[Form 4] IGM Biosciences, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Jakob Haldor Topsoe reported that on 08/14/2025 all direct and indirect holdings of IGM Biosciences common and non-voting common stock were disposed of as a result of a merger. Under the Agreement and Plan of Merger, each outstanding share was cancelled and converted into $1.247 in cash plus one contingent value right (CVR) governed by a Contingent Value Rights Agreement. The Form 4 shows 91,712 shares of Common Stock and 10,400,564 shares reported as disposed (indirect), and 5,044,295 Non-Voting Common Stock disposed with an underlying 1-for-1 conversion into Common Stock prior to the merger. After the reported transactions, the filing indicates 0 shares beneficially owned by the reporting person.

Positive

• Transaction completed under merger converting equity into cash and CVRs, providing defined consideration ($1.247 per share).
• Reporting person reduced to 0 beneficial ownership, clarifying post-transaction ownership status.

Negative

• Large block of shares disposed (reported indirect disposals of 10,400,564 Common Stock and 5,044,295 Non-Voting Common Stock) which removes these shares from public equity ownership.
• Related-party ownership structure (held via Topsoe Holding A/S with board members sharing voting/investment power) may complicate interpretation of prior control interests.

Insights

Securities Analyst

TL;DR: Form 4 discloses complete disposition of Topsoe-related holdings due to acquisition, converted to cash and a CVR, leaving the filer with no beneficial ownership.

The filing documents a transaction tied to a corporate takeover rather than open-market trades: Merger Sub merged into IGM Biosciences and all issued and outstanding shares were cancelled and converted into cash consideration of $1.247 per share plus one contractual contingent value right each. The reported disposals include both directly held Common Stock (91,712 shares) and substantial indirect holdings (10,400,564 Common Stock and 5,044,295 Non-Voting Common Stock underlying shares). The footnotes confirm prior direct ownership by Topsoe Holding A/S and shared voting/investment power among named board members. For investors, this filing documents the mechanics of ownership elimination under the merger and the replacement of equity with cash and CVRs.

Corporate Governance Expert

TL;DR: The Form 4 records governance-level holders relinquishing equity through a merger, with indirect holdings routed via Topsoe Holding A/S.

The disclosure clarifies that the reporting person’s equity interest was held through Topsoe Holding A/S and that related board members may share voting and investment power, a typical related-party ownership disclosure. The treatment of Non-Voting Common Stock—convertible 1-for-1 into Common Stock before the Merger—was noted and resulted in conversion exposure reflected in the transaction totals. The filing appropriately notes post-transaction beneficial ownership as zero, consistent with a completed acquisition that terminated public equity holdings.

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

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X

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

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^*

Topsoe Jakob Haldor

(Last) (First) (Middle)

C/O IGM BIOSCIENCES, INC.

325 E. MIDDLEFIELD ROAD

(Street)

MOUNTAIN VIEW CA 94043

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
IGM Biosciences, Inc. [ IGMS ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

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

3. Date of Earliest Transaction (Month/Day/Year)
08/14/2025

4. If Amendment, Date of Original Filed (Month/Day/Year)

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

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

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	08/14/2025		D		91,712(1)	D	(1)	0	D
Common Stock	08/14/2025		D		10,400,564(1)	D	(1)	0	I	See footnote(2)

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
Non-Voting Common Stock(3)	(3)	08/14/2025		D			5,044,295(1)	(3)	(3)	Common Stock	5,044,295	$0	0	I	See footnote(2)

Explanation of Responses:

1. Pursuant to the Agreement and Plan of Merger dated July 1, 2025, by and among IGM Biosciences, Inc. (the "Company"), Concentra Biosciences, LLC, a Delaware limited liability company ("Parent"), and Concentra Merger Sub V, Inc., a Delaware corporation and a wholly owned subsidiary of Parent ("Merger Sub"), on August 14, 2025, Merger Sub merged with and into the Company (the "Merger"), with the Company continuing as the surviving corporation and a wholly owned subsidiary of Parent. In connection with the Merger, each issued and outstanding share of the Company's Common Stock and Non-Voting Common Stock was cancelled and converted into the right to receive (i) an amount equal to $1.247 in cash and (ii) one contractual contingent value right (a "CVR") subject to the terms and conditions of a Contingent Value Rights Agreement.

2. Prior to the Merger, the shares were held directly by Topsoe Holding A/S. Jakob Haldor Topsoe, Christina Teng Topsoe, Anne Haugwitz-Hardenberg-Reventlow, Emil Oigaard, Thomas Schleicher and Birgitte Nielsen, members of the board of directors of Topsoe Holding A/S, may be deemed to share voting and investment power with respect to the shares reported herein and disclaim beneficial ownership of such shares, except to the extent of his or her pecuniary interest therein, if any.

3. Prior to the Merger, the shares of Non-Voting Common Stock were convertible into the Issuer's Common Stock on a 1-for-1 basis (subject to a 4.99% beneficial ownership limitation that may be increased or decreased by the holder of such shares) and had no expiration date.

	/s/ Jakob Haldor Topsoe	08/14/2025
	** 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.
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FAQ

What did Jakob Haldor Topsoe report on Form 4 for IGMS?

The Form 4 reports that on 08/14/2025 all reported Common Stock and Non-Voting Common Stock holdings were disposed of in connection with a merger, resulting in 0 shares beneficially owned after the transaction.

What consideration did IGM shareholders receive in the merger?

Each cancelled share was converted into $1.247 in cash plus one contingent value right (CVR) under a Contingent Value Rights Agreement, per the Form 4 footnote.

How many shares were reported disposed by the reporting person?

The filing shows disposal of 91,712 Common Stock (direct), 10,400,564 Common Stock (indirect), and 5,044,295 Non-Voting Common Stock (indirect underlying Common Stock).

Does the filing indicate continued ownership via affiliates?

Prior to the merger, the shares were held directly by Topsoe Holding A/S, and certain board members of Topsoe Holding A/S may be deemed to share voting and investment power; the Form 4 shows post-transaction beneficial ownership as 0.

Were the Non-Voting Common Stock convertible before the merger?

Yes. Footnote 3 states Non-Voting Common Stock were convertible into the issuer’s Common Stock on a 1-for-1 basis (subject to a 4.99% ownership limitation) and had no expiration date prior to the merger.