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): June 20, 2025

SilverBox Corp IV

(Exact Name of Registrant as Specified in Its Charter)

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:

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

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (17 CFR § 230.405) or Rule 12b-2 of the Securities Exchange Act of 1934 (17 CFR § 240.12b-2).

Emerging growth company x

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 7.01 Regulation FD Disclosure.

As previously announced on June 9, 2025, SilverBox Corp IV (“SBXD”) and Parataxis Holdings LLC (“Parataxis Holdings”) entered into a non-binding letter of intent for a potential business combination. On June 20, 2025, Parataxis Holdings issued a press release announcing a definitive agreement to acquire a controlling interest in Bridge Biotherapeutics, Inc., a Korean company listed on the KOSDAQ. A copy of the press release is attached hereto as Exhibit 99.1 and is incorporated by reference herein.

In addition, the following is a LinkedIn post by Joseph E. Reece, Founder Partner of SBXD:

Parataxis Holdings announces definitive agreement to establish a Bitcoin treasury company in South Korea

Read the press release of Parataxis Holdings here: Parataxis Holdings LLC Announces Definitive Agreement with Bridge Biotherapeutics, Inc. (KOSDAQ: 288330), to Bring Institutionally-Backed, Bitcoin Treasury Company to the South Korean Public Markets.

The information in this Current Report on Form 8-K, including Exhibit 99.1, is being furnished pursuant to Item 7.01 and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise be subject to the liabilities of that section, nor shall it be deemed to be incorporated by reference into any of the filings of SBXD under the Securities Act of 1933, as amended (the “Securities Act”), or the Exchange Act, whether made before or after the date hereof, regardless of any general incorporation language in any such filing.

Item 9.01 Financial Statements and Exhibits.

Additional Information and Where to Find It

If a definitive agreement is entered into in connection with the proposed business combination, a newly formed holding company (“PubCo”), SBXD and Parataxis Holdings will prepare and file a registration statement, including a proxy statement/prospectus of SBXD and PubCo, to be filed with the U.S. Securities and Exchange Commission (“SEC”). The proxy statement/prospectus will be mailed to SBXD’s shareholders. SBXD urges investors and other interested persons to read, when available, the proxy statement/prospectus, as well as other documents filed with the SEC, because these documents will contain important information about the proposed business combination. Such persons can also read SBXD’s Annual Report on Form 10-K for the fiscal year ended December 31, 2024 (the “SBXD Annual Report”), for a description of the security holdings of its officers and directors and their respective interests as security holders in the consummation of the proposed business combination. The proxy statement statement/prospectus, once available, and the SBXD Annual Report can be obtained, without charge, at the SEC’s web site (http://www.sec.gov).

Participants in the Solicitation

Parataxis Holdings, SBXD and PubCo and their respective directors, executive officers and other members of their management and employees, under SEC rules, may be deemed to be participants in the solicitation of proxies of SBXD’s shareholders in connection with the proposed business combination. Investors and security holders may obtain more detailed information regarding the names, affiliations and interests of SBXD’s directors and officers in SBXD’s Annual Report. Information regarding the persons who may, under SEC rules, be deemed participants in the solicitation of proxies to SBXD’s shareholders in connection with the proposed business combination will be set forth in the proxy statement/prospectus for the proposed business combination when available. Information concerning the interests of Parataxis Holdings’, SBXD’s and PubCo’s participants in the solicitation, which may, in some cases, be different than those of their respective equityholders generally, will be set forth in the proxy statement/prospectus relating to the proposed business combination when it becomes available.

Forward-Looking Statements

This Current Report on Form 8-K includes “forward-looking statements” with respect to SBXD and Parataxis Holdings within the meaning of the federal securities laws. The expectations, estimates, and projections of the businesses of Parataxis Holdings and SBXD may differ from their actual results and consequently, you should not rely on these forward-looking statements as predictions of future events. Words such as “expect,” “estimate,” “project,” “budget,” “forecast,” “anticipate,” “intend,” “plan,” “may,” “will,” “could,” “should,” “believes,” “predicts,” “potential,” “continue,” and similar expressions are intended to identify such forward-looking statements. These forward-looking statements include, without limitation, expectations with respect to execution of a definitive agreement with respect to the proposed business combination, future performance and anticipated financial impacts of the proposed business combination, the satisfaction of the closing conditions to the proposed business combination, and the timing of the completion of the proposed business combination. These forward-looking statements involve significant risks and uncertainties that could cause the actual results to differ materially from the expected results. Most of these factors are outside of the control of Parataxis Holdings and SBXD and are difficult to predict. Factors that may cause such differences 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 negotiations and any subsequent definitive agreements with respect to the proposed business combination, and the possibility that the terms and conditions set forth in any definitive agreements with respect to the proposed business combination may differ materially from the terms and conditions set forth in the term sheet; (2) the outcome of any legal proceedings that may be instituted against the parties following the announcement of the proposed business combination and any definitive agreements with respect thereto; (3) the inability to complete the proposed business combination and the related transactions, including due to failure to obtain approval of the shareholders of SBXD or other conditions to closing; (4) the inability to obtain or maintain the listing of PubCo’s common equity on a stock exchange following the proposed business combination; (5) the risk that the proposed business combination disrupts current plans and operations as a result of the announcement and consummation of the proposed business combination; (6) the ability to recognize the anticipated benefits of the proposed business combination, which may be affected by, among other things, competition, the ability of PubCo to grow and manage growth profitably and retain its key employees, and the demand in South Korea for digital assets; (7) costs related to the proposed business combination; (8) changes in applicable laws or regulations; and (9) other risks and uncertainties included in (x) the “Risk Factors” sections of the SBXD Annual Report and (y) other documents filed or to be filed with or furnished or to be furnished to the SEC by Parataxis Holdings, PubCo and SBXD. The foregoing list of factors is not exclusive. You should not place undue reliance upon any forward-looking statements, which speak only as of the date made. Parataxis Holdings and SBXD do not undertake or accept any obligation or undertaking to release publicly any updates or revisions to any forward-looking statements to reflect any change in their expectations or any change in events, conditions, or circumstances on which any such statement is based, except as required by law. Past performance by Parataxis Holdings’ or SBXD’s management teams and their respective affiliates is not a guarantee of future performance. Therefore, you should not place undue reliance on the historical record of the performance of Parataxis Holdings’ or SBXD’s management teams or businesses associated with them as indicative of future performance of an investment or the returns that Parataxis Holdings or SBXD will, or are likely to, generate going forward.

No Offer or Solicitation

This Current Report on Form 8-K shall not constitute a solicitation of a proxy, consent, or authorization with respect to any securities or in respect of the proposed business combination. This Current Report on Form 8-K shall also not constitute an offer to sell or the solicitation of an offer to buy any securities, nor shall there be any sale of securities in any states or jurisdictions in which such offer, solicitation, or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction. No offering of securities shall be made except by means of a prospectus meeting the requirements of Section 10 of the Securities Act.

SIGNATURE

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

ATTACHMENTS / EXHIBITS

EXHIBIT 99.1

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