# EDGAR Filing Document

**Accession Number:** 0001628098
**File Stem:** 0001415889-25-022121
**Filing Date:** 2025-8
**Character Count:** 40746
**Document Hash:** b26786d929a856e8762ad46e8ecc42f3
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001415889-25-022121.hdr.sgml**: 20250815

**ACCESSION NUMBER**: 0001415889-25-022121

**CONFORMED SUBMISSION TYPE**: SCHEDULE 13D/A

**PUBLIC DOCUMENT COUNT**: 3

**FILED AS OF DATE**: 20250815

**DATE AS OF CHANGE**: 20250815

**SUBJECT COMPANY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Disc Medicine, Inc.
- **CENTRAL INDEX KEY:** 0001816736
- **STANDARD INDUSTRIAL CLASSIFICATION:** PHARMACEUTICAL PREPARATIONS [2834]
- **ORGANIZATION NAME:** 03 Life Sciences
- **EIN:** 851613057
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** SCHEDULE 13D/A
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 005-91633
- **FILM NUMBER:** 251226023

**BUSINESS ADDRESS:**
- **STREET 1:** 321 ARSENAL STREET, SUITE 101
- **CITY:** WATERTOWN
- **STATE:** MA
- **ZIP:** 02472
- **BUSINESS PHONE:** (617) 674-9274

**MAIL ADDRESS:**
- **STREET 1:** 321 ARSENAL STREET, SUITE 101
- **CITY:** WATERTOWN
- **STATE:** MA
- **ZIP:** 02472

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** Gemini Therapeutics, Inc. /DE
- **DATE OF NAME CHANGE:** 20210209

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** FS Development Corp.
- **DATE OF NAME CHANGE:** 20200702
**FILED BY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Atlas Venture Fund X, L.P.
- **CENTRAL INDEX KEY:** 0001628098

**ORGANIZATION NAME:**
- **EIN:** 472435989
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** SCHEDULE 13D/A

**BUSINESS ADDRESS:**
- **STREET 1:** 400 TECHNOLOGY SQUARE
- **STREET 2:** 10TH FLOOR
- **CITY:** CAMBRIDGE
- **STATE:** MA
- **ZIP:** 02139
- **BUSINESS PHONE:** 857-201-2700

**MAIL ADDRESS:**
- **STREET 1:** 400 TECHNOLOGY SQUARE
- **STREET 2:** 10TH FLOOR
- **CITY:** CAMBRIDGE
- **STATE:** MA
- **ZIP:** 02139

## Exhibit 99.1

**Exhibit 99.1**

Transactions in Common Stock Durning the Past Sixty Days

---

| | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|
| Reporting Person | Nature of the Transaction | Amount of Securities Purchased/Sold | Weighted Average Price ($) | Date of Purchase/Sale | Low Price ($) | High Price ($) |
| Atlas X | Sale of Common Stock | 1184 | 61.13 | 7/18/2025 | 60.96 | 61.33 |
| AVOF | Sale of Common Stock | 664 | 61.13 | 7/18/2025 | 60.96 | 61.33 |
| Atlas X | Sale of Common Stock | 53215 | 60.97 | 7/23/2025 | 60.95 | 61.10 |
| AVOF | Sale of Common Stock | 29837 | 60.97 | 7/23/2025 | 60.95 | 61.10 |
| Atlas X | Sale of Common Stock | 23245 | 61.17 | 7/24/2025 | 60.95 | 61.55 |
| AVOF | Sale of Common Stock | 13033 | 61.17 | 7/24/2025 | 60.95 | 61.55 |
| Atlas X | Sale of Common Stock | 15146 | 61.04 | 7/30/2025 | 60.95 | 61.35 |
| AVOF | Sale of Common Stock | 8492 | 61.04 | 7/30/2025 | 60.95 | 61.35 |
| Atlas X | Sale of Common Stock | 705 | 60.95 | 8/5/2025 | 60.95 | 60.95 |
| AVOF | Sale of Common Stock | 395 | 60.95 | 8/5/2025 | 60.95 | 60.95 |
| Atlas X | Sale of Common Stock | 44520 | 61.15 | 8/13/2025 | 60.95 | 61.615 |
| AVOF | Sale of Common Stock | 24962 | 61.15 | 8/13/2025 | 60.95 | 61.615 |
| Atlas X | Sale of Common Stock | 12862 | 60.99 | 8/14/2025 | 60.95 | 61.11 |
| AVOF | Sale of Common Stock | 7212 | 60.99 | 8/14/2025 | 60.95 | 61.11 |

---

## Exhibit 99.2

**Exhibit 99.2**

JOINT FILING AGREEMENT

Pursuant to Rule 13d-1(k)(1) promulgated pursuant to the Securities Exchange Act of 1934, as amended, the undersigned agree that the attached Schedule 13D is being filed on behalf of each of the undersigned.

