This non-controlled multicentre phase II study is designed to assess the safety and to describe (in relation to children of higher age) the pharmacodynamics of recombinant ASNase (rASNase) for first-line treatment of infants (< 1 year of age at diagnosis) with de novo acute lymphoblastic leukaemia

Inclusion Criteria:

• Previously untreated T-lineage or precursor B-lineage ALL or biphenotypic leukaemia according to EGIL criteria.
• Morphological verification of the diagnosis, confirmed with cyto¬chemistry and immunophenotyping.
• Age < 1 year at diagnosis.
• Written informed consent of the parents or other legally authorised guardian of the patient.
• Treatment according to protocol INTERFANT 06

Exclusion Criteria:

• Mature B-lineage ALL, defined by the immunophenotypical presence of surface immunoglobulins or t(8;14) and breakpoint as in B-ALL.
• The presence of the t(9;22)(q34;q11) or bcr-abl fusion in the leukaemic cells.
• Systemic use of corticosteroids less than 4 weeks before diagnosis. Patients who received corticosteroids by aerosol are eligible.
• Known allergy to any ASNase preparation.
• Pre-existing known coagulopathy (e.g. haemophilia).
• Pre-existing pancreatitis.
• Liver insufficiency (bilirubin > 50 µmol/L; SGOT/SGPT > 10 x the upper limit of normal).