GlaxoSmithKline (GSK) has reported top-line results from the phase III STABILITY trial (STabilisation of Atherosclerotic plaque By Initiation of darapLadIb TherapY), evaluating the efficacy of its investigational Lp-PLA2 inhibitor darapladib in adults with chronic coronary heart disease (CHD).  Darapladib is not approved for use anywhere in the world.

The study did not meet the primary endpoint measure, which was time to first occurrence of any major adverse cardiovascular event (MACE) from the composite of myocardial infarction (heart attack), stroke, and cardiovascular death (relative risk reduction of 6%; p=0.199). There were greater reductions (nominal p<=0.05) in some of the pre-defined secondary endpoints that require further analysis. Additional data will be forthcoming from the second phase III study, SOLID-TIMI 52.

In STABILITY, the overall safety profile showed no major imbalance in serious adverse events between the active and placebo groups. Frequently reported adverse events included diarrhoea and odour which occurred at a similar frequency to that seen in phase II. Further analysis of the data is ongoing.

Commenting on the results, Patrick Vallance, president of Pharmaceuticals R&D, said, “Given the level of patient need in this area, we continue to investigate the role of Lp-PLA2 inhibition in coronary heart disease and other diseases. We will now work to better understand the data, including evaluation of the patient sub-groups, and await the outcome of a second phase III study of darapladib in acute coronary syndrome, called SOLID-TIMI 52, to determine our next steps.”

Full results of the STABILITY study will be submitted for presentation at a scientific meeting in 2014. The data from this study will contribute to any future regulatory submissions for darapladib.

Darapladib is a selective and orally active inhibitor of Lp-PLA2 (lipoprotein-associated phospholipase A2) currently being investigated as a potential agent for the reduction of cardiovascular events in patients with coronary heart disease. Lp-PLA2 is an enzyme that is found in blood and in atherosclerotic plaques. Atherosclerosis is characterized by the build-up of plaques of fat, cholesterol and other substances within the walls of arteries and is, in part, an inflammatory disease. When these plaques rupture they can block vital blood vessels, causing acute coronary syndromes (heart attacks) and strokes. Elevated Lp-PLA2 activity has been implicated in the development and progression of atherosclerosis.

STABILITY is the first of two phase III studies. It was a randomised, placebo-controlled double-blind, parallel group multi-centre, event-driven study in adults with chronic coronary heart disease. Patients were randomised to receive either 160mg darapladib or placebo in addition to standard of care. Standard of care could include a statin, aspirin and blood pressure medications.  The study enrolled more than 15,000 patients across 39 countries and continued until 1,500 major adverse cardiovascular events had occurred.

The primary endpoint was the composite of major adverse cardiovascular events (MACE): CV death, nonfatal myocardial infarction, and nonfatal stroke. The key secondary endpoints included major coronary events, total coronary events, individual components of MACE, and all-cause mortality.  

The second phase III study, SOLID-TIMI 52, evaluating the efficacy of darapladib in patients with acute coronary syndrome, is ongoing and expected to complete in 2014. This trial has enrolled over 13,000 patients in 36 countries. The study design of SOLID-TIMI 52 was published in the October 2011 edition of the American Heart Journal (M.L. O’Donoghue et al).

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