Extended-release carbidopa-levodopa (IPX066) compared with immediate-release carbidopa-levodopa in patients with Parkinson's disease and motor fluctuations: a phase 3 randomised, double-blind trial

Novel and experimental therapeutics for the management of motor and non-motor Parkinsonian symptoms

BACKGROUND  : Both motor and non-motor symptoms of Parkinson's disease (PD) have a substantial detrimental influence on the patient's quality of life. The most effective treatment remains oral levodopa. All currently known treatments just address the symptoms; they do not completely reverse the condition.

METHODOLOGY

In order to find literature on the creation of novel treatment agents and their efficacy for PD patients, we searched PubMed, Google Scholar, and other online libraries.

RESULTS

According to the most recent study on Parkinson's disease (PD), a great deal of work has been done in both the clinical and laboratory domains, and some current scientists have even been successful in developing novel therapies for PD patients.

CONCLUSION

The quality of life for PD patients has increased as a result of recent research, and numerous innovative medications are being developed for PD therapy. In the near future, we will see positive outcomes regarding PD treatment.

Safety and efficacy of continuous subcutaneous levodopa-carbidopa infusion (ND0612) for Parkinson's disease with motor fluctuations (BouNDless): a phase 3, randomised, double-blind, double-dummy, multicentre trial

BACKGROUND

Conventional oral levodopa therapy for the treatment of Parkinson's disease can be associated with variations in plasma concentrations. Levodopa infusion strategies might provide more consistent drug delivery and fewer motor fluctuations. We aimed to assess the safety and efficacy of a continuous 24 h/day subcutaneous infusion of ND0612 (a levodopa-carbidopa solution) compared with oral immediate-release levodopa-carbidopa for the treatment of motor fluctuations in people with Parkinson's disease.

METHODS

We conducted a phase 3, randomised, double-blind, double-dummy, active-controlled, multicentre trial at 117 academic and community neurology sites in 16 countries, including in Europe, Israel, and the USA. Eligible participants were men and women aged 30 years or older with a diagnosis of Parkinson's disease (Hoehn and Yahr stage ≤3 in the on state) who experienced at least 2·5 h/day of off time. Participants underwent an open-label run-in phase (<12 weeks), during which time optimal regimens were established for both oral immediate-release levodopa-carbidopa and for 24 h/day subcutaneous ND0612 infusion (levodopa-carbidopa 60·0/7·5 mg/mL), with supplemental oral levodopa-carbidopa if needed. Participants were then randomly assigned (1:1) to 12 weeks of double-blind treatment with their optimised regimen of either subcutaneous ND0612 or oral levodopa-carbidopa, with matching oral or subcutaneous placebo given as required to maintain blinding. Randomisation was done via an interactive web response system, stratified by region, using a permuted block schedule. Participants, study partners, treating investigators, study site personnel, and the sponsor were masked to treatment group allocation. The primary efficacy endpoint was the change from baseline (ie, time of randomisation, when all patients were receiving an optimised open-label ND0612 regimen) to end of the double-blind phase in total daily on time without troublesome dyskinesia, analysed by intention to treat. This trial is registered with ClinicalTrials.gov, NCT04006210, and is complete.

FINDINGS

Between Sept 30, 2019, and April 8, 2022, 381 participants were enrolled, of whom 259 (68%) were randomly assigned, 128 (49%) to subcutaneous ND0612 and 131 (51%) to oral levodopa-carbidopa. 243 (94%) participants completed the study. Treatment with subcutaneous ND0612 provided an additional 1·72 h (95% CI 1·08 to 2·36) of on time without troublesome dyskinesia compared with oral levodopa-carbidopa (change from baseline of -0·48 h [-0·94 to -0·02] with subcutaneous ND0612 vs -2·20 h [-2·65 to -1·74] with oral levodopa-carbidopa; p<0·0001). Significant treatment differences favouring subcutaneous ND0612 were also found in the first four of nine prespecified hierarchical outcomes of daily off time (-1·40 h [95% CI -1·99 to -0·80]), Movement Disorders Society-Unified Parkinson's Disease Rating Scale part II scores (-3·05 [-4·28 to -1·81]), Patients Global Impression of Change (odds ratio [OR] 5·31 [2·67 to 10·58]), and Clinical Global Impression of Improvement (OR 7·23 [3·57 to 14·64]). Hierarchical testing ended after the fourth secondary endpoint. Adverse events were reported by 287 (89%) of 322 participants during open-label ND0612 optimisation, and by 103 (80%) of 128 in the ND0612 group and 97 (74%) of 131 in the oral levodopa-carbidopa group during the double-blind phase. The most common adverse events were infusion-site reactions (266 [83%] participants during open-label ND0612, and 73 [57%] in the ND0612 group vs 56 [43%] in the oral levodopa-carbidopa group during the double-blind phase), most of which were mild. Serious adverse events in four participants in the ND0612 group were related to study treatment (infusion-site cellulitis [n=2], infusion-site abscess and infusion-site ulcer [n=1]; and paraesthesia and peripheral sensorimotor neuropathy [n=1]). One participant in the ND0612 group died during the double-blind phase, but the death was not related to study treatment (fall leading to traumatic brain injury).

INTERPRETATION

Results of this phase 3 study showed that subcutaneous ND0612 used in combination with oral immediate-release levodopa-carbidopa increased on time without troublesome dyskinesia and reduced off time, with a favourable benefit-risk profile. ND0612 might offer a safe and efficacious subcutaneous levodopa infusion approach to managing motor fluctuations in people with Parkinson's disease. The ongoing open-label extension phase will provide further information on the long-term efficacy and safety of treatment.

FUNDING

NeuroDerm.

A Review of Levodopa Formulations for the Treatment of Parkinson's Disease Available in the United States

Purpose: The safety and efficacy of levodopa formulations are evaluated to inform clinical decision making for the treatment of Parkinson's disease. Summary: Levodopa is a cornerstone of treatment for Parkinson's disease due to its proven efficacy. Although many patients can initially be managed using immediate release tablets, as their disease progresses they often require escalating doses as well as more frequent dosing to prevent wearing off effects. Additionally, patients who experience time in the off state may struggle with the delay between medication administration and onset of action. Therefore, to increase patient convenience as well as to enhance the pharmacokinetic profile of the levodopa, several other formulations have been developed. Levodopa coformulated with carbidopa is supplied as immediate release tablets, oral disintegrating tablets, controlled release tablets, extended release capsules, and a continuous enteral solution. Additionally, there is a levodopa inhalation powder available. As a result of their different absorption profiles, each formulation has unique safety and efficacy attributes. Consequently, while this expansion of levodopa formulations has substantially increased treatment options for patients, it has also increased the complexity of medical decision making for patients, providers, and health systems alike. Conclusion: Knowledge of the different pharmacokinetic, safety and efficacy profiles of the available levodopa formulations is critical for the effective management of Parkinson's disease on both the individual patient and population levels.

Medical, surgical, and physical treatments for Parkinson's disease

Although dopamine replacement therapy remains a core component of Parkinson's disease treatment, the onset of motor fluctuations and dyskinetic movements might require a range of medical and surgical approaches from a multidisciplinary team, and important new approaches in the delivery of dopamine replacement are becoming available. The more challenging, wide range of non-motor symptoms can also have a major impact on the quality of life of a patient with Parkinson's disease, and requires careful multidisciplinary management using evidence-based knowledge, as well as appropriately tailored strategies according to the individual patient's needs. Disease-modifying therapies are urgently needed to prevent the development of the most disabling refractory symptoms, including gait and balance difficulties, cognitive impairment and dementia, and speech and swallowing impairments. In the third paper in this Series, we present the latest evidence supporting the optimal treatment of Parkinson's disease, and describe an expert approach to many aspects of treatment choice where an evidence base is insufficient.

