Alemtuzumab is an anti CD52 monoclonal antibody. The CD52 antigen is present at the surface of B,T NK lymphocytes. It is expressed at various levels at the surface of ALL blast cells. Adult patients with ALL in relapse have less than 10% probability of long term survival. The present study will test the response rate (partial and complete remission) of refractory ALL or ALL in relapse. It is hoped that if a CR can be achieved, further consideration will be given for a hematopoietic stem cell transplant.

The use of G-CSF is justified by a possible increase in ADCC.

All patients receive Alemtuzumab in 3 successive phases:

Phase A: Test week: 3mg, then 10mg, then 30mg every other day for one week to test for tolerance.

Phase B: 30mg 3 times a week for 12 to 18 administrations until response or progression/failure has been documented.

Phase C: in patients in CR, maintenance with Alemtuzumab: 3 injections one week every 2 months.

Inclusion Criteria:

• Patients older than 15 years
• Refractory ALL
• ALL in relapse post chemotherapy or post transplant
• ALL blast cells expressing CD 52 antigen at any time during the evolution of the disease.
• Signed informed consent
• Patients under social security coverage
• Anti conceptional tablets in pre menopausal women.

Exclusion Criteria:

• Children below 15 years of age or aged 15
• Blast cells not expressing CD52 antigen (at all evaluations)
• HIV positivity
• ECOG Score 3 and 4
• Hypersensitivity to Alemtuzumab.
• Pregnancy or breast feeding.
• Other malignant disease in addition to ALL.