Hormone Mimicry

Abstract
Two research articles in this week9s Science [Livnah et al. (p. 464) and Wrighton et al. (p. 458)] report the isolation and structure of a 20-amino acid peptide that binds to and activates the receptor for erythropoietin but is not derived from the normal ligand. In his Perspective, Wells describes the unique selection procedure that allowed this accomplishment and what it means for drug development.