Effect of daily low dose mifepristone on the ovarian cycle and on dynamics of follicle growth

The immninent dawn of SPRMs in obstetrics and gynecology

Selective progesterone receptor modulators (SPRMs) have been developed since the late 70s when mifepristone was first described. They act through nuclear progesterone receptors and can have agonist or mixed agonist antagonist actions depending on the cell and tissue. Mifepristone has unique major antagonist properties allowing its use for pregnancy termination. Ulipristal acetate has been marketed in 2009 for emergency contraception and has been recently approved for preoperative myoma treatment. Further perspectives for SPRMs use include long term estrogen free contraception, endometriosis treatment. However long term applications will be possible only after confirmation of endometrial safety.

Effects of antiprogestins on the uterus

Progesterone-receptor modulators (PRMs) are progesterone-receptor ligands that can exert agonistic, antagonistic or mixed agonist-antagonist effects depending on the cellular context. The mechanisms of action of these compounds are still incompletely understood. PRMs already have several applications in women's health such as emergency contraception, pregnancy termination, management of early fetal demise and cervical maturation. The main indications that will be developed in the future include dysfunctional bleeding and preoperative treatment of uterine myomas. Other future indications may include estrogen-free contraception, treatment of endometriosis and prevention and treatment of breast cancer. However, the available data from mid- to long-term continuous administration studies has raised the issue of endometrial safety. For this reason, long-term applications of PRMs are currently postponed, although windows of treatment with a short course of progestin therapy, or even by a short interruption of treatment, could improve endometrial aspects if needed.

[Role of mifepristone for the treatment of uterine fibroid]

Mifepristone, a progesterone receptor antagonist steroid, can reduce uterine fibroid tumours' growth by several pathways. Its efficiency has been widely evaluated in symptomatic patients for more than 10 years. A significant decrease in fibroid tumours and uterine volume concomitant with better quality of life scores can be obtained with a daily administration of Mifepristone 5mg. Mifepristone can be compared with GnRH agonists in terms of efficiency. Observed adverse outcomes are hot flushes (38%), elevated hepatic enzymes (4%) and benign endometrial hyperplasia (28%). Hot flushes and endometrial hyperplasia are not observed with 5mg daily doses. Data suggest that many invasive procedures could be avoided with the routine use of Mifepristone for fibroid tumours care. However, published study periods are only three to 12 months: long lasting evaluation in larger groups of patients seems necessary before this treatment could be proposed as routine care.

Progesterone receptor modulators and the endometrium: changes and consequences

Progesterone receptor modulators (PRMs) have been used for contraceptive research, as well as for treatment of fibroids, endometriosis and heavy or irregular menstrual bleeding. Long-term treatment with these compounds results in changes to the endometrium resulting in potential confusion in trying to characterize endometrial biopsies. A meeting was held to discuss the properties of PRMs, the effects of perturbed hormonal control of the endometrium and the need for further understanding of the biology of progesterone receptor action to facilitate the development of new PRMs. A panel of pathologists was convened to evaluate endometrial changes associated with a minimum of three months of chronic treatment with PRMs. Four different agents were used in the treatment regimens but the pathologists were blinded to treatment regimen or agent. The panel agreed that the endometrial biopsies did not fit into a classification of either proliferative or secretory endometrium but exhibited an unusual architecture that could be characterized as glandular dilatation. There was little evidence of mitosis, consistent with a proposed anti-proliferative effect of PRMs. The panel concluded that the biopsies did not reveal evidence of safety concern and that pathologists and investigators familiar with endometrial effects of chronic PRM exposure should consider working with pharmaceutical companies and regulatory agencies to develop standard descriptions of PRM-associated endometrial changes as well as the types of histologic changes that would signal a need for intervention.

Changes in vaginal morphology, steroid receptor and natural antimicrobial content following treatment with low-dose mifepristone

BACKGROUND

We have previously shown that the antigestagen mifepristone is contraceptive when given in a daily dose of 5 mg, po. Epidemiological studies suggest that gestagen-only contraceptives may increase the risk of transmission of human immunodeficiency virus (HIV) due to effects on the vaginal defenses to infection. We investigate the effects of mifepristone on vaginal thickness, steroid receptor and natural antimicrobial content and pharmacokinetics of mifepristone.

