Selective butyrylcholinesterase inhibitors are considered promising drug candidates for the treatment of Alzheimer's disease. In this work, one rivastigmine-bambuterol hybrid (MTR-1) and fourteen of its analogues were synthesized, purified, and characterized. In vitro cholinesterase assays showed that all the compounds were more potent inhibitors of BChE when compared to AChE. Further investigations indicated that MTR-3 (IC50(AChE) > 100,000 nM, IC50(BChE) = 78 nM) was the best compound in the series, showing high butyrylcholinesterase selectivity and inhibition potency, the potential to permeate the blood-brain barrier, and longer-lasting BChE inhibition than bambuterol. These compounds could be used to discover novel specific BChE inhibitors for the treatment of Alzheimer's disease.

Alzheimer's disease (AD) is a chronic neurodegenerative disorder characterized by a progressive loss of cognitive and functional abilities associated with various behavioral disturbances. Its impact on public health and society as a whole is devastating. Slowing of the cognitive impairment, and improvements in disease duration, self-sufficiency and behavioral disturbances represent the best outcomes of pharmacologic therapy. Cholinesterase inhibitors (ChE-I) have been shown to be effective in treating the cognitive, behavioral, and functional deficits of AD. Rivastigmine is a dual inhibitor of both acetylcholine esterase (AChE) and butyrylcholinesterase (BuChE), enzymes involved in the hydrolysis of acetylcholine. Although this drug has been shown to be beneficial in patients with AD, its benefits are limited and their long-term effectiveness has not been well demonstrated.

Tau protein aggregations are important contributors to the etiology of Alzheimer's disease (AD). Hydromethylthionine (HMT) is a potent inhibitor of tau aggregation in vitro and in vivo and is being developed as a possible anti-dementia medication. HMT was also shown to affect the cholinergic system and to interact with mitochondria. Here, we used tau-transgenic (L1 and L66) and wild-type NMRI mice that were treated with HMT, rivastigmine and memantine and with combinations thereof, for 2-4 weeks. We measured HMT concentrations in both brain homogenates and isolated mitochondria and concentrations of glucose, lactate and pyruvate in brain by microdialysis. In isolated brain mitochondria, we recorded oxygen consumption of mitochondrial complexes by respirometry. While rivastigmine and memantine lowered mitochondrial respiration, HMT did not affect respiration in wild-type animals and increased respiration in tau-transgenic L1 mice. Glucose and lactate levels were not affected by HMT administration. The presence of HMT in isolated mitochondria was established. In summary, traditional anti-dementia drugs impair mitochondrial function while HMT has no adverse effects on mitochondrial respiration in tau-transgenic mice. These results support the further development of HMT as an anti-dementia drug.

Gait impairments are common in patients with Alzheimer's disease. Cholinesterase inhibitors are used to treat the symptoms of patients with Alzheimer's disease, but they have not been shown to reduce the severity of Alzheimer's disease-related gait disorders.

Rivastigmine (or Exelon) is a cholinesterase inhibitor, currently used as a symptomatic treatment for mild-to-moderate Alzheimer's disease (AD). Amyloid-β peptide (Aβ) generated from its precursor protein (APP) by β-secretase (or BACE1) and γ-secretase endoproteolysis. Alternative APP cleavage by α-secretase (a family of membrane-bound metalloproteases- Adamalysins) precludes the generation of toxic Aβ and yields a neuroprotective and neurotrophic secreted sAPPα fragment. Several signal transduction pathways, including protein kinase C and MAP kinase, stimulate α-secretase. We present data to suggest that rivastigmine, in addition to anticholinesterase activity, directs APP processing away from BACE1 and towards α-secretases. We treated rat neuronal PC12 cells and primary human brain (PHB) cultures with rivastigmine and the α-secretase inhibitor TAPI and assayed for levels of APP processing products and α-secretases. We subsequently treated 3×Tg (transgenic) mice with rivastigmine and harvested hippocampi to assay for levels of APP processing products. We also assayed postmortem human control, AD, and AD brains from subjects treated with rivastigmine for levels of APP metabolites. Rivastigmine dose-dependently promoted α-secretase activity by upregulating levels of ADAM-9, -10, and -17 α-secretases in PHB cultures. Co-treatment with TAPI eliminated rivastigmine-induced sAPPα elevation. Rivastigmine treatment elevated levels of sAPPα in 3×Tg mice. Consistent with these results, we also found elevated sAPPα in postmortem brain samples from AD patients treated with rivastigmine. Rivastigmine can modify the levels of several shedding proteins and directs APP processing toward the non-amyloidogenic pathway. This novel property of rivastigmine can be therapeutically exploited for disease-modifying intervention that goes beyond symptomatic treatment for AD.

