A Prospective Study On Drug Monitoring Of Pegasparaginase and Erwinia Asparaginase and Asparaginase Antibodies In Pediatric Acute Lymphoblastic Leukemia

A prospective drug monitoring study was performed to analyse the efficacy of very prolonged use of PEGasparaginase and Erwiniaasparaginase by assessing asparaginase activity, asparagine, glutamine levels and asparaginase antibodies in children with newly diagnosed acute lymphoblastic leukemia (ALL).

Children received 15 PEGasparaginase infusions (2,500 IU/m² every other week) according to the Dutch Childhood Oncology Group (DCOG)-ALL-10 medium risk intensification protocol after having received native E.coli asparaginase (5,000 IU/m² every 3 days, 8 doses in total) in the induction course. In case of an allergy to or silent inactivation of PEGasparaginase, Erwinia asparaginase (20,000 IU/m²2x-3x per week) was given. All asparaginase preparations were administered intravenously in one hour. Serum asparaginase activity, asparagine, glutamine levels and asparaginase antibodies were measured.

89 patients were enrolled in two centers to monitor the PEGasparaginase courses. 62/89 (70%) patients without clinical allergy to and without silent inactivation of PEGasparaginase had serum mean trough activity levels of 899 U/L which were much higher than requested. 20/89 (22%) of the patients showed an allergy and 7/89 (8%) silent inactivation in intensification. All 20 allergic patients (grade 1-4 Common Terminology Criteria Adverse Events) showed PEGasparaginase activity levels of zero. This was not due to the fact that the PEGasparaginase infusion was stopped, as 18 patients showed their allergic reactions at the second dose whereas the serum asparaginase activity level after the first full dose already appeared to be zero in all 18 cases. Moreover, in 4 patients with grade 1 allergy, the second full PEGasparaginase dose was given with pre-treatment of clemastine and hydrocortisone, also resulting in unmeasurable serum activity levels of PEGasparaginase.

59 children from 7 centers with allergy to or silent inactivation of PEGasparaginase who were switched to Erwinia asparaginase were enrolled to monitor the Erwiniaasparaginase courses.

Only 2/59 (3%) of the patients developed an allergy to Erwinia asparaginase. No patients with silent inactivation of Erwinia asparaginase were seen. Of the non-allergic Erwinia asparaginase patients, 55/57 (96%) had at least one serum Erwinia asparaginase trough activity level ≥ 100 U/L and 57/57 (100%) ≥ 50 U/L. In 65% and 85% of all samples had serum trough activity levels ≥ 100 U/L and ≥ 50 U/L, respectively. In 33% of patients, the administration frequency could be reduced from 3 times to 2 times per week based upon serum Erwinia asparaginase activity levels ≥ 100 U/L at 72 hours. Serum asparagine level was strongly depleted, but not always completely depleted in Erwinia asparaginase treated patients in contrast to PEGasparaginase. Serum glutamine level was slightly lowered by Erwiniaasparaginase, but no glutamine depletion was observed with both compounds. The presence of serum asparaginase antibodies is related to allergy to and silent inactivation of asparaginase, but predicting asparaginase allergy or silent inactivation is clinically not applicable because of the low specificity, 64% (95%-CI: 43%-82%).

The use of native E.coli asparaginase in induction leads to 22% allergy and 8% silent inactivation rates of PEGasparaginase in intensification. Therefore, PEGasparaginase should be used upfront already in the induction course instead of native E.coli asparaginase. The dose of PEGasparaginase of 2,500 IU/m² can be lowered. Switching to Erwinia asparaginase in case of allergy to or silent inactivation of PEGasparaginase leads to effective asparaginase activity levels in the majority of patients. Measuring serum asparaginase activity levels to monitor efficacy of asparaginase is preferred over serum asparagine levels and serum asparaginase antibodies. Therapeutic drug monitoring has now been implemented to individualize PEGasparaginase and Erwinia asparaginase dose and to detect silent inactivation in the current DCOG-ALL-11 protocol.

No relevant conflicts of interest to declare.