The US Food and Drug Administration has granted breakthrough therapy designation to GlaxoSmithKline's drisapersen for the potential treatment of patients with Duchenne muscular dystrophy.

The agency has concluded that the drug qualifies as breakthrough based on a Phase II study of drisapersen, which is licensed from Prosensa of the Netherlands. DMD is severely debilitating childhood neuromuscular disease that affects one in 3,500 live male births and is caused by mutations in the dystrophin gene.

Boys with DMD are usually diagnosed before the age of five and are in a wheelchair by 12; most don’t survive their mid-20s. GSK is looking at drisapersen in ambulant (Phases II and III) and non-ambulant boys (Phase I) with DMD who have dystrophin gene mutations which are amenable to an exon 51 skip (up to 13% of all patients). The dystrophin gene is the largest found in humans and has 79 axons.

Breakthrough therapy designation is distinct from the FDA's other fast-track programmes, such as accelerated approval and priority review, as it involves more intensive guidance from the agency on putting together an efficient drug development programme.

Debra Miller, chief executive of CureDuchenne, a US nonprofit organisation, noted that the new status "means the FDA has reviewed the data for drisapersen and will provide additional resources". It is a disease that progresses very quickly "and for which there’s currently no cure, so on behalf of the Duchenne community, we are grateful to the FDA for recognizing the need and potential for this drug", she added.

CureDuchenne committed significant funds at an early stage to Prosensa’s exon skipping work that led to the development of drisapersen. Ms Miller said that “these results validate our early efforts to fund novel research and offer hope for finding an effective and safe treatment".