1Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado, Aurora, CO, USA.
2Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, NIAID, Bethesda, MD, USA.
3Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, NIAID, Bethesda, MD, USA Gilead Sciences Inc., Foster City, CA, USA.
4School of Public Health, University of Colorado, Aurora, CO, USA.
5Gilead Sciences Inc., Foster City, CA, USA.
6Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado, Aurora, CO, USA firstname.lastname@example.org.
Ribavirin concentrations may impact hepatitis C virus (HCV) treatment outcome. We modelled ribavirin serum and intracellular ribavirin monophosphate (RBV-MP) and ribavirin triphosphate (RBV-TP) pharmacokinetics in red blood cells (RBC) using samples collected during the NIAID SPARE trial to explore associations with treatment outcome and the development of anaemia.
PATIENTS AND METHODS:
Individuals infected with HCV genotype 1 (GT1) received 400 mg of sofosbuvir and either low-dose or weight-based ribavirin as part of the NIAID SPARE trial. Concentrations were modelled using NONMEM and associated with treatment outcomes using unpaired t-tests or Pearson's rho correlations.
Average day 14 RBV-MP concentrations were higher in subjects with haemoglobin nadir <10 g/dL relative to patients with haemoglobin nadir ≥10 g/dL (6.54 versus 4.48 pmol/106 cells; P = 0.02). Additionally, day 14 RBV-MP average concentrations trended towards being higher in subjects that achieved sustained virological response (SVR) as compared with patients who relapsed (4.97 versus 4.09 pmol/106 cells; P = 0.07). Receiver operating characteristic curves suggested day 14 RBV-MP concentration thresholds of 4.4 pmol/106 cells for SVR (P = 0.06) and 6.1 pmol/106 cells for haemoglobin nadir <10 versus ≥10 g/dL (P = 0.02), with sensitivity and specificity ≥60%. Dosing simulations showed that 800 mg of ribavirin once daily produced day 14 RBV-MP concentrations within the 4.4-6.1 pmol/106 cells range.
RBV-MP concentrations in RBC at day 14 were related to anaemia and SVR. A therapeutic range was identified for RBV-MP in persons with HCV GT1 disease receiving 24 weeks of sofosbuvir plus ribavirin, suggesting a potential pharmacological basis for individualized ribavirin dosing in IFN-free regimens.