Heptanediamide,N,N'-bis[(1,4-dihydro-3-hydroxy-1,6-dimethyl-4-oxo-2-pyridinyl)methyl]-4-[3-[[(1,4-dihydro-3-hydroxy-1,6-dimethyl-4-oxo-2-pyridinyl)methyl]amino]-3-oxopropyl]-4-nitro-