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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

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FORM 8-K

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CURRENT REPORT

Pursuant to Section 13 or 15(d) of the

Securities Exchange Act of 1934

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Date of report (Date of earliest event reported): December 28, 2023

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Mustang Bio, Inc.

(Exact Name of Registrant as Specified in Charter)

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377 Plantation Street

Worcester, Massachusetts 01605

(Address of Principal Executive Offices)

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(781) 652-4500

(Registrant’s telephone number, including area code)

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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:

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

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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). ☐

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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. ☐

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Item 8.01. Other Events.

As previously disclosed, in connection with the sale of Mustang Bio, Inc.’s (the “Company”) leasehold interest in its cell processing facility located in Worcester, Massachusetts (the “Facility”) and associated assets relating to the manufacturing and production of cell and gene therapies at the Facility (the “Transaction”) to uBrigene (Boston) Biosciences, Inc., a Delaware corporation (“uBriGene”) and an indirect, wholly owned subsidiary of UBrigene (Jiangsu) Biosciences Co., Ltd., a Chinese contract development and manufacturing organization, the Company and uBriGene previously submitted a voluntary notice with the U.S. Committee on Foreign Investment in the United States (“CFIUS”) to obtain clearance for the Transaction, although obtaining such clearance was not a condition to closing the Transaction. Following an initial 45-day review period and subsequent 45-day investigation period, on November 13, 2023, CFIUS requested the Company and uBriGene withdraw and re-file their joint voluntary notice to allow more time for review and discussion regarding the nature and extent of national security risk posed by the Transaction. Upon CFIUS’s request, the Company and uBriGene submitted a request to withdraw and re-file their joint voluntary notice to CFIUS, and on November 13, 2023, CFIUS granted this request, accepted the joint voluntary notice and commenced a new 45-day review period on November 14, 2023. CFIUS’s new 45-day review was completed on December 28, 2023.  Because CFIUS has not yet concluded its action, the proceeding will transition to a second 45-day phase as CFIUS investigates the Transaction. CFIUS advised counsel for the Company that its investigation will be completed no later than February 12, 2024.

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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.

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