Mustang Bio Gallops Higher On Positive Gene Therapy Results For Deadly 'Bubble Boy Disease'

Shares of Mustang Bio Inc MBIO are skyrocketing to their highest level in about a year Thursday morning.

What Happened

The microcap biotech that develops next-gen cell and gene therapies for hematologic cancers, glioblastoma and rare genetic diseases announced Wednesday after the market close positive data for a lentiviral gene therapy, which it has licensed from the St. Jude Children's Research Hospital.

The lentiviral gene therapy is being evaluated for safety and efficacy in newly-diagnosed infants under two years old with X-line severe combined immunodeficiency, or XSCID, commonly called "bubble boy disease."

Why It's Important

Bubble boy disease is a deadly genetic disorder named after David Vetter, a young boy who had to live his entire life in a plastic bubble to evade infections but eventually died at the age of 12 following a failed treatment.

A lentiviral vector was used to transfer a normal copy of IL2RG gene to bone marrow cells of the infants, preceded by low exposure-targeted busulfan conditioning.

The Phase 1/2 trial data published in the New England Journal of Medicine was from eight infants with XSCID and followed for a median of 16.4 months.

The data showed that the therapy was well tolerated, and seven of the eight treated patients showed normalization of CD3+, CD4+ and CD4+ naïve T-cell and natural killer cell numbers within three to four months after treatment.

All the patients cleared previous infections and are growing normally, the company said. Seven of the eight treated patients have developed normal Immunoglobin M, or IgM, levels to date. Four of these seven have discontinued monthly intravenous immunoglobin therapy, and three of these four have responded to vaccines to date.

"All of these patients were able to come off of isolation and they've returned home with immune systems that were fully functional," said Ewelina Mamcarz, the lead investigator of the study.

Mustang said it will develop the lentiviral gene therapy commercially as MB-107.

What's Next

Mustang expects to transfer the IND from St. Jude to itself by the end of this year. Subsequently, patients from all three participating clinical trial sites will be processed at the company's Worcester, Massachusetts facility.

Mustang CEO Manuel Litchman said the company will also work towards expanding the use of this life-saving therapy to hundreds of patients with the disease who have been treated with hematopoietic stem cell transplantation but are experiencing decreasing T-cell immunity.

Mustang Bio shares were higher by 192 percent to $7.87. Fortress Biotech FBIO, which owns about 40 percent stake in Mustang Bio, was up 57 percent to $2.30 per share.

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