Just last week, biopharmaceutical company Mustang Bio announced Orphan Drug designation for its therapeutic candidate, MB-207. This unique lentiviral gene therapy is designed for previously treated patients with X-linked severe combined immunodeficiency (XSCID). In particular, previously treated patients used hematopoietic stem cell transplants.
MB-207
MB-207 is a lentiviral gene therapy, meaning it is delivered using lentivirus. According to Gene Therapy Net:
Lentivirus is a genus of the Retroviridae family, characterized by a long incubation period. Lentiviruses can deliver a significant amount of genetic information into the DNA of the host cell, so they are one of the most efficient methods of a gene delivery vector.
Researchers at the National Institute of Allergy and Infectious Diseases have been studying MB-207 for nearly 8 years. Currently, it is also being analyzed in two Phase 1/2 clinical trials for patients with XSCID (over 2 years old) who have previously been treated with hematopoietic stem cell transplants.
The FDA granted Orphan Drug and Rare Pediatric Disease designations to MB-207. These designations signify a treatment that meets an unmet need in patients with rare diseases (200,000 or less U.S. citizens). Upon receiving Orphan Drug designation, Mustang Bio also received tax credits and seven-year market exclusivity if the drug is approved. Moving forward, Mustang Bio hopes to submit investigational new drug (IND) applications to hold Phase 2 clinical trials to evaluate the safety, efficacy, and tolerability of MB-207.
XSCID
Also known as “bubble boy disease,” X-linked severe combined immunodeficiency (XSCID) is an inherited genetic disorder which almost only impacts males. This is because females would require two mutated or defective genes, while males only require one. Around 1 in 225,000 births have XSCID, caused by IL2RG gene mutations. According to the Genetics Home Reference:
The IL2RG gene provides instructions for making a protein that is critical for normal immune system function, [particularly] for the growth and maturation of developing immune system cells called lymphocytes. Lymphocytes defend the body against potentially harmful invaders, make antibodies, and help regulate the entire immune system.
Mutated genetic copies stop proper lymphocyte development and function. Next, the body is unable to fight infections. Because of this, patients with XSCID often experience frequent infections, skin rashes, thrush, and chronic diarrhea. Additional symptoms include pneumonia, poor growth and development, and bronchitis. Without treatment, XSCID is often fatal during infancy. In fact, many untreated patients do not live past two years old. Current treatments include hematopoietic stem cell transplants. In many cases, patients require immunoglobulin replacement therapies for their entire lives.
Learn more about XSCID here.
