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Individuals with Parkinson's disease (PD) and healthy adults demonstrate similar levels of visuomotor adaptation provided that the distortion is small or introduced gradually, and hence, implicit processes are engaged. Recently, implicit processes underlying visuomotor adaptation in healthy individuals have been proposed to include proprioceptive recalibration (i.e., shifts in one's proprioceptive sense of felt hand position to match the visual estimate of their hand experienced during reaches with altered visual feedback of the hand). In the current study, we asked if proprioceptive recalibration is preserved in PD patients. PD patients tested during their "off" and "on" medication states and age-matched healthy controls reached to visual targets, while visual feedback of their unseen hand was gradually rotated 30° clockwise or translated 4 cm rightwards of their actual hand trajectory. As expected, PD patients and controls produced significant reach aftereffects, indicating visuomotor adaptation after reaching with the gradually introduced visuomotor distortions. More importantly, following visuomotor adaptation, both patients and controls showed recalibration in hand position estimates, and the magnitude of this recalibration was comparable between PD patients and controls. No differences for any measures assessed were observed across medication status (i.e., PD off vs PD on). Results reveal that patients are able to adjust their sensorimotor mappings and recalibrate proprioception following adaptation to a gradually introduced visuomotor distortion, and that dopaminergic intervention does not affect this proprioceptive recalibration. These results suggest that proprioceptive recalibration does not involve striatal dopaminergic pathways and may contribute to the preserved visuomotor adaptation that arises implicitly in PD patients.

Background: In clinical trials that recruited patients with early Parkinson’s disease (PD), 4–15% of the participants with a clinical diagnosis of PD had normal dopamine transporter single photon emission computed tomography (DAT SPECT) scans, also called “scans without evidence of dopaminergic deficit” (SWEDD). Objective: To investigate in patients with a clinical diagnosis of PD, if specific clinical features are useful to distinguish patients with nigrostriatal degeneration from those that have no nigrostriatal degeneration. Methods: We performed a diagnostic test accuracy study. Patients that participated in the Levodopa in Early Parkinson’s disease trial, a clinical trial in patients with early PD, were asked to participate if they had not undergone DAT SPECT imaging earlier. The index tests were specific clinical features that were videotaped. A panel of six neurologists in training (NT), six general neurologists (GN), and six movement disorders experts (MDE) received a batch of ten videos consisting of all SWEDD subjects and a random sample of patients with abnormal DAT SPECT scans. The raters analyzed the videos for presence of specific signs and if they suspected the patient to have SWEDD. The reference test was visually assessed DAT SPECT imaging. Results: Of a total of 87 participants, three subjects were SWEDDs (3.4%). The overall intraclass correlation coefficient (ICC) of the Parkinsonian signs was poor to moderate with ICCs ranging from 0.14 to 0.67. NT correctly identified 50.0% of the SWEDD subjects, GN 33.3%, and MDE 66.7%. Conclusion: Our study suggests that the selected videotaped clinical features cannot reliably distinguish patients with a clinical diagnosis of PD and an abnormal DAT SPECT from patients with clinical PD and a SWEDD.

Background Helicobacter pylori (HP) infection has been associated with worse motor function in Parkinson's disease (PD). Objective We aimed to evaluate the effects of HP eradication on PD symptoms. Methods In this parallel-group, double-blind, randomized placebo-controlled, single-center trial, patients with PD with positive HP urea breath test and serology were block randomized (1:1) to receive standard eradication triple therapy or identically appearing placebo capsules for 1 week. Prespecified motor (International Parkinson and Movement Disorder Society Unified PD Rating Scale [MDS-UPDRS], timed tests, and home-based wearable sensor measurements), nonmotor (Leeds Dyspepsia Questionnaire and Montreal Cognitive Assessment), and quality-of-life (Parkinson's Disease Questionnaire-39) outcome measures were assessed at weeks 6, 12, 24, and 52. The primary outcome was the baseline-to-week 12 change in ON medication MDS-UPDRS motor scores. Lactulose-hydrogen breath testing for concomitant small intestinal bacterial overgrowth was performed at baseline and repeated at week 24, together with the urea breath test. Results A total of 310 patients were screened for eligibility and 80 were randomly assigned, of whom 67 were included in the full-analysis set (32 treatment group patients, 35 placebo patients). HP eradication did not improve MDS-UPDRS motor scores at week 12 (mean difference 2.6 points in favor of placebo, 95% confidence interval: -0.4 to 5.6, P = 0.089). There was no significant improvement in any motor, nonmotor, or quality-of-life outcome at weeks 12 and 52. Both the full-analysis and per-protocol analyses (based on eradication status) supported these conclusions. Small intestinal bacterial overgrowth status did not influence treatment results. Conclusions HP eradication does not improve clinical outcomes in PD, suggesting that there is no justification for routine HP screening or eradication with the goal of improving PD symptoms. © 2020 International Parkinson and Movement Disorder Society.

OBJECTIVE The objective of this study was to assess the 12-week efficacy and safety of oral glycopyrrolate for moderate-to-severe sialorrhea in Parkinson's disease (PD). BACKGROUND Chronic moderate-to-severe sialorrhea has a negative impact on quality of life in PD. There is no robust evidence for oral treatments for sialorrhea longer than 1 week. METHODS This was a 12-week, double-blinded, placebo-controlled, parallel phase II study in patients with PD and Movement Disorder Society-Unified Parkinson's Disease Rating Scale item 2.2 > 2. The intervention was glycopyrrolate up to 4.5 mg/d; the primary outcome was sialorrhea related-disability (Radboud Oral Motor Inventory for Parkinson's Disease-Saliva). We used an intention-to-treat analysis. A P

Debate is ongoing regarding when, why, and how to initiate pharmacotherapy for Parkinson's disease. Early initiation of dopaminergic therapies does not convey disease-modifying effects but does reduce disability. Concerns about the development of motor complications arising from the early initiation of levodopa, which led to misconceived levodopa-sparing strategies, have been largely mitigated by the outcomes of the PD MED and Levodopa in Early Parkinson's Disease (LEAP) studies. The LEAP study also showed the potential for early improvement in quality of life, even when disability is negligible. Until more effective methods of providing stable dopamine concentrations are developed, current evidence supports the use of levodopa as initial symptomatic treatment in most patients with Parkinson's disease, starting with low doses and titrating to therapeutic threshold. Monoamine oxidase-B inhibitors and dopamine agonists can be reserved as potential adjunct treatments later in the disease course. Future research will need to establish effective disease-modifying treatments, address whether patients' quality of life is substantially improved with early initiation of treatment rather than a wait and watch strategy, and establish whether new levodopa formulations will delay onset of dyskinesia.

