Apomorphine - pharmacological properties and clinical trials in Parkinson's disease

Monotherapy with infusion therapies - useful or not?

Infusion pump-based therapies are an effective treatment option for patients with advanced Parkinson´s disease. Achieving monotherapy with infusion-based therapies could simplify the treatment regimen, provide better medication adherence, reduce adverse events and drug interactions. This review presents the literature data on the efficacy, safety, and achievability of monotherapy with all available infusion-based therapies, including apomorphine, levodopa-carbidopa-intestinal gel (LCIG), levodopa-entacapone-carbidopa intestinal gel (LECIG), and foslevodopa-foscarbidopa (LDp/CDp). In summary, monotherapy is achievable and effective in most patients on intestinal levodopa infusion therapy and in some patients on apomorphine infusion. There is a need for further investigation of monotherapy compared to polytherapy, especially in new pump treatment options (LECIG and LDp/CDp). Future research should reveal which patients on infusion-based therapies could benefit from monotherapy, including identification of potential baseline predictors of achieving monotherapy in patients treated with specific infusion-based therapies.

Translation from Preclinical Research to Clinical Trials: Transdermal Drug Delivery for Neurodegenerative and Mental Disorders

Neurodegenerative diseases (NDs), particularly dementia, provide significant problems to worldwide healthcare systems. The development of therapeutic materials for various diseases has a severe challenge in the form of the blood-brain barrier (BBB). Transdermal treatment has recently garnered widespread favor as an alternative method of delivering active chemicals to the brain. This approach has several advantages, including low invasiveness, self-administration, avoidance of first-pass metabolism, preservation of steady plasma concentrations, regulated release, safety, efficacy, and better patient compliance. Topics include the transdermal method for therapeutic NDs, their classification, and the mechanisms that allow the medicine to enter the bloodstream through the skin. The paper also discusses the obstacles and potential outcomes of transdermal therapy, emphasizing the benefits and drawbacks of different approaches.

Synthetic aporphine alkaloids are potential therapeutics for Leigh syndrome

Mitochondrial diseases are mainly caused by dysfunction of mitochondrial respiratory chain complexes and have a variety of genetic variants or phenotypes. There are only a few approved treatments, and fundamental therapies are yet to be developed. Leigh syndrome (LS) is the most severe type of progressive encephalopathy. We previously reported that apomorphine, an anti- "off" agent for Parkinson's disease, has cell-protective activity in patient-derived skin fibroblasts in addition to strong dopamine agonist effect. We obtained 26 apomorphine analogs, synthesized 20 apomorphine derivatives, and determined their anti-cell death effect, dopamine agonist activity, and effects on the mitochondrial function. We found three novel apomorphine derivatives with an active hydroxy group at position 11 of the aporphine framework, with a high anti-cell death effect without emetic dopamine agonist activity. These synthetic aporphine alkaloids are potent therapeutics for mitochondrial diseases without emetic side effects and have the potential to overcome the low bioavailability of apomorphine. Moreover, they have high anti-ferroptotic activity and therefore have potential as a therapeutic agent for diseases related to ferroptosis.

How to Use the New European Academy of Neurology/Movement Disorder Society European Section Guideline for Invasive Therapies in Parkinson's Disease

BACKGROUND

The decision to choose invasive treatments for Parkinson's disease (PD) is complex and needs careful consideration.

OBJECTIVES

Although the recommendations of the European Academy of Neurology/Movement Disorder Society European Section guideline for invasive therapies of PD are useful, the different clinical profiles of people with PD who seek advice for possible invasive therapy need further attention.

METHODS AND RESULTS

Here we describe 8 clinical standard situations of people with PD unsatisfied with their current oral treatment where invasive therapies may be considered. These are PD patients presenting with the following symptoms: (1) severe motor fluctuations, (2) beginning of levodopa-responsive fluctuations, severe tremor at (3) young or (4) advanced age, (5) impulse control disorders and related behavioral disorders, (6) hallucinations and psychosis, (7) minimal cognitive impairment or mild dementia, and (8) patients in need of palliative care. For some of these conditions, evidence at lower level or simple clinical considerations exist.

CONCLUSIONS

There are no one-fits-all answers, but physician and patient should discuss each option carefully considering symptom profile, psychosocial context, availability of therapy alternatives, and many other factors. The current paper outlines our proposed approach to these circumstances.

Cortical and Striatal Astrocytes of Neonatal Rats Display Distinct Molecular and Pharmacological Characteristics of Dopamine Uptake

Astrocytes are crucial in the regulation of neurotransmitter homeostasis, and while their involvement in the dopamine (DA) tripartite synapse is acknowledged, it necessitates a more comprehensive investigation. In the present study, experiments were conducted on primary astrocyte cultures from the striatum and cortex of neonatal rats. The pharmacological intricacies of DA uptake, including dependence on time, temperature, and concentration, were investigated using radiolabelled [3H]-DA. The mRNA expression of transporters DAT, NET, PMAT, and OCTs was evaluated by qPCR. Notably, astrocytes from both brain regions exhibited prominent mRNA expression of NET and PMAT, with comparatively lower expression of DAT and OCTs. The inhibition of DA uptake by the DAT inhibitor, GBR12909, and NET inhibitors, desipramine and nortriptyline, impeded DA uptake in striatal astrocytes more than in cortical astrocytes. The mRNA expression of NET and PMAT was significantly upregulated in cortical astrocytes in response to the DA receptor agonist apomorphine, while only the mRNA expression of NET exhibited changes in striatal astrocytes. Haloperidol, a DA receptor antagonist, and L-DOPA, a DA precursor, did not induce significant alterations in transporter mRNA expression. These findings underscore the intricate and region-specific mechanisms governing DA uptake in astrocytes, emphasizing the need for continued exploration to unravel the nuanced dynamics of astrocytic involvement in the DA tripartite synapse.

Paradigms and Success Stories of Natural Products in Drug Discovery Against Neurodegenerative Disorders (NDDs)

Neurodegenerative disorders (NDDs) are multifaceted complex disorders that have put a great health and economic burden around the globe nowadays. The multi-factorial nature of NDDs has presented a great challenge in drug discovery and continuous efforts are in progress in search of suitable therapeutic candidates. Nature has a great wealth of active principles in its lap that has cured the human population since ancient times. Natural products have revealed several benefits over conventional synthetic medications and scientists have shifted their vision towards exploring the therapeutic potentials of natural products in the past few years. The structural mimicking of natural compounds to endogenous ligands has presented them as a potential therapeutic candidate to prevent the development of NDDs. In the presented review, authors have summarized demographical facts about various NDDs including Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD) and various types of sclerosis in the brain. The significant findings of new active principles of natural origin along with their therapeutic potentials on NDDs have been included. Also, a description of clinical trials and patents on natural products has been enlisted in this compilation. Although natural products have shown promising success in drug discovery against NDDs, still their use is associated with several ethical issues which need to be solved in the upcoming time.

