Inhibitor Report for: MSF

AIMS: To ascertain the tolerability profile of single and repeated oral doses of methanesulfonyl fluoride (MSF, SNX-001) in healthy aged subjects, and to determine the degree of erythrocyte acetylcholinesterase (AChE) inhibition induced by MSF after single and repeated oral doses.
METHODS: To calculate properly the kinetics and the duration of AChE inhibition, the effects of MSF were also studied in rodents. These experiments suggested that MSF administered three times per week should provide safe and efficacious AChE inhibition. In a randomized placebo-controlled phase I study, 3.6 mg, 7.2 mg or 10.8 mg MSF were then orally administered to 27 consenting healthy volunteers (aged 50 to 72 years). After a single dose phase and a 1 week wash-out period, the subjects received the same doses three times per week for 2 weeks.
RESULTS: Twenty-two out of the 27 subjects completed the study. Four patients withdrew due to adverse events (AEs) and one for non-compliance. Erythrocyte AChE was inhibited by a total of 33%, 46%, and 62% after 2 weeks of 3.6 mg, 7.2 mg and 10.8 mg MSF, respectively. No serious AEs occurred. The most frequent AEs were headache (27%), nausea (11%) and diarrhoea (8%).
CONCLUSIONS: MSF proved to be well tolerated even with repeated oral dosing. It is estimated that MSF provided a degree of AChE inhibition that should effectively enhance memory. This molecule deserves to be tested for efficacy in a pilot randomized controlled study in patients with Alzheimer's disease.

The purpose of the present study was to evaluate methanesulfonyl fluoride (MSF), a very long-acting CNS-selective acetylcholinesterase (AChE) inhibitor, as a palliative treatment for senile dementia of the Alzheimer type (SDAT). In experiment I, MSF (0.03-0.18 mg/kg) was administered orally to 10 normal volunteers to measure toxicity and establish dose/response function in erythrocyte AChE. MSF produced a dose-response function of %inhibition = (40)(Log10[MSF mg/kg] + 51.7) with no toxicity at these doses. Experiment II was a 16-week double-blind, placebo-controlled study of the safety and efficacy of MSF in doses of up to 0.18 mg/kg given three times per week in 5 men and 10 women (60-82 years), with Mini-Mental State Examination (MMSE) scores of 9-24, who had SDAT. MSF produced a mean of 89.5% inhibition of erythrocyte AChE in patients and improved cognitive performance as measured by the MMSE, Alzheimer Disease Assessment Scale-Cognitive Subscale (ADAS-COG), Global Deterioration Scale, and the Clinical Interview Based Impression of Change (CIBIC). Most of the improvement on the ADAS-COG was maintained 8 weeks after ending MSF. No patients left the study because of drug-related adverse events and there were no toxic effects. MSF may be a safe and effective palliative treatment for SDAT and further clinical trials in larger groups of patients are warranted.

Cholinesterase inhibitors, such as physostigmine and tetrahydroaminoacridine, have been found to alleviate some of the memory deficits characteristic of senile dementia of the Alzheimer's type (SDAT). Many toxic side effects, however, have been associated with the use of these compounds. Recently, a cholinesterase inhibitor, methanesulfonyl fluoride (MSF), was discovered to have low toxicity, central nervous system (CNS) selectivity, and a long therapeutic duration. The purpose of this research was to determine if MSF (1.5 mg/kg) would be effective in reducing or blocking amnesia induced by various doses of scopolamine (0.2, 0.6, and 2.0 mg/kg). One hundred and twenty-two female Sprague-Dawley albino rats were trained and retention tested in a Y-maze brightness discrimination task. MSF was highly effective in reducing scopolamine-induced amnesia.

AIMS: To ascertain the tolerability profile of single and repeated oral doses of methanesulfonyl fluoride (MSF, SNX-001) in healthy aged subjects, and to determine the degree of erythrocyte acetylcholinesterase (AChE) inhibition induced by MSF after single and repeated oral doses.
METHODS: To calculate properly the kinetics and the duration of AChE inhibition, the effects of MSF were also studied in rodents. These experiments suggested that MSF administered three times per week should provide safe and efficacious AChE inhibition. In a randomized placebo-controlled phase I study, 3.6 mg, 7.2 mg or 10.8 mg MSF were then orally administered to 27 consenting healthy volunteers (aged 50 to 72 years). After a single dose phase and a 1 week wash-out period, the subjects received the same doses three times per week for 2 weeks.
RESULTS: Twenty-two out of the 27 subjects completed the study. Four patients withdrew due to adverse events (AEs) and one for non-compliance. Erythrocyte AChE was inhibited by a total of 33%, 46%, and 62% after 2 weeks of 3.6 mg, 7.2 mg and 10.8 mg MSF, respectively. No serious AEs occurred. The most frequent AEs were headache (27%), nausea (11%) and diarrhoea (8%).
CONCLUSIONS: MSF proved to be well tolerated even with repeated oral dosing. It is estimated that MSF provided a degree of AChE inhibition that should effectively enhance memory. This molecule deserves to be tested for efficacy in a pilot randomized controlled study in patients with Alzheimer's disease.

