Business Combination Prospectus (Form 425)

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(d) OF THE

SECURITIES EXCHANGE ACT OF 1934

Date of Report (Date of earliest event reported): September 29, 2025

HCM II Acquisition Corp.

(Exact name of registrant as specified in its charter)

Cayman Islands		001-42252		98-1785406
(State or other jurisdiction of incorporation)		(Commission File Number)		(IRS Employer Identification No.)

100 First Stamford Place, Suite 330

Stamford, CT 06902

(Address of principal executive offices, including zip code)

Registrant's telephone number, including area code: (203) 930-2200

Not Applicable

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☒	Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐	Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐	Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐	Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class		Trading Symbol(s)		Name of each exchange on which registered
Units, each consisting of one share of Class A ordinary share and one-half of one Redeemable Warrant		HONDU		The Nasdaq Stock Market LLC
Class A ordinary shares, par value $0.0001 per share		HOND		The Nasdaq Stock Market LLC
Redeemable Warrants, each whole warrant exercisable for one Class A ordinary share at a price of $11.50 per share		HONDW		The Nasdaq Stock Market LLC

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 8.01. Other Events.

On September 29, 2025, HCM II Acquisition Corp. ("HCM II") and Terrestrial Energy Inc. ("Terrestrial Energy" or the "Company") jointly announced that the U.S. Securities and Exchange Commission (the "SEC") declared effective the Registration Statement on Form S-4, as amended (the "Registration Statement"), filed in connection with the previously announced proposed business combination (the "Business Combination") between HCM II and Terrestrial Energy. A copy of the press release is attached hereto as Exhibit 99.1 and is incorporated herein by reference.

Important Information for Shareholders

This communication does not constitute an offer to sell or the solicitation of an offer to buy any securities or constitute a solicitation of any vote or approval.

The Registration Statement has been declared effective by the SEC. The Registration Statement registers the securities to be issued by HCM II in connection with the Business Combination and included a proxy statement of HCM II and a prospectus of HCM II (the "Proxy Statement/Prospectus"), and each of Terrestrial Energy and HCM II may file with the SEC other relevant documents concerning the Business Combination. A definitive Proxy Statement/Prospectus and other relevant documents were mailed to HCM II stockholders as of the record date established for voting on the proposed Business Combination. INVESTORS OF HCM II AND TERRESTRIAL ENERGY ARE URGED TO READ THE REGISTRATION STATEMENT, THE PROXY STATEMENT/PROSPECTUS CONTAINED THEREIN (INCLUDING ALL AMENDMENTS AND SUPPLEMENTS THERETO) AND ALL OTHER DOCUMENTS RELATING TO THE BUSINESS COMBINATION FILED WITH THE SEC CAREFULLY AND IN THEIR ENTIRETY BECAUSE THEY CONTAIN IMPORTANT INFORMATION ABOUT HCM II, TERRESTRIAL ENERGY, AND THE BUSINESS COMBINATION.

Investors will be able to obtain free copies of the proxy statement/prospectus and other documents containing important information about HCM II and Terrestrial Energy through the website maintained by the SEC at http://www.sec.gov. In addition, the documents filed by HCM II may be obtained free of charge from HCM II's website at https://hcmacquisition.com/ or by written request to HCM II at 100 First Stamford Place, Suite 330, Stamford, CT 06902.

Participants in the Solicitation

HCM II and the Company, and their respective directors and executive officers, may be considered participants in the solicitation of proxies with respect to the potential transaction described in this communication under the rules of the SEC. Information about the directors and executive officers of HCM II is set forth in HCM II's filings with the SEC. Information regarding other persons who may, under the rules of the SEC, be deemed participants in the solicitation of the shareholders in connection with the potential transaction and a description of their direct and indirect interests are set forth in the Registration Statement (and included in the proxy statement/prospectus) and other relevant documents, which were filed with the SEC. These documents can be obtained free of charge from the sources indicated above.

Forward-Looking Statements

This Current Report on Form 8-K includes "forward-looking statements." These forward-looking statements include, but are not limited to, statements regarding our expectations, hopes, beliefs, intentions or strategies regarding the future. In addition, any statements that refer to projections, forecasts or other characterizations of future events or circumstances, including any underlying assumptions, are forward-looking statements. The words "anticipate," "believe," "continue," "could," "estimate," "expect," "intends," "may," "might," "plan," "possible," "potential," "predict," "project," "should," "would" and similar expressions may identify forward-looking statements, but the absence of these words does not mean that a statement is not forward-looking.

