* Drug showed undetectable virus levels after 12 weeks
* Achieved undetectable virus levels in 98 pct patients
* Shares up 9 pct pre-market
Sept 6 (Reuters) - Pharmasset Inc said its hepatitis C drug showed positive results in a mid-stage trial to treat patients who have not been previously treated for the infection.
In the mid-stage study, named PROTON, 98 percent of patients had no detectable virus levels in the blood 12 weeks after the treatment was completed.
Patients were given either 400 mg or 200 mg doses of the drug, PSI-7977, once daily for 12 weeks in combination with the current standard-of-care for hepatitis C — peginterferon alfa 2a and ribavirin.
Patients will now be monitored to check for virus levels 24 weeks after treatment completion, which is the main goal of the study, the company said in a statement.
Shares of the company were trading up 9 percent at $70 in pre-market trade. They closed at $64.20 on Friday on Nasdaq. (Reporting by Zeba Siddiqui in Bangalore; Editing by Roshni Menon)