A phase I, open-label, single-dose, mass balance study of 14C-labeled abiraterone acetate in healthy male subjects.

1. Metabolic disposition of (14)C-abiraterone acetate (AA), a prodrug of abiraterone was assessed in a phase I, open-label, single-dose (1000 mg, approximately 100 µCi) study in healthy males (18-55 years, N = 8). Blood, urine, and faecal samples were obtained at specified timepoints for determination of abiraterone concentrations in the plasma, total radioactivity (TR), and the metabolite profile. 2. Most plasma AA concentrations were below the limit of quantification. The mean maximum plasma concentration (Cmax) of abiraterone was 10.4 ng/mL, mean area under the plasma concentration-time curve (AUC) from 0 to the last measurable plasma concentration (AUC0-last) was 74.8 ng·h/mL. The exposures for TR in plasma (Cmax = 3429 ng·eq/mL; AUC0-last = 26,683 ng eq·h/mL) and whole blood (Cmax = 1836 ng·eq/mL; AUC0-last = 12,162 ng·eq·h/mL) were >300-fold higher than abiraterone exposure in plasma. The majority of TR resided in the plasma compartment of blood. 3. Main circulating metabolites were abiraterone sulfate and N-oxide abiraterone sulfate. The main metabolite excreted in urine was N-oxide abiraterone sulfate (4.22% of TR). Major components of TR in faeces were unchanged AA (55.3% of TR) and abiraterone (22.3% of TR). Mean recovery of TR in faeces was 87.9%, indicating faeces as primary route of excretion.

Validated RP-HPLC/UV method for the quantitation of abiraterone in rat plasma and its application to a pharmacokinetic study in rats.

A novel, simple, specific, sensitive and reproducible high-performance liquid chromatography (HPLC) assay method has been developed and validated for the estimation of abiraterone (ART) in rat plasma. The analytical procedure involves extraction of ART and diclofenac (internal standard, IS) from rat plasma with a simple liquid-liquid extraction process. The chromatographic analysis was performed on a Waters Alliance system with a Betasil C(18) column maintained at ambient room temperature and an isocratic mobile phase [acetonitrile-water-10 mm potassium dihydrogen phosphate (pH 3.0), 55:5:40, v/v/v] at a flow rate of 1.00 mL/min with a total run time of 10 min. The eluate was monitored using an UV detector set at 255 nm. Method validation was performed as per FDA guidelines and the results met the acceptance criteria. The calibration curve was linear over a concentration range of 93.4-3251 ng/mL (r(2) = 0.997). The intra- and inter-day precisions were 0.56-4.98 and 3.03-7.18, respectively, in rat plasma. The validated HPLC method was successfully applied to a pharmacokinetic study of ART in rats.

New agents for the management of castration-resistant prostate cancer.

OBJECTIVE: To review the activity of 3 new agents approved for the management of advanced castration-resistant prostate cancer (CRPC): sipuleucel-T, cabazitaxel, and abiraterone acetate. DATA SOURCES: Literature was accessed through MEDLINE (1977-June 2012) and abstracts from the American Society of Clinical Oncology (2000-2012) using the terms castration-resistant and hormone-refractory prostate cancer, sipuleucel-T, cabazitaxel, abiraterone, Provenge, Jevtana, and Zytiga. Reference citations from publications identified were also reviewed. STUDY SELECTION AND DATA EXTRACTION: Articles identified from the data sources in English on human subjects were evaluated. DATA SYNTHESIS: Options for patients with CRPC have been limited, with little to offer those who failed or could not tolerate docetaxel-based therapy. Three new drugs, with very different mechanisms of action, have changed that and will undoubtedly change the treatment paradigm for these patients. Each agent has demonstrated an impact on patient survival. Sipuleucel-T, the first immunotherapy approved for treatment of CRPC, improved median overall survival by 4.1 months and reduced the risk of death by 22% in a placebo-controlled trial of asymptomatic patients. Sipuleucel-T can be administered prior to docetaxel-based therapy. Cabazitaxel, a taxane chemotherapy agent, improved median overall survival by 2.4 months and reduced the risk of death by 30% in a Phase 3 trial of patients whose cancer progressed during or after docetaxel-based therapy. Abiraterone acetate, a hormonal therapy, improved median overall survival by 3.9 months and reduced the risk of death by 35% in patients with relapse during or after docetaxel-based therapy. CONCLUSIONS: The advent of new agents for the management of advanced CRPC has increased the choices for patients whose options were limited. Additional experience will determine the optimal sequencing of these agents, their roles in combination therapy, and their activity in patients with earlier disease.

