[SCHEDULE 13D/A] Arcellx, Inc. SEC Filing

Rhea-AI Filing Summary

Amendment No. 4 to Schedule 13D reports that New Enterprise Associates 15, L.P. ("NEA 15") now holds 3,045,262 shares of Arcellx, Inc. common stock, which the filing states represents 5.49% of the 55,458,912 shares outstanding used for the calculation. The amendment documents pro rata distributions on August 12, 2025: NEA 15 distributed 700,000 shares to its partners and NEA Partners 15 distributed 168,217 shares to its limited partners, resulting in NEA 15 holding the stated 3,045,262 shares.

The filing clarifies that the Reporting Persons (NEA entities and four named managers) acquired and hold the shares for investment purposes and currently have no present plans to effectuate transactions or corporate changes such as mergers, board changes, material asset sales or changes to capitalization. The cover sheets show shared voting and dispositive power over the NEA 15 Shares and reflect that Scott D. Sandell may be deemed to beneficially own additional small blocks held in trusts, giving him an aggregate 3,055,360 shares (5.51%).

Positive

• NEA 15 holds 3,045,262 shares of Arcellx common stock, representing 5.49% of outstanding shares
• Reporting Persons state the position is held for investment purposes and explicitly disclaim plans to effect corporate control changes
• Filing provides transparent detail on recent pro rata distributions and discloses recent manager transactions

Negative

• Certain managers received distributed shares and some of those shares were sold on August 13, 2025, as disclosed
• Beneficial ownership is reported as shared voting and dispositive power rather than sole control for NEA entities and managers

Insights

Financial Analyst

TL;DR: NEA entities report a 5.49% passive investment in ACLX via distributions; no planned corporate actions.

The filing documents a structural ownership update rather than an active campaign for control: NEA 15 holds 3,045,262 shares representing 5.49% based on 55,458,912 shares outstanding, and managers report shared voting and dispositive power. The distributions on August 12, 2025 reallocated previously-held NEA 15 shares to partners, and certain distributed shares were sold by some managers on August 13, 2025 as disclosed. The Reporting Persons explicitly state the shares are held for investment purposes and disavow current plans to pursue mergers, board changes, material dispositions, charter or bylaw amendments, delisting, or deregistration.

Corporate Governance Expert

TL;DR: This amendment is a disclosure of passive ownership and confirms no present intent to change governance or control at Arcellx.

The Schedule 13D/A clarifies beneficial ownership chains: NEA Partners 15 and NEA 15 GP, LLC may be deemed beneficial owners through general partner roles, and four named managers may be deemed beneficial holders as members of the GP. The filing attaches standard exhibits (joint filing agreement, recent transactions schedule, power of attorney) and reiterates that no contractual arrangements or plans exist to alter board composition, capital structure, or corporate governance at the issuer.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 4)

Arcellx, Inc.

(Name of Issuer)

Common Stock $0.001 par value per share

(Title of Class of Securities)

03940C100

(CUSIP Number)

Stephanie Brecher
New Enterprise Associates, 1954 Greenspring Drive, Suite 600
Timonium, MD, 21093
(410)842-4000

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

08/12/2025

(Date of Event Which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.

The information required on the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

SCHEDULE 13D

CUSIP No. 03940C100

1

Name of reporting person

New Enterprise Associates 15, L.P.

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

WC

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 3,045,262.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 3,045,262.00

11

Aggregate amount beneficially owned by each reporting person

3,045,262.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

5.49 %

14

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13D

CUSIP No. 03940C100

1

Name of reporting person

NEA Partners 15, L.P.

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 3,045,262.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 3,045,262.00

11

Aggregate amount beneficially owned by each reporting person

3,045,262.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

5.49 %

14

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13D

CUSIP No. 03940C100

1

Name of reporting person

NEA 15 GP, LLC

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 3,045,262.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 3,045,262.00

11

Aggregate amount beneficially owned by each reporting person

3,045,262.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

5.49 %

14

Type of Reporting Person (See Instructions)

OO

SCHEDULE 13D

CUSIP No. 03940C100

1

Name of reporting person

Forest Baskett

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 3,045,262.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 3,045,262.00

11

Aggregate amount beneficially owned by each reporting person

3,045,262.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

5.49 %

14

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13D

CUSIP No. 03940C100

1

Name of reporting person

Anthony A. Florence, Jr.

