IRON

SEC source: 0001193125-26-059760 · ownership.xml · nonDerivative · entry 1

Franchi Jean M. · CIK 0001653053 · Chief Financial Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 78,424

F1 · kind: This transaction represents shares sold by the Reporting Person to cover tax withholding obligations in connection with the vesting of certain restricted stock units previously reported in Table I. This sale is a "sell to cover" transaction and does not represent a discretionary transaction by the Reporting Person.

SEC source: 0001193125-26-047206 · ownership.xml · derivative · entry 2

Khara Rahul · CIK 0001951850 · Chief Legal Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 25,500

Underlying: Common Stock · 25,500 shares

Expires 2036-02-09

F3 · derivative.exercise_date: The shares underlying this option vest in 48 equal monthly installments commencing on March 10, 2026, subject to the Reporting Person's continued service on each such vesting date.

SEC source: 0001193125-26-047206 · ownership.xml · nonDerivative · entry 1

Khara Rahul · CIK 0001951850 · Chief Legal Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 55,026

F1 · shares: Represents restricted stock units ("RSUs"), each representing a contingent right to receive one share of the Issuer's Common Stock. The RSUs shall vest annually in four 25% installments commencing on February 15, 2027, subject to the Reporting Person's continued service on each such vesting date.

F2 · balance_after: Includes 233 shares purchased pursuant to the Disc Medicine, Inc. Amended and Restated 2021 Employee Stock Purchase Plan on January 30, 2026.

SEC source: 0001193125-26-047193 · ownership.xml · derivative · entry 2

Savage William Jacob · CIK 0001951852 · Chief Medical Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 25,500

Underlying: Common Stock · 25,500 shares

Expires 2036-02-09

F2 · derivative.exercise_date: The shares underlying this option shall vest in 48 equal monthly installments beginning on March 10, 2026, subject to the Reporting Person's continued service on each such vesting date.

SEC source: 0001193125-26-047193 · ownership.xml · nonDerivative · entry 1

Savage William Jacob · CIK 0001951852 · Chief Medical Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 95,845

F1 · shares: Represents restricted stock units ("RSUs"), each representing a contingent right to receive one share of the Issuer's Common Stock. The RSUs shall vest annually in four 25% installments commencing on February 15, 2027, subject to the Reporting Person's continued service on each such vesting date.

SEC source: 0001193125-26-047198 · ownership.xml · derivative · entry 2

Stephenson Pamela · CIK 0001767650 · Chief Commercial Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 25,500

Underlying: Common Stock · 25,500 shares

Expires 2036-02-09

F2 · derivative.exercise_date: The shares underlying this option vest in 48 equal monthly installments commencing on March 10, 2026, subject to the Reporting Person's continued service on each such vesting date.

SEC source: 0001193125-26-047198 · ownership.xml · nonDerivative · entry 1

Stephenson Pamela · CIK 0001767650 · Chief Commercial Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 86,529

F1 · shares: Represents restricted stock units ("RSUs"), each representing a contingent right to receive one share of the Issuer's Common Stock. The RSUs shall vest annually in four 25% installments commencing on February 15, 2027, subject to the Reporting Person's continued service on each such vesting date.

SEC source: 0001193125-26-047184 · ownership.xml · derivative · entry 2

Yu Jonathan Yen-Wen · CIK 0001951849 · Chief Operating Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 25,500

Underlying: Common Stock · 25,500 shares

Expires 2036-02-09

F2 · derivative.exercise_date: The shares underlying this option vest in 48 equal monthly installments commencing on March 10, 2026, subject to the Reporting Person's continued service on each such vesting date.

SEC source: 0001193125-26-047184 · ownership.xml · nonDerivative · entry 1

Yu Jonathan Yen-Wen · CIK 0001951849 · Chief Operating Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 57,555

F1 · shares: Represents restricted stock units ("RSUs"), each representing a contingent right to receive one share of the Issuer's Common Stock. The RSUs shall vest annually in four 25% installments commencing on February 15, 2027, subject to the Reporting Person's continued service on each such vesting date.

SEC source: 0001193125-26-047163 · ownership.xml · derivative · entry 2

Franchi Jean M. · CIK 0001653053 · Chief Financial Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 25,500

Underlying: Common Stock · 25,500 shares

Expires 2036-02-09

F2 · derivative.exercise_date: The shares underlying this option vest in 48 equal monthly installments commencing on March 10, 2026, subject to the Reporting Person's continued service on each such vesting date.

