Hyperuricemia results from an imbalance between the rates of production and excretion of uric acid. Longstanding hyperuricemia can lead to gout, which is characterized by the deposition of monosodium urate monohydrate crystals in the joints and periarticular structures. Because such deposits are resolved very slowly by lowering plasma urate with available drugs or other measures, the symptoms of gout may become chronic. Persistent hyperuricemia may also increase the risk of renal and cardiovascular diseases. Unlike most mammals, humans lack the enzyme uricase (urate oxidase) that catalyzes the oxidation of uric acid to a more soluble product. This review describes the development of a poly(ethylene glycol) (PEG) conjugate of recombinant porcine-like uricase with which a substantial and persistent reduction of plasma urate concentrations has been demonstrated in a Phase 2 clinical trial. Two ongoing Phase 3 clinical trials include systematic assessments of gout symptoms, tophus resolution and quality of life, in addition to the primary endpoint of reduced plasma urate concentration.