Delayed endometrial maturation induced by daily administration of the antiprogestin RU 486: a potential new contraceptive strategy

PXR mediates mifepristone-induced hepatomegaly in mice

Mifepristone (Mif), an effective synthetic steroidal antiprogesterone drug, is widely used for medical abortion and pregnancy prevention. Due to its anti-glucocorticoid effect, high-dose Mif is also used to treat Cushing's syndrome. Mif was reported to active pregnane X receptor (PXR) in vitro and PXR can induce hepatomegaly via activation and interaction with yes-associated protein (YAP) pathway. High-dose Mif was reported to induce hepatomegaly in rats and mice, but the underlying mechanism remains unclear. Here, the role of PXR was studied in Mif-induced hepatomegaly in C57BL/6 mice and Pxr-knockout mice. The results demonstrated that high-dose Mif (100 mg · kg^-1 · d^-1, i.p.) treatment for 5 days significantly induced hepatomegaly with enlarged hepatocytes and promoted proliferation, but low dose of Mif (5 mg · kg^-1 · d^-1, i.p.) cannot induce hepatomegaly. The dual-luciferase reporter gene assays showed that Mif can activate human PXR in a concentration-dependent manner. In addition, Mif could promote nuclear translocation of PXR and YAP, and significantly induced the expression of PXR, YAP, and their target proteins such as CYP3A11, CYP2B10, UGT1A1, ANKRD, and CTGF. However, Mif (100 mg · kg^-1 · d^-1, i.p.) failed to induce hepatomegaly in Pxr-knockout mice, as well as hepatocyte enlargement and proliferation, further indicating that Mif-induced hepatomegaly is PXR-dependent. In summary, this study demonstrated that PXR-mediated Mif-induced hepatomegaly in mice probably via activation of YAP pathway. This study provides new insights in Mif-induced hepatomegaly, and provides novel evidence on the crucial function of PXR in liver enlargement and regeneration.

Drug Methods for Arteficial Termination of Unwanted Pregnancy

All medical and surgical procedures are carried out in order to premature termnination of pregnancy, can be divided on medicament and surgical methods, according to the way of procedure.

Medications used today in order to break unwanted pregnancy are inhibitors of the synthetics of progesterone and antiprogesterone, prostaglandini and antimetabolite.

Mifepristone is a derivate of norethidrone, binds to the progesterone receptor with an affinity similar progesterone, but it does not activate them so as to act as an antiprogestine.

Metotrexat is an antimetabolite and is used in gynecology practice for more indication areas. It is used the most often in conservative treatment of ectopical pregnancy. Because of low price and accessibility in order to mifepristone, it was used for application in drug methods of inducative abortions.

Misoprostol is an anlogue PGE1, used in peroral pills.

The complication are very rare at aplication of mifepristone and misoprostole in the aim to the termination the early unwanted pregnancy. The appearance of more efficient procedure of drugs called out abortions, it does not mean taht decision for the abortion is more modest. The ease and safety should not help to make a decision.

Translational In Vivo Models for Women's Health: The Nonhuman Primate Endometrium--A Predictive Model for Assessing Steroid Receptor Modulators

Macaques and baboons display physiological responses to steroid hormones that are similar to those of women. Herein, we describe various uses of nonhuman primates for preclinical studies on menstruation, endometriosis, and as a model system to evaluate reproductive therapies and contraceptives. Our goal is to outline the strengths of the nonhuman primate model for studies leading to improved therapies for women.

Efficacy and tolerability of CDB-2914 treatment for symptomatic uterine fibroids: a randomized, double-blind, placebo-controlled, phase IIb study

OBJECTIVE

To evaluate the efficacy and tolerability of the P receptor modulator CDB-2914 (Ulipristal, CDB).

DESIGN

Randomized, placebo-controlled double-blind clinical trial.

SETTING

Clinical research center.

PATIENT(S)

Premenopausal women with symptomatic uterine fibroids.

INTERVENTION(S)

Once-daily oral CDB (10 or 20 mg) or placebo (PLC) for 12 weeks (treatment 1). A second 3-month treatment with CDB (treatment 2) was offered. A computer-generated blocked randomization was used.

MAIN OUTCOME MEASURE(S)

Magnetic resonance imaging (MRI)-determined total fibroid volume (TFV) change was the primary outcome; amenorrhea and quality of life (QOL) were secondary end points.

