Spyre Therapeutics: Fairmount agrees to 60-day lock-up

The agreement limits sales of Spyre securities without the underwriters’ representatives’ consent for 60 days after the October 5, 2026 final prospectus supplement.

Rhea-AI Filing Summary

Spyre Therapeutics, Inc. (SYRE) is the subject of an amendment by reporting persons Fairmount Funds Management LLC, Fairmount Healthcare Fund II L.P., Peter Harwin and Tomas Kiselak reporting a lock-up agreement tied to the company’s underwritten public offering, which closed October 7, 2026. They agreed to refrain from selling Spyre securities without the underwriters’ representatives’ consent for 60 days following the October 5, 2026 final prospectus supplement. The reporting persons state that their share counts have not changed since June 23, 2026. Their disclosed securities include 812,076 common shares owned, 9,100,160 common shares issuable upon conversion of Series A Preferred Stock, and 228,646 common shares issuable upon option exercise; the disclosure excludes 4,741,640 conversion shares above the 9.99% beneficial ownership limitation. They state that they did not purchase securities or otherwise participate in the offering.

Key Figures

Lock-up period: 60 days Beneficial ownership limitation: 9.99% Common shares owned: 812,076 shares +3 more

6 metrics

Lock-up period 60 days Following the date of the October 5, 2026 final prospectus supplement

Beneficial ownership limitation 9.99% Applied to the reporting persons’ securities

Common shares owned 812,076 shares Included in the reporting persons’ disclosed securities

Common shares issuable upon conversion 9,100,160 shares Issuable upon conversion of 227,504 shares of Series A Preferred Stock

Common shares issuable upon option exercise 228,646 shares Options currently exercisable or exercisable within 60 days

Excluded conversion shares 4,741,640 shares Issuable upon conversion of 118,541 shares of Series A Preferred Stock above the beneficial ownership limitation

Key Terms

beneficial ownership limitation, Series A Preferred Stock, Lock-Up Agreement, underwritten public offering

4 terms

beneficial ownership limitation financial

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

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 Series A Preferred Stock subject to the 9.99% beneficial ownership limitation"

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.

Lock-Up Agreement financial

"the Lock-Up Agreement with Jefferies LLC, TD Securities (USA) LLC"

A lock-up agreement is a contract that prevents company insiders and early investors from selling their shares for a fixed period after a stock sale, often after an initial public offering. It matters to investors because it temporarily limits the number of shares that can hit the market, which can keep the share price steadier; when the lock-up ends, a sudden increase in available shares can create extra volatility, revealing insiders’ confidence or lack thereof.

underwritten public offering financial

"the Company’s underwritten public offering of common stock"

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.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

How many Spyre shares do Fairmount’s reporting persons disclose?

The reporting persons list 812,076 common shares owned, 9,100,160 common shares issuable upon conversion of Series A Preferred Stock, and 228,646 common shares issuable upon option exercise. Their disclosure excludes 4,741,640 conversion shares above the 9.99% beneficial ownership limitation.

Did Fairmount participate in Spyre’s October 2026 offering?

No. The reporting persons state that they did not purchase any Spyre securities or otherwise participate in the underwritten public offering, which closed October 7, 2026.

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

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Available on EDGAR 10/09/2026 - 05:01 PM Accepted by SEC EDGAR 10/09/2026 - 05:00 PM Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 8)

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)

10/07/2026

(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 9,354,200.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 9,354,200.00

11

Aggregate amount beneficially owned by each reporting person

9,354,200.00

12

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

13

Percent of class represented by amount in Row (11)

9.19 %

14

Type of Reporting Person (See Instructions)

IA

Comment for Type of Reporting Person:

The securities represent 9,354,200 shares of common stock, $0.0001 par value per share (the "Common Stock") issuable upon conversion of 233,855 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 held directly by Fund II in excess of the beneficial ownership limitation of 9.99%. Row 13 is based on 101,764,627 shares of Common Stock outstanding as of October 7, 2026, consisting of (i) 92,181,781 shares of Common Stock outstanding as of October 7, 2026, as reported in the Company's final prospectus supplement filed pursuant to Rule 424(b)(5) dated October 5, 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) 9,422,760 shares of Common Stock underlying the 233,855 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 9,354,200.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 9,354,200.00

