Catechol-O-Methyltransferase Inhibitors in Parkinson’s Disease

Evolving Landscape of Parkinson's Disease Research: Challenges and Perspectives

Parkinson's disease (PD) is a progressive neurodegenerative disorder that primarily affects movement. It occurs due to a gradual deficit of dopamine-producing brain cells, particularly in the substantia nigra. The precise etiology of PD is not fully understood, but it likely involves a combination of genetic and environmental factors. The therapies available at present alleviate symptoms but do not stop the disease's advancement. Research endeavors are currently directed at inventing disease-controlling therapies that aim at the inherent mechanisms of PD. PD biomarker breakthroughs hold enormous potential: earlier diagnosis, better monitoring, and targeted treatment based on individual response could significantly improve patient outcomes and ease the burden of this disease. PD research is an active and evolving field, focusing on understanding disease mechanisms, identifying biomarkers, developing new treatments, and improving care. In this report, we explore data from the CAS Content Collection to outline the research progress in PD. We analyze the publication landscape to offer perspective into the latest expertise advancements. Key emerging concepts are reviewed and strategies to fight disease evaluated. Pharmacological targets, genetic risk factors, as well as comorbid diseases are explored, and clinical usage of products against PD with their production pipelines and trials for drug repurposing are examined. This review aims to offer a comprehensive overview of the advancing landscape of the current understanding about PD, to define challenges, and to assess growth prospects to stimulate efforts in battling the disease.

Decoding Neurodegeneration: A Review of Molecular Mechanisms and Therapeutic Advances in Alzheimer's, Parkinson's, and ALS

Neurodegenerative diseases, such as Alzheimer's, Parkinson's, ALS, and Huntington's, remain formidable challenges in medicine, with their relentless progression and limited therapeutic options. These diseases arise from a web of molecular disturbances-misfolded proteins, chronic neuroinflammation, mitochondrial dysfunction, and genetic mutations-that slowly dismantle neuronal integrity. Yet, recent scientific breakthroughs are opening new paths to intervene in these once-intractable conditions. This review synthesizes the latest insights into the underlying molecular dynamics of neurodegeneration, revealing how intertwined pathways drive the course of these diseases. With an eye on the most promising advances, we explore innovative therapies emerging from cutting-edge research: nanotechnology-based drug delivery systems capable of navigating the blood-brain barrier, gene-editing tools like CRISPR designed to correct harmful genetic variants, and stem cell strategies that not only replace lost neurons but foster neuroprotective environments. Pharmacogenomics is reshaping treatment personalization, enabling tailored therapies that align with individual genetic profiles, while molecular diagnostics and biomarkers are ushering in an era of early, precise disease detection. Furthermore, novel perspectives on the gut-brain axis are sparking interest as mounting evidence suggests that microbiome modulation may play a role in reducing neuroinflammatory responses linked to neurodegenerative progression. Taken together, these advances signal a shift toward a comprehensive, personalized approach that could transform neurodegenerative care. By integrating molecular insights and innovative therapeutic techniques, this review offers a forward-looking perspective on a future where treatments aim not just to manage symptoms but to fundamentally alter disease progression, presenting renewed hope for improved patient outcomes.

The development of paliperidone nanocrystals for the treatment of schizophrenia

Schizophrenia is a complex and chronic psychiatric disorder that significantly impacts patients' quality of life. Ranking 12th among 310 diseases and injuries that result in disability, the number of patients suffering from schizophrenia continues to rise, emphasizing the urgent need for developing effective treatments. Despite the availability of effective antipsychotic drugs, over 80% of patients taking oral antipsychotics experience relapses, primarily caused by non-adherence as the high dosing frequency is required. In this review, we discuss about schizophrenia, its incidence, pathological causes, influencing factors, and the challenges of the current medications. Specifically, we explore nanocrystal technology and its application to paliperidone, making it one of the most successful long-acting antipsychotic drugs introduced to the market. We highlight the clinical advantages of paliperidone nanocrystals, including improved adherence, efficacy, long-term outcomes, patient satisfaction, safety, and cost-effectiveness. Additionally, we address the physicochemical factors influencing the drug's half-life, which crucially contribute to long-acting medications. Further studies on nanocrystal-based long-acting medications are crucial for enhancing their effectiveness and reliability. The successful development of paliperidone nanocrystals holds great promise as a significant approach for drug development, with potential applications for other chronic disease management.

Clinical pharmacokinetics of levodopa and relevant add-on therapies for Parkinson's disease

INTRODUCTION

Parkinson's disease is a chronic neurodegenerative disease entity characterized by heterogeneity of symptoms and progression. Levodopa is an efficacious and well tolerated dopamine substituting drug for its therapy. Its O-methylation and generation of 3-O-methyldopa is enhanced by levodopa/dopa decarboxylase inhibitor formulations. Additional inhibition of catechol-O-methyltransferase is the relevant add on therapy for levodopa application. This pharmacologic approach increases the plasma appearance of levodopa and reduces 3-O-methyldopa synthesis. Available marketed compounds are entacapone, tolcapone and opicapone. Data on their effects on levodopa pharmacokinetics in patients are rare.

AREAS COVERED

This review describes the impact of this add-on therapy on the pharmacokinetic profile of levodopa and 3-O-methyldopa in plasma. The rationale was to perform a comparison with data from previously published pharmacokinetic trials with a standardized one time intake of levodopa/carbidopa without and with the available catechol-O-methyltransferase inhibitors.

EXPERT OPINION

Results of this analysis identified opicapone as the most efficacious inhibitor of catechol-O-methyltransferase in terms of changes of levodopa plasma concentrations. Opicapone induced higher levodopa plasma levels compared with the ones following application of levodopa/carbidopa alone or combined with entacapone or tolcapone. Co-administration of opicapone with its once daily intake regimen may support the efficacy of subcutaneous and intrajejunal levodopa infusions.

Synthesis, electrochemical properties, and antioxidant activity of sterically hindered catechols with 1,3,4-oxadiazole, 1,2,4-triazole, thiazole or pyridine fragments

A series of new RS-, RS-CH2- and R2N-CH2-functionalized сatechols with heterocyclic fragments such as 1,3,4-oxadiazole, 1,2,4-triazole, thiazole, or pyridine were synthesized by the reaction of 3,5-di-tert-butyl-o-benzoquinone or 3,5-di-tert-butyl-6-methoxymethylcatechol with different heterocyclic thiols. The S-functionalized catechols were prepared by the Michael reaction from 3,5-di-tert-butyl-o-benzoquinone and the corresponding thiols. The starting reagents such as substituted 1,3,4-oxadiazole-2-thiols and 4H-triazole-3-thiols are characterized by thiol-thione tautomerism, therefore their reactions with 3,5-di-tert-butyl-6-methoxymethylcatechol can proceed at the sulfur or nitrogen atom. In the case of mercapto-derivatives of thiazole or pyridine, this process leads to the formation of the corresponding thioethers with a methylene linker. At the same time, thiolated 1,3,4-oxadiazole or 1,2,4-triazole undergo alkylation at the nitrogen atom in the reaction with 3,5-di-tert-butyl-6-methoxymethylcatechol to form the corresponding thiones. The yield of reaction products ranges from 42 to 80%. The crystal structures of catechols with 3-nitropyridine or 1,3,4-oxadiazole-2(3H)-thione moieties were established by single-crystal X-ray analysis. The possibility of forming intra- and intermolecular hydrogen bonds has been established for these compounds. The electrochemical behavior of the studied compounds is influenced by several factors: the nature of the heterocycle and its substituents, the presence of a sulfur atom in the catechol ring, or a thione group in the heterocyclic core. The radical scavenging activity and antioxidant properties were determined using the reaction with synthetic radicals, the cupric reducing antioxidant capacity assay, the inhibition process of superoxide radical anion formation by xanthine oxidase, and the process of lipid peroxidation of rat liver (Wistar) homogenates in vitro.

