Development and Validation of a Quantitative LC-MS/MS Method for CDK4/6 Inhibitors Palbociclib, Ribociclib, Abemaciclib, and Abemaciclib-M2 in Human Plasma

Therapeutic Monitoring of Palbociclib, Ribociclib, Abemaciclib, M2, M20, and Letrozole in Human Plasma: A Novel LC-MS/MS Method

BACKGROUND

Therapeutic drug monitoring (TDM) using cyclin-dependent kinase inhibitors (CDK4/6is) is a novel approach for optimizing treatment outcomes. Currently, palbociclib, ribociclib, and abemaciclib are the available CDK4/6is and are primarily coadministered with letrozole. This study aimed to develop and validate an LC-MS/MS method for the simultaneous analysis of CDK4/6is, 2 active metabolites of abemaciclib (M2 and M20), and letrozole in human plasma for use in TDM studies.

METHODS

Sample pretreatment comprised protein precipitation with methanol and dilution of the supernatant with an aqueous mobile phase. Chromatographic separation was achieved using a reversed-phase XBridge BEH C18 column (2.5 μm, 3.0 × 75 mm XP), with methanol serving as the organic mobile phase and pyrrolidine-pyrrolidinium formate (0.005:0.005 mol/L) buffer (pH 11.3) as the aqueous mobile phase. A triple quadrupole mass spectrometer was used for the detection, with the ESI source switched from negative to positive ionization mode and the acquisition performed in multiple reaction monitoring mode.

RESULTS

The complete validation procedure was successfully performed in accordance with the latest regulatory guidelines. The following analytical ranges (ng/mL) were established for the tested compounds: 6-300, palbociclib and letrozole; 120-6000, ribociclib; 40-800, abemaciclib; and 20-400, M2 and M20. All results met the acceptance criteria for linearity, accuracy, precision, selectivity, sensitivity, matrix effects, and carryover. A total of 85 patient samples were analyzed, and all measured concentrations were within the validated ranges. The percent difference for the reanalyzed samples ranged from -11.2% to 7.0%.

CONCLUSIONS

A simple and robust LC-MS/MS method was successfully validated for the simultaneous quantification of CDK4/6is, M2, M20, and letrozole in human plasma. The assay was found to be suitable for measuring steady-state trough concentrations of the analytes in patient samples.

Dispersive liquid-liquid microextraction followed by sweeping micellar electrokinetic chromatography-tandem mass spectrometry for determination of six breast cancer drugs in human plasma

Herein, we have developed a novel method of aqueous-sample dispersive liquid-liquid microextraction (AqS-DLLME) followed by sweeping micellar electrokinetic chromatography-tandem mass spectrometry (MEKC-MS/MS) for simultaneous determination of breast cancer drugs letrozole, anastrozole, palbociclib, ribociclib, abemaciclib, and fulvestrant in human plasma. Coupling of MEKC to MS was possible due to the use of ammonium perfluorooctanoate (APFO) as a volatile surfactant. The MEKC and MS conditions were optimized to achieve a fast, sensitive, selective, and green analysis enabling full separation of the analytes within 16 min. Electrophoretic buffer was 125 mM APFO at apparent pH 10.5 in 32 % MeOH, while sheath liquid was 70 % MeOH with 0.2 % formic acid, delivered at 10 µL/min. Excellent extraction recoveries from plasma ranging from 89.4 to 104.9 % were obtained with a combination of protein precipitation and DLLME. The developed method was validated according to the ICH guidelines. Remarkable selectivity, accuracy (bias < 6.7 %), precision (RSD < 15.8 %), and stability (bias < 10.4 %) with insignificant matrix effect (RSD < 14.0 %) and no carry-over were obtained over a wide range of concentrations. Linearity with inter-day slope RSD lower than 8.7 % was demonstrated. With this method, very low concentrations could be detected after the injection of only 68.7 nL of the sample. The method was applied to plasma samples from six women currently receiving breast cancer treatment. Determined concentrations of the drugs of interest agreed with concentrations found in clinical studies, thus proving the suitability of the developed method for therapeutic drug monitoring as a superior alternative to published LC-MS methods.

