At present the pegylated long-acting form of L-asparaginase (PEG-ASP) is by far the most used therapeutic option in both adult and paediatric ALL patients due to a more prolonged effect, a reduced incidence of silent antibody and more rapid clearance of lymphoblasts than native asparaginase (Avramis et al., 2002). The gene discussed is ASPG; the disease is acute lymphoblastic leukemia.