RESULT(S)

Treatment 1 TFV increased 7% in the PLC group, but decreased 17% and 24% in the CDB10 and CDB20 groups. The TFV decreased further in treatment 2 (-11%). Amenorrhea occurred in 20/26 women taking CDB and none on PLC. Ovulation resumed after CDB. Hemoglobin improved only with CDB (11.9 ± 1.5 to 12.9 ± 1.0 g/dL) as did the Fibroid QOL Questionnaire symptom severity, energy/mood, and concern subscores, and overall QOL scores. The CDB was well tolerated, with no serious adverse events. Adverse events were unchanged during treatments.

CONCLUSION(S)

Administration of CDB-2914 for 3-6 months controls bleeding, reduces fibroid size, and improves QOL.

Effects of the progesterone receptor modulator VA2914 in a continuous low dose on the hypothalamic-pituitary-ovarian axis and endometrium in normal women: a prospective, randomized, placebo-controlled trial

CONTEXT

Progestin-only pills, the main hormonal alternative to ethinyl estradiol-containing pills in women bearing vascular risk factors, are poorly tolerated due to irregular bleeding. In contrast, progesterone receptor modulators can inhibit ovulation, alter endometrial receptivity, and improve cycle control.

OBJECTIVE

We evaluated the effects of a new progesterone receptor modulator, VA2914, administered continuously for 3 months, on ovulation and endometrial maturation.

DESIGN, SETTINGS, AND PATIENTS

Forty-six normal women were included in a prospective, placebo-controlled, randomized trial, conducted in four referral centers.

INTERVENTION

VA2914 (2.5, 5, or 10 mg/d) was administered continuously for 84 d. Pelvic ultrasound (treatment d 67 and 77), hormonal monitoring (FSH, LH, estradiol, and progesterone on treatment d 59, 63, 67, 70, 74, 77, 80, and 84), and endometrial biopsy (treatment d 77) were performed.

MAIN OUTCOME MEASURE

Ovulation inhibition was assessed by the absence of progesterone values above 3 ng/ml at any time during treatment month 3.

RESULTS

Anovulation was observed in 81.8% women in the 5-mg group and 80% in the 10-mg group, and amenorrhea occurred in 81.2 and 90% of cases in the 5- and 10-mg groups. We did not detect any cases of endometrial hyperplasia despite estradiol levels that remained in the physiological follicular phase range throughout treatment cycle 3.

CONCLUSIONS

Continuous low-dose VA2914 can induce amenorrhea and inhibit ovulation without down-regulating estradiol levels or inducing endometrial hyperplasia in normal women. Long-term studies with a larger population are required to confirm the contraceptive efficacy of this regimen.

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.

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.

The pharmacokinetics of mifepristone in humans reveal insights into differential mechanisms of antiprogestin action

The pharmacokinetics of mifepristone is characterized by rapid absorption, a long half-life of 25-30 h, and high micromolar serum concentrations following ingestion of doses of >/=100 mg of the drug. The serum transport protein-alpha 1-acid glycoprotein (AAG)-regulates the serum kinetics of mifepristone in man. Binding to AAG limits the tissue availability of mifepristone, explaining its low volume of distribution and low metabolic clearance rate of 0.55 L/kg per day. In addition, the similar serum levels of mifepristone following ingestion of single doses exceeding 100 mg can be explained by saturation of the binding capacity of serum AAG. Mifepristone is extensively metabolized by demethylation and hydroxylation, the initial metabolic steps being catalyzed by the cytochrome P-450 enzyme CYP3A4. The three most proximal metabolites, namely, monodemethylated, didemethylated and hydroxylated metabolites of mifepristone, all retain considerable affinity toward human progesterone and glucocorticoid receptors. Also, the serum levels of these three metabolites are in ranges similar to those of the parent mifepristone. Thus, the combined pool of mifepristone-plus its metabolites-seems to be responsible for the biological actions of mifepristone. Recent clinical studies on pregnancy termination and emergency contraception have focused on optimization of the dose of mifepristone. In these studies it has become apparent that the doses efficient for pregnancy termination differ from those needed in emergency contraception-mifepristone is effective in emergency contraception at a dose of 10 mg, which results in linear pharmacokinetics. However, the >/=200 mg doses of mifepristone needed for optimal abortifacient effects of mifepristone result in saturation of serum AAG and thus nonlinear pharmacokinetics. In view of the pharmacokinetic data, it may be speculated that dosing of mifepristone for pregnancy termination and for emergency contraception could be reduced to approximately 100 mg and 2-5 mg, respectively. It remains to be seen whether the newly synthesized, more selective antiprogestins will prove more efficacious in the clinical arena.

