PHILADELPHIA - There was no significant difference in Unified Parkinson’s Disease Rating Scale (UPDRS) scores between patients who received the calcium channel blocker isradipine and those who received placebo, according to the final results of the STEADY-PD III study, which will be presented at the annual meeting of the American Academy of Neurology.
Use of the drug to treat high blood pressure has been linked to lower risk of developing Parkinson’s disease, said study author Tanya Simuni, MD, a professor of neurology at Northwestern University, Chicago, in a news release.
“Unfortunately, the people who were taking isradipine did not have any difference in their Parkinson’s symptoms over the 3 years of the study, compared with the people who took a placebo,” Dr. Simuni said in the press release.
Hopes were high that isradipine might be the first drug to slow progression of Parkinson’s disease after promising animal studies and a phase 2 study showing no safety concerns, according to the news release.
The STEADY-PD III study, which was conducted at 54 Parkinson Study Group sites in the United States and Canada, included 336 participants with early Parkinson’s disease randomized to isradipine 10 mg daily or placebo. The median age of patients in the study was 62 years, and 68% were male. The median time from diagnosis was 0.9 years, and the mean UPDRS I-III score at baseline was 23.1, according to an abstract describing the study results.
The primary endpoint was change in UPDRS Part I-III score measured in the ON state from baseline to month 36 of treatment. That change over 36 months was 2.99 points in the isradipine arm and 3.26 points in the placebo arm, for a treatment effect of 0.27 points (95% confidence interval, –2.5 to 3.0; P = 0.85), investigators reported in the abstract. Adjustment for use of symptomatic therapy did not affect the comparison, the researchers noted.
Isradipine had no effect on secondary outcomes, including change in UPDRS-III in the OFF state, use of dopaminergic therapy, motor complications, or quality of life, investigators said in the abstract. Edema was the most notable side effect of isradipine treatment, investigators said.
These findings are “disappointing” but will not deter researchers in their work to find a treatment that will slow Parkinson’s disease progression, Dr. Simuni said in the news release. “Negative results are important because they provide a clear answer, especially for a drug that is commercially available,” she added.
Secondary analyses in progress will explore “biological and clinical correlates of disease progression” among the study participants, researchers said in their study abstract.
The study was supported by the National Institute of Neurological Disorders and Stroke (NINDS) and also received some funding from The Michael J. Fox Foundation for Parkinson’s Research. Dr. Simuni reported disclosures related to AbbVie, Acadia, Accorda, Adamas, Allergan, Anavex, Biogen, Denali, the Michael J. Fox Foundation, Neurocrine, NeuroDerm, NINDS, the Parkinson Foundation, PhotoPharmics, Revance, Roche, Sanofi, Sunovion, Sun Pharma, Takeda, Teva, Voyager, and US World Meds.