Mustang Bio and St. Jude Children’s Research Hospital Enter into Exclusive Worldwide License Agreement for a Ground-Breaking, Clinical-Stage Lentiviral Gene Therapy with Curative Potential for X-linked Severe Combined Immunodeficiency


New York, NY and Memphis, TN – Mustang Bio, Inc. (“Mustang”) (NASDAQ: MBIO), a Fortress Biotech
(NASDAQ: FBIO) Company focused on the development of novel immunotherapies based on proprietary chimeric antigen
receptor engineered T cell (CAR T) technology, and St. Jude Children’s Research Hospital (“St. Jude”), the nation’s leading
hospital dedicated to understanding, treating and curing childhood cancer and other life-threatening diseases, announced
today that they have partnered and entered into an exclusive worldwide license agreement for the development of a firstin-class ex vivo lentiviral gene therapy for the treatment of X-linked severe combined immunodeficiency (“X-SCID”), also
known as bubble boy disease. X-SCID is the most common form of severe combined immunodeficiency, affecting
approximately one in 50,000 to 100,000 newborns worldwide.
The therapy, which includes a low dose of busulfan prior to reinfusion of the patients’ own gene-modified blood stem
cells, is currently being evaluated in a Phase 1/2 multicenter trial in infants under the age of two at St. Jude, UCSF Benioff
Children’s Hospital San Francisco; and Seattle Children’s Hospital. This study, led by Ewelina Mamcarz, M.D., Assistant
Member at St. Jude, is the world’s first lentiviral gene therapy trial for infants with X-SCID. In addition, the therapy is being
investigated in patients over the age of two in a second Phase 1/2 trial at the National Institutes of Health (“NIH”). The
therapy was developed in the laboratory of Brian Sorrentino, M.D., Director of the Division of Experimental Hematology
at St. Jude.
Eight patients under the age of two with X-SCID have been treated to date, with results presented at the 21st Annual
Meeting of the American Society of Gene & Cell Therapy in May 2018. The therapy was well tolerated. In addition, six
patients achieved reconstituted immune systems within three to four months following treatment, with the remaining
two patients continuing to progress favorably in earlier stages of recovery. Two of these six patients have discontinued
monthly infusions of intravenous immunoglobulin, and the remaining patients, at earlier stages of recovery, continue to
progress favorably. In three patients who had disseminated infections prior to therapy, all infections resolved completely.
“Our therapy has been well tolerated thus far, and none of the infants required any blood product support after low dose
of busulfan,” Dr. Mamcarz said. “Most importantly, we observe recovery of all cells of the immune system, which is truly
an achievement over prior gene therapy trials, where B cell reconstitution did not occur, and patients required intravenous
immunoglobulin for life.”
Mustang and St. Jude believe there may be as many as 1,000 to 1,500 patients in the U.S. with X-SCID, as well as a similar
number in Europe, who continue to have significant impairment of immunity despite receiving previous allogeneic stem
cell transplantation and who therefore could be eligible for this gene therapy. In the NIH study, which was reported in the
April 2016 issue of Science Translational Medicine, five patients aged 10 to 23 years with progressively declining persistent
immune dysfunction after haploidentical hematopoietic stem cell transplant in infancy were treated with this ex vivo
lentiviral gene therapy. The therapy appeared to be safe, and follow-up data from two older patients demonstrated
immune system reconstitution and clinical improvement at 2 to 3 years following treatment. In three younger patients,
similar levels of gene-modified immune cells were also observed at 6 to 9 months following treatment.
“X-SCID is a devastating genetic disorder of the immune system that occurs in infant males who, without treatment, do
not live beyond infancy,” said Dr. Sorrentino. “We have seen compelling clinical data in which this X-SCID gene therapy
enabled immune system reconstitution and the resolution of disseminated infections. We look forward to working with
Mustang Bio to continue to advance the clinical development of this promising and potentially first-in-class gene therapy.”
Manuel Litchman, M.D., President and Chief Executive Officer of Mustang, said, “We are thrilled to announce the
expansion of our pipeline into gene therapy for patients with X-SCID, a natural fit for our Worcester, Mass. cell processing
facility. We look forward to working with St. Jude to advance this program through ongoing Phase 1/2 trials, with the goal
of providing a novel, long-term treatment to the more than 80 percent of infants who lack fully matched bone marrow
transplant donors and those patients who continue to have significant impairment of immunity. With our team’s extensive
expertise in viral vector design, manufacturing and transduction, we are building a fully integrated cell and gene therapy
company, with the goal of leveraging the transformative potential of these technologies to bring life-saving treatments to
patients in need.”
About Mustang Bio
