People who take certain immunosuppressants — medicines that dampen the immune system’s response — appear to have a lower risk of developing Parkinson’s disease, new research shows.
These findings support a role for the immune system in Parkinson’s, potentially raise the possibility of developing treatments to alter disease progression, at least in its early stages.
“The idea that a person’s immune system could be contributing to neurologic damage has been suggested for quite some time,” Brad Racette, MD, the Robert Allan Finke Professor of Neurology at Washington University School of Medicine in St. Louis and the study’s lead author, said in a university news story.
“We’ve found that taking certain classes of immunosuppressant drugs reduces the risk of developing Parkinson’s. One group of drugs in particular looks really promising and warrants further investigation to determine whether it can slow disease progression,” he added.
The study, “Immunosuppressants and Risk of Parkinson Disease. Annals of Clinical and Translational Neurology,” was published in the journal Annals of Clinical and Translational Neurology.
Researchers previously developed a computer program to analyze millions of medical records from the Medicare program in the U.S., using an algorithm that could predict a person’s risk to develop Parkinson’s disease.
While analyzing the data, researchers noticed a pattern — people taking medications that suppressed the immune system, such as those with different types of autoimmune diseases, had a lower risk of Parkinson’s.
To understand this possible connection, researchers then analyzed prescription drug data (Medicare Part D) on 48,295 people diagnosed with Parkinson’s in 2009 and 52,324 people without the disease who served as controls.
A total of 26 immunosuppressants were identified among the prescriptions, belonging to six different classes of immunosuppressive therapies.
Researchers identified which people had been treated with the immunosuppressants, and excluded those whose prescriptions were filled within 12 months of a Parkinson’s diagnosis or by a pre-set cutoff date.
This strategy reduced the cofounding effects that the therapies could have had in the early stages of the disease.
Analysis revealed that people taking two specific types of immunosuppressants — corticosteroids and inosine monophosphate dehydrogenase (IMDH) inhibitors — had a significantly lower risk of developing Parkinson’s.
Specifically, Parkinson’s risk was 20% lower in individuals who took corticosteroids such as prednisone (sold as Deltasone, among other brand names) and 35% lower among those prescribed with IMDH inhibitors. Among this class of immunosuppressants, often used to prevent organ rejection in transplant patients, mycophenolate (sold under the brand name CellCept) was associated with the lowest risk — a 45% decrease.
Because immunosuppressive therapies were prescribed to patients with autoimmune diseases — diseases like multiple sclerosis, lupus, type 1 diabetes and rheumatoid arthritis, in which the immune system becomes overactive and attacks healthy tissue — researchers re-analyzed the data by each specific disease. The results were maintained, which means that the lower risk was linked to immunosuppressant use and not to the underlying autoimmune disease.
Researchers believe this study “provides additional evidence of a potential role of the immune system in disease risk and potential therapeutic targets to modify risk of PD [Parkinson’s disease] and possibly even PD progression,” the researchers wrote.
“What we really need is a drug for people who are newly diagnosed, to prevent the disease from worsening,” Racette said. “It’s a reasonable assumption that if a drug reduces the risk of getting Parkinson’s, it also will slow disease progression, and we’re exploring that now.”
Although the use of immunosuppressants has to be considered with care, as they dampen immune responses and increase a person’s risk of infections and cancer, these findings support a potential neuroprotective role for these therapies.
“Our next step is to conduct a proof-of-concept study with people newly diagnosed with Parkinson’s disease to see whether these drugs have the effect on the immune system that we’d expect,” Racette said. “It’s too early to be thinking about clinical trials to see whether it modifies the disease, but the potential is intriguing.”