Gilead Sciences Inc., a biopharmaceutical company, has submitted a New Drug Application (NDA) to the US Food and Drug Administration (FDA) for an investigational, once-daily fixed-dose combination of the nucleotide analog polymerase inhibitor sofosbuvir (SOF), approved as Sovaldi in December 2013, and velpatasvir (VEL), an investigational pan-genotypic NS5A inhibitor, for the treatment of chronic genotype 1-6 hepatitis C virus (HCV) infection.

The NDA is supported by clinical studies exploring the use of 12 weeks of SOF/VEL for patients with genotype 1-6 HCV infection, including patients with compensated cirrhosis and 12 weeks of SOF/VEL with ribavirin for patients with decompensated cirrhosis.

"As the first fixed-dose combination of two pan-genotypic, direct-acting antivirals, SOF/VEL represents an important step forward in the treatment of patients with hepatitis C," said Norbert Bischofberger, PhD, executive vice president of research and development and chief scientific officer at Gilead.

"Genotype 1 is the most prevalent form of HCV in the United States, but worldwide, more than half of people living with HCV are infected with other genotypes. SOF/VEL complements our current HCV portfolio of Sovaldi and Harvoni, offering high cure rates and the potential to simplify treatment and eliminate the need for HCV genotype testing."

The FDA has assigned SOF/VEL a Breakthrough Therapy designation, which is granted to investigational medicines that may offer major advances in treatment over existing options. The NDA for SOF/VEL is supported by data from four phase 3 ASTRAL trials, which evaluated the fixed-dose combination in hepatitis C genotypes 1-6. Of the 1,035 patients treated with SOF/VEL for 12 weeks in the ASTRAL-1, ASTRAL-2 and ASTRAL-3 studies, 1,015 (98 per cent) achieved the primary efficacy endpoint of SVR12. The ASTRAL-4 study randomized 267 patients with decompensated cirrhosis (Child-Pugh class B) to receive 12 weeks of SOF/VEL with or without ribavirin (RBV), or 24 weeks of SOF/VEL. Those who received SOF/VEL plus RBV for 12 weeks achieved an SVR12 rate of 94 per cent, while those who received SOF/VEL for 12 weeks and 24 weeks achieved SVR12 rates of 83 per cent and 86 per cent, respectively.

Patients treated with SOF/VEL for 12 weeks in ASTRAL-1, ASTRAL-2 and ASTRAL-3 had similar adverse events compared with placebo-treated patients in ASTRAL-1. The most common adverse events were headache, fatigue and nausea. The most common adverse events in ASTRAL-4 were fatigue, nausea and headache.

Gilead plans to submit a regulatory application for approval of SOF/VEL in the European Union by the end of the year.

The SOF/VEL fixed-dose combination is an investigational product and its safety and efficacy have not been established.