Fairmount trims Apogee Therapeutics (APGE) stake but still holds near 10%

Rhea-AI Filing Summary

Apogee Therapeutics’ major shareholder Fairmount Funds has updated its ownership disclosure after a sizable share sale. Fairmount Healthcare Fund II L.P. and related parties now report beneficial ownership of up to 9.99% of Apogee’s common stock, using both common and non-voting common shares in the calculation and subject to a 9.99% beneficial ownership cap.

The filing shows Fairmount-related entities having voting and dispositive power over 6,031,979 shares of common stock, including shares issuable upon conversion of non-voting common stock. Fund II also holds 6,743,321 shares of non-voting common stock in total, which can convert to common stock within the ownership limits. On January 22, 2026, Fund II sold 1,750,000 shares of common stock in a block trade at $76.30 per share. Directors Peter Harwin and Tomas Kiselak each hold common shares and vested options but disclaim beneficial ownership of the option shares due to arrangements with Fairmount.

Insights

Equity ownership and governance analyst

Fairmount sold 1.75M Apogee shares but remains a near‑10% holder.

Fairmount Healthcare Fund II L.P. and related parties report beneficial ownership close to the 9.99% threshold, combining common stock and non-voting common stock that can convert subject to a beneficial ownership limitation. They list voting and dispositive power over 6,031,979 shares of common stock, while Fund II in total owns 6,743,321 shares of non-voting common stock.

The amendment records a block trade on January 22, 2026, where Fund II sold 1,750,000 shares of common stock at $76.30 per share. Despite this sale, Fairmount remains a significant shareholder, with Harwin and Kiselak each reporting 9.99% beneficial ownership when including Fund II’s holdings and vested options, though they disclaim beneficial ownership of option shares under their arrangements with Fairmount.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 4)

Apogee Therapeutics, Inc.

(Name of Issuer)

Common Stock, $0.00001 par value

(Title of Class of Securities)

03770N101

(CUSIP Number)

Ms. Erin O'Connor
Fairmount Funds Management LLC, 200 Barr Harbor Drive, Suite 400
West Conshohocken, PA, 19428
(267) 262-5300

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

01/22/2026

(Date of Event Which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.

The information required on the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

SCHEDULE 13D

CUSIP No. 03770N101

1

Name of reporting person

Fairmount Funds Management LLC

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 5,948,385.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 5,948,385.00

11

Aggregate amount beneficially owned by each reporting person

5,948,385.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

9.82 %

14

Type of Reporting Person (See Instructions)

IA

Comment for Type of Reporting Person:

The securities include (i) 298,647 shares of common stock, $0.00001 par value per share (the "Common Stock") and (ii) 5,649,738 shares of Common Stock issuable upon conversion of 5,649,738 shares of Non-Voting Common Stock, par value $0.00001 per share (the "Non-Voting Common Stock"), the conversion of which is subject to a beneficial ownership limitation of 9.99% of the outstanding Common Stock, both directly held by Fairmount Healthcare Fund II L.P., a Delaware limited partnership ("Fund II"). The securities exclude shares of Common Stock issuable upon conversion of shares of Non-Voting Common Stock held by Fund II in excess of the beneficial ownership limitation. Row 13 is based on 60,567,741 shares of Common Stock outstanding as of January 22, 2026, consisting of (i) 54,833,587 shares of Common Stock outstanding as of November 3, 2025, as reported in the Company's Form 10-Q filed on November 10, 2025, (ii) 84,416 shares underlying vested stock options owned by the Reporting Persons and (iii) 5,649,738 shares of Common Stock underlying the 5,649,738 shares of Non-Voting Common Stock owned by Fund II, applying the beneficial ownership limitation.

SCHEDULE 13D

CUSIP No. 03770N101

1

Name of reporting person

Fairmount Healthcare Fund II L.P.

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 5,948,385.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 5,948,385.00

11

Aggregate amount beneficially owned by each reporting person

5,948,385.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

9.82 %

14

Type of Reporting Person (See Instructions)

PN

Comment for Type of Reporting Person:

The securities include (i) 298,647 shares of Common Stock and (ii) 5,649,738 shares of Common Stock issuable upon conversion of 5,649,738 shares of Non-Voting Common Stock, the conversion of which is subject to a beneficial ownership limitation of 9.99% of the outstanding Common Stock, both directly held by Fund II. The securities exclude shares of Common Stock issuable upon conversion of shares of Non-Voting Common Stock held by Fund II in excess of the beneficial ownership limitation. Row 13 is based on 60,567,741 shares of Common Stock outstanding as of January 22, 2026, consisting of (i) 54,833,587 shares of Common Stock outstanding as of November 3, 2025, as reported in the Company's Form 10-Q filed on November 10, 2025, (ii) 84,416 shares underlying vested stock options owned by the Reporting Persons and (iii) 5,649,738 shares of Common Stock underlying the 5,649,738 shares of Non-Voting Common Stock owned by Fund II, applying the beneficial ownership limitation.