In this review, we discuss the opportunity for repurposing drugs for use in l -DOPA-induced dyskinesia (LID) in Parkinson's disease. LID is a particularly suitable indication for drug repurposing given its pharmacological diversity, translatability of animal-models, availability of Phase II proof-of-concept (PoC) methodologies and the indication-specific regulatory environment. A compound fit for repurposing is defined as one with appropriate human safety-data as well as animal safety, toxicology and pharmacokinetic data as found in an Investigational New Drug (IND) package for another indication. We first focus on how such repurposing candidates can be identified and then discuss development strategies that might progress such a candidate towards a Phase II clinical PoC. We discuss traditional means for identifying repurposing candidates and contrast these with newer approaches, especially focussing on the use of computational and artificial intelligence (AI) platforms. We discuss strategies that can be categorised broadly as: in vivo phenotypic screening in a hypothesis-free manner; in vivo phenotypic screening based on analogy to a related disorder; hypothesis-driven evaluation of candidates in vivo and in silico screening with a hypothesis-agnostic component to the selection. To highlight the power of AI approaches, we describe a case study using IBM Watson where a training set of compounds, with demonstrated ability to reduce LID, were employed to identify novel repurposing candidates. Using the approaches discussed, many diverse candidates for repurposing in LID, originally envisaged for other indications, will be described that have already been evaluated for efficacy in non-human primate models of LID and/or clinically. This article is part of the Special Issue entitled ‘Drug Repurposing: old molecules, new ways to fast track drug discovery and development for CNS disorders’.

Glutamatergic, noradrenergic, serotonergic, and cholinergic systems play a critical role in the basal ganglia circuitry. Targeting these non-dopaminergic receptors remains a focus of ongoing research to improve Parkinson's disease (PD) motor symptoms, without the potential side effects of dopamine replacement therapy. This review updates advancements in non-dopaminergic treatments for motor control in PD since 2013. To date, no non-dopaminergic selective drug has shown significant long-term efficacy as monotherapy in PD. The largest area of development in non-dopaminergic targets has been for motor complications of dopamine replacement therapy (motor fluctuations and dyskinesia). For treatment of motor fluctuations, safinamide, zonisamide, and istradefylline are currently approved, and novel glutamatergic and serotonergic drugs are in development. Long-acting formulations of amantadine are approved for treating dyskinesia. Several non-dopaminergic drugs have failed to show anti-dyskinetic efficacy, while some are still in development. Non-dopaminergic targets are also being pursued to treat specific motor symptoms of PD. For example, CX-8998 (a calcium channel modulator) is being evaluated for PD tremor and rivastigmine may improve gait dysfunction in PD. Drug repurposing continues to be a key strategy for non-dopaminergic targets in PD, but the field needs to increase discovery and availability of such drugs.

Prolonged treatment with L-3,4-dihydroxyphenylalanine (L-DOPA) leads to the development of uncontrolled movements (L-DOPA-induced dyskinesias (LID)) in Parkinson's disease (PD). There is currently only a single approved drug for the treatment of LID, a long-acting preparation of the NMDA antagonist, amantadine, that has variable benefits and side-effects. Therefore, new treatments for LID remain an unmet in PD.We review the current strategies for the management of LID; the pathogenic mechanisms underlying the development of LID, which provides the rationale for clinical trials of novel targets for LID and provide a review of phase II/III trials for emerging drugs for LID, with either positive results, or ongoing studies, reported between January 2014 and December 2019.There are several ongoing studies for agents that showed possible benefit at phase Ib/IIa for reducing LID. However, there are no new positive phase III double-blind randomized controlled clinical trials (DBRCT) for emerging treatments for LID. Generating better preclinical models, more precise recruitment tools and better outcome measures remain a priority. The pharmacology of drugs investigated for LID may be too selective; therefore, evaluating combinations of drugs is worthy of consideration as is the repurposing of existing drugs with multiple pharmacological targets.

Objective To update evidence‐based medicine recommendations for treating nonmotor symptoms in Parkinson's disease (PD). Background The International Parkinson and Movement Disorder Society Evidence‐Based Medicine Committee's recommendations for treatments of PD were first published in 2002, updated in 2011, and now updated again through December 31, 2016. Methods Level I studies testing pharmacological, surgical, or nonpharmacological interventions for the treatment of nonmotor symptoms in PD were reviewed. Criteria for inclusion and quality scoring were as previously reported. The disorders covered were a range of neuropsychiatric symptoms, autonomic dysfunction, disorders of sleep and wakefulness, pain, fatigue, impaired olfaction, and ophthalmologic dysfunction. Clinical efficacy, implications for clinical practice, and safety conclusions are reported. Results A total of 37 new studies qualified for review. There were no randomized controlled trials that met inclusion criteria for the treatment of anxiety disorders, rapid eye movement sleep behavior disorder, excessive sweating, impaired olfaction, or ophthalmologic dysfunction. We identified clinically useful or possibly useful interventions for the treatment of depression, apathy, impulse control and related disorders, dementia, psychosis, insomnia, daytime sleepiness, drooling, orthostatic hypotension, gastrointestinal dysfunction, urinary dysfunction, erectile dysfunction, fatigue, and pain. There were no clinically useful interventions identified to treat non‐dementia‐level cognitive impairment. Conclusions The evidence base for treating a range of nonmotor symptoms in PD has grown substantially in recent years. However, treatment options overall remain limited given the high prevalence and adverse impact of these disorders, so the development and testing of new treatments for nonmotor symptoms in PD remains a top priority. © 2019 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

BACKGROUND Pridopidine, in development for Huntington's disease, may modulate aberrant l-dopa-induced effects including l-dopa-induced dyskinesia (LID). OBJECTIVE This study investigated whether pridopidine could reduce LID in the MPTP macaque model of Parkinson's disease and characterized the observed behavioral effects in terms of receptor occupancy. METHODS The pharmacokinetic profile and effects of pridopidine (15-30 mg/kg) on parkinsonism, dyskinesia, and quality of on-time, in combination with l-dopa, were assessed in MPTP macaques with LID. Pridopidine receptor occupancy was estimated using known in vitro binding affinities to σ1 and dopamine D2 receptors, in vivo PET imaging, and pharmacokinetic profiling across different species. RESULTS Pridopidine produced a dose-dependent reduction in dyskinesia (up to 71%, 30 mg/kg) and decreased the duration of on-time with disabling dyskinesia evoked by l-dopa by 37% (20 mg/kg) and 60% (30 mg/kg). Pridopidine did not compromise the anti-parkinsonian benefit of l-dopa. Plasma exposures following the ineffective dose (15 mg/kg) were associated with full σ1 occupancy (>80%), suggesting that σ1 engagement alone is unlikely to account for the antidyskinetic benefits of pridopidine. Exposures following effective doses (20-30 mg/kg), while providing full σ1 occupancy, provide only modest dopamine D2 occupancy (

