Efficacy and safety of GLP-1 receptor agonists in Parkinson’s disease- a systematic review
Table of Contents
- GLP-1 Receptor Agonists in Parkinson’s Disease: What the RCT Data Show
- Abstract
- Study at a Glance
- Study Snapshot
- Study Facts Table
- What Researchers Actually Did
- Key Findings: Primary Outcomes
- Key Findings: Secondary Outcomes and Subgroup Analyses
- Results: Adverse Events and Safety Profile
- Statistical Approach and Rigor
- Read This Paper Through Nine Different Lenses
- What are GLP-1 receptor agonists?
- What were the primary outcomes of the study?
- Did GLP-1RAs show any significant benefits for Parkinson’s disease?
- What were the adverse events associated with GLP-1RAs?
- How does this study impact the use of GLP-1RAs in Parkinson’s disease?
- What is the biological rationale behind using GLP-1RAs in Parkinson’s?
- Which studies were included in the meta-analysis?
- What was the duration of the trials included in the study?
- How were adverse events assessed in the study?
- What are the implications for future research on GLP-1RAs in Parkinson’s?
- Read next
GLP-1 Receptor Agonists in Parkinson’s Disease: What the RCT Data Show
GLP-1 Receptor Agonists
Neuroprotection
Meta-Analysis
Disease-Modifying Therapy
- Whether GLP-1 receptor agonists improve motor or non-motor symptoms in Parkinson’s disease, based on pooled RCT data
- The one outcome where GLP-1RAs reached statistical significance, and why that result requires caution
- The gastrointestinal and systemic safety signals that complicate use in a population already burdened by autonomic dysfunction
- Why the biological rationale for GLP-1RAs in PD has not translated into consistent clinical benefit
Abstract
Background: Parkinson’s disease (PD) is a progressive neurodegenerative disorder with no proven disease-modifying therapies to date. Because changes in cerebral glucose metabolism and insulin resistance have been linked to PD pathophysiology, glucagon-like peptide-1 receptor agonists (GLP-1RAs), widely used for diabetes, have been investigated as potential neuroprotective treatments.
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Book a consultation →Methods: This study systematically assessed the efficacy and safety of GLP-1RAs in PD through a systematic review and meta-analysis of randomized controlled trials identified in PubMed, Embase, and the Cochrane Library. Primary outcomes were motor function improvements measured by the MDS-UPDRS Part III in both on- and off-medication states at study endpoints and at intermediate timepoints. Secondary outcomes included MDS-UPDRS Parts I, II, and IV, quality of life assessed by the PDQ-39, levodopa equivalent daily dose (LEDD), and adverse events.
Results: The meta-analysis found no statistically significant difference in favor of GLP-1RAs over placebo for motor and non-motor outcomes, except for PDQ-39 (MD: -0.75; 95% CI: [-1.34, -0.17]; P=0.01). GLP-1RAs were associated with a higher incidence of adverse events, especially gastrointestinal effects such as nausea, vomiting, and constipation.
Conclusions: Current evidence does not demonstrate consistent clinical benefit of using GLP-1RAs for treating motor or non-motor symptoms in PD, nor support GLP-1RAs as disease-modifying therapy, underscoring the need for further research.
