Tissue selectivity is a topic in distribution (pharmacology) and property of some drugs. It refers to when a drug occurs in disproportionate concentrations and/or has disproportionate effects in specific tissues relative to other tissues.An example of such drugs are selective estrogen receptor modulators (SERM) like tamoxifen, which show estrogenic effects in some tissues and antiestrogenic effects in other tissues. Another example is peripherally-selective drugs, which do not cross the blood-brain-barrier into the central nervous system and hence are tissue-selective for the periphery.
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 and antagonists is that their action is different in various tissues, thereby granting the possibility to selectively inhibit or stimulate estrogen-like action in various tissues.
Equilin is a naturally occurring estrogen sex hormone found in horses as well as a medication. It is one of the estrogens present in the estrogen mixtures known as conjugated estrogens and esterified estrogens. CEEs is the most commonly used form of estrogen in hormone replacement therapy (HRT) for menopausal symptoms in the United States. Estrone sulfate is the major estrogen in CEEs while equilin sulfate is the second major estrogen in the formulation, present as about 25% of the total.
Tamoxifen, sold under the brand name Nolvadex among others, is a selective estrogen receptor modulator used to prevent breast cancer in women and treat breast cancer in women and men. It is also being studied for other types of cancer. It has been used for Albright syndrome. Tamoxifen is typically taken daily by mouth for five years for breast cancer.
Raloxifene, sold under the brand name Evista among others, is a medication used to prevent and treat osteoporosis in postmenopausal women and those on glucocorticoids. For osteoporosis it is less preferred than bisphosphonates. It is also used to reduce the risk of breast cancer in those at high risk. It is taken by mouth.
Trenbolone is an androgen and anabolic steroid (AAS) of the nandrolone group which itself was never marketed. Trenbolone ester prodrugs, including trenbolone acetate and trenbolone hexahydrobenzylcarbonate, are or have been marketed for veterinary and clinical use. Trenbolone acetate is used in veterinary medicine in livestock to increase muscle growth and appetite, while trenbolone hexahydrobenzylcarbonate was formerly used clinically in humans but is now no longer marketed. In addition, although it is not approved for clinical or veterinary use, trenbolone enanthate is sometimes sold on the black market under the nickname Trenabol.
Toremifene, sold under the brand name Fareston among others, is a medication which is used in the treatment of advanced breast cancer in postmenopausal women. It is taken by mouth.
Tibolone, sold under the brand name Livial among others, is a medication which is used in menopausal hormone therapy and in the treatment of postmenopausal osteoporosis and endometriosis. The medication is available alone and is not formulated or used in combination with other medications. It is taken by mouth.
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 symptoms and estrogen deficiency in women and prostate cancer in men, among other indications, but has since been discontinued and is now no longer available. It is taken by mouth.
Hormonal therapy in oncology is hormone therapy for cancer and is one of the major modalities of medical oncology, others being cytotoxic chemotherapy and targeted therapy (biotherapeutics). It involves the manipulation of the endocrine system through exogenous or external administration of specific hormones, particularly steroid hormones, or drugs which inhibit the production or activity of such hormones. Because steroid hormones are powerful drivers of gene expression in certain cancer cells, changing the levels or activity of certain hormones can cause certain cancers to cease growing, or even undergo cell death. Surgical removal of endocrine organs, such as orchiectomy and oophorectomy can also be employed as a form of hormonal therapy.
Selective Androgen Receptor Modulators or SARMs are a class of androgen receptor ligands that maintain some of the desirable effects of androgens, such as preventing osteoporsis and muscle loss while reducing risks of developing prostate cancer. In the last 1990s, the first nonsteroidal SARM, an analog of bicalutamide, was discovered. They are intended to have the same kind of effects as androgenic drugs, such as anabolic-androgenic steroids, but be more selective in their action. As of early 2020, there are no SARMs which have been approved for therapeutic use by the U.S Food and Drug Administration.
Arzoxifene is a selective estrogen receptor modulator (SERM) of the benzothiophene group which was never marketed. It is a potent estrogen antagonist in mammary and uterine tissue while acting as an estrogen agonist to maintain bone density and lower serum cholesterol. Arzoxifene is a highly effective agent for prevention of mammary cancer induced in the rat by the carcinogen nitrosomethylurea and is significantly more potent than raloxifene in this regard. Arzoxifene is devoid of the uterotrophic effects of tamoxifen, suggesting that, in contrast to tamoxifen, it is unlikely that the clinical use of arzoxifene will increase the risk of developing endometrial carcinoma.
