# EDGAR Filing Document

**Accession Number:** 0001496323
**File Stem:** 0000950170-25-109761
**Filing Date:** 2025-8
**Character Count:** 21969
**Document Hash:** 1247d65982929739b56f1a977212e7b2
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0000950170-25-109761.hdr.sgml**: 20250818

**ACCESSION NUMBER**: 0000950170-25-109761

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

**PUBLIC DOCUMENT COUNT**: 3

**FILED AS OF DATE**: 20250818

**DATE AS OF CHANGE**: 20250818

**SUBJECT COMPANY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** IGM Biosciences, Inc.
- **CENTRAL INDEX KEY:** 0001496323
- **STANDARD INDUSTRIAL CLASSIFICATION:** PHARMACEUTICAL PREPARATIONS [2834]
- **ORGANIZATION NAME:** 03 Life Sciences
- **EIN:** 770349194
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** SCHEDULE 13D/A
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 005-91132
- **FILM NUMBER:** 251228328

**BUSINESS ADDRESS:**
- **STREET 1:** 325 E MIDDLEFIELD ROAD
- **CITY:** MOUNTAIN VIEW
- **STATE:** CA
- **ZIP:** 94043
- **BUSINESS PHONE:** 650-965-7873

**MAIL ADDRESS:**
- **STREET 1:** 325 E MIDDLEFIELD ROAD
- **CITY:** MOUNTAIN VIEW
- **STATE:** CA
- **ZIP:** 94043

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** Palingen, Inc.
- **DATE OF NAME CHANGE:** 20100712
**FILED BY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Topsoe Holding A/S
- **CENTRAL INDEX KEY:** 0001788357

**ORGANIZATION NAME:**
- **EIN:** 000000000
- **STATE OF INCORPORATION:** G7
- **FISCAL YEAR END:** 1231

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

**BUSINESS ADDRESS:**
- **STREET 1:** HALDOR TOPSOE ALLE 1
- **CITY:** KONGENS LYNGBY
- **STATE:** G7
- **ZIP:** 2800
- **BUSINESS PHONE:** 45 4527 2000

**MAIL ADDRESS:**
- **STREET 1:** HALDOR TOPSOE ALLE 1
- **CITY:** KONGENS LYNGBY
- **STATE:** G7
- **ZIP:** 2800

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** Haldor Topsoe Holding A/S
- **DATE OF NAME CHANGE:** 20190916

### Attached PDF Documents

**Attachment 1:** `ck0000000000-ex99_1.pdf`

_No text found in this document._

**Attachment 2:** `ck0000000000-ex99_a1.pdf`

_No text found in this document._

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

## SCHEDULE 13D

### Under the Securities Exchange Act of 1934

**(Amendment No. 3)**

**IGM Biosciences, Inc.**

*(Name of Issuer)*

**Common Stock, par value $0.01 per share**

*(Title of Class of Securities)*

**449585108**

*(CUSIP Number)*

**Topsoe Holding A/S**<br>Haldor Topsoes Alle 1 DK<br>Kgs. Lyngby G7 2800<br>45 4527 2000

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

**08/14/2025**

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

| **CUSIP No.** | **449585108** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Topsoe Holding A/S** | Name of reporting person<br>**Topsoe Holding A/S** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (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>**G7** | Citizenship or place of organization<br>**G7** | |
| 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>**0.00** |
| 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>**0.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**0.00** | Aggregate amount beneficially owned by each reporting person<br>**0.00** | |
| 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%** | Percent of class represented by amount in Row (11)<br>**0%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**OO** | Type of Reporting Person (See Instructions)<br>**OO** | |

---

| **CUSIP No.** | **449585108** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Jakob Haldor Topsoe** | Name of reporting person<br>**Jakob Haldor Topsoe** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**PF** | Source of funds (See Instructions)<br>**PF** | |
| 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>**G7** | Citizenship or place of organization<br>**G7** | |
| 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>**0.00** |
| 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>**0.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**0.00** | Aggregate amount beneficially owned by each reporting person<br>**0.00** | |
| 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%** | Percent of class represented by amount in Row (11)<br>**0%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**IN** | Type of Reporting Person (See Instructions)<br>**IN** | |