Study at a Glance
| Design | Systematic review and meta-analysis of 5 double-blind RCTs |
| Population | Adults with diagnosed Parkinson’s disease (most on levodopa); mean ages 57.8 to 64.2 years; majority male across 4 of 5 trials |
| Total N | 730 participants (range 62 to 255 per trial) |
| Interventions | Exenatide (2 trials), liraglutide, NLY01 (pegylated exenatide analog), lixisenatide; all subcutaneous |
| Primary Endpoint | MDS-UPDRS Part III (on- and off-medication) at endpoint and 6-month midpoint |
| Key Finding | No significant motor benefit at any timepoint; PDQ-39 showed a small, statistically significant improvement (MD: -0.75) that did not parallel motor or functional outcomes |
Study Snapshot
| Outcome | MD or RR (95% CI) | P value | I² | Favors |
|---|---|---|---|---|
| MDS-UPDRS III off-med (endpoint) | MD -0.66 [-2.36, 1.04] | 0.45 | 0% | Neither |
| MDS-UPDRS III off-med (midpoint) | MD 1.20 [-1.60, 4.00] | 0.40 | 0% | Neither |
| MDS-UPDRS III on-med (endpoint) | MD -0.47 [-4.39, 3.45] | 0.81 | 78% | Neither |
| MDS-UPDRS III on-med (midpoint) | MD 0.42 [-2.36, 3.20] | 0.77 | 50% | Neither |
| PDQ-39 | MD -0.75 [-1.34, -0.17] | 0.01 | 72% | GLP-1RA |
| Nausea (RR) | RR 2.67 [2.07, 3.44] | <0.00001 | 20% | Placebo |
| Vomiting (RR) | RR 3.91 [1.62, 9.43] | 0.002 | 0% | Placebo |
| Constipation (RR) | RR 1.89 [1.24, 2.87] | 0.003 | 22% | Placebo |
| Weight loss (RR) | RR 1.85 [1.39, 2.46] | <0.0001 | 51% | Placebo |
Study Facts Table
| Authors | Mendonça MF, Interaminense AC, Barros GSTR, Rabelo LA, de Oliveira PG, Sales RF, Lyra AMVC, e Silva HRS |
| Journal | Neurological Sciences, 2026; 47:484 |
| DOI | 10.1007/s10072-026-09084-3 |
| Design | Systematic review and meta-analysis; PRISMA 2020; PROSPERO registered (CRD420251230313) |
| Included Trials (N) | 5 RCTs; 730 total participants |
| Interventions | Exenatide 2 mg SC weekly (2 trials), liraglutide 1.8 mg SC weekly, NLY01 2.5 mg or 5 mg SC weekly, lixisenatide 20 mcg SC daily |
| Comparator | Placebo or placebo plus usual care (levodopa in 4 of 5 trials) |
| Follow-up Duration | 36 weeks (McGarry) to 96 weeks (Vijiaratnam) |
| Primary Endpoint | MDS-UPDRS Part III (on- and off-medication) at endpoint and 6-month midpoint |
| Primary Results | No significant difference on MDS-UPDRS III off-med at endpoint (MD -0.66; P=0.45) or midpoint (MD 1.20; P=0.40); no significant difference on-med at endpoint (MD -0.47; P=0.81) or midpoint (MD 0.42; P=0.77) |
| PDQ-39 | MD -0.75 (95% CI: -1.34 to -0.17); P=0.01; I²=72%; clinical relevance uncertain given magnitude and high heterogeneity |
| Key Adverse Events | Nausea (RR 2.67), vomiting (RR 3.91), constipation (RR 1.89), weight loss (RR 1.85); all significantly more frequent with GLP-1RAs |
| Funding | Article Processing Charge funded by CAPES (Brazil). Review received no public, private, or non-profit funding. |
| Conflicts of Interest | Authors declare no conflicts of interest |
What Researchers Actually Did
Mendonça and colleagues conducted a PRISMA 2020-compliant systematic review and meta-analysis, searching PubMed, Embase, and the Cochrane Library for randomized controlled trials published between January 2015 and September 2025. They required trials to be placebo-controlled, double-blind, and conducted in patients with diagnosed Parkinson’s disease, with no restriction on which GLP-1 receptor agonist was studied. Three independent reviewers screened 915 initial records; after duplicate removal and staged eligibility screening, five trials met inclusion criteria, yielding a combined sample of 730 randomized participants. Data extraction was performed in duplicate, with a fourth reviewer arbitrating disagreements. Risk of bias was assessed using the Cochrane RoB 2 tool.
