[Form 4] Disc Medicine, Inc. Insider Trading Activity

Rhea-AI Filing Summary

SEC Form 4 filing (07/25/2025) discloses that Disc Medicine (IRON) director Kevin Bitterman executed two open-market sales through affiliated Atlas Venture funds.

• 07/23/2025: 29,837 common shares sold at a weighted-average price of $60.97.
• 07/24/2025: 13,033 common shares sold at a weighted-average price of $61.17.

Following the transactions, Bitterman’s indirect ownership via Atlas funds decreased from roughly 676,839 to 633,969 shares. He also continues to hold an additional 420,549 shares in Opportunity II and 51,000 shares in Atlas XII, keeping his total indirect stake above 1.1 million shares. Bitterman remains a board member and reports no derivative activity.

Positive

• None.

Negative

• Director-level insider selling of 42,870 shares at ~$61 may be viewed as profit-taking and slightly reduces perceived insider confidence.

Insights

Securities Analyst

TL;DR: Modest insider sale (~43k shares) by director; stake remains large, so impact is limited.

The sale represents about 6% of Bitterman’s previously reported indirect holdings and occurs at ~$61, near recent highs, suggesting profit-taking rather than a change in thesis. With more than 1.1 million shares still held through Atlas funds, alignment with shareholders remains substantial. No option exercises or derivative conversions accompanied the sale, indicating routine portfolio management. Given Disc Medicine’s clinical-stage profile, insider behaviour is worth monitoring, but this single filing is unlikely to materially alter valuation.

Corporate Governance Expert

TL;DR: Transaction looks routine; no red flags on control or board commitment.

The transactions were made by venture funds, not directly by Bitterman, and are fully footnoted, maintaining transparency. Affirmations of potential pecuniary interest disclaimers align with Section 16 requirements. Bitterman remains a director and continues to hold a significant position, which preserves governance alignment. Frequency and size of future sales should be observed, but this filing alone does not signal governance concerns.

SEC Form 4

FORM 4

UNITED 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
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Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

1. Name and Address of Reporting Person^*

Bitterman Kevin

(Last) (First) (Middle)

C/O DISC MEDICINE, INC.

321 ARSENAL STREET, SUITE 101

(Street)

WATERTOWN MA 02472

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
Disc Medicine, Inc. [ IRON ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

3. Date of Earliest Transaction (Month/Day/Year)
07/23/2025

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

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)
			Code	V	Amount	(A) or (D)	Price
Common Stock	07/23/2025		S		29,837	D	$60.97(1)	647,002	I	See footnote(2)
Common Stock	07/24/2025		S		13,033	D	$61.17(3)	633,969	I	See footnote(2)
Common Stock								420,549	I	See footnote(4)
Common Stock								51,000	I	See footnote(5)

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)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

1. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $60.95 to $61.10 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. 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.

3. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $60.95 to $61.55 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.

4. 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.

5. 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.

	/s/ Ommer Chohan, Attorney-in-Fact	07/25/2025
	** Signature of Reporting Person	Date
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).
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FAQ

How many Disc Medicine (IRON) shares did Kevin Bitterman sell?

He sold 42,870 common shares across two transactions on 07/23 and 07/24 2025.

At what prices were the IRON shares sold?

Weighted-average prices were $60.97 on 07/23 and $61.17 on 07/24 2025.

What is Kevin Bitterman’s remaining stake in Disc Medicine?

After the sales, he indirectly owns 633,969 shares via Atlas Venture funds, plus 420,549 and 51,000 shares in separate funds.

Did the Form 4 report any option exercises or derivative transactions?

No. Table II shows no derivative security activity for the reporting period.

Does Kevin Bitterman still serve on the board of Disc Medicine?

Yes, the filing confirms his continued role as a director.