Spyre Therapeutics (SYRE) holders keep near-10% stake, agree to 60-day lock-up

Rhea-AI Filing Summary

Spyre Therapeutics' major shareholders have reaffirmed their stakes and agreed to a short-term lock-up. Fairmount Funds Management LLC and Fairmount Healthcare Fund II L.P. report beneficial ownership of 8,184,941 shares, or 9.09% of Spyre’s common stock, including common shares and Series A preferred stock on an as-converted basis, subject to a 9.99% beneficial ownership limitation. Individuals Peter Harwin and Tomas Kiselak each report beneficial ownership of 9,016,702 shares, or 9.99% of the class, combining direct holdings, options exercisable within 60 days, and Fund II’s preferred and common shares. The amendment notes that these ownership levels are unchanged from the prior amendment and is filed primarily to disclose that the reporting persons entered into a 60-day lock-up agreement in connection with the company’s underwritten public offering, during which they have agreed not to sell Spyre securities without underwriter consent.

Key Figures

Fairmount beneficial ownership: 8,184,941 shares Fairmount ownership percentage: 9.09% Harwin beneficial ownership: 9,016,702 shares +5 more

8 metrics

Fairmount beneficial ownership 8,184,941 shares Fairmount entities’ aggregate Spyre common stock beneficially owned

Fairmount ownership percentage 9.09% Percent of Spyre common stock class represented by Fairmount holdings

Harwin beneficial ownership 9,016,702 shares Peter Harwin’s aggregate beneficial ownership of Spyre common stock

Harwin ownership percentage 9.99% Percent of Spyre common stock class represented by Harwin’s holdings

Shares outstanding (Fairmount base) 90,060,297 shares Common shares deemed outstanding for Fairmount’s 9.09% calculation as of April 16, 2026

Shares outstanding (Harwin base) 90,257,374 shares Common shares deemed outstanding for Harwin’s 9.99% calculation as of April 16, 2026

Lock-up duration 60 days Period after final prospectus supplement date during which sales require underwriter consent

Convertible Series A in Item 5 3,912,800 shares Spyre common shares issuable from 97,820 Series A Preferred shares within 9.99% cap

Key Terms

beneficial ownership limitation, Series A Preferred Stock, Series B Preferred Stock, lock-up letter agreement, +2 more

6 terms

beneficial ownership limitation financial

"subject to the 9.99% beneficial ownership limitation applied to all of the securities owned"

A beneficial ownership limitation is a rule that caps the percentage of a company’s shares an investor can be treated as owning or controlling for voting, regulatory or tax purposes. It matters to investors because it can restrict how many shares a person or group can buy or vote, affect takeover chances, and influence share liquidity and value — like a speed limit that prevents any single driver from taking over the whole road.

Series A Preferred Stock financial

"shares of Common Stock issuable upon conversion of 104,171 shares of Series A Preferred Stock"

Series A preferred stock is a type of ownership share in a company that gives investors certain advantages, such as priority in receiving profits or getting their money back if the company is sold or goes bankrupt. It is often issued during early funding stages to attract investors by offering more security than common shares. This stock matters to investors because it provides a safer way to invest while still holding potential for future gains.

Series B Preferred Stock financial

"shares of Series A Preferred Stock and Series B Preferred Stock held directly by Fund II"

Series B preferred stock is a type of ownership share issued by a company that offers certain advantages over common stock, such as priority in receiving dividends or assets if the company is sold or liquidated. It is typically issued after an initial round of funding, making it a way for investors to support a company's growth while gaining some protections and benefits. This stock matters to investors because it often provides a more secure investment position with potential for future growth.

lock-up letter agreement financial

"entered into a customary lock-up letter agreement (the "Lock-Up Agreement") with Jefferies LLC"

underwritten public offering financial

"In connection with the Company's underwritten public offering of common stock that closed on April 16, 2026"

An underwritten public offering is when a company sells new shares of its stock to the public with the help of a financial firm, called an underwriter. The underwriter agrees to buy all the shares upfront, reducing the company's risk, and then sells them to investors. This process helps companies raise money quickly and confidently from a wide range of buyers.

final prospectus supplement financial

"from the date of the Company's final prospectus supplement related to the offering"

A final prospectus supplement is the definitive document that completes a public securities offering, spelling out the exact terms, number and price of shares or bonds being sold, key risks, and how the proceeds will be used. Investors treat it like the final recipe or instruction sheet for an investment: it replaces earlier drafts and provides the binding, detailed information needed to judge the value and risk before committing funds.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Accepted by SEC EDGAR 04/20/2026 - 06:00 PM Learn about SEC filing dates

FAQ

What ownership stake in Spyre Therapeutics (SYRE) does Fairmount report?

