Adaptin Bio, Inc.

1,901,482 shares of common stock by the selling stockholders

2,233,083 shares of common stock underlying warrants HELD by the selling stockholders

This prospectus supplement updates, amends and supplements the prospectus dated August 4, 2025 (as supplemented on August 14, 2025, October 6, 2025, November 14, 2025 and May 15, 2026, as may be further supplemented or amended from time to time, the “Prospectus”) which forms a part of our Registration Statement on Form S-1 (Registration No. 333-287338). Capitalized terms used in this prospectus supplement and not otherwise defined herein have the meanings specified in the Prospectus.

This prospectus supplement is being filed to update, amend and supplement the information included in the Prospectus with information contained in Amendment No. 1 to our Annual Report on Form 10-K for the fiscal year ended December 31, 2025, filed with the SEC on June 12, 2026 (the “Form 10-K/A”).

Accordingly, we have attached the Form 10-K/A and related exhibits, to this prospectus supplement.

This prospectus supplement is not complete without the Prospectus. This prospectus supplement should be read in conjunction with the Prospectus, which is to be delivered with this prospectus supplement, and is qualified by reference thereto, except to the extent that the information in this prospectus supplement updates or supersedes the information contained in the Prospectus. Please keep this prospectus supplement with your Prospectus for future reference.

Our common stock is currently quoted on the OTCQB Venture Market under the stock symbol “APTN.” On June 9, 2026, the last quoted price of our common stock as reported on the OTCQB was $6.18 per share.

Investing in our securities involves a high degree of risk. See “Risk Factors” beginning on page 8 of the Prospectus for a discussion of information that should be considered in connection with an investment in our securities.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the accuracy or adequacy of the disclosures in the prospectus. Any representation to the contrary is a criminal offense.

The date of this prospectus supplement is June 12, 2026

UNITED STATES 

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K/A

(Amendment No. 1)

☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the fiscal year ended December 31, 2025 

OR

☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the transition period from __________ to __________

Commission file number: 000-56583 

ADAPTIN BIO, INC. 

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code: (888)-609-1498 

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

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

Common Stock, $0.0001 par value per share

(Title of Class)

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Yes ☐ No ☒ 

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act. Yes ☐ No ☒ 

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes ☒ No ☐ 

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Yes ☒ No ☐ 

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

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. ☐ 

Indicate by check mark whether the registrant has filed a report on and attestation to its management’s assessment of the effectiveness of its internal control over financial reporting under Section 404(b) of the Sarbanes-Oxley Act (15 U.S.C. 7262(b)) by the registered public accounting firm that prepared or issued its audit report. ☐ 

If securities are registered pursuant to Section 12(b) of the Act, indicate by check mark whether the financial statements of the registrant included in the filing reflect the correction of an error to previously issued financial statements. ☐ 

Indicate by check mark whether any of those error corrections are restatements that required a recovery analysis of incentive-based compensation received by any of the registrant’s executive officers during the relevant recovery period pursuant to §240.10D-1(b). ☐

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Act). Yes ☐ No ☒ 

The aggregate market value (approximate) of the registrant’s common equity held by non-affiliates based on the most recent sales price of a share of the registrant’s common share on June 30, 2025 (the last business day of the registrant’s most recently completed second fiscal quarter) was $9.3 million.

As of June 11, 2026, 8,903,229 shares of common stock, par value $0.0001 per share, were issued and outstanding.

Documents Incorporated by Reference

Not applicable.

EXPLANATORY NOTE

On April 1, 2026, Adaptin Bio, Inc. (the “Company”) filed with the Securities and Exchange Commission (“SEC”) its Annual Report on Form 10-K for the year ended December 31, 2025 (the “Original Form 10-K”).

This Amendment No. 1 to Form 10-K (the “Form 10-K/A”) of the Company is being filed solely to amend Item 15(b) and Exhibit 23.1 to include an updated consent of WithumSmith+Brown, PC, the Company’s independent registered public accounting firm, to include references to a registration statement of the Company which was inadvertently omitted from the original consent filed.

This Form 10-K/A should be read in conjunction with the Original Form 10-K and includes only the portions of the Original Form 10-K being supplemented or amended by this Form 10-K/A. Other than as described in this explanatory note, this Form 10-K/A does not change any of the financial or other information set forth in the Original Form 10-K or the exhibits thereto. This Form 10-K/A does not reflect events that may have occurred subsequent to the filing of the Original Form 10-K.

PART IV

ITEM 15. EXHIBIT AND FINANCIAL STATEMENT SCHEDULES.

(b) Exhibits

The following list of exhibits includes exhibits submitted with this Form 10-K/A as filed with the SEC and others incorporated by reference to other filings.

SIGNATURES

Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

Pursuant to the requirements of the Securities Exchange Act of 1934, this report has been signed below by the following persons on behalf of the registrant and in the capacities and on the dates indicated.

Exhibit 23.1

Consent of Independent Registered Public Accounting Firm

We hereby consent to the incorporation by reference in the Registration Statement on Form S-1 (No. 333-287338) and on Form S-8 No. (333-289627) of Adaptin Bio, Inc. (“the Company”) of our report dated April 1, 2026, which includes an explanatory paragraph relating to the substantial doubt over the Company’s ability to continue as a going concern, relating to the consolidated financial statements which are comprised of the consolidated balance sheets, consolidated statements of operations, consolidated statements of changes in stockholders’ deficit, and the consolidated statements of cash flows, all of which appear in the Company’s Annual Report on Form 10-K for the year ended December 31, 2025.

/s/ WithumSmith+Brown, PC

East Brunswick, New Jersey

June 12, 2026

Exhibit 31.3

CERTIFICATION OF PRINCIPAL EXECUTIVE OFFICER PURSUANT TO EXCHANGE ACT RULE 13a-14(a)/15d-14(a)
AS ADOPTED PURSUANT TO SECTION 302 OF THE SARBANES-OXLEY ACT OF 2002

I, Michael Roberts, certify that:

Exhibit 31.4

CERTIFICATION OF PRINCIPAL FINANCIAL OFFICER PURSUANT TO EXCHANGE ACT RULE 13a-14(a)/15d-14(a)
AS ADOPTED PURSUANT TO SECTION 302 OF THE SARBANES-OXLEY ACT OF 2002

I, Timothy L. Maness, certify that: