Study population
Subjects were Japanese males aged between ≥ 20 and < 46 years, with a body mass index between ≥ 18.5 and < 25.0 kg m-2. Eligible subjects had no clinically problematic abnormalities regarding their medical findings, physiological examinations, and laboratory tests, and the investigator determined that there were no problems that would have prevented participation in this study. The following subjects were excluded: those who had a previous or current medical history of functional disorders related to the liver, heart, kidney, lungs, blood, gastrointestinal tract, or any other disorders that would preclude participation; a previous or current medical history of upper gastrointestinal disorders; a history of drug allergy; white blood cell count ≤ 4000 µL-1; neurological symptoms; a previous or current medical history of serious infectious diseases, including opportunistic infections within 1 year prior to administration of the drug; ingestion of grapefruit, grapefruit juice or foods containing these ingredients within 8 days prior to the start of administration of the study drug; or ingestion of St. John’s Wort or foods containing these ingredients within 15 days prior to the start of administration of the study drug.