Summary of evidence and research needs on the use of mifepristone in fertility regulation: consensus from the conference

The conference on the use of mifepristone to reduce unwanted pregnancy, sponsored by the World Health Organization, Concept Foundation and the Rockefeller Foundation, took place in Bellagio, Italy, between 24 and 28 September 2001. The objective of the conference was to review the scientific information and to evaluate the use of mifepristone for emergency contraception, luteal contraception and menstrual induction. Mifepristone is highly effective for emergency contraception but its advantages and disadvantages in comparison with levonorgestrel need to be further studied. Data indicate that mifepristone alone or in combination with misoprostol has potential for occasional use for women seeking help following repeated unprotected intercourse and/or when the interval between intercourse and treatment is more then 120 h. Administration of mifepristone immediately after ovulation seems to be an effective contraceptive method. However, before it can be used commonly, there is a need for a simple and inexpensive method to identify the right time in the cycle. Once-a-month treatment with mifepristone and misoprostol at the expected time of menstruation is not a practical method due to bleeding irregularities and timing of treatment. Menstrual induction with mifepristone and a suitable prostaglandin analogue is highly effective. A randomized comparison with manual vacuum aspiration is, however, needed before it can be recommended for routine use.

A role for the androgen receptor in the endometrial antiproliferative effects of progesterone antagonists

In women and nonhuman primates, treatment with progesterone antagonists suppresses estrogen-dependent mitotic activity in the endometrial glands. This antiproliferative effect is paradoxical, because progesterone antagonists do not bind to the estrogen receptor (ER). While this phenomenon has been termed a "functional noncompetitive antiestrogenic effect," it does not occur in all species or in all regions of the primate reproductive tract, so is best referred to as an "endometrial antiproliferative effect." Recent studies of ours in both women and macaques revealed that the endometrial androgen receptor (AR) was increased by progesterone antagonist treatment. Because androgens are known to suppress estrogen-dependent endometrial proliferation, we hypothesized that the AR was involved in the antiproliferative effects induced by progesterone antagonists. In a test of this hypothesis, we administered the antiandrogen, flutamide, along with progesterone antagonists to ovariectomized, estrogen-treated macaques. Flutamide counteracted the suppressive effects of the progesterone antagonists on endometrial wet weight, thickness, stromal compaction, and mitotic index. Hyaline degeneration of the spiral arteries was also blocked by flutamide. These data implicate the AR as a functional component of the mechanism through which progesterone antagonists induce endometrial antiproliferative effects in the presence of estrogens.

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.

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.

Mifepristone: a potential postcoital contraceptive

Mifepristone is an orally-active progesterone receptor antagonist. When a single dose of mifepristone is given in the mid- or late follicular phase, it may diminish or inhibit the luteinising hormone (LH) surge. In the early luteal phase, a single dose of mifepristone induces significant changes in the endometrium without affecting the hormonal levels or menstruation. When it is given in the mid-luteal phase, there will also be significant changes in the endometrium and some women may have two episodes of vaginal bleeding. A clinical trial suggests that a single dose of mifepristone in the early luteal phase may be an effective contraceptive agent but the lack of a cheap and easy method to identify the LH surge limits its clinical application. The administration of mifepristone alone or in combination with a prostaglandin does not appear to be an effective form of contraception. When used together with a prostaglandin, it may be an effective method for menstrual regulation but the cost and possible side effects of the prostaglandins limit its use. Mifepristone is a very effective method for emergency contraception. The incidence of side effects was also lower than that of the Yuzpe regimen. Lowering the dose of mifepristone from 600 to 10 mg does not decrease its efficacy but the incidence of delay in onset of the subsequent menses is reduced. Despite its efficacy, the reputation of mifepristone as an abortion pill may limit its access in many countries.

Progesterone antagonists increase androgen receptor expression in the rhesus macaque and human endometrium

