X0609 4 2026-09-02-05:00 false 0001921865 ASP Isotopes Inc. ASPI 0001744816 Mann Paul Elliot false C/O ASP ISOTOPES INC. 2200 ROSS AVENUE, SUITE 4575E DALLAS TX 75201 true true false false Chairman and CEO true Common Stock 2026-09-02-05:00 4 S false 83758 3.91 D 9496087 D Common Stock 2026-09-03-05:00 4 S false 83758 3.92 D 9412329 D Common Stock 2026-09-04-05:00 4 S false 83759 4.10 D 9328570 D Represents "sell to cover" sales effected pursuant to a Rule 10b5-1 trading plan adopted by the filing person on December 30, 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 $3.75 to $3.96, 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. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $3.875 to $3.98, inclusive. The reporting person undertakes to provide 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. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $3.925 to $4.26, inclusive. The reporting person undertakes to provide 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 2026-09-04