Hepatitis C late relapse in patients with directly acting antiviral-related sustained virological response at week 12

Aim: The aim of the present study was to identify, among the patients with failure to DAA regimen, those with a late relapse (after the achievement of a sustained virological response at week 12) and to characterize the clinical, epidemiological and virological features of these patients. Material and methods: A total of 129 HCV patients with non-response to an IFN-free regimen were enrolled. Sanger sequencing of NS3, NS5A and NS5B was performed at failure by home-made protocols. Results: Of the 129 patients enrolled, 8 (6.2%) experienced a breakthrough, 15 (11.7%) non-response, 99 (76.7%) a relapse by week 12 after the end of DAA therapy, and 7 (5.4%) a late relapse (after week 12; median 24 weeks, range 24-72). For two of the seven patients with a late relapse, a serum sample collected before the start of the DAA regimen was available; phylogenetic analysis showed no change in sequences of NS3, NS5A and NS5B regions, suggesting a reactivation of the initial HCV strain; for the remaining five patients, no serum collected before the DAA regimen was available, and thus, a re-infection cannot be excluded. Conclusions: Although a late relapse is infrequent, the study suggests a post-treatment follow-up of 72 weeks.