The Many Faces of Apomorphine: Lessons from the Past and Challenges for the Future

One-Step Synthesis of Chiral 9,10-Dihydrophenanthrenes via Ligand-Enabled Enantioselective Cascade β,γ-Diarylation of Acids

Pd(II)-catalyzed enantioselective C-H activation has emerged as a versatile platform for constructing point, axial, and planar chirality. Herein, we present an unexpected discovery of a Pd-catalyzed enantioselective cascade β,γ-methylene C(sp3)-H diarylation of free carboxylic acids using bidentate chiral mono-protected amino thioether ligands (MPAThio), enabling one-step synthesis of a complex chiral 9,10-dihydrophenanthrene scaffolds with high enantioselectivity. In this process, two methylene C(sp3)-H bonds and three C(sp2)-H bonds were activated, leading to the formation of four C-C bonds and three chiral centers in one pot. A plausible catalytic pathway starts with enantioselective β,γ-dehydrogenation to form chiral β,γ-cyclohexene. Intriguingly, this olefin serves as a norbornene-type reagent (presumably assisted by the carboxyl directing effect), relaying two successive Catellani arylation reactions and a C-H arylation reaction to furnish chiral 9,10-dihydrophenanthrenes along with meta-selective homocoupling products of iodoarene.

Phytochemicals in Drug Discovery-A Confluence of Tradition and Innovation

Phytochemicals have a long and successful history in drug discovery. With recent advancements in analytical techniques and methodologies, discovering bioactive leads from natural compounds has become easier. Computational techniques like molecular docking, QSAR modelling and machine learning, and network pharmacology are among the most promising new tools that allow researchers to make predictions concerning natural products' potential targets, thereby guiding experimental validation efforts. Additionally, approaches like LC-MS or LC-NMR speed up compound identification by streamlining analytical processes. Integrating structural and computational biology aids in lead identification, thus providing invaluable information to understand how phytochemicals interact with potential targets in the body. An emerging computational approach is machine learning involving QSAR modelling and deep neural networks that interrelate phytochemical properties with diverse physiological activities such as antimicrobial or anticancer effects.

Efficacy and safety of apomorphine pump infusion in Filipino patients insufficiently controlled on oral anti-Parkinson medications: an open-label, pilot study

BACKGROUND

Apomorphine hydrochloride is used in the management of advanced Parkinson disease (PD), either as a rescue medication for off periods during levodopa therapy or as a maintenance pump medication. This is the first study to describe the effects of apomorphine in Filipino patients with PD.

OBJECTIVE

To evaluate the safety and efficacy of apomorphine ampules (APO-go®) pump infusion in the treatment of motor fluctuations in patients inadequately controlled on oral anti-Parkinson medications.

METHODS

Patients diagnosed with PD who developed motor fluctuations with levodopa were evaluated at baseline and at the end of the study using the Modified Hoehn and Yahr (H&Y) Scale, the Unified Parkinson's Disease Rating Scale (UPDRS) and the Abnormal Involuntary Movement Scale (AIMS). After initial assessment, patients were administered 20 ampules of apomorphine hydrochloride 10 mg/mL by infusion pump over 20 days. Intention-to-treat (ITT) analysis included all patients who completed at least one posttreatment assessment. Motor disability based on modified H&Y scores, motor function and complications of therapy pre- and posttreatment were compared using Wilcoxon Signed Rank test. Chi-squared test was used to compare outcomes by age and sex. Frequencies of adverse reactions were recorded to evaluate the tolerability of the medication.

RESULTS

Ten patients (mean age 63 ± 9.7 years), 3 male and 7 female, were enrolled in the study. Patients were given apomorphine for at most 16 days. The doses used were 2.5 mg/0.50 mL (n = 2), 3 mg/0.60 mL (n = 6), 4 mg/0.80 mL (n = 1) and 7 mg/1.40 mL (n = 1). After obtaining the threshold dose, two patients discontinued treatment. Eight of nine patients showed significant improvement in H&Y scores after treatment (p < 0.017). There was marked improvement after 10 days of treatment in at least five of 10 patients in terms of motor function using UPDRS, which included tremor (p < 0.034), rigidity (p < 0.002), facial expression (p < 0.014), finger taps (p < 0.008), foot taps (p < 0.014) and gait (p < 0.006). Significant changes from pre- to posttreatment scores in the frequency of dyskinesias (p < 0.010) and dystonia (p < 0.025) were observed. Nine focus areas of AIMS showed significant improvements in the muscles of facial expression (p < 0.020), upper (p < 0.016) and lower extremities (p < 0.010), incapacitation by abnormal movement (p < 0.010) and patients' awareness of abnormal movements (p < 0.039). Six patients experienced adverse events, none of which were related to the study drug.

