVM VI or any of the Managing Members is a beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0001104659-18-037319 · a4.xml · derivative · entry 24

Polaris Venture Management Co. VI, L.L.C. · CIK 0001665594 · 10% owner

Polaris Venture Partners VI, L.P. · CIK 0001493463 · 10% owner

Polaris Venture Partners Founders' Fund VI, L.P. · CIK 0001575691 · 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 · 40,514 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.

F1 · derivative.exercise_price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.exercise_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.expiration_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F4 · ownership.nature: The reportable securities are owned directly by Polaris Venture Partners Founders' Fund VI, L.P. ("PVPFF VI"). PVM VI is the general partner of PVPFF VI. PVM VI may be deemed to have sole voting and dispositive power with respect to the shares held by PVPFF VI and the Managing Members may each be deemed to have shared voting and dispositive power with respect to the shares held by PVPFF VI. Each of PVM VI and the Managing Members disclaims beneficial ownership of these securities and this report shall not be deemed an admission that PVM VI or any of the Managing Members is a beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0001104659-18-037319 · a4.xml · derivative · entry 23

Polaris Venture Management Co. VI, L.L.C. · CIK 0001665594 · 10% owner

Polaris Venture Partners VI, L.P. · CIK 0001493463 · 10% owner

Polaris Venture Partners Founders' Fund VI, L.P. · CIK 0001575691 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 0

Underlying: Common Stock · 693,294 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.

F1 · derivative.exercise_price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.exercise_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.expiration_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F2 · ownership.nature: The reportable securities are owned directly by Polaris Venture Partners VI, L.P. ("PVP VI"). Polaris Venture Management Co. VI, L.L.C. ("PVM VI") is the general partner of PVP VI. PVM VI is managed by its managing members, one of whom is Dr. Amir Nashat, a member of the Issuer's Board of Directors (collectively, the "Managing Members"). PVM VI may be deemed to have sole voting and dispositive power with respect to the shares held by PVP VI and the Managing Members may each be deemed to have shared voting and dispositive power with respect to the shares held by PVP VI.

F3 · ownership.nature: Each of PVM VI and the Managing Members disclaims beneficial ownership of these securities and this report shall not be deemed an admission that PVM VI or any of the Managing Members is a beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0001104659-18-037319 · a4.xml · derivative · entry 22

Polaris Venture Management Co. VI, L.L.C. · CIK 0001665594 · 10% owner

Polaris Venture Partners VI, L.P. · CIK 0001493463 · 10% owner

Polaris Venture Partners Founders' Fund VI, L.P. · CIK 0001575691 · 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 · 15,233 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.

F1 · derivative.exercise_price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.exercise_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.expiration_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F4 · ownership.nature: The reportable securities are owned directly by Polaris Venture Partners Founders' Fund VI, L.P. ("PVPFF VI"). PVM VI is the general partner of PVPFF VI. PVM VI may be deemed to have sole voting and dispositive power with respect to the shares held by PVPFF VI and the Managing Members may each be deemed to have shared voting and dispositive power with respect to the shares held by PVPFF VI. Each of PVM VI and the Managing Members disclaims beneficial ownership of these securities and this report shall not be deemed an admission that PVM VI or any of the Managing Members is a beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0001104659-18-037319 · a4.xml · derivative · entry 21

Polaris Venture Management Co. VI, L.L.C. · CIK 0001665594 · 10% owner

Polaris Venture Partners VI, L.P. · CIK 0001493463 · 10% owner

Polaris Venture Partners Founders' Fund VI, L.P. · CIK 0001575691 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 0

Underlying: Common Stock · 260,670 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.

F1 · derivative.exercise_price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.exercise_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.expiration_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F2 · ownership.nature: The reportable securities are owned directly by Polaris Venture Partners VI, L.P. ("PVP VI"). Polaris Venture Management Co. VI, L.L.C. ("PVM VI") is the general partner of PVP VI. PVM VI is managed by its managing members, one of whom is Dr. Amir Nashat, a member of the Issuer's Board of Directors (collectively, the "Managing Members"). PVM VI may be deemed to have sole voting and dispositive power with respect to the shares held by PVP VI and the Managing Members may each be deemed to have shared voting and dispositive power with respect to the shares held by PVP VI.

