Perceptive Advisors (XFOR) reports 8.1% beneficial stake in X4 Pharmaceuticals

Rhea-AI Filing Summary

Perceptive Advisors LLC, Joseph Edelman, and Perceptive Life Sciences Master Fund, Ltd. report beneficial ownership of X4 Pharmaceuticals, Inc. Common Stock on an amended Schedule 13G. The Master Fund directly holds 7,933,491 shares of Common Stock and 151,515 Warrants that are immediately exercisable, for an aggregate of 8,085,006 shares deemed beneficially owned.

Based on 99,146,743 shares of Common Stock outstanding as of July 31, 2026, each Reporting Person’s beneficial ownership is 8.1%. All 8,085,006 shares are reported with shared voting and shared dispositive power, with no sole voting or dispositive power. The Warrants are subject to a 9.99% Beneficial Ownership Limitation.

Key Figures

Shares outstanding: 99,146,743 shares Beneficially owned shares: 8,085,006 shares Direct Common Stock holdings: 7,933,491 shares +4 more

7 metrics

Shares outstanding 99,146,743 shares Common Stock outstanding as of July 31, 2026, per Form 10-Q

Beneficially owned shares 8,085,006 shares Shares of Common Stock beneficially owned by each Reporting Person

Direct Common Stock holdings 7,933,491 shares Shares of Common Stock directly held by the Master Fund

Warrants exercisable 151,515 Warrants Warrants immediately exercisable for shares of Common Stock, subject to limitation

Ownership percentage 8.1% Percent of X4 Pharmaceuticals Common Stock held by each Reporting Person

Beneficial Ownership Limitation 9.99% Maximum percentage of Common Stock that may be beneficially owned after Warrant exercise

Shared voting power 8,085,006 shares Shares over which each Reporting Person has shared voting power

Key Terms

Beneficial Ownership Limitation, Warrants, beneficially own, shared dispositive power, +1 more

5 terms

Beneficial Ownership Limitation regulatory

"The terms of the Warrants provide that the Warrants may not be exercised if, after such exercise, the Reporting Persons would beneficially own, as determined in accordance with Section 13(d) of the Securities Exchange Act of 1934, as amended, more than 9.99% of the shares of Common Stock then issued and outstanding (the "Beneficial Ownership Limitation")."

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.

Warrants financial

"The Master Fund directly holds 7,933,491 shares of Common Stock and 151,515 Warrants immediately exercisable for shares of Common Stock, subject to the Beneficial Ownership Limitation (as defined below)."

Warrants are special documents that give you the right to buy a company's stock at a set price before a certain date. They are often used as a way for companies to attract investors or raise money, and their value can increase if the company's stock price goes up.

beneficially own regulatory

"The terms of the Warrants provide that the Warrants may not be exercised if, after such exercise, the Reporting Persons would beneficially own, as determined in accordance with Section 13(d) of the Securities Exchange Act of 1934, as amended, more than 9.99% of the shares of Common Stock then issued and outstanding"

Beneficially own means having the economic rights and risks of a security—such as the right to receive dividends, sell the shares, or profit from price changes—whether or not your name appears on the official share register. Think of it like renting a car: you use it and reap the benefits even if the title lists someone else. Investors care because beneficial ownership determines who truly controls value, must be disclosed under securities rules, and can signal potential influence or trading activity that affects a stock’s price.

shared dispositive power financial

"Shared Dispositive Power 8,085,006.00"

Schedule 13G regulatory

"The names of the persons filing this report (collectively, the "Reporting Persons") with respect to shares of Common Stock"

A Schedule 13G is a formal document that investors file with the government when they acquire a large ownership stake in a company, usually for investment purposes rather than control. It helps keep the public informed about who owns significant parts of a company's shares, which can influence how the company is managed and how investors make decisions. Filing this schedule is important for transparency and understanding the ownership landscape of publicly traded companies.

FAQ

What percentage of XFOR does Perceptive Advisors report owning in this Schedule 13G/A?

Perceptive Advisors, Joseph Edelman, and the Master Fund each report beneficial ownership of 8.1% of X4 Pharmaceuticals’ Common Stock, based on 99,146,743 shares outstanding as of July 31, 2026, as stated in the company’s Form 10-Q.

How many XFOR shares does Perceptive Life Sciences Master Fund directly hold?

Perceptive Life Sciences Master Fund directly holds 7,933,491 shares of X4 Pharmaceuticals Common Stock. It also holds 151,515 Warrants that are immediately exercisable for additional shares, subject to the stated Beneficial Ownership Limitation in the Warrants’ terms.

What is the total number of XFOR shares beneficially owned by the reporting group?

The Reporting Persons collectively report beneficial ownership of 8,085,006 shares of X4 Pharmaceuticals Common Stock. This figure includes 7,933,491 directly held shares plus 151,515 shares issuable upon exercise of Warrants, within the specified ownership cap.

What is the Beneficial Ownership Limitation described for XFOR Warrants in this filing?

