X4 Pharmaceuticals, Inc. (XFOR) is the subject of a Schedule 13G reporting that a group of Venrock-affiliated funds and individuals collectively beneficially own 5,555,047 shares of its common stock. This represents 5.6% of X4’s common shares, based on 99,146,743 shares outstanding as of July 31, 2026.
The reported holdings consist of 2,553,145 shares held by Venrock Healthcare Capital Partners III, L.P., 255,515 shares held by VHCP Co-Investment Holdings III, LLC, and 2,746,387 shares held by Venrock Healthcare Capital Partners EG, L.P. The reporting entities and individuals share voting and dispositive power over these shares as a group.
Positive
None.
Negative
None.
Key Figures
Beneficial ownership shares:5,555,047 sharesOwnership percentage:5.6%Shares outstanding:99,146,743 shares+3 more
6 metrics
Beneficial ownership shares5,555,047 sharesTotal X4 Pharmaceuticals common shares beneficially owned by the reporting group
Ownership percentage5.6%Percentage of X4 common stock beneficially owned by the reporting persons
Shares outstanding99,146,743 sharesX4 common shares outstanding as of July 31, 2026, used as ownership baseline
VHCP III holdings2,553,145 sharesCommon stock of X4 held by Venrock Healthcare Capital Partners III, L.P.
VHCP Co-Investment III holdings255,515 sharesCommon stock of X4 held by VHCP Co-Investment Holdings III, LLC
VHCP EG holdings2,746,387 sharesCommon stock of X4 held by Venrock Healthcare Capital Partners EG, L.P.
"sets forth the aggregate number of shares of common stock of the Issuer beneficially owned"
Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.
shared voting powerfinancial
"Shared Voting Power 5,555,047.00"
Shared voting power occurs when two or more parties jointly have the right to vote or decide how a block of company shares is cast, like co-owners who must agree before moving a piece of furniture. Investors care because who controls voting rights affects board elections, major corporate decisions and takeover outcomes, and shared control can alter regulatory disclosures and the practical influence any holder has over a company’s direction and value.
shared dispositive powerfinancial
"Shared Dispositive Power 5,555,047.00"
Schedule 13Gregulatory
"The Reporting Persons are members of a group for the purposes of this"
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.
Power of Attorneyregulatory
"Exhibit 24.1 Power of Attorney for Bong Koh"
A power of attorney is a legal document that allows one person to make decisions and act on behalf of another person, often in financial or legal matters. It’s like giving someone a trusted helper or agent the authority to handle important tasks if you are unable to do so yourself. This matters to investors because it can impact how their assets are managed or transferred if they become unable to oversee their affairs.
FAQ
AI-generated questions and answers. How Rhea-AI works. Not financial advice.
What percentage of X4 Pharmaceuticals (XFOR) does the Venrock group report owning?
The reporting Venrock-affiliated investors collectively beneficially own 5.6% of X4 Pharmaceuticals’ common stock, based on 99,146,743 shares outstanding as of July 31, 2026, as referenced in the company’s Form 10-Q filed with the SEC.
How many XFOR shares do the Venrock entities beneficially own in total?
The group reports beneficial ownership of 5,555,047 shares of X4 Pharmaceuticals common stock. This total reflects shares held by three Venrock-related funds, over which the reporting persons have shared voting and dispositive power.
How is the 5,555,047-share XFOR stake allocated among the Venrock funds?
The filing states that 2,553,145 shares are held by Venrock Healthcare Capital Partners III, L.P., 255,515 shares by VHCP Co-Investment Holdings III, LLC, and 2,746,387 shares by Venrock Healthcare Capital Partners EG, L.P.
What is the share count baseline used to calculate Venrock’s 5.6% stake in XFOR?
The 5.6% ownership percentage is based on 99,146,743 shares of common stock outstanding as of July 31, 2026, as reported in X4 Pharmaceuticals’ Quarterly Report on Form 10-Q filed with the SEC on August 6, 2026.
Who are the individual reporting persons in the X4 Pharmaceuticals (XFOR) Schedule 13G?
The filing lists Nimish Shah and Bong Y. Koh as individual reporting persons. They are described as voting members of VHCP Management III, LLC and VHCP Management EG, LLC, which are the general partners or managers of the Venrock funds holding the XFOR shares.
Do the Venrock reporting persons have shared or sole voting power over the XFOR shares?
Each reporting person reports 0 shares with sole voting power and 5,555,047 shares with shared voting and shared dispositive power, reflecting their coordinated control over the reported X4 Pharmaceuticals shares.
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
SCHEDULE 13G
UNDER THE SECURITIES EXCHANGE ACT OF 1934
X4 Pharmaceuticals, Inc.
(Name of Issuer)
Common Stock, $0.001 par value per share
(Title of Class of Securities)
98420X202
(CUSIP Number)
09/14/2026
(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
Venrock Healthcare Capital Partners III, L.P.
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
5,555,047.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
5,555,047.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
5,555,047.00
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)
5.6 %
12
Type of Reporting Person (See Instructions)
PN
SCHEDULE 13G
CUSIP Number(s):
98420X202
1
Names of Reporting Persons
VHCP Co-Investment Holdings III, 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
5,555,047.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
5,555,047.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
5,555,047.00
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)
5.6 %
12
Type of Reporting Person (See Instructions)
OO
SCHEDULE 13G
CUSIP Number(s):
98420X202
1
Names of Reporting Persons
Venrock Healthcare Capital Partners EG, L.P.
