# EDGAR Filing Document

**Accession Number:** 0001770593
**File Stem:** 0001193805-26-000145
**Filing Date:** 2026-2
**Character Count:** 9369
**Document Hash:** 65250077863fe2c8e52511edaef54b49
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001193805-26-000145.hdr.sgml**: 20260217

**ACCESSION NUMBER**: 0001193805-26-000145

**CONFORMED SUBMISSION TYPE**: 3/A

**PUBLIC DOCUMENT COUNT**: 2

**CONFORMED PERIOD OF REPORT**: 20251029

**FILED AS OF DATE**: 20260217

**DATE AS OF CHANGE**: 20260217

**REPORTING-OWNER**: 

**OWNER DATA:**
- **COMPANY CONFORMED NAME:** Sella Roberto Marco
- **CENTRAL INDEX KEY:** 0001770593

**ORGANIZATION NAME:**

**FILING VALUES:**
- **FORM TYPE:** 3/A
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 001-42252
- **FILM NUMBER:** 26644944

**MAIL ADDRESS:**
- **STREET 1:** 2400 MARKET STREET
- **STREET 2:** SUITE 302
- **CITY:** PHILADELPHIA
- **STATE:** PA
- **ZIP:** 19103
**ISSUER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Terrestrial Energy Inc. /DE/
- **CENTRAL INDEX KEY:** 0002019804
- **STANDARD INDUSTRIAL CLASSIFICATION:** FABRICATED PLATE WORK (BOILER SHOPS) [3443]
- **ORGANIZATION NAME:** 04 Manufacturing
- **EIN:** 981785406
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**BUSINESS ADDRESS:**
- **STREET 1:** 2730 W. TYVOLA ROAD, SUITE 100
- **CITY:** CHARLOTTE
- **STATE:** NC
- **ZIP:** 28217
- **BUSINESS PHONE:** 203-930-2200

**MAIL ADDRESS:**
- **STREET 1:** 2730 W. TYVOLA ROAD, SUITE 100
- **CITY:** CHARLOTTE
- **STATE:** NC
- **ZIP:** 28217

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** HCM II Acquisition Corp.
- **DATE OF NAME CHANGE:** 20240415

## Ex-24

**Exhibit 24**

**CONFIRMING STATEMENT**

This Statement confirms that the undersigned, Roberto Sella, has authorized and designated Grant Levine to execute and file on the undersigned's behalf all Forms 3, 4, and 5 (including any amendments thereto) that the undersigned may be required to file with the U.S. Securities and Exchange Commission as a result of the undersigned's ownership of or transactions in securities of Terrestrial Energy Inc. (the "Company"). The authority of Grant Levine under this Statement shall continue until the undersigned is no longer required to file Forms 3, 4, and 5 with regard to her ownership of or transactions in securities of the Company, unless earlier revoked in writing. The undersigned acknowledges that Grant Levine is not assuming any of the undersigned's responsibilities to comply with Section 16 of the Securities Exchange Act of 1934.

Date: January 22, 2026

---

| |
|:---|
| /s/ Roberto Sella |
| Roberto Sella |

---

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

## FORM 3/A

### STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

[ ] Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

[ ] Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

---

| | | |
|:---|:---|:---|
| **1. Name and Address of Reporting Person**<sup>*</sup><br>Sella Roberto Marco<br><sub>(Last) (First) (Middle)</sub><br>C/O LL FUNDS, LLC, 2400 MARKET STREET<br><sub>(Street)</sub><br>PHILADELPHIA, PA 19103<br><sub>(City) (State) (Zip)</sub> | **3. Date of Earliest Transaction (Month/Day/Year)**<br>2025-10-29 | **5. Relationship of Reporting Person(s) to Issuer**<br>(Check all applicable)<br>[ ] Director [X] 10% Owner<br>[ ] Officer (give title below) [ ] Other (specify below)<br>_ _ |
| **2. Issuer Name and Ticker or Trading Symbol**<br>Terrestrial Energy Inc. /DE/ [ IMSR ] | **4. If Amendment, Date of Original Filed (Month/Day/Year)**<br>  | **6. Individual or Joint/Group Filing (Check Applicable Line)**<br>[X] Form filed by One Reporting Person<br>[ ] Form filed by More than One Reporting Person |

