Selective Monoamine Oxidase Type B Inhibitors Research Articles

Structure-Based Design of Novel MAO-B Inhibitors: A Review.

With the significant growth of patients suffering from neurodegenerative diseases (NDs), novel classes of compounds targeting monoamine oxidase type B (MAO-B) are promptly emerging as distinguished structures for the treatment of the latter. As a promising function of computer-aided drug design (CADD), structure-based virtual screening (SBVS) is being heavily applied in processes of drug discovery and development. The utilization of molecular docking, as a helping tool for SBVS, is providing essential data about the poses and the occurring interactions between ligands and target molecules. The current work presents a brief discussion of the role of MAOs in the treatment of NDs, insight into the advantages and drawbacks of docking simulations and docking software, and a look into the active sites of MAO-A and MAO-B and their main characteristics. Thereafter, we report new chemical classes of MAO-B inhibitors and the essential fragments required for stable interactions focusing mainly on papers published in the last five years. The reviewed cases are separated into several chemically distinct groups. Moreover, a modest table for rapid revision of the revised works including the structures of the reported inhibitors together with the utilized docking software and the PDB codes of the crystal targets applied in each study is provided. Our work could be beneficial for further investigations in the search for novel, effective, and selective MAO-B inhibitors.

Synthetic approaches to unsymmetrical 2,5-disubstituted 1,3,4-oxadiazoles and their MAO-B inhibitory activity. A review

Selective monoamine oxidase type B (MAO-B) inhibitors are currently used as coadjuvants for treating early motor symptoms of Parkinson’s disease. Aiming at the elucidation of MAO-B inhibitors with 1,3,4-oxadiazole scaffolds, we make a comprehensive update on the new and old chemical methods employed for the synthesis of the unsymmetrical oxadiazole derivatives that lead to high yield compounds. We summarize a state of the selective MAO-B inhibitors with oxadiazole scaffold, describing the results, structures, structure-activity relationships (SARs) and medicinal chemistry strategies over the years. The analysis of the recent papers would facilitate tracking the increasing number of oxadiazole derivatives as new chemical spaces with MAO-B inhibitory potential designed to ensure the safe use of the compounds and elimination of the unwanted drug-drug interactions.

Cardiovascular and mortality risks in Parkinson's disease patients treated with entacapone

The controlled trial Stalevo Reduction in Dyskinesia Evaluation in Parkinson's Disease (STRIDE-PD) reported an unexpected increase in acute myocardial infarction (AMI) with entacapone use in patients with Parkinson's disease (PD). The authors investigated whether entacapone increased cardiovascular and mortality risk compared with the use of a non-levodopa dopamine agonist (DA) or a selective monoamine oxidase type-B inhibitor (MAOBI). Using national Medicare data, a new-user cohort of elderly patients with PD treated with entacapone was propensity score (PS) matched with new users of either DA or MAOBI. The PS model included variables for sociodemographics, cardiovascular disease, medications, prior PD treatment, and comorbidities. Cox proportional hazards regression was used to compare on-therapy time to event for AMI, stroke, and death with DA-MAOBI as a reference. Study cohorts included 8681 entacapone-treated and 17,362 DA-MAOBI-treated initators who were followed for 2569 and 5385 person-years, respectively. Cohorts were closely balanced for all covariates. During follow-up, there were 106 AMIs, 89 strokes, and 201 deaths. The hazard ratio (HR) and 95% confidence interval (CI) associated with entacapone use was 0.86 (95% CI, 0.57-1.30) for AMI, 0.85 (95% CI, 0.54-1.35) for stroke, and 0.79 (95% CI, 0.58-1.07) for death. The risk was unchanged for treatment of ≤ 6 months' and>6 months' duration and was unaffected by adjustment for time-varying levodopa use during follow-up. The risk of each endpoint was not differentially affected by diabetes, ischemic heart disease, or kidney failure status. However, the risk of stroke was modified by the presence (HR, 2.09; 95% CI, 0.98-4.45) or absence (HR, 0.51; 95% CI, 0.27-0.95) of advanced PD-related morbidities (P value for interaction=0.004). Entacapone was not associated with an increased risk of AMI, stroke, or death in elderly patients with PD.

