Saturn V Capital Management LP and Xiaoying Tian report beneficial ownership of 6,433,481 shares of X4 Pharmaceuticals, Inc. common stock, representing 7.36% of the class. The percentage is based on 87,436,688 shares outstanding as of October 31, 2025.
The shares are held across pooled investment vehicles and managed accounts (the “Clients”) for which Saturn V serves as investment manager. Saturn V and Ms. Tian have shared voting and dispositive power over all 6,433,481 shares, with no sole voting or dispositive power.
No individual Client holds or beneficially owns five percent or more of X4’s outstanding shares, and both Saturn V and Ms. Tian expressly disclaim beneficial ownership of the shares held by the Clients. The filing certifies that the securities were acquired and are held in the ordinary course of business and not for the purpose of changing or influencing control of X4 Pharmaceuticals.
Positive
None.
Negative
None.
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
(Title of Class of Securities)
98420X202
(CUSIP Number)
10/24/2025
(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
Saturn V Capital Management LP
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
6,433,481.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
6,433,481.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
6,433,481.00
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)
7.36 %
12
Type of Reporting Person (See Instructions)
IA
Comment for Type of Reporting Person: * Saturn V Capital Management LP acts as the investment manager of certain pooled investment vehicles and managed accounts (collectively the "Clients") in which such shares referred to above are held. As a result, Saturn V Capital Management LP possesses the power to vote and dispose or direct the disposition of all the shares beneficially owned by the Clients. No Client holds or beneficially owns five percent or more of the outstanding shares of the Issuer. Saturn V Capital Management LP disclaims beneficial ownership of any of the shares held by the Clients.
+ Based on 87,436,688 shares outstanding of the Issuer as of October 31, 2025, as set forth in the Issuer's Form 10-Q, filed November 5, 2025.
SCHEDULE 13G
CUSIP No.
98420X202
1
Names of Reporting Persons
Xiaoying Tian
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
6,433,481.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
6,433,481.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
6,433,481.00
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)
7.36 %
12
Type of Reporting Person (See Instructions)
IN
Comment for Type of Reporting Person: * Ms. Tian is the Managing Member of SVCM GP LLC, the general partner of Saturn V Capital Management LP, the Investment Manager of the Clients. As a result, Ms. Tian possesses the power to vote and dispose or direct the disposition of all the shares beneficially owned by the Clients. Ms. Tian disclaims beneficial ownership of any of the shares held by the Clients.
+ Based on 87,436,688 shares outstanding of the Issuer as of October 31, 2025, as set forth in the Issuer's Form 10-Q, filed November 5, 2025.
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:
Saturn V Capital Management LP, Xiaoying Tian
(b)
Address or principal business office or, if none, residence:
919 Congress Avenue, Suite 830, Austin, TX 78701
(c)
Citizenship:
Saturn V Capital Management LP is a Delaware Limited Partnership. Xiaoying Tian is a citizen of the United States.
(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:
Aggregate of all Reporting Persons: 6,433,481
Saturn V Capital Management LP - 6,433,481*
Xiaoying Tian - 6,433,481**
* Saturn acts as the investment manager for the Clients who hold the Shares described herein and referred to above. As a result, Saturn possesses the power to vote and dispose or direct the disposition of all the Shares beneficially owned by the Clients. No Client holds or beneficially owns five percent or more of the outstanding Shares of the Issuer. Saturn disclaims beneficial ownership of any of the Shares held by the Clients.
** Ms. Tian is the Managing Member of SVCM GP LLC, the general partner of Saturn, the Investment Manager of the Clients. As a result, Ms. Tian possesses the power to vote and dispose or direct the disposition of all the Shares beneficially owned by the Clients. Ms. Tian disclaims beneficial ownership of any of the Shares held by the Clients.
(b)
Percent of class:
Aggregate of all Reporting Persons: 7.36%+
Saturn V Capital Management LP - 7.36%+*
Xiaoying Tian - 7.36%+**
* Saturn acts as the investment manager for the Clients who hold the Shares described herein and referred to above. As a result, Saturn possesses the power to vote and dispose or direct the disposition of all the Shares beneficially owned by the Clients. No Client holds or beneficially owns five percent or more of the outstanding Shares of the Issuer. Saturn disclaims beneficial ownership of any of the Shares held by the Clients.
** Ms. Tian is the Managing Member of SVCM GP LLC, the general partner of Saturn, the Investment Manager of the Clients. As a result, Ms. Tian possesses the power to vote and dispose or direct the disposition of all the Shares beneficially owned by the Clients. Ms. Tian disclaims beneficial ownership of any of the Shares held by the Clients.
