Antiprogestogens, or antiprogestins, also known as progesterone antagonists or progesterone blockers, are a class of

drug A drug is any chemical substance that causes a change in an organism's physiology or psychology when consumed. Drugs are typically distinguished from food and substances that provide nutritional support. Consumption of drugs can be via insuffla ...

s which prevent

progestogen Progestogens, also sometimes written progestagens or gestagens, are a class of natural or synthetic steroid hormones that bind to and activate the progesterone receptors (PR). Progesterone is the major and most important progestogen in the body. ...

s like

progesterone Progesterone (P4) is an endogenous steroid and progestogen sex hormone involved in the menstrual cycle, pregnancy, and embryogenesis of humans and other species. It belongs to a group of steroid hormones called the progestogens and is the m ...

from mediating their

biological effect In evolutionary biology, function is the reason some object or process occurred in a system that evolved through natural selection. That reason is typically that it achieves some result, such as that chlorophyll helps to capture the energy of sunl ...

s in the body. They act by blocking the

progesterone receptor The progesterone receptor (PR), also known as NR3C3 or nuclear receptor subfamily 3, group C, member 3, is a protein found inside cells. It is activated by the steroid hormone progesterone. In humans, PR is encoded by a single ''PGR'' gene resid ...

(PR) and/or inhibiting or suppressing progestogen

production Production may refer to: Economics and business * Production (economics) * Production, the act of manufacturing goods * Production, in the outline of industrial organization, the act of making products (goods and services) * Production as a stati ...

. Antiprogestogens are one of three types of sex hormone antagonists, the others being

antiestrogen Antiestrogens, also known as estrogen antagonists or estrogen blockers, are a class of drugs which prevent estrogens like estradiol from mediating their biological effects in the body. They act by blocking the estrogen receptor (ER) and/or inhi ...

s and

antiandrogen Antiandrogens, also known as androgen antagonists or testosterone blockers, are a class of drugs that prevent androgens like testosterone and dihydrotestosterone (DHT) from mediating their biological effects in the body. They act by blocking the ...

s. Antiprogestogens are used as

abortifacient An abortifacient ("that which will cause a miscarriage" from Latin: ''abortus'' "miscarriage" and '' faciens'' "making") is a substance that induces abortion. This is a nonspecific term which may refer to any number of substances or medications, ...

s and

emergency contraceptive Emergency contraception (EC) is a birth control measure, used after sexual intercourse to prevent pregnancy. There are different forms of EC. Emergency contraceptive pills (ECPs), sometimes simply referred to as emergency contraceptives (ECs), ...

s and in the treatment of

uterine fibroid Uterine fibroids, also known as uterine leiomyomas or fibroids, are benign smooth muscle tumors of the uterus. Most women with fibroids have no symptoms while others may have painful or heavy periods. If large enough, they may push on the bl ...

s. They are also being studied in the treatment of

breast cancer Breast cancer is cancer that develops from breast tissue. Signs of breast cancer may include a lump in the breast, a change in breast shape, dimpling of the skin, milk rejection, fluid coming from the nipple, a newly inverted nipple, or a re ...

. Examples of antiprogestogens include the

weak

partial agonist In pharmacology, partial agonists are drugs that bind to and activate a given receptor, but have only partial efficacy at the receptor relative to a full agonist. They may also be considered ligands which display both agonistic and antagonistic e ...

mifepristone Mifepristone, also known as RU-486, is a medication typically used in combination with misoprostol to bring about a medical abortion during pregnancy and manage early miscarriage. This combination is 97% effective during the first 63 days of p ...

, the

selective progesterone receptor modulator A selective progesterone receptor modulator (SPRM) is an agent that acts on the progesterone receptor (PR), the biological target of progestogens like progesterone. A characteristic that distinguishes such substances from full receptor agonists (e ...

(SPRM)

ulipristal acetate Ulipristal acetate, sold under the brand name Ella among others, is a medication used for emergency contraception (birth control) and uterine fibroids. As emergency contraception it should be used within 120 hours of vaginally penetrating inter ...

, and the

silent antagonist A receptor antagonist is a type of receptor ligand or drug that blocks or dampens a biological response by binding to and blocking a receptor rather than activating it like an agonist. Antagonist drugs interfere in the natural operation of recep ...

aglepristone Aglepristone () (brand name Alizin; former developmental code names RU-46534, RU-534) is a synthetic, steroidal antiprogestogen related to mifepristone which is marketed by Virbac in several European countries for use in veterinary medicine. It i ...

. For

medical abortion A medical abortion, also known as medication abortion, occurs when drugs (medication) are used to bring about an abortion. Medical abortions are an alternative to surgical abortions such as vacuum aspiration or dilation and curettage. Medical ...

, mifepristone is combined with a

prostaglandin The prostaglandins (PG) are a group of physiologically active lipid compounds called eicosanoids having diverse hormone-like effects in animals. Prostaglandins have been found in almost every tissue in humans and other animals. They are derive ...

(e.g.,

gemeprost Gemeprost (16, 16-dimethyl-trans-delta2 PGE1 methyl ester) is an analogue of prostaglandin E1. Clinical use It is used as a treatment for obstetric bleeding. It is used with mifepristone to terminate pregnancy up to 24 weeks gestation. Side ...

). Several hundred antiprogestogens have been developed, but only three,

lilopristone Lilopristone ( INN) (developmental code names ZK-98734, ZK-734) is a synthetic, steroidal antiprogestogen with additional antiglucocorticoid activity which was developed by Schering and was patented in 1985. It is described as an abortifacient a ...

, and

onapristone Onapristone () (developmental code names ZK-89299, ZK-299) is a synthetic and steroidal antiprogestogen with additional antiglucocorticoid activity which was developed by Schering in and described in 1984 but was never marketed. in in It is a ...

, have been given to humans, and of these, only mifepristone has been approved and introduced for clinical use.

References

External links

*
Antiprogestin
entry in the public domain NCI Dictionary of Cancer Terms {{genito-urinary-drug-stub

See also

References

External links