Rapid and Sensitive LC-MS/MS Assay for Quantitation of Letrozole Using Solid-Phase Extraction from Human Blood Plasma and Its Application to Pharmacokinetic Studies

Synthesis and characterization of new surface modified magnetic nanoparticles and application for the extraction of letrozole from human plasma and analysis with HPLC-fluorescence

Acetic acid-functionalized magnetic nanoparticles modified by (3-amino-propyl)-tri-ethoxy silane was synthesized and used as a new solid-phases adsorbent. Infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), x-ray diffraction (XRD), energy-dispersive x-ray spectroscopy (EDX), vibrating sample magnetometer (VSM) and Electrophoretic Light Scattering (ELS) were used to characterize the modified nanoparticles. The molecular interaction between letrozole and nanoparticles (NPs) was studied using density functional theory (DFT) calculations. The developed nanoparticles were applied for dispersive solid-phase extraction of letrozole (an anticancer drug) from human plasma. Extracted letrozole was quantified using an isocratic HPLC/FL method. The extraction efficiency was optimized using one experiment at a time optimization method based on the adsorbent quantity, sample pH, adsorption time, desorption time, and elution solvent type/volume. The analysis method was fully validated according to the FDA guideline for bioanalytical method validation. The linear quantification range was 0.01-1 μg/mL and the lower limit of quantification (LLOQ) was 0.01 μg/mL. Plasma samples of 6 patients were analyzed and the measured letrozole concentrations range was 0.04-0.31 μg/mL. The newly synthesized magnetic nanoparticles were used successfully for the extraction of letrozole from spiked and clinical plasma samples. The developed method is a precise and simple method that is suitable for pharmacokinetic studies and clinical applications.

Evaluation of the pharmacokinetics of the simultaneous quantification of letrozole and palbociclib in rat plasma by a developed and validated HPLC–PDA

The US Food and Drug Administration (FDA) has affirmed the use of letrozole (LTZ) combined with palbociclib (PLB) to treat breast malignant tumor growth in postmenopausal women. A straightforward and extremely sensitive reversed-phase high-performance liquid chromatography method with photodiode array detection (RP-HPLC–PDA) was created and validated for the simultaneous determination of LTZ and PLB in rat plasma. The parameters used to give the best separation were a C18 column (150 mm × 4.6 mm, 3.5 μm) as the stationary phase with an isocratic mobile phase composed of methanol–30 mM ammonium acetate at a ratio of 60:40 (v/v), pH = 5.5, a flow rate of 0.8 mL/min, and detection wavelengths of 240 and 220 nm for LTZ and PLB, respectively. The developed method was assessed by the FDA rules over a range of 10–600 ng/mL for LTZ and PLB. The mean of %recovery of LTZ and PLB extracted from rat plasma by acetonitrile-based deproteinization was 91.06 ± 2.73 and 90.30 ± 1.95%, respectively, and the limits of detection were 5 ng/mL for LTZ and 7 ng/mL for PLB in rat plasma. The mean values of Tmax and Cmax were 6 ± 0.00 h and 266.96 ± 21.23 ng/mL for LTZ and 4 ± 0.00 h and 508.75 ± 61.56 ng/mL for PBL, respectively, after intraperitoneal administration of both drugs to rats. The developed HPLC–PDA method was demonstrated to be robust and was effectively applied to study the pharmacokinetics of LTZ and PLB in rat plasma.

Simultaneous quantification of palbociclib, ribociclib and letrozole in human plasma by a new LC-MS/MS method for clinical application

A novel LC-MS/MS method was developed for the quantification of the new cyclin dependent kinase inhibitors (CDKIs) palbociclib and ribociclib and the aromatase inhibitor letrozole used in combinatory regimen. The proposed method is appropriate to be applied in clinical practice due to the simple and fast sample preparation based on protein precipitation, the low amount of patient sample necessary for the analysis (10 μL) and the total run time of 6.5 min. It was fully validated according to FDA and EMA guidelines on bioanalytical method validation. The linearity was assessed (R2 within 0.9992-0.9983) over the concentration ranges of 0.3-250 ng/mL for palbociclib, 10-10000 ng/mL for ribociclib and 0.5-500 ng/mL for letrozole that properly cover the therapeutic plasma concentrations. A specific strategy was implemented to reduce the carryover phenomenon, formerly known for these CDKIs. This method was applied to quantify the Cmin of palbociclib, ribociclib and letrozole in plasma samples from patients enrolled in a clinical study. The same set of study samples was analysed twice in separate runs to assess the reproducibility of the method by means of the incurred samples reanalysis. The results corroborated the reliability of the analyte concentrations obtained with the bioanalytical method, already proved by the validation process. The percentage differences were always within ±10% for all the analytes and the R2 of the correlation graph between the two quantifications was equal to 0.9994.

A Review on Liquid Chromatography-Tandem Mass Spectrometry Methods for Rapid Quantification of Oncology Drugs

In the last decade, the tremendous improvement in the sensitivity and also affordability of liquid chromatography-tandem mass spectrometry (LC-MS/MS) has revolutionized its application in pharmaceutical analysis, resulting in widespread employment of LC-MS/MS in determining pharmaceutical compounds, including anticancer drugs in pharmaceutical research and also industries. Currently, LC-MS/MS has been widely used to quantify small molecule oncology drugs in various biological matrices to support preclinical and clinical pharmacokinetic studies in R&D of oncology drugs. This mini-review article will describe the state-of-the-art LC-MS/MS and its application in rapid quantification of small molecule anticancer drugs. In addition, efforts have also been made in this review to address several key aspects in the development of rapid LC-MS/MS methods, including sample preparation, chromatographic separation, and matrix effect evaluation.

SPE-UPLC-MS/MS assay for determination of letrozole in human plasma and its application to bioequivalence study in healthy postmenopausal Indian women

A rapid and sensitive ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method is described for determination of letrozole in human plasma. Following solid phase extraction (SPE) of letrozole and letrozole-d4 on Orochem DVB-LP cartridges, chromatography was performed on Acquity UPLC BEH C₁₈ (50 mm×2.1 mm, 1.7 µm) column using methanol-0.1% formic acid in water (85:15, v/v) as the mobile phase. Detection was carried out on a triple quadrupole mass spectrometer with an electrospray source, operated under positive ionization mode. Quantitation of letrozole and letrozole-d4 was done using multiple reaction monitoring (MRM) following the transitions at m/z 286.2→217.0 and m/z 290.2→221.0, respectively. The calibration plots were linear through the concentration range of 0.10-100 ng/mL (r²≥0.9990) using 100 µL human plasma. The extraction recovery of letrozole ranged from 94.3% to 96.2% and the intra-batch and inter-batch precision was ≤5.2%. The method was successfully applied to a bioequivalence study of letrozole after oral administration of 2.5 mg tablet formulation to 16 healthy postmenopausal Indian women. The assay reproducibility was also established through incurred sample reanalysis (ISR) of 74 subject samples.