Understanding and managing behavioural symptoms in Alzheimer's disease and related dementias: focus on rivastigmine

In Silico Investigation of Novel Compounds as Inhibitors of Acetylcholinesterase Enzyme for the Treatment of Alzheimer's Diseases

Alzheimer's disease (AD) is a "progressive, neurodegenerative disease that occurs when nerve cells in the brain die." There are only 4 drugs approved by the United States Food and Drug Administration (FDA). Three (donepezil, rivastigmine, and galantamine) out of these four drugs are anticholinesterase inhibitors, while the fourth one memantine is an N-methyl-D-aspartate (NMDA) receptor inhibitor. Currently, two immunotherapy drugs that target amyloid protein (donanemab and lecanemab) are being considered for the treatment of Alzheimer's disease at an early stage. All these drug molecules are still not the complete answer to the treatment of Alzheimer's disease. A recent report from the Office of National Statistics showed that AD is the leading cause of death in 2022. Therefore, there is an urgency to develop more drugs that can treat AD. Based on this urgency, we aim to investigate how bioactive and already approved drugs could be repurposed for inhibiting the anticholinesterase enzyme using computational studies. To achieve this, the data science tool-Python coding was compiled on Jupyter Notebook to mine bioactive compounds from the ChEMBL database. The most bioactive compounds obtained were further investigated using Molecular Operating Environment (MOE) software to carry out molecular docking and ligand analysis, and this was followed by molecular dynamics simulation production at 35 ns using GROMACS 2022.4 on Archer 2 machine. The molecular dynamic analysis was carried out using HeroMDanalysis software. Data mining of the ChEMBL database was carried out for lipase inhibitors, and this gave CHEMBL-ID 1240685, a peptide molecule, the most active compound at the time of data mining. Further literature studies gave Zoladex an FDA-approved drug for the treatment of breast cancer as another compound of interest. The in silico studies were carried out against the anticholinesterase enzyme using two FDA-approved drugs donepezil and galantamine as a template for comparing the in silico activities of the repurposed drugs. A very useful receptor for this study was PDB-1DX6, a cocrystallized galantamine inhibitor of acetylcholinesterase enzyme. The molecular docking analysis (using ligand interactions) and molecular dynamic analysis (root mean square deviation (RMSD) and root mean square fluctuation (RMSF)) showed that the two peptide molecules CHEMBL-1240685 and Zoladex gave the best binding energy and stability when compared to the FDA-approved drugs (donepezil and galantamine). Finally, further literature studies revealed that Zoladex affects memory reduction; therefore, it was dropped as a possible repurposed drug. Our research showed that CHEMBL-1240685 is a potential compound that could be investigated for the inhibition of anticholinesterase enzyme and might be another drug molecule that could be used to treat Alzheimer's disease.

Emotion Processing Dysfunction in Alzheimer's Disease: An Overview of Behavioral Findings, Systems Neural Correlates, and Underlying Neural Biology

We described behavioral studies to highlight emotional processing deficits in Alzheimer's disease (AD). The findings suggest prominent deficit in recognizing negative emotions, pronounced effect of positive emotion on enhancing memory, and a critical role of cognitive deficits in manifesting emotional processing dysfunction in AD. We reviewed imaging studies to highlight morphometric and functional markers of hippocampal circuit dysfunction in emotional processing deficits. Despite amygdala reactivity to emotional stimuli, hippocampal dysfunction conduces to deficits in emotional memory. Finally, the reviewed studies implicating major neurotransmitter systems in anxiety and depression in AD supported altered cholinergic and noradrenergic signaling in AD emotional disorders. Overall, the studies showed altered emotions early in the course of illness and suggest the need of multimodal imaging for further investigations. Particularly, longitudinal studies with multiple behavioral paradigms translatable between preclinical and clinical models would provide data to elucidate the time course and underlying neurobiology of emotion processing dysfunction in AD.

Is γ-secretase a beneficial inactivating enzyme of the toxic APP C-terminal fragment C99?

