DYN

SEC source: 0000950170-24-030479 · ownership.xml · nonDerivative · entry 5

Brumm Joshua T · CIK 0001528826 · Director · CEO & President

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 554,385

F3 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $27.27 to $27.49, inclusive.

SEC source: 0000950170-24-030479 · ownership.xml · nonDerivative · entry 4

Brumm Joshua T · CIK 0001528826 · Director · CEO & President

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 554,820

F2 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $26.20 to $27.18, inclusive.

SEC source: 0000950170-24-030479 · ownership.xml · nonDerivative · entry 3

Brumm Joshua T · CIK 0001528826 · Director · CEO & President

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 715,490

F1 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $25.20 to $26.19, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote of this Form 4.

SEC source: 0000950170-24-030479 · ownership.xml · nonDerivative · entry 2

Brumm Joshua T · CIK 0001528826 · Director · CEO & President

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 917,728

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

SEC source: 0000950170-24-030479 · ownership.xml · nonDerivative · entry 1

Brumm Joshua T · CIK 0001528826 · Director · CEO & President

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 708,316

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

SEC source: 0000950170-24-030485 · ownership.xml · nonDerivative · entry 2

HIGH SUSANNA GATTI · CIK 0001691005 · Chief Operating Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 159,092

F2 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $27.39 to $27.42, inclusive.

SEC source: 0000950170-24-030485 · ownership.xml · nonDerivative · entry 1

HIGH SUSANNA GATTI · CIK 0001691005 · Chief Operating Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 159,383

F1 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $26.32 to $27.30, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote of this Form 4.

SEC source: 0000950170-24-030484 · ownership.xml · derivative · entry 10

McNeill Jonathan · CIK 0001824673 · Chief Business Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: Not disclosed

Underlying: Common Stock · 3,841 shares

Expires 2030-07-30

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.

F9 · derivative.exercise_date: The option was granted on July 31, 2020, with 100% of the option to vest upon the clearance date of an IND application submitted to the FDA by the Company with respect to one ofitsproduct candidates. On July 5, 2022, in connection with the clearance by the FDA of the Company's IND application for DYNE-251, the Compensation Committee determined thattheperformance condition had been achieved.

SEC source: 0000950170-24-030484 · ownership.xml · derivative · entry 9

McNeill Jonathan · CIK 0001824673 · Chief Business Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 12,309

Underlying: Common Stock · 86,159 shares

Expires 2030-07-30

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

F8 · derivative.exercise_date: The option was granted on July 31, 2020. The shares underlying the option vest over four years in equal quarterly installments beginning on October 31, 2020.

SEC source: 0000950170-24-030484 · ownership.xml · nonDerivative · entry 5

McNeill Jonathan · CIK 0001824673 · Chief Business Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 141,184

F3 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $27.27 to $27.39, inclusive.

SEC source: 0000950170-24-030484 · ownership.xml · nonDerivative · entry 4

McNeill Jonathan · CIK 0001824673 · Chief Business Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 141,873

F2 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $26.25 to $27.19, inclusive.

SEC source: 0000950170-24-030484 · ownership.xml · nonDerivative · entry 3

McNeill Jonathan · CIK 0001824673 · Chief Business Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 196,521

F1 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $25.25 to $26.22, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote of this Form 4.

SEC source: 0000950170-24-030484 · ownership.xml · nonDerivative · entry 2

McNeill Jonathan · CIK 0001824673 · Chief Business Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 231,184

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: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $25.25 to $26.22, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote of this Form 4.

SEC source: 0000950170-24-030484 · ownership.xml · nonDerivative · entry 1

McNeill Jonathan · CIK 0001824673 · Chief Business Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 227,343

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

SEC source: 0000950170-24-029615 · ownership.xml · nonDerivative · entry 1

Beskrovnaya Oxana · CIK 0001824542 · Chief Scientific Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 154,433

F1 · shares: Represents shares automatically sold by the Reporting Person to satisfy tax withholding obligations in connection with the vesting of restricted stock units granted to the Reporting Person on November 15, 2023. The automatic sale of the Reporting Person's shares is provided for in a restricted stock unit agreement constituting a "binding contract" consistent with the affirmative defense to liability under Rule 10b5-1 and the sale does not represent a discretionary trade by the Reporting Person.

