Why were Arcellx (ACLX) CFO Michelle Gilson’s share sales executed?

The reported sales were broker-assisted transactions to satisfy Michelle Gilson’s tax withholding obligations from vesting restricted stock units. Footnotes clarify the sales were tied to RSU vesting, indicating they were tax-related rather than discretionary portfolio trades.

Arcellx (ACLX) CFO sells 11,291 shares to cover RSU tax obligations

Filing Impact

(Very High)

Filing Sentiment

(Negative)

Form Type

Rhea-AI Filing Summary

Arcellx, Inc. Chief Financial Officer Michelle Gilson exercised 20,496 shares of common stock on January 2, 2026 through a derivative conversion. On February 17, 2026, she sold a total of 11,291 shares in broker-assisted open-market transactions to satisfy tax withholding from vested RSUs, at weighted average prices of $69.2103 and $70.0125. After these transactions, she directly owned 53,541 shares of Arcellx common stock.

Insider Trade Summary

Net Seller: 11,291 shares ($784,783)

Net Sell 3 txns

Insider Gilson Michelle

Role CHIEF FINANCIAL OFFICER

Sold 11,291 shs ($785K)

Type	Security	Shares	Price	Value
Sale	Common Stock	7,141	$69.2103	$494K
Sale	Common Stock	4,150	$70.0125	$291K
Exercise	Common Stock	20,496	$0.00	--

Holdings After Transaction: Common Stock — 57,691 shares (Direct)

Footnotes (1)

Each restricted stock unit ("RSU") represents a contingent right to receive one share of the Issuer's Common Stock. Vesting of these RSUs previously reported in the Form 4 filed January 2, 2026. Represents a broker-assisted sale to satisfy the Reporting Person's tax withholding obligations in connection with the vesting of restricted stock units. Represents the weighted average share price of an aggregate total of 7,141 shares sold in the price range of $68.69 to $69.68 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. Represents the weighted average share price of an aggregate total of 4,150 shares sold in the price range of $69.69 to $70.55 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.

Form 4 Insider Transactions: What Each Field Means →

02/18/2026 - 05:19 PM

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).

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^*

Gilson Michelle

(Last)

(First)

(Middle)

C/O ARCELLX, INC.

800 BRIDGE PARKWAY

(Street)

REDWOOD CITY

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 FINANCIAL OFFICER

3. Date of Earliest Transaction (Month/Day/Year)
02/17/2026

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)
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	Amount	(A) or (D)	Price		6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
Common Stock⁽¹⁾	01/02/2026		M		20,496	A	$0	28,962	D
Common Stock	02/17/2026		S⁽²⁾		7,141	D	$69.2103⁽³⁾	57,691	D
Common Stock	02/17/2026		S⁽²⁾		4,150	D	$70.0125⁽⁴⁾	53,541	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)
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)	Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	8. Price of Derivative Security (Instr. 5)		10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)

Explanation of Responses:

1. Each restricted stock unit ("RSU") represents a contingent right to receive one share of the Issuer's Common Stock. Vesting of these RSUs previously reported in the Form 4 filed January 2, 2026.

2. Represents a broker-assisted sale to satisfy the Reporting Person's tax withholding obligations in connection with the vesting of restricted stock units.

3. Represents the weighted average share price of an aggregate total of 7,141 shares sold in the price range of $68.69 to $69.68 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 4,150 shares sold in the price range of $69.69 to $70.55 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.

	/s/ Michelle Gilson	02/18/2026
	** 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.

Source: View Original Filing on SEC EDGAR

FAQ

What insider transactions did Arcellx (ACLX) CFO Michelle Gilson report?

Arcellx CFO Michelle Gilson reported exercising 20,496 shares of common stock on January 2, 2026, then selling 11,291 shares on February 17, 2026. The sales were open-market, broker-assisted trades linked to tax withholding for vested restricted stock units.

How many Arcellx (ACLX) shares did the CFO sell and at what prices?

Michelle Gilson sold 7,141 shares at a weighted average price of $69.2103 and 4,150 shares at $70.0125. These February 17, 2026 broker-assisted open-market sales totaled 11,291 shares to cover tax obligations arising from RSU vesting.

How many Arcellx (ACLX) shares does the CFO own after these transactions?

Following the February 17, 2026 sales, Michelle Gilson directly owned 53,541 shares of Arcellx common stock. This figure reflects her remaining holdings after exercising 20,496 shares earlier and then disposing of 11,291 shares to cover RSU-related tax obligations.

What type of acquisition did Arcellx (ACLX) CFO report on January 2, 2026?

On January 2, 2026, Michelle Gilson acquired 20,496 shares of Arcellx common stock through an exercise or conversion of a derivative security. A footnote explains these shares relate to restricted stock units whose vesting had been previously reported in an earlier Form 4.