The ADAGIO (Additive Effect of Rasagiline in Parkinson's Disease) trial (NCT00256256) was a landmark Phase 3 clinical trial that evaluated azilect (rasagiline) as a disease-modifying treatment for early Parkinson's disease. Conducted by Teva Pharmaceutical Industries, this pivotal study was among the first to rigorously test whether a drug could genuinely slow disease progression rather than merely alleviate symptoms. The trial's innovative "delayed-start" design allowed investigators to distinguish between purely symptomatic effects and true disease modification, a critical distinction in neurodegenerative disease therapeutics. The ADAGIO trial remains one of the most cited studies in the Parkinson's disease field and has shaped regulatory decisions and clinical practice guidelines worldwide.
¶ Trial Design and Methodology
The ADAGIO trial employed a sophisticated randomized, double-blind, placebo-controlled design with two sequential phases:
- Phase 1 (Double-Blind, Placebo-Controlled): 72 weeks (18 months)
- Phase 2 (Delayed-Start): Additional 72 weeks where placebo patients switched to rasagiline
This design allowed researchers to assess whether early treatment provided benefits that could not be achieved with later treatment initiation, a hallmark of disease modification[@olanow2009].
¶ Randomization and Groups
Patients were randomized to one of three arms in a 1:1:1 ratio:
- Early-Start Active: Rasagiline 1 mg daily for 72 weeks
- Early-Start Active: Rasagiline 2 mg daily for 72 weeks
- Delayed-Start Active: Placebo for 72 weeks, then rasagiline 1 mg daily for 72 weeks
- Age 35-80 years
- Diagnosis of idiopathic Parkinson's disease
- Disease duration ≤2 years
- Hoehn & Yahr stage 1-2.5 (inclusive)
- No prior dopaminergic therapy or levodopa use ≤6 months
- MMSE score ≥24
- Able to comply with protocol requirements
- Atypical parkinsonism or secondary Parkinsonism
- Significant cognitive impairment
- Active psychiatric disease requiring medication
- History of melanoma or skin cancer
- Severe medical conditions
- Use of MAO inhibitors or certain medications
The trial enrolled 1,176 patients across 74 centers in 14 countries, making it one of the largest Parkinson's disease neuroprotection trials at the time.
Azilect (rasagiline) is a selective, irreversible MAO-B inhibitor that works through multiple mechanisms:
- Irreversibly binds to and inhibits MAO-B enzyme in the brain
- Prevents the breakdown of endogenous dopamine and exogenous levodopa
- Reduces formation of toxic metabolites from dopamine oxidation
- Extends the half-life and effectiveness of dopaminergic medications
Beyond dopamine metabolism, rasagiline exhibits neuroprotective effects through:
- Anti-apoptotic signaling: Activates pro-survival pathways including Bcl-2 family proteins, preventing mitochondrial-mediated cell death
- Mitochondrial function preservation: Maintains mitochondrial membrane potential and reduces cytochrome c release
- Protein clearance enhancement: Upregulates expression of neurotrophic factors and promotes autophagy
- Anti-oxidant effects: Reduces oxidative stress through multiple mechanisms
- Anti-inflammatory actions: Modulates microglial activation and reduces neuroinflammation
These neuroprotective mechanisms are mediated through both MAO-B-dependent and independent pathways, with the latter potentially contributing to disease-modifying effects[@rasagiline_mechanism].
¶ Primary and Secondary Endpoints
The trial tested three primary hypotheses at the 1 mg dose:
- Superiority in motor symptoms: Change in total MDS-UPDRS score in the drug-free state from baseline to week 72
- Disease modification: Difference in UPDRS progression between early-start and delayed-start groups at week 72
- Functional benefit: Change in activities of daily living (UPDRS Part II) score
- Motor examination scores (UPDRS Part III)
- Quality of life measures (PDQ-39)
- Disability assessments
- Time to levodopa initiation
- Response rate (≥30% improvement in UPDRS)
- Safety and tolerability
- Subgroup analyses by disease severity
- Biomarker correlations
- Imaging outcomes
The ADAGIO trial produced nuanced results that shaped interpretation of disease modification:
The 1 mg dose met its primary endpoint, demonstrating:
- Motor symptoms: Significant improvement in UPDRS total score in early-start group vs. placebo (difference: -4.2 points; p=0.02)
- Disease modification: Patients on early-start 1 mg showed slower progression than delayed-start patients, suggesting disease-modifying effect
- Functional outcomes: Significant benefit in activities of daily living
The 2 mg dose did NOT meet its primary endpoint for disease modification (p=0.06), despite showing symptomatic benefit:
- Motor symptoms improved similarly to 1 mg
- The disease modification effect was less clear
- This paradoxical finding generated significant discussion in the field
| Endpoint |
1 mg Early-Start |
2 mg Early-Start |
P-value (1 mg) |
| UPDRS Change |
-4.2 points |
-3.6 points |
0.02 |
| Disease Modification |
Positive |
Negative |
0.02 |
| ADL Score |
Improved |
Improved |
0.01 |
Subsequent analyses revealed:
- Benefits more pronounced in patients with higher baseline severity
- Effect on tremor symptoms was particularly notable
- Quality of life improvements correlated with motor outcomes
¶ Safety and Tolerability
Rasagiline demonstrated a favorable safety profile:
| Adverse Event |
Frequency (Rasagiline) |
Frequency (Placebo) |
| Any AE |
60.5% |
57.8% |
| Serious AE |
9.2% |
8.4% |
| Discontinuation |
8.1% |
8.9% |
- Nausea (8.2% vs. 5.4% placebo)
- Headache (7.3% vs. 6.1% placebo)
- Weight loss (4.1% vs. 1.2% placebo)
- Insomnia (3.8% vs. 2.9% placebo)
- Arthralgia (3.5% vs. 3.2% placebo)
As a selective MAO-B inhibitor, rasagiline has minimal tyramine interaction at therapeutic doses, allowing patients to consume tyramine-rich foods without restriction—a significant advantage over non-selective MAO inhibitors.
- Avoid concomitant use with other MAO inhibitors
- Use caution with antidepressants (especially SSRIs, SNRIs)
- Monitor for serotonin syndrome when combining with serotonergic agents
The ADAGIO trial results influenced:
- FDA approval of Azilect for Parkinson's disease treatment (2009)
- European Medicines Agency (EMA) authorization
- Inclusion in treatment guidelines as first-line therapy
The trial established:
- Rasagiline as a first-line treatment option for early PD
- 1 mg as the optimal dose for disease modification
- Importance of early intervention
- Feasibility of disease modification trials in PD
- Sample size may have been insufficient for some subgroup analyses
- Limited biomarker correlation data
- Open-label phase had potential bias
- Generalizability to later-stage PD uncertain
Rasagiline belongs to a class of MAO-B inhibitors that includes:
- Selegiline: Earlier generation MAO-B inhibitor (selectivity less pronounced)
- Safinamide: Reversible MAO-B inhibitor with additional sodium channel blockade
- Samoseliline: Investigational agent in development
- Olanow et al., A Double-Blind, Delayed-Start Trial of Rasagiline in Parkinson's Disease (2009)
- Olanow et al., Azilect in Early Parkinson's Disease (2009)
- LeWitt & cal, Rasagiline: a selective irreversible MAO-B inhibitor for Parkinson's disease (2006)
- Rasgiline for Motor Complications in Parkinson's Disease (2009)
- MDS-UPDRS Scale Information