IMSR

SEC source: 0001193125-26-421089 · ownership.xml · nonDerivative · entry 1

Irish Simon · CIK 0002091865 · Director · Chief Executive Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 2,312,834

SEC source: 0001193125-26-420002 · ownership.xml · nonDerivative · entry 1

BUCKMAN FREDERICK W · CIK 0001144845 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 18,669

SEC source: 0001193125-26-328808 · ownership.xml · derivative · entry 1

Cowan Pamela Beth · CIK 0002147170 · EVP, Engineering

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 299,401

Underlying: Common Stock · 299,401 shares

Expires 2036-07-29

F1 · derivative.exercise_date: Consists of options granted pursuant to the Terrestrial Energy Inc. 2025 Equity Incentive 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.

SEC source: 0001193125-26-318233 · ownership.xml · derivative · entry 1

McCarthy Kathryn Ann · CIK 0002146932 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 2,049

Underlying: Common Stock · 2,049 shares

Expires not disclosed

F1 · derivative.exercise_price: Each restricted stock unit represents a contingent right to acquire one share of Common Stock.

F2 · derivative.exercise_date: Consists of restricted stock units granted pursuant to the Terrestrial Energy Inc. 2025 Equity Incentive Plan. The restricted stock units vest in full on December 31, 2026, subject to the reporting person's continued service through the vesting date.

F2 · derivative.expiration_date: Consists of restricted stock units granted pursuant to the Terrestrial Energy Inc. 2025 Equity Incentive Plan. The restricted stock units vest in full on December 31, 2026, subject to the reporting person's continued service through the vesting date.

SEC source: 0001193125-26-155212 · ownership.xml · derivative · entry 2

Thrasher Brian Patrick · CIK 0002091861 · Chief Financial Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 58,236

Underlying: Common Stock · 58,236 shares

Expires 2036-04-12

F3 · derivative.exercise_date: Consists of options granted pursuant to the Terrestrial Energy Inc. 2025 Equity Incentive 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.

SEC source: 0001193125-26-155212 · ownership.xml · derivative · entry 1

Thrasher Brian Patrick · CIK 0002091861 · Chief Financial Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 49,917

Underlying: Common Stock · 49,917 shares

Expires not disclosed

F1 · derivative.exercise_price: Each restricted stock unit represents a contingent right to acquire one share of Common Stock.

F2 · derivative.exercise_date: Consists of restricted stock units granted pursuant to the Terrestrial Energy Inc. 2025 Equity Incentive Plan. The restricted stock units 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.

F2 · derivative.expiration_date: Consists of restricted stock units granted pursuant to the Terrestrial Energy Inc. 2025 Equity Incentive Plan. The restricted stock units 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.

SEC source: 0001193125-26-155213 · ownership.xml · derivative · entry 1

Millsap Steven M. · CIK 0002091729 · General Counsel

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 49,917

Underlying: Common Stock · 49,917 shares

Expires not disclosed

F1 · derivative.exercise_price: Each restricted stock unit represents a contingent right to acquire one share of Common Stock.

F2 · derivative.exercise_date: Consists of restricted stock units granted pursuant to the Terrestrial Energy Inc. 2025 Equity Incentive Plan. The restricted stock units 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.

F2 · derivative.expiration_date: Consists of restricted stock units granted pursuant to the Terrestrial Energy Inc. 2025 Equity Incentive Plan. The restricted stock units 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.

SEC source: 0001193125-26-155211 · ownership.xml · derivative · entry 1

Smith William F. · CIK 0002092633 · Chief Operating Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 32,787

Underlying: Common Stock · 32,787 shares

Expires 2036-04-12

F1 · derivative.exercise_date: Consists of options granted pursuant to the Terrestrial Energy Inc. 2025 Equity Incentive 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.

SEC source: 0001193125-26-155209 · ownership.xml · derivative · entry 3

LeBlanc David Michael · CIK 0002092979 · Director · Chief Technology Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 32,787

Underlying: Common Stock · 32,787 shares

Expires 2036-04-12

F1 · derivative.exercise_date: Consists of options granted pursuant to the Terrestrial Energy Inc. 2025 Equity Incentive 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.