Anticholinesterases (antiChEs) are used to treat Alzheimer's disease. The comparative effects of two antiChEs, methanesulfonyl fluoride (MSF) and donepezil, on the extracellular levels of ACh in the hippocampus were investigated by in vivo microdialysis in freely moving rats. MSF at 1 and 2 mg/kg produced a dose-dependent increase in ACh efflux from 10 min to at least 3 hrs after injection. At 2 mg/kg, the increase was still present at 24 hr. Donepezil at 1 mg/kg showed a similar but smaller effect, and, paradoxically, 2 mg/kg showed no consistent effect. MSF at 1 and 2 mg/kg decreased acetylcholinesterase activity in the hippocampus to 54.8 and 20.1% of control, respectively. These results suggest that MSF is a suitable candidate for the treatment of Alzheimer's disease.

There is increasing evidence that acetylcholinesterase (AChE) may have various specific developmental roles in brain development. Nevertheless, specific effects of AChE inhibition during early brain development have not been adequately described. Therefore, methanesulfonyl fluoride (MSF), an irreversible AChE inhibitor that shows high selectivity for the CNS was used to produce AChE inhibition in utero to study subsequent adult behaviors, sleep, and cholinergic markers. Rats exposed to MSF in utero showed a deficit in spatial learning tasks using appetitive motivation but, surprisingly, they performed equally well or better than controls when aversive motivation was used. One hypothesis was that MSF treatment in utero affected the response to stress. Tests of anxiety however showed no differences in basal levels of anxiety. Studies of sleep behavior, however, indicated a higher level of REM sleep which is only seen during the light phase of male rats exposed to MSF in utero as compared to controls. No differences in cholinergic markers in the brains of adults were found except that females exposed to MSF in utero had a higher level of ChAT activity in the synaptosomal fraction of the hippocampus. Even so, whether cholinergic alterations accompany the in utero MSF exposure remains to be determined. The failure to find widespread changes in cholinergic markers in the adult brains suggests changes in behaviors should be further investigated by testing the participation of postsynaptic mechanisms, measuring of cholinergic markers during earlier development periods and the possible participation of other neurotransmitter systems to clearly reveal the role of the cholinergic system following in utero MSF exposure.

Methanesulfonyl fluoride (MSF), a highly selective CNS inhibitor of acetylcholinesterase, has been recently demonstrated to promote improvement in cognitive performance in patients with senile dementia of Alzheimer type. Because a similar cognitive impairment may accompany stroke, we investigated in the present study whether treatment with MSF could produce beneficial effects in adult rats subjected to an experimental stroke model. Sprague-Dawley rats received transient 60 min intraluminal occlusion of the right middle cerebral artery (MCAo) and were given i.p. injections of either MSF (1 mg/kg at 24 and 48 h post-MCAo and 0.3 mg/kg thereafter every other day) or the vehicle, peanut oil, for 4 weeks. Behavioral tests and biochemical assays were performed at 28 days post-surgery. MSF treatment produced about 90% inhibition of acetylcholinesterase in the brain. Ischemic animals that received the vehicle displayed significant elevated body swing biased activity (84.8 +/- 10%) and significantly prolonged acquisition (398 +/- 62 s) and shortened retention (79 +/- 26 s) of the passive avoidance task. Interestingly, while the ischemic animals that received the MSF exhibited elevated body swing biased activity (87.7 +/- 8%), they performed significantly better in the passive avoidance task (255 +/- 36 s and 145 +/- 18 s in acquisition and retention) than the vehicle-treated animals. Moreover, whereas brains from both groups of animals revealed similar extent and degree of cerebral infarction, the MSF-treated ischemic animals showed more intense immunoreactivity, as well as a significantly higher number (10-15% increase) of septal choline acetyltransferase-positive cells than the vehicle-treated ischemic animals. These results show that MSF, possibly by preserving a functional cholinergic system, attenuated stroke-induced deficits in a simple learning and memory task.

Methanesulfonyl fluoride (MSF) is a CNS-selective acetylcholinesterase (AChE) inhibitor, currently being developed and tested for the treatment of symptoms of Alzheimer's disease. We have previously confirmed that a single in utero exposure to MSF at clinically appropriate doses inhibits AChE activity in fetal rat brain by 20%, and when administered throughout gestation, MSF achieves a 40% level of inhibition. Here, we show that rats chronically exposed in utero to MSF display marked sex-specific differences in morphological development of the cerebral cortical layers compared with controls at 7 days of age. Forebrain size and cortical thickness were increased in females and decreased in males. An analysis of gene expression in neonate brain on the day of birth revealed sex-specific differential expression of over 25 genes, including choline acetyltransferase (ChAT), which were affected by prenatal MSF exposure. Many of these genes are associated with sexual differentiation and brain development, while others are involved in more generalized cellular and metabolic processes. The changes observed in cortical morphology and gene expression suggest a critical developmental role for AChE in the fetal nervous system, most likely through its effect on cholinergic neurotransmission.

