Pharmacodynamic evaluation of the etonogestrel contraceptive implant initiated midcycle with and without ulipristal acetate: An exploratory study

OBJECTIVE

To estimate the incidence of ovulation suppression within five days of etonogestrel 68 mg implant insertion in the presence of a dominant follicle with and without same-day ulipristal acetate.

STUDY DESIGN

This single site non-masked, exploratory randomized trial recruited people age 18-35 years with regular menstrual cycles, no pregnancy risk, and confirmed ovulatory function. We initiated transvaginal ultrasound examinations on menstrual day 7-9 and randomized participants 1:1 to etonogestrel implant alone or with concomitant ulipristal acetate 30 mg oral when a dominant follicle reached ≥14 mm in diameter. We completed daily sonography and serum hormone levels for up to seven days or transitioned to labs alone if sonographic follicular rupture occurred. We defined ovulation as follicular rupture followed by progesterone >3 ng/mL. We calculated point estimates, risk ratios and 95% confidence intervals for ovulation for each group. Ovulation suppression of ≥44% in either group (the follicular rupture suppression rate with oral levonorgestrel emergency contraception), would prompt future method testing.

RESULTS

From October 2020 to October 2022, we enrolled 40 people and 39 completed primary outcome assessments: 20 with etonogestrel implant alone (mean follicular size at randomization: 15.2 mm ± 0.9 mm) and 19 with etonogestrel implant + ulipristal acetate (mean follicular size at randomization: 15.4 mm ± 1.2 mm, p = 0.6). Ovulation suppression occurred in 13 (65%) of etonogestrel implant-alone participants (Risk ratio 0.6 (95% CI: 0.3, 1.1), p = 0.08) and seven (37%) of implant + ulipristal acetate participants.

CONCLUSIONS

Ovulation suppression of the etonogestrel implant alone exceeds threshold testing for future research while the implant + ulipristal acetate does not.

IMPLICATIONS

Data are lacking on midcycle ovulation suppression for the etonogestrel implant with and without oral ulipristal acetate. In this exploratory study, ovulation suppression occurred in 65% of implant participants and 37% of implant + ulipristal acetate participants. Ovulation suppression of the implant alone exceeds threshold testing for future emergency contraception research.

Ulipristal (UPA) effects on rat ovaries: Unraveling follicle dynamics, ovulation inhibition, and safety implications for prolonged use

Ulipristal (UPA), a selective progesterone receptor modulator, has both agonistic and antagonistic effects on progesterone receptors. UPA suppresses ovulation by inhibiting the luteinizing hormone (LH) surge from the pituitary gland; however, the direct effect of UPA on ovarian tissue remains poorly studied. In the present study, we examined the effects of UPA on the ovaries of rats. Rats were treated for 28 days with UPA, and the effects of UPA on ovarian tissue were examined histologically and the expression of antioxidant genes and cell death markers were also investigated. UPA treatment increased the number of primordial follicles at each treatment group, primordial follicles increased at all dose levels, but the size/magnitude of the effect decreased with the increasing dose. The number of primary and antral follicles tended to increase with increasing UPA levels. Furthermore, the decrease in primary follicle number could be attributed to the exhaustion of follicles, but the examination of proliferation markers, oxidative stress markers, and cell death markers revealed no remarkable toxic effects on ovarian tissues. These results suggest that UPA treatment promotes follicle development at each stage but inhibits ovulation by suppressing the LH surge, resulting in an increase in atretic follicles or unruptured luteinized cysts. These results suggest that UPA may not have both toxic effects on the ovary and a direct local effect on ovarian follicles, but we should be careful about the effects of prolonged UPA treatment in patients with uterine fibroids on their future fecundity.

