Effect of food and polymorphisms in SLCO2B1, CYP3A4 and UGT1A4 on pharmacokinetics of abiraterone and its metabolites in Chinese volunteers.

AIMS: Abiraterone acetate, a prodrug of abiraterone (ABI), provides an efficient therapeutic option for metastatic castration-resistant prostate cancer patients. ABI undergoes extensive metabolism in vivo and is transformed into active metabolites Δ4 -abiraterone and 3-keto-5α-abiraterone as well as inactive metabolites abiraterone sulfate and abiraterone N-oxide sulfate. We aimed to examine the effect of polymorphisms in SLCO2B1, CYP3A4 and UGT1A4 on the pharmacokinetics of ABI and its metabolites. METHODS: In this study, 81 healthy Chinese subjects were enrolled and divided into 2 groups for fasted (n = 45) and fed (n = 36) studies. Plasma samples were collected after administering a 250 mg abiraterone acetate tablet followed by liquid chromatography-tandem mass spectrometry analysis. Genotyping was performed on a MassARRAY system. The association between SLCO2B1, CYP3A4, UGT1A4 genotype and pharmacokinetic parameters of ABI and its metabolites was assessed. RESULTS: Food effect study demonstrated high fat meal remarkedly increased systemic exposure of ABI and its metabolites. The geometric mean ratio and 90% confidence interval of area under the plasma concentration-time curve from time 0 to the time of the last quantifiable concentration (AUC0-t ) and maximum plasma concentration (Cmax ) of ABI in fed state vs. fasted state were 351.64% (286.86%-431.04%) and 478.45% (390.01%-586.94%), respectively, while the corresponding results were ranging from 145.11% to 269.42% and 150.10% to 478.45% for AUC0-t and Cmax of ABI metabolites in fed state vs. fasted state, respectively. The SLCO2B1 rs1077858 had a significant influence on AUC0-t and Cmax , while 7 other SLCO2B1 variants prolonged half-life of ABI under both fasted and fed conditions. As for ABI metabolites, the systemic exposure of Δ4 -abiraterone, abiraterone sulfate and abiraterone N-oxide sulfate as well as the elimination of 3-keto-5α-abiraterone were significantly affected by SLCO2B1 polymorphisms. Polymorphisms in CYP3A4 and UGT1A4 did not significantly affect pharmacokinetics of ABI and its metabolites. CONCLUSION: Polymorphisms in SLCO2B1 were significantly related to the pharmacokinetic variability of ABI and its metabolites under both fasted and fed conditions.

Evaluation of the food effect on a drospirenone only contraceptive containing 4 mg administered with and without high-fat breakfast in a randomised trial.

BACKGROUND: The objective of the present trial was to assess the difference in pharmacokinetics (PK) of an oral test preparation containing 4 mg drospirenone (DRSP) under fasting conditions compared to PK upon food intake after single dose administration. METHODS: Open label, single centre, two-treatment, two-sequence, crossover study in 24 healthy female volunteers, with duration of 1 day per sequence and with a real wash-out period of 14 days to investigate the relative bioavailability of DRSP with both forms of administration. The 90% confidence intervals (CI) were calculated for the intra-individual ratio (test with food vs. without food) of the PK endpoints Area under the curve; 0-72 h [AUC(0-72 h)] and maximal plasma concentration [Cmax] of DRSP. RESULTS: The 90% CI calculated by analysis of variance using logistic transformation (ANOVA-log) for the endpoint, intra-individual ratio (Test 'A' = with food intake) vs. Test 'B' = without food intake) of AUC(0-72 h) of drospirenone was between 104.72 and 111.36%. The 90% CI calculated by means of ANOVA- log for the endpoint intra-individual ratio (Test 'A' vs. Test 'B') of Cmax of DRSP was between 118.58 and 141.10%. The mean relative bioavailability of the test with food 'A' compared to the Test without food 'B' after single dose administration based on the endpoints AUC(0-72 h) was 107.99%; for the endpoint Cmax it was 129.35%. CONCLUSIONS: The rate of absorption, based on the endpoint Cmax of DRSP was increased by about 30% under fed conditions. With respect to consumer habits, this may represent a relevant benefit for contraceptive safety, as the time span between food consumption and pill intake does not play a role. IMPLICATIONS: Our results suggest that the food intake has no impact on the absorption of 4 mg DRSP in the management of contraception. This increases the contraceptive efficacy as no interference with food is expected when consuming the oral formulation under real life conditions. TRAIL REGISTRATION: Trial registration number: EudraCT-No: 2012-004,309-28.