Genetic, biochemical, and anatomical grounds led to the proposal of the amyloid cascade hypothesis centered on the accumulation of amyloid beta peptides (Aβ) to explain Alzheimer's disease (AD) etiology. In this context, a bulk of efforts have aimed at developing therapeutic strategies seeking to reduce Aβ levels, either by blocking its production (γ- and β-secretase inhibitors) or by neutralizing it once formed (Aβ-directed immunotherapies). However, so far the vast majority of, if not all, clinical trials based on these strategies have failed, since they have not been able to restore cognitive function in AD patients, and even in many cases, they have worsened the clinical picture. We here propose that AD could be more complex than a simple Aβ-linked pathology and discuss the possibility that a way to reconcile undoubted genetic evidences linking processing of APP to AD and a consistent failure of Aβ-based clinical trials could be to envision the pathological contribution of the direct precursor of Aβ, the β-secretase-derived C-terminal fragment of APP, βCTF, also referred to as C99. In this review, we summarize scientific evidences pointing to C99 as an early contributor to AD and postulate that γ-secretase should be considered as not only an Aβ-generating protease, but also a beneficial C99-inactivating enzyme. In that sense, we discuss the limitations of molecules targeting γ-secretase and propose alternative strategies seeking to reduce C99 levels by other means and notably by enhancing its lysosomal degradation.

[The efficacy of pharmacological approaches to therapy of the apathy syndrome in dementia disorders (the review)]

The article presents a literature review of psychopharmacological methods of treatment of the apathy syndrome, which is common in neurocognitive disorders. The review provides recommendations for the management of such patients, taking into account evidence-based medicine.

Systematic Review of Cholinesterase Inhibitors on Cognition and Behavioral Symptoms in Patients of Chinese Descent with Alzheimer's Disease, Vascular Dementia, or Mixed Dementia

Cholinesterase inhibitors (ChEIs) are the primary pharmacologic treatment for dementia. Their efficacy in patients of Chinese descent is not well described. We reviewed how ChEIs could affect cognition and behavioral and psychological symptoms (BPSD) in Chinese patients with Alzheimer’s disease (AD), vascular dementia (VaD), or mixed (AD with vascular component) dementia. MEDLINE, PsycINFO, EMBASE and CINAHL were systematically searched for controlled trials of ChEIs, including donepezil, galantamine, and rivastigmine, for Chinese patients with AD, VaD, or mixed dementia. Outcomes for cognition and BPSD were extracted for discussion. Fifty-four studies were identified. While one larger study found that dementia patients of Chinese descent treated with ChEIs had significantly higher mean Mini-Mental State Examination (MMSE) score, other studies showed no significant difference. Evidence on BPSD after use of ChEIs was also conflicting. ChEIs may be effective in improving cognition among patients of Chinese descent with dementia. Further studies are needed to examine the possible effects of ChEIs on BPSD in Chinese patients with dementia in view of the small number of studies and limitations in their methodologies.

Multi target neuroprotective and neurorestorative anti-Parkinson and anti-Alzheimer drugs ladostigil and m30 derived from rasagiline

Present anti-PD and -AD drugs have limited symptomatic activity and devoid of neuroprotective and neurorestorative property that is needed for disease modifying action. The complex pathology of PD and AD led us to develop several multi-target neuroprotective and neurorestorative drugs with several CNS targets with the ability for possible disease modifying activity. Employing the pharmacophore of our anti-parkinson drug rasagiline (Azilect, N-propagrgyl-1-R-aminoindan), we have developed a series of novel multi-functional neuroprotective drugs (A) [TV-3326 (N-propargyl-3R-aminoindan-5yl)-ethyl methylcarbamate)], with both cholinesterase-butyrylesterase and brain selective monoamine-oxidase (MAO) A/B inhibitory activities and (B) the iron chelator-radical scavenging-brain selective monoamine oxidase (MAO) A/B inhibitor and M30 possessing the neuroprotective and neurorescuing propargyl moiety of rasagiline, as potential treatment of AD, DLB and PD with dementia. Another series of multi-target drugs (M30, HLA-20 series) which are brain permeable iron chelators and potent selective brain MAO inhibitors were also developed. These series of drugs have the ability of regulating and processing amyloid precursor protein (APP) since APP and alpha-synuclein are metaloproteins (iron-regulated proteins), with an iron responsive element 5"UTR mRNA similar to transferring and ferritin. Ladostigil inhibits brain acetyl and butyrylcholinesterase in rats after oral doses. After chronic but not acute treatment, it inhibits MAO-A and -B in the brain. Ladostigil acts like an anti-depressant in the forced swim test in rats, indicating a potential for anti-depressant activity. Ladostigil prevents the destruction of nigrostriatal neurons induced by infusion of neurotoxin MPTP in mice. The propargylamine moiety of ladostigil confers neuroprotective activity against cytotoxicity induced by ischemia and peroxynitrite in cultured neuronal cells. The multi-target iron chelator M30 has all the properties of ladostigil and similar neuroprotective activity to ladostigil, but is not a ChE inhibitor. M30 has a neurorestorative activity in post-lesion of nigrostriatal dopamine neurons in MPTP, lacatcystin and 6-hydroxydopamine animal models of PD. The neurorestorative activity is related to the ability of the drug to activate hypoxia inducing factor (HIF) which induces the production of such neurotrophins as brain-derived neurotrophic factor (BDNF), vascular endothelial growth factor (VEGF) and erythropoietin as well as glia-derived neurotrophic factor (GDNF). The unique multiple actions of ladostigil and M30 make the potentially useful drugs for the treatment of dementia with Parkinsonian-like symptoms and depression.

