Pharmacokinetics and Immunogenicity of the First Doses of PEG-Asparaginase -An ALLTogether Pilot Study

Asp enzyme activity is measurable in plasma, and trough levels above 100 IU/l secure effect. Patients, who have their treatment truncated, have inferior outcome. For many years prolonged Asp treatment for 30 weeks has been part of most protocols worldwide, but a recent Nordic randomized study showed that less asparaginase (8 doses vs 15 doses intramuscularly (IM)) results in the same disease-free survival and significant less toxicity in the less intensive treatment arm (6).

Accordingly, in the current Western European protocol (ALLTogether) less Asp is now given. The Nordic Countries participate in this protocol.

Unlike in the previous Nordic protocol, NOPHO ALL2008, in ALLTogether Asp will be initiated early during induction (day 4 compared to day 30) and given intravenously (IV) and not IM. In February 2017 it was approved by the NOPHO Board to do more extensive pharmacokinetic studies of IM administered PEG-asparaginase, as it has not been shown if IM or IV is preferably in respect to minimizing the incidence of hypersensitivity. Most study groups in the world use IV administration, thus NOPHO has a unique chance to illuminate inactivation after IM administration, also in adult patients. Other groups have not published this.

For >50% of the patients in ALLTogether, the induction therapy has been reduced from 4 drugs to 3 drugs. This emphasizes the importance of optimal treatment from the beginning. Therapeutic Drug Monitoring (TDM) will identify patients without activity in order to change Asp preparation. Additional sampling close after the first dose of PEG-Asp is expected to identify these patients earlier, providing an opportunity to optimize their treatment for better disease-free survival.

The aim of this study is to identify serological parameters for prediction of hypersensitivity reaction after the first dose of PEG-Asp given IV on the ALLTogether protocol.