A groundbreaking pilot study has demonstrated that fecal microbiota transplantation (FMT) can be safely administered to Parkinson's disease patients over an extended six-month period, marking a significant milestone in exploring gut-brain axis interventions for neurodegenerative disorders. The research, published in npj Parkinson's Disease, represents the first clinical evaluation of prolonged FMT therapy in this patient population.
The study enrolled 12 participants with mild to moderate Parkinson's disease (8 females, 4 males; mean age 69.5 years) who received FMT enemas over six months. All patients were on L-dopa therapy with a mean daily equivalent dose of 684 mg and had an average disease duration of 6.9 years. Notably, 75% of participants met Rome IV criteria for functional constipation at baseline.
Safety Profile Establishes Treatment Feasibility
The primary safety outcomes demonstrated excellent tolerability, with 11 of 12 subjects (92%) completing the full treatment course. Only one serious adverse event occurred—a hospitalization for worsening motor symptoms after two months—which investigators deemed unlikely related to FMT given the patient's history of steady functional decline prior to enrollment.
Gastrointestinal adverse events were reported by 10 of 12 subjects (83%) as "probably" or "definitely" related to FMT, but these were transient and mild, occurring primarily during the induction phase. The most common side effects included increased flatulence (50%), abdominal pain (42%), constipation (42%), and bloating (42%). Importantly, no treatments were withheld due to adverse events.
Patient acceptability remained high throughout the study, with most participants rating FMT safety and acceptability above 70 on a 100-point visual analogue scale at both two and six months.
Quality of Life Improvements Show Early Promise
While the study was not primarily designed to assess efficacy, researchers observed a statistically significant improvement in quality of life scores at two months (PDQ-39 scores: baseline 34.7 vs. 2 months 25.3; p = 0.032). Additionally, trends toward improvement were noted in several non-motor symptom measures, including a 35% reduction in UPDRS Part I scores and a 16% reduction in UPDRS Part II scores at two months.
However, these improvements were not sustained at the six-month follow-up, suggesting that more frequent dosing may be necessary to maintain therapeutic benefits. The greatest improvements coincided with the induction phase involving weekly or fortnightly FMT enemas.
Motor Function Results Remain Inconclusive
Motor function outcomes showed mixed results. Mean daily OFF-time decreased from 4.8 hours at baseline to 3.8 hours at two months (p = 0.58), but returned to baseline levels by six months (4.4 hours). The study utilized Hauser Motor Diaries, considered a reliable and valid tool that may offer superior sensitivity in detecting changes in dopaminergic ON/OFF time compared to traditional UPDRS assessments.
Importantly, while no significant motor improvements were observed, there was also no deterioration in mean MDS-UPDRS III motor examination scores over the six-month treatment period, suggesting potential disease-modifying effects that warrant further investigation.
Treatment Protocol and Microbiome Analysis
The FMT protocol consisted of an induction phase with six donor FMT enemas over eight weeks, followed by a maintenance phase with four monthly enemas. Each 50 mL enema contained 12.5 g of donor feces sourced from Biomebank, a Therapeutic Goods Administration-accredited provider.
Microbiome analysis revealed no significant changes in alpha diversity, richness, or evenness of the gut microbiome throughout the study period. Researchers hypothesize this may be due to the enema-based delivery method, suggesting that alternative administration routes such as nasojejunal delivery might be more effective for achieving sustained microbiome changes.
Clinical Implications and Future Directions
The study's findings align with emerging evidence linking gut dysbiosis to Parkinson's disease pathogenesis. Alpha-synuclein pathology, a hallmark of the disease, is thought to begin in enteric neurons years before affecting central nervous system neurons, with the vagus nerve potentially facilitating spread from gut to brain.
Lead researcher observations suggest that the optimal frequency and duration of FMT required to achieve meaningful improvements in Parkinson's disease remains to be established. The transient nature of observed benefits during the more intensive induction phase indicates that sustained therapeutic effects may require more frequent dosing regimens.
Study Limitations and Next Steps
Researchers acknowledge several limitations, including the open-label design that introduces risk of observer bias and potential placebo effects, as well as the small sample size that limited statistical power. The lack of dietary control throughout treatment duration may have impacted FMT engraftment success.
Despite these limitations, the study's single-center, single-investigator design minimized inter-site variability, and the six-month duration represents among the longest FMT therapy trials in Parkinson's disease to date. The research establishes crucial safety data that will inform the design of larger, randomized, placebo-controlled trials needed to definitively assess FMT's therapeutic potential.
The findings support continued investigation into microbiome-targeted therapies for Parkinson's disease, with future research needed to determine optimal administration routes, dosing frequencies, and treatment durations. As the scientific community continues to unravel the complex gut-brain interactions in neurodegeneration, FMT and related interventions may emerge as important components of future therapeutic strategies for Parkinson's disease management.
