Ambenonium dichloride

Preparation, in vitro evaluation and molecular modelling of pyridinium-quinolinium/isoquinolinium non-symmetrical bisquaternary cholinesterase inhibitors.[Pubmed:24220173]

Bioorg Med Chem Lett. 2013 Dec 15;23(24):6663-6.

Two series of non-symmetrical bisquaternary pyridinium-quinolinium and pyridinium-isoquinolinium compounds were prepared as molecules potentially applicable in myasthenia gravis treatment. Their inhibitory ability towards human recombinant acetylcholinesterase and human plasmatic butyrylcholinesterase was determined and the results were compared to the known effective inhibitors such as Ambenonium dichloride, edrophonium bromide and experimental compound BW284C51. Two compounds, 1-(10-(pyridinium-1-yl)decyl)quinolinium dibromide and 1-(12-(pyridinium-1-yl)dodecyl)quinolinium dibromide, showed very promising affinity for acetylcholinesterase with their IC50 values reaching nM inhibition of acetylcholinesterase. These most active compounds also showed satisfactory selectivity towards acetylcholinesterase and they seem to be very promising as leading structures for further modifications and optimization. Two of the most promising compounds were examined in the molecular modelling study in order to find the possible interactions between the ligand and tested enzyme.

Preparation, in vitro screening and molecular modelling of symmetrical bis-quinolinium cholinesterase inhibitors--implications for early myasthenia gravis treatment.[Pubmed:21397501]

Bioorg Med Chem Lett. 2011 Apr 15;21(8):2505-9.

This paper describes the preparation and in vitro evaluation of 18 newly prepared bis-quinolinium inhibitors on human recombinant acetylcholinesterase (AChE) and human plasmatic butyrylcholinesterase (BChE). Their inhibitory (IC(50)) and was compared to the chosen standards Ambenonium dichloride, edrophonium chloride, BW284c51 and ethopropazine hydrochloride. One novel compound was found to be a promising inhibitor of hAChE (in nM range) and was better than edrophonium chloride or BW284c51, but was worse than ambenonium chloride. This compound also showed selectivity towards hAChE and it was confirmed as a non-competitive inhibitor of hAChE by kinetic analysis. A molecular modelling study further confirmed its binding to the peripheral active site of hAChE via apparent pi-pi or pi-cationic interactions.

Preparation and in vitro screening of symmetrical bis-isoquinolinium cholinesterase inhibitors bearing various connecting linkage--implications for early Myasthenia gravis treatment.[Pubmed:21236521]

Eur J Med Chem. 2011 Feb;46(2):811-8.

Inhibitors of acetylcholinesterase are compounds widely used in the treatment of various diseases, such as Alzheimer's disease, glaucoma and Myasthenia gravis (MG). Compounds used in the therapy of MG posses a positive charge in the molecule to ensure peripheral effect of action and minimal blood-brain barrier penetration. The most prescribed carbamate inhibitors are however known for many severe side effects related to the carbamylation of AChE. This paper describes preparation and in vitro evaluation of 20 newly prepared bis-isoquinolinium inhibitors of potential concern for MG. The newly prepared compounds were evaluated in vitro on human recombinant AChE and human plasmatic butyrylcholinesterase (BChE). Their inhibitory ability was expressed as IC50 and compared to chosen standards Ambenonium dichloride, edrophonium chloride, BW284c51 and ethopropazine hydrochloride. Three novel compounds presented promising inhibition (in nM range) of both enzymes in vitro better or similar to edrophonium and BW284c51, but worse to ambenonium. The novel inhibitors did not present higher selectivity toward AChE or BChE. The kinetic assay confirmed non-competitive inhibition of hAChE by two selected promising novel compounds. Two newly prepared compounds were also chosen for docking studies that confirmed apparent pi-pi or pi-cationic interactions aside the cholinesterases catalytic sites. The SAR findings were discussed.

Design, synthesis and biological evaluation of ambenonium derivatives as AChE inhibitors.[Pubmed:13679187]

Farmaco. 2003 Sep;58(9):917-28.

Ambenonium (1), an old AChE inhibitor, is endowed with an outstanding affinity and a peculiar mechanism of action that, taken together, make it a very promising pharmacological tool for the treatment of Alzheimer's disease (AD). Unfortunately, the bisquaternary structure of 1 prevents its passage through the blood brain barrier. In a search of centrally active ambenonium derivatives, we planned to synthesize tertiary amines of 1, such as 2 and 3. In addition, to add new insights into the binding mechanism of the inhibitor, we designed constrained analogues of ambenonium by incorporating the diamine functions into cyclic moieties (4-12). The biological evaluation of the new compounds has been assessed in vitro against human AChE and BChE. All tertiary amine derivatives resulted more than 1000-fold less potent than 1 and, unlike prototype, did not show any selectivity between the two enzymes. This result, because of recent findings concerning the role of BChE in AD, makes our compounds, endowed with a well-balanced profile of AChE/BChE inhibition, valuable candidates for further development. To better clarify the interactions that account for the high affinity of 1, docking simulations and molecular dynamics studies on the AChE-1 complex were also carried out.

Ambenonium is a rapidly reversible noncovalent inhibitor of acetylcholinesterase, with one of the highest known affinities.[Pubmed:1588924]

Mol Pharmacol. 1992 May;41(5):937-42.

Steady state patterns of inhibition of purified human erythrocyte acetylcholinesterase by three inhibitors were analyzed. Edrophonium acted essentially as a competitive inhibitor, whereas tacrine and ambenonium gave mixed competitive and uncompetitive inhibition with acetylthiocholine as substrate. Inhibition constants for the competitive components were 470 microM for edrophonium, 65 microM for tacrine, and 0.12 nM for ambenonium. The extremely high affinity of ambenonium permitted analysis of the rates of approach to steady state inhibition. These rates were characterized by a single exponential time course with rate constants, kexp, that showed a linear dependence when plotted against ambenonium concentration, at fixed substrate concentration. The intercepts of these plots were independent of the substrate concentration and indicated an ambenonium dissociation rate constant of 0.013 +/- 0.002 sec-1. The slope of the plot at the lowest substrate concentration approximated the ambenonium bimolecular or association rate constant and gave a value of 5.2 +/- 0.6 x 10(7) M-1 sec-1. Three models were examined to account for the nearly linear dependence of the slopes of these plots on the substrate concentration. These models indicated that ambenonium and acetylthiocholine competed for a peripheral anionic site in the acetyl-enzyme intermediate formed during substrate hydrolysis. The apparent equilibrium dissociation constant of acetylthiocholine for this peripheral site (1.2-1.4 mM) was significantly different from that calculated from substrate inhibition data (20.1 +/- 2.8 mM). We propose that acetylthiocholine can interact with the acetyl-enzyme both at the peripheral site and at the active site but that only the latter interaction inhibits substrate hydrolysis.