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 androgen receptor (AR) and/or inhibiting or suppressing androgen production. They can be thought of as the functional opposites of AR agonists, for instance androgens and anabolic steroids (AAS) like testosterone, DHT, and nandrolone and selective androgen receptor modulators (SARMs) like enobosarm. Antiandrogens are one of three types of sex hormone antagonists, the others being antiestrogens and antiprogestogens.
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 osteoporosis and muscle loss while reducing risks of developing prostate cancer. In the late 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. At present, there are no SARMs which have been approved for therapeutic use by the U.S. Food and Drug Administration.
Selective glucocorticoid receptor modulators (SEGRMs) and selective glucocorticoid receptor agonists (SEGRAs) formerly known as dissociated glucocorticoid receptor agonists (DIGRAs) are a class of experimental drugs designed to share many of the desirable anti-inflammatory, immunosuppressive, or anticancer properties of classical glucocorticoid drugs but with fewer side effects such as skin atrophy. Although preclinical evidence on SEGRAMs’ anti-inflammatory effects are culminating, currently, the efficacy of these SEGRAMs on cancer are largely unknown.
Prinaberel is a synthetic, nonsteroidal, and highly selective agonist of the ERβ subtype of the estrogen receptor. It is used in scientific research to elucidate the role of the ERβ receptor. Studies have indicated that selective ERβ agonists like prinaberel could be useful in the clinical treatment of a variety of medical conditions including inflammatory bowel disease, rheumatoid arthritis, endometriosis, and sepsis. Accordingly, prinaberel either was or still is under investigation by Wyeth for the treatment of some of these conditions.
Samidorphan, is an opioid antagonist which in the form of olanzapine/samidorphan is used in the treatment of schizophrenia and bipolar disorder. Samidorphan reduces the weight gain associated with olanzapine. Samidorphan is taken by mouth.
AZD-5423 is a nonsteroidal glucocorticoid and phase II experimental drug being developed by AstraZeneca and disclosed at the spring 2013 American Chemical Society meeting in New Orleans to treat respiratory diseases and in particular chronic obstructive pulmonary disease.
A nonsteroidal antiandrogen (NSAA) is an antiandrogen with a nonsteroidal chemical structure. They are typically selective and full or silent antagonists of the androgen receptor (AR) and act by directly blocking the effects of androgens like testosterone and dihydrotestosterone (DHT). NSAAs are used in the treatment of androgen-dependent conditions in men and women. They are the converse of steroidal antiandrogens (SAAs), which are antiandrogens that are steroids and are structurally related to testosterone.
Relamorelin is a synthetic peptide, centrally penetrant, selective agonist of the ghrelin/growth hormone secretagogue receptor (GHSR) which is under development by Allergan pharmaceuticals for the treatment of diabetic gastroparesis, chronic idiopathic constipation, and anorexia nervosa. It is a pentapeptide and an analogue of ghrelin with improved potency and pharmacokinetics. In humans, relamorelin produces increases in plasma growth hormone, prolactin, and cortisol levels, and, like other GHSR agonists, increases appetite. As of June 2015, relamorelin is in phase II clinical trials for diabetic gastroparesis and constipation. The United States Food and Drug Administration (FDA) has granted Fast Track designation to relamorelin for diabetic gastroparesis.
WAY-214156 is a synthetic nonsteroidal estrogen that acts as a highly selective agonist of the ERβ. It is 100-fold selective for the ERβ over the ERα with an IC50 of 4.2 nM (compare to estradiol with IC50 values of ~3–4 nM for both the ERα and ERβ). The drug is less selective for the ERβ than is prinaberel (ERB-041, WAY-202041), another selective ERβ agonist, but is more potent in comparison. WAY-214156 may produce anti-inflammatory effects via the ERβ and has been proposed as a potential treatment for inflammatory conditions such as rheumatoid arthritis.
Erteberel is a synthetic, nonsteroidal estrogen which acts as a selective ERβ agonist and is under development by Eli Lilly for the treatment of schizophrenia. It is specifically under investigation for the treatment of negative symptoms and cognitive impairment associated with the condition. As of 2015, it is in phase II clinical trials for this indication in the United States. Erteberel was also under investigation for the treatment of benign prostatic hyperplasia and reached phase II clinical studies for this use but failed to improve symptoms in men with the condition and development for this indication was discontinued. The drug has also been proposed as a potential novel treatment for glioblastoma.
Apararenone (INN) is a nonsteroidal antimineralocorticoid which is under development by Mitsubishi Tanabe Pharma for the treatment of diabetic nephropathies and non-alcoholic steatohepatitis. It was also previously being developed for the treatment of hypertension, but development was discontinued for this indication. Apararenone acts as a highly selective antagonist of the mineralocorticoid receptor, the receptor for aldosterone. As of 2017, it is in phase II clinical trials.