The effect of drug loading on the properties of abiraterone-hydroxypropyl beta cyclodextrin solid dispersions processed by solvent free KinetiSol® technology.

Abiraterone is a poorly water-soluble drug used in the treatment of prostate cancer. In our previous study, we reported that KinetiSol® processed solid dispersions (KSDs) based on hydroxypropyl ß-cyclodextrin (HPBCD) showed improved dissolution and pharmacokinetics of abiraterone. However, the nature of abiraterone-HPBCD interaction within the KSDs or the effect of drug loading on the physicochemical properties and in vivo performance of HPBCD-based KSDs remain largely unknown. We hypothesize that KinetiSol technology can prepare abiraterone-HPBCD complexes within KSDs and that increasing the drug loading beyond an optimal point reduces the in vitro and in vivo performance of these KSDs. To confirm our hypothesis, we developed KSDs with 10-50% w/w drug loading and analyzed them using X-ray diffractometry and modulated differential scanning calorimetry. We found that KSDs containing 10-30% drug were amorphous. Interestingly, two-dimensional solid-state nuclear magnetic resonance and Raman spectroscopy indicated that the abiraterone-HPBCD complexes were formed. At elevated temperatures, the 10% and 20% drug-loaded KSDs were physically stable, while the 30% drug-loaded KSD showed recrystallization of abiraterone. In vitro dissolution and in vivo pharmacokinetic performances improved as the drug loading decreased; we attribute this to increased noncovalent interactions between abiraterone and HPBCD at lower drug loadings. Overall, the 10% drug loaded KSD showed a dissolution enhancement of 15.7-fold compared to crystalline abiraterone, and bioavailability enhancement of 3.9-fold compared to the commercial abiraterone acetate tablet Zytiga®. This study is first to confirm that KinetiSol, a high-energy, solvent-free technology, is capable of forming abiraterone-HPBCD complexes. Furthermore, in terms of in vitro and in vivo performance, a 10% drug load is optimal.

A single-arm study to evaluate the transfer of drospirenone to breast milk after reaching steady state, following oral administration of 4 mg drospirenone in healthy lactating female volunteers.

OBJECTIVE: The primary objective of this trial was to assess the transfer of drospirenone to breast milk after daily administration of an oral test preparation containing 4 mg of drospirenone at the steady state. The secondary objective of the trial was to assess safety based on clinical and laboratory measurements and reporting of adverse events and/or adverse drug reactions. PATIENTS AND METHODS: This was an open label, non-comparative single-center study. Drospirenone 4 mg per day was the first postpartum contraceptive for the study participants who were no longer breastfeeding yet were still lactating. It was administered for 7 days to achieve steady-state concentration. All participants were volunteers who planned to use oral contraceptives as their family planning method in the future. RESULTS: Twelve volunteers completed the trial according to the protocol, and the samples of all 12 study completers were analyzed. The average concentration-time curve of drospirenone in plasma 24 h after the administration of the last dose (area under the curve (0-24 h)) was 635.33 ng h/mL and 120 h after the single repeated dose administration (area under the curve (0-120 h)) was 1180.57 ng h/mL, respectively. The average Cmax was 48.64 ng/mL.The average concentration-time curve of drospirenone in milk 24 h after the administration of the last dose (area under the curve (0-24 h)) was 134.35 ng h/mL and 120 h after the single repeated dose administration (area under the curve (0-120 h)) was 227.17 ng h/mL, respectively. The average Cmax was 10.34 ng/mL. CONCLUSION: On average, 18.13% of plasma drospirenone made it to breast milk and the highest concentration of drospirenone in breast milk was 17.55% of that in plasma. The total quantity of drospirenone passing to breast milk is on average 4478 ng during a 24-h period representing 0.11% of the maternal daily dose. Thus, at the recommended doses, no effects on breastfed newborns/infants are anticipated with drospirenone 4 mg.

A quick UPLC-MS/MS method for therapeutic drug monitoring of abiraterone and delta(4)-abiraterone in human plasma.