Disease Stage and Motor Fluctuation Duration Predict Drug Tolerability: A Real-Life, Prospective Italian Multicenter Study on the Use of Opicapone in Parkinson's Disease

BACKGROUND

Opicapone is a third-generation catechol-O-methyl-transferase inhibitor currently used for the treatment of motor fluctuations in Parkinson's disease. Its benefit and safety have been established by clinical trials; however, data about its use in a real-life context, and particularly in an Italian population of patients with Parkinson's disease, are missing.

OBJECTIVES

We aimed to gather data about the real-life tolerability/safety of opicapone when used for the treatment of Parkinson's disease-related motor fluctuations.

METHODS

We enrolled 152 consecutive patients with Parkinson's disease and followed them for 2 years after opicapone introduction. We obtained baseline clinical and demographical information, including disease duration, stage, phenotype, as well as axial and non-motor symptoms. We collected the reasons for any treatment interruption and adverse events emerging after opicapone introduction.

RESULTS

Eighty-nine (58%) patients reported adverse events and 46 (30%) patients discontinued the treatment. Adverse events occurred less frequently in "earlier" patients accordingly to the disease course and L-Dopa treatment pathway; a motor fluctuation duration ≥12 months and Hoehn and Yahr scale score ≥2.5 were the main predictors of therapy withdrawal.

CONCLUSIONS

This study confirms the good tolerability/safety profile of opicapone in a real-life setting and provides country-specific data for Italian patients with Parkinson's disease.

Sika Deer Velvet Antler Peptide Exerts Neuroprotective Effect in a Parkinson's Disease Model via Regulating Oxidative Damage and Gut Microbiota

Parkinson's disease (PD) is the second most common neurodegenerative disorder globally. Recognizing the potential of velvet antler in the nervous system, as shown in numerous studies, this research was aimed at evaluating the neuroprotective effects of Sika Deer velvet antler peptide (VAP), along with the underlying mechanisms in neurotoxin-induced PD models. Initially, a peptidomic analysis of the VAP, which comprised 189 varieties of peptides, was conducted using LC-MS. Nine sequences were identified as significant using Proteome Discoverer 2.5 software. In a cellular model of PD, where PC12 cells are treated with the neurotoxin 1-methyl-4-phenylpyridinium (MPP+), the administration of the VAP reduced the cell damage and apoptosis induced by MPP+. This protective effect was associated with a decrease in oxidative stress. This protective mechanism was found to be mediated through the activation of the SIRT1-dependent Akt/Nrf2/HO-1-signaling pathway. In animal models, specifically in mice with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD, the administration of the VAP effectively reduced the dopaminergic neuron damage and reversed the neurobehavioral deficits. They also diminished microglia activation and apoptosis, all without any noticeable adverse effects. Additionally, the VAP was observed to beneficially alter the gut microbiota, as marked by an increase in the abundances of Prevotellaceae, Helicobacteraceae, and Prevotella. These findings suggest that VAP exerts its neuroprotective effect against neurodegeneration by inhibiting oxidative stress and modulating gut microbiota.

Levodopa-Entacapone-Carbidopa Intestinal Gel Treatment in Advanced Parkinson's Disease: A Single-Center Study of 30 Patients

BACKGROUND

Levodopa-entacapone-carbidopa intestinal gel (LECIG) is a novel device assisted treatment option for advanced Parkinson's disease (PD). It has been available in Finland since 2020. There is paucity of scientific studies considering LECIG treatment in clinical practice.

OBJECTIVES

Objectives of this study were to evaluate the changes in medication, adverse events and early discontinuations of LECIG treatment in real life clinical practice.

METHODS

The records of 30 consecutive patients, who received LECIG between years 2020 and 2022 in Helsinki University Hospital, were retrospectively analyzed. Data considering changes in medication, discontinuations, and adverse events during the first six months of LECIG treatment was collected.

RESULTS

Mean levodopa equivalent daily dose (LEDD) rose significantly between baseline before LECIG and six months with treatment (1230 mg vs. 1570 mg, P = 0.001). Three patients were discarded during nasojejunal tube test phase and seven discontinued the treatment during six-month follow-up. Most common reasons for discontinuation were difficulty in finding suitable infusion rate and neuropsychiatric problems. Safety issues encountered were similar to those reported with levodopa-carbidopa intestinal gel (LCIG) treatment. One case of rhabdomyolysis due to severe dyskinesia during LECIG treatment was observed. Patients were satisfied with the small size of the pump system.

CONCLUSIONS

LEDD seems to increase during the first months of LECIG treatment. When compared to studies on LCIG, safety profile of LECIG appears similar, but early discontinuation rate is higher than expected. However, long-term studies are lacking. Only clear advantage to LCIG appears to be the smaller LECIG pump size.

Lipid-based nanoparticles for drug delivery in Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder that predominantly affects dopaminergic neurons in the substantia nigra and ventral tegmental area, resulting in symptoms such as tremors, muscle rigidity, bradykinesia, and potential cognitive and affective disturbances. The effective delivery of pharmacological agents to the central nervous system is hindered by various factors, including the restrictive properties of the blood‒brain barrier and blood‒spinal cord barrier, as well as the physicochemical characteristics of the drugs. Traditional drug delivery methods may not provide the therapeutic concentrations necessary for functional restoration in PD patients. However, lipid-based nanoparticles (NPs) offer new possibilities for enhancing the bioavailability of established treatment regimens and developing innovative therapies that can modify the course of the disease. This review provides a concise overview of recent advances in lipid-based NP strategies aimed at mitigating specific pathological mechanisms relevant to PD progression. This study also explores the potential applications of nanotechnological innovations in the development of advanced treatment modalities for individuals with PD.

Real-world evidence on levodopa dose escalation in patients with Parkinson's disease treated with istradefylline

OBJECTIVE

Istradefylline, a selective adenosine A2A receptor antagonist, is indicated in the US and Japan as adjunctive treatment to levodopa/decarboxylase inhibitors in adults with Parkinson's disease (PD) experiencing OFF time. This study aimed to observe patterns of dose escalation of levodopa over time in patients initiated on istradefylline.

METHODS

Using Japanese electronic health record data, interrupted time series analyses were used to compare levodopa daily dose (LDD, mg/day) gradients in patients before and after initiation of istradefylline. Data were analyzed by period relative to istradefylline initiation (Month 1): pre-istradefylline (Months -72 to 0), early istradefylline (Months 1 to 24), and late istradefylline (Months 25 to 72). Subgroup analyses included LDD before istradefylline initiation (<400, ≥400 to <600, ≥600 mg/day) and treatment with or without monoamine oxidase-B (MAO-B) inhibitors, catechol-O-methyltransferase (COMT) inhibitors, or dopamine agonists before istradefylline initiation.

RESULTS

The analysis included 4026 patients; mean (SD) baseline LDD was 419.27 mg (174.19). Patients receiving ≥600 mg/day levodopa or not receiving MAO-B inhibitors or COMT inhibitors demonstrated a significant reduction in LDD increase gradient for pre-istradefylline vs late-phase istradefylline (≥600 mg/day levodopa, -6.259 mg/day each month, p<0.001; no MAO-B inhibitors, -1.819 mg/day each month, p = 0.004; no COMT inhibitors, -1.412 mg/day each month, p = 0.027).

CONCLUSIONS

This real-world analysis of Japanese prescription data indicated that slowing of LDD escalation was observed in patients initiated on istradefylline, particularly in those receiving ≥600 mg/day levodopa, suggesting istradefylline may slow progressive LDD increases. These findings suggest that initiating istradefylline before other levodopa-adjunctive therapies may mitigate LDD increases, potentially reducing occurrence or severity of levodopa-induced complications in long-term istradefylline treatment.

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.

