8-[(3R)-3-[({[(3R)-1-[7-(but-2-ynyl)-3-hydroxy-1-[(4-methylquinazolin-2-yl)methyl]-2,6-dioxopurin-8-yl]hexahydropyridin-3-yl]amino}methyl)amino]hexahydropyridin-1-yl]-7-(but-2-ynyl)-3-methyl-1-[(4-methylquinazolin-2-yl)methyl]-1,2,3,6-tetrahydropurine-2,6-dione