Abiraterone acetate efficacy against prostate cancer is dependent on the circulating levels of abiraterone and its active metabolites, which present significant pharmacokinetic variability among patients. Thus, therapeutic drug monitoring can be performed to improve treatment outcomes. To support such studies, there are only a limited number of bioanalytical methods in current literature. This work presents a fast method to quantify abiraterone and D4A in plasma in 4 min by UPLC-MS/MS. Bioanalytical method validation was performed according to the recommendations of the US Food and Drug Administration. The method was linear within the range of 1-400 ng/ml for abiraterone and 0.2-20 ng/ml for D4A (r2 > 0.99). Based on the analysis of quality control samples at the lower limit of quantification, low, medium and high concentrations, the method was precise (CVabiraterone ≤ 9.72%; CVD4A ≤ 14.64%) and accurate (CVabiraterone 95.51-107.59%; CVD4A 98.04-99.89%). Application of the method to the quantification of abiraterone and D4A in 10 clinical samples revealed important variability in the conversion ratio of abiraterone to D4A (CV 90.85%). Considering the current literature, this is the fastest method to quantify abiraterone and D4A in plasma, allowing for optimization of the analytical routine.

Comparative pharmacokinetic estimates of drospirenone alone and in combination with ethinyl estradiol after single and repeated oral administration in healthy females.

OBJECTIVE: To determine the pharmacokinetics (PK) of drospirenone (DRSP), alone versus in combination with ethinyl estradiol (EE), after single and repeated administration. STUDY DESIGN: We conducted a single-centre, open-label, crossover, 2-treatment, 2-period, 2-sequence study in which non-micronized DRSP 4 mg or a combination of DRSP 3 mg and EE 0.02 mg were administered to healthy female subjects on day 1 to obtain a single-dose kinetic profile, and from day 4 to day 15 to obtain a repeated-dose kinetic profile. The maximum observed concentration (Cmax) and area under the concentration/time curve (AUC) were determined in a model-independent way using non dose corrected data. Statistical analysis was based on a parametric method (ANOVA-log). RESULTS: A total of 24 healthy female subjects were randomized 1:1 into the study. The mean relative, non-dose-corrected PK estimates after single-dose administration for the endpoints AUC(0-72h), AUC(0-24h) and Cmax were 543.5 ng*h/mL, 296.1 ng*h/mL and 27.3 ng/mL for DRSP alone, and 442.0 ng*h/mL, 264.7 ng*h/mL and 37.5 ng/mL for the DRSP/EE combination; p < 0.001. The mean relative, non-dose-corrected PK estimates after repeated dose administration for the endpoints AUC(0-72h), AUC(0-24h) and Cmax were 1066.8 ng*h/ml, 570.2 ng*h/mL and 41.0 ng/mL for DRSP alone, and 1394.5 ng*h/mL, 732.8 ng*h/mL and 61.4 ng/mL for the DRSP/EE combination; p < 0.001. CONCLUSIONS: DRSP alone exhibits a lower accumulation ratio than together with EE. The extent of systemic exposure at steady-state is about 32% less with the new formulation (AUC(0-24h), steady-state geometric mean ratio: 77.8%; 90% confidence interval: 74.6%-81.1%). This PK profile may be caused by EE. IMPLICATIONS: Our results suggest that metabolic pathways of DRSP can be inhibited by EE resulting in higher DRSP plasma concentrations in DRSP/EE formulations than in a DRSP-alone formulation. The enzymes CYP3A4 and SULT1A1 may play a role. Additional drug-drug-interaction studies are needed to better understand these metabolic pathways and their future clinical implications.

Inter- and intra-patient variability in pharmacokinetics of abiraterone acetate in metastatic prostate cancer.

PURPOSE: This study examined the inter- and intra-patient variability in pharmacokinetics of AA and its metabolites abiraterone and Δ(4)-abiraterone (D4A), and potential contributing factors. METHODS: AA administered daily for ≥4 weeks concurrently with androgen deprivation therapy (ADT) for mCRPC were included. Pharmacokinetic evaluation was performed at two consecutive visits at least 4 weeks apart. Plasma samples were collected 24 h after last dose of AA to obtain drug trough level (DTL) of two active metabolites, abiraterone and D4A. RESULTS: 39 plasma samples were obtained from 22 patients, with 17 patients had repeat DTL measurement. Considerable inter-patient variability in DTL was seen, with initial DTL for abiraterone ranging between 1.5 and 25.4 ng/ml (CV 61%) and for D4A between 0.2 and 2.5 ng/ml (CV 61%). Intra-patient variability in DTL for abiraterone varied between 0.85 and 336% and for D4A between 1.14 and 199%. There was no increase in AA exposure with use of dexamethasone (n = 5; DTL 13.9) compared with prednisone (n = 17; DTL 11.0 p = 0.5), dosing in fasted state (n = 13, DTL 12.1) compared to dosing in fed state (n = 9; DTL 11.1, p = 0.8), or chemotherapy-exposed (n = 10; DTL 8.9) compared to chemotherapy naïve (n = 12; DTL 14.0, p = 0.1). CONCLUSIONS: Our cohort demonstrated high inter- and intra-patient variability in both abiraterone and D4A with fixed dosing of AA, with no effect from choice of corticosteroids, prior use of chemotherapy, or dosing in fasting state. Monitoring DTL of AA may be necessary to minimise risk of patients being under-dosed and earlier development of resistance.

