Alfatradiol

Last updated • 3 min readFrom Wikipedia, The Free Encyclopedia

Alfatradiol
Alfatradiol skeletal.svg
Alfatradiol 3D ball.png
Clinical data
Trade names Avicis, Avixis, Ell-Cranell Alpha, Pantostin
Other names17α-Estradiol; 17-Epiestradiol; MX-4509; Estra-1,3,5(10)-triene-3,17α-diol; β-Estradiol (obsolete, misleading) [1]
AHFS/Drugs.com International Drug Names
Pregnancy
category
  • No studies
Routes of
administration
Topical
Drug class Estrogen; 5α-Reductase inhibitor
ATC code
  • None
Legal status
Legal status
Identifiers
  • (8R,9S,13S,14S,17R)-13-methyl-6,7,8,9,11,12,14,15,16,17-decahydrocyclopenta[a]phenanthrene-3,17-diol
CAS Number
PubChem CID
ChemSpider
UNII
ChEBI
ChEMBL
Chemical and physical data
Formula C18H24O2
Molar mass 272.388 g·mol−1
3D model (JSmol)
  • OC1CCC3C1(C)CCC(c2cc4)C3CCc2cc4O
  • InChI=1S/C18H24O2/c1-18-9-8-14-13-5-3-12(19)10-11(13)2-4-15(14)16(18)6-7-17(18)20/h3,5,10,14-17,19-20H,2,4,6-9H2,1H3/t14-,15-,16+,17-,18+/m1/s1 Yes check.svgY
  • Key:VOXZDWNPVJITMN-SFFUCWETSA-N Yes check.svgY
   (verify)

Alfatradiol, also known as 17α-estradiol and sold under the brand names Avicis, Avixis, Ell-Cranell Alpha, and Pantostin, is a weak estrogen and 5α-reductase inhibitor medication which is used topically in the treatment of pattern hair loss (androgenic alopecia or pattern baldness) in men and women. [1] [2] [3] [4] It is a stereoisomer of the endogenous steroid hormone and estrogen 17β-estradiol (or simply estradiol). [1]

Contents

Medical uses

Alfatradiol is used in form of an ethanolic solution for topical application on the scalp. Similarly to other drugs against alopecia, topical or oral, it has to be applied continuously to prevent further hair loss. [5] Regrowth of hair that was already lost is only possible to a limited extent. In general, advanced alopecia does not respond well to medical treatment, which has historically been thought to be a consequence of the hair roots being lost. [6]

A university-led study (including several authors who are advisors to companies such as Pfizer) in 103 women comparing alfatradiol to minoxidil, another topical hair loss treatment, found the latter to be more effective. In contrast to minoxidil, alfatradiol did not result in an increase of hair density or thickness, but only in slowing down or stabilization of hair loss in this study. [7] In an earlier study, no systemic side effects were noted, and 17α-estradiol was found to reduce androgenic hair loss, though it was not effective at growing new hair. [8]

Other efforts of alfatradiol had been directed at neurodegenerative diseases including Parkinson's. [9]

Other hair loss medications include ketoconazole, finasteride, and dutasteride.

Contraindications

Nothing is known about the use of alfatradiol during pregnancy or lactation, or in patients under 18 years of age. The package leaflet recommends against using it under these circumstances. [10]

Side effects

Local burning or itching is not an effect of alfatradiol, but of the ethanol in the solvent. The solution can stimulate sebum production. [10]

Pharmacology

Pharmacodynamics

Alfatradiol (top) and 17b-estradiol (bottom). 17-alpha- vs 17-beta-estradiol.svg
Alfatradiol (top) and 17β-estradiol (bottom).

Alfatradiol (17α-estradiol) is distinguished from estradiol (17β-estradiol), the predominant sex hormone in females, only by the stereochemistry of the carbon atom 17. In contrast to 17β-estradiol, 17α-estradiol, while it still binds to the estrogen receptor, has less or no feminizing estrogenic activity depending on its dosage and the tissue it is affecting. [11] Alfatradiol acts as an inhibitor of the enzyme 5α-reductase, which is responsible for the activation of testosterone to dihydrotestosterone, and which plays a role in regulating hair growth. [5] 17α-Estradiol has been studied as a therapeutic with potential to treat Alzheimer's and Parkinson's disease and other patients with neurodegenerative diseases. [12] 17α-Estradiol (as the sodium salt of its sulfated form) is a minor component (<10%) of hormone replacement products (such as conjugated estrogens, brand name Premarin), which have been studied and/or marketed in women and men since the 1930s. A survey of the effects of various forms of 17α-estradiol in humans on biochemical parameters, efficacy, estrogenicity, metabolism, safety, and tolerability has been published. [13]

