Merck tracks positive results, bleeding risk in second big vorapaxar study

Merck says that vorapaxar, its troubled blood thinner once considered the jewel in Schering-Plough's crown when the pharma giant bought it for $41 billion, hit its primary efficacy endpoint in a second major late-stage study. But Merck ($MRK) investigators also noted that while the drug--which proved too dangerous to continue the first study to its conclusion--looked positive on the top line, patients taking it also suffered from a significant increase in bleeding.

Vorapaxar has caused a lot of trouble for Merck, which once hoped that it had a blockbuster treatment on its hands when the deal for Schering-Plough went through. A year ago the company shut down the first big study after investigators tracked a dangerous increase in the risk of bleeding.

In this second study, TRA-2P, researchers were testing the treatment using a composite score for cardiovascular death, heart attack and stroke, paying particular attention to whether it would prevent clots. The data will be reviewed in March.

"In developing vorapaxar, Merck and our scientific collaborators set a very high bar--would the addition of vorapaxar to standard of care provide incremental benefit in preventing clots?" said Peter S. Kim, president, Merck Research Laboratories. "We are pleased that TRA-2P met its primary endpoint, and we look forward to discussing the results with the scientific community."

So where does it go from here? For Merck's part the pharma company says it will ponder all the data and then consider its options, including a potential regulatory filing. With one monumental pratfall and mixed results for the second study, plenty of questions beg to be answered first.

- here's the press release