A Phase II Study of Pacritinib in Patients with Myelofibrosis Previously Treated with Ruxolitinib


Full Title

A Randomized, Controlled Phase 3 Study of Pacritinib Versus Physician’s Choice in Patients with Primary Myelofibrosis, Post Polycythemia Vera Myelofibrosis, or Post-Essential Thrombocythemia Myelofibrosis with Severe Thrombocytopenia (Platelets Counts <50,000/L)


Myelofibrosis is a disease of the bone marrow. Ruxolitinib is a drug used to treat myelofibrosis that works by inhibiting an abnormal form of a protein called Jak. However, if ruxolitinib stops working or is not effective, there are very few other options for patients with myelofibrosis. In this study, researchers want to determine the effects of the investigational drug pacritinib in patients with myelofibrosis that persists despite ruxolitinib treatment, and to see if it is effective.

Pacritinib also inhibits Jak. Although ruxolitinib and pacritinib work in a similar way, pacritinib has been studied in patients with very low platelet counts and found to reduce spleen size in some of them. Ruxolitinib cannot be used in patients with very low platelet counts. Pacritinib may therefore benefit patients with myelofibrosis and low platelet counts.

Pacritinib is taken orally (by mouth). Patients will be randomly assigned to receive 100 mg of pacritinib once a day, 100 mg twice a day, or 200 mg twice a day.


To be eligible for this study, patients must meet several criteria, including but not limited to the following:

  • Patients must have primary myelofibrosis, post-polycythemia vera myelofibrosis, or post-essential thrombocythemia myelofibrosis.
  • Patients must have not responded well to prior ruxolitinib or could not tolerate this drug.
  • Patients must be able to walk and do routine activities for more than half of their normal waking hours.
  • This study is for patients age 18 and older.

For more information about this study and to inquire about eligibility, please contact Dr. Raajit Rampal at 212-639-2194.