SEC source: 0001193125-26-047163 · ownership.xml · nonDerivative · entry 1

Franchi Jean M. · CIK 0001653053 · Chief Financial Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 82,499

F1 · shares: Represents restricted stock units ("RSUs"), each representing a contingent right to receive one share of the Issuer's Common Stock. The RSUs shall vest annually in four 25% installments commencing on February 15, 2027, subject to the Reporting Person's continued service on each such vesting date.

SEC source: 0001193125-26-047146 · ownership.xml · derivative · entry 2

Quisel John D · CIK 0001586788 · Director · Chief Executive Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 82,800

Underlying: Common Stock · 82,800 shares

Expires 2036-02-09

F2 · derivative.exercise_date: The shares underlying this option vest in 48 equal monthly installments commencing on March 10, 2026, subject to the Reporting Person's continued service on each such vesting date.

SEC source: 0001193125-26-047146 · ownership.xml · nonDerivative · entry 1

Quisel John D · CIK 0001586788 · Director · Chief Executive Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 239,328

F1 · shares: Represents restricted stock units ("RSUs"), each representing a contingent right to receive one share of the Issuer's Common Stock. The RSUs shall vest annually in four 25% installments commencing on February 15, 2027, subject to the Reporting Person's continued service on each such vesting date.

SEC source: 0001193125-26-018320 · ownership.xml · derivative · entry 3

Khara Rahul · CIK 0001951850 · Chief Legal Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 21,270

Underlying: Common Stock · 1,000 shares

Expires 2032-12-28

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: The transactions reported by the Reporting Person were effected pursuant to a Rule 10b5-1 trading plan adopted on September 23, 2025.

F2 · derivative.exercise_date: The shares underlying this option vest in 48 equal monthly installments following December 29, 2022, subject to the Reporting Person's continued service on each such vesting date.

SEC source: 0001193125-26-018320 · ownership.xml · nonDerivative · entry 2

Khara Rahul · CIK 0001951850 · Chief Legal Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 37,793

F1 · kind: The transactions reported by the Reporting Person were effected pursuant to a Rule 10b5-1 trading plan adopted on September 23, 2025.

SEC source: 0001193125-26-018320 · ownership.xml · nonDerivative · entry 1

Khara Rahul · CIK 0001951850 · Chief Legal Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 38,793

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: The transactions reported by the Reporting Person were effected pursuant to a Rule 10b5-1 trading plan adopted on September 23, 2025.

SEC source: 0001193125-26-003075 · ownership.xml · derivative · entry 5

Khara Rahul · CIK 0001951850 · Chief Legal Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 22,270

Underlying: Common Stock · 6,500 shares

Expires 2032-12-28

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: The transactions reported by the Reporting Person were effected pursuant to a Rule 10b5-1 trading plan adopted on September 23, 2025.

F6 · derivative.exercise_date: The shares underlying this option vest in 48 equal monthly installments following December 29, 2022, subject to the Reporting Person's continued service on each such vesting date.

SEC source: 0001193125-26-003075 · ownership.xml · nonDerivative · entry 4

Khara Rahul · CIK 0001951850 · Chief Legal Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 37,793

F1 · kind: The transactions reported by the Reporting Person were effected pursuant to a Rule 10b5-1 trading plan adopted on September 23, 2025.

F5 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $79.10 to $79.49, inclusive.

F2 · balance_after: Includes 210 shares purchased pursuant to the Disc Medicine, Inc. Amended and Restated 2021 Employee Stock Purchase Plan on July 31, 2025.

SEC source: 0001193125-26-003075 · ownership.xml · nonDerivative · entry 3

Khara Rahul · CIK 0001951850 · Chief Legal Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 38,950

F1 · kind: The transactions reported by the Reporting Person were effected pursuant to a Rule 10b5-1 trading plan adopted on September 23, 2025.

F4 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $78.09 to $79.07, inclusive.

F2 · balance_after: Includes 210 shares purchased pursuant to the Disc Medicine, Inc. Amended and Restated 2021 Employee Stock Purchase Plan on July 31, 2025.

SEC source: 0001193125-26-003075 · ownership.xml · nonDerivative · entry 2

Khara Rahul · CIK 0001951850 · Chief Legal Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 43,943

F1 · kind: The transactions reported by the Reporting Person were effected pursuant to a Rule 10b5-1 trading plan adopted on September 23, 2025.

F3 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $77.09 to $78.07, 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 footnotes (3) through (5) to this Form 4.

F2 · balance_after: Includes 210 shares purchased pursuant to the Disc Medicine, Inc. Amended and Restated 2021 Employee Stock Purchase Plan on July 31, 2025.