SEC source: 0000950138-25-000045 · form4.xml · derivative · entry 2

BUCKMAN FREDERICK W · CIK 0001144845 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 7,879

Underlying: Common Stock · 1,176 shares

Expires not disclosed

F1 · derivative.exercise_price: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

F1 · derivative.exercise_date: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

F1 · derivative.expiration_date: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

SEC source: 0000950138-25-000045 · form4.xml · derivative · entry 1

BUCKMAN FREDERICK W · CIK 0001144845 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 6,703

Underlying: Common Stock · 6,703 shares

Expires not disclosed

F1 · derivative.exercise_price: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

F1 · derivative.exercise_date: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

F1 · derivative.expiration_date: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

SEC source: 0000950138-25-000043 · form4.xml · derivative · entry 2

JOHNSON WILLIAM D · CIK 0001183048 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 7,585

Underlying: Common Stock · 1,720 shares

Expires not disclosed

F1 · derivative.exercise_price: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

F1 · derivative.exercise_date: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

F1 · derivative.expiration_date: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

SEC source: 0000950138-25-000043 · form4.xml · derivative · entry 1

JOHNSON WILLIAM D · CIK 0001183048 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 5,865

Underlying: Common Stock · 5,865 shares

Expires not disclosed

F1 · derivative.exercise_price: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

F1 · derivative.exercise_date: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

F1 · derivative.expiration_date: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

SEC source: 0000950138-25-000041 · form4.xml · derivative · entry 2

Jones Robert Wood · CIK 0001398160 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 6,894

Underlying: Common Stock · 1,029 shares

Expires not disclosed

F1 · derivative.exercise_price: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

F1 · derivative.exercise_date: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

F1 · derivative.expiration_date: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

SEC source: 0000950138-25-000041 · form4.xml · derivative · entry 1

Jones Robert Wood · CIK 0001398160 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 5,865

Underlying: Common Stock · 5,865 shares

Expires not disclosed

F1 · derivative.exercise_price: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

F1 · derivative.exercise_date: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

F1 · derivative.expiration_date: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

SEC source: 0000950138-25-000039 · form4.xml · derivative · entry 2

Hill David John · CIK 0002091721 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 3,940

Underlying: Common Stock · 588 shares

Expires not disclosed

F1 · derivative.exercise_price: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

F1 · derivative.exercise_date: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

F1 · derivative.expiration_date: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

SEC source: 0000950138-25-000039 · form4.xml · derivative · entry 1

Hill David John · CIK 0002091721 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 3,352

Underlying: Common Stock · 3,352 shares

Expires not disclosed

F1 · derivative.exercise_price: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

F1 · derivative.exercise_date: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

F1 · derivative.expiration_date: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

SEC source: 0000950138-25-000036 · form4.xml · derivative · entry 2

Pardee Charles G · CIK 0001544340 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 5,909

Underlying: Common Stock · 882 shares

Expires not disclosed

F1 · derivative.exercise_price: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

F1 · derivative.exercise_date: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

F1 · derivative.expiration_date: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

SEC source: 0000950138-25-000036 · form4.xml · derivative · entry 1

Pardee Charles G · CIK 0001544340 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 5,027

Underlying: Common Stock · 5,027 shares

Expires not disclosed

F1 · derivative.exercise_price: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

F1 · derivative.exercise_date: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

F1 · derivative.expiration_date: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

SEC source: 0000950138-25-000034 · form4.xml · derivative · entry 2

MacDiarmid John Hugh · CIK 0002092518 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 6,894

Underlying: Common Stock · 1,029 shares

Expires not disclosed

F1 · derivative.exercise_price: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

F1 · derivative.exercise_date: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

F1 · derivative.expiration_date: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

SEC source: 0000950138-25-000034 · form4.xml · derivative · entry 1

MacDiarmid John Hugh · CIK 0002092518 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 5,865

Underlying: Common Stock · 5,865 shares

Expires not disclosed

F1 · derivative.exercise_price: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

F1 · derivative.exercise_date: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

F1 · derivative.expiration_date: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

SEC source: 0001213900-25-124579 · ownership.xml · derivative · entry 2

Matthews Shawn · CIK 0001855118 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 4,925

