SUMMARY/ABSTRACT One 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 this population. The venous access site is the most common source of these infections, and due to the high probabability of MRSA, it is common practice to empirically treat all suspected Gram-positive infections in HD patients with vancomycin. However, vancomycin has a very narrow therapeutic index that must be closely monitored. 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 removed by high-flux dialysis membranes during each HD session. Unfortunately, a trial and error dosing strategy remains the standard of care for HD patients, and as a result, sub-therapeutic concentrations are found in up to 86% of HD patients. This often leads to the emergence of vancomycin-resistant strains and an increased rate of treatment 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 chemistry lab. While these approaches have sufficient sensitivity, they require specialized, expensive instruments and are not in use at dialysis centers. Instead, dialysis patients receiving vancomycin have a blood sample drawn prior to dialysis, which is then sent to a reference laboratory. Because the turnaround time for reference lab results can be 48-72 hrs, patients are administered the next vancomycin dose prior to knowing whether or not levels should be adjusted. This expands the duration of sub-therapeutic dosing by 2-3 days and fosters growth of resistant bacterial strains in an already vulnerable host. To address this technical hurdle, Affinergy plans to develop a point-of-care lateral flow assay that will enable frequent, low complexity, accurate and affordable monitoring of vancomycin levels. Using our core technology of phage display biopanning, we have already identified a proprietary capture peptide and detection reagent that bind with submicromolar affinity to vancomycin. At the conclusion of Phase I, we will have a prototype lateral flow assay with established limits of quantitation. In Phase II, we will scale up production of our assay, optimize performance characteristics, establish storage 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 receiving vancomycin.