Boehringer Ingelheim has completed recruitment of patients into what it claims is the largest-ever secondary prevention trial involving patients who have suffered an ischaemic stroke.

The aim of the 20,000-patient study, called PRoFESS, will be demonstrate that extended release dipyridamole plus acetylsalicylic acid (ASA), a combination marketed by Boehringer Ingelheim as Aggrenox or Asasantin Retard, is superior in preventing secondary strokes compared with Plavix (clopidogrel), an antithrombotic drug sold by Bristol-Myers Squibb and Sanofi-Aventis.

The study will also examine whether Boehringer’s high blood pressure drug Micardis (telmisartan) will reduce the risk of further strokes compared with placebo when added to treatment.

Boehringer was prompted to start the trial after data from earlier studies showed that the combination of dipyridamole and aspirin was better than ASA alone for secondary prevention of strokes.

The ESPRIT study, published in The Lancet earlier this year, found a statistically significant 20% relative risk reduction of primary outcome events including stroke, deth from vascular causes and heart attack in patients treated with dipyridamole plus ASA compared with patients treated with ASA alone.

In 2004, the company re-jigged the design of PRoFESS after another trial showed that the combination of clopidogrel and ASA did not cut either vascular events or hospitalisation versus clopidogrel alone, and was accompanied with a significant increase in potentially fatal major bleeding. The original design of the study compared Aggrenox with clopidogrel plus ASA.

Aggrenox was Boehringer's tenth-largest product by sales in 2005, bringing in 172 million euros with ahealthy growth rate of nearly 18%. The company claims patent protection for the combination out to 2016.