Company: MBIO
Filing Date: 2025-04-01
Form Type: POS EX
Source: 0001104659-25-030659
Chunk: 1

Company: MUSTANG BIO, INC.
Filing Date: 2025-04-01
Form: POS EX
Chunk 1
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If this Form is a post-effective amendment filed
pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of
the earlier effective registration statement for the same offering. x

Indicate by check mark whether the registrant
is a large accelerated filer, an accelerated filer, a non-accelerated filer, 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.

| Large accelerated filer | ¨ | Accelerated filer         | ¨ |
| Non-accelerated filer   | x | Smaller reporting company | x |
|                         |   | 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 7(a)(2)(B) of the Securities Act. ¨

This Post-Effective Amendment No. 1 shall become effective upon filing with the Securities and Exchange Commission in accordance with Rule 462(d) under the Securities Act of 1933, as amended.

<div align='center'>EXPLANATORY NOTE</div>

This Post-Effective Amendment No. 1 (this
“Amendment”) to the Registration Statement on Form S-1 (File No. 333-284299) (the “Registration Statement”) of
Mustang Bio, Inc. (the “Company”) is being filed as an exhibits-only filing solely to include the consent of KPMG LLP with
respect to its report, dated March 28, 2025, relating to the consolidated financial statements of the Company contained in its Annual
Report on Form 10-K for the year ended December 31, 2024, filed herewith as Exhibit 23.1. Accordingly, this Amendment consists
only of the facing page, this explanatory note, Item 16 of Part II of the Registration Statement, the signature pages to the Registration
Statement and Exhibit 23.1. The report of KPMG LLP was filed in Prospectus Supplement No. 3, dated April 1, 2025, filed with the Securities
and Exchange Commission pursuant to Rule 424(b)(3). The prospect