[Form 4] Castellum, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Castellum, Inc. (CTM) insider sale and status changes reported on Form 4. Mark C. Fuller disposed of 500,000 shares of Common Stock on 09/03/2025 at $1.12 per share, leaving him with 6,113,659 shares beneficially owned. The filing states those holdings include 6,047,519 shares held by The Mark Chappelle Fuller Revocable Trust, 50,000 shares held by the Janice Lynn Dudley Revocable Trust, and 16,140 shares held directly by Mr. Fuller. The form also discloses that Mr. Fuller ceased to be a member of the company’s board effective May 28, 2025 and ceased to be an affiliate effective June 12, 2025. The report is signed by Mr. Fuller and shows a single reporting person filing.

Positive

• Full disclosure provided: The Form 4 clearly reports the transaction date, price, and post-transaction beneficial ownership.
• Substantial retained ownership: Even after the sale, Mr. Fuller beneficially owns 6,113,659 shares, preserving significant economic interest.

Negative

• Insider sale: Disposal of 500,000 shares at $1.12 may be viewed negatively by some investors.
• Departure from governance roles: Mr. Fuller ceased to be a director on May 28, 2025 and an affiliate on June 12, 2025, reducing formal oversight ties.

Insights

Corporate Governance Expert

TL;DR: Insider sold shares and formally ended board and affiliate status, reducing governance ties but retaining a large beneficial stake.

The 500,000-share sale at $1.12 and the separate statements that Mr. Fuller ceased board membership on May 28, 2025 and affiliate status on June 12, 2025 are material governance disclosures. Ceasing to be an affiliate typically changes reporting/related-party dynamics and may alter scrutiny on transactions, while continued substantial ownership (over 6.1 million shares) retains potential influence. The filing itself is straightforward and provides clear allocation of beneficial ownership across trusts and direct holdings.

Securities Analyst

TL;DR: A modest insider disposition occurred; ownership remains substantial, so market control risks persist.

The disposition of 500,000 shares at $1.12 reduces reported holdings but does not eliminate significant ownership: 6,113,659 shares remain beneficially owned. Transaction codes and pricing are fully disclosed on Form 4. The dates showing cessation of director and affiliate status are explicitly stated, which affects how future transactions may be reported. No derivative transactions or additional cash/compensation items are reported.

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
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X

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^*

Fuller Mark C

(Last) (First) (Middle)

1934 OLD GALLOWS ROAD

SUITE 350

(Street)

VIENNA VA 22182

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
Castellum, Inc. [ CTM ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

	Director		10% Owner
	Officer (give title below)	X	Other (specify below)
			Former Officer and Affiliate

3. Date of Earliest Transaction (Month/Day/Year)
09/03/2025

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	09/03/2025	09/03/2025	S		500,000	D	$1.12	6,113,659(1)(2)(3)	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. Includes (a) 6,047,519 common shares held by The Mark Chappelle Fuller Revocable Trust, Mark Fuller, TTEE, (b) 50,000 common shares held by Janice Lynn Dudley Revocable Trust, Janice Lynn Dudley TTEE, and (c) 16,140 common shares held by Mark Fuller.

2. Effective May 28, 2025, Mr. Fuller ceased to be a member of the Company's board of directors.

3. Effective June 12, 2025, Mr. Fuller ceased to be an affiliate of the Company.

Remarks:

	/s/ Mark C. Fuller	09/03/2025
	** 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 transaction did Mark C. Fuller report on Form 4 for CTM?

The report discloses a sale of 500,000 common shares on 09/03/2025 at a price of $1.12 per share.

How many Castellum (CTM) shares does Mark C. Fuller beneficially own after the transaction?

After the reported sale, Mr. Fuller beneficially owns 6,113,659 common shares.

What entities hold Mr. Fuller's CTM shares as disclosed?

Holdings include 6,047,519 shares in The Mark Chappelle Fuller Revocable Trust, 50,000 in the Janice Lynn Dudley Revocable Trust, and 16,140 held directly.

Did Mr. Fuller remain a director or affiliate of Castellum after these dates?

No. The filing states Mr. Fuller ceased to be a director effective May 28, 2025 and ceased to be an affiliate effective June 12, 2025.

Was this Form 4 filed by more than one reporting person?

No. The filing indicates it was submitted by one reporting person (Mark C. Fuller).