SCHEDULE 13D

CUSIP No. 03770N101

1

Name of reporting person

Peter Evan Harwin

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 93,374.00
8	Shared Voting Power 5,953,653.00
9	Sole Dispositive Power 93,374.00
10	Shared Dispositive Power 5,953,653.00

11

Aggregate amount beneficially owned by each reporting person

6,047,027.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

9.99 %

14

Type of Reporting Person (See Instructions)

IN, HC

Comment for Type of Reporting Person:

The securities include (a) 51,166 shares of Common Stock held directly by Mr. Harwin, (b) 42,208 shares of Common Stock underlying vested options held by Mr. Harwin* and (c) Fund II's direct holdings of (i) 298,647 shares of Common Stock and (ii) 5,655,066 shares of Common Stock issuable upon conversion of 5,655,066 shares of Non-Voting Common Stock, the conversion of which is subject to a beneficial ownership limitation of 9.99% of the outstanding Common Stock. The securities exclude shares of Common Stock issuable upon conversion of shares of Non-Voting Common Stock in excess of the beneficial ownership limitation. Row 13 is based on 60,530,801 shares of Common Stock outstanding as of January 22, 2026, consisting of (i) 54,833,587 shares of Common Stock outstanding as of November 3, 2025, as reported in the Company's Form 10-Q filed on November 10, 2025, (ii) 42,208 shares of Common Stock underlying vested options held by Mr. Harwin and (iii) 5,655,006 shares of Common Stock underlying the 5,655,006 shares of Non-Voting Common Stock owned by Fund II, subject to the beneficial ownership limitation. * Under Mr. Harwin's arrangement with Fairmount, Mr. Harwin holds the options for one or more investment vehicles managed by Fairmount (each, a "Fairmount Fund"). Mr. Harwin is obligated to turn over to Fairmount any net cash or stock received from the option for the benefit of such Fairmount Fund. Mr. Harwin therefore disclaims beneficial ownership of the option and underlying common stock.

SCHEDULE 13D

CUSIP No. 03770N101

1

Name of reporting person

Tomas Kiselak

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

SLOVAKIA

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 93,374.00
8	Shared Voting Power 5,953,653.00
9	Sole Dispositive Power 93,374.00
10	Shared Dispositive Power 5,953,653.00

11

Aggregate amount beneficially owned by each reporting person

6,047,027.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

9.99 %

14

Type of Reporting Person (See Instructions)

IN, HC

Comment for Type of Reporting Person:

The securities include (a) 51,166 shares of Common Stock held directly by Mr. Kiselak, (b) 42,208 shares of Common Stock underlying vested options held by Mr. Kiselak* and (c) Fund II's direct holdings of (i) 298,647 shares of Common Stock and (ii) 5,655,066 shares of Common Stock issuable upon conversion of 5,655,066 shares of Non-Voting Common Stock, the conversion of which is subject to a beneficial ownership limitation of 9.99% of the outstanding Common Stock. The securities exclude shares of Common Stock issuable upon conversion of shares of Non-Voting Common Stock in excess of the beneficial ownership limitation. Row 13 is based on 60,530,801 shares of Common Stock outstanding as of January 22, 2026, consisting of (i) 54,833,587 shares of Common Stock outstanding as of November 3, 2025, as reported in the Company's Form 10-Q filed on November 10, 2025, (ii) 42,208 shares of Common Stock underlying vested options held by Mr. Kiselak and (iii) 5,655,006 shares of Common Stock underlying the 5,655,006 shares of Non-Voting Common Stock owned by Fund II, subject to the beneficial ownership limitation. * Under Mr. Kiselak's arrangement with Fairmount, Mr. Kiselak holds the options for one or more investment vehicles managed by Fairmount (each, a "Fairmount Fund"). Mr. Kiselak is obligated to turn over to Fairmount any net cash or stock received from the option for the benefit of such Fairmount Fund. Mr. Kiselak therefore disclaims beneficial ownership of the option and underlying common stock.

