Concept Overview
flowchart TD
ideas_pde5_inhibitors_neurodeg["PDE5 Inhibitors for Neurodegeneration - Vascular"]
ideas_pde5_inhibitors_neurodeg["Concept"]
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ideas_pde5_inhibitors_neurodeg["Idea"]
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ideas_pde5_inhibitors_neurodeg["inv007-pde5-neuro"]
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ideas_pde5_inhibitors_neurodeg["Drugs"]
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Idea ID: inv007-pde5-neuro
Drugs: Sildenafil (Viagra), Tadalafil (Cialis)
Original Indication: Erectile dysfunction, pulmonary hypertension
Repurposed Indication: Alzheimer's Disease, Vascular Cognitive Impairment
Approach: Improve cerebral blood flow and endothelial function
Background
Drug Profile Phosphodiesterase type 5 (PDE5) inhibitors increase cGMP levels:
Sildenafil: Short half-life (4 hrs), approved for ED, PAHTadalafil: Long half-life (17.5 hrs), approved for ED, BPH, PAH...
Concept Overview
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Idea ID: inv007-pde5-neuro
Drugs: Sildenafil (Viagra), Tadalafil (Cialis)
Original Indication: Erectile dysfunction, pulmonary hypertension
Repurposed Indication: Alzheimer's Disease, Vascular Cognitive Impairment
Approach: Improve cerebral blood flow and endothelial function
Background
Drug Profile Phosphodiesterase type 5 (PDE5) inhibitors increase cGMP levels:
Sildenafil: Short half-life (4 hrs), approved for ED, PAHTadalafil: Long half-life (17.5 hrs), approved for ED, BPH, PAHCerebral Vascular Dysfunction in Neurodegeneration Vascular contributions to neurodegeneration:
Reduced cerebral blood flow - Early feature of AD/PDEndothelial dysfunction - Impaired vasodilation[Blood-brain barrier](/entities/blood-brain-barrier) breakdown - Permeability changesVascular risk factors - Hypertension, diabetes, atherosclerosis
Preclinical Evidence | Finding | Model | Reference |
Therapeutic Hypothesis PDE5 inhibitors improve neurodegeneration through:
cGMP-mediated vasodilation - Increased cerebral perfusionEndothelial protection - Improved BBB functionAnti-amyloid effects - Reduced APP processingNeurogenesis promotion - Stem cell activationAnti-inflammatory effects - Reduced glial activation
Clinical Evidence
Human Trials | Trial | Drug | N | Outcome | Reference |
Real-World Evidence
Large retrospective study: 70% reduced AD risk in PDE5i users
Mechanism plausible but confounding possible
Development Strategy
Stage 1: Patient Selection
Target vascular cognitive impairment (VCI)
Include patients with vascular risk factors
Use MRI perfusion as biomarker
Stage 2: Trial Design
Population: MCI due to vascular causes, or early AD with vascular riskEndpoints: Perfusion MRI, cognition (ADAS-Cog), [NfL](/biomarkers/neurofilament-light-chain-nfl)Duration: 12 months minimumStage 3: Regulatory Path
Orphan drug designation for VCI possible
Biomarker-based approval pathway
Expected Outcomes
Improved cerebral perfusion (10-20% increase on MRI)Slowed cognitive decline (25% reduction in decline rate)Reduced AD pathology (if CSF/blood biomarkers included)Risk Assessment
Risk Level: LowRationale: Established safety from cardiovascular useKnown risks: Hypotension, headache, visual changesDrug interactions: Nitrates (contraindicated), antihypertensivesCompetitive Landscape | Approach | Company | Stage | Mechanism |
See Also
[Alzheimer's Disease](/diseases/alzheimers-disease)
[Parkinson's Disease](/diseases/parkinsons-disease)
External Links
[PubMed](https://pubmed.ncbi.nlm.nih.gov/)
[KEGG Pathways](https://www.genome.jp/kegg/pathway.html)
References [@puzzo2015]: [Puzzo et al., PDE5 and synaptic plasticity (2015)](https://pubmed.ncbi.nlm.nih.gov/25582325/)
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