Synonyms: Cyclo(D-hexahydro-3-pyridazinecarbonyl-L-hexahydro-3-pyridazinecarbonyl-N-methyl-D-phenylalanyl-L-prolyl-D-phenylalanyl-N-hydroxy-L-isoleucyl);2H,12H-Dipyridazino[1,6-a:1',6'-d]pyrrolo[1,2-j][1,4,7,10,13,16]hexaazacyclooctadecine,cyclic peptide deriv.; L 156373