FDA approves Elzonris for blastic plasmacytoid dendritic cell neoplasm

Richard Pazdur

The FDA approved tagraxofusp-erzs for the treatment of blastic plasmacytoid dendritic cell neoplasm in adults and children aged 2 years and older.

Blastic plasmacytoid dendritic cell neoplasm — a rare and aggressive blood and bone marrow disorder that can affect many organs, including the skin and lymph nodes — occurs more commonly in men and those aged 60 years or older. It frequently presents as leukemia or evolves into acute leukemia.

“Prior to [this] approval, there had been no FDA-approved therapies for blastic plasmacytoid dendritic cell neoplasm,” Richard Pazdur, MD, director of the FDA’s Oncology Center of Excellence and acting director of the Office of Hematology and Oncology Products in the FDA’s Center for Drug Evaluation and Research, said in a press release. “The standard of care has been intensive chemotherapy followed by bone marrow transplantation. Many patients with blastic plasmacytoid dendritic cell neoplasm are unable to tolerate this intensive therapy, so there is an urgent need for alternative treatment options.”

Approval of tagraxofusp-erzs (Elzonris, Stemline Therapeutics) — a CD123-directed cytotoxin — was based, in part, on data from the multicenter, multicohort, open-label, single-arm STML-401-0114 clinical trial. Patients with untreated or relapsed/refractory blastic plasmacytoid dendritic cell neoplasm received 12 mcg/kg IV tagraxofusp-erzs over 15 minutes once daily on days 1 to 5 of a 21-day cycle.

Seven of 13 (53.8%; 95% CI, 25.1-80.8) previously untreated patients in the pivotal cohort achieved complete response or clinical complete response after a medial follow-up of 11.5 months. Median duration of response was not reached.

In a second cohort of 15 patients with relapsed or refractory disease, one patient achieved a complete response lasting 111 days, and one patient achieved a clinical complete response lasting 424 days.

Common adverse events that occurred in at least 30% of the cohort included capillary leak syndrome, nausea, fatigue, peripheral edema, pyrexia and weight increase. Most common laboratory abnormalities (incidence 50%) were decreases in albumin, platelets, hemoglobin, calcium and sodium, and increases in glucose and liver enzymes.

The labeling for tagraxofusp-erzs contains a boxed warning regarding the increased risk for capillary leak syndrome, which may be life-threatening or fatal.

Tagraxofusp-erzs also received breakthrough therapy, priority review and orphan drug designations.