Shares in US drugmaker Valeant Pharmaceuticals took a 14% hit yesterday after the company revealed that a late-stage trial of Viramidine for hepatitis C did not meet its expectations.

The study found that viramidine was not as effective as standard treatment for hepatitis C, but Valeant said it still had faith in the product and would continue to work towards a scheduled commercial launch in 2007. The company is conducting another Phase III trial of the drug.

Viramidine is intended as a safer and more effective alternative to the mainstay hepatitis C drug ribavirin, which is given alongside pegylated interferon alfa.

Better-tolerated and more effective therapies are needed as around 70% of the 7 million people with hepatitis C in the US, EU and Japan are infected with the difficult-to-treat genotype strain 1. Currently, only 40%-50% of these patients have a successful response to standard treatment.

The Phase III trial compared the combination of viramidine plus interferon to ribavirin plus interferon in patients with chronic hepatitis C who had not received any prior treatment for the infection. Viramidine was associated with significantly fewer side effects than those on ribavirin, particularly a lower incidence of anaemia (5% versus 24%), but failed to show that it was at least as effective as its rival.

Overall, 38% of patients in the viramidine arm achieved a sustained virologic response, compared to 52% of patients on ribavirin.

Valeant said the results showed that, at higher doses, viramidine was associated with greater efficacy. At optimal dosing according to body weight, virologic responses were seen in 62% of viramidine patients and 60% of those on ribavirin, it claimed.

Valeant’s shares closed at $16.03 yesterday.