Apalutamide (INN) (developmental code name ARN-509, also JNJ-56021927) is a non-steroidal antiandrogen that is under development for the treatment of prostate cancer. It is similar to enzalutamide both structurally and pharmacologically, acting as a selective competitive antagonist of the androgen receptor (AR), but shows some advantages, including greater potency and reduced central nervous system permeation. Apalutamide binds weakly to the GABAA receptor similarly to enzalutamide, but due to its relatively lower central concentrations, may have a lower risk of seizures in comparison. The drug has been found to be effective and well-tolerated in clinical trials thus far, with the most common side effects reported including fatigue, nausea, abdominal pain, and diarrhea. Apalutamide is currently in phase III clinical trials for castration-resistant prostate cancer. Recently, the acquired F876L mutation of the AR identified in advanced prostate cancer cells was found to confer resistance to both enzalutamide and apalutamide. A newer antiandrogen, darolutamide (ODM-201), is not affected by this mutation, nor has it been found to be affected by any other tested/well-known AR mutations.; Apalutamide may be effective in a subset of prostate cancer patients with acquired resistance to abiraterone acetate.