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Disc Medicine director funds sell 54K shares at $80

Director-affiliated Atlas Venture funds sold 54,496 Disc Medicine shares in early September 2026 under a pre-arranged Rule 10b5-1 trading plan.

Filing Impact
(Very High)
Filing Sentiment
(Negative)
Form Type
4

Rhea-AI Filing Summary

Disc Medicine, Inc. (IRON) reported that funds affiliated with director Kevin Bitterman sold an aggregate of 54,496 shares of Common Stock in open‑market transactions from September 1–3, 2026 at weighted average prices around $80 per share, pursuant to a Rule 10b5-1 trading plan adopted on July 30, 2026.

The shares were sold indirectly through Atlas Venture Opportunity Fund I, L.P., Atlas Venture Opportunity Fund II, L.P., and Atlas Venture Fund XII, L.P.; Bitterman is a member of entities that serve as their general partners and disclaims beneficial ownership of the securities held by these funds except to the extent of his pecuniary interest, if any.

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Insider Bitterman Kevin
Role Director
Sold 54,496 shs ($4.37M)
Type Security Shares Price Value
Sale Common Stock F1, F7, F2 2,810 $79.98 $225K
Sale Common Stock F1, F7, F3 2,339 $79.98 $187K
Sale Common Stock F1, F7, F4 54 $79.98 $4K
Sale Common Stock F1, F5, F2 26,542 $80.17 $2.13M
Sale Common Stock F1, F5, F3 22,090 $80.17 $1.77M
Sale Common Stock F1, F5, F4 511 $80.17 $41K
Sale Common Stock F1, F6, F2 10 $80.98 $809.80
Sale Common Stock F1, F6, F3 9 $80.98 $728.82
Sale Common Stock F1, F6, F4 2 $80.98 $161.96
Sale Common Stock F1, F2 70 $79.95 $6K
Sale Common Stock F1, F3 58 $79.95 $5K
Sale Common Stock F1, F4 1 $79.95 $79.95
Holdings After Transaction: Common Stock — 13,445 shares (Indirect, See footnote)
Footnotes (7)
  1. F1. Shares were sold pursuant to a Rule 10b5-1 trading plan adopted on July 30, 2026.
  2. F2. These shares are held by Atlas Venture Opportunity Fund I, L.P. ("Opportunity I"). The general partner of Opportunity I is Atlas Venture Associates Opportunity I, L.P. ("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.
  3. F3. These shares are held by Atlas Venture Opportunity Fund II, L.P. ("Opportunity II"). The general partner of Opportunity II is Atlas Venture Associates Opportunity II, L.P. ("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.
  4. F4. 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.
  5. F5. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $79.95 to $80.9421 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.
  6. F6. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $80.9677 to $81.0079 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.
  7. F7. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $79.95 to $80.28 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.
Total shares sold 54,496 shares Aggregate common stock sales by affiliated funds from September 1–3, 2026
Sale price per share (September 3, 2026) $79.98 per share Common stock sold indirectly on September 3, 2026
Sale price per share (September 2, 2026, primary block) $80.17 per share Common stock sold indirectly on September 2, 2026
Weighted average price range (September 2, 2026, block 1) $79.95–$80.9421 Multiple transactions aggregated into a weighted average price
Weighted average price range (September 2, 2026, block 2) $80.9677–$81.0079 Multiple transactions aggregated into a weighted average price
Weighted average price range (September 3, 2026) $79.95–$80.28 Multiple transactions aggregated into a weighted average price
Rule 10b5-1 plan adoption date July 30, 2026 Plan under which the reported sales were executed
Rule 10b5-1 trading plan regulatory
"Shares were sold pursuant to a Rule 10b5-1 trading plan adopted"
A Rule 10b5-1 trading plan is a pre-arranged schedule that allows company insiders to buy or sell stock at specific times, even if they have inside information. It helps prevent accusations of unfair trading by making these transactions look planned and transparent, rather than sneaky or illegal.
weighted average price financial
"The price reported in Column 4 is a weighted average price."
Weighted average price is the average price of a security where each trade or component is counted according to its size, so bigger trades pull the average more than smaller ones. Think of it like calculating the average cost of a grocery haul where items you bought more of have greater influence on the final per-item cost. Investors use it to understand the true average price paid or received, judge execution quality, and compare trading performance against market movement.
beneficial ownership financial
"disclaims beneficial ownership of such securities held by Opportunity I"
Beneficial ownership means the person or entity that actually enjoys the benefits of owning shares or other assets — such as receiving dividends, voting rights, or price gains — even if the legal title is held in another name. For investors it matters because knowing who truly controls and profits from a company reveals who can influence decisions, exposes potential conflicts of interest or hidden concentration of power, and affects transparency and risk in the stock.
pecuniary interest financial
"except to the extent of his pecuniary interest therein, if any."
general partner financial
"The general partner of Opportunity I is Atlas Venture Associates"
A general partner is the person or firm that runs an investment partnership and legally represents it — they make the day-to-day decisions, choose which assets to buy or sell, and are responsible for the partnership’s obligations. Investors care because the general partner’s judgment, risk-taking and fee and profit-sharing arrangements determine both the potential returns and the level of exposure to losses; think of the GP as the ship’s captain whose skill and honesty shape the voyage’s outcome.