Date: August 15, 2025

---

| | |
|:---|:---|
| **Atlas Venture Fund X, L.P.** | **Atlas Venture Fund X, L.P.** |
| By:  | Atlas Venture Associates X, L.P., its general partner |
| By: | Atlas Venture Associates X, LLC, its general partner |
| By: <u>/s/ Ommer Chohan</u> | By: <u>/s/ Ommer Chohan</u> |
| Name:  | Ommer Chohan |
| Title: | Chief Financial Officer |
| **Atlas Venture Associates X, L.P.** | **Atlas Venture Associates X, L.P.** |
| By: | Atlas Venture Associates X, LLC, its general partner |
| By: <u>/s/ Ommer Chohan</u> | By: <u>/s/ Ommer Chohan</u> |
| Name:  | Ommer Chohan |
| Title: | Chief Financial Officer |
| **Atlas Venture Associates X, LLC** | **Atlas Venture Associates X, LLC** |
| By: <u>/s/ Ommer Chohan</u> | By: <u>/s/ Ommer Chohan</u> |
| Name:  | Ommer Chohan |
| Title: | Chief Financial Officer |
| **Atlas Venture Fund XII, L.P.** | **Atlas Venture Fund XII, L.P.** |
| By:  | Atlas Venture Associates XII, L.P., its general partner |
| By: | Atlas Venture Associates XII, LLC, its general partner |
| By: <u>/s/ Ommer Chohan</u> | By: <u>/s/ Ommer Chohan</u> |
| Name:  | Ommer Chohan |
| Title: | Chief Financial Officer |
| **Atlas Venture Associates XII, L.P.** | **Atlas Venture Associates XII, L.P.** |
| By: | Atlas Venture Associates XII, LLC, its general partner |
| By: <u>/s/ Ommer Chohan</u> | By: <u>/s/ Ommer Chohan</u> |
| Name:  | Ommer Chohan |
| Title: | Chief Financial Officer |
| **Atlas Venture Associates XII, LLC** | **Atlas Venture Associates XII, LLC** |
| By: <u>/s/ Ommer Chohan</u> | By: <u>/s/ Ommer Chohan</u> |
| Name:  | Ommer Chohan |
| Title: | Chief Financial Officer |

---

---

| | |
|:---|:---|
| **Atlas Venture Opportunity Fund I, L.P.** | **Atlas Venture Opportunity Fund I, L.P.** |
| By:  | Atlas Venture Associates Opportunity I, L.P., its general partner |
| By: | Atlas Venture Associates Opportunity I, LLC, its general partner |
| By: <u>/s/ Ommer Chohan</u> | By: <u>/s/ Ommer Chohan</u> |
| Name:  | Ommer Chohan |
| Title: | Chief Financial Officer |
| **Atlas Venture Associates Opportunity I, L.P.** | **Atlas Venture Associates Opportunity I, L.P.** |
| By: | Atlas Venture Associates Opportunity I, LLC, its general partner |
| By: <u>/s/ Ommer Chohan</u> | By: <u>/s/ Ommer Chohan</u> |
| Name:  | Ommer Chohan |
| Title: | Chief Financial Officer |
| **Atlas Venture Associates Opportunity I, LLC** | **Atlas Venture Associates Opportunity I, LLC** |
| By: <u>/s/ Ommer Chohan</u> | By: <u>/s/ Ommer Chohan</u> |
| Name:  | Ommer Chohan |
| Title: | Chief Financial Officer |
| **Atlas Venture Opportunity Fund II, L.P.** | **Atlas Venture Opportunity Fund II, L.P.** |
| By:  | Atlas Venture Associates Opportunity II, L.P., its general partner |
| By: | Atlas Venture Associates Opportunity II, LLC, its general partner |
| By: <u>/s/ Ommer Chohan</u> | By: <u>/s/ Ommer Chohan</u> |
| Name:  | Ommer Chohan |
| Title: | Chief Financial Officer |
| **Atlas Venture Associates Opportunity II, L.P.** | **Atlas Venture Associates Opportunity II, L.P.** |
| By: | Atlas Venture Associates Opportunity II, LLC, its general partner |
| By: <u>/s/ Ommer Chohan</u> | By: <u>/s/ Ommer Chohan</u> |
| Name:  | Ommer Chohan |
| Title: | Chief Financial Officer |
| **Atlas Venture Associates Opportunity II, LLC** | **Atlas Venture Associates Opportunity II, LLC** |
| By: <u>/s/ Ommer Chohan</u> | By: <u>/s/ Ommer Chohan</u> |
| Name:  | Ommer Chohan |
| Title: | Chief Financial Officer |