Antiprogestins (APs) inhibit estradiol (E(2))-stimulated endometrial growth in women and nonhuman primates, but the mechanism of this "antiestrogenic" action is unknown. Here, we report that APs up-regulate endometrial androgen receptor (AR) in both women and macaques, an effect that might play a role in the antiproliferative effects of APs on the primate endometrium. In addition, because there are discrepancies in the literature on the regulation and localization of AR in the primate endometrium, we used both in situ hybridization and immunocytochemistry to evaluate hormonal influences on endometrial AR in women and macaques. In ovariectomized macaques, the following treatments were given for 4 weeks each: E(2) alone, E(2) + progesterone (P), E(2) + mifepristone (RU 486), and E(2) + P + RU 486. In women, samples were obtained during the normal menstrual cycle and after treatment with either RU 486 for 30 days at 2 mg/day, or after a single oral administration of 200 mg RU 486 on cycle day LH + 2. In macaques, E(2) significantly increased AR expression above vehicle controls; E(2) + RU 486 increased binding further; E(2) + P decreased AR binding; and E(2) + P + RU 486 treatment caused an intermediate elevation in AR binding. In macaques treated with E(2) alone, stromal AR staining was predominant, and P treatment suppressed that staining. E(2) + RU 486 or E(2) + P + RU 486 treatment produced a striking up-regulation of glandular epithelial AR staining and enhanced the stromal AR signal. In situ hybridization analyses confirmed the immunocytochemistry data. Similar induction of glandular AR staining and enhanced stromal AR staining were obtained in macaques treated with ZK 137 316 and ZK 230 211. During the natural cycle in women, stromal AR staining predominated and was greater in the proliferative than the late secretory phase. RU 486 treatment of women up-regulated glandular epithelial AR staining after either daily treatment for 30 days with 2 mg/day or after a single oral dose of 200 mg. In summary, endometrial AR was highest in the stroma during the human proliferative phase (or during E(2) treatment in macaques) and lowest during the late secretory phase in women (or after E(2) + P treatment in macaques). In both species, RU 486 induced AR expression in the glands and enhanced AR expression in stromal cells. Because androgens can antagonize E(2) action, enhanced endometrial AR expression induced by APs could play a role in the antiproliferative, "antiestrogenic" effects of APs in primates.

Synthesis and biological activity of a novel, highly potent progesterone receptor antagonist

Herein we describe the chemical synthesis and pharmacological characterization of a novel, highly potent progesterone receptor (PR) antagonist, ZK 230211. The introduction of a 17alpha-pentafluorethyl side chain in the D-ring of the steroid skeleton allowed the combination of high antiprogestagenic activity with little or no other endocrinological effects. In contrast to many other antiprogestins, ZK 230211 did not convert to an agonist in the presence of protein kinase A (PKA) activators and showed high antiprogestagenic activity on both PR isoforms PR-A and PR-B. This high antiprogestagenic activity could also be demonstrated in several in vivo models. Furthermore, this compound displayed only marginal antiglucocorticoid effects. In tumor models ZK 230211 exhibited strong antiproliferative action. The pharmacological properties of ZK 230211 may prove useful in the treatment of endometriosis, leiomyomas, breast cancer, and in hormone replacement therapy.

Single monthly administration of the anti-progestagen Org 31710 in users of the 75 microg desogestrel progestagen-only pill: effects on pituitary-ovarian activity

Endocrine and ultrasound effects were studied of an intermittent (every 28 days) oral administration of 150 mg of the anti-progestagen Org 31710 during the continued daily use of 75 microg desogestrel (DSG) for progestagen-only contraception. A randomized, double-blind, placebo-controlled two-centre study was conducted in 50 healthy volunteers. Serum luteinizing hormone (LH), follicle stimulating hormone (FSH), oestradiol and progesterone concentrations, and follicle number and size were studied, as well as endometrial thickness, which was assessed by transvaginal sonography at least twice weekly during a single medication cycle (cycle 3-5). Forty-eight women were evaluated (Org 31710, n = 25; placebo, n = 23). Seven ovulations were observed in the treated group versus none in the placebo group. LH concentrations were higher on days 9 and 11 and oestradiol concentrations lower on day 3 in the treated group, irrespective of whether ovulation occurred. No parameter could predict ovulation. Endometrial thickness was greater on cycle days 7-13 and 19 in the treated group. However, within the Org 31710 group, no significant differences were found in volunteers who did or did not ovulate. Observed differences may be attributed to a competitive effect of Org 31710 with progestagen-induced suppression of the pituitary-ovarian axis, altered oestradiol feedback mechanisms, and/or altered receptor availability.

Contraceptive efficacy of daily administration of 0.5 mg mifepristone

The antiprogestin mifepristone has shown potential to be used as a contraceptive. If 200 mg mifepristone is administered immediately after ovulation, the endometrium shows sufficient impairment of secretory development to prevent implantation. Low daily doses of mifepristone have been shown to reduce several of the local factors regarded as crucial for implantation in human endometrium. To find out if this regimen is sufficient to prevent pregnancy, 32 women were recruited for a study where 0.5 mg mifepristone was administered daily. A total of 141 cycles were studied. Five pregnancies occurred, which was significantly less than if no contraceptive method had been used. However, the dose chosen did not seem sufficient to act as a contraceptive although it is probably not possible to increase the dose without disturbing ovulation and bleeding pattern.