Apomorphine for Parkinson's disease: pharmacologic and clinical considerations

INTRODUCTION

In Parkinson's disease, dopamine depletion in the basal ganglia leads to symptoms including bradykinesia, gait abnormalities, and cognitive impairment. Even with treatment, the disease course leads to decreases in the amount of dopamine produced and released into the synapse. As dopamine production falls and the treatment course is insufficient to match the metabolic supply and demand, acute 'off' periods develop that cause reemergence of symptoms. Apomorphine is used to reverse these 'off' periods and restore function in patients with Parkinson's. This review will provide clinicians a concise article to read to learn more about apomorphine and its appropriate utilization.

AREAS COVERED

The research discussed is focused on the history, pharmacokinetics, and mechanism of action of Apomorphine. Its utilization as a treatment for Parkinson's Disease and its comparison to currently utilized drugs is also discussed in this review. We focused on articles published on PubMed and Google Scholar within the last 10 years, but in some instances had to go as far back as 1951 to include early articles published about apomorphine.

EXPERT OPINION

The expert opinion section focuses on the ways in which apomorphine could be administered in the future to better promote utilization and increase tolerability.

Practical use of apomorphine infusion in Parkinson's disease: lessons from the TOLEDO study and clinical experience

Subcutaneous apomorphine infusion is a device-aided therapy for Parkinson's disease that can be considered when motor fluctuations become persistent and are no longer adequately controlled by oral/transdermal medication. Apomorphine infusion is less invasive than enteral levodopa, deep brain stimulation or focused ultrasound, and is often indicated even when neurosurgical approaches are contraindicated. This article aims to provide practical guidance for doctors and nurses initiating and treating patients with apomorphine infusion, and is based on both trial data and clinical experience from movement disorders specialists. A post hoc analysis of data from the TOLEDO randomized clinical trial of apomorphine infusion was conducted along with an analysis of 'real world' experience from 13 movement disorders specialists using a questionnaire that focused on starting patients on apomorphine infusion. Practical guidelines for starting treatment with apomorphine infusion are provided taking into consideration the regional disparities in healthcare. Apomorphine infusion is straightforward to administer but to be successful it requires concordance from the patient and family, and clinical support from an experienced team of doctors and nurses, particularly in the early months of treatment.

Home initiation of apomorphine infusion: lessons from the COVID-19 pandemic and implications for current clinical practice

Starting Parkinson's disease (PD) patients on subcutaneous apomorphine (APO) infusion is generally undertaken on a hospital day-case basis. During the COVID-19 pandemic, day-case facilities were unavailable. To avoid delays in treatment, a new procedure was developed for initiation of APO therapy in the patient's home. A home initiation protocol was developed and followed for each patient in this analysis. The hospital team worked in collaboration with APO nurses provided by the manufacturer of APO therapies to implement initiation and undertake follow-up. In this analysis, 27 PD patients were initiated onto APO infusion and 21 (77.8%) achieved a therapeutic response. Home initiation of APO infusion can be undertaken successfully and has benefits for both patients and healthcare teams. This protocol will now continue as a standard of care at our centre.

Adopting the Rumsfeld approach to understanding the action of levodopa and apomorphine in Parkinson's disease

Dopaminergic therapies dominate the treatment of the motor and non-motor symptoms of Parkinson's disease (PD) but there have been no major advances in therapy in many decades. Two of the oldest drugs used appear more effective than others-levodopa and apomorphine-but the reasons for this are seldom discussed and this may be one cause for a lack of progress. This short review questions current thinking on drug action and looks at whether adopting the philosophy of ex-US Secretary of State Donald Rumsfeld reveals 'unknown' aspects of the actions of levodopa and apomorphine that provide clues for a way forward. It appears that both levodopa and apomorphine have a more complex pharmacology than classical views would suggest. In addition, there are unexpected facets to the mechanisms through which levodopa acts that are either forgotten as 'known unknowns' or ignored as 'unknown unknowns'. The conclusion reached is that we may not know as much as we think about drug action in PD and there is a case for looking beyond the obvious.

Non-oral continuous drug delivery based therapies and sleep dysfunction in Parkinson's disease

Continuous drug delivery (CDD) has emerged as a feasible and pragmatic therapeutic option for dopamine replacement therapy in advanced Parkinson's disease (PD). CDD aims to mimic the physiological tonic dopamine release from striatal dopaminergic neurons and thus reduces the severity and duration of motor and non-motor fluctuations partly related to pulsatile levodopa stimulation. Non-motor symptoms and fluctuations are ubiquitous in PD and include sleep dysfunction, a problem that occurs in over 90% of PD patients across all stages, from prodromal to palliative. In this review, we discuss the currently available and in development non-oral dopaminergic CDD strategies with a focus on their efficacy in the treatment of the burdensome sleep dysfunction in PD.

Current and novel infusion therapies for patients with Parkinson's disease

Advanced Parkinson's disease is characterized by periods of poor mobility, dyskinesia and progressive decline in functional independence of the affected person despite the manipulation of levodopa doses and the introduction of supplemental therapies such as catechol-O-methyl transferase inhibitors, monoamine oxidase-B inhibitors and dopamine agonists. The implementation of drug delivery systems allows to bypass problems related to irregular and often unpredictable intestinal absorption of oral levodopa, which significantly affects its bioavailability and contributes to the development and persistence of motor complications. Subcutaneous apomorphine and levodopa/carbidopa jejunal infusion systems have been available for many years and their efficacy is confirmed by randomized studies and long-term experience in many centers worldwide. Recently, a new formulation of levodopa/carbidopa infusion gel that includes the catechol-O-methyl transferase inhibitor Entacapone has been introduced to the market. The use of entacapone allows to reduce total daily dose of administered levodopa. Two different soluble formulations of levodopa/carbidopa (ND0612 and ABBV-951) have completed clinical development, and both can ensure subcutaneous delivery by a portable pump infusion system. ABBV-951 uses a foslevodopa/foscarbidopa formulation, both prodrugs to improve absorption and tolerability. Both systems provide effective improvement of motor complications and are likely to expand the therapeutic options in advanced patients. Future efforts should focus on the earlier detection of patients who are candidates for device-aided therapies, increasing appropriate referral and broadening the availability of these treatments globally.

