Mofegiline hydrochloride (MDL72974A) is a potent and selective enzyme-activated irreversible inhibitor of MAO-B; shows marked selectivity for the B form (IC50 = 680 and 3.6 nM for MAO-A and MAO-B).IC50 value: 3.6 nM [1]Target: MAO-Bin vitro: MDL72974 inhibits rat brain mitochondrial MAO in a concentration and time-dependent fashion and shows marked selectivity for the B form (IC50 = 680 and 3.6 nM for MAO-A and MAO-B, respectively) [1]. is also capable of inhibiting semicarbazide-sensitive amine oxidases (SSAOs) obtained from vascular tissues and sera of different species. The inhibition of SSAO by MDL-72974A was irreversible and time dependent. It was competitive without preincubation of the enzyme with the inhibitor and demonstrated a mixed-type of inhibition when the enzyme was preincubated with the inhibitor. The IC50 values were estimated to be 2 x 10(-9) M, 5 x 10(-9) M, 8 x 10(-8) M and 2 x 10(-8) M for SSAO from dog aorta, rat aorta, bovine aorta and human umbilical artery, respectively [2]. in vivo: After oral administration to rats, the compound shows preferential inhibition of brain MAO-B with ED50 values of 8 and 0.18 mg/kg p.o. for the A and B forms, respectively. Selectivity is retained on repeat dosing. MDL 72,974 did not significantly potentiate the cardiovascular effects of intraduodenually-administered tyramine in anaesthetized rats and had only minor indirect sympathomimatic effects in the pithed rat [1]. Male beagle dogs were given single p.o. (20 mg/kg) and i.v. (5 mg/kg) doses of [14C]-Mofegiline. Total radioactivity excreted in urine and feces over 96 hr was, respectively, 75.5 +/- 3.8 and 6.3 +/- 3.4% of the dose after p.o. and 67.9 +/- 0.5 and 3.9 +/- 2.4% after i.v. administration. Unchanged drug in urine represented 3% of the dose after po and less than 1% after i.v. administration. Mofegiline was thus extensively metabolized in dogs, and urinary excretion was the major route of elimination of metabolites [3].

[1]. Zreika M, et al. MDL 72,974: a potent and selective enzyme-activated irreversible inhibitor of monoamine oxidase type B with potential for use in Parkinson's disease. J Neural Transm Park Dis Dement Sect. 1989;1(4):243-54. [2]. Yu PH, et al. Inhibition of a type B monoamine oxidase inhibitor, (E)-2-(4-fluorophenethyl)-3-fluoroallylamine (MDL-72974A), on semicarbazide-sensitive amine oxidases isolated from vascular tissues and sera of different species. Biochem Pharmacol. 1992 Jan 22;43(2):307-12. [3]. Dow J, et al. Novel carbamate metabolites of mofegiline, a primary amine monoamine oxidase B inhibitor, in dogs and humans. Drug Metab Dispos. 1994 Sep-Oct;22(5):738-49.