Antiovulatory and postcoital antifertility activity of the antiprogestin CDB-2914 when administered as single, multiple, or continuous doses to rats

The present studies in rats were undertaken to investigate the potential of a new antiprogestin, CDB-2914, for use as an emergency postcoital contraceptive for women. When given orally at noon on the day of proestrus, both CDB-2914 and mifepristone displayed dose-dependent antiovulatory activity; however, CDB-2914 was about eight times more potent than mifepristone. Both antiprogestins were considerably less potent in blocking ovulation when injected subcutaneously. To evaluate antifertility activity during continuous low dose administration, rats were dosed orally with 0.5 mg of either CDB-2914 or mifepristone daily, commencing on the day of estrus and continuing for 24 days. Females were cohabited with proven fertile males on day 8 of treatment and were removed 1-3 days later after confirmed mating. The pregnancy rate was significantly reduced (p < 0.05) only in the CDB-2914-treated females; however, the mean number of normal implantation sites per pregnant rat was significantly reduced (p < 0.05) by mifepristone as compared with the vehicle control group. CDB-2914 was also found to prevent pregnancy when administered orally after mating from days 0-3 during tubal egg transport, or from days 4-6 during the pre- and peri-implantation periods. To determine the day of maximal sensitivity to CDB-2914, a single 2-mg dose per rat was given orally on days 0, 1, 2, 3, 4, or 5 postmating. This dose of CDB-2914 was without effect on pregnancy at days 0, 1, 2, or 3 postmating. In contrast, 2 mg CDB-2914 per rat was highly effective in blocking pregnancy when given on either day 4 or 5 postmating. Collectively, these data demonstrate that CDB-2914 is an orally active postcoital antifertility agent that is more potent than mifepristone in the rat. Hence, CDB-2914 may prove to be an effective emergency postcoital contraceptive in women.

Safety, tolerability, and pharmacokinetics of a novel, selective antiprogestagen (Org 31710) in healthy male volunteers

The safety and tolerability as well as pharmacokinetics of a new selective antiprogestagen, Org 31710, were studied after oral administration of single doses of 10, 25, 50, or 75 mg to 24 healthy male volunteers. Per dose-group, five subjects received active and one subject received placebo treatment. In subjects receiving 75 mg, the effects of Org 31710 on serum levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH), and testosterone were also studied. No adverse or seriously adverse events were observed. All doses of Org 31710 were well tolerated. Characterization of the Org 31710 plasma pharmacokinetics revealed a statistically significant deviation from linearity: the dose normalized Cmax (nCmax) and dose normalized area under the curve (nAUC) values were significantly lower for the higher dosages (p < 0.05). Furthermore, tmax tended to decrease (from 1.6 to 0.9 h), whereas the elimination half-life (t1/2) tended to increase (from on average 45 to 57 h) with increasing dose. Org 31710 did not have any effect on serum levels of FSH, LH, and testosterone. In conclusion, Org 31710 appears to be a safe and well-tolerated compound in the dosage range studied.

Chronic antiprogestin therapy produces a stable atrophic endometrium with decreased fibroblast growth factor: a 1-year primate study on contraception and amenorrhea

OBJECTIVE

To describe the efficacy of mifepristone in the prevention of menstrual bleeding and ovulation, with similar observations in comparison groups.

DESIGN

Prospective experimental study. Thirty-two cynomolgus monkeys were divided equally into four treatment groups (n = 8). Treatment lasted for 1 year.

INTERVENTION(S)

Group I received GnRH-agonist (GnRH-a) and in-sequence mifepristone, group II received mifepristone only, group III received GnRH-a only, and group IV received vehicle control.

MAIN OUTCOME MEASURE(S)

Serum estradiol and progesterone, menstrual bleeding, endometrial thickness, and endometrial expression of basic fibroblast growth factor (bFGF) as determined by immunohistochemistry.

RESULT(S)

Weekly progesterone determinations showed that mifepristone-treated monkeys seldom ovulated (6 ovulations in 8 years), compared with the controls (100 ovulations in 8 years), while maintaining early to midfollicular levels of circulating serum estradiol. The GnRH-a-only group also rarely ovulated, but was chronically and severely hypoestrogenic. The mifepristone-only group showed scant menstrual bleeding (5 days in 8 years) as compared with the menstrual frequency in control animals (422 days in 8 years). Endometrial proliferation, as determined by biopsy, was similarly minimal for both the GnRH-a and mifepristone groups, and statistically less than in control monkeys. Both the mifepristone and GnRH-a treatments suppressed endometrial gland expression of the angiogenesis polypeptide bFGF.

