Onapristone

Onapristone is a synthetic steroid that acts as an antiprogestogen. It was first developed in the 1980s and has been studied for use in a variety of medical conditions, including breast cancer, endometriosis, and menorrhagia. However, its development has been hindered by concerns about liver toxicity.

Pharmacology

Onapristone is a type I antiprogestogen, meaning it binds to the progesterone receptor and prevents it from activating. This is in contrast to type II antiprogestogens, which bind to the receptor and activate it in a way that is different from progesterone. Onapristone has a high affinity for the progesterone receptor and does not have any significant affinity for other steroid receptors.

Clinical uses

Onapristone has been studied for use in a variety of medical conditions. In breast cancer, it has been shown to inhibit the growth of cancer cells in vitro and in animal models. It has also been studied in endometriosis, a condition in which tissue similar to the lining of the uterus grows outside of the uterus. In addition, it has been investigated for use in menorrhagia, or heavy menstrual bleeding.

Safety

The development of onapristone has been hindered by concerns about liver toxicity. In clinical trials, some patients developed elevated liver enzymes, a sign of potential liver damage. As a result, the drug has not been approved for use in many countries.

See also

• Antiprogestogen
• Breast cancer
• Endometriosis
• Menorrhagia