CAMBRIDGE, Mass. ( TheStreet) -- Vertex Pharmaceuticals ( VRTX) announced new clinical data Tuesday demonstrating that nearly all hepatitis C patients who respond early and robustly to treatment with the company's experimental drug telaprevir achieve a cure after six months -- reducing the conventional treatment time for the disease in half. Vertex shares were up 4% to $38.40 in pre-market trading. The new telaprevir results come from a phase III study known as ILLUMINATE, which was designed to confirm the theory -- long held by Vertex -- that telaprevir could help cure hepatitis C patients with 24 weeks of total therapy instead of the 48 weeks of treatment currently considered the standard of care. The patients who seem to benefit from shortened therapy are ones whose virus becomes undetectable after just four weeks of taking telaprevir and stays suppressed through 12 weeks of the telaprevir treatment cycle. For this subgroup of hepatitis C patients who achieved a so-called "extended rapid viral response", or eRVR, treatment for 24 weeks led to a hepatitis C cure rate of 92%. By comparison, the eRVR patients who were treated for 48 weeks achieved a hepatitis C cure rate of 88%, according to results of the ILLUMINATE trial released Tuesday. "The viral cure rates seen in ILLUMINATE showed that there was no benefit to extending telaprevir-based therapy to 48 weeks for the majority of people," said Dr. Kenneth Sherman of the University of Cincinnati College of Medicine and a principal investigator of the trial, in a statement. In May, Vertex said results of a phase III study known as ADVANCE demonstrated that 75% of hepatitis C patients never treated before achieved a viral cure after receiving 24 weeks of total therapy, including a 12-week course of telaprevir. The 92% and 88% cure rates from the ILLUMINATE study were much higher because this study was designed specifically to identify a subgroup of hepatitis C patients who responded the earliest and most robustly to telaprevir treatment. Approximately 65% of the patients who were enrolled in the ILLUMINATE study achieved an eRVR and were therefore eligible for the shortened, six-month treatment regimen, said Vertex For all patients enrolled in the ILLUMINATE study, including those who did not achieve an eRVR, the cure rate was 72% after telaprevir treatment, or comparable to results from the ADVANCE study, said Vertex. Vertex and its partner Johnson & Johnson ( JNJ) plan to seek regulatory approval for telaprevir in the second half of the year, based on positive results from the ADVANCE study as well as another study of telaprevir in previously treated patients. Results from that study, known as REALIZE, will be announced next month.
Vertex said Tuesday that data from the ILLUMINATE study will be used to support telaprevir's approval application and drive home the point to regulators that it's possible to identify a group of hepatitis C patients who can benefit from shortened therapy. These data are particularly important to Vertex because it helps differentiate telaprevir from its main competition at this point for hepatitis C patients, namely Merck's ( MRK) experimental drug boceprevir. Treatment with boceprevir yielded hepatitis C cure rates of 63% and 66% but treatment duration ranged from 28 weeks to 48 weeks, according to results of a phase III study announced by Merck on Aug. 4. The results of the ILLUMINATE study fell within the expectation range of investors because they matched the results of earlier studies of telaprevir that also identified early responders. Vertex shares closed Monday at $37. -- Reported by Adam Feuerstein in Boston. Follow Adam Feuerstein on Twitter.