CONCLUSION(S)

Chronic mifepristone induced anovulation along with virtual amenorrhea, which suggests the worth of this novel hormonal contraceptive.

Endometrial integrin expression is independent of estrogen or progestin treatment in vitro

OBJECTIVE

To examine the regulation of endometrial integrin expression by estrogens and progestins in vitro.

DESIGN

Immunocytochemical study.

SETTING

Academic research unit.

PATIENT(S)

Twenty-five regularly cycling women without endometrial pathology, of whom seven had endometriosis.

INTERVENTION(S)

Endometrial cells obtained by aspiration curettage were treated with diethylstilbestrol, promegestone, and antiprogestin. Immunocytochemistry was performed with antibodies directed against integrins alpha 1 beta 1, alpha 2 beta 1, alpha 4 beta 1, alpha 5 beta 1, alpha v beta 3, and beta 3 integrin subunit.

MAIN OUTCOME MEASURE(S)

Semiquantitative staining score.

RESULT(S)

Endometrial cells express several integrins in vitro in a consistent and cell specific pattern. Neither differences between treated and untreated cells nor an effect of treatment duration or dosage were observed. Cells from patients with and without endometriosis showed similar patterns.

CONCLUSION(S)

The cellular distribution of integrin expression was similar to that described in vivo. In contrast, a steroid regulated expression could not be detected in vitro. Rather, a derepression by a factor not included in our model could be responsible for the cyclic appearance of some integrins. In endometriosis, no fundamental difference of integrin expression was detected.

Anti-implantation activity of luteal phase mifepristone administration is not mimicked by prostaglandin synthesis inhibitor or prostaglandin analogue in the rhesus monkey

The use of mifepristone as an anti-implantation agent in the primate has been explored in the rhesus monkey with two specific aims: (i) to determine the contraceptive efficacy of very low-dose mifepristone administered on mated cycle days 16, 17, and 18; and (ii) to test the hypothesis that alteration in endometrial prostaglandin milieu by using either prostaglandin analogue or prostaglandin synthesis inhibitor can intervene the antifertility effect induced by mifepristone. Thirty female monkeys were randomly assigned to one of the six treatment groups. Five monkeys in the control group (group 1) were subjected to mating during cycle days 8-22. Four out of five monkeys became pregnant in the first mated cycle (80%) with detection of serum mCG by 12.7 +/- 1.5 days after ovulation. In group 2, 12 mated cycles were studied in five monkeys, mifepristone [RU486, 2 mg/day/animal, s.c. in 1 ml vehicle (1:4, benzyl benzoate:olive oil, v/v)] was given on cycle days 16, 17, and 18. In this group, no pregnancy was observed, thus providing complete pregnancy protection. Though there was an apparent extension of treatment cycle lengths in five cases with no incidence of inter-menstrual bleeding or spotting, there were no significant changes in serum estradiol (E) and progesterone (P). In group 3, four monkeys received prostaglandin (PG) synthesis inhibitor, diclofenac sodium (D, 25 mg/day/animal, i.m.) on cycle days 16, 17, and 18 in seven ovulatory menstrual cycles. Four of these cycles (57%) resulted in normal pregnancies; however, mCG detection (16.8 +/- 1.2 days after ovulation) was significantly (p < 0.05) delayed as compared to group 1. In group 4, four monkeys received 100 micrograms misoprostol (M), a PGE1 analogue, by gavage on mated cycle days 16, 17, and 18. Four pregnancies occurred in five treatment cycles (80%) with normal profiles of serum E and Pi mCG was first detected 13.2 +/- 1.7 days after ovulation. In group 5, seven monkeys received same dosages of RU486 and D on mated cycle days 16, 17, and 18. One hundred percent pregnancy protection was observed with luteal phase lengthening in eight treatment cycles but with unaltered E and P profiles. In group 6, five monkeys in nine treatment cycles received same dosages of RU486 and M on mated cycle days 16, 17, and 18. One pregnancy occurred; evaluation of E and P levels showed that the drug was given in the preovulatory period, which delayed ovulation and implantation, as mCG was detected 19 days post-ovulation. A delay in vaginal bleeding was observed in four treatment cycles with unaltered E and P profiles. Low-dose mifepristone appears to be a potential candidate for luteal phase and post-coital emergency contraception. However, the hypothesis that altered endometrial prostaglandin milieu may be responsible for mediating the anti-implantation effect of RU486 does not appear to be tenable based on our results in the rhesus monkey.

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.