Liposome-Derived Nanosystems for the Treatment of Behavioral and Neurodegenerative Diseases: The Promise of Niosomes, Transfersomes, and Ethosomes for Increased Brain Drug Bioavailability

Psychiatric and neurodegenerative disorders are amongst the most prevalent and debilitating diseases, but current treatments either have low success rates, greatly due to the low permeability of the blood-brain barrier, and/or are connected to severe side effects. Hence, new strategies are extremely important, and here is where liposome-derived nanosystems come in. Niosomes, transfersomes, and ethosomes are nanometric vesicular structures that allow drug encapsulation, protecting them from degradation, and increasing their solubility, permeability, brain targeting, and bioavailability. This review highlighted the great potential of these nanosystems for the treatment of Alzheimer's disease, Parkinson's disease, schizophrenia, bipolar disorder, anxiety, and depression. Studies regarding the encapsulation of synthetic and natural-derived molecules in these systems, for intravenous, oral, transdermal, or intranasal administration, have led to an increased brain bioavailability when compared to conventional pharmaceutical forms. Moreover, the developed formulations proved to have neuroprotective, anti-inflammatory, and antioxidant effects, including brain neurotransmitter level restoration and brain oxidative status improvement, and improved locomotor activity or enhancement of recognition and working memories in animal models. Hence, albeit being relatively new technologies, niosomes, transfersomes, and ethosomes have already proven to increase the brain bioavailability of psychoactive drugs, leading to increased effectiveness and decreased side effects, showing promise as future therapeutics.

Opicapone versus entacapone: Head-to-head retrospective data-based comparison of healthcare resource utilization in people with Parkinson's disease new to catechol-O-methyltransferase (COMT) inhibitor treatment

BACKGROUND AND PURPOSE

Motor fluctuations are a significant driver of healthcare resource utilization (HCRU) in people with Parkinson's disease (pwPD). A common management strategy is to include catechol-O-methyltransferase (COMT) inhibition with either opicapone or entacapone in the levodopa regimen. However, to date, there has been a lack of head-to-head data comparing the two COMT inhibitors in real-world settings. The aim of this study was to evaluate changes in HCRU and effect on sleep medications when opicapone was initiated as first COMT inhibitor versus entacapone.

METHODS

In this retrospective cohort study, we assessed HCRU outcomes in pwPD naïve to COMT inhibition via UK electronic healthcare records (Clinical Practice Research Datalink and Hospital Episodes Statistics databases, June 2016 to December 2019). HCRU outcomes were assessed before (baseline) and after COMT inhibitor prescription at 0-6 months, 7-12 months and 13-18 months. Opicapone-treated pwPD were algorithm-matched (1:4) to entacapone-treated pwPD.

RESULTS

By 6 months, treatment with opicapone resulted in 18.5% fewer neurology outpatient visits compared to entacapone treatment; this effect was maintained until the last follow-up (18 months). In the opicapone group, the mean levodopa equivalent daily dose decreased over the first year and then stabilized, whereas the entacapone-treated group showed an initial decrease in the first 6 months followed by a dose increase between 7 and 18 months. Neither COMT inhibitor had a significant impact on sleep medication use.

CONCLUSIONS

This head-to-head study is the first to demonstrate, using 'real-world' data, that initiating COMT inhibition with opicapone is likely to decrease the need for post-treatment HCRU versus initiation of COMT inhibition with entacapone.

Unraveling the impact of 27-hydroxycholesterol in autoimmune diseases: Exploring promising therapeutic approaches

The role of 27-hydroxycholesterol (27-OHC) in autoimmune diseases has become a subject of intense research in recent years. This oxysterol, derived from cholesterol, has been identified as a significant player in modulating immune responses and inflammation. Its involvement in autoimmune pathogenesis has drawn attention to its potential as a therapeutic target for managing autoimmune disorders effectively. 27-OHC, an oxysterol derived from cholesterol, has emerged as a key player in modulating immune responses and inflammatory processes. It exerts its effects through various mechanisms, including activation of nuclear receptors, interaction with immune cells, and modulation of neuroinflammation. Additionally, 27-OHC has been implicated in the dysregulation of lipid metabolism, neurotoxicity, and blood-brain barrier (BBB) disruption. Understanding the intricate interplay between 27-OHC and autoimmune diseases, particularly neurodegenerative disorders, holds promise for developing targeted therapeutic strategies. Additionally, emerging evidence suggests that 27-OHC may interact with specific receptors and transcription factors, thus influencing gene expression and cellular processes in autoimmune disorders. Understanding the intricate mechanisms by which 27-OHC influences immune dysregulation and tissue damage in autoimmune diseases is crucial for developing targeted therapeutic interventions. Further investigations into the molecular pathways and signaling networks involving 27-OHC are warranted to unravel its full potential as a therapeutic target in autoimmune diseases, thereby offering new avenues for disease intervention and management.

Rational Design of Multifunctional Ferulic Acid Derivatives Aimed for Alzheimer's and Parkinson's Diseases

Ferulic acid has numerous beneficial effects on human health, which are frequently attributed to its antioxidant behavior. In this report, many of them are reviewed, and 185 new ferulic acid derivatives are computationally designed using the CADMA-Chem protocol. Consequently, their chemical space was sampled and evaluated. To that purpose, selection and elimination scores were used, which are built from a set of descriptors accounting for ADME properties, toxicity, and synthetic accessibility. After the first screening, 12 derivatives were selected and further investigated. Their potential role as antioxidants was predicted from reactivity indexes directly related to the formal hydrogen atom transfer and the single electron transfer mechanisms. The best performing molecules were identified by comparisons with the parent molecule and two references: Trolox and α-tocopherol. Their potential as polygenic neuroprotectors was investigated through the interactions with enzymes directly related to the etiologies of Parkinson's and Alzheimer's diseases. These enzymes are acetylcholinesterase, catechol-O-methyltransferase, and monoamine oxidase B. Based on the obtained results, the most promising candidates (FA-26, FA-118, and FA-138) are proposed as multifunctional antioxidants with potential neuroprotective effects. The findings derived from this investigation are encouraging and might promote further investigations on these molecules.

Opicapone Pharmacokinetics and Effects on Catechol- O -Methyltransferase Activity and Levodopa Pharmacokinetics in Patients With Parkinson Disease Receiving Carbidopa/Levodopa

OBJECTIVES

Levodopa (LD) administered with dopa decarboxylase inhibitor is predominantly metabolized in the periphery by catechol- O -methyltransferase (COMT) to 3- O -methyldopa (3-OMD). Catechol- O -methyltransferase inhibition can improve treatment outcomes by decreasing variability in circulating LD concentrations. Opicapone is a once-daily COMT inhibitor approved in the US adjunctive to carbidopa (CD)/LD in patients with Parkinson disease experiencing "OFF" episodes. This study aimed to evaluate the pharmacokinetics and pharmacodynamics of once-daily opicapone 50 mg adjunctive to CD/LD in patients with stable Parkinson disease.

METHODS

Once-daily opicapone 50 mg was administered the evenings of days 1 to 14. Participants were randomized to receive CD/LD (25/100 mg) every 3 or 4 hours (Q3H or Q4H). Participants received Q3H or Q4H CD/LD on days 1, 2, and 15 and their usual CD/LD regimen on other days. Serial blood samples were collected to determine plasma opicapone, LD, and 3-OMD concentrations and erythrocyte soluble COMT (S-COMT) activity. The effects of opicapone on S-COMT, LD, and 3-OMD were assessed. Mean (SD) values are presented.

RESULTS

Sixteen participants were enrolled. At steady-state (day 14), opicapone Cmax (peak plasma concentration) and AUC 0-last (area under the curve-time curve) were 459 ± 252 ng/mL and 2022 ± 783 ng/mL·h, respectively. Maximum COMT inhibition was 83.4 ± 4.9% of baseline on day 14. After opicapone administration, LD total AUC, peak concentration, and trough concentration increased; peak-to-trough fluctuation index decreased. Correspondingly, 3-OMD total AUC, peak concentration, and trough concentration decreased.

CONCLUSIONS

Adding once-daily opicapone 50 mg to LD resulted in marked and extended COMT inhibition, which increased systemic exposure to LD. These changes translated into higher trough concentrations and decreased peak-to-trough fluctuations for LD.