Abiraterone for the treatment of metastatic castrate-resistant prostate cancer.

OBJECTIVE: To review the clinical pharmacology, efficacy, and safety of abiraterone acetate for metastatic castrate-resistant prostate cancer (mCRPC) and evaluate the drug for health-system formulary inclusion. DATA SOURCES: Literature was identified through a search of MEDLINE (1977-February 2012) and International Pharmaceutical Abstracts (1977-February 2012) using the search term abiraterone. References of identified articles were reviewed. STUDY SELECTION AND DATA EXTRACTION: All clinical trials published in English were evaluated. Studies conducted in the setting of mCRPC were included in the literature review. DATA SYNTHESIS: Despite benefits from androgen deprivation for the treatment of prostate cancer, most patients experience disease progression within 12-48 months, a phase described as castrate resistant. Abiraterone is the only Food and Drug Administration-approved hormonal treatment option for mCRPC in men who have received docetaxel and is recommended as a second-line agent for this indication in the National Comprehensive Cancer Network prostate cancer guidelines. One Phase 3 study, 2 Phase 2 studies, and 2 Phase 1 studies conducted in the setting of second-line treatment of mCRPC were identified. Treatment with abiraterone was associated with at least a 50% reduction in prostate-specific antigen (PSA) in 38-51% of patients; PSA progression ranged from 5.6-10.2 months. The only study assessing mortality outcomes found a 13% absolute reduction in mortality (ie, 42% vs 55%; HR 0.65; 95% CI 0.54 to 0.77), relative to placebo, over a median 12.8 months of follow-up. Abiraterone has been compared only to placebo, not to existing treatment options. CONCLUSIONS: Abiraterone provides a moderate improvement in disease progression and mortality in a patient population with limited treatment options. It is recommended to add this medication to outpatient formularies restricted to second-line treatment of mCRPC.

Open-label, phase I, pharmacokinetic studies of abiraterone acetate in healthy men.

PURPOSE: To evaluate pharmacokinetics, safety, and tolerability of abiraterone acetate (AA) in healthy men. METHODS: Two phase I studies (dose-escalation study and dose-proportionality study) were conducted in healthy men aged 18-55 years. All subjects received 4 consecutive single doses of AA (250, 500, 750 and 1,000 mg). The dose-escalation study subjects (N = 33) received AA doses in a sequential manner, starting with the lowest dose. The dose-proportionality study subjects (N = 32) were randomly allocated (1:1:1:1) to receive each of the 4 doses in a four-way crossover design. RESULTS: A dose-related increase in abiraterone exposure was observed in both studies. Over the evaluated dose range, the mean abiraterone maximum plasma concentrations increased from 26 to 112 ng/mL in dose-escalation study and from 40 to 125 ng/mL in dose-proportionality study; the mean area under the plasma concentration-time curve from 0 to the last measurable plasma concentration increased from 155 to 610 ng.h/mL in dose-escalation study, and from 195 to 607 ng.h/mL in dose-proportionality study. In the dose-proportionality study, abiraterone exposure was dose proportional between 1,000 and 750 mg doses; however, the exposure was slightly greater than dose proportional when exposures at 500 and 250 mg doses were compared with the exposure at 1,000 mg. Single doses of AA were well tolerated in healthy men, and safety profile was consistent with its known toxicities in CRPC patients. CONCLUSION: Systemic exposure to abiraterone increased with increasing doses of AA (250-1,000 mg) in healthy men; AA was well tolerated in this population.

