Background Peginterferon plus ribavirin achieves sustained virological response (SVR) in fewer than half of patients with genotype 1 chronic hepatitis C virus infection treated for 48 weeks. We tested the efficacy of boceprevir, an NS3 hepatitis C virus oral protease inhibitor, when added to peginterferon alfa-2b and ribavirin. Methods In part 1 of this trial, undertaken in 67 sites in the USA, Canada, and Europe, 520 treatment-naive patients with genotype 1 hepatitis C virus infection were randomly assigned to receive peginterferon alfa-2b 1·5 μg/kg plus ribavirin 800-1400 mg daily for 48 weeks (PR48; n=104); peginterferon alfa-2b and ribavirin daily for 4 weeks, followed by peginterferon alfa-2b, ribavirin, and boceprevir 800 mg three times a day for 24 weeks (PR4/PRB24; n=103) or 44 weeks (PR4/PRB44; n=103); or peginterferon alfa-2b, ribavirin, and boceprevir three times a day for 28 weeks (PRB28; n=107) or 48 weeks (PRB48; n=103). In part 2, 75 patients were randomly assigned to receive either PRB48 (n=16) or low-dose ribavirin (400-1000 mg) plus peginterferon alfa-2b and boceprevir three times a day for 48 weeks (low-dose PRB48; n=59). Randomisation was by computer-generated code, and study personnel and patients were not masked to group assignment. The primary endpoint was SVR 24 weeks after treatment. Analysis was by intention to treat. This study is registered with ClinicalTrials.gov, number NCT00423670. Findings Patients in all four boceprevir groups had higher rates of SVR than did the control group (58/107 [54, 95 CI 44-64], p=0·013 for PRB28; 58/103 [56, 44-66], p=0·005 for PR4/PRB24; 69/103 [67, 57-76], p<0·0001 for PRB48; and 77/103 [75, 65-83], p<0·0001 for PR4/PRB44; vs 39/104 [38, 28-48] for PR48 control). Low-dose ribavirin was associated with a high rate of viral breakthrough (16/59 ), and a rate of relapse (six of 27 ) similar to control (12/51 ). Boceprevir-based groups had higher rates of anaemia (227/416  vs 35/104 ) and dysgeusia (111/416  vs nine of 104 ) than did the control group. Interpretaion In patients with untreated genotype 1 chronic hepatitis C infection, the addition of the direct-acting antiviral agent boceprevir to standard treatment with peginterferon and ribavirin after a 4-week lead-in seems to have the potential to double the sustained response rate compared with that recorded with standard treatment alone. Funding Merck.
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