Disc Medicine director reports 41,825-share sale

Shares held by entities associated with the director were sold under a Rule 10b5-1 trading plan adopted July 30, 2026.

Rhea-AI Filing Summary

Disc Medicine, Inc. (IRON) director Kevin Bitterman reported sales of 41,825 common shares held by Atlas Venture Opportunity Fund I, L.P., Atlas Venture Opportunity Fund II, L.P., and Atlas Venture Fund XII, L.P. across nine transactions from October 19 through October 21, 2026. Reported weighted-average prices were $79.97, $79.95, and $80.23 per share on those dates, respectively. The sales were made under a Rule 10b5-1 trading plan adopted July 30, 2026; Bitterman disclaims beneficial ownership except to the extent of his pecuniary interest, if any.

Insider Trade Summary 10b5-1

Net Seller: 41,825 shares

Net Sell 9 txns

Insider Bitterman Kevin

Role Director

Sold 41,825 shs ($3.35M)

Type	Security	Shares	Price	Value
Sale	Common Stock F1, F7, F3	13,783	$80.23	$1.11M
Sale	Common Stock F1, F7, F4	11,470	$80.23	$920K
Sale	Common Stock F1, F7, F5	266	$80.23	$21K
Sale	Common Stock F1, F6, F3	2,869	$79.95	$229K
Sale	Common Stock F1, F6, F4	2,388	$79.95	$191K
Sale	Common Stock F1, F6, F5	55	$79.95	$4K
Sale	Common Stock F1, F2, F3	5,937	$79.97	$475K
Sale	Common Stock F1, F2, F4	4,942	$79.97	$395K
Sale	Common Stock F1, F2, F5	115	$79.97	$9K

Holdings After Transaction: Common Stock — 12,991 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. 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 $80.2476 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.
3. F3. 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.
4. F4. 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.
5. F5. 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.
6. F6. 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 $80.00 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 $80.70 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.

Key Figures

Common shares sold: 41,825 shares Weighted-average sale price: $79.97 per share Weighted-average sale price: $79.95 per share +2 more

5 metrics

Common shares sold 41,825 shares Nine reported transactions from October 19 through October 21, 2026

Weighted-average sale price $79.97 per share Reported sales on October 19, 2026

Weighted-average sale price $79.95 per share Reported sales on October 20, 2026

Weighted-average sale price $80.23 per share Reported sales on October 21, 2026

Rule 10b5-1 trading plan adoption date July 30, 2026 Plan under which the reported sales were made

Key Terms

Rule 10b5-1 trading plan, weighted average price, beneficial ownership, pecuniary interest

4 terms

Rule 10b5-1 trading plan regulatory

"Shares were sold pursuant to a Rule 10b5-1 trading plan"

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 regulatory

"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"

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

How many IRON shares were sold, and at what prices?

Sales involved 41,825 Disc Medicine common shares held by Atlas Venture Opportunity Fund I, L.P., Atlas Venture Opportunity Fund II, L.P., and Atlas Venture Fund XII, L.P., from October 19 through October 21, 2026. The reported weighted-average prices were $79.97, $79.95, and $80.23 per share, respectively. The reported price ranges were $79.95-$80.2476, $79.95-$80.00, and $79.95-$80.70, respectively.

AI-generated analysis. How Rhea-AI works. Not financial advice.

Form 4 Insider Transactions: What Each Field Means →

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Available on EDGAR 10/21/2026 - 05:33 PM EDT Accepted by SEC EDGAR 10/21/2026 - 05:33 PM EDT Learn about SEC filing dates

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
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)

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

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
10/19/2026

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

X	Form 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)
			Code	V	Amount	(A) or (D)	Price
Common Stock	10/19/2026		S(1)		5,937	D	$79.97(2)	312,929	I	See footnote(3)
Common Stock	10/19/2026		S(1)		4,942	D	$79.97(2)	307,288	I	See footnote(4)
Common Stock	10/19/2026		S(1)		115	D	$79.97(2)	13,312	I	See footnote(5)
Common Stock	10/20/2026		S(1)		2,869	D	$79.95(6)	310,060	I	See footnote(3)
Common Stock	10/20/2026		S(1)		2,388	D	$79.95(6)	304,900	I	See footnote(4)
Common Stock	10/20/2026		S(1)		55	D	$79.95(6)	13,257	I	See footnote(5)
Common Stock	10/21/2026		S(1)		13,783	D	$80.23(7)	296,277	I	See footnote(3)
Common Stock	10/21/2026		S(1)		11,470	D	$80.23(7)	293,430	I	See footnote(4)
Common Stock	10/21/2026		S(1)		266	D	$80.23(7)	12,991	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. Shares were sold pursuant to a Rule 10b5-1 trading plan adopted on July 30, 2026.

2. 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 $80.2476 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.

3. 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.

4. 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.

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.

6. 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 $80.00 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 $80.70 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-Fact	10/21/2026
	** 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.
* Form 4: SEC 1474 (03-26)