MBIO / Mustang Bio, Inc. - Pengajuan SECLaporan Tahunan, Pernyataan Proksi

MUSTANG BIO, INC. Up to $4,750,000 Common Stock

Filed Pursuant to Rule 424(b)(5) Registration No. 333-279891 AMENDMENT NO. 3 DATED SEPTEMBER 5, 2025 to Prospectus Supplement dated June 19, 2024 (To Prospectus dated June 12, 2024) MUSTANG BIO, INC. Up to $4,750,000 Common Stock This Amendment No. 3 to Prospectus Supplement (this “Amendment”) further amends our prospectus supplement dated June 19, 2024 (the “Prospectus Supplement”). This Amendmen

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2025 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number 001-38191 MUST

Financial Statements and Exhibits, Other Events

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): July 7, 2025 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Number)

Mustang Bio Granted Orphan Drug Designation by U.S. FDA for MB-101 (IL13Ra2-targeted CAR T-cells) to Treat Astrocytomas and Glioblastoma In an ongoing Phase 1 trial published in Nature Medicine, MB-101 was well-tolerated and 50% of patients achieved

Exhibit 99.1 Mustang Bio Granted Orphan Drug Designation by U.S. FDA for MB-101 (IL13Ra2-targeted CAR T-cells) to Treat Astrocytomas and Glioblastoma In an ongoing Phase 1 trial published in Nature Medicine, MB-101 was well-tolerated and 50% of patients achieved stable disease or better with two partial responses and two complete responses lasting 7.5 and 66+ months, respectively Preclinical data

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2025 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number 001-38191 MUS

As filed with the Securities and Exchange Commission on April 4, 2025

As filed with the Securities and Exchange Commission on April 4, 2025 Registration No.

As filed with the Securities and Exchange Commission on April 1, 2025.

As filed with the Securities and Exchange Commission on April 1, 2025. Registration No. 333-284299 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Post-effective Amendment No. 1 to FORM S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 MUSTANG BIO, INC. (Exact name of registrant as specified in its charter) Delaware 2836 47-3828760 (State or Other Jurisdiction of

495,000 Shares of Common Stock 2,162,807 Pre-funded Warrants to Purchase up to 2,162,807 Shares of Common Stock 2,657,807 Series C-1 Warrants to Purchase up to 2,657,807 Shares of Common Stock 2,657,807 Series C-2 Warrants to Purchase up to 2,657,807

Filed Pursuant to Rule 424(b)(3) Registration No. 333-284299 PROSPECTUS SUPPLEMENT NO. 3 (to prospectus dated February 5, 2025) 495,000 Shares of Common Stock 2,162,807 Pre-funded Warrants to Purchase up to 2,162,807 Shares of Common Stock 2,657,807 Series C-1 Warrants to Purchase up to 2,657,807 Shares of Common Stock 2,657,807 Series C-2 Warrants to Purchase up to 2,657,807 Shares of Common Stoc

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K ☒ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the Fiscal Year Ended December 31, 2024 or ☐TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the Transition Period from to . Commission File No. 001-38191 MUSTANG BIO

Description of Securities of Mustang Bio, Inc. **

EXHIBIT 4.2 DESCRIPTION OF THE REGISTRANT’S SECURITIES REGISTERED PURSUANT TO SECTION 12 OF THE SECURITIES EXCHANGE ACT OF 1934 The following descriptions of our capital stock and of certain provisions of our Amended and Restated Certificate of Incorporation (“Certificate of Incorporation”), as amended, our Amended and Restated Bylaws (“Bylaws”), and of certain provisions of Delaware law do not pu

Insider Trading Policy**

Exhibit 19.1 Mustang Bio, Inc. is subject to the following Insider Trading Policy of Fortress Biotech, Inc. (“Fortress”), which is applicable to all Fortress subsidiaries. FORTRESS BIOTECH, INC. AND SUBSIDIARIES INSIDER TRADING POLICY January 22, 2024 PERSONS COVERED This Insider Trading Policy applies to Fortress Biotech, Inc. (“Fortress”) and each of its publicly traded and private subsidiaries

Financial Statements and Exhibits, Other Events

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): March 5, 2025 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Number

Mustang Bio Regains Compliance with Nasdaq Capital Market Requirement

Exhibit 99.1 Mustang Bio Regains Compliance with Nasdaq Capital Market Requirement WALTHAM, Mass., March 5, 2025 (GLOBE NEWSWIRE) - Mustang Bio, Inc. (“Mustang” or the “Company”) (Nasdaq: MBIO) today announced that it has received notice from The Nasdaq Stock Market LLC (“Nasdaq”) informing the Company that it has regained compliance with the Nasdaq Capital Market’s minimum stockholders’ equity re

SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 14C INFORMATION INFORMATION STATEMENT PURSUANT TO SECTION 14(C) OF THE SECURITIES EXCHANGE ACT OF 1934

SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 14C INFORMATION INFORMATION STATEMENT PURSUANT TO SECTION 14(C) OF THE SECURITIES EXCHANGE ACT OF 1934 Check the appropriate box: ¨ Preliminary Information Statement ¨ Confidential, for Use of the Commission Only (as permitted by Rule 14c-5(d)(2)) x Definitive Information Statement Mustang Bio, Inc. (Name of Registrant as Specified

495,000 Shares of Common Stock 2,162,807 Pre-funded Warrants to Purchase up to 2,162,807 Shares of Common Stock 2,657,807 Series C-1 Warrants to Purchase up to 2,657,807 Shares of Common Stock 2,657,807 Series C-2 Warrants to Purchase up to 2,657,807

Filed Pursuant to Rule 424(b)(3) Registration No. 333-284299 PROSPECTUS SUPPLEMENT NO. 2 (to prospectus dated February 5, 2025) 495,000 Shares of Common Stock 2,162,807 Pre-funded Warrants to Purchase up to 2,162,807 Shares of Common Stock 2,657,807 Series C-1 Warrants to Purchase up to 2,657,807 Shares of Common Stock 2,657,807 Series C-2 Warrants to Purchase up to 2,657,807 Shares of Common Stoc

Bill of Sale and Surrender Agreement, dated January 31, 2025, by and between Mustang Bio, Inc. and AbbVie Bioresearch Center Inc.

Exhibit 2.1 CERTAIN IDENTIFIED INFORMATION HAS BEEN EXCLUDED FROM THIS EXHIBIT BECAUSE IT IS BOTH (I) NOT MATERIAL AND (II) THE TYPE THAT THE REGISTRANT TREATS AS PRIVATE OR CONFIDENTIAL. [***] INDICATES THAT INFORMATION HAS BEEN REDACTED. BILL OF SALE AND SURRENDER AGREEMENT This BILL OF SALE AND SURRENDER AGREEMENT (this “Bill of Sale Agreement”) is made and entered into as of the 31st day of Ja

Mustang Bio Announces Sale of Fixed Assets and Exit of Facility

Exhibit 99.1 Mustang Bio Announces Sale of Fixed Assets and Exit of Facility Waltham, MA– February 27, 2025 – Mustang Bio, Inc. (“Mustang” or the “Company”) (Nasdaq: MBIO), a clinical-stage biopharmaceutical company focused on translating today’s medical breakthroughs in cell therapies into potential cures for difficult-to-treat cancers, today announced the exit of the lease for its manufacturing

Completion of Acquisition or Disposition of Assets, Other Events, Financial Statements and Exhibits

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): February 21, 2025 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Nu

First Amendment to Lease Agreement, dated February 7, 2025, by and between Mustang Bio, Inc. and WCS - 377 Plantation Street, Inc.

Exhibit 10.1 FIRST AMENDMENT TO LEASE AGREEMENT THIS FIRST AMENDMENT TO LEASE AGREEMENT (this “Amendment”) is made as of the 7th 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”).   RECITALS A.                Landlord and Tenant are parties to that certain

Submission of Matters to a Vote of Security Holders

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): February 19, 2025 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Nu

SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 14C INFORMATION INFORMATION STATEMENT PURSUANT TO SECTION 14(C) OF THE SECURITIES EXCHANGE ACT OF 1934

SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 14C INFORMATION INFORMATION STATEMENT PURSUANT TO SECTION 14(C) OF THE SECURITIES EXCHANGE ACT OF 1934 Check the appropriate box: x Preliminary Information Statement ¨ Confidential, for Use of the Commission Only (as permitted by Rule 14c-5(d)(2)) ¨ Definitive Information Statement Mustang Bio, Inc. (Name of Registrant as Specified

Entry into a Material Definitive Agreement, Termination of a Material Definitive Agreement

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): February 7, 2025 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Num

495,000 Shares of Common Stock 2,162,807 Pre-funded Warrants to Purchase up to 2,162,807 Shares of Common Stock 2,657,807 Series C-1 Warrants to Purchase up to 2,657,807 Shares of Common Stock 2,657,807 Series C-2 Warrants to Purchase up to 2,657,807

Filed Pursuant to Rule 424(b)(3) Registration No. 333-284299 PROSPECTUS SUPPLEMENT NO. 1 (to prospectus dated February 5, 2025) 495,000 Shares of Common Stock 2,162,807 Pre-funded Warrants to Purchase up to 2,162,807 Shares of Common Stock 2,657,807 Series C-1 Warrants to Purchase up to 2,657,807 Shares of Common Stock 2,657,807 Series C-2 Warrants to Purchase up to 2,657,807 Shares of Common Stoc

JOINT FILING AGREEMENT

Exhibit 1 JOINT FILING AGREEMENT The undersigned acknowledge and agree that the foregoing statement on Schedule 13G is filed on behalf of each of the undersigned and that all subsequent amendments to this statement on Schedule 13G may be filed on behalf of each of the undersigned without the necessity of filing additional joint filing agreements.