Endometrial effects of RU486 in primates--antiproliferative action despite signs of estrogen action and increased cyclin-B expression

Continuous antiprogestin administration to hormone replaced, castrate monkeys inhibits estrogen-induced endometrial proliferation through mechanisms which remains unclear. To elucidate the molecular mechanisms of RU486-induced endometrial suppression, we treated six intact female cynomolgus monkeys on cycle days 2-22 sequentially with placebo, RU486 (1 mg/kg/day) and levonorgestrel (LNG) (2 microg/kg/day) intramuscularly (i.m.), with uterine wedge sections and endometrial biopsies collected on day 22 of each cycle. The uterine sections were evaluated for morphology, mitosis and proliferating cell nuclear antigen (PCNA) immunohistochemistry. Changes in the mRNA levels of ER, PR, cyclin-B and tumour suppressor gene p21 were assessed using co-amplification with beta-actin by reverse transcriptase-polymerase chain reaction (RT-PCR). Administration of RU486 uniformly resulted in characteristic suppression of endometrium with few mitosis, dense stroma and simple glands, whereas the effects of LNG were less uniform. Following RU486 administration, the levels of endometrial ER and PR mRNA were comparable to proliferative phase endometrium, and significantly higher than those seen in the secretory endometrium, indicating that some of the biological actions of E2 were not inhibited during RU486 treatment. Despite scarce mitosis, PCNA was readily detectable in all samples. Curiously, in comparison to secretory phase controls, the levels of cyclin-B, but not p21, mRNA were markedly increased following RU486. The effects of LNG on the levels of these mRNA species varied, with mean levels falling between those of the secretory phase controls, and RU486-treated specimens. The increase in cyclin-B mRNA and lack of mitosis suggests that anti-proliferative actions of RU486 in the primate endometrium might be associated with a cell-cycle block at the G2-M interphase. Whether mechanisms similar to these are associated with the beneficial clinical effects of RU486 seen in the treatment of various hormone dependent maladies remains to be determined.

Identification of CYP3A4 as the principal enzyme catalyzing mifepristone (RU 486) oxidation in human liver microsomes

Various complementary approaches were used to elucidate the major cytochrome P450 (CYP) enzyme responsible for mifepristone (RU 486) demethylation and hydroxylation in human liver microsomes: chemical and immunoinhibition of specific CYPs; correlation analyses between initial rates of mifepristone metabolism and relative immunodetectable CYP levels and rates of CYP marker substrate metabolism; and evaluation of metabolism by cDNA-expressed CYP3A4. Human liver microsomes catalyzed the demethylation of mifepristone with mean (+/-SD) apparent K(m) and Vmax values of 10.6 +/- 3.8 microM and 4920 +/- 1340 pmol/min/mg protein, respectively; the corresponding values for hydroxylation of the compound were 9.9 +/- 3.5 microM and 610 +/- 260 pmol/min/mg protein. Progesterone and midazolam (CYP3A4 substrates) inhibited metabolite formation by up to 77%. The CYP3A inhibitors gestodene, triacetyloleandomycin, and 17 alpha-ethynylestradiol inhibited mifepristone demethylation and hydroxylation by 70-80%; antibodies to CYP3A4 inhibited these reactions by approximately 82 and 65%, respectively. In a bank of human liver microsomes from 14 donors, rates of mifepristone metabolism correlated significantly with relative immunodetectable CYP3A levels, rates of midazolam 1'-and 4-hydroxylation and rates of erythromycin N-demethylation, marker CYP3A catalytic activities (all r2 > or = 0.85 and P < 0.001). No significant correlations were observed for analyses with relative immunoreactive levels or marker catalytic activities of CYP1A2, CYP2C9, CYP2C19, CYP2D6, or CYP2E1. Recombinant CYP3A4 catalyzed mifepristone demethylation and hydroxylation with apparent K(m) values 7.4 and 4.1 microM, respectively. Collectively, these data clearly support CYP3A4 as the enzyme primarily responsible for mifepristone demethylation and hydroxylation in human liver microsomes.

