The results of a phase I/II study reveal that the selective aurora kinase A inhibitor alisertib might be an effective treatment of a range of solid tumours. Following oral administration of alisertib, partial responses to therapy were detected in some patients with breast (18%), small-cell lung (21%) or non-small-cell lung (4%), gastroesophageal (9%), or head and neck cancers (9%). In total, 43% of patients reported serious adverse events. Further testing, in phase III clinical trials, is required to establish the efficacy of alisertib.