Company: MBIO
Filing Date: 2025-04-01
Form Type: 424B3
Source: 0001104659-25-030657
Chunk: 222

Company: MUSTANG BIO, INC.
Filing Date: 2025-04-01
Form: 424B3
Chunk 222
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2023 |   |           1,911 | ​ | $                |   948.25 |
| Forfeited                      | ​ |          -1,320 | ​ | ​                |   911.70 |
| Vested                         |   |            -365 | ​ |                  | 1,205.20 |
| Nonvested at December 31, 2024 |   |             226 | ​ | $                |   746.70 |

As of December 31, 2024, the Company
had unrecognized stock-based compensation expense related to restricted stock units of approximately $25,000, which is expected to be
recognized over a weighted average period of approximately 1.5 years.

The following table summarizes stock-based compensation
expense for the years ended December 31, 2024 and 2023 (in thousands).

| ​                                      
 ​                                      | ​ 
 ​ 
 ​ | ​                               
 For the year ended December 31, |    ​ 
 2024 | ​ | ​ |    ​ 
 2023 | ​ 
 ​ |
|:---------------------------------------|:--|:--------------------------------|-----:|:--|:--|-----:|:--|
| General and administrative             | ​ | $                               |  200 | ​ | $ |  436 | ​ |
| Research and development               | ​ |                                 | -650 | ​ |   |  132 | ​ |
| Total stock-based compensation expense | ​ | $                               | -450 | ​ | $ |  568 | ​ |

Employee Stock Purchase Plan

In connection with our Employee Stock Purchase
Plan (“ESPP”), eligible employees of Mustang and Fortress can purchase the Company’s Common Stock at the end of a predetermined
offering period at 85% of the lower of the fair market value at the beginning or end of the offering period.

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Table of Contents

As of December 31, 2024, 2,562 shares
have been purchased, and 6,771 shares are available for future sale under the Company’s ESPP.

Note 11 - Income Taxes

The Company has accumulated net losses since inception and has not recorded an income tax provision or benefit during the years ended December 31, 2024 and 2023.

A reconciliation of the statutory U.S. federal
rate to the Company’s effective tax rate is as follows:

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