For continuous outcomes, pooled effects were estimated as mean differences with 95% confidence intervals using inverse-variance random-effects models, given anticipated between-drug heterogeneity. Dichotomous safety outcomes used Mantel-Haenszel fixed-effects models, justified by the similarity of adverse event profiles within the class. Because the McGarry et al. trial included two dose arms (NLY01 2.5 mg and 5 mg), each arm was treated as an independent comparison against a proportionally divided placebo group per Cochrane recommendations. Sensitivity analyses were performed by sequential trial removal for any outcome where I² exceeded 40%.
Key Findings: Primary Outcomes
- MDS-UPDRS Part III off-medication at endpoint (all 5 trials; n=707): MD -0.66 (95% CI: -2.36 to 1.04); P=0.45; I²=0%. No significant benefit.
- MDS-UPDRS Part III off-medication at 6-month midpoint (3 trials; Athauda, Hogg, Vijiaratnam): MD 1.20 (95% CI: -1.60 to 4.00); P=0.40; I²=0%. No significant benefit, with the point estimate numerically favoring placebo.
- MDS-UPDRS Part III on-medication at endpoint (4 trials; Athauda, Hogg, Meissner, Vijiaratnam): MD -0.47 (95% CI: -4.39 to 3.45); P=0.81; I²=78%. High heterogeneity prompted sensitivity analysis. Removing Athauda et al. reduced I² to 43% but the result remained non-significant (MD -2.30; P=0.09).
- MDS-UPDRS Part III on-medication at midpoint (4 trials): MD 0.42 (95% CI: -2.36 to 3.20); P=0.77; I²=50%. Removing Athauda et al. reduced I² to 0% but the result remained non-significant (MD -0.83; P=0.45).
- Dose-response (NLY01): The McGarry et al. trial’s 2.5 mg and 5 mg arms showed no differential effect, suggesting no dose-response gradient within the studied range for that agent.
Key Findings: Secondary Outcomes and Subgroup Analyses
- MDS-UPDRS Part I (non-motor experiences of daily living; all 5 trials): MD 0.00 (95% CI: -0.10 to 0.10); P=0.99; I²=0%. No difference.
- MDS-UPDRS Part II (motor experiences of daily living; all 5 trials): MD 0.10 (95% CI: -0.26 to 0.47); P=0.58; I²=75%. High heterogeneity. Removing Hogg et al. reduced I² to 1% and the result became statistically significant (MD 0.20; 95% CI: 0.10 to 0.31; P=0.0002), favoring placebo, meaning GLP-1RA patients performed marginally worse on functional daily living tasks in that sensitivity analysis.
- MDS-UPDRS Part IV (motor complications; 4 trials): MD -0.03 (95% CI: -0.34 to 0.28); P=0.85; I²=0%. No difference.
- PDQ-39 (quality of life; 4 trials; Meissner et al. excluded due to absent values): MD -0.75 (95% CI: -1.34 to -0.17); P=0.01; I²=72%. Statistically significant, favoring GLP-1RA. After removing Hogg et al., heterogeneity fell to 0% and the result remained significant (MD -0.70; 95% CI: -0.88 to -0.51; P<0.00001). The authors note the magnitude is small and the dissociation from motor and functional outcomes raises questions about the driver of this signal.
- LEDD (3 trials; Hogg et al. excluded for missing raw data): MD 7.70 (95% CI: -20.22 to 35.61); P=0.59; I²=0%. No significant reduction in levodopa requirement.
- No subgroup analyses by disease stage, sex, age, or comorbidity were feasible given the small number of included trials.
Results: Adverse Events and Safety Profile
Safety Summary: GLP-1RAs carried a consistently and significantly higher burden of adverse events compared with placebo across all five trials.
- Nausea: RR 2.67 (95% CI: 2.07 to 3.44); P<0.00001; I²=20%. 209 events in GLP-1RA group vs. 58 in placebo across 727 pooled participants.
