The in vitro metabolism and in vivo pharmacokinetic (PK) properties of DNDI-VL-2098, a potential oral agent for Visceral Leishmaniasis (VL) were studied and used to predict its human pharmacokinetics. DNDI-VL-2098 showed a low solubility (10μM) and was highly permeable (>200nm/s) in the Caco-2 model. It was stable in vitro in liver microsomes and hepatocytes and no metabolite was detectable in circulating plasma from dosed animals suggesting very slow, if any, metabolism of the compound. DNDI-VL-2098 was moderate to highly bound to plasma proteins across the species tested (94-98%). DNDI-VL-2098 showed satisfactory PK properties in mouse, hamster, rat and dog with a low blood clearance (<15% of hepatic blood flow except hamster), a volume of distribution of about 3 times total body water, acceptable half-life (1-6h across the species) and good oral bioavailability (37-100%). Allometric scaling of the preclinical PK data to human gave a blood half-life of approximately 20h suggesting that the compound could be a once-a-day drug. Based on the above assumptions, the minimum efficacious dose predicted for a 50kg human was 150mg and 300mg, using efficacy results in the mouse and hamster, respectively.

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We have used mutagenesis to investigate the potential N-glycosylation sites in the ␦ subunit of the mouse muscle acetylcholine receptor (AChR). Of the three sites, Asn 76 , Asn 143 , and Asn 169 , only the first two were glycosylated when the ␦ subunit was expressed in COS cells. Because the heterologously expressed ␦ subunit was similar in its properties to that expressed in C2 muscle cells, the sites of glycosylation are likely to be the same in both cases. In COS cells, mutations of the ␦ subunit that prevented glycosylation at either of the sites did not change its metabolic stability nor its steady-state level. These results are in contrast to those found previously for the ␣ subunit, in which glycosylation at a single site metabolically stabilized the polypeptide (Blount, P., and Merlie, J. P. (1990) J. Cell Biol. 111, 2613-2622). Mutations of the ␦ subunit that prevented glycosylation, however, decreased its ability to form an ␣␦ heterodimer when the ␣ and ␦ subunit were expressed together. When all four subunits of the AChR (␣, ␤, ␦, and ⑀) were coexpressed, mutation of the ␦ subunit to prevent glycosylation resulted in a reduced amount of fully assembled AChR and reduced surface AChR levels, consistent with the role of the heterodimer in the assembly reaction. These results suggest that glycosylation of the ␦ subunit at both Asn 76 and Asn 143 is needed for its efficient folding and/or its subsequent interaction with the ␣ subunit.The muscle nicotinic acetylcholine receptor (AChR), 1 a heterooligomeric membrane receptor, is the best understood member of a family of closely related ligand-gated ion channels that include the neuronal acetylcholine, GABA A , glycine, and serotonin 5-HT 3 receptors (1, 2). These receptors are clustered in the postsynaptic membrane, where they mediate rapid excitatory and inhibitory synaptic transmission. For each member of this family, the individual subunits are arranged in a pseudosymmetric array around an aqueous channel. Binding of the ligand opens the channel, allowing ions to flow through, thus changing the potential of the membrane (3, 4).The adult muscle nicotinic AChR is a pentamer of four subunits, ␣, ␤, ␦, and ⑀, with the stoichiometry ␣ 2 ␤␦⑀ (reviewed in Refs. 3-5). The subunits, which are homologous, each comprise four transmembrane domains with a large extracellular Nterminal domain, a large intracellular loop between the third and fourth transmembrane domains, and a small extracellular C-terminal domain (Fig. 1A) (6 -9). Each of the subunits is synthesized from a separate mRNA, and each undergoes translocation into the endoplasmic reticulum, where it undergoes post-translational processing, including signal sequence cleavage and glycosylation (10). Following synthesis, the ␣ subunit undergoes a folding reaction that appears to involve disulfide bond formation and that confers upon the ␣ subunit the ability to bind ␣-bungarotoxin (␣-BuTx; Refs. 11-13). The other subunits presumably undergo folding reactions as well, although it has not been possible to measur...

ZYDPLA1 is a potent, selective, long-acting oral DPP-4 inhibitor with potential to become once-a-week therapy for treatment of type 2 diabetes mellitus.

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The goal of this study was to examine the mechanisms of transport of gamma-aminobutyric acid (GABA) in the choroid plexus. Choroid plexus slices from the rabbit were depleted of ATP with 2,4-dinitrophenol. GABA accumulated in the choroid plexus slices in a concentrative manner in the presence of an inwardly-directed Na+ gradient. Uptake occurred in the presence of Cl-; replacement of Cl- with gluconate abolished uptake. SCN-, NO3- or Br- were able to support uptake in the absence of Cl- to a significant extent (80, 68 and 61% of control, respectively). GABA uptake was saturable (Km of 37 +/- 8.5 microM, Vmax of 409 +/- 43 nmol/g/min). Na+-driven GABA uptake was inhibited by beta-alanine (IC50 = 22.9 microM) and hypotaurine (IC50 = 21.9 microM) but less potently by nipecotic acid (IC50 = 244 microM) and hydroxy-nipecotic acid (IC50 = 284 microM). Betaine, L-(2,4)-diaminobutyric acid, guvacine and 4,5,6,7-tetrahydroisoxazolo[4,5-c]pyridin-3-ol were weak inhibitors (IC50 > 500 microM). GABA inhibited Na+-driven uptake of taurine (IC50 = 230 microM); taurine, however, did not inhibit GABA uptake (IC50 > 1 mM). RT-PCR, using degenerate primers for cloned GABA transporters, did not result in the amplification of a band from rat choroid plexus RNA. The location of the choroid plexus in the ventricles of the brain, and its role in the secretion of the cerebrospinal fluid, suggest a role for the choroid plexus Na+-GABA transporter in the disposition of GABA in the brain.

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