This clinical trial is designed for men and women with Dynamic International Prognostic Scoring System (DIPSS) intermediate-2 or high risk primary myelofibrosis (PMF), post essential thrombocythemia/polycythemia vera related MF (Post ET/PV MF) who are ineligible for treatment with a Janus kinase (JAK) inhibitor.

The purpose of this study is to evaluate the safety and effectiveness of an investigational new drug Reparixin to treat myelofibrosis. Investigational means Reparixin is not approved by the U.S. Food and Drug Administration (FDA). 

Participants will receive oral reparixin three times daily on a 4-week cycle for a study period of 6 cycles (24 weeks). After cycle 6, participants may continue receiving reparixin once daily on a 4-week cycle if at least stable disease is met until loss of response, disease progression, unacceptable toxicity, patient/physician withdrawal, or termination of study.