The purpose of this study is to to assess the effect of ATV 300 mg BID on the PK of raltegravir 400 mg BID, to assess the effect of raltegravir 400 mg BID on the PK of ATV 300 mg BID, and to assess the ECG effects of ATV 300 mg BID over 21 days, given with or without raltegravir 400 mg BID.

Inclusion Criteria:

• Healthy male and female subjects between the ages of 18 to 45 years old with a body mass index (BMI) of 18 to 32 kg/m²
• Prior to enrollment, subjects must have physical and laboratory test findings within normal limits, and women of childbearing potential (WOCBP) must have a negative pregnancy test

Exclusion Criteria:

• Any significant acute or chronic medical illness
• Evidence of organ dysfunction or any clinically significant deviation from normal in physical examination, vital signs, ECG or clinical laboratory determinations.
• Use of any prescription drugs or over-the-counter acid controllers within 4 weeks prior to study drug administration
• Use of any other drugs, including over-the-counter medications and herbal preparations within 1 week prior to study drug administration