Hydroxychloroquine (HCQ-PD)

The research record

This is the project's file for this landmark, as written and checked. Sources are listed at the end; anything not yet confirmed is marked "Not yet verified".

Who

Ottawa Hospital Research Institute (registered sponsor); principal investigator David Grimes (registry). A University of Ottawa page describes the project as led by Michael Schlossmacher, David Grimes and Tiago Mestre, with a family gift of $655,000. Registry record last updated 10 February 2025.

What happened

• Rationale studies. A Finnish nested case-control study (Paakinaho et al., Neurology 2022; 315 Parkinson's cases and 1,571 controls, all with rheumatoid arthritis) found that of the arthritis drugs studied only chloroquine or hydroxychloroquine was linked to lower risk: adjusted odds ratio 0.74 (95% CI 0.56 to 0.97). A Taiwanese Sjögren's syndrome cohort (Ju et al., Medicine 2019; 12,640 patients) found more Parkinson's in the syndrome and a higher risk with hydroxychloroquine (adjusted hazard ratio 1.46), though patients with Sjögren's differ from those with arthritis. A US Medicare study (Racette et al., 2018; 48,295 cases) linked corticosteroids and one class of immunosuppressant to lower risk; its abstract does not mention hydroxychloroquine. These are associations, not proof.
• Trial (NCT06816810). Phase 2, single group, no placebo, 40 planned people aged 35 to 80 with Parkinson's for 6 months to 4 years, Hoehn and Yahr 2 or less, MoCA of 24 or more, on stable medicines. 200 mg twice a day for 48 weeks plus 4 weeks of follow-up. There is no control arm: progression is compared with historical controls.
• Measures. Two primary: treatment-related adverse events, and delay of motor progression, defined as a rise of 4 or more points in MDS-UPDRS part III over 48 weeks compared with historical controls. Secondary: CGI and PGI scales, Hoehn and Yahr, PDQ-8.
• Registry rationale. HCQ interferes with lysosomes and autophagy and lowers cytokines; it reduced microglial activation in mouse multiple sclerosis models; and it was linked to less neurofilament light rise in a small primary progressive MS trial.
• Status. Not yet recruiting in the last record; estimated start March 2025, primary completion September 2026. I could not tell whether it began; the record is unchanged on 22 Oct 2026, so the estimated September 2026 primary completion has also passed with no update.

Why it moved us toward a cure

It extends the logic of landmark 264: a common drug linked to lower risk is tested for slowing. Parkinson's T cells react to synuclein (landmark 38), so an immune-modulating drug is plausible. Its value lies in cost and safety; a single-arm design is weak evidence.

Outcome

Open. The registry dates are probably stale and no results exist.

Sources

• ClinicalTrials.gov NCT06816810 (API re-read 22 Oct 2026)
• Paakinaho et al., Neurology 2022 (abstract read via Europe PMC, PMID 35064025)
• Racette et al., Ann Clin Transl Neurol 2018 (abstract via Europe PMC) · Ju et al., Medicine 2019 (abstract via Europe PMC) · uOttawa, Taller than PD (search summary only)
• Not yet verified: whether the trial opened; the registry's MS-trial claims; the Racette hydroxychloroquine figure (0.77) given in an earlier version could not be found in the abstract and was removed.