Pharmacologic Safety Concerns in Parkinson's Disease: Facts and Insights

ABSTRACTKnowledge and insight of pharmacologic safety issues and drug interactions are important for medical management of Parkinson's disease (PD). This review will discuss several topics, including apomorphine safety and interactions, impulsivity and excessive daytime somnolence associated with dopamine agonists (DAs), tolcapone hepatotoxicity, and monoamine oxidase type-B (MAO-B) inhibitor drug interactions. Initiation of apomorphine requires antiemetic prophylaxis to minimize nausea and orthostatic hypotension. Centrally acting antidopaminergic antiemetics will worsen parkinsonism and block the therapeutic effects of apomorphine and should be avoided. Additionally, serotonin 5-HT3 receptor antagonist antiemetics should be avoided on the basis of limited clinical data suggesting lack of efficacy for apomorphine-induced nausea. Dopamine-agonist-induced impulsivity and daytime somnolence are not uncommon. When severe, these effects can be disabling and unsafe. Tolcapone-induced hepatotoxicity has been significantly minimized with routine monitoring of liver enzymes, especially during the initial 6 months of therapy. Early detection of abnormal results will allow tolcapone discontinuation before progression to fulminant hepatotoxicity. In patients treated with selective MAO-B inhibitors, the risk of serotonin toxicity (ST) due to a concomitant serotonergic agent (e.g., antidepressants, dextromethorphan, serotonergic analgesics) or hypertensive crisis due to dietary tyramine or sympathomimetic amines appears to be minimal and is based on isolated case reports and overgeneralizations from nonselective MAO inhibitor pharmacology. Concerns about ST or hypertensive crisis should not preclude or restrict clinicians from using MAO-B inhibitors in patients with PD.

The effects of rasagiline on cognitive deficits in Parkinson's disease patients without dementia: A randomized, double‐blind, placebo‐controlled, multicenter study

Cognitive impairment can occur at all stages of Parkinson's disease. Rasagiline is a selective monoamine oxidase type-B inhibitor that enhances central dopaminergic transmission. Dopamine is thought to be involved in certain cognitive processes such as working memory. We assessed the effects of rasagiline on cognitive deficits in cognitively impaired, nondemented patients with Parkinson's disease. This was a randomized, double-blind, placebo-controlled prospective study. Patients with Parkinson's disease receiving stable dopaminergic treatment were assigned to receive rasagiline 1 mg/day or placebo for 3 months. Patients were eligible if they had impairment in 2 of 4 cognitive domains (attention, executive functions, memory, visuospatial functions) in the screening neuropsychological tests, yet did not fulfill criteria for Parkinson's disease dementia. Fifty-five patients were randomized; 48 patients completed the study. Patients in the rasagiline group showed significant improvement in digit span-backward compared with the placebo group (P = .04), with trends favoring rasagiline in digit span total and digit-ordering tests. Verbal fluency total score showed a significant difference in favor of rasagiline (P = .038), with trends favoring rasagiline in semantic fluency test and Stroop spontaneous corrections. The composite cognitive domain Z scores revealed a significant difference in favor of rasagiline compared with placebo in the attentional Z score (P < .005). There were no significant differences between the 2 groups in the other cognitive tests or cognitive domain Z scores. The monoamine oxidase type-B inhibitor rasagiline may exert beneficial effects on certain aspects of attention and executive functions in nondemented patients with Parkinson's disease with cognitive impairment.