---

## Table I - Non-Derivative Securities

---

|  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 1. Title of Security | 2. Transaction Date | 2A. Deemed Execution Date | 3. Transaction Code (V) | 3. Transaction Code (V) | 4. Securities Acquired (A) or Disposed of (D) | 4. Securities Acquired (A) or Disposed of (D) | 4. Securities Acquired (A) or Disposed of (D) | 5. Amount of Securities Beneficially Owned | 6. Ownership Form | 7. Nature of Indirect Beneficial Ownership |
| 1. Title of Security | 2. Transaction Date | 2A. Deemed Execution Date | Code | V | Amount | (A) or (D) | Price | 5. Amount of Securities Beneficially Owned | 6. Ownership Form | 7. Nature of Indirect Beneficial Ownership |
| Common Stock |  |  |  |  |  |  |  | 180316<sup>(1)</sup> | D |  |
| Common Stock |  |  |  |  |  |  |  | 12244088<sup>(1)</sup> | I | See footnote<sup>(2)</sup> |
| Common Stock |  |  |  |  |  |  |  | 807873<sup>(1)</sup> | I | See footnote<sup>(3)</sup> |
| Common Stock |  |  |  |  |  |  |  | 653334<sup>(1)</sup> | I | See footnote<sup>(4)</sup> |

---

## Table II - Derivative Securities

---

|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 1. Title of Derivative Security | 2. Conversion or Exercise Price | 3. Transaction Date | 3A. Deemed Execution Date | 4. Transaction Code (V) | 4. Transaction Code (V) | 5. Number of Derivative Securities Acquired (A) or Disposed of (D) | 5. Number of Derivative Securities Acquired (A) or Disposed of (D) | 6. Date Exercisable and Expiration Date | 6. Date Exercisable and Expiration Date | 7. Title and Amount of Underlying Securities | 7. Title and Amount of Underlying Securities | 8. Price of Derivative Security | 9. Number of Derivative Securities Beneficially Owned | 10. Ownership Form | 11. Nature of Indirect Beneficial Ownership |
| 1. Title of Derivative Security | 2. Conversion or Exercise Price | 3. Transaction Date | 3A. Deemed Execution Date | Code | V | (A) | (D) | Date Exercisable | Expiration Date | Title | Amount or Number of Shares | 8. Price of Derivative Security | 9. Number of Derivative Securities Beneficially Owned | 10. Ownership Form | 11. Nature of Indirect Beneficial Ownership |
| Warrants to purchase shares of Common Stock | $2.24 |  |  |  |  |  |  | 2024-06-12 | 2028-07-31 | Common Stock | 539117<sup>(1)</sup> |  |  | D |  |
| Warrants to purchase shares of Common Stock | $2.24 |  |  |  |  |  |  | 2024-06-12 | 2028-07-31 | Common Stock | 223515<sup>(1)</sup> |  |  | I | See footnote<sup>(2)(5)</sup> |
| Warrants to purchase shares of Common Stock | $2.24 |  |  |  |  |  |  | 2024-06-12 | 2028-07-31 | Common Stock | 59902<sup>(1)</sup> |  |  | I | See footnote<sup>(3)(5)</sup> |
| Warrants to purchase shares of Common Stock | $2.24 |  |  |  |  |  |  | 2025-02-21 | 2028-07-31 | Common Stock | 670544<sup>(1)</sup> |  |  | I | See footnote<sup>(3)(5)</sup> |

---

### Footnotes:

(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.

(5) Amendment made solely to correct the footnote designations in Table II, Item 6.

**Remarks:**
Exhibits List
24 - Confirming Statement

**Signature:** /s/ Grant Levine, attorney-in-fact  
**Date:** 2026-02-17

### Remarks:

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 4 (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.**