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

This study assesses the potential of using a TGFβ receptor inhibitor for the treatment of anemic patients with myeloproliferative neoplasms. TGFβ signaling is known to be abnormally high in patients with myeloproliferative neoplasms and it is thought that abnormal TGFβ signals cause many of the problems with blood cell formation in these diseases. The study design allows all patients to receive the study drug, vactosertib. The dose of vactosertib is individualized within a pre-set range based upon its effectiveness and tolerability. A total of up to 37 patients will be treated.

This is a two-tiered multi arm Phase 2 trial of vactosertib (TEW-7197) for the treatment of anemia in Ph-neg MPNs. Both tiers use a rule-based, accelerated dose escalation scheme to efficiently assess the potential of vactosertib to safely and effectively treat anemic patients with Ph-neg MPNs. The first tier of this trial (Tier 1) is an intra-patient dose finding study in 12 patients that uses a low starting dose of vactosertib for all patients. Treatment dose is escalated according to prospectively-defined rules, and a toxicity and treatment effect algorithm during the period of 16 weeks (4 treatment cycles). If pre-established efficacy and safety endpoints are met, then Tier 1 of the study will be followed by a Tier 2 expansion study with an additional 25 patients for a period of 24 weeks (6 treatment cycles).

Vactosertib will be administered concurrently with the patient's current treatment (if any). Prior to enrollment, patients must be on a stable dose of their current therapy for 3 months prior to entering the study. Supportive care measures including packed red blood cell (PRBC) transfusions for HGB \<7g/dL, or symptomatic anemia, will be permitted. Administration of erythropoiesis stimulating agents (ESAs), however, will not be permitted on the trial (patients recruited would have serum EPO \>125 U/L above which the benefit of ESAs is not supported).

Eligibility Criteria:
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 who are breastfeeding, or intend to breastfeed, during the study or in the 30 days following the last dose of study drug are excluded.