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 3,045,262.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 3,045,262.00

11

Aggregate amount beneficially owned by each reporting person

3,045,262.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

5.49 %

14

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13D

CUSIP No. 03940C100

1

Name of reporting person

Mohamad H. Makhzoumi

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 3,045,262.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 3,045,262.00

11

Aggregate amount beneficially owned by each reporting person

3,045,262.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

5.49 %

14

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13D

CUSIP No. 03940C100

1

Name of reporting person

Scott D. Sandell

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 7,910.00
8	Shared Voting Power 3,047,450.00
9	Sole Dispositive Power 7,910.00
10	Shared Dispositive Power 3,047,450.00

11

Aggregate amount beneficially owned by each reporting person

3,055,360.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

5.51 %

14

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13D

Item 1.	Security and Issuer
(a)	Title of Class of Securities: Common Stock $0.001 par value per share
(b)	Name of Issuer: Arcellx, Inc.
(c)	Address of Issuer's Principal Executive Offices: 800 Bridge Parkway, Redwood City, CALIFORNIA , 94065.
Item 1 Comment: This Amendment No. 4 ("Amendment No. 4") to Schedule 13D amends and supplements the Schedule 13D originally filed on February 17, 2022 (the "Schedule 13D"), Amendment No. 1 thereto filed on January 24, 2023 ("Amendment No. 1"), Amendment No. 2 thereto filed on June 23, 2023 ("Amendment No. 2") and Amendment No. 3 thereto filed on May 12, 2025 ("Amendment No. 3"), relating to the Common Stock of the Issuer. Certain terms used but not defined in this Amendment No. 4 have the meanings assigned thereto in the Schedule 13D (and Amendment No. 1, Amendment No. 2 and Amendment No. 3 thereto). Except as specifically provided herein, this Amendment No. 4 does not modify any of the information previously reported on the Schedule 13D (and Amendment No. 1, Amendment No. 2 and Amendment No. 3 thereto).
Item 2.	Identity and Background
(a)	New Enterprise Associates 15, L.P. ("NEA 15"), NEA Partners 15, L.P. ("NEA Partners 15"), which is the sole general partner of NEA 15; and NEA 15 GP, LLC ("NEA 15 LLC" and, together with NEA Partners 15, the "Control Entities"), which is the sole general partner of NEA Partners 15; and Forest Baskett ("Baskett"), Anthony A. Florence, Jr. ("Florence"), Mohamad H. Makhzoumi ("Makhzoumi") and Scott D. Sandell ("Sandell") (together, the "Managers"). The Managers are the managers of NEA 15 LLC. The persons named in this Item 2 are referred to individually herein as a "Reporting Person" and collectively as the "Reporting Persons."
(b)	The address of the principal business office of NEA 15, each Control Entity and Sandell is New Enterprise Associates, 1954 Greenspring Drive, Suite 600, Timonium, MD 21093. The address of the principal business office of Baskett and Makhzoumi is New Enterprise Associates, 2855 Sand Hill Road, Menlo Park, CA 94025. The address of the principal business office of Florence is New Enterprise Associates, 104 5th Avenue, 19th Floor, New York, NY 10011.
(c)	The principal business of NEA 15 is to invest in and assist growth-oriented businesses located principally in the United States. The principal business of NEA Partners 15 is to act as the sole general partner of NEA 15. The principal business of NEA 15 LLC is to act as the sole general partner of NEA Partners 15. The principal business of each of the Managers is to manage the Control Entities and a number of affiliated partnerships with similar businesses.
(d)	During the five years prior to the date hereof, none of the Reporting Persons has been convicted in a criminal proceeding or has been a party to a civil proceeding ending in a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.
(e)	During the five years prior to the date hereof, none of the Reporting Persons has been convicted in a criminal proceeding or has been a party to a civil proceeding ending in a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.
(f)	NEA 15 LLC is a limited liability company organized under the laws of the State of Delaware. NEA 15 and NEA Partners 15 are limited partnerships organized under the laws of the State of Delaware. Each of the Managers is a United States citizen.
Item 3.	Source and Amount of Funds or Other Consideration
	Not applicable.
Item 4.	Purpose of Transaction
