Effect of Plasma Protein Binding on in Vivo Activity and Brain Penetration of Glycine/NMDA Receptor Antagonists
摘要:
A major issue in designing drugs as antagonists at the glycine site of the NMDA receptor has been to achieve good in vivo activity. A series of 4-hydroxyquinolone glycine antagonists was found to be active in the DBA/2 mouse anticonvulsant assay, but improvements in in vitro affinity were not mirrored by corresponding increases in anticonvulsant activity. Here we show that binding of the compounds to plasma protein limits their brain penetration. Relative binding to the major plasma protein, albumin, was measured in two different ways: by a radioligand binding experiment or using an HPLC assay, for a wide structural range of glycine/NMDA site ligands. These measures of plasma protein binding correlate well (r = 0.84), and the HPLC assay has been used extensively to quantify plasma protein binding. For the 4-hydroxyquinolone series, binding to plasma protein correlates (r = 0.92) with log P (octanol/pH 7.4 buffer) over a range of log P values from 0 to 5. The anticonvulsant activity increases with in vitro affinity, but the slope of a plot of pED(50) versus pIC(50) is low (0.40); taking plasma protein binding into account in this plot increases the slope to 0.60. This shows that binding to albumin in plasma reduces the amount of compound free to diffuse across the blood-brain barrier. Further evidence comes from three other experiments: (a) Direct measurements of brain/blood ratios for three compounds (2, 16, 26) show the ratio decreases with increasing log P. (b) Warfarin, which competes for albumin binding sites dose-dependently, decreased the ED50 of 26 for protection against seizures induced by NMDLA. (c) Direct measurement of brain penetration using an in situ brain perfusion model in rat to measure the amount of drug crossing the blood/brain barrier showed that compounds 2, 26, and 32 penetrate the brain well in the absence of plasma protein, but this is greatly reduced when the drug is delivered in plasma. In the 4-hydroxyquinolones glycine site binding affinity increases with lipophilicity of the 3-substituent up to a maximum at a log P around 3, then does not improve further. When combined with increasing protein binding, this gives a parabolic relationship between predicted in vivo activity and log P, with a maximum log P value of 2.39. Finally, the plasma protein binding studies have been extended to other series of glycine site antagonists, and it is shown that for a. given log P these have similar protein binding to the 4-hydroxyquinolones, except for compounds that are not acidic. The results have implications for the design of novel glycine site antagonists, and it is suggested that it is necessary to either keep log P low or pK(a) high to obtain good central nervous system activity.
Rapid microwave-enhanced synthesis of 4-hydroxyquinolinones under solvent-free conditions
作者:Jos H.M Lange、Peter C Verveer、Stefan J.M Osnabrug、Geb M Visser
DOI:10.1016/s0040-4039(00)02244-9
日期:2001.2
potent and selective glycine-site NMDA receptor antagonists of pharmaceutical interest. A novel microwave-enhanced synthesis of such quinolinones under solvent-free conditions has been developed. The quinolinones are easily obtained in a one-potprocedure as a result of the formal amidation of a malonic ester derivative with an aniline and subsequent cyclisation of the intermediate malondianilides
An Efficient Route to 3-Aryl-Substituted Quinolin-2-one and 1,8-Naphthyridin-2-one Derivatives of Pharmaceutical Interest
作者:Christos A. Mitsos、Alexandros L. Zografos、Olga Igglessi-Markopoulou
DOI:10.1021/jo0340051
日期:2003.5.1
Reaction of arylacetic ester enolates with 2-alkoxy-4H-3,1-benzoxazin-4-ones offers a short and versatile synthetic route to 3-aryl-4-hydroxyquinolin-2(1H)-ones, through the cyclization of the beta-ketoesters produced. Similar reactions of 4H-pyrido[2,3-d][1,3]oxazin-4-ones with ester enolates afford 1-acyl-4-hydroxy-1,8-naphthyridin-2(1H)-ones in a convenient two-step, one-pot procedure.
A class of 4-hydroxy-2-(1 H)-quinolone derivatives, substituted at the 3-position by an optionally substituted aryl substituent, are selective non-competitive antagonists of NMDA receptors and/or are antagonists of AMPA receptors, and are therefore of utility in the treatment of conditions, such as neurodegenerative disorders, convulsions or schizophrenia, which require the administration of an NMDA and/or AMPA receptor antagonist.