UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the

Securities Exchange Act of 1934

Date of report (Date of earliest event reported): April 29, 2024

Mustang Bio, Inc.

(Exact Name of Registrant as Specified in Charter)

377 Plantation Street

Worcester, Massachusetts 01605

(Address of Principal Executive Offices)

(781) 652-4500

(Registrant’s telephone number, including area code)

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:

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

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).  ¨

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.  ¨

Securities Purchase Agreement

On April 29, 2024, Mustang Bio, Inc. (the “Company”) commenced a best efforts public offering (the “Offering”) of an aggregate of (i) 1,160,000 shares (the “Shares”) of common stock, par value $0.0001 per share ( “Common Stock”), of the Company, (ii) pre-funded warrants (the “Pre-Funded Warrants”) to purchase up to an aggregate of 15,717,638 shares of Common Stock (the “Pre-Funded Warrant Shares”), (iii) Series A-1 warrants (the “Series A-1 Warrants”) to purchase up to an aggregate of 16,877,638 shares of Common Stock (the “Series A-1 Common Warrant Shares”), (iv) Series A-2 warrants (the “Series A-2 Warrants”) to purchase up to an aggregate of 16,877,638 shares of Common Stock (the “Series A-2 Warrant Shares”), and (v) Series A-3 warrants (the “Series A-3 Warrants,” and together with the Series A-1 Warrants and Series A-2 Warrants, the “Warrants”) to purchase up to an aggregate of 16,877,638 shares of Common Stock (the “Series A-3 Warrant Shares”). Each Share or Pre-Funded Warrant was sold together with one Series A-1 Warrant to purchase one share of Common Stock, one Series A-2 Warrant to purchase one share of Common Stock, and one Series A-3 Warrant to purchase one share of Common Stock. The public offering price for each Share and accompanying Warrants was $0.237, and the public offering price for each Pre-Funded Warrant and accompanying Warrants was $0.2369. The Pre-Funded Warrants have an exercise price of $0.0001 per share, are exercisable immediately and will expire when exercised in full. Each Warrant will have an exercise price of $0.237 per share, will be exercisable beginning on the effective date of stockholder approval of the issuance of the shares upon exercise of the Warrants (“Warrant Stockholder Approval”). The Series A-1 Warrant will expire on the five-year anniversary of the Warrant Stockholder Approval. The Series A-2 Warrant will expire on the twenty four month anniversary of the Warrant Stockholder Approval. The Series A-3 Warrant will expire on the nine month anniversary of the Warrant Stockholder Approval.

The net proceeds of the Offering, after deducting the fees and expenses of the Placement Agent (as defined below), described in more detail below, and other offering expenses payable by the Company, but excluding the net proceeds, if any, from the exercise of the Warrants, is approximately $3.3 million. The Company intends to use the net proceeds from the Offering for working capital and general corporate purposes. The Offering closed on May 2, 2024.

In connection with the Offering, the Company entered into a securities purchase agreement (the “Purchase Agreement”) with a certain institutional investor (the “Investor”). Pursuant to the Purchase Agreement, the Company agreed not to issue, enter into any agreement to issue or announce the issuance or proposed issuance of any shares of Common Stock or any securities convertible into or exercisable or exchangeable for shares of Common Stock or file any registration statement or prospectus, or any amendment or supplement thereto for 90 days after the closing date of the Offering, subject to certain exceptions. In addition, the Company has agreed not to effect or enter into an agreement to effect any issuance of Common Stock or any securities convertible into or exercisable or exchangeable for shares of Common Stock involving a variable rate transaction (as defined in the Purchase Agreement) until the one-year anniversary of the closing date of the Offering, subject to certain exceptions.

The Purchase Agreement contains customary representations, warranties and agreements by the Company, customary conditions to closing, indemnification obligations of the Company and the purchasers, including for liabilities arising under the Securities Act of 1933, as amended (the “Securities Act”), other obligations of the parties and termination provisions. The representations, warranties and covenants contained in the Purchase Agreement were made only for the purposes of such agreements and as of specific dates, were solely for the benefit of the parties to such agreements and may be subject to limitations agreed upon by the contracting parties.