Underlying: Common Stock · 735 shares

Expires not disclosed

F1 · derivative.exercise_price: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

F1 · derivative.exercise_date: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

F1 · derivative.expiration_date: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

SEC source: 0001213900-25-124579 · ownership.xml · derivative · entry 1

Matthews Shawn · CIK 0001855118 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 4,190

Underlying: Common Stock · 4,190 shares

Expires not disclosed

F1 · derivative.exercise_price: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

F1 · derivative.exercise_date: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

F1 · derivative.expiration_date: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

SEC source: 0000950138-26-000002 · form4a.xml · derivative · entry 1

JOHNSON WILLIAM D · CIK 0001183048 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 6,894

Underlying: Common Stock · 1,029 shares

Expires not disclosed

F1 · derivative.exercise_price: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

F2 · shares: On December 22, 2025, the Reporting Person filed a Form 4 in which there was an inadvertent error in the number of reported restricted stock units.

F1 · derivative.exercise_date: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

F1 · derivative.expiration_date: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026.

SEC source: 0001213900-25-110214 · ownership.xml · derivative · entry 3

Matthews Shawn · CIK 0001855118 · Director

HCM Investor Holdings II, LLC · CIK 0002019800 · Former 10% Holder

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See Footnote

Disclosed balance after: 775,000

Underlying: Common Stock, par value $0.0001 per share · 3,500,000 shares

Expires 2030-10-28

F1 · price: On November 6, 2025, HCM Investor Holdings II, LLC (the "Sponsor") distributed an aggregate of 5,675,000 shares of common stock, par value $0.0001 per share of the Issuer ("Common Stock") and 4,275,000 Warrants, convertible to 4,275,000 shares of Common Stock, to its members as a distribution for no consideration in accordance with the terms of the Sponsor's limited liability company agreement. 2,755,000 shares of Common Stock and 775,000 Warrants were distributed to Shawn Matthews on such basis. Under Rule 16a-13 promulgated under the Securities Exchange Act of 1934, as a change in form of beneficial ownership, the reported distribution by the Sponsor (as it relates to Mr. Matthews' deemed beneficial ownership of the securities held by the Sponsor) to its members from the Sponsor, were exempt from Section 16 of the Securities Exchange Act of 1934.

F2 · ownership.nature: Shawn Matthews is the record holder of such securities. Shawn Matthews is the sole Managing Member of HCM Investor Holdings II, LLC and shares voting and investment discretion with respect to the securities held by HCM Investor Holdings II, LLC.

SEC source: 0001213900-25-110214 · ownership.xml · nonDerivative · entry 1

Matthews Shawn · CIK 0001855118 · Director

HCM Investor Holdings II, LLC · CIK 0002019800 · Former 10% Holder

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See Footnote

Disclosed balance after: 2,755,000

F1 · price: On November 6, 2025, HCM Investor Holdings II, LLC (the "Sponsor") distributed an aggregate of 5,675,000 shares of common stock, par value $0.0001 per share of the Issuer ("Common Stock") and 4,275,000 Warrants, convertible to 4,275,000 shares of Common Stock, to its members as a distribution for no consideration in accordance with the terms of the Sponsor's limited liability company agreement. 2,755,000 shares of Common Stock and 775,000 Warrants were distributed to Shawn Matthews on such basis. Under Rule 16a-13 promulgated under the Securities Exchange Act of 1934, as a change in form of beneficial ownership, the reported distribution by the Sponsor (as it relates to Mr. Matthews' deemed beneficial ownership of the securities held by the Sponsor) to its members from the Sponsor, were exempt from Section 16 of the Securities Exchange Act of 1934.

F2 · ownership.nature: Shawn Matthews is the record holder of such securities. Shawn Matthews is the sole Managing Member of HCM Investor Holdings II, LLC and shares voting and investment discretion with respect to the securities held by HCM Investor Holdings II, LLC.

SEC source: 0001213900-25-104323 · ownership.xml · derivative · entry 1

Irish Simon · CIK 0002091865 · Director · Chief Executive Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 166,298

Underlying: Common Stock · 166,298 shares

Expires not disclosed

F1 · derivative.exercise_price: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. The restricted stock units vest pro rata over a three year period following the grant date.