---

### UNITED STATES SECURITIES AND EXCHANGE COMMISSION
**Washington, D.C. 20549**

## SCHEDULE 13D

### Under the Securities Exchange Act of 1934

**(Amendment No. 4)**

**DISC MEDICINE, INC.**

*(Name of Issuer)*

**Common Stock, $0.0001 par value per share**

*(Title of Class of Securities)*

**254604101**

*(CUSIP Number)*

**Attention: Ommer Chohan, CFO**<br>Atlas Venture<br>300 Technology Square, 8th Floor<br>Cambridge MA 02139<br>(857) 201-2700

*(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)*

**08/13/2025**

*(Date of Event Which Requires Filing of this Statement)*

| **CUSIP No.** | **254604101** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Atlas Venture Fund X, L.P.** | Name of reporting person<br>**Atlas Venture Fund X, L.P.** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[ ] (a)<br>[x] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[ ] (a)<br>[x] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**WC** | Source of funds (See Instructions)<br>**WC** | |
| 5 | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | |
| 6 | Citizenship or place of organization<br>**DELAWARE** | Citizenship or place of organization<br>**DELAWARE** | |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 7 | Sole Voting Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 8 | Shared Voting Power<br>**1084527.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 9 | Sole Dispositive Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 10 | Shared Dispositive Power<br>**1084527.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**1084527.00** | Aggregate amount beneficially owned by each reporting person<br>**1084527.00** | |
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | |
| 13 | Percent of class represented by amount in Row (11)<br>**3.1%** | Percent of class represented by amount in Row (11)<br>**3.1%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**PN** | Type of Reporting Person (See Instructions)<br>**PN** | |

---

| **CUSIP No.** | **254604101** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**ATLAS VENTURE ASSOCIATES X, L.P.** | Name of reporting person<br>**ATLAS VENTURE ASSOCIATES X, L.P.** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[ ] (a)<br>[x] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[ ] (a)<br>[x] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**AF** | Source of funds (See Instructions)<br>**AF** | |
| 5 | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | |
| 6 | Citizenship or place of organization<br>**DELAWARE** | Citizenship or place of organization<br>**DELAWARE** | |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 7 | Sole Voting Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 8 | Shared Voting Power<br>**1084527.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 9 | Sole Dispositive Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 10 | Shared Dispositive Power<br>**1084527.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**1084527.00** | Aggregate amount beneficially owned by each reporting person<br>**1084527.00** | |
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | |
| 13 | Percent of class represented by amount in Row (11)<br>**3.1%** | Percent of class represented by amount in Row (11)<br>**3.1%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**PN** | Type of Reporting Person (See Instructions)<br>**PN** | |

---

| **CUSIP No.** | **254604101** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Atlas Venture Associates X, LLC** | Name of reporting person<br>**Atlas Venture Associates X, LLC** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[ ] (a)<br>[x] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[ ] (a)<br>[x] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**AF** | Source of funds (See Instructions)<br>**AF** | |
| 5 | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | |
| 6 | Citizenship or place of organization<br>**DELAWARE** | Citizenship or place of organization<br>**DELAWARE** | |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 7 | Sole Voting Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 8 | Shared Voting Power<br>**1084527.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 9 | Sole Dispositive Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 10 | Shared Dispositive Power<br>**1084527.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**1084527.00** | Aggregate amount beneficially owned by each reporting person<br>**1084527.00** | |
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | |
| 13 | Percent of class represented by amount in Row (11)<br>**3.1%** | Percent of class represented by amount in Row (11)<br>**3.1%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**OO** | Type of Reporting Person (See Instructions)<br>**OO** | |

