A cell-free, high-throughput screening service for accelerated GPCR ligand discovery

PROJECT SUMMARY The proposed Phase I STTR project is a partnership between a biotechnology company KXTbioIncand the University of North Carolina at Chapel Hill to develop an innovative high throughput screening service for identifying new drug candidates that act via G protein coupled receptorsGPCRsThis large protein superfamily has been the most successful source of therapeutic targetsaccounting forof all prescription pharmaceuticals in such diverse areas as cancercardiac dysfunctiondiabetescentral nervous system disordersobesityinflammationand painHoweverwith much of the low hanging fruit already pickedthe pace of GPCR drug discovery and development has slowed due to the challenges associated with obtainingD structures of GPCRs and performing structure activity studiesConcurrentlynew findings in GPCR pharmacology research have uncovered previously unknown intricacies of GPCR signaling that expanded their potential as targets for therapeutic interventions even furtherConsidering the decreasing productivity in the pharmaceutical industry and rising development costsmore effective methods of identifying GPCR drug candidates would be highly valuableAlthough crystal structures of GPCRs are now being generatedtheir utility will remain limited for the foreseeable futureVarious functional assays are currently the mainstay of GPCR screening effortsand rely on detecting downstream cellular signaling events initiated by changes in GPCR activityChosen for their strong and easy to measure signalsthese techniques are performed in live cell culturesmaking them prone to off target effects resulting in both false positives and false negativesintroducing higher variability and costsas well as reduced throughputKXTbio and UNC Chapel Hill aim to develop a new screening technology that would eliminate many of the drawbacks of the existing methodsThe new high throughput screeningHTSplatform will use purified GPCRs and G proteinsthus avoiding cell culturesGPCR activity will be monitored by the immediately ensuing G protein activation involving an exchange of the bound GDP molecule for a GTPThe fluorescent analog of GTP whose fluorescent yield increases upon G protein binding will be used in the assay as the signal sourceThis proposed real time HTS system can differentiate between agonistsantagonists and allosteric modulatorsusing a minimal number of componentsthus reducing artefacts and cell dependent effectsIn contrast to related G protein activation assays it does not require filtration and washing steps or radiolabelsIn this Phase I project KXTbio aims to deliver a proof of concept of the proposed HTS GPCR platformand if successfula Phase II project will followwhere the platform will be fully implementedtestedand optimized in a multi well plate formatKXTbio plans to commercialize it is as a service with a possibility of licensing the technology to drug discovery companies PROJECT NARRATIVE The goal of the proposed Phase I STTR project is to develop a new high throughput screening platform to greatly accelerate the discovery of drug candidates acting via G protein coupled receptorswhich are the targets ofof marketed pharmaceuticalsThe platform was designed expressly to eliminate the shortcomings of the existing methods to increase productivityand will be marketed to drug discovery companies