Efficacy and Tolerability of the Combination of Valproic Acid and Lenalidomide in the Treatment of Patients With Myelodysplastic Syndrome

Inclusion Criteria: * Cytologically/histologically confirmed primary myelodysplastic syndrome (pMDS) with a favorable risk profile, i.e., low or intermediate I risk group according to IPSS (\<10% blasts, no unfavorable karyotype) * platelet count ≥50.000/µl * absolute neutrophil count ≥1.000/µl * age ≥18 years at the time of signing the informed consent form * Karnofsky performance status \> 50% * written informed consent to participate * erythropoietin level \> 200 mU/ml or failure of previous therapy with erythropoietin * patients in whom allogeneic bone marrow transplantation, treatment with growth factors or immune therapy is not possible due to medical or biologic reasons or patients in whom such a therapy would be possible but who do not agree to such a therapy for personal reasons * females of childbearing potential (FCBP, see page 23) must agree to one reliable form of contraception or to practice complete abstinence from heterosexual intercourse during the following time periods related to this study: 1) for at least 4 weeks before starting study drug; 2) while participating in the study, even during treatment interruptions; and 3) for at least 4 weeks after discontinuation from the study. Exclusion Criteria: * patients with 5q deletion * MDS treated with experimental therapy or chemotherapy within 4 weeks prior to start of treatment with study drugs * previous treatment of MDS with valproic acid or lenalidomide as monotherapy patients suitable for chemotherapy, therapy with growth factors or allogeneic bone marrow transplantation and who are willing to start such a therapy * hypersensitivity to thalidomide * insufficient liver function (bilirubin, AST or ALT \> 2 x ULN) * hepatic disease \[details see full protocol\] * markedly impaired renal function (serum creatinine \> 2mg/dl) * pregnancy, breast feeding, lactation, refusal to use safe contraceptive methods during the study * psychiatric disease or addiction with impaired ability to act and make decisions according to one's free will * participation in another interventional study 4 weeks prior to or during this study * known hypersensitivity or allergies to one of the study drugs or their ingredients * plasmatic coagulation disorder