Mustang Bio, Inc. (“Mustang”), a Fortress Biotech Company, is a clinical‐stage biopharmaceutical company focused on the
development and commercialization of a broad range of proprietary chimeric antigen receptor engineered T cell (CAR T)
immunotherapies and gene therapies in areas of unmet need. 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 and
CRISPR/Cas9-enhanced CAR T therapies across multiple cancers, as well as lentiviral gene therapy for X-SCID. Mustang is
registered under the Securities Exchange Act of 1934, as amended, and files periodic reports with the U.S. Securities and
Exchange Commission. For more information, visit www.mustangbio.com.
About Fortress Biotech
Fortress Biotech, Inc. (“Fortress”) is a biopharmaceutical company dedicated to acquiring, developing and commercializing
novel pharmaceutical and biotechnology products. Fortress develops and commercializes products both within Fortress
and through certain of its subsidiary companies, also known as Fortress Companies. In addition to its internal development
programs, Fortress leverages its biopharmaceutical business expertise and drug development capabilities and provides
funding and management services to help the Fortress Companies achieve their goals. Fortress and the Fortress
Companies may seek licensing arrangements, acquisitions, partnerships, joint ventures and/or public and private
financings to accelerate and provide additional funding to support their research and development programs. For more
information, visit www.fortressbiotech.com.
About St. Jude Children’s Research Hospital
St. Jude Children’s Research Hospital (“St. Jude”) is leading the way the world understands, treats and cures childhood
cancer and other life-threatening diseases. It is the only National Cancer Institute-designated Comprehensive Cancer
Center devoted solely to children. Treatments developed at St. Jude have helped push the overall childhood cancer
survival rate from 20 percent to 80 percent since the hospital opened more than 50 years ago. St. Jude freely shares the
breakthroughs it makes, and every child saved at St. Jude means doctors and scientists worldwide can use that knowledge
to save thousands more children. Families never receive a bill from St. Jude for treatment, travel, housing and food —
because all a family should worry about is helping their child live. To learn more, visit www.stjude.org or follow St. Jude
on social media at @stjuderesearch.
Forward‐Looking Statements
This press release may contain “forward-looking statements” within the meaning of Section 27A of the Securities Act of
1933 and Section 21E of the Securities Exchange Act of 1934, each as amended. Such statements include, but are not
limited to, any statements relating to our growth strategy and product development programs and any other statements
that are not historical facts. Forward-looking statements are based on management’s current expectations and are subject
to risks and uncertainties that could negatively affect our business, operating results, financial condition and stock value.
Factors that could cause actual results to differ materially from those currently anticipated include: risks relating to our
growth strategy; our ability to obtain, perform under and maintain financing and strategic agreements and relationships;
risks relating to the results of research and development activities; risks relating to the timing of starting and completing
clinical trials; uncertainties relating to preclinical and clinical testing; our dependence on third-party suppliers; our ability
to attract, integrate and retain key personnel; the early stage of products under development; our need for substantial
additional funds; government regulation; patent and intellectual property matters; competition; as well as other risks
described in our SEC filings. We expressly disclaim any obligation or undertaking to release publicly any updates or
revisions to any forward-looking statements contained herein to reflect any change in our expectations or any changes in
events, conditions or circumstances on which any such statement is based, except as required by law.
Company Contact:
Jaclyn Jaffe
Mustang Bio, Inc.
(781) 652-4500
ir@mustangbio.com
Investor Relations Contact:
Jeremy Feffer
Managing Director, LifeSci Advisors, LLC
(212) 915-2568
jeremy@lifesciadvisors.com
Media Relations Contact:
Laura Bagby
6 Degrees
(312) 448-8098
lbagby@6degreespr.com
St. Jude Media Relations Contacts:
Michael Sheffield
Desk: (901) 595-0221
Cell: (901) 379-6072
Michael.Sheffield@stjude.org
media@stjude.org
Marvin Stockwell
Desk: (901) 595-6384
Cell: (901) 734-8766
marvin.stockwell@stjude.org
media@stjude.org

Shiwani Sharma

Shiwani Sharma is a Senior Editor at PharmaShots. She has in-depth knowledge of lifesciences industry including pharma and biotech sectors. She also covers news in field of Digital Health, Medtech and regulatory approvals from the US FDA, EU, and other global regulatory bodies in the industry. Additionally, she also writes Whitepapers, analysis reports, blogs on pharma and biotech industry. She is graduate in Biotechnology. She can be contacted on shiwani@pharmashots.com

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