Polyethylene glycol conjugated asparaginase (PEG-ASNase) can be substituted in cases of hypersensitivity to native Escherichia coli asparaginase. We measured asparagine (asn) levels in plasma after a single dose of 2,500 IU/m(2) i.v. PEG-ASNase (Oncaspar) in consolidation treatment of ALL and compared those with data from the previous protocol COALL-05-92. This protocol was similar to COALL-06-97, except that children had been given 45,000 IU/m(2) C-ASNase instead of PEG-ASNase.
Patients and methods: Between May 2000 and December 2001 seventy-one children (38 boys, 33 girls) with newly diagnosed ALL treated according to the multicenter protocol COALL-06-97 were investigated in this study. Four hundred and seventy-four plasma samples (71 patients) were analysed by ion exchange chromatography after column derivatization with o-phthaldialdehyde. For comparison data (350 plasma samples) from 51 patients treated according to the protocol COALL-05-92 were available. The same method for detection of asn in plasma was used.
Results: The median asparagine level in plasma after 2,500 IU/m(2) PEG-ASNase i.v. was below the limit of detection for at least 5 weeks in 81 % of the patients. When divided into high risk (HR) and low risk (LR) group, HR patients who had previously received one dose more of C-ASNase showed a markedly shorter depletion than the LR patients compatible with a higher risk of antibody formation and consequent silent inactivation after a higher number of exposures to ASNase. In the previous protocol COALL-05-92 median asn levels in plasma after 45,000 IU/m(2) native C-ASNase i.v. were below the limit of detection for at least 5 weeks in 65 % of the patients.
Conclusions: 2,500 IU/m(2) PEG-ASNase led to an equally long depletion of asn in plasma as did 45,000 IU/m(2) native C-ASNase i.v. used in COALL-05-92.