Effects of Ulipristal Acetate on Reactive Oxygen Species and Proinflammatory Cytokine Release by Epithelial and Stromal Cells from Human Endometrium and Endometriosis

Endometriosis is a condition characterized by increased oxidative stress and chronic inflammation, which can be treated with progestins and other progesterone receptor ligands. However, some patients are refractory to this treatment and the reason is uncertain. Here we investigated the effects of the selective progesterone receptor modulator ulipristal acetate (UPA) on proliferation, reactive oxygen species (ROS), and proinflammatory cytokine production by endometriotic cells and endometrial cells from women with histologically proven endometriosis (n = 22) and endometriosis-free controls (n = 6). Epithelial and stromal cells were isolated and treated in triplicate for 24 h with 1 μM, 10 μM, or 100 μM UPA. Cells were tested for proliferation and ROS production, while cell supernatants were assayed for interleukin (IL)-6, C-C motif chemokine ligand 2 (CCL2), and tumor necrosis factor (TNF)-α concentrations. Proliferation, ROS production, and IL-6 and CCL2 secretion were increased in non-stimulated epithelial and stromal cells from endometriotic lesions compared to endometrial cells from endometriosis patients and controls. UPA induced a dose-dependent increase of cell proliferation only in endometriosis, while enhancing ROS production by all cell types evaluated. UPA reduced CCL2 production in controls but failed to do that in endometriosis, whereas TNF-α was undetectable. We conclude that treatment of endometriotic cells with UPA stimulated in vitro proliferation and ROS production and failed to revert the proinflammatory cytokine excess that characterized these cells, unravelling possible mechanisms of drug resistance in the treatment of endometriosis.

NOMAC-E2 compares to LNG combined oral contraceptives in women over forty: real-world PRO-E2 study

OBJECTIVE

To investigate safety and effectiveness of NOMAC-E2 and levonorgestrel-containing COCs (COC_LNG) in users over 40.

METHODS

In this large, observational study, new users¹ of NOMAC-E2 and COC_LNG were recruited in Europe, Australia, and Latin America and followed-up via questionnaires. Incidence of venous thromboembolism (VTE) was expressed as incidence rate (IR; events/10⁴ women-years [WY]). Unintended pregnancy was expressed by the Pearl Index (PI; contraceptive failures/100 WY). Mood and weight changes were defined as mean changes in mood score and percentage of body weight.

RESULTS

Overall, 7,762 NOMAC-E2 and 6,059 COC_LNG users over 40 were followed-up. NOMAC-E2 showed no increased VTE risk compared to COC_LNG; confirmed events: 5 NOMAC-E2 (IR 5.9; 95% CI, 1.9-13.7) vs 4 COC_LNG (IR 5.9; 95% CI, 1.6-15.1). Unintended pregnancy did not differ substantially between cohorts; confirmed events: 4 NOMAC-E2 (PI 0.05; 95% CI, 0.01-0.13) vs 5 COC_LNG (PI 0.08; 95% CI, 0.03-0.18). No differential effect on mood and weight was observed between cohorts.

CONCLUSIONS

NOMAC-E2 can be considered a valid alternative to COC_LNG in perimenopausal women.

Potential candidate for oral pericoital contraception: evaluating ulipristal acetate plus cyclo-oxygenase-2 inhibitor for ovulation disruption

BACKGROUND

There remains considerable global unmet contraceptive need, with almost 200 million women reporting desire to limit or space childbearing without contraceptive use. Researchers have documented worldwide interest in an oral, on-demand contraceptive option were it available. Candidates for use include ulipristal acetate (UA), levonorgestrel and cyclo-oxygenase-2 (COX-2) inhibitors alone or in combination.

METHODS

We performed an exploratory, prospective study of matched menstrual cycles: one baseline cycle and one treatment cycle of UA 30 mg plus meloxicam 30 mg just prior to ovulation. The primary outcome was ovulation disruption, defined as unruptured dominant follicle for 5 days. Secondary outcomes included comparing cycle length, endometrial stripe thickness, and side effects.

