The FDA granted Pharmasset Inc., of Princeton, N.J., fast-track designation for PSI-938 for the treatment of chronic hepatitis C virus (HCV) infection. PSI-938 is an oral guanosine nucleotide analogue polymerase inhibitor of HCV. Pharmasset plans to initiate an interferon-free combination trial with PSI-938 and PSI-7977, an uracil nucleotide analogue, in the third quarter. In an earlier study, PSI-938 demonstrated potent antiviral activity, both as monotherapy and in combination with PSI-7977.