Vertex Hep-C Drug Shows Promise

As reported Saturday, 17 patients were enrolled in Arm D, but only nine of them made it through all 12 weeks of treatment. Of these nine, six had undetectable levels of virus measured 20 weeks after treatment stopped.

A 66% "cure" rate at 20 weeks is good, but the small number of patients makes the result difficult to interpret. Furthermore, the high number of patients who either discontinued treatment or relapsed after treatment raises questions about the viability of treating patients with only 12 weeks of telaprevir and standard of care.

It's likely that investors will view the Arm D results as somewhat of a disappointment.

Vertex's Partridge says Arm D is a proof of concept and that more data is necessary before passing judgment. A European version of PROVE 1 -- dubbed PROVE 2 -- is enrolling more patients and will provide a more definitive answer.

As I said above, exactly how long patients will require treatment is one of the unknowns about telaprevir. Additional data to be presented later this year from PROVE 1 and PROVE 2 should clarify this.

As it stands, however, Vertex believes that telaprevir will be dosed for 12 weeks, with standard of care (interferon plus ribavirin) dosing likely to last 12 to 24 weeks. (At its longest, that's 12 weeks of triple combination plus another 12 weeks of standard therapy.) Recall that current standard treatment calls for interferon and ribavirin to be dosed for 48 weeks.

The benefit shown by telaprevir does continue past four weeks, according to additional data presented Saturday.

After 12 weeks of treatment, 70% of telaprevir patients reported undetectable levels of virus compared to 39% of patients in the placebo arm.