Safety and tolerability of long-term apomorphine infusion in advanced Parkinson's disease: an Indian multi-center (APO-IND) experience

Advanced Parkinson's Disease (APD) is complicated by the emergence of motor and non-motor fluctuations, which are initially predictable and eventually become unpredictable, in part due to erratic gastric absorption and short half of oral levodopa. Attempts to manage such fluctuations with oral dopaminergic drugs often lead to disabling dyskinesias. Continuous Subcutaneous Apomorphine Infusion (CSAI), despite being approved for the treatment of APD since 1993, was approved in India only in 2019. We studied the safety, tolerability and efficacy of CSAI in Indian patients with APD in a registry design to raise local awareness of this important treatment. We conducted a prospective registry-based observational audit at 10 centers across different states of India. Patients with APD, not responding to or with significant side effects from oral dopaminergic therapy, were assessed at baseline and at month 6 and 12 following CSAI infusion. Fifty-one patients completed the study, CSAI significantly reduced the functional impact of dyskinesia (p < 0.01 at 6 months and p < 0.001 at 12 months). There was a significant improvement in the OFF-state from baseline (p < 0.01 at 6 months and p < 0.001 at 12 months) No discernible side effects were observed apart from mild site reaction (n = 7), nausea (n = 7) skin nodules (n = 2). CSAI demonstrated safety, efficacy, tolerability and improved quality of life in patients with APD, as shown in previous studies. Our study highlighted current existing inequalities in treatment availability, lack of awareness, knowledge gap, affordability and cost remains a concern regarding apomorphine use in Indian PD population.

Night-Time Apomorphine Infusion: Who Are the Best Candidates?

Background

We recently demonstrated in a randomized controlled trial (APOMORPHEE, NCT02940912) that night-time only subcutaneous apomorphine infusion improves sleep disturbances and insomnia in patients with advanced Parkinson's disease and moderate to severe insomnia.

Objectives

To identify the best candidates for receiving night-time only subcutaneous apomorphine infusion in routine care.

Methods

In this post-hoc analysis of APOMORPHEE, we compared the characteristics of patients according to whether they chose to continue night-time only subcutaneous apomorphine infusion at the end of the study period or not.

Results

Half of the patients (22/42) chose to continue the treatment. Off duration (day or night), painful Off dystonia, and insomnia severity at baseline were associated with night-time only apomorphine continuation. Multivariate analysis retained only Off duration as an independent predictor of continuation.

Conclusions

The best candidates for night-time only apomorphine are patients with severe and prolonged Off periods (day or night) and severe insomnia.

Dopamine agonists in Parkinson's disease: Impact of D1-like or D2-like dopamine receptor subtype selectivity and avenues for future treatment

Dopamine agonists (DAs) have demonstrated efficacy for the treatment of Parkinson's disease (PD) but are limited by adverse effects (AEs). DAs can vary considerably in their receptor subtype selectivity and affinity, chemical composition, receptor occupancy, and intrinsic activity on the receptor. Most currently approved DAs for PD treatment primarily target D2/D3 (D2-like) dopamine receptors. However, selective activation of D1/D5 (D1-like) dopamine receptors may enable robust activation of motor function while avoiding AEs related to D2/D3 receptor agonism. Full D1/D5 receptor-selective agonists have been explored in small, early-phase clinical studies, and although their efficacy for motor symptoms was robust, challenges with pharmacokinetics, bioavailability, cardiovascular AEs, and dyskinesia rates similar to levodopa prevented clinical advancement. Generally, repeated dopaminergic stimulation with full DAs is associated with frontostriatal dysfunction and sensitization that may induce plastic changes in the motor system, and neuroadaptations that produce long-term motor and nonmotor complications, respectively. Recent preclinical and clinical studies suggest that a D1/D5 receptor-selective partial agonist may hold promise for providing sustained, predictable, and robust motor control, while reducing risk for motor complications (e.g., levodopa-induced dyskinesia) and nonmotor AEs (e.g., impulse control disorders and excessive daytime sleepiness). Clinical trials are ongoing to evaluate this hypothesis. The potential emerging availability of novel dopamine receptor agonists with selective dopamine receptor pharmacology suggests that the older terminology "dopamine agonist" may need revision to distinguish older-generation D2/D3-selective agonists from D1/D5-selective agonists with distinct efficacy and tolerability characteristics.

Differential remodeling of subthalamic projections to basal ganglia output nuclei and locomotor deficits in 6-OHDA-induced hemiparkinsonian mice

The subthalamic nucleus (STN) controls basal ganglia outputs via the substantia nigra pars reticulata (SNr) and the globus pallidus internus (GPi). However, the synaptic properties of these projections and their roles in motor control remain unclear. We show that the STN-SNr and STN-GPi projections differ markedly in magnitude and activity-dependent plasticity despite the existence of collateral STN neurons projecting to both the SNr and GPi. Stimulation of either STN projection reduces locomotion; in contrast, inhibition of either the STN-SNr projection or collateral STN neurons facilitates locomotion. In 6-OHDA-hemiparkinsonian mice, the STN-SNr projection is dramatically attenuated, but the STN-GPi projection is robustly enhanced; apomorphine inhibition of the STN-GPi projection through D2 receptors is significantly augmented and improves locomotion. Optogenetic inhibition of either the STN-SNr or STN-GPi projection improves parkinsonian bradykinesia. These results suggest that the STN-GPi and STN-SNr projections are differentially involved in motor control in physiological and parkinsonian conditions.

RNA sequencing least shrew (Cryptotis parva) brainstem and gut transcripts following administration of a selective substance P neurokinin NK1 receptor agonist and antagonist expands genomics resources for emesis research

