Chicago—A blood pressure drug had shown promise in some small, early studies for slowing the progression of Parkinson’s disease, but a larger trial had disappointing results.

A presentation at the American Academy of Neurology’s 71st Annual Meeting in Philadelphia noted that isradipine does not show any benefit for Parkinson’s patients.

“Unfortunately, the people who were taking isradipine did not have any difference in their Parkinson’s symptoms over the three years of the study compared to the people who took a placebo,” pointed out study author Tanya Simuni, MD, of Northwestern University Feinberg School of Medicine in Chicago.

Results were from a phase III study involving 336 Parkinson’s patients at 54 sites in the United States and Canada as part of the Parkinson Study Group. During the trial, one-half of the participants received 10 mg of isradipine daily for 3 years, while the other half received a placebo.

The drug piqued researchers’ interest when an observational study suggested it was associated with a lower risk of developing Parkinson’s. An animal study was positive, and a phase II study in humans did not show any safety concerns.

“Of course, this is disappointing news for everyone with Parkinson’s disease and their families, as well as the research community,” Simuni said. “However, negative results are important because they provide a clear answer, especially for the drug that is commercially available. We will all continue to work to find a treatment that can slow down or even cure this disease.”

Isradipine is in the dihydropyridine class of calcium channel blockers and is used to treat mild-to-moderate essential hypertension.

Researchers had posited that because isradipine blocks the activity of specific channels in the neuron that allow calcium to enter, it could prevent the death of neurons that produce dopamine, thereby slowing Parkinson’s progression.

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