Current Treatments and New, Tentative Therapies for Parkinson’s Disease

Parkinson’s disease (PD) is a neurodegenerative pathology, the origin of which is associated with the death of neuronal cells involved in the production of dopamine. The prevalence of PD has increased exponentially. The aim of this review was to describe the novel treatments for PD that are currently under investigation and study and the possible therapeutic targets. The pathophysiology of this disease is based on the formation of alpha-synuclein folds that generate Lewy bodies, which are cytotoxic and reduce dopamine levels. Most pharmacological treatments for PD target alpha-synuclein to reduce the symptoms. These include treatments aimed at reducing the accumulation of alpha-synuclein (epigallocatechin), reducing its clearance via immunotherapy, inhibiting LRRK2, and upregulating cerebrosidase (ambroxol). Parkinson’s disease continues to be a pathology of unknown origin that generates a significant social cost for the patients who suffer from it. Although there is still no definitive cure for this disease at present, there are numerous treatments available aimed at reducing the symptomatology of PD in addition to other therapeutic alternatives that are still under investigation. However, the therapeutic approach to this pathology should include a combination of pharmacological and non-pharmacological strategies to maximise outcomes and improve symptomatological control in these patients. It is therefore necessary to delve deeper into the pathophysiology of the disease in order to improve these treatments and therefore the quality of life of the patients.

Signaling pathways in Parkinson's disease: molecular mechanisms and therapeutic interventions

Parkinson's disease (PD) is the second most common neurodegenerative disease worldwide, and its treatment remains a big challenge. The pathogenesis of PD may be related to environmental and genetic factors, and exposure to toxins and gene mutations may be the beginning of brain lesions. The identified mechanisms of PD include α-synuclein aggregation, oxidative stress, ferroptosis, mitochondrial dysfunction, neuroinflammation, and gut dysbiosis. The interactions among these molecular mechanisms complicate the pathogenesis of PD and pose great challenges to drug development. At the same time, the diagnosis and detection of PD are also one of obstacles to the treatment of PD due to its long latency and complex mechanism. Most conventional therapeutic interventions for PD possess limited effects and have serious side effects, heightening the need to develop novel treatments for this disease. In this review, we systematically summarized the pathogenesis, especially the molecular mechanisms of PD, the classical research models, clinical diagnostic criteria, and the reported drug therapy strategies, as well as the newly reported drug candidates in clinical trials. We also shed light on the components derived from medicinal plants that are newly identified for their effects in PD treatment, with the expectation to provide the summary and outlook for developing the next generation of drugs and preparations for PD therapy.

Translational molecular imaging and drug development in Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disorder that primarily affects elderly people and constitutes a major source of disability worldwide. Notably, the neuropathological hallmarks of PD include nigrostriatal loss and the formation of intracellular inclusion bodies containing misfolded α-synuclein protein aggregates. Cardinal motor symptoms, which include tremor, rigidity and bradykinesia, can effectively be managed with dopaminergic therapy for years following symptom onset. Nonetheless, patients ultimately develop symptoms that no longer fully respond to dopaminergic treatment. Attempts to discover disease-modifying agents have increasingly been supported by translational molecular imaging concepts, targeting the most prominent pathological hallmark of PD, α-synuclein accumulation, as well as other molecular pathways that contribute to the pathophysiology of PD. Indeed, molecular imaging modalities such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT) can be leveraged to study parkinsonism not only in animal models but also in living patients. For instance, mitochondrial dysfunction can be assessed with probes that target the mitochondrial complex I (MC-I), while nigrostriatal degeneration is typically evaluated with probes designed to non-invasively quantify dopaminergic nerve loss. In addition to dopaminergic imaging, serotonin transporter and N-methyl-D-aspartate (NMDA) receptor probes are increasingly used as research tools to better understand the complexity of neurotransmitter dysregulation in PD. Non-invasive quantification of neuroinflammatory processes is mainly conducted by targeting the translocator protein 18 kDa (TSPO) on activated microglia using established imaging agents. Despite the overwhelming involvement of the brain and brainstem, the pathophysiology of PD is not restricted to the central nervous system (CNS). In fact, PD also affects various peripheral organs such as the heart and gastrointestinal tract - primarily via autonomic dysfunction. As such, research into peripheral biomarkers has taken advantage of cardiac autonomic denervation in PD, allowing the differential diagnosis between PD and multiple system atrophy with probes that visualize sympathetic nerve terminals in the myocardium. Further, α-synuclein has recently gained attention as a potential peripheral biomarker in PD. This review discusses breakthrough discoveries that have led to the contemporary molecular concepts of PD pathophysiology and how they can be harnessed to develop effective imaging probes and therapeutic agents. Further, we will shed light on potential future trends, thereby focusing on potential novel diagnostic tracers and disease-modifying therapeutic interventions.

Gastrointestinal barriers to levodopa transport and absorption in Parkinson's disease

Levodopa is the gold standard for the symptomatic treatment of Parkinson's disease (PD). There are well documented motor and non-motor fluctuations, however, that occur almost inevitably once levodopa is started after a variable period in people with PD. Whilst brain neurodegenerative processes play a part in the pathogenesis of these fluctuations, a range of barriers across the gastrointestinal (GI) tract can alter levodopa pharmacokinetics, ultimately contributing to non-optimal levodopa response and symptoms fluctuations. GI barriers to levodopa transport and absorption include dysphagia, delayed gastric emptying, constipation, Helicobacter pylori infection, small intestinal bacterial overgrowth and gut dysbiosis. In addition, a protein-rich diet and concomitant medication intake can further alter levodopa pharmacokinetics. This can result in unpredictable or sub-optimal levodopa response, 'delayed on' or 'no on' phenomena. In this narrative review, we provided an overview on the plethora of GI obstacles to levodopa transport and absorption in PD and their implications on levodopa pharmacokinetics and development of motor fluctuations. In addition, management strategies to address GI dysfunction in PD are highlighted, including use of non-oral therapies to bypass the GI tract.

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.

Alzheimer's and Parkinson's disease therapies in the clinic

Alzheimer's disease (AD) and Parkinson's disease (PD) are the most prevalent neurodegenerative diseases, affecting millions and costing billions each year in the United States alone. Despite tremendous progress in developing therapeutics that manage the symptoms of these two diseases, the scientific community has yet to develop a treatment that effectively slows down, inhibits, or cures neurodegeneration. To gain a better understanding of the current therapeutic frontier for the treatment of AD and PD, we provide a review on past and present therapeutic strategies for these two major neurodegenerative disorders in the clinical trial process. We briefly recap currently US Food and Drug Administration-approved therapies, and then explore trends in clinical trials across the variables of therapy mechanism of disease intervention, administration route, use of delivery vehicle, and outcome measures, across the clinical phases over time for "Drug" and "Biologic" therapeutics. We then present the success rate of past clinical trials and analyze the intersections in therapeutic approaches for AD and PD, revealing the shift in clinical trials away from therapies targeting neurotransmitter systems that provide symptomatic relief, and towards anti-aggregation, anti-inflammatory, anti-oxidant, and regeneration strategies that aim to inhibit the root causes of disease progression. We also highlight the evolving distribution of the types of "Biologic" therapies investigated, and the slowly increasing yet still severe under-utilization of delivery vehicles for AD and PD therapeutics. We then briefly discuss novel preclinical strategies for treating AD and PD. Overall, this review aims to provide a succinct overview of the clinical landscape of AD and PD therapies to better understand the field's therapeutic strategy in the past and the field's evolution in approach to the present, to better inform how to effectively treat AD and PD in the future.

