[Form 4] Arcellx, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Heery Christopher, Chief Medical Officer of Arcellx, Inc. (ACLX), reported sales of company common stock under a Rule 10b5-1 trading plan. On 09/18/2025 he sold 3,343 shares at a weighted average price of $80.0085, leaving him with 34,427 shares beneficially owned after that transaction. On 09/19/2025 he sold an additional 300 shares at $80.00, leaving 34,127 shares beneficially owned. The Form 4 was signed by an attorney-in-fact on 09/19/2025.

The filing notes the sales were effected pursuant to a 10b5-1 plan entered March 23, 2025, and that the post-transaction totals include 284 shares acquired under the issuer's 2022 Employee Stock Purchase Plan on May 14, 2025. No derivative transactions or other changes were reported.

Insights

Securities Analyst

TL;DR: Insider sales under a pre-established 10b5-1 plan, modest in size relative to total holdings reported.

The reporting person, the Chief Medical Officer, executed two small open-market disposals totaling 3,643 shares at approximately $80 per share under a 10b5-1 plan dated March 23, 2025. The disclosure clarifies the weighted-average price and that the holdings include recent ESPP-acquired shares. This is a routine compliance disclosure; the 10b5-1 plan provides a non-speculative rationale for the timing of sales. No options, conversions, or other derivative activity are disclosed, and the filings show continued substantial direct ownership.

Corporate Governance Expert

TL;DR: Governance-wise, the filing is transparent and includes required explanatory detail about the 10b5-1 plan and ESPP shares.

The Form 4 includes the necessary explanations: plan date, weighted-average sale price disclosure, and a note on ESPP shares included in beneficial ownership totals. The form is signed via attorney-in-fact which is properly indicated. There are no unexplained transfers or complex arrangements; presentation is consistent with routine insider-reporting practices.

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
Estimated average burden
hours per response:			0.5

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

X

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

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)
09/18/2025

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	09/18/2025		S(1)		3,343	D	$80.0085(2)	34,427(3)	D
Common Stock	09/19/2025		S(1)		300	D	$80	34,127	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.

2. Represents the weighted average share price of an aggregate total of 3,343 shares sold in the price range of $80.00 to $80.055 by the Reporting Person. The Reporting Person undertakes to provide upon request by the Commission staff, the issuer or a security holder of the issuer, full information regarding the number of shares sold at each separate price.

3. Includes 284 shares acquired under the Issuer's 2022 Employee Stock Purchase Plan on May 14, 2025.

	/s/ Michelle Gilson, as Attorney-in-Fact	09/19/2025
	** 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 ACLX insider Heery Christopher report on Form 4?

He reported the sale of 3,343 shares on 09/18/2025 and 300 shares on 09/19/2025, executed under a Rule 10b5-1 plan.

At what price were the ACLX shares sold by the insider?

The weighted-average price for the 3,343-share sale was $80.0085 and the 300-share sale was at $80.00 per share.

When was the 10b5-1 trading plan established for the ACLX insider?

The Form 4 states the 10b5-1 plan was entered into on March 23, 2025.

How many ACLX shares does the reporting person own after these transactions?

The reporting person beneficially owned 34,427 shares after the 09/18/2025 sale and 34,127 shares after the 09/19/2025 sale.

Do the ownership totals include any recent employee plan purchases?

Yes, the totals include 284 shares acquired under Arcellx's 2022 Employee Stock Purchase Plan on May 14, 2025.