Management of OFF condition in Parkinson disease

Parkinson disease (PD) impacts nearly 1 million individuals in the United States. Nearly every patient with PD will require therapy with dopamine in the form of levodopa as the disease progresses. In more advanced stages of the disease, patients will experience motor fluctuations and require adjustment to their medication regimens to maintain good control of their symptoms. During the last 10 years, several new therapeutic treatment options have come to the market to treat motor fluctuations and improve patient quality of life. Some of these agents represent additional options to previously available drug classes, such as the catechol-O-methyl transferase (COMT) inhibitor, opicapone, and monoamine-oxidase B-inhibitor (MAO-B inhibitor), safinamide, as well as new dosage forms for available therapeutics. One new agent, istradefylline, has a novel mechanism in the treatment of PD. The place in therapy for these newer therapeutic options will be explored through a series of patient cases. This article focuses on evidence-based recommendations for the use of these newer options in the management of patients experiencing OFF episodes.

IPX203 vs Immediate-Release Carbidopa-Levodopa for the Treatment of Motor Fluctuations in Parkinson Disease: The RISE-PD Randomized Clinical Trial

Importance

Levodopa has a short half-life and a limited window of opportunity for absorption in the proximal small intestine. IPX203 is an oral, extended-release formulation of carbidopa-levodopa developed to address these limitations.

Objective

To assess the efficacy and safety of IPX203 vs immediate-release carbidopa-levodopa in patients with Parkinson disease who are experiencing motor fluctuations.

Design, Setting, and Participants

RISE-PD was a 20-week, randomized, double-blind, double-dummy, active-controlled, phase 3 clinical trial. The study was conducted between November 6, 2018, and June 15, 2021, at 105 academic and clinical centers in the US and Europe. Patients with Parkinson disease taking a total daily dose of 400 mg or more of levodopa and experiencing an average of 2.5 hours or more daily off-time were included in the study. A total of 770 patients were screened, 140 were excluded (those taking controlled-release carbidopa-levodopa apart from a single daily bedtime dose, Rytary (Amneal Pharmaceuticals), additional carbidopa or benserazide, or catechol O-methyl transferase inhibitors or who had a history of psychosis within the past 10 years), and 630 were enrolled in the trial.

Interventions

Following open-label immediate-release carbidopa-levodopa dose adjustment (3 weeks) and conversion to IPX203 (4 weeks), patients were randomized in a 1:1 ratio to double-blind, double-dummy treatment with immediate-release carbidopa-levodopa or IPX203 for 13 weeks.

Main Outcome and Measures

The primary end point was mean change in daily good on-time (ie, on-time without troublesome dyskinesia) from baseline to the end of the double-blind treatment period.

Results

A total of 630 patients (mean [SD] age, 66.5 [8.95] years; 396 [62.9%] men) were enrolled, and 506 patients were randomly assigned to receive IPX203 (n = 256) or immediate-release carbidopa-levodopa (n = 250). The study met its primary end point, demonstrating statistically significant improvement in daily good on-time for IPX203 compared to immediate-release carbidopa-levodopa (least squares mean, 0.53 hours; 95% CI, 0.09-0.97; P = .02), with IPX203 dosed a mean 3 times per day vs 5 times per day for immediate-release carbidopa-levodopa. Good on-time per dose increased by 1.55 hours with IPX203 compared to immediate-release carbidopa-levodopa (95% CI, 1.37-1.73; P < .001). IPX203 was well tolerated. The most common adverse events in the double-blind phase (IPX203 vs immediate-release carbidopa-levodopa) were nausea (4.3% vs 0.8%) and anxiety (2.7% vs 0.0%).

Conclusions and Relevance

In this study, IPX203 provided more hours of good on-time per day than immediate-release carbidopa-levodopa, even as IPX203 was dosed less frequently.

Trial Registration

ClinicalTrials.gov Identifier: NCT03670953.

Parkinson's disease updates: Addressing the pathophysiology, risk factors, genetics, diagnosis, along with the medical and surgical treatment

After only Alzheimer's disease (AD), Parkinson's disease (PD) is the second most prevalent neurodegenerative disease. The incidence of this disease increases with age, especially for those above 70 years old. There are many risk factors that are well-established in the contribution to the development of PD, such as age, gender, ethnicity, rapid eye movement sleep disorder, high consumption of dairy products, traumatic brain injury, genetics, and pesticides/herbicides. Interestingly, smoking, consumption of caffeine, and physical activities are the protective factors of PD. A deficiency of dopamine in the substantia nigra of the brainstem is the main pathology. This, subsequently, alters the neurotransmitter, causing an imbalance between excitatory and inhibitory signals. In addition, genetics is also involved in the pathogenesis of the disease. As a result, patients exhibit characteristic motor symptoms such as tremors, stiffness, bradykinesia, and postural instability, along with non-motor symptoms, including dementia, urinary incontinence, sleeping disturbances, and orthostatic hypotension. PD may resemble other diseases; therefore, it is important to pay attention to the diagnosis criteria. Parkinson's disease dementia can share common features with AD; this can include behavioral as well as psychiatric symptoms, in addition to the pathology being protein aggregate accumulation in the brain. For PD management, the administration of pharmacological treatment depends on the motor symptoms experienced by the patients. Non-pharmacological treatment plays a role as adjuvant therapy, while surgical management is indicated in chronic cases. This paper aims to review the etiology, risk factors, protective factors, pathophysiology, signs and symptoms, associated conditions, and management of PD.

Importance of time to ON versus wearing OFF in total daily OFF time experienced by patients with Parkinson's disease

Most patients with Parkinson's disease (PD) receiving levodopa (LD)/DOPA decarboxylase inhibitors develop motor fluctuations with an increasing amount of OFF time, negatively impacting patient quality of life. Herein, we review the evidence supporting the substantial, yet underappreciated contribution of delays in time to ON (including delayed ON and no ON) to total daily OFF time. Most clinical studies use patient diaries that do not capture time to ON and wearing OFF separately as related to LD dosing, and consequently, most OFF time has generally been attributed to wearing OFF. Hence, most treatment regimens focus on reducing wearing OFF by changing LD dosing/formulations and/or using "ON-extenders" (eg, catechol-o-methyltransferase inhibitors, monoamine oxidase-B inhibitors, extended-release amantadine, and adenosine A2A receptor antagonists). However, the literature describing approved treatments for PD that has focused on delays in time to ON is sparse and suggests this type of OFF may comprise more than twice the amount of total daily OFF time as wearing OFF. Here, we advocate for the importance of measuring and adequately addressing delays in time to ON and build support for the consistent inclusion of the time to ON measurement in future clinical trials.

Clinical Use of On-Demand Therapies for Patients with Parkinson's Disease and OFF Periods

On-demand therapies for Parkinson's disease (PD) provide rapid, reliable relief for patients experiencing OFF periods; however, practical guidelines on the use of these therapies are not generally available. This paper reviews the use of on-demand treatments. Motor fluctuations occur in nearly all patients with PD after long-term use of levodopa. As the goal of PD treatment is to provide good ON time, on-demand treatments that have a more rapid reliable onset than the slower-acting oral medications provide rapid relief for OFF periods. All current on-demand treatments bypass the gastrointestinal tract, providing dopaminergic therapy directly into the blood stream by subcutaneous injection, through the buccal mucosa, or by inhalation into the pulmonary circulation. On-demand treatments are fast acting (10- to 20-min onset), with maximum, reliable, and significant responses reached within 30 min after administration. Oral medications pass through the gastrointestinal tract and thus have slower absorption owing to gastroparesis and competition with food. On-demand therapies, by providing fast-acting relief, can have a positive impact on a patient's quality of life when patients are experiencing OFF periods.

Safety review of current pharmacotherapies for levodopa-treated patients with Parkinson's disease

INTRODUCTION

Levodopa remains the gold standard for treatment of Parkinson's disease (PD). Patients develop complications with disease progression, necessitating adjunctive therapy to control fluctuations in motor and non-motor symptoms and dyskinesia. Knowledge of medication safety and tolerability is critical to ascertain the benefit-risk ratio and select an adjunctive therapy that provides the highest chance for medication adherence. Posing a challenge are the sheer abundance of options, stemming from the development of several new drugs in recent years, as well as differences in commercial drug availability worldwide.

