BACKGROUND : Combination therapy with glecaprevir (GLE) and pibrentasvir (PIB) has high efficacy for pan-genotypic hepatitis C virus (HCV)-infected patients. However, the efficacy of the therapy for failures to prior direct-acting antiviral (DAA) regimens in real-world practice is not well known. METHODS : Thirty patients infected with HCV genotype 1b, 2a, 2b, or 3a who failed to respond during prior DAA therapies were treated with GLE/PIB for 12 weeks. HCV NS3 and NS5A drug resistance-associated variants (RAVs) were determined by direct sequencing. RESULTS : Twenty-eight out of 30 patients (93.3%) achieved SVR12 by GLE/PIB treatment. SVR12 rates were similar between patients with and without advanced liver fibrosis (94.7% and 91.0%, respectively). All 9 patients with genotype 2a, 2b, or 3a HCV infection achieved SVR12. However, two genotype 1b HCV-infected patients who failed previous daclatasvir plus asunaprevir treatment experienced HCV relapse after the end of GLE/PIB treatment. Direct sequence analysis showed the presence of NS3-D168E plus NS5A-L31I/P58S/Y93H RAVs in one patient and NS5A-L31F/P32del RAVs in another patient before GLE/PIB treatment. In the former patient, NS3-D168E plus NS5A-L31I/P58S/Y93H RAVs persisted, and additional NS5A-L28M/V75A variants emerged after HCV relapse. CONCLUSIONS : GLE/PIB treatment for HCV-infected patients who did not respond to prior DAA treatments was highly effective regardless of liver fibrosis stage. However, some genotype 1b HCV-infected patients, especially those with NS5A-P32del, may have low susceptibility to the treatment.