Computational Studies Applied to Linalool and Citronellal Derivatives Against Alzheimer's and Parkinson's Disorders: A Review with Experimental Approach

Alzheimer's and Parkinson's are neurodegenerative disorders that affect a great number of people around the world, seriously compromising the quality of life of individuals, due to motor and cognitive damage. In these diseases, pharmacological treatment is used only to alleviate symptoms. This emphasizes the need to discover alternative molecules for use in prevention. Using Molecular Docking, this review aimed to evaluate the anti-Alzheimer's and anti-Parkinson's activity of linalool and citronellal, as well as their derivatives. Before performing Molecular Docking simulations, the compounds' pharmacokinetic characteristics were evaluated. For Molecular Docking, 7 chemical compounds derived from citronellal, and 10 compounds derived from linalool, and molecular targets involved in Alzheimer's and Parkinson's pathophysiology were selected. According to the Lipinski rules, the compounds under study presented good oral absorption and bioavailability. For toxicity, some tissue irritability was observed. For Parkinson-related targets, the citronellal and linalool derived compounds revealed excellent energetic affinity for α-Synuclein, Adenosine Receptors, Monoamine Oxidase (MAO), and Dopamine D1 receptor proteins. For Alzheimer disease targets, only linalool and its derivatives presented promise against BACE enzyme activity. The compounds studied presented high probability of modulatory activity against the disease targets under study, and are potential candidates for future drugs.

Adverse event profiles of adjuvant treatment with opicapone in Parkinson's disease: A systematic review and meta-analysis

Background: Opicapone, a novel third-generation catechol-O-methyltransferase inhibitor, has demonstrated efficacy in Parkinson's Disease (PD) patients with end-of-dose motor fluctuations. Objective: This study aimed to compare the short-term (<6 months) and long-term (≥6 months) tolerability of opicapone adjuvant treatment in PD patients. Method: Electronic databases including PubMed, Embase, Web of Science and Cochrane library were searched for randomized controlled trials (RCTs) and observational studies. The end points included any treatment-related adverse events (TEAEs), serious TEAEs (SAEs) and treatment discontinuation. A random-effects model was used to generate overall incidences of TEAE. Results: Three RCTs, three RCT extension studies and three open-label studies involving 2177 PD patients were evaluated. In the short-term studies, there were reports of TEAEs with an incidence of ≥5% in individuals treated with opicapone 50 mg, including dyskinesia (14.1%), elevated blood creatine phosphokinase levels (8.0%) and urinary tract infection (6.0%). Any TEAEs, SAEs and treatment discontinuation all occurred at rates of 62.9%, 4.8% and 9.3%, respectively. TEAEs with opicapone 50 mg that were reported by more than 5% of patients in long-term studies included dyskinesia (16.1%), dry mouth (12.1%), medication effect decreased (12.1%), PD exacerbated (7.8%), blood creatine phosphokinase level raised (7.4%), nausea (6.1%) and insomnia (5.1%). The incidence of any TEAEs, SAEs and treatment discontinuation were, correspondingly, 73.2%, 8.7% and 8.4%. Conclusion: These studies demonstrated that opicapone was generally well-tolerated and had a low risk of adverse events, suggesting that it could be a valuable therapeutic choice for people with PD.

Approaching the Gut and Nasal Microbiota in Parkinson's Disease in the Era of the Seed Amplification Assays

Parkinson's disease (PD) is a neurodegenerative disorder often associated with pre-motor symptoms involving both gastrointestinal and olfactory tissues. PD patients frequently suffer from hyposmia, hyposalivation, dysphagia and gastrointestinal dysfunctions. During the last few years it has been speculated that microbial agents could play a crucial role in PD. In particular, alterations of the microbiota composition (dysbiosis) might contribute to the formation of misfolded α-synuclein, which is believed to be the leading cause of PD. However, while several findings confirmed that there might be an important link between intestinal microbiota alterations and PD onset, little is known about the potential contribution of the nasal microbiota. Here, we describe the latest findings on this topic by considering that more than 80% of patients with PD develop remarkable olfactory deficits in their prodromal disease stage. Therefore, the nasal microbiota might contribute to PD, eventually boosting the gut microbiota in promoting disease onset. Finally, we present the applications of the seed amplification assays to the study of the gut and olfactory mucosa of PD patients, and how they could be exploited to investigate whether pathogenic bacteria present in the gut and the nose might promote α-synuclein misfolding and aggregation.

CADMA-Chem: A Computational Protocol Based on Chemical Properties Aimed to Design Multifunctional Antioxidants

A computational protocol aimed to design new antioxidants with versatile behavior is presented. It is called Computer-Assisted Design of Multifunctional Antioxidants and is based on chemical properties (CADMA-Chem). The desired multi-functionality consists of in different methods of antioxidant protection combined with neuroprotection, although the protocol can also be used to pursue other health benefits. The dM38 melatonin derivative is used as a study case to illustrate the protocol in detail. This was found to be a highly promising candidate for the treatment of neurodegeneration, in particular Parkinson's and Alzheimer's diseases. This also has the desired properties of an oral-drug, which is significantly better than Trolox for scavenging free radicals, and has chelates redox metals, prevents the ●OH production, via Fenton-like reactions, repairs oxidative damage in biomolecules (lipids, proteins, and DNA), and acts as a polygenic neuroprotector by inhibiting catechol-O-methyl transferase (COMT), acetylcholinesterase (AChE) and monoamine oxidase B (MAOB). To the best of our best knowledge, CADMA-Chem is currently the only protocol that simultaneously involves the analyses of drug-like behavior, toxicity, manufacturability, versatile antioxidant protection, and receptor-ligand binding affinities. It is expected to provide a starting point that helps to accelerate the discovery of oral drugs with the potential to prevent, or slow down, multifactorial human health disorders.

Unveiling the biopathway for the design of novel COMT inhibitors

Catechol-O-methyltransferase (COMT) is an enzyme responsible for the O-methylation of biologically active catechol-based molecules. It has been associated with several neurological disorders, especially Parkinson's disease (PD), because of its involvement in catecholamine metabolism, and has been considered an important therapeutic target for central nervous system disorders. In this review, we summarize the biophysical, structural, and therapeutical relevance of COMT; the medicinal chemistry behind the development of COMT inhibitors and the application of computer-aided design to support the design of novel molecules; current methodologies for the biosynthesis, isolation, and purification of COMT; and revise existing bioanalytical approaches for the assessment of enzymatic activity in several biological matrices.

An Overview of Methods for L-Dopa Extraction and Analytical Determination in Plant Matrices

L-dopa is a precursor of dopamine used as the most effective symptomatic drug treatment for Parkinson's disease. Most of the L-dopa isolated is either synthesized chemically or from natural sources, but only some plants belonging to the Fabaceae family contain significant amounts of L-dopa. Due to its low stability, the unambiguous determination of L-dopa in plant matrices requires appropriate technologies. Several analytical methods have been developed for the determination of L-dopa in different plants. The most used for quantification of L-dopa are mainly based on capillary electrophoresis or chromatographic methods, i.e., high-performance liquid chromatography (HPLC), coupled to ultraviolet-visible or mass spectrometric detection. HPLC is most often used. This paper aims to give information on the latest developments in the chemical study of L-dopa, emphasizing the extraction, separation and characterization of this compound by chromatographic, electrochemical and spectral techniques. This study can help select the best possible strategy for determining L-dopa in plant matrices using advanced analytical methods.

Chalcones as Potential Ligands for the Treatment of Parkinson's Disease

Along with the increase in life expectancy, a significant increase of people suffering from neurodegenerative diseases (ND) has been noticed. The second most common ND, after Alzheimer’s disease, is Parkinson’s disease (PD), which manifests itself with a number of motor and non-motor symptoms that hinder the patient’s life. Current therapies can only alleviate those symptoms and slow down the progression of the disease, but not effectively cure it. So now, in addition to understanding the mechanism and causes of PD, it is also important to find a powerful way of treatment. It has been proved that in the etiology and course of PD, the essential roles are played by dopamine (DA) (an important neurotransmitter), enzymes regulating its level (e.g., COMT, MAO), and oxidative stress leading to neuroinflammation. Chalcones, due to their “simple” structure and valuable biological properties are considered as promising candidates for treatment of ND, also including PD. Here, we provide a comprehensive review of chalcones and related structures as potential new therapeutics for cure and prevention of PD. For this purpose, three databases (Pubmed, Scopus and Web of Science) were searched to collect articles published during the last 5 years (January 2018–February 2022). Chalcones have been described as promising enzyme inhibitors (MAO B, COMT, AChE), α-synuclein imaging probes, showing anti-neuroinflammatory activity (inhibition of iNOS or activation of Nrf2 signaling), as well as antagonists of adenosine A₁ and/or A_2A receptors. This review focused on the structure–activity relationships of these compounds to determine how a particular substituent or its position in the chalcone ring(s) (ring A and/or B) affects biological activity.