AREAS COVERED

This review evaluates the efficacy, safety, and tolerability of current US FDA-approved pharmacotherapies for levodopa-treated PD patients, including dopamine agonists, monoamine oxidase type-B inhibitors, catechol-O-methyltransferase inhibitors, the N-methyl-D-aspartate receptor antagonist amantadine, and the adenosine receptor antagonist istradefylline. Data were taken from pivotal phase III randomized controlled and post-surveillance studies, when available, that directly led to FDA-approval.

EXPERT OPINION

No strong evidence exists to support use of a specific adjunctive treatment for improving Off time. Only one medication has demonstrated improvement in dyskinesia in levodopa-treated PD patients; however, every patient cannot tolerate it and therefore adjunctive therapy should be tailored to an individual's symptoms and risk for specific adverse effects.

Levodopa-Induced Dyskinesias in Parkinson's Disease: An Overview on Pathophysiology, Clinical Manifestations, Therapy Management Strategies and Future Directions

Since its first introduction, levodopa has become the cornerstone for the treatment of Parkinson's disease and remains the leading therapeutic choice for motor control therapy so far. Unfortunately, the subsequent appearance of abnormal involuntary movements, known as dyskinesias, is a frequent drawback. Despite the deep knowledge of this complication, in terms of clinical phenomenology and the temporal relationship during a levodopa regimen, less is clear about the pathophysiological mechanisms underpinning it. As the disease progresses, specific oscillatory activities of both motor cortical and basal ganglia neurons and variation in levodopa metabolism, in terms of the dopamine receptor stimulation pattern and turnover rate, underlie dyskinesia onset. This review aims to provide a global overview on levodopa-induced dyskinesias, focusing on pathophysiology, clinical manifestations, therapy management strategies and future directions.

Parkinson's disease therapy: what lies ahead?

The worldwide prevalence of Parkinson's disease (PD) has been constantly increasing in the last decades. With rising life expectancy, a longer disease duration in PD patients is observed, further increasing the need and socioeconomic importance of adequate PD treatment. Today, PD is exclusively treated symptomatically, mainly by dopaminergic stimulation, while efforts to modify disease progression could not yet be translated to the clinics. New formulations of approved drugs and treatment options of motor fluctuations in advanced stages accompanied by telehealth monitoring have improved PD patients care. In addition, continuous improvement in the understanding of PD disease mechanisms resulted in the identification of new pharmacological targets. Applying novel trial designs, targeting of pre-symptomatic disease stages, and the acknowledgment of PD heterogeneity raise hopes to overcome past failures in the development of drugs for disease modification. In this review, we address these recent developments and venture a glimpse into the future of PD therapy in the years to come.

Off-time Treatment Options for Parkinson's Disease

Motor fluctuations (MF) are deemed by patients with Parkinson's disease (PD) as the most troublesome disease feature resulting from the increasing impairment in responsiveness to dopaminergic drug treatments. MF are characterized by the loss of a stable response to levodopa over the nychthemeron with the reappearance of motor (and non-motor) parkinsonian clinical signs at various moments during the day and night. They normally appear after a few years of levodopa treatment and with a variable, though overall increasing severity, over the disease course. The armamentarium of first-line treatment options has widened in the last decade with new once-a-daily compounds, including a catechol O-methyltransferase inhibitor - Opicapone-, two MAO-B inhibitors plus channel blocker - Zonisamide and Safinamide and one amantadine extended-release formulation - ADS5012. In addition to apomorphine injection or oral levodopa dispersible tablets, which have been available for a long time, new on-demand therapies such as apomorphine sublingual or levodopa inhaled formulations have recently shown efficacy as rescue therapies for Off-time treatment. When the management of MF becomes difficult in spite of oral/on-demand options, more complex therapies should be considered, including surgical, i.e. deep brain stimulation, or device-aided therapies with pump systems delivering continuous subcutaneous or intestinal levodopa or subcutaneous apomorphine formulation. Older and less commonly used ablative techniques (radiofrequency pallidotomy) may also be effective while there is still scarce data regarding Off-time reduction using a new lesional approach, i.e. magnetic resonance-guided focused ultrasound. The choice between the different advanced therapies options is a shared decision that should consider physician opinion on contraindication/main target symptom, patients' preference, caregiver's availability together with public health systems and socio-economic environment. The choice of the right/first add-on treatment is still a matter of debate as well as the proper time for an advanced therapy to be considered. In this narrative review, we discuss all the above cited aspects of MF in patients with PD, including their phenomenology, management, by means of pharmacological and advanced therapies, on-going clinical trials and future research and treatment perspectives.

Recent Advances in Drug Therapy for Parkinson's Disease

Parkinson's disease (PD) is a neurodegenerative disease manifesting with motor and non-motor symptoms. Current treatment mainly relies on medication as a symptomatic therapy modulating neurotransmitters. Dopamine replacement therapy has been established, and levodopa is the gold standard for treatment of PD. However, the emergence of motor complications, such as a wearing-off phenomenon, is a clinical problem. Both primary symptoms and motor complications have been targets for the development of treatments for PD. Recent progression in the management of motor complications is supported by newly developed agents and advances in device and formulation technology to deliver drugs continuously. Elucidation of the pathophysiology of PD and the development of disease-modifying therapy that affects the underlying fundamental pathophysiology of the disease are also progressing. In this review, we introduce current knowledge on developments concerning medications for patients with PD.

An Insight into the Molecular Mechanism of Mitochondrial Toxicant-induced Neuronal Apoptosis in Parkinson's Disease

Parkinson's disease (PD) is one of the most common progressive neurodegenerative disorders affecting approximately 1% of the world's population at the age of 50 and above. Majority of PD cases are sporadic and show symptoms after the age of 60 and above. At that time, most of the dopaminergic neurons in the region of substantia nigra pars compacta have been degenerated. Although in past decades, discoveries of genetic mutations linked to PD have significantly impacted our current understanding of the pathogenesis of this devastating disorder, it is likely that the environment also plays a critical role in the etiology of sporadic PD. Recent epidemiological and experimental studies indicate that exposure to environmental agents, including a number of agricultural and industrial chemicals, may contribute to the pathogenesis of several neurodegenerative disorders, including PD. Furthermore, there is a strong correlation between mitochondrial dysfunction and several forms of neurodegenerative disorders, including Alzheimer's disease (AD), Huntington's disease (HD), Amyotrophic lateral sclerosis (ALS) and PD. Interestingly, substantia nigra of patients with PD has been shown to have a mild deficiency in mitochondrial respiratory electron transport chain NADH dehydrogenase (Complex I) activity. This review discusses the role of mitochondrial toxicants in the selective degeneration of dopaminergic neurons targeting the electron transport system that leads to Parkinsonism.

Optimizing levodopa therapy, when and how? Perspectives on the importance of delivery and the potential for an early combination approach

INTRODUCTION

There is currently a resurgence of levodopa as the initial treatment of choice for most patients with Parkinson's disease, albeit at lower doses than previously used. The addition of adjuvant treatments (including MAO-B inhibitors, COMT inhibitors and dopamine agonists) is an established strategy to reduce motor complications that develop with sustained levodopa therapy.

AREAS COVERED

In this narrative review, the authors discuss the evidence underpinning current levodopa optimization strategies, during early disease and once motor complications occur. To support the discussion, the authors performed a broad PubMed search with the terms 'levodopa/L-dopa/L-Dopa, and Parkinson's disease,' restricted to clinical trials. There is now a wealth of evidence that improving levodopa delivery to the brain improves outcomes and we discuss how agents can be combined earlier in the course of disease to leverage the full potential of this strategy.

EXPERT OPINION

Levodopa remains the cornerstone of antiparkinsonian therapy. Several promising advances in formulation have been made and include novel extended-release oral drugs as well as non-oral delivery systems. However, evidence has long suggested that anti-parkinsonian medications may be better used in combination earlier in the disease, and consequently patients will benefit from low doses of several agents rather than ever larger levodopa doses.

