Advances in blood-brain barrier modeling in microphysiological systems highlight critical differences in opioid transport due to cortisol exposure.

Background: The United States faces a national crisis involving opioid medications, where currently more than 130 people die every day. To combat this epidemic, a better understanding is needed of how opioids penetrate into the central nervous system (CNS) to facilitate pain relief and, potentially, result in addiction and/or misuse. Animal models, however, are a poor predictor of blood-brain barrier (BBB) transport and CNS drug penetration in humans, and many traditional 2D cell culture models of the BBB and neurovascular unit have inadequate barrier function and weak or inappropriate efflux transporter expression.

Pharmacokinetics of Organic Cation Transporter 1 (OCT1) Substrates in Oct1/2 Knockout Mice and Species Difference in Hepatic OCT1-Mediated Uptake.

Organic cation transporter 1 (OCT1) plays a role in hepatic uptake of drugs, affecting in vivo exposure, distinguished primarily through pharmacogenetics of the gene. The role of OCT1 in vivo has not been confirmed, however, via drug-drug interactions that similarly affect exposure. In the current research, we used Oct1/2 knockout mice to assess the role of Oct1 in hepatic clearance and liver partitioning of clinical substrates and assess the model for predicting an effect of OCT1 function on pharmacokinetics in humans.

Enterohepatic circulation of glucuronide metabolites of drugs in dog.

The enterohepatic circulation (EHC) of drugs is often the result of the direct glucuronidation, excretion of the metabolite into bile, followed by hydrolysis to the aglycone by the gut microbiome and finally reabsorption of drug into the systemic circulation. The aim of present study to identify key factors in determining the EHC in dog for canagliflozin and DPTQ, two compounds cleared by UDP-glucuronosyltransferase (UGT) mediated O-alkyl glucuronidation and cytochrome P450 (P450) mediated oxidation. The pharmacokinetic profiles of the drugs were compared between bile duct cannulated (BDC) and intact beagle dogs after a single intravenous administration.

In Silico and in Vitro Assessment of OATP1B1 Inhibition in Drug Discovery.

The organic anion-transporting polypeptide 1B1 transporter belongs to the solute carrier superfamily and is highly expressed at the basolateral membrane of hepatocytes. Several clinical studies show drug-drug interactions involving OATP1B1, thereby prompting the International Transporter Consortium to label OATP1B1 as a critical transporter that can influence a compound's disposition. To examine OATP1B1 inhibition early in the drug discovery process, we established a medium-throughput concentration-dependent OATP1B1 assay.

QSAR Model of Unbound Brain-to-Plasma Partition Coefficient, K: Incorporating P-glycoprotein Efflux as a Variable.

We report development and prospective validation of a QSAR model of the unbound brain-to-plasma partition coefficient, K, based on the in-house data set of ∼1000 compounds. We discuss effects of experimental variability, explore the applicability of both regression and classification approaches, and evaluate a novel, model-within-a-model approach of including P-glycoprotein efflux prediction as an additional variable. When tested on an independent test set of 91 internal compounds, incorporation of P-glycoprotein efflux information significantly improves the model performance resulting in an R of 0.

Selective photodepletion of malignant T cells in extracorporeal photopheresis with selenorhodamine photosensitizers.

Extracorporeal photopheresis (ECP) has been used successfully in the treatment of erythrodermic cutaneous T cell lymphoma (CTCL), and other T cell-mediated disorders. Not all patients obtain a significant or durable response from ECP. The design of a selective photosensitizer that spares desirable lymphocytes while targeting malignant T cells may promote cytotoxic T cell responses and improve outcomes after ECP.

Brain Exposure of Two Selective Dual CDK4 and CDK6 Inhibitors and the Antitumor Activity of CDK4 and CDK6 Inhibition in Combination with Temozolomide in an Intracranial Glioblastoma Xenograft.

Effective treatments for primary brain tumors and brain metastases represent a major unmet medical need. Targeting the CDK4/CDK6-cyclin D1-Rb-p16/ink4a pathway using a potent CDK4 and CDK6 kinase inhibitor has potential for treating primary central nervous system tumors such as glioblastoma and some peripheral tumors with high incidence of brain metastases. We compared central nervous system exposures of two orally bioavailable CDK4 and CDK6 inhibitors: abemaciclib, which is currently in advanced clinical development, and palbociclib (IBRANCE; Pfizer), which was recently approved by the U.

Selenorhodamine photosensitizers for photodynamic therapy of P-glycoprotein-expressing cancer cells.

We examined a series of selenorhodamines with amide and thioamide functionality at the 5-position of a 9-(2-thienyl) substituent on the selenorhodamine core for their potential as photosensitizers for photodynamic therapy (PDT) in P-glycoprotein (P-gp) expressing cells. These compounds were examined for their photophysical properties (absorption, fluorescence, and ability to generate singlet oxygen), for their uptake into Colo-26 cells in the absence or presence of verapamil, for their dark and phototoxicity toward Colo-26 cells, for their rates of transport in monolayers of multidrug-resistant, P-gp-overexpressing MDCKII-MDR1 cells, and for their colocalization with mitochondrial specific agents in Colo-26 cells. Thioamide derivatives 16b and 18b were more effective photosensitizers than amide derivatives 15b and 17b.

