Disclosed are compounds that are derivatives of brevetoxin, or PbTx, pharmaceutical formulations comprising the compounds, and methods of regulating mucus transport in a cell, treating mucociliary dysfunction and diseases related to decreased mucus transport, wherein the compounds are of the Formula (I), and Formula (III): ##STR00001## wherein R, R.sub.1, R.sub.2, R.sub.3, A, n, and Y are as defined herein for each compound.