Triparanol (, ; brand name and development code MER/29, as well as many other brand names) was the first
synthetic cholesterol
Cholesterol is any of a class of certain organic molecules called lipids. It is a sterol (or modified steroid), a type of lipid. Cholesterol is biosynthesized by all animal cells and is an essential structural component of animal cell mem ...
-lowering
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 ...
.
It was patented in 1959 and introduced in the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
in 1960.
The developmental code name of triparanol, MER/29, became so well known that it became the registered trade name of the drug.
It was
withdrawn in 1962 due to severe
adverse effect
An adverse effect is an undesired harmful effect resulting from a medication or other intervention, such as surgery. An adverse effect may be termed a "side effect", when judged to be secondary to a main or therapeutic effect. The term complica ...
s such as
nausea
Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. While not painful, it can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the ...
and
vomiting
Vomiting (also known as emesis and throwing up) is the involuntary, forceful expulsion of the contents of one's stomach through the mouth and sometimes the Human nose, nose.
Vomiting can be the result of ailments like Food-poisoning, foo ...
,
vision loss
Visual impairment, also known as vision impairment, is a medical definition primarily measured based on an individual's better eye visual acuity; in the absence of treatment such as correctable eyewear, assistive devices, and medical treatment†...
due to irreversible
cataracts
A cataract is a cloudy area in the lens of the eye that leads to a decrease in vision. Cataracts often develop slowly and can affect one or both eyes. Symptoms may include faded colors, blurry or double vision, halos around light, trouble w ...
,
alopecia
Hair loss, also known as alopecia or baldness, refers to a loss of hair from part of the head or body. Typically at least the head is involved. The severity of hair loss can vary from a small area to the entire body. Inflammation or scarri ...
,
skin disorder
A skin condition, also known as cutaneous condition, is any medical condition that affects the integumentary system—the organ system that encloses the body and includes skin, nails, and related muscle and glands. The major function of this ...
s (e.g.,
dryness,
itching
Itch (also known as pruritus) is a sensation that causes the desire or reflex to scratch. Itch has resisted many attempts to be classified as any one type of sensory experience. Itch has many similarities to pain, and while both are unpleasan ...
,
peeling, and "fish-scale" texture), and accelerated
atherosclerosis
Atherosclerosis is a pattern of the disease arteriosclerosis in which the wall of the artery develops abnormalities, called lesions. These lesions may lead to narrowing due to the buildup of atheroma, atheromatous plaque. At onset there are usu ...
.
It is now considered to be obsolete.
The drug acts by inhibiting
24-dehydrocholesterol reductase, which catalyzes the final step of cholesterol
biosynthesis
Biosynthesis is a multi-step, enzyme-catalyzed process where substrates are converted into more complex products in living organisms. In biosynthesis, simple compounds are modified, converted into other compounds, or joined to form macromolecules. ...
, the conversion of
desmosterol
Desmosterol is a molecule similar to cholesterol. Desmosterol is the immediate precursor of cholesterol in the Bloch pathway of cholesterol biosynthesis. 24-dehydrocholesterol reductase catalyses the reduction of desmosterol to cholesterol. It i ...
into cholesterol.
Although effective in reducing cholesterol levels, this results in tissue accumulation of desmosterol, which in turn is responsible for the side effects of triparanol.
Unlike
statin
Statins, also known as HMG-CoA reductase inhibitors, are a class of lipid-lowering medications that reduce illness and mortality in those who are at high risk of cardiovascular disease. They are the most common cholesterol-lowering drugs.
Low- ...
s, triparanol does not inhibit
HMG-CoA reductase, the rate-limiting enzyme in cholesterol biosynthesis,
and in contrast to triparanol, statins can lower cholesterol levels without resulting in accumulation of intermediates like desmosterol.
