Pacritinib is primarily used in the treatment of myelofibrosis, a rare type of bone marrow disorder that disrupts the body's normal production of blood cells. It is specifically targeted for patients with thrombocytopenia, a condition characterized by low platelet counts, where other treatments may not be suitable. The drug works by inhibiting the JAK2 and FLT3 kinases, which are involved in the signaling pathways that contribute to the abnormal cell growth seen in myelofibrosis. By blocking these pathways, Pacritinib helps reduce symptoms such as an enlarged spleen, fatigue, and night sweats, improving the quality of life for patients. It is often considered when other JAK inhibitors are not effective or cannot be tolerated due to side effects.