Vandetanib, an orally active, small-molecule, multitargeted tyrosine kinase inhibitor, demonstrates potent inhibitory activity against vascular endothelial growth factor receptor (VEGFR)-2 and -3, epidermal growth factor receptor (EGFR) and the rearranged during transfection (RET) tyrosine kinase receptor. The large (n=331), randomized, double-blind, multinational ZETA trial compared vandetanib at a dosage of 300 mg once daily with placebo in patients with unresectable, locally advanced or metastatic, hereditary or sporadic, medullary thyroid cancer. During a median follow-up period of 2 years, vandetanib demonstrated statistically significant clinical benefits over placebo with respect to the primary endpoint, namely progression-free survival (PFS), and a range of secondary endpoints, which included objective response rate, disease control rate, time to worsening of pain and calcitonin biochemical response rate. The PFS benefit with vandetanib was mostly consistent across patient subgroups based on baseline characteristics and disease status. Although the correlation between RET mutation status and clinical outcome could not be clearly evaluated in this trial, it is notable that, among patients with sporadic disease, vandetanib not only demonstrated a PFS benefit in the subgroup confirmed as having a RET mutation, but also in the subgroup for whom the RET mutation status was unknown. Vandetanib was generally well tolerated in the ZETA trial; the majority of adverse events were manageable according to standard clinical practice alone or in combination with vandetanib dose reductions. The adverse event of most concern is corrected QT interval prolongation, particularly in view of the long terminal elimination half-life of the drug.