Terrestrial Energy Inc. (IMSR) is converting its prior S-1 and S-4 registration statements to Form S-3; the prospectus describes a primary offering of up to 53,325,182 shares of common stock, with no additional securities registered by this amendment. The prospectus also describes selling-securityholder resales of up to 14,887,245 shares and 1,267,599 Working Capital Warrants.
The primary shares are issuable upon warrant exercise or exchange of Exchangeable Shares. Terrestrial Energy receives no proceeds from securityholder resales or Exchangeable Share conversions; it receives cash from warrant exercises only when exercised for cash. Listed Warrants have an exercise price of $11.50 per share, and the company estimates approximately $225.6 million if all outstanding Listed Warrants are exercised for cash. Cashless exercises produce no cash proceeds; any proceeds received are intended for general corporate purposes. Some resale securities are subject to lock-up restrictions.
Terrestrial Energy Inc. registered for resale up to 2,263,805 shares of Common Stock issuable upon exercise of stock options held by selling stockholder Louis Plowden-Wardlaw. The options were awarded during his employment with Terrestrial Energy Development, Inc. before its business combination with Terrestrial Energy. He may sell all or part of the shares through public or private transactions.
Terrestrial Energy will receive no proceeds from resales. If all the options are exercised for cash, the company would receive approximately $1.6 million, which it intends to use for general corporate purposes.
Terrestrial Energy Inc. (IMSR) registered a primary offering of up to 2,310,937 common shares for former holders of convertible notes issued by its subsidiary, Terrestrial Energy Development, Inc. The shares are issuable under the note terms and are to be issued on approximately November 25, 2026, the 21st trading day following expiration of the applicable lock-up period; the number will be determined on that date.
Terrestrial Energy will receive no proceeds from this issuance. Separately, its base shelf prospectus lists $500,000,000 in securities it may offer from time to time, including common and preferred stock, debt securities, warrants, rights and units. Unless a prospectus supplement provides otherwise, net proceeds from base-shelf sales are for working capital and general corporate purposes.
Terrestrial Energy Inc. (IMSR) Chief Executive Officer Simon Irish reported the exercise/conversion of 55,432 restricted stock units on October 28, 2026, corresponding to the acquisition of 55,432 common shares. Afterward, his reported direct holdings included 2,879,846 common shares and 110,866 restricted stock units; indirect common-share holdings were 2,818,520 through an LLC and 52,255 through an IRA.
Terrestrial Energy Inc. (IMSR) said its board authorized a common-stock repurchase program of up to $25 million. The company may repurchase shares from time to time through open-market purchases, privately negotiated transactions, block trades or other means, including under a trading plan adopted in accordance with Rule 10b5-1 and in accordance with Rule 10b-18 and other applicable laws. Management will determine the timing, manner, price and amount of repurchases at its discretion based on general economic and market conditions, the company’s share price, capital requirements, applicable legal requirements and other factors.
The program will be funded from existing cash on hand, but it does not obligate the company to repurchase any particular amount. Terrestrial Energy may modify, suspend or discontinue the program at any time at its discretion without prior notice; the program expires October 22, 2027. The company had approximately 105.9 million shares of common stock outstanding as of October 23, 2026, including shares of common stock issuable upon exchange of outstanding exchangeable shares.
Terrestrial Energy Inc. CEO and director Simon Irish reported the exercise/conversion of 511,580 restricted stock units into 511,580 common shares on October 21, 2026. The units represented the vested portion of his award.
Following the transaction, his reported direct common-stock holdings were 2,824,414 shares. The report also lists indirect holdings of 2,818,520 shares through an LLC and 52,255 shares through an IRA.
Terrestrial Energy Inc. reported that Chief Commercial Officer David Woodward Williams received a grant of 152,672 stock options to buy common stock on October 19, 2026. The options have a $3.93-per-share exercise price and expire October 19, 2036. They vest in one-third increments on each of the first, second and third anniversaries of the grant date, subject to his continued service through each applicable vesting date.
Terrestrial Energy Inc. (IMSR) director Charles G. Pardee purchased 7,500 shares of common stock on October 14, 2026, at $2.95 per share. His directly held position after the purchase was 14,258 shares. The transaction was not reported under a Rule 10b5-1 plan.
Terrestrial Energy Inc. (IMSR) Chief Executive Officer and director Simon Irish purchased 16,900 common shares at $3.007 per share on October 13, 2026. His direct holdings after the purchase were 2,312,834 shares. He also reported indirect holdings of 2,818,520 shares through an LLC and 52,255 shares through an IRA. No Rule 10b5-1 plan is reported.