Progesterone receptor (PR; IC50 = 0.2 nM for PR in T47D cells); glucocorticoid receptor (GR; IC50 = 2.6 nM for GR in A549 cells); Endogenous Metabolite

Extensive research on more potent and selective antiprogestins was sparked by the discovery of mifepristone, the first competitive progesterone antagonist [1]. After four days of exposure to 10 μM mifepristone, which is near to plasma amounts that humans can achieve, cell growth was measured. NSC 119875 has a stronger antiproliferative effect on HeLa cells when coupled with mifepristone. The IC50 of NSC 119875 plus mifepristone (14.2 μM) in HeLa cells was less than that of NSC 119875 alone (34.2 μM), a roughly 2.5-fold difference. Mifepristone treatment caused NSC 119875 accumulation in HeLa cells to increase twofold above NSC 119875 alone, with a significant difference (p=0.009) from 0.79 to 1.52 μg/mg protein[2].

When NSC 119875 is used in isolation to treat cervical tumor xenograft animals, tumor development is inhibited in comparison to the control group. By the end of the research, the combination of NSC 119875 and Mifepristone at the doses employed resulted in an even more substantial (p<0.05) drop in tumor weight, with a fall of almost 50% when compared to the therapies alone[2]. A 4-day binge-like EtOH dosing regimen (3 to 5 g/kg/ig every 8 hours) is administered to adult male Sprague-Dawley rats in order to achieve peak blood EtOH levels (BELs) of less than 300 mg/dL. Animal subgroups are injected subcutaneously with Mifepristone (20 or 40 mg/kg in peanut oil). While pretreatment with Mifepristone (40 mg/kg) greatly lessens the severity of EtOH withdrawal, Mifepristone itself does not appreciably alter the behavior of animals that have never used EtOH. There is a noteworthy interaction between drug and food (F(5,55)=3.92, p<0.05), wherein mice treated with EtOH and given either vehicle or 20 mg/kg of Mifepristone exhibit considerably higher indications of EtOH withdrawal compared to animals treated with EtOH without EtOH. Significantly, and in a dose-dependent manner, therapy with 40 mg/kg of mifepristone lessens the severity of EtOH withdrawal[3].

A new series of phosphorus-containing 11beta-aryl-substituted steroids have been synthesized in an eight-step sequence involving a palladium-catalyzed coupling reaction to introduce a phosphorus group onto the aromatic ring. The compounds were evaluated for progesterone receptor (PR) antagonist activity in a T47D cell-based assay and for glucocorticoid receptor (GR) antagonist activity in an A549 cell-based assay. The structure-activity relationships of these compounds are discussed. Selected compounds were tested in vivo in a rat complement C3 assay[1].

We investigated the ability of mifepristone, an anti-progestin drug, to modulate the cytotoxic effect of cisplatin in two cervical cancer cell lines and in human xenograft cervical tumors. The effect of cisplatin alone or combined with mifepristone on cellular proliferation was studied with the XTT assay which use a tetrazolium dye {sodium3'-[1-(phenylamino-carbonyl)-3,4-tetrazolium],XTT}. Before and after treatment with mifepristone, the intracellular accumulation of cisplatin in cancer cells and tumors of mice was evaluated by HPLC. The expression of Bcl-2 and Bax genes was also assessed by a reverse transcriptase polymerase chain reaction (RT-PCR) and Western blotting. In addition, single agents and combination treatment in vivo studies were performed with the xenograft cervical model. Tumor measurements were carried out weekly. Analysis of the data by the isobologram method shows a synergistic antiproliferative effect produced by the combination of mifepristone with cisplatin only in the HeLa cervical cancer cell line but not in CaSki cells. The effect of mifepristone on cytotoxicity of cisplatin could be mediated, at least partially, by an increase of intracellular cisplatin accumulation, but not by changes in Bcl-2/Bax gene relation expression in these cells[2].

