Multiple dose ribavirin pharmacokinetic data are available for HCV patients who received ribavirin in combination with peginterferon alfa-2a. Following administration of 1200 mg/day with food for 12 weeks mean±SD (n=39; body weight >75 kg) AUC0-12hr was 25,361±7110 ng∙hr/mL and Cmax was 2748±818 ng/mL. The average time to reach Cmax was 2 hours. Trough ribavirin plasma concentrations following 12 weeks of dosing with food were 1662±545 ng/mL in HCV infected patients who received 800 mg/day (n=89), and 2112±810 ng/mL in patients who received 1200 mg/day (n=75; body weight >75 kg).
The terminal half-life of ribavirin following administration of a single oral dose of COPEGUS is about 120 to 170 hours. The total apparent clearance following administration of a single oral dose of COPEGUS is about 26 L/h. There is extensive accumulation of ribavirin after multiple dosing (twice daily) such that the Cmax at steady state was four-fold higher than that of a single dose.
Effect of Food on Absorption of Ribavirin
Bioavailability of a single oral dose of ribavirin was increased by co-administration with a high-fat meal. The absorption was slowed (Tmax was doubled) and the AUC0-192h and Cmax increased by 42% and 66%, respectively, when COPEGUS was taken with a high-fat meal compared with fasting conditions (see PRECAUTIONS and DOSAGE AND ADMINISTRATION).
Elimination and Metabolism
The contribution of renal and hepatic pathways to ribavirin elimination after administration of COPEGUS is not known. In vitro studies indicate that ribavirin is not a substrate of CYP450 enzymes.
A pharmacokinetic study in 42 subjects demonstrated there is no clinically significant difference in ribavirin pharmacokinetics among Black (n=14), Hispanic (n=13) and Caucasian (n=15) subjects.
The pharmacokinetics of ribavirin following administration of COPEGUS have not been studied in patients with renal impairment and there are limited data from clinical trials on administration of COPEGUS in patients with creatinine clearance <50 mL/min. Therefore, patients with creatinine clearance <50 mL/min should not be treated with COPEGUS (see WARNINGS and DOSAGE AND ADMINISTRATION).
The effect of hepatic impairment on the pharmacokinetics of ribavirin following administration of COPEGUS has not been evaluated. The clinical trials of COPEGUS were restricted to patients with Child-Pugh class A disease.
Pharmacokinetic evaluations in pediatric patients have not been performed.
Pharmacokinetic evaluations in elderly patients have not been performed.
Ribavirin pharmacokinetics, when corrected for weight, are similar in male and female patients.
In vitro studies indicate that ribavirin does not inhibit CYP450 enzymes.
In vitro data indicate ribavirin reduces phosphorylation of lamivudine, stavudine, and zidovudine. However, no pharmacokinetic (e.g., plasma concentrations or intracellular triphosphorylated active metabolite concentrations) or pharmacodynamic (e.g., loss of HIV/HCV virologic suppression) interaction was observed when ribavirin and lamivudine (n=18), stavudine (n=10), or zidovudine (n=6) were co-administered as part of a multi-drug regimen to HCV/HIV coinfected patients (see PRECAUTIONS: Drug Interactions).
In vitro, didanosine or its active metabolite (dideoxyadenosine 5'-triphosphate) is increased when didanosine is co-administered with ribavirin, which could cause or worsen clinical toxicities (see PRECAUTIONS: Drug Interactions).
Drugs Metabolized by Cytochrome P450
There was no effect on the pharmacokinetics of representative drugs metabolized by CYP 2C9, CYP 2C19, CYP 2D6 or CYP 3A4.
Treatment with PEGASYS® once weekly for 4 weeks in healthy subjects was associated with an inhibition of P450 1A2 and a 25% increase in theophylline AUC (see PRECAUTIONS: Drug Interactions).
The safety and effectiveness of PEGASYS in combination with COPEGUS for the treatment of hepatitis C virus infection were assessed in two randomized controlled clinical trials. All patients were adults, had compensated liver disease, detectable hepatitis C virus, liver biopsy diagnosis of chronic hepatitis, and were previously untreated with interferon. Approximately 20% of patients in both studies had compensated cirrhosis (Child-Pugh class A). Patients coinfected with HIV were excluded from these studies.
In Study NV15801 (described as Study 4 in the PEGASYS Package Insert), patients were randomized to receive either PEGASYS 180 µg sc once weekly (qw) with an oral placebo, PEGASYS 180 µg qw with COPEGUS 1000 mg po (body weight <75 kg) or 1200 mg po (body weight≥75 kg) or REBETRON™ (interferon alfa-2b 3 MIU sc tiw plus ribavirin 1000 mg or 1200 mg po). All patients received 48 weeks of therapy followed by 24 weeks of treatment-free follow-up. COPEGUS or placebo treatment assignment was blinded. Sustained virological response was defined as undetectable (<50 IU/mL) HCV RNA on or after study week 68. PEGASYS in combination with COPEGUS resulted in a higher SVR compared to PEGASYS alone or interferon alfa-2b and ribavirin ( Table 1). In all treatment arms, patients with viral genotype 1, regardless of viral load, had a lower response rate to PEGASYS in combination with COPEGUS compared to patients with other viral genotypes.