Alzheimer's disease (AD) is the most common form of dementia with no cure so far, probably due to the complexity of this multifactorial disease with diverse processes associated with its origin and progress. Several neuropathological hallmarks have been identified that encourage the search for new multitarget drugs. Therefore, following a multitarget approach, nine rivastigmine-indole (RIV-IND) hybrids (5a1-3, 5b1-3, 5c1-3) were designed, synthesized and evaluated for their multiple biological properties and free radical scavenging activity, as potential multitarget anti-AD drugs. The molecular docking studies of these hybrids on the active center of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) suggest their capacity to act as dual enzyme inhibitors with probable greater disease-modifying impact relative to AChE-selective FDA-approved drugs. Compounds 5a3 (IC50 = 10.9 µM) and 5c3 (IC50 = 26.8 µM) revealed higher AChE inhibition than the parent RIV drug. Radical scavenging assays demonstrated that all the hybrids containing a hydroxyl substituent in the IND moiety (5a2-3, 5b2-3, 5c2-3) have good antioxidant activity (EC50 7.8-20.7 µM). The most effective inhibitors of Aβ42 self-aggregation are 5a3, 5b3 and 5c3 (47.8-55.5%), and compounds 5b2 and 5c2 can prevent the toxicity induced by Aβ1-42 to cells. The in silico evaluation of the drug-likeness of the hybrids also showed that all the compounds seem to have potential oral availability. Overall, within this class of RIV-IND hybrids, 5a3 and 5c3 appear as lead compounds for anti-AD drug candidates, deserving further investigation.

Here we report a novel approach for preparation of a 6-day transdermal drug delivery system (TDDS) as treatment for mild to moderate Alzheimer's disease. The spray drying method was used to prepare microparticles containing the anti-Alzheimer drug, Rivastigmine, in combination with the natural polymer, chitosan, for transdermal drug delivery applications. The content of the drug was determined by High Performance Liquid Chromatography (HPLC) method which was validated as per FDA guidelines. The morphology and size range of the microparticles were determined; and the effect of drug concentration in the solution injected into the spray dryer on the particles characterizations was studied. The stability of Rivastigmine at high temperature was confirmed using FTIR analysis as well as a validate HPLC assay. The obtained results show that the drug was stable at high temperatures with 7 to 42% loading in the microparticles, and the higher drug concentrations of the solution injected into the spray dryer resulted in increase of the drug loading, surface drug and microparticles distortion. The TDDS containing the microparticles was also prepared with microparticle to dry adhesive ratios of 5, 10 and 15% using acrylic adhesive. Based on adhesion properties of the patches, gained from the probe tack and the peel adhesion 180° tests, and the 15% patch by having more drug content per unit area of the patch, and still having similar adhesion properties was compared to the microparticles-free patch of 5.1% Rivastigmine salt (equivalent to the drug content of the 15% patch) from the permeation point of view by using Franz cell diffusion over 6 days. The drug permeation rate from the microparticle-free patch was slower than the 15% microparticles patch, which is the result of crystallization of Rivastigmine salt in the acrylic adhesive. The 6-day-prepared TDDS can be considered as an alternative for one-week application of 6 Exelon patches.

