Inhibitor Report for: Ladostigil

OBJECTIVES: Alzheimer's disease (AD) is one of the most prevalent neurodegenerative disorders and a well-recognized cause of dementia with ageing. In this review, we have represented the ChE and MAO inhibitory potential of TV 3326 against AD based on current scientific evidence. KEY FINDINGS: The aetiology of AD is quite complex and not completely understood. However, it has been observed that AD involves the deposition of abnormal amyloid beta (Abeta), along with hyperphosphorylation of tau, oxidative stress, low acetylcholine (ACh) level and biometal dyshomeostasis. Due to the complex nature of AD aetiology, active research is required in the areas of development of multitarget drugs with 2 or more complementary biological functions, as they might represent significant progress in the AD treatment. Interestingly, it has been found that TV 3326 (i.e. ladostigil) is regarded as a novel therapeutic agent since it has the potential to cause inhibition of monoamine oxidase (MAO) A and B, and acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) in the brain. Furthermore, it has the capacity to reverse memory impairments, which further suggests the ability of this drug to elevate cholinergic activity in the brain. SUMMARY: TV 3326 can avert oxidative-nitrative stress and gliosis. It has also been confirmed that TV 3326 contains neuroprotective and anti-apoptotic properties. Therefore, this distinctive combined inhibition of ChE and MAO along with its neuroprotective property makes TV 3326 a useful drug in the treatment of AD.

(N-propargyl-(3R)-aminoindan-5-yl)-ethyl, methyl carbamate (TV3326), a known neuroprotective agent exhibiting the properties of both an inhibitor of monoamine oxidase (brain selective) and an inhibitor of acetylcholinesterase was administered to seven old rhesus monkeys well trained to perform versions of a delayed matching-to-sample (DMTS) task. An increasing dose regimen of TV3326 was administered orally according to a schedule that allowed the animals to perform the standard DMTS task and a self-titrating version of the DMTS task each week during the study. A distractor version of the task was administered during two of the doses of TV3326. Under the conditions of this experiment TV3326 failed to significantly affect accuracy on the standard DMTS task; however, the drug was very effective in improving the ability of subjects to titrate to longer-duration delay intervals in the titrating version of the task. The maximal drug-induced extension of the self-titrated delay interval amounted to a 36.7% increase above baseline. This increase in maximum delay duration occurred without a significant change in overall task accuracy. TV3326 also significantly improved task accuracy during distractor (interference) sessions. The compound was effective enough to return group performance efficiency to standard DMTS vehicle levels of accuracy. These results were independent of whether trials were associated with a distractor or non-distractor delay interval, and they were independent of delay interval. The lack of delay selectivity in task improvement by TV3326 may not be consistent with a selective effect on attention. TV3326 was not associated with any obvious side effect or untoward reaction of the animals to the drug. Thus, TV3326 may be expected to offer a significant positive cognitive outcome in addition to its reported neuroprotective action.

