Nanoparticle formulation of a poorly soluble cannabinoid receptor 1 antagonist improves absorption by rat and human intestine.

The inclusion of nanoparticles dispersed in a hydrophilic matrix is one of the formulation strategies to improve the bioavailability of orally administered Biopharmaceutics Classification System (BCS) class II and IV drugs by increasing their dissolution rate in the intestine. To confirm that the increased dissolution rate results in increased bioavailability, in vitro and in vivo animal experiments are performed, however, translation to the human situation is hazardous. In this study, we used a range of in vitro and ex vivo methods, including methods applying human tissue, to predict the in vivo oral bioavailability of a model BCS class II CB-1 antagonist, formulated as a nanoparticle solid dispersion. The enhanced dissolution rate from the nanoparticle formulation resulted in an increased metabolite formation in both rat and human precision-cut intestinal slices, suggesting increased uptake and intracellular drug concentration in the enterocytes. In Ussing chamber experiments with human tissue, both the metabolite formation and apical efflux of the metabolite were increased for the nanoparticulate solid dispersion compared with a physical mixture, in line with the results in intestinal slices. The pharmacokinetics of the different formulations was studied in rats in vivo. The nanoparticle formulation indeed improved the absorption of the cannabinoid receptor 1 (CB-1) antagonist and the delivery into the brain compared with the physical mixture. In conclusion, the combined approach provides a valuable set of tools to investigate the effects of formulation on the absorption of poorly soluble compounds in human intestine and may provide relevant information on the oral bioavailability in humans early in the development process.

Exploiting transport activity of p-glycoprotein at the blood-brain barrier for the development of peripheral cannabinoid type 1 receptor antagonists.

Although the CB1 receptor antagonist/inverse agonist rimonabant has positive effects on weight loss and cardiometabolic risk factors, neuropsychiatric side effects have prompted researchers to develop peripherally acting derivatives. Here, we investigated for a series of 3,4-diarylpyrazoline CB1 receptor antagonists if transport by the brain efflux transporter P-gp could be used as a selection criterion in the development of such drugs. All 3,4-diarylpyrazolines and rimonabant inhibited P-gp transport activity in membrane vesicles isolated from HEK293 cells overexpressing the transporter, but only the 1,1-dioxo-thiomorpholino analogue 23 exhibited a reduced accumulation (-38 ± 2%) in these cells, which could be completely reversed by the P-gp/BCRP inhibitor elacridar. In addition, 23 appeared to be a BCRP substrate, whereas rimonabant was not. In rats, the in vivo brain/plasma concentration ratio of 23 was significantly lower than for rimonabant (0.4 ± 0.1 vs 6.2 ± 1.6, p < 0.001). Coadministration of elacridar resulted in an 11-fold increase of the brain/plasma ratio for 23 (p < 0.01) and only 1.4-fold for rimonabant (p < 0.05), confirming the involvement of P-gp and possibly BCRP in limiting the brain entrance of 23 in vivo. In conclusion, these data support the conception that efflux via transporters such as P-gp and BCRP can limit the brain penetration of CB1 receptor antagonists, and that this property could be used in the development of peripheral antagonists.

Cannabinoid type 1 receptor antagonists modulate transport activity of multidrug resistance-associated proteins MRP1, MRP2, MRP3, and MRP4.

Cannabinoid type 1 (CB1) receptor antagonists have been developed for the treatment of obesity, but a major disadvantage is that they cause unwanted psychiatric effects. Selective targeting of peripheral CB1 receptors might be an option to circumvent these side effects. Multidrug resistance-associated proteins (MRPs) can influence the pharmacokinetics of drugs and thereby affect their disposition in the body. In this study, we investigated the interaction of the prototypic CB1 receptor antagonist rimonabant and a series of 3,4-diarylpyrazoline CB1 receptor antagonists with MRP1, MRP2, MRP3, and MRP4 in vitro. Their effect on ATP-dependent transport of estradiol 17-ß-D-glucuronide (E(2)17ßG) was measured in inside-out membrane vesicles isolated from transporter-overexpressing human embryonic kidney 293 cells. Rimonabant inhibited MRP1 transport activity more potently than MRP4 (K(i) of 1.4 and 4 µM, respectively), whereas the 3,4-diarylpyrazolines were stronger inhibitors of MRP4- than MRP1-mediated transport. A number of CB1 receptor antagonists, including rimonabant, stimulated MRP2 and MRP3 transport activity at low substrate concentrations but inhibited E(2)17ßG transport at high substrate concentrations. The interaction of 3,4-diarylpyrazolines and rimonabant with MRP1-4 indicates their potential for drug-drug interactions. Preliminary in vivo data suggested that for some 3,4-diarylpyrazolines the relatively lower brain efficacy may be related to their inhibitory potency against MRP4 activity. Furthermore, this study shows that the modulatory effects of the 3,4-diarylpyrazolines were influenced by their chemical properties and that small variations in structure can determine the affinity of these compounds for efflux transporters and thereby affect their pharmacokinetic behavior.

Preparation and characterization of liposomal formulations of neurotensin-degrading enzyme inhibitors.

Neurotensin-degrading enzyme (NTDE) inhibitors hold great potential for treating psychotic disorders. However, brain uptake of such compounds in vivo is generally low due to the presence of the blood-brain barrier. In this study, liposomal formulations of two NTDE inhibitors, named compound 1 (C1) and compound 2 (C2) were prepared. Association of these compounds with the liposomal bilayer, subsequent liposomal stability, and compound release in the presence of albumin was studied. Entrapment of the compounds in the liposomal bilayer showed the solubilizing properties of the liposomes. Size and polydispersity index of the compound-entrapped liposomes did not change over 1 month, showing colloidal stability of the liposomal drug formulations. The amount of compounds associated with the liposomes decreased within one day. After this, the association remained stable at 4°C. For C1, association remained stable at 37°C in HEPES buffered saline, and the compound was gradually released in the presence of bovine serum albumin. For C2, the release was rapid in both HBS and BSA at 37°C. In conclusion, the formulation of NTDE inhibitors C1 and C2 in liposomes has been demonstrated and holds promise to deliver NTDE inhibitors in vivo.