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Rapid assay to monitor vancomycin levels at the point of care in hemodialysis patients


SUMMARY/ABSTRACTOne in ten American adults suffer from chronic kidney disease, with over 425,000 end-stage renal disease(ESRD) patients receiving hemodialysis (HD) on a regular basis. The risk of methicillin-resistant S. aureus(MRSA) infections is 100-fold higher in HD patients, and septicemia is the second leading cause of death in thispopulation. The venous access site is the most common source of these infections, and due to the highprobabability of MRSA, it is common practice to empirically treat all suspected Gram-positive infections in HDpatients with vancomycin. However, vancomycin has a very narrow therapeutic index that must be closelymonitored. Vancomycin?s half-life increases from 6-12 hours in patients with normal kidney function up to 100-200 hours in patients with impaired kidney function, with variable amounts of circulating vancomycin removedby high-flux dialysis membranes during each HD session. Unfortunately, a trial and error dosing strategy remainsthe standard of care for HD patients, and as a result, sub-therapeutic concentrations are found in up to 86% ofHD patients. This often leads to the emergence of vancomycin-resistant strains and an increased rate oftreatment failure. Thus, in order to maintain an effective circulating vancomycin concentration in HD patients,clinicians need to shift to frequent serum measurements. Competitive immunoassays are currently used to measure vancomycin levels in a central clinical chemistrylab. While these approaches have sufficient sensitivity, they require specialized, expensive instruments and arenot in use at dialysis centers. Instead, dialysis patients receiving vancomycin have a blood sample drawn priorto dialysis, which is then sent to a reference laboratory. Because the turnaround time for reference lab resultscan be 48-72 hrs, patients are administered the next vancomycin dose prior to knowing whether or not levelsshould be adjusted. This expands the duration of sub-therapeutic dosing by 2-3 days and fosters growth ofresistant bacterial strains in an already vulnerable host. To address this technical hurdle, Affinergy plans todevelop a point-of-care lateral flow assay that will enable frequent, low complexity, accurate andaffordable monitoring of vancomycin levels. Using our core technology of phage display biopanning, we havealready identified a proprietary capture peptide and detection reagent that bind with submicromolar affinity tovancomycin. At the conclusion of Phase I, we will have a prototype lateral flow assay with established limits ofquantitation. In Phase II, we will scale up production of our assay, optimize performance characteristics, establishstorage conditions and determine stability. Finally, our assay will be validated in a dialysis patient population.Successful completion of this project will lead to improved therapeutic efficacy for dialysis patients receivingvancomycin.

Darby, Martyn
Affinergy, LLC
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