PROJECT SUMMARY This work is aimed to improve outcomes in patients with kidney disease through improved diagnostics. Nephron mass is a measure of the functional capacity of the kidney. Its measurement could be transformative in detecting susceptibility to and progression of kidney diseases. However, no clinical tools or assays currently exist to directly measure nephron mass. We have developed tools using a novel targeted contrast agent (RadioCF) to directly measure nephron mass using positron emission tomography (PET). This technology, RadioCF-PET, has the potential to provide a more accurate assessment of kidney health and aid clinical decisions for patient treatment. RadioCF-PET also has the potential to be used in the assessment and allocation of renal transplants. This proposal will establish the feasibility of RadioCF-PET to measure nephron mass using a human recombinant form of RadioCF (HrRadioCF) to minimize toxicity, control synthesis and demonstrate the potential of this technology for clinical use. We will measure nephron mass in mice in vivo using RadioCF-PET with human recombinant RadioCF. We will perform initial toxicity studies with HrRadioCF to establish the safety of this radiotracer in mice that will inform the safety and efficacy testing in a Phase II proposal. In Phase II, we will perform extensive toxicity studies and characterization of the agent to support an exploratory investigational new drug application. Future application of RadioCF-PET will first focus on the evaluation of donor kidneys before transplant in both live and deceased donors to monitor allograft health during transit, and then will be adapted to monitor graft function after transplantation. Transplant evaluation provides a pathway to in-patient use of this technology as a new screening tool to monitor kidney health. This technology also has the potential to monitor patients at risk for kidney disease, such as patients with diabetes, indicating a large potential market for impact.