- Vomiting: RR 3.91 (95% CI: 1.62 to 9.43); P=0.002; I²=0%. McGarry et al. excluded from pooling due to a single control-group event that could not be cleanly divided.
- Constipation: RR 1.89 (95% CI: 1.24 to 2.87); P=0.003; I²=22%. 65 events vs. 26 in pooled sample.
- Diarrhea: RR 1.42 (95% CI: 0.94 to 2.14); P=0.09; I²=0%. More frequent with GLP-1RAs but the between-group difference did not reach significance.
- Anxiety: RR 1.91 (95% CI: 0.63 to 5.73); P=0.25; I²=0%. More frequent with GLP-1RAs but not statistically significant.
- Weight loss: RR 1.85 (95% CI: 1.39 to 2.46); P<0.0001; I²=51%. 103 events vs. 46 in placebo. Sensitivity analysis removing Hogg et al. preserved significance (RR 1.61; P=0.001).
The authors flag that constipation, nausea, and slowed intestinal transit are already features of Parkinson’s disease autonomic dysfunction. GLP-1RA-induced gastrointestinal effects therefore carry particular clinical weight in this population, with potential downstream consequences for levodopa absorption and treatment adherence.
Statistical Approach and Rigor
The choice of random-effects models for continuous outcomes is appropriate given the class-level heterogeneity introduced by pooling structurally distinct agents (exenatide, liraglutide, lixisenatide, NLY01). The fixed-effects model for adverse events is more debatable but defensible
Read This Paper Through Nine Different Lenses
The same evidence can produce very different conclusions depending on the question being asked. Explore this study through multiple physician-guided interpretive frameworks.
Overview
This systematic review and meta-analysis of five randomized controlled trials found that GLP-1 receptor agonists do not produce statistically or clinically significant improvements in motor or non-motor outcomes in Parkinson’s disease. The only positive outcome was a small improvement in quality of life, which did not parallel motor or functional benefits.
The study highlights the need for further research to explore potential benefits and safety profiles of GLP-1RAs in specific subgroups or with different dosing regimens.
- No significant motor benefit from GLP-1RAs.
- Small improvement in quality of life noted.
- Higher incidence of gastrointestinal adverse events observed.
Patient Takeaway
While GLP-1 receptor agonists did not improve motor symptoms in Parkinson’s disease, they showed a small improvement in quality of life. However, these medications come with higher rates of gastrointestinal side effects such as nausea and constipation, which can be challenging for patients already dealing with autonomic dysfunction.
Patients should discuss the potential benefits and risks with their healthcare providers before considering GLP-1RAs as a treatment option.
- Small quality of life improvement noted.
- Higher rates of gastrointestinal side effects.
- Consideration of individual patient needs and preferences.
Clinician’s POV
Clinicians should be aware that GLP-1 receptor agonists do not provide significant motor benefits for Parkinson’s disease patients. The small improvement in quality of life must be weighed against the increased risk of gastrointestinal adverse events.
Further research is needed to determine if GLP-1RAs could be beneficial in specific subgroups or with different dosing strategies.
- No significant motor benefits observed.
- Small quality of life improvement noted.
- Increased risk of gastrointestinal side effects.
A Skeptical Read
The study suggests that GLP-1 receptor agonists do not provide significant motor or non-motor benefits for Parkinson’s disease. The small improvement in quality of life is not clinically meaningful and does not align with improvements in motor function.
Given the higher risk of gastrointestinal adverse events, skepticism about the use of GLP-1RAs as a treatment option is warranted until further research provides more evidence.
- No significant motor or non-motor benefits.
- Small quality of life improvement not clinically meaningful.
- Higher risk of gastrointestinal side effects.
Study Critic
The study design, while robust, includes a small number of trials and participants. The high heterogeneity across studies limits the generalizability of the findings.
Critics may argue that further research with larger sample sizes and longer follow-up periods is necessary to fully understand the potential role of GLP-1RAs in Parkinson’s disease management.
- Small number of trials included.
- High heterogeneity across studies.
