Merck clot drug seen unfit for stroke, shares fall

Merck & Co has stopped giving one of its most important experimental drugs, the blood clot preventer Vorapaxar, to some patients in two late-stage studies after it was deemed inappropriate for those who had suffered a stroke. Merck shares tumbled 6.7 percent after the news, as the market appeared to be writing off the value of a drug once thought to have multibillion-dollar sales potential - Reuters