CONCLUSION

Apomorphine hydrochloride pump infusion therapy is potentially effective and safe in the treatment of motor fluctuations in Filipino patients with PD. This pilot study springboards safe engagements of Filipino PD patients in multicenter, large-scale trials.

Clinical trial evaluating apomorphine oromucosal solution in Parkinson's disease patients

Apomorphine, used to treat OFF episodes in patients with Parkinson's disease (PD), is typically administered via subcutaneous injections. Administration of an oromucosal solution could offer a non-invasive and user-friendly alternative. This two-part clinical study evaluated the safety, tolerability, pharmacokinetics (PK), and dose proportionality of a novel apomorphine hydrochloride oromucosal solution, as well as its relative bioavailability to subcutaneous apomorphine injection and apomorphine sublingual film. In part A of the study, 12 patients with PD received 2 mg oromucosal apomorphine (4% weight/volume) and 2 mg subcutaneous apomorphine in a randomized order, followed by 4 and 8 mg oromucosal apomorphine. In part B of the study, 13 patients with PD received 7 mg oromucosal apomorphine (7% weight/volume) and 30 mg sublingual apomorphine in a randomized order, followed by 14 mg oromucosal apomorphine. Washout between dose administrations in both study parts was at least 2 days. Safety, tolerability, and PK were assessed pre- and post-dose. Both study parts showed that oromucosal apomorphine was generally well-tolerated. Observed side effects were typical for apomorphine administration and included asymptomatic orthostatic hypotension, yawning, fatigue, and somnolence. Oromucosal apomorphine exposure increased with dose, although less than dose proportional. The mean (SD) maximum exposure reached with 14 mg oromucosal apomorphine was 753.0 (298.6) ng*min/mL (area under the plasma concentration-time curve from zero to infinity) and 8.0 (3.3) ng/mL (maximum plasma concentration). This was comparable to exposure reached after 2 mg subcutaneous apomorphine and approximately half of the exposure observed with 30 mg sublingual apomorphine. In summary, clinically relevant plasma concentrations could be reached in PD patients without tolerability issues.

Terminal Care in Parkinson's Disease: Real-Life Use of Continuous Subcutaneous Apomorphine Infusion to Improve Patient Comfort

BACKGROUND

There are currently no recommendations on the therapeutic management of Parkinson's disease (PD) patients at the end of life.

OBJECTIVE

To describe a cohort of patients with PD who benefited from continuous subcutaneous apomorphine infusion (CSAI) initiation at the end of their life as comfort care.

METHODS

This real-life cohort includes 14 PD patients, who benefited from 24-h, low-dose CSAI (0.5-3 mg/h) in the context of terminal care. Patient's comfort (pain, rigidity, and/or ability to communicate) and occurrence of CSAI-related side-effects (nausea/vomiting, cutaneous and behavioral manifestations) were evaluated based on medical records.

RESULTS

All patients (age 62-94 years, disease duration 2-32 years) presented with late-stage PD and a compromised oral route. Treatment lasted from a few hours to 39 days. CSAI led to substantial functional improvement, with a good safety profile. Overall clinical comfort was deemed improved by the medical team, the patient, and/or caregivers.

CONCLUSIONS

CSAI might be a promising approach in PD terminal care, as it reduces motor symptoms and overall discomfort, with an apparent good safety profile. Use of the apomorphine pen, sublingual film or a classic syringe pump might be considered when apomorphine pumps are not available. Larger observational cohorts and randomized controlled trials are needed to establish the efficacy and tolerability of apomorphine in the context of terminal care and more broadly, in an advance care planning perspective.

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.

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.