Form of Pre-Funded Warrant

Exhibit 4.1 EXHIBIT A-2 PREFUNDED COMMON STOCK PURCHASE WARRANT MUSTANG BIO, INC. Warrant Shares: Initial Exercise Date: , 2025 THIS PREFUNDED COMMON STOCK PURCHASE WARRANT (the “Warrant”) certifies that, for value received, or its assigns (the “Holder”) is entitled, upon the terms and subject to the limitations on exercise and the conditions hereinafter set forth, at any time on or after the date

Form of Series C-1 and C-2 Warrant

Exhibit 4.2 EXHIBIT A-1 SERIES [C-1][C-2] COMMON STOCK PURCHASE WARRANT MUSTANG BIO, INC. Warrant Shares: Initial Exercise Date: , 2025 THIS SERIES [C-1][C-2] COMMON STOCK PURCHASE WARRANT (the “Warrant”) certifies that, for value received, or its assigns (the “Holder”) is entitled, upon the terms and subject to the limitations on exercise and the conditions hereinafter set forth, at any time on o

Mustang Bio Announces Closing of $8 Million Public Offering

Exhibit 99.2 Mustang Bio Announces Closing of $8 Million Public Offering WORCESTER, Mass., Feb. 10, 2025 (GLOBE NEWSWIRE) - Mustang Bio, Inc. (“Mustang” or the “Company”) (Nasdaq: MBIO), a clinical-stage biopharmaceutical company focused on translating today’s medical breakthroughs in cell therapies into potential cures for difficult-to-treat cancers, today announced the closing of its previously

Entry into a Material Definitive Agreement, Financial Statements and Exhibits, Other Events

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): February 5, 2025 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Num

Form of Securities Purchase Agreement

Exhibit 10.1 SECURITIES PURCHASE AGREEMENT This Securities Purchase Agreement (this “Agreement”) is dated as of February 5, 2025, between Mustang Bio, Inc., a Delaware corporation (the “Company”), and each purchaser identified on the signature pages hereto (each, including its successors and assigns, a “Purchaser” and collectively the “Purchasers”). WHEREAS, subject to the terms and conditions set

Mustang Bio Regains Compliance with Nasdaq Minimum Bid Price Requirement

Exhibit 99.3 Mustang Bio Regains Compliance with Nasdaq Minimum Bid Price Requirement WORCESTER, Mass., February 11, 2025 (GLOBE NEWSWIRE) - Mustang Bio, Inc. (“Mustang” or the “Company”) (Nasdaq: MBIO) today announced that it has received notice from The Nasdaq Stock Market LLC (“Nasdaq”) informing the Company that it has regained compliance with the minimum bid price requirement under Nasdaq Lis

Form of Placement Agent Warrant

Exhibit 4.3 PLACEMENT AGENT COMMON STOCK PURCHASE WARRANT MUSTANG BIO, INC. Warrant Shares: Initial Exercise Date: , 2025 THIS PLACEMENT AGENT COMMON STOCK PURCHASE WARRANT (the “Warrant”) certifies that, for value received, or its assigns (the “Holder”) is entitled, upon the terms and subject to the limitations on exercise and the conditions hereinafter set forth, at any time on or after the Stoc

February 6, 2025

Exhibit 99.1 February 6, 2025 Mustang Bio Announces Pricing of $8 Million Public Offering WORCESTER, Mass., Feb. 06, 2025 (GLOBE NEWSWIRE) - Mustang Bio, Inc. (“Mustang” or the “Company”) (Nasdaq: MBIO), a clinical-stage biopharmaceutical company focused on translating today’s medical breakthroughs in cell therapies into potential cures for difficult-to-treat cancers, today announced the pricing o

495,000 Shares of Common Stock 2,162,807 Pre-funded Warrants to Purchase up to 2,162,807 Shares of Common Stock 2,657,807 Series C-1 Warrants to Purchase up to 2,657,807 Shares of Common Stock 2,657,807 Series C-2 Warrants to Purchase up to 2,657,807

Table of Contents Filed Pursuant to Rule 424(b)(4) File No. 333-284299 PROSPECTUS 495,000 Shares of Common Stock 2,162,807 Pre-funded Warrants to Purchase up to 2,162,807 Shares of Common Stock 2,657,807 Series C-1 Warrants to Purchase up to 2,657,807 Shares of Common Stock 2,657,807 Series C-2 Warrants to Purchase up to 2,657,807 Shares of Common Stock Placement Agent Warrants to Purchase up to 1

Form of Placement Agent Warrant

Exhibit 4.19 PLACEMENT AGENT COMMON STOCK PURCHASE WARRANT MUSTANG BIO, INC. Warrant Shares: Initial Exercise Date: , 2025 THIS PLACEMENT AGENT COMMON STOCK PURCHASE WARRANT (the “Warrant”) certifies that, for value received, or its assigns (the “Holder”) is entitled, upon the terms and subject to the limitations on exercise and the conditions hereinafter set forth, at any time on or after the [St

Mustang Bio, Inc. 377 Plantation Street Worcester, Massachusetts 01605

Mustang Bio, Inc. 377 Plantation Street Worcester, Massachusetts 01605 VIA EDGAR February 5, 2025 Securities and Exchange Commission Division of Corporation Finance Office of Life Sciences 100 F Street, N.E. Washington, D.C. 20549 Attn: Tim Buchmiller Re: Mustang Bio, Inc. Registration Statement on Form S-1 (Reg. No. 333-284299) Request for Acceleration of Effective Date Ladies and Gentlemen: Purs

Filing Fee Table

Exhibit 107 Calculation of Filing Fee Tables Form S-1 (Form Type) Mustang Bio, Inc.

Form of Pre-Funded Warrant

Exhibit 4.18 EXHIBIT A-2 PREFUNDED COMMON STOCK PURCHASE WARRANT MUSTANG BIO, INC. Warrant Shares: Initial Exercise Date: , 2025 THIS PREFUNDED COMMON STOCK PURCHASE WARRANT (the “Warrant”) certifies that, for value received, or its assigns (the “Holder”) is entitled, upon the terms and subject to the limitations on exercise and the conditions hereinafter set forth, at any time on or after the dat

Form of Securities Purchase Agreement

Exhibit 10.46 SECURITIES PURCHASE AGREEMENT This Securities Purchase Agreement (this “Agreement”) is dated as of , 2025, between Mustang Bio, Inc., a Delaware corporation (the “Company”), and each purchaser identified on the signature pages hereto (each, including its successors and assigns, a “Purchaser” and collectively the “Purchasers”). WHEREAS, subject to the terms and conditions set forth in

As filed with the Securities and Exchange Commission on February 5, 2025.

Table of Contents As filed with the Securities and Exchange Commission on February 5, 2025.

Form of Series C-1 and C-2 Warrant

Exhibit 4.17 EXHIBIT A-1 SERIES [C-1][C-2] COMMON STOCK PURCHASE WARRANT MUSTANG BIO, INC. Warrant Shares: Initial Exercise Date: , 2025 THIS SERIES [C-1][C-2] COMMON STOCK PURCHASE WARRANT (the “Warrant”) certifies that, for value received, or its assigns (the “Holder”) is entitled, upon the terms and subject to the limitations on exercise and the conditions hereinafter set forth, at any time on

SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 14C INFORMATION INFORMATION STATEMENT PURSUANT TO SECTION 14(C) OF THE SECURITIES EXCHANGE ACT OF 1934

SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 14C INFORMATION INFORMATION STATEMENT PURSUANT TO SECTION 14(C) OF THE SECURITIES EXCHANGE ACT OF 1934 Check the appropriate box: ¨ Preliminary Information Statement ¨ Confidential, for Use of the Commission Only (as permitted by Rule 14c-5(d)(2)) x Definitive Information Statement Mustang Bio, Inc. (Name of Registrant as Specified

Amendments to Articles of Incorporation or Bylaws; Change in Fiscal Year, Material Modification to Rights of Security Holders, Financial Statements and Exhibits, Other Events

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): January 14, 2025 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Num

Certificate of Amendment to the Amended and Restated Certificate of Incorporation of Mustang Bio, Inc.

Exhibit 3.1

Mustang Bio Announces Reverse Stock Split

Exhibit 99.1 Mustang Bio Announces Reverse Stock Split WORCESTER, Mass., Jan. 14, 2025 - Mustang Bio, Inc. (“Mustang” or the “Company”) (Nasdaq: MBIO), a clinical-stage biopharmaceutical company focused on translating today’s medical breakthroughs in cell therapies into potential cures for difficult-to-treat cancers, today announced that it will effect a 1-for-50 reverse stock split of its issued

Filing Fee Table

Exhibit 107 Calculation of Filing Fee Tables Form S-1 (Form Type) Mustang Bio, Inc.

As filed with the Securities and Exchange Commission on January 15, 2025.

Table of Contents As filed with the Securities and Exchange Commission on January 15, 2025.

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): January 10, 2025 Mustang Bio, Inc

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): January 10, 2025 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Num

SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 14C INFORMATION INFORMATION STATEMENT PURSUANT TO SECTION 14(C) OF THE SECURITIES EXCHANGE ACT OF 1934

SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 14C INFORMATION INFORMATION STATEMENT PURSUANT TO SECTION 14(C) OF THE SECURITIES EXCHANGE ACT OF 1934 Check the appropriate box: x Preliminary Information Statement ¨ Confidential, for Use of the Commission Only (as permitted by Rule 14c-5(d)(2)) ¨ Definitive Information Statement Mustang Bio, Inc. (Name of Registrant as Specified

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): December 26, 2024 Mustang Bio, In

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): December 26, 2024 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Nu

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 Filed by Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ☒ Definiti

34,767,934 Shares of Common Stock underlying certain Common Warrants and Placement Agent Warrants

Filed Pursuant to Rule 424(b)(3) Registration No. 333-283420 PROSPECTUS 34,767,934 Shares of Common Stock underlying certain Common Warrants and Placement Agent Warrants This prospectus relates to the resale by the selling stockholders (the “Selling Stockholders”) identified in this prospectus under the section “The Selling Stockholders,” or their pledgees, donees, transferees or other successors

Mustang Bio, Inc. 377 Plantation Street Worcester, Massachusetts 01605

Mustang Bio, Inc. 377 Plantation Street Worcester, Massachusetts 01605 VIA EDGAR November 25, 2024 Securities and Exchange Commission Division of Corporation Finance Office of Life Sciences 100 F Street, N.E. Washington, D.C. 20549 Attn: Joshua Gorsky Re: Mustang Bio, Inc. Registration Statement on Form S-3 (Reg. No. 333-283420) Request for Acceleration of Effective Date Ladies and Gentlemen: Purs

As filed with the Securities and Exchange Commission on November 22, 2024

As filed with the Securities and Exchange Commission on November 22, 2024 Registration No.

Filing Fee Table

Exhibit 107 Calculation of Filing Fee Tables Form S-3 (Form Type) Mustang Bio, Inc.

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers, Notice of Delisting or Failure to Satisfy a Continued Listing Rule or Standard; Transfer of Listing

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): November 12, 2024 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Nu

MBIO / Mustang Bio, Inc. / ARMISTICE CAPITAL, LLC Passive Investment

SC 13G/A 1 armistice-mbio093024a1.htm UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 13G/A Under the Securities Exchange Act of 1934 (Amendment No. 1)* MUSTANG BIO, INC. (Name of Issuer) Common Stock, par value $0.0001 per share (Title of Class of Securities) 62818Q203 (CUSIP Number) September 30, 2024 (Date of Event Which Requires Filing of this Statement) Check th

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2024 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number 001-38191

Other Events, Shareholder Director Nominations

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): November 6, 2024 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Num

Mustang Bio Announces Exercise of Warrants for $4 Million Gross Proceeds

Exhibit 99.1 Mustang Bio Announces Exercise of Warrants for $4 Million Gross Proceeds WORCESTER, Mass., October 24, 2024 (GLOBE NEWSWIRE) - Mustang Bio, Inc. (“Mustang” or the “Company”) (Nasdaq: MBIO), a clinical-stage biopharmaceutical company focused on translating today’s medical breakthroughs in cell therapies into potential cures for difficult-to-treat cancers, today announced that it has en

Form of Indemnification Agreement

Exhibit 10.2 INDEMNITY AGREEMENT This Indemnity Agreement (this “Agreement”) dated as of , is made by and between Mustang Bio, Inc., a Delaware corporation (the “Company”), and (“Indemnitee”). Recitals A.            The Company desires to attract and retain the services of highly qualified individuals as directors, officers, employees and agents. B.            The Company’s bylaws (the “Bylaws”) r

Form of Series B-1 Warrant

Exhibit 4.1 NEITHER THIS SECURITY NOR THE SECURITIES FOR WHICH THIS SECURITY IS EXERCISABLE HAVE BEEN REGISTERED WITH THE SECURITIES AND EXCHANGE COMMISSION OR THE SECURITIES COMMISSION OF ANY STATE IN RELIANCE UPON AN EXEMPTION FROM REGISTRATION UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “SECURITIES ACT”), AND, ACCORDINGLY, MAY NOT BE OFFERED OR SOLD EXCEPT PURSUANT TO AN EFFECTIVE REGISTR