Monamine Oxidase Inhibitors

Monoamine oxidase type B (MAO-B) is the predominant isoform responsible for the metabolic breakdown of dopamine in the brain. Selective inhibition of brain MAO-B results in elevation of synaptosomal dopamine concentrations. Data have been reported regarding the selective MAO-B inhibitors, rasagiline and selegiline, for the symptomatic treatment of Parkinson disease (PD). Selegiline has demonstrated efficacy as monotherapy in patients with early PD (Deprenyl and Tocopherol Antioxidative Therapy of Parkinsonism study), but evidence of selegiline efficacy as adjunctive treatment in levodopa-treated PD patients with motor fluctuations is equivocal. A new formulation of selegiline (Zydis selegiline) has been evaluated in 2 small, placebo-controlled studies as adjunctive therapy to levodopa. The Zydis formulation allows pregastric absorption of selegiline, minimizing first-pass metabolism, and thereby increasing selegiline bioavailability and reducing the concentration of amphetamine metabolites. Rasagiline is a selective, second-generation, irreversible MAO-B inhibitor, with at least 5 times the potency of selegiline in vitro and in animal models. Rasagiline has demonstrated efficacy in 1 large, randomized, double-blind, placebo-controlled trial (TVP-1012 in Early Monotherapy for Parkinson's Disease Outpatients) as initial monotherapy in patients with early PD, and in 2 large, controlled trials (Parkinson's Rasagiline: Efficacy and Safety in the Treatment of "Off," Lasting Effect in Adjunct Therapy With Rasagiline Given Once Daily) as adjunctive treatment in levodopa-treated PD patients with motor fluctuations. Unlike selegiline, rasagiline is an aminoindan derivative with no amphetamine metabolites. A randomized clinical trial is underway to confirm preclinical and preliminary clinical data suggesting rasagiline has disease-modifying effects.

Remarkable Effect of Selegiline (L-Deprenyl), a Selective Monoamine Oxidase Type-B Inhibitor, in a Patient With Severe Refractory Depression

A 34-year-old man presented with severe refractory depression. He had failed to respond to various antidepressants, augmentation therapy with lithium carbonate, and modified electroconvulsive therapy. Switching from amoxapine 150 mg/day to selegiline 7.5 mg/day, a selective monoamine oxidase type-B inhibitor, produced a dramatic reduction in hypobulia and lassitude, leading to a complete remission of all depressive symptoms. The patient reverted to his former position at work after an interval of approximately 3 years. Although the biologic basis of the antidepressant effect of selegiline in this patient is unknown, it is suggested that the enhancement of dopaminergic neurotransmission or elevation of brain-derived neurotrophic factor levels in the brain by administration of selegiline is involved in the recovery of this patient from severe refractory depression. This report indicates the antidepressant effect of selegiline in a refractory depressed patient.

Neurotoxins and monoamine oxidase inhibition: new aspects.

Recent clinical studies suggest that selegiline (L-deprenyl) is useful in retarding the progress of Parkinson's disease, an effect that may be related to its inhibition of monoamine oxidase type B (MAO-B). Selegiline is also reported to prevent the toxic effects of the noradrenergic neurotoxin, N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4). This article reviews recent studies on the role of MAO-B and its inhibition in this neuroprotective action of selegiline. Male C57Bl/6 mice were given DSP-4 (50 mg/kg) 1 h, 24 h, or 4 days after the administration of selegiline (10 mg/kg) or the selective MAO-B inhibitor MDL 72974 (1.25 mg/kg) and then killed 1 week later for the assay of norepinephrine in the hippocampus. The MAO-B-inhibiting effects of selegiline or MDL 72974 were also determined after these same intervals. Selegiline and MDL 72974 produced comparable degrees of enzyme inhibition 1 h (> 95%), 24 h (> 90%), or 4 days (> 70%) after their administration. Given 1 h before, selegiline totally blocked the norepinephrine-depleting effects of DSP-4, but this protection declined sharply when 24 h or 4 days was allowed to elapse between selegiline and DSP-4 administration. MDL 72974 failed to protect at any time point. In vitro, no activity was observed when DSP-4 was used as a substrate for MAO. All of these findings suggest that the ability of selegiline to protect against DSP-4-induced neuronal degeneration does not depend on its inhibition of MAO-B.

L-deprenyl, a selective monoamine oxidase type-b inhibitor in endogenous depression

In a group of 12 endogenously depressed patients who failed to respond to a week of placebo medication, L-deprenyl, a selective type-B monoamine oxidase inhibitor, produced a significant improvement over the whole range of depressive symptomatology. This is the first reported study of the antidepressant properties of L-deprenyl using a lower dose range, where both selective inhibition of type-B monoamine oxidase (MAO) would occur and the patient would be protected from the hypertensive cheese reaction. The possibility of an MAO inhibitor relatively free from the risk of a cheese reaction and yet an effective antidepressant would be a valuable new therapeutic agent. In addition, monitoring the degree of inhibition of platelet MAO may be a useful way of determining the therapeutic dosage for individual patients.