Idea ID: inv007-zonisamide-pd
Drug: Zonisamide (Zonegran)
Original Indication: Epilepsy
Repurposed Indication: Parkinson's Disease
Approach: Adjunctive therapy for motor complications
Zonisamide is an FDA-approved anti-epileptic drug with multiple mechanisms of action:
- Carbonic anhydrase inhibition
- Na+ channel blockade
- T-type Ca2+ channel modulation
- Dopamine release enhancement
| Study |
Finding |
Reference |
| Phase 2 (2007) |
Significant OFF-time reduction |
Murata et al. |
| Phase 3 (Japan) |
Improved UPDRS motor scores |
Matsui et al. |
| Phase 3 (US) |
Modest benefit, 25mg optimal |
Hauser et al. |
- Japan: Approved for PD (2009)
- US/EU: Not approved, off-label use only
- Evidence level: Multiple positive RCTs
Zonisamide provides benefit in PD through:
- Dopaminergic effects - Enhances dopamine release
- Antioxidant properties - Reduces oxidative stress
- Anti-excitotoxic effects - Protects neurons
- Neuroinflammation modulation - Dampens glial activation
- Established efficacy in motor symptoms
- Good safety profile from epilepsy use
- Off-patent (generic available)
- Better understanding of mechanism in PD
- Combination therapy potential
- Disease-modifying potential unclear
- Biomarker-guided patient selection - Identify responders
- Combination trials - With levodopa or MAO-B inhibitors
- Neuroimaging studies - DaTscan to assess dopaminergic effects
- Long-term outcomes - Disease progression markers
¶ Competitive Landscape
| Drug |
Class |
Status |
Efficacy |
| Zonisamide |
AED |
Off-label |
Moderate |
| Amantadine |
NMDA antagonist |
Approved |
Moderate |
| Levodopa |
Dopamine precursor |
Gold standard |
High |
| MAO-B inhibitors |
Enzyme inhibitors |
Approved |
Moderate |
- 20-30% reduction in OFF-time
- 5-8 point improvement in UPDRS Part III
- Potential disease-modifying effects (unproven)
- Risk Level: Low
- Rationale: Drug has established safety from epilepsy
- Known risks: Weight loss, somnolence, renal stones
- Contraindications: Sulfonamide allergy