Relapse of tagraxofusp treated blastic plasmacytoid dendritic cell neoplasm with loss of CD123 expression

Abstract Tagraxofusp, a CD123-based-targeted immunotherapy, was recently approved to treat blastic plasmacytoid dendritic cell neoplasm (BPDCN) with excellent response. Also, subset of BPDCN shows resistance tagraxofusp. These resistant cases continue express CD123, which forms the basis continued utility tagraxofusp in newer combination chemotherapies overcome BPDCN. Herein, we report case an elderly male that achieved complete remission on initial primary treatment However, relapsed after 1.5 years while treatment, loss CD123 expression. At relapse, comprehensively immunophenotyped by flow cytometry (performed both peripheral blood and bone marrow specimen) immunohistochemical evaluation clot section. The at relapse diagnostic lack This highlights potential limitation current upcoming tagraxofusp-based multidrug therapies, least refractory We believe our will serve as sentinel incite future investigations involving alternate mechanisms BDPCN.