Feasibility and benefits of home initiation of subcutaneous apomorphine infusion for patients with Parkinson's disease: the APOKADO study

Continuous subcutaneous apomorphine infusion (CSAI) is used to treat patients with Parkinson's disease (PD) who are experiencing motor fluctuations. However, the need to initiate this treatment during a hospital stay may restrict patients' access to it. To assess the feasibility and benefits of initiating CSAI in the patient's own home. A French prospective multicenter longitudinal observational study (APOKADO) among patients with PD who required subcutaneous apomorphine, comparing in-hospital versus home initiation. Clinical status was assessed according to the Hoehn and Yahr score), the Unified Parkinson's Disease Rating Scale Part III, and the Montreal Cognitive Assessment. We assessed patients' quality of life with the 8-item Parkinson's Disease Questionnaire, rated the improvement in their clinical status on the 7-point Clinical Global Impression-Improvement scale, recorded adverse events, and ran a cost-benefit analysis. 145 patients with motor fluctuations were included in 29 centers (office and hospital). Of these, 106 (74%) were initiated onto CSAI at home, and 38 (26%) in hospital. At inclusion, the two groups were comparable for all demographic and PD characteristics. After 6 months, quality of life, adverse events and early dropout rates were similarly rare-across the two groups. Patients in the home group improved more quickly their quality of life and became more autonomous in managing the device than those in the hospital group, and their care costed less. This study shows that home (versus in-hospital) initiation of CSAI is feasible, improves patients' quality of life more quickly, with the same level of tolerance. It is also less expensive. This finding should make it easier for patients to access this treatment in the future.

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.

Intermittent Apomorphine Use for off Period Rescue in Parkinson's Disease: A Pragmatic Review of over Three Decades of Clinical Experience

Background

Although proven very efficacious as treatment for Parkinson's disease by Schwab as far back as the 1950s, and later confirmed by Cotzias and colleagues in the early 1970s, use of intermittent subcutaneous injections of the dopamine agonist apomorphine remains limited worldwide.

Objectives

To review evidence regarding use of intermittent, on-demand apomorphine as a treatment for off-period disability in Parkinson's disease.

Methods

A PRISMA-compliant structured literature search was carried out with a focus on clinical effect (motor improvement, daily off time decrease; latency, duration), antiemetic prophylaxis, and adverse events.

Results

Fifty-eight studies were evaluated. Apomorphine administration route was subcutaneous in 29 (50%), sublingual in 14 (24.1%), intranasal in 6 (10.3%), inhaled in 5 (8.6%), rectal in 3 (5.2%) and transdermal in 1 (1.7%). Irrespective of the route, motor disability improved 19% to 74% and daily off time decreased 3% to 68%, with subcutaneous having the fastest onset of action ranging from 6 to 24 minutes and lasting 28 to 96 minutes. Antiemetic prophylaxis was used in almost all studies. Systemic side effects like nausea and yawning were mild and well tolerated, but sedation led to discontinuation of subcutaneous apomorphine in 5.5%. Local side effects to subcutaneous administration did not result in discontinuation. Stomatitis with the early sublingual formulations led to discontinuation in nearly half of patients and was reduced to 16.7% with novel film strips.

Conclusions

Intermittent subcutaneous injections remain the most reliable and safest route of apomorphine administration, with an efficacy for off period treatment supported by nearly four decades of clinical experience.

Management of Motor Symptoms for Patients with Advanced Parkinson's Disease without Safe Oral Access: A Scoping Review

Context: Parkinson's disease (PD) is the second most common neurodegenerative disorder worldwide. Oral medications for control of motor symptoms are the mainstay of treatment. However, as the disease progresses, patients with PD may develop dysphagia that prohibits them from safely taking oral medications. Currently there are no clinical guidelines for managing distressing motor symptoms in patients with PD and severe dysphagia, which can therefore be quite challenging. Objectives: To provide an exhaustive summary of current literature on pharmacological interventions for patients with PD who do not have safe oral access in managing distressing motor symptoms. Indication, route, doses, frequency, outcome, and adverse effects will be discussed. Methods: A scoping review using Medline, Embase, CENTRAL, CINAHL, AgeLine, and PsycINFO databases (1946-2021) was conducted. Articles examining patients with PD and dysphagia who are eligible to receive palliative care or at end of life were included. Studies that included patients who were also on oral PD medications or received device-aided therapy were excluded from this review. Results: A total of 3821 articles were screened for title and abstract, 259 were selected for full-text review, and 20 articles were selected for data extraction. These included five case reports, one retrospective cohort study, one book chapter, and 13 narrative reviews. There are very few articles addressing the issue of treatment of patients with advanced PD who are unable to take oral medications. Although rotigotine patch and apormorphine injections are most frequently recommended, there are no clinical trials in this patient population to support those recommendations. Conclusion: This study highlights a need for further research examining the efficacy and dosing of nonoral medications in advanced PD with dysphagia.

