Onconova suggests that Ex-Rad protects cells exposed to radiation against DNA damage, and that the drug's mechanism of action does not involve scavenging free radicals or arresting the cell cycle. Instead, they claim it employs a "novel mechanism" involving "intracellular signaling, damage sensing, and DNA repair pathways".[4] Ex-RAD is a chlorobenzylsulfone derivative that works after free radicals have damaged DNA. Onconova CEO Ramesh Kumar believes this is a better approach than trying to scavenge free radicals.