Purpose of review To review recent advances in therapeutics for motor and nonmotor symptoms of Parkinson's disease. Recent findings Neuroprotection remains a large area of investigation with preliminary safety data on alpha synuclein immunotherapy and glucagon-like peptide-1 agonists. Novel Monoamine Oxidase B and Caetchol-O-methyltransferase-inhibitors for motor fluctuations have shown benefit and are recently approved for clinical use. Long-acting amantadine has also been approved to reduce dyskinesia. Alternative delivery strategies (sublingual, inhaled) dopaminergics may prove useful for rapid reversal of Parkinson's disease motor symptoms. Advanced therapies (surgery and infusional therapies) continue to be useful in subgroups of patients for motor complications with improved safety and also benefit on some nonmotor symptoms, including neuropsychiatric issues. Specific therapeutics for cognition, swallowing, sleep, and mood disorders had moderate to limited benefits. Exercise-based therapy appears beneficial at all stages of Parkinson's disease. Summary The motor symptoms of Parkinson's disease can be reasonably treated and managed. However, therapies to slow or prevent disease progression remain a focus of research. Despite increased studies, treating nonmotor symptoms remains a challenge and an ongoing priority.

Introduction Technological solutions for quantifying Parkinson's disease (PD) symptoms may provide an objective means to track response to treatment, including side effects such as levodopa-induced dyskinesia. Vision-based systems are advantageous as they do not require physical contact with the body and have minimal instrumentation compared to wearables. We have developed a vision-based system to quantify a change in dyskinesia as reported by patients using 2D videos of clinical assessments during acute levodopa infusions. Methods Nine participants with PD completed a total of 16 levodopa infusions, where they were asked to report important changes in dyskinesia (i.e. onset and remission). Participants were simultaneously rated using the UDysRS Part III (from video recordings analyzed post-hoc). Body joint positions and movements were tracked using a state-of-the-art deep learning pose estimation algorithm applied to the videos. 416 features (e.g. kinematics, frequency distribution) were extracted to characterize movements. The sensitivity and specificity of each feature to patient-reported changes in dyskinesia severity was computed and compared with physician-rated results. Results Features achieved similar or superior performance to the UDysRS for detecting the onset and remission of dyskinesia. The best AUC for detecting onset of dyskinesia was 0.822 and for remission of dyskinesia was 0.958, compared to 0.826 and 0.802 for the UDysRS. Conclusions Video-based features may provide an objective means of quantifying the severity of levodopa-induced dyskinesia, and have responsiveness as good or better than the clinically-rated UDysRS. The results demonstrate encouraging evidence for future integration of video-based technology into clinical research and eventually clinical practice.

Objective The objective of this review was to update evidence-based medicine recommendations for treating motor symptoms of Parkinson's disease (PD). Background The Movement Disorder Society Evidence-Based Medicine Committee recommendations for treatments of PD were first published in 2002 and updated in 2011, and we continued the review to December 31, 2016. Methods Level I studies of interventions for motor symptoms were reviewed. Criteria for inclusion and quality scoring were as previously reported. Five clinical indications were considered, and conclusions regarding the implications for clinical practice are reported. Results A total of 143 new studies qualified. There are no clinically useful interventions to prevent/delay disease progression. For monotherapy of early PD, nonergot dopamine agonists, oral levodopa preparations, selegiline, and rasagiline are clinically useful. For adjunct therapy in early/stable PD, nonergot dopamine agonists, rasagiline, and zonisamide are clinically useful. For adjunct therapy in optimized PD for general or specific motor symptoms including gait, rivastigmine is possibly useful and physiotherapy is clinically useful; exercise-based movement strategy training and formalized patterned exercises are possibly useful. There are no new studies and no changes in the conclusions for the prevention/delay of motor complications. For treating motor fluctuations, most nonergot dopamine agonists, pergolide, levodopa ER, levodopa intestinal infusion, entacapone, opicapone, rasagiline, zonisamide, safinamide, and bilateral STN and GPi DBS are clinically useful. For dyskinesia, amantadine, clozapine, and bilateral STN DBS and GPi DBS are clinically useful. Conclusions The options for treating PD symptoms continues to expand. These recommendations allow the treating physician to determine which intervention to recommend to an individual patient. © 2018 International Parkinson and Movement Disorder Society.

L-DOPA-induced dyskinesia (LID) remains a significant problem in the management of Parkinson's disease (PD). In rodent and macaque models of PD, delta opioid receptor agonists have anti-parkinsonian actions while mu opioid antagonists can reduce the expression of LID. DPI-289 is a novel molecule with a unique combination of opioid receptor DAMA actions: delta agonist (Ki: 0.73 nM); mu antagonist (Ki: 12 nM). We demonstrated that DPI-289 has oral bioavailability and established its pharmacokinetic profile in both rat and primate. We hypothesised that these combined DAMA actions would provide an enhancement of L-DOPA effect without an associated increase in dyskinesia. In parkinsonian 6-OHDA lesioned rats and MPTP-lesioned macaques, DPI-289 provided anti-parkinsonian actions as monotherapy and an enhancement of L-DOPA benefit. Thus, acute administration of DPI-289 (3 mg/kg, p.o.) to 6-OHDA-lesioned rats produced a significant reduction in forelimb asymmetry (by 48%) that was maintained throughout the fifteen-day repeat-treatment period. Importantly, and in contrast to L-DOPA administration (6 mg/kg, i.p.), these benefits were not compromised by the development of abnormal involuntary movements. In the macaque, as monotherapy, DPI-289 (10 and 20 mg/kg) had significant, though incomplete, anti-parkinsonian actions lasting approximately 4 h. These benefits were not associated with dyskinesia. In fact, over the 6 h period of observation, DPI-289 (20 mg/kg) decreased parkinsonism by 19% and increased activity by 67% compared to vehicle treatment. By contrast, while high-dose L-DOPA (LDh) alone alleviated parkinsonism (for 3 h) this benefit was accompanied by significant dyskinesia that was disabling in nature. LDh provided a 50% reduction in parkinsonism over 6 h and 151% increase in activity. The combination of DPI-289 (20 mg/kg) and a low-dose of L-DOPA (LDl) provided anti-parkinsonian benefits greater than LDl alone without eliciting any significant dyskinesia. Treatment with LDl alone provided only transient statistically significant anti-parkinsonian benefit. However, the combination of LDl and DPI-289 reduced parkinsonism for 6 h (duration of monitoring), with parkinsonism being reduced by 35% and activity increased by 90% but with no increase in dyskinesia over that observed with LDl alone. Thus, DPI-289 has potential to improve the benefits of dopaminergic therapy in Parkinson's disease.

