Schering-Plough has reported interim results from an ongoing phase IIa study of narlaprevir (SCH 900518), its investigational, once-daily protease inhibitor. Narlaprevir demonstrated potent antiviral activity in treatment-naive patients with chronic hepatitis C virus (HCV) genotype.
The study evaluated 12 weeks of narlaprevir 200mg or 40 mg once-daily or 100mg twice daily with low-dose ritonavir (100 mg) in combination with Pegintron (1.5 mcg/kg once weekly) and Rebetol (600-1400 mg daily), followed by Pegintron and Rebetol alone for an additional 12 or 36 weeks (24 or 48 weeks total).
The study included two treatment arms in which patients receive a 4-week lead-in of Pegintron and Rebetol prior to receiving narlaprevir 200 mg or 400 mg once-daily in the above regimen. All patients in the narlaprevir arms have completed narlaprevir dosing. The control arm is Pegintron and Rebetol alone for 48 weeks.
In this study, the rate of adverse events in the narlaprevir arms was similar to that in the peginterferon and ribavirin control arm, except for an increase in anemia and an increase in low neutrophil counts. The most frequently seen adverse events up through 12 weeks of treatment were fatigue, nausea, flu-like illness, headache and insomnia. No increase in skin adverse events beyond what was seen in the peginterferon and ribavirin control was observed.
John Vierling, professor of medicine and surgery, chief of hepatology at Baylor College of Medicine, Houston, said: “These interim results, while preliminary, are very encouraging, and showed that narlaprevir has potent antiviral activity in hepatitis C. In this study, once-daily narlaprevir greatly improved viral clearance at week 4 of treatment in genotype hepatitis C infection compared to the control group. We look forward to further results from this ongoing study.”