F3 · ownership.nature: Each of PVM VI and the Managing Members disclaims beneficial ownership of these securities and this report shall not be deemed an admission that PVM VI or any of the Managing Members is a beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0001104659-18-037319 · a4.xml · derivative · entry 20

Polaris Venture Management Co. VI, L.L.C. · CIK 0001665594 · 10% owner

Polaris Venture Partners VI, L.P. · CIK 0001493463 · 10% owner

Polaris Venture Partners Founders' Fund VI, L.P. · CIK 0001575691 · 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 · 28,028 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.

F1 · derivative.exercise_price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.exercise_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.expiration_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F4 · ownership.nature: The reportable securities are owned directly by Polaris Venture Partners Founders' Fund VI, L.P. ("PVPFF VI"). PVM VI is the general partner of PVPFF VI. PVM VI may be deemed to have sole voting and dispositive power with respect to the shares held by PVPFF VI and the Managing Members may each be deemed to have shared voting and dispositive power with respect to the shares held by PVPFF VI. Each of PVM VI and the Managing Members disclaims beneficial ownership of these securities and this report shall not be deemed an admission that PVM VI or any of the Managing Members is a beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0001104659-18-037319 · a4.xml · derivative · entry 19

Polaris Venture Management Co. VI, L.L.C. · CIK 0001665594 · 10% owner

Polaris Venture Partners VI, L.P. · CIK 0001493463 · 10% owner

Polaris Venture Partners Founders' Fund VI, L.P. · CIK 0001575691 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 0

Underlying: Common Stock · 479,634 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.

F1 · derivative.exercise_price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.exercise_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.expiration_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F2 · ownership.nature: The reportable securities are owned directly by Polaris Venture Partners VI, L.P. ("PVP VI"). Polaris Venture Management Co. VI, L.L.C. ("PVM VI") is the general partner of PVP VI. PVM VI is managed by its managing members, one of whom is Dr. Amir Nashat, a member of the Issuer's Board of Directors (collectively, the "Managing Members"). PVM VI may be deemed to have sole voting and dispositive power with respect to the shares held by PVP VI and the Managing Members may each be deemed to have shared voting and dispositive power with respect to the shares held by PVP VI.

F3 · ownership.nature: Each of PVM VI and the Managing Members disclaims beneficial ownership of these securities and this report shall not be deemed an admission that PVM VI or any of the Managing Members is a beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0001104659-18-037319 · a4.xml · derivative · entry 18

Polaris Venture Management Co. VI, L.L.C. · CIK 0001665594 · 10% owner

Polaris Venture Partners VI, L.P. · CIK 0001493463 · 10% owner

Polaris Venture Partners Founders' Fund VI, L.P. · CIK 0001575691 · 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 · 28,851 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.

F1 · derivative.exercise_price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.exercise_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.expiration_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F4 · ownership.nature: The reportable securities are owned directly by Polaris Venture Partners Founders' Fund VI, L.P. ("PVPFF VI"). PVM VI is the general partner of PVPFF VI. PVM VI may be deemed to have sole voting and dispositive power with respect to the shares held by PVPFF VI and the Managing Members may each be deemed to have shared voting and dispositive power with respect to the shares held by PVPFF VI. Each of PVM VI and the Managing Members disclaims beneficial ownership of these securities and this report shall not be deemed an admission that PVM VI or any of the Managing Members is a beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0001104659-18-037319 · a4.xml · derivative · entry 17

Polaris Venture Management Co. VI, L.L.C. · CIK 0001665594 · 10% owner

Polaris Venture Partners VI, L.P. · CIK 0001493463 · 10% owner

Polaris Venture Partners Founders' Fund VI, L.P. · CIK 0001575691 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 0

Underlying: Common Stock · 493,705 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.

F1 · derivative.exercise_price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.exercise_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.expiration_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F2 · ownership.nature: The reportable securities are owned directly by Polaris Venture Partners VI, L.P. ("PVP VI"). Polaris Venture Management Co. VI, L.L.C. ("PVM VI") is the general partner of PVP VI. PVM VI is managed by its managing members, one of whom is Dr. Amir Nashat, a member of the Issuer's Board of Directors (collectively, the "Managing Members"). PVM VI may be deemed to have sole voting and dispositive power with respect to the shares held by PVP VI and the Managing Members may each be deemed to have shared voting and dispositive power with respect to the shares held by PVP VI.

