Installation of Pargyline, a LSD1 Inhibitor, in the HDAC Inhibitory Template Culminated in the Identification of a Tractable Antiprostate Cancer Agent.

Pragmatic insertion of pargyline, a LSD1 inhibitor, as a surface recognition part in the HDAC inhibitory pharmacophore was planned in pursuit of furnishing potent antiprostate cancer agents. Resultantly, compound 14 elicited magnificent cell growth inhibitory effects against the PC-3 and DU-145 cell lines and led to remarkable suppression of tumor growth in human prostate PC-3 and DU-145 xenograft nude mouse models. The outcome of the enzymatic assays ascertained that the substantial antiproliferative effects of compound 14 were mediated through HDAC6 isoform inhibition as well as selective MAO-A and LSD1 inhibition. Moreover, the signatory feature of LSD1 inhibition by 14 in the context of H3K4ME2 accumulation was clearly evident from the results of western blot analysis. Gratifyingly, hydroxamic acid 14 demonstrates good human hepatocytic stability and good oral bioavailability in rats and exhibits enough promise to emerge as a therapeutic for the treatment of prostate cancer in the near future.

Propargylamine-derived multi-target directed ligands for Alzheimer's disease therapy.

Current options for the treatment of Alzheimers disease have been restricted to prescription of acetylcholinesterase inhibitors or N-methyl-d-aspartate receptor antagonist, memantine. Propargylamine-derived multi-target directed ligands, such as ladostigil, M30, ASS234 and contilisant, involve different pathways. Apart from acting as inhibitors of both cholinesterases and monoamine oxidases, they show improvement of cognitive impairment, antioxidant activities, enhancement of iron-chelating activities, protect against tau hyperphosphorylation, block metal-associated oxidative stress, regulate APP and Aß expression processing by the non-amyloidogenic α-secretase pathway, suppress mitochondrial permeability transition pore opening, and coordinate protein kinase C signaling and Bcl-2 family proteins. Other hybrid propargylamine derivatives are also reported.

Neuroprotective and neurorestorative potential of propargylamine derivatives in ageing: focus on mitochondrial targets.

The mitochondrial theory of ageing proposes that accumulation of damage to mitochondrial function and DNA mutation lead to ageing of humans and animals. It has been suggested that mitochondria play dynamic roles in regulating synaptogenesis and morphological/functional responses of synaptic activity, and thus, deteriorating of mitochondrial function (e.g., deficits of the mitochondrial respiratory enzymes, reduced calcium influx, increased accumulation of mitochondrial DNA defects/apoptotic proteins and impairment of mitochondrial membrane potential) can lead to severe neuronal energy deficit, and in the long run, to modifications in neuronal synapses and neurodegeneration in the ageing brain. Hence, considering the mechanisms by which mitochondrial impairment can lead to neuronal death, the development of neuroprotective molecules that target various mitochondrial pathogenic processes can be effective in the treatment of ageing and age-related neurodegenerative diseases. This review addresses several aspects of the neuroprotective effects of propargylamine derivatives (e.g., the monoamine oxidase-B inhibitors, selegiline and rasagiline and the multifunctional drugs, ladostigil, M30 and VAR10303) in ageing with a special focus on mitochondrial molecular protective mechanisms.

Propargylamine as functional moiety in the design of multifunctional drugs for neurodegenerative disorders: MAO inhibition and beyond.

Much progress has been made in designing analogues that can potentially confer neuroprotection against debilitating neurodegenerative disorders, yet the multifactorial pathogenesis of this cluster of diseases remains a stumbling block for the successful design of an 'ultimate' drug. However, with the growing popularity of the "one drug, multiple targets" paradigm, many researchers have successfully synthesized and evaluated drug-like molecules incorporating a propargylamine function that shows potential to serve as multifunctional drugs or multitarget-directed ligands. It is the aim of this review to highlight the reported activities of these propargylamine derivatives and their prospect to serve as drug candidates for the treatment of neurodegenerative disorders.

Effects of the neurotoxin MPTP and pargyline protection on extracellular energy metabolites and dopamine levels in the striatum of freely moving rats.