The prevention of tau protein aggregations is a therapeutic goal for the treatment of Alzheimer's disease (AD), and hydromethylthionine (HMT) (also known as leucomethylthioninium-mesylate [LMTM]), is a potent inhibitor of tau aggregation in vitro and in vivo. In two Phase 3 clinical trials in AD, HMT had greater pharmacological activity on clinical endpoints in patients not receiving approved symptomatic treatments for AD (acetylcholinesterase (AChE) inhibitors and/or memantine) despite different mechanisms of action. To investigate this drug interaction in an animal model, we used tau-transgenic L1 and wild-type NMRI mice treated with rivastigmine or memantine prior to adding HMT, and measured changes in hippocampal acetylcholine (ACh) by microdialysis. HMT given alone doubled hippocampal ACh levels in both mouse lines and increased stimulated ACh release induced by exploration of the open field or by infusion of scopolamine. Rivastigmine increased ACh release in both mouse lines, whereas memantine was more active in tau-transgenic L1 mice. Importantly, our study revealed a negative interaction between HMT and symptomatic AD drugs: the HMT effect was completely eliminated in mice that had been pre-treated with either rivastigmine or memantine. Rivastigmine was found to inhibit AChE, whereas HMT and memantine had no effects on AChE or on choline acetyltransferase (ChAT). The interactions observed in this study demonstrate that HMT enhances cholinergic activity in mouse brain by a mechanism of action unrelated to AChE inhibition. Our findings establish that the drug interaction that was first observed clinically has a neuropharmacological basis and is not restricted to animals with tau aggregation pathology. Given the importance of the cholinergic system for memory function, the potential for commonly used AD drugs to interfere with the treatment effects of disease-modifying drugs needs to be taken into account in the design of clinical trials.

Efficient drug delivery remains a critical challenge for treating neurodegenerative diseases, such as Alzheimer's disease (AD). Using innovative nanomaterials, delivering current medications like acetylcholinesterase inhibitors to the brain through the intranasal route is a promising strategy for managing AD. Here, we developed a unique combinational drug delivery system based on N,N,N-trimethyl chitosan nanoparticles (NPs). These NPs encapsulate rivastigmine, the most potent acetylcholinesterase inhibitor, along with insulin, a complementary therapeutic agent. The spherical NPs exhibited a zeta potential of 17.6 mV, a size of 187.00 nm, and a polydispersity index (PDI) of 0.29. Our findings demonstrate significantly improved drug transport efficiency through sheep nasal mucosa using the NPs compared to drug solutions. The NPs exhibited transport efficiencies of 73.3% for rivastigmine and 96.9% for insulin, surpassing the efficiencies of the drug solutions, which showed transport efficiencies of 52% for rivastigmine and 21% for insulin ex vivo. These results highlight the potential of a new drug delivery system as a promising approach for enhancing nasal transport efficiency. These combinational mucoadhesive NPs offer a novel strategy for the simultaneous cerebral delivery of rivastigmine and insulin, which could prove helpful in developing effective treatments of AD and other neurodegenerative conditions.

Acetylcholinesterase inhibitors (AChEis) including donepezil, galantamine and rivastigmine are used to treat Alzheimer's disease (AD). This study aimed to evaluate evidence from the case report literature for an association between these agents and risk of QT interval prolongation and Torsades de Pointes (TdP) arrhythmia.

