# EDGAR Filing Document

**Accession Number:** 0001770593
**File Stem:** 0001193805-26-000054
**Filing Date:** 2026-1
**Character Count:** 15605
**Document Hash:** 3def832e6fd8963ff400603fdeafae57
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001193805-26-000054.hdr.sgml**: 20260122

**ACCESSION NUMBER**: 0001193805-26-000054

**CONFORMED SUBMISSION TYPE**: SCHEDULE 13G

**PUBLIC DOCUMENT COUNT**: 2

**FILED AS OF DATE**: 20260122

**DATE AS OF CHANGE**: 20260122

**SUBJECT COMPANY**: 

**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

**FILING VALUES:**
- **FORM TYPE:** SCHEDULE 13G
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 005-94602
- **FILM NUMBER:** 26552479

**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
**FILED BY**: 

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

**ORGANIZATION NAME:**

**FILING VALUES:**
- **FORM TYPE:** SCHEDULE 13G

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

## Exhibit 99.1

**Exhibit 99.1**

<u>Joint Filer Agreement</u>

The undersigned hereby agree and acknowledge that the statement containing the information required by Schedule 13G, to which this agreement is attached as an exhibit, is filed on behalf of each of them, and any amendments or supplements to the Schedule 13G shall also be filed on behalf of each of them.

January 22, 2026

---

| | |
|:---|:---|
| By: | /s/ Roberto Sella |
| Name: | Roberto Sella |

---

**Roberto M. Sella 2012 Family Trust**

---

| | |
|:---|:---|
| By: | /s/ Roberto Sella |
| Name: | Roberto Sella |
| Title: | Grantor; Authorized Party |

---

**LL Charitable Foundation**

---

| | |
|:---|:---|
| By: | /s/ Roberto Sella |
| Name: | Roberto Sella |
| Title: | President; Director |

---

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

## SCHEDULE 13G

### Under the Securities Exchange Act of 1934

**Issuer:** Terrestrial Energy Inc.

**Title of Class of Securities:** Common Stock, par value $0.0001 per share

**CUSIP Number:** 881454102

**Date of Event Which Requires Filing of this Statement:** 10/29/2025

**Check the appropriate box to designate the rule pursuant to which this Schedule is filed:**

- [ ] Rule 13d-1(b)

- [x] Rule 13d-1(c)

- [ ] Rule 13d-1(d)

---

| 1. | Names of Reporting Persons<br>Roberto Marco Sella | Names of Reporting Persons<br>Roberto Marco Sella |
|:---|:---|:---|:---|
| 2. | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] |
| 3. | SEC Use Only | SEC Use Only |
| 4. | Citizenship or Place of Organization<br>X1 | Citizenship or Place of Organization<br>X1 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 5. | Sole Voting Power<br>719433.00 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 6. | Shared Voting Power<br>14659256.00 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 7. | Sole Dispositive Power<br>719433.00 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 8. | Shared Dispositive Power<br>14659256.00 |
| 9. | Aggregate Amount Beneficially Owned by Each Reporting Person<br>15378689.00 | Aggregate Amount Beneficially Owned by Each Reporting Person<br>15378689.00 |
| 10. | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] |
| 11. | Percent of Class Represented by Amount in Row (9)<br>14.34% | Percent of Class Represented by Amount in Row (9)<br>14.34% |
| 12. | Type of Reporting Person (See Instructions)<br>IN | Type of Reporting Person (See Instructions)<br>IN |

**Comment for Type of Reporting Person:** Based on 81,771,423 shares of common stock, par value $0.0001 per share ("Shares"), of Terrestrial Energy Inc., a Delaware corporation, (the "Issuer") outstanding as of December 15, 2025 and 24,011,029 Shares issuable upon the conversion of common shares and preferred shares of Terrestrial Energy Canada (Exchange) Inc. ("Exchange Shares"), as disclosed in Amendment No. 1 to the Issuer's Registration Statement on Form S-1 (File No. 333-291796) as declared effective by the Securities Exchange Commission (the "Commission") on December 23, 2025. The aggregation of the outstanding Shares and the Exchange Shares is based solely upon statements and disclosures made by the Issuer.

