Fosfestrol

Fosfestrol, sold under the brand name Honvan and also known as diethylstilbestrol diphosphate (DESDP), is an estrogen medication which is used in the treatment of prostate cancer in men.^[1][2][3] It is given by slow intravenous infusion once per day to once per week or by mouth once per day.^[3][2]

Fosfestrol

Clinical data
Trade names	Honvan, others
Other names	Diethylstilbestrol diphosphate; Stilbestrol diphosphate; DESDP; DESP; DES-DP; DES-P
AHFS/Drugs.com	International Drug Names
Routes of administration	Intravenous, by mouth
Drug class	Nonsteroidal estrogen; Estrogen ester
ATC code	L02AA04 (WHO)
Legal status
Legal status	In general: ℞ (Prescription only)
Identifiers
IUPAC name [4-[4-(4-phosphonooxyphenyl)hex-3-en-3-yl]phenoxy]phosphonic acid
CAS Number	522-40-7 Y 4719-75-9 (tetrasodium)
PubChem CID	3032325
ChemSpider	2297327 Y
UNII	A0E0NMA80F
KEGG	D00946 Y
ChEMBL	ChEMBL1200598 Y
CompTox Dashboard (EPA)	DTXSID3046906
ECHA InfoCard	100.007.573
Chemical and physical data
Formula	C18H22O8P2
Molar mass	428.314 g·mol−1
3D model (JSmol)	Interactive image
SMILES O=P(Oc1ccc(cc1)\C(=C(\c2ccc(OP(=O)(O)O)cc2)CC)CC)(O)O
InChI InChI=1S/C18H22O8P2/c1-3-17(13-5-9-15(10-6-13)25-27(19,20)21)18(4-2)14-7-11-16(12-8-14)26-28(22,23)24/h5-12H,3-4H2,1-2H3,(H2,19,20,21)(H2,22,23,24)/b18-17+ Y Key:NLORYLAYLIXTID-ISLYRVAYSA-N Y
(verify)

Side effects of fosfestrol include nausea and vomiting, cardiovascular complications, blood clots, edema, and genital skin reactions, among others.^[2] Fosfestrol is an estrogen, and hence is an agonist of the estrogen receptor, the biological target of estrogens like estradiol.^[2][1][4] It acts as a prodrug of diethylstilbestrol.^[2][1][5]

Fosfestrol was patented in 1941 and was introduced for medical use in 1955.^[6] It was previously marketed widely throughout the world, but now remains available in only a few countries.^[7][8][6][3]

Medical uses

Fosfestrol is used as a form of high-dose estrogen therapy in the treatment of castration-resistant prostate cancer.^[2] It is added once progression of metastases has occurred following therapy with other interventions such orchiectomy, gonadotropin-releasing hormone modulators, and nonsteroidal antiandrogens.^[2] Fosfestrol has also been used to prevent the testosterone flare at the start of gonadotropin-releasing hormone agonist therapy in men with prostate cancer.^[9]

Fosfestrol sodium is given at a dosage of 600 to 1200 mg/day by slow intravenous infusion over a period of 1 hour for a treatment duration of 5 to 10 days in men with prostate cancer.^[3][2] Following this, it is given at a dose of 300 mg/day for 10 to 20 days.^[3] Maintenance doses of fosfestrol sodium of 300 to 600 mg may be given four times per week.^[3] This may be gradually reduced to one 300 to 600-mg dose per week over a period of several months.^[3]

Fosfestrol sodium is also used to a lesser extent by oral administration initially at a dosage of 360 to 480 mg three times per day in the treatment of prostate cancer.^[3][2] Maintenance doses of 120 to 240 mg three times per day may be used and can be gradually reduced to 240 mg/day.^[3][2]

• v
• t
• e

Estrogen dosages for prostate cancer

Route/form	Estrogen	Dosage
Oral	Estradiol	1–2 mg 3x/day
	Conjugated estrogens	1.25–2.5 mg 3x/day
	Ethinylestradiol	0.15–3 mg/day
	Ethinylestradiol sulfonate	1–2 mg 1x/week
	Diethylstilbestrol	1–3 mg/day
	Dienestrol	5 mg/day
	Hexestrol	5 mg/day
	Fosfestrol	100–480 mg 1–3x/day
	Chlorotrianisene	12–48 mg/day
	Quadrosilan	900 mg/day
	Estramustine phosphate	140–1400 mg/day
Transdermal patch	Estradiol	2–6x 100 μg/day Scrotal: 1x 100 μg/day
IMTooltip Intramuscular or SC injection	Estradiol benzoate	1.66 mg 3x/week
	Estradiol dipropionate	5 mg 1x/week
	Estradiol valerate	10–40 mg 1x/1–2 weeks
	Estradiol undecylate	100 mg 1x/4 weeks
	Polyestradiol phosphate	Alone: 160–320 mg 1x/4 weeks With oral EE: 40–80 mg 1x/4 weeks
	Estrone	2–4 mg 2–3x/week
IV injection	Fosfestrol	300–1200 mg 1–7x/week
	Estramustine phosphate	240–450 mg/day
Note: Dosages are not necessarily equivalent. Sources: See template.