Fairmount Funds Management LLC and Fairmount Healthcare Fund II L.P. report beneficial ownership of 8,184,941 Spyre common shares, representing 9.09% of the class. This includes common stock and Series A preferred stock on an as-converted basis, subject to a 9.99% beneficial ownership cap.

How many Spyre Therapeutics shares does Peter Harwin beneficially own?

Peter Harwin reports beneficial ownership of 9,016,702 Spyre common shares, or 9.99% of the class. This combines his direct common stock, options exercisable within 60 days, and Fund II’s common and Series A preferred shares on an as-converted basis.

What is the lock-up agreement mentioned for Spyre Therapeutics (SYRE)?

The reporting persons entered a customary 60-day lock-up agreement with underwriters for Spyre’s underwritten public offering. For 60 days from the final prospectus supplement date, they agreed not to sell Spyre securities without underwriter representatives’ consent.

Did Fairmount or its principals buy shares in the Spyre public offering?

The filing states the reporting persons did not purchase any Spyre securities or otherwise participate in the underwritten public offering. Their reported ownership levels are unchanged from the prior amendment to the beneficial ownership statement.

What is the beneficial ownership limitation affecting Spyre preferred stock?

The reporting persons are subject to a 9.99% beneficial ownership limitation. As a result, shares issuable upon conversion of certain Series A and Series B preferred stock held by Fund II, above that threshold, are excluded from the reported beneficial ownership figures.

How many Spyre shares are used to calculate the reported ownership percentages?

For Fairmount and Fund II, the 9.09% stake is based on 90,060,297 Spyre common shares deemed outstanding. For Harwin and Kiselak, the 9.99% stake is based on 90,257,374 common shares deemed outstanding as of April 16, 2026.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 6)

SPYRE THERAPEUTICS, INC.

(Name of Issuer)

Common Stock, $0.0001 par value

(Title of Class of Securities)

00773J202

(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)

04/16/2026

(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).

schemaVersion:

SCHEDULE 13D

CUSIP Number(s): 00773J202

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 8,184,941.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 8,184,941.00

11

Aggregate amount beneficially owned by each reporting person

8,184,941.00

12

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

13

Percent of class represented by amount in Row (11)

9.09 %

14

Type of Reporting Person (See Instructions)

IA

Comment for Type of Reporting Person:

The securities include (i) 4,018,101 shares of common stock, $0.0001 par value per share (the "Common Stock") and (ii) 4,166,840 shares of Common Stock issuable upon conversion of 104,171 shares of Series A Preferred Stock, par value $0.0001 per share (the "Series A Preferred Stock"), held directly by Fairmount Healthcare Fund II L.P. ("Fund II"). The securities exclude shares of Common Stock issuable upon conversion of shares of Series A Preferred Stock and Series B Preferred Stock, par value $0.0001 per share (the "Series B Preferred Stock") held directly by Fund II in excess of the beneficial ownership limitation of 9.99%. Row 13 is based on 90,060,297 shares of Common Stock outstanding as of April 16, 2026, consisting of (i) 85,664,811 shares of Common Stock outstanding as of April 16, 2026, as reported in the Company's final prospectus supplement filed pursuant to Rule 424(b)(5) dated April 14, 2026, (ii) 228,646 shares underlying options that are currently exercisable or will be exercisable within 60 days of the date of this filing by the Reporting Persons and (iii) 4,166,840 shares of Common Stock underlying the 104,171 shares of Series A Preferred Stock owned by Fund II, applying the beneficial ownership limitation.

