Combination of 5-azacitidine and Lenalidomide in Myelodysplastic Syndromes (MDS) or Acute Myelogenous Leukemia (AML) Myelodysplastic Syndromes

Inclusion Criteria: * Understand and voluntarily sign an informed consent form. * Age \>=18 years at the time of signing the informed consent form. * Able to adhere to the study visit schedule and other protocol requirements. * Relapsed or refractory AML (\>30% blasts, FAB classification)with karyotype abnormalities involving monosomy 5 or del(5q) or MDS and t-MDS INT-2 or HIGH according to IPSS classification with karyotype abnormalities involving monosomy 5 or del(5q) either previously treated or untreated * Not eligible for an immediate allogeneic HSCT (due to donor unavailability) * All previous MDS or AML specific therapy with exception of corticosteroids not exceeding doses of 10mg/day prednisone must have been discontinued at least 1 week prior to study enrollment. * Non-hematological toxicity (except alopecia) resulting from previous treatment must be resolved to WHO CTC Grade ≤ 2. * ECOG performance status of \< 3 at study entry. * Laboratory test results within these ranges:Serum creatinine \<= 2.0 mg/dL, Total bilirubin \<= 3 x ULN, AST (SGOT) and ALT (SGPT) \<= 3 x ULN * Females of childbearing potential must agree to use a 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 28 days before starting study drug; 2) while participating in the study; and 3) for at least 28 days after discontinuation from the study. Exclusion Criteria: * Any serious medical condition, laboratory abnormality, or psychiatric illness that would prevent the subject from signing the informed consent form. * Pregnant or breast feeding females. (Lactating females must agree not to breast feed while on study). * Any condition, including the presence of laboratory abnormalities, which places the subject at unacceptable risk if he/she were to participate in the study or confounds the ability to interpret data from the study. * Known hypersensitivity to thalidomide, lenalidomide, 5-azacitidine or mannitol. * Myocardial infarction within 6 months before study entry, New York Heart Association Class III or IV heart failure, uncontrolled angina or severe uncontrolled ventricular arrhythmias. * The development of erythema nodosum if characterized by a desquamating rash while taking thalidomide or similar drugs. * Uncontrolled lung disease. * Known positive for HIV or acute infectious hepatitis, type A, B or C. * Participation in another clinical study in the 4 weeks prior to enrollment or during this study.