An orally-active drug for hepatitis C virus infection developed by Swiss drugmaker Roche has encouraging strong antiviral activity in a clinical trial.

In the Phase I trial, R1626, a polymerase inhibitor, achieved significant reductions in viral load in chronic hepatitis C patients infected with the difficult to treat genotype 1 virus. The findings were announced at the European Association for the Study of the Liver conference in Vienna, Austria, yesterday.

At present, all hepatitis C treatments are based on injectable interferon alpha products, given alongside oral ribavirin, a synthetic nucleoside that - while only modestly effective against hepatitis C in its own right - boosts the efficacy of interferon alpha. But while the newer pegylated (long-acting) interferons and ribavirin have transformed treatment, the combination still fails to clear the virus in around 50% of patients.

The hope is that a more effective oral treatment for hepatitis C could boost viral clearance rates – the ultimate goal of treatment – compared to interferon alpha alone, while also potentially allowing patients to maintain long-term maintenance therapy without the need for regular injections.

In this ongoing study, patients were randomised to receive either oral treatment with R1626 twice daily or placebo for 14 days, with 14 days of follow up. Further trials are planned to study how well R1626 works in combination with Roche's current hepatitis drugs, Pegasys (peginterferon alfa-2a) and its Copegus brand of ribavirin.

Other companies developing hepatitis C virus polymerase inhibitors include Novartis/Idenix with valopicitabine (Phase II), Japan Tobacco/Akros Pharma’s JTK-003 (Phase II) and JTK-109 (Phase I); and ViroPharma and Wyeth’s HCV-086 (Phase Ib) and HCV-796 (Phase I). Many other companies have agents at preclinical development stage.

Hepatitis C currently affects approximately 170 million individuals worldwide, making it more common than the HIV virus.

- Roche also reported data at the EASL showing that long-term treatment of hepatitis C genotypes 2 and 3 with Pegasys and Copegus cleared the virus from the blood of 76% of patients after 24 weeks of treatment, compared to 65% with the usual 16 week course.