MPN-467 Findings From an Observational, Multicenter, Retrospective Analysis of Patients With Blastic Plasmacytoid Dendritic Cell Neoplasm Treated With Tagraxofusp in the European Expanded Access Program.

Abstract

Blastic plasmacytoid dendritic cell neoplasm (BPDCN), an aggressive hematologic malignancy with poor prognosis, is characterized by clonal expansion of plasmacytoid dendritic tumor cells expressing specific markers including the interleukin-3 receptor alpha (CD123). Tagraxofusp (TAG) is a CD123-targeted therapy approved by the FDA and EMA. A global expanded access program (EAP) was implemented prior to TAG's EMA authorization to provide access to patients in real-world practice. Main objectives were rates of complete response and incidence/severity of capillary leak syndrome (CLS). Key secondary objectives included rate of patients bridged to transplantation, survival, safety, number of cycles administered. Non-interventional, retrospective analysis of BPDCN patients enrolled in the European EAP from 08.2019-12.2021. 57 European centers (Germany, France, Italy, Switzerland, United Kingdom, Spain, Austria). 76 adult (median age 64 years, range 21-85 years) and 4 pediatric patients with BPDCN confirmed by hematopathology with established marker panels (including CD123). TAG 12 mcg/kg was administered intravenously once daily on days 1-5 (up to day 10 allowed) of a 21-day cycle. Hospitalization was required for the first cycle (subsequent cycles allowed outpatient administration). Review of case report forms and individual records of patients who met criteria for TAG prior to regulatory approval. Most patients were male (78%), representing real-world distribution. Sixty-three patients received TAG first-line and 17 patients as second/or further line of treatment. The median number of cycles was 2.5 (range 1-8) in first-line and 2.6 (range 1-13) in second-line/further, respectively. No deaths due to CLS were reported. Adverse events (AEs) mainly occurred in cycle 1, with similar rates and severity in older vs younger patients. Analysis is ongoing; data on safety, efficacy, transplantation, and time-related parameters will be reported. The is the largest retrospective analysis of real-world clinical practice outside of a clinical trial in BPDCN patients treated with TAG. Adherence to the EAP and multidisciplinary training is thought to have positively affected prevention and management of CLS and other grade 3-4 AEs. These preliminary results confirm the feasibility and safety of TAG, including in elderly patients, with manageable safety.