Background In our clinical experience, people with Parkinson's disease (PwP) and their caregivers have difficulty understanding the complexities of the disease which has a multitude of symptoms and involved therapies. We undertook a Needs Assessment to understand the need for and to guide the development of an educational tool. Methods: We invited PwP, caregivers and health care providers (HCP) from across Canada to participate in an online survey to determine the need and desired content for such a tool. Results Respondents included 450 PwP, 335 caregivers and 96 HCP from across Canada. 86.5% of HCP reported that it was ‘very important’ for patients to understand issues in PD and 84.4% would use a visual aid to explain these issues. 81.9-95.7% of caregivers and PwP were not ‘very satisfied’ with the explanations of all domains in PD. Non-motor symptoms and cognitive issues were highly ranked by all groups as difficult to understand or explain. Older PwP, those with PD for less than 5 years and those who reported that their HCP spent less than 15 minutes counselling in each clinic visit were less likely to fully understand and be satisfied with the explanations of most issues in PD. Interpretation There is a need for better education of patients of issues in PD in the clinic setting. Older PwP recently diagnosed have the greatest educational needs. Potential users indicate that a visual aid would help and non-motor symptoms, particularly cognitive issues need to be a focus of such a tool. This article is protected by copyright. All rights reserved.

Parkinson's disease (PD) has long been seen as a disorder caused by degeneration of the dopaminergic system, leading to the classic motor manifestations of the disease. However, there is now overwhelming evidence that PD is more than a disease merely caused by dopamine depletion. It is well-known that a myriad of other neurotransmitters are affected by the disease process. One such neurotransmitter is serotonin (5-HT). 5-HT has been shown to play a role in several motor and nonmotor manifestations of PD, including tremor, cognition, depression and psychosis. 5-HT also seems to play a critical role in L-3,4-dihydroxyphenylalanine (L-DOPA)-induced dyskinesia. A breadth of preclinical studies and clinical trials have been conducted that aimed at modulating the 5-HT system in order to alleviate depression, cognitive deficits, psychosis, and dyskinesia. In this Review, we summarize recent advances in the 5-HT field in PD, but with a translational emphasis. We start by presenting a novel nonhuman primate model of PD that presents with dual dopamine and 5-HT lesions. We then present preclinical and clinical data that introduce new concepts, such as the use of biased and partial agonists, as well as molecules recently introduced to the field of PD, such as eltoprazine, pimavanserin, nelotanserin, and SYN-120, to enhance therapeutic benefit while minimizing adverse events, notably on parkinsonian disability.

Objective: To determine the relationship between alterations in resting state functional connectivity and social cognition dysfunction amongst patients with frontotemporal dementia (FTD), Alzheimer’s disease (AD), Parkinson’s disease (PD) and healthy controls (HC). Methods: Fifty-seven participants (FTD=10, AD=18, PD=19, and HC=10) underwent structural and functional imaging and completed the Awareness of Social Inference Test-Emotion Evaluation Test (TASIT-EET), Behavioral Inhibition System/Behavioral Activation System (BIS/BAS) scale, Revised Self-Monitoring Scale (RSMS), Interpersonal Reactivity Index (IRI), and Social Norms Questionnaire (SNQ). A multi-variate pattern analysis (MVPA) was carried out to determine activation differences between the groups. The clusters from the MVPA were used as seeds for the ROI-to-voxel analysis. Relationship between social cognition deficits and uncinate integrity was also investigated. Results: BOLD signal activation differed amongst the four groups of AD, PD, FTD and HC in the left inferior temporal gyrus-anterior division (L-ITG (ant)), right central opercular cortex (R-COp), right supramarginal gyrus, posterior division (R-SMG, post), right angular gyrus (R-AG), and R-ITG. The BOLD co-activation of the L-ITG (ant) with bilateral frontal pole (FP) and paracingulate gyrus was positively associated with IRI-perspective taking (PT) (r = .38, p = .007), SNQ total (r = .37, p = .009) and TASIT-EET (r = .47, p < .001). Conclusion: Patients with neurodegenerative diseases showed alterations in connectivity in brain regions important for social cognition compared with healthy controls. Functional connectivity correlated with performance on social cognition tasks and alterations could be responsible for some of the social cognition deficits observed in all neurodegenerative diseases.

Background: There is growing evidence that the serotonergic system, in particular serotonin 2A receptors, is involved in neuropsychiatric symptoms in Parkinson's disease (PD), including cognitive processing and visual hallucinations. However, the relationship between serotonin 2A receptor availability, visual hallucinations, and cognitive profile is unknown. The objective of this study was to investigate the level of serotonin 2A receptor availability in brain regions affected by visual hallucinations and to test the association with cognitive/behavioral changes in patients who have PD with visual hallucinations. Methods: Nondemented patients who had PD with (n = 11) and without (n = 8) visual hallucinations and age‐matched controls (n = 10) were recruited. All participants completed neuropsychological testing, which consisted of visuoperceptual, executive, memory, language, and frontal‐behavioral function. Positron emission tomography scans using [18F]setoperone, a serotonin 2A antagonist radioligand, were acquired in patients with PD, and a parametric binding potential map of [18F]setoperone was calculated with the simplified reference tissue model using the cerebellum as a reference. Results: Patients who had PD with visual hallucinations exhibited significantly lower scores on measures of executive and visuoperceptual functions compared with age‐matched controls. These changes were paralleled by decreased [18F]setoperone binding in the right insula, bilateral dorsolateral prefrontal cortex, right orbitofrontal cortex, right middle temporal gyrus, and right fusiform gyrus. The psychometric correlation analysis revealed significant relationships among tests associated with visuoperceptual function, memory and learning, and serotonin 2A binding in different prefrontal and ventral visual stream regions. There was also reduced serotonin 2A receptor binding in patients who had PD with depression. Conclusions: These findings support a complex interaction between serotonin 2A receptor function and cognitive processing in patients who have PD with visual hallucinations. Fil: Cho, Sang Soo. University of Toronto; Canadá Fil: Strafella, Antonio P.. University of Toronto; Canadá Fil: Duff Canning, Sarah. University of Toronto; Canadá Fil: Zurowski, Mateusz. University of Toronto; Canadá Fil: Vijverman, Anne Catherine. Onze‐Lieve‐Vrouw Hospital; Bélgica Fil: Bruno, Veronica Andrea. University of Toronto; Canadá. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Aquino, Camila C.. University of Toronto; Canadá Fil: Criaud, Marion. University of Toronto; Canadá Fil: Rusjan, Pablo M.. University of Toronto; Canadá Fil: Houle, Sylvain. University of Toronto; Canadá Fil: Fox, Susan H.. University of Toronto; Canadá

