Provided are acid addition salts of (Z)—N-[2-(diethylamino)ethyl]-2-methyl-7-(1,2 -dihydro-5-fluoro-2-oxo-3H-indol-3-ylidene)-4,5,6,7-tetrahydro-1H-indol-3-carboxamide, wherein the salt comprising at least one of a number of salts including L-malate, hydrochloride, phosphate, L-tartrate, benzenesulfonate, sulfate, methanesulfonate, succinate, citrate, fumarate, p-toluenesulfonate, hydrobromate, L-mandelate, lactate, acetate or maleate salt. Also provided is a pharmaceutical composition comprising the salt compounds, and a method of treatment by administering a therapeutically effective amount of the salt compounds as preparation of medicaments.