---

| 1. | Names of Reporting Persons<br>Roberto M. Sella 2012 Family Trust | Names of Reporting Persons<br>Roberto M. Sella 2012 Family Trust |
|:---|:---|:---|:---|
| 2. | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] |
| 3. | SEC Use Only | SEC Use Only |
| 4. | Citizenship or Place of Organization<br>PA | Citizenship or Place of Organization<br>PA |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 5. | Sole Voting Power<br>0.00 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 6. | Shared Voting Power<br>1538319.00 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 7. | Sole Dispositive Power<br>0.00 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 8. | Shared Dispositive Power<br>1538319.00 |
| 9. | Aggregate Amount Beneficially Owned by Each Reporting Person<br>1538319.00 | Aggregate Amount Beneficially Owned by Each Reporting Person<br>1538319.00 |
| 10. | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] |
| 11. | Percent of Class Represented by Amount in Row (9)<br>1.44% | Percent of Class Represented by Amount in Row (9)<br>1.44% |
| 12. | Type of Reporting Person (See Instructions)<br>OO | Type of Reporting Person (See Instructions)<br>OO |

**Comment for Type of Reporting Person:** Based on 81,771,423 Shares of the Issuer outstanding as of December 15, 2025 and 24,011,029 Shares issuable upon the conversion of the Exchange Shares, as disclosed in Amendment No. 1 to the Issuer's Registration Statement on Form S-1 (File No. 333-291796) as declared effective by the Commission on December 23, 2025. The aggregation of the outstanding Shares and the Exchange Shares is based solely upon statements and disclosures made by the Issuer.

---

| 1. | Names of Reporting Persons<br>LL Charitable Foundation | Names of Reporting Persons<br>LL Charitable Foundation |
|:---|:---|:---|:---|
| 2. | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] |
| 3. | SEC Use Only | SEC Use Only |
| 4. | Citizenship or Place of Organization<br>PA | Citizenship or Place of Organization<br>PA |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 5. | Sole Voting Power<br>0.00 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 6. | Shared Voting Power<br>653334.00 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 7. | Sole Dispositive Power<br>0.00 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 8. | Shared Dispositive Power<br>653334.00 |
| 9. | Aggregate Amount Beneficially Owned by Each Reporting Person<br>653334.00 | Aggregate Amount Beneficially Owned by Each Reporting Person<br>653334.00 |
| 10. | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] |
| 11. | Percent of Class Represented by Amount in Row (9)<br>0.62% | Percent of Class Represented by Amount in Row (9)<br>0.62% |
| 12. | Type of Reporting Person (See Instructions)<br>OO | Type of Reporting Person (See Instructions)<br>OO |

**Comment for Type of Reporting Person:** Based on 81,771,423 Shares of the Issuer outstanding as of December 15, 2025 and 24,011,029 Shares issuable upon the conversion of the Exchange Shares, as disclosed in Amendment No. 1 to the Issuer's Registration Statement on Form S-1 (File No. 333-291796) as declared effective by the Commission on December 23, 2025. The aggregation of the outstanding Shares and the Exchange Shares is based solely upon statements and disclosures made by the Issuer.

---

**Item 1(a). Name of Issuer:**
Terrestrial Energy Inc.

**Item 1(b). Address of Issuer's Principal Executive Offices:**
2730 W. Tyvola Road, Suite 100, Charlotte, NC 28217

**Item 2(a). Name of Person Filing:**
This statement is filed on behalf of the following persons (collectively, the "Reporting Persons"):

(i) Roberto Sella, an individual;

(ii) Roberto M. Sella 2012 Family Trust, (the "Trust"); and

(iii) LL Charitable Foundation (the "Foundation").

This Statement relates to Common Stock, par value $0.0001 per share (the "Shares") of the Issuer held by Roberto Sella, the Trust, and the Foundation. Mr. Sella is a principal owner and controlling person of the Trust and the Foundation, and in such capacity, may be deemed to beneficially own the Shares held by the Trust and the Foundation, respectively.