Psychotic symptoms are common in Parkinson's disease (PD) and are associated with poorer quality of life and increased caregiver burden. PD psychosis is correlated with several factors, such as more advanced disease, cognitive impairment, depression, and sleep disorders. The underlying causes of psychosis in PD thus involve a complex interplay between exogenous (e.g., drugs, intercurrent illnesses) and endogenous (e.g., PD disease pathology) factors. Current theories of the pathophysiology of PD psychosis have come from several neuropathological and neuroimaging studies that implicate pathways involving visual processing and executive function, including temporo-limbic structures and neocortical gray matter with altered neurotransmitter functioning (e.g., dopamine, serotonin, and acetylcholine). Treatment of PD psychosis requires a step-wise process, including initial careful investigation of treatable triggering conditions and a comprehensive evaluation with adjustment of PD medications and/or initiation of specific antipsychotic therapies. Clozapine remains the only recommended drug for the treatment of PD psychosis; however, because of regular blood monitoring, quetiapine is usually first-line therapy, although less efficacious. Emerging studies have focused on agents involving other neurotransmitters, including the serotonin 5-HT2A receptor inverse agonist pimavanserin, cholinesterase inhibitors, and antidepressants and anxiolytics.

In this review, the available evidence to guide clinicians regarding eligibility for deep brain stimulation (DBS) in the main conditions in which these forms of therapy are generally indicated—Parkinson’s disease (PD), tremor, and dystonia—is presented. In general, the literature shows that DBS is effective for PD, essential tremor, and idiopathic dystonia. In these cases, key points in patient selection must include the level of disability and inability to manage symptoms using the best available medical therapy. Results are, however, still not optimal when dealing with other aetiologies, such as secondary tremors and symptomatic dystonia. Also, in PD, issues such as age and neuropsychiatric profile are still debatable parameters. Overall, currently available literature is able to guide physicians on basic aspects of patient selection and indications for DBS; however, a few points are still debatable and controversial. These issues should be refined and clarified in future studies.

Levodopa-induced dyskinesia (LID) is a common consequence of effectively treating PD. Management depends on recognizing the pattern and timing, in response to levodopa doses. Thus LID can occur at the peak effect of levodopa (mainly chorea) or when the levels are lower or in-between doses (usually dystonia). In addition, evaluating the level of disability associated with the movements is important, as not all LID requires treatment. For peak-dose LID, reducing dopaminergic drugs is helpful. Specific treatment includes amantadine. Off period, or low-dose LID, often responds to increased dopamine levels by treating the OFF periods. Prevention of LID is key by keeping individual doses of levodopa as low as possible but with good motor control in the long term.

Objective To confirm that there is a diagnostic delay in Parkin-related Parkinson Disease and to explore possible factors causing such a delay. Methods We retrospectively analyzed our patients with mutations in the parkin RBR E3 ubiquitin protein ligase gene (PRKN). We collected a total of 34 patients and focused on 18 cases (14 homozygous, 4 compound heterozygous). An arbitrary cut-off of 10 years from disease onset to diagnosis was considered to define patients with delayed diagnosis. Results Eight of 18 cases had a significant delay in their diagnosis (25.3 ± 17 years). By comparing patients with and without a delayed diagnosis and subsequently, comparing these groups to a group of young onset PD negative for mutations of PRKN, SNCA, DJ1, PINK1, LRRK2, GBA, and ATP13A2, we identified a specific phenotype associated with a diagnostic delay: young age, lack of tremor, and involvement of lower limbs (particularly dystonia affecting gait) at the time of disease onset. Conclusions Our findings emphasize the diverse phenotypes associated with PRKN mutations and the related diagnostic challenges they present.

Background The pathogenesis of rest tremor in Parkinson's disease (PD) is incompletely understood. This symptom can be resistant to typical anti-PD medications. Therefore, new treatments are needed given the concern that this symptom causes to patients and family. Limited experience suggests that clozapine can have an important antitremor effect in PD. The mechanism(s) underlying this effect is not well understood, but could provide insight and impetus to the development of more-effective and safer antitremor therapies. Methods and Results Exemplifying the antitremor effects of clozapine, we describe a patient with tremor-predominant PD who obtained prominent reduction of rest tremor with clozapine treatment. We review the responses to this treatment in another 7 of our PD patients with treatment-resistant rest tremor. We also review the published literature on clozapine for tremor in PD and discuss its potential mechanisms of action and possible adverse effects. In our case series, there was a 64% reduction of tremor score after clozapine was initiated. The mechanism of tremor reduction remains unclear with possible involvement of anticholinergic, serotonergic, antihistaminergic, antiadrenergic, and antidopaminergic effects. Clozapine does have potential serious adverse effects. Conclusions Clozapine may be effective in controlling rest tremor in PD. Given the potential fatal side effects, if clozapine is to be initiated in PD patients, it has to be used cautiously with proper monitoring, preferably in specialized centers. We acknowledge that the number of patients in this case series is small. Further studies are needed to understand clozapine's mechanism of action in reducing tremor.

Background We have previously defined a parkinsonism-related metabolic brain network in rhesus macaques using a high-resolution research positron emission tomography camera. This brief article reports a descriptive pilot study to assess the reproducibility of network activity and regional glucose metabolism in independent parkinsonian macaques using a clinical positron emission tomography/CT camera. Methods [18F]fluorodeoxyglucose PET scans were acquired longitudinally over 3 months in three drug-naive parkinsonian and three healthy control cynomolgus macaques. Group difference and test–retest stability in network activity and regional glucose metabolism were evaluated graphically, using all brain images from these macaques. Results Comparing the parkinsonian macaques with the controls, network activity was elevated and remained stable over 3 months. Normalized glucose metabolism increased in putamen/globus pallidus and sensorimotor regions but decreased in posterior parietal cortices. Conclusions Parkinsonism-related network activity can be reliably quantified in different macaques with a clinical positron emission tomography/CT scanner and is reproducible over a period typically employed in preclinical intervention studies. This measure can be a useful biomarker of disease process or drug effects in primate models of Parkinson's disease. ©2015 International Parkinson and Movement Disorder Society

