AbbVie's oral, interferon-free regimen for treating hepatitis C (HCV) cured 96% of difficult-to-treat patients within just 12 weeks in a late-stage clinical trial, giving the firm a strong position in the race to get new, more convenient therapies on the market.

SAPPHIRE II, the second of six Phase III studies assessing its investigational three direct-acting-antiviral (3D) regimen plus ribavirin, included 394 in patients with genotype 1 (GT1) HCV infection, all of which previously failed pegylated interferon and ribavirin treatment, including around 49% of who had failed to respond at all.

Also of note, the majority of patients had GT1a disease, which is notoriously difficult to treat, but still 96% had achieved sustained virologic response at 12 weeks, compared to 97% of those with the GT1b type.

Data showed that virology relapse or breakthrough occurred in just 2% of patients receiving the 3D regimen plus ribavirin, and that three patients (1%) discontinued due to adverse events, lending further weight to its tolerability profile, a crucial factor in treatment particularly given the issues with interferon therapy.

On the downside, AbbVie's treatment regimen comes with a high pill burden, with patients having to take six pills a day in some cases. Nevertheless, some experts believe this is negated by short treatment duration.

Gilead, Merck & Co and Bristol-Myers Squibb are also developing HCV therapies without the need for interferon injections to access a market worth billions of dollars, that will only expand as low rates of diagnoses improve. On the other hand, whether these regimens will make it past global cost-regulators remains to be seen.

Gilead's Sovaldi was approved by US regulators just days ago as the first drug to demonstrate safety and efficacy to treat HCV infection without the need for interferon.