Pharmacologic treatment of apathy in dementia

Apathy in patients with dementia is common, underrecognized, and undertreated. We sought to improve understanding of the pharmacologic treatment of apathy in dementia by performing a systematic literature review of studies that used apathy outcome scales to document results of pharmacologic treatments for apathy. There is limited evidence of efficiency of pharmacotherapy for treatment of apathy in dementia. The best results were found for acetylcholinesterase inhibitors. There was some evidence of efficacy for memantine, but less evidence of efficacy for stimulants, calcium antagonists, and antipsychotics. There was no evidence to support the use of antidepressants or anticonvulsants. The research quality of studies was modest. Recommendations for standardizing research and for holistic evaluation and treatment are provided.

Validation of the Icelandic version of the Neuropsychiatric Inventory with Caregiver Distress (NPI-D)

BACKGROUND

Dementia is a complex and often debilitating illness, presenting with not only wide-ranging cognitive impairment but also neuropsychiatric challenges, which can have diverse consequences in quality of life for both patient and caregiver.

AIM

Studying the validity and reliability of an Icelandic translation of the Neuropsychiatric Inventory with Caregiver Distress (NPI-D).

METHODS

NPI-D was administered to 38 primary caregivers of dementia patients. The concurrent validity was explored by statistically comparing the NPI-D to the Behavioural Pathology in Alzheimer's Disease Rating Scale (BEHAVE-AD) and the Geriatric Depression Scale (GDS). Regarding caregiver distress, concurrent validity was established between NPI-D, BEHAVE-AD Global Rating and two other caregiver distress scales.

RESULTS

Significant correlation was found when total score on the BEHAVE-AD was compared with total score on the NPI-D. All NPI-D subscales achieved significant correlation with the corresponding BEHAVE-AD subscales apart from the 'depression/dysphoria subscale'. This NPI-D subscale correlated however, significantly with the GDS depression scale, a frequent and well validated measure of depressive symptoms in the elderly population. Cronbach's alpha coefficient indicated a high degree of overall internal consistency among the items of the NPI-D. Interestingly, apathy was the most frequent neuropsychiatric disturbance and the only subscale that differed significantly between dementia severity levels. Finally, when studying caregiver distress, the NPI-D showed good concurrent validity with other measures of caregiver burden and distress.

CONCLUSIONS

The results demonstrate an acceptable level of validity and reliability; therefore the Icelandic translation of the NPI-D is well suited for identifying neuropsychiatric symptoms in dementia and associated caregiver burden.

Non-pharmacological management of behavioural symptoms of dementia

This article describes a 6-month pilot project in which a community mental health team provided a dementia inreach service into 4 care homes in Birmingham, UK. The project included analysis of the impact of the service at the end of the project as well as a literature review of dementia care in care homes, and especially the issue of antipsychotic medication use and non-pharmacological approaches in managing behavioural and psychological symptoms of dementia (BPSD). The project included training care home staff in the management of BPSD; 2 questionnaires distributed at the beginning of the project found that 65% of care home staff felt a need for education and awareness, practical problem-solving and counselling in managing BPSD. Self-reported knowledge of common mental health problems and dementia increased in care home staff at the end of the project by a margin of 7% and 11% respectively. Reported confidence in managing behavioural problems increased by 9% among care home staff at the end of the project. The project achieved regular monitoring of psychotropic medications, and enabled the discharge of 14 out of 63 existing patients in the selected homes. The project also provided guidance for non-pharmacological techniques for management of BPSD, which included relaxation techniques, distraction techniques, reality orientation, reminiscence work, needs led therapy, music therapy, person-centred approach and behaviour therapy.