Estrogen
Estrogen or oestrogen is a category of sex hormone responsible for the development and regulation of the female reproductive system and secondary sex characteristics. There are three major endogenous estrogens that have estrogenic hormonal acti ...
is known to lower cholesterol levels, but produces
side effect
In medicine, a side effect is an effect, whether therapeutic or adverse, that is secondary to the one intended; although the term is predominantly employed to describe adverse effects, it can also apply to beneficial, but unintended, consequence ...
s like
gynecomastia
Gynecomastia (also spelled gynaecomastia) is the abnormal non-cancerous enlargement of one or both breasts in males due to the growth of breast tissue as a result of a hormone imbalance between estrogens and androgens. Updated by Brent Wisse (1 ...
and decreased
libido
Libido (; colloquial: sex drive) is a person's overall sexual drive or desire for sexual activity. Libido is influenced by biological, psychological, and social factors. Biologically, the sex hormones and associated neurotransmitters that act up ...
in men.
It was hoped that a drug could be developed that lacked overt estrogenic effects but still lowered cholesterol levels.
Triparanol is a
triphenylethanol
Triphenylethanol, or 1,1,2-triphenylethanol, is an organic compound with a condensed structural formula of , and is related to triphenylethylene, from which it can be prepared by hydration. It is the structural analog of two drugs, the never-marke ...
and was derived from
chlorotrianisene
Chlorotrianisene (CTA), also known as tri-''p''-anisylchloroethylene (TACE) and sold under the brand name Tace among others, is a nonsteroidal estrogen related to diethylstilbestrol (DES) which was previously used in the treatment of menopausal ...
(TACE), a
nonsteroidal A nonsteroidal compound is a drug that is not a steroid nor a steroid derivative. Nonsteroidal anti-inflammatory drugs (NSAIDs) are distinguished from corticosteroids as a class of anti-inflammatory agents.
List of nonsteroidal steroid receptor mod ...
triphenylethylene
Triphenylethylene (TPE) is a simple aromatic hydrocarbon that possesses weak estrogenic activity. Its estrogenic effects were discovered in 1937. TPE was derived from structural modification of the more potent estrogen diethylstilbestrol, which is ...
estrogen.
The nonsteroidal triphenylethanol
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 ...
ethamoxytriphetol
Ethamoxytriphetol (developmental code name MER-25) is a synthetic nonsteroidal antiestrogen that was studied clinically in the late 1950s and early 1960s but was never marketed. MER-25 was first reported in 1958, and was the first antiestrogen t ...
(MER-25) is a derivative of triparanol.
The
selective estrogen receptor modulator
Selective estrogen receptor modulators (SERMs), also known as estrogen receptor agonist/antagonists (ERAAs), are a class of drugs that act on the estrogen receptor (ER). A characteristic that distinguishes these substances from pure ER agonists a ...
clomifene
Clomifene, also known as clomiphene, is a medication used to treat infertility in women who do not ovulate, including those with polycystic ovary syndrome. Use results in a greater chance of twins. It is taken by mouth once a day, with a course ...
is also structurally related to triparanol.
The developers of triparanol jokingly referred to it as a "non-estrogenic estrogen" due to its lipid-lowering effects without other estrogenic effects.
See also
*
Azacosterol
*
Desmosterolosis
Desmosterolosis in medicine and biology is a defect in cholesterol biosynthesis. It results in an accumulation of desmosterol and a variety of associated symptoms. Only two cases have been reported as of 2007. The condition is due to inactivating ...
*
X-linked ichthyosis X-linked ichthyosis (abbreviated ''XLI'') is a skin condition caused by the hereditary deficiency of the steroid sulfatase (STS) enzyme that affects 1 in 2000 to 1 in 6000 males.
XLI manifests with dry, scaly skin and is due to deletions
or muta ...
*
Clomestrone
Clomestrone (brand names Arterolo, Atheran, Colesterel, Iposclerone, Liprotene, Persclerol, others; former developmental code name SC-8246), also known as 16α-chloroestrone 3-methyl ether, is a synthetic, steroidal, weak estrogen derived from ...
*
Mytatrienediol
Mytatrienediol (developmental code name SC-6924; former tentative brand names Manvene, Anvene), also known as 16α-methyl-16β-epiestriol 3-methyl ether or 16β-hydroxy-16α-methylestradiol 3-methyl ether, is a synthetic steroidal estrogen medic ...
References
{{Lipid modifying agents
24-Dehydrocholesterol reductase inhibitors
Tertiary alcohols
Diethylamino compounds
Hypolipidemic agents
Organochlorides
Phenol ethers
Withdrawn drugs