**Item 2(b). Address of Principal Business Office:**
2400 Market Street, Suite 302
Philadelphia, PA, 19103

**Item 2(c). Citizenship:**
(i) Roberto Sella, is a United States citizen;

(ii) the Trust is organized under the laws of Pennsylvania; and

(iii) the Foundation is organized under the laws of Pennsylvania.

**Item 2(d). Title of Class of Securities:**
Common Stock, par value $0.0001 per share

**Item 2(e). CUSIP Number:**
881454102

**Item 3. If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:**

(a) [ ] Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o).

(b) [ ] Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c).

(c) [ ] Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c).

(d) [ ] Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8).

(e) [ ] An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);

(f) [ ] An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);

(g) [ ] A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);

(h) [ ] A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);

(i) [ ] A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);

(j) [ ] A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), if filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:

(k) [ ] Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).

**Item 4. Ownership:**

**(a) Amount beneficially owned:**

The Reporting Persons held securities of Terrestrial Energy Inc., a Delaware corporation ("Old Terrestrial"). On October 29, 2025, Old Terrestrial consummated a business combination with the Issuer (the "Business Combination"), and the Reporting Persons received securities of the Issuer at the closing of the Business Combination. The securities reported on this statement include (i) 180,316 Shares held directly by Mr. Sella; (ii) 539,117 Shares issuable upon the exercise of warrants held by Mr. Sella, having an exercise price of $2.24 per share; (iii) 12,244,088 Shares held jointly by Mr. Sella and Mr. Sella's spouse (iv) 223,515 Shares issuable upon the exercise of warrants held jointly by Mr. Sella and his spouse, having an exercise price of $2.24 per share; (v) 807,873 Shares held by the Trust; (vi) 730,446 Shares issuable upon the exercise of warrants held by the Trust, having an exercise price of $2.24 per share; and (vii) 653,334 Shares held by the Foundation.

**(b) Percent of class:**

The following percentages are based on 81,771,423 Shares of the Issuer outstanding as of December 15, 2025 and 24,011,029 Shares issuable upon the conversion of the Exchange Shares. The aggregation of the outstanding Shares and the Exchange Shares is based solely upon statements and disclosures made by the Issuer.
(i) Mr. Sella: 12.38%
(ii) the Trust: 1.44%
(iii) the Foundation: 0.62%

**(c) Number of shares as to which the person has:**

**(i) Sole power to vote or to direct the vote:**

(i) Mr. Sella: 719,433
(ii) the Trust: 0
(iii) the Foundation 0

**(ii) Shared power to vote or to direct the vote:**

(i) Mr. Sella: 14,659,256
(ii) the Trust: 1,538,319
(iii) the Foundation: 653,334

**(iii) Sole power to dispose or to direct the disposition of:**

(i) Mr. Sella: 719,433
(ii) the Trust: 0
(iii) the Foundation 0

**(iv) Shared power to dispose or to direct the disposition of:**

(i) Mr. Sella: 14,659,256
(ii) the Trust: 1,538,319
(iii) the Foundation: 653,334

**Item 5. Ownership of Five Percent or Less of a Class.**

[x] If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than five percent of the class of securities, check the following.

**Item 6. Ownership of More than 5 Percent on Behalf of Another Person.**

See items 2 and 4 of this statement for more information.

**Item 7. Identification and Classification of the Subsidiary**

Not Applicable

**Item 8. Identification and Classification of Members of the Group**

Not Applicable

**Item 9. Notice of Dissolution of Group**

Not Applicable

**Item 10. Certification:**

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11.

### SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

**Roberto Marco Sella**

**Date:** 01/22/2026

**By:** /s/ Roberto Sella

**Name & Title:** Roberto Sella

**Roberto M. Sella 2012 Family Trust**

**Date:** 01/22/2026

**By:** /s/ Roberto Sella

**Name & Title:** Roberto Sella, as Authorized Party

**LL Charitable Foundation**

**Date:** 01/22/2026

**By:** /s/ Roberto Sella

**Name & Title:** Roberto Sella, its President and Director