The Hepatitis C virus is what scientists call very small. Here is an electron micrograph of one. The scale bar is 50 nanometers. Photo credit: Wikimedia/Rockefeller University

Hepatitis C is a viral infection that is usually spread through contact with infected blood. Prior to 1992, when testing of donated blood and organs became commonplace, many people were infected through blood transfusion and organ transplants. Now the most common method of infection is the sharing of needles or other equipment for injecting drugs. About 3.2 million people are estimated to have chronic hepatitis C infection in the U.S. Over decades, chronic infection can lead to liver failure and liver cancer. Hepatitis C is the leading indication for liver transplantation in the U.S. There is currently no vaccine.

Current medications for hepatitis C have some serious side effects and are sometimes only effective transiently, because the virus can develop resistance to the anti-viral medications. Current medications work by blocking the function of one of the virus’s components, so mutations in the virus can alter that component making the medicine ineffective.

A novel family of medicines has focused on targeting a part of the healthy liver cell that the virus uses to replicate. A specific kind of molecule called microRNA which is present in normal liver cells is required to bind to part of the hepatitis C for infection and viral replication to occur. This new family of medicines, called microRNA inhibitors, bind microRNA and prevent them from binding to hepatitis C.

A study published in this week’s New England of Medicine (NEJM) tested the effect of miravirsen, a microRNA inhibitor, in hepatitis C patients. This was a preliminary study designed to find the short-term effects on a small number of patients. Only 36 patients were enrolled in the study and they received five weekly injections of various doses of miraversen or of placebo.

The results were encouraging. The patients receiving miraversen had a large drop in the amount of hepatitis C virus detected in their blood. This effect lasted after the miraversen treatment was stopped. In a few patients the amount of hepatitis C in their blood fell below the limits of detection. There were no serious side effects, and none of the virus obtained from patients showed mutations suggesting resistance to the new drug.

Larger and more prolonged studies are needed before the miraversen is generally available, but besides the potential hope for hepatitis C patients, microRNA inhibitors may find utility in a number of other diseases.

Learn more:

A new drug shows promise of hepatitis C cure (Booster Shots, LA Times’ health blog)
‘Sponge’ Drug Shows Promise For Treating Hepatitis C (Shots, NPR’s Health blog)
Treatment of HCV Infection by Targeting MicroRNA (NEJM article)
Micromanaging Hepatitis C Virus (NEJM editorial)
Hepatitis C Information for the Public (Centers for Disease Control and Prevention)