AbbVie has been boosted by the news that regulators in the USA have agreed to fast-track its closely-watched oral hepatitis C treatment.

Specifically, AbbVie's all-oral triple direct-acting antiviral (DAA) combination with and without ribavirin for the treatment of genotype 1 HCV infection has been designated as a 'breakthrough therapy' by the US Food and Drug Administration. The drugs involved in the combo are ABT-450/r (protease inhibitor and ritonavir), ABT-267 (an NS5A inhibitor) and ABT-333 (a non-nucleoside polymerase inhibitor).

The designation is granted to expedite the development and review of a medicine if it is intended, alone or in combination, to treat a serious or life-threatening disease and if preliminary clinical evidence indicates substantial improvement over existing therapies. The breakthrough status is distinct from the FDA’s other mechanisms such as accelerated approval and priority review, although these can also be granted, and involves "more intensive FDA guidance on an efficient drug development programme", AbbVie noted.

The designation is based, in part, on positive data from a Phase IIb trial, known as Aviator, conducted in 571 patients infected with HCV GT1. New results from Aviator, which were presented at the European Association for the Study of the Liver congress in Amsterdam in April, showed that 99% of treatment-naive patients (n=79) achieved sustained viral response rates (SVR) after 12 weeks of therapy, while 96% achieved SVR24.

John Leonard, AbbVie's chief scientific officer, said that getting breakthrough therapy designation for the 3-DAA combination "reflects the potential of this regimen to be important in the treatment of HCV". The combo has now entered a Phase III programme which includes more than 2,000 patients with HCV GT1.

The FDA has issued a number of breakthrough designations since the first one was granted to Vertex Pharmaceuticals' cystic fibrosis drug Kalydeco (ivacaftor) at the beginning of 2013. Only a fortnight ago, the status was conferred on Bristol-Myers Squibb's interferon-free HCV drug daclatasvir in combination of daclatasvir with asunaprevir, an NS3 protease inhibitor and BMS-791325, an NS5B non-nucleoside polymerase inhibitor.