RESULTS

Nine participants completed all study procedures in both cycles. Ovulatory disruption occurred in 66.7% (n=6) of treatment cycles and all but one demonstrated features of ovulatory dysfunction. Cycle length (mean±SD) was longer in the treatment cycle (31.9±4.0 vs 28.6±3.5 days, p<0.01). Secondary outcomes did not differ between the two cycles.

CONCLUSIONS

UA plus the COX-2 inhibitor meloxicam disrupts ovulation at peak luteal surge and is a promising candidate for evaluation as a pericoital oral contraceptive.

TRIAL REGISTRATION NUMBER

NCT03354117.

The progesterone-receptor modulator, ulipristal acetate, drastically lowers breast cell proliferation

PURPOSE

The proliferation of breast epithelial cells increases during the luteal phase of the menstrual cycle, when they are exposed to progesterone, suggesting that ulipristal acetate, a selective progestin-receptor modulator (SPRM), may reduce breast cell proliferation with potential use in breast cancer chemoprevention.

METHODS

Women aged 18-39 were randomized 1:1 to ulipristal 10-mg daily or to a combination oral contraceptive (COC) for 84 days. Participants underwent a breast biopsy and breast MRI at baseline and at end of study treatment. Proliferation of breast TDLU cells was evaluated by Ki67 immunohistochemical stain. We evaluated the breast MRIs for background parenchymal enhancement (BPE). All slides and images were masked for outcome evaluation.

RESULTS

Twenty-eight treatment-compliant participants completed the study; 25 of whom had evaluable Ki67 results at baseline and on-treatment. From baseline to end of treatment, Ki67 % positivity (Ki67%+) decreased a median of 84% in the ulipristal group (N = 13; 2-sided p (2p) = 0.040) versus a median increase of 8% in the COC group (N = 12; 2p = 0.85). Median BPE scores decreased from 3 to 1 in the ulipristal group (p = 0.008) and did not decrease in the COC group.

CONCLUSION

Ulipristal was associated with a major decrease in Ki67%+ and BPE. Ulipristal would warrant further investigation for breast cancer chemoprevention were it not for concerns about its liver toxicity. Novel SPRMs without liver toxicity could provide a new approach to breast cancer chemoprevention.

TRIAL REGISTRATION

NCT02922127, 4 October 2016.

Pharmacodynamics and pharmacokinetics of a copper intrauterine contraceptive system releasing ulipristal acetate: A randomized proof-of-concept study

OBJECTIVES

To assess pharmacodynamic and pharmacokinetic outcomes of a novel copper (Cu) intrauterine system (IUS) releasing ulipristal acetate (UPA) in healthy women.

STUDY DESIGN

In this single-blinded, randomized proof-of-concept study, ovulatory women received one of three Cu-IUSs releasing low-dose UPA (5, 20 or 40 µg/d) for 12 weeks. The study included a baseline cycle, three 4-week treatment-cycles and 2 recovery cycles. Primary outcomes included effects of the IUS on bleeding profile, ovarian function, and the occurrence of progesterone receptor modulator associated endometrial changes (PAEC). Pharmacokinetics and safety profile were secondary outcomes. We compared outcomes in treatment-cycle 3 with baseline, using generalized linear mixed models with orthogonal contrasts.

RESULTS

We randomized 29 women (5 µg/d = 10, 20 µg/d = 10, 40 µg/d = 9). All had a successful IUS insertion; 27 completed the 12-week treatment period. Compared to baseline, the mean number of bleeding-only days at treatment-cycle 3 declined by 16.7% in the 5 µg/d group (3.6 vs 3.0, p = 0.66), 40.5% in the 20 µg/d group (4.2 vs 2.5, p = 0.14), and 77% in the 40 µg/d group (3.9 vs 0.9, p = 0.002). Most women reported reduction in the amount of bleeding: 4/8, 8/10, and 7/9 for the 5 µg/d, 20 µg/d, and 40 µg/d groups, respectively. During IUS use, ovulation occurred in most cycles [5 µg/d: 23/24 (96%), 20 µg/d: 26/30 (87%), 40 µg/d: 22/27 (81%)]. The frequency of PAEC at IUS removal was 1/10 (10%), 1/10 (10%) and 4/9 (44%) in the 5 µg/d, 20 µg/d, and 4 0 µg/d groups, respectively. No serious adverse events occurred.

