Heather Kiessling - 18 Dec 2025 Form 4 Insider Report for ASP Isotopes Inc. (ASPI)

Role: Chief Financial Officer
Signature: /s/ Donald Ainscow, as attorney-in-fact
Issuer symbol: ASPI
Transactions as of: 18 Dec 2025
Net transactions value: -$463,840
Form type: 4
Filing time: 29 Dec 2025, 21:30:09 UTC
Previous filing: 15 Apr 2025
SEC: View on sec.gov

Reporting Owners (1)

Name	Relationship	Address	Signature	Signature date	CIK
Kiessling Heather	Chief Financial Officer	C/O ASP ISOTOPES INC., 601 PENNSYLVANIA AVENUE NW SUITE 900, WASHINGTON	/s/ Donald Ainscow, as attorney-in-fact	29 Dec 2025	0002026548

Transactions Table

Type	Sym	Class	Transaction	Value $	Shares	Change %	* Price $	Shares After	Date	Ownership	Footnotes
transaction	ASPI	Common Stock	Sale	$463,840	-80,000	-9.8%	$5.80	732,500	18 Dec 2025	Direct	F1

* An asterisk sign (*) next to the price indicates that the price is likely invalid.

Explanation of Responses:

Id	Content
F1	The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $5.73 to $5.885, 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 1.

Content

The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $5.73 to $5.885, 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 1.