• Time to first major vascular event
  
• (defined as non-fatal myocardial infarction or coronary death
  
• non-fatal or fatal stroke, or revascularisation) by the end of study
  

• Major vascular events (non-fatal MI or cardiac death) by the end of the study
  
• stroke (fatal or non-fatal) by the end of the study
  
• Coronary or non-coronary revascularisation by the end of the study
  
• Mortality, both overall and in particular categories of causes of death
  
• Major cardiovascular events in people with a history of different diseases at the beginning of the study.
  

Cardiovascular disease is one of the leading causes of morbidity and mortality in the UK, as well as in the developed and the developing world. Finding new and safe treatments to reduce the burden of heart disease and strokes is therefore an important contribution to public health and in the wider public interest. HPS2-THRIVE aims to find out whether by combining niacin (a drug that has been available for 50 years) with a new drug laropiprant(which reduces the side-effects of niacin) is beneficial. All participants in HPS2-THRIVE will have established cardiovascular disease and therefore be at very high risk of recurrent vascular events (myocardial infarction, stroke or the need for arterial revascularisation). Two of the most important risk factors for recurrent events in such patients are the blood levels of LDL cholesterol with a positive association, and HDL cholesterol levels with a negative association.

HDL cholesterol has long been known to have a strong inverse correlation with CHD risk. But, randomized trial evidence for beneficial effects from raising HDL cholesterol is limited. One of the most effective HDL-raising agents is niacin but the tolerability of niacin has been severely limited by flushing and cutaneous side-effects, which appear to be mediated largely by prostaglandin D. Laropiprant is a selective prostaglandin D receptor antagonist that substantially reduces the frequency and intensity of niacin-induced flushing. Daily oral doses of extended release (ER) niacin plus Laropiprant 2g(formerly MK-0524A) have been well tolerated in early studies and increase HDL cholesterol by 20-25%. The trial will assess whether this increase in HDL cholesterol translates into clinical benefit as is expected from the observational evidence. In addition, all participants will also be provided with effective LDL-lowering therapy, as either simvastatin 40mg daily alone or with ezetimibe 10mg daily in a combination tablet.

The complementary effects on the HDL (good) and LDL (bad) cholesterol produced by extended release niacin/laropiprant 2 g daily and simvastatin 40 mg with or without ezetimibe 10 mg should provide an excellent treatment option for patients with vascular disease. However, no trials so far have demonstrated clearly that raising HDL cholesterol produces the expected reduction in cardiovascular risk. If HPS2-THRIVE is able to demonstrate reliably that raising HDL cholesterol reduces the risk of further cardiovascular events then this will be relevant to hundreds of millions of people worldwide.