F2 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $25.84 to $26.33, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote of this Form 4.

F3 · balance_after: Includes 140,948 unvested RSUs.

SEC source: 0000950170-24-029616 · ownership.xml · nonDerivative · entry 1

Brumm Joshua T · CIK 0001528826 · Director · CEO & President

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 554,385

F1 · shares: Represents shares automatically sold by the Reporting Person to satisfy tax withholding obligations in connection with the vesting of restricted stock units granted to the Reporting Person on November 15, 2023. The automatic sale of the Reporting Person's shares is provided for in a restricted stock unit agreement constituting a "binding contract" consistent with the affirmative defense to liability under Rule 10b5-1 and the sale does not represent a discretionary trade by the Reporting Person.

F2 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $25.84 to $26.32, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote of this Form 4.

F3 · balance_after: Includes 530,300 unvested RSUs.

SEC source: 0000950170-24-029614 · ownership.xml · nonDerivative · entry 1

HIGH SUSANNA GATTI · CIK 0001691005 · Chief Operating Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 186,291

F1 · shares: Represents shares automatically sold by the Reporting Person to satisfy tax withholding obligations in connection with the vesting of restricted stock units granted to the Reporting Person on November 15, 2023. The automatic sale of the Reporting Person's shares is provided for in a restricted stock unit agreement constituting a "binding contract" consistent with the affirmative defense to liability under Rule 10b5-1 and the sale does not represent a discretionary trade by the Reporting Person.

F2 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $25.84 to $26.33, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote of this Form 4.

F3 · balance_after: Includes 151,099 unvested RSUs.

SEC source: 0000950170-24-029609 · ownership.xml · nonDerivative · entry 2

Farwell Wildon · CIK 0001847941 · Chief Medical Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 153,175

F4 · kind: The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on July 14, 2023.

F5 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $26.20 to $26.23, inclusive.

SEC source: 0000950170-24-029609 · ownership.xml · nonDerivative · entry 1

Farwell Wildon · CIK 0001847941 · Chief Medical Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 154,732

F1 · shares: Represents shares automatically sold by the Reporting Person to satisfy tax withholding obligations in connection with the vesting of restricted stock units granted to the Reporting Person on March 2, 2021 and November 15, 2023. The automatic sale of the Reporting Person's shares is provided for in a restricted stock unit agreement constituting a "binding contract" consistent with the affirmative defense to liability under Rule 10b5-1 and the sale does not represent a discretionary trade by the Reporting Person.

F2 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $25.51 to $26.33, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote of this Form 4.

F3 · balance_after: Included 128,010 unvested RSUs.

SEC source: 0000950170-24-029607 · ownership.xml · nonDerivative · entry 1

McNeill Jonathan · CIK 0001824673 · Chief Business Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 141,184

F1 · shares: Represents shares automatically sold by the Reporting Person to satisfy tax withholding obligations in connection with the vesting of restricted stock units granted to the Reporting Person on November 15, 2023. The automatic sale of the Reporting Person's shares is provided for in a restricted stock unit agreement constituting a "binding contract" consistent with the affirmative defense to liability under Rule 10b5-1 and the sale does not represent a discretionary trade by the Reporting Person.

F2 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $25.84 to $26.33, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote of this Form 4.

F3 · balance_after: Includes 137,058 unvested RSUs.

SEC source: 0000950170-24-029603 · ownership.xml · nonDerivative · entry 1

Scalzo Richard William · CIK 0001789545 · SVP, Head of Finance & Admin.

