The present invention relates to a drying process of BIBW 2992 or the salts thereof, preferably the dimaleate salt, as well as of solid pharmaceutical formulations comprising BIBW2992 or a salt thereof, and to pharmaceutical compositions comprising BIBW 2992 or a salt thereof as the active product ingredient, characterized by a water activity of the formulation of not more than 0.20 or a water content (Karl-Fischer) of not more than 4.2%.