METHODS

In a pilot study, eight women were given mifepristone 5 mg/day for an average of 33 days. Ovarian function was assessed by measurement of estradiol and progesterone in blood and their metabolites in urine and by serial ultrasound of their ovaries. Vaginal biopsies were collected before (late proliferative) and after taking mifepristone.

RESULTS

All subjects showed a similar pattern of descending serum concentrations of mifepristone. The elimination phase half-life was 18+/-5.1 h (mean+/-SD). Mean Cmax measured at 1 h was 641.7 nmol/L (range, 502-740 nmol/L). All eight women reported amenorrhea for the duration of treatment and seven of eight women showed biochemical and ultrasound evidence of anovulation. There was no significant change in vaginal thickness following treatment [342+/-40 microm pretreatment, 303+/-69 microm posttreatment (mean+/-SEM); p>.05]. Estrogen (ERalpha, ERbeta) and androgen receptor were expressed in both vaginal epithelium and subepithelial stroma, whereas progesterone receptor was expressed predominantly in the subepithelial stroma. There was no change in receptor content and distribution following mifepristone treatment. Natural antimicrobial mRNA [secretory leukocyte protease inhibitor, human beta defensins mRNA (HBD1, HBD2, HBD3, HBD5), granulysin and elafin] was extracted from the vaginal tissues, and the content was unaffected by mifepristone treatment.

CONCLUSION

The absence of changes in vaginal thickness, steroid receptor and natural antimicrobial content and its distribution in this preliminary study suggests that in contrast to other estrogen-free contraceptives, mifepristone is unlikely to be associated with the increased risk of transmission of HIV and other sexually transmitted infections.

Management of patients receiving long-term treatment with mifepristone

OBJECTIVE

To determine clinical side effects and biochemical and hematological abnormalities in patients with nonresectable meningioma on long-term mifepristone (RU 486) therapy.

DESIGN

Long-term mifepristone administration in patients with meningioma.

SETTING

Outpatient clinic of a university hospital.

PATIENT(S)

Sixteen women and 9 men aged 22-80 years with nonresectable meningioma.

INTERVENTION(S)

Mifepristone (200 mg daily). One patient received treatment for more than 13 years; six received treatment for 10-12 years; five received treatment for 4-9 years; eight received treatment for 1-4 years; and the remainder received treatment for 4-10 months.

MAIN OUTCOME MEASURE(S)

Evaluation of side effects and of hematological and biochemical abnormalities.

RESULT(S)

Fatigue was observed in 22 of 25 patients. Endometrial hyperplasia occurred in one premenopausal woman and one postmenopausal woman. Another two women had endometrial thickening without hyperplasia. There were no consistent abnormalities in liver or renal function or in any other biochemical or hematological parameters. One subject (on long-term dexamethasone) developed hypoadrenalism, which responded to treatment.

CONCLUSION(S)

Mifepristone can be administered for prolonged periods. Ultrasound should be performed if irregular vaginal bleeding occurs. In asymptomatic women, it should be performed annually. If endometrial thickening is observed, then endometrial biopsy is recommended. Because biochemical hypothyroidism has been reported during long-term mifepristone therapy, thyroid function tests should be performed annually.

Systematic Review of Mifepristone for the Treatment of Uterine Leiomyomata

OBJECTIVE

To systematically review the effect of mifepristone on uterine leiomyoma size and symptoms and to summarize its adverse effects.

DATA SOURCES

A computerized search in MEDLINE, EMBASE, LILACS, and Cochrane databases from 1985 to 2002 and hand searches of conference proceedings from 1995 to 2002 were performed with the search terms "mifepristone" and "leiomyomata" and publication type "clinical trial."

METHODS OF STUDY SELECTION

Titles and abstracts were reviewed by 2 authors; there were no areas of disagreement. Inclusion criteria were clinical trials of daily mifepristone for uterine leiomyomata that measured uterine or leiomyoma volume before and after treatment.

