AML-392 Treatment of Blastic Plasmacytoid Dendritic Cell Neoplasm in Pediatric Patients With Tagraxofusp, a CD123-Targeted Therapy

Abstract

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is an aggressive hematologic malignancy that primarily affects older adults, with pediatric patients making up 10%-20% of all cases. The rarity of BPDCN in the pediatric population makes collecting robust safety and efficacy data challenging, and there is a paucity of data published for pediatric patients. Tagraxofusp (TAG, SL-401) targets CD123, a molecule that is overexpressed in all cases of BPDCN, and is the only approved drug for treatment of adult and pediatric patients with BPDCN. To further expand the safety and efficacy data of TAG therapy in pediatric/young adult patients with newly diagnosed (1L) or relapsed/refractory (R/R) BPDCN. Multicenter retrospective collation of case reports. Data were collated and summarized descriptively. A total of 6 cancer centers across the US and Europe. Data were collected from pediatric/young adult patients with BPDCN who received TAG during their course of treatment. All patients received 12 mcg/kg TAG, while 1 patient also received 7 mcg/kg TAG at second relapse. Safety was assessed via monitoring of adverse events (AEs) and laboratory abnormalities. Efficacy was evaluated through tumor responses and survival. Eight pediatric patients (n=5, 1L; n=3, R/R) were included. The median age was 15.5 years (range 2-21), and 7 of the 8 patients were female. The median number of TAG cycles was 3.5 (range 1-4). All AEs occurred during cycle 1. One patient experienced grade 2 capillary leak syndrome, which was treated and resolved. Two patients experienced hypoalbuminemia, 2 had transaminitis, and 1 experienced headache, all of which were manageable. Three patients reported no AEs. Three 1L patients achieved a complete response, including 1 patient with extensive disease (skin, bone marrow, and central nervous system involvement). Five patients (n=3, 1L; n=2, R/R) were bridged to stem cell transplant (SCT) and 7 patients are alive at the time of publication. TAG demonstrated promising antitumor efficacy in pediatric/young adult patients with BPDCN, enabling 75% of this pediatric cohort to be bridged to SCT. TAG had a manageable safety profile, similar to that reported for adults.