Background Some studies have suggested that chronic Helicobacter pylori (HP) infection can aggravate the neurodegenerative process in Parkinson's disease (PD), and targeted intervention could potentially modify the course of this disabling disease. We aimed to study the impact of HP infection on motor function, gastrointestinal symptoms, and quality of life in a large cohort of PD patients. Methods 102 consecutive PD patients underwent 13 C urea breath testing and blinded evaluations consisting of the Unified Parkinson's Disease Rating Scale (UPDRS) including “On”-medication motor examination (Part III), objective and quantitative measures of bradykinesia (Purdue Pegboard and timed gait), Leeds Dyspepsia Questionnaire, and PDQ-39 (a health-related quality of life questionnaire). Results 32.4% of PD patients were HP-positive. HP-positive patients were older (68.4 ± 7.3 vs. 63.8 ± 8.6 years, P = 0.009) and had worse motor function (UPDRS Part III 34.0 ± 13.0 vs. 27.3 ± 10.0, P = 0.04; Pegboard 6.4 ± 3.3 vs. 8.0 ± 2.7 pins, P = 0.04; and timed gait 25.1 ± 25.4 vs. 15.5 ± 7.6 s, P = 0.08). In the multivariate analysis, HP status demonstrated significant main effects on UPDRS Part III and timed gait. The association between HP status and these motor outcomes varied according to age. Gastrointestinal symptoms and PDQ-39 Summary Index scores did not differ between the two groups. Conclusions This is the largest cross-sectional study to demonstrate an association between HP positivity and worse PD motor severity.

Background and Objective: Pain is a frequent symptom in Parkinson’s disease (PD), and the therapeutic alternatives are scarce. The goal of this trial was to measure the effects of botulinum toxin type A (BTXA) in the treatment of limb pain in advanced PD. Methods: A randomized double-blind crossover versus placebo study of BTXA for limb pain in advanced Parkinson’s disease was conducted. Subjects received individualized BTXA/placebo dosing per pain distribution in limbs. The primary outcome was a measure of change in global pain on a numeric rating scale (NRS) at 4 and 12 weeks postinjection and on a visual analogue scale 12 weeks after treatment. Secondary outcomes included the percentage of responders, physician-rated clinical global impressions, MDS–UPDRS and PDQ–39 scores, and adverse events. Results: A total of 12 subjects completed the trial. Treatment with BTXA (average dose=241.66 U) produced a significant reduction in NRS score 4 weeks after the injections (–1.75 points, range from –3 to 7, p=0.033). However, there was no significant difference compared to placebo (p=0.70). Participants with dystonic pain showed a greater reduction in NRS score after 4 weeks when treated with BTXA (2.66 points vs. 0.75 for placebo). There were no significant differences for any of the secondary outcomes or significant adverse events. Conclusions: Targeted BTXA injections were safe in patients with limb pain and advanced PD; however, the present study failed to show a significant effect when compared to placebo. Further studies may be focused on evaluating the effect of BTXA particularly in dystonic pain. Contexte et objectifs: Ressentir de la douleur demeure un symptôme fréquent de la maladie de Parkinson. Cela dit, les solutions thérapeutiques continuent à être limitées. L’objectif de cet essai clinique a donc été de mesurer les effets de la toxine botulique de type A en ce qui regarde le soulagement de la douleur aux membres chez des sujets au stade avancé de la maladie de Parkinson. Méthodes: Nous avons mené une étude randomisée et croisée à double insu, contrôlée par placebo, au sujet de l’efficacité de la toxine botulique de type A dans le soulagement de la douleur. On a ainsi administré à nos sujets une posologie individualisée de toxine botulique de type A ainsi qu’un placebo en fonction de la distribution de la douleur à leurs membres. Le principal indicateur mesuré a porté, 4 et 12 semaines après les injections, sur les changements de scores obtenus sur l’échelle numérique de la douleur et, 12 semaines plus tard, sur l’échelle visuelle analogique. D’autres indicateurs secondaires ont également été mesurés : le pourcentage d’intervenants impliqués, les impressions cliniques d’ensemble de médecins, l’échelle d’évaluation unifiée de la maladie de Parkinson de la Movement Disorder Society, les scores obtenus au PDQ–39 et la fréquence d’évènements indésirables. Résultats: Au total, 12 sujets ont complété cet essai clinique. L’administration de toxine botulique de type A (dose moyenne=241,66 U) a produit, 4 semaines après les injections, une réduction importante des scores obtenus sur l’échelle numérique d’évaluation de la douleur (-1,75 points ; écart de -3 à 7 ; p=0,033). Cela dit, aucune différence notable n’a été observée par rapport au placebo (p=0,70). Chez les sujets souffrant de douleurs d’origine dystonique, on a pu observer, 4 semaines après les injections, la plus grande réduction des scores obtenus sur l’échelle numérique d’évaluation de la douleur (2,66 points contre 0,75 pour le placebo). Fait à noter, on n’a observé aucune différence notable quant aux indicateurs secondaires énumérés ci-dessus ou en ce qui regarde des évènements indésirables. Conclusions: Les injections ciblées de toxines botuliques de type A se sont avérées sans danger dans le cas de sujets au stade avancé de la maladie de Parkinson souffrant de douleurs aux membres. La présente étude n’a toutefois pas été en mesure de révéler un effet notable des toxines botuliques de type A après comparaison avec un placebo. Cela étant, il se peut que des études ultérieures se penchent sur les effets de ces toxines, en particulier en ce qui regarde les douleurs d’origine dystonique. Fil: Bruno, Veronica Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. University Health Network; Canadá Fil: Freitas, Maria Eliza. University Health Network; Canadá Fil: Mancini, Deborah. University Health Network; Canadá Fil: Lui, Jane P.. University Health Network; Canadá Fil: Miyasaki, Janis. University of Alberta; Canadá Fil: Fox, Susan H.. University Health Network; Canadá

Motor complications are a consequence of chronic treatment of Parkinson’s disease (PD) and include motor fluctuations (wearing-off phenomenon) and levodopa-induced dyskinesia. Both can have a significant impact on functionality and quality of life and thus proper recognition and management is essential. The phenomenology and temporal relationship of motor complications to the schedule of levodopa dosing can be helpful in characterizing them. There are several therapeutic approaches to motor complications, including pharmacological and surgical options. The current review summarizes the different types of motor complications according to phenomenology and the currently available medical treatments, including ongoing trials for management of this condition.

