IMSR insider filing lists 134,109 options at $2.237, expiring 2043

Rhea-AI Filing Summary

Terrestrial Energy Inc. (IMSR) reported an insider ownership update via Form 3 following an event on 10/28/2025. The filing shows a director holds stock options to purchase 134,109 shares of common stock at an exercise price of $2.237 per share.

The options are listed as exercisable beginning 01/29/2024 and expire on 01/29/2043. According to the plan terms, they vest in one-third increments on each of the first, second, and third anniversaries of the grant date, subject to continued service. No non-derivative holdings were reported in Table I, and the reported derivative position is held directly.

SEC Form 3

FORM 3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person^*

JOHNSON WILLIAM D

(Last) (First) (Middle)

2730 W. TYVOLA ROAD, SUITE 100

(Street)

CHARLOTTE NC 28217

(City) (State) (Zip)

2. Date of Event Requiring Statement (Month/Day/Year)
10/28/2025

3. Issuer Name and Ticker or Trading Symbol
Terrestrial Energy Inc. /DE/ [ IMSR ]

4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

5. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Beneficially Owned
1. Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Stock Option (Right to Buy)	01/29/2024(1)	01/29/2043	Common Stock	134,109	$2.237	D

Explanation of Responses:

1. Consists of options granted pursuant to the Terrestrial Energy Inc. 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.

Remarks:

Exhibit List - Exhibit 24.1 - Power of Attorney

	/s/ Steven M. Millsap, pursuant to Power of Attorney	11/07/2025
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 5 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
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FAQ

What did Terrestrial Energy (IMSR) disclose in this Form 3?

A director reported stock options covering 134,109 shares at an exercise price of $2.237 per share.

What is the vesting schedule for the reported IMSR options?

They vest in one-third increments on each of the first, second, and third anniversaries of the grant date, subject to continued service.

When do the IMSR options become exercisable and when do they expire?

They are listed as exercisable from 01/29/2024 and expire on 01/29/2043.

What was the event date triggering this insider filing for IMSR?

The event date requiring the statement was 10/28/2025.

Does the Form 3 show any non-derivative IMSR share ownership?

No non-derivative securities were reported in Table I.

Is the reported IMSR options ownership direct or indirect?

The options are held directly.

Under which plan were the options granted?

They were granted under the Terrestrial Energy Inc. Second Amended and Restated 2024 Stock Option Plan.