Simon Irish, Chief Executive Officer and Director of Terrestrial Energy Inc. /DE/ (NASDAQ:IMSR), filed a Statement of Changes in Beneficial Ownership on October 26, 2026, reporting an RSU conversion transaction dated October 21, 2026.

Key Highlights

  • Transaction type: 511,580 restricted stock units were converted to common stock via transaction code M on October 21, 2026.
  • Acquisition price: Shares were acquired at $0, representing the vested portion of an RSU award.
  • Direct holdings after transaction: Irish directly holds 2,824,414 shares of common stock following the reported transaction.
  • Indirect holdings: Irish also holds 2,818,520 shares through an LLC and 52,255 shares through an IRA.
  • Remaining RSUs: 511,580 restricted stock units remain beneficially owned by Irish following the transaction.
  • Reporting person role: Irish serves as both Chief Executive Officer and Director of the issuer.

RSU Vesting Event for Terrestrial Energy CEO Simon Irish

According to the filing, Simon Irish, who serves as Chief Executive Officer and Director of Terrestrial Energy Inc. /DE/, reported the conversion of 511,580 restricted stock units into an equal number of shares of common stock on October 21, 2026. The transaction was recorded at a price of $0, consistent with the standard mechanics of an RSU settlement. Each restricted stock unit represents a contingent right to receive one share of common stock, as described in the filing's footnotes.

The filing discloses that the restricted stock units vest in one-half increments on each of the first and second anniversaries of the grant date, subject to Irish's continued employment through each applicable vesting date, with accelerated vesting available in certain events. Following the conversion, Irish directly holds 2,824,414 shares of common stock. He also holds shares indirectly: 2,818,520 through an LLC and 52,255 through an IRA. An additional 511,580 restricted stock units remain outstanding and are directly held by Irish, according to the filing. The filing was signed by Brian Thrasher as Attorney-in-Fact on October 26, 2026.

Terrestrial Energy Inc. /DE/ is listed on NASDAQ under the ticker symbol IMSR. The company is associated with advanced nuclear technology development. The filing was submitted individually, with the box for a single reporting person checked, and it covers only the October 21, 2026 transaction date as the date of the earliest reported transaction.

What Was Disclosed

The filing reports the conversion of 511,580 vested restricted stock units into common stock by CEO Simon Irish on October 21, 2026, at $0 per share, along with his resulting direct and indirect beneficial ownership positions in Terrestrial Energy Inc. /DE/.