Long duration response in Parkinson's disease: levodopa revisited

Is it all the RAGE? Defining the role of the receptor for advanced glycation end products in Parkinson's disease

The receptor for advanced glycation end products (RAGE) is a transmembrane receptor that belongs to the immunoglobulin superfamily and is extensively associated with chronic inflammation in non-transmissible diseases. As chronic inflammation is consistently present in neurodegenerative diseases, it was largely assumed that RAGE could act as a critical modulator of neuroinflammation in Parkinson's disease (PD), similar to what was reported for Alzheimer's disease (AD), where RAGE is postulated to mediate pro-inflammatory signaling in microglia by binding to amyloid-β peptide. However, accumulating evidence from studies of RAGE in PD models suggests a less obvious scenario. Here, we review physiological aspects of RAGE and address the current questions about the potential involvement of this receptor in the cellular events that may be critical for the development and progression of PD, exploring possible mechanisms beyond the classical view of the microglial activation/neuroinflammation/neurodegeneration axis that is widely assumed to be the general mechanism of RAGE action in the adult brain.

Drugs to Treat Neuroinflammation in Neurodegenerative Disorders

Neuroinflammation is associated with disorders of the nervous system, and it is induced in response to many factors, including pathogen infection, brain injury, toxic substances, and autoimmune diseases. Astrocytes and microglia have critical roles in neuroinflammation. Microglia are innate immune cells in the central nervous system (CNS), which are activated in reaction to neuroinflammation-inducing factors. Astrocytes can have pro- or anti-inflammatory responses, which depend on the type of stimuli presented by the inflamed milieu. Microglia respond and propagate peripheral inflammatory signals within the CNS that cause low-grade inflammation in the brain. The resulting alteration in neuronal activities leads to physiological and behavioral impairment. Consequently, activation, synthesis, and discharge of various pro-inflammatory cytokines and growth factors occur. These events lead to many neurodegenerative conditions, such as Alzheimer's disease, Parkinson's disease, and multiple sclerosis discussed in this study. After understanding neuroinflammation mechanisms and the involvement of neurotransmitters, this study covers various drugs used to treat and manage these neurodegenerative illnesses. The study can be helpful in discovering new drug molecules for treating neurodegenerative disorders.

Inhaled levodopa for threatening impending OFF episodes in managing Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder that leads to the degeneration of dopaminergic neurons resulting in a widespread pathology of motor and non-motor symptoms. Oral levodopa remains the most effective symptomatic treatment of PD, but motor complications such as Off episodes occur over time. The spectrum of manifestation of OFF episodes varies, e.g., early morning akinesia, end-of-dose wearing OFF, delayed ON, suboptimal ON and dose failure. The functional disability substantially impacts the quality of life for PD patients. An innovative on-demand therapy to treat Off episodes was approved for patients receiving oral levodopa/dopa deacarboxylase inhibitor: inhaled levodopa powder (Inbrija®). The pulmonary delivery of inhaled levodopa powder provides a predictable and fast treatment effect, independent of gastrointestinal dysfunctions or food intake, which could affect levodopa absorption. Levodopa is administered with a breath-actuated inhaler device and the approved dose is 84 mg per Off episode. During the pivotal SPAN-PD phase III trial, significant improvement in Unified Parkinson Disease Rating Scale III score was measured 30 min post-dose at week 12. Improvement was already seen for the first measured time point 10 min post-dose. No differences in pulmonary function was observed when using inhaled levodopa powder regularly for up to 12 months. Inhaled levodopa powder was also approved for early morning Off episodes. The aim of this review article is to give an overview of the different clinical studies of the innovative inhaled levodopa powder, a new on-demand therapy to treat Off episodes in PD.

Quantified Striatal Dopaminergic Denervation as Predictor for Motor Outcomes in Parkinson's Disease

Background

A hallmark of Parkinson's disease (PD) is progressive loss of dopamine terminals in the basal ganglia, with clinical symptoms including motor and non-motor manifestations such as bradykinesia, rigidity, and cognitive impairment. Dopamine transporter single-photon emission computed tomography (DaT-SPECT) can be used to assess dopaminergic denervation by detecting loss of striatal dopamine transporters (DaT).

Objective

We examined DaT binding scores' (DaTbs) association with motor outcomes in PD and explored its usefulness as a predictor of disease progression. Faster dopaminergic denervation in the basal ganglia was hypothesized to have stronger correlation and predictive value for poor motor outcomes.

Methods

Data was analyzed from the Parkinson's Progression Markers Initiative. DaTbs in the putamen and caudate nucleus were correlated with Movement Disorders Society Unified Parkinson's Disease Rating Scale (MDS-UPDRS) scores for walking and balance difficulties, gait difficulties, and presence of dyskinesias. A predictive model using baseline speed of drop in DaT binding score was performed for each motor outcome.

