Summary Box: Merck reports anti-clot drug data

STRIKE TWO: A second study shows Merck's experimental anti-clotting drug vorapaxar increased risk of dangerous internal bleeding, including inside the skull. The study, called TRA-2P, did show vorapaxar lowered risk of heart attack, stroke and death.

DIM FUTURE: Merck's already taken a $1.7 billion charge over vorapaxar after it flopped in the earlier study. It's to release full results of the latest study in late March.

ANALYST VIEW: Citi's John Boris thinks approval is unlikely. If it happens, he writes, vorapaxar has "limited commercial" opportunity.