Development, validation and application of a sensitive LC-MS/MS method for the quantification of thalidomide in human serum, cells and cell culture medium

Thalidomide measurement in plasma and dried plasma spot by SPE combined with UHPLC-MS/MS for therapeutic drug monitoring

Aims: To validate an SPE-ultra-HPLC-MS/MS method for thalidomide (THD) measurement in dried plasma spot (DPS). Methods: Extraction included acetonitrile/water clean-up and online SPE. The LOD, LLOQ, linearity, precision, accuracy, recovery, matrix effect, process efficiency, carryover, stability, drug interference and dilution integrity were assessed. Results: The method was linear from 50 to 2000 ng/ml with a LOD of 20 ng/ml and LLOQ of 50 ng/ml. The coefficient of variation for precision was 0.4-7.9% for intra-assay and 1.3-8.9% for interassay and accuracy was 81.4-97.1%. Adequate matrix effect (100.6-107.0%), recovery (88.7-105.0%) and process efficiency (91.3-109.3%) were registered. DPS was stable for 14 days at room temperature and 45°C and for 4 months at -80°C. The method was applied to quantify THD in both wet plasma and DPS from patients with cutaneous lupus receiving THD treatment. The difference between THD wet plasma and DPS concentration was <15%. Conclusion: The method is suitable to quantify THD in DPS.

Establishment of an in vitro method of rabbit embryo toxicity with toxicokinetics study

This report introduces a novel method, rabbit whole embryo culture (WEC) combined with toxicokinetics (TK), for toxicity testing. Rodent WEC has been extensively used for in vitro screening of developmental toxicity. To improve the reliability of in vitro data, it is important to consider TK and species specificity. To test the utility and effectiveness of this method, we investigated the toxic effect of thalidomide on rabbit embryos and its behavior in test systems both in vitro and in vivo under the same experimental condition. The data showed that thalidomide induced embryo malformations such as embryonic brain hypoplasia, short limb buds, and declined embryonic growth both in vitro and in vivo. The toxic effect increased with the increasing exposure of the embryo to thalidomide. In addition, we observed similar toxic effects and exposure-effect relationships in vivo and in vitro. Therefore, we preliminarily conclude that this new method can effectively predict and explain thalidomide toxicity. Furthermore, we investigated the behavior of test compounds in the WEC system for the first time, and this method is expected to be an important technique for in vitro toxicity study after extensive verification.

An Exploration of Advancement in Analytical Methodology for Quantification of Anticancer Drugs in Biomatrices

Significant numbers of newer anticancer drugs are regularly entering into the market worldwide to fight against different types of cancers. Analytical methodologies are being developed to quantitate those molecules in a variety of matrices during their drug development stages. Selection of biological matrices for developing bioanalytical methods is based on the mechanism of action, site of action, site of metabolism and route of excretion of the drugs or their metabolites. In this review, we have described the current scenario and advancements in bioanalytical techniques for quantification of different anticancer drugs in a variety of biomatrices with a special emphasis on sample preparation techniques. We have discussed and summarized different bioanalytical aspects for anticancer drugs, which can give direction to the researcher for choosing appropriate techniques for their quantification needs.

Simultaneous Determination of Thalidomide and Dexamethasone in Rat Plasma by Validated HPLC and HPTLC With Pharmacokinetic Study

Two validated chromatographic methods have been developed for the simultaneous determination of thalidomide (THD) and dexamethasone (DEX) in rat plasma using paracetamol (PAR) as an internal standard (IS). Chromatographic analysis was achieved firstly by HPLC method on C18 column (150 × 4.6 mm2 i.d., 5 μm) and a mobile phase composed of ethanol:water (containing 0.1% acetic acid) (70:30, v/v) at the flow rate of 0.6 mL min-1. The second method was HPTLC method which depended on using a developing system of methylene chloride:acetone:ethyl acetate (7:4:1, by volume). In both methods, PAR was used as an IS. The developed methods have been validated as per FDA guidelines. All parameters were tested using quality control samples (LQC, MQC and HQC). All the obtained parameters were within the acceptance criteria. In the same way, the two methods were successfully used to study the pharmacokinetic parameters of both THD and DEX after their intra-peritoneal administration. Moreover, results obtained after administration of each drug alone were compared to those obtained after their administration together. The drugs showed drug-drug interactions when administered in combination, meaning that monitoring of such combination is very important.

