This phase 1 clinical study investigating a single-dose of AAFP 500 mg under both fed and fasted conditions in healthy male subjects was conducted in compliance with the International Conference on Harmonisation Good Clinical Practice guidelines and the Declaration of Helsinki. Registration of this study in ClinicalTrials.gov was not necessary based on exclusion criteria for phase 1 drug trials (https://clinicaltrials.gov/ct2/manage-recs/fdaaa#footnote1). All subjects provided written informed consent before any treatment was initiated, and the protocol was reviewed and approved by an institutional review board (Aspire IRB, 11491 Woodside Avenue, Santee, California 92071, USA).
Normal healthy male subjects aged 18–50 years with a body mass index between 18 and 30 kg/m2 who met additional inclusion/exclusion criteria were enrolled in the study. Subjects were required to be in good health based on physical examination, recording of vital signs, electrocardiogram, and clinical laboratory testing (hematology, biochemistry, and urinalysis). Subjects who used prescription medications or tested positive for drugs of abuse and alcohol at the screening visit were excluded from the study.
This was a single-center, randomized, open-label, two-period crossover study of food effects. In period 1 of the study, enrolled subjects were admitted to the study site (PAREXEL International, Early Phase Clinical Unit, Baltimore, MD, USA) the evening before the morning dose of AAFP. All subjects underwent a 10-h overnight fast. The following morning, subjects were randomized to receive AAFP 500 mg (4 × 125-mg AAFP tablets) under either fed or fasted conditions. Subjects randomized to the fed condition consumed an entire standard high-fat FDA breakfast (two eggs fried in butter, two strips of bacon, two slices of toast with butter, 113.4 g of hash brown potatoes, and 226.8 g of whole milk)  30 min before AAFP 500 mg administration. Subjects randomized to the fasted condition were administered AAFP 500 mg with 240 mL of water. This group remained in the fasted state until 4 h after taking the dose of AAFP.
In period 2 of the study, the subjects returned to the same study site following a 7-day washout period. The same study procedures as in period 1 were performed; however, the subjects followed the order of their randomly assigned treatment sequences and crossed over to the opposite fed or fasted condition from period 1. In this study, each subject served as his own control.
Subjects were confined to the study site for collection of blood samples for pharmacokinetic evaluation of plasma abiraterone concentration until 48 h after AAFP administration for both periods 1 and 2. Blood samples (approximately 6 mL) were collected in each study period at − 0.75 h, and at 0.25, 0.5, 1, 1.5, 2, 3, 4, 6, 8, 12, 24, 36, and 48 h after dosing. AAFP tablets were manufactured by Mayne Pharma Group Ltd. for Churchill Pharmaceuticals LLC.
Blood Sample Collection and Bioanalytical Assay
Blood samples (approximately 6 mL) for pharmacokinetic analyses were collected into 6-mL tripotassium ethylenediaminetetraacetic acid-containing tubes and immediately placed on ice. Plasma was separated by centrifugation at 4 °C, transferred to appropriately labeled polypropylene specimen containers, frozen at − 20 °C within 1 h of collection, then stored at − 20 °C. Samples were then shipped on dry ice to the bioanalytical laboratory for analysis. Plasma samples were analyzed for abiraterone concentrations using a validated bioanalytical assay (Sannova Analytical, Somerset, NJ, USA).
The samples were extracted using the liquid–liquid extraction method and analyzed using reverse-phase liquid chromatography. The analytes were detected using tandem mass spectrometry. The lower limit of quantitation for abiraterone was 0.651 ng/mL. The upper limit of quantitation for abiraterone was 203.519 ng/mL. Plasma drug concentrations identified as below the limit of quantification were entered as zero. A calibration curve consisting of 2 control blanks, 2 zero standards, and 10 nonzero calibration standards covering a concentration range of 0.651–203.519 ng/mL for abiraterone were analyzed with every sample batch. Quality control standards for abiraterone were also analyzed with every sample batch. Internal standard peak area ratio values were used to set up the calibration curve and to determine quality control and unknown sample concentrations. Linear regression for abiraterone was used to obtain the best fit of the data for the calibration curve.
All subjects who received AAFP 500 mg under both fed and fasted conditions who had sufficient plasma concentrations for calculating C
max and AUC from time 0 to the time (t) of the last quantifiable concentration (C
) were included in the pharmacokinetic population. The following plasma pharmacokinetic parameters were determined: AUC0–t
as calculated by the linear trapezoidal method; AUC from time 0 to infinity (AUC0–∞) approximated by linear trapezoidal summation and extrapolated to infinity by addition of C
max; time to maximum measured plasma concentration (T
max); apparent elimination rate constant (K
e) as determined by linear regression of the terminal points of the log-linear concentration–time curve; and apparent terminal elimination half-life (T
1/2) calculated as loge(2)/K
e or 0.693/K
All subjects who received AAFP were included in the safety population. Assessments included physical examination, recording of vital signs, electrocardiogram, clinical laboratory testing (hematology, biochemistry, and urinalysis), and recording of adverse events (AEs). AE assessments and concomitant medications were assessed throughout the clinical study.
Based on a previous companion study, a sample size of 22 subjects was deemed sufficient to provide statistical power to detect a 20% difference in the reference mean between fed and fasted conditions . Assuming a screen failure/dropout rate of 15%, enrollment of 26 subjects was planned. A parametric general linear model was applied to the pharmacokinetic parameters (AUC, C
max, and T
1/2). The model included sequence, subject-within-sequence, period, and condition. The sequence effect was tested using the subject-within-sequence effect, and all other effects were tested using the residual error of the model. Analysis of variance (ANOVA) for a crossover design was used to examine the differences between the two dose conditions (fed vs. fasted). A null hypothesis of zero difference in a parameter between the two conditions was assessed at the 0.05 level, with the alternative hypothesis of nonzero differences. T
max was compared for the fed versus fasted conditions using the nonparametric Wilcoxon signed rank test.
To evaluate relative bioavailability, AUC and C
max parameters were analyzed on a log scale using the parametric general linear model to assess bioequivalence between AAFP 500 mg under fed versus fasted conditions. The two one-sided t test hypotheses were tested at the 0.05 level by constructing a 90% confidence interval (CI) for the geometric mean ratio. Bioequivalence was concluded if the 90% CI of the ratio was within 0.80 and 1.25 for AUC and C
max parameters; otherwise, relative bioavailability for AUCs and C
max were expressed based on the least square means ratio values.