In vitro effects of opicapone on activity of human UDP-glucuronosyltransferases isoforms

Catechol-O-methyltransferase (COMT) inhibitors are widely used as an add-on treatment to levodopa in adults with Parkinson's disease. It has been evidenced that the second-generation COMT inhibitors entacapone and tolcapone are potent inhibitors on human UDP-glucosyltransferases (UGTs), while the effect of the third-generation COMT inhibitor opicapone on human UGTs activities is unclear. The purpose of this study is to systemically investigate the effects of opicapone on human UGTs activities, and also to assess the potential risk of drug-drug interactions (DDIs) associated with opicapone. Our results indicated that opicapone is a broad-spectrum inhibitor of UGTs. Particularly, opicapone exhibited potent inhibition against UGT1A1, 1A7, 1A8, 1A9, and 1A10, with a range of inhibition constant K_i values of 1.31-10.58 µM. Furthermore, the DDI risk was quantitatively predicted by using the in vitro-in vivo extrapolation (IVIVE). The prediction suggested that co-administration of opicapone at 25 mg/day or 50 mg/day with drugs primarily cleared by hepatic UGT1A9 or intestinal UGT1A1, 1A7, 1A8, 1A9, or 1A10 might result in potential DDI via inhibition of intestinal or hepatic UGTs.

Advances in Membrane-Bound Catechol-O-Methyltransferase Stability Achieved Using a New Ionic Liquid-Based Storage Formulation

Membrane-bound catechol-O-methyltransferase (MBCOMT), present in the brain and involved in the main pathway of the catechol neurotransmitter deactivation, is linked to several types of human dementia, which are relevant pharmacological targets for new potent and nontoxic inhibitors that have been developed, particularly for Parkinson’s disease treatment. However, the inexistence of an MBCOMT 3D-structure presents a blockage in new drugs’ design and clinical studies due to its instability. The enzyme has a clear tendency to lose its biological activity in a short period of time. To avoid the enzyme sequestering into a non-native state during the downstream processing, a multi-component buffer plays a major role, with the addition of additives such as cysteine, glycerol, and trehalose showing promising results towards minimizing hMBCOMT damage and enhancing its stability. In addition, ionic liquids, due to their virtually unlimited choices for cation/anion paring, are potential protein stabilizers for the process and storage buffers. Screening experiments were designed to evaluate the effect of distinct cation/anion ILs interaction in hMBCOMT enzymatic activity. The ionic liquids: choline glutamate [Ch][Glu], choline dihydrogen phosphate ([Ch][DHP]), choline chloride ([Ch]Cl), 1- dodecyl-3-methylimidazolium chloride ([C12mim]Cl), and 1-butyl-3-methylimidazolium chloride ([C4mim]Cl) were supplemented to hMBCOMT lysates in a concentration from 5 to 500 mM. A major potential stabilizing effect was obtained using [Ch][DHP] (10 and 50 mM). From the DoE 146% of hMBCOMT activity recovery was obtained with [Ch][DHP] optimal conditions (7.5 mM) at −80 °C during 32.4 h. These results are of crucial importance for further drug development once the enzyme can be stabilized for longer periods of time.

Practical pearls to improve the efficacy and tolerability of levodopa in Parkinson's disease

INTRODUCTION

Levodopa is the most effective medication for the treatment of motor symptoms of Parkinson's disease (PD). Several factors may affect the efficacy and tolerability of levodopa. These include the timing, dosage and administration of levodopa, concomitant drugs, food, PD-associated non motor symptoms, and various neurologic and non-neurologic comorbidities. If not appropriately addressed, these issues may limit levodopa efficacy, tolerability, and compliance.

AREAS COVERED

This article reviews the basics of the metabolism of orally administered levodopa, its side effects, and the factors that may affect its tolerability and efficacy. We provide several practical pearls to improve the tolerability and efficacy of levodopa.

EXPERT OPINION

Protein-rich food delays and reduces levodopa absorption. Hence, levodopa should preferably be administered in a relatively empty stomach. Carbidopa dosing is crucial as it not only enhances the entry of levodopa into the central nervous system, but also reduces levodopa's peripheral adverse effects. Patients experiencing the early side effects such as nausea/vomiting should be prescribed with anti-nausea medications that do not block dopamine receptors. Non-oral routes of administration can be used to obviate persistent gastrointestinal side effects. Implementation of these and other tips may help improve the tolerability and efficacy of levodopa.

The potential protective effects of estradiol and 2-methoxyestradiol in ischemia reperfusion-induced kidney injury in ovariectomized female rats

AIMS

Investigating the impact of 17β estradiol (E2) and its endogenous non-hormonal metabolite 2-methoxyestradiol (2ME) on renal ischemia-reperfusion (RIR) induced kidney injury in ovariectomized (OVX) rats and the role of catechol-O-methyltransferase (COMT) in their effects.

MAIN METHODS

Eighty female rats were allocated into eight groups. Control group, Sham group, OVX group, OVX and RIR group, OVX + RIR + E2 group, OVX + RIR + 2ME group, OVX + RIR + E2 + Entacapone group and OVX + RIR + 2ME + Entacapone group, respectively. Twenty-four hours post RIR, creatinine (Cr) and blood urea nitrogen (BUN) were determined in serum, while malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), Glutathione (GSH), myeloperoxidase (MPO), as well as the expressions of COMT, hypoxia inducible factor-1α (HIF-1α) and tyrosine hydroxylase (TH) were assessed in the kidney tissues.

KEY FINDINGS

Serum Cr, BUN, MPO, as well as HIF-1α and TH expressions were significantly higher with concomitant decrease in COMT expression, SOD and CAT activities and GSH content observed in OVX and RIR group compared to sham group. E2 and 2ME treatment significantly ameliorated all parameters measured in OVX and RIR rats. On the other hand, Entacapone significantly decreased the effect of E2, with no effect on 2ME treatment.

SIGNIFICANCE

E2 ameliorates RIR-induced kidney injury and this effect is mediated, at least in part, via its COMT-mediated conversion to 2ME. Thus, 2ME by the virtue of its pleiotropic pharmacological effects can be used as a safe and effective treatment of RIR injury.

Effects of One-Day Application of Levodopa/Carbidopa/Entacapone versus Levodopa/Carbidopa/Opicapone in Parkinson’s Disease Patients

The catechol-O-methyltransferase inhibitors entacapone and opicapone prolong the efficacy of conventional oral levodopa/dopa decarboxylase inhibitor formulations through an increase in levodopa plasma bioavailability. Catechol-O-methyltransferase inhibitors influence the homocysteine metabolism associated with levodopa/dopa decarboxylase application. The objectives of this study were to compare the impact of additional single-day entacapone or opicapone intake on the pharmacokinetic plasma behaviour of levodopa, 3-O-methyldopa and total homocysteine in 15 Parkinson’s disease patients, with concomitant scoring of motor symptoms, under standardized conditions. The patients received opicapone plus two doses of 100 mg levodopa/carbidopa and, one week later, two doses of levodopa/carbidopa/entacapone or vice versa. Levodopa, 3-O-methyldopa and total homocysteine were determined with reversed-phase high-performance liquid chromatography. Levodopa bioavailability and its maximum concentration were higher with opicapone. The computed peak-to-trough difference was lower after the second levodopa administration with entacapone. The fluctuation index of levodopa did not differ between both conditions. 3-O-methyldopa decreased on both days. Homocysteine levels did not significantly vary between both conditions. A significant homocysteine decrease occurred with entacapone, but not with opicapone. Motor behaviour improved with entacapone, but not with opicapone. Opicapone baseline scores were significantly better, and thus the potential for the improvement in motor symptoms was lower compared with the entacapone condition. The higher levodopa bioavailability with opicapone suggests that it is more efficacious than entacapone for the amelioration of “off” phenomena in fluctuating patients when co-administered with a levodopa/dopa decarboxylase inhibitor regimen. Both compounds prevented an increase in homocysteine, which is a metabolic marker for an impaired capacity in the performance of methylation processes.

