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

Rhea-AI Filing Summary

IGM Biosciences completed a merger in which all outstanding common and non-voting shares were cancelled and converted into cash and contingent value rights. Under the merger agreement, each share of common and non-voting stock was converted into $1.247 in cash plus one contractual contingent value right (CVR) governed by a separate CVR agreement. Reporting person Christina Teng Topsoe reported disposals tied to the transaction: 54,235 shares disposed directly and 10,410,364 shares disposed indirectly (comprised of 10,400,564 and 9,800 shares held through affiliated entities), and 5,044,295 non-voting shares (underlying common shares) were disposed in the derivative table; following the transactions the reported beneficial ownership is zero. The filing states pre-merger shareholdings were held through Topsoe Holding A/S and Pillarcater LLC with related disclosure of shared voting or pecuniary interests.

Positive

• Every share converted into $1.247 cash plus one contractual CVR, providing immediate cash consideration to holders
• Reporting person’s beneficial ownership reduced to zero, indicating completion of the conversion process under the merger
• Form 4 discloses indirect holdings and affiliated entities (Topsoe Holding A/S, Pillarcater LLC), improving transparency

Negative

• None.

Insights

M&A Specialist

TL;DR: The transaction reflects a completed acquisition where equity holders received a fixed cash consideration plus contingent value rights, eliminating reported public holdings.

The Form 4 documents the mechanical securities conversion that follows a merger: all classes of the issuer's equity were cancelled and converted into $1.247 cash per share and a CVR. The large aggregate disposals reported—over 10 million shares indirectly and several million non-voting shares—are consistent with a contractually mandated conversion rather than market sales. For investors, this is a material liquidity event that ends the filer’s public equity exposure and replaces equity upside with a CVR and fixed cash consideration.

Corporate Governance Expert

TL;DR: The filing discloses standard insider reporting after a change-in-control; beneficial ownership disclosures show holdings held through related entities.

The report identifies the reporting person as a director and 10% owner and shows pre-merger holdings held indirectly through Topsoe Holding A/S and Pillarcater LLC, with disclaimers of shared voting or pecuniary power. The Form 4 properly records the post-transaction beneficial ownership as zero. This filing documents compliance with Section 16 reporting obligations following a corporate transaction, and highlights the use of affiliated entities and trusts in holding arrangements.

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 Christina Teng

(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		54,235(1)	D	(1)	0	D
Common Stock	08/14/2025		D		10,400,564(1)	D	(1)	0	I	See footnote(2)
Common Stock	08/14/2025		D		9,800(1)	D	(1)	0	I	See footnote(3)

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(4)	(4)	08/14/2025		D			5,044,295(1)	(4)	(4)	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 were held by Pillarcater LLC. The Reporting Person is the sole manager of Pillarcater LLC, which is wholly owned by CT Foundation (a South Dakota Trust) of which the Reporting Person is the sole beneficiary.

4. 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/ Christina Teng 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.
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.

FAQ

What did IGM Biosciences (IGMS) shareholders receive in the merger?

Each share of Common Stock and Non-Voting Common Stock was converted into $1.247 in cash and one contractual contingent value right (CVR) per share.

How many shares did Christina Teng Topsoe report disposing of?

The filing reports 54,235 shares disposed directly, 10,400,564 shares disposed indirectly (plus 9,800 indirect), and 5,044,295 non-voting shares reflected in the derivative table.

Does the filing show any remaining beneficial ownership by the reporting person?

Following the reported transactions, the filing shows 0 shares beneficially owned by the reporting person.

Through which entities were the pre-merger shares held?

Pre-merger shares were held through Topsoe Holding A/S and Pillarcater LLC; the filing discloses related individuals who may share voting or pecuniary power and notes a trust beneficiary structure.

What does the CVR referenced in the filing represent?

The CVR is a contractual contingent value right governed by a separate Contingent Value Rights Agreement; the Form 4 confirms each share was converted into one CVR along with cash.