Improving levodopa delivery: IPX203, a novel extended-release carbidopa-levodopa formulation

Introduction

IPX203 is a novel oral extended-release (ER) formulation of carbidopa (CD) and levodopa (LD) developed to address the short half-life and limited area for absorption of LD in the gastrointestinal tract. This paper presents the formulation strategy of IPX203 and its relationship to the pharmacokinetics (PK) and pharmacodynamic profile of IPX203 in Parkinson's disease (PD) patients.

Methods

IPX203 was developed with an innovative technology containing immediate-release (IR) granules and ER beads that provides rapid LD absorption to achieve desired plasma concentration and maintaining it within the therapeutic range for longer than can be achieved with current oral LD formulations. The PK and pharmacodynamics of IPX203 were compared with IR CD-LD in a Phase 2, open-label, rater-blinded, multicenter, crossover study in patients with advanced PD.

Results

Pharmacokinetic data showed that on Day 15, LD concentrations were sustained above 50% of peak for 6.2 h with IPX203 vs. 3.9 h with IR CD-LD (P = 0.0002). Pharmacodynamic analysis demonstrated that mean MDS-UPDRS Part III scores prior to administration of the first daily dose were significantly lower among patients receiving IPX203 than IR CD-LD (LS mean difference -8.1 [25.0], P = 0.0255). In a study conducted in healthy volunteers, a high-fat, high-calorie meal delayed plasma LD T_max by 2 h, and increased C_max and AUC_tau by approximately 20% compared with a fasted state. Sprinkling capsule contents on applesauce did not affect PK parameters.

Conclusion

These data confirm that the unique design of IPX203 addresses some of the limitations of oral LD delivery.

Interventions for preventing falls in Parkinson's disease

BACKGROUND

Most people with Parkinson's disease (PD) experience at least one fall during the course of their disease. Several interventions designed to reduce falls have been studied. An up-to-date synthesis of evidence for interventions to reduce falls in people with PD will assist with informed decisions regarding fall-prevention interventions for people with PD.

OBJECTIVES

To assess the effects of interventions designed to reduce falls in people with PD.

SEARCH METHODS

CENTRAL, MEDLINE, Embase, four other databases and two trials registers were searched on 16 July 2020, together with reference checking, citation searching and contact with study authors to identify additional studies. We also conducted a top-up search on 13 October 2021.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) of interventions that aimed to reduce falls in people with PD and reported the effect on falls. We excluded interventions that aimed to reduce falls due to syncope.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane Review procedures. Primary outcomes were rate of falls and number of people who fell at least once. Secondary outcomes were the number of people sustaining one or more fall-related fractures, quality of life, adverse events and economic outcomes. The certainty of the evidence was assessed using GRADE.

MAIN RESULTS

This review includes 32 studies with 3370 participants randomised. We included 25 studies of exercise interventions (2700 participants), three studies of medication interventions (242 participants), one study of fall-prevention education (53 participants) and three studies of exercise plus education (375 participants). Overall, participants in the exercise trials and the exercise plus education trials had mild to moderate PD, while participants in the medication trials included those with more advanced disease. All studies had a high or unclear risk of bias in one or more items. Illustrative risks demonstrating the absolute impact of each intervention are presented in the summary of findings tables. Twelve studies compared exercise (all types) with a control intervention (an intervention not thought to reduce falls, such as usual care or sham exercise) in people with mild to moderate PD. Exercise probably reduces the rate of falls by 26% (rate ratio (RaR) 0.74, 95% confidence interval (CI) 0.63 to 0.87; 1456 participants, 12 studies; moderate-certainty evidence). Exercise probably slightly reduces the number of people experiencing one or more falls by 10% (risk ratio (RR) 0.90, 95% CI 0.80 to 1.00; 932 participants, 9 studies; moderate-certainty evidence).  We are uncertain whether exercise makes little or no difference to the number of people experiencing one or more fall-related fractures (RR 0.57, 95% CI 0.28 to 1.17; 989 participants, 5 studies; very low-certainty evidence). Exercise may slightly improve health-related quality of life immediately following the intervention (standardised mean difference (SMD) -0.17, 95% CI -0.36 to 0.01; 951 participants, 5 studies; low-certainty evidence). We are uncertain whether exercise has an effect on adverse events or whether exercise is a cost-effective intervention for fall prevention. Three studies trialled a cholinesterase inhibitor (rivastigmine or donepezil). Cholinesterase inhibitors may reduce the rate of falls by 50% (RaR 0.50, 95% CI 0.44 to 0.58; 229 participants, 3 studies; low-certainty evidence). However, we are uncertain if this medication makes little or no difference to the number of people experiencing one or more falls (RR 1.01, 95% CI 0.90 to 1.14230 participants, 3 studies) and to health-related quality of life (EQ5D Thermometer mean difference (MD) 3.00, 95% CI -3.06 to 9.06; very low-certainty evidence). Cholinesterase inhibitors may increase the rate of non fall-related adverse events by 60% (RaR 1.60, 95% CI 1.28 to 2.01; 175 participants, 2 studies; low-certainty evidence). Most adverse events were mild and transient in nature.  No data was available regarding the cost-effectiveness of medication for fall prevention. We are uncertain of the effect of education compared to a control intervention on the number of people who fell at least once (RR 10.89, 95% CI 1.26 to 94.03; 53 participants, 1 study; very low-certainty evidence), and no data were available for the other outcomes of interest for this comparisonWe are also uncertain (very low-certainty evidence) whether exercise combined with education makes little or no difference to the number of falls (RaR 0.46, 95% CI 0.12 to 1.85; 320 participants, 2 studies), the number of people sustaining fall-related fractures (RR 1.45, 95% CI 0.40 to 5.32,320 participants, 2 studies), or health-related quality of life (PDQ39 MD 0.05, 95% CI -3.12 to 3.23, 305 participants, 2 studies). Exercise plus education may make little or no difference to the number of people experiencing one or more falls (RR 0.89, 95% CI 0.75 to 1.07; 352 participants, 3 studies; low-certainty evidence). We are uncertain whether exercise combined with education has an effect on adverse events or is a cost-effective intervention for fall prevention.  AUTHORS' CONCLUSIONS: Exercise interventions probably reduce the rate of falls, and probably slightly reduce the number of people falling in people with mild to moderate PD.  Cholinesterase inhibitors may reduce the rate of falls, but we are uncertain if they have an effect on the number of people falling. The decision to use these medications needs to be balanced against the risk of non fall-related adverse events, though these adverse events were predominantly mild or transient in nature. Further research in the form of large, high-quality RCTs are required to determine the relative impact of different types of exercise and different levels of supervision on falls, and how this could be influenced by disease severity. Further work is also needed to increase the certainty of the effects of medication and further explore falls prevention education interventions both delivered alone and in combination with exercise.

Molecular Mechanisms and Therapeutic Strategies for Levodopa-Induced Dyskinesia in Parkinson's Disease: A Perspective Through Preclinical and Clinical Evidence

Parkinson's disease (PD) is the second leading neurodegenerative disease that is characterized by severe locomotor abnormalities. Levodopa (L-DOPA) treatment has been considered a mainstay for the management of PD; however, its prolonged treatment is often associated with abnormal involuntary movements and results in L-DOPA-induced dyskinesia (LID). Although LID is encountered after chronic administration of L-DOPA, the appearance of dyskinesia after weeks or months of the L-DOPA treatment has complicated our understanding of its pathogenesis. Pathophysiology of LID is mainly associated with alteration of direct and indirect pathways of the cortico-basal ganglia-thalamic loop, which regulates normal fine motor movements. Hypersensitivity of dopamine receptors has been involved in the development of LID; moreover, these symptoms are worsened by concurrent non-dopaminergic innervations including glutamatergic, serotonergic, and peptidergic neurotransmission. The present study is focused on discussing the recent updates in molecular mechanisms and therapeutic approaches for the effective management of LID in PD patients.

