Quantitative determination of proxalutamide in rat plasma and tissues using liquid chromatography/tandem mass spectrometry.

RATIONALE: Proxalutamide is a novel drug for the treatment of prostate cancer. However, to date, there are almost no reports on the pharmacokinetics of proxalutamide in vivo. This study developed a liquid chromatography/tandem mass spectrometry (LC/MS/MS) method to determine the concentrations of proxalutamide in biological samples for pharmacokinetic studies. METHODS: Chromatographic separation was achieved on a Kromasil 100-5C8 column followed by gradient elution using a Shimadzu HPLC system. MS was performed in positive ion electrospray ionization mode using a SCIEX API 4000 triple quadrupole system. A simple and rapid one-step protein precipitation method was used for sample processing, and a low sample volume of 10 µL was used for processing and analysis. RESULTS: The method was validated to show good selectivity, sensitivity, precision, and accuracy. Good linearity (r2 > 0.99) was observed for rat plasma (range: 2-5000 ng/mL) and rat tissue homogenates (range: 2-2000 ng/mL). The extraction recovery was above 98%, and no significant matrix effect was observed. This method was successfully applied to investigate the pharmacokinetics and tissue distribution of proxalutamide in rats. CONCLUSIONS: A rapid and sensitive LC/MS/MS method was developed and validated to determine the quantity of proxalutamide in rat plasma and tissue homogenates and to further study the pharmacokinetic parameters of proxalutamide in a rat model. The results showed that proxalutamide had good oral bioavailability and wide tissue distribution in vivo.

A novel dried blood spot LC-MS/MS method for the quantification of apalutamide in mouse whole blood: Application to pharmacokinetic study in mice.

A simple, sensitive and rapid assay method has been developed and validated for the estimation of apalutamide on mouse dried blood spots (DBS) using liquid chromatography coupled to tandem mass spectrometry with electrospray ionization in the positive-ion mode. The method utilizes liquid extraction of apalutamide from 3 mm punched disks from DBS cards (spiked or study samples). The extracted sample was chromatographed on an Atlantis dC18 column using gradient elution with 0.2% formic acid and acetonitrile at a flow rate of 1.00 mL/min. The total run time was 3.0 min. The MS/MS ion transitions monitored were m/z 478 → 450 for apalutamide and m/z 481 → 453 for the IS (apalutamide-d3 ). Method validation was performed as per regulatory guidelines. The assay was linear in the range of 0.95-2030 ng/mL. The intra- and inter-day precisions were in the ranges of 2.37-8.53 and 6.76-11.5%, respectively. Stability studies showed that apalutamide was stable on DBS cards for one month. This novel method has been applied to analyze the DBS samples of apalutamide obtained from a pharmacokinetic study in mice.

Validation of an LC-ESI-MS/MS method for the determination of apalutamide, a novel non-steroidal anti-androgen in mice plasma and its application to a pharmacokinetic study in mice.

A sensitive, specific, selective and rapid LC-ESI-MS/MS method has been developed and validated for the quantification of apalutamide in mice plasma using apalutamide-d3 as an internal standard (I.S.). Sample preparation was accomplished through a simple protein precipitation process. Chromatography of apalutamide and the I.S. was achieved on an Atlantis dC18 column using an isocratic mobile phase comprising 0.2% formic acid in water and acetonitrile (20:80, v/v) delivered at a flow rate of 0.8 mL/min. LC-MS/MS was operated under the multiple reaction-monitoring mode (MRM) using the electrospray ionization technique in positive ion mode and the transitions of m/z 478 → 450 and m/z 481 → 453 were used to measure the derivative of apalutamide and the I.S, respectively. The total chromatographic run time was 2.5 min and the elution of apalutamide and I.S. occurred at 1.10 and 1.09 min, respectively. Method validation was performed as per regulatory guidelines and the results met the acceptance criteria. Linearity was established in the concentration range of 1.02-2030 ng/mL (r > 0.995) for apalutamide. The intra- and inter-day accuracy and precision for apalutamide in mice plasma were in the range of 2.11-8.44 and 2.51-6.09%, respectively. Apalutamide was found to be stable under various stability conditions. This novel method has been applied to a pharmacokinetic study in mice.

Microenvironmental pH-modified solid dispersions to enhance the dissolution and bioavailability of poorly water-soluble weakly basic GT0918, a developing anti-prostate cancer drug: preparation, characterization and evaluation in vivo.

The aim of the present work was to design a pH-modified solid dispersion (pH(M)-SD) that can improve the dissolution and bioavailability of poorly water-soluble weakly basic GT0918, a developing anti-prostate cancer drug. To select the appropriate acidifiers, a solubility test was carried out first. Solid dispersions (SDs) containing GT0918 and polyvinylpyrrolidone (PVP) were prepared using a solvent evaporation method and were characterized using dissolution studies in different media. The solid states of the SDs were investigated using scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC) and Fourier transformed infrared spectroscopy (FTIR). The in vivo pharmacokinetics of the pH(M)-SDs tablets were also studied in beagle dogs compared to the conventional tablets. The optimized pH(M)-SD (GT0918/PVP/citric acid, 1:2:2 weight ratio) exhibited a significant improvement in the dissolution behavior compared to both the physical mixture and the binary SDs. Solid-state characterization revealed that the amorphous formation of GT0918 in the SDs and the strong H-bonding were only found in the pH(M)-SDs containing citric acid. Furthermore, the GT0918-loaded pH(M)-SD tablets showed a higher AUC and a lower tmax compared to the conventional tablets. Accordingly, the pH(M)-SD might be an efficient route for enhancing the dissolution and bioavailability of poorly water-soluble GT0918.

ARN-509: a novel antiandrogen for prostate cancer treatment.

Continued reliance on the androgen receptor (AR) is now understood as a core mechanism in castration-resistant prostate cancer (CRPC), the most advanced form of this disease. While established and novel AR pathway-targeting agents display clinical efficacy in metastatic CRPC, dose-limiting side effects remain problematic for all current agents. In this study, we report the discovery and development of ARN-509, a competitive AR inhibitor that is fully antagonistic to AR overexpression, a common and important feature of CRPC. ARN-509 was optimized for inhibition of AR transcriptional activity and prostate cancer cell proliferation, pharmacokinetics, and in vivo efficacy. In contrast to bicalutamide, ARN-509 lacked significant agonist activity in preclinical models of CRPC. Moreover, ARN-509 lacked inducing activity for AR nuclear localization or DNA binding. In a clinically valid murine xenograft model of human CRPC, ARN-509 showed greater efficacy than MDV3100. Maximal therapeutic response in this model was achieved at 30 mg/kg/d of ARN-509, whereas the same response required 100 mg/kg/d of MDV3100 and higher steady-state plasma concentrations. Thus, ARN-509 exhibits characteristics predicting a higher therapeutic index with a greater potential to reach maximally efficacious doses in man than current AR antagonists. Our findings offer preclinical proof of principle for ARN-509 as a promising therapeutic in both castration-sensitive and castration-resistant forms of prostate cancer.