Opicapone versus placebo in the treatment of Parkinson’s disease patients with end-of-dose motor fluctuation-associated pain: rationale and design of the randomised, double-blind OCEAN (OpiCapone Effect on motor fluctuations and pAiN) trial

Background

Optimisation of dopaminergic therapy may alleviate fluctuation-related pain in Parkinson’s disease (PD). Opicapone (OPC) is a third-generation, once-daily catechol-O-methyltransferase inhibitor shown to be generally well tolerated and efficacious in reducing OFF-time in two pivotal trials in patients with PD and end-of-dose motor fluctuations. The OpiCapone Effect on motor fluctuations and pAiN (OCEAN) trial aims to investigate the efficacy of OPC 50 mg in PD patients with end-of-dose motor fluctuations and associated pain, when administered as adjunctive therapy to existing treatment with levodopa/dopa decarboxylase inhibitor (DDCi).

Methods

OCEAN is a Phase IV, international, multicentre, randomised, double-blind, placebo-controlled, parallel-group, interventional trial in PD patients with end-of-dose motor fluctuations and associated pain. It consists of a 1-week screening period, 24-week double-blind treatment period and 2-week follow-up period. Eligible patients will be randomised 1:1 to OPC 50 mg or placebo once daily while continuing current treatment with levodopa/DDCi and other chronic, stable anti-PD and/or analgesic treatments. The primary efficacy endpoint is change from baseline in Domain 3 (fluctuation-related pain) of the King’s Parkinson’s disease Pain Scale (KPPS). The key secondary efficacy endpoint is change from baseline in Domain B (anxiety) of the Movement Disorder Society-sponsored Non-Motor rating Scale (MDS-NMS). Additional secondary efficacy assessments include other domains and total scores of the KPPS and MDS-NMS, the Parkinson’s Disease Questionnaire (PDQ-8), the MDS-sponsored Unified Parkinson’s Disease Rating Scale (MDS-UPDRS) Parts III and IV, Clinical and Patient’s Global Impressions of Change, and change in functional status via Hauser’s diary. Safety assessments include the incidence of treatment-emergent adverse events. The study will be conducted in approximately 140 patients from 50 clinical sites in Germany, Italy, Portugal, Spain and the United Kingdom. Recruitment started in February 2021 and the last patient is expected to complete the study by late 2022.

Discussion

The OCEAN trial will help determine whether the use of adjunctive OPC 50 mg treatment can improve fluctuation-associated pain in PD patients with end-of-dose motor fluctuations. The robust design of OCEAN will address the current lack of reliable evidence for dopaminergic-based therapy in the treatment of PD-associated pain.

Trial registration

EudraCT number 2020–001175-32; registered on 2020-08-07.

Neurodegenerative Disorders and the Current State, Pathophysiology, and Management of Parkinson's Disease

In the last few decades, major knowledge has been gained about pathophysiological aspects and molecular pathways behind Parkinson's Disease (PD). Based on neurotoxicological studies and postmortem investigations, there is a general concept of how environmental toxicants (neurotoxins, pesticides, insecticides) and genetic factors (genetic mutations in PD-associated proteins) cause depletion of dopamine from substantia nigra pars compacta region of the midbrain and modulate cellular processes leading to the pathogenesis of PD. α-Synuclein, a neuronal protein accumulation in oligomeric form, called protofibrils, is associated with cellular dysfunction and neuronal death, thus possibly contributing to PD propagation. With advances made in identifying loci that contribute to PD, molecular pathways involved in disease pathogenesis are now clear, and introducing therapeutic strategy at the right time may delay the progression. Biomarkers for PD have helped monitor PD progression; therefore, personalized therapeutic strategies can be facilitated. In order to further improve PD diagnostic and prognostic accuracy, independent validation of biomarkers is required.

Redefining the strategy for the use of COMT inhibitors in Parkinson's disease: the role of opicapone

INTRODUCTION

Levodopa remains the gold-standard Parkinson's disease (PD) treatment, but the inevitable development of motor complications has led to intense activity in pursuit of its optimal delivery.

AREAS COVERED

Peripheral inhibition of dopa-decarboxylase has long been considered an essential component of levodopa treatment at every stage of illness. In contrast, only relatively recently have catechol-O-methyltransferase (COMT) inhibitors been utilized to block the other major pathway of degradation and optimize levodopa delivery to the brain. First and second-generation COMT inhibitors were deficient because of toxicity, sub-optimal pharmacokinetics or a short duration of effect. As such, they have only been employed once 'wearing-off' has developed. However, the third-generation COMT inhibitor, opicapone has overcome these difficulties and exhibits long-lasting enzyme inhibition without the toxicity observed with previous generations of COMT inhibitors. In clinical trials and real-world PD studies opicapone improves the levodopa plasma profile and results in a significant improvement in ON time in 'fluctuating' disease, but it has not yet been included in the algorithm for early treatment.

EXPERT OPINION

This review argues for a shift in the positioning of COMT inhibition with opicapone in the PD algorithm and lays out a pathway for proving its effectiveness in early disease.

Management of systemic risk factors ahead of dental implant therapy: A beard well lathered is half shaved

As the most successful therapy for missing teeth, dental implant has become increasingly prevalent around the world. A lot of papers have reported diverse local risk factors affecting the success and survival rate of dental implants, either for a short or a long period. However, there are also many types of systemic disorders or relatively administrated medicine that may jeopardize the security and success of dental implant treatment. Additionally, the coronavirus disease 2019 pandemic also poses a challenge to dental implant clinicians. Some of these risk factors are clinically common but to some extent unfamiliar to dentists, thus optimal measurements are often lacking when they occur in dental clinics. In this review, we analyze potential systemic risk factors that may affect the success rate of dental implants. Some of them may affect bone mineral density or enhance the likelihood of local infection, thus impeding osseointegration. Others may even systemically increase the risk of the surgery and threaten patients' life. In order to help novices receive high-risk patients who need to get dental implant treatment in a more reasonable way, we accordingly review recent research results and clinical experiments to discuss promising precautions, such as stopping drugs that impact bone mineral density or the operation, and addressing any perturbations on vital signs.

Emerging Pharmacotherapies for Motor Symptoms in Parkinson's Disease

Parkinson's disease (PD) is the second commonest neurodegenerative disorder in the older adult and is characterized by progressive disabling motor symptoms of bradykinesia, tremor, rigidity, postural instability and also non motor symptoms that affect quality of life. The pharmacotherapy of PD consists of oral, transdermal, and subcutaneous medications, as well as invasive advanced therapies at later stages of the disease. PD medications are often started as monotherapy but with the progression of the illness often there is a need to add more medications and frequently comprises of a challenging polypharmacotherapy. Adverse effects of pharmacotherapy often add to the problems of adequate treatment. Patients and physicians have to prioritize treatment goals on the most disabling symptoms and the safest and most effective treatments. Almost every year newer medications and modes of delivery continue to be researched and added to the therapeutic armamentarium. This review article outlines existing and emerging pharmacotherapies for motor symptoms in 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.

Immunotherapies for Parkinson's disease: Progression of Clinical Development

Parkinson's disease is a common neurodegenerative disease affecting the movement and wellbeing of most elderlies. The manifestations of Parkinson's disease often include resting tremor, stiffness, bradykinesia and muscular rigidity. The typical hallmark of Parkinson's disease is the destruction of neurons in the substantia nigra and the presence of Lewy bodies in different compartments of the central nervous system. Due to various limitations to the currently available treatments, immunotherapies have emerged to be the new approach to Parkinson's disease treatment. This approach shows some positive outcomes on the efficacy in removing the aggregated species of alpha-synuclein, which is believed to be one of the causes of Parkinson's disease. In this review, an overview of how alpha-synuclein contributes to Parkinson's disease and the effects of a few new immunotherapeutic treatments, including BIIB054 (cinpanemab), MEDI1341, AFFITOPE and PRX002 (prasinezumab) that are currently under clinical development, will be discussed.