Current palliative pharmacotherapy of Alzheimer's disease based on the cholinergic hypothesis led to the development of four cholinesterase inhibitors. These compounds can bring prolongation of the symptom-free period in some patients. This is the first report directly comparing donepezil and rivastigmine plasma and brain levels in in-vivo study. Donepezil and rivastigmine were applied i.m. to rats; the dose was calculated from clinical recommendations. The samples were analysed on an Agilent 1260 Series LC with UV/VIS detector. An analytical column (Waters Spherisorb S5 W (250 mm × 4.6 i.d.; 5 μm particle size)) with guard column (Waters Spherisorb S5 W (30 mm × 4.6 mm i.d.)) was used. The mobile phase contained acetonitrile and 50 mM sodium dihydrogen phosphate (17:83; v/v); pH 3.1. The LLOQ in rat plasma was 0.5 ng/mL for donepezil and 0.8 ng/mL for rivastigmine, and the LLOQ in rat brain was 1.0 ng/mL for donepezil and 1.1 ng/mL for rivastigmine. Both compounds showed ability to target the central nervous system, with brain concentrations exceeding those in plasma. Maximum brain concentration after i.m. administration was reached in the 36 (8.34 ± 0.34 ng/mL) and 17 minute (6.18 ± 0.40 ng/mL), respectively for donepezil and rivastigmine. The differences in brain profile can be most easily expressed by plasma/brain AUCtotal ratios: donepezil ratio in the brain was nine-times higher than in plasma and rivastigmine ratio was less than two-times higher than in plasma.

To sustain the effect of rivastigmine, a hydrophilic cholinesterase inhibitor, nanobased formulations were prepared. The efficacy of the prepared rivastigmine liposomes (RLs) in comparison to rivastigmine solution (RS) was assessed in an aluminium chloride (AlCl(3))-induced Alzheimer's model.

With the goal of combating the multi-faceted Alzheimer's disease (AD), a series of Rivastigmine-Benzimidazole (RIV-BIM) hybrids was recently reported by us as multitarget-directed ligands, thanks to their capacity to tackle important hallmarks of AD. In particular, they exhibited antioxidant activity, acted as cholinesterase inhibitors, and inhibited amyloid-β (Aβ) aggregation. Herein, we moved forward in this project, studying their ability to chelate redox-active biometal ions, Cu(II) and Fe(III), with widely recognized roles in the generation of oxidative reactive species and in protein misfolding and aggregation in both AD and Parkinson's disease (PD). Although Cu(II) chelation showed higher efficiency for the positional isomers of series 5 than those of series 4 of the hybrids, the Aβ-aggregation inhibition appears more dependent on their capacity for fibril intercalation than on copper chelation. Since monoamine oxidases (MAOs) are also important targets for the treatment of AD and PD, the capacity of these hybrids to inhibit MAO-A and MAO-B was evaluated, and they showed higher activity and selectivity for MAO-A. The rationalization of the experimental evaluations (metal chelation and MAO inhibition) was supported by computational molecular modeling studies. Finally, some compounds showed also neuroprotective effects in human neuroblastoma (SH-SY5Y cells) upon treatment with 1-methyl-4-phenylpyridinium (MPP+), a neurotoxic metabolite of a Parkinsonian-inducing agent.

Alzheimer's disease (AD) is the most serious and prevalent neurodegenerative disorder still without cure. Since its aetiology is diverse, recent research on anti-AD drugs has been focused on multi-target compounds. In this work, seven novel hybrids (RIV-BIM) conjugating the active moiety of the drug rivastigmine (RIV) with 2 isomeric hydroxyphenylbenzimidazole (BIM) units were developed and studied. While RIV assures the inhibition of cholinesterases, BIM provides further appropriate properties, such as inhibition of amyloid β-peptide (Aβ) aggregation, antioxidation and metal chelation. The evaluated biological properties of these hybrids included antioxidant activity; inhibition of acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and Aβ42 aggregation; as well as promotion of cell viability and neuroprotection. All the compounds are better inhibitors of AChE than rivastigmine (IC50 = 32.1 µM), but compounds of series 5 are better inhibitors of BChE (IC50 = 0.9-1.7 µM) than those of series 4. Series 5 also showed good capacity to inhibit self- (42.1-58.7%) and Cu(II)-induced (40.3-60.8%) Aβ aggregation and also to narrow (22.4-42.6%) amyloid fibrils, the relevant compounds being 5b and 5d. Some of these compounds can also prevent the toxicity induced in SH-SY5Y cells by Aβ42 and oxidative stress. Therefore, RIV-BIM hybrids seem to be potential drug candidates for AD with multi-target abilities.

