Arcellx, Inc. (ACLX) has a significant shareholder group led by Paradigm BioCapital reporting passive ownership of its common stock. The reporting persons, including Paradigm BioCapital Advisors LP, its general partner, Senai Asefaw, M.D., and Paradigm BioCapital International Fund Ltd., collectively report beneficial ownership of 5,724,016 shares of common stock, representing 9.9% of the class, as of the close of business on December 31, 2025. This percentage is based on 57,822,871 shares outstanding as of October 31, 2025 as disclosed by Arcellx. The group certifies that the shares were not acquired and are not held for the purpose of changing or influencing control of Arcellx, indicating a passive investment stance rather than an activist position.
Positive
None.
Negative
None.
FAQ
How much of Arcellx (ACLX) stock does Paradigm BioCapital beneficially own?
Paradigm BioCapital and related reporting persons beneficially own 5,724,016 shares of Arcellx common stock. This stake represents 9.9% of the outstanding class, based on 57,822,871 shares reported outstanding by Arcellx as of October 31, 2025.
Who are the reporting persons in this Arcellx (ACLX) Schedule 13G/A filing?
The filing lists Paradigm BioCapital Advisors LP, Paradigm BioCapital Advisors GP LLC, Senai Asefaw, M.D., and Paradigm BioCapital International Fund Ltd. as reporting persons. The Fund and certain managed accounts directly hold the Arcellx common stock reported.
What percentage of Arcellx (ACLX) does Paradigm BioCapital International Fund Ltd. hold?
Paradigm BioCapital International Fund Ltd. beneficially owns 5,055,581 shares of Arcellx common stock. This position represents 8.7% of the class, calculated using 57,822,871 Arcellx shares outstanding as of October 31, 2025, as disclosed by the company.
Is Paradigm BioCapital an activist investor in Arcellx (ACLX) according to this filing?
The filing states the securities were not acquired and are not held to change or influence control of Arcellx. This certification indicates a passive investment intent rather than an activist or control-seeking position in the company.
What date does the Arcellx (ACLX) Schedule 13G/A ownership information reflect?
The beneficial ownership information is given as of the close of business on December 31, 2025, identified as the “Date of Event” requiring the filing. The ownership percentages use Arcellx’s outstanding share count as of October 31, 2025.
How is the 9.9% Arcellx (ACLX) ownership stake calculated in this Schedule 13G/A?
The 9.9% figure comes from 5,724,016 shares beneficially owned divided by 57,822,871 Arcellx shares outstanding. The outstanding share count is taken from Arcellx’s Form 10-Q filed November 5, 2025, which reported that number as of October 31, 2025.
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
SCHEDULE 13G
UNDER THE SECURITIES EXCHANGE ACT OF 1934
(Amendment No. 3)
Arcellx, Inc.
(Name of Issuer)
Common Stock, $0.001 par value per share
(Title of Class of Securities)
03940C100
(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.
03940C100
1
Names of Reporting Persons
Paradigm BioCapital Advisors 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
5,724,016.00
6
Shared Voting Power
0.00
7
Sole Dispositive Power
5,724,016.00
8
Shared Dispositive Power
0.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
5,724,016.00
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)
9.9 %
12
Type of Reporting Person (See Instructions)
PN
SCHEDULE 13G
CUSIP No.
03940C100
1
Names of Reporting Persons
Paradigm BioCapital Advisors GP 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
5,724,016.00
6
Shared Voting Power
0.00
7
Sole Dispositive Power
5,724,016.00
8
Shared Dispositive Power
0.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
5,724,016.00
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)
9.9 %
12
Type of Reporting Person (See Instructions)
OO
Comment for Type of Reporting Person: limited liability company
SCHEDULE 13G
CUSIP No.
03940C100
1
Names of Reporting Persons
Senai Asefaw, M.D.
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
5,724,016.00
6
Shared Voting Power
0.00
7
Sole Dispositive Power
5,724,016.00
8
Shared Dispositive Power
0.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
5,724,016.00
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)
9.9 %
12
Type of Reporting Person (See Instructions)
IN
SCHEDULE 13G
CUSIP No.
03940C100
1
Names of Reporting Persons
Paradigm BioCapital International 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
5,055,581.00
6
Shared Voting Power
0.00
7
Sole Dispositive Power
5,055,581.00
8
Shared Dispositive Power
0.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
5,055,581.00
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)
8.7 %
12
Type of Reporting Person (See Instructions)
CO
SCHEDULE 13G
Item 1.
(a)
Name of issuer:
Arcellx, Inc.
(b)
Address of issuer's principal executive offices:
800 Bridge Parkway, Redwood City, CA 94065
Item 2.
(a)
Name of person filing:
This Schedule 13G is filed by the following (the "Reporting Persons"): (1) Paradigm BioCapital Advisors LP (the "Adviser"); (2) Paradigm BioCapital Advisors GP LLC (the "Adviser GP"); (3) Senai Asefaw, M.D. ("Senai Asefaw"); and (4) Paradigm BioCapital International Fund Ltd. (the "Fund"). The Fund is a private investment vehicle. The Fund and one or more separately managed accounts managed by the Adviser (the "Account") directly beneficially own the Common Stock reported in this statement. The Adviser is the investment manager of the Fund and the Account. The Adviser GP is the general partner of the Adviser. Senai Asefaw is the managing member of the Adviser GP. The Adviser, the Adviser GP and Senai Asefaw may be deemed to beneficially own the Common Stock directly beneficially owned by the Fund and the Account. Each Reporting Person disclaims beneficial ownership with respect to any Common Stock other than the Common Stock directly beneficially owned by such Reporting Person.
(b)
Address or principal business office or, if none, residence:
The principal business office of the Fund is c/o Walkers, 190 Elgin Avenue, George Town, Grand Cayman KY1-9001, Cayman Islands. The principal business office of the Adviser, the Adviser GP and Senai Asefaw is 767 Third Avenue, 17th Floor, New York, NY 10017.
(c)
Citizenship:
For citizenship or place of organization see Item 4 of the cover page of each Reporting Person.
(d)
Title of class of securities:
Common Stock, $0.001 par value per share
(e)
CUSIP No.:
03940C100
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:
See Item 9 on the cover page for each Reporting Person, and Item 2, which information is given as of the close of business on December 31, 2025, the Date of Event which requires the filing of this Schedule 13G.
(b)
Percent of class:
See Item 11 on the cover page for each Reporting Person. The percentages of beneficial ownership contained herein are based on 57,822,871 shares of Common Stock outstanding as of October 31, 2025 as reported by the Issuer in its Form 10-Q filed with the SEC on November 5, 2025.
(c)
Number of shares as to which the person has:
(i) Sole power to vote or to direct the vote:
See Item 5 on the cover page for each Reporting Person.
(ii) Shared power to vote or to direct the vote:
See Item 6 on the cover page for each Reporting Person.
(iii) Sole power to dispose or to direct the disposition of:
See Item 7 on the cover page for each Reporting Person.
(iv) Shared power to dispose or to direct the disposition of:
See Item 8 on the cover page for each Reporting Person.
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.
