Merck’s experimental blood thinner Vorapaxar shows promise in significantly reducing the risk of dying from heart attack or stroke, but the associated risk of hemorrhage has some experts wondering if the drug will make it past United States drug regulators.
Vorapaxar is an anti-platelet medicine that works differently that aspirin or the popular warfarin (Coumadin). It is in a new class of medications known as thrombin receptor antagonists, which work by stopping a process that normally allows the blood’s platelets to stick together and form clots.
The medication is designed to prevent heart attacks and strokes and was tested in patients who have had previous heart attacks, strokes or peripheral artery disease.
The drug showed the best results in heart attack patients, with a reduced risk of dying from a future heart attack or stroke by as much as 20 percent. The drug also offered an additional 13 percent reduction in the risk of dying from heart attack or stroke within three years.
On the flip side, patients in the study who suffered a previous stroke and took Vorapaxar had significantly more bleeding events after three years – 4.2 percent for those on the drug compared to 2.5 percent taking a placebo. The risk of brain bleeds was highest in people who had suffered previous strokes.
The risk was so great that stroke patients involved in the clinical trials were told to leave the study early because of the acute risk for brain bleeds.
Merck had hoped Vorapaxar would be a blockbuster drug that would provide a safer alternative to the long-used warfarin, but now the company is wondering if it will be considered safe enough for Food and Drug Administration (FDA) approval.
In October 2010, the FDA approved the blood thinner Pradaxa (dabigatran) to prevent strokes in patients with a specific abnormal heart rhythm. Pradaxa is in a new class of antigoagulants called direct thrombin inhibitors, which work by preventing blood clots from forming in the body.
In November 2011, Pradaxa manufacturer Boehringer Ingelheim confirmed that in clinical trials 260 people had suffered a fatal bleed while taking the drug. A month later, the FDA notified the public that it was reviewing reports of bleeding in patients taking Pradaxa.
Source: Medical Xpress