Paritaprevir and ombitasvir are effective for Japanese patients with HCV genotype 1b

Viekirax (ombitasvir and paritaprevir with ritonavir) was highly effective in curing hepatitis C without the accompaniment of dasabuvir (Exviera) in Japanese people with genotype 1b hepatitis C infection in the GIFT 1 trial, researchers reported last month at the International Liver Congress in Vienna, Austria.

Viekirax and Exviera are direct-acting antivirals developed by AbbVie. In the European Union, they have been approved as separate products, recommended for use in combination with each other, for treatment of genotype 1 infection. In the United States, they have been approved as a co-packaged product called Viekira Pak, for treatment of genotype 1.

However, due to a genetic difference in the way that Japanese people metabolise paritaprevir, it is possible to dose Viekira without Exviera.

The GIFT-1 study was a phase III trial designed to evaluate the safety and efficacy of ombitasvir and paritaprevir with ritonavir, dosed as a fixed-dose once-daily tablet for 12 weeks, in Japanese people with genotype 1b infection. Genotype 1b is the predominant form of hepatitis C in Japan, accounting for at least 70% of cases.

The study enrolled previously untreated and treatment-experienced patients. The double-blind study randomised 363 people in the ratio 2:1 to receive ombitasvir and paritaprevir with ritonavir (n = 215), or to placebo (n = 106) for 12 weeks. People with cirrhosis (n = 42) received open-label active drug treatment. Participants were also stratified by baseline factors that might affect response.

The primary study endpoint was virological response 12 weeks after completion of treatment (SVR12). A total of 94.6% of participants without cirrhosis and 90.5% of people with cirrhosis achieved SVR12 and there was no substantive difference in virological response between previously untreated and treatment-experienced participants (94.2% vs 96.1%).

Similarly there was no significant difference in a pre-planned analysis of response according to baseline characteristics. Among the previously untreated group, baseline viral load below 100,000 IU/ml or ineligibility for interferon did not affect response. Among treatment-experienced people, there was no difference in response according to previous treatment non-response or relapse.

One on-treatment virologic failure occurred in a treatment-experienced participant and one in a participant with cirrhosis. Seven people experienced virologic rebound after completing treatment and before 12 weeks post-treatment, while a further 6 people were lost to follow up or discontinued treatment due to adverse events, and were also counted as virologic failures in the analysis.

Nine people receiving active drug experienced serious adverse events. The most common adverse events were nasopharyngitis (16.7%), headache (8.8%), and peripheral oedema (5.1%).