Abstract The study by Kelly and colleagues, published in the September 1, 2003, issue of Clinical Cancer Research, established the safety and biologic activity of the first-in-class histone deacetylase inhibitor, vorinostat, which was administered intravenously. Subsequent studies led to the development of oral vorinostat and the regulatory approval of vorinostat for cutaneous T-cell lymphomas, which opened the door for the next generation of inhibitors. Clin Cancer Res; 21(10); 2198–200. ©2015 AACR. See related article by Kelly et al., Clin Cancer Res 2003;9(10) September 1, 2003;3578–88