SCHEDULE 13D

Item 1.	Security and Issuer
(a)	Title of Class of Securities: Common Stock, $0.00001 par value
(b)	Name of Issuer: Apogee Therapeutics, Inc.
(c)	Address of Issuer's Principal Executive Offices: 221 Crescent Street, Building 17, Suite 102b, Waltham, MASSACHUSETTS , 02453.
Item 1 Comment: This Amendment No. 4 amends and supplements the statement on Schedule 13D originally filed with the Securities and Exchange Commission (the "SEC") on July 21, 2023, Amendment No. 1 filed on January 31, 2024, Amendment No. 2 filed on April 1, 2024, and Amendment No. 3 filed on October 14, 2025 (as amended, the "Statement" or the "Schedule 13D") by the Reporting Persons with respect to the Common Stock of the Company. Unless otherwise defined herein, capitalized terms used in this Amendment No. 4 shall have the meanings ascribed to them in the Statement. Unless amended or supplemented below, the information in the Statement remains unchanged.
Item 5.	Interest in Securities of the Issuer
(a)	The information in rows 11 and 13 of each of the cover pages (including the explanatory note in the "Comments") of this Amendment No. 4 is incorporated by reference herein.
(b)	The information in rows 7 through 10 of each of the cover pages of this Amendment No. 4 is incorporated by reference herein. In the aggregate, the Reporting Persons have voting and dispositive power over 6,031,979 shares of Common Stock, which is comprised of the following: (i) 298,647 shares of Common Stock held by Fund II; (ii) 5,546,584 shares of Common Stock issuable upon conversion of 5,546,584 shares of Non-Voting Common Stock, held by Fund II, reflecting the beneficial ownership limitation of 9.99% of the outstanding Common Stock; (iii) 51,166 shares of Common Stock held by Mr. Harwin; (iv) 42,208 shares of Common Stock underlying vested options held by Mr. Harwin; (v) 51,166 shares of Common Stock held by Mr. Kiselak; and (vi) 42,208 shares of Common Stock underlying vested options held by Mr. Kiselak. In total, the Fund II currently owns 6,743,321 shares of Non-Voting Common Stock.
(c)	Item 5(c) of the Schedule 13D is hereby amended and supplemented as follows: On January 22, 2026, Fund II sold in a block trade a total of 1,750,000 shares of Common Stock at a price of $76.30 per share.
Item 6.	Contracts, Arrangements, Understandings or Relationships With Respect to Securities of the Issuer
	Company Stock Options On June 17, 2025, in their respective capacities as members of the Company's board of directors, Mr. Harwin and Mr. Kiselak were each granted stock options by the Company representing the right to purchase 14,461 shares of Common Stock. The options will vest on the one-year anniversary of the grant date, subject to Mr. Harwin and Mr. Kiselak's continued service to the Company on such vesting date. Under Mr. Harwin's and Mr. Kiselak's respective arrangements with Fairmount Funds Management, Mr. Harwin and Mr. Kiselak hold the options for one or more Fairmount Funds and are obligated to turn over to Fairmount Funds Management any net cash or stock received from the option for the benefit of such Fairmount Fund. Mr. Harwin and Mr. Kiselak therefore each disclaim beneficial ownership of their respective options and underlying common stock.
Item 7.	Material to be Filed as Exhibits.
	99.1 Joint Filing Agreement (incorporated by reference to Exhibit 99.1 to the Schedule 13D filed with the SEC on October 14, 2025)

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Fairmount Funds Management LLC

Signature:	/s/ Peter Harwin
Name/Title:	Peter Harwin, Managing Member
Date:	01/22/2026

Signature:	/s/ Tomas Kiselak
Name/Title:	Tomas Kiselak, Managing Member
Date:	01/22/2026

Fairmount Healthcare Fund II L.P.

Signature:	/s/ Peter Harwin
Name/Title:	Peter Harwin, Managing Member
Date:	01/22/2026

Signature:	/s/ Tomas Kiselak
Name/Title:	Tomas Kiselak, Managing Member
Date:	01/22/2026

Peter Evan Harwin

Signature:	/s/ Peter Harwin
Name/Title:	Peter Harwin
Date:	01/22/2026

Tomas Kiselak

Signature:	/s/ Tomas Kiselak
Name/Title:	Tomas Kiselak
Date:	01/22/2026

FAQ

How much of Apogee Therapeutics (APGE) does Fairmount currently report owning?

The reporting persons tied to Fairmount Funds report beneficial ownership of up to 9.99% of Apogee Therapeutics’ common stock, based on share counts and calculations detailed in the filing.

How many Apogee Therapeutics (APGE) shares do the Fairmount reporting persons control voting and dispositive power over?

The reporting persons state they have voting and dispositive power over 6,031,979 shares of Apogee common stock, including shares issuable upon conversion of non-voting common stock within the 9.99% ownership limit.

What recent Apogee Therapeutics (APGE) share sale did Fairmount disclose?

On January 22, 2026, Fairmount Healthcare Fund II L.P. sold 1,750,000 shares of Apogee common stock in a block trade at $76.30 per share.

What is the role of non-voting common stock in Fairmount’s Apogee (APGE) position?

The securities include Apogee non-voting common stock that is convertible into common stock, but conversions are limited by a 9.99% beneficial ownership cap. Fund II in total owns 6,743,321 non-voting common shares.

What are the reported beneficial ownership percentages for Peter Harwin and Tomas Kiselak in Apogee (APGE)?

Both Peter Harwin and Tomas Kiselak report beneficial ownership of 9.99% of Apogee’s common stock, including their direct holdings, vested options, and Fund II’s holdings, while disclaiming beneficial ownership of certain option shares.

Do Apogee (APGE) directors Harwin and Kiselak personally benefit from their stock options?

The filing states that Harwin and Kiselak each hold Apogee stock options, but under their arrangements with Fairmount Funds Management they must turn over any net cash or stock from these options to Fairmount, and each disclaims beneficial ownership of the options and underlying shares.