5-[4-(benzyloxy)phenyl]-1,3,4-oxadiazol-2(3H)-one derivatives and related analogues: new reversible, highly potent, and selective monamine oxidase type B inhibitors.
Thirty-three new 5-[4-(benzyloxy)phenyl]-1,3,4-oxadiazol-2(3H)-one derivatives including related analogues, designed as inhibitors of monoamine oxidase type B (MAO B), were synthesized and investigated both in vitro and ex vivo for their abilities to inhibit selectively rat brain MAO B over MAO A. Three inhibitors were found to act as reversible, highly potent, and selective MAO B inhibitors, namely the nitrile derivative 5-[4-(benzyloxy)phenyl]-3-(2-cyanoethyl)-1,3,4-oxadiazol-2(3H)-one (12a) and two closely related homologues, the corresponding oxadiazolethione 13a and the alcohol 14b. Their IC50 (MAO B) values are in the low nanomolar range of 1.4-4.6 nM and their selectivities, estimated by the ratio of IC50 values (A/B), are from 3200 to > 71,400. Compound 12a exhibited the highest activity against MAO B. Its IC50 was evaluated to be 1.4 nM with a quasitotal selectivity (> 71,400) toward this enzyme. In ex vivo studies, 12a showed a reversible and short duration of action. MAO B was markedly inhibited with the oral dose of 1 mg/kg without any alteration of MAO A, and the inhibition almost did not exceed 24 h. Its ED50 (1 h after oral administration) was evaluated to be 0.56 mg (1.7 mumol)/kg. Remarkably, MAO A was not affected at doses as high as 1500 mg/kg, po. In addition, no apparent toxicity or behavioral anomaly was observed during the treatment even at the maximum administrated dose. SAR studies emphasize the existence of three binding sites to the enzyme with a special importance of the terminal phenyl. Analysis of the inhibition kinetics indicated that 12a acts in a two-step mechanism as a competitive, slow, and tight-binding inhibitor of MAO B with a Ki value of 0.22 microM and an overall Ki* value at equilibrium of 0.7 nM.
Mazouz
F
F
Laboratoire de Chimie Organique Médicale, Faculté de Médecine Xavier Bichat, Université Paris 7, France.
Gueddari
S
S
Burstein
C
C
Mansuy
D
D
Milcent
R
R
D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000201:enzymology*; D007700:Kinetics; D008297:Male; D008928:Mitochondria / Q000201:enzymology; D015394:Molecular Structure; D008996:Monoamine Oxidase Inhibitors / Q000138:chemical synthesis* / Q000494:pharmacology; D010069:Oxadiazoles / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013329:Structure-Activity Relationship
D008996:Monoamine Oxidase Inhibitors; D010069:Oxadiazoles; C081104:5-(4-(benzyloxy)phenyl)-3-(2-cyanoethyl)-1,3,4-oxadiazol-2(3H)-one