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 121,955

F1 · shares: Represents shares automatically sold by the Reporting Person to satisfy tax withholding obligations in connection with the vesting of restricted stock units granted to the Reporting Person on November 15, 2023. The automatic sale of the Reporting Person's shares is provided for in a restricted stock unit agreement constituting a "binding contract" consistent with the affirmative defense to liability under Rule 10b5-1 and the sale does not represent a discretionary trade by the Reporting Person.

F2 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $25.84 to $26.33, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote of this Form 4.

F3 · balance_after: Includes 118,605 unvested RSUs.

SEC source: 0000950170-24-024300 · ownership.xml · derivative · entry 9

Brumm Joshua T · CIK 0001528826 · Director · CEO & President

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 342,681

Underlying: Common Stock · 36,637 shares

Expires 2030-07-30

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

F7 · derivative.exercise_date: The option was granted on July 31, 2020. The shares underlying the option vest over four years in equal quarterly installments through July 31, 2024.

SEC source: 0000950170-24-024300 · ownership.xml · derivative · entry 8

Brumm Joshua T · CIK 0001528826 · Director · CEO & President

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 44,500

Underlying: Common Stock · 57,843 shares

Expires 2030-07-30

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

F7 · derivative.exercise_date: The option was granted on July 31, 2020. The shares underlying the option vest over four years in equal quarterly installments through July 31, 2024.

SEC source: 0000950170-24-024300 · ownership.xml · nonDerivative · entry 6

Brumm Joshua T · CIK 0001528826 · Director · CEO & President

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 563,471

F2 · kind: The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on June 29, 2023.

F6 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $29.58 to $29.88, inclusive.

F1 · balance_after: Includes 530,300 unvested RSUs.

SEC source: 0000950170-24-024300 · ownership.xml · nonDerivative · entry 5

Brumm Joshua T · CIK 0001528826 · Director · CEO & President

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 564,885

F2 · kind: The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on June 29, 2023.

F5 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $28.56 to $29.56, inclusive.

F1 · balance_after: Includes 530,300 unvested RSUs.

SEC source: 0000950170-24-024300 · ownership.xml · nonDerivative · entry 4

Brumm Joshua T · CIK 0001528826 · Director · CEO & President

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 638,975

F2 · kind: The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on June 29, 2023.

F4 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $27.50 to $28.48, inclusive.

F1 · balance_after: Includes 530,300 unvested RSUs.

SEC source: 0000950170-24-024300 · ownership.xml · nonDerivative · entry 3

Brumm Joshua T · CIK 0001528826 · Director · CEO & President

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 657,951

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 · balance_after: Includes 530,300 unvested RSUs.

SEC source: 0000950170-24-024299 · ownership.xml · derivative · entry 8

McNeill Jonathan · CIK 0001824673 · Chief Business Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 24,260 shares

Expires 2029-02-25

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

F7 · derivative.exercise_date: The option was granted on February 26, 2019. The shares underlying the option vest over four years, with 25% of the shares vesting on February 1, 2020 and the remaining shares vesting in equal quarterly installments thereafter.

SEC source: 0000950170-24-024299 · ownership.xml · nonDerivative · entry 6

McNeill Jonathan · CIK 0001824673 · Chief Business Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 143,618

F2 · kind: The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on June 29, 2023.

F6 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $29.58 to $29.88, inclusive.

F1 · balance_after: Includes 137,058 unvested RSUs.

SEC source: 0000950170-24-024299 · ownership.xml · nonDerivative · entry 5

McNeill Jonathan · CIK 0001824673 · Chief Business Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 145,060

F2 · kind: The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on June 29, 2023.

F5 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $28.56 to $29.51, inclusive.

F1 · balance_after: Includes 137,058 unvested RSUs.

SEC source: 0000950170-24-024299 · ownership.xml · nonDerivative · entry 4

McNeill Jonathan · CIK 0001824673 · Chief Business Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 153,775

F2 · kind: The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on June 29, 2023.

F4 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $27.50 to $28.48, inclusive.

F1 · balance_after: Includes 137,058 unvested RSUs.