Multifunctional neuroprotective derivatives of rasagiline as anti-Alzheimer's disease drugs

The recent therapeutic approach in which drug candidates are designed to possess diverse pharmacological properties and act on multiple targets has stimulated the development of the multimodal drugs, ladostigil (TV3326) [(N-propargyl-(3R) aminoindan-5yl)-ethyl methyl carbamate] and the newly designed multifunctional antioxidant iron chelator, M-30 (5-[N-methyl-N-propargylaminomethyl]-8-hydroxyquinoline). Ladostigil combines, in a single molecule, the neuroprotective/neurorestorative effects of the novel anti-Parkinsonian drug and selective monoamine oxidase (MAO)-B inhibitor, rasagiline (Azilect, Teva Pharmaceutical Co.) with the cholinesterase (ChE) inhibitory activity of rivastigmine. A second derivative of rasagiline, M-30 was developed by amalgamating the propargyl moiety of rasagiline into the skeleton of our novel brain permeable neuroprotective iron chelator, VK-28. Preclinical experiments showed that both compounds have anti-Alzheimer's disease activities and thus, the clinical development is oriented toward treatment of this type of dementia. This review discusses the multimodal effects of two rasagiline-containing hybrid molecules, namely ladostigil and M-30, concerning their neuroprotective molecular mechanisms in vivo and in vitro, including regulation of amyloid precursor protein processing, activation of protein kinase C, and mitogen-activated protein kinase signaling pathways, inhibition of cell death markers and upregulation of neurotrophic factors. Altogether, these scientific findings make these multifunctional compounds potentially valuable drugs for the treatment of Alzheimer's disease.

Importance of circadian rhythmicity in the cholinergic treatment of Alzheimer's disease: focus on galantamine*

OBJECTIVE AND SCOPE: This review article used data from an extensive literature search (including MEDLINE database searches) to explore the relationships between sleep, memory and Alzheimer's disease (AD). The importance of taking into account circadian rhythmicity and acetylcholine (ACh) levels when considering acetylcholinesterase inhibitors, galantamine in particular, in the treatment of patients with AD is discussed.

REVIEW FINDINGS

Moderate changes of circadian rhythms may occur as part of the normal ageing process, but patients with AD exhibit circadian rhythm disturbances extending beyond those observed in non-demented elderly and this may lead to severe disruption of the sleep-wake cycle. Indeed, ACh plays an active role in maintaining a normal sleep pattern, which is important for memory consolidation. Low levels of ACh during slow-wave sleep compared with wakefulness have been shown to be critical for the consolidation of declarative memory. This suggests the existence of a circadian rhythm in central cholinergic transmission which modulates memory processes, with high ACh levels during wakefulness and reduced levels during slow-wave sleep. When using cholinesterase inhibitors to stimulate central cholinergic transmission in AD, respecting the natural circadian fluctuations of central cholinergic transmission may therefore be an important factor for patient improvement. Interfering with nocturnal cholinergic activity can add to memory problems and induce sleep disorders. Available data suggest that the type of cholinesterase inhibitor used and the time of administration may be critical with regard to the possible development of such disturbances. Plasma levels of galantamine, for example, are high during the waking day and lower at night, supporting a cholinergic stimulation that mirrors the physiological circadian rhythm of cholinergic activity. This may have beneficial implications with regard to sleep and memory.

CONCLUSIONS

The pharmacokinetic properties of cholinesterase inhibitors may need to be taken into account to avoid interference with sleep architecture and to achieve optimum benefits from treatment on cognitive processes.

Anticonvulsants for the treatment of behavioral and psychological symptoms of dementia: a literature review

OBJECTIVE

To review and summarize the currently available data on the use of anticonvulsant mood stabilizers (carbamazepine, valproic acid, gabapentin, lamotrigine, topiramate) in the treatment of behavioral and psychological symptoms of dementia (BPSD); to determine whether these medications can be recommended for routine clinical use.

