Safinamide in neurological disorders and beyond: Evidence from preclinical and clinical studies

Safety comparisons among monoamine oxidase inhibitors against Parkinson's disease using FDA adverse event reporting system

Monoamine oxidase B (MAO-B) inhibitors are used to control Parkinson's disease (PD). Selegiline, rasagiline, and safinamide are widely used as MAO-B inhibitors worldwide. Although these drugs inhibit MAO-B, there are pharmacological and chemical differences, such as the inhibitory activity, the non-dopaminergic properties in safinamide, and the amphetamine-like structure in selegiline. MAO-B inhibitors may differ in adverse events (AEs). However, differences in actual practical clinics are not fully investigated. A retrospective study was conducted using FAERS, the largest database of spontaneous adverse events. AE signals for MAO-B inhibitors, including selegiline, rasagiline, and safinamide, were detected using the reporting odds ratio method and compared. Hypocomplementemia, hepatic cyst, hepatic function abnormal, liver disorder and cholangitis were detected for selegiline as drug-specific signals. The amphetamine effect was not confirmed for any of the three MAO-B inhibitors. The tyramine reaction was detected as an AE signal only for rasagiline. Moreover, the REM sleep behavior disorder was not detected as an AE signal for safinamide, suggesting that non-dopaminergic effects might be beneficial. Considering the differences in AEs for MAO-B inhibitors will assist with the appropriate PD medication.

Recent Progress in the Development of New Antiepileptic Drugs with Novel Targets

Background

Epilepsy is a chronic neurological disorder that affects approximately 50-70 million people worldwide. Epilepsy has a significant economic and social burden on patients as well as on the country. The recurrent, spontaneous seizure activity caused by abnormal neuronal firing in the brain is a hallmark of epilepsy. The current antiepileptic drugs provide symptomatic relief by restoring the balance of excitatory and inhibitory neurotransmitters. Besides, about 30% of epileptic patients do not achieve seizure control. The prevalence of adverse drug reactions, including aggression, agitation, irritability, and associated comorbidities, is also prevalent. Therefore, researchers should focus on developing more effective, safe, and disease-modifying agents based on new molecular targets and signaling cascades.

Summary

This review overviews several clinical trials that help identify promising new targets like lactate dehydrogenase inhibitors, c-jun n-terminal kinases, high mobility group box-1 antibodies, astrocyte reactivity inhibitors, cholesterol 24-hydroxylase inhibitors, glycogen synthase kinase-3 beta inhibitors, and glycolytic inhibitors to develop a new antiepileptic drug.

Key messages

Approximately 30% of epileptic patients do not achieve seizure control. The current anti-seizure drugs are not disease modifying, cure or prevent epilepsy. Lactate dehydrogenase inhibitor, cholesterol 24-hydroxylase inhibitor, glycogen synthase kinase-3 beta inhibitors, and mTOR inhibitors have a promising antiepileptogenic effect.

Evaluation of developmental toxicity of safinamide in zebrafish larvae (Danio rerio)

Monoamine oxidase-B (MAO-B), as a principal metabolizing enzyme, plays important roles in the metabolism of catecholamines and xenobiotics in the central nervous system and peripheral tissues. Safinamide, the third-generation reversible MAO-B inhibitor, has potential to alleviate many neurological diseases such as Parkinson's disease (PD) and depression. Exposure to clinical psychotropic drugs often has adverse effects on fetuses. Currently, a variety of studies of safinamide focus on its curative effect and pharmacological effect, while its side effect of embryonic development is barely studied. In this study, we used zebrafish as a model to evaluate the embryonic developmental toxicity of safinamide. Our results revealed that higher concentrations (30 μM) of safinamide treatment caused a decrease in hatching rate and an increase in malformation and mortality in zebrafish larvae. Meanwhile, we observed that lower safinamide exposure (10 μM) increased the body length of zebrafish larvae and resulted in hyperactivity-like behaviors. In addition, an increased trend in dopamine (DA) level was found in 3.3 μM and 10 μM safinamide-exposed groups. Transcriptome analysis identified that safinamide exposure may disturb a variety of physiological processes such as neuroactive ligand-receptor interaction signaling pathway. In summary, our study reveals that safinamide may cause developmental defects in zebrafish larvae and provides insights into its toxic reactions in early develoment.