The least shrew is among the subset of animals that are capable of vomiting and therefore serves as a valuable research model for investigating the biochemistry, molecular biology, pharmacology, and genomics of emesis. Both nausea and vomiting are associated with a variety of illnesses (bacterial/viral infections, bulimia, exposure to toxins, gall bladder disease), conditions (pregnancy, motion sickness, emotional stress, overeating) and reactions to drugs (chemotherapeutics, opiates). The severe discomfort and intense fear associated with the stressful symptoms of nausea and emesis are the major reason for patient non-compliance when being treated with cancer chemotherapeutics. Increased understanding of the physiology, pharmacology and pathophysiology underlying vomiting and nausea can accelerate progress for developing new antiemetics. As a major animal model for emesis, expanding genomic knowledge associated with emesis in the least shrew will further enhance the laboratory utility of this model. A key question is which genes mediate emesis, and are they expressed in response to emetics/antiemetics. To elucidate the mediators of emesis, in particular emetic receptors, their downstream signaling pathways, as well as the shared emetic signals, we carried out an RNA sequencing study focused on the central and peripheral emetic loci, the brainstem and gut. Thus, we sequenced RNA extracted from brainstem and gut tissues from different groups of least shrews treated with either a neurokinin NK1 receptor selective emetic agonist, GR73632 (5 mg/kg, i.p.), its corresponding selective antagonist netupitant (5 mg/kg, i.p.), a combination of these two agents, versus their corresponding vehicle-pretreated controls and drug naïve animals. The resulting sequences were processed using a de novo transcriptome assembly and used it to identify orthologs within human, dog, mouse, and ferret gene sets. We compared the least shrew to human and a veterinary species (dog) that may be treated with vomit-inducing chemotherapeutics, and the ferret, another well-established model organism for emesis research. The mouse was included because it does not vomit. In total, we identified a final set of 16,720 least shrew orthologs. We employed comparative genomics analyses as well as gene ontology enrichment, KEGG pathway enrichment and phenotype enrichment to better understand the molecular biology of genes implicated in vomiting.

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.

Monoamine-oxidase Type B Inhibitors and Cognitive Functions in Parkinson's Disease: Beyond the Primary Mechanism of Action

Symptoms of cognitive impairment are rather common since the early stage of Parkinson's disease (PD); they aggravate with disease progression and may lead to dementia in a significant proportion of cases. Worsening of cognitive symptoms in PD patients depends on the progression of subcortical dopaminergic damage as well as the involvement of other brain neurotransmitter systems in cortical and subcortical regions. Beyond the negative impact on disability and quality of life, the presence and severity of cognitive symptoms may limit adjustments of dopamine replacement therapy along the disease course. This review focuses on the consequences of the administration of monoamine-oxidase type Binhibitors (MAOB-I) on cognition in PD patients. Two drugs (selegiline and rasagiline) are available for the treatment of motor symptoms of PD as monotherapy or in combination with L-DOPA or dopamine agonists in stable and fluctuating patients; a further drug (safinamide) is usable in fluctuating subjects solely. The results of available studies indicate differential effects according to disease stage and drug features. In early, non-fluctuating patients, selegiline and rasagiline ameliorated prefrontal executive functions, similarly to other dopaminergic drugs. Benefit on some executive functions was maintained in more advanced, fluctuating patients, despite the tendency of worsening prefrontal inhibitory control activity. Interestingly, high-dose safinamide improved inhibitory control in fluctuating patients. The benefit of high-dose safinamide on prefrontal inhibitory control mechanisms may stem from its dual mechanism of action, allowing reduction of excessive glutamatergic transmission, in turn secondary to increased cortical dopaminergic input.

Advances in the Therapeutic Use of Non-Ergot Dopamine Agonists in the Treatment of Motor and Non-Motor Symptoms of Parkinson's Disease

Dopamine (DA) agonists, as an excellent dopamine replacement therapy for patients with early and advanced Parkinson's disease (PD), play a vital role in controlling motor and several nonmotor symptoms. Besides, the application of DA agonists may delay levodopa therapy and the associated risk of motor complications. Indeed, each DA agonist has unique pharmacokinetic and pharmacodynamic characteristics and therefore has different therapeutic efficacy and safety profile. The comorbidities, significant non-motor manifestations, concomitant medications, and clinical features of PD individuals should guide the selection of a specific DA agonist to provide a more patient-tailored treatment option. Thorough knowledge of DA agonists helps clinicians better balance clinical efficacy and side effects. Therefore, this review refers to recent English-written articles on DA agonist therapy for PD patients and summarizes the latest findings on non-ergot DA agonists as well as the advantages and disadvantages of each compound to help clinicians in the selection of a specific DA agonist. In addition, novel D1/D5 partial agonists and new formulations of DA agonists are also discussed.

Levodopa-Induced Dyskinesia in Parkinson's Disease: Pathogenesis and Emerging Treatment Strategies

The most commonly used treatment for Parkinson's disease (PD) is levodopa, prescribed in conjunction with carbidopa. Virtually all patients with PD undergo dopamine replacement therapy using levodopa during the course of the disease's progression. However, despite the fact that levodopa is the "gold standard" in PD treatments and has the ability to significantly alleviate PD symptoms, it comes with side effects in advanced PD. Levodopa replacement therapy remains the current clinical treatment of choice for Parkinson's patients, but approximately 80% of the treated PD patients develop levodopa-induced dyskinesia (LID) in the advanced stages of the disease. A better understanding of the pathological mechanisms of LID and possible means of improvement would significantly improve the outcome of PD patients, reduce the complexity of medication use, and lower adverse effects, thus, improving the quality of life of patients and prolonging their life cycle. This review assesses the recent advancements in understanding the underlying mechanisms of LID and the therapeutic management options available after the emergence of LID in patients. We summarized the pathogenesis and the new treatments for LID-related PD and concluded that targeting pathways other than the dopaminergic pathway to treat LID has become a new possibility, and, currently, amantadine, drugs targeting 5-hydroxytryptamine receptors, and surgery for PD can target the Parkinson's symptoms caused by LID.

Why do 'OFF' periods still occur during continuous drug delivery in Parkinson's disease?

Continuous drug delivery (CDD) is used in moderately advanced and late-stage Parkinson’s disease (PD) to control motor and non-motor fluctuations (‘OFF’ periods). Transdermal rotigotine is indicated for early fluctuations, while subcutaneous apomorphine infusion and levodopa-carbidopa intestinal gel are utilised in advanced PD. All three strategies are considered examples of continuous dopaminergic stimulation achieved through CDD. A central premise of the CDD is to achieve stable control of the parkinsonian motor and non-motor states and avoid emergence of ‘OFF’ periods. However, data suggest that despite their efficacy in reducing the number and duration of ‘OFF’ periods, these strategies still do not prevent ‘OFF’ periods in the middle to late stages of PD, thus contradicting the widely held concepts of continuous drug delivery and continuous dopaminergic stimulation. Why these emergent ‘OFF’ periods still occur is unknown. In this review, we analyse the potential reasons for their persistence. The contribution of drug- and device-related involvement, and the problems related to site-specific drug delivery are analysed. We propose that changes in dopaminergic and non-dopaminergic mechanisms in the basal ganglia might render these persistent ‘OFF’ periods unresponsive to dopaminergic therapy delivered via CDD.

Analisi di impatto di budget di un nuovo sistema di cura in pazienti affetti da malattia di Parkinson

Objective:

To estimate the economic impact of the introduction of a new care system based on apomorphine and Patient Support Program for motor fluctuations (“on-off” phenomena) in patients with Parkinson’s disease which are not sufficiently controlled by oral anti-Parkinson medication in Italy.

