Abstract:
Sofosbuvir along with ribavirin is being widely used for treatment of HCV in Pakistan but it may show
delayed response and reoccurrence of disease in some cases. The aim of the study was to investigate pharmacokinetics and concentration effect analysis of sofosbuvir. HCV patients (n=100) received 400 mg sofosbuvir along with low dose or weight based ribavirin (400 mg). Nonlinear mixed effects modeling (NONMEM) and unpaired t-test were used for the association of concentrations and treatment outcomes. Average day 10 sofosbuvir metabolite BM 331007 concentration was higher in patients having haemoglobin nadir value <10 g/dl compared to the patients having heamoglobin nadir value >10 g/dl (5.34 versus 4.87 pmol/106 cells; p=0.03). The average concentration trends of GS331007 at day 10 was towards being higher in the patients achieved sustained virologic response (SVR) as compare to the patients relapsed (5.19 versus 4.86 pmol/106 cells; p=0.05). Sofosbuvir (GS331007) thresholds concentration (suggested at day 10 through
receiver operating characteristic curve) was 5.4 pmol/106 cells for SVR (p=0.05) and haemoglobin nadir cells was 6.3 pmol/106 with sensitivity and specificity of ≥60%. Dosing simulations shows that 400 mg sofosbuvir twice daily produce day 10 concentration range of 5.4 to 6.7 pmol/10 6 cells. The range of therapeutic values was identified for HCV patients receiving sofosbuvir in combination with ribavirin for 24 weeks, suggesting a potential pharmaceutical basis for individualized therapeutic dosing.
