Use of the Cassette-Dosing Approach to Assess Brain Penetration in Drug Discovery

ABSTRACT: The objective of the present study was to examine the cassette dosing method in determination of brain-to-plasma concentration ratio (area under the concentration-time profiles for plasma/area under the concentration-time profiles for brain, K p ). Eleven model compounds, amprenavir, citalopram, digoxin, elacridar, imatinib, (3S,6S,12aS)-1,2,3,4,6,7,12,12a-octahydro-9-methoxy-6-(2-methylpropyl)-1,4-dioxopyrazino[1,2:1,6]pyrido[3,4-b]indole-3-propanoic acid 1,1-dimethylethyl ester (Ko143), loperamide, prazosin, quinidine, sulfasalazine, and verapamil, were selected to compare their K p determined from discrete dosing in wild-type mice and their K p from cassette dosing in wild-type, Mdr1a/1b(؊/؊), Bcrp1(؊/؊), and Mdr1a/1b(؊/؊)/Bcrp1(؊/؊) mice at 1 to 3 mg/kg. The mice brain and plasma were collected at 0.25, 1, and 3 h and were analyzed using high-performance liquid chromatography-tandem mass spectrometry methods. The K p determined from discrete dosing versus cassette dosing in the wild-type mice were within 2-fold for all the compounds except sulfasalazine and Ko143. The brain concentrations of sulfasalazine and Ko143 and the plasma concentrations of Ko143 were below the lower limit of quantitation. In addition, the K p values estimated by mass spectrometry responses, namely the ratio of compound peak area to internal standard peak area, were within 2-fold of the K p observed from the actual concentrations. Furthermore, the ratios of K p in Mdr1a/1b(؊/؊), Bcrp1(؊/؊), and Mdr1a/1b(؊/؊)/ Bcrp1(؊/؊) mice versus the K p in the wild-type mice from cassette dosing were consistent with the ones reported in the literature where the compounds were dosed discretely. These results demonstrate that drug-drug interactions at the blood-brain barrier are unlikely at a subcutaneous dose of 1 to 3 mg/kg and support the use of the cassette dosing approach to assess brain penetration in drug discovery

GluN2A NMDA Receptor Enhancement Improves Brain Oscillations, Synchrony, and Cognitive Functions in Dravet Syndrome and Alzheimer's Disease Models.

NMDA receptors (NMDARs) play subunit-specific roles in synaptic function and are implicated in neuropsychiatric and neurodegenerative disorders. However, the in vivo consequences and therapeutic potential of pharmacologically enhancing NMDAR function via allosteric modulation are largely unknown. We examine the in vivo effects of GNE-0723, a positive allosteric modulator of GluN2A-subunit-containing NMDARs, on brain network and cognitive functions in mouse models of Dravet syndrome (DS) and Alzheimer's disease (AD). GNE-0723 use dependently potentiates synaptic NMDA receptor currents and reduces brain oscillation power with a predominant effect on low-frequency (12-20 Hz) oscillations. Interestingly, DS and AD mouse models display aberrant low-frequency oscillatory power that is tightly correlated with network hypersynchrony. GNE-0723 treatment reduces aberrant low-frequency oscillations and epileptiform discharges and improves cognitive functions in DS and AD mouse models. GluN2A-subunit-containing NMDAR enhancers may have therapeutic benefits in brain disorders with network hypersynchrony and cognitive impairments

Cholinesterases: Structure, Role, and Inhibition

Acetilkolinesteraza (AChE; E.C. 3.1.1.7) i butirilkolinesteraza (BChE; E.C. 3.1.1.8) enzimi su koji se zbog svoje uloge u organizmu intenzivno istražuju unutar područja biomedicine i toksikologije. Iako strukturno homologni, ovi enzimi razlikuju se prema katalitičkoj aktivnosti, odnosno specifi čnosti prema supstratima koje mogu hidrolizirati te selektivnosti za vezanje mnogih liganada. U ovom radu dan je pregled dosadašnjih istraživanja kolinesteraza i njihovih interakcija s ligandima i inhibitorima te su izdvojene aminokiseline aktivnog mjesta koje sudjeluju u tim interakcijama.Enzymes acetylcholinesterase (AChE; E.C. 3.1.1.7) and butyrylcholinesterase (BChE; E.C. 3.1.1.8) have intensively been investigated in biomedicine and toxicology due to important role in organisms. Even if structurally homologous, they differ in catalytic activity, specificity, for substrates, and selectivity in binding to many ligands. This paper compiles the results of research on cholinesterases and their interactions with ligands and inhibitors, and identifies amino acids of active sites involved in these interactions

Comparison of in vitro – in vivo extrapolation of biliary clearance using an empirical scaling factor versus transport‐based scaling factors in sandwich‐cultured rat hepatocytes

Biliary clearance (CL b ) is often underestimated by in vitro – in vivo extrapolation from sandwich‐cultured hepatocytes (SCHs). The objective of this study was to compare the performance of a universal correction factor with transporter‐based correction factors in correcting underestimation of CL b . The apparent in vitro CL b of a training set of 21 compounds was determined using the SCH model and extrapolated to apparent in vivo CL b (CL b, app ). A universal correction factor (10.2) was obtained by a linear regression of the predicted CL b, app and observed in vivo CL b of training set compounds and applied to an independent test set ( n = 20); the corrected CL b predictions of 13 compounds were within twofold error of observed values. Furthermore, two transporter‐based correction factors (Organic anion transporting polypeptides/multidrug‐resistance‐related protein 2 and diffusion/P‐glycoprotein) were estimated by linear regression analysis of training set compounds. The applications of the two correction factors to the test set resulted in improved prediction precision. In conclusion, both the universal correction factor and transporter‐based correction factors provided reasonable corrections of CL b values, which are often underestimated by the SCH model. The use of transporter‐based correction factors resulted in an even greater improvement of predictions for compounds with intermediate‐to‐high CL b values. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 102:2837–2850, 2013Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/99050/1/23620_ftp.pd