Clinical Utility of Opicapone in the Management of Parkinson's Disease: A Short Review on Emerging Data and Place in Therapy

Parkinson’s disease (PD) is a prevalent neurodegenerative disorder, and levodopa (L-dopa) remains the most efficacious drug treatment for PD and a gold-standard for symptom control. Nonetheless, a significant majority of PD patients develop motor fluctuations over their disease course, with a significant impact on quality-of-life, meaning control of such complications translates into a fundamental clinical need. Catechol-O-methyl transferase (COMT) inhibitors (COMT-i) are used as first-line adjuvant therapy to L-dopa for end-of-dose (EoD) motor fluctuations, since they increase L-dopa availability in the brain by inhibiting its peripheral metabolism. Opicapone (OPC), a once-daily, long-acting COMT-i, is the most recent and potent of its class, having been licensed in Europe in 2016 as an add-on to preparations of L-dopa/DOPA decarboxylase inhibitors in PD patients with EoD motor fluctuations. More recently, it has also received approval in the USA and Japan in 2020. Two high-quality positive efficacy studies (double-blind Phase III clinical trials) established OPC efficacy with significant reduction in OFF time (average 60 minutes vs placebo), without concomitant increase of distressing dyskinesias during ON time. These beneficial effects were sustained in open-label extension studies, without unexpected safety issues or adverse events, with dyskinesia having been the most frequent complaint. OPC also avoids liver toxicity and gastrointestinal issues compared with previous COMT-i. In this review, we aimed to cover OPC’s lifecycle (synthesis to commercialization), its clinical pharmacological data, safety, tolerability and pharmacovigilance evidence, and discuss its role in the management of motor fluctuations in PD as well as its emerging place in international recommendations.

The dynamics of nigrostriatal system damage and neurobehavioral changes in the rotenone rat model of Parkinson's disease

Subcutaneous administration of rotenone to rats is currently a widely used method of reproducing Parkinson's disease (PD) symptoms, due to its convenience and effectiveness. Despite this, its influence on the temporal dynamics of parkinsonism development has yet to be investigated. The present study characterizes behavioral and neurochemical disruptancies underlying the dynamics of parkinsonism development in rats, induced by chronic subcutaneous administration of 2 mg/kg rotenone over the course of 18 days. In this article, the presence of two stages of pathology development in the model in question - the premotor and motor disability stages - are illustrated through a complex assessment of animal behavior, the development of an original neurological symptoms scale, and the establishment of the dynamics of histological and neurochemical changes in the brain. The premotor stage was observed up to 3 days of rotenone administration, and was characterized by a decrease in the motivational component of behavior, shown both in the food-getting task and in the "sucrose preference" test. A 30 % decrease in the number of cells in the substantia nigra pars compacta by the 3rd day of rotenone administration was also shown during the premotor stage. No changes in the metabolism of dopamine and other monoamine mediators were observed at this time. At the same time, acute administration of rotenone caused an increase in the GSH / GSSG ratio by 69 %. The motor stage developed after a decrease in the number of cells in the SNpc by more than 30 %, and was characterized by changes in the dopaminergic system, leading up to a 71 % reduction in dopamine levels in the striatum. It was shown that starting from 4 to 6 days of rotenone injection, experimental group animals begin to develop motor symptoms of Parkinson's disease, including bradykinesia, rigidity and postural instability. The development of motor impairment in all rats of this group was accompanied by significantly reduced activity of the antioxidant system in brain frontal lobe tissue homogenates, as compared to intact rats. Thus, in the used model of rotenone-induced parkinsonism, the dynamics of neuropathology development are described and the premotor stage of the disease is highlighted, which allows future using of this model in developing new approaches for treatment of parkinsonism at an early stage.

Pharmacokinetics of Opicapone and Its Metabolites in Healthy White and Chinese Subjects

Opicapone (OPC) is a third-generation catechol-O-methyltransferase inhibitor developed to treat Parkinson disease and motor fluctuations. This open-label, single-center, phase 1 study aimed to evaluate the pharmacokinetics (PK) of OPC and its metabolites when administered as single and multiple doses in healthy White and Chinese subjects. The study enrolled a total of 30 White and Chinese healthy subjects, equally balanced among groups. The first dose of OPC was administered orally as a single dose of 50 mg on day 1, followed by a 10-day once-daily treatment from day 5 to day 14. Plasma concentrations of OPC and its metabolites were measured at 0 to 72 and 0 to 144 hours after dosing for single dose and multiple dose, respectively. Moreover, urine concentrations of OPC and its metabolite were measured 0 to 24 hours after dosing. PK parameters were derived from noncompartmental analysis. Geometric mean ratios and 90% confidence intervals for the main PK parameters were conducted to evaluate the ethnic difference between White and Chinese subjects. The plasma and urine exposure of OPC and its metabolites in Chinese subjects were similar to those in White subjects. These results indicated that ethnicity had no significant impact on PK of OPC between White and Chinese subjects.

Experimental Dopamine Reuptake Inhibitors in Parkinson's Disease: A Review of the Evidence

Parkinson’s disease (PD) is the second most chronic neurodegenerative disorder worldwide. Deficit of monoamines, particularly dopamine, causes an individually varying compilation of motor and non-motor features. Constraint of presynaptic uptake extends monoamine stay in the synaptic cleft. This review discusses possible benefits of dopamine reuptake inhibition for the treatment of PD. Translation of this pharmacologic principle into positive clinical study results failed to date. Past clinical trial designs did not consider a mandatory, concomitant stable inhibition of glial monoamine turnover, i.e. with monoamine oxidase B inhibitors. These studies focused on improvement of motor behavior and levodopa associated motor complications, which are fluctuations of motor and non-motor behavior. Future clinical investigations in early, levodopa- and dopamine agonist naïve patients shall also aim on alleviation of non-motor symptoms, like fatigue, apathy or cognitive slowing. Oral levodopa/dopa decarboxylase inhibitor application is inevitably necessary with advance of PD. Monoamine reuptake (MRT) inhibition improves the efficacy of levodopa, the blood brain barrier crossing metabolic precursor of dopamine. The pulsatile brain delivery pattern of orally administered levodopa containing formulations results in synaptic dopamine variability. Ups and downs of dopamine counteract the physiologic principle of continuous neurotransmission, particularly in nigrostriatal, respectively mesocorticolimbic pathways, both of which regulate motor respectively non-motor behavior. Thus synaptic dopamine pulsatility overwhelms the existing buffering capacity. Onset of motor and non-motor complications occurs. Future MRT inhibitor studies shall focus on a stabilizing and preventive effect on levodopa related fluctuations of motor and non-motor behavior. Their long-term study designs in advanced levodopa treated patients shall allow a cautious adaptation of oral l-dopa therapy combined with a mandatory inhibition of glial monoamine turnover. Then the evidence for a preventive and beneficial, symptomatic effect of MRT inhibition on motor and non-motor complications will become more likely.

Opicapone for Parkinson's disease: clinical evidence and future perspectives

Since 2016, opicapone (OPC), a potent third-generation, long-acting, once-daily, peripheral catechol-O-methyltransferase inhibitor, is approved as an add-on to levodopa in Parkinson's disease patients with motor fluctuations. OPC 50 mg has showed to be able in reducing OFF time by an average of about 60 min daily compared with placebo, to further reduce OFF-time of about 39 min, when switched from ENT to OPC and to be safe. These beneficial effects of OPC were maintained for 1 year. Recently, several post hoc analysis and few pilot observational open-label studies, have suggested its efficacy and wider applicability for different phenotypes of motor complications and for Parkinson's disease stages. Here we review OPC applicability and perspectives, in the light of the more recently published analysis.