Selinexor and Pacritinib in JAK Inhibitor-naïve MF Patients With Cytopenias

Inclusion Criteria: * Adults ≥ 18 years of age capable of providing informed consent * Pathologically confirmed diagnosis of PMF, post-ET MF, or post-PV MF as per the World Health Organization (WHO) diagnostic criteria - Intermediate-1, Intermediate-2, or High-Risk disease by the Dynamic International Prognostic Scoring System (DIPSS) * Eastern Cooperative Oncology Group (ECOG) performance status ≤ 2 * Baseline splenomegaly ≥ 5cm palpable below the left costal margin and in the midclavicular line OR ≥ 450cc by imaging (i.e. ultrasound, CT, MRI) * Baseline anemia, defined by hemoglobin \< 10 g/dL within 28 days prior to Cycle 1 Day 1 * Baseline thrombocytopenia, defined by platelet count 50-150 x 109/L without platelet transfusions within 28 days prior to Cycle 1 Day 1 * Adequate organ function as demonstrated by the following within 28 days prior to Cycle 1 Day 1: * ALT (SGPT) and/or AST (SGOT) ≤ 3x the upper limit of normal (ULN), or ≤ 4 x ULN if, upon judgment of the treating physician, it is believed to be due to MF-related extramedullary hematopoiesis (EMH); * Direct bilirubin ≤ 1.5 x ULN; or ≤ 2x ULN if, upon judgment of the treating physician, it is believed to be due to MF-related extramedullary hematopoiesis (EMH) or documented Gilbert's syndrome; * Creatinine clearance ≥ 30 mL/min; * Prothrombin time (PT) and activated partial thromboplastin time (aPTT) ≤ 1.5 × ULN (Exceptions to coagulation parameters may be considered for patients who are taking concomita…