Adult male Sprague-Dawley rats were subjected to a 4-day binge-like EtOH administration regimen (3 to 5 g/kg/i.g. every 8 hours designed to produce peak blood EtOH levels (BELs) of <300 mg/dl). Subgroups of animals received s.c. injection of the GR antagonist mifepristone (20 or 40 mg/kg in peanut oil at 0800 hours on each of the 4 days prior to withdrawal). BELs were assessed at 0900 and 1500 hours on Days 2 (D2) and 4 (D4) of the regimen. BEL, blood corticosterone levels (BCLs), and EtOH withdrawal-associated behavioral abnormalities were assessed 10 to 12 hours after the final EtOH administration. Results: Daily mean EtOH doses for D1 to D4 of the regimen were 14.4, 9.9, 7.1, and 8.6 g/kg, respectively. The EtOH gavage regimen produced mean BELs of 255 mg/dl at 0900 on D2 and 156.2 mg/dl at 0900 on D4 of the regimen. Withdrawal from the EtOH exposure regimen, beginning 10 hours after the last EtOH administration, produced significant elevations in BCL and behavioral abnormalities including tremors, stereotypy, and "wet dog shakes." Mifepristone administration did not alter food intake or weight during the 4-day regimen, nor were there drug-dependent differences in BEL or BCL on withdrawal day. Although mifepristone produced no significant changes in behavior of EtOH-naïve animals, pretreatment with mifepristone (40 mg/kg) significantly reduced the severity of EtOH withdrawal.[3]

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In vivo studies showed that the combination of these agents has a significant antitumor activity against HeLa xenograft tumors. Our results suggest that mifepristone can improve the efficacy of the antiproliferative effect of cisplatin in vitro and in vivo. This anti-hormonal drug therapy may be a useful candidate for further evaluation in combination with other antineoplastic drugs in the treatment of cancer, particularly with cisplatin.[2]

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Formulated in Constant release pellets; 0.5 or 1 mg/day; Implanted s.c. with pellets

SK-OV-3 ovarian cancer cells are injected into immunosuppressed mice.

Absorption, Distribution and Excretion
The absolute bioavailability of a 20 mg oral dose is 69%
Fecal: 83%; Renal: 9%.
The absolute bioavailability of oral mifepristone is 69%.
Protein binding: Very high (98%); predominantly to albumin and alpha1- acid glycoprotein.
Time to peak concentration: 90 minutes after a 600 mg oral dose.
Peak plasma concentration: 1.98 mg/L following a single 600 mg oral dose.
Fecal; 83% of a 600 mg dose over 11 days. Renal; 9% of a 600 mg dose over 11 days.

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Metabolism / Metabolites
Hepatic. Hepatic, by Cytochrome P450 3A4 isoenzyme to the N-monodemethylated metabolite (RU 42 633); RU 42 698, which results from the loss of two methyl groups from position 11 beta; and RU 42 698, which results from terminal hydroxylation of the 17–propynyl chain.
Hepatic, by Cytochrome P450 3A4 isoenzyme to the N-monodemethylated metabolite (RU 42 633); RU 42 698, which results from terminal hydroxylation of the 17-propynyl chain.
Mifepristone has known human metabolites that include Monodemethylated mifepristone and 17alpha-hydroxymifepristone.
Hepatic. Hepatic, by Cytochrome P450 3A4 isoenzyme to the N-monodemethylated metabolite (RU 42 633); RU 42 698, which results from the loss of two methyl groups from position 11 beta; and RU 42 698, which results from terminal hydroxylation of the 17–propynyl chain.
Route of Elimination: Fecal: 83%; Renal: 9%.
Half Life: 18 hours

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Biological Half-Life
18 hours
Terminal: 18 hours; begins slowly and becomes more rapid with time.

Toxicity Summary
Mifepristone is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death. Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.

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Interactions
Excessive bleeding may occur with concomitant use of anticoagulant therapy and mifepristone.

[1]. Jiang W, et al. New progesterone receptor antagonists: phosphorus-containing 11beta-aryl-substituted steroids. Bioorg Med Chem. 2006 Oct 1;14(19):6726-32.
[2]. Jurado R, et al. NSC 119875 cytotoxicity is increased by mifepristone in cervical carcinoma: an in vitro and in vivo study. Oncol Rep. 2009 Nov;22(5):1237-45.
[3]. Sharrett-Field L, et al. Mifepristone Pretreatment Reduces Ethanol Withdrawal Severity In Vivo. Alcohol Clin Exp Res. 2013 Aug;37(8):1417-23.
[4]. Yuehua You, et al. Progesterone Promotes Endothelial Nitric Oxide Synthase Expression Through Enhancing Nuclear Progesterone receptor-SP1 Formation. Am J Physiol Heart Circ Physiol. 2020 Jul 3

Therapeutic Uses
Abortifacient Agents, Steroidal; Contraceptives, Oral, Synthetic; Contraceptives, Postcoital, Synthetic; Hormone Antagonists; Luteolytic Agents; Menstruation-Inducing Agents
Mifepristone is indicated in combination with misoprostol for the medical termination of intrauterine pregnancy of 49 days duration or less. /Included in US product labeling/