Evaluation of the Pharmacokinetics of Abiraterone Acetate and Abiraterone Following Single-Dose Administration of Abiraterone Acetate to Healthy Subjects.

BACKGROUND AND OBJECTIVE: Following oral administration of abiraterone acetate, the parent compound abiraterone acetate is rapidly metabolized to abiraterone. To our knowledge, bioanalytical methods to date have not been able to detect the parent compound in human plasma, and bioassay was only performed on the metabolite. A highly sensitive bioanalytical method was developed and validated to measure plasma concentrations of the parent compound. In this study, both analytes were assayed and used to evaluate the full pharmacokinetic profile of abiraterone acetate tablets. METHODS: This was an open-label, single-dose, one-period, one-treatment, pharmacokinetic study performed in 18 healthy subjects. Each subject was administered four tablets (corresponding to a total dose of 1000 mg) of abiraterone acetate. Blood samples for pharmacokinetic analysis were collected up to 60 h post-dose. Subjects' plasma concentrations for abiraterone acetate were assayed using highly sensitive validated bioanalytical methods with a lower limit of quantitation (LLOQ) of 0.5 pg/ml for abiraterone acetate and 0.1 ng/ml for abiraterone. Safety assessments were performed throughout the study. RESULTS: The pharmacokinetic results for abiraterone acetate showed a mean for the maximum plasma concentration (Cmax) of 54.67 ± 68.30 pg/ml, and a median time to maximum concentrations (tmax) of 5.53 h (range 2.67-35.00 h). The means for area under the concentration-time curve (AUC) from time 0 h to infinity (AUCinf) and AUC from time zero h to the time of the last measurable abiraterone acetate concentrations (AUCt) were 386.13 ± 266.80 pg·h/ml and 460.07 ± 378.78 pg·h/ml, respectively. The apparent elimination half-life (t1/2) showed a mean of 8.98 ± 3.92 h. None of the adverse events that affected three subjects (16.7%) were related to the study drug. CONCLUSION: The ability to detect the low plasma abiraterone acetate concentrations, in addition to abiraterone, resulted in a complete characterization of the pharmacokinetics of abiraterone acetate that was not possible with other analytical methods that only measured the metabolite. The development of new bioanalytical methods such as these will allow for a more thorough understanding of the pharmacokinetics of abiraterone acetate, and this, in turn, can have an impact on both future examinations into abiraterone acetate pharmacokinetic behaviour and the evaluation of its generic formulations.

Confirmation of the drug-drug interaction potential between cobicistat-boosted antiretroviral regimens and hormonal contraceptives.

BACKGROUND: Cobicistat (COBI), a CYP3A inhibitor, is a pharmacokinetic enhancer that increases exposures of the HIV protease inhibitors (PIs) atazanavir (ATV) and darunavir (DRV). The potential drug interaction between COBI-boosted PIs and hormonal contraceptives, which are substrates of intestinal efflux transporters and extensively metabolized by CYP enzymes, glucuronidation and sulfation, was evaluated. METHODS: This was a Phase I, open-label, two cohort (n=18/cohort), fixed-sequence study in healthy females that evaluated the drug-drug interaction (DDI) between multiple-dose ATV+COBI or DRV+COBI and single-dose drospirenone/ethinyl estradiol (EE). DDIs were evaluated using 90% confidence intervals of the geometric least-squares mean ratios of the test (drospirenone/EE+boosted PI) versus reference (drospirenone/EE) using lack of DDI boundaries of 70-143%. Safety was assessed throughout the study. RESULTS: 29/36 participants completed the study. Relative to drospirenone/EE alone, drospirenone area under the plasma concentration versus time curve extrapolated to infinity (AUCinf) was 1.6-fold and 2.3-fold higher, and maximum observed plasma concentration (Cmax) was unaltered, upon coadministration with DRV+COBI and ATV+COBI, respectively. EE AUCinf decreased 30% with drospirenone/EE + DRV+COBI and was unchanged with ATV+COBI + drospirenone/EE, relative to drospirenone/EE alone. Study treatments were generally well tolerated. The majority of adverse events were mild and consistent with known safety profiles of the compounds. CONCLUSIONS: Consistent with COBI-mediated CYP3A inhibition, drospirenone exposure increased following coadministration with COBI-containing regimens, with a greater increase with ATV+COBI. Thus, clinical monitoring for drospirenone-associated hyperkalaemia is recommended with DRV+COBI and ATV+COBI should not be used with drospirenone. Lower EE exposure with DRV+COBI may be attributed to inductive effects of DRV on CYP enzymes and/or intestinal efflux transporters (that is, P-gp) involved in EE disposition.

