A Phase 3 Study of Pacritinib in Patients With Primary Myelofibrosis, Post Polycythemia Vera Myelofibrosis, or Post-Essential Thrombocythemia Myelofibrosis

This study is for adults aged 18 or over who have been diagnosed with primary myelofibrosis, or myelofibrosis that has developed from polycythemia vera or essential thrombocythemia.

You would need to have a very low platelet count (below 50,000/μL) and your spleen would need to be enlarged – specifically, at least 5cm below your ribs as felt by a doctor. You should also be experiencing certain myelofibrosis symptoms that add up to a specific score on a symptom questionnaire.

It's important that you have not previously been treated with more than one JAK2 inhibitor (a type of drug sometimes used for myelofibrosis), or have had no or very limited previous exposure to them. Your overall health and organ function (like heart, liver, and kidneys) would also need to be within acceptable limits as determined by medical tests.

If you are eligible and choose to take part, you will be randomly assigned to one of two treatment groups: two out of three participants will receive pacritinib, and one out of three will receive a standard treatment chosen by your doctor from a pre-approved list. You will take the assigned medication twice a day. The treatment will continue as long as it's helping you, doesn't cause unbearable side effects, or until your condition gets worse. You won't be able to switch between the study treatments.

Throughout the study, you'll have regular visits for assessments, which will include physical examinations, blood tests, and imaging scans like MRIs or CT scans, particularly to check your spleen size. You will also complete questionnaires about your symptoms. Even if you stop taking the study medication early, you should continue with all scheduled check-ups for at least 24 weeks, unless you withdraw consent, your condition changes significantly (e.g., needing a splenectomy), or the study ends. The total duration of your participation will depend on your individual response to treatment.