Highly efficient radiosynthesis and biological evaluation of [18F]safinamide, a radiolabelled anti-parkinsonian drug for PET imaging

As an add-on drug approved for Parkinson's disease treatment, safinamide has multiple functions, such as selective and reversible monoamine oxidase-B inhibition, voltage-sensitive sodium/potassium channel blockage, and glutamate release inhibition. Meanwhile, safinamide shows tremendous therapeutic potential in the context of other central nervous system diseases (e.g., ischaemic stroke, amyotrophic lateral sclerosis, depression, etc.).  In this work, [18F]safinamide, which is safinamide labelled by the positron-emitting radionuclide [18F]fluorine, was synthesized automatically based on iodonium ylide precursors with high radiochemical yield and high molar activity. Density functional theory was applied to calculate the Gibbs free energy change during iodonium ylide-mediated fluorination and to interpret the effect of tetraethylammonium (TEA+) as the counter cation in these reactions to improve the nucleophilicity of [18F/19F]fluoride. In addition, positron emission tomography studies on Sprague Dawley rats were carried out to determine the imaging characteristics, pharmacokinetics, and metabolism of the [18F]safinamide radiotracer. The results displayed the complete biodistribution of the radiotracer, especially in rat brains, and revealed that [18F]safinamide has moderate brain uptake, rapid and reversible binding kinetics, and good stability.

Modulation of Reactive Oxygen Species Homeostasis as a Pleiotropic Effect of Commonly Used Drugs

Age-associated diseases represent a growing burden for global health systems in our aging society. Consequently, we urgently need innovative strategies to counteract these pathological disturbances. Overwhelming generation of reactive oxygen species (ROS) is associated with age-related damage, leading to cellular dysfunction and, ultimately, diseases. However, low-dose ROS act as crucial signaling molecules and inducers of a vaccination-like response to boost antioxidant defense mechanisms, known as mitohormesis. Consequently, modulation of ROS homeostasis by nutrition, exercise, or pharmacological interventions is critical in aging. Numerous nutrients and approved drugs exhibit pleiotropic effects on ROS homeostasis. In the current review, we provide an overview of drugs affecting ROS generation and ROS detoxification and evaluate the potential of these effects to counteract the development and progression of age-related diseases. In case of inflammation-related dysfunctions, cardiovascular- and neurodegenerative diseases, it might be essential to strengthen antioxidant defense mechanisms in advance by low ROS level rises to boost the individual ROS defense mechanisms. In contrast, induction of overwhelming ROS production might be helpful to fight pathogens and kill cancer cells. While we outline the potential of ROS manipulation to counteract age-related dysfunction and diseases, we also raise the question about the proper intervention time and dosage.

Safinamide protects against amyloid β (Aβ)-induced oxidative stress and cellular senescence in M17 neuronal cells

Alzheimer’s disease (AD) is a neurodegenerative disorder that is pathologically related to oxidative stress and cellular senescence. Safinamide is one of the clinically prescribed monoamine oxidase B (MAOB) inhibitors. It has been reported to possess therapeutic potential in neurological disorders. However, the therapeutic potential of safinamide in AD is still under investigation. In this study, we explored the effect of safinamide in amyloid (Aβ)_1–42 oligomers-stimulated M17 neuronal cells. We established the in vitro model with M17 cells by treating them with 1 μM Aβ_1-42 oligomers with or without safinamide (100 or 200 nM). The results show that safinamide ameliorated Aβ_1-42 oligomers-induced oxidative stress in M17 cells as revealed by the decreased reactive oxygen species (ROS) production and reduced glutathione (GSH) content. Safinamide treatment significantly ameliorated senescence-associated-β-galactosidase (SA-β-gal)-positive cells and telomerase activity. Further, we show that safinamide treatment resulted in decreased mRNA and protein expressions of p21 and plasminogen activator inhibitor-1 (PAI-1). Moreover, silencing of Sirtuin1 (SIRT1) abolished the effects of safinamide on the mRNA levels of p21 and PAI-1, as well as SA-β-gal-positive cells in Aβ_1-42 oligomers-induced M17 cells. In conclusion, we reveal that safinamide exerted a protective function on M17 cells from Aβ_1-42 oligomers induction-caused oxidative stress and cellular senescence through SIRT1 signaling. These present results provide meaningful evidence that safinamide may be medically developed for the prevention and therapy of AD.

