The study consists of two phases: a dose escalation phase and a cohort expansion phase. The dose escalation phase will follow a 3+3 design with a starting dose of 100 mg twice daily, and a treatment duration of 4 weeks. Patients will be able to participate in more than one dose level.~During the cohort expansion phase, up to 24 patients will be treated at the dose determined appropriate based on safety, pharmacokinetic and pharmacodynamic results from the dose escalation phase, for a period of up to 6 months. Patients from the dose escalation phase will be able to participate in the cohort expansion phase.~There will be no washout period between dose escalation and dose expansion cohorts.
This study will be an open-label phase 1/2a study to evaluate the safety and tolerability of PXS-5505 in patients with primary, postpolycythemia vera (PV) or post-essential thrombocythemia (ET) myelofibrosis.