The aim of this study is to evaluate the safety and efficacy of Carfilzumib, which is a novel biological agent used in the treatment of multiple myeloma in preventing graft-versus-host disease, after stem cells transplantation from unrelated donors.

Inclusion Criteria:

1. Patients with MDS/AML
2. 18 years or older and willing and able to comply with the protocol requirements.
3. LVEF ≥ 40%. 2-D transthoracic echocardiogram (ECHO) is the preferred method of evaluation. Multigated Acquisition Scan (MUGA) is acceptable if ECHO is not available.
4. Patients undergoing 8-10/10 HLA matched unrelated and unmanipulated PBSC transplantation
5. Patients conditioned with reduced intensity or reduced toxicity conditioning i.e. Fludarabine combine with Treosulfan or 2-4 days of I.V Busulfan.
6. Patients must sign written informed consent.
7. Adequate birth control in fertile patients.

Exclusion Criteria:

1. Patients undergoing other type of transplantation or with other type of basic disease other than AML or MDS.
2. Patients with respiratory failure (DLCO < 30%).
3. Active congestive heart failure (New York Heart Association [NYHA] Class III to IV), symptomatic ischemia, or conduction abnormalities uncontrolled by conventional intervention.
4. Patients with > grade II liver renal toxicity.
5. Psychiatric conditions/disease that impair the ability to give informed consent or to adequately co-operate
6. Bilirubin > 3.0 mg/dl, transaminases > 3 times upper normal limit
7. Creatinine > 2.0 mg/dl
8. ECOG-Performance status > 2
9. Uncontrolled infection
10. Pregnancy or lactation
11. CNS disease involvement
12. Pleural effusion or ascites > 1 liter.