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

Rhea-AI Filing Summary

IGM Biosciences (IGMS) insiders reported completion of a tender offer and merger on 08/14/2025, pursuant to which Concentra Biosciences, LLC acquired outstanding voting and non-voting shares. The Form 4 shows the reporting persons disposed of substantial holdings: 3,763,362 and 357,048 shares of Common Stock and 9,886,217 and 834,707 shares of Non-Voting Common Stock (reported as convertible into Common Stock) as a result of the transaction, with $1.247 per share cash consideration plus one contingent value right per share under the merger agreement. The dispositions reflect holdings held by affiliated funds and partnerships managed or advised by Baker Bros. entities; the filing discloses indirect pecuniary interests and clarifies that certain individuals disclaim direct beneficial ownership except for pecuniary interests. Felix J. Baker resigned as a director immediately before closing.

Positive

• Merger completed delivering cash consideration of $1.247 per share plus a contingent value right to shareholders
• Clear disclosure of indirect ownership, fund structures, and disclaimers reduces ambiguity about insider control and voting authority

Negative

• Large disposals of Common and Non-Voting Common Stock (totaling millions of shares) materially reduce reported insider holdings
• Director resignation (Felix J. Baker) immediately prior to closing signals governance change at the issuer

Insights

Securities Analyst

TL;DR: Insider dispositions are a mechanical result of the merger; large volume reflects acquisition consideration, not open-market sales.

The Form 4 documents large disposals tied to the closing of a cash-and-CVR merger at $1.247 per share plus contingent value rights, which explains the reported reductions in beneficial ownership for multiple Baker-affiliated entities. The volume disposed is sizable relative to typical insider trades but consistent with a change-in-control exit rather than a signalling sale. Disclosure clarifies indirect interests through managed funds and standard disclaimers about beneficial ownership.

M&A Specialist

TL;DR: The filing records consummation of a completed merger and the resultant transfer of equity to the buyer, with governance changes noted.

The notice confirms the effective merger date and the mechanics: cash consideration plus a non-transferable CVR per share, conversion features for non-voting stock subject to ownership limits, and the resignation of a director immediately prior to closing. These items are material to shareholders because they finalize change of control terms and terminate prior insider voting 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

OMB APPROVAL

OMB Number:			3235-0287
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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^*

BAKER BROS. ADVISORS LP

(Last) (First) (Middle)

860 WASHINGTON STREET, 3RD FLOOR

(Street)

NEW YORK NY 10014

(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)

	Director		10% Owner
	Officer (give title below)	X	Other (specify below)
			Former 10% owner and director

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)

	Form filed by One Reporting Person
X	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		U(1)		357,048	D	(1)	0	I	See Footnotes(2)(3)(4)(5)(6)(7)
Common Stock	08/14/2025		U(1)		3,763,362	D	(1)	0	I	See Footnotes(3)(4)(5)(6)(7)(8)

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(9)	(9)	08/14/2025		U(1)			834,707	(9)	(9)	Common Stock	834,707	$0	0	I	See Footnotes(2)(3)(4)
Non-Voting Common Stock(9)	(9)	08/14/2025		U(1)			9,886,217	(9)	(9)	Common Stock	9,886,217	$0	0	I	See Footnotes(3)(4)(8)

1. Name and Address of Reporting Person^*

BAKER BROS. ADVISORS LP

(Last) (First) (Middle)

860 WASHINGTON STREET, 3RD FLOOR

(Street)

NEW YORK NY 10014

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

	Director		10% Owner
	Officer (give title below)	X	Other (specify below)
			Former 10% owner and director

1. Name and Address of Reporting Person^*

667, L.P.

(Last) (First) (Middle)

860 WASHINGTON STREET, 3RD FLOOR

(Street)

NEW YORK NY 10014

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

	Director		10% Owner
	Officer (give title below)	X	Other (specify below)
			Former 10% owner and director

1. Name and Address of Reporting Person^*

Baker Brothers Life Sciences LP

(Last) (First) (Middle)

860 WASHINGTON STREET, 3RD FLOOR

(Street)

NEW YORK NY 10014

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

	Director		10% Owner
	Officer (give title below)	X	Other (specify below)
			Former 10% owner and director

1. Name and Address of Reporting Person^*

BAKER FELIX

(Last) (First) (Middle)

860 WASHINGTON STREET, 3RD FLOOR

(Street)