Development of novel PLGA nanoparticles with co-encapsulation of docetaxel and abiraterone acetate for a highly efficient delivery into tumor cells.

Co-encapsulation of abiraterone acetate (AbrA) and docetaxel (Dtx) in polymeric nanoparticles as novel prototypes for prostate cancer treatment combining hormonal and chemotherapy was designed. Nanoparticles (NPs) composed of poly(dl-lactide-co-glycolide) (PLGA) were prepared by single-emulsion solvent evaporation technique and characterized in terms of morphology with atomic force microscopy and transmission electron microscopy. HPLC method for simultaneous determination of AbrA and Dtx encapsulation efficacy was developed. Also differential scanning calorimetry and Fourier-transform infrared spectroscopy were provided. To study the effectiveness of cellular internalization and distribution of NPs with AbrA and Dtx co-encapsulation (NP-AbrA/Dtx), a fluorescence microscopy was utilized. NPs prepared had size 256.3 ±9.4 nm and zeta potential -18.4 ±1.4 mV. Encapsulation efficacy for AbrA was 68.7% and for Dtx was 74.3%. NPs were able to control the AbrA and Dtx release within 24 h. The mathematical model of drug release was performed. The results obtained from confocal microscopy showed the effective accumulation of the NP-AbrA/Dtx in the cytoplasm of cells. Synthesized NPs possessed satisfactory parameters and a biphasic release profile, proceeding by the Fick diffusion mechanism, which provide prolonged release of the drugs and maintenance of their concentration. It was shown that NPs loaded with AbrA and Dtx exhibited a high cytotoxic activity on the LNCaP cell line, similar to the combination of free drugs of AbrA and Dtx, but in contrast to the combination of substances, had a synergistic mechanism of action. Our findings support the potential use of developed NPs in further in vivo studies. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1150-1158, 2019.

HSD3B1(1245A>C) variant regulates dueling abiraterone metabolite effects in prostate cancer.

BACKGROUND: A common germline variant in HSD3B1(1245A>C) encodes for a hyperactive 3ß-hydroxysteroid dehydrogenase 1 (3ßHSD1) missense that increases metabolic flux from extragonadal precursor steroids to DHT synthesis in prostate cancer. Enabling of extragonadal DHT synthesis by HSD3B1(1245C) predicts for more rapid clinical resistance to castration and sensitivity to extragonadal androgen synthesis inhibition. HSD3B1(1245C) thus appears to define a subgroup of patients who benefit from blocking extragonadal androgens. However, abiraterone, which is administered to block extragonadal androgens, is a steroidal drug that is metabolized by 3ßHSD1 to multiple steroidal metabolites, including 3-keto-5α-abiraterone, which stimulates the androgen receptor. Our objective was to determine if HSD3B1(1245C) inheritance is associated with increased 3-keto-5α-abiraterone synthesis in patients. METHODS: First, we characterized the pharmacokinetics of 7 steroidal abiraterone metabolites in 15 healthy volunteers. Second, we determined the association between serum 3-keto-5α-abiraterone levels and HSD3B1 genotype in 30 patients treated with abiraterone acetate (AA) after correcting for the determined pharmacokinetics. RESULTS: Patients who inherit 0, 1, and 2 copies of HSD3B1(1245C) have a stepwise increase in normalized 3-keto-5α-abiraterone (0.04 ng/ml, 2.60 ng/ml, and 2.70 ng/ml, respectively; P = 0.002). CONCLUSION: Increased generation of 3-keto-5α-abiraterone in patients with HSD3B1(1245C) might partially negate abiraterone benefits in these patients who are otherwise more likely to benefit from CYP17A1 inhibition. FUNDING: Prostate Cancer Foundation Challenge Award, National Cancer Institute.

Quantitation of the anticancer drug abiraterone and its metabolite Δ(4)-abiraterone in human plasma using high-resolution mass spectrometry.