Sublingual apomorphine therapy as an alternative to complex continuous infusion pumps in advanced Parkinson's disease treatment: a district nurse-led intervention

In the UK, Parkinson's disease (PD) is estimated to affect an annual incidence of 15-20 per 100 000 of the population over the age of 60. Service users living with advanced-stage PD require the use of apomorphine, which is generally used to control symptoms. The district nursing service plays a key role in monitoring and in the administration of apomorphine therapy. Although apomorphine is effective, skin problems such as nodules are commonly reported adverse events that can complicate efficiency of treatment. A sublingual delivery route to apomorphine has been known for years as a feasible alternative to subcutaneous route. Collaboration between the multidisciplinary team is essential to meet the complex needs of service users with advanced PD. However, due to the increase in demands of the district nurse service, this time crucial intervention can be unpredictable to meet. An alternative route can enable district nurses to become less task-orientated. However, an increased risk of oral cavity related adverse events should be taken into consideration with the sublingual administration of apomorphine.

Phenols in Pharmaceuticals: Analysis of a Recurring Motif

Phenols and phenolic ethers are significant scaffolds recurring both in nature and among approved small-molecule pharmaceuticals. This compendium presents the first comprehensive compilation and analysis of the structures of U.S. FDA-approved molecules containing phenol or phenolic ether fragments. This dataset comprises 371 structures, which are strongly represented by natural products. A total of 55 of the compounds described here are on the World Health Organization's list of essential medicines. Structural analysis reveals significant differences in the physicochemical properties imparted by phenols versus phenol ethers, each having benefits and drawbacks for drug developability. Despite trends over the past decade to increase the fraction of sp³ centers in drug leads, thereby "escaping flatland", phenols and phenolic ethers are represented in 62% of small-molecule drugs approved in 2020, suggesting that this aromatic moiety holds a special place in drugs and natural products.

Ankk1 Loss of Function Disrupts Dopaminergic Pathways in Zebrafish

Ankyrin repeat and kinase domain containing 1 (ANKK1) is a member of the receptor-interacting protein serine/threonine kinase family, known to be involved in cell proliferation, differentiation and activation of transcription factors. Genetic variation within the ANKK1 locus is suggested to play a role in vulnerability to addictions. However, ANKK1 mechanism of action is still poorly understood. It has been suggested that ANKK1 may affect the development and/or functioning of dopaminergic pathways. To test this hypothesis, we generated a CRISPR-Cas9 loss of function ankk1 zebrafish line causing a 27 bp insertion that disrupts the ankk1 sequence introducing an early stop codon. We found that ankk1 transcript levels were significantly lower in ankk1 mutant (ankk127ins) fish compared to their wild type (ankk1+/+) siblings. In ankk1+/+ adult zebrafish brain, ankk1 protein was detected in isocortex, hippocampus, basolateral amygdala, mesencephalon, and cerebellum, resembling the mammalian distribution pattern. In contrast, ankk1 protein was reduced in the brain of ankk127ins/27ins fish. Quantitative polymerase chain reaction analysis revealed an increase in expression of drd2b mRNA in ankk127ins at both larval and adult stages. In ankk1+/+ adult zebrafish brain, drd2 protein was detected in cerebral cortex, cerebellum, hippocampus, and caudate homolog regions, resembling the pattern in humans. In contrast, drd2 expression was reduced in cortical regions of ankk127ins/27ins being predominantly found in the hindbrain. No differences in the number of cell bodies or axonal projections detected by anti-tyrosine hydroxylase immunostaining on 3 days post fertilization (dpf) larvae were found. Behavioral analysis revealed altered sensitivity to effects of both amisulpride and apomorphine on locomotion and startle habituation, consistent with a broad loss of both pre and post synaptic receptors. Ankk127ins mutants showed reduced sensitivity to the effect of the selective dopamine receptor antagonist amisulpride on locomotor responses to acoustic startle and were differentially sensitive to the effects of the non-selective dopamine agonist apomorphine on both locomotion and habituation. Taken together, our findings strengthen the hypothesis of a functional relationship between ANKK1 and DRD2, supporting a role for ANKK1 in the maintenance and/or functioning of dopaminergic pathways. Further work is needed to disentangle ANKK1’s role at different developmental stages.

