IMSR CEO Form 3 details direct, indirect and derivative holdings

Rhea-AI Filing Summary

Terrestrial Energy Inc. (IMSR) filed a Form 3 disclosing its CEO and director’s initial beneficial ownership. Reported common stock holdings include 2,295,934 shares direct, 2,818,520 shares indirect through an LLC, and 52,255 shares indirect through a defined benefit plan.

Derivative holdings include multiple stock options (some currently exercisable) with stated exercise prices such as $2.237, $2.0133, and $0.2013 (the latter expressed in Canadian dollars). The filing lists RSUs for 1,023,160 shares that vest in two equal installments on the first and second anniversaries of grant, warrants for 44,703 (direct) and 89,406 (indirect via the plan) shares, and contingent value rights tied to a $7.905 redemption price threshold. The positions reflect awards and exchanges completed in connection with the closing of a business combination.

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^*

Irish Simon

(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
X	Officer (give title below)		Other (specify below)
	Chief Executive Officer

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)
Common Stock, par value $0.0001 per share ("Common Stock")	2,295,934(1)	D
Common Stock	2,818,520(1)	I	Through LLC
Common Stock	52,255(1)	I	Through Defined Benefit Plan

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)	(2)	06/16/2038	Common Stock	24,140	$2.0133	D
Stock Option (Right to Buy)	(2)	01/24/2031	Common Stock	107,288	$2.237	D
Stock Option (Right to Buy)	(2)	12/31/2029	Common Stock	178,812	$0.2013(7)	D
Stock Option (Right to Buy)	(2)	12/31/2034	Common Stock	2,279,850	$0.2013(7)	D
Stock Option (Right to Buy)	(2)	12/31/2028	Common Stock	178,812	$0.2013(7)	D
Stock Option (Right to Buy)	(2)	12/31/2034	Common Stock	2,172,563	$0.2013(7)	D
Stock Option (Right to Buy)	05/19/2023(3)	05/19/2032	Common Stock	98,347	$2.237	D
Stock Option (Right to Buy)	(2)	01/01/2043	Common Stock	21,905	$2.237	D
Stock Option (Right to Buy)	(2)	01/01/2044	Common Stock	26,286	$2.237	D
Stock Option (Right to Buy)	(2)	01/01/2045	Common Stock	4,381	$2.237	D
Stock Option (Right to Buy)	04/01/2024(3)	04/01/2043	Common Stock	89,406	$2.237	D
Stock Option (Right to Buy)	07/14/2024(3)	07/14/2033	Common Stock	178,812	$2.237	D
Restricted Stock Units	10/21/2026(4)	10/21/2035	Common Stock	1,023,160	(4)	D
Warrants (Right to Buy)	(5)	07/31/2028	Common Stock	44,703	$2.237	D
Warrants (Right to Buy)	(5)	07/31/2028	Common Stock	89,406	$2.237	I	Through Defined Benefit Plan
Contingent Value Right	(6)	(6)	Common Stock	(6)	(6)	D
Contingent Value Right	(6)	(6)	Common Stock	(6)	(6)	I	Through Defined Benefit Plan

Explanation of Responses:

1. 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.

2. Consists of options granted pursuant to the Legacy Terrestrial Second Amended and Restated 2024 Stock Option Plan. The options are currently exercisable.

3. 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.

4. 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.

5. Consists of Legacy Terrestrial warrants to purchase common stock that are currently exercisable.

6. 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).

7. Price is expressed in Canadian dollars.

	/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.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

FAQ

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

An initial statement of beneficial ownership by the CEO and director, covering direct, indirect, and derivative holdings.

How many common shares does the IMSR CEO hold directly and indirectly?

Direct: 2,295,934 shares. Indirect: 2,818,520 shares (through an LLC) and 52,255 shares (through a defined benefit plan).

What derivative securities are listed for IMSR’s CEO?

Multiple stock options (some currently exercisable), RSUs for 1,023,160 shares, warrants of 44,703 (direct) and 89,406 (indirect), and contingent value rights.

What are key exercise prices and currency notes on the options?

Exercise prices include $2.237, $2.0133, and $0.2013, with the $0.2013 price stated in Canadian dollars.

How do the RSUs for IMSR vest?

They vest in two equal installments on the first and second anniversaries of the grant date, subject to continued employment and certain accelerations.

What triggers the contingent value rights (CVRs)?

Additional shares may be issued if the 20-day VWAP after the lock-up is less than 75% of the $7.905 redemption price.

What corporate event explains these holdings?

Securities were received or exchanged at the closing of a business combination between New Terrestrial and Legacy Terrestrial.