Mark your calendars, Fools: May is going to be a solid month for drug approvals.

The multiyear marathon between Schering-Plough and Vertex Pharmaceuticals (Nasdaq: VRTX) to develop the next-generation hepatitis C drug is finally coming to a close. Vertex announced yesterday that the Food and Drug Administration has accepted its New Drug Application to market telaprevir. Not surprisingly, given the unmet need, the agency will give telaprevir a priority review, so Vertex should hear back on or before May 23.

Merck (NYSE: MRK), which took over development of boceprevir when it bought Schering-Plough, announced a few weeks ago that the FDA had accepted its application with a priority review, as well. Since one drug isn't all that material to Merck's business, the company didn't feel compelled to give an exact date of the submission, so we don't know exactly when the FDA will come back with a decision.

If you want to put it on your calendar, you'll need a highlighter to mark off the potential weeks that Merck could hear. If the FDA took the same amount of time to review the applications, and the two companies announced the acceptance the same amount of time after they heard from the agency -- two big ifs -- Merck's PDUFA date is May 9. Perhaps the drugmaker will give investors an exact PDUFA date on its fourth-quarter earnings call.

In the big picture, which company launches first in the U.S. or Europe -- where Merck will go up against Vertex's marketing partner Johnson & Johnson (NYSE: JNJ) -- doesn't really matter. A few weeks or even a difference of a month or two doesn't really matter compared with who has the better drug.

Vertex clearly has the advantage here. While the drugs haven't been compared head to head, telaprevir appears to work better in every patient population tested so far.

While I think telaprevir is a best-in-class drug, I'm hesitant to invest because everyone else seems to think the same thing. The drugmaker has a market cap of more than $8 billion. That's substantially larger than companies like Dendreon (Nasdaq: DNDN) and Onyx Pharmaceuticals (Nasdaq: ONXX), which already have drugs on the market. Sure, the hepatitis C market is largely untapped, but there's a heck of a lot of sales already baked into that $8 billion.

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