Method:

A Budget Impact model was developed to evaluate the new care system in patients with Parkinson’s disease over a 3-years’ time horizon. The comparator treatments included in the analysis were treatments based on apomorphine and levodopa + carbidopa. The analysis was conducted from a National Health Service (NHS) perspective. Costs included in the analysis were acquisition costs and device costs. A deterministic sensitivity analysis was carried out to evaluate the uncertainty of the parameters used. A break-even analysis was conducted to identify the minimum number of subjects that would need to be treated with the new care system to obtain a positive Budget Impact (World With – World Without = 0).

Results:

The analysis shows that the introduction of the new care system based on apomorphine could generate a cost saving incurred by the NHS of over € 5.7 million in 3 years. Break-even analysis shows that if it were possible to intercept with the new treatment at least 9 patients treated with apomorphine, there would not be an increase in costs for the NHS.

Conclusion:

The new care system would respond to the unmet needs of patients with Parkinson’s disease by generating a reduction in the expenditure incurred by NHS.

Anticancer efficacy of endo- and exogenous potent ligands acting at dopaminergic receptor-expressing cancer cells

Cancer is one of the most common and dreaded diseases affecting the vastness of society. Unfortunately, still some people die especially when cancer is not diagnosed and thus caught early enough. On the other hand, using available chemo- or radiotherapy may result in serious side effects. Therefore, cancer-specific medications seem to be the most desired and safe therapy. Knowing that some cancers are characterized by overexpression of specific receptors on the cell surface, target-mediated drugs could serve as a unique and effective form of therapy. In line with this, recently dopaminergic receptors were presented important in cancer therapy as several dopaminergic ligands revealed their efficacy in tumor growth reduction as well as in apoptosis mediation. Unfortunately, the indication of whether DA receptor agonists or antagonists are the best choices in cancer treatment is quite difficult, since both of them may exert either pro- or anticancer effects. In this review, we analyze the therapeutic efficacy of compounds, both of exogenous and endogenous origin, targeting dopaminergic receptor-expressing cancers.

Levodopa–entacapone–carbidopa intestinal gel infusion in advanced Parkinson’s disease: real-world experience and practical guidance

As Parkinson’s disease (PD) progresses, treatment needs to be adapted to maintain symptom control. Once patients develop advanced PD, an optimised regimen of oral and transdermal medications may no longer provide adequate relief of OFF periods and motor complications can emerge. At this point, patients may wish to consider a device-aided therapy (DAT) that provides continuous dopaminergic stimulation to help overcome these issues. Levodopa–entacapone–carbidopa intestinal gel (LECIG) infusion is a recently developed DAT option. The aim of this article is twofold: (1) to give an overview of the pharmacokinetics of LECIG infusion and clinical experience to date of its use in patients with advanced PD, including real-world data and patient-reported outcomes from a cohort of patients treated in Sweden, the first country where it was introduced, and (2) based on that information to provide practical guidance for healthcare teams starting patients on LECIG infusion, whether they are transitioning from oral medications or from other DATs, including recommendations for stepwise dosing calculation and titration. In terms of clinical efficacy, LECIG infusion has been shown to have a similar effect on motor function to standard levodopa–carbidopa intestinal gel (LCIG) infusion but, due to the presence of entacapone in LECIG, the bioavailability of levodopa is increased such that lower overall levodopa doses can be given to achieve therapeutically effective plasma concentrations. From a practical standpoint, LECIG infusion is delivered using a smaller cartridge and pump system than LCIG infusion. In addition, for patients previously treated with LCIG infusion who have an existing percutaneous endoscopic transgastric jejunostomy (PEG-J) system, this is compatible with the LECIG infusion system. As it is a relatively new product, the long-term efficacy and safety of LECIG infusion remain to be established; however, real-world data will continue to be collected and analysed to provide this information and help inform future clinical decisions.

A deep eutectic-based, self-emulsifying subcutaneous depot system for apomorphine therapy in Parkinson's disease

Parkinson’s disease (PD) is a progressive disorder of the central nervous system that affects motor control. While subcutaneous injection of apomorphine (Apokyn) is clinically used to alleviate intermittent episodes of dyskinesia, the treatment requires multiple injections of the drug per day, significantly deterring patient compliance. We introduce a deep eutectic-based ternary solvent system that self-emulsifies in situ following subcutaneous injection and entraps apomorphine, allowing a 48-h duration of detectable drug concentration in the plasma of pigs, which is a remarkable improvement over the clinical comparator. The results from the animal studies support the self-emulsifying system as a potent, long-lasting therapeutic for PD patients and potentially for other therapeutics that have a similar delivery challenge.

Apomorphine, a dopamine agonist, is a highly effective therapeutic to prevent intermittent off episodes in advanced Parkinson’s disease. However, its short systemic half-life necessitates three injections per day. Such a frequent dosing regimen imposes a significant compliance challenge, especially given the nature of the disease. Here, we report a deep eutectic-based formulation that slows the release of apomorphine after subcutaneous injection and extends its pharmacokinetics to convert the current three-injections-a-day therapy into an every-other-day therapy. The formulation comprises a homogeneous mixture of a deep eutectic solvent choline-geranate, a cosolvent n-methyl-pyrrolidone, a stabilizer polyethylene glycol, and water, which spontaneously emulsifies into a microemulsion upon injection in the subcutaneous space, thereby entrapping apomorphine and significantly slowing its release. Ex vivo studies with gels and rat skin demonstrate this self-emulsification process as the mechanism of action for sustained release. In vivo pharmacokinetics studies in rats and pigs further confirmed the extended release and improvement over the clinical comparator Apokyn. In vivo pharmacokinetics, supported by a pharmacokinetic simulation, demonstrate that the deep eutectic formulation reported here allows the maintenance of the therapeutic drug concentration in plasma in humans with a dosing regimen of approximately three injections per week compared to the current clinical practice of three injections per day.