CONCLUSIONS

Reduction in bleeding, low incidence of PAEC, and no serious adverse events are reassuring findings of the novel Cu-UPA-IUS. The 20 µg/d seems the lowest dose promoting a favorable bleeding profile and limiting PAEC.

IMPLICATIONS

The preliminary results of this short-term study of a novel copper intrauterine system (IUS) delivering ulipristal acetate showed reduction of bleeding, low incidence of progesterone receptor modulator associated endometrial changes, and absence of serious adverse events. By preventing copper-induced increase in bleeding, this IUS could provide a noncontraceptive benefit, especially for women with low hemoglobin.

The selective progesterone receptor modulator, telapristone acetate, is a mixed antagonist/agonist in the human and mouse endometrium and inhibits pregnancy in mice

OBJECTIVE

To investigate the effect of the selective progesterone receptor modulator, telapristone acetate (CDB-4124), on endometrial biology and reproductive outcomes. Ovariectomized and hormone-treated CD1 female mice, CD1 female mice with xenotransplants of reconstructed human endometrial tissue, mated wildtype female mice, and cultured human endometrial stromal cells (hESCs) were treated with CDB-4124, followed by the assessment of endometrial cell deoxyribonucleic acid (DNA) proliferation, stromal decidual response, and embryo implantation.

DESIGN

Experimental study.

SETTING

Academic research laboratory.

PATIENTS

Healthy volunteer women from the community were recruited for endometrial biopsies.

ANIMALS

CD1 out-bred mice (Charles River Laboratories) and nude mice, NU/J (Jackson Laboratories, Bar Harbor, ME).

INTERVENTION

Treatment of mice and hESCs with CDB-4124.

MAIN OUTCOME MEASURE

The effect of CDB-4124 on endometrial cell morphology and DNA synthesis, decidual response, and mouse embryo implantation.

RESULTS

CDB-4124 inhibited estradiol-induced epithelial DNA synthesis in the mouse uterus and xenotransplanted human endometrium. This antiproliferative effect was less than that of progesterone (P4) and was observed when CDB-4124 was administered alone or concomitantly with P4. In the uterine epithelium, CDB-4124 acted as a P4 agonist and partial antagonist. In contrast, CDB-4124 acted as a complete P4 antagonist in the uterine stroma, where it blocked P4's action to induce a decidual response in the pseudopregnant mouse uterus and wildtype mouse uterus after copulation. In mated female mice, CDB-4124 impaired embryo implantation. Similarly, CDB-4124 inhibited the morphological and biochemical transformations of hESCs to decidual cells in vitro.

CONCLUSION

CDB-4124 exerts mixed P4 antagonistic/agonistic effects in the human and mouse endometrium, which result in failed embryo implantation because of the absence of stromal decidualization.

[Emergency contraception : practical guideline]

The goal of emergency contraception (EC) is to avoid unintended pregnancies after unprotected sexual intercourse (UPSI) or incorrect use of regular contraception. EC is intended for occasional use and does not replace effective regular contraception. A thorough understanding of EC is mandatory for optimal use of EC by healthcare professionals. Three EC methods are available in Belgium : oral levonorgestrel (LNG), oral ulipristal acetate (UA) and copper intrauterine device (Cu-IUD). EC should be offered as soon as possible after UPSI. The guidance aims to summarise the available evidence on EC methods, mechanism of action, and advantages/disadvantages of each method.