F3 · ownership.nature: Each of PVM VI and the Managing Members disclaims beneficial ownership of these securities and this report shall not be deemed an admission that PVM VI or any of the Managing Members is a beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0001104659-18-037319 · a4.xml · derivative · entry 16

Polaris Venture Management Co. VI, L.L.C. · CIK 0001665594 · 10% owner

Polaris Venture Partners VI, L.P. · CIK 0001493463 · 10% owner

Polaris Venture Partners Founders' Fund VI, L.P. · CIK 0001575691 · 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 · 19,340 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.

F1 · derivative.exercise_price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.exercise_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.expiration_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F4 · ownership.nature: The reportable securities are owned directly by Polaris Venture Partners Founders' Fund VI, L.P. ("PVPFF VI"). PVM VI is the general partner of PVPFF VI. PVM VI may be deemed to have sole voting and dispositive power with respect to the shares held by PVPFF VI and the Managing Members may each be deemed to have shared voting and dispositive power with respect to the shares held by PVPFF VI. Each of PVM VI and the Managing Members disclaims beneficial ownership of these securities and this report shall not be deemed an admission that PVM VI or any of the Managing Members is a beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0001104659-18-037319 · a4.xml · derivative · entry 15

Polaris Venture Management Co. VI, L.L.C. · CIK 0001665594 · 10% owner

Polaris Venture Partners VI, L.P. · CIK 0001493463 · 10% owner

Polaris Venture Partners Founders' Fund VI, L.P. · CIK 0001575691 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 0

Underlying: Common Stock · 330,948 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.

F1 · derivative.exercise_price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.exercise_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F1 · derivative.expiration_date: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F2 · ownership.nature: The reportable securities are owned directly by Polaris Venture Partners VI, L.P. ("PVP VI"). Polaris Venture Management Co. VI, L.L.C. ("PVM VI") is the general partner of PVP VI. PVM VI is managed by its managing members, one of whom is Dr. Amir Nashat, a member of the Issuer's Board of Directors (collectively, the "Managing Members"). PVM VI may be deemed to have sole voting and dispositive power with respect to the shares held by PVP VI and the Managing Members may each be deemed to have shared voting and dispositive power with respect to the shares held by PVP VI.

F3 · ownership.nature: Each of PVM VI and the Managing Members disclaims beneficial ownership of these securities and this report shall not be deemed an admission that PVM VI or any of the Managing Members is a beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0001104659-18-037319 · a4.xml · nonDerivative · entry 14

Polaris Venture Management Co. VI, L.L.C. · CIK 0001665594 · 10% owner

Polaris Venture Partners VI, L.P. · CIK 0001493463 · 10% owner

Polaris Venture Partners Founders' Fund VI, L.P. · CIK 0001575691 · 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: 156,395

F4 · ownership.nature: The reportable securities are owned directly by Polaris Venture Partners Founders' Fund VI, L.P. ("PVPFF VI"). PVM VI is the general partner of PVPFF VI. PVM VI may be deemed to have sole voting and dispositive power with respect to the shares held by PVPFF VI and the Managing Members may each be deemed to have shared voting and dispositive power with respect to the shares held by PVPFF VI. Each of PVM VI and the Managing Members disclaims beneficial ownership of these securities and this report shall not be deemed an admission that PVM VI or any of the Managing Members is a beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0001104659-18-037319 · a4.xml · nonDerivative · entry 13

Polaris Venture Management Co. VI, L.L.C. · CIK 0001665594 · 10% owner

Polaris Venture Partners VI, L.P. · CIK 0001493463 · 10% owner

Polaris Venture Partners Founders' Fund VI, L.P. · CIK 0001575691 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 2,676,311

F2 · ownership.nature: The reportable securities are owned directly by Polaris Venture Partners VI, L.P. ("PVP VI"). Polaris Venture Management Co. VI, L.L.C. ("PVM VI") is the general partner of PVP VI. PVM VI is managed by its managing members, one of whom is Dr. Amir Nashat, a member of the Issuer's Board of Directors (collectively, the "Managing Members"). PVM VI may be deemed to have sole voting and dispositive power with respect to the shares held by PVP VI and the Managing Members may each be deemed to have shared voting and dispositive power with respect to the shares held by PVP VI.