Available forms

Fosfestrol is available in the form of solutions for intravenous administration and tablets for oral administration.^[10]

Side effects

Side effects of fosfestrol include nausea and vomiting in 80% of patients (with 1 in 25 cases, or 4%, resulting in death), cardiovascular complications (18% with fosfestrol plus adriamycin relative to 2% with adriamycin alone) such as thrombosis (2 in 25 cases, or 8%), edema (44% requiring diuretic therapy), and skin reactions such as burning, itching, or pain in the genital area (40%).^[2][1] In addition, weight gain, feminization, and gynecomastia may occur.^[1]

Pharmacology

Pharmacodynamics

Testosterone levels with no treatment and with various estrogens in men with prostate cancer.^[11] Determinations were made with an early radioimmunoassay (RIA).^[11] Source was Shearer et al. (1973).^[11]

Fosfestrol is an estrogen, or an agonist of the estrogen receptors.^[2][1][4] It is inactive itself and acts as a prodrug of diethylstilbestrol.^[2][1][5] Similarly to diethylstilbestrol, fosfestrol has powerful antigonadotropic effects and strongly suppresses testosterone levels in men.^{[2][1][12][13]} It decreases testosterone levels into the castrate range within 12 hours of the initiation of therapy.^[1] Fosfestrol may also act by other mechanisms, such as via direct cytotoxic effects in the prostate gland.^[2][1]

Pharmacokinetics

The pharmacokinetics of fosfestrol have been studied.^[2][14][1]

Chemistry

See also: Nonsteroidal estrogen, Estrogen ester, and List of estrogen esters § Diethylstilbestrol esters

Fosfestrol is a synthetic nonsteroidal estrogen of the stilbestrol group.^[15][3] It is an estrogen ester; specifically, it is the diphosphate ester of diethylstilbestrol.^[15][3]

Fosfestrol is provided both as the free base and as a tetrasodium salt.^[2][3] In terms of dose equivalence, 300 mg anhydrous fosfestrol sodium is equal to about 250 mg fosfestrol.^[3]

A polymer of fosfestrol, polydiethylstilbestrol phosphate, was developed as a long-acting estrogen for potential use in veterinary medicine, but was never marketed.^{[16][17][18][19][20][21]}

History

Fosfestrol was first patented in 1941 and was mentioned in the literature by Huggins.^[6][22] Conjugated estrogens and diethylstilbestrol sulfate, which are water-soluble estrogens, were first reported to be effective in the treatment of prostate cancer via intravenous administration in 1952.^[23][22] Starting in October 1952, Flocks and colleagues studied intravenous fosfestrol in the treatment of prostate cancer, publishing their findings in 1955.^[22] Fosfestrol was first introduced for medical use in 1955 under the brand names Stilphostrol and ST 52 in the United States and France, respectively.^[6]

Society and culture

Generic names

Fosfestrol is the generic name of the drug and its INNTooltip International Nonproprietary Name, BANTooltip British Approved Name, and JANTooltip Japanese Accepted Name, while diethylstilbestrol diphosphate is its USANTooltip United States Adopted Name and fosfestrolo is its DCITTooltip Denominazione Comune Italiana.^{[15][7][8][3]} It is also known as stilbestrol diphosphate.^[15][7][8] Fosfestrol sodium is its INNMTooltip International Nonproprietary Name and BANMTooltip British Approved Name.^{[15][7][8][3]}

Brand names

Brand names of fosfestrol include Cytonal, Difostilben, Honovan, Honvan, Honvol, Honvon, Fosfostilben, Fostrolin, ST 52, Stilbetin, Stilbol, Stilbostatin, Stilphostrol, and Vagestrol, among others.^{[15][7][8][6]}

Availability

Fosfestrol has been marketed widely throughout the world, including in the United States, Canada, Europe, Asia, Latin America, and South Africa, among other areas of the world.^[7][8][3][6] However, today, it appears to remain available only in a few countries, including Bangladesh, Egypt, India, Oman, and Tunisia.^[8][3]

See also

• Estramustine phosphate