ASP Isotopes (ASPI) CFO sells 23,124 shares to cover RSU taxes

Rhea-AI Filing Summary

ASP Isotopes Inc.’s Chief Financial Officer, Heather Kiessling, reported an open-market sale of 23,124 shares of common stock at a weighted average price of $6.28 per share. According to the footnotes, these were “sell to cover” trades under a Rule 10b5-1 trading plan to satisfy tax withholding from quarterly vesting of a restricted stock award.

After the transaction, she directly holds 1,526,252 shares of ASP Isotopes common stock, indicating that the sale represents a small portion of her overall equity position and is tied to a pre-arranged, tax-related mechanism rather than a discretionary reduction in holdings.

Insider Trade Summary 10b5-1

Net Seller: 23,124 shares ($145,219)

Net Sell 1 txn

Insider Kiessling Heather

Role Chief Financial Officer

Sold 23,124 shs ($145K)

Type	Security	Shares	Price	Value
Sale	Common Stock	23,124	$6.28	$145K

Holdings After Transaction: Common Stock — 1,526,252 shares (Direct, null)

Footnotes (1)

1. Represents "sell to cover" sales effected pursuant to a Rule 10b5-1 trading plan adopted by the filing person on December 19, 2025 to cover tax withholding obligations in connection with the quarterly vesting of a restricted stock award. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $6.13 to $6.52, 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 this footnote.

Key Figures

Shares sold: 23,124 shares Average sale price: $6.28 per share Post-transaction holdings: 1,526,252 shares +1 more

4 metrics

Shares sold 23,124 shares Open-market sale to cover taxes under Rule 10b5-1 plan

Average sale price $6.28 per share Weighted average price for reported transactions

Post-transaction holdings 1,526,252 shares Common stock directly held after the sale

Price range of sales $6.13–$6.52 per share Range of individual trade prices noted in footnote

Key Terms

Rule 10b5-1 trading plan, sell to cover, restricted stock award, weighted average price

4 terms

Rule 10b5-1 trading plan regulatory

"sales effected pursuant to a Rule 10b5-1 trading plan adopted by the filing person"

A Rule 10b5-1 trading plan is a pre-arranged schedule that allows company insiders to buy or sell stock at specific times, even if they have inside information. It helps prevent accusations of unfair trading by making these transactions look planned and transparent, rather than sneaky or illegal.

sell to cover financial

"Represents "sell to cover" sales effected pursuant to a Rule 10b5-1 trading plan"

Sell to cover is when a person who receives company stock through options or awards sells just enough shares immediately to pay required taxes, exercise costs, or fees, keeping the rest. Think of it like cashing part of a bonus to cover the tax bill so you can keep the remainder. For investors, it can create predictable small selling pressure and slightly change the number of shares actually held by insiders without increasing long‑term dilution.

restricted stock award financial

"tax withholding obligations in connection with the quarterly vesting of a restricted stock award"

A restricted stock award is company shares given to an employee or executive that cannot be sold or fully owned until certain conditions—like staying with the company for a set time or hitting performance targets—are met. Think of it as a gift that only becomes yours after you fulfill specific obligations; for investors, these awards matter because they can increase the total shares outstanding when they vest, reveal how management is being paid and motivated, and create potential selling pressure when restrictions lift.

weighted average price financial

"The price reported in Column 4 is a weighted average price"

Weighted average price is the average price of a security where each trade or component is counted according to its size, so bigger trades pull the average more than smaller ones. Think of it like calculating the average cost of a grocery haul where items you bought more of have greater influence on the final per-item cost. Investors use it to understand the true average price paid or received, judge execution quality, and compare trading performance against market movement.

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Form 4 Insider Transactions: What Each Field Means →

Available on EDGAR 07/02/2026 - 09:45 PM Accepted by SEC EDGAR 07/02/2026 - 09:45 PM Learn about SEC filing dates

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^*

Kiessling Heather

(Last) (First) (Middle)

C/O ASP ISOTOPES INC.

2200 ROSS AVENUE, SUITE 4575E

(Street)

DALLAS TEXAS 75201

(City) (State) (Zip)

UNITED STATES

(Country)

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 Financial Officer

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
07/01/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

4. If Amendment, Date of Original Filed (Month/Day/Year)

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	07/01/2026		S(1)		23,124	D	$6.28(2)	1,526,252	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. Represents "sell to cover" sales effected pursuant to a Rule 10b5-1 trading plan adopted by the filing person on December 19, 2025 to cover tax withholding obligations in connection with the quarterly vesting of a restricted stock award.

2. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $6.13 to $6.52, 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 this footnote.

	/s/ Donald Ainscow, as attorney-in-fact	07/02/2026
	** 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.
* Form 4: SEC 1474 (03-26)

FAQ

What did ASP Isotopes (ASPI) CFO Heather Kiessling report in this Form 4?

Heather Kiessling reported selling 23,124 shares of ASP Isotopes common stock. The sales were executed under a pre-arranged Rule 10b5-1 plan to cover tax withholding resulting from the quarterly vesting of a restricted stock award, not a discretionary sale.

At what price did the ASPI CFO’s Form 4 sales occur?

The Form 4 lists a weighted average sale price of $6.28 per ASP Isotopes share. Footnotes state the actual trades occurred in multiple transactions within a price range from $6.13 to $6.52 per share, all contributing to the reported average.

How many ASP Isotopes (ASPI) shares does the CFO hold after this transaction?

Following the reported sales, Heather Kiessling directly holds 1,526,252 shares of ASP Isotopes common stock. This indicates the 23,124 shares sold were a relatively small portion of her total position, primarily used to satisfy tax obligations tied to vested restricted stock.

Was the ASPI CFO’s stock sale part of a Rule 10b5-1 trading plan?

Yes. The filing’s footnote explains the sales were executed under a Rule 10b5-1 trading plan adopted on December 19, 2025. The plan’s purpose was to sell shares automatically to cover tax withholding obligations from quarterly vesting of a restricted stock award.

What is the purpose of the ASP Isotopes CFO’s “sell to cover” transaction?

The sale was designed to cover tax withholding obligations connected to the quarterly vesting of a restricted stock award. Instead of paying taxes in cash, a portion of vested shares was sold under a pre-arranged Rule 10b5-1 plan, generating funds to satisfy those obligations.