Company: MBIO
Filing Date: 2025-04-01
Form Type: 424B3
Source: 0001104659-25-030657
Chunk: 38

Company: MUSTANG BIO, INC.
Filing Date: 2025-04-01
Form: 424B3
Chunk 38
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 efficacy in an expanded patient population. |

| ● | Phase 4: The FDA may request phase 4 post-marketing studies to find out more about the drug’s long-term risks, benefits, and optimal use, or to test the drug in different patient populations. |

The length of time necessary to complete clinical
trials varies significantly and may be difficult to predict. Clinical results are frequently susceptible to varying interpretations that
may delay, limit or prevent regulatory approvals. Additional factors that can cause delay or termination of our clinical trials, or that
may increase the costs of these trials, include:

| ● | slow patient enrollment due to the nature of the clinical trial plan, the proximity of patients to clinical sites, the eligibility criteria for participation in the study or other factors; |

| ● | inadequately trained or insufficient personnel at the study site to assist in overseeing and monitoring clinical trials or delays in approvals from a study site’s review board; |

| ● | longer treatment time required to demonstrate efficacy or determine the appropriate product dose; |

| ● | insufficient supply of the product candidates; |

| ● | adverse medical events or side effects in treated patients; and |

| ● | ineffectiveness of the product candidates. |

In addition, the FDA, or equivalent foreign regulatory
authority, or a data safety monitoring committee for a clinical trial may place a clinical trial on hold or terminate it if it concludes
that subjects are being exposed to an unacceptable health risk, or for futility. Any drug is likely to produce some toxicity or undesirable
side effects in animals and in humans when administered at sufficiently high doses and/or for a sufficiently long period of time. Unacceptable
toxicity or side effects may occur at any dose level at any time in the course of studies in animals designed to identify unacceptable
effects of a product candidate, known as toxicological studies, or clinical trials of product candidates. The appearance of any unacceptable
toxicity or side effect could cause us or regulatory authorities to interrupt, limit, delay or abort the development of any of our product
candidates and could ultimately prevent approval by the FDA or foreign regulatory authorities for any or all targeted indications.

Sponsors of drugs may apply for a special protocol
assessment (“SPA”) from the FDA for studies intended to form the primary basis of an efficacy claim. The SPA process is a
procedure by which the FDA provides official evaluation and written guidance on the design and size of proposed protocols that are intended
to form the basis for an NDA or BLA. However,