---

| **CUSIP No.** | **449585108** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Christina Teng Topsoe** | Name of reporting person<br>**Christina Teng Topsoe** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**PF** | Source of funds (See Instructions)<br>**PF** | |
| 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>**G7** | Citizenship or place of organization<br>**G7** | |
| 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>**0.00** |
| 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>**0.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**0.00** | Aggregate amount beneficially owned by each reporting person<br>**0.00** | |
| 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%** | Percent of class represented by amount in Row (11)<br>**0%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**IN** | Type of Reporting Person (See Instructions)<br>**IN** | |

---

| **CUSIP No.** | **449585108** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Anne Haugwitz-Hardenberg-Reventlow** | Name of reporting person<br>**Anne Haugwitz-Hardenberg-Reventlow** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**PF** | Source of funds (See Instructions)<br>**PF** | |
| 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>**G7** | Citizenship or place of organization<br>**G7** | |
| 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>**0.00** |
| 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>**0.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**0.00** | Aggregate amount beneficially owned by each reporting person<br>**0.00** | |
| 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%** | Percent of class represented by amount in Row (11)<br>**0%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**IN** | Type of Reporting Person (See Instructions)<br>**IN** | |

---

| **CUSIP No.** | **449585108** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Emil Oigaard** | Name of reporting person<br>**Emil Oigaard** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**PF** | Source of funds (See Instructions)<br>**PF** | |
| 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>**G7** | Citizenship or place of organization<br>**G7** | |
| 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>**0.00** |
| 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>**0.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**0.00** | Aggregate amount beneficially owned by each reporting person<br>**0.00** | |
| 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%** | Percent of class represented by amount in Row (11)<br>**0%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**IN** | Type of Reporting Person (See Instructions)<br>**IN** | |

---

| **CUSIP No.** | **449585108** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Thomas Schleicher** | Name of reporting person<br>**Thomas Schleicher** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**PF** | Source of funds (See Instructions)<br>**PF** | |
| 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>**G7** | Citizenship or place of organization<br>**G7** | |
| 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>**0.00** |
| 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>**0.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**0.00** | Aggregate amount beneficially owned by each reporting person<br>**0.00** | |
| 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%** | Percent of class represented by amount in Row (11)<br>**0%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**IN** | Type of Reporting Person (See Instructions)<br>**IN** | |

---

| **CUSIP No.** | **449585108** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Birgitte Nielsen** | Name of reporting person<br>**Birgitte Nielsen** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**PF** | Source of funds (See Instructions)<br>**PF** | |
| 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>**G7** | Citizenship or place of organization<br>**G7** | |
| 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>**0.00** |
| 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>**0.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**0.00** | Aggregate amount beneficially owned by each reporting person<br>**0.00** | |
| 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%** | Percent of class represented by amount in Row (11)<br>**0%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**IN** | Type of Reporting Person (See Instructions)<br>**IN** | |

---

**Item 1. Security and Issuer**

**(a) Title of Class of Securities:**
Common Stock, par value $0.01 per share

**(b) Name of Issuer:**
IGM Biosciences, Inc.

**(c) Address of Issuer's Principal Executive Offices:**
325 E MIDDLEFIELD ROAD, MOUNTAIN VIEW, CA, 94043

AMENDMENT NO. 3 TO SCHEDULE 13D

This Amendment No. 3 to Schedule 13D amends and supplements the information provided in the previously filed Statement on Schedule 13D filed with the Securities and Exchange Commission on July 19, 2023, as amended to date (the "Schedule 13D"), jointly on behalf of Topsoe Holding A/S (formerly Haldor Topsoe Holding A/S) ("Topsoe Holding"), Jakob Haldor Topsoe, Christina Teng Topsoe, Anne Haugwitz-Hardenberg-Reventlow, Emil Oigaard, Thomas Schleicher and Birgitte Nielsen (each a "Reporting Person" and collectively, the "Reporting Persons").

