[March 2026] In a small clinical study published in April 2025, fifteen PD patients were recruited to Karolinksa Hospital in Sweden for a 12-week open-label trial of montelukast taken 20 mg twice a day. Patients underwent ratings with the Movement Disorder Society Unified Parkinson Disease Rating Scale (MDS-UPDRS), the Montreal Cognitive Assessment (MoCA), Beck's Depression Inventory (BDI), Parkinson's Disease Questionnaire-39 (PDQ-39), [11C]PBR28-PET, and lumbar punctures before and during montelukast treatment.

All patients completed the study. No serious adverse events related to treatment were reported. MDS-UPDRS total scores improved by 6.9 points. Montreal Cognitive Assessment scores also showed significant improvement. Biogen in their lecanemab clinical trail did not use the Montreal Cognitive Assessment tests but rather used a different series of cognitive tests. As a comparison, their testing showed that lecanemab treated patients did not show cognitive improvement but only a small (27 percent) slowing of decline. This suggests that montelukast taken 20 mg twice a day is a far more effective treatment than lecanemab for treating patients experiencing cognitive decline.

https://pmc.ncbi.nlm.nih.gov/articles/PMC12006882/

The purpose of this trial is to see if high dosages of montelukast given twice a day slow down Parkinson's disease progression. 

Participants in the treated group are receiving up to 30 mg of montelukast twice a day in the form of patented VersaFilm buccal tablets developed by Intelgenx Technologies. Participants consist of up to 90 people with early to moderate PD who are also on levodopa. The duration of treatment is 18 months, followed by a 3 month washout. The clinical trial began in February 2024 and the estimated end of the trial is 31 December 2026.

Initially Karolinska signed a contract with Intelgenx to supply VersaFilm for their Parkinson's trial. This was during the time period when Intelgenx was conducting its own Alzheimer's clinical trial. In April 2024, Intelgenx's Alzheimer's trial was completed and preliminary results showed that participants taking 30 mg twice a day had cognitive improvement. Intelgenx's biggest creditor Atai Life Sciences months later forced Intelgenx into bankruptcy and took over Intelgenx and their trial. Atai has made no effort to come up with the final results of the Intelgenx trial. I have to wonder what Atai's motive is and if it will provide the correct dosages to the Karolinska trial. 

I emailed the principal investigator Dr Per Svenningsson in 2025 and again in early 2026, but I did not get any reply so I don't know if he actually read them. I suggested that he switch to using generic montelukast in his trial. I also suggested that Karolinska should have the montelukast medication provided by Atai randomly tested for the correct dosage.

https://parkinsonsnewstoday.com/news/phase-2-trial-montelukast-oral-film-starts-dosing/

https://euclinicaltrials.eu/ctis-public/view/2023-504278-39-00

https://www.clinicaltrialsarena.com/news/intelgenx-alzheimers-disease-trial/