Bacterial L-asparaginase (ASNase), hydrolyzing L-asparagine (Asn), is an indispensable component used in the treatment of acute lymphoblastic leukemia (ALL) and certain lymphoma entities. Native Erwinia chrysanthemi-derived ASNase (n-crisantaspase) has been approved as a second-line drug for treating patients exhibiting allergy syndromes to native and pegylated Escherichia coli-derived ASNase (EC-ASNase). However, it still induces hypersensitivity in at least 17 % of treated patients. In the present study, we investigated the pharmacological activity, immunogenicity and anti-leukemic activity of a new pegylated recombinant crisantaspase (PEG-r-crisantaspase). The results demonstrate that when compared to n-crisantaspase in vivo, PEG-r-crisantaspase maintains a complete depletion of plasma Asn for up to 72 h with a 50-fold lower dose. In mice receiving PEG-r-crisantaspase, specific antibodies against the enzyme were undetectable, indicating a lower immunogenicity of the pegylated enzyme. In vitro, PEG-r-crisantaspase exhibits similar cytotoxic effects (EC50 < 5 × 10(-4) U/mL for the most sensitive cell lines) to n-crisantaspase on various leukemia and lymphoma cells and was shown to be more efficient than EC-ASNase. Three repeated PEG-r-crisantaspase injections (2-20 U/Kg) prevented leukemia development in leukemia-bearing mice for 17 days and significantly prolonged animal survival to 7-12 days. Therefore, PEG-r-crisantaspase appears to be a promising drug candidate for ALL treatment and should be further explored in experimental and clinical trials.