SEC FORM 3

Please wait

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

OMB APPROVAL

OMB Number:			3235-0104
Estimated average burden
hours per response:			0.5

1. Name and Address of Reporting Person^*

Sella Roberto Marco

(Last)

(First)

(Middle)

C/O LL FUNDS, LLC, 2400 MARKET STREET

(Street)

PHILADELPHIA

19103

(City)

(State)

(Zip)

2. Date of Event Requiring Statement (Month/Day/Year)
10/29/2025

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

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

Director	X	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)
Common Stock	180,316⁽¹⁾	D
Common Stock	12,244,088⁽¹⁾	I	See footnote⁽²⁾
Common Stock	807,873⁽¹⁾	I	See footnote⁽³⁾
Common Stock	653,334⁽¹⁾	I	See footnote⁽⁴⁾

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)
1. Title of Derivative Security (Instr. 4)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	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)
Warrants to purchase shares of Common Stock	06/12/2024	07/31/2028	Common Stock	539,117⁽¹⁾	$2.24	D
Warrants to purchase shares of Common Stock	06/12/2024	07/31/2028	Common Stock	223,515⁽¹⁾	$2.24	I	See footnote⁽³⁾
Warrants to purchase shares of Common Stock	06/12/2024	07/31/2028	Common Stock	59,902⁽¹⁾	$2.24	I	See footnote⁽⁴⁾
Warrants to purchase shares of Common Stock	02/21/2025	07/31/2028	Common Stock	670,544⁽¹⁾	$2.24	I	See footnote⁽⁴⁾

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 persons 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. Represents securities jointly held by the reporting person and the reporting person's spouse. The reporting person disclaims beneficial ownership of the securities held jointly with his spouse except to the extent of his pecuniary interest therein

3. Represents securities held by Roberto M. Sella 2012 Family Trust (the "Trust"), of which the reporting person is the trustee. The reporting person may be deemed to have voting and dispositive power over the shares held by the Trust. The reporting person disclaims beneficial ownership of the securities held by the Trust except to the extent of his pecuniary interest therein.

4. Represents securities held by LL Charitable Foundation (the "Foundation"), of which the reporting person is the president. The reporting person may be deemed to have voting and dispositive power over the shares held by the Foundation. The reporting person disclaims beneficial ownership of the securities held by the Foundation except to the extent of his pecuniary interest therein.

Remarks:

Exhibits List 24 - Confirming Statement

	/s/ Grant Levine, attorney-in-fact	01/22/2026
	** 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.