Recent Contributions of Mass Spectrometry-Based "Omics" in the Studies of Breast Cancer

Breast cancer (BC) is one of the most heterogeneous groups of cancer. As every biotype of BC is unique and presents a particular "omic" signature, they are increasingly characterized nowadays with novel mass spectrometry (MS) strategies. BC therapeutic approaches are primarily based on the two features of human epidermal growth factor receptor 2 (HER2) and estrogen receptor (ER) positivity. Various strategic MS implementations are reported in studies of BC also involving data independent acquisitions (DIAs) of MS which report novel differential proteomic, lipidomic, proteogenomic, phosphoproteomic, and metabolomic characterizations associated with the disease and its therapeutics. Recently many "omic" studies have aimed to identify distinct subsidiary biotypes for diagnosis, prognosis, and targets of treatment. Along with these, drug-induced-resistance phenotypes are characterized by "omic" changes. These identifying aspects of the disease may influence treatment outcomes in the near future. Drug quantifications and characterizations are also done regularly and have implications in therapeutic monitoring and in drug efficacy assessments. We report these studies, mentioning their implications toward the understanding of BC. We briefly provide the MS instrumentation principles that are adopted in such studies as an overview with a brief outlook on DIA-MS strategies. In all of these, we have chosen a model cancer for its revelations through MS-based "omics".

Simple and rapid quantification of ribociclib in rat plasma by protein precipitation and LC-MS/MS: An application to pharmacokinetics of ribociclib nanoparticles in rats

Ribociclib is a cyclin-dependent kinase (CDK4/6) inhibitor and is a standard of care for treating metastatic breast cancer. The drug has moderate oral bioavailability and exhibits permeability-controlled absorption. Novel formulations to enhance ribociclib pharmacokinetics are being developed and tested in rats. This requires developing analytical assays for quantifying ribociclib monitoring in rat plasma. We present a fully validated, sensitive, and simple LC-MS/MS method for measuring ribociclib in rat plasma. Ribociclib-D6 was utilized as an internal standard, and a simple protein precipitation procedure with acetonitrile was used in sample preparation. Excellent assay linearity was observed over a standard curve concentration of 1.008-1027.624 ng/mL. Acceptable intra- and inter-day accuracy and reproductivity were demonstrated for ribociclib quality controls (bias and CV% within ±15%). Complete extraction recovery of ribociclib was achieved, and a negligible matrix effect of analyte to internal standard ratio was observed. Ribociclib was stable at various conditions, including bench-top, freeze-thaw, and short-term stability. Overall, the presented method is simple, sensitive, accurate, and precise and was successfully applied to quantify ribociclib in plasma samples from a pharmacokinetic study of ribociclib suspension and nanoparticle formulation in rats.

Optimisation of Solid-Phase Extraction and LC-MS/MS Analysis of Six Breast Cancer Drugs in Patient Plasma Samples

In the development of bioanalytical LC-MS methods for the determination of drugs in plasma samples in a clinical setting, adequate sample preparation is of utmost importance. The main goals are to achieve the selective extraction of the analytes of interest and attain thorough matrix removal while retaining acceptable ecological properties, cost-effectiveness, and high throughput. Solid-phase extraction (SPE) offers a versatile range of options, from the selection of an appropriate sorbent to the optimisation of the washing and elution conditions. In this work, the first SPE method for the simultaneous extraction of six anticancer drugs used in novel therapeutic combinations for advanced breast cancer treatment-palbociclib, ribociclib, abemaciclib, anastrozole, letrozole, and fulvestrant-was developed. The following sorbent chemistries were tested: octylsilyl (C8), octadecylsilyl (C18), hydrophilic-lipophilic balance (HLB), mixed-mode cation-exchange (MCX and X-C), and mixed-mode weak cation-exchange (WCX), with different corresponding elution solvents. The samples were analysed using LC-MS/MS, with a phenyl column (150 × 4.6 mm, 2.5 μm). The best extraction recoveries (≥92.3%) of all analytes were obtained with the C8 phase, using methanol as the elution solvent. The optimised method was validated in the clinically relevant ranges, showing adequate precision (inter-day RSD ≤ 14.3%) and accuracy (inter-day bias -12.7-13.5%). Finally, its applicability was successfully proven by the analysis of samples from breast cancer patients.