Amantadine delayed release/extended release capsules significantly reduce OFF time in Parkinson's disease

Maintaining consistent levodopa benefits while simultaneously controlling dyskinesia can be difficult. Recently, an amantadine delayed release/extended release (DR/ER) formulation (Gocovri^®) indicated for dyskinesia received additional FDA approval as an adjunct to levodopa for the treatment of OFF episodes. We evaluated OFF time reductions with amantadine-DR/ER in a pooled analysis of two phase III amantadine-DR/ER trials (NCT02136914, NCT02274766) followed by a 2-year open-label extension trial (NCT02202551). OFF outcomes were analyzed for the mITT population, as well as stratified by baseline OFF time of ≥2.5 h/day or <2.5 h/day. At Week 12, mean placebo-subtracted treatment difference in OFF time was −1.00 [−1.57, −0.44] h in the mITT population (n = 196), −1.2 [−2.08, −0.32] h in the ≥2.5 h subgroup (n = 102) and −0.77 [−1.49, −0.06] in the <2.5 h subgroup (n = 94). Amantadine-DR/ER-treated participants showed reduced MDS-UPDRS Part IV motor fluctuation subscores by week 2 that were maintained below baseline to Week 100.

COMT Inhibitors in the Management of Parkinson's Disease

Levodopa treatment remains the gold standard for Parkinson's disease, but shortcomings related to the pharmacological profile, notably, oral administration and the consequent occurrence of motor complications, have led to the development of several add-on levodopa treatments or to research to improve the method of delivery. Motor fluctuations, and to a lesser extent non-motor fluctuations, concern half of the patients with Parkinson's disease after 5 years of disease and patients identified them as one of their most bothersome symptoms. Catechol-O-methyl transferase inhibitors (COMT-Is) are one of the recommended first-line levodopa add-on therapies for the amelioration of end-of dose motor fluctuations in patient with advanced Parkinson's disease. Currently, two peripheral COMT-Is are considered as first-line choices - entacapone (ENT), which was approved by the US Food and Drug Administration in 1999 and the European Committee in 1998; and opicapone (OPC), which was approved by the European Committee in 2016. A second-line COMT-I that requires regular hepatic monitoring, tolcapone (TOL), was approved by the Food and Drug Administration in 1998 and the European Committee in 1997. Of note, OPC also received Food and Drug Administration approval in 2021, but it is still only marketed in a few countries, including Germany, UK, Spain, Portugal, Italy, Japan, and USA, while ENT and TOL have a wider market. Our narrative review summarizes the pharmacokinetic/pharmacodynamic properties, clinical efficacy in terms of motor fluctuations, motor/non-motor symptoms, quality of life, and safety data of these three COMT-Is, as evidenced by randomized clinical trials, as well as by real-life observational studies. Overall, a phase III non-inferiority trial showed a similar effect between ENT and OPC on off-time (-60.8 min/day and -40.3 min/day, vs placebo, respectively), with a possible additional off-time reduction of 39 min/day, obtained when there is a switch from ENT to OPC. Concomitantly, TOL can reduce off-time by an average of 98 min/day. A significant though discrete concomitant reduction on the Unified Parkinson's Disease Rating Scale motor section (2-3 points) is obtained with all three drugs vs placebo. Data on quality of life are fewer and more heterogeneous, with positive results obtained especially in open-label studies. Effects on non-motor symptoms were investigated as secondary outcome only in a few studies, frequently by means of non-specific scales and a benefit was observed in open-label studies. Dopaminergic adverse effects were the most frequent, dyskinesia being the most common for the three drugs eventually requiring levodopa dose reductions. No urine discoloration and a very low incidence of diarrhea were found with OPC compared with ENT and TOL. Regular hepatic monitoring is needed only for TOL. A combination of COMT-Is with new formulations of levodopa, including the subcutaneous, intrajejunal, or new extended-release formulation, merits further exploration to improve the management of both mild and severe motor fluctuations.

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

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

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

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OFF episodes persist despite conventional treatment.

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

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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.

An Update on Medical and Surgical Treatments of Parkinson's Disease

Parkinson’s disease (PD) is characterized by degeneration of dopaminergic neurons in the substantia nigra pars compacta and other neuronal populations. The worldwide prevalence of PD is over 7 million and has been increasing more rapidly than many other neurodegenerative disorders. PD symptoms can be broadly divided into motor (slowness, stiffness, tremor) and non-motor symptoms (such as depression, dementia, psychosis, orthostatic hypotension). Patients can also have prodromal symptoms of rapid eye movement sleep behavior disorder, hyposmia, and constipation. The diagnosis of PD is mainly clinical, but dopamine transporter single-photon emission computed tomography can improve the accuracy of the diagnosis. Dopamine based therapies are used for the treatment of motor symptoms. Non-motor symptoms are treated with other medications such as selective serotonin reuptake inhibitors (depression/anxiety), acetylcholinesterase inhibitors (dementia), and atypical antipsychotics (psychosis). Patients with motor fluctuations or uncontrolled tremor, benefit from deep brain stimulation. Levodopa-carbidopa intestinal gel is an alternative to deep brain stimulation for uncontrolled motor fluctuations. Rehabilitative therapies such as physical, occupational, and speech therapy are important during all stages of the disease. Management of PD is complex but there have been significant advancements in the treatment of motor and non-motor symptoms over the past few years. This review discusses the updates in the medical and surgical management of PD.

Nanomedicine against Alzheimer's and Parkinson's Disease

Alzheimer's and Parkinson's are the two most rampant neurodegenerative disorders worldwide. Existing treatments have a limited effect on the pathophysiology but are unable to fully arrest the progression of the disease. This is due to the inability of these therapeutic molecules to efficiently cross the blood-brain barrier. We discuss how nanotechnology has enabled researchers to develop novel and efficient nano-therapeutics against these diseases. The development of nanotized drug delivery systems has permitted an efficient, site-targeted, and controlled release of drugs in the brain, thereby presenting a revolutionary therapeutic approach. Nanoparticles are also being thoroughly studied and exploited for their role in the efficient and precise diagnosis of neurodegenerative conditions. We summarize the role of different nano-carriers and RNAi-conjugated nanoparticle-based therapeutics for their efficacy in pre-clinical studies. We also discuss the challenges underlying the use of nanomedicine with a focus on their route of administration, concentration, metabolism, and any toxic effects for successful therapeutics in these diseases.

Amantadine ER (Gocovri®) Significantly Increases ON Time Without Any Dyskinesia: Pooled Analyses From Pivotal Trials in Parkinson's Disease

Background: Clinical trials for antiparkinsonian drugs aimed at managing motor complications typically use patient diaries to divide levodopa-induced dyskinesias (LID) into "troublesome" and "non-troublesome" categories. Yet, given the choice, most patients would prefer to live without experiencing any dyskinesia. However, the concept of evaluating time spent ON without any dyskinesia as an outcome has never been tested. We conducted analyses of pooled Gocovri pivotal trial data in order to evaluate the extent to which Gocovri increased the time PD patients spent ON without dyskinesia (troublesome or non-troublesome), beyond its already identified improvement in reducing troublesome dyskinesia. Methods: Patients enrolled in phase 3 trials (EASE LID [NCT02136914] or EASE LID 3 [NCT02274766]) recorded time spent in the following PD diary states at baseline and Week 12 (endpoint): asleep, OFF, ON with troublesome dyskinesia, ON with non-troublesome dyskinesia, and ON without dyskinesia. Mixed model repeated measures analyses with estimated Cohen D effect sizes were performed on the modified intent to treat population to evaluate changes in time spent in these states. Results: Patients randomized to receive Gocovri showed an increase in ON time without dyskinesia and corresponding decreases in ON time with dyskinesia and OFF time vs. placebo. Treatment effects were statistically significant for Gocovri vs. placebo starting at Week 2 and were sustained until Week 12. On MMRM analysis at Week 12, patients in the Gocovri group showed an adjusted mean ± SE increase over placebo of 2.9 ± 0.6 h in ON time without dyskinesia (Cohen D effect size 0.79) and an adjusted mean ± SE decrease of -1.9 ± 0.6 h in ON time with dyskinesia (troublesome + non-troublesome) (Cohen D effect size 0.49), that included a -1.5 ± 0.4 h placebo-adjusted reduction in ON time with troublesome dyskinesia and a -0.6 ± 0.4 h reduction in ON time with non-troublesome dyskinesia. OFF time was reduced by -1.0 ± 0.3 h compared to placebo. Conclusions: Gocovri treatment more than doubled the daily time patients spent ON without dyskinesia. These results suggest that the Gocovri treatment effect was driven by a reduction in overall motor complications including ON time with both troublesome and non-troublesome dyskinesia as well as time spent OFF.

