The researchers initially began testing the drug in about 150 patients who had advanced-stage myelofibrosis or were newly diagnosed (in 2007) with high-intermediate or high-risk disease. Ongoing work will focus on 115 of these patients.
Verstovsek and his colleagues have so far found that one month after treatment with INCB018424, about half of the patients experienced a 50 percent reduction in symptom scores, and nearly 60 percent of these patients maintained this drop a half-year out.
Between 70 percent and 82 percent of the patients experienced a minimum of a 25 percent reduction in spleen size after taking the experimental drug for two months -- a drop that endured for more than a year.
And MRI scans revealed that by the six-month treatment mark, on average, patients achieved a reduction in spleen size of about one-third, with nearly half experiencing a spleen size shrinkage of 35 percent or more.
Improvement in the ability to exercise and average weight gains of about 15 to 20 pounds following one-year of treatment were also evident, the report indicated.
Even patients who did not have the JAK2 mutation that the drug was designed to attack seemed to benefit from the new treatment, the researchers said.
"This suggests that patients who do not have specific mutations still have a very active JAK signaling pathway and can benefit from JAK inhibition," Verstovsek said. "However, because the drug also inhibits normal JAK2, it can lead to low blood counts that can limit dosing."
Dr. Mark H. Kirschbaum, director of developmental therapeutics and acting chair of hematology at the Nevada Cancer Institute in Las Vegas, called the research "a first breakthrough" in the attempt to tackle myelofibrosis.
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