Alfatradiol binds to the ERα and ERβ with 58% and 11% of the relative binding affinity of 17β-estradiol. [14] However, it has 100-fold lower estrogenic activity relative to estradiol, [15] which may in part be due to differences in the intrinsic activity of the two compounds.[ citation needed ] On the other hand, alfatradiol has been found to bind to and activate the brain-expressed ER-X with a greater potency than estradiol, indicating that it may be the predominant endogenous ligand for the receptor. [16] In contrast to estradiol, alfatradiol is not a ligand of the G protein-coupled estrogen receptor (affinity >10 μM). [17]

Affinities of estrogen receptor ligands for the ERα and ERβ
Ligand Other names Relative binding affinities (RBA, %)a Absolute binding affinities (Ki, nM)aAction
ERα ERβ ERα ERβ
Estradiol E2; 17β-Estradiol1001000.115 (0.04–0.24)0.15 (0.10–2.08)Estrogen
Estrone E1; 17-Ketoestradiol16.39 (0.7–60)6.5 (1.36–52)0.445 (0.3–1.01)1.75 (0.35–9.24)Estrogen
Estriol E3; 16α-OH-17β-E212.65 (4.03–56)26 (14.0–44.6)0.45 (0.35–1.4)0.7 (0.63–0.7)Estrogen
Estetrol E4; 15α,16α-Di-OH-17β-E24.03.04.919Estrogen
Alfatradiol17α-Estradiol20.5 (7–80.1)8.195 (2–42)0.2–0.520.43–1.2Metabolite
16-Epiestriol 16β-Hydroxy-17β-estradiol7.795 (4.94–63)50 ? ?Metabolite
17-Epiestriol 16α-Hydroxy-17α-estradiol55.45 (29–103)79–80 ? ?Metabolite
16,17-Epiestriol 16β-Hydroxy-17α-estradiol1.013 ? ?Metabolite
2-Hydroxyestradiol 2-OH-E222 (7–81)11–352.51.3Metabolite
2-Methoxyestradiol 2-MeO-E20.0027–2.01.0 ? ?Metabolite
4-Hydroxyestradiol 4-OH-E213 (8–70)7–561.01.9Metabolite
4-Methoxyestradiol 4-MeO-E22.01.0 ? ?Metabolite
2-Hydroxyestrone 2-OH-E12.0–4.00.2–0.4 ? ?Metabolite
2-Methoxyestrone 2-MeO-E1<0.001–<1<1 ? ?Metabolite
4-Hydroxyestrone 4-OH-E11.0–2.01.0 ? ?Metabolite
4-Methoxyestrone 4-MeO-E1<1<1 ? ?Metabolite
16α-Hydroxyestrone 16α-OH-E1; 17-Ketoestriol2.0–6.535 ? ?Metabolite
2-Hydroxyestriol 2-OH-E32.01.0 ? ?Metabolite
4-Methoxyestriol 4-MeO-E31.01.0 ? ?Metabolite
Estradiol sulfate E2S; Estradiol 3-sulfate<1<1 ? ?Metabolite
Estradiol disulfate Estradiol 3,17β-disulfate0.0004 ? ? ?Metabolite
Estradiol 3-glucuronide E2-3G0.0079 ? ? ?Metabolite
Estradiol 17β-glucuronide E2-17G0.0015 ? ? ?Metabolite
Estradiol 3-gluc. 17β-sulfate E2-3G-17S0.0001 ? ? ?Metabolite
Estrone sulfate E1S; Estrone 3-sulfate<1<1>10>10Metabolite
Estradiol benzoate EB; Estradiol 3-benzoate10 ? ? ?Estrogen
Estradiol 17β-benzoate E2-17B11.332.6 ? ?Estrogen
Estrone methyl ether Estrone 3-methyl ether0.145 ? ? ?Estrogen
ent-Estradiol 1-Estradiol1.31–12.349.44–80.07 ? ?Estrogen
Equilin 7-Dehydroestrone13 (4.0–28.9)13.0–490.790.36Estrogen
Equilenin 6,8-Didehydroestrone2.0–157.0–200.640.62Estrogen
17β-Dihydroequilin 7-Dehydro-17β-estradiol7.9–1137.9–1080.090.17Estrogen
17α-Dihydroequilin 7-Dehydro-17α-estradiol18.6 (18–41)14–320.240.57Estrogen
17β-Dihydroequilenin 6,8-Didehydro-17β-estradiol35–6890–1000.150.20Estrogen
17α-Dihydroequilenin 6,8-Didehydro-17α-estradiol20490.500.37Estrogen
Δ8-Estradiol 8,9-Dehydro-17β-estradiol68720.150.25Estrogen
Δ8-Estrone 8,9-Dehydroestrone19320.520.57Estrogen
Ethinylestradiol EE; 17α-Ethynyl-17β-E2120.9 (68.8–480)44.4 (2.0–144)0.02–0.050.29–0.81Estrogen
Mestranol EE 3-methyl ether ?2.5 ? ?Estrogen
Moxestrol RU-2858; 11β-Methoxy-EE35–435–200.52.6Estrogen
Methylestradiol 17α-Methyl-17β-estradiol7044 ? ?Estrogen