SEC source: 0001193125-26-003075 · ownership.xml · nonDerivative · entry 1

Khara Rahul · CIK 0001951850 · Chief Legal Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 44,293

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: The transactions reported by the Reporting Person were effected pursuant to a Rule 10b5-1 trading plan adopted on September 23, 2025.

F2 · balance_after: Includes 210 shares purchased pursuant to the Disc Medicine, Inc. Amended and Restated 2021 Employee Stock Purchase Plan on July 31, 2025.

SEC source: 0001193125-25-335678 · ownership.xml · derivative · entry 6

Savage William Jacob · CIK 0001951852 · Chief Medical Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 29,905

Underlying: Common Stock · 99 shares

Expires 2032-12-28

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

F2 · derivative.exercise_date: The shares underlying this option vest in 48 equal monthly installments following December 29, 2022, subject to the Reporting Person's continued service on each such vesting date.

SEC source: 0001193125-25-335678 · ownership.xml · derivative · entry 5

Savage William Jacob · CIK 0001951852 · Chief Medical Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 2,628

Underlying: Common Stock · 219 shares

Expires 2031-09-13

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_date: The shares underlying this option are fully vested and exercisable as of the date hereof

SEC source: 0001193125-25-335678 · ownership.xml · derivative · entry 4

Savage William Jacob · CIK 0001951852 · Chief Medical Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 3,550

Underlying: Common Stock · 2,825 shares

Expires 2031-09-13

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_date: The shares underlying this option are fully vested and exercisable as of the date hereof

SEC source: 0001193125-25-335678 · ownership.xml · nonDerivative · entry 3

Savage William Jacob · CIK 0001951852 · Chief Medical Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 78,845

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: 0001193125-25-335678 · ownership.xml · nonDerivative · entry 2

Savage William Jacob · CIK 0001951852 · Chief Medical Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 78,746

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: 0001193125-25-335678 · ownership.xml · nonDerivative · entry 1

Savage William Jacob · CIK 0001951852 · Chief Medical Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 78,527

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: 0001193125-25-327173 · ownership.xml · derivative · entry 2

Quisel John D · CIK 0001586788 · Director · Chief Executive Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 186,120

Underlying: Common Stock · 12,300 shares

Expires 2030-03-10

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_date: The shares underlying this option are fully vested and exercisable as of the date hereof.

SEC source: 0001193125-25-327173 · ownership.xml · nonDerivative · entry 1

Quisel John D · CIK 0001586788 · Director · Chief Executive Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 184,128

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: 0001591747-25-000008 · form4-12182025_111250.xml · nonDerivative · entry 3

Bitterman Kevin · CIK 0001591747 · Director

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 14,013

F1 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $91.2501 to $91.52 inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in footnote.

F4 · ownership.nature: These shares are held by Atlas Venture Fund XII, L.P. ("Atlas XII"). The general partner of Atlas XII is Atlas Venture Associates XII, L.P. ("Associates XII"). Atlas Venture Associates XII, LLC ("Associates XII LLC") is the general partner of Associates XII. The Reporting Person is a member of Associates XII LLC and disclaims beneficial ownership of such securities held by Atlas XII, except to the extent of his pecuniary interest therein, if any.

SEC source: 0001591747-25-000008 · form4-12182025_111250.xml · nonDerivative · entry 2

Bitterman Kevin · CIK 0001591747 · Director

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 337,485

F1 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $91.2501 to $91.52 inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in footnote.

F3 · ownership.nature: These shares are held by Atlas Venture Opportunity Fund II, LP ("Opportunity II"). The general partner of Opportunity II is Atlas Venture Associates Opportunity II, LP ("Associates II"). Atlas Venture Associates Opportunity II, LLC ("Associates II LLC") is the general partner of Associates II. The Reporting Person is a member of Associates II LLC and disclaims beneficial ownership of such securities held by Opportunity II, except to the extent of his pecuniary interest therein, if any.

SEC source: 0001591747-25-000008 · form4-12182025_111250.xml · nonDerivative · entry 1

Bitterman Kevin · CIK 0001591747 · Director

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 349,210

F1 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $91.2501 to $91.52 inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in footnote.

F2 · ownership.nature: These shares are held by Atlas Venture Opportunity Fund I, LP ("Opportunity I"). The general partner of Opportunity I is Atlas Venture Associates Opportunity I, LP ("Associates I"). Atlas Venture Associates Opportunity I, LLC ("Associates I LLC") is the general partner of Associates I. The Reporting Person is a member of Associates I LLC and disclaims beneficial ownership of such securities held by Opportunity I, except to the extent of his pecuniary interest therein, if any.

