Drug & Device Development

Pharmasset upbeat on drug for resistant hep C strain: CEO

Last Updated: 2011-11-11 17:37:20 -0400 (Reuters Health)

By Anand Basu

(Reuters) - Pharmasset Inc expects its all-oral hepatitis C combination therapy to work equally well in patients infected with the hard-to-treat genotype 1 strain of the virus as it did in genotypes 2 and 3, its chief executive said.

"Our drug's nucleotide works against all types of viruses the same," Chief Executive Schaefer Price told Reuters.

"So for us, there should be no difference in genotype 1, 2, 3, 4, 5 or 6. They should all be addressable equally the same."

Pharmasset's PSI-7977 is a nucleotide polymerase inhibitor .

In a small 10-patient trial testing the drug in combination with ribavarin in patients with HCV 2 or 3 genotype, the drug showed 100% cure rates after 12 weeks of treatment.

Pharmasset's Price agreed that replicating a 100% cure rate will be difficult in larger trials, but expects to see a 90% cure rate in genotype 1 patients.

"If you look at the differences between genotype 2 (and) genotype 3, they are completely different viruses and yet the drug performed exactly the same," Price said.

Having started a late-stage study for its combination therapy, Pharmasset is currently leading the race to develop an all-oral hepatitis C therapy without using the injectable drug interferon -- which causes flu-like symptoms that lead many patients to stop or delay treatment.

Merck's Victrelis and Vertex's Incivek, which were both recently approved, need to be taken in a three-drug combination with the earlier standard of care -- interferon and ribavirin.

About 70% of hepatitis C patients in the United States are infected with the genotype 1 strain.

Currently, the most potent hepatitis C drug, Incivek, has a cure rate of 66% and treatment time of 24 weeks.

However, comparing PSI-7977's data with Incivek would be premature, as Pharmasset's trial was small and only included patients with genotype 2 or 3, and not genotype 1.

The company plans to file a new drug application for PSI-7977 in the second half of 2013, and hopes for approval and launch in the first half of 2014.