Last month, Merck informed physicians in the U.S. of the results of a pharmacokinetic study assessing interactions between Victrelis™, the company’s protease inhibitor (PI) drug boceprevir for the treatment of the hepatitis C virus (HCV), and certain HIV antiretroviral (ARV) drugs.
In May of 2011, two PIs were approved by the U.S. Food and Drug Administration for use in HCV genotype 1 patients: Victrelis and Vertex Pharmaceutical’s telaprevir (Incivek™). These drugs help augment the standard HCV combination therapy of interferon and ribavirin.
According to a Merck press release, administration of Victrelis with the ARV ritonavir (Norvir®) in combination with atazanavir (Reyataz®) or darunavir (Prezista®), or with lopinavir/ritonavir (Kaletra®) resulted in reduced concentrations of both classes of drugs in the blood. Merck stated that these drug interactions may be “clinically significant” for patients infected with both chronic HCV and HIV, decreasing the effectiveness of the medicines when administered together. Merck has shared these data with regulatory authorities in the countries where Victrelis is approved or under review. It is now up to these agencies to review the data and consider changes in labeling.
In December 2011, a group of Maryland physicians published provisional treatment guidelines for the use of PIs in patients co-infected with HIV and HCV in the journal Clinical Infectious Diseases. Although the new PIs were not approved for use in co-infected patients, interim data showed that these patients had a higher virological response when a PI was added to peginterferon/ribavirin and that adverse events were no different than patients with HCV alone. Physicians are interested in the possible off-label use of these drugs in co-infected patients because: their liver disease progression is more accelerated; pegylated interferon/ribavirin is less effective for them; and liver transplantation is neither highly successful nor widely available to them.
“Though Victrelis™ is not indicated for the treatment of chronic HCV in those who are also infected with HIV, we recognize that some physicians have prescribed or may be considering prescribing Victrelis™ for patients taking ritonavir-boosted HIV protease inhibitors. We felt it was important to share these data as part of our commitment to patient safety and transparency,” said Robin Isaacs, vice president, Clinical Research, Infectious Diseases, Merck Research Laboratories. “What is most critical to remember is that all patients taking medicines for chronic HCV or HIV, or both, should not discontinue their medication regimens without first consulting with their physicians.”
Source: Merck press release dated February 8, 2012