The invention provides compositions, including pharmaceutical preparations, which comprise one or more substituted thiophene, benzofuran, pyrimidinetrione, dihydropyridine, tetrahydrocarbazol or anthraquinone compounds. The invention also features methods of use of such compositions in increasing activity of mutant-cystic fibrosis transmembrane conductance regulator protein in a cell, e.g. by increasing ion transport in a mutant-CFTR.