Jakafi Side Effects May Be Linked to PML Brain Disease: Report

Side effects of a drug used to treat bone marrow disease could be linked to a risk of a serious and often deadly brain virus, known as progressive multifocal leukoencephalopathy or PML, according to a new report.  

Doctors from the U.K. submitted a case study published in the New England Journal of Medicine this week about a patient who took the myelofiibrosis drug Jakafi and later developed the serious brain disease.

While the report indicates that the patient improved in some areas after being taken off of the drug, researchers were unable to confirm that Jakafi caused the PML brain infection.

Progressive multifocal leukoencephalopathy is an aggressive brain disease that is believed to be caused by the common JC virus. Many suspect that the virus becomes active after drugs suppress the immune system. In many cases, the infection results in death.

Symptoms of PML could include changes in mood, unusual behavior, confusion, memory loss, weakness or loss of strength on one side of the body, or problems with vision, speech or walking.

According to the case study, the patient, a 75-year-old man, had been receiving twice daily 20 mg doses of Jakafi for several weeks and responding positively. About 10 weeks into the treatment he began to show signs of cognitive impairment and speech problems. The symptoms worsened over time leading to confusion, gait instability and severe speech problems.

An MRI showed damage to the white matter of the patient’s brain that were consistent with PML. Researchers tested for the JC virus but did not find it. A brain biopsy later confirmed that patient suffered from PML and he was taken off Jakafi, but neurologic deterioration continued at a rapid pace. While the patient regained some motor skills, the neurological damage has not recovered.

Researchers concluded that the case suggests that Jakafi side effects are associated with a risk of PML.

Other drugs linked to PML, such as Tysabri and Gilenya, have been highly restricted by the FDA due to the risk to patients. Tysabri was recalled at one point before being re-released under more stringent safety measures.

Jakafi (ruxolitinib), also known as Jakavi, is manufactured and distributed by Incyte Pharmaceuticals and Novartis. It was approved by the FDA in 2011 for the treatment of intermediate or high-risk myleofibrosis. It is the only Incyte product approved for use in the U.S.