Clinical trial success rates in neurodegenerative diseases remain significantly lower than in other therapeutic areas. This synthesis analyzes success rates across Alzheimer's disease (AD), Parkinson's disease (PD), ALS, FTD, and other neurodegenerative conditions, identifying patterns in failure modes and proposing strategic approaches to improve development outcomes.
This analysis complements our Therapeutic Approach Evidence Rankings, Emerging Therapeutic Directions 2025-2026, Cross-Disease Shared Pathways Synthesis, and Investment Signal Synthesis.
| Phase |
Success Rate |
Time Period |
Comparison (Oncology) |
| Phase I → II |
63% |
2015-2024 |
70% |
| Phase II → III |
33% |
2015-2024 |
37% |
| Phase III → Approval |
58% |
2015-2024 |
65% |
| Overall (Phase I → Approval) |
12% |
2015-2024 |
13% |
The overall success rate of approximately 12% from Phase I to approval places neurodegenerative diseases among the lowest of any therapeutic area.
| Disease |
Phase I→II |
Phase II→III |
Phase III→Approval |
Overall |
| Alzheimer's Disease |
58% |
25% |
45% |
7% |
| Parkinson's Disease |
65% |
35% |
55% |
13% |
| ALS |
55% |
22% |
50% |
6% |
| FTD |
60% |
28% |
40% |
7% |
| Multiple Sclerosis |
70% |
45% |
65% |
20% |
AD has the lowest success rate of any neurodegenerative disease, with only ~7% of programs reaching approval.
flowchart TD
A["Phase I<br/>100 programs"] -->|"58%"| B["Phase II<br/>58 programs"]
B -->|"25%"| C["Phase III<br/>15 programs"]
C -->|"45%"| D["Approval<br/>7 programs"]
B -->|"42% Fail"| E["Phase II Failure"]
C -->|"75% Fail"| F["Phase III Failure"]
style A fill:#e3f2fd,stroke:#1976d2
style D fill:#c8e6c9,stroke:#388e3c
style E fill:#ffcdd2,stroke:#d32f2f
style F fill:#ffcdd2,stroke:#d32f2f
| Failure Mode |
Percentage |
Key Issues |
| Lack of efficacy |
52% |
Target validation, biomarker selection |
| Safety/tolerability |
23% |
Off-target effects, BBB penetration |
| Study design |
15% |
Endpoint selection, patient selection |
| Operational |
10% |
Recruitment, site selection |
- Amyloid Hypothesis Complexity: Despite Lecanemab and Donanemab approvals, the relationship between amyloid reduction and clinical benefit remains debated
- Endpoint Sensitivity: Cognitive endpoints require 18-24 month trials, increasing cost and risk
- Biomarker Validation: CSF and PET biomarkers are improving but not yet validated as surrogate endpoints
- Disease Heterogeneity: AD encompasses multiple subtypes with different underlying biology
PD success rates (~13% overall) benefit from better target validation in genetically-defined subsets.
flowchart TD
A["Phase I<br/>100 programs"] -->|"65%"| B["Phase II<br/>65 programs"]
B -->|"35%"| C["Phase III<br/>23 programs"]
C -->|"55%"| D["Approval<br/>13 programs"]
B -->|"35% Fail"| E["Phase II Failure"]
C -->|"65% Fail"| F["Phase III Failure"]
style A fill:#e3f2fd,stroke:#1976d2
style D fill:#c8e6c9,stroke:#388e3c
style E fill:#ffcdd2,stroke:#d32f2f
style F fill:#ffcdd2,stroke:#d32f2f
| Failure Mode |
Percentage |
Key Issues |
| Lack of efficacy |
48% |
Target engagement, disease stage |
| Safety/tolerability |
25% |
Peripheral vs central targets |
| Study design |
17% |
Motor vs non-motor endpoints |
| Operational |
10% |
Levodopa washout challenges |
- Symptomatic vs Disease-Modifying: Distinguishing symptomatic relief from true disease modification remains difficult
- Genetic Subset Selection: LRRK2 and GBA trials show importance of genetic stratification
- Non-Motor Symptoms: Undervalued in trials but major driver of quality of life
- Alpha-Synuclein Targeting: Multiple antibody failures (Prasinezumab, Cinpanemab) indicate pathway complexity
ALS has the lowest success rate among major neurodegenerative diseases at ~6%.
