Ulodesine (BCX4208) is a new, orally active, highly potent inhibitor of purine nucleoside phosphorylase (PNP) for the treatment of hyperuricemia and gout. Inhibition of PNP reduces the substrates available for XO to form uric acid. The drug is currently under development for the management of hyperuricemia in chronic gout. Two Phase II clinical trials have shown promising results regarding urate-lowering effect in both as monotherapy and in combination with allopurinol. Ulodesine shows no interaction with CYP450 isoforms and has no hepatic metabolism; therefore, no drug interactions were expected. Following the successful outcome of the Phase IIb clinical trial, Phase III development of ulodesine is planned. One concern regarding the use of ulodesine is its impact on T cells. Lack of PNP is associated with immunodeficiency and autoimmune disorders.