[SCHEDULE 13D/A] IGM Biosciences, Inc. SEC Filing

Rhea-AI Filing Summary

Amendment No. 3 to Schedule 13D filed jointly by Topsoe Holding A/S and certain related individuals supplements prior Schedule 13D disclosures regarding IGM Biosciences, Inc. The filing states the Reporting Persons do not beneficially own any shares of IGM common stock and have ceased to beneficially own 5% or more of the company as of August 14, 2025. It discloses the Merger Agreement dated July 1, 2025 under which Concentra Biosciences will acquire all outstanding IGM shares via a cash tender offer of $1.247 per share plus one contingent value right (CVR), followed by a merger. Other items reference incorporated exhibits and a joint filing agreement.

Positive

• The filing discloses the Merger Agreement including the cash component of the offer ($1.247 per share) and that a CVR will be issued, providing investors with concrete transaction terms.
• Reporting Persons confirm zero beneficial ownership, removing ambiguity about their current stake and potential voting influence.

Negative

• Reporting Persons have ceased to beneficially own 5% or more of IGM as of August 14, 2025, indicating prior large holders no longer hold a significant reported position.
• No additional details on CVR economics or governance effects are provided in this amendment, leaving uncertainty about contingent payout mechanics and any related rights.

Insights

Financial Analyst

TL;DR This amendment confirms a disclosed merger with a specific cash price plus a CVR and that the reporting group no longer holds a 5% stake.

The filing provides material transaction detail: the Merger Agreement specifies an $1.247 cash payment per share plus a contingent value right, and contemplates a subsequent merger. The Reporting Persons state they beneficially own 0 shares and ceased to own ≥5% as of August 14, 2025. For investors, the explicit offer price structure and the confirmation that prior significant holders no longer report beneficial ownership remove uncertainty about these parties' stakes and potential voting alignment in the deal.

Corporate Governance Expert

TL;DR The amendment documents ownership changes and furnishes the Merger Agreement reference but contains no new governance commitments or arrangements.

The Schedule 13D/A updates identity/background details and confirms execution of a joint filing agreement as Exhibit 99.1. It does not disclose additional side agreements, voting arrangements, or contingent governance rights tied to the CVR. From a governance perspective, the filing is informative but neutral: it clarifies ownership and transaction terms without revealing novel governance provisions that would materially alter control dynamics beyond the announced acquisition.

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
Haldor Topsoes Alle 1 DK,
Kgs. Lyngby, G7, 2800
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)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.

The information required on the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

SCHEDULE 13D

CUSIP No. 449585108

1

Name of reporting person

Topsoe Holding A/S

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

WC

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DENMARK

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 0.00

11

Aggregate amount beneficially owned by each reporting person

0.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

0 %

14

Type of Reporting Person (See Instructions)