Apomorphine Reduces A53T α-Synuclein-Induced Microglial Reactivity Through Activation of NRF2 Signalling Pathway

The chiral molecule, apomorphine, is currently used for the treatment of Parkinson’s disease (PD). As a potent dopamine receptor agonist, this lipophilic compound is especially effective for treating motor fluctuations in advanced PD patients. In addition to its receptor-mediated actions, apomorphine has also antioxidant and free radical scavenger activities. Neuroinflammation, oxidative stress, and microglia reactivity have emerged as central players in PD. Thus, modulating microglia activation in PD may be a valid therapeutic strategy. We previously reported that murine microglia are strongly activated upon exposure to A53T mutant α-synuclein. The present study was designed to investigate whether apomorphine enantiomers could modulate this A53T-induced microglial activation. Taken together, the results provided evidence that apomorphine enantiomers decrease A53T-induced microgliosis, through the activation of the NRF2 signalling pathway, leading to a lower pro-inflammatory state and restoring the phagocytic activity. Suppressing NRF2 recruitment (trigonelline exposure) or silencing specifically Nfe2l2 gene (siRNA treatment) abolished or strongly decreased the anti-inflammatory activity of apomorphine. In conclusion, apomorphine, which is already used in PD patients to mimic dopamine activity, may also be suitable to decrease α-synuclein-induced microglial reactivity.

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.

Long-term effect of apomorphine infusion in advanced Parkinson's disease: a real-life study

Long-term effects of continuous subcutaneous apomorphine infusion (CSAI) on health-related quality of life (HRQoL) and predictors of CSAI discontinuation are poorly known. Data from consecutive advanced Parkinson’s disease patients treated in routine care were retrospectively collected over 24 months after CSAI initiation, with a focus on the 39-item Parkinson’s disease questionnaire (PDQ-39). We determined predictors of CSAI discontinuation and HRQoL improvement using multiple regression analysis. Of the 110 subjects evaluated over a 2-year period, 35% discontinued CSAI. Of those who continued treatment, HRQoL remained stable with a sustained reduction in motor fluctuations. The observed effect on dyskinesias was mild and transient. Of note, patients with preexisting impulse control disorders showed an overall good tolerability. PDQ-39 was the only baseline predictor of HRQoL improvement after 2 years of treatment. The presence of dyskinesias, poorer psychological status, shorter disease duration, male sex, and worse OFF state were predictors of discontinuation. Best candidates for CSAI are patients with: (i) poor baseline HRQoL and (ii) marked motor fluctuations.

Targeting COVID-19 in Parkinson's Patients: Drugs Repurposed

The last couple of months have witnessed the world in a state of virtual standstill. The SARS-CoV-2 virus has overtaken the globe to economic and social lockdown. Many patients with COVID-19 have compromised immunity, especially in an aged population suffering from Parkinson 's disease (PD). Alteration in dopaminergic neurons and deficiency of dopamine in PD patients are the most common symptoms affecting 1% population above the age of 60 years. The compromised immune system and inflammatory manifestation in PD patients make them an easy target. The most common drugs under trial for COVID-19 are remdesivir, favipiravir, chloroquine and hydroxychloroquine, azithromycin along with adjunct drugs like amantadine with some monoclonal antibodies. Presently, clinically US FDA approved drugs in PD include Levodopa, catechol-O-methyl transferase (COMT) inhibitors, (Entacapone and Tolcapone), dopamine agonists (Bromocriptine, Ropinirole, Pramipexole, and Rotigotine), monoamine oxidase B (MAO-B) inhibitors (Selegiline and Rasagiline), amantadine and antimuscarinic drugs. The drugs have established mechanisms of action on PD patients with known pharmacodynamics and pharmacokinetic properties along with dose and adverse effects. Conclusion and relevance of this review focus on the drugs that can be tried on PD patients with SAR CoV-2 infection, in particular, amantadine that has been approved by all the developed countries as a common drug possessing both antiviral properties by downregulation of CTSL, lysosomal pathway disturbance and change in pH necessary to uncoat the viral proteins and anti- Parkinson properties. To deal with the significant prognostic adverse effect of SARS-CoV-2 on PD, the present-day treatment options, clinical presentation and various mechanisms are the need of the hour.

Importance of Nanoparticles for the Delivery of Antiparkinsonian Drugs

Parkinson's disease (PD) affects around ten million people worldwide and is considered the second most prevalent neurodegenerative disease after Alzheimer's disease. In addition, there is a higher risk incidence in the elderly population. The main PD hallmarks include the loss of dopaminergic neurons and the development of Lewy bodies. Unfortunately, motor symptoms only start to appear when around 50-70% of dopaminergic neurons have already been lost. This particularly poses a huge challenge for early diagnosis and therapeutic effectiveness. Actually, pharmaceutical therapy is able to relief motor symptoms, but as the disease progresses motor complications and severe side-effects start to appear. In this review, we explore the research conducted so far in order to repurpose drugs for PD with the use of nanodelivery systems, alternative administration routes, and nanotheranostics. Overall, studies have demonstrated great potential for these nanosystems to target the brain, improve drug pharmacokinetic profile, and decrease side-effects.

Rotigotine Transdermal Patch for Motor and Non-motor Parkinson's Disease: A Review of 12 Years' Clinical Experience

Motor and non-motor symptoms (NMS) have a substantial effect on the health-related quality of life (QoL) of patients with Parkinson's disease (PD). Transdermal therapy has emerged as a time-tested practical treatment option, and the rotigotine patch has been used worldwide as an alternative to conventional oral treatment for PD. The efficacy of rotigotine on motor aspects of PD, as well as its safety and tolerability profile, are well-established, whereas its effects on a wide range of NMS have been described and studied but are not widely appreciated. In this review, we present our overall experience with rotigotine and its tolerability and make recommendations for its use in PD and restless legs syndrome, with a specific focus on NMS, underpinned by level 1-4 evidence. We believe that the effective use of the rotigotine transdermal patch can address motor symptoms and a wide range of NMS, improving health-related QoL for patients with PD. More specifically, the positive effects of rotigotine on non-motor fluctuations are also relevant. We also discuss the additional advantages of the transdermal application of rotigotine when oral therapy cannot be used, for instance in acute medical emergencies or nil-by-mouth or pre/post-surgical scenarios. We highlight evidence to support the use of rotigotine in selected cases (in addition to general use for motor benefit) in the context of personalised medicine.

Long-term safety and efficacy of apomorphine infusion in Parkinson's disease patients with persistent motor fluctuations: Results of the open-label phase of the TOLEDO study

INTRODUCTION

The randomized, double-blind phase (DBP) of the TOLEDO study confirmed the efficacy of apomorphine infusion (APO) in reducing OFF time in PD patients with persistent motor fluctuations despite optimized oral/transdermal therapy. Here we report safety and efficacy results including the 52-week open-label phase (OLP).

METHODS

All patients completing the 12-week DBP (including those switching early to open-label treatment) were offered OLP entry. The primary objective was the evaluation of long-term safety of APO.