- Need for larger, longer-term studies.
Compared to Past Research
Past studies have explored the potential neuroprotective effects of GLP-1 receptor agonists based on their impact on cerebral glucose metabolism and insulin resistance in Parkinson’s disease. However, these initial findings did not consistently translate into clinical benefits as demonstrated by this meta-analysis.
The lack of significant motor or non-motor improvements suggests that further investigation is needed to understand the biological mechanisms underlying the potential benefits of GLP-1RAs.
- Initial studies suggested neuroprotective effects.
- No consistent clinical benefits observed in this study.
- Need for further understanding of biological mechanisms.
Practical Considerations
Practically, the findings suggest that GLP-1 receptor agonists should not be considered as a primary treatment option for motor or non-motor symptoms in Parkinson’s disease due to their lack of significant benefits and increased risk of gastrointestinal adverse events.
Clinicians may consider these medications only if other treatments have failed and the potential quality of life improvement outweighs the risks.
- No significant motor or non-motor benefits.
- Increased risk of gastrointestinal side effects.
- Consideration of alternative treatment options.
Future Directions
Future research should focus on exploring the potential benefits and safety profiles of GLP-1 receptor agonists in specific subgroups of Parkinson’s disease patients, such as those with advanced disease or particular genetic mutations.
Investigating different dosing regimens and combination therapies may also provide insights into whether GLP-1RAs can offer any clinical benefit in this population.
- Explore benefits in specific subgroups.
- Investigate different dosing regimens.
- Consider combination therapies.
Misreadings & Bad-Faith Takes
A common misreading of the study is that GLP-1 receptor agonists offer significant benefits for Parkinson’s disease, which is not supported by the findings. The small improvement in quality of life does not translate into meaningful motor or functional improvements.
Another potential misinterpretation is that the increased risk of gastrointestinal adverse events is negligible, which is not accurate given the burden these side effects can place on patients with Parkinson’s disease.
- Misreading: Significant benefits for Parkinson’s.
- Misreading: Negligible gastrointestinal risks.
- Importance of understanding study limitations.
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What are GLP-1 receptor agonists?
GLP-1 receptor agonists (GLP-1RAs) are medications originally developed for diabetes that have been investigated for their potential neuroprotective effects in Parkinson’s disease.
What were the primary outcomes of the study?
The primary outcomes were improvements in motor function measured by the MDS-UPDRS Part III in both on- and off-medication states at study endpoints and intermediate timepoints.
Did GLP-1RAs show any significant benefits for Parkinson’s disease?
No statistically significant difference was found in favor of GLP-1RAs over placebo for motor or non-motor outcomes, except for a small improvement in quality of life measured by the PDQ-39.
What were the adverse events associated with GLP-1RAs?
GLP-1RAs were associated with higher incidences of gastrointestinal adverse events such as nausea, vomiting, and constipation.
How does this study impact the use of GLP-1RAs in Parkinson’s disease?
The study suggests that current evidence does not support the use of GLP-1RAs as a treatment for motor or non-motor symptoms in Parkinson’s disease, nor as a disease-modifying therapy.
What is the biological rationale behind using GLP-1RAs in Parkinson’s?
The rationale is based on changes in cerebral glucose metabolism and insulin resistance linked to PD pathophysiology, suggesting potential neuroprotective effects.
Which studies were included in the meta-analysis?
The meta-analysis included five double-blind randomized controlled trials involving 730 participants with Parkinson’s disease.
What was the duration of the trials included in the study?
The follow-up duration varied from 36 weeks to 96 weeks across different trials.
How were adverse events assessed in the study?
Adverse events were assessed using Mantel-Haenszel fixed-effects models, justified by the similarity of adverse event profiles within the GLP-1RA class.
What are the implications for future research on GLP-1RAs in Parkinson’s?
The findings underscore the need for further research to explore potential benefits and safety of GLP-1RAs in specific subgroups or with different dosing regimens.
