Understanding Hepatitis C Virus Drug Resistance: Clinical Implications for Current and Future Regimens.

Viral resistance to direct-acting antiviral drugs may impact their effectiveness during treatment of hepatitis C virus (HCV) infection. Most data on HCV drug resistance concern genotypes 1 and 3. The clinical impact of resistance to HCV nonstructural protein 5A (NS5A) inhibitors and a practical approach to indications and methods for resistance testing are discussed.