NEW YORK NY 10014

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

	Director		10% Owner
	Officer (give title below)	X	Other (specify below)
			Former 10% owner and director

1. Name and Address of Reporting Person^*

BAKER JULIAN

(Last) (First) (Middle)

860 WASHINGTON STREET, 3RD FLOOR

(Street)

NEW YORK NY 10014

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

	Director		10% Owner
	Officer (give title below)	X	Other (specify below)
			Former 10% owner and director

1. Name and Address of Reporting Person^*

Baker Bros. Advisors (GP) LLC

(Last) (First) (Middle)

860 WASHINGTON STREET, 3RD FLOOR

(Street)

NEW YORK NY 10014

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

	Director		10% Owner
	Officer (give title below)	X	Other (specify below)
			Former 10% owner and director

Explanation of Responses:

1. Reflects the completion of a tender offer by Concentra Biosciences, LLC (the "Parent"), to purchase all of the issued and outstanding shares of voting and non-voting common stock ("Shares") of the IGM Biosciences, Inc. (the "Issuer") for (i) $1.247 per Share in cash plus (ii) one non-transferable contractual contingent value right for each Share in connection with the consummation of the transactions (the "Merger") contemplated by the Agreement and Plan of Merger, dated as of July 1, 2025, by and among the Issuer, the Parent and Concentra Merger Sub V, Inc. ("Merger Sub"), a wholly owned subsidiary of Parent, pursuant to which, at the effective time of the Merger on August 14, 2025, Merger Sub merged with and into the Issuer, with the Issuer surviving as a subsidiary of Parent.

2. As a result of their ownership interest in (i) Baker Biotech Capital, L.P. and (ii) 667, L.P. ("667"), Julian C. Baker and Felix J. Baker each may have been deemed to have had an indirect pecuniary interest in common stock of the Issuer ("Common Stock") reported as disposed in Table I and securities reported as disposed in Table II that were held directly by or that were held for the benefit of 667, a limited partnership of which the sole general partner is Baker Biotech Capital, L.P., a limited partnership of which the sole general partner is Baker Biotech Capital (GP), LLC, due to their interest in 667 and Baker Biotech Capital, L.P.'s right to receive an allocation of a portion of the profits from 667.

3. Baker Bros. Advisors LP (the "Adviser") serves as the investment adviser to 667 and Baker Brothers Life Sciences, L.P. ("Life Sciences", and togeher with 667, the "Funds"). In connection with the services provided by the Adviser, the Adviser receives an asset-based management fee that does not confer any pecuniary interest in the securities held directly by the Funds or for the benefit of the Funds. The Adviser GP is the Adviser's sole general partner. Julian C. Baker and Felix J. Baker are managing members of the Adviser GP. The Adviser has complete and unlimited discretion and authority with respect to the investment and voting power of the securities held directly by the Funds or for the benefit of the Funds. The general partners of the Funds relinquished to the Adviser all discretion and authority with respect to the investment and voting power of the securities held directly by the Funds or for the benefit of the Funds.

4. Julian C. Baker, Felix J. Baker, the Adviser GP and the Adviser disclaim beneficial ownership of the securities held directly by the Funds or for the benefit of the Funds except to the extent of their pecuniary interest therein, and this report shall not be deemed an admission that any of Julian C. Baker, Felix J. Baker, the Adviser GP or the Adviser is or was a beneficial owner of such securities for purposes of Section 16 or any other purpose.

5. Includes the disposal of 12,098 shares of Common Stock previously issued to Felix J. Baker pursuant to the Issuer's Outside Director Compensation Policy (the "Stock Incentive Plan") in lieu of director retainer fees in his previous capacity as a director of the Issuer and 892 shares of Common Stock previously issued to Dr. Kelvin Neu, a former employee of the Adviser, pursuant to the Stock Incentive Plan in lieu of director retainer fees, and 11,210 shares of Common Stock received previously from the exercise of 11,210 non-qualified options exercisable solely into Common Stock ("Stock Options") that were issued to Dr. Neu in his previous capacity as a director of the Issuer, of which the Funds were deemed to own a portion.

