GlaxoSmithKline's experimental platelet-boosting drug Promacta has been granted priority review by U.S. health regulators, boosting prospects for its early launch, Europe's biggest drugmaker said on Monday.
A priority review means the U.S. Food and Drug Administration is likely to decide within six months whether to approve the treatment, faster than the usual 10-month review period.
Glaxo, which views the medicine as a potential blockbuster, said it also planned to submit a marketing application in 2008 for the drug in Europe, where it will be sold as Revolade.
Shares in the group were 0.4 percent higher at 11.06 pounds in a sharply weaker London stock market.
Nomura Code analyst Mike Ward, who sees sales potential of well over $1 billion, said the decision was good news, since the presence of a rival experimental drug from Amgen Inc meant a priority review had not been certain.
"It's a nice tick in the box for Glaxo," he said.
The drug, known generically as eltrombopag, was discovered as a result of a research collaboration between Glaxo and Ligand Pharmaceuticals Inc and is a key new product for the British-based group, which faces declining sales of older drugs.
Ligand stock jumped 8 percent to $3.66 in early U.S. trade.
The product is designed to treat idiopathic thrombocytopenia purpura (ITP), an autoimmune disease which results in low blood platelet counts.
Because platelets contribute to blood clotting, patients with low counts bleed more easily than others, heal more slowly and bruise more often.
"The FDA designation of our submission for priority review is very encouraging and brings us closer to offering physicians and their patients eltrombopag," Paolo Paoletti, Glaxo's head of oncology medicine, said in a statement.
Amgen's competing Nplate medicine, which already has U.S. priority review status, is given by injection, while Promacta is taken as a more convenient pill.
Both drugs work by stimulating platelet production. Existing ITP treatments work to decrease platelet destruction and can cause serious side effects.
There are an estimated 15,000 to 30,000 new cases of ITP in U.S. adults and children each year, based on a U.S. government population estimate and a disease prevalence estimate from the Annual Review of Medicine.