Rasagiline (N-propargyl-1-(R)-aminoindan) is a selective, irreversible monoamine oxidase B (MAO B) inhibitor which has been developed as an anti-Parkinson drug. In controlled monotherapy and as adjunct to L-dopa it has shown anti-Parkinson activity. In cell culture (PC-12 and neuroblastoma SH-SY5Y cells) it exhibits neuroprotective and anti-apoptotic activity against several neurotoxins (SIN-1, MPTP, 6-hydroxydopamine and N-methyl-(R)-salsolinol) and ischemia. In vivo, it reduces the sequelae of traumatic brain injury in mice and speeds their recovery. The neuroprotective activity of rasagaline does not result from MAO B inhibition, since its S-enantiomer, TVP1022, which has 1000-fold weaker MAO inhibitory activity, exhibits similar neuroprotective properties. Introduction of a carbamate moiety into the rasagiline molecule to confer cholinesterase inhibitory activity for the treatment of Alzheimer's disease, resulted in compounds TV3326 [(N-Propargyl-(3R)Aminoindan-5-YL)-Ethyl Methyl Carbamate] and its S-enantiomer TV3279 [(N-Propargyl-(3S)Aminoindan-5-YL)-Ethyl Methyl Carbamate], which retain the neuroprotective activities of rasagiline and TVP1022. They also antagonize scopolamine-induced impairments in spatial memory. In addition, TV3326 exhibits brain-selective MAO A and B inhibitory activity after chronic administration and has antidepressant-like activity in the forced swim test. This is associated with an increase in brain levels of serotonin. The anti-apoptotic activity of these propargylamine-containing derivatives may be related to their ability to delay the opening of voltage-dependent anion channels (VDAC), which are part of the mitochondrial permeability transition pore. The propargylamine moiety is responsible for the increase in the mitochondrial family of Bcl-2 proteins, prevention in the fall in mitochondrial membrane potential, prevention of the activation of caspase 3, and of translocation of glyceraldehyde-3-phosphate dehydrogenase from the cytoplasm to the nucleus. The latter processes are closely associated with neurotoxin-induced apoptosis. Rasagiline interacts with and prevents the binding of PKI 1195 to the pro-apoptotic peripheral benzodiazepine receptor, which together with Bcl-2, hexokinase, porin, and adenine nucleotide translocator constitutes part of the VDAC. Furthermore, rasagiline, TV3326 and TV3279 are able to influence the processing of amyloid precursor protein by activation of alpha-secretase and increasing the release of soluble alpha APP in rat PC-12 and human neuroblastoma SH-SY5Y cells and in rat and mice cortex and hippocampus. This process has been shown to involve the upregulation of PKC and MAP kinase. It is quite likely that the induction of Bcl-2 and activation of PKC by rasagiline and TV3326 is closely linked to the anti-apoptotic action of these drugs and their ability to process APP by activation of alpha-secretase.

OBJECTIVES: Alzheimer's disease (AD) is one of the most prevalent neurodegenerative disorders and a well-recognized cause of dementia with ageing. In this review, we have represented the ChE and MAO inhibitory potential of TV 3326 against AD based on current scientific evidence. KEY FINDINGS: The aetiology of AD is quite complex and not completely understood. However, it has been observed that AD involves the deposition of abnormal amyloid beta (Abeta), along with hyperphosphorylation of tau, oxidative stress, low acetylcholine (ACh) level and biometal dyshomeostasis. Due to the complex nature of AD aetiology, active research is required in the areas of development of multitarget drugs with 2 or more complementary biological functions, as they might represent significant progress in the AD treatment. Interestingly, it has been found that TV 3326 (i.e. ladostigil) is regarded as a novel therapeutic agent since it has the potential to cause inhibition of monoamine oxidase (MAO) A and B, and acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) in the brain. Furthermore, it has the capacity to reverse memory impairments, which further suggests the ability of this drug to elevate cholinergic activity in the brain. SUMMARY: TV 3326 can avert oxidative-nitrative stress and gliosis. It has also been confirmed that TV 3326 contains neuroprotective and anti-apoptotic properties. Therefore, this distinctive combined inhibition of ChE and MAO along with its neuroprotective property makes TV 3326 a useful drug in the treatment of AD.

The novel drugs, ladostigil (TV3326) and TV3279, are R and S isomers, respectively, derived from a combination of the carbamate cholinesterase (ChE) inhibitor, rivastigmine, and the pharmacophore of the monoamine oxidase (MAO) B inhibitor, rasagiline. They were developed for the treatment of comorbidity of dementia with Parkinsonism. In the present study, we determined the effects of these drugs on both aminergic neurotransmitter levels and motor behavioral activity in naive and in L-dopa- or L-tryptophan-induced rats. Chronic treatment of rats with ladostigil (52 mg kg(-1) for 21 days) inhibited hippocampal and striatal MAO A and B activities by >90%, increased striatal levels of dopamine and serotonin, and inhibited striatal ChE activity by approximately 50%. Chronic TV3279 (26 mg kg(-1) for 21 days) similarly inhibited approximately 50% of striatal ChE activity, but did not affect MAO activity or amine levels. In sharp contrast to the inductive effect of the MAO A/B inhibitor, tranylcypromine (TCP), on stereotyped hyperactivity in response to L-dopa (50 mg kg(-1)) or L-tryptophan (100 mg kg(-1)), ladostigil completely inhibited these behavioral hyperactivity syndromes. Accordingly, acute rivastigmine (2 mg kg(-1)) and chronic TV3279 abolished the ability of TCP to initiate L-dopa-induced hyperactivity, while scopolamine (0.5 mg kg(-1)) reversed the inhibitory effect of chronic ladostigil on L-dopa-induced hyperactivity, suggesting that ladostigil may attenuate successive locomotion by activating central cholinergic muscarinic receptors.Finally, while chronic ladostigil administration to naive rats resulted in preserved spontaneous motor behavior, acute treatment with ladostigil decreased motor performance, compared to control animals. In contrast, chronic as well as acute treatments with TV3279 reduced spontaneous motor activity. Thus, the aminergic potentiation by ladostigil may counteract its cholinergic inhibitory effect on spontaneous motor behavior. Our results suggest that potentiation of both aminergic and cholinergic transmission systems by ladostigil contributes equally to motor behavior performance, which is substantially impaired in comorbidity of dementia with Parkinsonism including dementia with Lewy bodies (DLB).

