The invention provides compositions, pharmaceutical preparations and methods for inhibition of cystic fibrosis transmembrane conductance regulator protein (CFTR) that are useful for the study and treatment of CFTR-mediated diseases and conditions. The compositions and pharmaceutical preparations of the invention may comprise one or more thiazolidinone compounds, and may additionally comprise one or more pharmaceutically acceptable carriers, excipients and/or adjuvants. The methods of the invention comprise, in certain embodiments, administering to a patient suffering from a CFTR-mediated disease or condition, an efficacious amount of a thiazolidinone compound. In other embodiments the invention provides methods of inhibiting CFTR that comprise contacting cells in a subject with an effective amount of a thiazolidinone compound. In addition, the invention features a non-human animal model of CFTR-mediated disease which model is produced by administration of a thiazolidinone compound to a non-human animal in an amount sufficient to inhibit CFTR.