SEC source: 0000950170-24-024299 · ownership.xml · nonDerivative · entry 3

McNeill Jonathan · CIK 0001824673 · Chief Business Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 167,878

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 · balance_after: Includes 137,058 unvested RSUs.

SEC source: 0000950170-24-024298 · ownership.xml · derivative · entry 7

Scalzo Richard William · CIK 0001789545 · SVP, Head of Finance & Admin.

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 9,311 shares

Expires 2030-01-05

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

F6 · derivative.exercise_date: The option was granted on January 6, 2020. The shares underlying the option vest over four years, with 25% of the shares vesting on December 2, 2020 and the remaining shares vesting in equal quarterly installments thereafter.

SEC source: 0000950170-24-024298 · ownership.xml · nonDerivative · entry 5

Scalzo Richard William · CIK 0001789545 · SVP, Head of Finance & Admin.

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 124,228

F2 · kind: The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on July 11, 2023.

F5 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $28.55 to $28.83, inclusive.

F1 · balance_after: Includes 118,605 unvested RSUs.

SEC source: 0000950170-24-024298 · ownership.xml · nonDerivative · entry 4

Scalzo Richard William · CIK 0001789545 · SVP, Head of Finance & Admin.

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 124,792

F2 · kind: The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on July 11, 2023.

F4 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $27.50 to $28.48, inclusive.

F1 · balance_after: Includes 118,605 unvested RSUs.

SEC source: 0000950170-24-024298 · ownership.xml · nonDerivative · entry 3

Scalzo Richard William · CIK 0001789545 · SVP, Head of Finance & Admin.

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 133,539

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 · balance_after: Includes 118,605 unvested RSUs.

SEC source: 0001415889-24-006764 · form4-03052024_100352.xml · nonDerivative · entry 2

Atlas Venture Opportunity Fund I, L.P. · CIK 0001759241 · 10% owner

Atlas Venture Associates Opportunity I, L.P. · CIK 0001780065 · 10% owner

Atlas Venture Associates Opportunity I, LLC · CIK 0001780066 · 10% owner

Atlas Venture Opportunity Fund II, L.P. · CIK 0001885327 · 10% owner

Atlas Venture Associates Opportunity II, LP · CIK 0001935814 · 10% owner

Atlas Venture Associates Opportunity II, LLC · CIK 0001935810 · 10% owner

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

10b5-1 filing: Plan reported

Ownership: Indirect · See footnote

Disclosed balance after: 847,388

F4 · kind: This transaction was made pursuant to a Rule 10b5-1 trading plan adopted by Atlas Venture Opportunity Fund II, L.P. on January 10, 2024.

F2 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $29.95 to $30.20 inclusive. The Reporting Persons undertake to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

F5 · ownership.nature: The shares are owned directly by Atlas Venture Opportunity Fund II, L.P. ("AVOF II"). Atlas Venture Associates Opportunity II, L.P. ("AVAO II LP") is the general partner of AVOF II. Atlas Venture Associates Opportunity II, LLC ("AVAO II LLC") is the general partner of AVAO II LP. Each of AVAO II LP and AVAO II LLC disclaims Section 16 beneficial ownership of the securities held by AVOF II, except to the extent of its pecuniary interest therein, if any.

SEC source: 0001415889-24-006764 · form4-03052024_100352.xml · nonDerivative · entry 1

Atlas Venture Opportunity Fund I, L.P. · CIK 0001759241 · 10% owner

Atlas Venture Associates Opportunity I, L.P. · CIK 0001780065 · 10% owner

Atlas Venture Associates Opportunity I, LLC · CIK 0001780066 · 10% owner

Atlas Venture Opportunity Fund II, L.P. · CIK 0001885327 · 10% owner

Atlas Venture Associates Opportunity II, LP · CIK 0001935814 · 10% owner

Atlas Venture Associates Opportunity II, LLC · CIK 0001935810 · 10% owner

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

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 1,458,691

F1 · kind: This transaction was made pursuant to a Rule 10b5-1 trading plan adopted by Atlas Venture Opportunity Fund I, L.P. on January 10, 2024.