Pharmacotoxicology entails the study of the consequences of toxic exposure to pharmaceutical drugs and agents in the health care field. The field of pharmacotoxicology also involves the treatment and prevention of pharmaceutically induced side effects. Pharmacotoxicology can be separated into two different categories: pharmacodynamics, and pharmacokinetics.
Estetrol (E4), or oestetrol, is one of the four natural estrogenic steroid hormones found in humans, along with estrone (E1), estradiol (E2), and estriol (E3), estetrol is a major estrogen in the body. In contrast to estrone and estradiol, estetrol is a native estrogen of fetal life. Estetrol is produced exclusively by the fetal liver and is found in dectable levels only during pregnancy, with relatively high levels in the fetus and lower levels in the maternal circulation.
In the field of pharmacology, a selective receptor modulator or SRM is a type of drug that has different effects in different tissues. A SRM may behave as an agonist in some tissues while as an antagonist in others. Hence selective receptor modulators are sometimes referred to as tissue selective drugs or mixed agonists / antagonists. This tissue selective behavior is in contrast to many other drugs that behave either as agonists or antagonists regardless of the tissue in question.
Menerba, also known as Menopause Formula 101 (MF-101), is a botanical drug candidate that acts as a selective estrogen receptor modulator (SERM) which is being studied for its potential to relieve hot flashes associated with menopause. Menerba, an estrogen receptor beta (ERβ) agonist (ERBA), is part of a new class of receptor subtype-selective estrogens, which is selective in transcriptional regulation to one of the two known estrogen receptor (ER) subtypes. Menerba consists of 22 herbs that have been used historically in traditional Chinese medicine.
Ospemifene is an oral medication indicated for the treatment of dyspareunia – pain during sexual intercourse – encountered by some women, more often in those who are post-menopausal. Ospemifene is a selective estrogen receptor modulator (SERM) acting similarly to an estrogen on the vaginal epithelium, building vaginal wall thickness which in turn reduces the pain associated with dyspareunia. Dyspareunia is most commonly caused by "vulvar and vaginal atrophy."
A nonsteroidal estrogen is an estrogen with a nonsteroidal chemical structure. The most well-known example is the stilbestrol estrogen diethylstilbestrol (DES). Although nonsteroidal estrogens formerly had an important place in medicine, they have gradually fallen out of favor following the discovery of toxicities associated with high-dose DES starting in the early 1970s, and are now almost never used. On the other hand, virtually all selective estrogen receptor modulators (SERMs) are nonsteroidal, with triphenylethylenes like tamoxifen and clomifene having been derived from DES, and these drugs remain widely used in medicine for the treatment of breast cancer among other indications. In addition to pharmaceutical drugs, many xenoestrogens, including phytoestrogens, mycoestrogens, and synthetic endocrine disruptors like bisphenol A, are nonsteroidal substances with estrogenic activity.
Triparanol was the first synthetic cholesterol-lowering drug. It was patented in 1959 and introduced in the United States 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 effects such as nausea and vomiting, vision loss due to irreversible cataracts, alopecia, skin disorders, and accelerated atherosclerosis. It is now considered to be obsolete.
Bisdehydrodoisynolic acid (BDDA), as the (Z)-isomer ( -BDDA), is a synthetic, nonsteroidal estrogen related to doisynolic acid that was never marketed. It is one of the most potent estrogens known, although it has more recently been characterized as a selective estrogen receptor modulator (SERM). BDDA and other doisynolic acid derivatives display relatively low affinity accompanied by disproportionately high estrogenic potency in vivo, which was eventually determined to be due to transformation into metabolites with greater estrogenic activity. The drug was discovered in 1947 as a degradation product of the reaction of equilenin or dihydroequilenin with potassium hydroxide. It is the seco-analogue of equilenin, while doisynolic acid is the seco-analogue of estrone. These compounds, along with diethylstilbestrol, can be considered to be open-ring analogues of estradiol. The methyl ether of BDDA, doisynoestrol, is also an estrogen, and in contrast to BDDA, has been marketed.