We randomly assigned 419 patients with HCV genotype 1b infection ( PEARL-III study ) and 305 patients with genotype 1a infection ( PEARL-IV study ) to 12 weeks of ABT-450 / r-ombitasvir ( at a once-daily dose of 150 mg of ABT-450 , 100 mg of ritonavir , and 25 mg of ombitasvir ) , dasabuvir ( 250 mg twice daily ) , and ribavirin administered according to body weight or to matching placebo for ribavirin .