IRON director reports multi‑day sales; indirect holdings updated

Rhea-AI Filing Summary

Disc Medicine (IRON) director reported open‑market sales of common stock on 10/15/2025–10/17/2025. Transactions were executed in multiple tranches at weighted‑average prices, including ranges from $76.75–$77.60 and up to $92.15.

Following the sales, indirect holdings reported were 442,036 shares held by Atlas Venture Opportunity Fund I, LP; 385,549 shares held by Atlas Venture Opportunity Fund II, LP; and 51,000 shares held by Atlas Venture Fund XII, L.P. The reporting person is a member of the respective general partners and disclaims beneficial ownership beyond any pecuniary interest.

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

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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).

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)
10/15/2025

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	10/15/2025		S		19,542	D	$77.16(1)	481,079	I	See footnote(2)
Common Stock	10/15/2025		S		2,618	D	$77.76(3)	478,461	I	See footnote(2)
Common Stock	10/16/2025		S		1,425	D	$77.11(4)	477,036	I	See footnote(2)
Common Stock	10/17/2025		S		1,125	D	$84.89	475,911	I	See footnote(2)
Common Stock	10/17/2025		S		1,125	D	$84.89	419,424	I	See footnote(5)
Common Stock	10/17/2025		S		3,000	D	$86.13(6)	472,911	I	See footnote(2)
Common Stock	10/17/2025		S		3,000	D	$86.13(6)	416,424	I	See footnote(5)
Common Stock	10/17/2025		S		5,066	D	$87.37(7)	467,845	I	See footnote(2)
Common Stock	10/17/2025		S		5,065	D	$87.37(7)	411,359	I	See footnote(5)
Common Stock	10/17/2025		S		13,014	D	$88.91(8)	454,831	I	See footnote(2)
Common Stock	10/17/2025		S		13,014	D	$88.91(8)	398,345	I	See footnote(5)
Common Stock	10/17/2025		S		2,251	D	$89.7(9)	452,580	I	See footnote(2)
Common Stock	10/17/2025		S		2,251	D	$89.7(9)	396,094	I	See footnote(5)
Common Stock	10/17/2025		S		10,094	D	$90.66(10)	442,486	I	See footnote(2)
Common Stock	10/17/2025		S		10,095	D	$90.66(10)	385,999	I	See footnote(5)
Common Stock	10/17/2025		S		450	D	$91.88(11)	442,036	I	See footnote(2)
Common Stock	10/17/2025		S		450	D	$91.88(11)	385,549	I	See footnote(5)
Common Stock								51,000	I	See footnote(12)

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 $76.75 to $77.60 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 (1), (3), (4), (6), (7), (8), (9), (10) and (11).

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 $77.75 to $77.77 inclusive.

4. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $76.52 to $77.30 inclusive.

5. 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.

6. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $85.91 to $86.90 inclusive.

7. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $87.12 to $88.03 inclusive.

8. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $88.17 to $89.04 inclusive.

9. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $89.25 to $90.23 inclusive.

10. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $90.25 to $91.24 inclusive.

11. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $91.37 to $92.15 inclusive.

12. 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	10/17/2025
	** 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 the Disc Medicine (IRON) Form 4 disclose?

A director reported multiple open‑market sales on 10/15/2025–10/17/2025 at weighted‑average prices, with ranges from $76.75–$77.60 and up to $92.15.

How many shares were sold in specific transactions?

Examples include 19,542 shares at a weighted‑average $77.16 and 13,014 shares at a weighted‑average $88.91, among other tranches.

What indirect holdings remained after the reported sales?

Reported indirect holdings were 442,036 shares (Atlas Venture Opportunity Fund I, LP), 385,549 shares (Atlas Venture Opportunity Fund II, LP), and 51,000 shares (Atlas Venture Fund XII, L.P.).

Were prices reported as single points or ranges?

Prices were reported as weighted‑average figures with ranges, such as $90.25–$91.24 and $91.37–$92.15, with full breakdowns available upon request.

Is the ownership direct or through entities?

The transactions and holdings are reported as indirect through Atlas Venture funds; the reporting person disclaims beneficial ownership beyond any pecuniary interest.

Were any derivative securities involved?

No. The derivative securities table shows no acquisitions or dispositions of derivative instruments.

What is the reporter’s relationship to Disc Medicine (IRON)?

The reporting person is a director of Disc Medicine, Inc.