Historically, clinical trials of regimens to treat chronic infection with hepatitis C virus (HCV) have used, as their primary efficacy endpoint, a sustained virological response (SVR)-defined as HCV RNA levels below a designated threshold of quantification-24 weeks after the end of treatment (SVR24). More recently, regulatory authorities have begun to accept SVR at 12 weeks post-treatment (SVR12) as a valid efficacy endpoint because of its high rate of concordance with SVR24. However, the concordance between SVR12 and SVR24 has not been systematically assessed with new regimens of recently approved direct-acting antiviral agents. The aim of this study was to assess the concordance between SVR at various post-treatment time points in phase III clinical trials of sofosbuvir (SOF)-containing regimens. We conducted a retrospective analysis of five trials enrolling 863 patients infected with HCV genotypes 1-6. The concordance between SVR at 4 weeks post-treatment (SVR4) and SVR12, and between SVR12 and SVR24, were determined, as well as positive predictive values (PPVs) and negative predictive values (NPVs). Overall, 779 of 796 patients (98.0%) with an SVR4 also achieved an SVR12, making the PPV of SVR4 for SVR12 98% and the NPV 100%. Of the 779 patients with an SVR12, 777 (99.7%) also achieved an SVR24, making the PPV of SVR12 for SVR24 >99% and the NPV 100%. Of patients who relapsed post-therapy, 77.6% did so within 4 weeks of completing therapy. Conclusion: Data from phase III studies demonstrate that with SOF-based regimens, with or without interferon, SVR12 and SVR24 correlate closely. Thus, SVR12 can be used effectively to determine "cure" rates in trials and in clinical practice.
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