ARantagonistit

AR antagonists, also known as antiandrogens, are drugs that inhibit androgen receptor signaling by blocking the binding of androgens to the receptor or by interfering with the receptor’s activity. They are primarily used to treat conditions driven by androgens, most notably prostate cancer, and may be used in other androgen-dependent disorders or in conjunction with hormone therapies.

Mechanism of action varies among agents. Most are competitive antagonists at the AR ligand-binding domain, preventing activation by testosterone and dihydrotestosterone. Others impede AR’s nuclear translocation, hinder AR-DNA binding, or disrupt recruitment of coactivator proteins. Some compounds promote degradation of the receptor, reducing AR availability in cells.

Medical uses and examples. In prostate cancer, AR antagonists are used with androgen deprivation therapy for metastatic castration-sensitive disease and for castration-resistant disease when AR signaling remains a driver. First-generation agents include flutamide, nilutamide, and bicalutamide; second-generation agents include enzalutamide, apalutamide, and darolutamide. These drugs may also be used to prevent testosterone flare at the start of GnRH agonist therapy in some regimens. AR antagonists are being studied in other AR-driven conditions and in combination therapies.

Resistance and safety. Resistance commonly arises from AR gene amplification, mutations in the ligand-binding domain that convert antagonists into agonists, or expression of AR splice variants lacking the LBD. Side effects vary but often include fatigue, hot flashes, gynecomastia, breast pain, and sexual dysfunction; some agents carry risks of liver toxicity or CNS effects such as rare seizures. Monitoring of liver function and clinical symptoms is part of management.

Development and research. Ongoing work includes AR degraders and non-LBD targeting strategies, with aims to overcome resistance and expand indications; combination approaches with chemotherapy or targeted therapies are also pursued.