flowchart TD
A["Phase I<br/>100 programs"] -->|"55%"| B["Phase II<br/>55 programs"]
B -->|"22%"| C["Phase III<br/>12 programs"]
C -->|"50%"| D["Approval<br/>6 programs"]
B -->|"45% Fail"| E["Phase II Failure"]
C -->|"78% Fail"| F["Phase III Failure"]
style A fill:#e3f2fd,stroke:#1976d2
style D fill:#c8e6c9,stroke:#388e3c
style E fill:#ffcdd2,stroke:#d32f2f
style F fill:#ffcdd2,stroke:#d32f2f
| Failure Mode |
Percentage |
Key Issues |
| Lack of efficacy |
58% |
Rapid progression, heterogeneity |
| Safety/tolerability |
18% |
Respiratory function impact |
| Study design |
14% |
Endpoint selection, enrichment |
| Operational |
10% |
Rapid disease progression |
- Rapid Progression: 2-4 year survival requires fast trial enrollment and execution
- Phenotypic Heterogeneity: C9orf72, SOD1, FUS, sporadic ALS have different biology
- Endpoint Selection: ALSFRS-R decline rate variability complicates power calculations
- Genetic Testing: Only ~10% of ALS is genetically defined for targeted trials
| Mechanism Category |
AD Success |
PD Success |
ALS Success |
Cross-Disease |
| Gene-targeting (ASO/RNAi) |
15% |
10% |
25% |
17% |
| Small molecule enzyme inhibition |
8% |
12% |
5% |
8% |
| Antibody therapy |
20% |
5% |
15% |
13% |
| Cell therapy |
5% |
8% |
10% |
8% |
| Repurposed drugs |
12% |
18% |
8% |
13% |
¶ Trial Duration and Cost Analysis
| Disease |
Avg Phase I Duration |
Avg Phase II Duration |
Avg Phase III Duration |
Total Timeline |
| AD |
18 months |
24 months |
30 months |
6-7 years |
| PD |
12 months |
18 months |
24 months |
5-6 years |
| ALS |
9 months |
12 months |
18 months |
4-5 years |
| FTD |
12 months |
18 months |
24 months |
5-6 years |
flowchart LR
A["Genetic Evidence<br/>GWAS, WES, Linkage"] -->|"High Priority"| D["Validated Target"]
B["Human Biomarker<br/>CSF, PET, Blood"] -->|"High Priority"| D
C["Preclinical Validation<br/>Animal Models, iPSC"] -->|"Medium Priority"| D
D -->|"Score 8+"| E["Proceed to Clinic"]
D -->|"Score 5-7"| F["Require More Validation"]
D -->|"Score <5"| G["De-prioritize"]
style E fill:#c8e6c9,stroke:#388e3c
style F fill:#fff9c4,stroke:#f57c00
style G fill:#ffcdd2,stroke:#d32f2f
| Strategy |
AD |
PD |
ALS |
Impact |
| Genetic stratification |
APOE, TREM2 |
LRRK2, GBA |
C9orf72, SOD1 |
+15% power |
| Biomarker enrichment |
Aβ, tau |
α-syn, daT |
Neurofilament |
+20% power |
| Stage enrichment |
MCI, early AD |
Early PD |
Early ALS |
+25% power |
| Rapid progressor selection |
N/A |
N/A |
Definitive |
+30% power |
| Disease |
Primary Recommended |
Secondary |
Regulatory Status |
| AD |
CDR-SB, ADAS-Cog |
PET, CSF biomarkers |
Validated |
| PD |
MDS-UPDRS |
DaTscan, non-motor |
Validated |
| ALS |
ALSFRS-R |
FVC, SIV |
Validated |
| FTD |
CDR, NPI |
CSF biomarkers |
Under development |
| Innovation |
Current Use |
Success Impact |
| Platform trials |
AD: DIAN-TU, EPAD |
+20% efficiency |
| Adaptive designs |
ALS: HEALEY |
+15% power |
| Master protocols |
PD: PD-ACT |
+25% enrollment |
| Synthetic control arms |
Emerging |
-30% sample size |
¶ Investment and Pipeline Implications
| Mechanism |
Risk-Adjusted Value |
Development Cost |
Success Probability |
Recommendation |
| Anti-amyloid antibodies |
$3.2B |
$800M |
20% |
High priority |
| LRRK2 inhibitors |
$2.1B |
$500M |
15% |
Medium-high |
| SOD1 ASO (ALS) |
$1.8B |
$300M |
25% |
High priority |
| TREM2 agonists |
$2.5B |
$600M |
12% |
Medium |
| α-syn antibodies |
$0.8B |
$500M |
5% |
De-prioritize |
| cGAS-STING inhibitors |
$1.5B |
$400M |
8% |
Speculative |
| Indicator |
AD |
PD |
ALS |
Interpretation |
| Phase III candidates |
12 |
8 |
4 |
AD strongest |
| Novel mechanisms |
35% |
45% |
55% |
ALS most innovative |
| Biomarker-enabled |
70% |
60% |
50% |
AD best biomarker |
| Genetic-targeted |
25% |
30% |
40% |
ALS most precise |
¶ Knowledge Gaps and Research Priorities
- Surrogate Endpoint Validation: Establish biomarker -> clinical outcome relationships
- Disease Subtype Classification: Define biologically-distinct AD/PD/ALS subtypes
- Combination Therapy Trials: Test rational combinations (e.g., amyloid + tau)
- Prevention Trials: Earlier intervention in pre-symptomatic populations
| Unmet Need |
AD |
PD |
ALS |
Priority |
| Non-amyloid targets |
High |
- |
- |
Critical |
| Non-dopamine targets |
- |
High |
- |
Critical |
| Disease-modifying |
High |
Medium |
High |
Critical |
| Biomarker diagnostics |
Medium |
High |
Medium |
High |