Pegloticase: a new biologic for treating advanced gout

Pegloticase immunogenicity: the relationship between efficacy and antibody development in patients treated for refractory chronic gout

INTRODUCTION

The efficacy of pegloticase, a polyethylene glycol (PEG)-conjugated mammalian recombinant uricase, approved for chronic refractory gout, can be limited by the development of antibodies (Ab). Analyses from 2 replicate, 6-month, randomized controlled trials were performed to characterize Ab responses to pegloticase.

METHODS

Anti-pegloticase, anti-PEG, and anti-uricase Ab were determined by validated enzyme-linked immunosorbent assays. Ab titers were analyzed for possible relationships with serum pegloticase concentrations, serum uric acid (sUA) lowering, and risk of infusion reactions (IRs).

RESULTS

Sixty-nine (41%) of 169 patients receiving pegloticase developed high titer anti-pegloticase Ab (> 1:2430) and 40% (67/169) developed anti-PEG Ab; 1 patient receiving placebo developed high titer anti-pegloticase Ab. Only 14% (24/169) of patients developed anti-uricase Ab, usually at low titer. In responders, patients showing sustained UA lowering, mean anti-pegloticase titers at week 25 (1:837 ± 1687 with biweekly and 1:2025 ± 4506 with monthly dosing) were markedly lower than in nonresponders (1:34,528 ± 42,228 and 1:89,658 ± 297,797, respectively). Nonresponder status was associated with reduced serum pegloticase concentrations. Baseline anti-pegloticase Ab, evident in 15% (31/212) of patients, did not predict subsequent loss of urate-lowering response. Loss of sUA response preceded IRs in 44 of 56 (79%) pegloticase-treated patients.

CONCLUSIONS

Loss of responsiveness to pegloticase is associated with the development of high titer anti-pegloticase Ab that increase clearance of pegloticase and are associated with a loss of the sUA lowering effect and increased IR risk. Pre-infusion sUA can be used as a surrogate for the presence of deleterious anti-pegloticase Ab.

TRIAL REGISTRATION

NCT00325195. Registered 10 May 2006, NCT01356498. Registered 27 October 2008.

Hyperuricemia and gout: new concepts in diagnosis and management

Gout is a chronic, progressive condition for which hyperuricemia is the primary risk factor. The initial episodes of gout may be brief, only lasting for 3 to 5 days, and patients may experience pain-free intercritical periods that last from months to years. However, as the disease progresses, acute gout flares become more frequent and prolonged (typically lasting ≥ 5-10 days). Chronic gouty arthritis develops, with shorter pain-free intervals; tophi become visible and interarticular joint damage occurs. Patients with advanced gout experience chronic pain and a decreased quality of life. Gout prevalence has increased significantly over time. Despite the increase in the number of gout cases, the disease is often mismanaged, especially in primary care. Hyperuricemia is inadequately controlled as a result of suboptimal dosing with urate-lowering drugs, intolerance to therapy, or poor patient compliance. This review article provides a comprehensive discussion of gout pathophysiology, risk factors, and approaches to treatment that encourage the clinician to appreciate hyperuricemia as a multifaceted disorder and manage the condition optimally.