A process for preparing 7-methyl-5-(3-piperazin-1-ylmethyl-[1,2,4]oxadiazol-5-yl)-2-(4-trifluoromethoxybenzyl)-2,3-dihydroisoindol-1-one, having the structure below: or an acid salt thereof, the process comprising: reacting tert-butyl piperazine-1-carboxylate with bromoacetonitrile, in an organic solvent in the presence of a base and subsequent reaction with hydroxylamine or an acid salt thereof to form 4-(N-hydroxycarbamimidoylmethyl)-piperazine-1-carboxylic acid tert-butyl ester; reacting 5-bromo-2-iodo-1,3-dimethyl-benzene in an ether solvent with a Grignard reagent and carbon dioxide gas to form 4-bromo-2,6-dimethylbenzoic acid; heating 4-bromo-2,6-dimethylbenzoic acid with N-bromosuccinimide and a radical initiator in an organic solvent and subsequent reduction of over-brominated products with a reducing agent to form 5-bromo-7-methyl-3H-isobenzofuran-1-one; heating 5-bromo-7-methyl-3H-isobenzofuran-1-one with 4-(trifluoromethoxy)-benzylamine in an anhydrous solvent with trimethylaluminium to form 4-bromo-2-hydroxymethyl-6-methyl-N-(4-trifluoromethoxy-benzyl)-benzamide; reacting 4-bromo-2-hydroxymethyl-6-methyl-N-(4-trifluoromethoxy-benzyl)-benzamide with methanesulphonyl chloride and a base in an organic solvent to form 5-bromo-7-methyl-2-(4-trifluoromethoxy-benzyl)-2,3-dihydro-isoindol-1-one; heating 5-bromo-7-methyl-2-(4-trifluoromethoxy-benzyl)-2,3-dihydro-isoindol-1-one in the presence of zinc cyanide, 1, 1 '-bis(diphenylphospino)ferrocene and tris(dibenzylideneacetone)-dipalladium in an organic solvent to form 7-methyl-1-oxo-2-(4-trifluoromethoxy-benzyl)-2,3-dihydro-1H-isoindole-5-carbonitrile; hydrolysis of 7-methyl-1-oxo-2-(4-trifluoromethoxy-benzyl)-2,3-dihydro-1H-isoindole-5-carbonitrile in a solvent with a hydroxide solution to form 7-methyl-1-oxo-2-(4-trifluoromethoxy-benzyl)-2,3-dihydro-1 H-isoindole-5-carboxylic acid; reacting 7-methyl-1-oxo-2-(4-trifluoromethoxy-benzyl)-2,3-dihydro-1H-isoindole-5-carboxylic acid in an organic solvent with thionyl chloride or another chlorinating agent and reacting the product with tert-butyl 4-[ -2-amino-2-hydroxyimino)ethyl]-piperazine-1-carboxylate in the presence of a base to form 4- {5-[7-methyl-1-oxo-2-(4-trifluoromethoxy-benzyl)-2,3-dihydro-1H-isoindol-5-yl]-[1,2,4]oxadiazol-3-ylmethyl}-piperazine-1-carboxylic acid tert-butyl ester, and decarboxylating 4- {5-[7-methyl-1-oxo-2-(4-trifluoromethoxy-benzyl)-2,3-dihydro-1H-isoindol- 5-yl]-[1,2,4]oxadiazol-3-ylmethyl}-piperazine-1-carboxylic acid tert-butyl ester by heating with acid in a solvent, to form 7-methyl-5-(3-piperazin-1-ylmethyl-[1,2,4]oxadiazol-5-yl)-2-(4-trifluoromethoxy-benzyl)-2,3-dihydro-isoindol-1-one or an acid salt thereof. reacting tert-butyl piperazine-1-carboxylate with bromoacetonitrile, in an organic solvent in the presence of a base and subsequent reaction with hydroxylamine or an acid salt thereof to form 4-(N-hydroxycarbamimidoylmethyl)-piperazine-1-carboxylic acid tert-butyl ester; reacting 5-bromo-2-iodo-1,3-dimethyl-benzene in an ether solvent with a Grignard reagent and carbon dioxide gas to form 4-bromo-2,6-dimethylbenzoic acid; heating 4-bromo-2,6-dimethylbenzoic acid with N-bromosuccinimide and a radical initiator in an organic solvent and subsequent reduction of over-brominated products with a reducing agent to form 5-bromo-7-methyl-3H-isobenzofuran-1-one; heating 5-bromo-7-methyl-3H-isobenzofuran-1-one with 4-(trifluoromethoxy)-benzylamine in an anhydrous solvent with trimethylaluminium to form 4-bromo-2-hydroxymethyl-6-methyl-N-(4-trifluoromethoxy-benzyl)-benzamide; reacting 4-bromo-2-hydroxymethyl-6-methyl-N-(4-trifluoromethoxy-benzyl)-benzamide with methanesulphonyl chloride and a base in an organic solvent to form 5-bromo-7-methyl-2-(4-trifluoromethoxy-benzyl)-2,3-dihydro-isoindol-1-one; heating 5-bromo-7-methyl-2-(4-trifluoromethoxy-benzyl)-2,3-dihydro-isoindol-1-one in the presence of zinc cyanide, 1, 1 '-bis(diphenylphospino)ferrocene and tris(dibenzylideneacetone)-dipalladium in an organic solvent to form 7-methyl-1-oxo-2-(4-trifluoromethoxy-benzyl)-2,3-dihydro-1H-isoindole-5-carbonitrile; hydrolysis of 7-methyl-1-oxo-2-(4-trifluoromethoxy-benzyl)-2,3-dihydro-1H-isoindole-5-carbonitrile in a solvent with a hydroxide solution to form 7-methyl-1-oxo-2-(4-trifluoromethoxy-benzyl)-2,3-dihydro-1 H-isoindole-5-carboxylic acid; reacting 7-methyl-1-oxo-2-(4-trifluoromethoxy-benzyl)-2,3-dihydro-1H-isoindole-5-carboxylic acid in an organic solvent with thionyl chloride or another chlorinating agent and reacting the product with tert-butyl 4-[ -2-amino-2-hydroxyimino)ethyl]-piperazine-1-carboxylate in the presence of a base to form 4- {5-[7-methyl-1-oxo-2-(4-trifluoromethoxy-benzyl)-2,3-dihydro-1H-isoindol-5-yl]-[1,2,4]oxadiazol-3-ylmethyl}-piperazine-1-carboxylic acid tert-butyl ester, and decarboxylating 4- {5-[7-methyl-1-oxo-2-(4-trifluoromethoxy-benzyl)-2,3-dihydro-1H-isoindol- 5-yl]-[1,2,4]oxadiazol-3-ylmethyl}-piperazine-1-carboxylic acid tert-butyl ester by heating with acid in a solvent, to form 7-methyl-5-(3-piperazin-1-ylmethyl-[1,2,4]oxadiazol-5-yl)-2-(4-trifluoromethoxy-benzyl)-2,3-dihydro-isoindol-1-one or an acid salt thereof.