Proposed Drug to Treat Oculopharyngeal Muscular Dystrophy Gains Orphan Drug Designation

Benitec Biopharma, an Australia-based drug developer, has received the FDA’s Orphan Drug designation for BB-301, an investigational drug for the treatment of oculopharyngeal muscular dystrophy (OPMD). The proposed drug is a single-vector (gene therapy construct) system that uses DNA-directed RNA interference to silence expression of the mutant PABPN1 gene that is associated with OPMD. The drug adds back a copy of the normal version of the gene to restore genetic function. BB-301 also received an orphan designation for BB-301 from the European Medicines Agency in 2017.

OPMD is a genetic condition, characterized by muscle weakness, that has been reported in approximately 29 counties, with the largest cluster of cases present in people of French descent in Quebec, Canada. Symptoms begin in a patient’s adulthood, generally after age 40. The first symptom of this condition is typically ptosis, followed by dysphagia. Some patients experience atrophy of the tongue or weakness in other facial muscles, and they may aspirate food or liquids, which can cause aspiration pneumonia.

While current treatments for OPMD focus on the specific signs and symptoms of the condition in individuals—such as treating ptosis with plastic surgery or treating dysphagia with surgery on the cricopharyngeal muscle—BB-301, if approved, would address the genetic cause of OPMD.

Greg West, CEO of Benitec, said in a statement, “We are very pleased to have received Orphan Drug Designation from the FDA for BB-301, as it is another significant step forward for a key program in our pipeline. We believe BB-301 represents a promising new approach for the treatment of OPMD and has the potential to make a meaningful impact for patients who have this debilitating disease.”

West added that, if the development program for BB-301 proves to be successful, it may act as a proof-of-concept for the company’s “silence and replace” technology for other therapeutic targets.

Benitec hopes to advance BB-301 to human clinical trials by the end of this year. According to the company, nonclinical safety studies and manufacturing work are currently underway, and Benitec plans to file an Investigational New Drug Application with the FDA by the fourth quarter of 2018.