Nantahala Capital discloses 2.8% X4 Pharmaceuticals (XFOR) stake in 13G/A update

Rhea-AI Filing Summary

X4 Pharmaceuticals received an updated ownership report from Nantahala Capital Management and its principals. As of December 31, 2025, the reporting group may be deemed to beneficially own 2,449,468 shares of common stock, representing 2.80% of the outstanding shares.

The filing shows that Nantahala, Wilmot B. Harkey, and Daniel Mack share voting and dispositive power over these shares through funds and separately managed accounts. They certify the holdings are kept in the ordinary course of business and are not intended to change or influence control of X4 Pharmaceuticals.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 1)

X4 PHARMACEUTICALS, INC

(Name of Issuer)

Common Stock, par value $0.001 per share

(Title of Class of Securities)

98420X202

(CUSIP Number)

12/31/2025

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

SCHEDULE 13G

CUSIP No. 98420X202

1

Names of Reporting Persons

Nantahala Capital Management, LLC

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

MASSACHUSETTS

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 2,449,468.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 2,449,468.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

2,449,468.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

2.80 %

12

Type of Reporting Person (See Instructions)

IA

SCHEDULE 13G

CUSIP No. 98420X202

1

Names of Reporting Persons

Wilmot B. Harkey

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 2,449,468.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 2,449,468.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

2,449,468.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

2.80 %

12

Type of Reporting Person (See Instructions)

HC

SCHEDULE 13G

CUSIP No. 98420X202

1

Names of Reporting Persons

Daniel Mack

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 2,449,468.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 2,449,468.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

2,449,468.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

2.80 %

12

Type of Reporting Person (See Instructions)

HC

SCHEDULE 13G

Item 1.
(a)	Name of issuer: X4 PHARMACEUTICALS, INC
(b)	Address of issuer's principal executive offices: 61 NORTH BEACON STREET 4TH FLOOR BOSTON, MASSACHUSETTS, 02134
Item 2.
(a)	Name of person filing: (1) Nantahala Capital Management, LLC ("Nantahala") (2) Wilmot B. Harkey (3) Daniel Mack (together the "Reporting Persons")
(b)	Address or principal business office or, if none, residence: 130 Main St. 2nd Floor, New Canaan, Connecticut 06840
(c)	Citizenship: (1) Nantahala is a Massachusetts limited liability company. (2) Each of Messrs. Harkey and Mack is a citizen of the United States of America.
(d)	Title of class of securities: Common Stock, par value $0.001 per share
(e)	CUSIP No.: 98420X202
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: As of December 31, 2025, Nantahala may be deemed to be the beneficial owner of 2,449,468 Shares held by funds and separately managed accounts under its control, and as the managing members of Nantahala, each of Messrs. Harkey and Mack may be deemed to be a beneficial owner of those Shares.
(b)	Percent of class: As of December 31, 2025, each of the Reporting Persons may be deemed to be the beneficial owner of the following percentage of the total number of Shares outstanding: (1) Nantahala Capital Management, LLC ("Nantahala") : 2.80% (2) Wilmot B. Harkey: 2.80% (3) Daniel Mack: 2.80%
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: (1) Nantahala Capital Management, LLC ("Nantahala") : 0 Shares. (2) Wilmot B. Harkey: 0 Shares. (3) Daniel Mack: 0 Shares.
	(ii) Shared power to vote or to direct the vote: (1) Nantahala Capital Management, LLC ("Nantahala") : 2,449,468 Shares. (2) Wilmot B. Harkey: 2,449,468 Shares. (3) Daniel Mack: 2,449,468 Shares.
	(iii) Sole power to dispose or to direct the disposition of: (1) Nantahala Capital Management, LLC ("Nantahala") : 0 Shares. (2) Wilmot B. Harkey: 0 Shares. (3) Daniel Mack: 0 Shares.
	(iv) Shared power to dispose or to direct the disposition of: (1) Nantahala Capital Management, LLC ("Nantahala") : 2,449,468 Shares. (2) Wilmot B. Harkey: 2,449,468 Shares. (3) Daniel Mack: 2,449,468 Shares.
Item 5.	Ownership of 5 Percent or Less of a Class.
	Ownership of 5 percent or less of a class
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	Not Applicable
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	If a parent holding company has filed this schedule, pursuant to Rule 13d-1(b)(ii)(G), so indicate under Item 3(g) and attach an exhibit stating the identity and the Item 3 classification of the relevant subsidiary. If a parent holding company has filed this schedule pursuant to Rule 13d-1(c) or Rule 13d-1(d), attach an exhibit stating the identification of the relevant subsidiary. Each of Messrs. Harkey and Mack is filing this Schedule 13G as a control person in respect of shares beneficially owned by Nantahala, an investment adviser as described in ss. 240.13d-1(b)(1)(ii)(E). See Item 4(a).
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11.

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.

Nantahala Capital Management, LLC

Signature:	/s/ Taki Vasilakis
Name/Title:	Taki Vasilakis / Chief Compliance Officer
Date:	02/13/2026

Wilmot B. Harkey

Signature:	/s/ Wilmot B. Harkey
Name/Title:	Wilmot B. Harkey
Date:	02/13/2026

Daniel Mack

Signature:	/s/ Daniel Mack
Name/Title:	Daniel Mack
Date:	02/13/2026

FAQ

What percentage of X4 Pharmaceuticals (XFOR) does Nantahala Capital report owning?

Nantahala Capital and its principals report beneficial ownership of 2.80% of X4 Pharmaceuticals’ common stock. This stake equals 2,449,468 shares as of December 31, 2025, according to their amended Schedule 13G/A filing.

How many X4 Pharmaceuticals (XFOR) shares are beneficially owned by Nantahala Capital?

The reporting group may be deemed to beneficially own 2,449,468 shares of X4 Pharmaceuticals common stock. These shares are held through funds and separately managed accounts controlled by Nantahala Capital as of December 31, 2025.

Who are the reporting persons in the X4 Pharmaceuticals (XFOR) Schedule 13G/A?

The filing lists three reporting persons: Nantahala Capital Management, LLC, Wilmot B. Harkey, and Daniel Mack. Harkey and Mack are managing members of Nantahala and may be deemed beneficial owners of the same 2,449,468 X4 Pharmaceuticals shares.

Do Nantahala and its principals seek control of X4 Pharmaceuticals (XFOR)?

They state the shares were acquired and are held in the ordinary course of business and not for the purpose of changing or influencing control of X4 Pharmaceuticals. The certification explicitly disclaims any control-seeking intent, except in limited proxy nomination circumstances.

What voting power does Nantahala Capital have over X4 Pharmaceuticals (XFOR) shares?

The reporting group reports zero sole voting power and shared voting power over 2,449,468 shares. They also report shared dispositive power over the same number of shares, reflecting control through funds and separately managed accounts under Nantahala’s management.

Why is this X4 Pharmaceuticals (XFOR) filing labeled Schedule 13G/A Amendment No. 1?

It is an amendment to a prior Schedule 13G, updating the ownership information for Nantahala and its principals. As of December 31, 2025, they report holding 2.80% of X4 Pharmaceuticals’ common stock, which is now below the 5% threshold.