METHODS

Literature search in five databases (PubMed, MEDLINE, EMBASE, PsychINFO and COCHRANE collaboration) and analysis of the randomized controlled double-blinded clinical trials found therein.

RESULTS

A total of seven RCTs were identified (two for carbamazepine and five for valproate). One study showed statistically significant improvement of BPSD in the medication group in comparison to the placebo group; five studies showed no significant differences; one study showed statistically significant worsening of the symptoms in the medication group vs. placebo. The majority of the studies reported significantly more frequent adverse effects in the medication group.

CONCLUSION

Although clearly beneficial in some patients, anticonvulsant mood stabilizers cannot be recommended for routine use in the treatment of BPSD at the present time.

Pharmacological management of behavioural and psychological disturbance in dementia

Behavioural and psychological symptoms in patients with dementia are common, distressing and often difficult to manage. This review evaluates a range of drugs commonly used to manage these symptoms including antipsychotics, anticonvulsants, antidementia drugs and antidepressants. The risks and benefits of individual treatments are discussed and the relatively poor evidence base and need for further research is highlighted.

Les symptômes psychologiques et comportementaux de la démence : description et prise en charge

Behavioral and Psychological Symptoms in Dementia (BPSD) are, beside cognitive disorders, major features of Alzheimer's disease and related disorders. Diagnosis is important to enhance our knowledge of the pathophysiology of dementia and of their functional consequences for patients and caregivers. Pharmacological and non-pharmacological management of dementia depends to a large extent on the presence of BPSD. A committee of geriatricians, neurologists and psychiatrists specialized in dementia (THEMA 2) has promoted an epidemiological, diagnostic and therapeutic update in this field. This work was based on the BPSD Consensus Conference Report edited in 2000 by the International Psychogeriatric Association. This report was updated with the most recent literature reports, and was adapted to the French environment. This paper is a synthesis of this meeting, validated and corrected by the entire Thema 2 group.

Treatment of behavioural and psychiatric symptoms in dementia: implications of recent safety warnings

Atypical antipsychotics are commonly used off-label to treat behavioural and psychiatric symptoms in dementia (BPSD), particularly in elderly care homes. Much of this use is inappropriate, and trials have shown an increased likelihood of serious cerebrovascular adverse events (CVAEs) such as stroke and transient ischemic attack (TIA) in elderly patients. The aetiology of this risk is not known, but may be related to metabolic effects and excess weight gain. Based on a review of published trials with risperidone and olanzapine that shows a three-fold increase in stroke risk in elderly patients with dementia, regulators in Europe and the USA now recommend against using these agents for behavioural control, particularly in patients with a history of cerebrovascular disease. When making prescribing decisions, physicians should pay careful attention to risk versus benefit with psychotropics. Antipsychotics should be regarded only as rescue medications for acute-onset (over hours or days) or for severe chronic BPSD, or used in patients who are aggressive and/or represent a danger to themselves or others. If atypical antipsychotics are prescribed, physicians should screen for risk factors for both stroke and cardiovascular disease when initiating treatment, and regular monitoring should be undertaken if patients with chronic behavioural problems receive antipsychotic maintenance therapy. International guidelines are now required that direct prescribers in the appropriate use of alternative therapies for BPSD. Cholinesterase inhibitors (ChEIs), particularly rivastigmine, can delay the onset and reduce the severity of neuropsychiatric symptoms in dementia, and decrease the requirement for antipsychotic and other psychotropic medications. Evidence suggests that they may be more appropriate for the control of chronic (over weeks to months) mild-to-moderate BPSD.

Effects of galantamine on behavioural and psychological disturbances and caregiver burden in patients with Alzheimer's disease

BACKGROUND

Behavioural and psychological disturbances occur in up to 90% of patients with Alzheimer's disease (AD), have a substantial impact on both patients and caregivers, and are often associated with the decision to institutionalise patients. Galantamine (Reminyl) is a dual-acting cholinergic treatment that improves cognitive and functional performance, delays the onset of behavioural symptoms and decreases behaviour-associated caregiver distress.

OBJECTIVE

To assess the impact of galantamine on behavioural disturbances and associated caregiver burden in non-institutionalised patients with AD.

