Mifepristone used for inducing aboion acts on:

Mifepristone, also known as RU-486, is a medication typically used in combination with misoprostol to bring about an aboion during pregnancy. This combination is 97% effective during the first 63 days of pregnancy. It is also effective in the second trimester of pregnancy. Mifepristone blocks a natural substance progesterone that is needed for pregnancy to continue. Mifepristone is a derivative of norethindrone with antiprogestin action. It binds to progesterone receptors in the endometrium and decidua, resulting in necrosis and detachment of POCs.