Vertex hep C drug shows real promise, limitations

By Bill Berkrot

NEW YORK (Reuters) - A closely watched hepatitis C drug being developed by Vertex Pharmaceuticals Inc continues to promise improvement over current treatments, according to analysts who have viewed brief summaries of data from highly anticipated clinical trials.

The summaries, known as abstracts, of data to be presented in full next month at the American Association for the Study of Liver Diseases annual meeting also suggest some limitations and side effects from the drug, telaprevir, analysts said.

"The incremental information provided by Vertex and the (study's) investigators continues to suggest that telaprevir will deliver a sustained virological response (SVR) of 70 percent, or thereabouts, in real world efficacy," Geoff Porges, an analyst with Sanford Bernstein, wrote in a research note.

Other analysts also said the available data appears to add up to an SVR of at least 70 percent in the clinical trial known as PROVE-2. An SVR rate higher than 50 percent is considered to be positive and 75 percent would be viewed as a major success, analysts have said.

SVR is a measure of patients in whom the hepatitis C virus has reached undetectable levels and appears to have been cleared from the system.

The studies are also attempting to show that by adding telaprevir to standard therapy of pegylated interferon and ribavirin there would be a lower relapse rate and significantly shorter treatment duration than without the Vertex drug.

"These results continue to show the potential that telaprevir has to enhance the efficacy of the current standard of care and provide a higher cure rate for patients with hepatitis C virus," said Jason Kolbert, an analyst for Susquehanna Financial Group.

Kolbert did note a potentially worrisome higher patient dropout rate with the PROVE-2 trial than in the earlier PROVE-1 study - 12.5 percent versus 10.9 percent - and the persistence of a troublesome rash seen with many patients who receive the Vertex drug.

Porges said data in the abstracts appear to debunk Vertex assertions that telaprevir could be effectively used without ribavirin, and that ribavirin was the cause of the rash seen in earlier combination studies.

Based on available PROVE-2 data, Porges said, within 12 weeks 25 percent of patients in the telaprevir-plus-interferon group saw the virus rebound from previously low levels compared with 4 percent in the triple-therapy group.

"This means that pegylated interferon with telaprevir but without ribavirin is a non-starter as a regimen for further study," Porges said.

He added that from further analysis of the data, "it is now clear that telaprevir, not ribavirin, was the cause of the rash observed in combination treated patients in PROVE-1."

The limitations "do leave the window open for competitors to enter the market" but do not affect telaprevir's immediate market potential, Porges said.

Vertex shares were up 56 cents, or 1.5 percent, at $39.00 in early afternoon trade on Nasdaq.