The neurotoxin MPTP is known to induce dopamine release and depletion of ATP in the striatum of rats. Therefore, we studied the changes induced by MPTP and pargyline protection both on striatal dopamine release and on extracellular energy metabolites in freely moving rats, using dual asymmetric-flow microdialysis. A dual microdialysis probe was inserted in the right striatum of rats. MPTP (25mg/kg, 15mg/kg, 10mg/kg) was intraperitoneally administered for three consecutive days. MAO-B inhibitor pargyline (15mg/kg) was systemically administered before neurotoxin administration. The first MPTP dose induced an increase in dialysate dopamine and a decrease of DOPAC levels in striatal dialysate. After the first neurotoxin administration, increases in striatal glucose, lactate, pyruvate, lactate/pyruvate (L/P) and lactate/glucose (L/G) ratios were observed. Subsequent MPTP administrations showed a progressive reduction of dopamine, glucose and pyruvate levels with a concomitant further increase in lactate levels and L/P and L/G ratios. At day 1, pargyline pre-treatment attenuated the MPTP-induced changes in all studied analytes. Starting from day 2, pargyline prevented the depletion of dopamine, glucose and pyruvate while reduced the increase of lactate, L/P ratio and L/G ratio. These in vivo results suggest a pargyline neuroprotection role against the MPTP-induced energetic impairment consequent to mitochondrial damage. This neuroprotective effect was confirmed by TH immunostaining of the substantia nigra.

Propargylamine-derived multitarget-directed ligands: fighting Alzheimer's disease with monoamine oxidase inhibitors.

Alzheimer's disease (AD) is a complex neurodegenerative disorder with a multifaceted pathogenesis. There are at present three Food and Drug Administration-approved drugs based on the "one drug, one target" paradigm (donepezil, galantamine and rivastigmine) that improve symptoms by inhibiting acetylcholinesterase. However, apart from the beneficial palliative properties, cholinergic drugs have shown little efficacy to prevent the progression of the disease evidencing the unsuitability of this strategy for the complex nature of AD. By contrast, the multifactorial nature of this neurodegenerative disorder supports the most current innovative therapeutic approach based on the "one drug, multiple targets" paradigm, which suggests the use of compounds with multiple activities at different target sites. Accordingly, the also called multitarget-directed ligand (MTDL) approach has been the subject of increasing attention by many research groups, which have developed a variety of hybrid compounds acting on very diverse targets. The therapeutic potential of monoamine oxidase inhibitors (MAOI) in AD has been suggested due to their demonstrated neuroprotective properties besides their enhancing effect on monoaminergic transmission. Especially, those containing a propargylamine moiety are of particular interest due to their reported beneficial actions. Therefore, targeting MAO enzymes should be considered in therapeutic interventions. This review makes a special emphasis on MTDLs that commonly target MAO enzymes. There is at present an urgent need for real disease-modifying therapies for AD and the MTDL approach makes a breakthrough for the development of new drugs capable of addressing the biological complexity of this disorder.

KDM1 is a novel therapeutic target for the treatment of gliomas.

Glioma development is a multistep process, involving alterations in genetic and epigenetic mechanisms. Understanding the mechanisms and enzymes that promote epigenetic changes in gliomas are urgently needed to identify novel therapeutic targets. We examined the role of histone demethylase KDM1 in glioma progression. KDM1 was overexpressed in gliomas and its expression positively correlated with histological malignancy. Knockdown of KDM1 expression or its pharmacological inhibition using pargyline or NCL-1 significantly reduced the proliferation of glioma cells. Inhibition of KDM1 promoted up regulation of the p53 target genes p21 and PUMA. Patient-derived primary GBM cells expressed high levels of KDM1 and pharmacological inhibition of KDM1 decreased their proliferation. Further, KDM1 inhibition reduced the expression of stemness markers CD133 and nestin in GBM cells. Mouse xenograft assays revealed that inhibition of KDM1 significantly reduced glioma xenograft tumor growth. Inhibition of KDM1 increased levels of H3K4-me2 and H3K9-Ac histone modifications, reduced H3K9-me2 modification and promoted expression of p53 target genes (p21 and PUMA), leading to apoptosis of glioma xenograft tumors. Our results suggest that KDM1 is overexpressed in gliomas and could be a potential therapeutic target for the treatment of gliomas.

Lysine-specific histone demethylase 1 inhibitors control breast cancer proliferation in ERα-dependent and -independent manners.