F3 · ownership.nature: Each of PVM VI and the Managing Members disclaims beneficial ownership of these securities and this report shall not be deemed an admission that PVM VI or any of the Managing Members is a beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0001104659-18-037319 · a4.xml · nonDerivative · entry 12

Polaris Venture Management Co. VI, L.L.C. · CIK 0001665594 · 10% owner

Polaris Venture Partners VI, L.P. · CIK 0001493463 · 10% owner

Polaris Venture Partners Founders' Fund VI, L.P. · CIK 0001575691 · 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: 148,508

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

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F4 · ownership.nature: The reportable securities are owned directly by Polaris Venture Partners Founders' Fund VI, L.P. ("PVPFF VI"). PVM VI is the general partner of PVPFF VI. PVM VI may be deemed to have sole voting and dispositive power with respect to the shares held by PVPFF VI and the Managing Members may each be deemed to have shared voting and dispositive power with respect to the shares held by PVPFF VI. Each of PVM VI and the Managing Members disclaims beneficial ownership of these securities and this report shall not be deemed an admission that PVM VI or any of the Managing Members is a beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0001104659-18-037319 · a4.xml · nonDerivative · entry 11

Polaris Venture Management Co. VI, L.L.C. · CIK 0001665594 · 10% owner

Polaris Venture Partners VI, L.P. · CIK 0001493463 · 10% owner

Polaris Venture Partners Founders' Fund VI, L.P. · CIK 0001575691 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 2,541,341

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

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F2 · ownership.nature: The reportable securities are owned directly by Polaris Venture Partners VI, L.P. ("PVP VI"). Polaris Venture Management Co. VI, L.L.C. ("PVM VI") is the general partner of PVP VI. PVM VI is managed by its managing members, one of whom is Dr. Amir Nashat, a member of the Issuer's Board of Directors (collectively, the "Managing Members"). PVM VI may be deemed to have sole voting and dispositive power with respect to the shares held by PVP VI and the Managing Members may each be deemed to have shared voting and dispositive power with respect to the shares held by PVP VI.

F3 · ownership.nature: Each of PVM VI and the Managing Members disclaims beneficial ownership of these securities and this report shall not be deemed an admission that PVM VI or any of the Managing Members is a beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0001104659-18-037319 · a4.xml · nonDerivative · entry 10

Polaris Venture Management Co. VI, L.L.C. · CIK 0001665594 · 10% owner

Polaris Venture Partners VI, L.P. · CIK 0001493463 · 10% owner

Polaris Venture Partners Founders' Fund VI, L.P. · CIK 0001575691 · 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: 131,966

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

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F4 · ownership.nature: The reportable securities are owned directly by Polaris Venture Partners Founders' Fund VI, L.P. ("PVPFF VI"). PVM VI is the general partner of PVPFF VI. PVM VI may be deemed to have sole voting and dispositive power with respect to the shares held by PVPFF VI and the Managing Members may each be deemed to have shared voting and dispositive power with respect to the shares held by PVPFF VI. Each of PVM VI and the Managing Members disclaims beneficial ownership of these securities and this report shall not be deemed an admission that PVM VI or any of the Managing Members is a beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0001104659-18-037319 · a4.xml · nonDerivative · entry 9

Polaris Venture Management Co. VI, L.L.C. · CIK 0001665594 · 10% owner

Polaris Venture Partners VI, L.P. · CIK 0001493463 · 10% owner

Polaris Venture Partners Founders' Fund VI, L.P. · CIK 0001575691 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 2,258,251

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

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F2 · ownership.nature: The reportable securities are owned directly by Polaris Venture Partners VI, L.P. ("PVP VI"). Polaris Venture Management Co. VI, L.L.C. ("PVM VI") is the general partner of PVP VI. PVM VI is managed by its managing members, one of whom is Dr. Amir Nashat, a member of the Issuer's Board of Directors (collectively, the "Managing Members"). PVM VI may be deemed to have sole voting and dispositive power with respect to the shares held by PVP VI and the Managing Members may each be deemed to have shared voting and dispositive power with respect to the shares held by PVP VI.

