Stemline Therapeutics, Inc. announced that its SL-401 has received Orphan Drug designation from the US Food and Drug Administration (FDA) for the treatment of blastic plasmacytoid dendritic cell neoplasm (BPDCN), a rare and aggressive hematologic malignancy for which there is no effective treatment. SL-401 also has Orphan Drug status for the treatment of acute myeloid leukaemia (AML).

SL-401 is a novel targeted therapy directed to the interleukin-3 receptor (IL-3R) present on tumour bulk and cancer stem cells (CSCs) of multiple hematologic cancer indications. SL-401 has demonstrated single agent clinical activity in patients with advanced hematologic cancers, including BPDCN, AML, and myelodysplastic syndrome (MDS).

"We are focused on the rapid development of SL-401 due to its potential for the treatment of IL-3R-expressing hematologic malignancies," commented Eric K Rowinsky, MD, chief medical officer and head of Research and Development at Stemline. "SL-401 is demonstrating robust clinical activity in heavily-pretreated patients with BPDCN who are refractory to available therapies, including high-dose chemotherapy and allogeneic stem cell transplantation. This Orphan Drug designation provides us with a number of benefits that further strengthen our SL-401 program. Stemline will progress SL-401 into pivotal trials in BPDCN and AML in the near-term, and we will continue to evaluate SL-401 in a wide range of additional IL-3R-expressing hematopoietic malignancies."

Orphan Drug designation is granted by the FDA's Office of Orphan Products Development for drugs that are expected to provide significant therapeutic advantage over existing treatments and that target conditions affecting 200,000 or fewer US patients annually. Orphan Drug designation qualifies a company for several benefits under the Orphan Drug Act of 1983. The benefits apply across all stages of drug development and include accelerated approval process; seven years of market exclusivity following marketing approval; tax credits on US clinical trials; eligibility for Orphan Drug grants; and waiver of Prescription Drug User Fee Act (PDUFA) and certain other administrative fees.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and aggressive hematologic cancer for which there is no effective treatment, carries a poor prognosis and represents an unmet medical need. BPDCN had previous names, including blastic NK cell lymphoma and agranular CD4+/CD56+ hematodermic neoplasm, until 2008 at which time the World Health Organization (WHO) renamed this disease BPDCN. The disease most commonly affects middle-aged and older patients and is approximately three times more common in men than women. BPDCN derives from plasmacytoid dendritic cells, which are specialized cells of the immune system. BPDCN cells express high levels of IL-3R. BPDCN, which has features of both leukemias as well as lymphomas, typically presents with skin lesions, and often also involves the bone marrow and blood, and can also involve the spleen and lymph nodes. BPDCN proliferation in the bone marrow results in decreased blood cell counts, which can lead to serious infections, anemia, bleeding, and invariably death. Although BPDCN can be controlled for brief periods with standard chemotherapy, including high-dose chemotherapy with bone marrow transplantation, overall prognosis remains poor and the median overall survival from diagnosis is approximately 12 months. There are currently no approved therapies for BPDCN, and an optimal therapeutic regimen for BPDCN has not yet been established.

Stemline Therapeutics, Inc. is a clinical-stage biopharmaceutical company developing novel oncology therapeutics that target both cancer stem cells (CSCs) as well as the tumour bulk.