Lysine specific demethylase 1 (LSD1, also known as KDM1) is a histone modifying enzyme that regulates the expression of many genes important in cancer progression and proliferation. It is present in various transcriptional complexes including those containing the estrogen receptor (ER). Indeed, inhibition of LSD1 activity and or expression has been shown to attenuate estrogen signaling in breast cancer cells in vitro, implicating this protein in the pathogenesis of cancer. Herein we describe experiments that utilize small molecule inhibitors, phenylcyclopropylamines, along with small interfering RNA to probe the role of LSD1 in breast cancer proliferation and in estrogen-dependent gene transcription. Surprisingly, whereas we have confirmed that inhibition of LSD1 strongly inhibits proliferation of breast cancer cells, we have determined that the cytostatic actions of LSD1 inhibition are not impacted by ER status. These data suggest that LSD1 may be a useful therapeutic target in several types of breast cancer; most notably, inhibitors of LSD1 may have utility in the treatment of ER-negative cancers for which there are minimal therapeutic options.

Effects of diphenyl diselenide on depressive-like behavior in ovariectomized mice submitted to subchronic stress: involvement of the serotonergic system.

RATIONALE: The transition to menopause is associated with an increased risk of depressed mood. OBJECTIVES: This study was conducted to investigate whether diphenyl diselenide [(PhSe)2] treatment could reduce the effects of postmenopausal depression-like behavior in ovariectomized female mice submitted to subchronic stress exposure. METHODS: Mice were divided into four groups: sham, (PhSe)2, ovariectomy (OVX), and OVX + (PhSe)2. Animals were ovariectomized/sham-operated and subjected to stress session once a day for 7 days from the fifth to the 11th day after OVX. The behavioral tests (open field, tail suspension (TST), and forced swimming (FST)) were performed on the 14th day after OVX. Mice were treated orally once a day with vehicle (canola oil, 10 ml/kg) or (PhSe)2 (10 mg/kg; 10 ml/kg) 30 min before being exposed to subchronic stress, or from the 11th to the 14th day. Paroxetine (8 mg/kg i.p.) and pargyline (30 mg/kg i.p.) were used as positive controls. The involvement of serotonergic receptor subtypes in the antidepressant-like effect of (PhSe)2 was assessed in the FST using WAY 100635 (0.1 mg/kg s.c.), ritanserin (1 mg/kg i.p.), and ondansetron (1 mg/kg i.p.) as serotonergic antagonists. Monoamine oxidase (MAO) A and B activities were also determined. RESULTS: The prolongation of immobility time in TST and FST in OVX mice submitted to subchronic stress was prevented by (PhSe)2 treatment. Ritanserin and ondansetron blocked the antidepressive-like effect of (PhSe)2, suggesting the involvement of 5-HT(2A/2C) and 5-HT3 receptor subtypes. Both paroxetine and pargyline were effective in reducing the immobility time of stressed OVX mice in the FST. No alterations in locomotor activity were observed. Although (PhSe)2 had inhibited in vitro MAO-A and MAO-B activities, none of the groups presented alterations neither in ex vivo MAO-A nor in MAO-B activity. CONCLUSIONS: (PhSe)2 treatment could influence mood and behavior, indicating a promising role of this organoselenium compound in the management of postmenopausal depressive symptoms.

Functional mechanism of neuroprotection by inhibitors of type B monoamine oxidase in Parkinson's disease.

Neuroprotective therapy has been proposed for age-related neurodegenerative disorders, including Parkinson's disease. Inhibitors of type B monoamine oxidase (MAOB-Is), rasagiline and (-)deprenyl, are the most promising candidate neuroprotective drugs. Clinical trials of rasagiline in patients with Parkinson's disease suggest that rasagiline may have some disease-modifying effects. Results using animal and cellular models have proved that the MAOB-Is protect neurons by the intervention of 'intrinsic' mitochondrial apoptotic cascade and the induction of prosurvival antiapoptotic Bcl-2 and neurotrophic factors. Rasagiline-related MAOB-Is prevent mitochondrial permeability transition induced by various insults and activation of subsequent apoptotic cascades: cytochrome c release, casapase activation, and condensation and fragmentation of nuclear DNA. MAOB-Is increase transcription of prosurvival genes through activating the nuclear transcription factor-(NF) system. Rasagiline increases the protein and mRNA levels of GDNF in dopaminergic SH-SY5Y cells, whereas (-)deprenyl increases those of BDNF. Systemic administration of (-)deprenyl and rasagiline increases these neurotrophic factors in the cerebrospinal fluid from patients with Parkinson's disease and nonhuman primates. This review presents recent advances in our understanding of the neuroprotection offered by MAOB-Is and possible evaluation of neuroprotective efficacy in clinical samples is discussed.

