Stemline Therapeutics, Inc. presented data from ELZONRIS® (tagraxofusp) Phase 1/2 clinical trials in myelofibrosis (oral presentation) and multiple myeloma, at the 2019 ASH annual meeting. Myelofibrosis:Clinical Trial of ELZONRIS in Patients with Intermediate or High-Risk, Relapsed/Refractory Myelofibrosis (MF) - ELZONRIS demonstrated efficacy (spleen size reductions and total symptom score [TSS] reductions) with a predictable and manageable safety profile, including in patients with poor prognostic factors, such as thrombocytopenia, CMML-type features/monocytosis, and clonal evolution, 45% (9/20) of patients had symptom burden reduction, including 3 with symptom response per IWG-MRT 2013 MF response criteria, 53% (8/15) of patients with baseline splenomegaly >= 5cm experienced a spleen size reduction; 20% (3/15) had a reduction >35% (specifically 100%, 47% and 46% reductions), 100% (5/5) of patients with CMML-type features/monocytosis experienced a spleen size reduction, and 40% (2/5) of these patients had a reduction >35%, 64% (7/11) of patients with thrombocytopenia (platelet count < 100x109/L) experienced a spleen size reduction, and 18% (2/11) had a reduction >35%; 60% (3/5) of patients with thrombocytopenia (platelet count < 50x109/L) experienced a spleen size reduction, and 20% (1/5) had a reduction >35%, Most common treatment related adverse events (TRAEs) include alanine aminotransferase increase, headache, hypoalbuminemia (all 17%), anemia, and thrombocytopenia (both 14%), There was one case of capillary leak syndrome (CLS), which was grade 3 and 43% overall survival (OS) at 18 months; 29% OS at 2 years. Next Steps: Expansion of Phase 2 trial to include additional sites is underway, Patient enrollment and follow up continues to inform design of potential registration-directed trial of ELZONRIS in patients with relapsed/refractory MF, including poor prognosis patients with: Thrombocytopenia, and/or Monocytosis (CD123-overexpressed subsets). Other areas of evaluation in MF: An additional ASH presentation demonstrated that ELZONRIS, either alone or in combination with ruxolitinib, had preclinical activity against primary MF patient samples, including those in accelerated phase and with high molecular risk profiles where current therapeutic options beyond ruxolitinib are limited and CD123 expression is evident. These data support further evaluation of tagraxofusp in MF, not only as single agent but potentially in combination with Jak inhibitors. Multiple Myeloma: Clinical Trial of ELZONRIS in Patients with Relapsed/Refractory Multiple Myeloma (MM): ELZONRIS, in combination with pomalidomide (POM) and dexamethasone (DEX), demonstrated activity and a predictable and manageable safety profile in heavily pretreated patients with relapsed/refractory MM, 56% of patients (5/9) who received ELZONRIS in combination with POM+DEX had partial responses (PRs), Notably, these patients also had decreases in their plasmacytoid dendritic cells (pDCs), a cell type implicated in myeloma growth and aggressiveness, and the cell of origin of blastic plasmacytoid dendritic cell neoplasm (BPDCN) and Given these clinical data, ELZONRIS may offer a novel mechanism of action and future therapeutic option for patients with MM. Given these encouraging early results, potential avenues for further ELZONRIS development are being assessed, including evaluating additional patients with this and/or potentially other regimens including in combination with daratumumab or novel agents such as XPO1 inhibitors. Moreover, the clinical knockdown of pDCs in MM patients may also be relevant with respect to other diseases, such as chronic myelomonocytic leukemia (CMML), MF and certain acute myeloid leukemia (AML) patient subsets, where pDCs have been similarly implicated in the aggressiveness of these malignancies.