The FDA is expected to decide by Thursday whether to approve the blood thinner or, possibly, issue an approvable letter, which would, of course, mean a delay. Given that Lilly stock hasn’t moved lately - in fact, it hit a 52-week low last Friday, The Wall Street Journal notes - most investors seem to be betting an outright agency approval is unlikely.

“Without the benefit of an FDA advisory meeting, which was widely expected, it is much more difficult to handicap the probability of approval,” write Barbara Ryan, a Deutsche Bank analyst, in an investor note. “In our view, an approvable letter, subject to minor details in labeling, would be a relief.”

Why? The newly cautious FDA recently bounced Merck’s Cordaptive cholesterol drug, for instance, and so Ryan suggests a non-approvable letter will be issued for prasugrel “due primarily to the uncertainties around the increased risk of major bleeding associated with this therapy” and that the FDA may want to see the results of a 10,300-patient trial under way. A non-approval, however, is unlikely, she adds.

Last winter, Lilly released a study showing prasugrel lowered the risk of cardiovascular death, non-fatal heart attacks or non-fatal strokes when compared with Plavix, the $7 billion gorilla of blood thinngers. But the med caused some patients to experience a statistically significant increase in major bleeding compared to those treated with Plavix, which is marketed by Bristol-Myers Squibb and Sanofi-Aventis.

Overall, for every 1,000 people treated with prasugrel compared to Plavix, there were 23 fewer heart attacks and an additional six major bleeding complications. As a result, Ryan believes many cardiologists will be cautious before readily embracing prasugrel.