Abiraterone acetate is administered as a prodrug to patients with metastatic, castration-resistant prostate cancer (mCRPC) and is readily metabolized into the potent 17a-hydroxylase/17,20-lyase (CYP17) enzyme inhibitor and androgen receptor inhibitor abiraterone and Δ(4)-abiraterone (D4A), respectively. To investigate pharmacokinetic variability in abiraterone acetate metabolism we developed highly sensitive liquid chromatography/mass spectrometry (LC/MS) assays for the simultaneous quantitation of abiraterone and D4A in human plasma using high-resolution mass spectrometry (HRMS) on an Orbitrap mass spectrometer. This study demonstrates the quantitative performance of HRMS and compares the conventional Parallel Reaction Monitoring (PRM) mode of quantitation with the unconventional Full scan MS mode conducted at high resolution (>70,000 resolution). The use of HRMS for quantitation of abiraterone and D4A yielded assays that were linear over a broad concentration range (0.074-509.6 ng/mL for abiraterone; 0.075-59.93 ng/mL for D4A) in both Full scan MS and PRM modes. The assay precision for abiraterone and D4A was below 5% in PRM mode and 7% in Full scan MS mode. Accuracies fell within 98-107% for abiraterone and 104-112% for D4A in PRM mode, and 96-116% for abiraterone and 96-105% for D4A in Full scan MS mode, each meeting the acceptance criteria of FDA approved guidelines for bioanalytical methods The PRM analysis of abiraterone and D4A provided high specificity and reduced background interference, however the Full scan MS detection at a resolution of 70,000 was advantageous in that it required minimal optimization, was simple to implement, yielded comparable quantitative characteristics to PRM and the data is useful for re-analysis. Use of the assays were demonstrated for quantitation of these metabolites in steady state trough level plasma of seventeen (17) patients with mCRPC, demonstrating the inter-patient variability of up to 10-fold concentration.

Prospective International Randomized Phase II Study of Low-Dose Abiraterone With Food Versus Standard Dose Abiraterone In Castration-Resistant Prostate Cancer.

Purpose Abiraterone acetate (AA) is a standard of care for metastatic castration-resistant prostate cancer (CRPC). Despite a large food effect, AA was administered under fasting conditions in its pivotal trials. We sought to test the hypothesis that low-dose AA (LOW; 250 mg with a low-fat meal) would have comparable activity to standard AA (STD; 1,000 mg fasting) in patients with CRPC. Patients and Methods Patients (n = 72) with progressive CRPC from seven institutions in the United States and Singapore were randomly assigned to STD or LOW. Both arms received prednisone 5 mg twice daily. Prostate-specific antigen (PSA) was assessed monthly, and testosterone/dehydroepiandrosterone sulfate were assessed every 12 weeks with disease burden radiographic assessments. Plasma was collected for drug concentrations. Log change in PSA, as a pharmacodynamic biomarker for efficacy, was the primary end point, using a noninferiority design. Progression-free survival (PFS), PSA response (≥ 50% reduction), change in androgen levels, and pharmacokinetics were secondary end points. Results Thirty-six patients were accrued to both arms. At 12 weeks, there was a greater effect on PSA in the LOW arm (mean log change, -1.59) compared with STD (-1.19), and noninferiority of LOW was established according to predefined criteria. The PSA response rate was 58% in LOW and 50% in STD, and the median PFS was approximately 9 months in both groups. Androgen levels decreased similarly in both arms. Although there was no difference in PSA response or PFS, abiraterone concentrations were higher in STD. Conclusion Low-dose AA (with low-fat breakfast) is noninferior to standard dosing with respect to PSA metrics. Given the pharmacoeconomic implications, these data warrant consideration by prescribers, payers, and patients. Additional studies are indicated to assess the long-term efficacy of this approach.

Phase I/II trial of cabazitaxel plus abiraterone in patients with metastatic castration-resistant prostate cancer (mCRPC) progressing after docetaxel and abiraterone.