Access to emergency contraception in Kansas City clinics

OBJECTIVE

To assess the accessibility of ulipristal acetate (UPA) and copper intrauterine devices (IUDs) for emergency contraception (EC) in reproductive health centers in the Kansas City metropolitan area.

STUDY DESIGN

Using a secret shopper method, two female investigators called the reproductive health centers listed as EC providers on the nonprofit website bedsider.org that were located within 25 miles of the University of Kansas Medical Center. We categorized clinics as Title X providers vs. not according to the grantee list from the Office of Population Affairs. Investigators inquired about obtaining a UPA prescription by phone, the availability of the copper IUD for EC and time to first available appointment for EC. We evaluated correlates of EC access and provision with Fisher's Exact Tests.

RESULTS

We identified 40 clinics as potential EC providers. Some clinics reported that UPA could be prescribed by phone to existing patients (13/40, 32%), while others reported that women must meet with a provider first (15/40, 38%). Few clinics offered copper IUDs as EC (3/40, 8%). Title X clinic status did not predict provision of UPA by phone or copper IUDs as EC. The average time to next available appointment was 9±9 days to discuss EC and 13±9 days for a copper IUD.

CONCLUSIONS

Accessing the most efficacious forms of EC in a timely fashion presents many logistic challenges for women.

IMPLICATIONS

Healthcare systems should streamline protocols, train providers and improve rapid-access referral networks to facilitate timely provision of UPA and copper IUDs for EC.

[New recommendations from the World Health Organization (WHO) for the use of contraceptive methods]

The Medical Eligibility Criteria for Contraceptive Use of the World Health Organization have been updated recently. These criteria constitute a guideline for the selection of family planning methods appropriated for women and men with known medical conditions or personal characteristics of medical relevance. The guidelines last updating incorporates recommendations for the use of a new emergency contraceptive pill and three long-acting hormonal methods, and revises some previously established recommendations. This article provides information on the last edition of such document and aims to contribute to its dissemination.

Emergency contraception: A multispecialty survey of clinician knowledge and practices

OBJECTIVES

To assess knowledge and provision of emergency contraception (EC), particularly the most effective methods.

STUDY DESIGN

A web-based survey was distributed to a cross-sectional convenience sample of healthcare providers across specialties treating reproductive-aged women. The survey was sent to 3260 practicing physicians and advanced practice clinicians in 14 academic centers between February 2013 and April 2014. We analyzed responses by provider specialty using multivariable logistic regression.

RESULTS

The final sample included 1684 providers (response rate=51.7%). Ninety-five percent of the respondents had heard of levonorgestrel (LNG) EC. Among reproductive health specialists, 81% provide LNG EC in their practice, although only half (52%) had heard of ulipristal acetate (UPA) and very few provide it (14%). The majority in family medicine (69%) and emergency medicine (74%) provide LNG, in contrast to 42% of internists and 55% of pediatricians. However, the more effective methods [UPA and copper intrauterine device (IUD)] were little known and rarely provided outside of reproductive health specialties; 18% of internists and 14% of emergency medicine providers had heard of UPA and 4% provide it. Only 22% of emergency providers and 32% of pediatricians had heard of the copper IUD used as EC. Among reproductive health specialists, only 36% provide copper IUD as EC in their practice. Specialty, provider type and proportion of women of reproductive age in the practice were related to knowledge and provision of some forms of EC.

CONCLUSIONS

Awareness and provision of the most effective EC methods, UPA and the copper IUD (which are provider dependent), are substantially lower than for LNG EC, especially among providers who do not focus on reproductive health.

IMPLICATIONS

In our sample of 1684 healthcare providers from diverse specialties who treat reproductive-aged women, knowledge and provision of the most effective forms of EC (UPA and the copper IUD) are far lower than for LNG EC. Women should be offered the full range of EC methods.