Real-World Experience with Carbidopa-Levodopa Extended-Release Capsules (Rytary®): Results of a Nationwide Dose Conversion Survey

Background

The introduction of carbidopa-levodopa extended-release (CD-LD ER) capsules (Rytary®) did not go as smoothly as expected, largely due to difficulty around dose conversion from available immediate-release (IR) levodopa (LD) formulations. The dose conversion table in the CD-LD ER prescribing information was similar to the table used in the pivotal clinical trial and is considered by many prescribing HCPs to be less than optimal. By the end of the dose conversion period in that trial, dosing in 76% of subjects was adjusted for symptom control; roughly 60% of patients required a higher dose and about half required more frequent administration than the recommended TID dosing.

Objective

The primary objective of our nationwide (US) survey was to determine the dose conversion strategy most commonly employed by CD-LD ER frequent prescribers. The survey also aimed to explore additional features regarding CD-LD ER use in clinical practice.

Methods

A survey consisting of 21 multiple-choice questions was developed and administered to experts in the use of CD-LD ER, based on prescription volume.

Results

Of the 394 HCPs who were invited to participate, 90 (23%) HCPs completed the survey. All respondents were aware of the dose conversion table; the largest group did not find the table to be helpful and did not use it to convert patients to CD-LD ER. The most common strategy in calculating the CD-LD ER dose was based on the total daily LD IR dose, with the majority of that group initiating dose conversion by doubling the total daily LD dose from CD-LD IR and administering CD-LD ER one less time per day.

Conclusion

Overall, most survey respondents agreed that a good starting point for CD-LD ER conversion could be doubling the daily LD IR dose and administering it one time less frequently. Moreover, rapid patient follow-up after initial dose conversion to allow for further dose adjustments plays a critical role in achieving success. Gaining experience over time is important for satisfactory conversion.

Update on Parkinson's Disease Therapy

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Development, Efficacy and Safety of Once-daily, Bedtime, Extended-release Amantadine (Gocovri®) to Treat Dyskinesia and OFF Time in Parkinson’s Disease

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Patient Preferences for Treating "OFF" Episodes in Parkinson's Disease: A Discrete Choice Experiment

INTRODUCTION

Several on-demand treatments are available for management of "OFF" episodes in patients with Parkinson's disease (PD). We evaluated patients' preferences for features of theoretical on-demand treatment options.

METHODS

In a discrete choice experiment, US adults with self-reported PD of ≥5 years, or <5 years with "OFF" episodes, taking oral carbidopa/levodopa, selected between pairs of theoretical on-demand treatments that varied by mode of administration (with and without mode-specific adverse events [AEs]), time to FULL "ON," duration of "ON," and out-of-pocket cost for a 30-day supply. Data were analyzed with a random parameters logit model; results were used to calculate relative importance of treatment attributes, preference shares, and willingness to pay.

RESULTS

Among 300 respondents, 98% had "OFF" episodes. Across the range of attribute levels included in the survey, avoiding $90 cost was most important to respondents, followed by a preferable mode of administration with associated AEs and decreasing time to FULL "ON." Duration of "ON" was relatively less important. On average, respondents preferred a theoretical dissolvable sublingual film versus other theoretical treatments with alternative modes of administration. Respondents were willing to pay $28-$52 US dollars to switch from least- to more-preferred mode of administration with associated AEs, $58 to reach FULL "ON" in 15 versus 60 min, and $9 to increase duration of FULL "ON" from 1 to 2 h.

CONCLUSION

Respondents with PD valued lower out-of-pocket cost and a sublingual mode of administration with its associated AEs when choosing an on-demand treatment for "OFF" episodes.

Research on developing drugs for Parkinson's disease

Current treatments for Parkinson's disease (PD) are mainly dopaminergic drugs. However, dopaminergic drugs are only symptomatic treatments and limited by several side effects. Recent studies into drug development focused on emerging new molecular mechanisms, including nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, nuclear receptor-related 1 (Nurr1), adenosine receptor A2, nicotine receptor, metabotropic glutamate receptors (mGluRs), and glucocerebrosidase (GCase). Also, immunotherapy and common pathological mechanisms shared with Alzheimer's Disease (AD) and diabetes have attracted much attention. In this review, we summarized the development of preclinical and clinical studies of novel drugs and the improvement of dopaminergic drugs to provide a prospect for PD treatment.

Therapeutic Strategies to Treat or Prevent Off Episodes in Adults with Parkinson's Disease

Parkinson's disease is a chronic, neurodegenerative disease, which manifests with a mixture of motor, cognitive and behavioural symptoms. Levodopa is the most effective antiparkinsonian treatment to date, although chronic use engenders a mixture of complications in a substantial proportion of patients. Amongst these is the occurrence of episodes of worsening symptoms-'off' phenomena. These episodes can manifest with either motor or non-motor symptoms or a combination of these features and have been found to have profound impacts on patients' quality of life. Although preventative measures are poorly evidenced, avoiding excessive total daily levodopa intake in selected populations that are deemed to be of a higher risk for developing these episodes warrants further exploration. Methods to improve levodopa bioavailability and delivery to the brain are currently available and are of value in addressing these episodes once they have become established. These include modifications to levodopa formulations as well as the use of complimentary agents that improve levodopa bioavailability. The deployment of device-assisted approaches is a further dimension that can be considered in addressing these debilitating episodes. This review summarises the clinical manifestations of 'off' phenomena and the current approaches to treat them. Although we briefly discuss clinical advances on the horizon, the predominant focus is on existing, established treatments.

Duration of benefit per Dose: Carbidopa-Levodopa immediate release vs. extended release capsules (Rytary®)

BACKGROUND

For patients with Parkinson's disease, clinicians commonly assess duration of benefit for individual doses of levodopa in order to consider medication changes.

OBJECTIVE

To determine the mean duration of ON time per dose and mean duration of ON time without troublesome dyskinesia (WoTD) per dose of CD-LD IR vs. CD-LD ER in the ADVANCE-PD trial.

METHODS

We performed a post hoc analysis of the ADVANCE-PD trial. Mean ON time per dose and ON time WoTD was calculated at baseline and end-of-study (EOS). Changes were compared between CD-LD IR and CD-LD ER (Rytary®) treatment groups using an ANCOVA model.

RESULTS

Mean (SD) baseline ON time per dose of CD-LD IR (n = 393) was 2.20 h. Patients randomized to double-blind treatment with CD-LD IR (n = 192) experienced an increase in mean ON time per dose from baseline to EOS from 2.24 h to 2.38 h. In comparison, patients randomized to double-blind treatment with CD-LD ER (n = 201) experienced an increase in mean ON time per dose from baseline (on CD-LD IR) to EOS (on CD-LD ER) from 2.17 h to 3.55 h. Conversion and optimization with CD-LD ER increased ON time per dose by 1.21 h more than optimization of CD-LD IR (p < 0.0001). Similarly, CD-LD ER increased ON time WoTD per dose by 1.16 h more than CD-LD IR (p < 0.0001).

CONCLUSION

In the ADVANCE-PD trial, CD-LD ER significantly increased ON time per dose compared to CD-LD IR (+1.21 h, p < 0.0001) and provided significantly more ON time per dose (3.55 h vs 2.38 h, p < 0.0001).