+ Based on 87,436,688 shares outstanding of the Issuer as of October 31, 2025, as set forth in the Issuer's Form 10-Q, filed November 5, 2025.
(c)
Number of shares as to which the person has:
(i) Sole power to vote or to direct the vote:
Saturn V Capital Management LP - 0
Xiaoying Tian - 0
(ii) Shared power to vote or to direct the vote:
Saturn V Capital Management LP - 6,433,481*
Xiaoying Tian - 6,433,481**
* Saturn acts as the investment manager for the Clients who hold the Shares described herein and referred to above. As a result, Saturn possesses the power to vote and dispose or direct the disposition of all the Shares beneficially owned by the Clients. No Client holds or beneficially owns five percent or more of the outstanding Shares of the Issuer. Saturn disclaims beneficial ownership of any of the Shares held by the Clients.
** Ms. Tian is the Managing Member of SVCM GP LLC, the general partner of Saturn, the Investment Manager of the Clients. As a result, Ms. Tian possesses the power to vote and dispose or direct the disposition of all the Shares beneficially owned by the Clients. Ms. Tian disclaims beneficial ownership of any of the Shares held by the Clients.
(iii) Sole power to dispose or to direct the disposition of:
Saturn V Capital Management LP - 0
Xiaoying Tian - 0
(iv) Shared power to dispose or to direct the disposition of:
Saturn V Capital Management LP - 6,433,481*
Xiaoying Tian - 6,433,481**
* Saturn acts as the investment manager for the Clients who hold the Shares described herein and referred to above. As a result, Saturn possesses the power to vote and dispose or direct the disposition of all the Shares beneficially owned by the Clients. No Client holds or beneficially owns five percent or more of the outstanding Shares of the Issuer. Saturn disclaims beneficial ownership of any of the Shares held by the Clients.
** Ms. Tian is the Managing Member of SVCM GP LLC, the general partner of Saturn, the Investment Manager of the Clients. As a result, Ms. Tian possesses the power to vote and dispose or direct the disposition of all the Shares beneficially owned by the Clients. Ms. Tian disclaims beneficial ownership of any of the Shares held by the Clients.
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 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.
Saturn V Capital Management LP
Signature:
Xiaoying Tian
Name/Title:
Xiaoying Tian, Managing Member of SVCM GP LLC, the General Partner of Saturn V Capital Management LP
What ownership stake in X4 Pharmaceuticals (XFOR) does Saturn V report?
The filing reports that Saturn V Capital Management LP and Xiaoying Tian beneficially own 6,433,481 X4 Pharmaceuticals common shares, representing 7.36% of the class, based on 87,436,688 shares outstanding as of October 31, 2025, per X4’s Form 10-Q.
Who holds the X4 Pharmaceuticals (XFOR) shares reported in this Schedule 13G?
The shares are held by pooled investment vehicles and managed accounts advised by Saturn V Capital Management LP (the “Clients”). Saturn V acts as investment manager and can vote and dispose of these shares, while each individual Client owns less than five percent of X4’s outstanding stock.
What role does Xiaoying Tian play in the X4 Pharmaceuticals (XFOR) holdings?
Xiaoying Tian is the Managing Member of GP LLC, the general partner of Saturn V Capital Management LP. Through this role, she shares power to vote and dispose of 6,433,481 X4 shares held by the Clients, while disclaiming personal beneficial ownership of those shares.
Does Saturn V intend to influence control of X4 Pharmaceuticals (XFOR)?
The certification states the X4 Pharmaceuticals securities were acquired and are held in the ordinary course of business and not for the purpose of changing or influencing control of the issuer, nor in connection with any transaction designed to have that effect, other than limited proxy nomination activities.
How is the 7.36% ownership in X4 Pharmaceuticals (XFOR) calculated?
The reported 7.36% ownership is calculated using a denominator of 87,436,688 X4 Pharmaceuticals common shares outstanding. That share count is taken from X4’s Form 10-Q, which states this outstanding amount as of October 31, 2025 for the company’s common stock.
Do Saturn V or its Clients hold more than 5% individually of X4 Pharmaceuticals (XFOR)?
The filing states that no individual Client advised by Saturn V Capital Management LP holds or beneficially owns five percent or more of X4 Pharmaceuticals’ outstanding common shares. The reported 7.36% position reflects the aggregate holdings across all such Clients combined.
