Mustang Bio Announces Exclusive Worldwide License Agreement with Leiden University Medical Centre for Clinical-Stage Lentiviral Gene Therapy with Curative Potential for RAG1 Severe Combined Immunodeficiency

WORCESTER, Mass. – 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 announced that the company has executed an exclusive license agreement with Leiden University Medical Centre (“LUMC”) for a first-in-class ex vivo lentiviral gene therapy for the treatment of RAG1 severe combined immunodeficiency (“RAG1-SCID”).

The therapy, which includes low-dose conditioning prior to reinfusion of the patients’ own gene-modified blood stem cells, is currently being evaluated in a Phase 1/2 multicenter clinical trial in Europe. The ongoing clinical trial recently enrolled its first patient, and additional clinical sites are expected to be added in the near future. The RAG1-SCID program has been granted Orphan Drug Designation by the European Medicines Agency.

Mustang also established an ongoing partnership with Frank J. Staal, Ph.D., professor of Molecular Stem Cell Biology and molecular immunologist, whose laboratory developed the therapy. Dr. Staal will continue the development of additional lentiviral gene therapies in his lab, to which Mustang Bio has rights under the agreement.

The RAG1-SCID therapy expands the pipeline of ex vivo lentiviral gene therapies currently in development at Mustang. The Company’s lead programs, MB-107 and MB-207, are being investigated for the treatment of X-linked severe combined immunodeficiency (“XSCID”). A pivotal multicenter trial studying MB-107 is expected to enroll its first patient in the first quarter of 2022. XSCID and RAG1-SCID make up almost 60% of all SCID cases¹ combined.

Manuel Litchman, M.D., President and Chief Executive Officer of Mustang said, “We are excited to add RAG1-SCID to the Mustang portfolio as it enables us to leverage our lentiviral gene therapy expertise and experience and our state-of-the-art cell processing facility. Mustang is establishing itself as the leader in developing treatments for patients with severe combined immunodeficiency, an area of high unmet need. We have made great progress in moving our XSCID therapy into a registrational trial and look forward to similarly advancing this RAG1-SCID therapy to make it available for patients in need of life-saving treatment.”

Severe combined immunodeficiency (SCID) due to complete recombinase-activating gene-1 (RAG1) deficiency is a rare, genetic severe combined immunodeficiency disorder due to null mutations in the RAG1 gene resulting in less than 1% of wild type V(D)J recombination activity. Patients present with neonatal onset of life-threatening, severe, recurrent infections by opportunistic fungal, viral and bacterial micro-organisms, as well as skin rashes, chronic diarrhea, failure to thrive and fever. Immunologic observations include profound T- and B-cell lymphopenia, low or absent serum immunoglobulins, and normal natural killer cell counts. As is the case with other types of SCID, RAG1-SCID is fatal in infancy unless immune reconstitution is achieved with hematopoietic stem cell transplantation (HSCT).

About Mustang Bio
Mustang Bio, Inc. (“Mustang”) is 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. Mustang aims to acquire rights to these technologies by licensing or otherwise acquiring an ownership interest, to fund research and development, and to outlicense or bring the technologies to market. Mustang has partnered with top medical institutions to advance the development of CAR T therapies across multiple cancers, as well as lentiviral gene therapies for severe combined immunodeficiency. Mustang is registered under the Securities Exchange Act of 1934, as amended, and files periodic reports with the U.S. Securities and Exchange Commission (“SEC”). Mustang was founded by Fortress Biotech, Inc. (NASDAQ: FBIO). For more information, visit

About Leiden University Medical Centre (“LUMC”)
LUMC is a modern university medical center for research, education and patient care with a high quality profile and a strong scientific orientation. Its unique research practice, ranging from pure fundamental medical research to applied clinical research, places LUMC among the world top. Researchers at LUMC work together around 10 Research Themes: Academic Pharma, Neuroscience, Cell Tissue & Organ (Tx), Medical Genomics, Prevention & Lifestyle, Lifecourse Epidemiology and Geroscience, Immunity, Cancer, Cardio-Vascular, Infection.

LUMC strongly underpins the idea that ‘Science is the driving force behind innovative healthcare’. Outcomes of top level fundamental, translational and clinical research by LUMC researchers form a strong basis for innovative and qualitative healthcare on a national, European and international level.

Jaclyn Jaffe and Bill Begien
Mustang Bio, Inc.
(781) 652-4500
[email protected]

Daniel Ferry
LifeSci Advisors, LLC
(617) 430-7576
[email protected]

Tony Plohoros
6 Degrees
(908) 591-2839
[email protected]

¹Fischer A et al. Nat Rev Dis Primers. 2015; article number 15061; doi: 10.1038/nrdp.2015.61