RESULTS

Eighty-four patients entered the OLP (40 previously on APO, 44 on placebo) and 59 patients (70.2%) completed the study. The safety profile of APO was consistent with experience from extensive clinical use. Common treatment-related adverse events (AEs) were mild or moderate infusion site nodules, somnolence and nausea. Fourteen (16.7%) patients discontinued the OLP due to AEs, those involving >1 patient were infusion site reactions (n = 4) and fatigue (n = 2); hemolytic anemia occurred in one case. Reduction in daily OFF time and improvement in ON time without troublesome dyskinesia were sustained for up to 64 weeks. Pooled data for week 64 (n = 55) showed a mean (SD) change from DBP baseline in daily OFF time of -3.66 (2.72) hours and in ON time without troublesome dyskinesia of 3.31 (3.12) hours. Mean (±SD) daily levodopa-equivalent dose decreased from DBP baseline to week 64 by 543 mg (±674) and levodopa dose by 273 mg (±515).

CONCLUSIONS

The safety and efficacy of APO infusion were demonstrated with long-term use for persistent motor fluctuations, allowing substantial reductions in oral PD medication.

Characterization of neurotransmitters and related metabolites in Daphnia magna juveniles deficient in serotonin and exposed to neuroactive chemicals that affect its behavior: A targeted LC-MS/MS method

Neurotransmitters are endogenous metabolites that play a crucial role within an organism, at the chemical synapses. There is a growing interest in their analytical determination for understanding the neurotoxic effect of contaminants. Daphnia magna represents an excellent aquatic model for these environmental studies, due to its similarities with vertebrates in several neurotransmitters and related gene pathways and because of its wide application in ecotoxicological studies. Within this study, an accurate and sensible method of analysis of 17 neurotransmitters and related precursors and metabolites was developed. The method was validated in terms of sensitivity, reproducibility, precision, and accuracy, and also matrix effect was evaluated. As an independent probe of method validation and applicability, the method was applied to two different scenarios. First, it was used for the study of neurotransmitter levels in genetically mutated tryptophan hydrolase D. magna clones, confirming the absence of serotonin and its metabolite 5-HIAA. Additionally, the method was applied for determining the effects of chemical compounds known to affect different neurotransmitter systems and to alter Daphnia behavior. Significant changes were observed in 13 of the analyzed neurotransmitters across treatments, which were related to the neurotransmitter systems described as being affected by these neurochemicals. These two studies, which provide results on the ways in which the neurotransmitter systems in D. magna are affected, have corroborated the applicability of the presented method, of great importance due to the suitability of this organism for environmental neurotoxicity studies.

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.

The Choice Between Advanced Therapies for Parkinson's Disease Patients: Why, What, and When?

When oral dopaminergic medication falls short in the treatment of Parkinson’s disease, patients are left with motor response fluctuations and dyskinesias that may have a large impact on functioning in daily life. They may benefit from one of the currently available advanced treatments, namely deep brain stimulation, continuous levodopa-carbidopa intestinal gel, and continuous subcutaneous apomorphine infusion. The indication, choice between the separate advanced treatments and the timing can be challenging and will be discussed against the background of the progressive nature of the disease, the heterogeneity of disease manifestation and variable patient characteristics.

An evaluation of subcutaneous apomorphine for the treatment of Parkinson's disease

INTRODUCTION

Heterogeneity of symptoms and individual variability of progression characterizes Parkinson's disease. Unmet therapeutic needs include a cure, disease modification, and improvement of available marketed dopamine-substituting compounds. Personalized treatment, tailored to the patients' needs and symptoms, aims to ameliorate impaired motor behavior and non-motor features. Injection or infusion of apomorphine is a therapeutic option for more advanced patients with severe levodopa associated motor complications.

AREAS COVERED

This narrative review summarizes the subcutaneous administration, efficacy, and side effects of the non-ergot derivative dopamine agonist apomorphine following a non-systematic literature research.

EXPERT OPINION

Subcutaneous apomorphine hydrochloride application rapidly terminates intervals with severe motor impairment with bolus injections. Oscillation of motor behavior well responds to continuous apomorphine infusions. Long-term application of the commercially available apomorphine hydrochloride solution sooner or later affects skin and oral mucosa. Onset of skin nodules associated with subcutaneous tissue inflammation probably results from the antioxidant preservative sodium metabisulfite in the apomorphine solution. Addition of another better tolerated and safer antioxidant instead of sodium metabisulphite or use of an already available concentrated apomorphine-free base formulation will enhance its future use, its tolerability, safety, and acceptance of subcutaneous and sublingual application.

Establishing apomorphine treatment in Thailand: understanding the challenges and opportunities of Parkinson's disease management in developing countries

INTRODUCTION

The increasing global burden of Parkinson's disease (PD) poses a particular challenge for developing countries, such as Thailand, when delivering care to a geographically diverse populace with limited resources, often compounded by a lack of expertise in the use of certain PD medications, such as device-aided therapies (DAT).

AREAS COVERED

A panel of local, regional, and international PD experts convened to review the unmet needs of PD in Thailand and share insights into effective delivery of DAT, focusing on experience with apomorphine infusion. Despite its proven efficacy and safety, implementation of apomorphine infusion as a new option was not straightforward. This has prompted a range of health-care professional and patient-focused initiatives, led by the Chulalongkorn Center of Excellence for Parkinson's Disease and Related Disorders in Bangkok, to help establish a more coordinated approach to PD management throughout the country and ensure patients have access to suitable treatments.

EXPERT OPINION

Overcoming the challenges of education, proficiency, resource capacity and standard of care for PD patients in developing countries requires a coordinated effort both nationally and beyond. The best practices identified in Thailand following the introduction of apomorphine infusion might be helpful for other countries when implementing similar programs.

Management of Advanced Therapies in Parkinson's Disease Patients in Times of Humanitarian Crisis: The COVID-19 Experience

Background

Although the COVID-19 pandemic is affecting a relatively small proportion of the global population, its effects have already reached everyone. The pandemic has the potential to differentially disadvantage chronically ill patients, including those with Parkinson's disease (PD). The first health care reaction has been to limit access to clinics and neurology wards to preserve fragile patients with PD from being infected. In some regions, the shortage of medical staff has also forced movement disorders neurologists to provide care for patients with COVID-19.

Objective

To share the experience of various movement disorder neurologists operating in different world regions and provide a common approach to patients with PD, with a focus on those already on advanced therapies, which may serve as guidance in the current pandemic and for emergency situations that we may face in the future.

