Leflunomide in Combination With Decitabine

The goal of this interventional clinical trial is to evaluate the safety and tolerability of leflunomide in combination with decitabine as treatment for patients with relapsed or refractory myelodysplastic syndromes (R/R MDS). The main question this study aims to answer are to evaluate and estimate the maximum tolerated doses and/or biologically active doses of the combination of leflunomide-decitabine in participants. Decitabine will be administered at a dose of 20 mg/m2 by continuous intravenous infusion over one hour repeated daily for 5 days with repeating cycle every 4 weeks. Leflunomide is administered orally at 10 to 20 mg once daily (without a loading dose) for 14 to 21 days, as part of a 28-day treatment cycle in adult subjects with R/R MDS. After 12 cycles (study duration) responding patients can continue progression with the assigned doses.