Background: Abiraterone and cabazitaxel improve survival in patients with metastatic castration-resistant prostate cancer (mCRPC). We conducted an open-label phase I/II trial of cabazitaxel plus abiraterone to assess the antitumor activity and tolerability in patients with progressive mCRPC after docetaxel (phase I), and after docetaxel and abiraterone (phase II) (NCT01511536). Patients and methods: The primary objectives were to determine the maximum tolerated dose (MTD) and dose-limiting toxicities (DLTs) of cabazitaxel plus abiraterone (phase I), and the prostate-specific antigen (PSA) response defined as a ≥ 50% decrease confirmed ≥3 weeks later with this combination (phase II). Results: Ten patients were enrolled in the phase I component; nine were evaluable. No DLTs were identified. The MTD was established as the approved doses for both drugs (cabazitaxel 25 mg/m2 every 3 weeks and abiraterone 1000 mg once daily). Daily abiraterone treatment did not impact on cabazitaxel clearance. Twenty-seven patients received cabazitaxel plus abiraterone plus prednisone (5 mg twice daily) in phase II. The median number of cycles administered (cabazitaxel) was seven (range: 1-28). Grade 3-4 treatment-emergent adverse events included asthenia (in 5 patients; 14%), neutropenia (in 5 patients; 14%) and diarrhea (in 3 patients; 8%). Nine patients (24%) required dose reductions of cabazitaxel. Of 26 evaluable patients, 12 achieved a PSA response [46%; 95% confidence interval (CI): 26.6-66.6%]. Median PSA-progression-free survival was 6.9 months (95% CI: 4.1-10.3 months). Of 14 patients with measurable disease at baseline, 3 (21%) achieved a partial response per response evaluation criteria in solid tumors. Conclusions: The combination of cabazitaxel and abiraterone has a manageable safety profile and shows antitumor activity in patients previously treated with docetaxel and abiraterone.

Relation between plasma trough concentration of abiraterone and prostate-specific antigen response in metastatic castration-resistant prostate cancer patients.

BACKGROUND: Abiraterone (ABI) is a major oral agent for the treatment of metastatic castration-resistant prostate cancer (mCRPC) patients but its systemic exposure is subject to a large inter-individual variability. We aimed to explore the relationship between ABI trough plasma concentration and prostate-specific antigen (PSA) response in mCRPC patients and to identify the critical determinants for its activity. PATIENTS AND METHODS: This is a monocentric prospective observational study in mCRPC patients treated with ABI. The plasmatic concentration of ABI at steady state was measured using liquid chromatography with fluorescence detection. The primary objective was to study the relationship between mean ABI plasma exposure (ABI Cmin) and 3-month PSA response. RESULTS: From 2012 to 2016, 61 mCRPC patients were eligible for pharmacokinetic/pharmacodynamic assessment. Thirty-eight patients experienced PSA response (62%, [confidence interval {CI} 95% 50-78]). In univariate analysis, ABI Cmin was 1.5-fold higher in responders: 12.0 ng/mL (CI 95% 9.4-15.6) versus 8.0 ng/mL (CI 95% 5.8-11.6; P = 0.0015). In multivariate analysis, only ABI Cmin was independently associated with PSA response (odds ratio = 1.12 [CI 95% 1.01-1.25], P = 0.004). By receiver operating characteristic analysis, the optimal threshold for ABI Cmin was 8.4 ng/mL. Progression-free survival (PFS) was significantly higher in patients with ABI Cmin above 8.4 ng/mL (hazard ratio 0.55, [CI 95% 0.31-0.99], 12.2 [CI 95% 9.2-19.5] versus 7.4 [CI 95% 5.5-14.7] months otherwise, P = 0.044). CONCLUSIONS: We showed that ABI trough concentration correlates with PSA response and PFS. Moreover, we could determine a cut-off value of plasmatic concentration for PSA response. Altogether, ABI concentration monitoring appears as a new approach to improve clinical outcome in mCPRC patients.

Drospirenone intake alters plasmatic steroid levels and cyp17a1 expression in gonads of juvenile sea bass.

Drospirenone (DRO) is one of the most widely used progestins in contraceptive treatments and hormone replacement therapies. The pharmacokinetics and potential toxicological effects of DRO were investigated in juvenile sea bass (Dicentrarchus labrax) exposed through the diet (0.01-10 µg DRO/g) for up to 31 days. DRO was detected in the blood (4-27 ng/mL) of fish exposed to the highest concentration, with no significant bioaccumulation over time and no alteration of hepatic metabolizing enzymes, namely, CYP1A and CYP3A-catalysed activities and UDP-glucuronyltransferase (UGT). Pregnenolone (P5), progesterone (P4), 17α-hydroxyprogesterone (17P4), 17α-hydroxypregnenolone (17P5), androstenedione (AD) and testosterone (T) were determined in plasma and gene expression of cyp17a1, cyp19a1a and cyp11ß analysed by qRT-PCR in gonads. The significant increase in plasmatic levels of 17P5, 17P4 and AD detected after 31 days exposure to 10 ng DRO/g together with the increased expression of cyp17a1 in females evidence the ability of DRO to alter steroid synthesis at low intake concentrations (7 ng DRO/day). However, the potential consequences of this steroid shift for female reproduction remain to be investigated.

