A second-generation antisense oligonucleotide targeting heat shock protein 27 (Hsp27) with potential antitumor and chemosensitizing activities. Hsp27 antisense oligonucleotide OGX-427 suppresses tumor cell expression of Hsp27, which may induce tumor cell apoptosis and enhance tumor cell sensitivity to cytotoxic agents. Hsp27, a chaperone belonging to the small heat shock protein (sHsp) group of proteins, is a cytoprotective protein that supports cell survival under conditions of stress; it has been found to be over-expressed in a variety of human cancers.