Levodopa remains the most potent drug to treat motor symptoms in Parkinson's disease (PD); however, motor fluctuations and levodopa-induced dyskinesia that occur with long-term use restrict some of its therapeutic value. Despite these limitations, the medical treatment of PD strives for continuous relief of symptoms using different strategies throughout the course of the illness: increasing the half-life of levodopa, using 'levodopa-sparing agents' and adding non-dopaminergic drugs. New options to 'improve' delivery of levodopa are under investigation, including long-acting levodopa, nasal inhalation and continuous subcutaneous or intrajejunal administration of levodopa. Long-acting dopamine agonists were recently developed and are undergoing further comparative studies to investigate potential superiority over the immediate-release formulations. Non-dopaminergic drugs acting on adenosine receptors, cholinergic, adrenergic, serotoninergic and glutamatergic pathways are newly developed and many are being evaluated in Phase II and Phase III trials. This article focuses on promising novel therapeutic approaches for the management of PD motor symptoms and motor complications. We will provide an update since 2011 on new formulations of current drugs, new drugs with promising results in Phase II and Phase III clinical trials, old drugs with new possibilities and some new potential strategies that are currently in Phase I and II of development (study start date may precede 2011 but are included as study is still ongoing or full data have not yet been published). Negative Phase II and Phase III clinical trials published since 2011 will also be briefly mentioned.

The neural mechanisms underlying levodopa‐induced dyskinesia (LID) in Parkinson's disease (PD) may involve histamine (H2) receptors on striatopallidal pathways. We recently demonstrated that the clinically available oral histamine H2 receptor antagonist (H2 RA), famotidine, can reduce l‐dopa‐induced chorea in MPTP‐lesioned macaques. We hypothesized that famotidine may be useful in the treatment of LID in PD patients. We performed a proof‐of‐concept, double‐blind, randomized, multiple cross‐over (4×) trial. Seven PD subjects with bothersome dyskinesia were randomized to oral famotidine 80, 120, and 160 mg/day and placebo. Each subject was randomized to receive each of the four treatment phases for 14 days followed by a 7‐day wash‐out period between each treatment phase. The primary outcome measure was change in the Unified Dyskinesia Rating Scale (UDysRS; part III) between placebo and famotidine. Secondary outcomes were UDysRS (parts I and II), Global Impression of Change, Lang‐Fahn Activities of Daily Living Dyskinesia Scale, Unified Parkinson's Disease Rating part III, and adverse events (AEs). Outcomes were evaluated pre‐ and post‐treatment per dose and analyzed using a mixed‐effects linear model. There was no significant effect of famotidine treatment on any of the primary or secondary outcome measures compared to placebo (each dose and all doses combined). There were no significant AEs. Even though the sample size of the current study is limited, famotidine seems to be safe in patients with PD and LID, but showed no potential as an antidyskinetic agent.

The pathological processes underlying Parkinson's disease (PD) involve more than dopamine cell loss within the midbrain. These non-dopaminergic neurotransmitters include noradrenergic, serotonergic, glutamatergic, and cholinergic systems within cortical, brainstem and basal ganglia regions. Several non-dopaminergic treatments are now in clinical use to treat motor symptoms of PD, or are being evaluated as potential therapies. Agents for symptomatic monotherapy and as adjunct to dopaminergic therapies for motor symptoms include adenosine A2A antagonists and the mixed monoamine-B inhibitor (MAO-BI) and glutamate release agent safinamide. The largest area of potential use for non-dopaminergic drugs is as add-on therapy for motor fluctuations. Thus adenosine A2A antagonists, safinamide, and the antiepileptic agent zonisamide can extend the duration of action of levodopa. To reduce levodopa-induced dyskinesia, drugs that target overactive glutamatergic neurotransmission can be used, and include the non-selective N-methyl D-aspartate antagonist amantadine. More recently, selective metabotropic glutamate receptor (mGluR₅) antagonists are being evaluated in phase II randomized controlled trials. Serotonergic agents acting as 5-HT2A/2C antagonists, such as the atypical antipsychotic clozapine, may also reduce dyskinesia. 5-HT1A agonists theoretically can reduce dyskinesia, but in practice, may also worsen PD motor symptoms, and so clinical applicability has not yet been shown. Noradrenergic α2A antagonism using fipamezole can potentially reduce dyskinesia. Several non-dopaminergic agents have also been investigated to reduce non-levodopa-responsive motor symptoms such as gait and tremor. Thus the cholinesterase inhibitor donepezil showed mild benefit in gait, while the predominantly noradrenergic re-uptake inhibitor methylphenidate had conflicting results in advanced PD subjects. Tremor in PD may respond to muscarinic M4 cholinergic antagonists (anticholinergics), but tolerability is often poor. Alternatives include β-adrenergic antagonists such as propranolol. Other options include 5-HT2A antagonists, and drugs that have mixed binding properties involving serotonin and acetylcholine, such as clozapine and the antidepressant mirtazapine, can be effective in reducing PD tremor. Many other non-dopaminergic agents are in preclinical and phase I/II early stages of study, and the reader is directed to recent reviews. While levodopa remains the most effective agent to treat motor symptoms in PD, the overall approach to using non-dopaminergic drugs in PD is to reduce reliance on levodopa and to target non-levodopa-responsive symptoms.

We examined the frequency of Parkinson disease with mild cognitive impairment (PD-MCI) and its subtypes and the accuracy of 3 cognitive scales for detecting PD-MCI using the new criteria for PD-MCI proposed by the Movement Disorders Society. Nondemented patients with Parkinson's disease completed a clinical visit with the 3 screening tests followed 1 to 3 weeks later by neuropsychological testing. Of 139 patients, 46 met Level 2 Task Force criteria for PD-MCI when impaired performance was based on comparisons with normative scores. Forty-two patients (93%) had multi-domain MCI. At the lowest cutoff levels that provided at least 80% sensitivity, specificity was 44% for the Montreal Cognitive Assessment and 33% for the Scales for Outcomes in Parkinson's Disease-Cognition. The Mini-Mental State Examination could not achieve 80% sensitivity at any cutoff score. At the highest cutoff levels that provided specificity of at least 80%, sensitivities were low (≤44%) for all tests. When decline from estimated premorbid levels was considered evidence of cognitive impairment, 110 of 139 patients were classified with PD-MCI, and 103 (94%) had multi-domain MCI. We observed dramatic differences in the proportion of patients who had PD-MCI using the new Level 2 criteria, depending on whether or not decline from premorbid level of intellectual function was considered. Recommendations for methods of operationalizing decline from premorbid levels constitute an unmet need. Among the 3 screening tests examined, none of the instruments provided good combined sensitivity and specificity for PD-MCI. Other tests recommended by the Task Force Level 1 criteria may represent better choices, and these should be the subject of future research.