---

| **CUSIP No.** | **254604101** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Atlas Venture Fund XII, L.P.** | Name of reporting person<br>**Atlas Venture Fund XII, L.P.** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[ ] (a)<br>[x] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[ ] (a)<br>[x] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**WC** | Source of funds (See Instructions)<br>**WC** | |
| 5 | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | |
| 6 | Citizenship or place of organization<br>**DELAWARE** | Citizenship or place of organization<br>**DELAWARE** | |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 7 | Sole Voting Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 8 | Shared Voting Power<br>**51000.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 9 | Sole Dispositive Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 10 | Shared Dispositive Power<br>**51000.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**51000.00** | Aggregate amount beneficially owned by each reporting person<br>**51000.00** | |
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | |
| 13 | Percent of class represented by amount in Row (11)<br>**0.1%** | Percent of class represented by amount in Row (11)<br>**0.1%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**PN** | Type of Reporting Person (See Instructions)<br>**PN** | |

---

| **CUSIP No.** | **254604101** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Atlas Venture Associates XII, L.P.** | Name of reporting person<br>**Atlas Venture Associates XII, L.P.** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[ ] (a)<br>[x] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[ ] (a)<br>[x] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**AF** | Source of funds (See Instructions)<br>**AF** | |
| 5 | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | |
| 6 | Citizenship or place of organization<br>**DELAWARE** | Citizenship or place of organization<br>**DELAWARE** | |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 7 | Sole Voting Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 8 | Shared Voting Power<br>**51000.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 9 | Sole Dispositive Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 10 | Shared Dispositive Power<br>**51000.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**51000.00** | Aggregate amount beneficially owned by each reporting person<br>**51000.00** | |
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | |
| 13 | Percent of class represented by amount in Row (11)<br>**0.1%** | Percent of class represented by amount in Row (11)<br>**0.1%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**PN** | Type of Reporting Person (See Instructions)<br>**PN** | |

---

| **CUSIP No.** | **254604101** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Atlas Venture Associates XII, LLC** | Name of reporting person<br>**Atlas Venture Associates XII, LLC** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[ ] (a)<br>[x] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[ ] (a)<br>[x] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**AF** | Source of funds (See Instructions)<br>**AF** | |
| 5 | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | |
| 6 | Citizenship or place of organization<br>**DELAWARE** | Citizenship or place of organization<br>**DELAWARE** | |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 7 | Sole Voting Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 8 | Shared Voting Power<br>**51000.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 9 | Sole Dispositive Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 10 | Shared Dispositive Power<br>**51000.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**51000.00** | Aggregate amount beneficially owned by each reporting person<br>**51000.00** | |
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | |
| 13 | Percent of class represented by amount in Row (11)<br>**0.1%** | Percent of class represented by amount in Row (11)<br>**0.1%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**OO** | Type of Reporting Person (See Instructions)<br>**OO** | |

---

| **CUSIP No.** | **254604101** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Atlas Venture Opportunity Fund I, L.P.** | Name of reporting person<br>**Atlas Venture Opportunity Fund I, L.P.** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[ ] (a)<br>[x] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[ ] (a)<br>[x] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**AF** | Source of funds (See Instructions)<br>**AF** | |
| 5 | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | |
| 6 | Citizenship or place of organization<br>**DELAWARE** | Citizenship or place of organization<br>**DELAWARE** | |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 7 | Sole Voting Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 8 | Shared Voting Power<br>**592908.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 9 | Sole Dispositive Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 10 | Shared Dispositive Power<br>**592908.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**592908.00** | Aggregate amount beneficially owned by each reporting person<br>**592908.00** | |
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | |
| 13 | Percent of class represented by amount in Row (11)<br>**1.7%** | Percent of class represented by amount in Row (11)<br>**1.7%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**PN** | Type of Reporting Person (See Instructions)<br>**PN** | |

