[Form 4] Arcellx, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Arcellx insider sales disclosed on Form 4: Christopher Heery, identified as a director and Chief Medical Officer, reported multiple sales of Arcellx common stock on 09/30/2025 executed under a Rule 10b5-1 trading plan established on March 23, 2025. The filings show three sale transactions totaling 21,034 shares — 5,300 shares at a weighted average price of $80.5518, 14,204 shares at a weighted average price of $81.4584, and 1,530 shares at a weighted average price of $82.198. Following those reported transactions the Form lists beneficial ownership amounts of 16,358, 2,154, and 624 shares on the respective lines. The Form 4 is signed and dated 09/30/2025.

Positive

• Trades executed under a Rule 10b5-1 plan (entered 03/23/2025), which provides a documented pre-arranged trading schedule
• Complete disclosure of weighted average prices for each aggregate sale lot, with willingness to provide per-price breakdowns upon request

Negative

• Insider sold a total of 21,034 shares on 09/30/2025, which may be perceived as significant liquidity by investors
• Form lists multiple post-transaction beneficial ownership figures (16,358; 2,154; 624) that could require clarification about aggregation or separate holdings

Insights

Financial Analyst

TL;DR: Insider sold 21,034 shares under a pre-established 10b5-1 plan; transactions look routine rather than event-driven.

The Form 4 documents three separate sales by Christopher Heery on 09/30/2025 totaling 21,034 shares at weighted average prices between $80.55 and $82.20. The use of a Rule 10b5-1 plan (entered 03/23/2025) indicates these trades were made under an automated schedule, which generally reduces the implication of trading on non-public information. The filing also reports post-transaction beneficial ownership figures of 16,358, 2,154, and 624 shares on the respective reported lines, as recorded on the form. For investors, these are disclosure items confirming insider liquidity but they do not, by themselves, change company fundamentals.

Corporate Governance Expert

TL;DR: Disclosure complies with Section 16 timing and cites a 10b5-1 plan; documentation appears procedurally standard.

The Form 4 identifies the reporting person as both a director and an officer (Chief Medical Officer) and discloses sales under a 10b5-1 trading plan established on 03/23/2025. That explicit disclosure of the plan and weighted average prices supports regulatory transparency. The signature block shows the form was signed on 09/30/2025. There are no derivative transactions reported and no amendments noted. From a governance perspective, the filing appears to meet routine disclosure requirements without indicating any corrective or exceptional measures.

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

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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)
09/30/2025

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	09/30/2025		S(1)		5,300	D	$80.5518(2)	16,358	D
Common Stock	09/30/2025		S(1)		14,204	D	$81.4584(3)	2,154	D
Common Stock	09/30/2025		S(1)		1,530	D	$82.198(4)	624	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 5,300 shares sold in the price range of $80.00 to $80.90 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. Represents the weighted average share price of an aggregate total of 14,204 shares sold in the price range of $81.08 to $82.07 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.

4. Represents the weighted average share price of an aggregate total of 1,530 shares sold in the price range of $82.09 to $82.33 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.

	Michelle Gilson	09/30/2025
	** 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 Arcellx insider Christopher Heery report on Form 4 (ACLX)?

The Form 4 reports that Christopher Heery sold an aggregate of 21,034 shares of Arcellx common stock on 09/30/2025 under a Rule 10b5-1 trading plan.

When was the 10b5-1 trading plan established for the reported sales?

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

What were the weighted average sale prices reported on the Form 4?

The filing discloses weighted average prices of $80.5518, $81.4584, and $82.198 for the three reported sale aggregates.

How many shares were sold in each reported transaction?

The Form 4 shows sales of 5,300, 14,204, and 1,530 shares on 09/30/2025.

Does the Form 4 report any option or derivative transactions?

No. Table II (derivative securities) contains no reported transactions; all reported transactions are in common stock.