Degeneration of nigrostriatal dopamine neurons and cholinergic cortical neurones are the main pathological features of Parkinson's disease (PD) and for the cognitive deficit in dementia of the Alzheimer' type (AD) and in dementia with Lewy bodies (DLB), respectively. Many PD and DLB subjects have dementia and depression resulting from possible degeneration of cholinergic and noradrenergic and serotonergic neurons. On the other hand, AD patients may also develop extrapyramidal features as well as depression. In both PD and AD there is, respectively, accumulation of iron within the melanin containing dopamine neurons of pars compacta and with in the plaques and tangle. It has been suggested that iron accumulation may contribute to the oxidative stress induced apoptosis reported in both diseases. This may result from increased glia hydrogen peroxide producing monoamine oxidase (MAO) activity that can generate of reactive hydroxyl radical formed from interaction of iron and hydrogen peroxide. We have therefore prepared a series of novel bifunctional drugs from the neuroprotective-antiapoptotic antiparkinson monoamine oxidase B inhibitor, rasagiline, by introducing a carbamate cholinesterase (ChE) inhibitory moiety into it. Ladostigil (TV-3326, N-propargyl-3R-aminoindan-5yl)-ethyl methylcarbamate), has both ChE and MAO-AB inhibitory activity, as potential treatment of AD and DLB or PD subjects with dementia Being a brain selective MAO-AB inhibitor it has limited potentiation of the pressor response to oral tyramine and exhibits antidepressant activity similar to classical non-selective MAO inhibitor antidepressants by increasing brain serotonin and noradrenaline. Ladostigil inhibits brain acetyl and butyrylcholinesterase in rats and antagonizes scopolamine-induced inhibition of spatial learning. Ladostigil like MAO-B inhibitor it prevents MPTP Parkinsonism in mice model and retains the in vitro and in vivo neuroprotective activity of rasagiline. Ladostigil, rasagiline and other propargylamines have been demonstrated to have neuroprotective activity in several in vitro and in vivo models, which have been shown be associated with propargylamines moiety, since propargylamines itself possess these properties. The mechanism of neuroprotective activity has been attributed to the ability of propargylamines-inducing the antiapoptotic family proteins Bcl-2 and Bcl-xl, while decreasing Bad and Bax and preventing opening of mitochondrial permeability transition pore. Iron accumulates in brain regions associated with neurodegenerative diseases of PD, AD, amyotrophic lateral sclerosis and Huntington disease. It is thought to be involved in Fenton chemistry oxidative stress observed in these diseases. The neuroprotective activity of propargylamines led us to develop several novel bifunctional iron chelator from our prototype brain permeable iron chelators, VK-28, possessing propargylamine moiety (HLA-20, M30 and M30A) to iron out iron from the brain. These compounds have been shown to have iron chelating and monoamine oxidase A and B selective brain inhibitory and neuroprotective-antiapoptotic actions.

Individuals with neurodegenerative diseases such as Parkinson's disease or Alzheimer's disease are benefiting from drugs developed to act on a single molecular target. However, current pharmacological approaches are limited in their ability to modify significantly the course of the disease, and offer incomplete and transient benefit to patients. New therapeutic strategies comprise drug candidates designed specifically to act on multiple neural and biochemical targets for the treatment of cognition impairment, motor dysfunction, depression and neurodegeneration. Examples include the development of single molecular entities that combine two or more of the following properties: (i) cholinesterase inhibition; (ii) activation or inhibition of specific subtypes of acetylcholine receptors or alpha-adrenoceptors; (iii) anti-inflammatory activity; (iv) monoamine oxidase inhibition; (v) catechol-O-methyl transferase inhibition; (vi) nitric oxide production; (vii) neuroprotection; (viii) anti-apoptotic activity; and (ix) activation of mitochondrial-dependent cell-survival genes and proteins. These bi- or multi-functional compounds might provide greater symptomatic efficacy, and better utility as potential neuroprotective disease-modifying drugs.

