The purpose of this study is to determine the effect of EFV (Efavirenz) and TDF (Tenofovir disoproxil fumarate) on the pharmacokinetics of TVR (Telaprevir) and to determine the effect of TVR on the pharmacokinetics of EFV and TDF. Pharmacokinetics means how the drug is absorbed into the bloodstream, distributed in the body and eliminated from the body. Furthermore, the short-term safety and tolerability of giving TVR, EFV and TDF together will be evaluated.

The trial will enroll 20 Healthy volunteers. All participants will receive 4 different treatments:

Treatment A: TVR every 8 hours alone for 6 days with an additional morning intake on Day 7. Treatment B: EFV + TDF once daily alone for 7 days. Treatment C: TVR every 8 hours + EFV once daily + TDF once daily for 7 days. Treatment D: TVR every 12 hours + EFV once daily + TDF once daily for 7 days.

All participants will start with Treatment A followed by a 7 or 8-day washout period. Subsequently, participants will start with Treatment B. At the end of Treatment B, participants will be randomized (this is assigned to one of the two sequences by chance) to continue without a washout period with Sequence 1 (Treatment C followed by D without a washout) or Sequence 2 (Treatment D followed by C without a washout). Participants will thus receive daily EFV and TDF for a total of 21 consecutive days, with addition of 2 different dosages of TVR for the last 14 days.

TVR will be taken with food, 30 minutes after the start of a meal. EFV and TDF should be taken on an empty stomach (2.5 hours after start of breakfast). Pharmacokinetic profiles of TVR and VRT-127394 (R-diastereomer of TVR) will be measured up to 8 hours after intake of the morning dose on Day 7 of Treatments A and C, and up to 12 hours after intake of the morning dose on Day 7 of Treatment D. Pharmacokinetic profiles of EFV and tenofovir will be measured up to 24 hours after intake on Day 7 of Treatments B, C, and D. Safety and tolerability evaluations will be recorded at regular intervals throughout the trial period. Treatment A: TVR every 8 hours alone for 6 days with an additional morning intake on Day 7. Treatment B: EFV + TDF once daily alone for 7 days. Treatment C: TVR every 8 hours + EFV once daily + TDF once daily for 7 days. Treatment D: TVR every 12 hours + EFV once daily + TDF once daily for 7 days.

Inclusion Criteria:

• Females should be post-menopausal (amenorrheal for at least 3 years), or have undergone tubal ligation (or other permanent birth control methods), or hysterectomy (total), or oophorectomy (bilateral)
• Normal weight at screening as defined by a body mass index (BMI, weight in kg divided by the square of height in meters) of 18 to 30 kg/m2, extremes included
• Normal 12-lead ECG at screening
• Healthy on the basis of a physical examination, medical history, ECG, vital signs, and the results of blood biochemistry, blood coagulation and hematology tests and a urinalysis carried out at screening
• Nonsmoking or smoking no more than 10 cigarettes, or 2 cigars, or 2 pipes per day for at least 3 months before study screening.

Exclusion Criteria:

• No history or presence of relevant drug or food allergies, cardiovascular or central nervous system disease, clinically significant pathology, mental disease or psychiatric disorders, chronic skin disease, or drug abuse
• Current use of prescription medication
• Regular treatment with over-the-counter medications
• Consumption of herbal medications or dietary supplements
• A history of drug or alcohol abuse or addiction within 2 years prior to dosing, or a positive test for alcohol or drugs
• Participation in a clinical study within 2 months or 5 half lives of the investigational drug prior to the screening visit
• No positive HIV test or hepatitis A, B or C infection
• Having any history of renal disease
• Male subjects with female partners that are pregnant, or planning to become pregnant during the study or within 90 days of the last dose of study drug.