BAPST. A Combo of Common use drugs as metabolic therapy of cancer-a theoretical proposal

Advances in cancer therapy have yet to impact worldwide cancer mortality. Poor cancer drug affordability is one of the factors limiting mortality burden strikes. Up to now, cancer drug repurposing had no meet expectations concerning drug affordability. The three FDA-approved cancer drugs developed under repurposing -all-trans-retinoic acid, arsenic trioxide, and thalidomide- do not differ in price from other drugs developed under the classical model. Though additional factors affect the whole process from inception to commercialization, the repurposing of widely used, commercially available, and cheap drugs may help. This work reviews the concept of the malignant metabolic phenotype and its exploitation by simultaneously blocking key metabolic processes altered in cancer. We elaborate on a combination called BAPST, which stands for the following drugs and pathways they inhibit: Benserazide (glycolysis), Apomorphine (glutaminolysis), Pantoprazole (Fatty-acid synthesis), Simvastatin (mevalonate pathway), and Trimetazidine (Fatty-acid oxidation). Their respective primary indications are: • Parkinson's disease (benserazide and apomorphine). • Peptic ulcer disease (pantoprazole). • Hypercholesterolemia (simvastatin). • Ischemic heart disease (trimetazidine). When used for their primary indication, the literature review on each of these drugs shows they have a good safety profile and lack predicted pharmacokinetic interaction among them. Most importantly, the inhibitory enzymatic concentrations required for inhibiting their cancer targets enzymes are below the plasma concentrations observed when these drugs are used for their primary indication. Based on that, we propose that the regimen BAPTS merits preclinical testing.

Intrathecal and intracerebroventricular dopamine for Parkinson's disease

While CDD directly to the CSF can provide a constant delivery of the dopaminergic drug resulting in a more stable treatment effect without the limitations of traditional oral therapy without peripheral effects, it is still young and longitudinal data is lacking. These experimental therapies show promise and further investigation into their efficacy and safety could extend the frontiers for management of PD.

Apomorphine for the Treatment of Erectile Dysfunction: Systematic Review and Meta-Analysis

Sublingual apomorphine could be an option in patients with erectile dysfunction who cannot take phosphodiesterase type 5 inhibitors (e.g., using nitrates). We have completed a systematic review to evaluate the effects of sublingual apomorphine comparing with placebo for treating erectile dysfunction. The evidence searching process finished on 9 January 2019. We included nine randomized controlled trials (RCTs). Treatment length varied from 4 to 8 weeks and doses ranged from 2 to 6 mg. The percent of successful sexual intercourse attempts per ingested dose of apomorphine was evaluated in eight studies. All the studies found that apomorphine was better than placebo (6-27% more successful intercourse attempts than with placebo), but differences were not statistically significant in one study done in patients previously treated with radical prostatectomy. Regarding erectile function scores, three studies reported higher improvement on the erectile function scores for apomorphine. Differences with placebo were not clinically relevant in another two studies, one in which only diabetic patients were included and one in which only patients with radical prostatectomy were involved. Discontinuation of treatment due to adverse events was higher for apomorphine, particularly for higher doses. Available evidence suggests that sublingual apomorphine is more effective than placebo, except for patients previously treated with radical prostatectomy, and is generally well tolerated at doses of 2 or 3 mg. Nowadays, sublingual apomorphine is the only licensed oral drug for erectile dysfunction not absolutely contraindicated with nitrates use, and more RCTs should be performed to evaluate its effects and safety for treating ED.

