Pacritinib w/ Talazoparib in Pts w/ Myeloproliferative Neoplasms Unresponsive to JAK2 Inhibition

This is a prospective phase I dose-escalation study, with the primary objective to access the MTD and find the RP2D of talazoparib, given in combination with standard of care dosing of pacritinib. Subjects must have a diagnosis of a myeloproliferative neoplasm and progressed or become intolerant to any JAK2 directed therapy. To be eligible for the therapy, patients are required to consent to a bone marrow biopsy at the beginning of study treatment. The treatment protocol involves initiating pacritinib on day -7 (lead-in phase, starting day -7 for cycle 1) with a standard of care dose of 200mg twice daily (BID). Subsequently, talazoparib will be given on day 1 of the treatment cycle. Cohort 1 will enroll patients at the starting dose of 0.25mg talazoparib for 14 days (dose level 1) and DLT (dose-limiting toxicity) rate will inform the subsequent dose levels (DLs). Investigators plan to use a Bayesian Optimal Interval Design (BOIN) to determine the maximum tolerated dose (MTD) in patients with Ph-MPNs (Philadelphia chromosome negative myeloproliferative neoplasms) who have either not responded to or cannot tolerate ruxolitinib monotherapy. Subjects who are currently receiving JAK2-directed therapy will undergo a one-day washout period before starting the study treatment, as abrupt discontinuation of JAK2 inhibition can lead to side effects. This brief interval allows for the resolution of any lingering effects before initiating the new treatment. A bone marrow aspirate and or biopsy will be obtained to assess response to therapy at the end of each cycle of treatment (28 days), prior to beginning the next cycle as per physician discretion. Peripheral blood and bone marrow mononuclear cells will be checked for γ-H2AX (histone H2A family X) at set time points as a biomarker assay to assess for DNA damage in the same manner as the pre-clinical models published in our previous studies. Patients may remain on study drug unless they experience an unacceptable toxicity, fail to show a benefit, or they attain remission and it is felt by the investigator that they can proceed to an allogenic stem cell transplant.