Form of Investor Inducement Agreement

Exhibit 10.1 MUSTANG BIO, INC. October 24, 2024 Holder of Common Stock Purchase Warrants Re: Inducement Offer to Exercise Common Stock Purchase Warrants Dear Holder: Mustang Bio, Inc. (the “Company”) is pleased to offer to you the opportunity to exercise the warrants to purchase shares of the Company’s common stock, par value $0.0001 per share (the “Common Stock”), set forth on Exhibit A hereto (t

Form of Series B-2 Warrant

Exhibit 4.2 NEITHER THIS SECURITY NOR THE SECURITIES FOR WHICH THIS SECURITY IS EXERCISABLE HAVE BEEN REGISTERED WITH THE SECURITIES AND EXCHANGE COMMISSION OR THE SECURITIES COMMISSION OF ANY STATE IN RELIANCE UPON AN EXEMPTION FROM REGISTRATION UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “SECURITIES ACT”), AND, ACCORDINGLY, MAY NOT BE OFFERED OR SOLD EXCEPT PURSUANT TO AN EFFECTIVE REGISTR

Form of October 2024 Wainwright Warrant

Exhibit 4.3 NEITHER THIS SECURITY NOR THE SECURITIES FOR WHICH THIS SECURITY IS EXERCISABLE HAVE BEEN REGISTERED WITH THE SECURITIES AND EXCHANGE COMMISSION OR THE SECURITIES COMMISSION OF ANY STATE IN RELIANCE UPON AN EXEMPTION FROM REGISTRATION UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “SECURITIES ACT”), AND, ACCORDINGLY, MAY NOT BE OFFERED OR SOLD EXCEPT PURSUANT TO AN EFFECTIVE REGISTR

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers, Entry into a Material Definitive Agreement, Unregistered Sales of Equity Securities, Financial Statements and Exhibits, Other Events

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): October 23, 2024 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Num

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): September 10, 2024 Mustang Bio, I

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): September 10, 2024 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File N

MUSTANG BIO, INC. Up to $2,249,382 Common Stock

Filed Pursuant to Rule 424(b)(5) Registration No. 333-279891 AMENDMENT NO. 2 DATED AUGUST 16, 2024 to Prospectus Supplement dated June 19, 2024 (To Prospectus dated June 12, 2024) MUSTANG BIO, INC. Up to $2,249,382 Common Stock This Amendment No. 2 to Prospectus Supplement (this “Amendment”) amends our prospectus supplement dated June 19, 2024 (the “Prospectus Supplement”). This Amendment should b

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2024 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number 001-38191 MUST

Mustang Bio, Inc. 377 Plantation Street Worcester, Massachusetts 01605

Mustang Bio, Inc. 377 Plantation Street Worcester, Massachusetts 01605 VIA EDGAR July 25, 2024 Securities and Exchange Commission Division of Corporation Finance Office of Life Sciences 100 F Street, N.E. Washington, D.C. 20549 Attn: Lauren S. Hamill Re: Mustang Bio, Inc. Registration Statement on Form S-1 (Reg. No. 333-280927) Request for Acceleration of Effective Date Ladies and Gentlemen: Pursu

As filed with the Securities and Exchange Commission on July 19, 2024.

As filed with the Securities and Exchange Commission on July 19, 2024. Registration Statement No. 333- UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Form S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 Mustang Bio, Inc. (Exact name of registrant as specified in its charter) Delaware 2834 47-3828760 (State or Other Jurisdiction of Incorporation or Organization)

Filing Fee Table

Exhibit 107 Calculation of Filing Fee Tables Form S-1 (Form Type) Mustang Bio, Inc.

SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 14C INFORMATION INFORMATION STATEMENT PURSUANT TO SECTION 14(C) OF THE SECURITIES EXCHANGE ACT OF 1934

SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 14C INFORMATION INFORMATION STATEMENT PURSUANT TO SECTION 14(C) OF THE SECURITIES EXCHANGE ACT OF 1934 Check the appropriate box: ¨ Preliminary Information Statement ¨ Confidential, for Use of the Commission Only (as permitted by Rule 14c-5(d)(2)) x Definitive Information Statement Mustang Bio, Inc. (Name of Registrant as Specified

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): June 27, 2024 Mustang Bio, Inc. (

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): June 27, 2024 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Number

MUSTANG BIO, INC. Up to $2,646,352 Common Stock

Filed Pursuant to Rule 424(b)(5) Registration No. 333-279891 AMENDMENT NO. 1 DATED July 3, 2024 to Prospectus Supplement dated June 19, 2024 (To Prospectus dated June 12, 2024) MUSTANG BIO, INC. Up to $2,646,352 Common Stock This Amendment No. 1 to Prospectus Supplement (this “Amendment”) amends our prospectus supplement dated June 19, 2024 (the “Prospectus Supplement). This Amendment should be re

Asset Purchase Agreement, dated June 27, 2024, by and between the Company and uBriGrene (Boston) Biosciences, Inc.

Exhibit 1.1 CERTAIN IDENTIFIED INFORMATION HAS BEEN EXCLUDED FROM THIS EXHIBIT BECAUSE IT IS BOTH (I) NOT MATERIAL AND (II) THE TYPE THAT THE REGISTRANT TREATS AS PRIVATE OR CONFIDENTIAL. [***] INDICATES THAT INFORMATION HAS BEEN REDACTED. ASSET PURCHASE AGREEMENT BY AND BETWEEN MUSTANG BIO, INC., AND UBRIGENE (BOSTON) BIOSCIENCES INC., Dated as of June 27, 2024 Exhibits Exhibit A Bill of Sale and

MBIO / Mustang Bio, Inc. / Fortress Biotech, Inc. - SC 13D/A Activist Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13D (Amendment No. 3) Under the Securities Exchange Act of 1934 MUSTANG BIO, INC. (Name of Issuer) Common Stock, $0.0001 Par Value (Title of Class of Securities) 62818Q203 (CUSIP Number) Fortress Biotech, Inc. c/o Lindsay A. Rosenwald, M.D. 1111 Kane Concourse, Suite 301 Bay Harbor Islands, FL 33154 (781) 652-4500 (Na

SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 14C INFORMATION INFORMATION STATEMENT PURSUANT TO SECTION 14(C) OF THE SECURITIES EXCHANGE ACT OF 1934

SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 14C INFORMATION INFORMATION STATEMENT PURSUANT TO SECTION 14(C) OF THE SECURITIES EXCHANGE ACT OF 1934 Check the appropriate box: x Preliminary Information Statement ¨ Confidential, for Use of the Commission Only (as permitted by Rule 14c-5(d)(2)) ¨ Definitive Information Statement Mustang Bio, Inc. (Name of Registrant as Specified

Entry into a Material Definitive Agreement, Unregistered Sales of Equity Securities, Financial Statements and Exhibits, Other Events

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): June 19, 2024 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Number

Form of June 2024 Wainwright Warrant

EXHIBIT 4.3 NEITHER THIS SECURITY NOR THE SECURITIES FOR WHICH THIS SECURITY IS EXERCISABLE HAVE BEEN REGISTERED WITH THE SECURITIES AND EXCHANGE COMMISSION OR THE SECURITIES COMMISSION OF ANY STATE IN RELIANCE UPON AN EXEMPTION FROM REGISTRATION UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “SECURITIES ACT”), AND, ACCORDINGLY, MAY NOT BE OFFERED OR SOLD EXCEPT PURSUANT TO AN EFFECTIVE REGISTR

Form of June 2024 Pre-funded Warrant

Exhibit 4.1 PREFUNDED COMMON STOCK PURCHASE WARRANT MUSTANG BIO, INC. Warrant Shares: Initial Exercise Date: , 2024 THIS PREFUNDED COMMON STOCK PURCHASE WARRANT (the “Warrant”) certifies that, for value received, or its assigns (the “Holder”) is entitled, upon the terms and subject to the limitations on exercise and the conditions hereinafter set forth, at any time on or after the date hereof (the

Form of Securities Purchase Agreement, dated June 19, 2024, by and between the Company and the purchaser party thereto

exhibit 10.1 SECURITIES PURCHASE AGREEMENT This Securities Purchase Agreement (this “Agreement”) is dated as of June 19, 2024, between Mustang Bio, Inc., a Delaware corporation (the “Company”), and each purchaser identified on the signature pages hereto (each, including its successors and assigns, a “Purchaser” and collectively the “Purchasers”). WHEREAS, subject to the terms and conditions set fo

Mustang Bio Announces $2.5 Million Registered Direct Offering Priced At-the-Market Under Nasdaq Rules

Exhibit 99.1 Mustang Bio Announces $2.5 Million Registered Direct Offering Priced At-the-Market Under Nasdaq Rules WORCESTER, Mass., June 20, 2024 (GLOBE NEWSWIRE) - Mustang Bio, Inc. (“Mustang” or the “Company”) (Nasdaq: MBIO), a clinical-stage biopharmaceutical company focused on translating today’s medical breakthroughs in cell therapies into potential cures for difficult-to-treat cancers, toda

Form of June 2024 Warrant

Exhibit 4.2 NEITHER THIS SECURITY NOR THE SECURITIES FOR WHICH THIS SECURITY IS EXERCISABLE HAVE BEEN REGISTERED WITH THE SECURITIES AND EXCHANGE COMMISSION OR THE SECURITIES COMMISSION OF ANY STATE IN RELIANCE UPON AN EXEMPTION FROM REGISTRATION UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “SECURITIES ACT”), AND, ACCORDINGLY, MAY NOT BE OFFERED OR SOLD EXCEPT PURSUANT TO AN EFFECTIVE REGISTR

Mustang Bio Announces Closing of $2.5 Million Registered Direct Offering Priced At-the-Market Under Nasdaq Rules

Exhibit 99.2 Mustang Bio Announces Closing of $2.5 Million Registered Direct Offering Priced At-the-Market Under Nasdaq Rules WORCESTER, Mass., June 21, 2024 (GLOBE NEWSWIRE) - Mustang Bio, Inc. (“Mustang” or the “Company”) (Nasdaq: MBIO), a clinical-stage biopharmaceutical company focused on translating today’s medical breakthroughs in cell therapies into potential cures for difficult-to-treat ca

3,025,000 Shares of Common Stock 3,105,000 Pre-Funded Warrants to Purchase up to 3,105,000 Shares of Common Stock Up to 3,105,000 Shares of Common Stock Underlying the Pre-Funded Warrants

Filed Pursuant to Rule 424(b)(5) Registration No. 333-279891 PROSPECTUS SUPPLEMENT To the Prospectus dated June 12, 2024 3,025,000 Shares of Common Stock 3,105,000 Pre-Funded Warrants to Purchase up to 3,105,000 Shares of Common Stock Up to 3,105,000 Shares of Common Stock Underlying the Pre-Funded Warrants We are offering 3,025,000 shares of our common stock, par value $0.0001 per share (“common

MUSTANG BIO, INC.