Conclusion

Most of us were unprepared to deal with this condition given that in many health care systems, telemedicine has been only marginally available or only limited to email or telephone contacts. In addition, to ensure sufficient access to intensive care unit beds, most elective procedures (including deep brain stimulation or the initiation of infusion therapies) have been postponed. We all hope there will soon be a time when we will return to more regular hospital schedules. However, we should consider this crisis as an opportunity to change our approach and encourage our hospitals and health care systems to facilitate the remote management of chronic neurological patients, including those with advanced PD.

A Novel G Protein-Biased and Subtype-Selective Agonist for a G Protein-Coupled Receptor Discovered from Screening Herbal Extracts

Subtype selectivity and functional bias are vital in current drug discovery for G protein-coupled receptors (GPCRs) as selective and biased ligands are expected to yield drug leads with optimal on-target benefits and minimal side-effects. However, structure-based design and medicinal chemistry exploration remain challenging in part because of highly conserved binding pockets within subfamilies. Herein, we present an affinity mass spectrometry approach for screening herbal extracts to identify active ligands of a GPCR, the 5-HT_2C receptor. Using this method, we discovered a naturally occurring aporphine 1857 that displayed strong selectivity for activating 5-HT_2C without activating the 5-HT_2A or 5-HT_2B receptors. Remarkably, this novel ligand exhibited exclusive bias toward G protein signaling for which key residues were identified, and it showed comparable in vivo efficacy for food intake suppression and weight loss as the antiobesity drug, lorcaserin. Our study establishes an efficient approach to discovering novel GPCR ligands by exploring the largely untapped chemical space of natural products.

Apomorphine: The Initial Indian Experience in Relation to Response Tests and Pumps

Background:

Apomorphine is an option for continuous dopaminergic therapy in Parkinson's disease (PD). However, its effects in varied populations are limited due to its availability.

Objective:

To assess the efficacy and outcomes of apomorphine in Indian patients.

Materials and Methods:

Retrospective analysis of PD patients who underwent apomorphine response test (ART), along with the subset, who went on to apomorphine pumps.

Results:

Twenty-nine confirmed PD patients underwent ART and all PD patients showed good clinical response. 19 subjects developed adverse events which included: nausea (n-15, 51.7%), vomiting (n-10, 34.4%), sleepiness (n-08; 27.5%), yawning (n-07, 24.1%), postural hypotension (n-03, 10.3%), dizziness (n-03, 10.3%), and profuse sweating (n-01, 3.4%). Apomorphine pumps were initiated in six subjects, with significant clinical improvement. Adverse events on pump included subcutaneous nodules, nausea, hypersexuality. Two among them subsequently discontinued the pump primarily due to financial constraints.

Conclusions:

Apomorphine adds up to the armamentarium for treatment of PD patients in India with good clinical responses.

Dopaminergic Effect on Non-Motor Symptoms in Late Stage Parkinson's Disease

BACKGROUND

Non-motor symptoms (NMS) are common in late stage Parkinson's disease (PD), as the frequency and severity of most of these symptoms increase with advancing disease.

OBJECTIVE

To assess effect of dopaminergic therapy on NMS in late stage PD and to investigate relationships between dopaminergic effect on NMS and on motor function.

METHOD

Thirty PD patients in Hoehn and Yahr (HY) stages IV and V in "on" were included. Dopaminergic effect on non-motor symptomatology was assessed by the modified version of the Non-Motor Symptoms Scale (NMSS) in the "off" and the "on" state during a standardized L-dopa test, in parallel also assessing motor function.

RESULTS

NMS were common and many of the symptoms occurred in >80% of the individuals. The highest NMSS scores were seen within the NMSS domains 3: mood/apathy and 7: urinary in both the "off" and the "on" state. There was a statistically significant (p < 0.001) improvement in the modified NMSS total score (median) from 79 in "off" to 64 in "on". There were statistically significant differences between the "off" and the "on" state for domains 2: sleep/fatigue, 3: mood/apathy, 5: attention/memory, 6: gastrointestinal and 7: urinary. The differences in the NMSS score between the "off" and the "on" state were in general larger for motor responders than for motor non-responders. In motor non-responders, differences of the NMSS score between the "off" and the "on" state were found for the total score, domain 3: mood/apathy and its item 11-flat moods.

CONCLUSION

There is an effect of dopaminergic medication on NMS in late stage PD, to some extent also for those with a non-significant response on motor function during L-dopa test. It is therefore of importance to optimize dopaminergic therapy in order to give the most effective symptomatic treatment possible.

Emergencies and critical issues in Parkinson's disease

Complications from Parkinson’s disease may develop over the disease course, sometimes unexpectedly, and require prompt or even urgent medical intervention. The most common are associated with aggravation of motor symptoms; serious non-motor complications, such as psychosis, orthostatic hypotension or sleep attacks, also occur. Here we review such complications, their clinical presentation, precipitating factors and management, including those related to using device-aided therapies. Early recognition and prompt attention to these critical situations is challenging, even for the Parkinson’s disease specialist, but is essential to prevent serious problems.

Apomorphine rescues reactive oxygen species-induced apoptosis of fibroblasts with mitochondrial disease

Mitochondrial disease is a genetic disorder in which individuals suffer from energy insufficiency. The various clinical phenotypes of mitochondrial disease include Leigh syndrome (LS), myopathy encephalopathy lactic acidosis and stroke-like episodes (MELAS). Thus far, no curative treatment is available, and effective treatment options are eagerly awaited. We examined the cell protective effect of an existing commercially available chemical library on fibroblasts from four patients with LS and MELAS and identified apomorphine as a potential therapeutic drug for mitochondrial disease. We conducted a cell viability assay under oxidative stress induced by L-butionine (S, R)-sulfoximine (BSO), a glutathione synthesis inhibitor. Among the chemicals of library, 4 compounds (apomorphine, olanzapine, phenothiazine and ethopropazine) rescued cells from death induced by oxidative stress much more effectively than idebenone, which was used as a positive control. The EC₅₀ value showed that apomorphine was the most effective compound. Apomorphine also significantly improved all of the assessed oxygen consumption rate values by the extracellular flux analyzer for fibroblasts from LS patients with complex I deficiency. In addition, the elevation of the Growth Differentiation Factor-15 (GDF-15), a biomarker of mitochondrial disease, was significantly reduced by apomorphine. Among 441 apomorphine-responsive genes identified by the microarray, apomorphine induced the expression of genes that inhibit the mammalian target of rapamycin (mTOR) activity and inflammatory responses, suggesting that apomorphine induced cell survival via a new potential pathway. In conclusion, apomorphine rescued fibroblasts from cell death under oxidative stress and improved the mitochondrial respiratory activity and appears to be potentially useful for treating mitochondrial disease.