Integration of in silico and in vitro tools for scaffold optimization during drug discovery: predicting P-glycoprotein efflux.

In silico tools are regularly utilized for designing and prioritizing compounds to address challenges related to drug metabolism and pharmacokinetics (DMPK) during the process of drug discovery. P-Glycoprotein (P-gp) is a member of the ATP-binding cassette (ABC) transporters with broad substrate specificity that plays a significant role in absorption and distribution of drugs that are P-gp substrates. As a result, screening for P-gp transport has now become routine in the drug discovery process.

Thiorhodamines containing amide and thioamide functionality as inhibitors of the ATP-binding cassette drug transporter P-glycoprotein (ABCB1).

Twelve thiorhodamine derivatives have been examined for their ability to stimulate the ATPase activity of purified human P-glycoprotein (P-gp)-His(10), to promote uptake of calcein AM and vinblastine into multidrug-resistant, P-gp-overexpressing MDCKII-MDR1 cells, and for their rates of transport in monolayers of multidrug-resistant, P-gp-overexpressing MDCKII-MDR1 cells. The thiorhodamine derivatives have structural diversity from amide and thioamide functionality (N,N-diethyl and N-piperidyl) at the 5-position of a 2-thienyl substituent on the thiorhodamine core and from diversity at the 3-amino substituent with N,N-dimethylamino, fused azadecalin (julolidyl), and fused N-methylcyclohexylamine (half-julolidyl) substituents. The julolidyl and half-julolidyl derivatives were more effective inhibitors of P-gp than the dimethylamino analogues.

Chalcogenopyrylium compounds as modulators of the ATP-binding cassette transporters P-glycoprotein (P-gp/ABCB1) and multidrug resistance protein 1 (MRP1/ABCC1).

Twenty-seven chalcogenopyrylium derivatives varying in the heteroatom of the pyrylium core and substituents at the 2-, 4-, and 6-positions were examined for their effect on human MRP1-mediated uptake of tritiated estradiol glucuronide into inside-out membrane vesicles, their affinity for and ability to stimulate the ATPase activity of purified human P-glycoprotein (P-gp)-His(10), and their ability to promote uptake of calcein AM and vinblastine in multidrug-resistant cells. Differences in their effects on MRP1 and P-gp activity were noted, and a second set of thiopyrylium compounds with systematic substituent changes was examined to refine these differences further. Derivatives with tert-butyl substituents in the 2- and 6-positions had the lowest inhibitory activity toward both transporters.

Rhodamine inhibitors of P-glycoprotein: an amide/thioamide "switch" for ATPase activity.

We have examined 46 tetramethylrosamine/rhodamine derivatives with structural diversity in the heteroatom of the xanthylium core, the amino substituents of the 3- and 6-positions, and the alkyl, aryl, or heteroaryl group at the 9-substituent. These compounds were examined for affinity and ATPase stimulation in isolated MDR3 CL P-gp and human P-gp-His(10), for their ability to promote uptake of calcein AM and vinblastine in multidrug-resistant MDCKII-MDR1 cells, and for transport in monolayers of MDCKII-MDR1 cells. Thioamide 31-S gave K(M) of 0.

Breast cancer resistance protein interacts with various compounds in vitro, but plays a minor role in substrate efflux at the blood-brain barrier.

Expression of breast cancer resistance protein (Bcrp) at the blood-brain barrier (BBB) has been revealed recently. To investigate comprehensively the potential role of Bcrp at the murine BBB, a chemically diverse set of model compounds (cimetidine, alfuzosin, dipyridamole, and LY2228820) was evaluated using a multiexperimental design. Bcrp1 stably transfected MDCKII cell monolayer transport studies demonstrated that each compound had affinity for Bcrp and that polarized transport by Bcrp was abolished completely by the Bcrp inhibitor chrysin.

Chalcogenopyrylium dyes as inhibitors/modulators of P-glycoprotein in multidrug-resistant cells.

A series of chalcogenopyrylium dyes were evaluated as modulators/inhibitors of P-glycoprotein (Pgp). Their ability to inhibit verapamil (VER)-dependent ATPase activity (IC(50) values) in lipid-activated, mouse Cys-less mdr3 Pgp was determined. Their ability to promote calcein-AM (CAM) uptake in MDCKII-MDR1 cells and their capacity to be transported by Pgp in monolayers of MDCKII-MDR1 cells were also evaluated.

ATP occlusion by P-glycoprotein as a surrogate measure for drug coupling.

The multidrug efflux pump P-glycoprotein (Pgp) couples drug transport to ATP hydrolysis. Previously, using a synthetic library of tetramethylrosamine ( TMR) analogues, we observed significant variation in ATPase stimulation ( V m (D)). Concentrations required for half-maximal ATPase stimulation ( K m (D)) correlated with ATP hydrolysis transition-state stabilization and ATP occlusion (EC 50 (D)) at a single site.