TABULATION, INTEGRATION, AND RESULTS

Data from each article were abstracted by 2 reviewers. The search identified 6 before-and-after clinical trials involving a total of 166 women with symptomatic uterine leiomyomata. The subjects received 5 to 50 mg/d of mifepristone for 3 to 6 months. No study was placebo-controlled or blinded. Meta-analytic techniques were not performed due to variation in outcome and mifepristone dose. Daily treatment with all doses of mifepristone resulted in reductions in uterine and leiomyoma volumes ranging from 27% to 49% and 26% to 74%, respectively. Mifepristone treatment reduced the prevalence and severity of dysmenorrhea, menorrhagia, and pelvic pressure. Rates of amenorrhea ranged from 63% to 100%. Transient elevations in transaminases occurred in 4%. Endometrial hyperplasia was detected in 10 (28%) of 36 women screened by endometrial biopsy.

CONCLUSION

Published trials of mifepristone showed reduction in leiomyoma size and improvement in symptoms. A notable adverse effect of mifepristone was development of endometrial hyperplasia.

Chronic low-dose antiprogestin impairs preimplantation embryogenesis, but not oocyte nuclear maturation or fertilization in rhesus monkeys

Continual administration of low doses of the antiprogestin ZK137316 permits ovarian/menstrual cyclicity, but prevents pregnancy in female rhesus monkeys. The sites of contraceptive action remain unknown. This study determined whether chronic, low-dose antiprogestin exposure during follicular development impairs oocyte maturation in vivo, as well as fertilization and preimplantation embryogenesis in vitro. Adult, female rhesus monkeys exhibiting normal menstrual cycles received vehicle (n=9) or 0.03 mg ZK137316 (n=8)/kg body weight i.m. daily for 3 months. Controlled ovarian stimulation with recombinant gonadotropins was initiated in the 3rd month. Oocytes collected from preovulatory follicles were evaluated for nuclear maturity and inseminated in vitro. Preimplantation embryonic development was monitored in vitro. The total number of oocytes and percentage collected at each nuclear stage were similar in both groups. More (P<0.05) atretic oocytes were recovered following antiprogestin relative to vehicle treatment. Fertilization rates and percentages of embryos that progressed to the morula stage were similar between groups, but antiprogestin-treated females exhibited less (P<0.05) normal cleavage. Embryonic development was accelerated by 1 day (P<0.05) from the 16-cell to the morula stage in the antiprogestin group relative to vehicle. Despite this, the majority of embryos became blastocysts within 6 days in vitro in the antiprogestin group, but fewer expanded (P=0.09) and hatched (P<0.05) compared to vehicle. During in vivo treatment with chronic, low-dose antiprogestin, oocytes retained their ability to resume and complete meiosis as well as fertilize following insemination in vitro. However, preimplantation embryogenesis in vitro was impaired, particularly during the later stages of blastocyst development. Thus, antiprogestin exposure during follicular development altered oocyte functions that are critical for normal preimplantation embryogenesis; this may contribute to pregnancy prevention.

Effects of onapristone on postmenopausal endometrium

The progesterone antagonist mifepristone (RU486, Exelgyn) has been shown to exert a paradoxical agonist effect on postmenopausal endometrium. We conducted a study to investigate the effects of the 'pure' antiprogestin onapristone (ZK 98 299, Schering AG) on postmenopausal endometrium. Seventeen postmenopausal subjects (45-62 years), took 2 mg of oestradiol and either placebo, 1 mg onapristone or 10 mg of onapristone, daily for 56 days. An endometrial biopsy was performed during the final week of treatment and assessed for histology and immunohistochemistry for oestrogen receptors (ER), progesterone (PR), androgen receptors (AR) and the cell proliferation marker Ki 67. FSH fell in all 14 subjects who completed the study, consistent with the effect of oestradiol treatment. There was a dose-dependent additive effect of onapristone on suppression of gonadotrophins. All endometrial biopsies showed proliferative endometrium. A similar pattern and intensity of immunostaining of ER, PR and Ki 67 was observed in all groups, with positive immunoreactivity in both glands and stroma. AR immunostaining was observed in both glands and stroma from all subjects, but there was an increase in intensity of immunostaining within the glandular epithelium of women receiving 10 mg onapristone. The antiprogestin onapristone, in contrast to mifepristone, is not agonistic on postmenopausal endometrium and does not exert obvious antiproliferative effects. It does however cause a dose dependent suppression of FSH and LH release.

