Tagraxofusp Refractory Blastic Plasmacytoid Dendritic Cell Neoplasm With Loss of CD123 Expression: Case and Review of Literature

Abstract Background: Tagraxofusp, a CD123 based targeted immunotherapy, was recently approved to treat blastic plasmacytoid dendritic cell neoplasm (BPDCN) with excellent response. Also, a subset of BPDCN showed resistance to tagraxofusp. These resistant cases continue to express CD123, which forms the basis of the continued utility of tagraxofusp in newer combination chemotherapies to overcome resistance in BPDCN. Case presentation: Herein we report a case of an elderly male with BPDCN that initially achieved complete remission on primary treatment with tagraxofusp. However, BPDCN relapsed after 1.5 years while on treatment with loss of CD123 expression. Conclusions: This case highlights a potential limitation of current and upcoming tagraxofusp based therapies, at least in a subset of refractory BPDCN. We believe our report will serve as a sentinel to incite future investigations involving alternate resistance mechanisms in BDPCN.