A critical review of apomorphine hydrochloride sublingual film for the treatment of Parkinson's disease 'OFF' episodes

Introduction: Parkinson's disease (PD) is a neurodegenerative disorder defined by its motor features. Levodopa therapy is the gold standard therapy, but over time, response is impeded by the development of motor fluctuations, including 'off' episodes where PD symptoms reemerge. Sublingual apomorphine offers a new, novel, and effective therapy developed for treatment of 'off' episodes. Areas covered: Apomorphine is an old dopamine agonist developed as a subcutaneous injectable rescue therapy for 'off' periods in PD that was approved in the United States in 2004. We will discuss its history, chemistry and clinical use. We will also cover the recent development and approval of sublingual apomorphine film that offers a novel formulation and provides effective treatment for 'off' episodes including results of the phase 3 randomized, double-blinded, placebo-controlled study. Oral mucosal side effects, which were mild to moderate and reversible in most patients experiencing them, will be discussed. Expert opinion: The new sublingual apomorphine is safe and effective for relief of 'off' periods that impact quality of life. Its ease of use will be beneficial to those with needle phobia and device challenges with currently available injectable and inhaled therapeutics. Side effect profile is an improvement from previous attempts at sublingual formulation.

Improving the Delivery of Levodopa in Parkinson's Disease: A Review of Approved and Emerging Therapies

Levodopa is the most effective drug for the treatment of Parkinson's disease, but its use as an oral medication is complicated by its erratic absorption, extensive metabolism and short plasma half-life. On long-term use and with disease progression, there is a high incidence of motor and non-motor complications, which remain a major clinical and research challenge. It is widely accepted that levodopa needs to be administered using formulations that result in good and consistent bioavailability and the physiologically relevant and continuous formation of dopamine in the brain to maximise its efficacy while avoiding and reversing 'wearing off' and dyskinesia. However, the physicochemical properties of levodopa along with its pharmacokinetic and pharmacodynamic profile make it difficult to deliver the drug in a manner that fulfils these criteria. In this review, we examine the problems associated with the administration of levodopa in Parkinson's disease and how the use of novel technologies and delivery devices is leading to a more consistent and sustained levodopa delivery with the aim of controlling motor function as well as non-motor symptoms.

Medical Management and Prevention of Motor Complications in Parkinson's Disease

Levodopa is the most effective medication for the treatment of the motor symptoms of Parkinson's disease. However, over time, the clinical response to levodopa becomes complicated by a reduction in the duration and reliability of motor improvement (motor fluctuations) and the emergence of involuntary movements (levodopa-induced dyskinesia). Strategies that have been attempted in an effort to delay the development of these motor complications include levodopa sparing and continuous dopaminergic therapy. Once motor complications occur, a wide array of medical treatments is available to maximize motor function through the day while limiting dyskinesia. Here, we review the clinical features, epidemiology, and risk factors for the development of motor complications, as well as strategies for their prevention and medical management.

Therapeutic strategies for Parkinson's disease: promising agents in early clinical development

INTRODUCTION

To date, no drug has demonstrated clinically indisputable neuroprotective efficacy in Parkinson's disease (PD). We also have no effective symptomatic treatment for disabling symptoms such as balance problems, and dementia, and we need to improve the efficacy and safety profile of drugs currently used in the management of motor complications.

AREAS COVERED

We examine the agents which appear to have most therapeutic promise based on concepts, feasibility in a reasonable time frame, and available clinical data and place an emphasis on disease-modifying treatments. PUBMED and Clinicaltrials.gov databases were searched for Phase I and II randomized trials for symptomatic or disease-modifying treatments considering only studies that began since 2010 or that were completed after 2015, up to 30 April 2020.

EXPERT OPINION

Encouraging progress has been made in our understanding of molecular pathways. We find passive immunization approaches against α-synuclein, LRRK2 kinase inhibitors, and treatment that can increase GCase activity, which have shown some efficacy on both GBA-mutated and non-mutated PD patients. The recognition of non-dopaminergic impairment and the prominent role of non-motor symptoms have prompted the development of trials on compounds that could tackle different neurotransmitter systems. Future approaches will encompass more personalized medicine strategies based on molecular signatures and non-motor phenotypes.

Parkinson's disease: etiopathogenesis and treatment

The concept of 'idiopathic' Parkinson's disease (PD) as a single entity has been challenged with the identification of several clinical subtypes, pathogenic genes and putative causative environmental agents. In addition to classic motor symptoms, non-motor manifestations (such as rapid eye movement sleep disorder, anosmia, constipation and depression) appear at prodromic/premotor stage and evolve, along with cognitive impairment and dysautonomia, as the disease progresses, often dominating the advanced stages of the disease. The key molecular pathogenic mechanisms include α-synuclein misfolding and aggregation, mitochondrial dysfunction, impairment of protein clearance (associated with deficient ubiquitin-proteasome and autophagy-lysosomal systems), neuroinflammation and oxidative stress. The involvement of dopaminergic as well as noradrenergic, glutamatergic, serotonergic and adenosine pathways provide insights into the rich and variable clinical phenomenology associated with PD and the possibility of alternative therapeutic approaches beyond traditional dopamine replacement therapies.One of the biggest challenges in the development of potential neuroprotective therapies has been the lack of reliable and sensitive biomarkers of progression. Immunotherapies such as the use of vaccination or monoclonal antibodies directed against aggregated, toxic α-synuclein.as well as anti-aggregation or protein clearance strategies are currently investigated in clinical trials. The application of glucagon-like peptide one receptor agonists, specific PD gene target agents (such as GBA or LRRK2 modifiers) and other potential disease modifying drugs provide cautious optimism that more effective therapies are on the horizon. Emerging therapies, such as new symptomatic drugs, innovative drug delivery systems and novel surgical interventions give hope to patients with PD about their future outcomes and prognosis.

Carbidopa and Levodopa Extended Release Capsules in Patients with and without Troublesome and Non-Troublesome Dyskinesia

BACKGROUND

Carbidopa (CD) and levodopa (LD) extended release (CD-LD ER) capsules are designed to combine both immediate and extended release pharmacokinetics. In the phase 3, randomized, double-blind, ADVANCE-PD trial, patients randomized to CD-LD ER experienced a 1.17-hour greater reduction in OFF time compared to patients randomized to CD-LD IR (p < 0.0001).

OBJECTIVE

To compare CD-LD IR optimization to CD-LD ER conversion based on patient dyskinesia status at baseline using data from the ADVANCE-PD trial.

METHODS

This was a retrospective analysis of the ADVANCE-PD study. Patients were categorized by dyskinesia status at baseline into 1) those who had No Dyskinesia (ND), 2) those who had Non-Troublesome Dyskinesia Only (NTDO), and 3) those who had Troublesome Dyskinesia (TD).

RESULTS

Comparative reductions in OFF time favoring CD-LD ER over CD-LD IR were similar for the ND (-1.08 h, p = 0.0071, n = 183) and NTDO (-1.12 h, p = 0.0104, n = 131) groups, and smaller for the TD group (-0.82 h, p = 0.2382, n = 79). Reductions in OFF time for both CD-LD ER conversion and CD-LD IR adjustment were largest within the ND group and smallest within the TD group (CD-LD ER: ND -2.86 h, NTDO -2.11 h, TD -1.36 h; CD-LD IR: ND -1.78 h, NTDO -0.99 h, TD -0.55 h).

CONCLUSION

Responses to both CD-LD IR adjustment and CD-LD ER conversion depended on baseline dyskinesia status. Significant reductions in OFF time with CD-LD ER compared to CD-LD IR were observed in the ND and NTDO groups. In the TD group, comparing CD-LD ER conversion to CD-LD IR optimization, benefits were still observed, but there was less reduction in OFF time, less reduction in troublesome dyskinesia, and fewer patients self-rated themselves much or very much improved than in the ND and NTDO groups. These data suggest that in clinical practice, the best chances for success with conversion from CD-LD IR to CD-LD ER are in patients without TD.

