Hepatitis C virus (HCV) can infect the liver, causing inflammation. This inflammation leads to healthy liver tissue being replaced with scar tissue in a process called fibrosis. If left untreated, this scarring eventually encompasses the entire liver (cirrhosis). The development of cirrhosis paves the way for complications, including internal bleeding, serious infections, kidney dysfunction and problems with thinking clearly and memory. Cirrhosis also increases the risk of developing liver cancer.
Until the past several years, standard treatment for chronic HCV infection was a combination of long-lasting interferon (injected weekly) and daily use of the broad-spectrum antiviral drug ribavirin. This combination was taken for up to 48 weeks in some cases. However, these therapies were not highly effective and had many troublesome side effects.
Interferon and ribavirin work in general ways, such as activating the immune system’s antiviral defence system. In the past decade, drugs have been developed that specifically target HCV proteins and enzymes. These new and emerging drugs are called direct-acting antivirals (DAAs). Examples of DAAs that are licensed in Canada and other high-income countries include the following:
What’s more, pharmaceutical companies such as Abbvie, Gilead Sciences, Merck and Janssen are developing other potent once-daily therapies that should be able to treat all or most strains of HCV. If all goes well in clinical trials, these emerging therapies should become licensed over the next several years.
The promise of DAAs
DAAs in use today have several advantages over older HCV therapies, such as the following:
- They are highly effective (in clinical trials cure rates are often between 90% and 100%).
- They can be taken orally once or twice daily.
- Therapy usually is prescribed for only 12 weeks.
- Side effects are generally mild.
All of these factors make DAAs an attractive option for doctors, nurses and patients.
The arrival of DAAs has stimulated policy planners, public health officials and researchers who study epidemics to envision the large-scale use of DAAs so that the health of many people living with HCV can be improved and the spread of the virus can be reduced. It has also inspired researchers, doctors, nurses and public health officials to go even further than thinking about reducing the spread of HCV. They have begun to speculate about making massive changes to the HCV epidemic to the point where, at least in theory, virtually all people with HCV in a city, region or country might be cured over time. Essentially, this will mean the eradication of a viral epidemic—an exciting idea.
In upcoming CATIE News bulletins, we will review two simulations where researchers have assessed the impact of large-scale programs that offer HCV testing and treatment and how these might change the trajectory of the HCV epidemic in North America. One team has examined this issue using data from the United States. The other team has used data from the province of British Columbia in Canada.
Author: Sean R. Hosein/CATIE