Patients with mild forms of dementia and age-related memory impairment have just begun to benefit from pharmacotherapy developed over the last several years. However, current approaches do not significantly modify the course of neurodegeneration or of the aging process, and they offer limited and transient benefit to many patients. The goal of this review is to summarize new potential approaches in which molecules have been developed expressly to target multiple brain systems for the treatment of memory and cognition impairment. Some of these approaches include the development of single molecular entities that combine activity as cholinesterase inhibitors, muscarinic cholinergic M2 receptor antagonists, nicotinic acetylcholine receptor agonists, alpha(2)-adrenergic agonists, or monoamine oxidase inhibitors. Many of the bi-functional compounds discussed have improved efficacy as cognitive enhancing agents and/or they offer potential for neuroprotection and disease modification. It is likely that syndromes such as Alzheimer's disease will require multiple drug therapy to address the varied pathological aspects of the disease. Even if the strategy of combining drugs with different therapeutic targets is workable, the development of multi-functional compounds will obviate the challenge of administering multiple single drug entities with potentially different degrees of bioavailability, pharmacokinetics, and metabolism. Also, the simplification of the therapeutic regimen for individuals with AD who have difficulty with compliance is important.

Insufficient cholinergic neurotransmission in AD is responsible for a progressive loss of cognition and motor capacities. The cholinergic hypothesis has provided the rationale for the current treatment approaches based on acetylcholinesterase inhibitors. However, recent data focus on the complex nature of AD and disclose the involvement of other neurotransmitters such as serotonin, noradrenalin, dopamine, histamine, excitatory amino acids and neuropeptides among others. Interestingly, recent research has revealed that in severe AD brains the levels of AChE are considerably reduced whereas BuChE activity increases, thus aggravating the toxicity of beta A. In such instances, it is possible that BuChE may be a more suitable target than AChE. Oxidative stress has been implicated in CNS degenerative disorders such as AD and PD. Therefore, owing to their capacity to inhibit oxidative damage, MAOIs are potential candidates as anti-Alzheimer drugs. More recently, a novel drug--TV3326--was designed, based upon two pharmacophores: the carbamate moiety from rivastigmine, an AChE inhibitor; and the propargyl group from rasagiline, a MAO inhibitor. This drug exhibits cholinesterase and selective brain MAO inhibitory activities, reduces apoptosis and stimulates the processing of APP alpha, hence reducing the possibility of generation of the toxic beta A. Thus, TV3326 may be expected to contribute positively to the cognitive benefits of Alzheimer's patients. Anyhow, the development of drugs with several targets and diverse pharmacological properties may conclusively demonstrate the most beneficial therapy.

The major side effect with the use of first generation of non selective monoamine oxidase (MAO) inhibitors as neuropsychiatric drugs was what became known as the "cheese reaction". Namely, potentiation of sympathomimetic activity of ingested tyramine present in cheese and other food stuff, resulting from its ability to release noradrenaline, when prevented from metabolism by MAO. The identification of two forms of MAO, termed types A and B and their selective irreversible inhibitors resolved some of this problems. However irreversible MAO-A inhibitors continue to induce a cheese reaction, whereas MAO-B inhibitors at their selective dosage did not and led to introduction of L-deprenyl (selegiline) as an anti-Parkinson drug, since dopamine is equally well metabolized by both enzyme forms. The cheese reaction is a consequence of inhibition of MAO-A, the enzyme responsible for metabolism of noradrenaline and serotonin, located in peripheral adrenergic neurons. The consequence of these findings were the development of reversible MAO-A inhibitors (RIMA), moclobemide and brofaromin, as antidepressants and possible anti-Parkinson activity, with limited tyramine potentiation, since the amine can displace the inhibitor from its binding site on the enzyme. It has always been deemed a greater pharmacological advantage to inhibit both forms of the enzymes to get the full functional activities of the amine neurotransmitters, and without inducing a "cheese reaction". This was not possible until recently, with the development of the novel cholinesterase-brain selective MAO-AB inhibitor, TV3326 (N-propargyl-(3R)-aminoidnan-5-yl-ethyl methylcarbamate hemitartiate), a carbamate derivative of the irreversible MAO-B inhibitor anti-Parkinson drug, rasagiline. This drug is a brain selective MAO-A and B inhibitor, with little inhibition of liver and small intestine enzymes. Pharmacologically it has limited tyramine potentiation, very similar to moclobemide and being a MAO-AB inhibitor it has the antidepressant, anti-Parkinson and anti-Alzheimer activities in the respective models used to develop such drugs.

