Systematic Development and Validation of a RP-HPLC Method for Estimation of Abiraterone Acetate and its Degradation Products.

The present study described the development of a reversed-phase liquid chromatographic method for the estimation of abiraterone acetate by Quality by Design (QbD) approach. Using an isocratic solvent system for the mobile phase, the chromatographic estimation of analyte was performed on a Hypersil BDS C18 column using mobile phase mixture containing acetonitrile and water with pH adjusted with 0.1% v/v orthophosphoric acid (15:85%v/v ratio), flow rate 1.0 mL.min-1 and detection at 250 nm using photodiode array detector. Systematic development of the chromatographic method was carried out by factor screening using a half-factorial design which suggested organic modifier (%), flow rate (mL.min-1) and autosampler temperature (°C) as influential variables. Further, the method was optimized by Box-Behnken design and trials performed were evaluated for the area under peak, retention time, theoretical plate count and tailing factor as the responses. Validation of the developed method showed good linearity, accuracy, precision and sensitivity. Evaluation of the stability-indicating profile of the method using forced degradation studies revealed the formation of a possible degradation product under acidic and alkaline conditions, while no such degradation product peaks were observed under the oxidative environment. Overall, the study construed the successful development of HPLC assay method for pharmaceutical applications.

Identification, Characterization and High-Performance Liquid Chromatography Quantification for Process-Related Impurities in Abiraterone Acetate Bulk Drug.

During the synthesis of abiraterone acetate bulk drug in some laboratory batches, two unreported impurities were detected by high-performance liquid chromatography analysis at levels ranging from 0.05 to 0.10% according to the United States Pharmacopeia method. The structures of two impurities were characterized and confirmed by NMR and MS, which were proposed to be [3ß-acetoxy-16-(3ß-acetoxy-androsta-5,16-dien-17-yl)-17-(3-pyridyl)-androsta-5,16-di-ene] and [3ß-acetoxy-16-(3ß-acetoxy-androsta-5,16-dien-17-yl)-17-androsta-5,16-di-ene]. It was proved that these impurities come into being during the preparation process of penultimate intermediate (abiraterone). The newly developed LC-UV method was used to monitor the impurity profile in the penultimate intermediate (abiraterone), which was validated by its satisfactory specificity, precision, accuracy and sensitivity. The probable origin of the impurity was also discussed.

Early PSA response is an independent prognostic factor in patients with metastatic castration-resistant prostate cancer treated with next-generation androgen pathway inhibitors.

BACKGROUND: The optimal use of new therapies in metastatic castration-resistant prostate cancer (mCRPC) remains to be clarified. Prostate-specific antigen (PSA) response used as a pharmacodynamic end-point may help identify patients with early resistance to new androgen receptor-pathway inhibitors. We aimed to determine the clinical significance of early PSA response (EPR) during therapy with enzalutamide, abiraterone acetate (AA) and orteronel in mCRPC. METHODS: Data from patients recruited in clinical trials were studied. PSA values were obtained at baseline and 28 d after treatment initiation. EPR defined as a decline >50% from baseline was calculated according to the Prostate Cancer Working Group 2 criteria. The effects of clinical characteristics on radiographic progression-free survival (rPFS) and overall survival (OS) were examined using the Cox model. RESULTS: EPR was assessed in 118 patients treated in clinical trials and was found to be associated with longer rPFS and OS (P < 0.0001 for both). Median rPFS was 13.9 and 5.6 months (hazard ratio [HR]:0.38, P < 0.001) for patients with and without an EPR, respectively. Median OS was 32.2 months in patients with an EPR and 15.9 months in patients without an EPR (HR: 0.4, P < 0.01). EPR remained prognostic for OS in multivariate analyses (HR: 0.5, p=0.009) that included validated pre-therapeutic prognostic factors for mCRPC. Prognostic values of EPR for rPFS and OS were confirmed in an independent cohort of 95 AA-treated non-trial patients. CONCLUSIONS: EPR is an independent prognostic factor in patients with mCRPC treated with next-generation androgen pathway inhibitors and may be useful for the therapeutic management of these patients.