SEC source: 0001104659-25-121740 · tm2530644-8_4seq1.xml · nonDerivative · entry 20

Bitterman Kevin · CIK 0001591747 · Director

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 14,161

F10 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $91.00 to $91.705 inclusive.

F6 · ownership.nature: These shares are held by Atlas Venture Fund XII, L.P. ("Atlas XII"). The general partner of Atlas XII is Atlas Venture Associates XII, L.P. ("Associates XII"). Atlas Venture Associates XII, LLC ("Associates XII LLC") is the general partner of Associates XII. The Reporting Person is a member of Associates XII LLC and disclaims beneficial ownership of such securities held by Atlas XII, except to the extent of his pecuniary interest therein, if any.

SEC source: 0001104659-25-121740 · tm2530644-8_4seq1.xml · nonDerivative · entry 19

Bitterman Kevin · CIK 0001591747 · Director

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 337,698

F10 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $91.00 to $91.705 inclusive.

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

SEC source: 0001104659-25-121740 · tm2530644-8_4seq1.xml · nonDerivative · entry 18

Bitterman Kevin · CIK 0001591747 · Director

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 349,603

F10 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $91.00 to $91.705 inclusive.

F2 · ownership.nature: These shares are held by Atlas Venture Opportunity Fund I, LP ("Opportunity I"). The general partner of Opportunity I is Atlas Venture Associates Opportunity I, LP ("Associates I"). Atlas Venture Associates Opportunity I, LLC ("Associates I LLC") is the general partner of Associates I. The Reporting Person is a member of Associates I LLC and disclaims beneficial ownership of such securities held by Opportunity I, except to the extent of his pecuniary interest therein, if any.

SEC source: 0001104659-25-121740 · tm2530644-8_4seq1.xml · derivative · entry 21

Bitterman Kevin · CIK 0001591747 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 7,000 shares

Expires 2032-12-28

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.

F11 · derivative.exercise_date: Fully Vested.

SEC source: 0001104659-25-121740 · tm2530644-8_4seq1.xml · nonDerivative · entry 17

Bitterman Kevin · CIK 0001591747 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 0

F9 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $91.79 to $91.95 inclusive.

SEC source: 0001104659-25-121740 · tm2530644-8_4seq1.xml · nonDerivative · entry 16

Bitterman Kevin · CIK 0001591747 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 7,000

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: 0001104659-25-121740 · tm2530644-8_4seq1.xml · nonDerivative · entry 15

Bitterman Kevin · CIK 0001591747 · Director

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 28,520

F8 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $92.00 to $92.48 inclusive.

F6 · ownership.nature: These shares are held by Atlas Venture Fund XII, L.P. ("Atlas XII"). The general partner of Atlas XII is Atlas Venture Associates XII, L.P. ("Associates XII"). Atlas Venture Associates XII, LLC ("Associates XII LLC") is the general partner of Associates XII. The Reporting Person is a member of Associates XII LLC and disclaims beneficial ownership of such securities held by Atlas XII, except to the extent of his pecuniary interest therein, if any.

SEC source: 0001104659-25-121740 · tm2530644-8_4seq1.xml · nonDerivative · entry 14

Bitterman Kevin · CIK 0001591747 · Director

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 30,092

F7 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $91.00 to $91.99 inclusive.

F6 · ownership.nature: These shares are held by Atlas Venture Fund XII, L.P. ("Atlas XII"). The general partner of Atlas XII is Atlas Venture Associates XII, L.P. ("Associates XII"). Atlas Venture Associates XII, LLC ("Associates XII LLC") is the general partner of Associates XII. The Reporting Person is a member of Associates XII LLC and disclaims beneficial ownership of such securities held by Atlas XII, except to the extent of his pecuniary interest therein, if any.

SEC source: 0001104659-25-121740 · tm2530644-8_4seq1.xml · nonDerivative · entry 13

Bitterman Kevin · CIK 0001591747 · Director

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 356,364

F8 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $92.00 to $92.48 inclusive.

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

SEC source: 0001104659-25-121740 · tm2530644-8_4seq1.xml · nonDerivative · entry 12

Bitterman Kevin · CIK 0001591747 · Director

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 358,413

F7 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $91.00 to $91.99 inclusive.

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

SEC source: 0001104659-25-121740 · tm2530644-8_4seq1.xml · nonDerivative · entry 11

Bitterman Kevin · CIK 0001591747 · Director

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 385,501

F8 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $92.00 to $92.48 inclusive.