Except as supplemented herein, such statements, as heretofore amended and supplemented, remain unchanged in all material respects and in full force and effect. Capitalized terms used but not defined herein have the meaning ascribed to such term in the Schedule 13D, as amended.

Responses to each item of this Amendment No. 3 to Schedule 13D are incorporated by reference into the response to each other item, as applicable.

**Item 4. Purpose of Transaction**

Item 4 of Schedule 13D is hereby amended and supplemented as follows:

On July 1, 2025, the Issuer entered into an Agreement and Plan of Merger (the "Merger Agreement") with Concentra Biosciences, LLC, a Delaware limited liability company ("Concentra"), and Concentra Merger Sub V, Inc., a Delaware corporation and a wholly owned subsidiary of Concentra ("Merger Sub"). The Merger Agreement provides for, among other things: (i) the acquisition of all of the Issuer's outstanding shares of common stock, par value $0.01 per share (the "Common Stock"), by Concentra through a cash tender offer (the "Offer"), for a price per share of the Common Stock of (A) $1.247 in cash (the "Cash Amount"), subject to applicable tax withholding and without interest; plus (B) one contingent value right (a "CVR") (such amount being the "CVR Amount" and the Cash Amount plus the CVR Amount, collectively being the "Offer Price") and (ii) the merger of Merger Sub with and into the Issuer (the "Merger") with the Issuer surviving the Merger.

The foregoing description of the Merger Agreement and the transactions contemplated thereby is qualified in its entirety by reference to the full text of the Merger Agreement, a copy of which is attached as Exhibit 2.1 to the Issuer's Current Report on Form 8-K filed with the U.S. Securities and Exchange Commission (the "SEC") on July 1, 2025.

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

**(a)**
The information contained in rows 7, 8, 9, 10, 11 and 13 on each of the cover pages of this Schedule 13D and the information set forth or incorporated in Items 2, 3, 4 and 6 is incorporated by reference in its entirety into this Item 5.

Item 5 of Schedule 13D is hereby amended and supplemented as follows:

The Reporting Persons do not beneficially own any shares of common stock.

**(b)**
Regarding the number of shares as to which such person has: (i) sole power to vote or to direct the vote: See line 7 of cover sheets (ii) shared power to vote or to direct the vote: See line 8 of cover sheets (iii) sole power to dispose or to direct the disposition: See line 9 of cover sheets (iv) shared power to dispose or to direct the disposition: See line 10 of cover sheets.

**(c)**
Except as set forth in Item 4 above, none of the Reporting Persons has effected any transactions in the Common Stock during the last 60 days.

**Item 6. Contracts, Arrangements, Understandings or Relationships With Respect to Securities of the Issuer.**

The information set forth in Items 3, 4 and 5 of this Statement is incorporated by reference into this Item 6.

### 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:** Topsoe Holding A/S

**Signature:** By: /s/ Henrik Gaarn Bak

**Name/Title:** Henrik Gaarn Bak, Managing Director

**Date:** 08/18/2025

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:** Jakob Haldor Topsoe

**Signature:** /s/ Jakob Haldor Topsoe

**Name/Title:** Jakob Haldor Topsoe

**Date:** 08/18/2025

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:** Christina Teng Topsoe

**Signature:** /s/ Christina Teng Topsoe

**Name/Title:** Christina Teng Topsoe

**Date:** 08/18/2025

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:** Anne Haugwitz-Hardenberg-Reventlow

**Signature:** /s/ Anne Haugwitz-Hardenberg-Reventlow

**Name/Title:** Anne Haugwitz-Hardenberg-Reventlow

**Date:** 08/18/2025

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:** Emil Oigaard

**Signature:** /s/ Emil Oigaard

**Name/Title:** Emil Oigaard

**Date:** 08/18/2025

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:** Thomas Schleicher

**Signature:** /s/ Thomas Schleicher

**Name/Title:** Thomas Schleicher

**Date:** 08/18/2025

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:** Birgitte Nielsen

**Signature:** /s/ Birgitte Nielsen

**Name/Title:** Birgitte Nielsen

**Date:** 08/18/2025