Hep C Tests Predict Best MedsApril 18, 2016
Newer, more effective Hepatitis C medications are helping more people than ever conquer the virus. However, this new generation of drugs also creates drug resistance – a biological phenomena characterized by the virus mutating to survive. In an effort to match potential drug resistance with these new medications, a diagnostic company has launched new tests that predict which drug is most likely to work on a specific strain of Hepatitis C.
Treatment for the Hepatitis C virus is in the midst of a transformation, revolutionizing the outcome of this persistent liver infection. Up until three years ago, the only approved treatment for Hepatitis C left a lot to be desired. The dated regimen of pegylated interferon and ribavirin required up to one year of swallowing multiple daily pills and getting frequent injections – yet had just a 50 percent success rate and created severe side effects. But since late 2013, several new direct-acting viral medications were approved that have a 90 percent or higher success rate in just two to three months of treatment.
Hepatitis C drug resistance happens when the Hepatitis C virus becomes resistant to one or more direct-acting antiviral agents (the new class of Hepatitis C drugs). The Hepatitis C virus, like any strong microorganism, has the ability to adapt to its environment by genetically mutating. These mutations help the virus escape the body’s defenses and the direct-acting antiviral drugs used to fight it.
Hepatitis C has a tremendous capability to reproduce, yielding over a trillion copies each day. However, the copies are not always exact replicates:
- Small genetic code changes can result in a quasispecies.
- Amounting to a small genetic difference, quasispecies are still the same Hepatitis C genotype and subtype.
- Experts surmise that quasispecies are why Hepatitis C frequently leads to chronic illness and why it is such a challenging virus to eradicate.
Quest Diagnostics has developed blood tests that enable doctors to determine if a patient’s Hepatitis C virus has a mutation that would limit a particular drug’s effectiveness. If a virus mutates during treatment, a patient would then need to switch to another medicine.
The FDA has recently approved several direct-acting antivirals that act by inhibiting the NS5A protein, which influences hepatitis C viral replication.
- In January 2016, Zepatier (elbasvir and grazoprevir) was approved for adults with Hepatitis C genotypes 1 or 4.
- In July 2015, Daklinza™ (daclatasvir), in combination with sofosbuvir with or without ribavirin, was approved for Hepatitis C genotypes 1 or 3. In 2016, Daklinza was also approved for those with Hepatitis C with HIV-1 co-infection, advanced cirrhosis, and post-liver transplant recurrence of Hepatitis C.
Prescribing information for both Zepatier and Daklinza recommends laboratory testing to determine the presence of certain drug-resistance NS5A mutations in patients with genotype 1a. However, clinicians believe that testing for drug resistance is wise for all patients on direct-acting antiviral therapy. Identifying a drug-resistant mutation can enable a physician to determine when a direct-acting antiviral drug will be ineffective so a different medication can be used.
Using genetic testing to circumvent drug resistant regimens is an important step in the battle against Hepatitis C. Besides saving patients and insurers from the cost of medications that won’t be effective, this type of specific testing will allow for a higher level of treatment customization. Putting the medical community one step ahead of this virus’s evolving quasispecies mutations, the customization led by Quest will eventually mean doom for the future of the Hepatitis C virus.
http://abcnews.go.com/Business/wireStory/quest-diagnostics-launches-test-picking-hepatitis-drug-38401643, Linda A. Johnson, AP, Retrieved April 15, 2016, ABC News, 2016.
https://hepatitisc.net/treatment/drug-resistance/, Drug Resistance, Retrieved April 17, 2016, Health Union, LLC, 2016.
http://www.prnewswire.com/news-releases/quest-launches-new-hepatitis-c-virus-test-capabilities-for-recently-fda-approved-antiviral-therapies-300251919.html, Quest Launches New Hepatitis C Virus Test Capabilities for Recently FDA-approved Antiviral Therapies, Retrieved April 15, 2016, PR Newswire Association, LLC, 2016.