Carbamic acid, [2-[[3-[2-(4-amino-1,2,5-oxadiazol-3-yl)-1-ethyl-4-(3-hydroxy-3-methyl-1- butynyl)-1H-imidazo[4,5-c]pyridin-6-yl]phenyl]amino]-2-oxoethyl]-, 1,1-dimethylethyl ester