Filed Pursuant to Rule 424(b)(5) Registration No. 333-279891 Prospectus Supplement dated June 19, 2024 (To Prospectus dated June 12, 2024) MUSTANG BIO, INC. This prospectus supplement supplements and amends certain information contained in the prospectus dated June 12, 2024 (the “ATM Prospectus”), relating to the offer and sale of shares of our common stock, par value $0.0001 per share (the “commo

Mustang Bio, Inc. 377 Plantation Street Worcester, Massachusetts 01605

Mustang Bio, Inc. 377 Plantation Street Worcester, Massachusetts 01605 VIA EDGAR June 10, 2024 Securities and Exchange Commission Division of Corporation Finance Office of Life Sciences 100 F Street, N.E. Washington, D.C. 20549 Attn: Jason Drory Re: Mustang Bio, Inc. Registration Statement on Form S-3 (Reg. No. 333-279891) Request for Acceleration of Effective Date Ladies and Gentlemen: Pursuant t

Entry into a Material Definitive Agreement, Termination of a Material Definitive Agreement, Financial Statements and Exhibits

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): May 31, 2024 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Number)

Form of Indenture, between the Registrant and one or more trustees to be named.

Exhibit 4.11 MUSTANG BIO, INC. and Trustee INDENTURE Dated as of DEBT SECURITIES CROSS-REFERENCE TABLE(1) Section of Trust Indenture Act of 1939, as amended Section of Indenture 310(a) 6.09 310(b) 6.08 6.10 310(c) Inapplicable 311(a) 6.13 311(b) 6.13 311(c) Inapplicable 312(a) 4.01 4.04 312(b) 4.04(c) 312(c) 4.04(c) 313(a) 4.03 313(b) 4.03 313(c) 4.03 313(d) 4.03 314(a) 3.05 and 4.02 314(b) Inappl

At the Market Offering Agreement, dated May 31, 2024, by and between the Company and H.C. Wainwright & Co., LLC

Exhibit 1.2 AT THE MARKET OFFERING AGREEMENT May 31, 2024 H.C. Wainwright & Co., LLC 430 Park Avenue New York, New York 10022 Ladies and Gentlemen: Mustang Bio, Inc., a corporation organized under the laws of Delaware (the “Company”), confirms its agreement (this “Agreement”) with H.C. Wainwright & Co., LLC (the “Manager”) as follows: 1.             Definitions. The terms that follow, when used in

As filed with the Securities and Exchange Commission on May 31, 2024

As filed with the Securities and Exchange Commission on May 31, 2024 Registration Statement No.

Filing Fees Exhibit.

Exhibit 107 Calculation of Filing Fee Tables Form S-3 (Form Type) Mustang Bio, Inc.

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): May 16, 2024 Mustang Bio, Inc. (E

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): May 16, 2024 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Number)

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2024 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number 001-38191 MUS

2,743,530 Shares of Common Stock

Filed Pursuant to Rule 424(b)(3) Registration No. 333-275997 PROSPECTUS 2,743,530 Shares of Common Stock This prospectus relates to the resale by the selling stockholders (the “Selling Stockholders”) identified in this prospectus under the section “The Selling Stockholders,” of up to 2,743,530 shares of our common stock, par value $0.0001 per share (“Common Stock”), issuable upon the exercise of c

Mustang Bio Announces Pricing of $4 Million Public Offering

Exhibit 99.1 Mustang Bio Announces Pricing of $4 Million Public Offering WORCESTER, Mass., April 29, 2024 - Mustang Bio, Inc. (“Mustang” or the “Company”) (Nasdaq: MBIO), a clinical-stage biopharmaceutical company focused on translating today’s medical breakthroughs in cell and gene therapies into potential cures for difficult-to-treat cancers and rare genetic diseases, today announced the pricing

Form of May 2024 Pre-Funded Warrant

Exhibit 4.1 EXHIBIT A-2 PREFUNDED COMMON STOCK PURCHASE WARRANT MUSTANG BIO, INC. Warrant Shares: Initial Exercise Date: , 2024 THIS PREFUNDED COMMON STOCK PURCHASE WARRANT (the “Warrant”) certifies that, for value received, or its assigns (the “Holder”) is entitled, upon the terms and subject to the limitations on exercise and the conditions hereinafter set forth, at any time on or after the date

Mustang Bio Announces Closing of $4 Million Public Offering Potential Additional Gross Proceeds Upon Cash Exercise of Warrants of Up to $12 Million

Exhibit 99.2 Mustang Bio Announces Closing of $4 Million Public Offering Potential Additional Gross Proceeds Upon Cash Exercise of Warrants of Up to $12 Million WORCESTER, Mass., May 2, 2024 (GLOBE NEWSWIRE) - Mustang Bio, Inc. (“Mustang” or the “Company”) (Nasdaq: MBIO), a clinical-stage biopharmaceutical company focused on translating today’s medical breakthroughs in cell and gene therapies into

Form of May 2024 Series A-1, A-2, and A-3 Warrant

Exhibit 4.2 EXHIBIT A-1 SERIES [A-1][A-2][A-3] COMMON STOCK PURCHASE WARRANT MUSTANG BIO, INC. Warrant Shares: Initial Exercise Date: , 2024 THIS SERIES [A-1][A-2][A-3] COMMON STOCK PURCHASE WARRANT (the “Warrant”) certifies that, for value received, or its assigns (the “Holder”) is entitled, upon the terms and subject to the limitations on exercise and the conditions hereinafter set forth, at any

Other Events, Entry into a Material Definitive Agreement, Financial Statements and Exhibits

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) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Numbe

Form of May 2024 Placement Agent Warrant

Exhibit 4.3 PLACEMENT AGENT COMMON STOCK PURCHASE WARRANT MUSTANG BIO, INC. Warrant Shares: Issue Date: May 2, 2024 THIS PLACEMENT AGENT COMMON STOCK PURCHASE WARRANT (the “Warrant”) certifies that, for value received, or its assigns (the “Holder”) is entitled, upon the terms and subject to the limitations on exercise and the conditions hereinafter set forth, at any time on or after the Stockholde

Warrant Agreement Amendment, dated April 29, 2024, by and between the Company and the holder thereto

Exhibit 10.2 April 29, 2024 Holder of Warrants to Purchase Common Stock set forth on Exhibit A attached hereto Re: Amendment to Existing Warrants Dear Holder: Reference is hereby made to the offering on Form S-1 (File No. 333-278006) on or about the date hereof (the “Offering”) by Mustang Bio, Inc. (the “Company”) of its common stock, par value $0.0001 per share (“Common Stock”), and/or other secu

Form of Securities Purchase Agreement, dated April 29, 2024, by and between the Company and the purchaser party thereto

Exhibit 10.1 SECURITIES PURCHASE AGREEMENT This Securities Purchase Agreement (this “Agreement”) is dated as of April 29, 2024, between Mustang Bio, Inc., a Delaware corporation (the “Company”), and each purchaser identified on the signature pages hereto (each, including its successors and assigns, a “Purchaser” and collectively the “Purchasers”). WHEREAS, subject to the terms and conditions set f

1,160,000 Shares of Common Stock 15,717,638 Pre-funded Warrants to Purchase up to 15,717,638 Shares of Common Stock 16,877,638 Series A-1 Warrants to Purchase up to 16,877,638 Shares of Common Stock 16,877,638 Series A-2 Warrants to Purchase up to 16

Filed Pursuant to Rule 424(b)(4) Registration No. 333-278006 PROSPECTUS 1,160,000 Shares of Common Stock 15,717,638 Pre-funded Warrants to Purchase up to 15,717,638 Shares of Common Stock 16,877,638 Series A-1 Warrants to Purchase up to 16,877,638 Shares of Common Stock 16,877,638 Series A-2 Warrants to Purchase up to 16,877,638 Shares of Common Stock 16,877,638 Series A-3 Warrants to Purchase up

Filing Fee Table

Exhibit 107 Calculation of Filing Fee Tables Form S-1 (Form Type) Mustang Bio, Inc.

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.

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) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Numbe

Form of Series A-1, Series A-2, and Series A-3 Warrant offered hereby

Exhibit 4.9 EXHIBIT A-1 SERIES [A-1][A-2][A-3] COMMON STOCK PURCHASE WARRANT MUSTANG BIO, INC. Warrant Shares:                                                             Initial Exercise Date: , 2024 THIS SERIES [A-1][A-2][A-3] COMMON STOCK PURCHASE WARRANT (the “Warrant”) certifies that, for value received, or its assigns (the “Holder”) is entitled, upon the terms and subject to the limitations

Mustang Bio, Inc. 377 Plantation Street Worcester, Massachusetts 01605

Mustang Bio, Inc. 377 Plantation Street Worcester, Massachusetts 01605 VIA EDGAR April 29, 2024 Securities and Exchange Commission Division of Corporation Finance Office of Life Sciences 100 F Street, N.E. Washington, D.C. 20549 Attn: Tim Buchmiller Re: Mustang Bio, Inc. Registration Statement on Form S-1 (Reg. No. 333-275997) Request for Acceleration of Effective Date Ladies and Gentlemen: Pursua

Mustang Bio, Inc. 377 Plantation Street Worcester, Massachusetts 01605

Mustang Bio, Inc. 377 Plantation Street Worcester, Massachusetts 01605 VIA EDGAR April 29, 2024 Securities and Exchange Commission Division of Corporation Finance Office of Life Sciences 100 F Street, N.E. Washington, D.C. 20549 Attn: Jimmy McNamara Re: Mustang Bio, Inc. Registration Statement on Form S-1 (Reg. No. 333-278006) Request for Acceleration of Effective Date Ladies and Gentlemen: Pursua

As filed with the Securities and Exchange Commission on April 29, 2024.

As filed with the Securities and Exchange Commission on April 29, 2024. Registration No. 333-278006 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Amendment No. 2 to FORM S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 MUSTANG BIO, INC. (Exact name of registrant as specified in its charter) Delaware (State or other jurisdiction of incorporation or organization)

As filed with the Securities and Exchange Commission on April 29, 2024.

As filed with the Securities and Exchange Commission on April 29, 2024. Registration Statement No. 333-275997 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Amendment No. 1 to Form S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 Mustang Bio, Inc. (Exact name of registrant as specified in its charter) Delaware 2834 47-3828760 (State or Other Jurisdiction of Inco

Form of Securities Purchase Agreement

  Exhibit 10.40   SECURITIES PURCHASE AGREEMENT   This Securities Purchase Agreement (this “Agreement”) is dated as of , 2024, between Mustang Bio, Inc., a Delaware corporation (the “Company”), and each purchaser identified on the signature pages hereto (each, including its successors and assigns, a “Purchaser” and collectively the “Purchasers”).   WHEREAS, subject to the terms and conditions set

As filed with the Securities and Exchange Commission on April 29, 2024.

As filed with the Securities and Exchange Commission on April 29, 2024. Registration No. 333-278006 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Amendment No. 3 to FORM S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 MUSTANG BIO, INC. (Exact name of registrant as specified in its charter) Delaware (State or other jurisdiction of incorporation or organization)

430 Park Avenue | New York, NY 10022 | 212.356.0500 | www.hcwco.com Member: FINRA/SIPC

April 29, 2024 VIA EDGAR U.S. Securities and Exchange Commission Division of Corporate Finance Washington, DC 20549 Re:          Mustang Bio, Inc. Registration Statement on Form S-1 (Registration No. 333-278006) - Concurrence in Acceleration Request Ladies and Gentlemen: H.C. Wainwright & Co., LLC (“Wainwright”), solely acting as placement agent on a best-efforts basis in an offering pursuant to t

Costs Associated with Exit or Disposal Activities

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 10, 2024 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Numbe

Form of Pre-Funded Warrant offered hereby

Exhibit 4.8 EXHIBIT A-2 PREFUNDED COMMON STOCK PURCHASE WARRANT MUSTANG BIO, INC. Warrant Shares: Initial Exercise Date: , 2024 THIS PREFUNDED COMMON STOCK PURCHASE WARRANT (the “Warrant”) certifies that, for value received, or its assigns (the “Holder”) is entitled, upon the terms and subject to the limitations on exercise and the conditions hereinafter set forth, at any time on or after the date

As filed with the Securities and Exchange Commission on April 2, 2024.

