The present invention relates to a new process for manufacturing 1 -(4-fluorobenzyl)-3-(4-iso- butoxyphenyl)-1 -(1 -methylpiperidin-4-yl)urea, with the INN name pimavanserin, and its hemi- tartrate salt. Said process comprises the following step: contacting 2-(4-isobutoxyphenyl)acetic acid with N-(4-fluorobenzyl)-1 -methylpiperidin-4-amine in the presence of a base and diphe- nylphosphoryl azide (DPPA) to obtain pimavanserin.
