[Form 4] Arcellx, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Arcellx insider sale disclosed: Chief Medical Officer Christopher Heery reported a sale of 73 shares of Arcellx common stock on 09/29/2025 at $80.16 per share, leaving him with 21,658 shares held directly. The filing states the sale was executed under a Rule 10b5-1 trading plan established on March 23, 2025, indicating the transaction followed a prearranged compliance program.

This disclosure is a routine insider disposition that documents the number of shares sold, the price, and the resulting direct ownership stake; no derivative transactions or other material changes in ownership are reported.

Positive

• Sale executed under a Rule 10b5-1 trading plan, indicating preplanned, compliant insider activity
• Reporting person retains 21,658 shares directly after the transaction, demonstrating ongoing ownership

Negative

• None.

Insights

Securities Analyst

TL;DR: Small, preplanned insider sale under a 10b5-1 plan; unlikely to be material to ACLX investors.

The reported sale of 73 shares at $80.16, reducing direct holdings to 21,658 shares, appears procedural and executed under a Rule 10b5-1 plan dated March 23, 2025. Given the small size of the transaction relative to reported post-sale holdings, this is unlikely to affect company valuation or signal a change in insider confidence. The filing shows compliance with SEC insider-trading frameworks and contains no derivative activity or other unusual items.

Corporate Governance Expert

TL;DR: Transaction reflects governance best practice by using a documented trading plan.

The disclosure that the sale was effected pursuant to a formal Rule 10b5-1 plan is a positive governance signal because it documents preauthorization and reduces concerns about opportunistic timing. The filing lists only a modest outright sale and confirms the reporting persons role as Chief Medical Officer. No additional governance issues or material ownership changes are evident from this Form 4.

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
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Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

1. Name and Address of Reporting Person^*

Heery Christopher

(Last) (First) (Middle)

C/O ARCELLX, INC.

800 BRIDGE PARKWAY

(Street)

REDWOOD CITY CA 94065

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
Arcellx, Inc. [ ACLX ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	CHIEF MEDICAL OFFICER

3. Date of Earliest Transaction (Month/Day/Year)
09/29/2025

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	09/29/2025		S(1)		73	D	$80.16	21,658	D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

1. The sale of shares reported on this Form 4 was effected pursuant to a Rule 10b5-1 trading plan entered into by the Reporting Person on March 23, 2025.

	Michelle Gilson	09/29/2025
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

FAQ

What did the Arcellx (ACLX) Form 4 disclose about insider activity?

The Form 4 reports that Chief Medical Officer Christopher Heery sold 73 shares of Arcellx common stock at $80.16 per share on 09/29/2025.

How many Arcellx (ACLX) shares does the reporting person own after the sale?

After the reported transaction the reporting person directly owns 21,658 shares of Arcellx common stock.

Was the sale of ACLX shares prearranged?

Yes. The filing states the sale was effected under a Rule 10b5-1 trading plan established on March 23, 2025.

Did the Form 4 disclose any derivative transactions for ACLX?

No. The Form 4 shows only a non-derivative sale of common stock; no derivative securities were reported.

What is the reporting persons role at Arcellx (ACLX)?

The reporting person is identified as the companys Chief Medical Officer.