The antibody-based delivery of interleukin-2 (IL-2) to extracellular targets expressed in the easily accessible tumor-associated vasculature has shown potent anti-leukemic activity in xenograft and immunocompetent murine models of acute myeloid leukemia (AML), especially in combination with cytarabine. Here, we report our experiences in four patients with relapsed AML after allogeneic hematopoietic stem cell transplantation (allo-HSCT), who were treated with the immunocytokine F16-IL2, in combination with low-dose cytarabine (LDAC). One patient with disseminated extramedullary AML lesions achieved a complete metabolic response in PET/CT, which lasted three months. Two out of three patients with bone marrow (BM) relapse achieved a blast reduction with transient molecular negativity. One of the two enjoyed a short complete remission before AML relapse occurred two months after the first infusion of F16-IL2. In line with a site-directed delivery of the cytokine, F16-IL2 led to an extensive infiltration of immune effector cells in the BM. Grade 2 fevers were the only non-hematological side effects in two patients. Grade 3 cytokine-release syndrome developed in the other two patients, but was manageable in both cases with glucocorticoids. The concept of specifically targeting IL-2 to the leukemia-associated stroma deserves further evaluation in clinical trials, especially in patients who relapse after allo-HSCT.
- Received September 23, 2014.
- Revision received January 5, 2015.
- Accepted January 30, 2015.
- Copyright © 2015, American Association for Cancer Research.