Inclusion Criteria:

- B-precursor ALL patients in complete hematological remission with molecular failure
or molecular relapse starting at any time after consolidation I of front-line therapy
within GMALL standards or at any time outside GMALL standards.

- Patients must have a molecular marker for evaluation of minimal residual disease
which is either Bcr/abl at any detection level or individual rearrangements of
immunoglobulin or TCR-genes measured by an assay with a sensitivity of minimum 10-4:
At least one individual marker at a quantitative level ³10-4.

- ECOG Performance Status < 2

- Ability to understand and willingness to sign a written informed consent

- Signed and dated written informed consent is available

Exclusion Criteria:

- Current extra medullar involvement

- History of or current relevant CNS pathology (except migraine/headache and/or
previous infiltration of cerebrospinal fluid (CSF) by ALL)

- Current infiltration of cerebrospinal fluid by ALL

- History of or current autoimmune disease

- Autologous stem cell transplantation within 6 weeks prior to study entry

- Any prior allogeneic stem cell transplantation

- Cancer chemotherapy within 4 weeks prior to study treatment (except for intrathecal
prophylaxis and/or low dose maintenance therapy such as vincalkaloids,
mercaptopurine, methotrexate, steroids)

- Radiotherapy within 4 weeks prior to study treatment

- Therapy with monoclonal antibodies (Rituximab, MabCampath) within 6 weeks prior to
study treatment

- Known hypersensitivity to immunoglobulins or to any other component of the study drug
formulation

- Presence of human anti-murine antibodies (HAMA)

- Abnormal bone marrow, renal or hepatic function

- Indication for a hypercoagulative state

- History of malignancy other than ALL within 5 years prior to study entry, with the
exception of basal cell carcinoma of the skin or cervix carcinoma in situ

- Active severe infection, any other concurrent disease or medical condition that are
deemed to interfere with the conduct of the study as judged by the investigator

- Known infection with human immunodeficiency virus (HIV) or chronic infection with
hepatitis B virus (HbsAg positive) or hepatitis C virus (anti-HCV positive

- Pregnant or nursing women

- Women of childbearing potential not willing to use an effective form of contraception
during participation in the study and at least 3 months thereafter or male patients
not willing to ensure effective contraception dur-ing participation in the study and
at least three months thereafter