---

| **CUSIP No.** | **254604101** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Atlas Venture Associates Opportunity I, L.P.** | Name of reporting person<br>**Atlas Venture Associates Opportunity I, L.P.** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[ ] (a)<br>[x] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[ ] (a)<br>[x] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**AF** | Source of funds (See Instructions)<br>**AF** | |
| 5 | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | |
| 6 | Citizenship or place of organization<br>**—** | Citizenship or place of organization<br>**—** | |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 7 | Sole Voting Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 8 | Shared Voting Power<br>**592908.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 9 | Sole Dispositive Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 10 | Shared Dispositive Power<br>**592908.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**592908.00** | Aggregate amount beneficially owned by each reporting person<br>**592908.00** | |
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | |
| 13 | Percent of class represented by amount in Row (11)<br>**1.7%** | Percent of class represented by amount in Row (11)<br>**1.7%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**PN** | Type of Reporting Person (See Instructions)<br>**PN** | |

---

| **CUSIP No.** | **254604101** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Atlas Venture Associates Opportunity I, LLC** | Name of reporting person<br>**Atlas Venture Associates Opportunity I, LLC** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[ ] (a)<br>[x] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[ ] (a)<br>[x] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**AF** | Source of funds (See Instructions)<br>**AF** | |
| 5 | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | |
| 6 | Citizenship or place of organization<br>**DELAWARE** | Citizenship or place of organization<br>**DELAWARE** | |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 7 | Sole Voting Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 8 | Shared Voting Power<br>**592908.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 9 | Sole Dispositive Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 10 | Shared Dispositive Power<br>**592908.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**592908.00** | Aggregate amount beneficially owned by each reporting person<br>**592908.00** | |
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | |
| 13 | Percent of class represented by amount in Row (11)<br>**1.7%** | Percent of class represented by amount in Row (11)<br>**1.7%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**PN** | Type of Reporting Person (See Instructions)<br>**PN** | |

---

| **CUSIP No.** | **254604101** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Atlas Venture Opportunity Fund II, L.P.** | Name of reporting person<br>**Atlas Venture Opportunity Fund II, L.P.** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[ ] (a)<br>[x] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[ ] (a)<br>[x] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**AF** | Source of funds (See Instructions)<br>**AF** | |
| 5 | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | |
| 6 | Citizenship or place of organization<br>**DELAWARE** | Citizenship or place of organization<br>**DELAWARE** | |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 7 | Sole Voting Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 8 | Shared Voting Power<br>**420549.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 9 | Sole Dispositive Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 10 | Shared Dispositive Power<br>**420549.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**420549.00** | Aggregate amount beneficially owned by each reporting person<br>**420549.00** | |
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | |
| 13 | Percent of class represented by amount in Row (11)<br>**1.2%** | Percent of class represented by amount in Row (11)<br>**1.2%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**PN** | Type of Reporting Person (See Instructions)<br>**PN** | |

---

| **CUSIP No.** | **254604101** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Atlas Venture Associates Opportunity II, LP** | Name of reporting person<br>**Atlas Venture Associates Opportunity II, LP** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[ ] (a)<br>[x] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[ ] (a)<br>[x] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**AF** | Source of funds (See Instructions)<br>**AF** | |
| 5 | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | |
| 6 | Citizenship or place of organization<br>**—** | Citizenship or place of organization<br>**—** | |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 7 | Sole Voting Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 8 | Shared Voting Power<br>**420549.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 9 | Sole Dispositive Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 10 | Shared Dispositive Power<br>**420549.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**420549.00** | Aggregate amount beneficially owned by each reporting person<br>**420549.00** | |
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | |
| 13 | Percent of class represented by amount in Row (11)<br>**1.2%** | Percent of class represented by amount in Row (11)<br>**1.2%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**PN** | Type of Reporting Person (See Instructions)<br>**PN** | |

---

| **CUSIP No.** | **254604101** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Atlas Venture Associates Opportunity II, LLC** | Name of reporting person<br>**Atlas Venture Associates Opportunity II, LLC** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[ ] (a)<br>[x] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[ ] (a)<br>[x] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**AF** | Source of funds (See Instructions)<br>**AF** | |
| 5 | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | |
| 6 | Citizenship or place of organization<br>**DELAWARE** | Citizenship or place of organization<br>**DELAWARE** | |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 7 | Sole Voting Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 8 | Shared Voting Power<br>**420549.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 9 | Sole Dispositive Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 10 | Shared Dispositive Power<br>**420549.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**420549.00** | Aggregate amount beneficially owned by each reporting person<br>**420549.00** | |
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | |
| 13 | Percent of class represented by amount in Row (11)<br>**1.2%** | Percent of class represented by amount in Row (11)<br>**1.2%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**OO** | Type of Reporting Person (See Instructions)<br>**OO** | |

