Mode-of Action

The chimeric and Fc-optimized IgG1 antibody FLYSYN binds specifically and with high avidity to the human fms-like tyrosine kinase 3 (FLT3). An increased expression of this cell surface receptor is measured on leukemic blast cells in 70% to 100% of acute myeloid leukemia (AML) patients, while only small amounts of FLT3 are expressed on monocytes and progenitor stem cells, avoiding off-target binding and stem cell toxicity. Therefore, FLT3 is a suitable and highly selective target for therapeutic antibodies to treat leukemia patients. FLYSYN contains a genetic optimization of its Fc-part resulting in optimized binding to cells expressing the Fc receptor, particularly Natural Killer (NK) cells, and thus substantially improved antibody dependent cell-mediated cytotoxicity (ADCC).





FLYSYN is a monospecific antibody for the treatment of acute myeloid leukemia (AML) patients at a stage of minimum residual disease (MRD). Most acute myeloid leukemia (AML) patients achieve complete remission (CR) with minimal residual disease (MRD) status after regular chemotherapy, but the majority of these patients relapse to AML within several months, requiring additional courses of chemotherapy or stem cell transplantation. FLYSYN is intended to delay or prevent such relapse in AML patients with MRD.

Approximately 20,000 and 27,000 new cases of acute myeloid leukemia (AML) occur annually in the United States and Europe, respectively. Acute myeloid leukemia occurs mainly in elderly patients and the mean age of diagnosis is approximately 70 years. The average five year survival rate for acute myeloid leukemia is 26%. Consequently there is a high medical need for effective treatments of the disease.



Development Stage

FLYSYN is currently evaluated in a First-in-Man clinical study at the University Hospitals of Tuebingen and Ulm in patients with acute myeloid leukemia (AML) with minimal residual disease (MRD).


For AML Patients interested in our clinical study:


More information about the clinical study can be found at the following links:


FLYSYN is subject to granted patents in the EU, USA, China and Japan.