Chloroethynylnorgestrel (developmental code name WY-4355) is a

steroid A steroid is a biologically active organic compound with four rings arranged in a specific molecular configuration. Steroids have two principal biological functions: as important components of cell membranes that alter membrane fluidity; and a ...

progestin A progestogen, also referred to as a progestagen, gestagen, or gestogen, is a type of medication which produces effects similar to those of the natural product, natural female sex hormone progesterone in the body. A progestin is a ''synthetic co ...

of the

19-nortestosterone Nandrolone, also known as 19-nortestosterone, is an androgen and anabolic steroid (AAS) which is used in the form of esters such as nandrolone decanoate (brand name Deca-Durabolin) and nandrolone phenylpropionate (brand name Durabolin). Nandrolon ...

group related to

norgestrel Norgestrel, sold under the brand name Ovral among others, is a progestin medication which is used in birth control pills and in menopausal hormone therapy. It is available both in combination with an estrogen and alone. It is taken by mouth. S ...

that was investigated as an oral contraceptive in the 1970s but was never marketed. In combination with

mestranol Mestranol, sold under the brand names Enovid, Norinyl, and Ortho-Novum among others, is an estrogen medication which has been used in birth control pills, menopausal hormone therapy, and the treatment of menstrual disorders. It is formulated in c ...

, similarly to

ethynerone Ethynerone (INN, USAN), also known as 17α-(2-chloroethynyl)estra-4,9-dien-17β-ol-3-one, is a steroidal progestin of the 19-nortestosterone group that was first reported in 1961 but was never marketed. Under the developmental code name MK-665, ...

and anagestone acetate (and certain other

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, including

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 ...

and several other

17α-hydroxyprogesterone 17α-Hydroxyprogesterone (17α-OHP), also known as 17-OH progesterone (17-OHP), or hydroxyprogesterone (OHP), is an endogenous progestogen steroid hormone related to progesterone. It is also a chemical intermediate in the biosynthesis of many ot ...

derivatives), chloroethynylnorgestrel was found to produce striking mammary tumors in beagle

dog The dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a domesticated descendant of the wolf. Also called the domestic dog, it is derived from the extinct Pleistocene wolf, and the modern wolf is the dog's nearest living relative. Do ...

s after administration at very high dosages (10- to 25-fold human clinical dosages) for prolonged periods of time. This resulted in the discontinuation of its development, along with that of ethynerone and anagestone acetate, as well as the removal of several progestins, including chlormadinone acetate,

medroxyprogesterone acetate Medroxyprogesterone acetate (MPA), also known as depot medroxyprogesterone acetate (DMPA) in injectable form and sold under the brand name Depo-Provera among others, is a hormonal medication of the progestin type. It is used as a method of bi ...

, and megestrol acetate, from various markets as contraceptives (although medroxyprogesterone acetate has since been reintroduced). Subsequent research revealed that the risk is species-dependent and unique to canines and that there is no similar risk for humans.

References

Abandoned drugs Estranes Organochlorides Progestogens {{steroid-stub