Mustang Bio, a biopharmaceutical company, has been working with St. Jude Children’s Research Hospital to develop MB-107, a lentiviral gene therapy to treat X-linked severe combined immunodeficiency. Mustang Bio developed the drug and has struck a partnership with St. Jude in order to conduct their clinical trial. Patients at the children’s hospital participated in phases one and two, with the first including newly diagnosed infants, and the second involving children over the age of two. After MB-107 received the Regenerative Medicine Advanced Therapy (RMAT) designation from the FDA in August, Mustang Bio hopes to develop the treatment for commercial use.
About X-Linked Severe Combined Immunodeficiency (SCID)
X-linked severe combined immunodeficiency (SCID) is an immune system disorder in which the body is prone to persistent and recurrent infections. Those with SCID do not have the immune cells necessary to fight off these infections. The exact incidence of this disorder is unknown, but it is estimated to affect one in every 50,000 to 100,000 newborns. Because it is an X-linked condition, nearly everybody with this disorder is male.
SCID is caused by a mutation on the IL2RG gene, which provides instructions for a protein needed for immune system function. Immune system cells called lymphocytes require this protein, and without it they cannot make antibodies (which are necessary for fighting infection) or regulate the entire system.
Symptoms of SCID are the infections that come due to the lack of strength in the immune system. Common infections include chronic diarrhea, ear infections, skin rashes, fungal infections like thrush, fevers, and respiratory infections. Those with SCID also develop slower than other children.
Diagnosis comes within a child’s first year of life. Doctors tend to notice persistent symptoms, including eight or more ear infections, two or more cases of pneumonia, infections that do not resolve after treatment of antibiotics, failure to thrive, persistent thrush, and deep-seated infections. A family history of SCID also points to a diagnosis. Testing lymphocyte levels is a common form of diagnosis as well.
Treatment includes orphan treatments that have been approved by the FDA and bone marrow transplants. Pegademase bovine is an enzyme replacement therapy used to treat SCID, and Elapegademase-lvlr was approved by the FDA in October of 2018. In terms of bone marrow transplants, also known as stem cell transplants, donors are usually a sibling that does not have SCID. These transplants are not always successful, and it can be difficult to find a donor who is a genetic match.
About MB-107
MB-107 is a gene therapy developed by Mustang Bio. It was recently evaluated in a clinical trial at St. Jude Children’s Research Hospital, with Phase I being conducted on infants who have recently been diagnosed and Phase II being conducted on children over two who have already had stem cell transplants. The data from this study was published in The New England Journal of Medicine.
Highlights of the data show that neither group of participants faced serious adverse effects, and every participant had hematopoietic recovery within the following three to four weeks. Nine of the eleven children had normal T-cell and NK-cell numbers in the following three to four months. Five patients are now off of intravenous immunoglobulin therapy.
Researchers working on MB-107 are very happy with the results of this trial, and it reinforces their beliefs that this gene therapy is an alternative to current SCID treatments. They hope that this therapy will not only continue to develop, but that it will continue to better the lives of those with SCID.
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