METHODS

This was a 3-month, open-label, multicentre study in Switzerland. Patients with mild-to-moderate AD received galantamine (escalated from 8 to 24 mg/day over 8 weeks). The primary outcome was the Neuropsychiatric Inventory (NPI) for patients who completed 3 months treatment (observed cases, OC). Secondary outcomes included the Nurses' Observation Scale for Geriatric patients (NOSGER), and the Clinical Global Impression (CGI) of change.

RESULTS

124 patients (mean age 75.2 years, 55.6% women) received galantamine and were included in the intention-to-treat (ITT) safety analysis. Significant improvements in NPI scores versus baseline were seen in the OC analysis (p < 0.05, N = 91); mean total NPI scores (+/- SE) were reduced from 14.9 +/- 1.2 at baseline to 11.3 +/- 1.2 at month 3. Eleven out of 12 NPI domains were improved. Anxiety, aberrant motor behaviour, delusions, euphoria and night-time-behaviour all improved by > 30%. Symptoms with the highest baseline frequency and severity improved by 19-27%. A significant reduction in total NPI caregiver burden was observed at month 3 (p < 0.05). Despite this short assessment period the NOSGER evaluation and physicians' CGI also showed improvement. Adverse events (AEs) were mostly gastrointestinal.

CONCLUSION

Galantamine significantly reduced behavioural disturbances after 3 months in this population and this had a positive impact on behaviour-related caregiver burden. Galantamine showed the expected safety profile and was well tolerated.

Risk of Antipsychotic Drug Use in Patients with Alzheimer???s Disease Treated with Rivastigmine

BACKGROUND AND OBJECTIVE

Cholinesterase inhibitors may offer some improvement in the behavioural symptoms of Alzheimer's disease. The dual inhibitory mechanism of action of rivastigmine (inhibition of acetylcholinesterase and butyrylcholinesterase) may improve behavioural symptoms and may delay the need for antipsychotics. This study was conducted to investigate the effect of rivastigmine on the time to first antipsychotic drug use among patients with Alzheimer's disease, compared with patients with Alzheimer's disease not treated with a cholinesterase inhibitor.

DESIGN AND METHODS

This study used MarketScan research databases from 1 January 1999 to 31 March 2002. Patients were included if they: (a). were diagnosed with Alzheimer's disease on two occasions or filled a prescription for rivastigmine for the first time during the index period from 1 July 2000 to 31 December 2001; (b). were 65 years of age and older; (c). had continuous health and prescription insurance coverage during the entire study period; and (d). had not used an antipsychotic medication within 18 months prior to their index Alzheimer's disease prescription or diagnosis. The 'no cholinesterase inhibitor' group included patients who were newly diagnosed with Alzheimer's disease, but did not use any cholinesterase inhibitors. Chi-square, Student's t-, and log-rank tests were used to test differences in study variables between groups. Cox proportional hazards models were used to estimate predicted risk of first antipsychotic drug use.

RESULTS

The study included 497 patients in the rivastigmine group and 749 patients in the 'no cholinesterase inhibitor' group. The rivastigmine group patients were younger compared with the 'no cholinesterase inhibitor' group patients (p < 0.01). The overall usage of antipsychotics was considerably lower for patients taking rivastigmine (9.8%) compared with those not taking cholinesterase inhibitors (25.6%). Patients taking rivastigmine were 64% less likely (relative risk = 0.36; p < 0.0001) to take antipsychotics compared with patients not taking cholinesterase inhibitors, after adjusting for demographic covariates, comorbid conditions, and use of other CNS drugs and anticonvulsants. Age was the only other factor that influenced antipsychotic use; older patients were significantly more likely to start antipsychotics than younger patients.

CONCLUSION

This study provides initial evidence that patients with Alzheimer's disease treated with rivastigmine have a reduced risk of initiating therapy with an antipsychotic drug compared with patients who receive no cholinesterase inhibitor treatment. These findings may imply that rivastigmine use could delay the onset of behavioural symptoms that require treatment with antipsychotic medications.

