The phase 3 CRYSTAL trial investigated the efficacy of combining lesinurad (200 mg or 400 mg), a selective urate transporter inhibitor, with febuxostat treatment for tophaceous gout. The proportion of patients achieving serum urate levels <5.0 mg/dl at 6 months (the primary end point) was higher among patients receiving 400 mg lesinurad in addition to 80 mg febuxostat than among patients receiving febuxostat alone. At all other time points (up to 12 months), 200 mg lesinurad plus febuxostat was more effective than 400 mg lesinurad plus febuxostat in achieving the target levels of serum urate.