Long-term safety of pegloticase in chronic gout refractory to conventional treatment

Objective To evaluate the long-term safety (up to 3years) of treatment with pegloticase in patients with refractory chronic gout. Methods This open-label extension (OLE) study was conducted at 46 sites in the USA, Canada and Mexico. Patients completing either of two replicate randomised placebo-controlled 6-month trials received pegloticase 8mg every 2weeks (biweekly) or every 4weeks (monthly). Safety was evaluated as the primary outcome, with special interest in gout flares and infusion-related reactions (IRs). Secondary outcomes included urate-lowering and clinical efficacy. Results Patients (n=149) received a mean +/- SD of 28 +/- 18 pegloticase infusions and were followed for a mean of 25 +/- 11months. Gout flares and IRs were the most frequently reported adverse events; these were least common in patients with a sustained urate-lowering response to treatment and those receiving biweekly treatment. In 10 of the 11 patients with a serious IR, the event occurred when uric acid exceeded 6mg/dl. Plasma and serum uric acid levels remained <6mg/dl in most randomised controlled trial (RCT)-defined pegloticase responders throughout the OLE study and were accompanied by sustained and progressive improvements in tophus resolution and flare incidence. Conclusions The safety profile of long-term pegloticase treatment was consistent with that observed during 6months of RCT treatment; no new safety signals were identified. Improvements in clinical status, in the form of flare and tophus reduction initiated during RCT pegloticase treatment in patients maintaining goal range urate-lowering responses were sustained or advanced during up to 2.5years of additional treatment.