Rationale for considering that propargylamines might be neuroprotective in Parkinson's disease.

A neuroprotective therapy that slows or stops disease progression is the major unmet medical need in Parkinson's disease (PD). Current evidence indicates that cell death in PD occurs, at least in part, by way of a signal-mediated apoptotic process. This raises the possibility that anti-apoptotic agents might be neuroprotective in PD. Propargylamines have been demonstrated to be potent anti-apoptotic agents in both in vitro and in vivo studies, presumably by maintaining glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as a dimer and thereby preventing its nuclear translocation where it blocks upregulation of anti-apoptotic proteins. Selegiline is a monamine oxidase type B (MAO-B) inhibitor that incorporates a propargyl ring within its molecular structure. It was shown to delay the need for symptomatic therapy in untreated PD patients in the DATATOP study, but interpretation is confounded by its symptomatic effects. Rasagiline is another MAO-B inhibitor that contains a propargyl ring and has protective effects in laboratory models. A clinical trial utilizing a delayed start design demonstrated that patients initiated on rasagiline at baseline are improved at one year in comparison to patients initiated on placebo and switched to rasagiline at 6 months even though both groups were on the same treatment for the last 6 months of the study. These results argue against the benefit being due to a symptomatic effect and are consistent with rasagiline having a protective effect.

Gastric pentadecapeptide BPC 157 effective against serotonin syndrome in rats.

Serotonin syndrome commonly follows irreversible monoamine oxidase (MAO)-inhibition and subsequent serotonin (5-HT) substrate (in rats with fore paw treading, hind limbs abduction, wet dog shake, hypothermia followed by hyperthermia). A stable gastric pentadecapeptide BPC 157 with very safe profile (inflammatory bowel disease clinical phase II, PL-10, PLD-116, PL-14736, Pliva) reduced the duration of immobility to a greater extent than imipramine, and, given peripherally, has region specific influence on brain 5-HT synthesis (alpha-[14C]methyl-L-tryptophan autoradiographic measurements) in rats, different from any other serotonergic drug. Thereby, we investigate this peptide (10 microg, 10 ng, 10 pg/kg i.p.) in (i) full serotonin syndrome in rat combining pargyline (irreversible MAO-inhibition; 75 mg/kg i.p.) and subsequent L-tryptophan (5-HT precursor; 100 mg/kg i.p.; BPC 157 as a co-treatment), or (ii, iii) using pargyline or L-tryptophan given separately, as a serotonin-substrate with (ii) pargyline (BPC 157 as a 15-min posttreatment) or as a potential serotonin syndrome inductor with (iii) L-tryptophan (BPC 157 as a 15 min-pretreatment). In all experiments, gastric pentadecapeptide BPC 157 contrasts with serotonin-syndrome either (i) presentation (i.e., particularly counteracted) or (ii) initiation (i.e., neither a serotonin substrate (counteraction of pargyline), nor an inductor for serotonin syndrome (no influence on L-tryptophan challenge)). Indicatively, severe serotonin syndrome in pargyline + L-tryptophan rats is considerably inhibited even by lower pentadecapeptide BPC 157 doses regimens (particularly disturbances such as hyperthermia and wet dog shake thought to be related to stimulation of 5-HT2A receptors), while the highest pentadecapeptide dose counteracts mild disturbances present in pargyline rats (mild hypothermia, feeble hind limbs abduction). Thereby, in severe serotonin syndrome, gastric pentadecapeptide BPC 157 (alone, no behavioral or temperature effect) has a beneficial activity, which is likely, particular, and mostly related to a rather specific counteraction of 5-HT2A receptors phenomena.

Rasagiline: neurodegeneration, neuroprotection, and mitochondrial permeability transition.

