Drug discovery company Benitec Biopharma has received orphan drug status for a treatment for oculopharyngeal muscular dystrophy, a rare genetic condition that starts after the age of 40.

The powerful US regulator the Food & Drug Administration (FDA) gave the designation to a gene therapy called BB-301.

Orphan drugs treat diseases so rare that drug companies are reluctant to develop them, as there is little commercial pay off. The status gives the drug developer tax reductions, fast track regulatory approvals, an exclusivity period, and an exemption from FDA application fees.

Oculopharyngeal muscular dystrophy is characterised by muscle weakness that begins in adulthood, typically after 40. The first symptom is usually droopy eyelids followed by difficulty swallowing.

Benitec’s (ASX:BLT) gene therapy treatment silences the expression of the mutant gene associated with oculopharyngeal muscular dystrophy, while at the same time adding a normal version of the gene to restore its function.

The company wants to reach human trials by the end of 2018.

Benitec opened on Monday morning up 7 per cent to 23c.