As filed with the Securities and Exchange Commission on April 2, 2024. Registration No. 333-278006 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Amendment No. 1 to FORM S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 MUSTANG BIO, INC. (Exact name of registrant as specified in its charter) Delaware (State or other jurisdiction of incorporation or organization)

Form of Warrant offered hereby

Exhibit 4.9 EXHIBIT A-1 COMMON STOCK PURCHASE WARRANT MUSTANG BIO, INC. Warrant Shares: Initial Exercise Date: , 2024 THIS COMMON STOCK PURCHASE WARRANT (the “Warrant”) certifies that, for value received, or its assigns (the “Holder”) is entitled, upon the terms and subject to the limitations on exercise and the conditions hereinafter set forth, at any time on or after the [Stockholder Approval Da

Form of Placement Agent Warrant

Exhibit 4.10 PLACEMENT AGENT COMMON STOCK PURCHASE WARRANT MUSTANG BIO, INC. Warrant Shares: Initial Exercise Date: , 2024 THIS PLACEMENT AGENT COMMON STOCK PURCHASE WARRANT (the “Warrant”) certifies that, for value received, or its assigns (the “Holder”) is entitled, upon the terms and subject to the limitations on exercise and the conditions hereinafter set forth, at any time on or after the [St

Form of Securities Purchase Agreement

Exhibit 10.40 SECURITIES PURCHASE AGREEMENT This Securities Purchase Agreement (this “Agreement”) is dated as of , 2024, between Mustang Bio, Inc., a Delaware corporation (the “Company”), and each purchaser identified on the signature pages hereto (each, including its successors and assigns, a “Purchaser” and collectively the “Purchasers”). WHEREAS, subject to the terms and conditions set forth in

Other Events

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): March 28, 2024 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Numbe

Filing Fee Table

Exhibit 107 Calculation of Filing Fee Tables Form S-1 (Form Type) Mustang Bio, Inc.

As filed with the Securities and Exchange Commission on March 15, 2024.

As filed with the Securities and Exchange Commission on March 15, 2024. Registration No. 333- UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 MUSTANG BIO, INC. (Exact name of registrant as specified in its charter) Delaware (State or other jurisdiction of incorporation or organization) 2836 (Primary Standard I

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): March 13, 2024 Mustang Bio, Inc.

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): March 13, 2024 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Numbe

Form of Option Agreement under the Mustang Bio, Inc. 2016 Incentive Plan

Exhibit 10.28 MUSTANG BIO, INC. 2016 INCENTIVE PLAN STOCK OPTION AGREEMENT Unless otherwise defined herein, the terms defined in the 2016 Incentive Plan (the “Plan”) shall have the same defined meanings in this Stock Option Agreement. I.NOTICE OF STOCK OPTION GRANT Name: Address: The undersigned Optionee has been granted an Option to purchase shares of Common Stock of the Company (“Common Stock”),

Mustang Bio Reports Full-Year 2023 Financial Results and Recent Corporate Highlights

Exhibit 99.1 Mustang Bio Reports Full-Year 2023 Financial Results and Recent Corporate Highlights Worcester, MA – March 11, 2024 – Mustang Bio, Inc. (“Mustang” or the “Company”) (Nasdaq: MBIO), a clinical-stage biopharmaceutical company focused on translating today’s medical breakthroughs in cell and gene therapies into potential cures for difficult-to-treat cancers and rare genetic diseases, toda

Form of Restricted Stock Unit Agreement under the Mustang Bio, Inc. 2016 Incentive Plan

Exhibit 10.29 MUSTANG BIO, INC. 2016 STOCK INCENTIVE PLAN RESTRICTED STOCK UNIT AWARD AGREEMENT This Restricted Stock Unit Award Agreement (this “Agreement”) is made and entered into between Mustang Bio, Inc. (the “Company”) and [] (“Grantee”), effective as of [] (such date the “Date of Grant”). This Agreement sets forth the terms and conditions associated with the Company’s award to Grantee of Re

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K ☒ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the Fiscal Year Ended December 31, 2023 or ☐TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the Transition Period from to . Commission File No. 001-38191 MUSTANG BIO

Compensation Clawback Policy **

Exhibit 97 MUSTANG BIO, INC. Clawback Policy October 2, 2023 The Board of Directors (“Board”) of Mustang Bio, Inc. (“Company”) believes that it is in the best interests of the Company and its shareholders to adopt this Clawback Policy (“Policy”) which provides for the recoupment of certain executive compensation in the event of an Accounting Restatement (as defined below). This Policy is designed

Form of Director Stock Award Agreement under the Mustang Bio, Inc. Non-Employee Directors Compensation Plan

Exhibit 10.30 Annual Director Equity Award R E S T R I C T E D S T O C K A W A R D C E R T I F I C A T E Non-transferable G R A N T TO (“Grantee”) by Mustang Bio, Inc. (the “Company”) of shares of its common stock, $0.0001 par value (the “Shares”) pursuant to and subject to the provisions of the Mustang Bio, Inc. 2016 Incentive Plan (the “Plan”) and the Amended and Restated Non-Employee Directors

Description of Securities of Mustang Bio, Inc. **

EXHIBIT 4.2 DESCRIPTION OF THE REGISTRANT’S SECURITIES REGISTERED PURSUANT TO SECTION 12 OF THE SECURITIES EXCHANGE ACT OF 1934 The following descriptions of our capital stock and of certain provisions of our Amended and Restated Certificate of Incorporation (“Certificate of Incorporation”), as amended, our Amended and Restated Bylaws (“Bylaws”), and of certain provisions of Delaware law do not pu

Financial Statements and Exhibits, Results of Operations and Financial Condition

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): March 11, 2024 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Numbe

US62818Q2030 / Mustang Bio, Inc. / ARMISTICE CAPITAL, LLC Passive Investment

SC 13G 1 armistice-mbio123123.htm UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. )* MUSTANG BIO, INC. (Name of Issuer) Common Stock, par value $0.0001 per share (Title of Class of Securities) 62818Q203 (CUSIP Number) December 31, 2023 (Date of Event Which Requires Filing of this Statement) Check the approp

Other Events

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): February 12, 2024 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Nu

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers, Financial Statements and Exhibits

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): January 19, 2024 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Num

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): December 28, 2023 Mustang Bio, In

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): December 28, 2023 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Nu

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers

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): December 11, 2023 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Nu

As filed with the Securities and Exchange Commission on December 11, 2023.

As filed with the Securities and Exchange Commission on December 11, 2023. Registration Statement No. 333- UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Form S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 Mustang Bio, Inc. (Exact name of registrant as specified in its charter) Delaware 2834 47-3828760 (State or Other Jurisdiction of Incorporation or Organizat

Filing Fee Table

Exhibit 107.1 Calculation of Filing Fee Tables Form S-1 (Form Type) Mustang Bio, Inc. (Exact Name of Registrant as Specified in its Charter) Table 1: Newly Registered Securities Security Type Security Class Title Fee Calculation Rule(1) Amount Registered(2) Proposed Maximum Offering Price Per Unit(1) Maximum Aggregate Offering Price(1) Fee Rate Amount of Registration Fee Equity Common Stock, par v

Mustang Bio Presents Updated Phase 1/2 Multicenter Clinical Data for MB-106 at the 2023 American Society of Hematology (ASH) Annual Meeting Data showed favorable safety profile, complete response rate and durability in the treatment of patients with

Exhibit 99.1 Mustang Bio Presents Updated Phase 1/2 Multicenter Clinical Data for MB-106 at the 2023 American Society of Hematology (ASH) Annual Meeting Data showed favorable safety profile, complete response rate and durability in the treatment of patients with relapsed or refractory indolent B-cell Non-Hodgkin Lymphoma 100% of patients with follicular lymphoma achieved a complete response; no oc

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): December 11, 2023 Mustang Bio, In

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): December 11, 2023 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Nu

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2023 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number 001-38191

Financial Statements and Exhibits, Results of Operations and Financial Condition

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): November 14, 2023 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Nu

Mustang Bio Reports Third Quarter 2023 Financial Results and Recent Corporate Highlights

Exhibit 99.1 Mustang Bio Reports Third Quarter 2023 Financial Results and Recent Corporate Highlights Worcester, MA – November 14, 2023 – Mustang Bio, Inc. (“Mustang”) (Nasdaq: MBIO), a clinical-stage biopharmaceutical company focused on translating today’s medical breakthroughs in cell and gene therapies into potential cures for difficult-to-treat cancers and rare genetic diseases, today announce

Mustang Bio Announces MB-106 CD20-Targeted CAR-T Data Selected for Presentation at 65th American Society of Hematology (ASH) Annual Meeting Updated interim data from Mustang’s multicenter Phase 1/2 clinical trial demonstrate favorable safety and effi

Exhibit 99.1 Mustang Bio Announces MB-106 CD20-Targeted CAR-T Data Selected for Presentation at 65th American Society of Hematology (ASH) Annual Meeting Updated interim data from Mustang’s multicenter Phase 1/2 clinical trial demonstrate favorable safety and efficacy profile of MB-106 in heavily pre-treated lymphoma patients Worcester, MA – November 2, 2023 – Mustang Bio, Inc. (“Mustang”) (Nasdaq:

Financial Statements and Exhibits, Other Events

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): November 2, 2023 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Num

Form of Wainwright Warrant

Exhibit 4.3 NEITHER THIS SECURITY NOR THE SECURITIES FOR WHICH THIS SECURITY IS EXERCISABLE HAVE BEEN REGISTERED WITH THE SECURITIES AND EXCHANGE COMMISSION OR THE SECURITIES COMMISSION OF ANY STATE IN RELIANCE UPON AN EXEMPTION FROM REGISTRATION UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “SECURITIES ACT”), AND, ACCORDINGLY, MAY NOT BE OFFERED OR SOLD EXCEPT PURSUANT TO AN EFFECTIVE REGISTR

Form of Pre-funded Warrant

Exhibit 4.1 FORM OF PRE-FUNDED COMMON STOCK PURCHASE WARRANT Mustang Bio, Inc. Warrant Shares: [] Issue Date:, 2023 Initial Exercise Date: , 2023 THIS PRE-FUNDED COMMON STOCK PURCHASE WARRANT (the “Warrant”) certifies that, for value received, or its assigns (the “Holder”) is entitled, upon the terms and subject to the limitations on exercise and the conditions hereinafter set forth, at any time o

920,000 Shares of Common Stock Pre-Funded Warrants to Purchase up to 1,668,236 Shares of Common Stock Up to 1,668,236 Shares of Common Stock Underlying the Pre-Funded Warrants

Filed Pursuant to Rule 424(b)(5) Registration No. 333-255476 PROSPECTUS SUPPLEMENT To the Prospectus dated May 24, 2021 920,000 Shares of Common Stock Pre-Funded Warrants to Purchase up to 1,668,236 Shares of Common Stock Up to 1,668,236 Shares of Common Stock Underlying the Pre-Funded Warrants We are offering 920,000 shares of our common stock, par value $0.0001 per share (“Common Stock”), and pr