A holder will not have the right to exercise any portion of the Warrants or Pre-Funded Warrants if the holder (together with its affiliates) would beneficially own in excess of 4.99% or 9.99%, as applicable, of the number of shares of Common Stock outstanding immediately after giving effect to the exercise, as such percentage ownership is determined in accordance with the terms of the Warrants or the Pre-Funded Warrants, respectively.

Pursuant to an Engagement Letter (as amended, the “Engagement Letter”) with H.C. Wainwright & Co., LLC (the “Placement Agent”), the Company agreed to pay the Placement Agent in connection with the Offering (i) a cash fee equal to 7.0% of the aggregate gross proceeds received in the Offering, (ii) a management fee equal to 1.0% of the aggregate gross proceeds received in the Offering, (iii) up to $100,000 for fees and expenses of the Placement Agent’s counsel and other out of pocket expenses, (iv) a non-accountable expense allowance of $25,000 and (v) $15,950 for the clearing expenses.

Also pursuant to the Engagement Letter, the Company, in connection with the Offering, agreed to issue to the Placement Agent or its designees warrants (the “Placement Agent Warrants”) to purchase up to an aggregate of 1,012,658 shares of Common Stock (the “Placement Agent Warrant Shares”) (which represents 6.0% of the Shares and Pre-Funded Warrants sold in the Offering). The Placement Agent Warrants have an exercise price of $0.2963 per share and will expire on April 29, 2029.

The Shares, the Pre-Funded Warrants, the Pre-Funded Warrant Shares, the Series A-1 Warrants, the Series A-1 Warrant Shares, Series A-2 Warrants, the Series A-2 Warrant Shares, Series A-3 Warrants, the Series A-3 Warrant Shares, the Placement Agent Warrants and the Placement Agent Warrant Shares were offered by the Company pursuant to a Registration Statement on Form S-1 originally filed on March 15, 2024, as amended (including the prospectus forming a part of such Registration Statement), with the Securities and Exchange Commission (the “SEC”) under the Securities Act (File No. 333-278006), and declared effective by the SEC on April 29, 2024.

Warrant Amendment Agreement

In connection with the Offering, the Company also entered into a warrant amendment agreement (the “Warrant Amendment Agreement”) with the Investor. Under the Warrant Amendment Agreement, the Company agreed to amend certain existing warrants to purchase up to 2,588,236 shares of common stock that were previously issued in October 2023 to the Investor, with an exercise price of $1.58 per share (the “Existing Warrants”), in consideration for their purchase of the securities in the Offering, as follows: (i) lower the exercise price of the Existing Warrants to $0.237 per share, (ii) provide that the Existing Warrants, as amended, will not be exercisable until the receipt of Warrant Stockholder Approval for the exercisability of the Warrants in the Offering, and (iii) extend the original expiration date of the Existing Warrants by five years following the receipt of such Warrant Stockholder Approval. The Warrant Amendment Agreement became effective on May 2, 2024.

The foregoing description of the Purchase Agreement, the Warrant Amendment Agreement, the Pre-Funded Warrants, the Series A-1 Warrants, the Series A-2 Warrants, the Series A-3 Warrants and the Placement Agent Warrants is not complete and is qualified in its entirety by reference to the full text of the form of Purchase Agreement, the form of Pre-Funded Warrant, the form of Series A-1, A-2 and A-3 Warrant, form of Placement Agent Warrant and form of Warrant Amendment Agreement, copies of which are filed as Exhibits 10.1, 4.1, 4.2, 4.3, and 10.2, respectively, to this Current Report on Form 8-K and are incorporated herein by reference.

On April 29, 2024, the Company issued a press release announcing the pricing of the Offering and on May 2, 2024, the Company issued a press release announcing the closing of the Offering. A copy of each such press release is attached as Exhibit 99.1 and 99.2, respectively, to this Current Report on Form 8-K and are hereby incorporated by reference herein.

(d) Exhibits

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.