Intra-patient Dose Escalation Study to Investigate Safety and Feasibility of Vactosertib in Treating Anemic MPN Patients

Inclusion Criteria: Patients who meet the WHO 2016 criteria for a Ph-neg MPN (including PV, ET, MF, MDS/MPN, MPN-U). * Patients with MF must have DIPSS+ Intermediate or High-risk MF (primary of post-PV/ET). * For patients receiving cytoreductive therapy, they should be on a stable dose of current cytoreductive therapy for at least 3 months prior to C1D1. * Anemia as defined by HGB \< 10 g/dL, or transfusion of ≥ 2 packed red blood cell (PRBC) unit within the past 4 weeks with HGB ≤8.5g/dL. * Ineligible, unsuitable or refractoriness to ESA therapy defined as any of the following: * Serum erythropoietin (EPO) \>125 U/L. * Proven ESA unsuitability is defined by history of any of the following: * Loss of erythroid hematologic improvement while receiving stable or increased ESA dose; or * ESA-attributed toxicity that, in the treating physician's opinion, makes ESA therapy unsuitable for subject. * ESA refractoriness defined by lack of erythroid hematologic improvement to ESA:27 * Less than 1.5 g/dL increase in hemoglobin after at least 6 weeks of ESA therapy; or * Ongoing transfusion dependence that has not been reduced by \> 4U over an 8-week period compared to ESA pre-treatment 8 weeks. * Acceptable Cardiovascular status Exclusion Criteria: * Any other serious medical condition which in the Investigator's opinion would preclude safe participation in the study. * Patients with history of TIA or stroke within the past 12 months are excluded. * Female subjects wh…