Mifepristone

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Cat Number

API84371653

CAS Number

84371-65-3

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CAS Number

84371-65-3

EINECS

617-559-7

Storage

Store at room temperature

Synonyms

Mifegyne; Mifeprex; RU-486; Korlym; Mifepristona; RU-38486; Mifepristonum

Molecular Formula

C29H35NO2

Molecular Weight

429.6

Smiles

CC#C[C@@]1(CC[C@@H]2[C@@]1(C[C@@H](C3=C4CCC(=O)C=C4CC[C@@H]23)C5=CC=C(C=C5)N(C)C)C)O

Appearance

Pale yellow solid

Melting Point

195-198°C

Boiling Point

628.6°C at 760 mmHg

Relative Density

1.18

General Description

Mifepristone is a synthetic steroid with a dimethylaminophenyl group and a propynyl chain, belonging to the class of 19-norsteroids. Its chemical structure is 11β-[p-(dimethylamino)phenyl]-17β-hydroxy-17α-(1-propynyl)estra-4,9-dien-3-one. Mifepristone is a white to off-white powder, practically insoluble in water but soluble in organic solvents. It is a potent antiprogestin with weak antiglucocorticoid activity.

Mechanism of Action

Mifepristone acts as a competitive antagonist at the progesterone receptor, blocking the action of progesterone and preventing the maintenance of the endometrium. It also has a significant antiglucocorticoid effect by blocking the glucocorticoid receptor, leading to increased ACTH and cortisol secretion. The drug inhibits the action of progesterone on the myometrium and cervix, leading to the termination of pregnancy.

Application

Mifepristone is indicated for the termination of early intrauterine pregnancy (up to 70 days gestation) in combination with misoprostol. It is also used for the management of Cushing's syndrome and for the treatment of uterine fibroids and endometriosis. The drug is also being investigated for the treatment of certain cancers and psychiatric disorders.

This review discusses mifepristone as a potential adjuvant for glioblastoma treatment. Mifepristone, a progesterone/glucocorticoid receptor antagonist, has anti-tumor activity, low cytotoxicity to healthy cells, and modulates chemosensitivity. Adding mifepristone to temozolomide-based therapy may improve patient response, though mechanisms are not fully known.

Fig. 1 Schematic portrayal of resistance mechanisms of glioblastoma. (Llaguno-Munive M, et al., 2021)

References

Llaguno-Munive M, et al. Mifepristone Repurposing in Treatment of High-Grade Gliomas. Front Oncol. 2021;11:606907.

This is the protocol for the CATALYST trial, a two‑part study evaluating hypercortisolism in difficult‑to‑control type 2 diabetes. Part 1 screens ~1000 participants with a 1 mg dexamethasone suppression test. Those with cortisol >1.8 µg/dL proceed to part 2, a randomized double‑blind trial comparing mifepristone (Korlym®) to placebo for 24 weeks. The primary endpoint is change in HbA1c.

Fig. 2 Dexamethasone suppression test (DST) procedure. (DeFronzo RA, et al., 2024)

References

DeFronzo RA, et al. Study protocol for a prospective, multicentre study of hypercortisolism in patients with difficult-to-control type 2 diabetes (CATALYST): prevalence and treatment with mifepristone. BMJ Open. 2024;14(7):e081121.

Does Mifepristone require protection from light during long-term storage?

Yes, it is photosensitive. UV exposure can cause photodegradation and discoloration of the dimethylaminophenyl ring. Store in light-resistant containers, preferably amber glass.

What is the recommended storage temperature for Mifepristone?

Store at controlled room temperature (15-25°C). Avoid excessive heat above 30°C, which can accelerate oxidative degradation.

Is Mifepristone stable in tablet formulations with standard excipients?

Yes, when formulated with moisture-protective packaging.

How is the impurity mifepristone N-oxide (an oxidative degradation product) monitored?

This degradation product is quantified using a stability-indicating HPLC method, ensuring it remains within ICH qualification thresholds.