Mitochondria are involved directly in cell survival and death. The assumption has been made that drugs that protect mitochondrial viability and prevent apoptotic cascade-induced mitochondrial permeability transition pore (MPTp) opening will be cytoprotective. Rasagiline (N-propargyl-1R-aminoindan) is a novel, highly potent irreversible monoamine oxidase (MAO) B inhibitor anti-Parkinson drug. Unlike selegiline, it is not derived from amphetamine, and is not metabolized to neurotoxic L-methamphetamine derivative. In addition, it does not have sympathomimetic activity. Rasagiline is effective as monotherapy or adjunct to levodopa for patients with early and late Parkinson's disease (PD) and adverse events do not occur with greater frequency in subjects receiving rasagiline than in those on placebo. Phase III controlled studies indicate that it might have a disease-modifying effect in PD that may be related to its neuroprotective activity. Its S isomer, TVP1022, is more than 1,000 times less potent as an MAO inhibitor. Both drugs, however, have neuroprotective activity in neuronal cell cultures in response to various neurotoxins, and in vivo in response to global ischemia, neurotrauma, head injury, anoxia, etc., indicating that MAO inhibition is not a prerequisite for neuroprotection. Their neuroprotective effect has been demonstrated to be associated directly with the propargylamine moiety, which protects mitochondrial viability and MTPp by activating Bcl-2 and protein kinase C (PKC) and by downregulating the proapoptotic FAS and Bax protein families. Rasagiline and its derivatives also process amyloid precursor protein (APP) to the neuroprotective, neurotrophic, soluble APP alpha (sAPPalpha) by PKC- and MAP kinase-dependent activation of alpha-secretase. The identification of the propargylamine moiety as the neuroprotective component of rasagiline has led us to development of novel bifunctional anti-Alzheimer drugs (ladostigil) possessing cholinesterase and brain-selective MAO inhibitory activity and a similar neuroprotective mechanism of action.

Novel bifunctional drugs targeting monoamine oxidase inhibition and iron chelation as an approach to neuroprotection in Parkinson's disease and other neurodegenerative diseases.

Iron has been shown to accumulates at site where neurons degenerate in neurodegenerative diseases of Parkinson's disease, Alzheimer's disease, Huntington disease, amyotrophic lateral sclerosis and Friedreich ataxia. Iron is thought to participate or initiate oxidative stress via generation of reactive oxygen species (ROS), such as hydroxyl radical. Iron chelators are neuroprotective and prevent 6-hydroxydoapmine and MPTP dopaminergic neurotoxicity in rats and mice. However, their action on monoamine oxidase (MAO) A and B have not been determined previously since MAO-B inhibitors have been shown to be neuroprotective in cellular and animal models of Parkinson's disease. The chelators 8-hydroxyquinoline, O-phenanthroline, 2,2'-dipyridyl, U74500A and U74600F showed a preference for inhibition of rat brain mitochondrial MAO-A over MAO-B. Their IC(50) ranged from 10(-3) M to 10(-6) M, with 21-amino steroids (U74500A and U74006F) showing a greater selectivity and potency for MAO-A. Desferrioxamine (desferal), a prototype potent iron chelator, exhibited relatively poor MAO inhibitory. The inhibitions of MAO-A and B by 21-amino steroids (Lazaroids) were time dependent and irreversible. Those initiated by 8-hydroxyquinoline, 2,2'-dipyridyl and O-phenanthroline were fully reversible by enzyme dilution experiments. Both Fe(2+) and Fe(3+) reverse the MAO-A and B inhibition induced by the latter chelators, but not those initiated by 21-amino steroids. The data infer that either the inhibition of MAO by 21-amino steroids is either the resultant of their conversion to an irreversible covalently bound ligand or that the iron chelation moiety and MAO inhibitory activity in these compounds are not mutually shared. The results suggest that bifunctional brain penetrable drugs with iron chelating property and MAO inhibitory activity in could be the most feasible approach for neuroprotection in neurodegenerative diseases. Such drug would prevent participation of elevated iron in oxidative stress and formation of reactive hydroxyl radical, via its interaction with H(2)O2 (Fenton chemistry), generated as a consequence MAO and other oxidative enzyme reactions to generative cytotoxic reactive hydroxyl radical. We have now developed several of these compounds with neuroprotective, MAO inhibitory and iron chelating properties from our prototype iron chelators, VK-28 possessing propargylamine moiety of our anti-parkinson drug, rasagiline.

TCH346 prevents motor symptoms and loss of striatal FDOPA uptake in bilaterally MPTP-treated primates.