---

**Item 1. Security and Issuer**

**(a) Title of Class of Securities:**
Common Stock, $0.0001 par value per share

**(b) Name of Issuer:**
DISC MEDICINE, INC.

**(c) Address of Issuer's Principal Executive Offices:**
321 ARSENAL STREET, SUITE 101, WATERTOWN, MA, 02472

This Amendment No. 4 to Schedule 13D ("Amendment No. 4") is being filed as an amendment to the statement on Schedule 13D relating to common stock, par value $0.0001 per share of Disc Medicine, Inc., a Delaware corporation, as filed with the Securities and Exchange Commission (the "SEC") on February 16, 2021 (the "Initial Schedule 13D") and later amended on February 14, 2023 ("Amendment No. 1") , September 21, 2023 ("Amendment No. 2") and January 24, 2024 ("Amendment No. 3" and together with the Initial Schedule 13D, Amendment No. 1 and Amendment No. 2 the "Prior Schedule 13D"). All capitalized terms not otherwise defined herein shall have the meanings ascribed to the terms in the Prior Schedule 13D. The Prior Schedule 13D is hereby amended and supplemented as follows and, except as expressly amended below, the Prior Schedule 13D remains in full force and effect.

**Item 5. Interest in Securities of the Issuer**

**(a)**
As of the date hereof, Atlas X is the record owner of 1,084,527 shares of Common Stock. AVA X LP is the general partner of Atlas X and AVA X LLC is the general partner of AVA X LP. Each of Atlas X, AVA X LP and AVA X LLC has shared voting and dispositive power over the shares held by Atlas X. As such, each of Atlas X, AVA X LP and AVA X LLC may be deemed to beneficially own the shares held by Atlas X.

As of the date hereof, Atlas XII is the record owner of 51,000 shares of Common Stock. AVA XII LP is the general partner of Atlas XII and AVA XII LLC is the general partner of AVA XII LP. Each of Atlas XII, AVA XII LP and AVA XII LLC has shared voting and dispositive power over the shares held by Atlas XII. As such, each of Atlas XII, AVA XII LP and AVA XII LLC may be deemed to beneficially own the shares held by Atlas XII.

As of the date hereof, AVOF is the record owner of 592,908 shares of Common Stock. AVAO LP is the general partner of AVOF and AVAO LLC is the general partner of AVAO LP. Each of AVOF, AVAO LP and AVAO LLC has shared voting and dispositive power over the shares held by AVOF. As such, each of AVOF, AVAO LP and AVAO LLC may be deemed to beneficially own the shares held by AVOF.

As of the date hereof, AVOF II is the record owner of 420,549 shares of Common Stock. AVAO II LP is the general partner of AVOF II and AVAO II LLC is the general partner of AVAO II LP. Each of AVOF II, AVAO II LP and AVAO II LLC has shared voting and dispositive power over the shares held by AVOF II. As such, each of AVOF II, AVAO II LP and AVAO II LLC may be deemed to beneficially own the shares held by AVOF II.

Each of the Fund X Reporting Persons, Fund XII Reporting Persons, Opportunity Fund Reporting Persons and Opportunity Fund II Reporting Persons may be deemed to beneficially own 3.1%, 0.1%, 1.7% and 1.2%, respectively, of the Issuer's outstanding Common Stock, which percentages are calculated based upon 34,765,581 shares of Common Stock outstanding as of July 31, 2025, as reported in the Issuer's Quarterly Report pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 for the quarterly period ended June 30 on Form 10-Q, filed with the Securities and Exchange Commission on August 7, 2025.

Collectively, the Reporting Persons beneficially own an aggregate of 2,148,984 shares of Common Stock, which represents an estimated 6.2% of the Issuer's outstanding Common Stock. The Fund X Reporting Persons, Fund XII Reporting Persons, Opportunity Fund Reporting Persons and the Opportunity Fund II Reporting Persons are under common control and as a result, the Reporting Persons may be deemed to be members of a group. However, the Reporting Persons disclaim such group membership, and this Schedule 13D shall not be deemed an admission that the Reporting Persons are members of a group for purposes of Section 13 or for any other purposes.

