Receptor binding assay

AstraZeneca has filed a patent application on novel bis-aryl compounds as CB1/CB2 agonists that lack CNS penetration and thus avoid the unwanted side effects associated with activation of central CBi receptors [210]. Over 100 compounds are specifically claimed e.g. (321). Compounds were tested in receptor binding assays using human CBi and CB2 receptor preparations. Respective K values were in the ranges 50-5,000 and 15-2,800 nM, although no specific data were presented. 

Product and services of interest include genomics, proteomics, custom research and services, and instruments, accessories, consumables and software. PerkinElmer proprietary technologies include time-resolved fluorescence which is employed in the sensitive Wallac DELFIA system and Wallac LANCE homogeneous assay system, and fluorescence polarization, [FP]2 , a robust fluorescence-based technique for receptor binding assays that is both fast and easy-to-use. 

A recent report on a NR2B selective NMDA receptor antagonist (9) supports the findings of Kalvass and Maurer [56], Rapid equilibration between plasma and CNS coupled with the lack of Pgp substrate activity led the authors to assume that plasma-free and brain-free drug concentrations were equivalent. An ex vivo receptor binding assay showed 50% occupancy at a total plasma concentration of 230 nM. Given a rat-free fraction of 15.3%, the authors concluded that 50% brain occupancy occurred at 35 nM unbound brain concentration, which was in reasonable agreement with the measured Ki of 3.4 nM versus the human receptor. 

Because the chemical structure of a molecule encodes its biological properties, structure has long served as the primary variable and determinant for the discovery of new drugs by medicinal chemists. For this reason, systematic structural modification has been the primary tool of choice to isolate and enhance a desired biologic activity. Moreover, with the relatively recent development of in vitro receptor-binding assays, combinatorial methods of chemical synthesis, and computer graphics, the overall approach to structural modification has become increasingly sophisticated. 

Enzyme assays—both kinetic and end-point radiocoordination of proteins, lipid assays, receptor binding assays and tissue-culture techniques... 

Harris, A., Cox, S., Bums, D., and Norey, C., Miniaturization of fluorescence polarization receptor-binding assays using CyDye-labeled ligands, /. Biomol. Screen., 8,410,2003. 

Figure 12.1 Examples of in vitro binding assays correlating with ADRs. Marketed drugs with known ADR profiles were tested in three different in vitro receptor binding assays and their IC50S (concentration required to achieve 50% inhibition) were determined. The percentage of drugs having (black bars) and not having (dotted bars) the stated ADR is...

The results of the receptor binding assay performed using this compound, IA, are shown in Table 4 where it is clear that affinity to the human B2 receptor is improved with respect to compound I. This data is supportive of the notion that the C-terminal residue(s) in this new series of bradykinin antagonist compounds interact with a hydrophobic environment, perhaps within the transmembrane domain of the receptor as previously suggested. 

Design can be used to achieve an enhancement in potency, should a suitable receptor binding assay be available. This presupposes knowledge of the receptor, at best from an X-ray diffraction study of the receptor-... 

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