FAQ

What insider activity did IRON disclose for Kevin Bitterman in this Form 4?
The filing reports that funds affiliated with director Kevin Bitterman sold an aggregate of 54,496 shares of Disc Medicine common stock in open‑market transactions from September 1–3, 2026 at weighted average prices of about $80 per share.

Were the IRON insider sales by Kevin Bitterman made under a Rule 10b5-1 plan?
Yes. The footnotes state the shares were sold pursuant to a Rule 10b5-1 trading plan adopted on July 30, 2026, indicating the trades were pre-arranged under that plan.

How many Disc Medicine (IRON) shares were sold on each main date?
On September 3, 2026, affiliated funds sold 5,203 shares at $79.98. On September 2, 2026, they sold 49,164 shares at weighted average prices of $80.17 and $80.98. On September 1, 2026, they sold 129 shares at $79.95.

Who actually holds the IRON shares involved in these transactions?
The shares are held by Atlas Venture Opportunity Fund I, L.P., Atlas Venture Opportunity Fund II, L.P., and Atlas Venture Fund XII, L.P.. The footnotes explain these funds and their general partners hold the shares, not Kevin Bitterman personally.

Does Kevin Bitterman claim full beneficial ownership of the IRON shares sold?
No. The filing states that Kevin Bitterman disclaims beneficial ownership of the securities held by the Atlas Venture funds, except to the extent of his pecuniary interest in them, if any.

What price ranges applied to the IRON insider sales reported here?
For certain transactions, the filing reports weighted average prices. On September 2, 2026, prices ranged from $79.95 to $80.9421 and from $80.9677 to $81.0079. On September 3, 2026, prices ranged from $79.95 to $80.28.

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SEC Form 4
FORM 4UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940
OMB APPROVAL
OMB Number:3235-0287
Estimated average burden
hours per response:0.5
Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).
X
Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.
1. Name and Address of Reporting Person*
Bitterman Kevin
(Last)(First)(Middle)
C/O DISC MEDICINE, INC.
321 ARSENAL STREET, SUITE 101
(Street)
WATERTOWN MASSACHUSETTS 02472
(City)(State)(Zip)
UNITED STATES
(Country)		2. Issuer Name and Ticker or Trading Symbol
Disc Medicine, Inc. [ IRON ] 		5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
XDirector10% Owner
Officer (give title below)Other (specify below)
2a. Foreign Trading Symbol
3. Date of Earliest Transaction (Month/Day/Year)
09/01/2026		6. Individual or Joint/Group Filing (Check Applicable Line)
XForm filed by One Reporting Person
Form filed by More than One Reporting Person
4. If Amendment, Date of Original Filed (Month/Day/Year)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year)2A. Deemed Execution Date, if any (Month/Day/Year)3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4)
CodeVAmount(A) or (D)Price
Common Stock09/01/2026S(1)70D$79.95349,140ISee footnote(2)
Common Stock09/01/2026S(1)58D$79.95337,427ISee footnote(3)
Common Stock09/01/2026S(1)1D$79.9514,012ISee footnote(4)
Common Stock09/02/2026S(1)26,542D$80.17(5)322,598ISee footnote(2)
Common Stock09/02/2026S(1)22,090D$80.17(5)315,337ISee footnote(3)
Common Stock09/02/2026S(1)511D$80.17(5)13,501ISee footnote(4)
Common Stock09/02/2026S(1)10D$80.98(6)322,588ISee footnote(2)
Common Stock09/02/2026S(1)9D$80.98(6)315,328ISee footnote(3)
Common Stock09/02/2026S(1)2D$80.98(6)13,499ISee footnote(4)
Common Stock09/03/2026S(1)2,810D$79.98(7)319,778ISee footnote(2)
Common Stock09/03/2026S(1)2,339D$79.98(7)312,989ISee footnote(3)
Common Stock09/03/2026S(1)54D$79.98(7)13,445ISee footnote(4)
Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (Month/Day/Year)3A. Deemed Execution Date, if any (Month/Day/Year)4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 6. Date Exercisable and Expiration Date (Month/Day/Year)7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4)
CodeV(A)(D)Date ExercisableExpiration DateTitleAmount or Number of Shares
Explanation of Responses:
1. Shares were sold pursuant to a Rule 10b5-1 trading plan adopted on July 30, 2026.
2. These shares are held by Atlas Venture Opportunity Fund I, L.P. ("Opportunity I"). The general partner of Opportunity I is Atlas Venture Associates Opportunity I, L.P. ("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.
3. These shares are held by Atlas Venture Opportunity Fund II, L.P. ("Opportunity II"). The general partner of Opportunity II is Atlas Venture Associates Opportunity II, L.P. ("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.
4. 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.
5. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $79.95 to $80.9421 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.
6. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $80.9677 to $81.0079 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.
7. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $79.95 to $80.28 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.
/s/ Ommer Chohan, Attorney-in-Fact09/03/2026
** Signature of Reporting PersonDate
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
* Form 4: SEC 1474 (03-26)

Source: View Original Filing on SEC EDGAR