[144] Arcellx, Inc. SEC Filing

Rhea-AI Filing Summary

Arcellx, Inc. (ACLX) filed a Form 144 notifying the proposed sale of 37,486 common shares through Morgan Stanley Smith Barney on 09/18/2025 with an aggregate market value of $2,864,680.12. The filing lists total shares outstanding as 55,458,912, meaning the proposed sale equals approximately 0.0676% of outstanding shares. The securities being offered were acquired through three routes: restricted stock units granted on 01/02/2025 (28,208 shares), participation in an employee stock purchase plan on 05/12/2023 (1,483 shares), and previously exercised stock options on 09/03/2024 (7,795 shares). No securities were reported sold in the past three months. The filer certifies they are not aware of undisclosed material adverse information.

Positive

• Full disclosure of acquisition history showing RSUs, ESPP purchases, and exercised options, which clarifies the nature of holdings.
• Broker and execution date provided (Morgan Stanley Smith Barney; 09/18/2025), meeting Rule 144 notice requirements.

Negative

• Large aggregate dollar value of $2,864,680.12 may attract investor attention despite representing a small share percentage.

Insights

Financial Analyst

TL;DR: Routine insider liquidity event; size is small relative to company equity and sourced from compensation awards.

The filing reports a proposed sale of 37,486 common shares valued at $2.86 million, executed through Morgan Stanley Smith Barney. Acquisition details show the shares originate from standard compensation mechanisms: restricted stock units, an employee stock purchase plan, and exercised options. Given the total outstanding share count of 55.46 million, the sale represents roughly 0.0676% of shares outstanding, which is immaterial to capital structure. This appears to be an insider liquidity transaction rather than a corporate financing or change in control signal.

Compliance/Risk Analyst

TL;DR: Form 144 is complete for required fields and includes standard seller representation; no recent sales reported.

The notice identifies the broker, proposed sale date, and explicit acquisition history for the securities to be sold, satisfying disclosure expectations under Rule 144. The filer affirms no undisclosed material adverse information and indicates no securities were sold by the account in the prior three months. There are no statements here of Rule 10b5-1 plan adoption dates or other special instructions, and the signature block/explicit dates are not shown in the provided extract.

Form 144 Filer Information	UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Form 144 NOTICE OF PROPOSED SALE OF SECURITIES PURSUANT TO RULE 144 UNDER THE SECURITIES ACT OF 1933
FORM 144

144: Filer Information

Filer CIK
Filer CCC
Is this a LIVE or TEST Filing?	LIVE TEST
Submission Contact Information
Name
Phone
E-Mail Address

144: Issuer Information

Name of Issuer

SEC File Number

Address of Issuer

Phone

Name of Person for Whose Account the Securities are To Be Sold

See the definition of "person" in paragraph (a) of Rule 144. Information is to be given not only as to the person for whose account the securities are to be sold but also as to all other persons included in that definition. In addition, information shall be given as to sales by all persons whose sales are required by paragraph (e) of Rule 144 to be aggregated with sales for the account of the person filing this notice.

Relationship to Issuer

144: Securities Information

Title of the Class of Securities To Be Sold	Name and Address of the Broker	Number of Shares or Other Units To Be Sold	Aggregate Market Value	Number of Shares or Other Units Outstanding	Approximate Date of Sale	Name the Securities Exchange
Common	Morgan Stanley Smith Barney LLC Executive Financial Services 1 New York Plaza 8th Floor New York NY 10004	37486	2864680.12	55458912	09/18/2025	NASDAQ

Furnish the following information with respect to the acquisition of the securities to be sold and with respect to the payment of all or any part of the purchase price or other consideration therefor:

144: Securities To Be Sold

Title of the Class	Date you Acquired	Nature of Acquisition Transaction	Name of Person from Whom Acquired	Is this a Gift?	Date Donor Acquired	Amount of Securities Acquired	Date of Payment	Nature of Payment *
Common	01/02/2025	Restricted Stock Units	Issuer			28208	01/02/2025	N/A
Common	05/12/2023	Employee Stock Purchase Plan	Issuer			1483	05/12/2023	Cash
Common	09/03/2024	Previously Exercised Stock Options	Issuer			7795	09/03/2024	Cash

* If the securities were purchased and full payment therefor was not made in cash at the time of purchase, explain in the table or in a note thereto the nature of the consideration given. If the consideration consisted of any note or other obligation, or if payment was made in installments describe the arrangement and state when the note or other obligation was discharged in full or the last installment paid.

Furnish the following information as to all securities of the issuer sold during the past 3 months by the person for whose account the securities are to be sold.

144: Securities Sold During The Past 3 Months

Nothing to Report

144: Remarks and Signature

Remarks

Date of Notice

Date of Plan Adoption or Giving of Instruction, If Relying on Rule 10b5-1

ATTENTION:

The person for whose account the securities to which this notice relates are to be sold hereby represents by signing this notice that he does not know any material adverse information in regard to the current and prospective operations of the Issuer of the securities to be sold which has not been publicly disclosed. If such person has adopted a written trading plan or given trading instructions to satisfy Rule 10b5-1 under the Exchange Act, by signing the form and indicating the date that the plan was adopted or the instruction given, that person makes such representation as of the plan adoption or instruction date.

Signature

ATTENTION: Intentional misstatements or omission of facts constitute Federal Criminal Violations (See 18 U.S.C. 1001)

FAQ

What does the ACLX Form 144 report?

The filing reports a proposed sale of 37,486 common shares of Arcellx, to be executed via Morgan Stanley Smith Barney on 09/18/2025 with aggregate value $2,864,680.12.

How were the ACLX shares being sold acquired?

The shares were acquired as restricted stock units (28,208) on 01/02/2025, via an employee stock purchase plan (1,483) on 05/12/2023, and from previously exercised stock options (7,795) on 09/03/2024.

Does the filing show recent sales by the same person?

The Form 144 states "Nothing to Report" for securities sold during the past three months, indicating no reported recent sales in that period.

What broker will handle the sale and where will the shares trade?

The broker listed is Morgan Stanley Smith Barney LLC, Executive Financial Services, and the exchange indicated is NASDAQ.

What portion of ACLX outstanding shares does this sale represent?

The filing lists 55,458,912 shares outstanding; the proposed sale of 37,486 represents approximately 0.0676% of outstanding shares.