	NEA 15 acquired the NEA 15 Shares for investment purposes. Depending on market conditions, its continuing evaluation of the business and prospects of the Issuer and other factors, NEA 15 and the other Reporting Persons may dispose of or acquire additional shares of the Issuer. Except as set forth above, none of the Reporting Persons has any present plans which relate to or would result in: (a) The acquisition by any person of additional securities of the Issuer, or the disposition of securities of the Issuer; (b) An extraordinary corporate transaction, such as a merger, reorganization or liquidation, involving the Issuer or any of its subsidiaries; (c) A sale or transfer of a material amount of assets of the Issuer or any of its subsidiaries; (d) Any change in the present board of directors or management of the Issuer, including any plans or proposals to change the number or term of directors or to fill any existing vacancies on the board; (e) Any material change in the present capitalization or dividend policy of the Issuer; (f) Any other material change in the Issuer's business or corporate structure; (g) Changes in the Issuer's charter, bylaws or instruments corresponding thereto or other actions which may impede the acquisition of control of the Issuer by any person; (h) Causing a class of securities of the Issuer to be delisted from a national securities exchange or to cease to be authorized to be quoted in an inter-dealer quotation system of a registered national securities association; (i) A class of equity securities of the Issuer becoming eligible for termination of registration pursuant to Section 12(g)(4) of the Securities Exchange Act of 1934; or (j) Any action similar to any of those enumerated above.
Item 5.	Interest in Securities of the Issuer
(a)	NEA 15 is the record owner of the NEA 15 Shares (as defined below). As the general partner of NEA 15, NEA Partners 15 may be deemed to own beneficially the NEA 15 Shares. As the sole general partner of NEA Partners 15, NEA 15 LLC may be deemed to own beneficially the NEA 15 Shares. As members of NEA 15 LLC, each of the Managers may be deemed to own beneficially the NEA 15 Shares. Each Reporting Person disclaims beneficial ownership of the NEA 15 Shares other than those shares which such person owns of record. The percentage of outstanding Common Stock of the Issuer which may be deemed to be beneficially owned by each Reporting Person is set forth on Line 13 of such Reporting Person's cover sheet. Such percentage was calculated based on 55,458,912 shares of Common Stock reported by the Issuer to be outstanding as of August 1, 2025, on the Issuer's Form 10-Q filed with the Securities and Exchange Commission on August 7, 2025.
(b)	Regarding the number of shares as to which such person has: (i) sole power to vote or to direct the vote: See line 7 of cover sheets (ii) shared power to vote or to direct the vote: See line 8 of cover sheets (iii) sole power to dispose or to direct the disposition: See line 9 of cover sheets (iv) shared power to dispose or to direct the disposition: See line 10 of cover sheets.
(c)	On August 12, 2025, NEA 15 made a pro rata distribution of 700,000 shares of Common Stock of the Issuer to its general partner and its limited partners for no consideration (the "NEA 15 Distribution"). NEA Partners 15 acquired 168,217 shares of Common Stock of the Issuer as a result of the NEA 15 Distribution and, subsequent to the NEA 15 Distribution, on August 12, 2025, made a pro rata distribution of 168,217 shares of Common Stock of the Issuer to its limited partners for no consideration (the "NEA Partners 15 Distribution"). NEA 15 now holds a total of 3,045,262 shares of Common Stock of the Issuer (the "NEA 15 Shares"). On August 12, 2025, Baskett, Florence, Makhzoumi and Sandell received shares in the NEA Partners 15 Distribution (either directly or indirectly via entities or trusts for which they may be deemed to have a beneficial ownership interest), certain of which shares were sold on August 13, 2025. Schedule A attached hereto as Exhibit 2 describes all transactions in the Issuer's Common Stock that were effected during the past 60 days by the Reporting Persons. As of August 14, 2025, the Blue Mountain Trust, dated April 29, 2019 (the "Blue Mountain Trust") is the record owner of 7,910 shares of Common Stock (the "Blue Mountain Trust Shares"). As trustee of the Blue Mountain Trust, Sandell may be deemed to own beneficially the Blue Mountain Trust Shares. As of August 14, 2025, Sandell may be deemed to own beneficially the 1,094 shares of Common Stock held by the Scott Sandell Rising River Trust, dated December 20, 2012 and the 1,094 shares of Common Stock held by the Jennifer Ayer Sandell Rising River Trust, dated December 20, 2012.
(d)	No other person is known to have the right to receive or the power to direct the receipt of dividends from, or any proceeds from the sale of, Common Stock beneficially owned by any of the Reporting Persons.
(e)	Not applicable.
Item 6.	Contracts, Arrangements, Understandings or Relationships With Respect to Securities of the Issuer
	Not applicable.
Item 7.	Material to be Filed as Exhibits.
	Exhibit 1 - Agreement regarding filing of joint Schedule 13D. Exhibit 2 - Schedule A: Transactions during the past 60 days. Exhibit 3 - Power of Attorney regarding filings under the Securities Exchange Act of 1934, as amended

