How it is administered

Pacritinib is taken by mouth as a capsule. The recommended dose is 200 mg orally twice daily. You can take it with or without food. Swallow the capsules whole—do not open, break, or chew them. If you miss a dose, skip it and take the next dose at your regular time; do not take two doses at once.

How it works

Pacritinib is a type of medicine called a kinase inhibitor. It works by blocking certain proteins in the body, specifically JAK2, FLT3, and IRAK1, which are involved in the growth and function of blood cells. In myelofibrosis, these proteins can become overactive, leading to abnormal blood cell production and an enlarged spleen.

By inhibiting these proteins, pacritinib helps to reduce the size of the spleen and improve symptoms related to myelofibrosis. It is especially useful for patients with low platelet counts, as it is less likely to worsen this condition compared to some other treatments. Pacritinib does not significantly inhibit JAK1, which may help reduce certain side effects.

Who Should take it

Pacritinib is indicated for adults with intermediate or high-risk primary or secondary myelofibrosis (including post-polycythemia vera or post-essential thrombocythemia) who have a platelet count below 50 × 10⁹/L.

It is especially considered for patients who have low platelet counts and may not tolerate other treatments. The main goal is to reduce spleen size and improve symptoms. Your doctor will determine if pacritinib is right for you based on your blood counts and overall health.

Who should not take it

You should not take pacritinib if you are currently using strong CYP3A4 inhibitors or inducers, as these can significantly change how much pacritinib is in your body and may increase the risk of side effects or reduce its effectiveness.

Pacritinib should also be avoided in patients with active bleeding, those with a baseline QTc interval over 480 msec (a heart rhythm issue), or if you have not resolved a serious infection. Always tell your doctor about all medications and supplements you are taking.

Commonly used with

Pacritinib is often used as a single agent for myelofibrosis, especially in patients with low platelet counts. In clinical studies, it was compared to other treatments such as ruxolitinib, hydroxyurea, glucocorticoids, erythropoietic agents, immunomodulatory agents, and others, but is not typically combined with them.

Your doctor will decide if pacritinib should be used alone or if supportive care (such as transfusions or antibiotics) is needed.

Commonly tested with

In clinical trials, pacritinib was tested against a variety of other treatments for myelofibrosis, including ruxolitinib, hydroxyurea, glucocorticoids, erythropoietic agents, immunomodulatory agents, mercaptopurine, danazol, interferons, cytarabine, and melphalan. These were used as 'best available therapy' comparators, not in combination with pacritinib.