Study to determine the safety, tolerability and pharmacokinetics of BILR 355 BS plus low dose ritonavir in healthy male volunteers.

Inclusion Criteria:

1. Males who meet the following criteria:

   Based upon a complete medical history, including the physical examination, vital signs (BP, PR), 12-lead ECG, clinical laboratory tests

   • No finding deviating from normal (except as noted below) and of clinical relevance
   • No evidence of a clinically relevant concomitant disease

2. Age ≥18 years and <60

3. BMI ≥18.5 and BMI ≤29.9 kg/m2 (Body Mass Index)

4. Signed and dated written informed consent prior to admission to the study in accordance with Good Clinical Practice and the local legislation

Exclusion Criteria:

1. Current and medically relevant gastrointestinal, hepatic, renal, respiratory, cardiovascular, metabolic, immunological or hormonal disorders
2. Surgery of gastrointestinal tract (except appendectomy)
3. Diseases of the central nervous system (such as epilepsy) or psychiatric disorders or neurological disorders
4. History of relevant orthostatic hypotension, fainting spells or blackouts
5. Chronic or relevant acute infections
6. History of allergy/hypersensitivity (including drug allergy) which is deemed relevant to the trial as judged by the investigator
7. Intake of drugs with a long half-life (>24 hours) within one month prior to administration of study drug or during the trial
8. Use of drugs within 10 days prior to administration or during the trial, which might reasonably influence the results of the trial based on the knowledge at the time of protocol preparation
9. Participation in another trial with an investigational drug within one month prior to administration or during the trial
10. Smoker
11. Inability to refrain from smoking on trial days
12. Alcohol abuse (more than 60 g/day)
13. Drug abuse
14. Recent blood donation (more than 100 mL within 4 weeks prior to administration or during the trial)
15. Excessive physical activities (within 1 week prior to administration or during the trial)
16. Any laboratory value outside the normal reference range that is of clinical relevance
17. Inability to comply with dietary regimen of study centre
18. Infected with hepatitis B or hepatitis C viruses (defined as either being hepatitis B surface antigen, hepatitis B core antibody, or hepatitis C antibody positive)
19. HIV-1 infected as defined by a positive HIV ELISA test