Development and validation of a highly sensitive method for the determination of abiraterone in rat and human plasma by LC-MS/MS-ESI: application to a pharmacokinetic study.

A highly sensitive, rapid assay method has been developed and validated for the estimation of abiraterone (ART) in rat and human plasma with liquid chromatography coupled to tandem mass spectrometry and electrospray ionization in the positive-ion mode. The assay procedure involves extraction of ART and phenacetin (internal standard, IS) from rat and human plasma with a simple protein precipitation extraction process. Chromatographic separation was achieved using an isocratic mobile (10 mm ammonium acetate:acetonitrile, 10:90, v/v) at a flow-rate of 0.70 mL/min on an Atlantis dC(18) column maintained at 40 °C with a total run time of 3.5 min. The MS/MS ion transitions monitored were 350.3 → 156.0 for ART and 180.2 → 110.1 for IS. Method validation was performed as per FDA guidelines and the results met the acceptance criteria. The lower limit of quantitation achieved was 0.20 ng/mL and the linearity range extended from 0.20 to 201 ng/mL. The intra- and inter-day precisions were in the ranges 2.39-10.4 and 4.84-9.53% in rat plasma and 3.82-10.8 and 6.97-8.94% in human plasma.

Phase I clinical trial of the CYP17 inhibitor abiraterone acetate demonstrating clinical activity in patients with castration-resistant prostate cancer who received prior ketoconazole therapy.

PURPOSE: Abiraterone acetate is a prodrug of abiraterone, a selective inhibitor of CYP17, the enzyme catalyst for two essential steps in androgen biosynthesis. In castration-resistant prostate cancers (CRPCs), extragonadal androgen sources may sustain tumor growth despite a castrate environment. This phase I dose-escalation study of abiraterone acetate evaluated safety, pharmacokinetics, and effects on steroidogenesis and prostate-specific antigen (PSA) levels in men with CPRC with or without prior ketoconazole therapy. PATIENTS AND METHODS: Thirty-three men with chemotherapy-naïve progressive CRPC were enrolled. Nineteen patients (58%) had previously received ketoconazole for CRPC. Bone metastases were present in 70% of patients, and visceral involvement was present in 18%. Three patients (9%) had locally advanced disease without distant metastases. Fasted or fed cohorts received abiraterone acetate doses of 250, 500, 750, or 1,000 mg daily. Single-dose pharmacokinetic analyses were performed before continuous daily dosing. RESULTS: Adverse events were predominantly grade 1 or 2. No dose-limiting toxicities were observed. Hypertension (grade 3, 12%) and hypokalemia (grade 3, 6%; grade 4, 3%) were the most frequent serious toxicities and responded to medical management. Confirmed > or = 50% PSA declines at week 12 were seen in 18 (55%) of 33 patients, including nine (47%) of 19 patients with prior ketoconazole therapy and nine (64%) of 14 patients without prior ketoconazole therapy. Substantial declines in circulating androgens and increases in mineralocorticoids were seen with all doses. CONCLUSION: Abiraterone acetate was well tolerated and demonstrated activity in CRPC, including in patients previously treated with ketoconazole. Continued clinical study is warranted.

Phase I clinical trial of a selective inhibitor of CYP17, abiraterone acetate, confirms that castration-resistant prostate cancer commonly remains hormone driven.

