IRON · Disc Medicine, Inc.

These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted on March 12, 2026.

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.

These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted on March 12, 2026.

These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted on March 12, 2026.

The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $74.62 to $75.50, inclusive.

These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted on March 12, 2026.

The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $75.83 to $76.29, inclusive.

These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted on March 12, 2026.

The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $73.62 to $74.60, 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), (3) and (4) to this Form 4.

These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted on March 12, 2026.

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

These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted on March 12, 2026.

These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted on March 17, 2026.

These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted on March 17, 2026.

These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted on March 17, 2026.

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.

The transactions reported by the Reporting Person were effected pursuant to a Rule 10b5-1 trading plan adopted on March 19, 2026.

The transactions reported by the Reporting Person were effected pursuant to a Rule 10b5-1 trading plan adopted on March 19, 2026.

The transactions reported by the Reporting Person were effected pursuant to a Rule 10b5-1 trading plan adopted on March 19, 2026.

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

The transactions reported by the Reporting Person were effected pursuant to a Rule 10b5-1 trading plan adopted on March 19, 2026.

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

The transactions reported by the Reporting Person were effected pursuant to a Rule 10b5-1 trading plan adopted on March 19, 2026.

The transactions reported by the Reporting Person were effected pursuant to a Rule 10b5-1 trading plan adopted on March 19, 2026.

These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted on March 17, 2026.

These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted on March 17, 2026.

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.

These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted on March 17, 2026.

These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted on March 17, 2026.

The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $72.50 to $72.68, 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 this footnote (2) to this Form 4.

These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted on March 17, 2026.

These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted on March 17, 2026.

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.

The shares underlying this option vest upon the first to occur of (i) the date of the Company's 2027 annual meeting of its stockholders, or (ii) the one-year anniversary of the grant date, subject to the Reporting Person's continued service on such vesting date.

The transactions reported by the Reporting Person were effected pursuant to a Rule 10b5-1 trading plan adopted on March 19, 2026.

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

The shares underlying this option vest upon the first to occur of (i) the date of the Company's 2027 annual meeting of its stockholders, or (ii) the one-year anniversary of the grant date, subject to the Reporting Person's continued service on such vesting date.

These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted on March 12, 2026.

The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $69.35 to $70.33, 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 footnotes (2), (3) and (4) to this Form 4.

The shares underlying this option vest upon the first to occur of (i) the date of the Company's 2027 annual meeting of its stockholders, or (ii) the one-year anniversary of the grant date, subject to the Reporting Person's continued service on such vesting date.

These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted on March 12, 2026.

The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $70.36 to $71.35, inclusive.

The transactions reported by the Reporting Person were effected pursuant to a Rule 10b5-1 trading plan adopted on March 19, 2026.

These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted on March 12, 2026.

The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $71.36 to $71.85, inclusive.

These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted on March 12, 2026.

The transactions reported by the Reporting Person were effected pursuant to a Rule 10b5-1 trading plan adopted on March 19, 2026.

The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $70.40 to $71.38, inclusive.

These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted on March 12, 2026.

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

The shares underlying this option vest upon the first to occur of (i) the date of the Company's 2027 annual meeting of its stockholders, or (ii) the one-year anniversary of the grant date, subject to the Reporting Person's continued service on such vesting date.

The transactions reported by the Reporting Person were effected pursuant to a Rule 10b5-1 trading plan adopted on March 19, 2026.

The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $69.35 to $70.34, 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), (3) and (4) to this Form 4.

The shares underlying this option vest upon the first to occur of (i) the date of the Company's 2027 annual meeting of its stockholders, or (ii) the one-year anniversary of the grant date, subject to the Reporting Person's continued service on such vesting date.

The shares underlying this option vest upon the first to occur of (i) the date of the Company's 2027 annual meeting of its stockholders, or (ii) the one-year anniversary of the grant date, subject to the Reporting Person's continued service on such vesting date.

The transactions reported by the Reporting Person were effected pursuant to a Rule 10b5-1 trading plan adopted on March 19, 2026.

The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $71.45 to $71.81, inclusive.

The shares underlying this option vest upon the first to occur of (i) the date of the Company's 2027 annual meeting of its stockholders, or (ii) the one-year anniversary of the grant date, subject to the Reporting Person's continued service on such vesting date.

This option was granted to the Reporting Person, a director of the Issuer. The proceeds of any sale of shares of common stock issued to the Reporting Person upon exercise of this option will be transferred to Atlas Venture Life Science Advisors, LLC and as such, the Reporting Person disclaims ownership of such securities reported herein for purposes of Section 16 of the Securities Exchange Act of 1934, as amended, except to the extent of his pecuniary interest therein, if any.

These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted on March 17, 2026.

The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $69.40 to $70.19, inclusive.

These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted on March 17, 2026.

The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $68.37 to $69.36, 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.

These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted on March 17, 2026.

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

These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted on March 17, 2026.

These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted on March 17, 2026.

These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted on March 17, 2026.

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

These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted on September 25, 2025.

The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $69.07 to $69.43, 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 footnote (2) to this Form 4.

These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted on October 2, 2025.

The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $65.50 to $66.39, 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.

These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted on September 25, 2025.

These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted on October 2, 2025.

The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $66.57 to $67.00, inclusive.

These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted on October 2, 2025.

The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $66.03 to $66.88, inclusive.