The good news for Merck (NYSE: MRK) is that its newly acquired hepatitis C treatment, boceprevir, is better than the current offerings. The bad news is that the drug doesn't look as good as Vertex Pharmaceuticals' (Nasdaq: VRTX) telaprevir, based on stellar data released in May.

Boceprevir, which Merck got from Schering-Plough, was able to lower virus levels to undetectable levels -- essentially cure -- in 63% to 66% of patients who had not been treated before, depending on how long boceprevir was added to the standard of care. Patients who just got the standard of care were cured 38% of the time.

By contrast, telaprevir reached as high as a 75% cure rate, although the control group also fared better with a cure rate of 44%. The difference in the standard-of-care groups makes the comparison between the trials difficult. Vertex used Roche's Pegasys and Copegus, while Merck used its own Pegintron and Rebetol, which could account for some of the differences.

The difference could also be because of a different mix of African-Americans in the two trials, because it turned out that they often had lower cure rates. If you look at just the non-African-Americans in the boceprevir trial, the cure rates increase to between 67% and 69% for boceprevir and 40% for the control group. African-Americans, on the other hand, had cure rates of 42% to 53%, compared with 23% for the control group.

Until a head-to-head trial is run -- likely sometime after both boceprevir and telaprevir are on the market -- the comparison between trials is the best we have. For now, Vertex and marketing partner Johnson & Johnson (NYSE: JNJ) have the best absolute number out there for patients new to treatment.

While Vertex had previously set the bar for Merck in patients new to treatment, Merck has turned the tables by releasing data from a second trial with patients who had failed therapy. In that trial, boceprevir cured between 59% and 66% of patients, compared with just 21% in patients who got just the standard of care. Vertex could put the nail in boceprevir's coffin if it can beat those numbers in a phase 3 trial whose results are expected next month.

Maybe "coffin" is too strong a word because Merck's data should certainly be good enough to get boceprevir on the market, and some doctors will prescribe it despite the seemingly better data from telaprevir. In fact, Vertex's top spot isn't really safe considering that Roche, InterMune (Nasdaq: ITMN), Bristol-Myers Squibb (NYSE: BMY), and Gilead Sciences (Nasdaq: GILD) are all gunning for it with hepatitis C treatments of their own.

The first leg of the hepatitis C race is coming to a close, but the marathon of next-generation drugs is just beginning.

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Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. Johnson & Johnson is a Motley Fool Income Investor selection, and Motley Fool Options recommended buying calls on the stock. The Fool has a disclosure policy.