[Selective progesterone receptor modulators and their therapeutical use]

Currently developed selective progesterone receptor modulators (SPRMs) are steroid derived compounds with a bulky radical substitution at carbon 11. They interact with progesterone receptor and exert antagonistic or/and agonistic effects. Mifepristone was approved for pregnancy termination and ulipristal acetate as emergency contraception and pharmacological therapy of uterine fibroids. SPRMs inhibit endometrial proliferation and myoma growth, this suggests a therapeutical effect in cases of endometriosis and other estrogen-dependent diseases.

Ulipristal acetate taken 48-120 hours after intercourse for emergency contraception

OBJECTIVE

To evaluate the efficacy and safety of ulipristal acetate as emergency contraception in women presenting 48-120 hours after receiving ulipristal acetate for unprotected intercourse.

METHODS

Women aged 18 years or older with regular cycles who presented for emergency contraception 48 to 120 hours after unprotected intercourse were enrolled in 45 Planned Parenthood clinics and treated with a single dose of 30 mg ulipristal acetate. Pregnancy status was determined by high-sensitivity urinary human chorionic gonadotropin testing and return of menses.

RESULTS

A total of 1,241 women were evaluated for efficacy. Twenty-six were pregnant at follow-up, for a pregnancy rate of 2.1% (95% confidence interval 1.4-3.1%). These results satisfy the protocol-defined statistical criteria for success because the pregnancy rate was lower than both the estimated expected pregnancy rate and a predefined clinical irrelevance threshold. In addition, efficacy did not decrease over time: pregnancy rates were 2.3% (1.4-3.8%), 2.1% (1.0-4.1%), and 1.3% (0.1-4.8%) for intervals of 48 to 72 hours, more than 72 to 96 hours, and more than 96 to 120 hours, respectively. Adverse events were mainly mild or moderate, the most frequent being headache, nausea, and abdominal pain. Cycle length increased a mean of 2.8 days, whereas the duration of menstrual bleeding did not change.

CONCLUSION

Ulipristal acetate is effective and well-tolerated for emergency contraception 48-120 hours after unprotected intercourse.

LEVEL OF EVIDENCE

II.

Effects of progesterone receptor blockers on human granulosa-luteal cell culture secretion of progesterone, estradiol, and relaxin

We have developed culture methods for human luteinizing granulosa cells (GLC) that support the timely and dynamic secretion of estrogen (estradiol-17beta; E(2)), progesterone (P(4)), and relaxin (Rlx) in patterns that mimic serum hormone concentrations during the luteal phase of the menstrual cycle. Additional hCG, to simulate rescue of the corpus luteum, prevented the normal decline in GLC hormone production. To test the importance of the P(4) receptor in P(4) production, GLC were treated in vitro with two P(4) receptor antagonists. Human GLC received one of two hCG support protocols: a Baseline group simulating the normal luteal phase or a Rescue group simulating early pregnancy. Baseline and Rescue groups were treated with either RU-486 or HRP2000 either early or late in the cell culture period. The effects of treatments or control on ovarian steroid and peptide hormone production were determined (significant difference was P < 0.05). In the Rescue group, late treatment resulted in an immediate and dramatic decline in E(2), P(4), and Rlx secretion to nearly nondetectable levels within 1 day after treatment, and hormones remained depressed for the remaining 10 days of culture. In contrast, early treatment resulted in a decline in steroid hormone secretion that returned to control levels within 5 days of cessation of treatment, and Rlx secretion was delayed for approximately 5 days more than in controls. The data support the hypothesis that P(4) may be a required autocrine factor, not only for its own production but also for the maintenance of full endocrine function of the corpus luteum.