(N-propargyl-(3R)-aminoindan-5-yl)-ethyl, methyl carbamate (TV3326), a known neuroprotective agent exhibiting the properties of both an inhibitor of monoamine oxidase (brain selective) and an inhibitor of acetylcholinesterase was administered to seven old rhesus monkeys well trained to perform versions of a delayed matching-to-sample (DMTS) task. An increasing dose regimen of TV3326 was administered orally according to a schedule that allowed the animals to perform the standard DMTS task and a self-titrating version of the DMTS task each week during the study. A distractor version of the task was administered during two of the doses of TV3326. Under the conditions of this experiment TV3326 failed to significantly affect accuracy on the standard DMTS task; however, the drug was very effective in improving the ability of subjects to titrate to longer-duration delay intervals in the titrating version of the task. The maximal drug-induced extension of the self-titrated delay interval amounted to a 36.7% increase above baseline. This increase in maximum delay duration occurred without a significant change in overall task accuracy. TV3326 also significantly improved task accuracy during distractor (interference) sessions. The compound was effective enough to return group performance efficiency to standard DMTS vehicle levels of accuracy. These results were independent of whether trials were associated with a distractor or non-distractor delay interval, and they were independent of delay interval. The lack of delay selectivity in task improvement by TV3326 may not be consistent with a selective effect on attention. TV3326 was not associated with any obvious side effect or untoward reaction of the animals to the drug. Thus, TV3326 may be expected to offer a significant positive cognitive outcome in addition to its reported neuroprotective action.

The anti Parkinson drug, rasagiline [R-(+)-N-propargyl-1-aminoindan], an inhibitor of type B monoamine oxidase, has been shown to suppress apoptosis induced by neurotoxins and oxidative stress. A series of novel propargylaminoindans with a carbamate moiety to inhibit cholinesterase were developed from phamacophore of rasagiline to protect or rescue deteriorated neurons in Alzheimer's and Lewy Body disease and provide a beneficial effect on the cognitive deficits. Rasagiline analogues were found to protect dopaminergic SH-SY5Y cells against apoptosis induced by peroxynitrite donor. SIN-1. TV3326, [(N-propargyl)-(3R)-aminoindan-5-yl]-ethyl methyl carbamate, was as effective as rasagiline in preventing apoptosis, followed by its S-enantiomer, TV3279. The anti-apoptotic-neuroprotective activity was shown to reside in the propargylamine and not the carbamate moiety. This resulted in stabilization of the mitochondrial membrane potential, the collapse of which initiates the apoptotic cascade.

(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.

Two novel neuroprotective cholinesterase (ChE) inhibitors, TV3326 and TV3279 [(N-propargyl-(3R) and (3S) aminoindan-5-yl)-ethyl methyl carbamate], respectively were derived from rasagiline, for the treatment of Alzheimer's disease (AD). TV3326 also inhibits monoamine oxidase (MAO)-A and B, while its S-isomer, TV3279, lacks MAO-inhibitory activity. The actions of these drugs in the regulation of the amyloid precursor protein (APP) processing using rat PC12 and human SH-SY5Y neuroblastoma cells were examined. Both isomers stimulated the release of the non-amyloidogenic alpha-secretase form of soluble APP (sAPPalpha) from these cell lines. The increases in sAPPalpha, induced by TV3326 and TV3279, were dose-dependent (0.1-100 micro M) and blocked by the hydroxamic acid-based metalloprotease inhibitor, Ro31-9790, suggesting mediation via alpha-secretase activity. Using several signal transduction inhibitors, the involvement of protein kinase C (PKC), mitogen-activated protein (MAP) kinase, and tyrosine kinase-dependent pathways in the enhancement of sAPPalpha release by TV3326 and TV3279 was identified. In addition, both drugs directly induced the phosphorylation of p44 and p42 MAP kinase, which was abolished by the specific inhibitors of MAP kinase activation, PD98059 and U0126. These data suggest a novel pharmacological mechanism, whereby these ChE inhibitors regulate the secretary processes of APP via activation of the MAP kinase pathway.

