Onapristone

**Semantic type:** Pharmacologic Substance

**Definition:** An orally bioavailable progesterone receptor (PR) antagonist, with potential antineoplastic activity. Upon oral administration, onapristone binds to the PR and inhibits both PR activation and the associated expression of PR-responsive genes. This may inhibit PR-mediated proliferative effects in cancer cells overexpressing PR. In addition, onapristone may downregulate cancer stem cell mobilization and block immune evasion. PR is expressed on certain cancer cell types and plays a key role in tumor cell proliferation and survival.

**Synonyms:** - ONAPRISTONE