The aim of the study is to see if apricitabine or tipranavir affect the levels of each other in the blood (pharmacokinetic interaction) when they are dosed together.

Apricitabine is a new NRTI in development for treatment of drug resistant HIV. Tipranavir is a recently licensed protease inhibitor for treatment of drug resistant HIV. Tipranavir affects the plasma concentration of some other drugs when they are used together with tipranavir. This study will examine whether the pharmacokinetics of apricitabine are changed when it is dosed together with tipranavir compared to apricitabine alone. Also, the pharmacokinetics of tipranavir will be examined at steady state when it is dosed alone and when it is dosed together with apricitabine. Information on the safety and tolerability of the two drugs when dosed together will also be obtained.

Inclusion Criteria:

• healthy males 18-40 years old
• non-smokers
• no clinically significant medical history

Exclusion Criteria:

• current or relevant previous medical history of significance
• hepatitis B, hepatitis C, or HIV positive
• current use of prescription or OTC medications
• use of illicit substances or alcohol (>14 drinks/week)