F2 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $29.95 to $30.20 inclusive. The Reporting Persons undertake to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

F3 · ownership.direct: The shares are held directly by Atlas Venture Opportunity Fund I, L.P. ("AVOF I"). The general partner of AVOF I is Atlas Venture Associates Opportunity I, L.P. ("AVAO I LP"). Atlas Venture Associates Opportunity I, LLC ("AVAO I LLC") is the general partner of AVAO I LP. Each of AVAO I LP and AVAO I LLC disclaims Section 16 beneficial ownership of the securities held by AVOF I, except to the extent of its pecuniary interest therein, if any.

SEC source: 0001415889-24-006766 · form4-03052024_100311.xml · nonDerivative · entry 2

Rhodes Jason P · CIK 0001577014 · Director

10b5-1 filing: Plan reported

Ownership: Indirect · See footnote

Disclosed balance after: 847,388

F4 · kind: This transaction was made pursuant to a Rule 10b5-1 trading plan adopted by Atlas Venture Opportunity Fund II, L.P. on January 10, 2024.

F2 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $29.95 to $30.20 inclusive. The Reporting Persons undertake to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

F5 · ownership.nature: The shares are owned directly by Atlas Venture Opportunity Fund II, L.P. ("AVOF II"). Atlas Venture Associates Opportunity II, LP ("AVAO II LP") is the general partner of AVOF II. Atlas Venture Associates Opportunity II, LLC ("AVAO II LLC") is the general partner of AVAO II LP. The Reporting Person is a member of AVAO II LLC and disclaims Section 16 beneficial ownership of such securities held by AVOF II, except to the extent of his pecuniary interest therein, if any.

SEC source: 0001415889-24-006766 · form4-03052024_100311.xml · nonDerivative · entry 1

Rhodes Jason P · CIK 0001577014 · Director

10b5-1 filing: Plan reported

Ownership: Indirect · See footnote

Disclosed balance after: 1,458,691

F1 · kind: This transaction was made pursuant to a Rule 10b5-1 trading plan adopted by Atlas Venture Opportunity Fund I, L.P. on January 10, 2024.

F2 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $29.95 to $30.20 inclusive. The Reporting Persons undertake to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

F3 · ownership.nature: The shares are held directly by Atlas Venture Opportunity Fund I, L.P. ("AVOF I"). The general partner of AVOF I is Atlas Venture Associates Opportunity I, L.P. ("AVAO I LP"). Atlas Venture Associates Opportunity I, LLC ("AVAO I LLC") is the general partner of AVAO I LP. The reporting person is a member of AVAO I LLC and disclaims beneficial ownership of such securities held by AVOF I, except to the extent of his pecuniary interest therein, if any.

SEC source: 0000950170-24-024300 · ownership.xml · derivative · entry 7

Brumm Joshua T · CIK 0001528826 · Director · CEO & President

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 102,343

Underlying: Common Stock · 5,520 shares

Expires 2030-07-30

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

F7 · derivative.exercise_date: The option was granted on July 31, 2020. The shares underlying the option vest over four years in equal quarterly installments through July 31, 2024.

SEC source: 0000950170-24-024300 · ownership.xml · nonDerivative · entry 2

Brumm Joshua T · CIK 0001528826 · Director · CEO & President

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 563,471

F2 · kind: The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on June 29, 2023.

F3 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $27.50 to $27.58, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in the footnotes of this Form 4.

F1 · balance_after: Includes 530,300 unvested RSUs.

SEC source: 0000950170-24-024300 · ownership.xml · nonDerivative · entry 1

Brumm Joshua T · CIK 0001528826 · Director · CEO & President

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 568,991

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 · balance_after: Includes 530,300 unvested RSUs.