11

Aggregate amount beneficially owned by each reporting person

9,354,200.00

12

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

13

Percent of class represented by amount in Row (11)

9.19 %

14

Type of Reporting Person (See Instructions)

PN

Comment for Type of Reporting Person:

The securities represent 9,354,200 shares of Common Stock issuable upon conversion of 233,855 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 held directly by Fund II in excess of the beneficial ownership limitation of 9.99%. Row 13 is based on 101,764,627 shares of Common Stock outstanding as of October 7, 2026, consisting of (i) 92,181,781 shares of Common Stock outstanding as of October 7, 2026, as reported in the Company's final prospectus supplement filed pursuant to Rule 424(b)(5) dated October 5, 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) 9,422,760 shares of Common Stock underlying the 233,855 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

Harwin Peter Evan

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 9,665,600.00
9	Sole Dispositive Power 520,361.00
10	Shared Dispositive Power 9,665,600.00

11

Aggregate amount beneficially owned by each reporting person

10,185,961.00

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 9,665,600 shares of Common Stock issuable upon conversion of 241,640 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 held directly by Fund II in excess of the beneficial ownership limitation of 9.99%. Row 13 is based on 101,961,704 shares of Common Stock outstanding as of October 7, 2026, consisting of (i) 92,181,781 shares of Common Stock outstanding as of October 7, 2026, as reported in the Company's final prospectus supplement filed pursuant to Rule 424(b)(5) dated October 5, 2026, (iii) 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) 9,665,600 shares of Common Stock underlying the 241,640 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

Kiselak Tomas

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 9,665,600.00
9	Sole Dispositive Power 520,361.00
10	Shared Dispositive Power 9,665,600.00

11

Aggregate amount beneficially owned by each reporting person

10,185,961.00

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 9,665,600 shares of Common Stock issuable upon conversion of 241,640 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 held directly by Fund II in excess of the beneficial ownership limitation of 9.99%. Row 13 is based on 101,961,704 shares of Common Stock outstanding as of October 7, 2026, consisting of (i) 92,181,781 shares of Common Stock outstanding as of October 7, 2026, as reported in the Company's final prospectus supplement filed pursuant to Rule 424(b)(5) dated October 5, 2026, (iii) 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) 9,665,600 shares of Common Stock underlying the 241,640 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 Fairmount Funds. 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. 8 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, Amendment No. 5 filed on October 17, 2025, and Amendment No. 6 filed on April 20, 2026, and Amendment No. 7 filed on June 23, 2026 (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. 7 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. 8 is being filed solely to report the Reporting Persons' entry into a lock-agreement in connection with the Company's underwritten public offering; the number of shares of Common Stock and Series A Preferred Stock beneficially owned by the Reporting Persons has not changed since Amendment No. 7 to the Statement, filed on June 23, 2026.
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. 8 is incorporated by reference herein. Together, the Reporting Persons' securities include (i) 812,076 shares of Common Stock owned by the Reporting Persons, (ii) 9,100,160 shares of Common Stock issuable upon conversion of 227,504 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 and (iii) 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. The securities exclude 4,741,640 shares of Common Stock issuable upon conversion of 118,541 shares of Series A 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. 8 is incorporated by reference herein.
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 October 7, 2026, the Reporting Persons entered into a customary lock-up letter agreement (the "Lock-Up Agreement") with Jefferies LLC, TD Securities (USA) LLC, Leerink Partners LLC and Stifel, Nicolaus & Company, Incorporated, acting as the representatives of the underwriters (collectively, the "Representatives") 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 following the date of the final prospectus supplement for 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 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 October 7, 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:	10/09/2026

Signature:	/s/ Tomas Kiselak
Name/Title:	Tomas Kiselak, Managing Member
Date:	10/09/2026

Fairmount Healthcare Fund II L.P.

Signature:	/s/ Peter Harwin
Name/Title:	Peter Harwin, Managing Member
Date:	10/09/2026

Signature:	/s/ Tomas Kiselak
Name/Title:	Tomas Kiselak, Managing Member
Date:	10/09/2026

Harwin Peter Evan

Signature:	/s/ Peter Harwin
Name/Title:	Peter Harwin
Date:	10/09/2026

Kiselak Tomas

Signature:	/s/ Tomas Kiselak
Name/Title:	Tomas Kiselak
Date:	10/09/2026