Background l -3,4-dihydroxyphenylalanine ( l -DOPA)-induced dyskinesia (LID) are a complication of chronic dopamine replacement therapy in Parkinson's disease (PD). Recent studies have suggested that the mechanisms underlying development and expression of LID in PD may involve epigenetic changes that include deacetylation of striatal histone proteins. We hypothesised that inhibition of histone deacetylase, the enzyme responsible of histone deacetylation, would alleviate LID. Methods Four female common marmoset (Callithrix jacchus) were rendered parkinsonian by administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Following stabilisation of the parkinsonian phenotype, marmosets were primed to exhibit dyskinesia with chronic administration of l -DOPA. We then investigated the effects of the brain-penetrant histone deacetylase inhibitor, RGFP109 (30 mg/kg p.o. once daily for 6 days), on LID and l -DOPA anti-parkinsonian efficacy. Results RGFP109 had no acute effects on dyskinesia after single or 6 days once-daily treatment (both P > 0.05). However, one week following cessation of RGFP109, dyskinesia and duration of ON-time with disabling dyskinesia were reduced by 37% and 50%, respectively (both P l -DOPA alone. There was no change in anti-parkinsonian actions of, or ON-time duration afforded by, l -DOPA (P > 0.05). Conclusions Histone deacetylation inhibition may represent a novel approach to reverse established LID in PD and improve quality of the anti-parkinsonian benefit provided by l -DOPA.

L-3,4-Dihydroxyphenylalanine (L-DOPA) remains the most effective symptomatic treatment of Parkinson's disease (PD). However, long-term administration of L-DOPA is marred by the emergence of abnormal involuntary movements, i.e., L-DOPA-induced dyskinesia (LID). Years of intensive research have yielded significant progress in the quest to elucidate the mechanisms leading to the development and expression of dyskinesia and maintenance of the dyskinetic state, but the search for a complete understanding is still ongoing. Herein, we summarize the current knowledge of the pharmacology of LID in PD. Specifically, we review evidence gathered from postmortem and pharmacological studies, both preclinical and clinical, and discuss the involvement of dopaminergic and nondopaminergic systems, including glutamatergic, opioid, serotonergic, γ-aminobutyric acid (GABA)-ergic, adenosine, cannabinoid, adrenergic, histaminergic, and cholinergic systems. Moreover, we discuss changes occurring in transcription factors, intracellular signaling, and gene expression in the dyskinetic phenotype. Inasmuch as a multitude of neurotransmitters and receptors play a role in the etiology of dyskinesia, we propose that to optimally alleviate this motor complication, it may be necessary to develop combined treatment approaches that will target simultaneously more than one neurotransmitter system. This could be achieved via three ways as follows: 1) by developing compounds that will interact simultaneously to a multitude of receptors with the required agonist/antagonist effect at each target, 2) by targeting intracellular signaling cascades where the signals mediated by multiple receptors converge, and/or 3) to regulate gene expression in a manner that has effects on signaling by multiple pathways.

Background/Aims: To assess the impact of mild cognitive impairment (MCI) or cognitive decline on health-related quality of life (HR-QOL) in Parkinson's disease (PD). Methods: HR-QOL measured by the Parkinson Disease Quality of Life Questionnaire (PDQ-39), MCI according to Movement Disorder Society Task Force criteria and cognitive decline from premorbid baseline were assessed in non-demented PD patients at 6 movement disorder clinics. Results: Among 137 patients, after adjusting for education, gender, disease duration, and Movement Disorder Society Unified Parkinson's Disease Rating Scale total score, MCI was associated with worse scores within the PDQ-39 dimension of communication (p = 0.008). Subjects were divided into tertiles of cognitive decline from premorbid level. Scores in the dimension of stigma were worst in the second tertile of cognitive decline (p = 0.03). MCI was associated with worse social support scores in the second tertile of cognitive decline (p = 0.008). Conclusion: MCI and cognitive decline from premorbid baseline are associated with reduced HR-QOL in communication, stigma, and social support domains. The cognitive decline from premorbid baseline modifies the association between MCI and HR-QOL in PD and knowing both will allow a better appreciation of difficulties patients face in daily life.

Levodopa remains the most effective treatment for Parkinson’s disease and is considered the gold standard therapy. However, disease progression and changes in the gastrointestinal tract result in a declining window of treatment response in a majority of patients. Efforts have been made recently to improve levodopa bioavailability either by developing more effective oral formulations or by innovating routes of administration (intestinal infusion, transcutaneous or inhaled levodopa). IPX066 is a novel levodopa–carbidopa (LD/CD) oral formulation combining immediate-release (IR) and extended-release (ER) LD/CD recently approved in the USA and the EU. Levodopa–carbidopa intestinal gel (LCIG) is an approved therapy consisting of a suspension of levodopa and carbidopa infused directly into the proximal jejunum via a percutaneous endoscopic gastrojejunostomy (PEG-J) tube through a portable infusion pump. Ongoing studies are evaluating the ‘accordion pill’ (AP09004), an ER LD/CD formulation with gastroretentive properties. ND0612 is a proprietary liquid formulation of LD/CD that enables subcutaneous administration via a small patch-pump device, and CVT-301 is a levodopa inhalation powder with rapid onset of action; both are currently in active studies. Other novel formulations have been discontinued, including DM-1992, which is a bilayer formulation containing an IR LD/CD layer and an ER LD/CD layer with gastroretentive properties, and XP21279, a novel oral levodopa prodrug that is absorbed from the small and large intestine by high-capacity nutrient transporters expressed throughout the gastrointestinal system. ODM-101 is a new oral formulation of levodopa/carbidopa/entacapone that contains a higher amount of carbidopa (65 or 105 mg), but no active studies are underway. The current review aims to summarize the pharmacokinetic aspects, clinical efficacy, and potential adverse events of novel levodopa formulations currently available or under development.

Parkinson's disease is primarily caused by dysfunction of dopaminergic neurons, however, nondopaminergic (ND) systems are also involved. ND targets are potentially useful to reduce doses of levodopa or to treat nonlevodopa-responsive symptoms. Recent studies have investigated the role of ND drugs for motor and nonmotor symptoms. Adenosine A2A receptor antagonists, mixed inhibitors of sodium/calcium channels and monoamine oxidase-B have recently been found to improve motor fluctuations. N-methyl-d-aspartate receptor antagonists and serotonin 5HT1B receptor agonists demonstrated benefit in levodopa-induced dyskinesia. Conversely, studies using antiepileptic drugs and adrenoreceptor antagonist had conflicting results. Moreover, metabotropic glutamate receptor antagonists also failed to improve symptoms. The current review summarizes the most recent findings on ND drugs over the last 2 years.