Microtubule affinity-regulating kinase (MARK4) plays a key role in Alzheimer's disease (AD) development as its overexpression is directly linked to increased tau phosphorylation. MARK4 is a potential drug target of AD and is thus its structural features are employed in the development of new therapeutic molecules. Donepezil (DP) and rivastigmine tartrate (RT) are acetylcholinesterase (AChE) inhibitors and are used to treat symptomatic patients of mild to moderate AD. In keeping with the therapeutic implications of DP and RT in AD, we performed binding studies of these drugs with the MARK4. Both DP and RT bound to MARK4 with a binding constant (K) of 107 M-1. The temperature dependency of binding parameters revealed MARK-DP complex to be guided by static mode while MARK-RT complex to be guided by both static and dynamic quenching. Both drugs inhibited MARK4 with IC50 values of 5.3 μM (DP) and 6.74 μM (RT). The evaluation of associated enthalpy change (ΔH) and entropy change (ΔS) implied the complex formation to be driven by hydrogen bonding making it seemingly strong and specific. Isothermal titration calorimetry further advocated a spontaneous binding. In vitro observations were further complemented by the calculation of binding free energy by molecular docking and interactions with the functionally-important residues of the active site pocket of MARK4. This study signifies the implications of AChE inhibitors, RT, and DP in Alzheimer's therapy targeting MARK4.

Targeted delivery of neurological therapeutic to the brain has been attracting more and more attention to the treatment of central nervous system (CNS) diseases. Nonetheless, the main obstacle in this road map is the existence of a blood-brain barrier (BBB) which limits the penetration efficiency of most CNS drugs into the brain parenchyma. This present investigation describes a facile synthetic strategy to prepare a highly biocompatible calcium-doped mesoporous silica nanoparticles (MSNs) functionalized by polysorbate-80 (PS) as targeting ligand to deliver rivastigmine (RV) into the brain via crossing the BBB. The developed nanosystem was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), Zeta potential, and N2-adsorption-desorption analysis. In vitro hemolysis studies were carried out to confirm the biocompatibility of the nanocarriers. Our in vivo studies in an animal model of rats showed that the RV-loaded nanosystem was able to enhance the brain-to-plasma concentration ratio, brain uptake clearance, and plasma elimination half-life of the drug compared to the free one drug following intravenous (IV) administration. The results revealed that functionalization of MSNs by PS is crucial to deliver RV into the brain, suggesting PS-functionalized MSNs could be an effective carrier to deliver RV to the brain while overcoming BBB.

Higher-level gait disorder (HLGD) in older adults is characterized by postural instability, stepping dysrhythmicity, recurrent falls and progressive immobility. Cognitive impairments are frequently associated with HLGD.

Rivastigmine is a pseudo-irreversible cholinesterase inhibitor used for therapy of Alzheimer's disease and non-Alzheimer dementia syndromes. In humans, rivastigmine can cause significant gastrointestinal side effects that can limit its clinical use. The aim of this study was to assess the impact of rivastigmine on gastric motor function by means of electrogastrography (EGG) in experimental pigs.

Gait impairment is common in people with Parkinson's disease. There is a lack of effective interventions to target this debilitating complication and therefore a need to identify new therapeutic options. An underlying cholinergic deficit contributes to both the gait and cognitive dysfunction seen in Parkinson's disease. The combined impact of both impairments can be assessed in gait tasks performed with concomitant cognitive tasks. The aim of this trial is to evaluate the impact of a cholinesterase inhibitor on cognitive function and gait performance in people with established Parkinson's disease.

The treatment of depression in old age is complicated by frequent co-morbidity with cognitive impairment. Anti-dementia drugs have some efficacy to improve cognitive performance and there is an inconsistent literature regarding the effect of such drugs on depressive symptoms. Here, we have investigated whether anti-dementia drugs would have antidepressant-like and pro-cognitive effects in a well-validated animal model of depression and cognitive impairment, chronic mild stress (CMS).