Merck ($MRK) has notified doctors that its new hepatitis C drug Victrelis interferes with commonly used AIDS drugs. Victrelis can reduce the effectiveness of the HIV-fighters--and vice-versa--Merck said in a letter to healthcare professionals that was issued after a study found lower blood levels of several HIV meds in patients using Victrelis. The study also showed that Victrelis blood levels were diminished in patients using certain HIV drugs.
The drug interaction news isn't good for Victrelis, because up to 15% of hepatitis C patients are also HIV-positive, said ISI Group's Mark Schoenebaum. The study's conclusions could cut Victrelis sales by as much as one-quarter, Schoenebaum said. Victrelis sales have been lagging behind the other big new hepatitis C treatment, Incivek, from Vertex Pharmaceuticals ($VRTX). While Incivek saw net product revenues of $456.8 million in the fourth quarter for Incivek, Victrelis brought in $87 million (up from $31 million during the previous quarter).
Doctors already had questions about Victrelis therapy for co-infected patients. In a Sermo Survey published here last summer, infectious disease specialists said they wanted to see data on Victrelis use in patients who also had HIV. Incivek has been studied in that patient population, so some physicians were using it exclusively in their HIV-positive patients.
FDA said in a safety communication the Victrelis label would be updated with information about the drug interactions. In the meantime, the agency advised doctors to monitor their patients using these drugs together to make sure they're responding to hepatitis C treatment and their HIV levels don't rebound.