The popular cancer drug, rituximab may increase the risk of acquiring an often fatal viral brain infection, known as progressive multifocal leukoencephalitis (PML),scientists have revealed.
The worries about this possible harmful effect of rituximab emerged after MRI brain scans and biopsies were conducted on a 57-year-old lawyer in New York and an 83-year-old woman in Chicago, both of whom had been taking the drug before they developed the brain infection.
The two patients are currently part of a new study from the Northwestern University Feinberg School of Medicine RADAR project, an international consortium of physicians that collaborate to identify adverse reactions to medications and devices, which is being led by Dr. Charles Bennett.
Knowing more about the suggested link between rituximab and PML is important because, besides its use as a cancer drug, this medicine is also used for treating rheumatoid arthritis, multiple sclerosis, lupus erythematosus and autoimmune anaemias.
Bennett has revealed that, from 1997 to 2008, as many as 57 patients with anemia, rheumatoid arthritis or lymphoma developed the fatal brain disease after taking rituximab.
They died an average of two months after being diagnosed, he said.
"Rituximab is one of the most prominent drugs in a new class called monoclonal antibodies. It's now the third monoclonal antibody that is associated with PML," added Bennett.
The researcher points out that the brain infection is often overlooked and undiagnosed because it is so subtle at first.
"People may think it's early Alzheimer's disease or depression. Many of these patients have cancer and when they die, people assume it's the cancer that killed them," he said.
He admitted that it was yet to be found out how rituximab is connected to the brain virus and who might be at risk.
Bennett said that the study results illustrate a need for caution in prescribing rituximab.
"The drug has tremendous usefulness in lymphoma, but as its use expands to diseases that are not cancer, we might have to reconsider the risk benefit. Some cancer patients take this drug chronically for non-fatal chronic leukemia where the risk-benefit calculations differ from lymphoma," he said.
He suggested if people on rituximab develop any strange neurological symptoms like forgetfulness, disorientation or mood changes, their doctors should be alerted.
A research article on the study has been published in the journal Blood.