D-Tubocurarine, a reversible peripheral inhibitor of cholinesterases accelerates methanesulfonylation of Drosophila melanogaster wild type and W359L mutant. The kinetic evaluation of the process was performed in a step-by-step analysis. The second order overall sulfonylation rate constants, determined from classical residual activity measurements, were used in the subsequent analysis of progress curves. The latter were obtained by measuring the hydrolysis of acetylthiocholine in a complex reaction system of enzyme, substrate, irreversible and reversible inhibitor. The underlying kinetic mechanisms, from such a complex data, could only be untangled by targeted inspection and successive incorporation of reaction steps for which experimental evidence existed. The study showed that the peripheral ligand D-tubocurarine, by binding at the entrance into the active site of the two investigated enzymes (Golicnik et al., Biochemistry 40 (2001) 1214), enhances the affinity for small methanesulfonylfluoride, rather to speeding up the formation of a stable covalent enzyme-inhibitor complex. The specific arrangements at the rim of the active site of each individual enzyme dictate the actual events which can be detected by kinetic means.

The purpose of the present study was to evaluate methanesulfonyl fluoride (MSF), a very long-acting CNS-selective acetylcholinesterase (AChE) inhibitor, as a palliative treatment for senile dementia of the Alzheimer type (SDAT). In experiment I, MSF (0.03-0.18 mg/kg) was administered orally to 10 normal volunteers to measure toxicity and establish dose/response function in erythrocyte AChE. MSF produced a dose-response function of %inhibition = (40)(Log10[MSF mg/kg] + 51.7) with no toxicity at these doses. Experiment II was a 16-week double-blind, placebo-controlled study of the safety and efficacy of MSF in doses of up to 0.18 mg/kg given three times per week in 5 men and 10 women (60-82 years), with Mini-Mental State Examination (MMSE) scores of 9-24, who had SDAT. MSF produced a mean of 89.5% inhibition of erythrocyte AChE in patients and improved cognitive performance as measured by the MMSE, Alzheimer Disease Assessment Scale-Cognitive Subscale (ADAS-COG), Global Deterioration Scale, and the Clinical Interview Based Impression of Change (CIBIC). Most of the improvement on the ADAS-COG was maintained 8 weeks after ending MSF. No patients left the study because of drug-related adverse events and there were no toxic effects. MSF may be a safe and effective palliative treatment for SDAT and further clinical trials in larger groups of patients are warranted.

One consistent finding in senile dementia of the Alzheimer's type is that the brain has reduced ability to synthesize acetylcholine. This has been related, in part, to memory dysfunctions. Although a cholinergic deficit is not singularly responsible for symptoms of dementia, treatment strategies have been designed to facilitate cholinergic activity by inhibiting acetylcholinesterase (AChE). To minimize toxicity, however, a cholinesterase inhibitor selective for only AChE would be an ideal treatment. The purpose of this study was to determine the selectivity of physostigmine, metrifonate, methanesulfonyl fluoride and tetrahydroaminoacridine (tacrine) toward AChE as compared with butyrylcholinesterase (BChE) in human cortex. The results show that methanesulfonyl fluoride is selective as an inhibitor of AChE as compared with BChE. Physostigmine inhibited AChE more than BChE. Metrifonate was found to inhibit BChE more than AChE. Tetrahydroaminoacridine inhibited both enzymes in a complex way.

Aged (24-month-old) rats were treated chronically with methanesulfonyl fluoride (MSF), an acetylcholinesterase (AChE) inhibitor with selectivity for central nervous system AChE, or with injection vehicle alone. Twelve 0.22 mg/kg IP injections were given over 4 weeks. MSF rats showed significantly greater speed and accuracy on a 1 trial/day discriminative reward learning task. The chronic MSF treatment resulted in a 56% decrease in brain AChE activity but no discernable locomotor side effects and no liver damage as indicated by aspartate transferase activity.

Cholinesterase inhibitors, such as physostigmine and tetrahydroaminoacridine, have been found to alleviate some of the memory deficits characteristic of senile dementia of the Alzheimer's type (SDAT). Many toxic side effects, however, have been associated with the use of these compounds. Recently, a cholinesterase inhibitor, methanesulfonyl fluoride (MSF), was discovered to have low toxicity, central nervous system (CNS) selectivity, and a long therapeutic duration. The purpose of this research was to determine if MSF (1.5 mg/kg) would be effective in reducing or blocking amnesia induced by various doses of scopolamine (0.2, 0.6, and 2.0 mg/kg). One hundred and twenty-two female Sprague-Dawley albino rats were trained and retention tested in a Y-maze brightness discrimination task. MSF was highly effective in reducing scopolamine-induced amnesia.