Effects of two antiprogestins on early pregnancy in the long-tailed macaque (Macaca fascicularis)

The abortifacient effects of mifepristone and HRP 2000 were compared in gravid long-tailed macaques. Thirty-six animals were studied with treatment administered either by the oral (0.5 or 5.0 mg/kg; N = 5 per antiprogestin per dose) or intramuscular (i.m.) routes (0.5 mg/kg; N = 5 per antiprogestin) on gestational days (GD) 23-26; six vehicle controls were included. Blood samples were collected for assay of progesterone (P4) and each of the antiprogestins (pre-treatment, daily GD 23-28, every other day GD 30-40), and animals were monitored sonographically throughout gestation. Results of these studies indicated high rates of abortion with i.m. administration (3/5 mifepristone, 4/5 HRP 2000) and 5.0 mg/kg oral route (4/5, 2/5, respectively), with less effects noted at oral doses of 0.5 mg/kg (2/5, 0/5, respectively). No early abortions were observed in the control groups. Following daily i.m. treatment, peak levels of 8-16 ng/ml mifepristone were detected whereas 6-10 ng/ ml of HRP 2000 were noted (GD 26-27). No serum levels of mifepristone were detected following either of the oral doses whereas serum levels of 2-6 ng/ml HRP 2000 were noted with high dose oral administratation. Results of these studies suggest: (1) both antiprogestins are roughly comparable in terminating early pregnancy although HRP 2000 may be more efficacious when administered i.m. whereas mifepristone may be more effective when administered orally; (2) similar levels of biological activity are seen with the i.m. and high dose oral dosing regimens, with little or no activity with the oral low dose; and (3) infants resulting from surviving pregnancies were not affected by early gestation exposure.

Contraceptive implants

Available contraceptive implants appeal to women of diverse cultural and socioeconomic background because they offer long-term contraception, safety, effectiveness, reversibility and lack of estrogenic side-effects. Experience with Norplant I indicates that despite some side-effects the continuation rate is the highest for any reversible method of contraception. Disruption of the menstrual cycle is the main reason for discontinuation, hence research effort needs to focus on the mechanism of progestogen-induced endometrial bleeding and appropriate therapy. Implant service programs should have trained and skilled personnel who can provide adequate counseling that complements any public education effort and also provides effective services. Because contraceptive implants offer no protection against sexually transmitted infections, those who engage in high-risk sexual behavior should be encouraged to use condoms as well.

A comparison of the pregnancy-terminating potencies of three anti-progestins in guinea-pigs, and the effects of sulprostone

The anti-progestins mifepristone, lilopristone (ZK 98734) and HRP 2000 were equipotent at terminating the pregnancy of guinea-pigs during mid-gestation, although mifepristone was more effective at low doses. Sulprostone administration on the day following anti-progestin treatment tended to increase the effectiveness of mifepristone and HRP 2000, without affecting the time interval between the start of the anti-progestin treatment and the day of abortion. It is concluded that, of the three afferent anti-progestins used, none is more potent than the other two at terminating pregnancy in the animal model used. The co-administration of a prostaglandin E2 (PGE2) analogue tends to increase the effectiveness of the anti-progestin.

Evaluation of RU-27987 as a ligand to determine the progesterone receptor

RU-27987, a synthetic progestin, which was recently developed by Roussel Uclaf, Paris, was tested for its validity as a ligand to determine the progesterone receptor in breast cancer. The results were compared to those obtained with R-5020 and ORG-2058, two ligands that are already in use worldwide. The intra- and interassay variation of receptor determination was similar for all 3 ligands. Receptor levels were analyzed with each of the 3 progestins in control cytosols and in 26 mammary carcinoma samples. A good correlation between receptor levels was found although the values of ORG-2058 were somewhat lower, but not significantly. This resulted in a lower proportion of receptor positive samples for ORG-2058 (11/26) compared to R-5020 (13/26) and RU-27987 (14/26). The affinity to the progesterone and to the glucocorticoid receptor, as well as the precision of the Scatchard plot analysis were comparable for the 3 ligands tested. Intra- and interassay variation of receptor determination were also similar. We therefore conclude, that RU-27987 is a suitable ligand to determine progesterone receptor in mammary carcinoma.