The technology relates in part to compositions comprising modified Caspase-9 polypeptides, compositions comprising nucleic acids coding for modified Caspase-9 polypeptides, chimeric modified Caspase-9 polypeptides, and methods of use thereof, including methods for cell therapy. Methods for cell therapy include modifying transfused cells to express an inducible modified Caspase-9 protein, with reduced basal activity in the absence of the inducer.