The adverse side effects of certain hepatitis C medications can now be replicated and observed in Petri dishes and test tubes, thanks to a research team led by Craig Cameron, the Paul Berg Professor of Biochemistry and Molecular Biology at Penn State University. "The new method not only will help us to understand the recent failures of hepatitis C antiviral drugs in some patients in clinical trials," said Cameron. "It also could help to identify medications that eliminate all adverse effects." The team's findings, published in the current issue of the journal PLOS Pathogens may help pave the way toward the development of safer and more-effective treatments for hepatitis C, as well as other pathogens such as SARS and West Nile virus.
First author Jamie Arnold, a research associate in Cameron's lab at Penn State, explained that the hepatitis C virus (HCV), which affects over 170,000,000 people worldwide, is the leading cause of liver disease and, although antiviral treatments are effective in many patients, they cause serious side effects in others. "Many antiviral medications for treating HCV are chemical analogs for the building blocks of RNA that are used to assemble new copies of the virus's genome, enabling it to replicate," he said. "These medications are close enough to the virus's natural building blocks that they get incorporated into the virus's genome. But they also are different in ways that lead to the virus's incomplete replication. The problem, however, is that the medication not only mimics the virus's genetic material, but also the genetic material of the patient. So, while the drug causes damage to the virus, it also may affect the patient's own healthy tissues."
A method to reveal these adverse side effects in the safety of a laboratory setting, rather than in clinical trials where patients may be placed at risk, has been developed by the research team, which includes Cameron; Arnold; Suresh Sharma, a research associate in Cameron's lab; other scientists at Penn State; and researchers from other academic, government, and corporate labs. "We have taken anti-HCV medications and, in Petri dishes and test tubes, we have shown that these drugs affect functions within a cell's mitochondria," Cameron explained. "The cellular mitochondria --- a tiny structure known as 'the powerhouse of the cell' that is responsible for making energy known as ATP -- is affected by these compounds and is likely a major reason why we see adverse effects." Cameron noted that scientists have known for some time that certain individuals have "sick" mitochondria. Such individuals are likely more sensitive to the mitochondrial side effects of antiviral drugs.
"We know that antiviral drugs, including the ones used to treat HCV, affect even normal, healthy mitochondria by slowing ATP output," Arnold added. "While a person with normal mitochondria will experience some ATP and mitochondrial effects, a person who is already predisposed to mitochondrial dysfunction will be pushed over the 'not enough cellular energy' threshold by the antiviral drug. The person's mitochondria simply won't be able to keep up."