The invention relates to novel crystalline forms of (2S)-2-tert-butoxy-2-(4-(2,3- dihydropyrano[4,3,2-de]quinolin-7-yl)-2-methylquinolin-3-yl)acetic acid, the hydrochloride salt thereof, novel crystalline forms of the hydrochloride salt, methods for the preparation thereof, pharmaceutical compositions thereof and their use in the treatment of Human Immunodeficiency Virus (HIV) infection.