F1 · derivative.exercise_date: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. The restricted stock units vest pro rata over a three year period following the grant date.

F1 · derivative.expiration_date: Each restricted stock unit represents a contingent right to acquire one share of Common Stock. The restricted stock units vest pro rata over a three year period following the grant date.

SEC source: 0001213900-25-104334 · ownership.xml · nonDerivative · entry 1

Connor Michael J · CIK 0002029946 · Former Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 25,000

F1 · price: Upon closing of the business combination (the "Business Combination") between the Issuer (which was formerly known as HCM II Acquisition Corp. or "HCM II") and Terrestrial Energy Inc. ("Terrestrial") the reporting person acquired these securities in exchange for the reporting person's securities in Terrestrial pursuant to the terms and conditions of the business combination agreement, by and among HCM, Terrestrial and HCM II Merger Sub Inc. (the "BCA"). The reporting person resigned as a director of HCM II upon the closing of the Business Combination.

SEC source: 0001213900-25-104333 · ownership.xml · nonDerivative · entry 1

Brenner Andrew Scott · CIK 0002030321 · Former Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 25,000

F1 · price: Upon closing of the business combination (the "Business Combination") between the Issuer (which was formerly known as HCM II Acquisition Corp. or "HCM II") and Terrestrial Energy Inc. ("Terrestrial") the reporting person acquired these securities in exchange for the reporting person's securities in Terrestrial pursuant to the terms and conditions of the business combination agreement, by and among HCM, Terrestrial and HCM II Merger Sub Inc. (the "BCA"). The reporting person resigned as a director of HCM II upon the closing of the Business Combination.

SEC source: 0001213900-25-104331 · ownership.xml · derivative · entry 4

Matthews Shawn · CIK 0001855118 · Director

HCM Investor Holdings II, LLC · CIK 0002019800 · Former 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See Footnote

Disclosed balance after: 1,267,599

Underlying: Common Stock, par value $0.0001 per share · 1,267,599 shares

Expires 2030-10-28

F4 · ownership.nature: Mr. Matthews is the sole managing member of Hondo Holdings LLC, which is registered owner of these warrants, and Mr. Matthews holds voting and investment power with respect to warrants held of record by Hondo Holdings LLC.

SEC source: 0001213900-25-104331 · ownership.xml · derivative · entry 3

Matthews Shawn · CIK 0001855118 · Director

HCM Investor Holdings II, LLC · CIK 0002019800 · Former 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See Footnote

Disclosed balance after: 4,275,000

Underlying: Common Stock, par value $0.0001 per share · 4,275,000 shares

Expires 2030-10-28

F2 · ownership.nature: Mr. Matthews is the sole managing member of HCM Investor Holdings II, LLC (the "Sponsor"), which is registered owner of these shares and warrants, and Mr. Matthews holds voting and investment power with respect to shares and warrants held of record by the Sponsor.

SEC source: 0001213900-25-104331 · ownership.xml · nonDerivative · entry 2

Matthews Shawn · CIK 0001855118 · Director

HCM Investor Holdings II, LLC · CIK 0002019800 · Former 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 533,514

F3 · price: Upon closing of 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 BCA.

SEC source: 0001213900-25-104331 · ownership.xml · nonDerivative · entry 1

Matthews Shawn · CIK 0001855118 · Director

HCM Investor Holdings II, LLC · CIK 0002019800 · Former 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See Footnote

Disclosed balance after: 5,675,000

F1 · price: Upon closing of the business combination (the "Business Combination") between the Issuer (which was formerly known as HCM II Acquisition Corp. or "HCM II") and Terrestrial Energy Inc. ("Terrestrial") the reporting person acquired these securities in exchange for the reporting person's securities in Terrestrial pursuant to the terms and conditions of the business combination agreement, dated March 26, 2025 and as amended on October 28, 2025, by and among HCM II, Terrestrial and HCM II Merger Sub Inc. (the "BCA"). The reporting person resigned as an officer of HCM II upon the closing of the Business Combination.