Identification of C10 nitrogen-containing aporphines with dopamine D1 versus D5 receptor selectivity

New aporphines containing C10 nitrogen substituents (viz. nitro, aniline or amide moieties), were synthesized and evaluated for affinity at human serotonin 5-HT_1A and 5-HT_2A receptors and at human dopamine D₁, D₂ and D₅ receptors. Two series of analogs were investigated: series A which contain a sole C10 nitrogen substituent on the tetracyclic aporphine core and series B which are 1,2,10-trisubstituted aporphines. Remarkably, compounds from both series lacked affinity for the D₅ receptor, thus attaining D₁ versus D₅ selectivity. Compound 20c was the most potent D₁ ligand identified. Docking studies at D₁ and D₅ receptors indicate that the binding mode of 20c at the D₁ receptor allows for stronger hydrophobic contacts, (primarily with Phe residues) as compared to the D₅ receptor, accounting for its D₁ versus D₅ selectivity. Considering the lack of affinity for the D₅ receptor (and low affinity at other receptors tested), compound 20c represents an interesting starting point for further structural diversification of aporphines as sub-type selective D₁ receptor tools.

Merging the Pathophysiology and Pharmacotherapy of Tics

Background

Anatomically, cortical-basal ganglia-thalamo-cortical (CBGTC) circuits have an essential role in the expression of tics. At the biochemical level, the proper conveyance of messages through these circuits requires several functionally integrated neurotransmitter systems. In this manuscript, evidence supporting proposed pathophysiological abnormalities, both anatomical and chemical is reviewed. In addition, the results of standard and emerging tic-suppressing therapies affecting nine separate neurotransmitter systems are discussed. The goal of this review is to integrate our current understanding of the pathophysiology of Tourette syndrome (TS) with present and proposed pharmacotherapies for tic suppression.

Methods

For this manuscript, literature searches were conducted for both current basic science and clinical information in PubMed, Google-Scholar, and other scholarly journals to September 2018.

Results

The precise primary site of abnormality for tics remains undetermined. Although many pathophysiologic hypotheses favor a specific abnormality of the cortex, striatum, or globus pallidus, others recognize essential influences from regions such as the thalamus, cerebellum, brainstem, and ventral striatum. Some prefer an alteration within direct and indirect pathways, whereas others believe this fails to recognize the multiple interactions within and between CBGTC circuits. Although research and clinical evidence supports involvement of the dopaminergic system, additional data emphasizes the potential roles for several other neurotransmitter systems.

Discussion

A greater understanding of the primary neurochemical defect in TS would be extremely valuable for the development of new tic-suppressing therapies. Nevertheless, recognizing the varied and complex interactions that exist in a multi-neurotransmitter system, successful therapy may not require direct targeting of the primary abnormality.

New tricks for an old dog: A repurposing approach of apomorphine

Apomorphine is a 150-year old nonspecific dopaminergic agonist, currently indicated for treating motor fluctuations in Parkinson's disease. At the era of drug repurposing, its pleiotropic biological functions suggest other possible uses. To further explore new therapeutic and diagnostic applications, the available literature up to July 2018 was reviewed using the PubMed and Google Scholar databases. As many of the retrieved articles consisted of case reports and preclinical studies, we adopted a descriptive approach, tackling each area of research in turn, to give a broad overview of the potential of apomorphine. Apomorphine may play a role in neurological diseases like restless legs syndrome, Huntington's chorea, amyotrophic lateral sclerosis, Alzheimer's disease and disorders of consciousness, but also in sexual disorders, neuroleptic malignant(-like) syndrome and cancer. Further work is needed in both basic and clinical research; current developments in novel delivery strategies and apomorphine derivatives are expected to open the way.

Apomorphine effects on the hippocampus

Apomorphine is a non-specific dopamine receptor agonist that has been used in the treatment of some diseases and mental disorders. Its use has particularly well documented in Parkinson's disease (PD). The dopaminergic agonists like apomorphine are related to oxidative processes that could induce cell damage and the functional impairment of some structures in the brain. However, most information about apomorphine in literature is focused on the improvement of the motor problems characteristic of PD, but little is known about the effects on cognitive behaviors and brain structures indirectly related to motor function. The presence of dopaminergic receptors in the hippocampus has recently been discovered, in connection with cognitive behaviors like learning and memory, these receptors are needed in neuronal plasticity. There has been a growing interest to know if this structure could be compromised by the effect of apomorphine and elucidate if part of the cognitive impairment present in the PD is due to the effect of apomorphine. In this mini-review, we summarized how apomorphine has been used since its creation, we discuss the latest information about its effect on the hippocampus and also the future perspectives to fully understand the effects of this compound.