Glaxo heart drug seen promising despite trial miss

MUNICH, Sept 2 (Reuters) - An experimental drug designed to fight heart disease in a new way missed its goal in a mid-stage clinical test but researchers and its developer, GlaxoSmithKline (GSK.L), said the results were nonetheless encouraging.

Patrick Serruys of the Erasmus Medical Center, Rotterdam, said darapladib prevented the expansion of the so-called necrotic core of arterial plaques, which can lead to a rupture and blockage of blood vessels, triggering a heart attack.

Glaxo had also hoped to show, using ultrasound imaging inside patients' arteries, that darapladib had a significant impact on the "deformability" of plaques.

A second primary endpoint was reduction in blood levels of an inflammatory marker called C-reactive protein.

In fact, the one-year Phase II study, involving 330 patients, found no statistically significant difference in either of these two measures among those taking the drug and those on a placebo, Serruys told the European Society of Cardiology annual meeting.

Darapladib, which Glaxo discovered with Human Genome Sciences (HGSI.O), targets an enzyme called Lp-PLA2 that is linked to artery-clogging plaques.

Serruys said it could open a "new era" in treatment.

"Our study suggests that the potential plaque-stabilising effects of darapladib may represent an important approach in treating atherosclerosis and reducing cardiovascular risk," he said.

UBS analysts estimate annual sales of darapladib might eventually top 5 billion pounds ($9 billion) a year, if it works. But the project remains high risk and is still many years from reaching the market.

Patrick Vallance, Glaxo's head of drug discovery and leader of the darapladib project team, said Glaxo remained committed to developing the medicine, despite the mixed trial results. "It halted the progression of necrotic core...frankly, that is the key measure," he told Reuters.

Glaxo already said in April that it was pushing ahead with a final-stage Phase III study of darapladib, which Vallance said should start by the end of this year.

That trial will recruit more than 10,000 at-risk patients and assess the benefits -- in terms of heart attacks, stroke and deaths -- of giving them darapladib on top of standard drugs.

"It will take several years, not only because these studies take time to recruit but because event rates and stablisation of plaque may not be an instantaneous biological reaction," he said.

Darapladib is designed to offer something above and beyond the statin class of cholesterol-fighting treatments.

Finding new drugs that can offer additional benefits is a risky business, however, as highlighted by the failure of Pfizer (PFE.N) torcetrapib product in 2006. (Editing by Louise Ireland)