SCHEDULE 13D

CUSIP Number(s): 00773J202

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 8,184,941.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 8,184,941.00

11

Aggregate amount beneficially owned by each reporting person

8,184,941.00

12

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

13

Percent of class represented by amount in Row (11)

9.09 %

14

Type of Reporting Person (See Instructions)

PN

Comment for Type of Reporting Person:

The securities include (i) 4,018,101 shares of Common Stock and (ii) 4,166,840 shares of Common Stock issuable upon conversion of 104,171 shares of Series A Preferred Stock held directly by Fund II. The securities exclude shares of Common Stock issuable upon conversion of shares of Series A Preferred Stock and Series B Preferred Stock held directly by Fund II in excess of the beneficial ownership limitation of 9.99%. Row 13 is based on 90,060,297 shares of Common Stock outstanding as of April 16, 2026, consisting of (i) 85,664,811 shares of Common Stock outstanding as of April 16, 2026, as reported in the Company's final prospectus supplement filed pursuant to Rule 424(b)(5) dated April 14, 2026, (ii) 228,646 shares underlying options that are currently exercisable or will be exercisable within 60 days of the date of this filing by the Reporting Persons and (iii) 4,166,840 shares of Common Stock underlying the 104,171 shares of Series A Preferred Stock owned by Fund II, applying the beneficial ownership limitation.

SCHEDULE 13D

CUSIP Number(s): 00773J202

1

Name of reporting person

Peter 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 520,361.00
8	Shared Voting Power 8,496,341.00
9	Sole Dispositive Power 520,361.00
10	Shared Dispositive Power 8,496,341.00

11

Aggregate amount beneficially owned by each reporting person

9,016,702.00

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

Comment for Type of Reporting Person:

The securities include (a) 406,038 shares of Common Stock held directly by Mr. Harwin, (b) 114,323 shares of Common Stock issuable upon the exercise of options that are currently exercisable or will be exercisable within 60 days of the date of this filing held directly by Mr. Harwin*, and (c) Fund II's direct holdings of (i) 4,018,101 shares of Common Stock and (ii) 4,478,240 shares of Common Stock issuable upon conversion of 111,956 shares of Series A Preferred Stock held directly by Fund II. The securities exclude shares of Common Stock issuable upon conversion of shares of Series A Preferred Stock and Series B Preferred Stock held directly by Fund II in excess of the beneficial ownership limitation of 9.99%. Row 13 is based on 90,257,374 shares of Common Stock outstanding as of April 16, 2026, consisting of (i) 85,664,811 shares of Common Stock outstanding as of April 16, 2026, as reported in the Company's final prospectus supplement filed pursuant to Rule 424(b)(5) dated April 14, 2026, (ii) 114,323 shares of Common Stock underlying options that are currently exercisable or will be exercisable within 60 days of the date of this filing by Mr. Harwin and (iii) 4,478,240 shares of Common Stock underlying the 111,956 shares of Series A Preferred Stock owned by Fund II, applying 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 Number(s): 00773J202

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 520,361.00
8	Shared Voting Power 8,496,341.00
9	Sole Dispositive Power 520,361.00
10	Shared Dispositive Power 8,496,341.00

11

Aggregate amount beneficially owned by each reporting person

9,016,702.00

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

Comment for Type of Reporting Person:

