Patients will be enrolled sequentially in cohorts and treated at different dose levels of F16IL2 and a fixed dose of cytarabine. All patients first receive an initial run-in dose of 30 Mio IU of F16IL2 on day 1 and escalating doses of F16IL2 on day 1, 8, 15 and 22. Patients will be treated with cytarabine (5 mg twice daily s.c. for 10 days). The following F16IL2 administration will be at the dose of the respective cohort (days 8, 15 and 22).