Acute myeloid leukemia is most often diagnosed in patients older than 60 years of age. Overall, these patients have a poor prognosis, partly because they are typically unable to tolerate intensive chemotherapy regimens traditionally offered to younger individuals. Furthermore, responses attained in these older patients are not durable, with most experiencing relapse within 1-2 years. Therefore, new strategies are needed to improve the outcome of older patients with acute myeloid leukemia. Tosedostat is an orally available aminopeptidase inhibitor shown to have activity in leukemia. This commentary discusses the background and results of an ongoing Phase II evaluation of tosedostat in elderly patients with relapsed or refractory acute myeloid leukemia. The data available to date is analyzed and future perspectives regarding the development of this agent is discussed.