Experimental Drug Shows Promise for Bone Marrow Disorder
WEDNESDAY, Sept. 15 -- In ongoing early stage research, an experimental drug appears to go some distance toward reducing the tell-tale inflammatory impact of the deadly bone marrow disorder known as myelofibrosis.
Indications that the oral drug -- called INCB018424 -- shows promise are reported in the Sept. 16 issue of the New England Journal of Medicine.
"The problem with myelofibrosis is the lack of available therapies for patients; there are none approved for this disease today," study lead author Dr. Srdan Verstovsek, an associate professor at the M.D. Anderson Cancer Center's department of leukemia in Houston, said in a news release from the center.
"This experimental drug is the first to target one of the underlying abnormalities in the malignant cells that cause myelofibrosis," Verstovsek added. "It provides unprecedented reduction of enlarged spleens that are a central characteristic of the disease, and relieves pain, fatigue and other symptoms, improving quality of life."
For reasons as yet poorly understood, myelofibrosis occurs when aggressive bone marrow cells "scar" bone marrow, the soft, fatty tissue inside bones. The process so severely curtails the bone marrow's ability to produce blood cells that anemia results.
In turn, the liver and spleen attempt to take up the blood production slack, causing these organs to swell to painful proportions and impinging on the stomach and bowels. This prompts malnutrition, weight loss, fatigue, and a progressively debilitating loss of the ability to bend and move properly, according to background information in the news release.
An estimated 3,000 Americans are newly afflicted with the disease each year, with an average life expectancy of between five to seven years. There is no known cure or effective treatment, leaving doctors few resources for the alleviation of pain and suffering.
The drug currently being tested is designed to shut down the abnormal activity of JAK2 gene mutations, which have been found to be responsible for the over-growth of bone marrow cells, and have been linked to many cases of myelofibrosis.
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.
Kirschbaum cautioned, however, that researchers had initially held out hope that the drug under investigation might even have a more dramatic impact on symptoms, given the key role JAK2 mutations appear to play in development of the disease.
"But at least there was some palliation for a group of patients," Kirschbaum said. "And this certainly represents an encouraging first step towards more definitive treatment for this nasty disorder."
The study was funded by Incyte Corporation, which developed the JAK2-inhibitor, and Verstovsek has received research funding from the company. The research is ongoing in the United States, Canada, Australia and Europe.
For more on myelofibrosis, visit the U.S. National Library of Medicine.
Posted: September 2010
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