Mifepristone: a potential contraceptive

Use of standard estrogen-progestin contraception remains problematic in several subgroups of patients (e.g., those in whom exogenous estrogens are contraindicated, such as survivors of hormone-dependent cancer, or patients with endometriosis or uterine fibroids). In addition, the postcoital contraception, even if already available, remains at least underused. Additionally, continuous intake of contraceptive steroids is under increasing scrutiny. Would antiprogestins, and specifically the applications of mifepristone such as the ones reviewed in this article offer significant improvements at such problematic occasions? The most attractive novel contraceptive application of mifepristone is that of emergency postcoital contraception after unprotected intercourse. In addition, various options in the endometrial category, specifically those requiring drug administration only during a limited time, might be used in the future. Mifepristone might offer contraceptive and therapeutic relief to patients suffering from endometriosis or uterine fibroids, both conditions that have been shown to benefit from mifepristone therapy. However, the use of mifepristone in contraceptive preparations that are widely available would pose an additional problem of possible misuse of the compound, the reason for currently limiting access to mifepristone. However, such risk should be easily avoidable in the case of postcoital contraception in which only one dose of mifepristone is needed. Regarding the future of mifepristone, and more broadly that of antiprogestins in contraception, the authors believe that they will have a place in the future contraceptive armament. As already emphasized, the strongest clinical areas are those of immediate postcoital and endometrial contraception. Additional studies evaluating parenteral modes of administration, the long-term endometrial effects, and safety and metabolic effects of prolonged antiprogestin administration are needed before mifepristone can be considered a part of the contraceptive arena.

Contraception with anti-progesterone

Anti-progesterones have potential as contraceptives, acting either by the inhibition of ovulation or the inhibition of endometrial development. Clinical studies have shown that once-a-month treatment with Mifepristone in the early luteal phase is an effective contraceptive method, and that emergency post-coital contraception with Mifepristone is at least as effective as other methods currently used. Recent studies indicate that the endometrium is more susceptible to Mifepristone than are the hypothalamic and pituitary regions, and it may therefore be possible to develop a new contraceptive method based on low daily or once-weekly doses of Mifepristone that does not influence ovarian function.

Onapristone (ZK 98.299): a potential antiprogestin for endometrial contraception

OBJECTIVES

The effects of the antiprogestin onapristone (ZK 98.299) on fertility; menstrual cycle length; duration of menses; serum estradiol, progesterone, and cortisol concentrations; and endometrial morphologic features were studied in adult bonnet monkeys.

STUDY DESIGN

Five animals were treated subcutaneously with the vehicle and another nine with either 2.5 (n = 4) or 5 mg of onapristone per animal (n = 5). Treatment was initiated on day 5 of the first treatment cycle, and thereafter onapristone was administered every third day for four to seven consecutive cycles. The females were placed with adult males during the periovulatory period, which was assessed by frequent analysis of serum estradiol concentrations. In the final treatment cycle an endometrial biopsy was performed on day 8 after a midcycle estradiol peak in the ovulatory cycle, or around day 20 if the cycle was anovulatory. Blood samples for estradiol, progesterone, and cortisol measurement were collected every third day, except for the periovulatory period when sampling was more frequent.

RESULTS

Each of the five animals treated with the vehicle became pregnant: one in the first, three in the second, and one in the third mated cycle, whereas only one of nine treated with onapristone became pregnant. Four animals treated with 2.5 mg of onapristone for 17 cycles and another four treated with a 5 mg dose for 21 cycles did not conceive. In eight animals that did not conceive the first three treatment cycles of six were ovulatory, and in the remaining two animals two cycles of each were ovulatory. During treatment the mean menstrual cycle length was not altered significantly; however, in one it was shortened and in another two it was prolonged. Similarly, the mean duration of menses was not significantly affected, but in some cycles it was reduced. Moreover, there was only slight bleeding in some treatment cycles. Ovulation occurred in 30 of 45 treatment cycles, including the final treatment cycle during which the biopsy was taken, as indicated by serum estradiol and progesterone concentrations. In some of the ovulatory cycles prolonged treatment suppressed luteal activity; however, in the ovulatory cycles the duration of follicular and luteal phases was not significantly affected. In the anovulatory cycles there was a delayed increase in serum estradiol concentrations, suggesting a partial inhibition of folliculogenesis. In treated animals endometrial growth and development was retarded and rendered out of phase. In animals treated with the higher (5 mg) onapristone does the endometrial glands had partially regressed, the secretory activity was blocked, and stromal compaction was evident. The treatment had no significant effect on serum cortisol levels.

CONCLUSIONS

This study demonstrates that low-dose onapristone treatment throughout the menstrual cycle prevents pregnancy without disturbing the menstrual cycle and ovulation in the majority of cycles. However, anovulation and luteal insufficiency occurred in some animals during prolonged treatment. The contraceptive effect in the ovulatory cycles seems primarily related to the retardation of endometrial development resulting in the inhibition of endometrial receptivity. It appears likely that a dose or treatment regimen of onapristone that will inhibit endometrial receptivity and prevent implantation without affecting the menstrual cycle even on prolonged treatment could be identified.