RATIONALE: A high incidence of depression is found in subjects with Alzheimer's disease (AD), in whom many antidepressants are contraindicated because they have anticholinergic activity. We have designed a new cholinesterase inhibitor TV3326 [( N-propargyl-(3R) aminoindan-5-yl)-ethyl methyl carbamate] for the treatment of AD, which has neuroprotective activities and also blocks monoamine oxidase (MAO) A and B in the brain but not in the intestine after chronic administration. OBJECTIVES: To examine the antidepressant and anxiolytic potential of TV3326 in rats and compare them with those of its R isomer TV3279, which lacks MAO-inhibitory activity, and of amitriptyline and moclobemide.
METHODS: Each of the drugs was administered orally, acutely or once daily for 2 weeks, and its effect was evaluated on the behavior of rats in the forced swim test (FST) and plus maze (EPM) test.
RESULTS: Immobility in the FST was reduced by 56% after acute and chronic administration of amitriptyline (10 mg/kg) and by 42% after acute administration of moclobemide (20 mg/kg) and by 63% when this drug was given chronically. TV3326 (26 mg/kg) only reduced immobility (by 44%) when given chronically and inhibited brain MAO-A and -B by more than 66%. TV3279 had no significant effect in the FST. All the drugs except TV3326 increased anxiogenic activity in rats in EPM, as indicated by a more than 50% decrease in the time in open arms after chronic administration.
CONCLUSIONS: TV3326 has potential antidepressant-like activity when given in a dose regimen that causes significant inhibition of brain MAO-A and -B. Together with its neuroprotective properties, this action could make TV3326 a potentially valuable drug for the treatment of dementia in patients with depression.

TV-3326 is a novel cholinesterase inhibitor that produces irreversible brain-selective inhibition of monoamine oxidase (MAO)-A and B and has antidepressant-like activity in rats after chronic oral administration. This study determined whether TV-3326 would cause less potentiation than other irreversible MAO-inhibitors of the blood pressure (BP) response to oral tyramine in conscious rabbits. Dose-response curves were established for the increase in BP induced by tyramine (5-200 mg/kg) administered orally via a naso-pharyngeal tube. From these, the dose that increased BP by 30 mmHg (ED(30)) was computed for each rabbit before and after oral administration of clorgyline, 1 mg/kg for one week, tranylcypromine 10 mg/kg, once, moclobemide, 20 mg/kg 3 times and TV-3326, 26 mg/kg for 2 weeks. Clorgyline, tranylcypromine and TV-3326 inhibited brain MAO-A by 90%; the former two inhibited intestinal MAO-A by 85-97% but TV-3326 had no effect. Tranylcypromine and clorgyline produced 6 and 20-fold increases in the pressor response to tyramine while TV-3326, like moclobemide, only potentiated it 2-fold. If TV-3326 is found to produce as little potentiation of the tyramine response in human subjects, it may be a potentially useful therapeutic agent for the treatment of Alzheimer's disease with depression.

Two novel neuroprotective cholinesterase (ChE) inhibitors, TV3326, (N-propargyl-(3R) aminoindan-5-yl)-ethyl methyl carbamate, and TV3279, (N-propargyl-(3S) aminoindan-5-yl)-ethyl methyl carbamate, were derived from rasagiline for the treatment of Alzheimer's disease (AD). TV3326 also inhibits monoamine oxidase (MAO)-A and -B, whereas its S-isomer, TV3279, lacks MAO inhibitory activity. The action of these drugs in the regulation of amyloid precursor protein (APP) processing, using rat PC12 and human SH-SY5Y neuroblastoma cells, was examined. Both isomers stimulated the release of the non-amyloidogenic a-secretase form of soluble APP (sAPPalpha) from these cell lines. The increases in sAPPalpha, induced by TV3326 and TV3279, were dose-dependent (0.1-100 mM) and blocked by the hydroxamic acid-based metalloprotease inhibitor, Ro31-9790, suggesting mediation via a-secretase activity. Using several signal transduction inhibitors, we identified the involvement of protein kinase C (PKC), mitogen-activated protein (MAP) kinase, and tyrosine kinase-dependent pathways in the enhancement of sAPPalpha release by TV3326 and TV3279. In addition, both drugs directly induced the phosphorylation of p44 and p42 MAP kinase, which was abolished by the specific inhibitors of MAP kinase activation, PD98059 and U0126. These data suggest a novel pharmacological mechanism whereby these ChE inhibitors regulate the secretory processes of APP via activation of the MAP kinase pathway.

