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

Rhea-AI Filing Summary

IGM Biosciences, Inc. (IGMS) – Form 4 filing dated 07/02/2025

Baker Bros. Advisors LP and affiliated investment funds (667, L.P. and Baker Brothers Life Sciences, L.P.) reported the receipt of 953 fully-vested restricted stock units (RSUs) on 06/30/2025. The RSUs were issued to Felix J. Baker in lieu of a $11,500 board retainer under the company’s Outside Director Compensation Policy. No cash was paid for the shares (price reported as $0).

Post-transaction indirect beneficial ownership stands at

• 357,048 common shares held for the benefit of 667, L.P.
• 3,763,362 common shares held for the benefit of Baker Brothers Life Sciences, L.P.

The Baker entities remain both “10% owners” and directors by deputization of IGMS.

The filing is administrative in nature—reflecting routine director compensation rather than open-market buying or selling—and does not alter the group’s sizable strategic stake in the company.

Positive

• Continued large insider ownership: Baker-controlled funds still hold over 4 million shares, maintaining strong alignment with public shareholders.
• Transparency and timely Section 16 compliance reinforces good corporate governance practices.

Negative

• None.

Insights

Financial Analyst

TL;DR: Routine RSU grant; total Baker Bros. stake unchanged—neutral for valuation.

This Form 4 records a small, non-cash grant of 953 RSUs to Felix Baker for board service, leaving the Baker complex with roughly 4.1 million IGMS shares across two funds. Because the shares were issued in lieu of director fees at no cost, there is no signal of incremental insider buying pressure or fundamental change in conviction. The group’s >10 % ownership and board influence remain intact, underscoring long-term alignment but providing no new catalyst.

Corporate Governance Specialist

TL;DR: Filing confirms compliance with Section 16; immaterial transaction.

The disclosure demonstrates proper reporting of director compensation under Section 16 rules. All parties explicitly disclaim beneficial ownership beyond their pecuniary interests, highlighting robust governance procedures. Material impact is negligible, yet continued transparency from a large shareholder is positive for investors’ trust.

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
Estimated average burden
hours per response:			0.5

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)

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

3. Date of Earliest Transaction (Month/Day/Year)
06/30/2025

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	06/30/2025		A		953(1)	A	$0	357,048	I	See Footnotes(2)(3)(4)(5)(6)(7)(8)
Common Stock	06/30/2025		A		953(1)	A	$0	3,763,362	I	See Footnotes(3)(4)(5)(6)(7)(8)(9)

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

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

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

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

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

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

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

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

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

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

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

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

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

Explanation of Responses:

1. Includes 953 restricted stock units (each, an "RSU") of IGM Biosciences, Inc. (the "Issuer") issued to Felix J. Baker, a managing member of Baker Bros. Advisors (GP) LLC (the "Adviser GP"), pursuant to the Issuer's Outside Director Compensation Policy (the "Stock Incentive Plan") in lieu of director retainer fees of $11,500. The RSUs are fully vested. Felix J. Baker serves on the Issuer's board of directors (the "Board") as a representative of 667, L.P. ("667") and Baker Brothers Life Sciences, L.P. ("Life Sciences", and together with 667, the "Funds") and their affiliates and control persons.

2. After giving effect to the transaction reported herein and as a result of their ownership interest in (i) Baker Biotech Capital, L.P. and (ii) 667, Julian C. Baker and Felix J. Baker each may be deemed to have an indirect pecuniary interest in common stock of the Issuer ("Common Stock") reported in column 5 of Table I held directly by or 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 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 a beneficial owner of such securities for purposes of Section 16 or any other purpose.

5. Includes beneficial ownership of 11,145 shares of Common Stock previously issued to Felix J. Baker pursuant to the Stock Incentive Plan in lieu of director retainer fees in his capacity as a director 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 soley 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 are deemed to own a portion.

6. The acquisitions of RSUs reported on this form represent a single grant of 953 RSUs on Table I. The 953 RSUs are reported for each of the Funds as each has an indirect pecuniary interest in such securities.

7. 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 service on 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 are entitled to an indirect proportionate pecuniary interest in the Stock Options and RSUs. 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 be deemed to have 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).

8. 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.

9. After giving effect to the transaction reported herein and 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 be deemed to have an indirect pecuniary interest in Common Stock reported in column 5 of Table I held directly by or 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.

Remarks:

Felix J. Baker, a managing member of Baker Bros. Advisors (GP) LLC, the sole general partner of Baker Bros. Advisors LP, is a director of IGM Biosciences, Inc. (the "Issuer"). By virtue of their representation on the board of directors of the Issuer, for purposes of Section 16 of the Securities Exchange Act of 1934, as amended, the reporting persons other than Felix J. Baker are deemed directors by deputization of the Issuer.

	By: Baker Bros. Advisors LP, Name: Scott L. Lessing, Title: President /s/ Scott L. Lessing	07/02/2025
	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	07/02/2025
	/s/ Felix J. Baker	07/02/2025
	/s/ Julian C. Baker	07/02/2025
	By: Baker Bros. Advisors (GP) LLC, Name: Scott L. Lessing, Title: President /s/ Scott L. Lessing	07/02/2025
	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	07/02/2025
	** 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

How many IGMS shares did Baker Bros. acquire in the latest Form 4?

953 fully-vested restricted stock units were granted on 06/30/2025.

What is Baker Bros.’ total indirect ownership in IGMS after the transaction?

Approximately 357,048 shares via 667, L.P. and 3,763,362 shares via Baker Brothers Life Sciences, L.P.

Was any cash paid for the RSUs reported on this Form 4?

No. The RSUs were issued at $0 in lieu of a $11,500 director retainer fee.

Why are the reporting persons classified as 10% owners of IGMS?

Their aggregate holdings exceed 10 % of IGMS outstanding common stock, triggering Section 16 reporting.

Does the filing indicate insider sentiment toward IGMS stock?

The grant is routine compensation rather than a discretionary purchase, so it offers no strong sentiment signal.