Dagrocorat is a nonsteroidal but steroid-like selective glucocorticoid receptor modulator (SGRM) which was under development for the treatment of rheumatoid arthritis but was never marketed. It is described as a partial agonist and "dissociable" agonist of the glucocorticoid receptor. The drug reached phase I clinical trials prior to the discontinuation of its development. The C2α dihydrogen phosphate ester of dagrocorat, fosdagrocorat, was also under investigation, but its development was terminated as well.
Mibampator is a positive allosteric modulator (PAM) of the AMPA receptor (AMPAR), an ionotropic glutamate receptor, which was under development by Eli Lilly for the treatment of agitation/aggression in Alzheimer's disease but was never marketed. It reached phase II clinical trials prior to the discontinuation of its development.
Relacorilant is an antiglucocorticoid which is under development by Corcept Therapeutics for the treatment of Cushing's syndrome. It is also under development for the treatment of solid tumors and alcoholism. The drug is a nonsteroidal compound and acts as an antagonist of the glucocorticoid receptor. As of December 2017, it is in phase II clinical trials for Cushing's syndrome and phase I/II clinical studies for solid tumors, while the clinical phase for alcoholism is unknown.
BMS-641988 is a nonsteroidal antiandrogen which was developed by Bristol-Myers Squibb for the treatment of prostate cancer but was never marketed. It acts as a potent competitive antagonist of the androgen receptor (AR) (Ki = 10 nM; IC50 = 56 nM). The drug was found to have 20-fold higher affinity for the AR than bicalutamide in MDA-MB-453 cells, and showed 3- to 7-fold the antiandrogenic activity of bicalutamide in vitro. It may have some weak partial agonist activity at the androgen receptor. BMS-641988 is transformed by CYP3A4 into BMS-570511, and this metabolite is then reduced to BMS-501949 by cytosolic reductases. All three compounds show similar antiandrogenic activity. In addition to its antiandrogenic activity, BMS-641988 shows activity as a negative allosteric modulator of the GABAA receptor, and can produce seizures in animals at sufficiently high doses. It also shows some drug-induced QT prolongation. BMS-641988 reached phase I clinical trials prior to the discontinuation of its development. The clinical development of BMS-641988 was terminated due to the occurrence of a seizure in a patient during a phase I study.
EM-5854 is a steroidal antiandrogen which was under development by Endoceutics, Inc. for the treatment of prostate cancer. It was first described in a patent in 2008, and was further characterized in 2012. EM-5854 reached phase I/II clinical trials for the treatment of prostate cancer but development was discontinued in March 2019.
β-LGND2, also known as ERβ-selective ligand 2 or as GTx-878, is a synthetic nonsteroidal estrogen and selective ERβ agonist which was under development by GTx for the treatment of benign prostatic hyperplasia, prostatitis, and rheumatoid arthritis but was never marketed. It shows approximately 25-fold selectivity for activation of the ERβ over the ERα (EC50 = 2 nM and 52 nM, respectively). β-LGND2 is an isoquinolinone derivative.
WAY-204688, also known as SIM-688, is a synthetic nonsteroidal estrogen and nuclear factor κB (NF-κB) inhibitor which was originated by ArQule and Wyeth and was under development by Wyeth for the treatment of rheumatoid arthritis, non-specific inflammation, and sepsis but was never marketed. It is a "pathway-selective" estrogen receptor (ER) ligand which inhibits NF-κB with an IC50 of 122 nM and with maximal inhibition relative to estradiol of 94%. Inhibition of NF-κB by WAY-204688 appears to be dependent on agonism of the ERα, as it is reversed by the ERα antagonist fulvestrant, but is not dependent on the ERβ. In contrast to the case of NF-κB inhibition, WAY-204688 produces only slight elevation of creatine kinase in vitro, a measure of classical estradiol effects. It reached phase I clinical trials prior to the discontinuation of its development.
Mevidalen (developmental code name LY-3154207) is a dopaminergic drug which is under development for the treatment of Lewy body disease, including those with Parkinson's disease. It acts as a selective positive allosteric modulator (PAM) of the dopamine D1 receptor. The drug is orally active and crosses the blood–brain barrier. It is a tetrahydroisoquinoline and is a close analogue of DETQ, another D1 receptor PAM. Mevidalen has been found to have wakefulness-promoting effects in sleep-deprived humans. Side effects of mevidalen have been reported to include increased heart rate and blood pressure, insomnia, dizziness, nausea, vomiting, anxiety, nervousness, fatigue, headaches, palpitations, and contact dermatitis, as well as falls in those with dementia. As of March 2022, mevidalen is in phase 2 clinical trials for the treatment of Lewy body disease. Besides for movement disorders and dementia, D1 receptor PAMs like mevidalen might have value in the treatment of certain neuropsychiatric disorders, such as depression, excessive somnolence, and attention deficit hyperactivity disorder.