Diethylstilbestrol DES; Stilbestrol129.5 (89.1–468)219.63 (61.2–295)0.040.05Estrogen
Hexestrol Dihydrodiethylstilbestrol153.6 (31–302)60–2340.060.06Estrogen
Dienestrol Dehydrostilbestrol37 (20.4–223)56–4040.050.03Estrogen
Benzestrol (B2) 114 ? ? ?Estrogen
Chlorotrianisene TACE1.74 ?15.30 ?Estrogen
Triphenylethylene TPE0.074 ? ? ?Estrogen
Triphenylbromoethylene TPBE2.69 ? ? ?Estrogen
Tamoxifen ICI-46,4743 (0.1–47)3.33 (0.28–6)3.4–9.692.5SERM
Afimoxifene 4-Hydroxytamoxifen; 4-OHT100.1 (1.7–257)10 (0.98–339)2.3 (0.1–3.61)0.04–4.8SERM
Toremifene 4-Chlorotamoxifen; 4-CT ? ?7.14–20.315.4SERM
Clomifene MRL-4125 (19.2–37.2)120.91.2SERM
Cyclofenil F-6066; Sexovid151–152243 ? ?SERM
Nafoxidine U-11,000A30.9–44160.30.8SERM
Raloxifene 41.2 (7.8–69)5.34 (0.54–16)0.188–0.5220.2SERM
Arzoxifene LY-353,381 ? ?0.179 ?SERM
Lasofoxifene CP-336,15610.2–16619.00.229 ?SERM
Ormeloxifene Centchroman ? ?0.313 ?SERM
Levormeloxifene 6720-CDRI; NNC-460,0201.551.88 ? ?SERM
Ospemifene Deaminohydroxytoremifene0.82–2.630.59–1.22 ? ?SERM
Bazedoxifene  ? ?0.053 ?SERM
Etacstil GW-56384.3011.5 ? ?SERM
ICI-164,384 63.5 (3.70–97.7)1660.20.08Antiestrogen
Fulvestrant ICI-182,78043.5 (9.4–325)21.65 (2.05–40.5)0.421.3Antiestrogen
Propylpyrazoletriol PPT49 (10.0–89.1)0.120.4092.8ERα agonist
16α-LE2 16α-Lactone-17β-estradiol14.6–570.0890.27131ERα agonist
16α-Iodo-E2 16α-Iodo-17β-estradiol30.22.30 ? ?ERα agonist
Methylpiperidinopyrazole MPP110.05 ? ?ERα antagonist
Diarylpropionitrile DPN0.12–0.256.6–1832.41.7ERβ agonist
8β-VE2 8β-Vinyl-17β-estradiol0.3522.0–8312.90.50ERβ agonist
Prinaberel ERB-041; WAY-202,0410.2767–72 ? ?ERβ agonist
ERB-196 WAY-202,196 ?180 ? ?ERβ agonist
Erteberel SERBA-1; LY-500,307 ? ?2.680.19ERβ agonist
SERBA-2  ? ?14.51.54ERβ agonist
Coumestrol 9.225 (0.0117–94)64.125 (0.41–185)0.14–80.00.07–27.0Xenoestrogen
Genistein 0.445 (0.0012–16)33.42 (0.86–87)2.6–1260.3–12.8Xenoestrogen
Equol 0.2–0.2870.85 (0.10–2.85) ? ?Xenoestrogen
Daidzein 0.07 (0.0018–9.3)0.7865 (0.04–17.1)2.085.3Xenoestrogen
Biochanin A 0.04 (0.022–0.15)0.6225 (0.010–1.2)1748.9Xenoestrogen
Kaempferol 0.07 (0.029–0.10)2.2 (0.002–3.00) ? ?Xenoestrogen
Naringenin 0.0054 (<0.001–0.01)0.15 (0.11–0.33) ? ?Xenoestrogen
8-Prenylnaringenin 8-PN4.4 ? ? ?Xenoestrogen
Quercetin <0.001–0.010.002–0.040 ? ?Xenoestrogen
Ipriflavone <0.01<0.01 ? ?Xenoestrogen
Miroestrol 0.39 ? ? ?Xenoestrogen
Deoxymiroestrol 2.0 ? ? ?Xenoestrogen
β-Sitosterol <0.001–0.0875<0.001–0.016 ? ?Xenoestrogen
Resveratrol <0.001–0.0032 ? ? ?Xenoestrogen
α-Zearalenol 48 (13–52.5) ? ? ?Xenoestrogen
β-Zearalenol 0.6 (0.032–13) ? ? ?Xenoestrogen
Zeranol α-Zearalanol48–111 ? ? ?Xenoestrogen
Taleranol β-Zearalanol16 (13–17.8)140.80.9Xenoestrogen
Zearalenone ZEN7.68 (2.04–28)9.45 (2.43–31.5) ? ?Xenoestrogen
Zearalanone ZAN0.51 ? ? ?Xenoestrogen
Bisphenol A BPA0.0315 (0.008–1.0)0.135 (0.002–4.23)19535Xenoestrogen
Endosulfan EDS<0.001–<0.01<0.01 ? ?Xenoestrogen
Kepone Chlordecone0.0069–0.2 ? ? ?Xenoestrogen
o,p'-DDT 0.0073–0.4 ? ? ?Xenoestrogen
p,p'-DDT 0.03 ? ? ?Xenoestrogen
Methoxychlor p,p'-Dimethoxy-DDT0.01 (<0.001–0.02)0.01–0.13 ? ?Xenoestrogen
HPTE Hydroxychlor; p,p'-OH-DDT1.2–1.7 ? ? ?Xenoestrogen
Testosterone T; 4-Androstenolone<0.0001–<0.01<0.002–0.040>5000>5000Androgen
Dihydrotestosterone DHT; 5α-Androstanolone0.01 (<0.001–0.05)0.0059–0.17221–>500073–1688Androgen
