The present invention concerns pharmaceutical formulations of ARN-509, which can be administered to a mammal, in particular a human, suffering from an androgen receptor (AR)-related disease or condition, in particular cancer, more in particular prostate cancer, including but not limited to castration-resistant prostate cancer, metastatic castration resistant prostate cancer, chemotherapy-naive metastatic castration resistant prostate cancer, biochemically relapsed hormone sensitive prostate cancer, or high-risk, non-metastatic castration-resistant prostate cancer. In one aspect, these formulations comprise a solid dispersion of ARN-509, a poly(meth)acrylate copolymer and HPMCAS. In one aspect, the solid dispersion of ARN-509, a poly(meth)acrylate copolymer and HPMCAS is obtainable, in particular is obtained, by melt-extruding a mixture comprising ARN-509, a poly(meth)acrylate copolymer and HPMCAS and optionally subsequently milling said melt-extruded mixture. In one aspect, the solid dispersion of ARN-509, a poly(meth)acrylate copolymer and HPMCAS is obtainable, in particular is obtained, by spray drying a mixture comprising ARN-509, a poly(meth)acrylate copolymer and HPMCAS in a suitable solvent.