FMR LLC discloses 9.7% X4 Pharmaceuticals (XFOR) stake on Schedule 13G/A

Rhea-AI Filing Summary

FMR LLC and Abigail P. Johnson report a significant passive ownership stake in X4 Pharmaceuticals, Inc. common stock on an amended Schedule 13G. They beneficially own 8,499,100 shares, representing 9.7% of the outstanding common stock, with sole dispositive power over all reported shares.

The filing states 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, or in connection with any control-related transaction.

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

(Title of Class of Securities)

98420X202

(CUSIP Number)

10/31/2025

(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

FMR 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

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 8,499,100.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 8,499,100.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

8,499,100.00

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)

9.7 %

12

Type of Reporting Person (See Instructions)

HC

SCHEDULE 13G

CUSIP No. 98420X202

1

Names of Reporting Persons

Abigail P. Johnson

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 0.00
7	Sole Dispositive Power 8,499,100.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

8,499,100.00

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)

9.7 %

12

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13G

Item 1.
(a)	Name of issuer: X4 Pharmaceuticals, Inc
(b)	Address of issuer's principal executive offices: 61 NORTH BEACON STREET, BOSTON, MASSACHUSETTS, 02134
Item 2.
(a)	Name of person filing: FMR LLC
(b)	Address or principal business office or, if none, residence: 245 Summer Street, Boston, Massachusetts 02210
(c)	Citizenship: Not applicable
(d)	Title of class of securities: COMMON STOCK
(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: 8,499,100.00
(b)	Percent of class: 9.7%
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: Please see the responses to Items 5 and 6 on the cover page.
	(ii) Shared power to vote or to direct the vote: 0.00
	(iii) Sole power to dispose or to direct the disposition of: 8,499,100.00
	(iv) Shared power to dispose or to direct the disposition of: 0.00
Item 5.	Ownership of 5 Percent or Less of a Class.
	Not Applicable
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required. One or more other persons are known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, the COMMON STOCK of X4 PHARMACEUTICALS INC. No one other person's interest in the COMMON STOCK of X4 PHARMACEUTICALS INC is more than five percent of the total outstanding COMMON STOCK.
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. See attached Exhibit 99.
Item 8.	Identification and Classification of Members of the Group.
	If a group has filed this schedule pursuant to §240.13d-1(b)(1)(ii)(J), so indicate under Item 3(j) and attach an exhibit stating the identity and Item 3 classification of each member of the group. If a group has filed this schedule pursuant to §240.13d-1(c) or §240.13d-1(d), attach an exhibit stating the identity of each member of the group. Not applicable.
Item 9.	Notice of Dissolution of Group.
	Notice of dissolution of a group may be furnished as an exhibit stating the date of the dissolution and that all further filings with respect to transactions in the security reported on will be filed, if required, by members of the group, in their individual capacity. See Item 5. 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.

FMR LLC

Signature:	Stephanie J. Brown
Name/Title:	Duly authorized under Power of Attorney effective as of January 3, 2023, by and on behalf of FMR LLC and its direct and indirect subsidiaries*
Date:	02/04/2026

Abigail P. Johnson

Signature:	Stephanie J. Brown
Name/Title:	Duly authorized under Power of Attorney effective as of January 26, 2023, by and on behalf of Abigail P. Johnson**
Date:	02/04/2026

Comments accompanying signature: * This power of attorney is incorporated herein by reference to Exhibit 24 to the Schedule 13G filed by FMR LLC on January 10, 2023, accession number: 0000315066-23-000003. ** This power of attorney is incorporated herein by reference to Exhibit 24 to the Schedule 13G filed by FMR LLC on January 31, 2023, accession number: 0000315066-23-000038.

Exhibit Information

Please see Exhibit 99 for 13d-1(k) (1) agreement.

FAQ

What ownership stake in X4 Pharmaceuticals (XFOR) does FMR LLC report?

FMR LLC reports beneficial ownership of 8,499,100 X4 Pharmaceuticals common shares, representing 9.7% of the class. The firm has sole dispositive power over these shares, indicating it controls decisions to sell or hold them on behalf of its clients.

Is FMR LLC’s stake in X4 Pharmaceuticals (XFOR) considered a passive investment?

Yes. The filing certifies the securities were acquired and are held in the ordinary course of business, not to change or influence control of X4 Pharmaceuticals. It also states the holdings are not part of any control-related transaction, supporting a passive investment intent.

What role does Abigail P. Johnson have in the X4 Pharmaceuticals (XFOR) holdings?

Abigail P. Johnson is listed as a reporting person with beneficial ownership of 8,499,100 X4 shares, or 9.7% of the class. She has sole dispositive power over these shares, while voting power figures are reported as zero in the cover-page details.

Do other parties share in the economic interest of X4 Pharmaceuticals (XFOR) shares held by FMR LLC?

Yes. The filing notes one or more other persons may receive dividends or sale proceeds from the X4 common stock. However, no single such person has an interest exceeding 5% of X4’s total outstanding common stock, so individual beneficiaries are not named.

What is the significance of the 10/31/2025 date in the X4 Pharmaceuticals (XFOR) Schedule 13G/A?

The date 10/31/2025 is identified as the event date requiring the Schedule 13G amendment. It marks when ownership levels or relevant conditions changed enough to trigger this updated disclosure about FMR LLC’s and Abigail P. Johnson’s X4 Pharmaceuticals holdings.

How is voting power over X4 Pharmaceuticals (XFOR) shares described in the filing?

FMR LLC reports 8,499,100 shares with sole voting power and zero shared voting power in the cover information. For Abigail P. Johnson, the cover data show zero sole and zero shared voting power, while she has sole dispositive power over the same share amount.