Company: MBIO
Filing Date: 2025-02-27
Form Type: 424B3
Source: 0001104659-25-018303
Chunk: 12

Company: MUSTANG BIO, INC.
Filing Date: 2025-02-27
Form: 424B3
Chunk 12
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| Title: President & CEO |                     |     | Title: VP Corporate Treasurer  |                      |

<div align='center'>JOINDER</div>

Landlord hereby joins in executing
this Bill of Sale Agreement solely for the purpose of agreeing that (i) Buyer shall be permitted to enter the Leased Premises during the
Inspection Period for the purpose set forth in Paragraph 2 above, and (ii) pursuant to the Mustang Amendment, the Mustang Lease shall
terminate as of the Transfer Date.

| LANDLORD:                         |                      |
| WCS - 377 Plantation Street, Inc. |                      |
| a Delaware corporation            |                      |
| By:                               | /s/ Marcy Culverwell |
| Name: Marcy Culverwell            |                      |
| Title: President                  |                      |

<div align='center'>7</div>

Exhibit 10.1

<div align='center'>FIRST</div>

THIS FIRST AMENDMENT TO LEASE
AGREEMENT (this “Amendment”) is made as of the 7 day of February,
2025 (“Effective Date”) between WCS - 377 Plantation Street, Inc., a Massachusetts
nonprofit corporation (“Landlord”), and Mustang Bio, Inc., a Delaware corporation
(“Tenant”).

A.Landlord and Tenant are parties to that certain Lease Agreement dated as of October 27, 2017 (the “ Lease”) whereby Tenant leased from Landlord approximately 27,043 rentable square feet of space located on the first floor of the Building at 377 Plantation Street, Worcester, Massachusetts (the “ Premises”).

B.The Base Term (as defined in the Lease) of the Lease is currently scheduled to expire on October 31, 2026 (the “ Termination Date”).

C.Landlord and Tenant desire to enter into this Amendment to provide for earlier expiration of the Base Term of the Lease and to otherwise amend the Lease on the terms and conditions set forth in this Amendment.

FOR VALUE RECEIVED, Landlord
and Tenant agree as follows:

1.Defined Terms and Recitals.Unless otherwise defined or indicated herein, all capitalized terms used in this Amendment shall have the definitions ascribed to them in the Lease. The Recitals are incorporated herein.

2.Early Termination. The Base Term of the Lease currently is scheduled to expire on the Termination Date. Notwithstanding anything to the contrary contained in the Lease, the Base Term of the Lease shall terminate earlier than the Termination