The patient will have been treated according to the Interfant-06 protocol where they will have received standard induction therapy. If the patient is eligible for the current study, blinatumomab will be added to standard arm (1B) of the Interfant-06 protocol. The patient will receive 1 course of blinatumomab. The blinatumomab course (15 micrograms/m2/day) consists of a 4-week continuous intravenous infusion. The patient will be closely monitored during the first 72 hours of treatment and will be admitted to the hospital preferably for the full 4 weeks of the blinatumomab infusion with a minimum admission of 7 days. Following treatment with blinatumomab, the patient wil lrecommence standard treatment according to Interfant-06 (protocol 1B).