The neuroprotective efficacy of the propargylamine TCH346 was studied in the primate model of Parkinson's disease, the bilaterally MPTP-treated monkey. Male rhesus monkeys received 2.5 mg MPTP into the left carotid artery and, 8 weeks later, 1.25 mg MPTP into the right carotid artery. Starting 2 h after the second MPTP infusion, either 0.014 mg/kg TCH346 or its solvent was subcutaneously injected twice per day for 14 days. The first MPTP treatment induced mild Parkinson symptoms, reduced right limb movements, and reduced FDOPA uptake in the left striatum. The second MPTP treatment made Parkinson symptoms worse, reduced left limb movements, and reduced FDOPA uptake in the right striatum of solvent-treated monkeys. In contrast, the second MPTP treatment did not further worsen motor symptoms and did not decrease FDOPA uptake in the right striatum of TCH346-treated monkeys. Although the effects of the second MPTP treatment were largely prevented, the effects of the first MPTP treatment were not reversed by TCH346. Immunohistochemical examination confirmed the dramatic loss of dopamine cells in vehicle-treated monkeys and the preservation of these neurons in the right brain side of the TCH346-treated animals. In conclusion, systemic administration of TCH346 prevented motor symptoms and nigrostriatal degeneration induced by MPTP in primates.

Neuroprotection by deprenyl and other propargylamines: glyceraldehyde-3-phosphate dehydrogenase rather than monoamine oxidase B.

Deprenyl and other propargylamines are clinically beneficial in Parkinson's disease (PD). The benefits were thought to depend on monoamine oxidase B (MAO-B) inhibition. A large body of research has now shown that the propargylamines increase neuronal survival independently of MAO-B inhibition by interfering with apoptosis signaling pathways. The propargylamines bind to glyceraldehyde-3-phosphate dehydrogenase (GAPDH). The GAPDH binding is associated with decreased synthesis of pro-apoptotic proteins like BAX, c-JUN and GAPDH but increased synthesis of anti-apoptotic proteins like BCL-2, Cu-Zn superoxide dismutase and heat shock protein 70. Anti-apoptotic propargylamines that do not inhibit MAO-B are now in PD clinical trial.

Therapeutic effect of neuronal nitric oxide synthase inhibitor (7-nitroindazole) against MPTP neurotoxicity in mice.

Effects of neuronal nitric oxide synthase (nNOS) inhibitor (7-nitroindazole), nonselective NOS inhibitor (N(G)-nitro-L-arginine methyl ester; L-NAME), and monoamine oxidase inhibitor (pargyline) were studied on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mice. The mice received four intraperitoneal injections of MPTP at 1-h intervals. A significant depletion in dopamine and DOPAC concentration was observed in the striatum from 1 day after MPTP treatment. The pretreatment of 7-nitroindazole and pargyline, but not L-NAME, dose-dependently protected against MPTP-induced depletion in dopamine content 3 days after MPTP treatment. Our histochemical study also showed that 7-nitroindazole and pargyline can prevent a marked decrease in the nigral cells and a marked increase in astrocytes in striatum 7 days after MPTP treatment. The protective effect of 7-nitroindazole against MPTP-induced dopamine and DOPAC depletion in the striatum was not attenuated by intraperitoneal pretreatment with L-arginine. Furthermore, the posttreatment of 7-nitroindazole or pargyline protected against MPTP-induced depletion of dopamine content. These results demonstrate that the protective mechanism by which 7-nitroindazole counteracts MPTP neurotoxicity in mice may be due not only to inhibition of nNOS, but also to MAO-B inhibition. Furthermore, our study suggests that the posttreatment of 7-nitroindazole and pargyline can prevent a significant decrease in dopamine levels in the striatum of MPTP-treated mice. These findings have important implications for the therapeutic time window and choice of nNOS or MAO inhibitors in patients with Parkinson's disease.

Aliphatic propargylamines as symptomatic and neuroprotective treatments for neurodegenerative diseases.

Over the past several years, we have developed a number of novel aliphatic propargylamine-related compounds. These can be divided into 14 main chemical families. These families have been shown to possess members that selectively and stereochemically (i.e. R-enantiomer) rescue neurons from p53-dependent apoptosis in vitro. In contrast, no rescue has been observed by the enantiomers of the opposite configuration or in p53-independent apoptosis. In vivo, several compounds have been shown to possess neural rescue properties in models of unilateral hypoxia/ischaemia, focal ischaemia, facial nerve axotomy, pmn mice, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse and MPTP non-human primate. Our prototype compound, R-2HMP, has been shown to be metabolised in a manner analogous to that of R-deprenyl but devoid of amphetaminergic metabolites. These compounds have been shown to be active through an interaction with the same binding site as R-deprenyl and CGP 3466. This site is suggested to be the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH).