Pegloticase. An excessively dangerous and inadequately evaluated hypouricaemic drug

When severe gout with tophi persists despite treatment with allopurinol, a xanthine oxidase inhibitor, the hypouricaemic drug of choice is probenecid, a uricosuric agent, in the absence of a better alternative. Pegloticase is a pegylated recombinant uricase. This enzyme catabolises uric acid into allantoin, a water-soluble substance that is excreted by the kidneys. Pegloticase has been granted EU marketing authorisation in patients who continue to have severe gout attacks despite treatment with a xanthine oxidase inhibitor such as allopurinol. Pegloticase has not been compared with probenecid nor has it been evaluated in patients who have no other treatment options. Two double-blind, randomised, placebo-controlled trials have been conducted. They lasted only 6 months and involved 212 patients in whom allopurino/therapy had failed, usually because of serious adverse effects. Pegloticase lowered uric acid levels but increased the frequency of gout flares early during treatment. At best, it had only a minor symptomatic effect on pain and disability. Its long-term effects are unknown. About 10% of patients had a serious adverse effect attributed to pegloticase, including reactions during the infusion, anaphylactic reactions, and skin infections. Thrombocytopenia and severe cardiac adverse effects are other probable adverse effects. About 90% of patients treated with pegloticase developed anti-pegloticase antibodies. Given the limited short-term symptomatic efficacy and the absence of comparative long-term evaluation, patients should not be exposed to the potentially serious adverse effects of pegloticase. Probenecid is a better choice when allopurinol is ineffective or poorly tolerated. Currently, patients with no remaining therapeutic options should simply continue to receive symptomatic treatment of gout attacks.