F2 · ownership.nature: Mr. Matthews is the sole managing member of HCM Investor Holdings II, LLC (the "Sponsor"), which is registered owner of these shares and warrants, and Mr. Matthews holds voting and investment power with respect to shares and warrants held of record by the Sponsor.

SEC source: 0001213900-25-104332 · ownership.xml · nonDerivative · entry 1

Loveless Jacob · CIK 0001855174 · Former Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 25,000

F1 · price: Upon closing of the business combination (the "Business Combination") between the Issuer (which was formerly known as HCM II Acquisition Corp. or "HCM II") and Terrestrial Energy Inc. ("Terrestrial") the reporting person acquired these securities in exchange for the reporting person's securities in Terrestrial pursuant to the terms and conditions of the business combination agreement, by and among HCM, Terrestrial and HCM II Merger Sub Inc. (the "BCA"). The reporting person resigned as a director of HCM II upon the closing of the Business Combination.

SEC source: 0001140361-24-037986 · form4.xml · derivative · entry 1

Brenner Andrew Scott · CIK 0002030321 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 25,000

Underlying: Class A Ordinary Shares · 25,000 shares

Expires not disclosed

F1 · derivative.exercise_price: The Class B ordinary shares are automatically convertible into the shares of the Issuer's Class A ordinary shares at the time of the Issuer's initial business combination on a one-for-one basis, subject to adjustment pursuant to certain anti-dilution rights, and have no expiration date. The Class B ordinary shares are subject to forfeiture under certain circumstances relating to the reporting person's service on the Issuer's Board of Directors.

F2 · kind: As contemplated by the securities purchase agreement between HCM Investor Holdings II, LLC (the "Sponsor") and the reporting person, dated August 19, 2024, the Sponsor assigned 25,000 Class B ordinary shares to the reporting person in connection with reporting person's appointment to the Issuer's Board of Directors.

F1 · derivative.exercise_date: The Class B ordinary shares are automatically convertible into the shares of the Issuer's Class A ordinary shares at the time of the Issuer's initial business combination on a one-for-one basis, subject to adjustment pursuant to certain anti-dilution rights, and have no expiration date. The Class B ordinary shares are subject to forfeiture under certain circumstances relating to the reporting person's service on the Issuer's Board of Directors.

F1 · derivative.expiration_date: The Class B ordinary shares are automatically convertible into the shares of the Issuer's Class A ordinary shares at the time of the Issuer's initial business combination on a one-for-one basis, subject to adjustment pursuant to certain anti-dilution rights, and have no expiration date. The Class B ordinary shares are subject to forfeiture under certain circumstances relating to the reporting person's service on the Issuer's Board of Directors.

SEC source: 0001140361-24-037982 · form4.xml · derivative · entry 1

Connor Michael J · CIK 0002029946 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 25,000

Underlying: Class A Ordinary Shares · 25,000 shares

Expires not disclosed

F1 · derivative.exercise_price: The Class B ordinary shares are automatically convertible into the shares of the Issuer's Class A ordinary shares at the time of the Issuer's initial business combination on a one-for-one basis, subject to adjustment pursuant to certain anti-dilution rights, and have no expiration date. The Class B ordinary shares are subject to forfeiture under certain circumstances relating to the reporting person's service on the Issuer's Board of Directors.

F2 · kind: As contemplated by the securities purchase agreement between HCM Investor Holdings II, LLC (the "Sponsor") and the reporting person, dated August 19, 2024, the Sponsor assigned 25,000 Class B ordinary shares to the reporting person in connection with reporting person's appointment to the Issuer's Board of Directors.

F1 · derivative.exercise_date: The Class B ordinary shares are automatically convertible into the shares of the Issuer's Class A ordinary shares at the time of the Issuer's initial business combination on a one-for-one basis, subject to adjustment pursuant to certain anti-dilution rights, and have no expiration date. The Class B ordinary shares are subject to forfeiture under certain circumstances relating to the reporting person's service on the Issuer's Board of Directors.

