* Boceprevir rapid responders reach 82 pct SVR
* 55 pct SVR in null responders after 48-week regimen
By Bill Berkrot
NEW YORK, Nov 1 (Reuters) - The addition of Schering-Plough Corp’sSGP.N experimental hepatitis C drug boceprevir after four weeks of treatment with standard medicines led to highly encouraging sustained response rates in a mid-stage study.
The triple combination of boceprevir and the current treatments of pegylated-interferon and ribavirin appeared to knock out the virus at double the rate of the standard drugs alone, according to researchers.
Among patients who had a rapid response to the combination therapy, the cure rate, or those in whom the virus remained undetectable after completing treatment, exceeded 80 percent, according to data to be presented at the American Association for the Study of Liver Diseases (AASLD) meeting in Boston.
Boceprevir is in a race with Vertex Pharmaceuticals Inc’s (VRTX.O) telaprevir to become the first of a next generation of antiviral hepatitis C medicines called protease inhibitors. Both appear to be highly promising advances in the treatment of the serious liver disease based on early clinical results.
“The next decade for hepatitis C not only holds substantial promise for those who have not been treated, but those who have already been treated with standard of care also look like they are going to derive substantial benefits from this new generation of therapies,” Dr Paul Kwo, lead investigator of the boceprevir study, said in an interview.
The 595-patient boceprevir study was designed to test the triple combination in a response guided therapy. The idea is to enable physicians to tailor duration of therapy — either 28 or 48 weeks — based on a patient’s early response to treatment, and to help cut the risk of developing resistance to the drug.
All patients in the the study received the standard drugs for four weeks before adding boceprevir, which is given three time a day, in order to determine the level of response to the current drugs before the triple combination therapy began.
Among the null responders, 25 percent of patients who received 28 weeks of therapy achieved sustained viral response (SVR), while 55 percent who were treated for 48 weeks reached sustained viral response.
The percentage of patients in whom the virus is undetectable at least 24 weeks after completing treatment yields the critical measure known as sustained viral response, or SVR, which is tantamount to a cure.
The 55 percent response was impressive, Kwo said, because “these are the individuals who are the most difficult to treat in our clinics.”
Among patients who had a rapid viral response — defined as the virus being cleared after the initial four-week lead-in treatment plus four weeks on the triple combination — there was an 82 percent SVR rate after completing a 28-week regimen.
Patients who did not have a rapid viral response but reached undetectable virus levels by treatment week 16 (up to 12 weeks of therapy including boceprevir) had a 79 percent SVR rate after completing a 48-week regimen.
By comparison, those who received only the standard drugs for 48 weeks had a 38 percent SVR rate.
The ability to successfully treat patients for 28 weeks rather than 48 would be a huge advantage as current drugs can be difficult to tolerate and often lead to flu-like symptoms for the duration of the treatment period.
The most common adverse events in patients receiving boceprevir were fatigue, anemia, nausea and headache. While anemia occurred in about half the patients, incidence of discontinuation due to anemia was “extremely low,” Kwo said.
“It’s very exciting data, but larger studies will have to confirm what we see as signals in this very small but promising study,” Kwo said. (Reporting by Bill Berkrot; editing by Andre Grenon))