Arcellx (NASDAQ: ACLX) CMO reports RSU grant, share vesting details

Rhea-AI Filing Summary

Arcellx, Inc. reported insider equity activity by its chief medical officer, Christopher Heery. On January 2, 2026, he received an award of 67,708 restricted stock units (RSUs), each representing a contingent right to one share of common stock, vesting in equal annual installments over four years if he remains a service provider.

On January 2, 3 and 6, 2026, previously granted RSUs were converted to common stock in transactions coded "M," resulting in acquisitions of 13,021, 16,520 and 13,064 common shares, respectively, all at a stated price of $0 per share. Following these transactions, Heery held 43,199 shares of common stock directly, along with RSU holdings shown in the derivative table.

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

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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).

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)
01/02/2026

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	01/02/2026		M		13,021	A	$0	13,615(1)	D
Common Stock	01/03/2026		M		16,520	A	$0	30,135	D
Common Stock	01/06/2026		M		13,064	A	$0	43,199	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
Restricted Stock Unit	(2)	01/02/2026		A		67,708		(3)	(3)	Common Stock	67,708	$0	67,708	D
Restricted Stock Unit	(2)	01/02/2026		M			13,021	(4)	(4)	Common Stock	13,021	$0	13,021	D
Restricted Stock Unit	(2)	01/03/2026		M			16,520	(5)	(5)	Common Stock	16,520	$0	0	D
Restricted Stock Unit	(2)	01/06/2026		M			13,064	(6)	(6)	Common Stock	13,064	$0	39,194	D

Explanation of Responses:

1. Includes 284 shares acquired under the Issuer's 2022 Employee Stock Purchase Plan on May 14, 2025, and 310 shares acquired under the Issuer's 2022 Employee Stock Purchase Plan on November 14, 2024.

2. Each restricted stock unit ("RSU") represents a contingent right to receive one share of the Issuer's Common Stock.

3. Subject to the Reporting Person continuing to be a Service Provider (as defined in the Issuer's 2022 Equity Incentive Plan) through each applicable vesting date, one-fourth (1/4th) of the RSUs subject to the award will vest each year following the RSU Grant Date on the same day of the month as the RSU Grant Date (or, if there is no corresponding day in a particular month, then the last day of the month) over four (4) years. "RSU Grant Date" shall mean January 2, 2026.

4. Subject to the Reporting Person continuing to be a Service Provider (as defined in the Issuer's 2022 Equity Incentive Plan) through each applicable vesting date, one-third (1/3rd) of the RSUs subject to the award will vest each year following the RSU Grant Date on the same day of the month as the RSU Grant Date (or, if there is no corresponding day in a particular month, then the last day of the month) over three (3) years. "RSU Grant Date" shall mean January 2, 2024.

5. Subject to the Reporting Person continuing to be a Service Provider (as defined in the Issuer's 2022 Equity Incentive Plan) through each applicable vesting date, one-third (1/3rd) of the RSUs subject to the award will vest each year following the RSU Grant Date on the same day of the month as the RSU Grant Date (or, if there is no corresponding day in a particular month, then the last day of the month) over three (3) years. "RSU Grant Date" shall mean January 3, 2023.

6. Subject to the Reporting Person continuing to be a Service Provider (as defined in the Issuer's 2022 Equity Incentive Plan) through each applicable vesting date, one-fourth (1/4th) of the RSUs subject to the award will vest each year following the RSU Grant Date on the same day of the month as the RSU Grant Date (or, if there is no corresponding day in a particular month, then the last day of the month) over four (4) years. "RSU Grant Date" shall mean January 6, 2025.

	/s/ Michelle Gilson, as Attorney-in-Fact	01/06/2026
	** Signature of Reporting Person	Date
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FAQ

What insider activity did Arcellx (ACLX) report for its CMO?

The chief medical officer, Christopher Heery, reported a new award of 67,708 RSUs on January 2, 2026, and multiple RSU conversions into common stock at $0 per share over January 2–6, 2026.

How many Arcellx RSUs were granted to Christopher Heery in January 2026?

Heery was granted 67,708 restricted stock units on January 2, 2026, each RSU representing a contingent right to receive one share of Arcellx common stock.

How do the newly granted Arcellx RSUs vest for the CMO?

Subject to Heery continuing as a service provider, one-fourth of the 67,708 RSUs will vest each year following the January 2, 2026 grant date, on the same day of the month (or the last day of the month if no corresponding day), over four years.

What common stock did the Arcellx CMO acquire through RSU conversions?

Through RSU conversions coded "M," Heery acquired 13,021 common shares on January 2, 2026, 16,520 shares on January 3, 2026, and 13,064 shares on January 6, 2026, each at a stated price of $0 per share.

How many Arcellx common shares did the CMO hold after these transactions?

After the reported transactions, Heery beneficially owned 43,199 Arcellx common shares directly, as shown in the non-derivative securities table.

What do the Arcellx Form 4 footnotes say about the RSUs?

The footnotes state that each RSU represents a contingent right to receive one share of Arcellx common stock and describe vesting schedules requiring Heery to continue as a service provider under the 2022 Equity Incentive Plan.