Table 1 Sustained Virologic Response (SVR) to Combination Therapy (Study NV15801 )
Ribavirin 1000 mg or 1200 mg
COPEGUS 1000 mg or 1200 mg
|Difference in overall treatment response (PEGASYS/COPEGUS– Interferon alfa-2b/ribavirin) was 9% (95% CI 2.3, 15.3).|
|All patients||197/444 (44%)||65/224 (29%)||241/453 (53%)|
|Genotype 1||103/285 (36%)||29/145 (20%)||132/298 (44%)|
|Genotypes 2-6||94/159 (59%)||36/79 (46%)||109/155 (70%)|
In Study NV15942 (described as Study 5 in the PEGASYS Package Insert), all patients received PEGASYS 180 µg sc qw and were randomized to treatment for either 24 or 48 weeks and to a COPEGUS dose of either 800 mg or 1000 mg/1200 mg (for body weight<75 kg/≥75 kg). Assignment to the four treatment arms was stratified by viral genotype and baseline HCV viral titer. Patients with genotype 1 and high viral titer (defined as >2 × 106 HCV RNA copies/mL serum) were preferentially assigned to treatment for 48 weeks.
HCV 1 and 4 - Irrespective of baseline viral titer, treatment for 48 weeks with PEGASYS and 1000 mg or 1200 mg of COPEGUS resulted in higher SVR (defined as undetectable HCV RNA at the end of the 24-week treatment-free follow-up period) compared to shorter treatment (24 weeks) and/or 800 mg COPEGUS.
HCV 2 and 3 - Irrespective of baseline viral titer, treatment for 24 weeks with PEGASYS and 800 mg of COPEGUS resulted in a similar SVR compared to longer treatment (48 weeks) and/or 1000 mg or 1200 mg of COPEGUS (see Table 2).
The numbers of patients with genotype 5 and 6 were too few to allow for meaningful assessment.
Table 2 Sustained Virologic Response as a Function of Genotype (Study NV15942 )
|24 Weeks Treatment||48 Weeks Treatment|
|PEGASYS + |
1000 mg or 1200 mg
1000 mg or 1200 mg
|Genotype 1||29/101 (29%)||48/118 (41%)||99/250 (40%)||138/271 (51%)|
|Genotypes 2, 3||79/96 (82%)||116/144 (81%)||75/99 (76%)||117/153 (76%)|
|Genotype 4||0/5 (0%)||7/12 (58%)||5/8 (63%)||9/11 (82%)|
Other Treatment Response Predictors
Treatment response rates are lower in patients with poor prognostic factors receiving pegylated interferon alpha therapy. In studies NV15801 and NV15942, treatment response rates were lower in patients older than 40 years (50% vs. 66%), in patients with cirrhosis (47% vs. 59%), in patients weighing over 85 kg (49% vs. 60%), and in patients with genotype 1 with high vs. low viral load (43% vs. 56%). African-American patients had lower response rates compared to Caucasians.
Paired liver biopsies were performed on approximately 20% of patients in studies NV15801 and NV15942. Modest reductions in inflammation compared to baseline were seen in all treatment groups.
In studies NV15801 and NV15942, lack of early virologic response by 12 weeks (defined as HCV RNA undetectable or >2log10 lower than baseline) was grounds for discontinuation of treatment. Of patients who lacked an early viral response by 12 weeks and completed a recommended course of therapy despite a protocol-defined option to discontinue therapy, 5/39 (13%) achieved an SVR. Of patients who lacked an early viral response by 24 weeks, 19 completed a full course of therapy and none achieved an SVR.
CHC and Coinfection with HIV (CHC/HIV): Study NR15961
In Study NR15961 (described as Study 6 in the PEGASYS Package Insert), patients with CHC/HIV were randomized to receive either PEGASYS 180 µg sc once weekly (qw) plus an oral placebo, PEGASYS 180 µg qw plus COPEGUS 800 mg po daily or ROFERON®-A (interferon alfa-2a), 3 MIU sc tiw plus COPEGUS 800 mg po daily. All patients received 48 weeks of therapy and sustained virologic response (SVR) was assessed at 24 weeks of treatment-free follow-up. COPEGUS or placebo treatment assignment was blinded in the PEGASYS treatment arms. All patients were adults, had compensated liver disease, detectable hepatitis C virus, liver biopsy diagnosis of chronic hepatitis C, and were previously untreated with interferon. Patients also had CD4+ cell count ≥200 cells/µL or CD4+ cell count ≥100 cells/µL but <200 cells/µL and HIV-1 RNA <5000 copies/mL, and stable status of HIV. Approximately 15% of patients in the study had cirrhosis. Results are shown in Table 3.
Table 3 Sustained Virologic Response in Patients With Chronic Hepatitis C Coinfected With HIV (Study NR15961 )
COPEGUS 800 mg
COPEGUS 800 mg
|All patients||33 (11%) ||58 (20%) ||116 (40%)*|
|Genotype 1||12/171 (7%)||24/175 (14%)||51/176 (29%)|
|Genotypes 2, 3||18/89 (20%)||32/90 (36%)||59/95 (62%)|
Treatment response rates are lower in CHC/HIV patients with poor prognostic factors (including HCV genotype 1, HCV RNA >800,000 IU/mL, and cirrhosis) receiving pegylated interferon alpha therapy. Geographic region is not a prognostic factor for response. However, poor prognostic factors occur more frequently in the US population than in the non-US population.
Of the patients who did not demonstrate either undetectable HCV RNA or at least a 2log10 reduction from baseline in HCV RNA titer by 12 weeks of PEGASYS and COPEGUS combination therapy, 2% (2/85) achieved an SVR.
In CHC patients with HIV coinfection who received 48 weeks of PEGASYS alone or in combination with COPEGUS treatment, mean and median HIV RNA titers did not increase above baseline during treatment or 24 weeks posttreatment.