Pfizer and Bayer revealed study results that may give their drugs a foothold in a $10-billion-a-year market to prevent clots that cause strokes and deadly lung damage. The research provided evidence that Pfizer's apixaban and Bayer’s Xarelto are as safe as warfarin. Head-to-head tests between each drug and warfarin will be the only way to know for sure how each will measure up, said Alfred Bove, a cardiologist at Temple 's School of Medicine. Price will also play a role, Bove said. "The companies that are smart and position their prices for these things in a range that makes sense are going to win," he said. "It's better to have two or three similar drugs on the market so they compete."