Results

All motor outcomes had mild, significantly negative correlation with DaTbs in the putamen and caudate nucleus, with similar degree of correlation per region. Speed of drop was predictive of only substantial gait difficulties when evaluated in the putamen but not the caudate.

Conclusions

These findings suggest that analyzing speed of drop in DaTbs, which occurs early in the motor phase of the disease, may be helpful for predicting clinical outcomes in PD. Longer observation of this cohort may provide further data to investigate DaTbs as a prognostic marker in PD.

Efficacy of rehabilitation robot-assisted gait training on lower extremity dyskinesia in patients with Parkinson's disease: A systematic review and meta-analysis

BACKGROUND

Robot-assisted training is used as a new rehabilitation training method for the treatment of motor dysfunction in neurological diseases. Robot-assisted gait training (RAGT) has been reported to treat motor dysfunction in patients with Parkinson's disease (PD). The purpose of this study was to summarize previous clinical studies comparing the effectiveness of RAGT and conventional training for lower extremity dyskinesia in PD patients.

METHODS

PubMed, Cochrane library, Scopus, Embase, EBSCO, Web of Science, CNKI, and Wanfang databases were searched. This study included all randomized controlled trials (RCTs) compared lower extremity RAGT with conventional training on motor impairment in PD patients. The retrieval time limit is from the establishment of the database to October 2022. Two researchers independently screened the literature, extracted data, assessed the risk of bias of included studies, and then used RevMan 5.3 software for meta-analysis.

RESULTS

A total of 14 RCTs with 572 patients were included. The results showed that compared with the control group, RAGT significantly improved the motor function evaluation-related indicators 10MWT, 6MWT, TUG and UPDRS III, 10MWT [MD= 0.08, 95 % CI (0.01, 0.14), P = 0.03], 6MWT [MD= 42.83, 95 % CI (22.05, 63.62), P < 0.0001], TUG[MD= -1.81, 95 % CI (-2.55, -1.08), P < 0.0001], UPDRS III [MD= - 3.82, 95 % CI (-4.27, -3.37), P < 0.00001]; For the balance function evaluation index BBS [MD= 3.33, 95 % CI (2.76, 3.89), P < 0.00001], the above results were significantly different significance.

CONCLUSION

The currently limited evidence suggests that RAGT provides evidence for the effectiveness of lower extremity motor function and balance dysfunction, and RAGT can significantly improve motor and balance function in PD patients.

Evaluation of the PREDIGT score’s performance in identifying newly diagnosed Parkinson’s patients without motor examination

Several recent publications described algorithms to identify subjects with Parkinson’s disease (PD). In creating the “PREDIGT Score”, we previously developed a hypothesis-driven, simple-to-use formula to potentially calculate the incidence of PD. Here, we tested its performance in the ‘De Novo Parkinson Study’ (DeNoPa) and ‘Parkinson’s Progression Marker Initiative’ (PPMI); the latter included participants from the ‘FOllow Up persons with Neurologic Disease’ (FOUND) cohort. Baseline data from 563 newly diagnosed PD patients and 306 healthy control subjects were evaluated. Based on 13 variables, the original PREDIGT Score identified recently diagnosed PD patients in the DeNoPa, PPMI + FOUND and the pooled cohorts with area-under-the-curve (AUC) values of 0.88 (95% CI 0.83–0.92), 0.79 (95% CI 0.72–0.85), and 0.84 (95% CI 0.8–0.88), respectively. A simplified version (8 variables) generated AUC values of 0.92 (95% CI 0.89–0.95), 0.84 (95% CI 0.81–0.87), and 0.87 (0.84–0.89) in the DeNoPa, PPMI, and the pooled cohorts, respectively. In a two-step, screening-type approach, self-reported answers to a questionnaire (step 1) distinguished PD patients from controls with an AUC of 0.81 (95% CI 0.75–0.86). Adding a single, objective test (Step 2) further improved classification. Among seven biological markers explored, hyposmia was the most informative. The composite AUC value measured 0.9 (95% CI 0.88–0.91) in DeNoPa and 0.89 (95% CI 0.84–0.94) in PPMI. These results reveal a robust performance of the original PREDIGT Score to distinguish newly diagnosed PD patients from controls in two established cohorts. We also demonstrate the formula’s potential applicability to enriching for PD subjects in a population screening-type approach.