Post Stroke Safinamide Treatment Attenuates Neurological Damage by Modulating Autophagy and Apoptosis in Experimental Model of Stroke in Rats

Exploring and repurposing a drug have become a lower risk alternative. Safinamide, approved for Parkinson's disease, has shown neuroprotection in various animal models of neurological disorders. The present study aimed to explore the potential of safinamide in cerebral ischemia/reperfusion (I/R) in rats. Sprague-Dawley rats were used in middle cerebral artery occlusion model of stroke. The effective dose of safinamide was selected based on the results of neurobehavioral parameters and reduction in infarct size assessed 24 h post-reperfusion. For sub-acute study, the treatment with effective dose was extended for 3 days and effects on neurobehavioral parameters, infarct size (TTC staining and MRI), oxidative stress parameters (MDA, GSH, SOD, NOX-2), inflammatory cytokines (TNF-α, IL-1β, IL-10), apoptosis (Bax, Bcl-2, cleaved caspase-3 expression, and TUNEL staining), and autophagy (pAMPK, Beclin-1, LC3-II expression) were studied. The results of dose selection study showed significant reduction (p < 0.05) in infarct size and improvement in neurobehavioral parameters with safinamide (80 mg/kg). In sub-acute study, safinamide showed significant (p < 0.05) improvement in motor coordination and infarct size reduction. Additionally, safinamide treatment significantly normalized altered redox homeostasis and inflammatory cytokine levels. However, no change was observed in expression of NOX-2 in I/R or safinamide treatment group when compared with sham. I/R induced deranged expression of apoptotic markers and increased TUNEL positive cells in cortex were significantly normalized with safinamide treatment. Further, safinamide significantly (p < 0.05) induced the expressions of autophagic proteins (Beclin-1 and LC3-II) in cortex. Overall, the results demonstrated neuroprotective potential of safinamide via anti-oxidant, anti-inflammatory, anti-apoptotic, and autophagy inducing properties. Thus, safinamide can be explored for repurposing in ischemic stroke after further exploration.

Ion Channels as New Attractive Targets to Improve Re-Myelination Processes in the Brain

Multiple sclerosis (MS) is the most demyelinating disease of the central nervous system (CNS) characterized by neuroinflammation. Oligodendrocyte progenitor cells (OPCs) are cycling cells in the developing and adult CNS that, under demyelinating conditions, migrate to the site of lesions and differentiate into mature oligodendrocytes to remyelinate damaged axons. However, this process fails during disease chronicization due to impaired OPC differentiation. Moreover, OPCs are crucial players in neuro-glial communication as they receive synaptic inputs from neurons and express ion channels and neurotransmitter/neuromodulator receptors that control their maturation. Ion channels are recognized as attractive therapeutic targets, and indeed ligand-gated and voltage-gated channels can both be found among the top five pharmaceutical target groups of FDA-approved agents. Their modulation ameliorates some of the symptoms of MS and improves the outcome of related animal models. However, the exact mechanism of action of ion-channel targeting compounds is often still unclear due to the wide expression of these channels on neurons, glia, and infiltrating immune cells. The present review summarizes recent findings in the field to get further insights into physio-pathophysiological processes and possible therapeutic mechanisms of drug actions.

The Current Evidence for the Use of Safinamide for the Treatment of Parkinson's Disease

Introduction

Parkinson’s therapeutic interventions are only symptomatic. An optimal treatment should therefore address the largest number of motor and non-motor symptoms, to manage patients at best. Safinamide is one of the most recent approved drugs for fluctuating patients, in add-on to levodopa, that remains the gold standard treatment. It has a unique mechanism of action, both dopaminergic (as MAO-B inhibitor) and glutamatergic (through Na⁺ channel blockade). Results from Phase III trials, post-hoc analyses and real-life experiences suggest a beneficial effect on motor (such as tremor, bradykinesia, rigidity and gait) and non-motor (pain, mood, sleep) symptoms.

Areas Covered

Here, the authors discuss clinical efficacy and safety of safinamide, identifying the patients’ profiles that could benefit most. A search in PubMed was performed in September 2020, with no time limits. Publications’ abstracts were reviewed.

Conclusion

Safinamide is peculiar due to its double mechanism of action. Its benefits in improving motor functions and fluctuations, and some non-motor symptoms, could have a valuable impact on patients’ quality of life (QoL), together with its safety profile.