NEW YORK ( TheStreet) -- Pharmasset (Nasdaq: VRUS) is trading at unusually high volume Friday with 4.3 million shares changing hands. It is currently at 4.1 times its average daily volume and trading down $13.02 (-16.4%) at $66.38 as of 1:26 p.m. ET. Pharmasset has a market cap of $5.9 billion and is part of the health care sector and drugs industry. Shares are up 260.6% year to date as of the close of trading on Thursday. Pharmasset, Inc., a clinical-stage pharmaceutical company, focuses on discovering, developing, and commercializing novel drugs to treat viral infections. TheStreet Ratings rates Pharmasset as a sell. The company's weaknesses can be seen in multiple areas, such as its deteriorating net income, weak operating cash flow and feeble growth in its earnings per share. You can view the full Pharmasset Ratings Report. See all heavy volume stocks in our stocks moving on unusual volume list or get investment ideas from our investment research center. Interested in other stocks that are falling on unusually high volume? Get free SMS text alerts sent to you when the action happens by texting HVDOWN to 95370 or select from multiple alert options.