Transport of thalidomide by the human intestinal caco-2 monolayers

Development of a physiologically based pharmacokinetic model for intravenous lenalidomide in mice

PURPOSE

Lenalidomide is used widely in B-cell malignancies for its immunomodulatory activity. It is primarily eliminated via the kidneys, with a significant proportion of renal elimination attributed to active processes. Lenalidomide is a weak substrate of P-glycoprotein (P-gp), though it is unclear whether P-gp is solely responsible for lenalidomide transport. This study aimed to determine whether the current knowledge of lenalidomide was sufficient to describe the pharmacokinetics of lenalidomide in multiple tissues.

METHODS

A physiologically based pharmacokinetic model was developed using the Open Systems Pharmacology Suite to explore the pharmacokinetics of lenalidomide in a variety of tissues. Data were available for mice dosed intravenously at 0.5, 1.5, 5, and 10 mg/kg, with concentrations measured in plasma, brain, heart, kidney, liver, lung, muscle, and spleen. P-gp expression and activity were sourced from the literature.

RESULTS

The model predictions in plasma, liver, and lung were representative of the observed data (median prediction error 13%, - 10%, and 30%, respectively, with 90% confidence intervals including zero), while other tissue predictions showed sufficient similarity to the observed data. Contrary to the data, model predictions for the brain showed no drug reaching brain tissue when P-gp was expressed at the blood-brain barrier. The data were better described by basolateral transporters at the intracellular wall. Local sensitivity analysis showed that transporter activity was the most sensitive parameter in these models for exposure.

CONCLUSION

As P-gp transport at the blood-brain barrier did not explain the observed brain concentrations alone, there may be other transporters involved in lenalidomide disposition.

Systematic evaluation of the impact of solid-state polymorphism on the bioavailability of thalidomide

Thalidomide (TLD) is used to treat erythema nodosum leprosum (ENL), multiple myeloma, aphthous ulceration and wasting syndrome in HIV patients. The API can be found in two crystalline habits known as α-TLD and β-TLD. The saturation solubility (C_s) and the dissolution profiles under non-sink and sink conditions of both polymorphs were assessed. In addition, mini-capsules containing α-TLD or β-TLD without excipients were orally given (10 mg/kg) to Wistar rats. An intravenous (i.v.) dose was also administrated (5 mg/kg). The C_s values for α-TLD and β-TLD were not significantly different (α = 56.2 ± 0.5 μg·mL^-1; β = 55.2 ± 0.2 μg·mL^-1). However, the dissolution profile of α-TLD presented the fastest rate and the largest extension of drug dissolution than that from β-TLD (80% in 4 h versus 55% in 4 h). The α-TLD provided a more favorable pharmacokinetic than the β-TLD (maximum plasma concentration - C_max: 5.4 ± 0.90 μg·mL^-1versus 2.6 ± 0.2 μg·mL^-1; area under the curve of the concentration-time profile from time zero to infinity - AUC_0-∞: 44.3 ± 8.8 μg·h·mL^-1versus 33.9 ± 4.7 μg·h·mL^-1; absolute bioavailability - F: 92.2 ± 18.5% versus 70.5 ± 9.9%, respectively). Drug suppliers and pharmaceutical companies should strictly control the technological processes involved in the TLD API synthesis as well as in the production of the pharmaceutical dosage form in order to guarantee the inter-batch homogeneity and therefore, product compliance.

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.

Absorption and metabolism of piceatannol in rats

Piceatannol (trans-3,3',4,5'-tetrahydroxystilbene), a natural analogue of resveratrol, has multiple biological functions. Nevertheless, piceatannol's biological fate is yet to be determined. In this study, we evaluated the absorption and metabolism of piceatannol in rats. Furthermore, the area under the plasma concentration curves (AUC) and metabolic pathway of piceatannol were compared with those of resveratrol. We determined the plasma concentrations of piceatannol, resveratrol, and their respective metabolites following their intragastric administration. Resveratrol metabolites were only conjugates, whereas piceatannol metabolites were piceatannol conjugates, O-methyl piceatannol, and its conjugates. The AUC for piceatannol, resveratrol, and their metabolites increased in a dose-dependent manner (90-360 μmol/kg). The AUC for total piceatannol was less than that for total resveratrol, whereas the AUC for piceatannol (8.6 μmol·h/L) after piceatannol and resveratrol coadministration was 2.1 times greater than that for resveratrol (4.1 μmol·h/L). The greater AUC for piceatannol was a result of its higher metabolic stability.

