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Potential Parkinson’s Therapy Harnesses Immune System Cells

Researchers have found the drug sargramostim, currently used to boost the immune systems of people undergoing chemotherapy, to be relatively safe in people with Parkinson’s disease (PD). This result opens the door to testing its ability to protect the brain cells affected by PD. The results of this small, phase I clinical trial appear in the March 23 online edition of npj | Parkinson’s Disease.

Scientists have long known that inflammation — an attack by immune system cells in the body — contributes to the brain cell death that underlies PD. But there are other immune cells that quiet and regulate the immune system. In studies of animal models of PD, researchers have shown that the drug sargramostim can transform the destructive immune cells into ones that regulate the immune system and nourish and repair the brain. The drug is already approved by the US Food and Drug Administration (FDA) and is currently used to boost the immune system in certain cancer patients who have had chemotherapy.

For the new study, researchers led by Howard E. Gendelman, M.D., at the University of Nebraska Medical Center in Omaha, recruited 20 people with PD and 17 healthy people of similar age as study participants. Half of the participants with PD received an injection of sargramostim under the skin every day for 56 days. The remaining 10 participants with PD injected a placebo (saline). Healthy participants served as a non-PD control group for comparison.

The study was double-blinded, meaning neither participants nor medical personnel knew who got which treatment. Researchers gave blood tests to participants before, during and after treatment to measure a battery of blood and immune system markers. They also monitored participants’ PD symptoms using a standard rating scale and gave them a brain scan called magnetoencephalography.

Results

  • In those who received sargramostim, the number and function of regulatory T cells (immune cells that soothe inflammation) increased.
  • Both the brain scans and the rating scale scores suggested an improvement in movement symptoms among participants who received sargramostim, but the number of participants was too small to draw a firm conclusion.
  • Side effects included irritation around the injection site and bone pain, similar to those noted when the drug was tested for other uses.
  • One participant with a history of cerebrovascular disease suffered a stroke during the study.

What Does It Mean?

This study illustrates a new approach to PD therapy — manipulating the immune system to protect the brain cells affected by PD. The advantage of the drug tested here is that it is already approved by the FDA for other indications, meaning if it is found to be effective, it could be more quickly approved for Parkinson’s.

This was the first clinical trial in people with Parkinson’s to test a drug that may transform a harmful immune system response into a potentially helpful one. It showed that the drug was relatively safe and tolerated by the study participants.

Measurements of blood biomarkers indicated that the drug had similar effects in people as it had shown in animals. It’s important to note that this early study could not show whether sargramostim was able to slow down or cure Parkinson’s.

This study, by indicating safety of the drug in PD, may pave the way for additional studies into the drug’s safety and effectiveness in larger numbers of people with PD.

Reference

Gendelman HE, Zhang Y, Santamaria P, et al. (2017). Evaluation of the Safety and Immunomodulatory Effects of Sargramostim in Randomized, Double-Blind Phase 1 Clinical Parkinson’s Disease Trial. npj Parkinson’s Disease doi:10.1038/s41531-017-0013-5 http://dx.doi.org/10.1038/s41531-017-0013-5

Monday, April 3, 2017
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