PURPOSE: Studies indicate that castration-resistant prostate cancer (CRPC) remains driven by ligand-dependent androgen receptor (AR) signaling. To evaluate this, a trial of abiraterone acetate-a potent, selective, small-molecule inhibitor of cytochrome P (CYP) 17, a key enzyme in androgen synthesis-was pursued. PATIENTS AND METHODS: Chemotherapy-naïve men (n = 21) who had prostate cancer that was resistant to multiple hormonal therapies were treated in this phase I study of once-daily, continuous abiraterone acetate, which escalated through five doses (250 to 2,000 mg) in three-patient cohorts. RESULTS: Abiraterone acetate was well tolerated. The anticipated toxicities attributable to a syndrome of secondary mineralocorticoid excess-namely hypertension, hypokalemia, and lower-limb edema-were successfully managed with a mineralocorticoid receptor antagonist. Antitumor activity was observed at all doses; however, because of a plateau in pharmacodynamic effect, 1,000 mg was selected for cohort expansion (n = 9). Abiraterone acetate administration was associated with increased levels of adrenocorticotropic hormone and steroids upstream of CYP17 and with suppression of serum testosterone, downstream androgenic steroids, and estradiol in all patients. Declines in prostate-specific antigen >or= 30%, 50%, and 90% were observed in 14 (66%), 12 (57%), and 6 (29%) patients, respectively, and lasted between 69 to >or= 578 days. Radiologic regression, normalization of lactate dehydrogenase, and improved symptoms with a reduction in analgesic use were documented. CONCLUSION: CYP17 blockade by abiraterone acetate is safe and has significant antitumor activity in CRPC. These data confirm that CRPC commonly remains dependent on ligand-activated AR signaling.

Humoral pathway for local transfer of the priming pheromone androstenol from the nasal cavity to the brain and hypophysis in anaesthetized gilts.

It is generally accepted that pheromones act by stimulating of the dendritic receptors of the olfactory neurones massed in the olfactory epithelium. This study was designed to ascertain whether it is possible for the boar pheromone androstenol (5alpha-androst-16-en-3-ol) to be transported from the nasal cavity of anaesthetized gilts to the brain and hypophysis via local transfer from the blood in the perihypophyseal vascular complex. The experiment was performed on days 18-21 of the porcine oestrous cycle (crossbred gilts, n = 6). Tritiated androstenol (3H-A; total amount 10(8) d.p.m. (758 ng)) was applied for 1 min onto the respiratory part of the nasal mucosa, 4-6 cm from the opening of the nares. Arterial blood samples from the aorta and from the carotid rete were collected every 2 min during the 60 min period following administration of the steroid. Total radioactive venous effluent from the head was removed and an adequate volume of homologous blood was transfused into the heart through the carotid external vein. At the end of the experiment gilts were killed and tissue samples of the hypophysis and some brain structures were collected to measure radioactivity. In addition, corresponding control tissues were collected from three untreated gilts and from three heads of gilts 60 min after 3H-A was applied post mortem into the nasal cavity. The concentration of 3H-A was significantly higher (P < 0.0001) in the arterial blood of the carotid rete than that of aorta. The mean rate of 3H-A counter current transfer from venous to arterial blood in the perihypophyseal vascular complex, expressed as the ratio of the 3H-A concentration in arterial blood of the carotid rete to the 3H-A concentration in blood sampled simultaneously from the aorta, was 1.96 +/- 0.1. The concentration of 3H-A in plasma from the venous effluent from the head ranged from 1.3 to 1.8 pg x ml(-1). During the 60 min period of the experiment, 0.68% of the total applied dose of 3H-A was resorbed from the nasal cavity into the venous blood. Moreover, we found that 3H-A was present in the olfactory bulb (P <0.01), amygdala, septum, hypothalamus, adenohypophysis, neurohypophysis (P > 0.05) and perihypophyseal vascular complex (P < 0.01). These results demonstrate that, in anaesthetized gilts, the boar pheromone androstenol may be resorbed from the nasal mucosa, transferred in the perihypophyseal vascular complex into arterial blood supplying the brain and hypophysis, and then arrested in the hypophysis and certain brain structures. We suggest that in addition to the standard neural pathway for signalling pheromones, another pathway exists whereby androstenol, as a priming pheromone, may be resorbed from the nasal cavity into the bloodstream and then pass locally from the perihypophyseal vascular complex into the arterial blood supplying the brain and hypophysis, thus avoiding the first passage metabolism in the liver.

