This invention relates to a crystalline form of (10R)-7-amino-12-fluoro-2,10,16-trimethyl-5-oxo-10,15,16,17-tetrahydro-2H-8,4-(metheno)pyrazolo[4,3-h] [2,5,11]benzoxadiazacyclo-tetradecine-3-carbonitrile (lorlatinib) free base (Form 7). This invention also relates to pharmaceutical compositions comprising Form 7, and to methods of using Form 7 and such compositions in the treatment of abnormal cell growth, such as cancer, in a mammal.