OO

SCHEDULE 13D

CUSIP No. 449585108

1

Name of reporting person

Jakob Haldor Topsoe

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

PF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DENMARK

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 0.00

11

Aggregate amount beneficially owned by each reporting person

0.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

0 %

14

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13D

CUSIP No. 449585108

1

Name of reporting person

Christina Teng Topsoe

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

PF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DENMARK

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 0.00

11

Aggregate amount beneficially owned by each reporting person

0.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

0 %

14

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13D

CUSIP No. 449585108

1

Name of reporting person

Anne Haugwitz-Hardenberg-Reventlow

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

PF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DENMARK

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 0.00

11

Aggregate amount beneficially owned by each reporting person

0.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

0 %

14

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13D

CUSIP No. 449585108

1

Name of reporting person

Emil Oigaard

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

PF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DENMARK

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 0.00

11

Aggregate amount beneficially owned by each reporting person

0.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

0 %

14

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13D

CUSIP No. 449585108

1

Name of reporting person

Thomas Schleicher

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

PF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DENMARK

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 0.00

11

Aggregate amount beneficially owned by each reporting person

0.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

0 %

14

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13D

CUSIP No. 449585108

1

Name of reporting person

Birgitte Nielsen

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

PF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DENMARK

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 0.00

11

Aggregate amount beneficially owned by each reporting person

0.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

0 %

14

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13D

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, CALIFORNIA , 94043.
Item 1 Comment: 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 2.	Identity and Background
(a)	Item 2 of Schedule 13D is hereby amended and supplemented as follows: (a), (b), (c) and (f) This Statement is being filed jointly on behalf of Topsoe Holding, a Danish stock-based corporation whose principal business, through its subsidiary operating companies, is catalysis and chemical processing, Jakob Haldor Topsoe, Christina Teng Topsoe, Anne Haugwitz-Hardenberg-Reventlow, Emil Oigaard, Thomas Schleicher and Birgitte Nielsen. The business address and principal office of each Reporting Person is Haldor Topsoes Alle, 1 DK-2800, Kgs. Lyngby, Denmark. Attached as Annex 1 is a chart setting forth, with respect to each executive officer and director of the Topsoe Holding, his or her name, residence or business address, present principal occupation or employment (along with the name, principal business and address of any corporation or other organization in which such employment is conducted) and citizenship, in each case as of the date hereof.
Item 3.	Source and Amount of Funds or Other Consideration
	Not 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.
(d)	No other person is known to have the right to receive or the power to direct the receipt of dividends from, or any proceeds from the sale of, Common Stock beneficially owned by any of the Reporting Persons.
(e)	Each of the Reporting Persons has ceased to beneficially own five percent (5%) or more of the Issuer's common stock as of August 14, 2025.
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.
Item 7.	Material to be Filed as Exhibits.
	Exhibit Number Description Exhibit 99.1 Joint Filing Agreement, dated as of August 18, 2025, between Topsoe Holding A/S, Jakob Haldor Topsoe, Christina Teng Topsoe, Anne Haugwitz-Hardenberg-Reventlow Emil Oigaard.

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.

Topsoe Holding A/S

Signature:	By: /s/ Henrik Gaarn Bak
Name/Title:	Henrik Gaarn Bak, Managing Director
Date:	08/18/2025

Jakob Haldor Topsoe

Signature:	/s/ Jakob Haldor Topsoe
Name/Title:	Jakob Haldor Topsoe
Date:	08/18/2025

Christina Teng Topsoe

Signature:	/s/ Christina Teng Topsoe
Name/Title:	Christina Teng Topsoe
Date:	08/18/2025

Anne Haugwitz-Hardenberg-Reventlow

Signature:	/s/ Anne Haugwitz-Hardenberg-Reventlow
Name/Title:	Anne Haugwitz-Hardenberg-Reventlow
Date:	08/18/2025

Emil Oigaard

Signature:	/s/ Emil Oigaard
Name/Title:	Emil Oigaard
Date:	08/18/2025

Thomas Schleicher

Signature:	/s/ Thomas Schleicher
Name/Title:	Thomas Schleicher
Date:	08/18/2025

Birgitte Nielsen

Signature:	/s/ Birgitte Nielsen
Name/Title:	Birgitte Nielsen
Date:	08/18/2025

FAQ

What merger terms are disclosed in the IGM Biosciences (IGMS) Schedule 13D/A?

The filing references a Merger Agreement dated July 1, 2025 under which Concentra will acquire IGM through a tender offer paying $1.247 cash per share plus one contingent value right (CVR) and then merge the company.

Do Topsoe Holding or the named individuals own IGM shares after this amendment?

No. The Reporting Persons state they do not beneficially own any shares of IGM common stock and have ceased to beneficially own 5% or more as of August 14, 2025.

Which exhibit documents joint filing or agreements included with this amendment?

The amendment lists Exhibit 99.1 as the Joint Filing Agreement dated August 18, 2025 among the Reporting Persons.

Does the Schedule 13D/A report any transactions in the last 60 days by the Reporting Persons?

Except for the Merger Agreement disclosure, the filing states that none of the Reporting Persons effected any transactions in the common stock during the last 60 days.

Where is IGM Biosciences' principal executive office listed in the filing?

The filing lists IGM Biosciences' principal executive offices at 325 E Middlefield Road, Mountain View, California 94043.