Vertex Shareholders Stay Vexed

What's the SVR12 result for Arm D of the study? Using the most generous analysis, the SVR12 would be a robust 81% (13/16 patients). But using a stricter calculus, the SVR12 would be a less rosy 65% (13/20 patients).

For this reason, pay attention to both the numerator and the denominator used to analyze the upcoming telaprevir data. There are pros and cons for using either calculation, which go a long way toward explaining why there's so much uncertainty about the upcoming presentation. (And I did warn you that this column would get wonky.)

Other things to keep in mind about the upcoming data:

Pay attention to the side-effect profile of telaprevir and the reporting of any toxicities or adverse events that might have caused patients to discontinue treatment.

The SVR12 data will be a good measure of telaprevir's efficacy, but it's not enough. For a hepatitis C drug to receive FDA approval, patients must have undetectable virus for 24 weeks, or six months, following the end of treatment. Generally speaking, about 50% of treatment-naive hepatitis C patients are cured (achieve SVR24) on the currently marketed drugs.

If Vertex doesn't succeed with its home-run strategy of treating patients for only three months, the game is far from over. As I said above, the majority of patients in the Prove 1 study are being treated with three months of telaprevir in combination with either 24 or 48 weeks of interferon and ribavirin.