The United States Food and Drug Administration (FDA) is updating information on Victrelis (boceprevir). The drug is used as a hepatitis C (HCV) protease inhibitor. It is combined with various ritonavir-boosted human immunodeficiency virus (HIV) protease inhibitors.

The FDA is stating that it cannot recommend use of the drug at this time, because it appears to reduce effectiveness of other medications and has been seen to cause HCV and HIV to increase in the bloodstream. This is known as the viral load, and obviously leads to the diseases becoming more potent and aggressive.

Ritonavir-boosted HIV protease inhibitors include ritonavir-boosted Reyataz (atazanavir), ritonavir-boosted Prezista (darunavir), and Kaletra (lopinavir/ritonavir). Ritonavir is an HIV protease inhibitor that is taken as a small dose along with other HIV protease inhibitors in order to increase their levels in the blood and make them more effective. This is known as ritonavir boosting.

The FDA states that patients should not simply stop taking their medicines on FDA advice, but must seek consultation with their physician as to the best course of action for their particular situation.

The FDA also issues advice for healthcare professionals who are treating patients with chronic HCV and HIV, using Victrelis where the patient was taking antiretroviral therapy in the form of ritonavir-boosted protease inhibitors. The patient’s response to the drug combination should be closely monitored for any unexpected increase in virus levels.

The FDA has already issued a warning about Victerlis in Feb. 2012, stating that using Victrelis while taking any one of the three ritonavir-boosted HIV protease inhibitors appeared to reduce the desired blood levels of both medicines. Obviously this is undesirable because lower blood levels of the drug can lead to less effective treatment and higher viral load.

The FDA goes on to remind healthcare professionals that there is only limited information on the use and effectiveness of Victrelis and ritonavir-boosted HIV protease inhibitors when they are used together in patients infected with both HIV and HCV. A small clinical trial studied treatment of patients with both HIV and HCV, where the HCV infection was treated with either peginterferon/ribavirin or boceprivir plus peginterferon/ribavirin and whose HIV infection was treated with ritonavir-boosted atazanavir, ritonavir-boosted darunavir, lopinavir/ritonavir, or raltegravir (Isentress).

People who took boceprevir plus peginterferon/ribavirin were more likely to have undetectable HCV viral loads 12 weeks after completing HCV treatment than individuals who received peginterferon/ribavirin alone. Overall, seven patients had HIV virologic rebound, 3/64 randomized to receive boceprevir with peginterferon/ribavirin and 4/34 randomized to peginterferon/ribavirin alone. Preliminary results of this clinical trial were presented at the 19th Conference on Retroviruses and Opportunistic Infections on March 6, 2012. The clinical trial abstract is online.

The FDA says that the findings of the drug-drug interaction study and the clinical trial, has caused it to revise the Victrelis drug label to state that co-administration of Victrelis with ritonavir-boosted Reyataz (atazanavir), ritonavir-boosted Prezista (darunavir), or Kaletra (lopinavir/ritonavir) to patients infected with both chronic HCV and HIV is not recommended at this time.

There is a larger clinical trial in process, to look at HCV treatment with boceprevir and peginterferon/ribavirin, where patients have both HCV and HIV and are taking antiretroviral treatment that use ritonavir-boosted HIV protease inhibitors. The FDA intends to update any new information it has about the co-use of the drugs.

Written by Rupert Shepherd