In long-term carcinogenicity studies with fosamprenavir in mice and rats, there were increases in hepatocellular adenomas and hepatocellular carcinomas in mice at exposure levels equivalent to 0.1 to 0.3-fold those in humans given 700 mg of fosamprenavir plus 100mg ritonavir twice daily, and increases in hepatocellular adenomas and thyroid follicular cell adenomas in rats at exposure levels equivalent to 0.3 to 0.6-fold those in humans given 700 mg of fosamprenavir plus 100mg ritonavir twice daily.