Here, we describe the preclinical efficacy and safety of the bispecific CD123/CD16A innate cell engager “AFM28”, demonstrating superior activity against AML and MDS patient-derived LSPCs and blasts in vitro compared to an Fc-enhanced CD123-targeting antibody, especially towards CD123low and/or CD64+ leukemic cells. The gene discussed is FCGR1A; the disease is myelodysplastic syndrome.