Treatment Strategies in Alzheimer???s Disease with a Focus on Early Pharmacological Interventions

Complex interactive effects of genetic predisposition, neurochemical changes and disease comorbidity have been elucidated in the genesis of dementia syndromes. Alzheimer's disease is the most prevalent type of dementia in developed Western countries. In Alzheimer's disease, pharmacological treatment aims at symptomatic relief, disease modification or disease prevention. Cholinesterase inhibitors are established for the treatment of mild-to-moderate Alzheimer's disease. In Europe and the US, memantine is approved for the treatment of moderate-to-severe Alzheimer's disease. To date, there are no drugs with a disease modifying action that have proven efficacy in randomised, double-blind, placebo-controlled clinical trials. In patients not fulfilling the diagnostic criteria for early Alzheimer's disease, e.g. mild cognitive impairment, the efficacy of several drugs, mainly cholinesterase inhibitors, is currently tested in prospective studies by determining the conversion rate to Alzheimer's disease. However, prevention and disease-modifying strategies raise ethical questions because interventions are focused on non-diseased elderly at risk, which means that emphasis should be not only on efficacy but also on long-term safety. No disease-modifying strategy can presently be offered to patients; however, given the pace of recent research there is optimism that slowing progression of Alzheimer's disease will soon be possible.

Attenuation of MPTP-induced dopaminergic neurotoxicity by TV3326, a cholinesterase-monoamine oxidase inhibitor

(R)-[(N-propargyl-(3R) aminoindan-5-yl) ethyl methyl carbamate] (TV3326) is a novel cholinesterase and brain-selective monoamine oxidase (MAO)-A/-B inhibitor. It was developed for the treatment of dementia co-morbid with extra pyramidal disorders (parkinsonism), and depression. On chronic treatment in mice it attenuated striatal dopamine depletion induced by MPTP and prevented the reduction in striatal tyrosine hydroxylase activity, like selective B and non-selective MAO inhibitors. TV3326 preferentially inhibits MAO-B in the striatum and hippocampus, and the degree of MAO-B inhibition correlates with the prevention of MPTP-induced dopamine depletion. Complete inhibition of MAO-B is not necessary for full protection from MPTP neurotoxicity. Unlike that seen after treatment with other MAO-A and -B inhibitors, recovery of striatal and hippocampal MAO-A and -B activities from inhibition by TV3326 did not show first-order kinetics. This has been attributed to the generation of a number of metabolites by TV3326 that cause differential inhibition of these enzymes. Inhibition of brain MAO-A and -B by TV3326 resulted in significant elevations of dopamine, noradrenaline and serotonin in the striatum and hippocampus. This may explain its antidepressant-like activity, resembling that of moclobemide in the forced-swim test in rats.

A novel cholinesterase and brain-selective monoamine oxidase inhibitor for the treatment of dementia comorbid with depression and Parkinson's disease

Degeneration of cholinergic cortical neurons is one of the main reasons for the cognitive deficit in dementia of the Alzheimer type (AD) and in dementia with Lewy bodies (DLB). Many subjects with AD and DLB have extrapyramidal dysfunction and depression resulting from degeneration of dopaminergic, noradrenergic and serotoninergic neurons. We prepared a novel drug, TV-3326 (N-propargyl-3R-aminoindan-5yl)-ethyl methylcarbamate), with both cholinesterase (ChE) and monoamine oxidase (MAO) inhibitory activity, as potential treatment of AD and DLB. TV-3326 inhibits brain acetyl and butyrylcholinesterase (BuChE) in rats after oral doses of 10-100 mg/kg. After chronic but not acute treatment, it inhibits MAO-A and -B in the brain by more than 70% but has almost no effect on these enzymes in the small intestine in rats and rabbits. The brain selectivity results in minimal potentiation of the pressor response to oral tyramine. TV-3326 acts like other antidepressants in the forced swim test in rats, indicating a potential for antidepressant activity. Chronic treatment of mice with TV-3326 (26 mg/kg) prevents the destruction of nigrostriatal neurons by the neurotoxin MPTP (N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine). In addition to ChE and MAO inhibition, the propargylamine moiety of TV-3326 confers neuroprotective activity against cytotoxicity induced by ischemia and peroxynitrite in cultured neuronal cells that results from prevention of the fall in mitochondrial membrane potential and antiapoptotic activity. These unique multiple actions of TV-3326 make it a potentially useful drug for the treatment of dementia with Parkinsonian-like symptoms and depression.