F2 · ownership.nature: These shares are held by Atlas Venture Opportunity Fund I, LP ("Opportunity I"). The general partner of Opportunity I is Atlas Venture Associates Opportunity I, LP ("Associates I"). Atlas Venture Associates Opportunity I, LLC ("Associates I LLC") is the general partner of Associates I. The Reporting Person is a member of Associates I LLC and disclaims beneficial ownership of such securities held by Opportunity I, except to the extent of his pecuniary interest therein, if any.

SEC source: 0001104659-25-121740 · tm2530644-8_4seq1.xml · nonDerivative · entry 10

Bitterman Kevin · CIK 0001591747 · Director

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 389,422

F7 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $91.00 to $91.99 inclusive.

F2 · ownership.nature: These shares are held by Atlas Venture Opportunity Fund I, LP ("Opportunity I"). The general partner of Opportunity I is Atlas Venture Associates Opportunity I, LP ("Associates I"). Atlas Venture Associates Opportunity I, LLC ("Associates I LLC") is the general partner of Associates I. The Reporting Person is a member of Associates I LLC and disclaims beneficial ownership of such securities held by Opportunity I, except to the extent of his pecuniary interest therein, if any.

SEC source: 0001193125-25-321440 · ownership.xml · nonDerivative · entry 3

Savage William Jacob · CIK 0001951852 · Chief Medical Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 75,702

F1 · kind: The transactions reported by the Reporting Person were effected pursuant to a Rule 10b5-1 trading plan adopted on June 26, 2025.

SEC source: 0001193125-25-321440 · ownership.xml · nonDerivative · entry 2

Savage William Jacob · CIK 0001951852 · Chief Medical Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 76,002

F1 · kind: The transactions reported by the Reporting Person were effected pursuant to a Rule 10b5-1 trading plan adopted on June 26, 2025.

F3 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $91.03 to $91.99, inclusive.

SEC source: 0001193125-25-321440 · ownership.xml · nonDerivative · entry 1

Savage William Jacob · CIK 0001951852 · Chief Medical Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 85,153

F1 · kind: The transactions reported by the Reporting Person were effected pursuant to a Rule 10b5-1 trading plan adopted on June 26, 2025.

F2 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $90.02 to $90.97, 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 footnotes (2) and (3) to this Form 4.

SEC source: 0001104659-25-121740 · tm2530644-8_4seq1.xml · nonDerivative · entry 9

Bitterman Kevin · CIK 0001591747 · Director

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 41,519

F4 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $93.52 to $94.255 inclusive.

F6 · ownership.nature: These shares are held by Atlas Venture Fund XII, L.P. ("Atlas XII"). The general partner of Atlas XII is Atlas Venture Associates XII, L.P. ("Associates XII"). Atlas Venture Associates XII, LLC ("Associates XII LLC") is the general partner of Associates XII. The Reporting Person is a member of Associates XII LLC and disclaims beneficial ownership of such securities held by Atlas XII, except to the extent of his pecuniary interest therein, if any.

SEC source: 0001104659-25-121740 · tm2530644-8_4seq1.xml · nonDerivative · entry 8

Bitterman Kevin · CIK 0001591747 · Director

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 42,890

F3 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $92.52 to $93.3796 inclusive.

F6 · ownership.nature: These shares are held by Atlas Venture Fund XII, L.P. ("Atlas XII"). The general partner of Atlas XII is Atlas Venture Associates XII, L.P. ("Associates XII"). Atlas Venture Associates XII, LLC ("Associates XII LLC") is the general partner of Associates XII. The Reporting Person is a member of Associates XII LLC and disclaims beneficial ownership of such securities held by Atlas XII, except to the extent of his pecuniary interest therein, if any.

SEC source: 0001104659-25-121740 · tm2530644-8_4seq1.xml · nonDerivative · entry 7

Bitterman Kevin · CIK 0001591747 · Director

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 44,430

F1 · price: The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $91.5289 to $92.4325 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 footnotes (1), (3), (4), (7), (8), (9) and (10).

F6 · ownership.nature: These shares are held by Atlas Venture Fund XII, L.P. ("Atlas XII"). The general partner of Atlas XII is Atlas Venture Associates XII, L.P. ("Associates XII"). Atlas Venture Associates XII, LLC ("Associates XII LLC") is the general partner of Associates XII. The Reporting Person is a member of Associates XII LLC and disclaims beneficial ownership of such securities held by Atlas XII, except to the extent of his pecuniary interest therein, if any.