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