Biotransformation XLVII: transformations of 5-ene steroids in Fusarium culmorum culture.

The course of the transformation of six 5-ene steroids with varying substituents at C-17 or/and C-3: dehydroepiandrosterone (DHEA), 5-androsten-3beta,17beta-diol, 17alpha-methyl-5-androsten-3beta,17beta-diol, 5-androsten-17-one, 5-androsten-3beta-ol and pregnenolone by Fusarium culmorum was investigated. Three substrates with oxygen functions at C-3 and C-17 i.e. DHEA, 5-androsten-3beta,17beta-diol and 17alpha-methyl-5-androsten-3beta,17beta-diol were hydroxylated entirely at 7alpha-axial, allylic position. The mixture of 7alpha-hydroxy- and 7alpha,15alpha-dihydroxyderivatives was formed during the transformation of pregnenolone and 5-androsten-17-one, from the latter 2alpha,7alpha-dihydroxyderivative was also obtained. 7alpha,15alpha- Dihydroxyderivative was the only product isolated from the 5-androsten-3beta-ol post-transformation mixture. The time-course of the DHEA transformation by F. culmorum shows that the substrate induces 7alpha-hydroxylase activity. DHEA was transformed by androstenedione induced F. culmorum cultures to a larger extent than by a noninduced microorganism; the selectivity of the transformation remained unchanged.

Humoral pathway for transfer of the boar pheromone, androstenol, from the nasal mucosa to the brain and hypophysis of gilts.

Signaling and priming pheromones play an important role in intraspecies behavioral and sexual interactions and in the control of reproduction. It is generally accepted that pheromones act by stimulating the dendritic receptors in the mucus-imbedded cilia of olfactory neurons massed in the olfactory epithelium. The boar pheromone androstenol, known to induce sexual behavior in pigs, is 1 of 2 pheromones that have been chemically defined, tritiated and thus made available for use in studies. In Experiment 1, sexually mature cyclic gilts at Days 16 to 21 of the estrous cycle were humanely killed and the heads separated from the bodies. The heads were attached to a perfusion system using heated, oxygenated, heparinized, autologous blood. A total amount of 10(8) dpm (758 ng) of 3H-5 alpha-androstenol (3HA) was either infused into the angularis oculi veins that drain the nasal cavities (n = 7) over a 5-min period or applied through intranasal catheters onto the mucose surface (n = 16) for 2 min. In both groups frequent blood samples were collected from the carotid rete and from venous effluent. Concentration of 3HA in the arterial blood of the carotid rete after direct (into angularis oculi veins) or indirect (onto the nasal mucosa) administration of 3HA into veins draining the nasal cavities was significantly higher than background radioactivity before 3HA administration (P < 0.0001 and P < 0.05, respectively). The 3HA was selectively accumulated (compared with the respective control tissue) in the neurohypophysis (P < 0.001), adenohypophysis (P < 0.01), ventromedial hypothalamus (P < 0.05), corpus mammillare (P < 0.01), and perihypophyseal vascular complex (P < 0.001). In a second in vitro experiment, active uptake of 3HA into the nasal mucosa of the proximal, respiratory segment of the nasal cavity was observed. These results demonstrate a humoral pathway for the transfer of pheromones from the nasal cavity to the hypophysis and brain. Androstenol was taken up by the respiratory part of the nasal mucosa, resorbed into blood, transported to the cavernous sinus and transferred into the arterial blood of the carotid rete (supplying the hypophysis and brain), and then selectively accumulated in the hypophysis and certain brain structures.

