The aim of this work is to evaluate the impact of the timing of pre-infusion serum uric acid (sUA) test results for use in applying stopping rules for pegloticase to identify patients at risk for infusion reactions (IRs) while on therapy.

Data from the phase 3 clinical trials of pegloticase were reviewed and individual uric acid levels of the 85 patients who received the approved regimen of biweekly infusions were examined in relation to the occurrence of IRs.

Of the 22 patients (26%) who experienced an IR on pegloticase therapy without uric acid stopping rules, only seven (8%) would have had IRs if pegloticase therapy had been discontinued after two consecutive pre-infusion sUA levels above 6 mg/dl. If pegloticase therapy was stopped after a single pre-infusion sUA above 6 mg/dl, only two patients (2%) would have experienced IRs during the clinical studies.

A pre-infusion sUA level functions as a highly accurate biomarker for identification of patients who are at risk of IRs while on pegloticase therapy. Stopping pegloticase in patients who have a rise in pre-infusion uric acid levels to above 6 mg/dl while on therapy would result in most IRs being avoided.

Horizon Pharma.