**(b)**
As of the date hereof, each of Atlas X, AVA X LP and AVA X LLC have shared voting power and shared dispositive power over 1,084,527 shares of Common Stock.

As of the date hereof, each of Atlas XII, AVA XII LP and AVA XII LLC have shared voting power and shared dispositive power over 51,000 shares of Common Stock.

As of the date hereof, each of AVOF, AVAO LP and AVAO LLC have shared voting power and shared dispositive power over 592,908 shares of Common Stock.

As of the date hereof, each of AVOF II, AVAO II LP and AVAO II LLC have shared voting power and shared dispositive power over 420,549 shares of Common Stock.

**(c)**
The transactions in the common stock by the Reporting Persons during the past sixty days are set forth in Exhibit 99.1 and are incorporated herein by reference.

### SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

**Reporting Person:** Atlas Venture Fund X, L.P.

**Signature:** /s/ Ommer Chohan

**Name/Title:** By: Atlas Venture Associates X, L.P., its general partner, By: Atlas Venture Associates X, LLC, its general partner, By Ommer Chohan, CFO

**Date:** 08/15/2025

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

**Reporting Person:** ATLAS VENTURE ASSOCIATES X, L.P.

**Signature:** /s/ Ommer Chohan

**Name/Title:** By: Atlas Venture Associates X, LLC, its general partner, By Ommer Chohan, CFO

**Date:** 08/15/2025

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

**Reporting Person:** Atlas Venture Associates X, LLC

**Signature:** /s/ Ommer Chohan

**Name/Title:** Ommer Chohan, CFO

**Date:** 08/15/2025

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

**Reporting Person:** Atlas Venture Fund XII, L.P.

**Signature:** /s/ Ommer Chohan

**Name/Title:** By: Atlas Venture Associates XII, L.P., its general partner, By: Atlas Venture Associates XII, LLC, its general partner, By Ommer Chohan, CFO

**Date:** 08/15/2025

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

**Reporting Person:** Atlas Venture Associates XII, L.P.

**Signature:** /s/ Ommer Chohan

**Name/Title:** By: Atlas Venture Associates XII, LLC, its general partner, By Ommer Chohan, CFO

**Date:** 08/15/2025

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

**Reporting Person:** Atlas Venture Associates XII, LLC

**Signature:** /s/ Ommer Chohan

**Name/Title:** Ommer Chohan, CFO

**Date:** 08/15/2025

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

**Reporting Person:** Atlas Venture Opportunity Fund I, L.P.

**Signature:** /s/ Ommer Chohan

**Name/Title:** By: Atlas Venture Associates Opportunity I, L.P., its GP, By: Atlas Venture Associates Opportunity I, LLC, its GP, By Ommer Chohan, CFO

**Date:** 08/15/2025

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

**Reporting Person:** Atlas Venture Associates Opportunity I, L.P.

**Signature:** /s/ Ommer Chohan

**Name/Title:** By: Atlas Venture Associates Opportunity I, LLC, its GP, By Ommer Chohan, CFO

**Date:** 08/15/2025

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

**Reporting Person:** Atlas Venture Associates Opportunity I, LLC

**Signature:** /s/ Ommer Chohan

**Name/Title:** Ommer Chohan, CFO

**Date:** 08/15/2025

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

**Reporting Person:** Atlas Venture Opportunity Fund II, L.P.

**Signature:** /s/ Ommer Chohan

**Name/Title:** By: Atlas Venture Associates Opportunity II, L.P., its GP, By: Atlas Venture Associates Opportunity II, LLC, its GP, By Ommer Chohan, CFO

**Date:** 08/15/2025

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

**Reporting Person:** Atlas Venture Associates Opportunity II, LP

**Signature:** /s/ Ommer Chohan

**Name/Title:** By: Atlas Venture Associates Opportunity II, LLC, its GP, By Ommer Chohan, CFO

**Date:** 08/15/2025

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

**Reporting Person:** Atlas Venture Associates Opportunity II, LLC

**Signature:** /s/ Ommer Chohan

**Name/Title:** Ommer Chohan, CFO

**Date:** 08/15/2025