A number of studies have shown that the selective monoamine oxidase (MAO)-B inhibitor l-selegiline has neuroprotective activities in several cell culture systems and in vivo. The suggestion has been made that the propargyl moiety in this molecule may have some intrinsic neuroprotective activity not related to its ability to bind covalently to MAO B and inhibit it. We have therefore developed a number of novel drugs based on rasagiline (N-propargyl-1R-(+)-aminoindan), a potent anti-Parkinson-propargyl-containing MAO-B inhibitor drug with structural resemblance to selegiline, for the treatment of Alzheimer's disease. These drugs possess a carbamate moiety for cholinesterase (ChE), and a propargyl group for MAO inhibition. The R-enantiomer of these compounds (TV3326) has ChE and MAO inhibitory activities in vivo and retains the neuroprotective properties of rasagiline. It also exhibits anti-depressant activity in animal models. The S-enantiomer does not inhibit MAO and has no anti-depressant activity, but it has similar ChE inhibitory and neuroprotective activities. Thus MAO inhibition by propargylamines is not a pre-requisite for neuroprotection. Rather, propargylamines have some intrinsic neuroprotective property whose mechanism of action requires further elucidation.

TV3326, (N-propargyl-(3R)-aminoindan-5-yl-ethyl,methyl carbamate) was prepared in order to combine the neuroprotective effects of rasagiline, a selective inhibitor of monoamine oxidase (MAO)-B with the cholinesterase (ChE) inhibitory activity of rivastigmine as a potential treatment for Alzheimer's disease. The study reported here examined the neuroprotective effects of TV3326 against various insults in vitro and in vivo. TV3326 caused a dose related (10-500 microM) reduction in death induced in NGF differentiated rat pheochromocytoma (PC12) cells by 3-4 hour exposure to oxygen-glucose deprivation. A single s.c. injection of TV3326 given five minutes after closed head injury in mice significantly reduced the cerebral edema, and accelerated the recovery of motor function and spatial memory several days later. Unilateral icv injection of streptozotocin (STZ) 1.5 mg in rats, caused specific damage to myelinated neurones in the fornix and corpus callosum accompanied by microgliosis. Three bilateral injections of STZ, 0.25 mg each, caused more widespread damage, and a marked impairment in spatial memory. Chronic oral treatment with TV3326 (75 mumols/kg) reduced the neuronal damage and microgliosis and almost completely prevented the memory impairment. The neuroprotective effect in PC12 cells may be due to a combination of ChE inhibition and antiapoptotic activity. The latter does not result from ChE inhibition. It is associated with the presence of the propargyl group, since it occurs with other propargylamines that do not inhibit MAO, but not with drugs that inhibit only ChE.

