The present invention provides crystals, and compositions thereof, wherein the crystals include a malic acid salt of N-[2-(diethylamino)ethyl]-5-[(5-fluoro-1,2-dihydro-2-oxo-3H-indol-3-ylide- ne)methyl]-2,4-dimethyl-1H-pyrrole-3-carboxamide. Methods of preparing such crystals are also disclosed.