On the intent-to-treat basis (this means that all dropouts are counted as failures of treatment) PROVE 1, 12 + 12 arm would show that SVR is 60% (PROVE 2 should be at 70%, a 20% gain over SOC). Let us consider a hypothetical case that reduction in the TVR treatment time by one third (from 12wks to 8wks) cuts the dropout rate from 17% to 10%(this is possible), but leads to a loss only 2% in SVR. If this is the case, the 7% gain in patient retention rate translates to a gain of about 2.6% (from A Fierstein's paper 37% of dropouts are cured). So the improvement in efficacy is marginal. However, suffering from severe rash by the patients undergoing trials would be far less. This would improve the success potential of the application to be submitted to the FDA.
A better design of Phase III should include a flexible arm in which only those patients achieving UND at the ends of both 4 wks AND 8 wks of dosing(a majority belongs to this group) are eligible for stopping at 9th wk, but patients who miss either one of criteria takes for up to 12 wks of TVR followed by another flexible periods of IFN/RVN, depending on their PCR status. HCV mutation status can be added to the criteria determining the length of treatments.
Excellent response to my question -- I get the impression that there is the possibility of many more people achieving SVR's with treatment durations of less than 12 + 12. It may be a matter of appropriately identifying those candidates that are best suited for a shorter study group at this point (you seem to agree with this idea in principle).
Although a study group receiving the combination of drugs for durations of less than 12 + 12 may not be at the top of the VRTX list at this point in time, I think it is very exciting that this possibility even exists! Will be interesting to see what the FDA thinks.
The study results are showing the potency of Telaprevir is proving to be very worthy of greater attention from all those in the HCV community.