Interim results from a Phase 2 clinical trial show that 74 percent of HIV-positive participants taking Incivek, in combination with peginterferon-alfa and ribavirin, had undetectable hepatitis C virus levels after 24 weeks of treatment, compared to 55 percent of participants taking peginterferon-alfa and ribavirin alone.

The response rate is similar to that reported last month for Victrelis (boceprevir) in a Phase 2 clinical trial in people with HIV (see related AIDS Beacon news).

“As HIV treatments have improved, liver disease associated with hepatitis C has become a leading cause of death among people who are co-infected, so offering patients a better chance at a cure for hepatitis C while maintaining their suppression of HIV would be a major advance in treatment,” said Dr. Kenneth Sherman, a professor of medicine at the University of Cincinnati College of Medicine and lead investigator of the trial, in a press release.

The results were presented today at the 62nd Annual Meeting of the American Association for the Study of Liver Diseases in San Francisco.

Based on the results, Vertex Pharmaceuticals, which developed Incivek (telaprevir), stated that it will initiate a Phase 3 trial of the drug in people with HIV by the end of the year. The trial will evaluate both a 24-week and 48-week treatment course for hepatitis C.

“As we prepare for our new Phase 3 study to evaluate Incivek combination therapy in a much larger group of people who are co-infected, data from this study give us hope that in the future we’ll be able to help more co-infected patients clear the virus,” said Dr. Robert Kauffman, senior vice president and chief medical officer at Vertex.

HIV and hepatitis C virus co-infection is very common; researchers estimate that a quarter to a third of people with HIV also have hepatitis C. People who are infected with both viruses are less likely to spontaneously clear the hepatitis C virus from their systems than people with hepatitis C only. Co-infected patients are also less likely to respond to hepatitis C treatment, which currently consists of Pegasys (peginterferon-alfa-2a) or PegIntron (peginterferon-alfa-2b) plus ribavirin (Rebetol, Copegus) for 48 weeks.

Incivek, which was approved by the United States Food and Drug Administration in May of this year for the treatment of hepatitis C (in combination with peginterferon-alfa and ribavirin), has been shown to improve hepatitis C cure rates compared to peginterferon-alfa and ribavirin alone.

However, it was not approved at the time for people with both HIV and hepatitis C, due to lack of information on efficacy in people who are co-infected.

In this ongoing Phase 2 study, researchers are comparing the efficacy of Incivek plus Pegasys and ribavirin to Pegasys and ribavirin alone in adult patients with both hepatitis C and HIV.

The trial includes 60 HIV-positive adults with genotype-1 hepatitis C. Twenty-two percent of participants are not on antiretroviral therapy, 40 percent are taking Atripla (efavirenz/emtricitabine/tenofovir), and 38 percent are taking Norvir (ritonavir)-boosted Reyataz (atazanavir) plus Viread (tenofovir) and Emtriva (emtricitabine) or Epivir (lamivudine).

The average participant age at the start of the study was 46 years old. Most (88 percent) are male; 27 percent are African-American. None of the participants have previously been treated for hepatitis C.

Study participants were randomly assigned to receive 12 weeks of Incivek or a placebo, both in combination with Pegasys and ribavirin, followed by 36 weeks of Pegasys and ribavirin alone.

Patients taking Atripla took a larger dose of Incivek (1,125 mg every eight hours) than patients taking a Reyataz-based regimen or no antiretrovirals (750 mg every eight hours).

Results showed that after 24 weeks, 74 percent of participants taking Incivek had undetectable levels of hepatitis C virus, compared to 55 percent of participants taking only Pegasys and ribavirin.

CD4 (white blood cell) counts dropped in both the Incivek and placebo groups during the course of the study, although there was no difference in the magnitude of the change between the two groups. All participants successfully maintained undetectable HIV viral loads throughout the 24 weeks.

The most common side effects in participants taking Incivek were abdominal pain, vomiting, nausea, fever, dizziness, depression, and itchiness. No participants contracted the severe rash that is a known possible side effect of Incivek (see related AIDS Beacon news).

Overall, 27 percent of participants discontinued treatment during the first 24 weeks; 2 percent discontinued due to side effects, 7 percent due to non-adherence to the drug regimen, and the rest for other reasons.

For more information, please see the press release from Vertex Pharmaceuticals.