Mustang Bio Announces Closing of $4.4 Million Registered Direct Offering Priced At-the-Market Under Nasdaq Rules

Exhibit 99.2 Mustang Bio Announces Closing of $4.4 Million Registered Direct Offering Priced At-the-Market Under Nasdaq Rules Worcester, MA – October 30, 2023 – Mustang Bio, Inc. (“Mustang” or the “Company”) (Nasdaq: MBIO), a clinical-stage biopharmaceutical company focused on translating today’s medical breakthroughs in cell and gene therapies into potential cures for difficult-to-treat cancers a

Form of Warrant

Exhibit 4.2 NEITHER THIS SECURITY NOR THE SECURITIES FOR WHICH THIS SECURITY IS EXERCISABLE HAVE BEEN REGISTERED WITH THE SECURITIES AND EXCHANGE COMMISSION OR THE SECURITIES COMMISSION OF ANY STATE IN RELIANCE UPON AN EXEMPTION FROM REGISTRATION UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “SECURITIES ACT”), AND, ACCORDINGLY, MAY NOT BE OFFERED OR SOLD EXCEPT PURSUANT TO AN EFFECTIVE REGISTR

Mustang Bio Announces $4.4 Million Registered Direct Offering Priced At-the-Market Under Nasdaq Rules

Exhibit 99.1 Mustang Bio Announces $4.4 Million Registered Direct Offering Priced At-the-Market Under Nasdaq Rules Worcester, MA – October 26, 2023 – Mustang Bio, Inc. (“Mustang” or the “Company”) (Nasdaq: MBIO), a clinical-stage biopharmaceutical company focused on translating today’s medical breakthroughs in cell and gene therapies into potential cures for difficult-to-treat cancers and rare gen

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): October 26, 2023 Mustang Bio, Inc

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): October 26, 2023 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Num

Form of Securities Purchase Agreement, dated October 26, 2023, by and between the Company and the purchaser party thereto

Exhibit 10.1 FORM OF SECURITIES PURCHASE AGREEMENT This Securities Purchase Agreement (this “Agreement”) is dated as of October 26, 2023, between Mustang Bio, Inc., a Delaware corporation (the “Company”), and each purchaser identified on the signature pages hereto (each, including its successors and assigns, a “Purchaser” and collectively the “Purchasers”). WHEREAS, subject to the terms and condit

Mustang Bio Announces FDA Acceptance of IND Application for MB-109, a Novel Combination of MB-101 (IL13Rα2‐targeted CAR-T cell therapy) and MB-108 (HSV-1 oncolytic virus), for the Treatment of Recurrent Glioblastoma and High-Grade Astrocytoma MB‐101

Exhibit 99.1 Mustang Bio Announces FDA Acceptance of IND Application for MB-109, a Novel Combination of MB-101 (IL13Rα2‐targeted CAR-T cell therapy) and MB-108 (HSV-1 oncolytic virus), for the Treatment of Recurrent Glioblastoma and High-Grade Astrocytoma MB‐101 (IL13Rα2‐targeted CAR-T cell therapy) and MB-108 (HSV-1 oncolytic virus) are separately well tolerated in patients with recurrent GBM in

Financial Statements and Exhibits, Other Events

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): October 26, 2023 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Num

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): September 28, 2023 Mustang Bio, I

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): September 28, 2023 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File N

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August 28, 2023 VIA EDGAR Christine Torney and Vanessa Robertson Division of Corporation Finance Office of Life Sciences United States Securities and Exchange Commission 100 F Street, N.

Mustang Bio Announces First Data from Ongoing Multicenter Phase 1/2 Clinical Trial Evaluating MB-106 CAR T Cell Therapy Initial data show clinical responses from four of four indolent lymphoma patients, including complete response in follicular lymph

Exhibit 99.1 Mustang Bio Announces First Data from Ongoing Multicenter Phase 1/2 Clinical Trial Evaluating MB-106 CAR T Cell Therapy Initial data show clinical responses from four of four indolent lymphoma patients, including complete response in follicular lymphoma patient previously treated with CD19 CAR T cell therapy Aligns with ongoing results from investigator-sponsored trial at Fred Hutch t

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): August 16, 2023 Mustang Bio, Inc.

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): August 16, 2023 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Numb

Mustang Bio Reports Second Quarter 2023 Financial Results and Recent Corporate Highlights

Exhibit 99.1 Mustang Bio Reports Second Quarter 2023 Financial Results and Recent Corporate Highlights Worcester, MA – August 14, 2023 – Mustang Bio, Inc. (“Mustang”) (Nasdaq: MBIO), a clinical-stage biopharmaceutical company focused on translating today’s medical breakthroughs in cell and gene therapies into potential cures for difficult-to-treat cancers and rare genetic diseases, today announced

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2023 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number 001-38191 MUST

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): August 14, 2023 Mustang Bio, Inc.

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): August 14, 2023 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Numb

As filed with the Securities and Exchange Commission on July 31, 2023

As filed with the Securities and Exchange Commission on July 31, 2023 Registration No.

Filing Fee Table

Exhibit 107 Calculation of Filing Fee Tables Form S-8 (Form Type) Mustang Bio, Inc.

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): July 28, 2023 Mustang Bio, Inc. (

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): July 28, 2023 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Number

Manufacturing Services Agreement, dated July 28, 2023, between the Company and uBriGene (Boston) Biosciences, Inc.

Exhibit 10.1 MASTER SERVICE AGREEMENT This MASTER SERVICE AGREEMENT (this “Agreement”), effective as of this 28th day of July 2023 (the “Effective Date”), between Mustang Bio, Inc. (“Customer”), having its principal place of business at One Mercantile Place, Worcester, Massachusetts 01605, and uBriGene (Boston) Biosciences Inc. (“uBriGene”) and, inter alia, a site generally applicable to manufactu

Mustang Bio Announces Amendment and Closing of Strategic Manufacturing Partnership Transaction with uBriGene (Boston) Biosciences Transaction and reduction in operating expenses enhance Mustang’s cash position

Exhibit 99.1 Mustang Bio Announces Amendment and Closing of Strategic Manufacturing Partnership Transaction with uBriGene (Boston) Biosciences Transaction and reduction in operating expenses enhance Mustang’s cash position Worcester, MA – July 31, 2023 – Mustang Bio, Inc. (“Mustang” or the “Company”) (Nasdaq: MBIO), a clinical-stage biopharmaceutical company focused on translating today’s medical

Second Amendment to Asset Purchase Agreement, dated July28, 2023, between the Company and uBriGene (Boston) Biosciences, Inc.

Exhibit 2.3 SECOND AMENDMENT TO ASSET PURCHASE AGREEMENT This SECOND AMENDMENT TO ASSET PURCHASE AGREEMENT (this “Agreement”) is dated as of July 28, 2023 (the “Effective Date”), and entered into by and among uBriGene (Boston) Biosciences, Inc., a Delaware corporation (“Buyer”) and Mustang Bio, Inc., a Delaware corporation (the “Seller” and, together with the Buyer, each, a “Party” and, collective

Sub-Contracting Manufacturing Services Agreement, dated July 28, 2023, between the Company and uBriGene (Boston) Biosciences, Inc.

Exhibit 10.2 MASTER SERVICE AGREEMENT This MASTER SERVICE AGREEMENT (this “Agreement”), effective as of this 28th day of July 2023 (the “Effective Date”), between, uBrigene (Boston) Biosciences Inc. (“Customer”), a Delaware corporation, and Mustang Bio, Inc. (“CDMO”), a Delaware corporation with a site generally applicable to manufacturing or production of cell and gene therapies located at 377 Pl

Second Amendment to Sublease, dated April 27, 2023, between the Company and The Paul Revere Life Insurance Company

Exhibit 10.2 SECOND AMENDMENT TO SUBLEASE THIS SECOND AMENDMENT TO SUBLEASE (this “Amendment”) is entered into as of the 27 day of April, 2023 (the “Effective Date”) by and between THE PAUL REVERE LIFE INSURANCE COMPANY, a Massachusetts corporation (the “Sublessor”), having a notice address of c/o Unum Group, 1 Fountain Square, Suite 120, Chattanooga, Tennessee 37402, Attn: Corporate Real Estate D

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): July 18, 2023 Mustang Bio, Inc. (

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): July 18, 2023 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Number

Third Amendment to Sublease, dated June 15, 2023, between the Company and The Paul Revere Life Insurance Company

Exhibit 10.3 THIRD AMENDMENT TO SUBLEASE THIS THIRD AMENDMENT TO SUBLEASE (this “Amendment”) is entered into as of the 15th day of June, 2023 (the “Effective Date”), by and between THE PAUL REVERE LIFE INSURANCE COMPANY, a Massachusetts corporation (the “Sublessor”), having a notice address of c/o Unum Group, 1 Fountain Square, Suite 120, Chattanooga, Tennessee 37402, Attn: Corporate Real Estate D

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): July 10, 2023 Mustang Bio, Inc. (

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): July 10, 2023 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Number

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): June 29, 2023 Mustang Bio, Inc. (

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): June 29, 2023 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Number

First Amendment to Asset Purchase Agreement, dated June 29, 2023, between the Company and uBriGene (Boston) Biosciences, Inc.

Exhibit 2.2 Execution Version FIRST AMENDMENT TO ASSET PURCHASE AGREEMENT This FIRST AMENDMENT TO ASSET PURCHASE AGREEMENT (this “Agreement”) is dated as of June 29, 2023 (the “Effective Date”), and entered into by and among uBriGene (Boston) Biosciences, Inc., a Delaware corporation (“Buyer”) and Mustang Bio, Inc., a Delaware corporation (the “Seller” and, together with the Buyer, each, a “Party”

Amendment No. 2 to the Mustang Bio, Inc. 2019 Employee Stock Purchase Plan, dated June 21, 2023 †

Exhibit 10.1 AMENDMENT NO. 2 TO THE MUSTANG BIO, INC. 2019 EMPLOYEE STOCK PURCHASE PLAN This amendment (the “Amendment”) to the Mustang Bio, Inc. 2019 Employee Stock Purchase Plan, as amended (the “Plan”), is hereby adopted this 21 day of June, 2023, by the Board of Directors (the “Board”) of Mustang Bio, Inc. (the “Company”). WITNESETH: WHEREAS, the Company adopted the Plan for the purposes set f

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): June 21, 2023 Mustang Bio, Inc. (

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): June 21, 2023 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Number

Mustang Bio Announces Strategic Manufacturing Partnership and Portfolio Updates uBriGene (Boston) Biosciences to acquire Mustang Bio’s Worcester manufacturing facility for total consideration of up to $11 million and enters into strategic manufacturi

Exhibit 99.1 Mustang Bio Announces Strategic Manufacturing Partnership and Portfolio Updates uBriGene (Boston) Biosciences to acquire Mustang Bio’s Worcester manufacturing facility for total consideration of up to $11 million and enters into strategic manufacturing partnership to support MB-106 and future pipeline Company optimizes resources to focus on advancing lead CD20 CAR T program, GBM progr

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): May 17, 2023 Mustang Bio, Inc. (E

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): May 17, 2023 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Number)

Asset Purchase Agreement, dated May 18, 2023, between the Company and uBriGene (Boston) Biosciences, Inc.

