Non-competitive androgen receptor inhibition in vitro and in vivo

TLDR

Androgen receptor (AR) inhibitors are used to treat multiple human diseases, including hirsutism, benign prostatic hypertrophy, and prostate cancer, but all available anti‑androgens target only ligand binding, either by reducing hormone availability or by competitive antagonism. The study aims to characterize two non‑ligand AR inhibitors, pyrvinium pamoate and harmol hydrochloride, as potential therapeutic strategies. Using a cell‑based AR conformation assay, the authors identified and characterized pyrvinium pamoate and harmol hydrochloride as non‑ligand inhibitors of AR activity. Both compounds act via distinct non‑competitive mechanisms, synergize with competitive antagonists, and in vivo pyrvinium suppresses AR‑dependent gene expression and induces prostate atrophy, while harmol blocks AR DNA occupancy.

Abstract

Androgen receptor (AR) inhibitors are used to treat multiple human diseases, including hirsutism, benign prostatic hypertrophy, and prostate cancer, but all available anti-androgens target only ligand binding, either by reduction of available hormone or by competitive antagonism. New strategies are needed, and could have an important impact on therapy. One approach could be to target other cellular mechanisms required for receptor activation. In prior work, we used a cell-based assay of AR conformation change to identify non-ligand inhibitors of AR activity. Here, we characterize 2 compounds identified in this screen: pyrvinium pamoate, a Food and Drug Administration-approved drug, and harmol hydrochloride, a natural product. Each compound functions by a unique, non-competitive mechanism and synergizes with competitive antagonists to disrupt AR activity. Harmol blocks DNA occupancy by AR, whereas pyrvinium does not. Pyrvinium inhibits AR-dependent gene expression in the prostate gland in vivo, and induces prostate atrophy. These results highlight new therapeutic strategies to inhibit AR activity.