Point-of-care (POC) diagnostic assay for 5-fluorouracil (5-FU) quantitation to enable dose adjustment and detect dihydropyrimidine dehydrogenase (DPD) deficiency.

e19562 Background: 5-FU is used in the treatment of 275,000 U.S. cancer patients each year. Patient variability in 5-FU metabolism causes many patients to be under dosed with 5-FU while other patients with slow clearance are overexposed, resulting in 1300 US deaths per year. Monitoring 5-FU levels in individual patients has demonstrated that efficacy and safety can be improved significantly. Wellstat is developing a point-of-care (POC) diagnostic system for monitoring 5-FU levels, giving physicians results in less than 15 minutes. This will enable the rapid detection of 5-FU overexposure due to clearance issues, including DPD deficiency (3-5% of the population) during infusion or following oral administration of capecitabine. Rapid detection of overexposure allows timely intervention with a potential antidote (e.g. uridine triacetate) while real-time detection of suboptimal 5-FU levels allows physicians to safely administer more efficacious doses. Methods: A proprietary monoclonal antibody specific for 5-FU and conjugated with a ruthenium chelate forms the basis of an electrochemiluminescence (ECL) assay. The concentration of 5-FU is inversely correlated to the generation of light. The assay can use whole blood without centrifugation and can deliver POC results in less than 15 minutes. Results: This ECL assay exhibited exquisite sensitivity (lower detection limit < 5 ng/mL) and a dynamic range to 30,000 ng/mL. The calibrator curve range was 9.6 – 30,000 ng/mL 5-FU with coefficients of variation < 7% for quantitation. Minimal cross-reactivity was observed with capecitabine (0.08%), dihydro-5-FU (2.6%) and uracil (0.9%). Chemotherapies commonly co-administered with 5-FU did not interfere. Conclusions: The assay is capable of accurately monitoring 5-FU in plasma, providing results over a wide dynamic range. The POC analyzer system will permit monitoring of 5-FU during infusion and after oral 5-FU prodrugs, enabling identification of patients overexposed to 5-FU due to DPD deficiency or other clearance problems and allowing for individualized 5-FU treatment with improved efficacy and diminished side effects.