The main objective of this trial is to evaluate the efficacy and toxicity of intensive immuno-suppression with ATG + CSA versus best supportive care in patients with transfusion dependent low and intermediate risk myelodysplastic syndrome (MDS).

This trial will answer the question whether immuno-suppression improves hematopoesis and reduces transfusion requirements analogous to patients with aplastic anemia as the short-term outcome, and whether immuno-suppression accelerates leukemic transformation and influences survival as the long-term outcome.

Primary endpoint: best response (CR + PR) rate at month 6

Hypoplastic MDS, or MDS subtype RA, RAS or RAEB with ≤ 10% blasts, or RAEB with 10-20% blasts and the patient refusing or not eligible for the MDS high risk protocol (EORTC 06961)

• Transfusion dependence < 24 months or neutrophils < 0.5 × 109/l.
• ECOG/SAKK performance status ≤ 2
• Age > 18 years
• No active uncontrolled infection
• No prior chemotherapy or radiotherapy
• No history of heart failure, clinically relevant cardiac arrhythmia or other hemato-oncological disease