F3 · ownership.nature: Each of PVM VI and the Managing Members disclaims beneficial ownership of these securities and this report shall not be deemed an admission that PVM VI or any of the Managing Members is a beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0001104659-18-037319 · a4.xml · nonDerivative · entry 8

Polaris Venture Management Co. VI, L.L.C. · CIK 0001665594 · 10% owner

Polaris Venture Partners VI, L.P. · CIK 0001493463 · 10% owner

Polaris Venture Partners Founders' Fund VI, L.P. · CIK 0001575691 · 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: 91,452

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

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F4 · ownership.nature: The reportable securities are owned directly by Polaris Venture Partners Founders' Fund VI, L.P. ("PVPFF VI"). PVM VI is the general partner of PVPFF VI. PVM VI may be deemed to have sole voting and dispositive power with respect to the shares held by PVPFF VI and the Managing Members may each be deemed to have shared voting and dispositive power with respect to the shares held by PVPFF VI. Each of PVM VI and the Managing Members disclaims beneficial ownership of these securities and this report shall not be deemed an admission that PVM VI or any of the Managing Members is a beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0001104659-18-037319 · a4.xml · nonDerivative · entry 7

Polaris Venture Management Co. VI, L.L.C. · CIK 0001665594 · 10% owner

Polaris Venture Partners VI, L.P. · CIK 0001493463 · 10% owner

Polaris Venture Partners Founders' Fund VI, L.P. · CIK 0001575691 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 1,564,957

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

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F2 · ownership.nature: The reportable securities are owned directly by Polaris Venture Partners VI, L.P. ("PVP VI"). Polaris Venture Management Co. VI, L.L.C. ("PVM VI") is the general partner of PVP VI. PVM VI is managed by its managing members, one of whom is Dr. Amir Nashat, a member of the Issuer's Board of Directors (collectively, the "Managing Members"). PVM VI may be deemed to have sole voting and dispositive power with respect to the shares held by PVP VI and the Managing Members may each be deemed to have shared voting and dispositive power with respect to the shares held by PVP VI.

F3 · ownership.nature: Each of PVM VI and the Managing Members disclaims beneficial ownership of these securities and this report shall not be deemed an admission that PVM VI or any of the Managing Members is a beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0001104659-18-037319 · a4.xml · nonDerivative · entry 6

Polaris Venture Management Co. VI, L.L.C. · CIK 0001665594 · 10% owner

Polaris Venture Partners VI, L.P. · CIK 0001493463 · 10% owner

Polaris Venture Partners Founders' Fund VI, L.P. · CIK 0001575691 · 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: 76,219

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

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F4 · ownership.nature: The reportable securities are owned directly by Polaris Venture Partners Founders' Fund VI, L.P. ("PVPFF VI"). PVM VI is the general partner of PVPFF VI. PVM VI may be deemed to have sole voting and dispositive power with respect to the shares held by PVPFF VI and the Managing Members may each be deemed to have shared voting and dispositive power with respect to the shares held by PVPFF VI. Each of PVM VI and the Managing Members disclaims beneficial ownership of these securities and this report shall not be deemed an admission that PVM VI or any of the Managing Members is a beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0001104659-18-037319 · a4.xml · nonDerivative · entry 5

Polaris Venture Management Co. VI, L.L.C. · CIK 0001665594 · 10% owner

Polaris Venture Partners VI, L.P. · CIK 0001493463 · 10% owner

Polaris Venture Partners Founders' Fund VI, L.P. · CIK 0001575691 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 1,304,287

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

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F2 · ownership.nature: The reportable securities are owned directly by Polaris Venture Partners VI, L.P. ("PVP VI"). Polaris Venture Management Co. VI, L.L.C. ("PVM VI") is the general partner of PVP VI. PVM VI is managed by its managing members, one of whom is Dr. Amir Nashat, a member of the Issuer's Board of Directors (collectively, the "Managing Members"). PVM VI may be deemed to have sole voting and dispositive power with respect to the shares held by PVP VI and the Managing Members may each be deemed to have shared voting and dispositive power with respect to the shares held by PVP VI.

F3 · ownership.nature: Each of PVM VI and the Managing Members disclaims beneficial ownership of these securities and this report shall not be deemed an admission that PVM VI or any of the Managing Members is a beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0001104659-18-037319 · a4.xml · nonDerivative · entry 4

Polaris Venture Management Co. VI, L.L.C. · CIK 0001665594 · 10% owner

Polaris Venture Partners VI, L.P. · CIK 0001493463 · 10% owner

Polaris Venture Partners Founders' Fund VI, L.P. · CIK 0001575691 · 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: 48,191