F1 · derivative.expiration_date: The Class B ordinary shares are automatically convertible into the shares of the Issuer's Class A ordinary shares at the time of the Issuer's initial business combination on a one-for-one basis, subject to adjustment pursuant to certain anti-dilution rights, and have no expiration date. The Class B ordinary shares are subject to forfeiture under certain circumstances relating to the reporting person's service on the Issuer's Board of Directors.

SEC source: 0001140361-24-037984 · form4.xml · derivative · entry 1

Matthews Shawn · CIK 0001855118 · Director · Chairman and CEO · 10% owner

HCM Investor Holdings II, LLC · CIK 0002019800 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See Footnote

Disclosed balance after: 5,675,000

Underlying: Class A Ordinary Shares · 75,000 shares

Expires not disclosed

F1 · derivative.exercise_price: The Class B ordinary shares are automatically convertible into the shares of the Issuer's Class A ordinary shares at the time of the Issuer's initial business combination on a one-for-one basis, subject to adjustment pursuant to certain anti-dilution rights, and have no expiration date.

F2 · kind: In connection with the Issuer's initial public offering and the appointment of Messrs. Andrew Brenner, Michael Connor, and Jacob Loveless to the Issuer's Board of Directors, HCM Investor Holdings II, LLC (the "Sponsor") assigned 25,000 Class B ordinary shares to each of Messrs. Andrew Brenner, Michael Connor, and Jacob Loveless.

F1 · derivative.exercise_date: The Class B ordinary shares are automatically convertible into the shares of the Issuer's Class A ordinary shares at the time of the Issuer's initial business combination on a one-for-one basis, subject to adjustment pursuant to certain anti-dilution rights, and have no expiration date.

F1 · derivative.expiration_date: The Class B ordinary shares are automatically convertible into the shares of the Issuer's Class A ordinary shares at the time of the Issuer's initial business combination on a one-for-one basis, subject to adjustment pursuant to certain anti-dilution rights, and have no expiration date.

F3 · ownership.nature: These Class B ordinary shares are held directly by the Sponsor, acquired pursuant to a subscription agreement dated as of April 4, 2024 by and among the Sponsor and the registrant and a share capitalization authorized by the SPAC on April 4, 2024. Shawn Matthews, the Chairman and Chief Executive Officer of the registrant, is the managing member of the Sponsor. Mr. Matthews has sole voting and dispositive control over the shares held by the Sponsor and may be deemed the beneficial owner of such shares. Mr. Matthews disclaims beneficial ownership over any securities owned by the Sponsor in which he does not have any pecuniary interest.

SEC source: 0001140361-24-037978 · form4.xml · derivative · entry 1

Loveless Jacob · CIK 0001855174 · Director

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 25,000

Underlying: Class A Ordinary Shares · 25,000 shares

Expires not disclosed

F1 · derivative.exercise_price: The Class B ordinary shares are automatically convertible into the shares of the Issuer's Class A ordinary shares at the time of the Issuer's initial business combination on a one-for-one basis, subject to adjustment pursuant to certain anti-dilution rights, and have no expiration date. The Class B ordinary shares are subject to forfeiture under certain circumstances relating to the reporting person's service on the Issuer's Board of Directors.

F2 · kind: As contemplated by the securities purchase agreement between HCM Investor Holdings II, LLC (the "Sponsor") and the reporting person, dated August 19, 2024, the Sponsor assigned 25,000 Class B ordinary shares to the reporting person in connection with reporting person's appointment to the Issuer's Board of Directors.

F1 · derivative.exercise_date: The Class B ordinary shares are automatically convertible into the shares of the Issuer's Class A ordinary shares at the time of the Issuer's initial business combination on a one-for-one basis, subject to adjustment pursuant to certain anti-dilution rights, and have no expiration date. The Class B ordinary shares are subject to forfeiture under certain circumstances relating to the reporting person's service on the Issuer's Board of Directors.

F1 · derivative.expiration_date: The Class B ordinary shares are automatically convertible into the shares of the Issuer's Class A ordinary shares at the time of the Issuer's initial business combination on a one-for-one basis, subject to adjustment pursuant to certain anti-dilution rights, and have no expiration date. The Class B ordinary shares are subject to forfeiture under certain circumstances relating to the reporting person's service on the Issuer's Board of Directors.