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