Nandrolone 19-Nortestosterone; 19-NT0.010.2376553Androgen
Dehydroepiandrosterone DHEA; Prasterone0.038 (<0.001–0.04)0.019–0.07245–1053163–515Androgen
5-Androstenediol A5; Androstenediol6173.60.9Androgen
4-Androstenediol 0.50.62319Androgen
4-Androstenedione A4; Androstenedione<0.01<0.01>10000>10000Androgen
3α-Androstanediol 3α-Adiol0.070.326048Androgen
3β-Androstanediol 3β-Adiol3762Androgen
Androstanedione 5α-Androstanedione<0.01<0.01>10000>10000Androgen
Etiocholanedione 5β-Androstanedione<0.01<0.01>10000>10000Androgen
Methyltestosterone 17α-Methyltestosterone<0.0001 ? ? ?Androgen
Ethinyl-3α-androstanediol 17α-Ethynyl-3α-adiol4.0<0.07 ? ?Estrogen
Ethinyl-3β-androstanediol 17α-Ethynyl-3β-adiol505.6 ? ?Estrogen
Progesterone P4; 4-Pregnenedione<0.001–0.6<0.001–0.010 ? ?Progestogen
Norethisterone NET; 17α-Ethynyl-19-NT0.085 (0.0015–<0.1)0.1 (0.01–0.3)1521084Progestogen
Norethynodrel 5(10)-Norethisterone0.5 (0.3–0.7)<0.1–0.221453Progestogen
Tibolone 7α-Methylnorethynodrel0.5 (0.45–2.0)0.2–0.076 ? ?Progestogen
Δ4-Tibolone 7α-Methylnorethisterone0.069–<0.10.027–<0.1 ? ?Progestogen
3α-Hydroxytibolone 2.5 (1.06–5.0)0.6–0.8 ? ?Progestogen
3β-Hydroxytibolone 1.6 (0.75–1.9)0.070–0.1 ? ?Progestogen
Footnotes:a = (1) Binding affinity values are of the format "median (range)" (# (#–#)), "range" (#–#), or "value" (#) depending on the values available. The full sets of values within the ranges can be found in the Wiki code. (2) Binding affinities were determined via displacement studies in a variety of in-vitro systems with labeled estradiol and human ERα and ERβ proteins (except the ERβ values from Kuiper et al. (1997), which are rat ERβ). Sources: See template page.
Selected biological properties of endogenous estrogens in rats
Estrogen ER Tooltip Estrogen receptor RBA Tooltip relative binding affinity (%) Uterine weight (%) Uterotrophy LH Tooltip Luteinizing hormone levels (%) SHBG Tooltip Sex hormone-binding globulin RBA Tooltip relative binding affinity (%)
Control100100
Estradiol (E2) 100506 ± 20+++12–19100
Estrone (E1) 11 ± 8490 ± 22+++ ?20
Estriol (E3) 10 ± 4468 ± 30+++8–183
Estetrol (E4) 0.5 ± 0.2 ?Inactive ?1
17α-Estradiol4.2 ± 0.8 ? ? ? ?
2-Hydroxyestradiol 24 ± 7285 ± 8+b31–6128
2-Methoxyestradiol 0.05 ± 0.04101Inactive ?130
4-Hydroxyestradiol 45 ± 12 ? ? ? ?
4-Methoxyestradiol 1.3 ± 0.2260++ ?9
4-Fluoroestradiol a180 ± 43 ?+++ ? ?
2-Hydroxyestrone 1.9 ± 0.8130 ± 9Inactive110–1428
2-Methoxyestrone 0.01 ± 0.00103 ± 7Inactive95–100120
4-Hydroxyestrone 11 ± 4351++21–5035
4-Methoxyestrone 0.13 ± 0.04338++65–9212
16α-Hydroxyestrone 2.8 ± 1.0552 ± 42+++7–24<0.5
2-Hydroxyestriol 0.9 ± 0.3302+b ? ?
2-Methoxyestriol 0.01 ± 0.00 ?Inactive ?4
Notes: Values are mean ± SD or range. ERRBA = Relative binding affinity to estrogen receptors of rat uterine cytosol. Uterine weight = Percentage change in uterine wet weight of ovariectomized rats after 72 hours with continuous administration of 1 μg/hour via subcutaneously implanted osmotic pumps. LH levels = Luteinizing hormone levels relative to baseline of ovariectomized rats after 24 to 72 hours of continuous administration via subcutaneous implant. Footnotes:a = Synthetic (i.e., not endogenous). b = Atypical uterotrophic effect which plateaus within 48 hours (estradiol's uterotrophy continues linearly up to 72 hours). Sources: See template.