Progesterone antagonists and progesterone receptor modulators: an overview

Since the original description of the structure of the antiprogestin, mifepristone, was published, numerous related compounds have been synthesized which may function as progesterone antagonists (PAs) or progesterone receptor modulators (PRMs). The latter are mixed agonists-antagonists. Both PAs and PRMs have therapeutic applications in female health care. Mifepristone is predominantly a PA and displays only minimum agonist activity in certain systems. Together with a prostaglandin, mifepristone can terminate pregnancies of less than 9 weeks duration, and it may also be used at later gestational ages. Mifepristone causes expulsion of the uterine contents following intrauterine fetal death. A mifepristone-prostaglandin combination has been shown to be very effective treatment in women with menses delay of 11 days or less. Many PAs and PRMs display antiproliferative effects in the endometrium. Serum estradiol levels however remain in the early to mid-follicular phase range. For this reason, they have application in the treatment of endometriosis and myoma without being associated with bone loss and hypoestrogenism. PRMs may also find application in the treatment of dysfunctional bleeding as well as an adjunct to estrogens in hormone replacement therapy in postmenopausal women. Many PAs have contraceptive potential by suppressing follicular development and blocking the LH surge. Low doses may also be potential contraceptives by retarding endometrial maturation without affecting ovulation or inducing bleeding. Mifepristone is an excellent agent for use as an emergency "postcoital" contraceptive. PAs may also be useful in IVF programs to prevent a premature LH surge and to delay the emergence of the implantation window. In addition to their use in women's health care, mifepristone and several other PAs are potent antiglucocorticoid agents and may be used to treat ACTH-independent Cushing's syndrome. They may also be used in the treatment of tumors containing steroid receptors and in other situations which require suppression of the ACTH-cortisol axis.

Low-dose antiprogestin treatment prevents pregnancy in rhesus monkeys and is reversible after 1 year of treatment

BACKGROUND

Administration of low doses of an antiprogestin to rhesus monkeys permits ovarian/menstrual cyclicity, suppresses endometrial proliferation and prevents pregnancy without adverse or toxic side-effects after 5-6 months of daily treatment. The purpose of this study was to test the reversibility with respect to restoration of fertility after 1 year of low-dose antiprogestin treatment.

METHODS

This experiment included a daily 1 year vehicle- or antiprogestin-treatment interval followed by a 9 month post-treatment interval for adult, female rhesus monkeys (n = 5/group) of proven fertility and exhibiting regular menstrual cycles. Co-habitation occurred with a male of proven fertility and vaginal swabs were taken to identify the presence of sperm during the treatment (antiprogestin females) and post-treatment intervals (vehicle and antiprogestin females).

RESULTS

Mating and vaginal sperm were evident in all antiprogestin females during, and, in both groups, after treatment. Based on ultrasonography, none of the antiprogestin-treated females became pregnant during the treatment interval. However, upon cessation of treatment, pregnancy rates were similar between antiprogestin-treated (3/5) relative to vehicle-treated (4/5) females with live, healthy infants born in both groups. There were no differences between groups in fetal measurements, gestation lengths, live birth rates and infant weights.

CONCLUSIONS

The reversal of the anti-fertility effects of chronic, low-dose antiprogestin treatment supports the clinical feasibility of potent and selective antiprogestins as potential contraceptives for women.

Effect of long-term treatment with low-dose mifepristone on the endometrium

BACKGROUND

Mifepristone in low daily doses has contraceptive potential by inhibiting ovulation and menstruation. Because follicular development is maintained, the endometrium is exposed to estrogen for prolonged periods unopposed by progesterone.

METHODS

Endometrial biopsies were collected from 90 women in Edinburgh and Shanghai before (late proliferative) and 60 and 120 days after taking 2 or 5 mg mifepristone per day for 120 days.