Preparation, characterization, and in vitro intestinal permeability evaluation of thalidomide-hydroxypropyl-β-cyclodextrin complexes

Thalidomide is emerging as a therapeutic agent with renewed clinical importance, presenting anti-inflammatory, immunomodulatory, and antineoplasic properties. In this work, we studied the complexation of thalidomide with cyclodextrins as a strategy to circumvent the poor aqueous solubility of the drug. Thalidomide-hydroxypropyl-β-cyclodextrin complexes were obtained by kneading method and were characterized by differential scanning calorimetry, powder X-ray diffractometry, and scanning electronic microscopy. The aqueous solubility and in vitro dissolution of thalidomide were significantly improved through the complexation. Physicochemical analysis of the complexes in solid state revealed a decreased crystallinity of the complexed drug in comparison with free thalidomide. Thalidomide was able to dissociate from the complexes and permeates across intestinal epithelial Caco-2 cells with a favorable high permeability profile equivalent to that of the free drug. In summary, the present results suggest that thalidomide-hydroxypropyl-β-cyclodextrin complexes could be regarded as a promising strategy for improving the gastrointestinal absorption of thalidomide.

Enantioselectivity of thalidomide serum and tissue concentrations in a rat glioma model and effects of combination treatment with cisplatin and BCNU

Thalidomide is currently under evaluation as an anti-angiogenic agent in cancer treatment, alone and in combination with cytotoxic agents. Thalidomide is a racemate with known pharmacologic and pharmacokinetic enantioselectivity. In a previous study with thalidomide combination chemotherapy, we found evidence of anti-tumour synergy. In this study, we examined whether the synergy involved altered pharmacokinetics of thalidomide enantiomers. Adult female F344 rats were implanted with 9L gliosarcoma tumours intracranially, subcutaneously (flank), or both. Effectiveness of oral thalidomide alone, and with intraperitoneal BCNU or cisplatin combination chemotherapy, was assessed after several weeks treatment. Presumed pseudo steady-state serum, tumour and other tissues, collected after treatment, were assayed for R- and S-thalidomide by chiral HPLC. Both serum and tissue concentrations of R-thalidomide were 40–50% greater than those of S-thalidomide. Co-administration of BCNU or cisplatin with thalidomide did not alter the concentration enantioselectivity. Poor correlation of concentration with subcutaneous anti-tumour effect was found for individual treatments, and with all treatments for intracranial tumours. The consistency of the enantiomer concentration ratios across treatments strongly suggests that the favourable anti-tumour outcomes from interactions between thalidomide and the cytotoxic agents BCNU and cisplatin did not have altered enantioselectivity of thalidomide pharmacokinetics as their basis.

Determination of CH330331, a novel 4-anilinoquinazoline inhibitor of epidermal growth factor receptor tyrosine kinase, in human Caco-2 monolayers by high performance liquid chromatography with ultraviolet detection: Application to a trans-epithelial transport study

4-Anilinoquinazolines (e.g. Iressa and Glivec) are a class of epidermal growth factor receptor tyrosine kinase (EGFR-TK) inhibitors widely used to treat non-small cell lung cancer and other tumors. However, low clinical response rate, resistance, and host toxicity of currently available EGFR-TK inhibitors prompt the development of second generation of TK inhibitors with improved efficacy, selectivity, and less resistance. CH330331 is a recently synthesized novel 4-anilinoquinazoline analog with confirmed anticancer activity in vitro and in vivo. To predict its oral pharmacokinetic behavior and transport nature in the intestine before entering clinical trials, we have developed and validated a high performance liquid chromatographic (HPLC) method for the determination of CH330331 in Caco-2 (a human colon cancer cell line) monolayers. The developed HPLC method was sensitive and reliable, with acceptable accuracy (90-110% of nominal values) and precision (intra- and inter-assay R.S.D.<10%). The total running time was within 10 min, with acceptable separation of the target analytes. The lower limit of quantitation (LLOQ) value for CH330331 was 200 ng/ml when an aliquot of 100 microl sample was injected onto the HPLC. The validated HPLC method was applied to characterize the epithelial transport of CH330331 in Caco-2 monolayers. The transport of CH330331 across the Caco-2 monolayers from the apical to basolateral side was 8- to 10-fold higher than that from the basolateral to apical side. Co-incubation of sodium azide or MK-571, but not verapamil, significantly inhibited the apical to basolateral transport of CH330331. These findings provide initial evidence that the intestinal absorption of CH330331 is mediated by an active mechanism. Further studies are required to explore the interaction of CH330331 with ATP-binding cassette transporters and the possible influence on its pharmacokinetics and pharmacodynamics.