(2Z)-3-{[(2R)-4-oxo-4-[3-(trifluoromethyl)-5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazin-7-yl]-1-(2,4,5-trifluorophenyl)but-2-yl]amino}-1-[3-(trifluoromethyl)-5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazin-7-yl]-4-(2,4,5-trifluorophenyl)but-2-en-1-one