A validated LC-MS/MS method for the simultaneous determination of thalidomide and its two metabolites in human plasma: Application to a pharmacokinetic assay

An accurate and sensitive LC-MS/MS method for determining thalidomide, 5-hydroxy thalidomide and 5'-hydroxy thalidomide in human plasma was developed and validated using umbelliferone as an internal standard. The analytes were extracted from plasma (100 μL) by liquid-liquid extraction with ethyl acetate and then separated on a BETASIL C₁₈ column (4.6 × 150 mm, 5 μm) with mobile phase composed of methanol-water containing 0.1% formic acid (70:30, v/v) in isocratic mode at a flow rate of 0.5 mL/min. The detection was performed using an API triple quadrupole mass spectrometer in atmospheric pressure chemical ionization mode. The precursor-to-product ion transitions m/z 259.1 → 186.1 for thalidomide, m/z 273.2 → 161.3 for 5-hydroxy thalidomide, m/z 273.2 → 146.1 for 5'-hydroxy thalidomide and m/z 163.1 → 107.1 for umbelliferone (internal standard, IS) were used for quantification. The calibration curves were obtained in the concentrations of 10.0-2000.0 ng/mL for thalidomide, 0.2-50.0 ng/mL for 5-hydroxy thalidomide and 1.0-200.0 ng/mL for 5'-hydroxy thalidomide. The method was validated with respect to linear, within- and between-batch precision and accuracy, extraction recovery, matrix effect and stability. Then it was successfully applied to estimate the concentration of thalidomide, 5-hydroxy thalidomide and 5'-hydroxy thalidomide in plasma samples collected from Crohn's disease patients after a single oral administration of thalidomide 100 mg.

Structural basis of lenalidomide-induced CK1α degradation by the CRL4(CRBN) ubiquitin ligase

Thalidomide and its derivatives, lenalidomide and pomalidomide, are immune modulatory drugs (IMiDs) used in the treatment of haematologic malignancies. IMiDs bind CRBN, the substrate receptor of the CUL4-RBX1-DDB1-CRBN (also known as CRL4(CRBN)) E3 ubiquitin ligase, and inhibit ubiquitination of endogenous CRL4(CRBN) substrates. Unexpectedly, IMiDs also repurpose the ligase to target new proteins for degradation. Lenalidomide induces degradation of the lymphoid transcription factors Ikaros and Aiolos (also known as IKZF1 and IKZF3), and casein kinase 1α (CK1α), which contributes to its clinical efficacy in the treatment of multiple myeloma and 5q-deletion associated myelodysplastic syndrome (del(5q) MDS), respectively. How lenalidomide alters the specificity of the ligase to degrade these proteins remains elusive. Here we present the 2.45 Å crystal structure of DDB1-CRBN bound to lenalidomide and CK1α. CRBN and lenalidomide jointly provide the binding interface for a CK1α β-hairpin-loop located in the kinase N-lobe. We show that CK1α binding to CRL4(CRBN) is strictly dependent on the presence of an IMiD. Binding of IKZF1 to CRBN similarly requires the compound and both, IKZF1 and CK1α, use a related binding mode. Our study provides a mechanistic explanation for the selective efficacy of lenalidomide in del(5q) MDS therapy. We anticipate that high-affinity protein-protein interactions induced by small molecules will provide opportunities for drug development, particularly for targeted protein degradation.

Structure of the DDB1-CRBN E3 ubiquitin ligase in complex with thalidomide

In the 1950s, the drug thalidomide, administered as a sedative to pregnant women, led to the birth of thousands of children with multiple defects. Despite the teratogenicity of thalidomide and its derivatives lenalidomide and pomalidomide, these immunomodulatory drugs (IMiDs) recently emerged as effective treatments for multiple myeloma and 5q-deletion-associated dysplasia. IMiDs target the E3 ubiquitin ligase CUL4-RBX1-DDB1-CRBN (known as CRL4(CRBN)) and promote the ubiquitination of the IKAROS family transcription factors IKZF1 and IKZF3 by CRL4(CRBN). Here we present crystal structures of the DDB1-CRBN complex bound to thalidomide, lenalidomide and pomalidomide. The structure establishes that CRBN is a substrate receptor within CRL4(CRBN) and enantioselectively binds IMiDs. Using an unbiased screen, we identified the homeobox transcription factor MEIS2 as an endogenous substrate of CRL4(CRBN). Our studies suggest that IMiDs block endogenous substrates (MEIS2) from binding to CRL4(CRBN) while the ligase complex is recruiting IKZF1 or IKZF3 for degradation. This dual activity implies that small molecules can modulate an E3 ubiquitin ligase and thereby upregulate or downregulate the ubiquitination of proteins.