AN-260 is a novel inhibitor of the free-radical producing enzyme, xanthine oxidase (XO), with potency 200 times greater than the generic XO inhibitor allopurinol. In experimental models of congestive heart failure (CHF) in rodents, swine, and dogs, AN-260 has demonstrated profound benefit in extending survival, decreasing cardiac hypertrophy, and improving cardiac contractility. XO inhibitors act as sensitizers of actin-myosin coupling to intracellular calcium; hence they increase cardiac contractility without concomitantly increasing myocardial oxygen consumption. This attribute makes AN-260 highly attractive as a novel therapeutic approach to treat acute exacerbations of CHF. Phase 1 clinical trials are expected to begin in 2006.