6. Pursuant to the policies of the Adviser, Felix J. Baker does not have any right to any of the Issuer's securities issued as compensation for his previous service on the board of directors of the Issuer (the "Board") and Dr. Neu, a former employee of the Adviser, does not have any right to any of the Issuer's securities issued as compensation for his previous service on the Board and the Funds were entitled to an indirect proportionate pecuniary interest in the Stock Options and restricted stock units (each an "RSU"). Solely as a result of their ownership interest in (i) the general partners of the Funds and (ii) the Funds, Felix J. Baker and Julian C. Baker may have been deemed to have had an indirect pecuniary interest in the Stock Options, RSUs and any Common Stock acquired upon the exercise of Stock Options or vesting of RSUs (i.e. no direct pecuniary interest).

7. Pursuant to the policies of the Adviser, the Adviser has voting and dispositive power over the Common Stock received in lieu of director retainer fees, Stock Options, RSUs and any Common Stock received as a result of the exercise of Stock Options.

8. As a result of their ownership interest in (i) Baker Brothers Life Sciences Capital, L.P. and (ii) Life Sciences, Julian C. Baker and Felix J. Baker each may have been deemed to have had an indirect pecuniary interest in Common Stock reported as disposed in Table I and securities reported as disposed in Table II that were held directly by or that were held for the benefit of Life Sciences, a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital, L.P., a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital (GP), LLC, due to their interest in Life Sciences and Baker Brothers Life Sciences Capital, L.P.'s right to receive an allocation of a portion of the profits from Life Sciences.

9. Represents non-voting common stock of the Issuer ("Non-Voting Common Stock") with no expiration date that was convetible at any time at the option of the holder on a 1-for-1 basis without consideration into Common Stock to the extent that after giving effect to such conversion, the holders thereof, together with their affiliates and any members of a Section 13(d) group with such holders, would have beneficially owned, for purposes of Rule 13d-3 under the Securities Act of 1934, as amended, no more than 4.99% of the outstanding shares of Common Stock (the "Beneficial Ownership Limitation") following such conversion. By written notice to the Issuer, the Funds may have from time to time been able to increase or decrease the Beneficial Ownership Limitation applicable to that Fund to any other percentage not in excess of 19.99%. Any such change would not have been effective until the 61st day after such notice is delivered to the Issuer.

Remarks:

Felix J. Baker, a managing member of Baker Bros. Advisors (GP) LLC, the sole general partner of Baker Bros. Advisors LP, resigned as a director of IGM Biosciences, Inc. (the "Issuer") immediatley prior to the closing of the merger with Concentra Biosciences, LLC. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, the reporting persons other than Felix J. Baker are no longer deemed directors by deputization of the Issuer.

	By: Baker Bros. Advisors LP, Name: Scott L. Lessing, Title: President /s/ Scott L. Lessing	08/18/2025
	Baker Bros. Advisors LP, Mgmt. Co. and Inv. Adviser to 667, L.P., pursuant to authority granted by Baker Biotech Capital, L.P., GP to 667, L.P. Name: Scott L. Lessing, Title: President /s/ Scott L. Lessing	08/18/2025
	/s/ Felix J. Baker	08/18/2025
	/s/ Julian C. Baker	08/18/2025
	By: Baker Bros. Advisors (GP) LLC, Name: Scott L. Lessing, Title: President /s/ Scott L. Lessing	08/18/2025
	Baker Bros. Advisors LP, Mgmt. Co. and Inv. Adviser to BAKER BROTHERS LIFE SCIENCES, L.P., pursuant to authority granted by Baker Brothers Life Sciences Capital, L.P., GP to Baker Brothers Life Sciences, L.P., /s/ Name: Scott L. Lessing, Title: President	08/18/2025
	** Signature of Reporting Person	Date
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FAQ

What did the Form 4 for IGMS report on 08/14/2025?

The Form 4 reports the completion of a tender offer and merger on 08/14/2025 resulting in dispositions of large blocks of Common and Non-Voting Common Stock by Baker-affiliated funds.

What consideration did IGM shareholders receive in the merger?

Shareholders received $1.247 per share in cash plus one non-transferable contingent value right per share under the merger agreement.

Why were large share amounts reported as disposed in the filing?

The reported disposals reflect the transfer of issued and outstanding voting and non-voting shares to the buyer as part of the merger, not open-market insider sales.

Did any insiders change roles as a result of the transaction?

Yes. Felix J. Baker resigned as a director immediately prior to the closing of the merger.

Are the reported holdings direct or indirect?

The filing states the reported holdings were held by funds and limited partnerships managed or advised by Baker Bros. entities, and the individuals may have indirect pecuniary interests rather than direct beneficial ownership.