OBJECTIVE: To review the role and utility of baseline resistance testing with 
currently available and pipeline genotype 1 hepatitis C virus (HCV) treatment.
DATA SOURCES: Authors reviewed liver meeting abstracts for data on 
currently-available and pipeline genotype 1 retreatment regimens from January 1, 
2015, to March 23, 2017. Additional trials were identified from a review of 
clinicaltrials.gov using the pipeline medication names.
STUDY SELECTION AND DATA EXTRACTION: Authors identified reports of current and 
pipeline genotype 1 retreatment regimens. Seven references were clinical study 
results presented at the meetings of the American Association for the Study of 
Liver Diseases and the European Association for the Study of the Liver, and 2 
studies were from clinicaltrials.gov .
DATA SYNTHESIS: Retreatment trial data of currently available salvage regimens 
indicate that baseline NS5A resistance-associated substitutions (RASs) may 
decrease sustained virological response (SVR) rates when retreating with 
ledipasvir/sofosbuvir but are not affected when using elbasvir/grazoprevir + 
sofosbuvir + ribavirin, paritaprevir/ritonavir/ombitasvir + dasabuvir + 
sofosbuvir, or sofosbuvir/velpatasvir + ribavirin. Pipeline data indicate that 
baseline NS5A RASs do not affect SVR rates when retreating with 
sofosbuvir/velpatasvir/voxilaprevir or glecaprevir/pibrentasvir.
CONCLUSIONS: Baseline resistance testing was used for decisional support for 3 
clinical scenarios in patients with HCV genotype 1 infection at the time of 
manuscript submission. Pending the approval of 2 new direct-acting antiviral 
regimens in the third quarter of 2017, the rapidly evolving HCV treatment 
guidelines will likely reflect a decreased clinical utility for resistance 
testing.