Exhibit 1.1 Execution Version CERTAIN IDENTIFIED INFORMATION HAS BEEN EXCLUDED FROM THIS EXHIBIT BECAUSE IT IS BOTH (I) NOT MATERIAL AND (II) THE TYPE THAT THE REGISTRANT TREATS AS PRIVATE OR CONFIDENTIAL. [***] INDICATES THAT INFORMATION HAS BEEN REDACTED. ASSET PURCHASE AGREEMENT BY AND BETWEEN MustAng Bio, INC., AND UBRIGENE (BOSTON) BIOSCIENCES INC., Dated as of May 18, 2023 TABLE OF CONTENTS

Mustang Bio Reports First Quarter 2023 Financial Results and Recent Corporate Highlights

Exhibit 99.1 Mustang Bio Reports First Quarter 2023 Financial Results and Recent Corporate Highlights Worcester, MA – May 12, 2023 – Mustang Bio, Inc. (“Mustang”) (Nasdaq: MBIO), a clinical-stage biopharmaceutical company focused on translating today’s medical breakthroughs in cell and gene therapies into potential cures for hematologic cancers, solid tumors and rare genetic diseases, today announ

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2023 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number 001-38191 MUS

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): May 12, 2023 Mustang Bio, Inc. (E

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): May 12, 2023 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Number)

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 Filed by Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ☒ Definiti

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A INFORMATION Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934

DEFA14A 1 tmb-20230428xdefa14a.htm DEFA14A UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A INFORMATION Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 Filed by the Registrant. ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as

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 14, 2023 Mustang Bio, Inc.

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 14, 2023 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Numbe

Amendment No. 3 to At Market Issuance Sales Agreement, dated April 14, 2023, between the Registrant B. Riley Securities, Inc., Cantor Fitzgerald & Co. and H.C. Wainwright & Co., LLC

EX-1.1 2 tmb-20230414xex1d1.htm EX-1.1 Exhibit 1.1 AMENDMENT NO. 3 TO AT MARKET ISSUANCE SALES AGREEMENT April 14, 2023 B. Riley Securities, Inc. 299 Park Avenue, 21st Floor New York, NY 10171 Cantor Fitzgerald & Co. 110 East 59th Street New York, NY 10022 H.C. Wainwright & Co., LLC 430 Park Avenue New York, NY 10022 Ladies and Gentlemen: Mustang Bio, Inc., a Delaware corporation (the “Company”),

MUSTANG BIO, INC. Up to $7,957,618.46 Common Stock

Filed Pursuant to Rule 424(b)(5) Registration No. 333-249657 AMENDMENT NO. 1 DATED April 14, 2023 to Prospectus Supplement dated December 4, 2020 (To Prospectus dated December 4, 2020) MUSTANG BIO, INC. Up to $7,957,618.46 Common Stock This Amendment No. 1 to Prospectus Supplement (this “Amendment”) amends our prospectus supplement dated December 4, 2020 (the “Prospectus Supplement). This Amendmen

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 11, 2023 Mustang Bio, Inc.

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 11, 2023 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Numbe

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): March 28, 2023 Mustang Bio, Inc.

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): March 28, 2023 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Numbe

Certificate of Amendment of the Amended and Restated Certificate of Incorporation of Mustang Bio, Inc., dated April 3, 2023

Exhibit 3.1 CERTIFICATE OF AMENDMENT TO THE AMENDED AND RESTATED CERTIFICATE OF INCORPORATION OF MUSTANG BIO, INC. Mustang Bio, Inc. (the “Corporation”), a corporation organized and existing under and by virtue of the General Corporation Law of the State of Delaware (the “DGCL”), does hereby certify: 1.The Amended and Restated Certificate of Incorporation of the Corporation, as amended, is hereby

Mustang Bio Announces Reverse Stock Split

Exhibit 99.1 Mustang Bio Announces Reverse Stock Split Worcester, MA– April 3, 2023 – Mustang Bio, Inc. (“Mustang” or the “Company”) (Nasdaq: MBIO), a clinical-stage biopharmaceutical company focused on translating today’s medical breakthroughs in cell and gene therapies into potential cures for hematologic cancers, solid tumors and rare genetic diseases, today announced that it will effect a 15-f

Amended and Restated Bylaws of Mustang Bio, Inc.

Exhibit 3.2 AMENDED AND RESTATED BYLAWS OF MUSTANG BIO, INC. Adopted March 28, 2023 I.CORPORATE OFFICES 1.1Registered Office The registered office of the corporation shall be in the City of Dover, County of Kent, State of Delaware. The name of the registered agent of the corporation at such location is Incorporating Services, Ltd. 1.2Other Offices The board of directors may at any time establish o

Sublease Agreement by and between Mustang Bio, Inc., and The Paul Reverse Life Insurance Company, dated June 14, 2022

Exhibit 10.22 SUBLEASE This sublease (this “Sublease”) is made as of June 14, 2022 (the “Effective Date”), by and between THE PAUL REVERE LIFE INSURANCE COMPANY, a Massachusetts corporation (the “Sublessor”), having a notice address of c/o Unum Group, 1 Fountain Square, Suite 120, Chattanooga, Tennessee 37402, Attn: Corporate Real Estate Department, and MUSTANG BIO, INC., a Delaware corporation (t

Description of Securities of Mustang Bio, Inc. **

EXHIBIT 4.3 DESCRIPTION OF THE REGISTRANT’S SECURITIES REGISTERED PURSUANT TO SECTION 12 OF THE SECURITIES EXCHANGE ACT OF 1934 DESCRIPTION OF CAPITAL STOCK When used herein, the terms “Company,” “we,” “our,” and “us” refer to Mustang Bio, Inc. Capital Stock The Company is authorized to issue 200,000,000 shares of common stock with a par value of $0.0001 per share, of which 1,000,000 shares are de

First Amendment to Sublease Agreement by and between Mustang Bio, Inc. and The Paul Revere Life Insurance Company, dated October 25, 2022

Exhibit 10.23 FIRST AMENDMENT TO SUBLEASE THIS FIRST AMENDMENT TO SUBLEASE (this “Amendment”) is entered into as of the 25thday of October , 2022 (the “Effective Date”), by and between THE PAUL REVERE LIFE INSURANCE COMPANY, a Massachusetts corporation (the “Sublessor”), having a notice address of c/o Unum Group, 1 Fountain Square, Suite 120, Chattanooga, Tennessee 37402, Attn: Corporate Real Esta

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K ☒ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the Fiscal Year Ended December 31, 2022 or ☐TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the Transition Period from to . Commission File No. 001-38191 MUSTANG BIO

Mustang Bio Reports Full-Year 2022 Financial Results and Recent Corporate Highlights

Exhibit 99.1 Mustang Bio Reports Full-Year 2022 Financial Results and Recent Corporate Highlights Worcester, MA – March 29, 2023 – Mustang Bio, Inc. (“Mustang”) (Nasdaq: MBIO), a clinical-stage biopharmaceutical company focused on translating today’s medical breakthroughs in cell and gene therapies into potential cures for hematologic cancers, solid tumors and rare genetic diseases, today announce

Financial Statements and Exhibits, Results of Operations and Financial Condition

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): March 29, 2023 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Numbe

  SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549

    SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549   SCHEDULE 14C INFORMATION   INFORMATION STATEMENT PURSUANT TO SECTION 14(C) OF THE SECURITIES EXCHANGE ACT OF 1934   Check the appropriate box:   ¨ Preliminary Information Statement   ¨ Confidential, for Use of the Commission Only (as permitted by Rule 14c-5(d)(2))   x Definitive Information Statement   Mustang Bio, Inc. (Name of Regis

  SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549

    SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549   SCHEDULE 14C INFORMATION   INFORMATION STATEMENT PURSUANT TO SECTION 14(C) OF THE SECURITIES EXCHANGE ACT OF 1934   Check the appropriate box:   x Preliminary Information Statement   ¨ Confidential, for Use of the Commission Only (as permitted by Rule 14c-5(d)(2))   ¨ Definitive Information Statement   Mustang Bio, Inc. (Name of Regis

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): March 3, 2023 Mustang Bio, Inc. (

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): March 3, 2023 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Number

MBIO / Mustang Bio Inc / Fortress Biotech, Inc. - SC 13D/A Activist Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13D (Amendment No. 2) Under the Securities Exchange Act of 1934 MUSTANG BIO, INC. (Name of Issuer) Common Stock, $0.0001 Par Value (Title of Class of Securities) 62818Q104 (CUSIP Number) Fortress Biotech, Inc. c/o Lindsay A. Rosenwald, M.D. 1111 Kane Concourse, Suite 301 Bay Harbor Islands, FL 33154 (781) 652-4500 (Na

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): December 7, 2022 Mustang Bio, Inc

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): December 7, 2022 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Num

First Amendment to Loan and Security Agreement by and between Mustang Bio, Inc., the Borrower, the Lenders and Runway Growth Finance Corp. (as agent), dated December 7, 2022

Exhibit 10.1 FIRST AMENDMENT TO LOAN AND SECURITY AGREEMENT This First Amendment to Loan and Security Agreement (as amended, restated, supplemented or otherwise modified from time to time, this “Amendment”) is entered into as of December 7, 2022, by and among MUSTANG BIO, INC., a Delaware corporation (“Borrower Representative”), and each other Person party to the Loan Agreement (as defined below)

Other Events

? ? 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): November 18, 2022 ? Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) ? Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents ? UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.

Mustang Bio Reports Third Quarter 2022 Financial Results and Recent Corporate Highlights

Exhibit 99.1 ? ? Mustang Bio Reports Third Quarter 2022 Financial Results and Recent Corporate Highlights ? Worcester, MA? November 14, 2022 ? Mustang Bio, Inc. (?Mustang?) (Nasdaq: MBIO), a clinical-stage biopharmaceutical company focused on translating today?s medical breakthroughs in cell and gene therapies into potential cures for hematologic cancers, solid tumors and rare genetic diseases, to

Financial Statements and Exhibits, Results of Operations and Financial Condition

? ? 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): November 14, 2022 ? Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) ? Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (

Mustang Bio Reports Second Quarter 2022 Financial Results and Recent Corporate Highlights

Exhibit 99.1 ? ? Mustang Bio Reports Second Quarter 2022 Financial Results and Recent Corporate Highlights ? Worcester, MA? August 11, 2022 ? Mustang Bio, Inc. (?Mustang?) (NASDAQ: MBIO), a clinical-stage biopharmaceutical company focused on translating today?s medical breakthroughs in cell and gene therapies into potential cures for hematologic cancers, solid tumors and rare genetic diseases, tod

Financial Statements and Exhibits, Results of Operations and Financial Condition

? ? 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): August 11, 2022 ? Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) ? Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Co

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents ? UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.

Filing Fee Table

Exhibit 107.1 Calculation of Filing Fee Tables Form S-8 (Form Type) Mustang Bio, Inc. (Exact Name of Registrant as Specified in its Charter) Table 1: Newly Registered Securities Security Type Security Class Title Fee Calculation Rule(1) Amount Registered(2) Proposed Maximum Offering Price Per Unit(1) Maximum Aggregate Offering Price(1) Fee Rate Amount of Registration Fee Equity Common Stock, par v

As filed with the Securities and Exchange Commission on July 15, 2022

As filed with the Securities and Exchange Commission on July 15, 2022 Registration No.

