Sunitinib and its active metabolite (SU012662) are selective inhibitors of multiple receptor tyrosine kinases associated with tumour growth and angiogenesis. The clinical efficacy of oral sunitinib has been demonstrated in patients with advanced gastrointestinal stromal tumours (GIST). In a phase III, randomised, double-blind, placebo-controlled, multicentre trial in patients with metastatic and/or unresectable GIST following unsuccessful imatinib therapy, the median time to tumour progression and median progression-free survival time were > or =4-fold longer in patients receiving sunitinib 50 mg/day than in those receiving placebo, in 6-week cycles consisting of 4 weeks of treatment followed by a 2-week rest period. Sunitinib also exhibited antitumour activity in patients with advanced renal cell carcinoma (RCC) following unsuccessful cytokine therapy. In two multicentre, single-arm, phase II clinical trials in patients with cytokine-refractory metastatic RCC, partial responses were reported in 40% and 43% of patients receiving sunitinib 50 mg/day for 4 weeks followed by 2 weeks without treatment in 6-week cycles; 27% and 22% of patients achieved stable disease for > or =3 months. Sunitinib was more effective than interferon-alpha as a first-line therapy in patients with metastatic RCC. In a large, well designed, phase III trial in previously untreated patients, progression-free survival was significantly longer in patients receiving sunitinib 50 mg/day in 6-week cycles (4 weeks of treatment followed by a 2-week rest period) compared with those receiving interferon-alpha 9MU three times weekly (47.3 vs 24.9 weeks). In general, sunitinib was well tolerated in patients with GIST and RCC, with adverse events usually being of mild or moderate severity.