Yang B et al. - Cyst expansion in polycystic kidney disease (PKD) involves progressive fluid accumulation, which is believed to require chloride transport by the cystic fibrosis transmembrane conductance regulator (CFTR) protein. Herein is reported that small-molecule CFTR inhibitors of the thiazolidinone and glycine hydrazide classes slow cyst expansion in in vitro and in vivo models of PKD.