Disclosed are methods for the preparation of amorphous N-[(3aR,4R,4aR,5aS,6S,6aS)-3,3a,4,4a,5,5a,6,6a-octahydro-1,3-dioxo-4,6-ethenocycloprop[f]isoindo1-2(1H)-yl]-4-(trifluoromethyl)-benzamide for the treatment or prophylaxis of viral infections and diseases associated therewith, particularly those viral infections and associated diseases caused by the orthopoxvirus. Also disclosed are methods for the preparation of amorphous solid dispersion of N-[(3aR,4R,4aR,5aS,6S,6aS)-3,3a,4,4a,5,5a,6,6a-octahydro-1,3-dioxo-4,6-ethenocycloprop[f]isoindo1-2(1H)-yl]-4-(trifluoromethyl)-benzamide.