The securities include (a) 406,038 shares of Common Stock held directly by Mr. Kiselak, (b) 114,323 shares of Common Stock issuable upon the exercise of options that are currently exercisable or will be exercisable within 60 days of the date of this filing held directly by Mr. Kiselak*, and (c) Fund II's direct holdings of (i) 4,018,101 shares of Common Stock and (ii) 4,478,240 shares of Common Stock issuable upon conversion of 111,956 shares of Series A Preferred Stock held directly by Fund II. The securities exclude shares of Common Stock issuable upon conversion of shares of Series A Preferred Stock and Series B Preferred Stock held directly by Fund II in excess of the beneficial ownership limitation of 9.99%. Row 13 is based on 90,257,374 shares of Common Stock outstanding as of April 16, 2026, consisting of (i) 85,664,811 shares of Common Stock outstanding as of April 16, 2026, as reported in the Company's final prospectus supplement filed pursuant to Rule 424(b)(5) dated April 14, 2026, (ii) 114,323 shares of Common Stock underlying options that are currently exercisable or will be exercisable within 60 days of the date of this filing by Mr. Kiselak and (iii) 4,478,240 shares of Common Stock underlying the 111,956 shares of Series A Preferred Stock owned by Fund II, applying 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, $0.0001 par value
(b)	Name of Issuer: SPYRE THERAPEUTICS, INC.
(c)	Address of Issuer's Principal Executive Offices: 221 Crescent Street, Building 23, Suite 105, Waltham, MASSACHUSETTS , 02453.
Item 1 Comment: This Amendment No. 6 amends and supplements the statement on Schedule 13D originally filed with the Securities and Exchange Commission (the "SEC") on June 30, 2023, Amendment No. 1 filed on November 29, 2023, Amendment No. 2 filed on December 11, 2023, Amendment No. 3 filed on December 29, 2023, Amendment No. 4 filed on April 25, 2024, and Amendment No. 5 filed on October 17, 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. 6 shall have the meanings ascribed to them in the Statement. Unless amended or supplemented below, the information in the Statement remains unchanged. This Amendment No. 6 is being filed solely to report the Reporting Persons' entry into a lock-agreement with the Company in connection with the Company's underwritten public offering; the number of shares of Common Stock, Series A Preferred Stock, and Series B Preferred Stock beneficially owned by the Reporting Persons has not changed since Amendment No. 5 to the Statement, filed on October 17, 2025.
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. 6 is incorporated by reference herein. Together, the Reporting Persons' securities include (i) 4,830,177 shares of Common Stock, (ii) 228,646 shares of Common Stock issuable upon the exercise of options held by the Reporting Persons that are currently exercisable or will be exercisable within 60 days of the date of this filing and, (iii) 3,912,800 shares of Common Stock issuable upon conversion of 97,820 shares of Series A Preferred Stock subject to the 9.99% beneficial ownership limitation applied to all of the securities owned by the Reporting Persons. The securities exclude shares of Common Stock issuable upon conversion of 248,225 shares of Series A Preferred Stock and 16,667 shares of Series B Preferred Stock held directly by Fund II in excess of the beneficial ownership limitation of 9.99%.
(b)	The information in rows 7 through 10 of each of the cover pages of this Amendment No. 6 is incorporated by reference herein.
(c)	None
Item 6.	Contracts, Arrangements, Understandings or Relationships With Respect to Securities of the Issuer
	Lock-Up Agreement In connection with the Company's underwritten public offering of common stock that closed on April 16, 2026, the Reporting Persons entered into a customary lock-up letter agreement (the "Lock-Up Agreement") with Jefferies LLC, Goldman Sachs & Co. LLC, Evercore Group L.L.C. and Guggenheim Securities, LLC as the representatives (the "Representatives") of the underwriters to an underwriting agreement with the Company. Pursuant to the Lock-Up Agreement, the Reporting Persons agreed to refrain from selling shares of the Company's securities without the consent of the Representatives, and other customary lock-up conditions, for a period of 60 days from the date of the Company's final prospectus supplement related to the offering. The Reporting Persons did not purchase any securities of the Company or otherwise participate in the offering. The foregoing description of the Lock-Up Agreement does not purport to be complete and is qualified in its entirety by reference to the form of the Lock-Up Agreement, which is filed as Exhibit 99.2 to this Schedule 13D and incorporated herein by reference.
Item 7.	Material to be Filed as Exhibits.
	99.1 Joint Filing Agreement 99.1 (incorporated by reference to Exhibit 99.1 of the Reporting Persons' Schedule 13D filed with the SEC on October 17, 2025). 99.2 Lock-Up Agreement (incorporated by reference to Exhibit A to the Underwriting Agreement filed as Exhibit 1.1 of the Company's Form 8-K filed with the SEC on April 16, 2026).

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:	04/20/2026

Signature:	/s/ Tomas Kiselak
Name/Title:	Tomas Kiselak, Managing Member
Date:	04/20/2026

Fairmount Healthcare Fund II L.P.

Signature:	/s/ Peter Harwin
Name/Title:	Peter Harwin, Managing Member
Date:	04/20/2026

Signature:	/s/ Tomas Kiselak
Name/Title:	Tomas Kiselak, Managing Member
Date:	04/20/2026

Peter Harwin

Signature:	/s/ Peter Harwin
Name/Title:	Peter Harwin
Date:	04/20/2026

Tomas Kiselak

Signature:	/s/ Tomas Kiselak
Name/Title:	Tomas Kiselak
Date:	04/20/2026