Major passive holding: T. Rowe Price discloses 6.28M ACLX shares (11.3%)

Rhea-AI Filing Summary

T. Rowe Price Investment Management, Inc. reports holding 6,275,907 shares of Arcellx Inc. common stock, representing 11.3% of the class. The filing shows 6,135,986 shares with sole voting power and 6,275,204 shares with sole dispositive power, with no shared voting or dispositive power reported. The filer states these shares are held in the ordinary course of business and not for the purpose of influencing control. The Schedule 13G classification and disclosed holdings indicate a material passive stake above the 5% reporting threshold.

Positive

• Material passive ownership disclosed: 6,275,907 shares (11.3% of class) exceeds the 5% reporting threshold
• Consolidated voting and dispositive power: majority of shares shown with sole voting and sole dispositive power

Negative

• None.

Insights

Financial Analyst

TL;DR: A material passive stake of 11.3% by a major asset manager signals notable ownership but no active control intent.

T. Rowe Price's reported position of 6.28 million shares represents a significant minority stake in Arcellx that exceeds the 5% reporting threshold, creating potential investor interest in who the large passive holders are. The split between sole voting power and dispositive power indicates centralized voting authority within the reporting entity. Because this is a Schedule 13G filing and the filer certifies passive intent, the immediate governance impact is limited; however, the stake is large enough to matter in shareholder votes if voting positions shift.

Corporate Governance Expert

TL;DR: The filing documents significant ownership without asserted intent to influence control, limiting immediate governance implications.

The filer explicitly states the securities are held in the ordinary course of business and not to influence control, consistent with a passive Schedule 13G disclosure. With sole voting power over most shares reported, the holder could still exercise influence indirectly, but the absence of shared power and the passive certification suggest current behavior is non-activist. For governance monitoring, other filings or statements would be needed to detect any change from passive to active intent.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

ARCELLX INC

(Name of Issuer)

COMMON STOCK

(Title of Class of Securities)

03940C100

(CUSIP Number)

08/31/2025

(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

T. Rowe Price Investment Management, Inc.

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

MARYLAND

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 6,135,986.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 6,275,204.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

6,275,907.00

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)

11.3 %

12

Type of Reporting Person (See Instructions)

IA

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: T. Rowe Price Investment Management, Inc.
(b)	Address or principal business office or, if none, residence: 1307 Point Street, Baltimore, MD 21231
(c)	Citizenship: Maryland
(d)	Title of class of securities: COMMON STOCK
(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: 6275907
(b)	Percent of class: 11.3 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 6135986
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: 6275204
	(iv) Shared power to dispose or to direct the disposition of: 0
Item 5.	Ownership of 5 Percent or Less of a Class.
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. T. Rowe Price Investment Management, Inc. hereby declares and affirms that the filing of Schedule 13G shall not be construed as an admission that Price Investment Management is the beneficial owner of the securities referred to, which beneficial ownership is expressly denied.

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.

T. Rowe Price Investment Management, Inc.

Signature:	Ellen York
Name/Title:	Vice President
Date:	09/08/2025

FAQ

How many Arcellx (ACLX) shares does T. Rowe Price report owning?

T. Rowe Price reports beneficial ownership of 6,275,907 shares of Arcellx common stock.

What percentage of ACLX does the filing report?

The filing reports an ownership stake equal to 11.3% of the class.

Does the Schedule 13G indicate T. Rowe Price intends to influence control of Arcellx (ACLX)?

No; the filing certifies the shares are held in the ordinary course of business and were not acquired to change or influence control.

How much voting power does T. Rowe Price report for ACLX shares?

The filer reports 6,135,986 shares with sole voting power and 0 shared voting power.

How much dispositive power does the filer report over ACLX shares?

The filing shows 6,275,204 shares with sole dispositive power and 0 shared dispositive power.