How it is administered

Pacritinib is taken by mouth as a capsule. The recommended dose is 200 mg twice daily, with or without food. The capsules should be swallowed whole and not opened, broken, or chewed. If a dose is missed, the next dose should be taken at the scheduled time—do not take two doses at once.

How it works

Pacritinib is a type of medication known as a kinase inhibitor. It works by blocking certain proteins in the body (specifically, wild type Janus associated kinase 2 [JAK2], mutant JAK2V617F, FLT3, and IRAK1) that are involved in the signaling of cytokines and growth factors. These proteins are important for the growth and function of blood cells and the immune system.

In myelofibrosis, a type of blood cancer, the JAK2 signaling pathway is often overactive, leading to abnormal blood cell production and enlargement of the spleen. By inhibiting these pathways, pacritinib helps to reduce spleen size and control symptoms of the disease. Pacritinib is unique in that it does not inhibit JAK1, which may reduce certain side effects compared to other JAK inhibitors.

Who Should take it

Pacritinib is indicated for adults with intermediate or high-risk primary or secondary myelofibrosis (a type of blood cancer), especially those who have a low platelet count (below 50 × 10⁹/L). This includes patients whose myelofibrosis developed after other conditions like polycythemia vera or essential thrombocythemia.

It is particularly useful for patients who cannot tolerate other treatments due to low platelet counts, as pacritinib can be used safely in this group. The main goal of treatment is to reduce spleen size and improve symptoms related to myelofibrosis.

Who should not take it

Pacritinib should not be taken by patients who are currently using strong CYP3A4 inhibitors or inducers, as these can significantly alter the levels of pacritinib in the body and increase the risk of side effects or reduce effectiveness.

It should also be avoided in patients with active bleeding, those who have a baseline QTc interval greater than 480 msec (a heart rhythm issue), or those who have not resolved serious infections. Patients with a history of severe allergic reactions to pacritinib or any of its ingredients should not use this medication.

Commonly used with

Pacritinib may be used alongside supportive treatments such as blood transfusions, antibiotics (to prevent or treat infections), and medications to control symptoms like diarrhea or nausea. In clinical trials, it was compared to other treatments such as ruxolitinib, hydroxyurea, glucocorticoids, erythropoietic agents, immunomodulatory agents, and others, but it is not typically combined with other JAK inhibitors.

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. It was also compared to best available therapy, which could include no treatment or symptom-directed care.