This legacy page has been migrated to the canonical page at Parkinson's Disease Knowledge Gaps. However, this page is retained to provide a focused summary of the highest-priority research gaps in Parkinson's disease for quick reference.
Parkinson's disease (PD) is the second most common neurodegenerative disorder after Alzheimer's disease, affecting approximately 10 million people worldwide. Despite decades of research, fundamental questions about disease mechanisms, progression, and treatment remain unanswered. This page summarizes the critical knowledge gaps that, if addressed, could transform PD treatment and prevention.
The research landscape has evolved significantly with three major advances between 2024-2026:
The Parkinson's disease research landscape has entered a new era marked by three transformative advances that have fundamentally changed how we approach disease understanding, clinical trial design, and therapeutic development. These advances represent not merely incremental progress but qualitative shifts in our ability to diagnose, stratify, and treat PD.
The demonstration that lixisenatide, a GLP-1 receptor agonist approved for type 2 diabetes, can slow motor progression in early Parkinson's disease represents the first reproducible disease-modifying signal in PD clinical trials since the levodopa era. The phase 2 randomized controlled trial showed a statistically significant difference in Unified Parkinson's Disease Rating Scale (UPDRS) motor scores between treatment and placebo groups over 12 months[1:1].
Mechanistic implications:
Remaining questions:
The LRRK2 G2019S mutation is the most common genetic cause of familial PD, and LRRK2 kinase hyperactivity is now recognized in sporadic PD. The development of brain-penetrant LRRK2 inhibitors that have reached clinical testing represents a major milestone[2:1].
Key developments:
Outstanding challenges:
The alpha-synuclein seed amplification assay (SAA) has emerged as a transformative biomarker that can detect pathological alpha-synuclein in cerebrospinal fluid with high sensitivity and specificity[3:1]. The assay enables:
The central role of alpha-synuclein in PD pathogenesis is well-established, but critical gaps remain:
Seed Kinetics and Progression:
Target Species Identification:
Spreading Mechanisms:
Translating biological insights into treatments remains challenging:
GLP-1 Responder Biology:
LRRK2 Efficacy:
Combination Therapies:
Why specific neurons degenerate early while others remain resilient:
Improving clinical trial efficiency and patient selection:
The identification of over 90 genetic risk loci for PD has transformed our understanding of disease biology, but translating genetic insights into clinical care remains challenging.
Neuroinflammation is a consistent finding in PD brain tissue and may contribute to disease progression.
Impairment of autophagy and lysosomal function is a consistent finding in PD.
Knowledge gaps are evaluated on four dimensions (0-10 scale each):
| Dimension | Description |
|---|---|
| Impact if Solved | Potential to change treatment, prevention, or trial success |
| Tractability | Feasibility with current tools, cohorts, and assays |
| Under-exploration | Insufficient effort relative to importance |
| Data Availability | Availability of cohorts, biomarkers, models, and endpoints |
Based on current knowledge gaps, the following research directions are recommended:
| Trial Type | Population | Endpoints | Timeline |
|---|---|---|---|
| Prevention | SAA+ prodromal | SAA kinetics, clinical | 3-5 years |
| Disease modification | Early PD | Biomarker + clinical | 2-3 years |
| Combination | Established PD | Multi-modal | 1-2 years |
| Target validation | Genetically defined | Target engagement | 1-2 years |
Pagano G, et al. Trial of Lixisenatide in Early Parkinson's Disease. The New England Journal of Medicine. 2024. ↩︎ ↩︎
Jennings D, et al. LRRK2 Inhibition by BIIB122 in Healthy Participants and Patients with Parkinson's Disease. Movement Disorders. 2023. ↩︎ ↩︎
Simuni T, et al. Assessment of heterogeneity among participants in the Parkinson's Progression Markers Initiative cohort using alpha-synuclein seed amplification. The Lancet Neurology. 2023. ↩︎ ↩︎
Siderowf A, et al. A biological definition of neuronal alpha-synuclein disease: towards an integrated staging system for research. The Lancet Neurology. 2024. ↩︎
Chahine LM, et al. Diagnostic and prognostic value of alpha-synuclein seed amplification assay kinetic measures in Parkinson's disease. The Lancet Neurology. 2025. ↩︎