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

New Enterprise Associates 15, L.P.

Signature:	/s/ Zachary Bambach
Name/Title:	Zachary Bambach as attorney-in-fact for Anthony A. Florence Jr., Managing Partner and Co-Chief Executive Officer
Date:	08/14/2025

Signature:	/s/ Zachary Bambach
Name/Title:	Zachary Bambach as attorney-in-fact for Mohamad H. Makhzoumi, Managing Partner and Co-Chief Executive Officer
Date:	08/14/2025

NEA Partners 15, L.P.

Signature:	/s/ Zachary Bambach
Name/Title:	Zachary Bambach as attorney-in-fact for Anthony A. Florence Jr., Managing Partner and Co-Chief Executive Officer
Date:	08/14/2025

Signature:	/s/ Zachary Bambach
Name/Title:	Zachary Bambach as attorney-in-fact for Mohamad H. Makhzoumi, Managing Partner and Co-Chief Executive Officer
Date:	08/14/2025

NEA 15 GP, LLC

Signature:	/s/ Zachary Bambach
Name/Title:	Zachary Bambach as attorney-in-fact for Anthony A. Florence Jr., Managing Partner and Co-Chief Executive Officer
Date:	08/14/2025

Signature:	/s/ Zachary Bambach
Name/Title:	Zachary Bambach as attorney-in-fact for Mohamad H. Makhzoumi, Managing Partner and Co-Chief Executive Officer
Date:	08/14/2025

Forest Baskett

Signature:	/s/ Zachary Bambach
Name/Title:	Zachary Bambach as attorney-in-fact for Forest Baskett
Date:	08/14/2025

Anthony A. Florence, Jr.

Signature:	/s/ Zachary Bambach
Name/Title:	Zachary Bambach as attorney-in-fact for Anthony A. Florence Jr.
Date:	08/14/2025

Mohamad H. Makhzoumi

Signature:	/s/ Zachary Bambach
Name/Title:	Zachary Bambach as attorney-in-fact for Mohamad H. Makhzoumi
Date:	08/14/2025

Scott D. Sandell

Signature:	/s/ Zachary Bambach
Name/Title:	Zachary Bambach as attorney-in-fact for Scott D. Sandell
Date:	08/14/2025

Comments accompanying signature:

This Amendment No. 4 to Schedule 13D was executed by Zachary Bambach on behalf of the individuals listed above pursuant to a Power of Attorney, a copy of which is attached as Exhibit 2.

FAQ

How many Arcellx (ACLX) shares does NEA 15 report owning?

The filing states NEA 15 holds 3,045,262 shares, equal to 5.49% of the 55,458,912 shares used in the calculation.

Did the filing report any plans by NEA to change Arcellx's board or strategy?

No. The Reporting Persons explicitly state they have no present plans to effect board changes, mergers, material asset sales, changes to capitalization or dividend policy, or similar actions.

What transactions occurred on August 12, 2025, per the filing?

NEA 15 made a pro rata distribution of 700,000 shares to partners; NEA Partners 15 received 168,217 shares and then distributed those shares pro rata to its limited partners on August 12, 2025.

Does any individual Reporting Person hold additional shares outside NEA 15?

Yes. The filing reports Scott D. Sandell may be deemed to beneficially own 3,055,360 shares (5.51%), which includes the 7,910 shares held by the Blue Mountain Trust and other small trust holdings.

Are there any contracts or arrangements between the Reporting Persons and Arcellx reported?

No. Item 6 of the filing states Not applicable, indicating no contracts, arrangements or understandings with respect to Arcellx securities are reported.