Rasagiline (N-propargyl-1-(R)-aminoindan) is a selective, irreversible monoamine oxidase B (MAO B) inhibitor which has been developed as an anti-Parkinson drug. In controlled monotherapy and as adjunct to L-dopa it has shown anti-Parkinson activity. In cell culture (PC-12 and neuroblastoma SH-SY5Y cells) it exhibits neuroprotective and anti-apoptotic activity against several neurotoxins (SIN-1, MPTP, 6-hydroxydopamine and N-methyl-(R)-salsolinol) and ischemia. In vivo, it reduces the sequelae of traumatic brain injury in mice and speeds their recovery. The neuroprotective activity of rasagaline does not result from MAO B inhibition, since its S-enantiomer, TVP1022, which has 1000-fold weaker MAO inhibitory activity, exhibits similar neuroprotective properties. Introduction of a carbamate moiety into the rasagiline molecule to confer cholinesterase inhibitory activity for the treatment of Alzheimer's disease, resulted in compounds TV3326 [(N-Propargyl-(3R)Aminoindan-5-YL)-Ethyl Methyl Carbamate] and its S-enantiomer TV3279 [(N-Propargyl-(3S)Aminoindan-5-YL)-Ethyl Methyl Carbamate], which retain the neuroprotective activities of rasagiline and TVP1022. They also antagonize scopolamine-induced impairments in spatial memory. In addition, TV3326 exhibits brain-selective MAO A and B inhibitory activity after chronic administration and has antidepressant-like activity in the forced swim test. This is associated with an increase in brain levels of serotonin. The anti-apoptotic activity of these propargylamine-containing derivatives may be related to their ability to delay the opening of voltage-dependent anion channels (VDAC), which are part of the mitochondrial permeability transition pore. The propargylamine moiety is responsible for the increase in the mitochondrial family of Bcl-2 proteins, prevention in the fall in mitochondrial membrane potential, prevention of the activation of caspase 3, and of translocation of glyceraldehyde-3-phosphate dehydrogenase from the cytoplasm to the nucleus. The latter processes are closely associated with neurotoxin-induced apoptosis. Rasagiline interacts with and prevents the binding of PKI 1195 to the pro-apoptotic peripheral benzodiazepine receptor, which together with Bcl-2, hexokinase, porin, and adenine nucleotide translocator constitutes part of the VDAC. Furthermore, rasagiline, TV3326 and TV3279 are able to influence the processing of amyloid precursor protein by activation of alpha-secretase and increasing the release of soluble alpha APP in rat PC-12 and human neuroblastoma SH-SY5Y cells and in rat and mice cortex and hippocampus. This process has been shown to involve the upregulation of PKC and MAP kinase. It is quite likely that the induction of Bcl-2 and activation of PKC by rasagiline and TV3326 is closely linked to the anti-apoptotic action of these drugs and their ability to process APP by activation of alpha-secretase.

The antiapoptotic and neuroprotective activity of irreversible monoamine oxidase (MAO) B inhibitor, rasagiline [R(+)-N-propargyl-1-aminioindan], its S-isomer (TVP1022) and TV 3219, a novel anti-Alzheimer cholinesterase-MAO inhibitor drug derived from rasagiline were examined in PC12 cells cultures and in vivo. We found that these drugs have potent antiapoptotic and neuroprotective activities in response to serum and NGF withdrawal in partially neuronally differentiated PC12 cells and prevent the fall in mitochondrial membrane potential, the first step in cell death. Closed head injury studies in mice have shown that both rasagiline and TVP1022 are neuroprotective. All these compounds possess a propargyl moiety, which normally is responsible for irreversible inactivation of MAO, as is seen with rasagiline. However, neither TVP1022 nor TV3219 are MAO inhibitors, both share the antiapoptotic and neuroprotective actions of rasagiline, indicating that MAO inhibition is not a prerequisite for neuroprotection and that the propargyl moiety exhibits intrinsic neuroprotective pharmacological activity that requires identification.

TV3326, [(N-propargyl-(3R) aminoindan-5-yl)-ethyl methyl carbamate] is a novel aminoindan derivative of the selective irreversible monoamine oxidase (MAO)-B inhibitor, rasagiline (N-propargyl-(1R)-aminoindan), possessing both cholinesterase (ChE) and MAO-inhibitory activity. In doses of 35-100 micromoles/kg administered orally to rats, it inhibits ChE by 25-40% and antagonises scopolamine-induced impairments in spatial memory. After daily administration of 75 micromoles/kg for 2 weeks, TV3326 does not show any motor stimulant effects but significantly reduces immobility in the forced swim test, an action consistent with that of known antidepressants. This could result from more than 70% inhibition of both MAO-A and B in the brain that occurs under these conditions, since it is not shared by the S-isomer, TV3279, which does not block MAO. TV3326 also shows selectivity for brain MAO, even after 2 months of daily administration, with little or no effect on the enzyme in the intestinal tract and liver. This reduces the likelihood of it producing the "cheese effect" if administered with tyramine-containing foods or beverages. TV3326 and TV3279 protect against ischemia-induced cytotoxicity in PC12 cells and reduce the oedema, deficits in motor function and memory after closed head injury in mice. These neuroprotective effects do not result from MAO inhibition. The pharmacological actions of TV3326 could be of clinical importance for the treatment of AD, and the drug is currently in development for this purpose.