Society and culture

Generic names

Alfatradiol is the generic name of the drug and its INN Tooltip International Nonproprietary Name. [2] It is also known as 17α-estradiol. [1]

Brand names

Alfatradiol is marketed under the brand names Avicis, Avixis, Ell-Cranell Alpha, and Pantostin. [2]

Availability

Alfatradiol is available in Germany and several Latin American countries, including Argentina, Brazil, and Mexico.

Research

Alfatradiol administered systemically improved metabolic function, reduced insulin resistance, decreased intra-abdominal fat, and decreased inflammation in old male mice without inducing feminization, suggesting potential usefulness in the treatment of type 2 diabetes. [18]

See also

Related Research Articles

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<span class="mw-page-title-main">5α-Dihydroethisterone</span> Chemical compound

5α-Dihydroethisterone is an active metabolite of the formerly clinically used but now-discontinued progestin ethisterone and the experimental and never-marketed hormonal antineoplastic agent ethynylandrostanediol (HE-3235). Its formation from its parent drugs is catalyzed by 5α-reductase in tissues that express the enzyme in high amounts like the liver, skin, hair follicles, and prostate gland. 5α-DHET has significant affinity for steroid hormone receptors and may contribute importantly to the activities of its parent drugs.

<span class="mw-page-title-main">17α-Ethynyl-3β-androstanediol</span> Chemical compound

17α-Ethynyl-3β-androstanediol is a synthetic estrogen and a 17α-substituted derivative of 3β-androstanediol which was never marketed.

<span class="mw-page-title-main">Minoxidil sulfate</span> Chemical compound

Minoxidil sulfate, also known as minoxidil sulfate ester or minoxidil N-O-sulfate, is an active metabolite of minoxidil and is the active form of this agent. Minoxidil acts as a prodrug of minoxidil sulfate. Minoxidil sulfate is formed from minoxidil via sulfotransferase enzymes, with the predominant enzyme responsible, at least in hair follicles, being SULT1A1. Minoxidil sulfate acts as a potassium channel opener, among other actions, and has vasodilating, hypotensive, and trichogenic or hypertrichotic effects. Its mechanism of action in terms of hair growth is still unknown, although multiple potential mechanisms have been implicated.

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