“Limited treatment options have rendered this disease as an area of urgent unmet medical need. I am pleased to see that a new, efficacious, and safe treatment option is now available to these patients,” said John Mascarenhas, MD, director of the Center of Excellence for Blood Cancers and Myeloid Disorders at Mount Sinai Icahn School of Medicine in New York City, and a lead investigator of the pacritinib clinical trials in a press release issued by CTI BioPharma, the manufacturer of the drug. MF is a chronic but rare blood cancer that affects roughly 18,000 people in the United States, most of whom are older than 65, according to the MPN Research Foundation. The disease causes the overproduction of abnormal blood cells and the formation of scar tissue in the bone marrow where blood cells are manufactured, further impairing the production of normal red and white blood cells and platelets. As MF progresses, greater numbers of abnormal cells are produced within the bone marrow and eventually within other areas of the body, such as the spleen. It can cause an enlarged spleen (splenomegaly), and symptoms related to low numbers of blood cells, including impaired clotting, anemia, and infection. Other common symptoms include fatigue, night sweats, itching, bone and joint pain, weight loss, and fever. About 25 percent of patients suffer from a severe and potentially life-threatening low level of platelets (thrombocytopenia), the cells that enable the body to form blood clots. These patients are not eligible for ruxolitinib and fedratinib. “Ruxolitinib and fedratinib are excellent drugs,” explained Dr. Mascarenhas. “But they are limited by thrombocytopenia, so if you have a platelet count of 50,000 or less, you are not amenable to these two options. That’s where pacritinib fits in.” The drug’s approval was based on data from phase 2 and phase 3 studies in over 600 patients assigned to receive either pacratinib or the best available therapy. Findings published in May 2018 in JAMA Oncology, from both the initial trials and retrospective safety and efficacy evaluations showed that, compared with best available therapy, pacritinib reduced spleen size by 35 percent or more, improved symptoms such as fatigue by as much as 50 percent, improved platelet counts, and reduced the need for transfusions. The recommended dosage for pacritinib is 200 mg orally, twice a day. The fact that pacritinib does not further lower platelet counts is believed to be a result of the fact that it targets a different series of signals in the cell than that targeted by ruxolitinib and fedratinib. Although the manufacturer has not yet announced pricing information, pacritinib will likely be priced similar to ruxolitinib, which is approximately $16,000 for a 60-day supply or $90,000 for a year.
