6-tert-Butyl-8-fluoro-2-{2-hydroxymethyl-3-[1-methyl-5-(4-methyl-3,4,5,6-tetrahydro-2H-[1,2']bipyrazinyl-5'-ylamino)-6-oxo-1,6-dihydro-pyridazin-3-yl]-phenyl}-2H-phthalazin-1-one