PTC Therapeutics said a committee of the European Medicines Agency recommended against a conditional approval to its drug for the treatment of a rare muscular disorder, sending its shares down nearly 30 per cent in premarket trading.

PTC joined a list of companies struggling with setbacks to their drugs to treat Duchenne muscular dystrophy (DMD), a rare genetic disorder which causes muscle degeneration and eventual death in young boys.

Prosensa Holding NV’s partner GlaxoSmithKline handed back the rights to its DMD drug less than two weeks ago after the failure of a key trial, forcing the smaller company to consider developing the drug on its own.

Sarepta Therapeutics lost almost two-thirds of its market value in November after the FDA said the design and goals of its trial might not be sufficient to get approval for its muscular disorder drug.

PTC said it plans to request the European Committee for Medicinal Products for Human Use for a re-examination. It was seeking a conditional approval, granted to treatments that show early benefit.

The drug, ataluren, is intended to treat a form of DMD which occurs due to a type of genetic mutation known as a nonsense mutation.

Nonsense mutation leads to a premature end to the translation of a gene into a protein. About 15 per cent of DMD cases are caused by nonsense mutations, according to the US National Institutes of Health.

Ataluren is designed to interact with a part of the cell known as a ribosome, enabling it to manufacture a protein called dystrophin, the absence of which causes muscle weakening in patients with DMD.

The drug is being tested in a late-stage study for DMD, with results expected in mid-2015. PTC is also testing it as a treatment for cystic fibrosis caused by nonsense mutations.

PTC Therapeutics shares closed at $26.22 on the Nasdaq yesterday. (Reuters)