Comparative efficacy of surgical approaches to disease modification in Parkinson disease

Parkinson’s disease (PD) may optimally be treated with a disease-modifying therapy to slow progression. We compare data underlying surgical approaches proposed to impart disease modification in PD: (1) cell transplantation therapy with stem cell-derived dopaminergic neurons to replace damaged cells; (2) clinical trials of growth factors to promote survival of existing dopaminergic neurons; (3) subthalamic nucleus deep brain stimulation early in the course of PD; and (4) abdominal vagotomy to lower risk of potential disease spread from gut to brain. Though targeted to engage potential mechanisms of PD these surgical approaches remain experimental, indicating the difficulty in translating therapeutic concepts into clinical practice. The choice of outcome measures to assess disease modification separate from the symptomatic benefit will be critical to evaluate the effect of the disease-modifying intervention on long-term disease burden, including imaging studies and clinical rating scales, i.e., Unified Parkinson Disease Rating Scale. Therapeutic interventions will require long follow-up times (i.e., 5–10 years) to analyze disease modification compared to symptomatic treatments. The promise of invasive, surgical treatments to achieve disease modification through mechanistic approaches has been constrained by the reality of translating these concepts into effective clinical trials.

Should “on-demand” treatments for Parkinson’s disease OFF episodes be used earlier?

•

OFF episodes are common in patients as Parkinson’s disease progresses.

•

OFF episodes are typically managed with “ON-extenders” and changes in levodopa dosing.

•

OFF episodes persist despite conventional treatment.

•

“On-demand” therapies can rapidly improve OFF symptoms.

•

A shift to earlier complementary use of “on-demand” therapies should be considered.

We discuss a shift in the treatment paradigm for OFF episode management in patients with Parkinson’s disease, based on clinical experience in the United States (US). Three “on-demand” treatments are currently available in the US as follows: subcutaneous apomorphine, levodopa inhalation powder, and sublingual apomorphine. We empirically propose that “on-demand” treatments can be utilized as a complementary treatment when OFF episodes emerge and can be utilized when needed rather than reserving these treatments only until other treatment approaches (adjustment of baseline treatment and/or addition of adjunctive treatment with “ON-extenders”) have failed. Current treatment approaches combine “ON-extenders” with increasing levodopa dosing and/or frequency to treat OFF episodes. Yet, OFF episodes often persist, with a substantial amount of daily OFF time. OFF episode treatment is hindered by variable gastrointestinal (GI) absorption of oral levodopa, reflecting GI dysmotility and protein competition. Novel “on-demand” treatments bypass the gut and can improve OFF symptoms more rapidly and reliably than oral levodopa. With the emergence of novel “on-demand” treatments, we conclude that a shift in treatment paradigm to the earlier, complementary use of these medications be considered.

A Phase II Study to Evaluate the Safety and Efficacy of Prasinezumab in Early Parkinson's Disease (PASADENA): Rationale, Design, and Baseline Data

Background: Currently available treatments for Parkinson's disease (PD) do not slow clinical progression nor target alpha-synuclein, a key protein associated with the disease. Objective: The study objective was to evaluate the efficacy and safety of prasinezumab, a humanized monoclonal antibody that binds aggregated alpha-synuclein, in individuals with early PD. Methods: The PASADENA study is a multicenter, randomized, double-blind, placebo-controlled treatment study. Individuals with early PD, recruited across the US and Europe, received monthly intravenous doses of prasinezumab (1,500 or 4,500 mg) or placebo for a 52-week period (Part 1), followed by a 52-week extension (Part 2) in which all participants received active treatment. Key inclusion criteria were: aged 40-80 years; Hoehn & Yahr (H&Y) Stage I or II; time from diagnosis ≤2 years; having bradykinesia plus one other cardinal sign of PD (e.g., resting tremor, rigidity); DAT-SPECT imaging consistent with PD; and either treatment naïve or on a stable monoamine oxidase B (MAO-B) inhibitor dose. Study design assumptions for sample size and study duration were built using a patient cohort from the Parkinson's Progression Marker Initiative (PPMI). In this report, baseline characteristics are compared between the treatment-naïve and MAO-B inhibitor-treated PASADENA cohorts and between the PASADENA and PPMI populations. Results: Of the 443 patients screened, 316 were enrolled into the PASADENA study between June 2017 and November 2018, with an average age of 59.9 years and 67.4% being male. Mean time from diagnosis at baseline was 10.11 months, with 75.3% in H&Y Stage II. Baseline motor and non-motor symptoms (assessed using Movement Disorder Society-Unified Parkinson's Disease Rating Scale [MDS-UPDRS]) were similar in severity between the MAO-B inhibitor-treated and treatment-naïve PASADENA cohorts (MDS-UPDRS sum of Parts I + II + III [standard deviation (SD)]; 30.21 [11.96], 32.10 [13.20], respectively). The overall PASADENA population (63.6% treatment naïve and 36.4% on MAO-B inhibitor) showed a similar severity in MDS-UPDRS scores (e.g., MDS-UPDRS sum of Parts I + II + III [SD]; 31.41 [12.78], 32.63 [13.04], respectively) to the PPMI cohort (all treatment naïve). Conclusions: The PASADENA study population is suitable to investigate the potential of prasinezumab to slow disease progression in individuals with early PD. Trial Registration: NCT03100149.