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Drug Warnings
Confirmed or suspected ectopic pregnancy, undiagnosed adnexal mass, or IUD currently in place. Chronic adrenal failure or concurrent long-term corticosteroid therapy. Known hypersensitivity to mifepristone, misoprostol, or other prostaglandins. Hemorrhagic disorders, inherited porphyrias, or concurrent anticoagulant therapy.
Vaginal bleeding that is heavier than associated with a normal menses occurs in almost all women receiving mifepristone and misoprostol. Based on clinical studies, bleeding or spotting should be expected for an average of 9-16 days. ... Excessive bleeding may require treatment with vasoconstrictors, saline infusions, and/or blood transfusions or curettage.
Severe vaginal bleeding may occur following spontaneous, surgical, or medical abortion (including following mifepristone administration). Prolonged heavy vaginal bleeding (i.e. soaking through 2 thick full-size sanitary pads per hour for 2 consecutive hours) may be a sign of incomplete abortion or other complications, and prompt medical or surgical intervention maybe required to prevent the development of hypovolemic shock. Patients should be advised to seek immediate medical attention if prolonged heavy vaginal bleeding or syncope occurs following mifepristone administration.
Serious bacterial infections (including very rare cases of fatal septic shock) have been reported following mifepristone administration; a causal relationship to the mifepristone-misoprostol regimen has not been established. Clinicians should consider the possibility of infection if sustained fever (temperature of 38 degrees C or higher persisting for more than 4 hours), severe abdominal pain, or pelvic tenderness occurs within several days of medical abortion. Atypical presentations of serious infection and sepsis (i.e., presence of significant leukocytosis, tachycardia, or hemoconcentration without fever, severe abdominal pain, pelvic tenderness) may also occur.
For more Drug Warnings (Complete) data for MIFEPRISTONE (14 total), please visit the HSDB record page.

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Pharmacodynamics
Mifepristone is a synthetic steroid with antiprogestational effects indicated for the medical termination of intrauterine pregnancy through 49 days' pregnancy. Doses of 1 mg/kg or greater of mifepristone have been shown to antagonize the endometrial and myometrial effects of progesterone in women. During pregnancy, the compound sensitizes the myometrium to the contraction-inducing activity of prostaglandins. Mifepristone also exhibits antiglucocorticoid and weak antiandrogenic activity. The activity of the glucocorticoid dexamethasone in rats was inhibited following doses of 10 to 25 mg/kg of mifepristone. Doses of 4.5 mg/kg or greater in human beings resulted in a compensatory elevation of adrenocorticotropic hormone (ACTH) and cortisol.

C29H35NO2

429.59

429.266

C, 81.08; H, 8.21; N, 3.26; O, 7.45

84371-65-3

Mifepristone (Standard); 84371-65-3; Mifepristone-d3;Mifepristone-13C,d3; 109345-60-0 (methochloride)

55245

Yellow powder

1.2±0.1 g/cm3

628.6±55.0 °C at 760 mmHg

195-198°C

334.0±31.5 °C

0.0±1.9 mmHg at 25°C

1.623

4.95

1

3

3

32

921

5

C[C@@]12[C@](O)(C#CC)CC[C@H]1[C@@H]1CCC3=CC(CCC3=C1[C@@H](C1C=CC(N(C)C)=CC=1)C2)=O

VKHAHZOOUSRJNA-GCNJZUOMSA-N

InChI=1S/C29H35NO2/c1-5-15-29(32)16-14-26-24-12-8-20-17-22(31)11-13-23(20)27(24)25(18-28(26,29)2)19-6-9-21(10-7-19)30(3)4/h6-7,9-10,17,24-26,32H,8,11-14,16,18H2,1-4H3/t24-,25+,26-,28-,29-/m0/s1

(8S,11R,13S,14S,17S)-11-(4-(dimethylamino)phenyl)-17-hydroxy-13-methyl-17-(prop-1-yn-1-yl)-6,7,8,11,12,13,14,15,16,17-decahydro-1H-cyclopenta[a]phenanthren-3(2H)-one

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

Solubility in Formulation 1: ≥ 2.5 mg/mL (5.82 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (5.82 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.5 mg/mL (5.82 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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Solubility in Formulation 4: 10 mg/mL (23.28 mM) in 0.5% CMC-Na/saline water (add these co-solvents sequentially from left to right, and one by one), suspension solution; with ultrasonication.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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 (Please use freshly prepared in vivo formulations for optimal results.)