Pharmacology of novel steroidal inhibitors of cytochrome P450(17) alpha (17 alpha-hydroxylase/C17-20 lyase).

Medical or surgical castration for the treatment of prostatic cancers prevents androgen production by the testes, but not by the adrenals. Inhibition of the key enzyme for androgen biosynthesis, cytochrome P450(17) alpha, could prevent androgen production from both sources. The in vivo effects of 17-(3-pyridyl)androsta-5,16-dien-3 beta-ol (CB7598) and 17-(3-pyridyl)androsta-5,16-dien-3-one (CB7627), novel potent steroidal inhibitors of this enzyme, on WHT mice were compared with those of castration and two clinically active compounds, ketoconazole and flutamide. Flutamide and surgical castration caused significant reductions in the weights of the ventral prostate and seminal vesicles. CB7598, in its 3 beta-O-acetate form (CB7630), and CB7627 caused significant reductions in the weights of the ventral prostate, seminal vesicles, kidneys and testes when administered once daily for 2 weeks. Ketoconazole, given on the same schedule, caused no reductions. Plasma testosterone was reduced to < or = 0.1 nM by CB7630, despite a 3- to 4-fold increase in the plasma level of luteinizing hormone. Adrenal weights were unchanged following treatment with CB7630 or CB7627 but were markedly increased following ketoconazole, indicating no inhibition of corticosterone production by these steroidal compounds. These results indicate that CB7598, CB7630 or CB7627 may be useful in the treatment of hormone-dependent prostatic cancers.

[Pharmacokinetics of epostane in rats].

After rats were given (ig) epostane 50, 100 and 200 mg.kg-1, plasma concentrations of epostane were determined by HPLC. According to concentration versus time data, the pharmacokinetic model of epostane in all rats followed a pattern of one-compartment model. The pharmacokinetic parameters of the three doses were found to be as follows: Ka were 0.578 h-1, 0.553 h-1 and 0.439 h-1; K were 0.308 h-1, 0.282 h-1 and 0.224 h-1; T1/2 were 2.27 h, 2.54 h, 3.12 h and AUC were 786.89 micrograms.h.ml-1, 1644.43 micrograms.h.ml-1, and 3335.35 micrograms.h-1.ml-1 respectively. The tissue distribution of epostane in rats were as follows: highest in adrenal, liver, gastrointestinal tract, uterus and ovary; next in kidney, heart, brain, lung and spleen. The peak concentration times were about 3 h and comparable to plasma peak time. Plasma protein binding of epostane was determined by equilibrant dialysis of the plasma of rats given the drug and found that the degree of binding was not correlated with drug dosage under our experimental conditions. Little epostane was found in the bile, urine and feces. It appears that epostane might have undergone extensive biotransformation in the rat body.

[Pharmacokinetics of epostane in rabbits by HPLC method].

Epostane (Epo), a 3 beta-hydroxysteroid dehydrogenase inhibitor, interrupted pregnancy in rats, rhesus monkeys, and women. Epo concentrations in serum were determined by high performance liquid chromatography (HPLC) at 0.25, 0.5, 1, 2, 4, 8, 16, 32, and 48 h after intragastric Epo 96 mg.kg-1 in rabbits. The concentration-time curve exhibited a 2-compartment open model. The pharmacokinetic parameters were: T1/2ka 0.79 +/- 0.08 h, T1/2 alpha 0.96 +/- 0.08 h, T1/2 beta 6.6 +/- 1.5 h, Vc 14 +/- 3 ml.kg-1, AUC 12.0 +/- 1.9 micrograms.h.ml-1, Tmax 1.8 +/- 0.5 h, Cmax 3.3 +/- 0.5 microgram.ml-1. After rat copora luteum were incubated with hCG 10 IU.ml-1 and Epo 10 or 100 micrograms.ml-1 for 18 and 48 h, luteal cells showed various degrees of degeneration and progesterone production was significantly inhibited.