Sample collection and bioanalytical assay
SAD
In all three cohorts of the SAD stage, blood samples for ibrexafungerp concentration were collected predose (0 hour), and at 0.5, 1, 1.5, 2, 3, 4, 5, 6, 8, 12, 16, 24, 36, 48, 72, and 96 hours postdose. In 450 mg cohort of MAD stage, blood samples were collected predose (0 hour), and at 0.5, 1, 1.5, 2, 4, 6, 8, 12, and 24 hours postdose on day 1; predose (0 hour) from day 5 to day 7; at 0.5, 1, 2, 4, 6, 8, 12, 24, 48, 72, and 96 hours postdose on day 7. In 750 mg cohort of MAD stage, blood samples were collected predose (0 hour), and at 2, 4, 6, and 8 hours postdose in the morning and evening on day 1; predose (0 hour) from day 2 to day 6; predose (0 hour), and 2, 4, 6, 8, 12, 16, 24, 36, 48, 72, 96, and 120 hours postdose on day 7.A validated HPLC-MS/MS assay was used to quantify the concentrations of ibrexafungerp in human plasma. Samples were pretreated by protein precipitation extraction. The calibration range was 5.00–5,000 ng/mL. The sensitivity of this method was 5.00 ng/mL. The maximum of intra-run and inter-run precision (CV%) were 5.27 and 4.32, respectively. The range of intra-run and inter-run accuracy (Bias%) were −0.67 ~ 11.50 and 1.44 ~ 9.07, separately. Moreover, matrix effect, selectivity, dilution, carryover, and stability were also validated. All performance characteristics of the bioanalytical method met the acceptable requirement. All samples were collected, stored, and analyzed under conditions confirmed by analyte stability during validation studies.