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

Rhea-AI Filing Summary

IGM Biosciences completed a merger on August 14, 2025 that converted all outstanding common stock into cash and contingent value rights. Under the Agreement and Plan of Merger, Merger Sub merged into IGM with IGM surviving as a wholly owned subsidiary of Concentra Biosciences, LLC (Parent). Each share of IGM common stock was cancelled and converted into $1.247 in cash plus one contractual contingent value right (CVR) governed by a Contingent Value Rights Agreement. Reporting person M. Kathleen Behrens, a director, reported dispositions of all her previously held shares, including shares held directly and indirectly through trusts, resulting in zero common shares beneficially owned following these transactions.

Positive

• Merger completed on August 14, 2025 converting all common stock into specified consideration
• Each share converted into $1.247 cash plus one contractual contingent value right (CVR)
• Form 4 discloses zero beneficial common stock ownership for the reporting person after the transaction, reflecting full conversion

Negative

• Reporting person no longer holds any common stock following the merger (reported beneficial ownership = 0)
• Equity holders' ownership in public common stock was cancelled, removing direct exposure to public equity in IGM

Insights

M&A Specialist

TL;DR: The Form 4 reports a completed merger that converted equity into cash plus CVRs, ending public common stock ownership.

The filing documents a closing-level transaction where Merger Sub merged into IGM and all issued common shares were cancelled for consideration of $1.247 per share in cash and one CVR per share under a Contingent Value Rights Agreement. For holders and insiders, this is a disposition by operation of merger rather than open-market sales. The reporting person’s listed holdings across direct and trust accounts were reduced to zero shares, consistent with the conversion of equity at closing.

Corporate Governance Expert

TL;DR: Director M. Kathleen Behrens reports trustee-held and direct holdings cancelled in the merger, with filings appropriately reflecting zero retained common stock.

The Form 4 shows the reporter’s status as a director and trustee for multiple trusts that held IGM shares prior to the Merger. The explanatory footnotes identify trust-held shares converted in the transaction. The form indicates proper Section 16 reporting for insider dispositions resulting from the corporate transaction, with the reported per-share cash consideration and issuance of CVRs as the remaining contingent instrument for former shareholders.

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^*

BEHRENS M KATHLEEN

(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		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		22,222(1)	D	(1)	0	D
Common Stock	08/14/2025		D		330,700(1)	D	(1)	0	I	See footnote(2)
Common Stock	08/14/2025		D		29,807(1)	D	(1)	0	I	See footnote(3)
Common Stock	08/14/2025		D		29,806(1)	D	(1)	0	I	See footnote(4)

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

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 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 in the name of KBW 2005 Trust for which Reporting Person is the Trustee.

3. Prior to the Merger, the shares were held in the name of Non-Exempt Trust for Patrick R. Wilsey Under the Alfred S. Wilsey, Jr. Revocable Trust for which Reporting Person is a Trustee.

4. Prior to the Merger, the shares were held in the name of Non-Exempt Trust for Shannon K. Wilsey Under the Alfred S. Wilsey, Jr. Revocable Trust for which Reporting Person is a Trustee.

	/s/ M. Kathleen Behrens	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 the Form 4 for IGMS report on August 14, 2025?

The Form 4 reports that a merger closed on August 14, 2025 converting all IGM common stock into $1.247 cash per share and one contingent value right (CVR), and that the reporting person’s common shares were disposed and reduced to zero.

Who filed the Form 4 and what is their relationship to IGMS?

The filing was made by M. Kathleen Behrens, who is identified as a director of IGM Biosciences and a trustee for multiple trusts that held shares prior to the merger.

Why were the shares reported as disposed of on the Form 4?

The explanatory notes state that the dispositions occurred pursuant to the Agreement and Plan of Merger in which Merger Sub merged into IGM and all issued common stock was cancelled and converted into the cash and CVR consideration.

What consideration did former IGM shareholders receive in the merger?

Each issued and outstanding share of IGM common stock was converted into $1.247 in cash plus one contractual CVR under the Contingent Value Rights Agreement.

Did the reporting person hold shares indirectly prior to the merger?

Yes. Footnotes state some shares were held in the name of trust accounts (e.g., KBW 2005 Trust and non-exempt trusts under the Alfred S. Wilsey, Jr. Revocable Trust) for which the reporting person served as trustee; those trust-held shares were converted in the merger.