Simon Irish - Oct 28, 2025 Form 3 Insider Report for Terrestrial Energy Inc. /DE/ (IMSR)

Role
Chief Executive Officer, Director
Signature
/s/ Steven M. Millsap, pursuant to Power of Attorney
Stock symbol
IMSR
Transactions as of
Oct 28, 2025
Transactions value $
$0
Form type
3
Date filed
11/7/2025, 06:33 PM
SEC
View on sec.gov

Reporting Owners (1)

Name Relationship Address Signature Signature date CIK
Irish Simon Chief Executive Officer, Director 2730 W. TYVOLA ROAD, SUITE 100, CHARLOTTE /s/ Steven M. Millsap, pursuant to Power of Attorney 2025-11-07 0002091865

Transactions Table

Type Sym Class Transaction Value $ Shares Change % * Price $ Shares After Date Ownership Footnotes
holding IMSR Common Stock, par value $0.0001 per share ("Common Stock") 2.3M Oct 28, 2025 Direct F1
holding IMSR Common Stock 2.82M Oct 28, 2025 Through LLC F1
holding IMSR Common Stock 52.3K Oct 28, 2025 Through Defined Benefit Plan F1

Derivative Securities (e.g., puts, calls, warrants, options, convertible securities)

Type Sym Class Transaction Value $ Shares Change % * Price $ Shares After Date Underlying Class Amount Exercise Price Ownership Footnotes
holding IMSR Stock Option (Right to Buy) Oct 28, 2025 Common Stock 24.1K $2.01 Direct F2
holding IMSR Stock Option (Right to Buy) Oct 28, 2025 Common Stock 107K $2.24 Direct F2
holding IMSR Stock Option (Right to Buy) Oct 28, 2025 Common Stock 179K $0.20 Direct F2, F7
holding IMSR Stock Option (Right to Buy) Oct 28, 2025 Common Stock 2.28M $0.20 Direct F2, F7
holding IMSR Stock Option (Right to Buy) Oct 28, 2025 Common Stock 179K $0.20 Direct F2, F7
holding IMSR Stock Option (Right to Buy) Oct 28, 2025 Common Stock 2.17M $0.20 Direct F2, F7
holding IMSR Stock Option (Right to Buy) Oct 28, 2025 Common Stock 98.3K $2.24 Direct F3
holding IMSR Stock Option (Right to Buy) Oct 28, 2025 Common Stock 21.9K $2.24 Direct F2
holding IMSR Stock Option (Right to Buy) Oct 28, 2025 Common Stock 26.3K $2.24 Direct F2
holding IMSR Stock Option (Right to Buy) Oct 28, 2025 Common Stock 4.38K $2.24 Direct F2
holding IMSR Stock Option (Right to Buy) Oct 28, 2025 Common Stock 89.4K $2.24 Direct F3
holding IMSR Stock Option (Right to Buy) Oct 28, 2025 Common Stock 179K $2.24 Direct F3
holding IMSR Restricted Stock Units Oct 28, 2025 Common Stock 1.02M Direct F4
holding IMSR Warrants (Right to Buy) Oct 28, 2025 Common Stock 44.7K $2.24 Direct F5
holding IMSR Warrants (Right to Buy) Oct 28, 2025 Common Stock 89.4K $2.24 Through Defined Benefit Plan F5
holding IMSR Contingent Value Right Oct 28, 2025 Common Stock Direct F6
holding IMSR Contingent Value Right Oct 28, 2025 Common Stock Through Defined Benefit Plan F6
* An asterisk sign (*) next to the price indicates that the price is likely invalid.

Explanation of Responses:

Id Content
F1 Upon closing of the business combination (the "Business Combination") between Terrestrial Energy Inc., a Delaware corporation formerly known as HCM II Acquisition Corp. ("New Terrestrial"), and Terrestrial Energy Development Inc., a Delaware corporation formerly known as Terrestrial Energy Inc. ("Legacy Terrestrial"), the reporting person acquired these securities in exchange for the reporting person's securities in Legacy Terrestrial pursuant to the terms and conditions of the Business Combination Agreement, dated as of March 26, 2025, by and among HCM II Acquisition Corp., HCM II Merger Sub Inc. and Legacy Terrestrial.
F2 Consists of options granted pursuant to the Legacy Terrestrial Second Amended and Restated 2024 Stock Option Plan. The options are currently exercisable.
F3 Consists of options granted pursuant to the Legacy Terrestrial Second Amended and Restated 2024 Stock Option Plan. The options vest in one-third increments on each of the first, second and third anniversaries of the grant date, subject to the reporting person's continued service through each applicable vesting date and accelerated vesting in certain events.
F4 Each restricted stock unit represents a contingent right to acquire one share of Common Stock. The restricted stock units vest in one-half increments on each of the first and second anniversaries of the grant date, subject to Mr. Irish's continued employment through each applicable vesting date and accelerated vesting in certain events.
F5 Consists of Legacy Terrestrial warrants to purchase common stock that are currently exercisable.
F6 Consists of contingent value right issued upon conversion of Legacy Terrestrial convertible notes in connection with the Business Combination. Each contingent value right entitles the holder to receive additional shares of Common Stock in the event that the volume weighed average price of the Common Stock for the twenty (20) trading days beginning on the trading day immediately following expiration of the lock-up period contemplated by the applicable Legacy Terrestrial convertible note is less than seventy-five percent (75%) of the redemption price ($7.905).
F7 Price is expressed in Canadian dollars.