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

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F4 · ownership.nature: The reportable securities are owned directly by Polaris Venture Partners Founders' Fund VI, L.P. ("PVPFF VI"). PVM VI is the general partner of PVPFF VI. PVM VI may be deemed to have sole voting and dispositive power with respect to the shares held by PVPFF VI and the Managing Members may each be deemed to have shared voting and dispositive power with respect to the shares held by PVPFF VI. Each of PVM VI and the Managing Members disclaims beneficial ownership of these securities and this report shall not be deemed an admission that PVM VI or any of the Managing Members is a beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0001104659-18-037319 · a4.xml · nonDerivative · entry 3

Polaris Venture Management Co. VI, L.L.C. · CIK 0001665594 · 10% owner

Polaris Venture Partners VI, L.P. · CIK 0001493463 · 10% owner

Polaris Venture Partners Founders' Fund VI, L.P. · CIK 0001575691 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 824,653

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

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F2 · ownership.nature: The reportable securities are owned directly by Polaris Venture Partners VI, L.P. ("PVP VI"). Polaris Venture Management Co. VI, L.L.C. ("PVM VI") is the general partner of PVP VI. PVM VI is managed by its managing members, one of whom is Dr. Amir Nashat, a member of the Issuer's Board of Directors (collectively, the "Managing Members"). PVM VI may be deemed to have sole voting and dispositive power with respect to the shares held by PVP VI and the Managing Members may each be deemed to have shared voting and dispositive power with respect to the shares held by PVP VI.

F3 · ownership.nature: Each of PVM VI and the Managing Members disclaims beneficial ownership of these securities and this report shall not be deemed an admission that PVM VI or any of the Managing Members is a beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0001104659-18-037319 · a4.xml · nonDerivative · entry 2

Polaris Venture Management Co. VI, L.L.C. · CIK 0001665594 · 10% owner

Polaris Venture Partners VI, L.P. · CIK 0001493463 · 10% owner

Polaris Venture Partners Founders' Fund VI, L.P. · CIK 0001575691 · 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: 19,340

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

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F4 · ownership.nature: The reportable securities are owned directly by Polaris Venture Partners Founders' Fund VI, L.P. ("PVPFF VI"). PVM VI is the general partner of PVPFF VI. PVM VI may be deemed to have sole voting and dispositive power with respect to the shares held by PVPFF VI and the Managing Members may each be deemed to have shared voting and dispositive power with respect to the shares held by PVPFF VI. Each of PVM VI and the Managing Members disclaims beneficial ownership of these securities and this report shall not be deemed an admission that PVM VI or any of the Managing Members is a beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0001104659-18-037319 · a4.xml · nonDerivative · entry 1

Polaris Venture Management Co. VI, L.L.C. · CIK 0001665594 · 10% owner

Polaris Venture Partners VI, L.P. · CIK 0001493463 · 10% owner

Polaris Venture Partners Founders' Fund VI, L.P. · CIK 0001575691 · 10% owner

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

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 330,948

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

F1 · price: Each share of Preferred Stock automatically converted into Common Stock, for no additional payment or consideration, on a 2.8548-for-1 basis upon the closing of the Issuer's initial public offering on May 29, 2018 and had no expiration date.

F2 · ownership.nature: The reportable securities are owned directly by Polaris Venture Partners VI, L.P. ("PVP VI"). Polaris Venture Management Co. VI, L.L.C. ("PVM VI") is the general partner of PVP VI. PVM VI is managed by its managing members, one of whom is Dr. Amir Nashat, a member of the Issuer's Board of Directors (collectively, the "Managing Members"). PVM VI may be deemed to have sole voting and dispositive power with respect to the shares held by PVP VI and the Managing Members may each be deemed to have shared voting and dispositive power with respect to the shares held by PVP VI.

F3 · ownership.nature: Each of PVM VI and the Managing Members disclaims beneficial ownership of these securities and this report shall not be deemed an admission that PVM VI or any of the Managing Members is a beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

SEC source: 0001104659-18-037318 · a4.xml · derivative · entry 1

Mahanthappa Nagesh K. · CIK 0001740430 · Director · President and CEO

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 147,295

Underlying: Common Stock · 147,295 shares

Expires 2028-05-23

F1 · derivative.exercise_date: This option was granted on May 23, 2018 and following the closing of the Issuer's initial public offering on May 29, 2018, the vesting period for the stock option commenced and the stock option shall vest and become exercisable in 16 equal quarterly installments with the first quarterly amount to vest on August 29, 2018.