BACKGROUND: Angiogenesis is implicated in the pathophysiology and progression of myelodysplastic syndromes (MDS). Vatalanib (PTK787/ZK222584; Novartis and Schering AG) inhibits receptor tyrosine kinases of vascular endothelial growth factor, platelet derived growth factor and c-Kit. We examined whether vatalanib induces hematological responses in MDS and/or delays progression to acute myeloid leukemia (AML) or death. METHODS: Two cohorts were studied. Vatalanib 1250 mg orally was given once daily (cohort 1) or 750-1250 mg once daily in an intra-patient dose escalating schedule (cohort 2) in 28-day cycles to 155 patients with MDS; 142 patients were evaluable for response and 153 for toxicity. RESULTS: The median age was 70.5 years; 51 % had low risk (International Prognostic Scoring System {IPSS} Low/Intermediate-1) and 32 % had high risk (IPSS Intermediate-2/High) MDS. Hematological improvement was achieved in 7/142 (5 %) patients; all 7 were among the 47 patients able to remain on vatalanib for at least 3 months (hematological improvement achieved in 15 % of these 47 patients). For patients with low risk and high risk MDS, respectively, median progression-free survivals were 15 and 6 months, median times to transformation to AML were 28 and 6 months, and median overall survivals were 36 and 10 months. The most frequent non-hematological adverse events grade ≥ 2 were fatigue, nausea or vomiting, dizziness, anorexia, ataxia, diarrhea, and pain. Two deaths (one intra-cerebral hemorrhage and one sudden death) were possibly related to vatalanib. CONCLUSIONS: Vatalanib induces improvement in blood counts in a small proportion of MDS patients. Clinical applicability is limited by side effects.