At a time when rivals are cutting back on cardiovascular research, the drugmaker is launching an expensive three-year clinical trial involving more than 15,000 patients worldwide to test an experimental med called darapladib, which is the first in a new class of drugs targeting an enzyme linked to the plaque that clogs arteries.

The idea, of course, is to see whether patients live longer and have fewer heart attacks and strokes when given the drug, which is designed to outdo the cholesterol-lowering statins by reducing the risk of plaques rupturing and blocking blood vessels, thereby triggering heart attacks. UBS analysts estimate annual sales might eventually top $7.7 billion, although approval is still years away.

Glaxo’s decision to invest heavily in the new approach contrasts with Pfizer’s decision to abandon research into heart disease. “We are prepared to take a risk in an area where risk-taking is necessary if we’re going to change the treatment paradigm,” Patrick Vallance, Glaxo’s head of drug discovery, tells Reuters (see Glaxo statement).

However, mixed results from a Phase II clinical trial involving 330 patients, which reported at a medical meeting last September, prompted most analysts to express caution about the prospects. The study found darapladib prevented the expansion of the so-called necrotic core of arterial plaques, which can break up and block arteries.

But the study failed to meet its primary goals of reducing the “deformability” of plaques and in cutting blood levels of an inflammatory marker called C-reactive protein, raising doubts about how useful the drug will be in clinical practice.

The new 15,000-patient study, called STABILITY, hopes to answer this question by comparing darapladib to placebo when both are given in addition to standard care that may include statins, aspirin and blood pressure meds in people with chronic coronary heart disease. The trial will be stopped after approximately 1,500 cases of major adverse cardiovascular events are recorded, which Glaxo expects to take around three years.

A second large event-driven study of the drug in patients who have experienced acute coronary syndrome is scheduled to start in late 2009 and also last around three years. Vallance tells Reuters it is possible both trials might last longer than three years if event rates were slower than anticipated.

The lengthy trial means darapladib would not reach the market until well after generic versions of Pfizer’s Lipitor arrive in 2011.

Source: Reuters