Pharmacokinetic interaction between the CYP3A4 inhibitor ketoconazole and the hormone drospirenone in combination with ethinylestradiol or estradiol.

AIMS: The present study was conducted to investigate the influence of the strong CYP3A4 inhibitor ketoconazole (KTZ) on the pharmacokinetics of drospirenone (DRSP) administered in combination with ethinylestradiol (EE) or estradiol (E2). METHODS: This was a randomized, multicentre, open label, one way crossover, fixed sequence study with two parallel treatment arms. A group sequential design allowed terminating the study for futility after first study cohort. About 50 healthy young women were randomized 1 : 1 to 'DRSP/EE' or 'DRSP/E2'. Subjects in the 'DRSP/EE' group received DRSP 3 mg/EE 0.02 mg (YAZ®, Bayer) once daily for 21 to 28 days followed by DRSP 3 mg/EE 0.02 mg once daily plus KTZ 200 mg twice daily for 10 days. Subjects in the 'DRSP/E2' group received DRSP 3 mg/E2 1.5 mg (research combination) once daily for 21 to 28 days followed by DRSP 3 mg/E2 1.5 mg once daily plus KTZ 200 mg twice daily for 10 days. RESULTS: Oral co-administration of DRSP/EE or DRSP/E2 and KTZ resulted in an increase in DRSP exposure (AUC(0,24 h)) in both treatment groups: DRSP/EE group: 2.68-fold DRSP increase (90% CI 2.44, 2.95); DRSP/E2 group: 2.30-fold DRSP increase (90% CI 2.08, 2.54). EE and estrone (metabolite of E2) exposures were increased ~1.4-fold whereas E2 exposure was largely unaffected by KTZ co-administration. CONCLUSIONS: A moderate pharmacokinetic drug-drug interaction between DRSP and KTZ was demonstrated in this study. No relevant changes of medical concern were detected in the safety data collected in this study.

Pharmacokinetics of abiraterone in healthy Japanese men: dose-proportionality and effect of food timing.

PURPOSE: Abiraterone acetate (AA) was recently approved for castration-resistant prostate cancer in Japan. Two phase 1 studies were conducted to assess the pharmacokinetics of abiraterone after single-dose administration in Japanese healthy men and to evaluate the effects of food timing on abiraterone pharmacokinetics after single-dose administration of AA in Japanese and Caucasian healthy men. METHODS: In the dose-proportionality study, subjects (n = 30 Japanese) were randomly assigned to receive single doses of 250, 500, and 1,000 mg AA, and in the food-timing study, subjects (n = 22 Japanese and n = 23 Caucasian) randomly received single doses of 1,000 mg AA under fasted (overnight) and three different modified fasting conditions. RESULTS: Mean C(max) and AUC(∞) for abiraterone increased dose-dependently in Japanese healthy men; however, 90 % confidential interval (CI) was outside the predefined dose-proportionality criteria. Based on geometric mean ratios and 90 % CIs (versus overnight fasting condition), abiraterone exposure (AUC) increased significantly with dosing 1 h premeal, 2 h postmeal, or in between two meals 4 h apart by 57 %, 595 %, and 649 %, respectively. CONCLUSION: No clinically meaningful difference was observed in the pharmacokinetics of abiraterone between Caucasian and Japanese subjects.

Clinical trial simulation to evaluate population pharmacokinetics and food effect: capturing abiraterone and nilotinib exposures.

The objectives of this study were to determine (1) the accuracy with which individual patient level exposure can be determined and (2) whether a known food effect can be identified in a trial simulation of a typical population pharmacokinetic trial. Clinical trial simulations were undertaken using NONMEM VII to assess a typical oncology pharmacokinetic trial design. Nine virtual trials for each compound were performed for combinations of different levels of between-occasion variability, number of patients in the trial, and magnitude of a food covariate on oral clearance. Less than 5% and 20% bias and precision were obtained in individual clearance estimated for both abiraterone and nilotinib using this design. This design resulted in biased and imprecise population clearance estimates for abiraterone. The between-occasion variability in most trials was captured with less than 30% of percent bias and precision. The food effect was detectable as a statistically significant covariate on oral clearance for abiraterone and nilotinib with percent bias and precision of the food covariate less than 20%. These results demonstrate that clinical trial simulation can be used to explore the ability of specific trial designs to evaluate the power to identify individual and population level exposures, covariate, and variability effects.