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): March 13, 2024

Mustang Bio, Inc.

(Exact Name of Registrant as Specified in Charter)

377 Plantation Street

Worcester, Massachusetts 01605

(Address of Principal Executive Offices)

(781) 652-4500

(Registrant’s telephone number, including area code)

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 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). ¨

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.  ¨

On March 13, 2024, Mustang Bio, Inc. (the “Company”) received a deficiency letter (the “Letter”) from the Listing Qualifications Department (the “Staff”) of The Nasdaq Stock Market LLC (“Nasdaq”) notifying the Company that it was not in compliance with the minimum stockholders’ equity requirement for continued listing on the Nasdaq Capital Market under Nasdaq Listing Rule 5550(b)(1). Nasdaq Listing Rule 5550(b)(1) requires companies listed on the Nasdaq Capital Market to maintain stockholders’ equity of at least $2,500,000 (the “Stockholders’ Equity Requirement”). The Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2023, reported stockholders’ equity of $123,000. The Letter further noted that as of its date, the Company did not have a market value of listed securities of $35 million, or net income from continued operations of $500,000 in the most recently completed fiscal year or in two of the last three most recently completed fiscal years, the alternative quantitative standards for continued listing on the Nasdaq Capital Market.

The Letter has no immediate effect on the Company’s continued listing on the Nasdaq Capital Market, subject to the Company’s compliance with the other continued listing requirements. In accordance with Nasdaq rules, the Company has been provided 45 calendar days, or until April 29, 2024, to submit a plan to regain compliance (the “Compliance Plan”). If the Compliance Plan is acceptable to the Staff, it may grant an extension of 180 calendar days from the date of the Letter. If the Staff does not accept the Compliance Plan, the Staff will provide written notification to the Company that the Compliance Plan has been rejected. At that time, the Company may appeal the Staff’s determination to a Nasdaq Hearings Panel.

The Company intends to submit a Compliance Plan on or before April 29, 2024. Further, the Company intends to take all reasonable measures available to regain compliance under the Nasdaq Listing Rules and remain listed on Nasdaq. However, there can be no assurance that Nasdaq will approve the Compliance Plan or that the Company will ultimately regain compliance with all applicable requirements for continued listing.

Neither the Letter nor the Company’s noncompliance have an immediate effect on the listing or trading of the Company’s common stock, which will continue to trade on the Nasdaq Capital Market under the symbol “MBIO.”

Forward-Looking Statements

This Current Report on Form 8-K contains “forward-looking statements” within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934, each as amended. Such statements are often indicated by terms such as “anticipate,” “believe,” “could,” “estimate,” “expect,” “goal,” “intend,” “look forward to,” “may,” “plan,” “potential,” “predict,” “project,” “should,” “will,” “would” and similar expressions. Actual events or results may differ materially from those described in this Current Report on Form 8-K due to a number of risks and uncertainties. Risks and uncertainties include, among other things, risks related to the satisfaction of the conditions necessary to transfer the lease of the Company’s manufacturing facility and receive the contingent payment in connection with the Company’s sale of its manufacturing facility in the anticipated timeframe or at all; whether the purchaser of the Company’s manufacturing facility is able to successfully perform its obligation to produce the Company’s products under the manufacturing services agreement on a timely basis and to acceptable standards; disruption from the sale of the Company’s manufacturing facility making it more difficult to maintain business and operational relationships; negative effects of the announcement or the consummation of the transaction on the market price of the Company’s common stock; significant transaction costs; the development stage of the Company’s primary product candidates, the Company’s ability to obtain, perform under, and maintain financing and strategic agreements and relationships; risks relating to the results of research and development activities; risks relating to the timing of starting and completing clinical trials; uncertainties relating to preclinical and clinical testing; the Company’s dependence on third-party suppliers; the Company’s ability to attract, integrate and retain key personnel; the early stage of products under development; the Company’s need for substantial additional funds; government regulation; patent and intellectual property matters; competition; as well as other risks described in Part I, Item 1A, “Risk Factors,” in the Company’s most recent Annual Report on Form 10-K, subsequent Quarterly Reports on Form 10-Q, and the other filings the Company makes with the Securities and Exchange Commission. The Company expressly disclaims any obligation or undertaking to release publicly any updates or revisions to any forward-looking statements contained herein to reflect any change in the Company’s expectations or any changes in events, conditions or circumstances on which any such statement is based, except as required by applicable law, and the Company claims the protection of the safe harbor for forward-looking statements contained in the Private Securities Litigation Reform Act of 1995.

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.