The Warrants include a 9.99% Beneficial Ownership Limitation. They may not be exercised if, after exercise, the Reporting Persons would beneficially own more than 9.99% of X4 Pharmaceuticals’ outstanding Common Stock, as determined under Section 13(d) rules.

Do the XFOR reporting holders have sole or shared voting power over the shares?

Perceptive Advisors, Joseph Edelman, and the Master Fund each report 0 shares with sole voting or dispositive power and 8,085,006 shares with shared voting and shared dispositive power over X4 Pharmaceuticals Common Stock as of the reported date.

What XFOR share count was used to compute the 8.1% ownership figure?

The 8.1% ownership calculation is based on 99,146,743 X4 Pharmaceuticals Common shares outstanding as of July 31, 2026, as reported in the company’s Form 10-Q filed on August 6, 2026, which the Reporting Persons reference for their percentage.

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Available on EDGAR 08/14/2026 - 05:22 PM Accepted by SEC EDGAR 08/14/2026 - 05:21 PM Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 2)

X4 PHARMACEUTICALS, INC.

(Name of Issuer)

Common Stock, par value $0.001 per share

(Title of Class of Securities)

98420X202

(CUSIP Number)

06/30/2026

(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)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): 98420X202

1

Names of Reporting Persons

Perceptive Advisors 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 0.00
6	Shared Voting Power 8,085,006.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 8,085,006.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

8,085,006.00

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)

8.1 %

12

Type of Reporting Person (See Instructions)

IA

SCHEDULE 13G

CUSIP Number(s): 98420X202

1

Names of Reporting Persons

Joseph Edelman

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 8,085,006.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 8,085,006.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

8,085,006.00

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)

8.1 %

12

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13G

CUSIP Number(s): 98420X202

1

Names of Reporting Persons

Perceptive Life Sciences Master Fund, Ltd.

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

CAYMAN ISLANDS

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 8,085,006.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 8,085,006.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

8,085,006.00

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)

8.1 %

12

Type of Reporting Person (See Instructions)

CO

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
Item 2.
(a)	Name of person filing: The names of the persons filing this report (collectively, the "Reporting Persons") with respect to shares of Common Stock, par value $0.001 per share (the "Common Stock") of X4 PHARMACEUTICALS, INC. (the "Issuer") are: Perceptive Advisors LLC ("Perceptive Advisors") Joseph Edelman ("Mr. Edelman") Perceptive Life Sciences Master Fund, Ltd. (the "Master Fund")
(b)	Address or principal business office or, if none, residence: The address of the principal business office of each of the Reporting Persons is: 51 Astor Place, 10th Floor New York, NY 10003
(c)	Citizenship: Perceptive Advisors is a Delaware limited liability company Mr. Edelman is a United States citizen The Master Fund is a Cayman Islands corporation
(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: The information required by this item with respect to each Reporting Person is set forth in Rows 5 through 9 and 11 of the cover pages to this Schedule 13G. The ownership percentages reported are based on 99,146,743 shares of Common Stock outstanding as of July 31, 2026, as reported in the Issuer's Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission on August 6, 2026. Neither Perceptive Advisors nor Mr. Edelman directly holds any shares of Common Stock or any Warrants. The Master Fund directly holds 7,933,491 shares of Common Stock and 151,515 Warrants immediately exercisable for shares of Common Stock, subject to the Beneficial Ownership Limitation (as defined below). The terms of the Warrants provide that the Warrants may not be exercised if, after such exercise, the Reporting Persons would beneficially own, as determined in accordance with Section 13(d) of the Securities Exchange Act of 1934, as amended, more than 9.99% of the shares of Common Stock then issued and outstanding (the "Beneficial Ownership Limitation"). As of the date hereof, the Beneficial Ownership Limitation permits the Reporting Persons to exercise Warrants for an aggregate of 151,515 shares of Common Stock. Perceptive Advisors serves as the investment manager of the Master Fund. Mr. Edelman is the managing member of Perceptive Advisors.
(b)	Percent of class: Perceptive Advisors: 8.1% Mr. Edelman: 8.1% Master Fund: 8.1%
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: Perceptive Advisors: 0 Mr. Edelman: 0 Master Fund: 0
	(ii) Shared power to vote or to direct the vote: Perceptive Advisors: 8,085,006 Mr. Edelman: 8,085,006 Master Fund: 8,085,006
	(iii) Sole power to dispose or to direct the disposition of: Perceptive Advisors: 0 Mr. Edelman: 0 Master Fund: 0
	(iv) Shared power to dispose or to direct the disposition of: Perceptive Advisors: 8,085,006 Mr. Edelman: 8,085,006 Master Fund: 8,085,006
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.
	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.
	Not Applicable
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 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.

Perceptive Advisors LLC

Signature:	/s/ Joseph Edelman
Name/Title:	Joseph Edelman, Managing Member
Date:	08/14/2026

Joseph Edelman

Signature:	/s/ Joseph Edelman
Name/Title:	Joseph Edelman
Date:	08/14/2026

Perceptive Life Sciences Master Fund, Ltd.

Signature:	/s/ Joseph Edelman
Name/Title:	Joseph Edelman, Managing Member
Date:	08/14/2026