Patients with myelofibrosis, a rare type of slow-growing leukemia, have few options for relief from one of the most pernicious symptoms: an enlarged spleen, as well as low blood counts, which sometimes require transfusions. But a new study, coupled with results from a previous phase 3 study, shows significant benefit compared with available therapies.
Myelofibrosis is a disorder in which mutant blood stem cells disrupt the production of healthy blood cells, resulting in scarring of the normally spongy bone marrow. Because the compromised bone marrow cannot produce an adequate amount of blood cells, the liver and spleen try to make up for it, causing the organs to swell.
The condition affects about 3,000 people in the U.S. annually, with more than one-fourth of patients eventually developing bone marrow failure and anemia, as well as acute myeloid leukemia. All myelofibrosis patients have an autonomously activated Janus kinase (JAK) signaling pathway, which regulates blood cell production, and presents a target for cancer therapies.
In the recent randomized phase 3 study, researchers showed that ruxolitinib, a JAK inhibitor, delivered rapid, significant and lasting spleen-size reduction in patients, although it did not improve blood counts. After 24 weeks, 31.9 percent of 146 patients receiving the drug achieved 35 percent or greater reduction in spleen size compared with 0 percent of 73 patients receiving the best available therapy. Side effects of the therapy include anemia and thrombocytopenia.
"This therapy has the potential to significantly change the treatment landscape for these patients, and could greatly improve their outlook," says Alessandro Vannucchi, MD, of the University of Florence in Italy. "…We've urgently needed new treatments for this condition."