SEC source: 0000950170-24-024299 · ownership.xml · derivative · entry 7

McNeill Jonathan · CIK 0001824673 · Chief Business Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 24,260

Underlying: Common Stock · 4,268 shares

Expires 2029-02-25

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

F7 · derivative.exercise_date: The option was granted on February 26, 2019. The shares underlying the option vest over four years, with 25% of the shares vesting on February 1, 2020 and the remaining shares vesting in equal quarterly installments thereafter.

SEC source: 0000950170-24-024299 · ownership.xml · nonDerivative · entry 2

McNeill Jonathan · CIK 0001824673 · Chief Business Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 143,618

F2 · kind: The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on June 29, 2023.

F3 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $27.50 to $27.58, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in the footnotes of this Form 4.

F1 · balance_after: Includes 137,058 unvested RSUs.

SEC source: 0000950170-24-024299 · ownership.xml · nonDerivative · entry 1

McNeill Jonathan · CIK 0001824673 · Chief Business Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 147,886

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 · balance_after: Includes 137,058 unvested RSUs.

SEC source: 0000950170-24-024298 · ownership.xml · derivative · entry 6

Scalzo Richard William · CIK 0001789545 · SVP, Head of Finance & Admin.

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 9,311

Underlying: Common Stock · 3,429 shares

Expires 2030-01-05

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

F6 · derivative.exercise_date: The option was granted on January 6, 2020. The shares underlying the option vest over four years, with 25% of the shares vesting on December 2, 2020 and the remaining shares vesting in equal quarterly installments thereafter.

SEC source: 0000950170-24-024298 · ownership.xml · nonDerivative · entry 2

Scalzo Richard William · CIK 0001789545 · SVP, Head of Finance & Admin.

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 124,228

F2 · kind: The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on July 11, 2023.

F3 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices within the range of $27.50 to $27.58, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this Form 4.

F1 · balance_after: Includes 118,605 unvested RSUs.

SEC source: 0000950170-24-024298 · ownership.xml · nonDerivative · entry 1

Scalzo Richard William · CIK 0001789545 · SVP, Head of Finance & Admin.

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 127,657

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 · balance_after: Includes 118,605 unvested RSUs.

SEC source: 0001415889-24-005777 · form4-02292024_120212.xml · nonDerivative · entry 18

Atlas Venture Fund XI, L.P. · CIK 0001708269 · 10% owner

Atlas Venture Associates XI, L.P. · CIK 0001780068 · 10% owner

Atlas Venture Associates XI, LLC · CIK 0001780067 · 10% owner

Atlas Venture Opportunity Fund I, L.P. · CIK 0001759241 · 10% owner

Atlas Venture Associates Opportunity I, L.P. · CIK 0001780065 · 10% owner

Atlas Venture Associates Opportunity I, LLC · CIK 0001780066 · 10% owner

Atlas Venture Opportunity Fund II, L.P. · CIK 0001885327 · 10% owner

Atlas Venture Associates Opportunity II, LP · CIK 0001935814 · 10% owner

Atlas Venture Associates Opportunity II, LLC · CIK 0001935810 · 10% owner

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

10b5-1 filing: Plan reported

Ownership: Indirect · See footnote

Disclosed balance after: 864,487

F7 · kind: This transaction was made pursuant to a Rule 10b5-1 trading plan adopted by Atlas Venture Opportunity Fund II, L.P. on January 10, 2024.

F12 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $25.25 to $25.255 inclusive.

F8 · ownership.nature: The shares are owned directly by Atlas Venture Opportunity Fund II, L.P. ("AVOF II"). Atlas Venture Associates Opportunity II, L.P. ("AVAO II LP") is the general partner of AVOF II. Atlas Venture Associates Opportunity II, LLC ("AVAO II LLC") is the general partner of AVAO II LP. Each of AVAO II LP and AVAO II LLC disclaims Section 16 beneficial ownership of the securities held by AVOF II, except to the extent of its pecuniary interest therein, if any.