Randomized, open-label, parallel group study in a group of 75 healthy subjects, to evaluate the safety and toleration of 2 different doses of lersivirine administered either fed or fasted (proposed Phase 3 formulation) given over 21 days, compared to lersivirine 500 mg QD (Phase 2b formulation). The pharmacokinetics of lersivirine in each group will also be evaluated.

Inclusion Criteria:

• Healthy male and/or female subjects.
• Body Mass Index (BMI) of 17.5 to 30.5 kg/m2; and a total body weight >50 kg (110 lbs).
• Subjects who are willing and able to comply with scheduled visits, treatment plan, laboratory tests, and other study procedures.

Exclusion Criteria:

• Use of tobacco- or nicotine-containing products in excess of the equivalent of 5 cigarettes per day.
• Use of prescription or nonprescription drugs and dietary supplements within 7 days or 5 half-lives (whichever is longer) prior to the first dose of study medication.
• Evidence or history of clinically significant hematological, renal, endocrine, pulmonary, gastrointestinal, cardiovascular, hepatic, psychiatric, neurologic, or allergic disease (including drug allergies, but excluding untreated, asymptomatic, seasonal allergies at time of dosing).