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
5,555,047.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
5,555,047.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
5,555,047.00
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)
5.6 %
12
Type of Reporting Person (See Instructions)
PN
SCHEDULE 13G
CUSIP Number(s):
98420X202
1
Names of Reporting Persons
VHCP Management III, 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
5,555,047.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
5,555,047.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
5,555,047.00
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)
5.6 %
12
Type of Reporting Person (See Instructions)
OO
SCHEDULE 13G
CUSIP Number(s):
98420X202
1
Names of Reporting Persons
VHCP Management EG, 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
5,555,047.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
5,555,047.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
5,555,047.00
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)
5.6 %
12
Type of Reporting Person (See Instructions)
OO
SCHEDULE 13G
CUSIP Number(s):
98420X202
1
Names of Reporting Persons
Nimish Shah
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
5,555,047.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
5,555,047.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
5,555,047.00
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)
5.6 %
12
Type of Reporting Person (See Instructions)
IN
SCHEDULE 13G
CUSIP Number(s):
98420X202
1
Names of Reporting Persons
Bong Y. Koh
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
5,555,047.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
5,555,047.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
5,555,047.00
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)
5.6 %
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, 4th Floor, Boston, MA, 02134.
Item 2.
(a)
Name of person filing:
The names of the persons filing this report (collectively, the "Reporting Persons") are:
Venrock Healthcare Capital Partners III, L.P. ("VHCP III")
VHCP Co-Investment Holdings III, LLC ("VHCP Co-Investment III")
Venrock Healthcare Capital Partners EG, L.P. ("VHCP EG")
VHCP Management III, LLC ("VHCP Management III")
VHCP Management EG, LLC ("VHCP Management EG")
Nimish Shah ("Shah")
Bong Koh ("Koh")
The Reporting Persons are members of a group for the purposes of this Schedule 13G.
(b)
Address or principal business office or, if none, residence:
New York Office:
7 Bryant Park, 23rd Floor
New York, NY 10018
Palo Alto Office:
3340 Hillview Avenue
Palo Alto, CA 94304
(c)
Citizenship:
All of the entities were organized in Delaware. Shah and Koh are both United States citizens.
(d)
Title of class of securities:
Common Stock, $0.001 par value per share
(e)
CUSIP Number(s):
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:
Row 9 of each Reporting Person's cover page to this Schedule 13G sets forth the aggregate number of shares of common stock of the Issuer beneficially owned by such Reporting Person and is incorporated by reference.
The Reporting Persons' ownership of the Issuer's securities consists of (i) 2,553,145 shares of common stock held by VHCP III, (ii) 255,515 shares of common stock held by VHCP Co-Investment III, and (iii) 2,746,387 shares of common stock held by held by VHCP EG.
VHCP Management III is the general partner of VHCP III and the manager of VHCP Co-Investment III. VHCP Management EG is the general partner of VHCP EG. Messrs. Shah and Koh are the voting members of VHCP Management III and VHCP Management EG.
(b)
Percent of class:
Row 11 of each Reporting Person's cover page to this Schedule 13G sets forth the percentage of the shares of common stock of the Issuer beneficially owned by such Reporting Person and is incorporated by reference. The percentage set forth in each row 11 is based upon 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 (the "SEC") on August 6, 2026.
(c)
Number of shares as to which the person has:
(i) Sole power to vote or to direct the vote:
Row 5 of each Reporting Person's cover page to this Schedule 13G sets forth the sole power to vote or to direct the vote of securities of the Issuer beneficially owned by such Reporting Person and is incorporated by reference.
(ii) Shared power to vote or to direct the vote:
Row 6 of each Reporting Person's cover page to this Schedule 13G sets forth the shared power to vote or to direct the vote of securities of the Issuer beneficially owned by such Reporting Person and is incorporated by reference.
(iii) Sole power to dispose or to direct the disposition of:
Row 7 of each Reporting Person's cover page to this Schedule 13G sets forth the sole power to dispose or to direct the disposition of securities of the Issuer beneficially owned by such Reporting Person and is incorporated by reference.
(iv) Shared power to dispose or to direct the disposition of:
Row 8 of each Reporting Person's cover page to this Schedule 13G sets forth the shared power to dispose or to direct the disposition of securities of the Issuer beneficially owned by such Reporting Person and is incorporated by reference.
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.
Venrock Healthcare Capital Partners III, L.P.
Signature:
/s/ Sherman G. Souther
Name/Title:
By VHCP Management III, LLC, its General Partner, By Sherman G. Souther, Authorized Signatory
Date:
09/21/2026
VHCP Co-Investment Holdings III, LLC
Signature:
/s/ Sherman G. Souther
Name/Title:
By VHCP Management III, LLC, its Manager, By Sherman G. Souther, Authorized Signatory
Date:
09/21/2026
Venrock Healthcare Capital Partners EG, L.P.
Signature:
/s/ Sherman G. Souther
Name/Title:
By VHCP Management EG, LLC, its General Partner, By Sherman G. Souther, Authorized Signatory
Date:
09/21/2026
VHCP Management III, LLC
Signature:
/s/ Sherman G. Souther
Name/Title:
By Sherman G. Souther, Authorized Signatory
Date:
09/21/2026
VHCP Management EG, LLC
Signature:
/s/ Sherman G. Souther
Name/Title:
By Sherman G. Souther, Authorized Signatory
Date:
09/21/2026
Nimish Shah
Signature:
/s/ Sherman G. Souther
Name/Title:
By Sherman G. Souther, Attorney-in-fact
Date:
09/21/2026
Bong Y. Koh
Signature:
/s/ Sherman G. Souther
Name/Title:
By Sherman G. Souther, Attorney-in-fact
Date:
09/21/2026
Exhibit Information
Exhibit 24.1 Power of Attorney for Bong Koh
Exhibit 24.2 Power of Attorney for Nimish Shah
Exhibit 99.1 Joint Filing Agreement
