Pharmasset, Inc. (NASDAQ:IART) reported that dosing has begun in Part 2 of a Phase 1 study. This is the first clinical study combining a purine (PSI-938) and a pyrimidine (PSI-7977) nucleotide analog for HCV, and is designed to evaluate once daily doses of PSI-7977 and PSI-938 in patients with HCV who have not been treated previously.