Tagraxofusp, a novel CD123-directed cytotoxin to treat blastic plasmacytoid dendritic cell neoplasm

Tagraxofusp is a toxin-cytokine fusion protein consisting of engineered diphtheria toxin (DT) and interleukin-3 (IL-3). The IL-3 domain binds to the cluster of differentiation 123 (CD123) and translocates DT into the cytosol, which leads to cell death. Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and aggressive hematologic malignancy with a strong expression of CD123. Historical data show that the prognosis of BPDCN is poor, with a median overall survival of 9 to 13 months. On December 21, 2018, the United States Food and Drug Administration (FDA) approved tagraxofusp for the treatment of adults and children with newly diagnosed or relapsed/refractory BPDCN, becoming the first FDA-approved drug for this disease. In this review, we examine the preclinical studies and phase I/II clinical studies that led to FDA approval of tagraxofusp, focusing on its molecular pharmacology, pharmacokinetics, efficacy and safety profile. We also discuss future directions regarding BPDCN management.