Evaluate Effects of Multiple Doses of Rifampin and Clarithromycin on the Single Dose Pharmacokinetics of Deflazacort

This is an open label, parallel 2-arm, 2-period, fixed-sequence study in 58 healthy adult non-tobacco using male and female subjects divided into 2 cohorts, with 29 subjects in each arm of the study (Cohorts A and B). Cohort A: On Day 1 of Period 1 a single oral dose of deflazacort (Treatment A) will be administered followed by PK sampling for 24 hours for 21 desacetyl DFZ and, if data permit, deflazacort. In Period 2, multiple oral doses of rifampin will be administered once daily (QD) for 10 consecutive days with a single oral dose of deflazacort coadministered on Day 10 (Treatment B). Pharmacokinetic sampling for 21-desacetyl-DFZ and, if data permit, deflazacort will be taken for 24 hours following deflazacort dosing on Day 10. Morning urine collection will be used to measure 6β-hydroxycortisol and free cortisol concentrations on Days 1, 4, 8, and 10 to evaluate the level of cytochrome P450 (CYP) enzyme induction. Cohort B: On Day 1 of Period 1 a single oral dose of deflazacort (Treatment C) will be administered followed by PK sampling for 24 hours for 21-desacetyl-DFZ and, if data permit, deflazacort. In Period 2, multiple oral doses of clarithromycin will be administered twice daily (BID) for 4 consecutive days with a single oral dose of deflazacort coadministered on the morning of Day 4 (Treatment D). Pharmacokinetic sampling for 21 desacetyl-DFZ and, if data permit, deflazacort will be taken for 24 hours following deflazacort dosing on Day 4. Both Cohorts A and B: There will be at least 24 hours between the dose in Period 1 and the first dose in Period 2. Safety will be monitored throughout the study by repeated clinical and laboratory evaluations. The clinic will attempt to contact subjects using their standard procedures approximately 14 days after the last study drug administration to determine if any adverse events (AEs) have occurred since the last dose of study drug. Subjects who terminate the study early will be contacted if the Principal Investigator (PI) deems necessary. Cohort A: Treatments A and B are described as follows: Treatment A (Period 1): 18 mg deflazacort (3 x 6 mg tablets) at Hour 0 on Day 1, following an overnight fast. Treatment B (Period 2): 600 mg rifampin (2 x 300 mg capsules) administered at Hour 0 after an overnight fast every 24 hours for 10 days (within ± 1 hour of dosing time on Day 1), with 18 mg deflazacort (3 x 6 mg tablets) coadministered on Day 10. Cohort B: Treatments C and D are described as follows: Treatment C (Period 1): 18 mg deflazacort (3 x 6 mg tablets) at Hour 0 on Day 1, following an overnight fast. Treatment D (Period 2): 500 mg clarithromycin (1 x 500 mg tablets) administered at Hour 0 and Hour 12, under fasting conditions, approximately every 12 hours, for 4 days (within ± 1 hour of dosing times on Day 1), with 18 mg deflazacort (3 x 6 mg tablets) coadministered at Hour 0 on the morning of Day 4. The final dose of clarithromycin will be given at Hour 12 in the evening of Day 4. All study drugs in both cohorts will be administered orally with approximately 240 mL of water.