In Reply I thank Herold et al for their thoughtful letter and their commitment to improving the drug development process for children with cancer. As a leader of an international collaborative childhood cancer research organization, in my experience—contrary to their conclusion—the process surrounding pediatric investigation plan approvals is delaying the onset of a number of pediatric phase 1 cancer trials. While it is fully appreciated that completed early-phase trials have been accepted in the past by the European Medicines Agency, it is likely the effect of regulatory uncertainty1 that leads a number of biopharmaceutical industry sponsors to delay the onset of pediatric clinical research until a pediatric investigation plan is approved.