Disc Medicine director sells 1,689 shares

Disc Medicine, Inc. (IRON) reported that director Kevin Bitterman, through venture funds with which he is associated, reported sales totaling 1,689 shares of common stock on September 4, 2026 at a weighted average price of $79.96 per share.

Rhea-AI Filing Summary

Disc Medicine, Inc. (IRON) reported that director Kevin Bitterman, through venture funds with which he is associated, reported sales totaling 1,689 shares of common stock on September 4, 2026 at a weighted average price of $79.96 per share.

The sales were made pursuant to a Rule 10b5-1 trading plan adopted on July 30, 2026. The 912-share block was sold by Atlas Venture Opportunity Fund I, L.P., the 759-share block by Atlas Venture Opportunity Fund II, L.P., and the 18-share block by Atlas Venture Fund XII, L.P.; Bitterman disclaims beneficial ownership of these securities except to the extent of any pecuniary interest.

Insider Trade Summary 10b5-1

Net Seller: 1,689 shares

Net Sell 3 txns

Insider Bitterman Kevin

Role Director

Sold 1,689 shs ($135K)

Type	Security	Shares	Price	Value
Sale	Common Stock F1, F2, F3	912	$79.96	$73K
Sale	Common Stock F1, F2, F4	759	$79.96	$61K
Sale	Common Stock F1, F2, F5	18	$79.96	$1K

Holdings After Transaction: Common Stock — 13,427 shares (Indirect, See footnote)

Footnotes (5)

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 $79.98 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.

Key Figures

Total shares sold: 1,689 shares Weighted average sale price: $79.96 per share Price range of sales: $79.95–$79.98 per share +5 more

8 metrics

Total shares sold 1,689 shares Aggregate common stock sales reported for September 4, 2026

Weighted average sale price $79.96 per share Average price across multiple sale transactions on September 4, 2026

Price range of sales $79.95–$79.98 per share Range of prices for the multiple sale transactions referenced in footnotes

Shares sold by Atlas Venture Opportunity Fund I, L.P. 912 shares Common stock sold indirectly associated with Kevin Bitterman

Shares sold by Atlas Venture Opportunity Fund II, L.P. 759 shares Common stock sold indirectly associated with Kevin Bitterman

Shares sold by Atlas Venture Fund XII, L.P. 18 shares Common stock sold indirectly associated with Kevin Bitterman

Rule 10b5-1 plan adoption date July 30, 2026 Date the trading plan governing these sales was adopted

Number of sale transactions reported 3 transactions Non-derivative open-market or private sales of common stock

Key Terms

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

5 terms

Rule 10b5-1 trading plan regulatory

"Shares were sold pursuant to a Rule 10b5-1 trading plan adopted on July 30, 2026"

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"

indirect ownership financial

"These shares are held by Atlas Venture Opportunity Fund I, L.P."

FAQ

What insider transaction did Disc Medicine (IRON) disclose for Kevin Bitterman?

Disc Medicine disclosed that director Kevin Bitterman, through affiliated Atlas Venture funds, reported selling 1,689 shares of Disc Medicine common stock on September 4, 2026 in open-market or private transactions at a weighted average price of $79.96 per share, as described in the filing.

At what prices were the 1,689 IRON shares sold in this Form 4 filing?

The filing reports a weighted average price of $79.96 per share. Footnotes state the shares were sold in multiple transactions at prices ranging from $79.95 to $79.98 per share, inclusive, and that detailed trade breakdowns are available upon request.

Were the IRON share sales by Kevin Bitterman under a Rule 10b5-1 plan?

Yes. The filing states the shares were sold pursuant to a Rule 10b5-1 trading plan that was adopted on July 30, 2026. This indicates the trades followed a pre-established plan rather than being discretionary at the time of sale.

Which entities actually sold the IRON shares reported for Kevin Bitterman?

The shares were sold by Atlas Venture Opportunity Fund I, L.P. (912 shares), Atlas Venture Opportunity Fund II, L.P. (759 shares), and Atlas Venture Fund XII, L.P. (18 shares). Bitterman is associated with their general partners and disclaims beneficial ownership except for any pecuniary interest.

Does the Form 4 state Kevin Bitterman’s remaining IRON share holdings?

No. For each reported transaction, the Form 4’s field for shares owned following the transaction is left blank. The filing therefore discloses the shares sold but does not state Bitterman’s remaining holdings in Disc Medicine common stock.

Is Kevin Bitterman a director or officer of Disc Medicine (IRON) according to this filing?

According to the Form 4, Kevin Bitterman is a director of Disc Medicine, Inc. The report does not identify him as an officer or ten percent owner; only the director box is marked for his relationship to the issuer.

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Available on EDGAR 09/09/2026 - 04:24 PM Accepted by SEC EDGAR 09/09/2026 - 04:23 PM 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)
09/04/2026

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	09/04/2026		S(1)		912	D	$79.96(2)	318,866	I	See footnote(3)
Common Stock	09/04/2026		S(1)		759	D	$79.96(2)	312,230	I	See footnote(4)
Common Stock	09/04/2026		S(1)		18	D	$79.96(2)	13,427	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 $79.98 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.

	/s/ Ommer Chohan, Attorney-in-Fact	09/09/2026
	** 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)