[Form 4] ASP Isotopes Inc. Insider Trading Activity

Rhea-AI Filing Summary

Robert Ainscow, Chief Operating Officer of ASP Isotopes Inc. (ASPI), reported multiple transactions on September 8-9, 2025. On 09/08/2025 he executed "sell to cover" sales under a Rule 10b5-1 plan totaling 8,438 shares at a weighted average price of $8.5263 to cover tax withholding from vested restricted stock. On 09/09/2025 he was granted or exercised employee stock options: option grants/exercises include 150,000 options at $0.25, 12,000 options at $2, and 135,000 options at $2, increasing beneficial ownership by option awards to positions listed. Net-share settlements of option exercises resulted in withholding of 4,396, 2,813, and 31,652 shares. After the reported transactions the filing person beneficially owned 1,669,693 shares.

Positive

• Use of a Rule 10b5-1 plan for the 09/08/2025 sales provides an affirmative defense and indicates pre-planned execution.
• Detailed disclosure of vesting schedules and net-share settlement amounts enhances transparency about compensation-related equity changes.
• Reporting person retains significant ownership with 1,669,693 shares beneficially owned following the transactions.

Negative

• Sell-to-cover transactions reduced outstanding shares by 8,438 shares on 09/08/2025, reflecting dilution of insider holdings for tax settlement.
• Net-share settlements withheld 38,861 shares (4,396 + 2,813 + 31,652) in connection with option exercises, reducing reported beneficial ownership available for sale.

Insights

Securities Analyst

TL;DR: Routine insider tax-related share sales and option activity under employee plans; not an unusual disclosure.

The filing documents a Rule 10b5-1 "sell to cover" sale of 8,438 shares at a weighted average price of $8.5263 executed to satisfy tax withholding on vested restricted stock awards, and multiple option-related transactions on 09/09/2025: grants/exercises of 150,000 options at $0.25, 12,000 at $2, and 135,000 at $2. The filing also reports net-share settlements withholding 4,396; 2,813; and 31,652 shares to pay exercise/tax obligations. The reporting person remains a significant beneficial holder with 1,669,693 shares after activity. This is primarily administrative compensation and tax-settlement activity rather than an open-market disposition for liquidity.

Corporate Governance Expert

TL;DR: Disclosure shows use of a 10b5-1 trading plan and standard net-share settlements for option exercises, consistent with typical insider practices.

The filing explicitly states a 10b5-1 plan adopted June 9, 2025 was used for "sell to cover" transactions to satisfy tax withholding. The filing also details vesting schedules for the listed option grants (various grant dates and vesting schedules are included) and confirms no open-market sales were used to satisfy exercise prices or tax liabilities aside from the 10b5-1 sales. From a governance perspective, the report provides clear traceability of compensation-related equity flows and compliance with Section 16 reporting.

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).

X

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^*

Ainscow Robert

(Last) (First) (Middle)

C/O ASP ISOTOPES INC.

601 PENNSYLVANIA AVENUE NW SUITE 900

(Street)

WASHINGTON DC 20004

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
ASP Isotopes Inc. [ ASPI ]

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

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	Chief Operating Officer

3. Date of Earliest Transaction (Month/Day/Year)
09/08/2025

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	09/08/2025		S(1)		8,438	D	$8.5263(2)	1,411,554	D
Common Stock	09/09/2025		M		150,000	A	$0.25	1,564,554	D
Common Stock	09/09/2025		F(3)		4,396	D	$8.53	1,557,158	D
Common Stock	09/09/2025		M		12,000	A	$2	1,569,158	D
Common Stock	09/09/2025		F(3)		2,813	D	$8.53	1,566,345	D
Common Stock	09/09/2025		M		135,000	A	$2	1,701,345	D
Common Stock	09/09/2025		F(3)		31,652	D	$8.53	1,669,693	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
Employee Stock Option (right to buy)	$0.25	09/09/2025		M			150,000	10/04/2024(4)	10/04/2031	Common Stock	150,000	$0	0	D
Employee Stock Option (right to buy)	$2	09/09/2025		M			12,000	04/04/2023(5)	04/04/2032	Common Stock	12,000	$0	0	D
Employee Stock Option (right to buy)	$2	09/09/2025		M			135,000	06/10/2025(6)	06/10/2032	Common Stock	135,000	$0	0	D

Explanation of Responses:

1. Represents "sell to cover" sales effected pursuant to a Rule 10b5-1 trading plan adopted by the filing person on June 9, 2025 to cover tax withholding obligations in connection with the vesting of restricted stock awards.

2. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $8.31 to $8.79, inclusive. The reporting person undertakes to provide ASP Isotopes Inc. (the "Company"), any stockholder of the Company, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in Footnote 2.

3. Represents shares withheld by the Company in connection with net share settlement to satisfy the exercise price associated with the reporting person's exercise of employee stock options. No shares were sold by the reporting person to satisfy the exercise price or any tax liability.

4. These options vested in thirty-six equal installments beginning on the last day of month after the option's grant date. The option was granted on October 4, 2021.

5. These options vested in a single installment 12 months after the grant date. The option was granted on April 4, 2022.

6. These options vested in thirty-six equal installments beginning on the last day of month after the option's grant date. The option was granted on June, 10, 2022.

Remarks:

	/s/ Donald Ainscow, as attorney-in-fact	09/10/2025
	** 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 did ASPI COO Robert Ainscow disclose in the Form 4?

He reported "sell to cover" sales under a 10b5-1 plan of 8,438 shares at a weighted average $8.5263 and multiple option-related transactions on 09/09/2025.

Why were shares sold on 09/08/2025 according to the Form 4?

The filing states the sales were "sell to cover" transactions pursuant to a Rule 10b5-1 trading plan adopted June 9, 2025 to cover tax withholding on vested restricted stock awards.

How many shares does Robert Ainscow beneficially own after these transactions?

The Form 4 reports he beneficially owns 1,669,693 shares following the reported transactions.

What option activity is detailed in the Form 4 for ASPI?

On 09/09/2025 the filing reports option-related entries: 150,000 options at $0.25, 12,000 at $2, and 135,000 at $2, with vesting schedules noted from grant dates in 2021 and 2022.

Were any shares sold to satisfy exercise prices or taxes for option exercises?

The filing states no shares were sold by the reporting person to satisfy the exercise price or any tax liability; instead, shares were withheld by the Company for net-share settlement.