It may be many years before the symptoms of hepatitis C infection appear. However, once they do, the consequences are significant: patients may have developed fibrosis, cirrhosis or even liver cancer, with the end result being liver failure. Even if diagnosed early, there’s no guarantee of a cure. Only around half of patients respond to the standard therapy of an interferon plus the antiviral drug ribavirin, and while two add-on antiviral therapies were approved in 2011, the treatment period is long with no guarantee of a cure, and for non-responders treatment options remain limited.
A new drug with a different mechanism is being developed by Bristol-Myers Squibb, in conjunction with Pharmasset. Daclatasvir targets non-structural protein 5A, which is an important component of the viral replication process, although its precise role in this remains unclear.1 The drug is active in single oral doses, and may have potential as part of a treatment regimen that avoids the use of interferon, and in patients who do not respond to standard therapy.
In an open label Phase IIa study, 10 patients with chronic hepatitis C genotype 1b infection who did not respond to standard therapy were given daclatasvir in once daily 60mg doses, plus another experimental drug, BMS-790052, which is an NSP 3 protease inhibitor, in initial twice-daily 600mg doses, later reduced to 200mg twice a day.2 Nine patients completed 24 weeks of treatment, with the 10th discontinuing after 10 weeks. In those who completed the course, HCV RNA was undetectable at week 8, and remained so until the end of the trial, with all achieving a sustained virologic response. It was also undetectable post-treatment in the patient who discontinued.
Daclatasvir has also been investigated as monotherapy in a double blind, placebo-controlled, sequential panel, multiple ascending dose study.3 Thirty patients with chronic geno-type 1 hepatitis C infection were randomised to receive a 14 day course of the drug, in once daily doses of 1, 10, 30, 60 or 100mg, 30mg twice a day, or placebo. There was no evidence of antiviral activity in the placebo group, but the mean maximum decline of 2.8 to 4.1 log IU/ml. Most experienced viral rebound on or before day 7 of treatment, which was associated with viral variants that had previously been implicated in resistance development. It was well tolerated in all dose groups.
references
1. M. Gao et al. Nature 2010, 465, 96
2. K. Chayama et al. Hepatology, 2011, doi 10.1002/hep24724, epub ahead of print
3. R.E. Nettles et al. Hepatology, 2011, doi 10.1002/hep.24609, epub ahead of print