RESULTS

Ovulation and menstruation were inhibited in >90% of cycles and estrogen production was similar to that observed during the follicular phase of the control cycle. By 120 days, endometrial thickness increased significantly in women in Edinburgh but decreased in Shanghai. Endometrial histology showed inactive proliferative or cystic changes with dense stroma. There was a significant decrease in markers of proliferation, i.e. mitotic index and Ki67 staining. There were no pregnancies in a total of 200 women-months in 50 sexually active women who used no other method of contraception.

CONCLUSIONS

We confirm that ovulation and menstruation were suppressed in the majority of cycles and there was asynchrony between ovarian activity and endometrial histology, which showed no signs of hyperplasia or atypia. These preliminary data suggest that daily low-dose mifepristone is potentially a safe estrogen-free contraceptive pill which has the added health benefit of amenorrhoea.

New developments in contraceptive drugs for use by women

Since the oral contraceptive pill was first marketed in 1959, advances in contraceptive drugs for women have been limited to variations on the theme of oestrogen in combination with progestogen or progestogen alone. Alterations to the pill regimen, new progestogens and new delivery systems have increased choice but while these advances significantly improve acceptability, side effects and risks remain essentially unchanged. New ideas are in short supply. Antiprogesterones offer a new approach with a variety of dose regimens but their development has been seriously hampered by the politics associated with their abortifacient action. Other hormone antagonists as contraceptives seem a long way off. Immunocontraception is still at a very early stage. Genes, whose products are uniquely concerned with reproductive processes, promise new targets but radically new contraceptive drugs for women appear distant.

Screening for antiproliferative actions of mifepristone. Differential endometrial responses of primates versus rats

This laboratory has previously shown the capability of the antiprogestin, mifepristone, to noncompetitively inhibit estrogen-induced endometrial proliferation in nonhuman primates. In the following study, use of the rat uterine weight bioassay was compared against a primate (Macaca fascicularis) uterine bioassay to identify the noncompetitive/antiproliferative effects of mifepristone. These uterine bioassays were contrasted for reasons of identifying a comparative laboratory rodent model that could substitute for the need to use primate models in the screening of potential antiprogestins, thereby saving time, cost, and primate resources. Results of the primate experiment showed that mifepristone decreased endometrial proliferation in a dose-dependent manner; importantly, this decrease occurred in the presence of sustained physiologic serum 17 beta-estradiol (E2) levels. However, in the rat model, results showed that mifepristone altered uterine wet weight and blotted weight values only in those animals receiving pharmacological doses of E2 (p < 0.05). Based on the results summarized herein, use of this rat uterine weight bioassay as a substitute for primate models is not recommended for screening and identification of "interesting" antiprogestins. Apparently, the endometrial noncompetitive antiestrogenic/antiproliferative effects of mifepristone, observed repeatedly in these laboratory primates, do not operate in the rat uterine tissue.

Pharmacokinetics of mifepristone after low oral doses

Relatively low doses of the antiprogestin mifepristone (RU 486) have recently proven to be efficient for a variety of possible clinical uses of the drug. However, the pharmacokinetics after low single oral doses have not been characterized. We evaluated the pharmacokinetics of mifepristone following single ingestion of 2 and 25 mg in five women as well as repeated ingestion of 8 mg in two women. Maximal serum concentrations were reached rapidly (within 0.5-2 h) with all doses used. Serum mifepristone concentrations were proportional to the oral doses taken. The mean (+/- SD) areas under the concentration curves (AUCs) (0-24 h) were 1134 (+/- 144), 4846 (+/- 64), and 17,015 (+/- 4,421) h x ng/mL following 2, 8, and 25 mg doses, respectively. No cumulative increases in serum concentrations were detected with prolonged daily administration of 8 mg of mifepristone. The study subjects appeared to vary in their ability to metabolize mifepristone, as two different half-lives (t1/2) emerged after both 2 and 25 mg single doses (24.2 +/- 0.6 [SD] h for three subjects; and 44.4 +/- 1.8 [SD] h for two subjects). We conclude that within the dose range of 2-25 mg/day, the pharmacokinetics of mifepristone are linear, unlike those seen following ingestion of higher daily doses. Keeping in mind previously published data on the biological effects of low dose mifepristone administration, these data infer that certain effects of the drug, such as inhibition of ovulation, might be achieved at serum concentrations of approximately 100 ng/mL.