(2S,3R)-2-({[(4R,7S,10S,13R,16S,19R)-13-(1H-indol-3-ylmethyl)-19-{[(2R)-2-amino-3-(2-naphthyl)propanoyl]amino}-10-[4-(acetylamino)butyl]-16-[(4-hydroxyphenyl)methyl]-6,9,12,15,18-pentaoxo-7-(prop-2-yl)-1,2-dithia-5,8,11,14,17-pentazacycloicosan-4-yl]carbonyl}amino)-3-hydroxybutanamide acetic acid