Pivekimab Sunirine in Blastic Plasmacytoid Dendritic Cell Neoplasm

PURPOSE: Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a unique myeloid malignancy with CD123 interleukin-3 receptor-α overexpression and poor prognosis. METHODS: This phase I/II, open-label, multicenter study evaluated pivekimab sunirine (PVEK), a novel CD123 antibody-drug conjugate, 0.045 mg/kg once every 3 weeks, in adults with frontline (no previous systemic therapy and de novo BPDCN or coexisting hematologic malignancy) or relapsed/refractory BPDCN (ClinicalTrials.gov identifier: NCT03386513) The primary end point in the primary analysis population (PAP; frontline de novo) was composite complete response (CCR; CR+ clinical CR) rate. RESULTS: Of 84 patients, 33 had frontline BPDCN (22 de novo [20 in PAP]; 11 with previous or concomitant malignancy) and 51 had relapsed/refractory disease. The median (range) age was 72 (63-76) years. In the PAP (n = 20), the CCR rate was 75% (95% CI, 51 to 91; n = 15; median duration: 10.6 [95% CI, 3.8 to not reached] months) and the median overall survival (OS) was 16.6 (95% CI, 7.2 to not reached) months. Eight of these 15 (53%) patients proceeded to stem-cell transplant (SCT). The corresponding rate for relapsed/refractory disease was 14% (95% CI, 6 to 26; n = 7; median duration: 9.2 [95% CI, 2.4 to not reached] months), and the median OS was 5.8 (95% CI, 3.9 to 8.4) months. Adverse events (AEs) included peripheral edema (54%), fatigue (26%), and infusion-related reactions (26%). Grade ≥3 events included neutropenia (16%), thrombocytopenia (14%), and peripheral edema (12%). Serious AEs included pneumonia (6%) and febrile neutropenia (5%). Two on-treatment cases of reversible veno-occlusive disease (VOD) occurred. Of the total 19 patients who proceeded to SCT, VOD was reported in five patients (four with relapsed/refractory BPDCN). CONCLUSION: PVEK, with convenient dosing, led to high, durable responses, especially in frontline BPDCN, and a manageable safety profile.