Amendments to Articles of Incorporation or Bylaws; Change in Fiscal Year, Financial Statements and Exhibits

? ? 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): July 6, 2022 ? Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) ? Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commi

Certificate of Amendment of the Amended and Restated Certificate of Incorporation of Mustang Bio, Inc., dated July 5, 2022

Exhibit 3.1 CERTIFICATE OF AMENDMENT TO THE AMENDED AND RESTATED CERTIFICATE OF INCORPORATION OF MUSTANG BIO, INC. Mustang Bio, Inc. (the ?Corporation?), a corporation organized and existing under and by virtue of the Delaware General Corporation Law (the ?DGCL?), does hereby certify: (1) The Amended and Restated Certificate of Incorporation of the Corporation, as amended, is hereby amended by del

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers, Financial Statements and Exhibits, Submission of Matters to a Vote of Security Holders

? ? 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): June 21, 2022 ? Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) ? Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Comm

Third Amendment to Mustang Bio, Inc. 2016 Equity Incentive Plan, dated June 21, 2022 †

Exhibit 10.1 THIRD AMENDMENT TO THE MUSTANG BIO, INC. 2016 INCENTIVE PLAN This Amendment to the Mustang Bio, Inc. 2016 Incentive Plan (the ?Plan?), is hereby adopted, effective as of the date indicated below. WITNESETH: WHEREAS, Mustang Bio, Inc. (the ?Company?) adopted the Plan for the purposes set forth therein; and WHEREAS, pursuant to Section 15.1 of the Plan, the Board of Directors the Compan

Notice of Delisting or Failure to Satisfy a Continued Listing Rule or Standard; Transfer of Listing

? ? 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): May 24, 2022 ? Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) ? Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commi

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents ? UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.

Financial Statements and Exhibits, Results of Operations and Financial Condition

? ? 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): May 12, 2022 ? Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) ? Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commi

Mustang Bio Reports First Quarter 2022 Financial Results and Recent Corporate Highlights Data from two programs selected for oral presentations at the upcoming American Society of Gene & Cell Therapy 25th Annual Meeting and the European Hematology As

Exhibit 99.1 Mustang Bio Reports First Quarter 2022 Financial Results and Recent Corporate Highlights Data from two programs selected for oral presentations at the upcoming American Society of Gene & Cell Therapy 25th Annual Meeting and the European Hematology Association 2022 Hybrid Congress this quarter Worcester, MA? May 12, 2022 ? Mustang Bio, Inc. (?Mustang?) (NASDAQ: MBIO), a clinical-stage

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A INFORMATION Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A INFORMATION Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant x Filed by a Party other than the Registrant ? Check the appropriate box: ? Preliminary Proxy Statement ? Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.  )

TABLE OF CONTENTS UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549? SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ?) Filed by Registrant ? ? Filed by a Party other than the Registrant ? ? Check the appropriate box: ? Preliminary Proxy Statement ? ? Confidential, for Use of the Commission Only (as permitted by Rul

CONSULTING AGREEMENT

Exhibit 99.1 CONSULTING AGREEMENT This Consulting Agreement (the ?Agreement?) is made effective as of March 17, 2022 (the ?Effective Date?), by and between Mustang Bio, Inc., a Delaware corporation, with its principal place of business being 377 Plantation Street, Worcester, MA 01605 (the ?Company?) and Danforth Advisors, LLC, a Massachusetts limited liability company, with its principal place of

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers, Financial Statements and Exhibits

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 18, 2022 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Numbe

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.  )

TABLE OF CONTENTS UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549? SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ?) Filed by Registrant ? ? Filed by a Party other than the Registrant ? ? Check the appropriate box: ? Preliminary Proxy Statement ? ? Confidential, for Use of the Commission Only (as permitted by Rul

Description of Securities of Mustang Bio, Inc. **

EXHIBIT 4.3 ? DESCRIPTION OF THE REGISTRANT?S SECURITIES REGISTERED PURSUANT TO SECTION 12 OF THE SECURITIES EXCHANGE ACT OF 1934 DESCRIPTION OF CAPITAL STOCK ? When used herein, the terms ?Company,? ?we,? ?our,? and ?us? refer to Mustang Bio, Inc. ? Capital Stock The Company is authorized to issue 125,000,000 shares of common stock with a par value of $0.0001 per share, of which 1,000,000 shares

Mustang Bio Reports Full-Year 2021 Financial Results and Recent Corporate Highlights

Exhibit 99.1 Mustang Bio Reports Full-Year 2021 Financial Results and Recent Corporate Highlights Worcester, MA ? March 23, 2022 ? Mustang Bio, Inc. (?Mustang?) (NASDAQ: MBIO), a clinical-stage biopharmaceutical company focused on translating today?s medical breakthroughs in cell and gene therapies into potential cures for hematologic cancers, solid tumors and rare genetic diseases, today announce

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K

Table of Contents ? ? UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.

Financial Statements and Exhibits, Results of Operations and Financial Condition

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): March 23, 2022 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Numbe

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers

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): March 11, 2022 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Numbe

LOAN AND SECURITY AGREEMENT

Exhibit 99.1 LOAN AND SECURITY AGREEMENT This LOAN AND SECURITY AGREEMENT (as amended, restated, supplemented or otherwise modified from time to time, this ?Agreement?) dated as of March 4, 2022 (the ?Closing Date?) is entered into among MUSTANG BIO, INC., a Delaware corporation (?Borrower Representative?), and each other Person party hereto as a borrower from time to time (collectively, ?Borrower

Warrant to Purchase Common Stock issued to Runway Growth Finance Corp., dated March 4, 2022

Exhibit 4.1 THIS WARRANT AND THE SHARES ISSUABLE HEREUNDER HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE ?ACT?), OR THE SECURITIES LAWS OF ANY STATE AND, EXCEPT AS SET FORTH IN SECTIONS 5.3 AND 5.4 BELOW, MAY NOT BE OFFERED, SOLD, PLEDGED OR OTHERWISE TRANSFERRED UNLESS AND UNTIL REGISTERED UNDER SAID ACT AND LAWS OR IN FORM AND SUBSTANCE SATISFACTORY TO THE COMPANY, S

Entry into a Material Definitive Agreement, Financial Statements and Exhibits

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): March 4, 2022 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Number

Financial Statements and Exhibits, Results of Operations and Financial Condition

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): November 12, 2021 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Nu

Mustang Bio Reports Third Quarter 2021 Financial Results and Recent Corporate Highlights

Exhibit 99.1 Mustang Bio Reports Third Quarter 2021 Financial Results and Recent Corporate Highlights Worcester, MA ? November 12, 2021 ? Mustang Bio, Inc. (?Mustang?) (NASDAQ: MBIO), a clinical-stage biopharmaceutical company focused on translating today?s medical breakthroughs in cell and gene therapies into potential cures for hematologic cancers, solid tumors and rare genetic diseases, today a

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents ? UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.

Changes in Registrant's Certifying Accountant

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): September 28, 2021 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File N

Letter from BDO USA, LLP to the Securities and Exchange Commission dated September 22, 2021, incorporated by

Exhibit 16.1 Tel: 617-422-0700 Fax: 617-422-0909 www.bdo.com One International Place Boston, MA 02110 September 22, 2021 Securities and Exchange Commission 100 F Street N.E. Washington, D.C. 20549 We have been furnished with a copy of the response to Item 4.01 of Form 8-K for the event that occurred on September 20, 2021, to be filed by our former client, Mustang Bio, Inc. We agree with the statem

Financial Statements and Exhibits, Changes in Registrant's Certifying Accountant

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): September 20, 2021 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File N

Financial Statements and Exhibits, Results of Operations and Financial Condition

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): August 16, 2021 Mustang Bio, Inc. (Exact Name of Registrant as Specified in Charter) Delaware 001-38191 47-3828760 (State or Other Jurisdiction of Incorporation) (Commission File Numb

Mustang Bio Reports Second Quarter 2021 Financial Results and Recent Corporate Highlights

Exhibit 99.1 Mustang Bio Reports Second Quarter 2021 Financial Results and Recent Corporate Highlights Worcester, MA ? August 16, 2021 ? Mustang Bio, Inc. (?Mustang?) (NASDAQ: MBIO), a clinical-stage biopharmaceutical company focused on translating today?s medical breakthroughs in cell and gene therapies into potential cures for hematologic cancers, solid tumors and rare genetic diseases, today an

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents ? UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.

Amended and Restated Exclusive License Agreement dated August 13, 2021 by and between Mustang Bio, Inc. and City of Hope (PSCA).*

? Exhibit 10.7 ? CERTAIN IDENTIFIED INFORMATION HAS BEEN EXCLUDED FROM THE EXHIBIT BECAUSE IT BOTH (I) IS NOT MATERIAL AND (II) WOULD BE COMPETITIVELY HARMFUL IF PUBLICLY DISCLOSED. SUCH EXCLUDED INFORMATION HAS BEEN MARKED WITH ?[*].? ? AMENDED AND RESTATED EXCLUSIVE LICENSE AGREEMENT ? THIS AMENDED AND RESTATED EXCLUSIVE LICENSE AGREEMENT (the ?Agreement?) is made and entered into as of August 1

Amended and Restated Exclusive License Agreement dated August 13, 2021 by and between Mustang Bio, Inc. and City of Hope (HER2).*

? Exhibit 10.8 ? CERTAIN IDENTIFIED INFORMATION HAS BEEN EXCLUDED FROM THE EXHIBIT BECAUSE IT BOTH (I) IS NOT MATERIAL AND (II) WOULD BE COMPETITIVELY HARMFUL IF PUBLICLY DISCLOSED. SUCH EXCLUDED INFORMATION HAS BEEN MARKED WITH ?[*].? ? ? AMENDED AND RESTATED EXCLUSIVE LICENSE AGREEMENT ? THIS AMENDED AND RESTATED EXCLUSIVE LICENSE AGREEMENT (the ?Agreement?) is made and entered into as of August

Amended and Restated Exclusive License Agreement dated August 13, 2021 by and between Mustang Bio, Inc. and City of Hope (CS1).*

Exhibit 10.6 CERTAIN IDENTIFIED INFORMATION HAS BEEN EXCLUDED FROM THE EXHIBIT BECAUSE IT BOTH (I) IS NOT MATERIAL AND (II) WOULD BE COMPETITIVELY HARMFUL IF PUBLICLY DISCLOSED. SUCH EXCLUDED INFORMATION HAS BEEN MARKED WITH ?[*].? AMENDED AND RESTATED EXCLUSIVE LICENSE AGREEMENT THIS AMENDED AND RESTATED EXCLUSIVE LICENSE AGREEMENT (the ?Agreement?) is made and entered into as of August 13, 2021

As filed with the Securities and Exchange Commission on July 30, 2021

As filed with the Securities and Exchange Commission on July 30, 2021 File No. 333- UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM S-8 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 MUSTANG BIO, INC. (Exact name of registrant as specified in its charter) Delaware 47-3828760 (State or other jurisdiction of incorporation or organization) (IRS Employer Identificat

Form S-8, filed with the Commission on July 30, 2021 (File No. 333-258310)

As filed with the Securities and Exchange Commission on July 30, 2021 File No. 333- UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM S-8 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 MUSTANG BIO, INC. (Exact name of registrant as specified in its charter) Delaware 47-3828760 (State or other jurisdiction of incorporation or organization) (IRS Employer Identificat