A Healthy Heart and a Healthy Brain: Looking at Mitophagy

Mitochondrial dysfunction is a hallmark of aging and is a major contributor to neurodegenerative diseases and various cardiovascular disorders. Mitophagy, a specialized autophagic pathway to remove damaged mitochondria, provides a critical mechanism to maintain mitochondrial quality. This function has been implicated in a tissue's ability to appropriately respond to metabolic and to bioenergetic stress, as well as to recover from mitochondrial damage. A global decline in mitophagic flux has been postulated to be linked to pathological alterations that occur in the heart and the brain as well as a general age-dependent decline in organ function. Cellular observation suggests multiple mechanistically distinct pathways converge upon and activate mitophagy. Over the past decade, additional molecular components within mitophagy have been discovered, including several disease-associated genes that are functionally implicated in mitophagy. However, the pathophysiological role of mitophagy, and how it is regulated within normal physiology or various disease states, is less well established. Here, we will review the evidence that a decline in mitophagy contributes to impaired mitochondrial homeostasis and may be particularly detrimental to postmitotic neurons and cardiomyocytes. We will discuss mitophagy's pathological significance in both neurodegenerative diseases and cardiovascular disorders. Additionally, signaling pathways regulating mitophagy are reviewed, with emphasis placed on how these pathways might contribute to disease progression. Understanding mitophagy's role in the mechanisms of disease pathogenesis should allow for the development of more efficient strategies to battle pathological conditions associated with mitochondrial dysfunction.

Tapentadol Prevents Motor Impairments in a Mouse Model of Dyskinesia

The motor features in Parkinson's disease (PD) are associated with the degeneration of dopaminergic cells in the substantia nigra in the brain. Thus, the gold-standard in PD therapeutics still consists of dopamine replacement with levodopa. However, as the disease progresses, this therapeutic option becomes less effective and can be accompanied by levodopa-induced complications. On the other hand, several other neuronal pathways have been implicated in the pathological mechanisms of PD. In this context, the development of alternative therapeutic options that modulate non-dopaminergic targets is emerging as a major goal in the field. In a phenotypic-based screen in a zebrafish model of PD, we identified tapentadol as a candidate molecule for PD. The therapeutic potential of an agent that modulates the opioid and noradrenergic systems has not been explored, despite the implication of both neuronal pathways in parkinsonism. Therefore, we assessed the therapeutic properties of this µ-opioid receptor agonist and norepinephrine reuptake inhibitor in the 6-hydroxydopamine mouse model of parkinsonism. We further submitted 6-hydroxydopamine-lesioned mice to chronic treatment with levodopa and evaluated the effects of tapentadol during levodopa OFF states and on levodopa-induced dyskinesia. Importantly, we found that tapentadol halted the aggravation of dyskinesia and improved the motor impairments during levodopa OFF states. Altogether, our findings raise the hypothesis that concomitant modulation of µ-opioid receptor and norepinephrine transporter might constitute relevant intervention strategies in PD and that tapentadol holds therapeutic potential that may be translated into the clinical practice.

From OFF to ON—Treating OFF Episodes in Parkinson’s Disease

In Parkinson’s disease (PD), OFF episodes continue to present a serious burden for patients, and their effective management remains a substantial unmet clinical need. Understanding of the pathophysiology of OFF episodes has advanced in recent years, providing valuable insights for improved treatments. OFF episodes generally appear 3–5 years after starting levodopa treatment, but can begin much earlier. They are characterized by motor symptoms (including tremor, rigidity, slowness, incoordination, and weakness) and are almost always associated with some non-motor symptoms (including psychological symptoms, pain, urinary problems, swallowing difficulties, and shortness of breath). In PD, higher doses of levodopa are associated with increased risk of motor and non-motor complications, which are notable limitations for longterm therapy. Their occurrence is associated with intermittent levodopa delivery and consequent fluctuating plasma levels. These issues can be offset using lower levodopa doses where possible, incremental dose increases, and combinations of levodopa with other pharmacological agents. OFF episodes in PD can be caused by gastroparesis and/or by Helicobacter pylori infection, which delays delivery of levodopa. These issues can be addressed using new formulations for continuous intrajejunal administration. In addition, pen injector, intranasal, and inhaled dosing systems have been studied and may provide relief via non-intestinal routes. Other approaches include deep-brain stimulation, which is effective but is restricted by costs and potential adverse events. This report presents the highlights of a satellite symposium held at the 14th International Conference on Alzheimer’s & Parkinson’s Diseases (AD/PD™ 2019), Lisbon, Portugal, which discussed the nature of OFF episodes in PD, associated risk factors and the potential of current and future treatments to effectively manage them and increase ON time.

Contemporary Options for the Management of Motor Complications in Parkinson's Disease: Updated Clinical Review

Parkinson's disease (PD) is a chronic, progressive condition affecting around 1% of the population older than 60 years. Upon long-term treatment with levodopa, the mainstay of treatment in PD, most patients, especially younger ones exposed to higher doses, will experience symptoms related to end-of-dose deterioration, peak-dose dyskinesias, and other motor fluctuations. Therapeutic strategies are grounded on modification of oral levodopa pharmacokinetics to extend levodopa benefit and development of new routes of drug delivery (e.g., levodopa/carbidopa intestinal gel infusion) or long-acting formulations of existing dopaminergic drugs to prolong the duration of striatal dopamine receptors stimulation. As our understanding of the pathophysiology of motor complications evolves, our therapeutic armamentarium is actively expanding and the focus of research is now actively pointing to the new non-dopaminergic agents acting both within the basal ganglia and in other brain regions (e.g., drugs acting on glutamate, GABA, serotonin, and calcium channels). Despite the fact that trials comparing the different therapeutic strategies are lacking, we aimed at devising practical evidence- and experience-guided suggestions for the clinical management of motor complications, emphasizing that this should always be an individualized endeavor. This review summarizes the pharmacological management of motor complications in PD, including new formulations and routes of delivery, and the newer released drugs such as istradefylline, opicapone, safinamide, and zonisamide. Advanced therapeutic strategies for selected cases such as treatment with apomorphine and surgical techniques (deep brain stimulation) are also discussed. A comprehensive knowledge of the available options and evidence is fundamental for the successful management of these challenging complications.

From medications to surgery: advances in the treatment of motor complications in Parkinson's disease

Motor complications are responsible for the large burden of disability and poor quality of life in Parkinson’s disease (PD). The pulsatile nature of stimulation with oral dopaminergic therapies due to relatively short pharmacokinetic profiles and dysfunctional gastrointestinal absorption have been attributed to the development of PD motor complications. In this review, we will provide an overview of the pharmacologic and surgical therapies currently available and under investigation for the treatment of motor fluctuations and dyskinesia.

Levodopa-induced skin disorders in patients with Parkinson disease: a systematic literature review approach

The use of levodopa for treatment of Parkinson's disease is a well-established clinical practice. Data about the true incidence and severity of cutaneous complications associated with the use of levodopa are largely lacking. Aim of this review was to evaluate the quality of evidence referring to the skin disorders caused by levodopa treatment for Parkinson's disease. Thirty of 1084 studies were included; 8 randomized controlled trials and 22 case reports in a total of 2749 patients. Malignant melanoma was the most frequent oral levodopa-related skin disorder followed by allergic cutaneous reactions, alopecia, vitiligo, skin hyperpigmentation, Laugier-Hunziker syndrome, Henoch-Schönlein syndrome, pseudobullous morphea and scleroderma-like illness. Naranjo scores ranged from 2 to 8. Regarding levodopa clinical trials, the most frequent skin complication was peripheral edema, followed by malignant melanoma. Although evidence is not robust, melanoma is the most frequent and possible fatal levodopa-associated skin disorder, while other skin allergic or immunological reactions are less common and reversible. Although levodopa treatment may induce melanogenesis and promote melanomagenesis, existing evidence does not support an association between levodopa therapy and induction or progression of malignant melanoma. The suggested association with melanoma may reflect the well-documented association of Parkinson's disease with melanoma rather than the exposure to the drug. Nevertheless, until a solid conclusion can be drawn, the use of levodopa in the context of malignant melanoma should be considered with caution. Well-designed prospective studies are needed to determine the cause and effect relationship between levodopa and skin disorders.