The forward-looking statements contained in this Form 8-K are based on our current expectations and beliefs concerning future developments and their potential effects on HCM II and the Company. There can be no assurance that future developments affecting HCM II and the Company will be those that we have anticipated. These forward-looking statements speak only as of the date this Form 8-K is actually delivered and involve a number of risks, uncertainties (some of which are beyond our control) or other assumptions that may cause actual results or performance to be materially different from those expressed or implied by these forward-looking statements. Should one or more of these risks or uncertainties materialize, or should any of our assumptions prove incorrect, actual results may vary in material respects from those projected in these forward-looking statements. Factors that may cause actual results to differ materially from current expectations include, but are not limited to: (1) the occurrence of any event, change or other circumstances that could give rise to the termination of the definitive agreements with respect to the Business Combination; (2) the outcome of any legal proceedings that may be instituted against HCM II, the Company, the combined company or others following the announcement of the Business Combination and any definitive agreements with respect thereto; (3) the inability to complete the Business Combination due to the failure to obtain approval of the shareholders of HCM II or to satisfy other conditions to closing; (4) changes to the proposed structure of the Business Combination that may be required or appropriate as a result of applicable laws or regulations or as a condition to obtaining regulatory approval of the Business Combination; (5) the ability of HCM II to meet stock exchange listing standards following the consummation of the Business Combination; (6) the risk that the Business Combination disrupts current plans and operations of the Company as a result of the announcement and consummation of the Business Combination; (7) the ability to recognize the anticipated benefits of the Business Combination, which may be affected by, among other things, competition, the ability of the combined company to grow and manage growth profitably, maintain relationships with customers and suppliers and retain its management and key employees; (8) costs related to the Business Combination, including the reorganization described in the business combination agreement; (9) changes in applicable laws or regulations; (10) the possibility that the Company or the combined company may be adversely affected by other economic, business, and/or competitive factors; (11) the amount of redemption requests made by HCM II shareholders and (12) other risk factors described herein as well as the risk factors and uncertainties described in that certain prospectus of HCM II dated August 15, 2024 and the HCM II's other filings with the SEC, as well as any further risks and uncertainties to be contained in the proxy statement/prospectus filed after the date hereof. In addition, there may be additional risks that neither HCM II or Company presently know, or that HCM II or Company currently believe are immaterial, that could also cause actual results to differ from those contained in the forward-looking statements. Nothing in this communication should be regarded as a representation by any person that the forward-looking statements set forth herein will be achieved or that any of the contemplated results of such forward-looking statements will be achieved. You should not place undue reliance on forward-looking statements, which speak only as of the date they are made.

None of HCM II, the Company, any placement agent nor any of their respective affiliates, officers, employees or agents, makes any representation or warranty, either express or implied, in relation to the fairness, reasonableness, adequacy, accuracy, completeness or reliability of the information, statements or opinions, whichever their source, contained in this Form 8-K or any oral information provided in connection herewith, or any data it generates and accept no responsibility, obligation or liability (whether direct or indirect, in contract, tort or otherwise) in relation to any of such information. HCM II, the Company and their respective affiliates, officers, employees and agents further expressly disclaim any and all liability relating to or resulting from the use of this Form 8-K and any errors therein or omissions therefrom. Further, the information contained herein is preliminary, is provided for discussion purposes only, is only a summary of key information, is not complete and is subject to change without notice.

In addition, the information contained in this Form 8-K is provided as of the date hereof and may change, and neither HCM II nor the Company undertakes any obligation to update or revise any forward-looking statements, whether as a result of new information, inaccuracies, future events or otherwise, except as may be required under applicable securities laws.

Item 9.01. Financial Statements and Exhibits.

(d)

Exhibits.

Exhibit Number		Description
99.1*		Press Release, dated September 29, 2025.
104		Cover Page Interactive Data File (formatted as Inline XBRL and contained in Exhibit 101).

*	This exhibit is furnished pursuant to Item 7.01 hereof and should not be deemed to be "filed" under the Securities Exchange Act of 1934, as amended.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, as amended, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

	HCM II ACQUISITION CORP.
	By:	/s/ Shawn Matthews
	Name:	Shawn Matthews
	Title:	Chief Executive Officer
Date: September 29, 2025

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