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

Rhea-AI Filing Summary

Director Kevin Bitterman reported a series of open-market sales of Disc Medicine, Inc. common stock executed on 10/07/2025 and 10/08/2025. The filings show 90,000 shares sold across multiple transactions at weighted average prices ranging roughly from $68.00 to $72.62, reducing his reported indirect beneficial holdings to 500,621 shares held through affiliated Atlas Venture funds. The sales are disclosed under Section 16 and were signed by an attorney-in-fact on 10/09/2025. The report identifies the holdings as indirect via Atlas Venture entities and includes footnotes describing the fund ownership structure and weighted-average price ranges for each tranche sold.

Positive

• None.

Negative

• Director-associated funds sold 90,000 shares on 10/07/2025–10/08/2025
• Weighted-average sale prices ranged approximately from $68.00 to $72.62, indicating exits across multiple price points
• Reported beneficial ownership fell to 500,621 shares following the transactions, reducing the reported fund stake

Insights

Corporate Governance Expert

Insider sold material stake via fund vehicles; filing shows compliance.

These transactions show a director-associated manager selling 90,000 shares across two days, with holdings recorded as indirect via Atlas Venture funds. The structure and footnotes clarify the sales were by the funds and the reporting person disclaims direct beneficial ownership except for any pecuniary interest.

The key dependency is that the holdings are indirect through venture funds, which often trade for fund-level liquidity rather than personal reasons. Monitor subsequent Section 16 filings for follow-up sales or purchases within 30 days if applicable.

Equity Markets Expert

Sales executed at prices ~$68–$72.62 reduce reported stake to 500,621 shares.

The reported weighted-average price ranges indicate the sales were executed in multiple tranches, likely over several market trades. The price range and volume—90,000 shares—are large enough to be noticed by market participants depending on the stock's daily volume.

Watch for any pattern of continued disposals or fund-level liquidity events in the coming weeks, which could affect short-term supply-demand dynamics for the stock.

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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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).

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 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)
10/07/2025

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	10/07/2025		S		11,378	D	$68.01(1)	579,243	I	See footnote(2)
Common Stock	10/07/2025		S		6,661	D	$69.01(3)	572,582	I	See footnote(2)
Common Stock	10/08/2025		S		8,219	D	$68.26(4)	564,363	I	See footnote(2)
Common Stock	10/08/2025		S		12,386	D	$69.31(5)	551,977	I	See footnote(2)
Common Stock	10/08/2025		S		25,400	D	$70.54(6)	526,577	I	See footnote(2)
Common Stock	10/08/2025		S		12,689	D	$71.51(7)	513,888	I	See footnote(2)
Common Stock	10/08/2025		S		13,267	D	$72.39(8)	500,621	I	See footnote(2)
Common Stock								420,549	I	See footnote(9)
Common Stock								51,000	I	See footnote(10)

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 $68.00 to $68.12 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), (5), (6), (7) and (8).

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 $69.00 to $69.08 inclusive.

4. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $68.01 to $69.00 inclusive.

5. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $69.0173 to $69.9882 inclusive.

6. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $70.0293 to $71.028 inclusive.

7. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $71.03 to $72.0233 inclusive.

8. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $72.0474 to $72.6152 inclusive.

9. 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.

10. 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	10/09/2025
	** 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).
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.

FAQ

What did Disc Medicine (IRON) insider Kevin Bitterman report on Form 4?

The filing shows the reporting person associated with Atlas Venture sold a total of 90,000 shares on 10/07/2025 and 10/08/2025, at weighted-average prices roughly between $68.00 and $72.62.

How much beneficial ownership does the reporting person hold after these transactions?

After the reported sales, the filings show indirect beneficial ownership of 500,621 shares held through Atlas Venture-related funds.

Were the shares sold directly by Kevin Bitterman or through fund vehicles?

The filings state the shares are held and sold by Atlas Venture funds (Opportunity I, Opportunity II, Atlas XII). The reporting person disclaims direct beneficial ownership of those fund-held shares except for any pecuniary interest.

What were the price ranges for the sales reported on Form 4?

Footnotes list weighted-average sale price ranges across tranches: approximately $68.00–$68.12, $69.00–$69.99, $70.03–$71.03, and $72.05–$72.62 for different blocks.

When was the Form 4 signed and filed?

The signature block shows the form was signed by an attorney-in-fact on 10/09/2025.