First, I would like to congratulate the Vertex team who worked on the Zenith trial. Today's press release regarding the quad arm of Zenith trial is surprisingly good.
I'll do my best to answer your excellent questions.
1) There are IFN-intolerant people and IFN-non-responsive people. The former is only 4% of GT1 patients (= % of people who dropped out of IFN/RBV treatment). The null responders are about 1/3 of population. So, there are less than 40% of population who can benefit only minimally from IFN/RBV.
2) 70% is my wild guess. No body has ever tested and reported the chance of cure beyond week 24 following all-oral treatment. Viral particles hidden inside cells are NOT easy to kill even with immune boosting, and it is difficult to imagine that an all-oral can achieve a 90% SVR rate. Abbotts quad achieved an SVR of 9 out of 10. But if they treat 1000 GT1 patients, the chance is about 70%, I would think. They should check for a UND at least at 48 weeks post-treatment, not just 24 weeks.
3) On the other hand, as Dr. Peter Mueller stated in the earnings CC,safety or viral breakthrough has not triggered the stopping criteria in the all-oral arms up to week 10 of 12 wk arms. If this continues through EOT, then we may see an SVR rate of 80%.
4) Even VRUS' drug which is touted as pan-genotype may have sub-populations of GT1 who are non-responsive to the treatment.
5) Since nobody can tell who would be responsive or non-responsive to an all-oral, until a method to predict is found, it would be the best to treat with a quad as in the Zenith trial. So, I agree with you. Some patients, however, prefer less side effects than a better chance of cure.