The progestin ST 1435--rapid metabolism in man

Nestorone nanosuspension-loaded dissolving microneedles array patch: A promising novel approach for "on-demand" hormonal female-controlled peritcoital contraception

"On demand" hormonal female-controlled pericoital contraception is one strategy which could be used to minimize the impact of unintended pregnancy. Nestorone (NES) is a potent contraceptive, with relatively few side effects in comparison with other contraceptives. NES presents an attractive option for "on demand" pericoital contraceptive. Unfortunately, the drug is inactive if taken orally, but it has high progestational activity and antiovulatory potency if administered parenterally. Current drug delivery systems, such as a transdermal hydrogel are not so satisfactory. Dissolving microneedles array (DMNs) are an attractive alternative, minimally-invasive, delivery system. In this study, we report, for the first time, development of tip-loaded NES-nanosuspension (NES-NS)-loaded bilayer DMNs to deliver NES intradermally for subsequent release. NES-NS was prepared and optimised, freeze-dried and then used to fabricate DMNs using a blend of two biocompatible polymers, namely poly(vinyl alcohol) and poly(vinyl pyrrolidone). Both NES-NS and the NES-NS-loaded DMNs were fully characterised and the performance of the DMNs was evaluated in vivo using Sprague Dawley rats. Results showed that the finalised NES-NS had particle size and PDI values of 666.06 ± 1.86 nm and 0.183 ± 0.01, respectively. The NES-NS-DMNs had relatively high tips-localised drug loading (approximately 2.26 ± 1.98 mg/array) and exhibited satisfactory mechanical and insertion properties. In Sprague Dawley rats, DMNs delivered NES into the skin, with the drug then appearing in blood and rapidly reaching its maximum concentration (C_max of 32.68 ± 14.06 ng/mL) within 1h post-DMNs application. Plasma levels above 3.4 ng/mL were maintained for 2 days. This suggests that DMNs are a promising drug delivery system that could be used to deliver NES as an "On demand" hormonal female-controlled pericoital contraceptive.

Pharmacokinetics, metabolism and serum concentrations of progestins used in contraception

Many different forms of hormonal contraception are used by millions of women worldwide. These contraceptives differ in the dose and type of synthetic progestogenic compound (progestin) used, as well as the route of administration and whether or not they contain estrogenic compounds. There is an increasing awareness that different forms of contraception and different progestins have different side-effect profiles, in particular their cardiovascular effects, effects on reproductive cancers and susceptibility to infectious diseases. There is a need to develop new methods to suit different needs and with minimal risks, especially in under-resourced areas. This requires a better understanding of the pharmacokinetics, metabolism, serum and tissue concentrations of progestins used in contraception as well as the biological activities of progestins and their metabolites via steroid receptors. Here we review the current knowledge on these topics and identify the research gaps. We show that there is a paucity of research on most of these topics for most progestins. We find that major impediments to clear conclusions on these topics include a lack of standardized methodologies, comparisons between non-parallel clinical studies and variability of data on serum concentrations between and within studies. The latter is most likely due, at least in part, to differences in intrinsic characteristics of participants. The review highlights the importance of insight on these topics in order to provide the best contraceptive options to women with minimal risks.

Simultaneous assay of segesterone acetate (Nestorone®), estradiol, progesterone, and estrone in human serum by LC-MS/MS

OBJECTIVE

To develop a method to simultaneously quantify the synthetic contraceptive progestin segesterone acetate (Nestorone®, NES) and the endogenous steroid hormones estradiol (E2), progesterone (P4), and estrone (E1) in human serum samples by liquid chromatography-tandem mass spectrometry (LC-MS/MS).

STUDY DESIGN

We analyzed 615 serum samples collected from 67 reproductive-age women actively using a contraceptive vaginal ring (CVR) designed to release NES (200 mcg/d) and E2 (75-200 mcg/d). Samples were taken prior to and up to 30 days after CVR insertion and analyzed for concentrations of NES, E2, P4, and E1 in human serum using a Shimadzu Nexera-LCMS-8050 LC-MS/MS platform. Precision, accuracy, and sensitivity for all analytes were determined across multiple assays.

RESULTS

The assay ranges for NES, E2, P4, and E1 in this analytical method were 10 pg/mL to 10 ng/mL with a lower limit of quantification of 10 pg/mL for all targets. Assay precisions were less than or equal to 14.5% and accuracies ranged from 87.0% to 110.8%. When applied to the 615 clinical samples, 550 samples had quantifiable concentrations of NES (value range 0.014-1471 ng/mL). Similarly, 595 samples had quantifiable concentrations of E2 (0.010-0.312 ng/mL), 596 samples had quantifiable concentrations of P4 (0.010-5.791 ng/mL), and 609 samples had quantifiable concentrations of E1 (0.010-0.416 ng/mL).

CONCLUSIONS

The LC-MS/MS platform results in a robust, accurate, and sensitive method for the simultaneous quantification of NES and endogenous steroid hormones in human serum.

IMPLICATIONS

The analytical method described allows for the simultaneous quantification of NES and endogenous steroids and can be used to monitor NES concentrations during clinical trials and subject adherence to treatment with NES.

Nestorone® as a Novel Progestin for Nonoral Contraception: Structure-Activity Relationships and Brain Metabolism Studies

Nestorone® (NES) is a potent nonandrogenic progestin being developed for contraception. NES is a synthetic progestin that may possess neuroprotective and myelin regenerative potential as added health benefits. In receptor transactivation experiments, NES displayed greater potency than progesterone to transactivate the human progesterone receptor (PR). This was confirmed by docking experiments where NES adopts the same docking position within the PR ligand-binding domain (LBD) as progesterone and forms additional stabilizing contacts between 17α-acetoxy and 16-methylene groups and PR LBD, supporting its higher potency than progesterone. The analog 13-ethyl NES also establishes similar contacts as NES with Met909, leading to comparable potency as NES. In contrast, NES is not stabilized within the human androgen receptor LBD, leading to negligible androgen receptor transactivation. Because progesterone acts in the brain by both PR binding and indirectly via binding of the metabolite allopregnanolone to γ-aminobutyric acid type A receptor (GABAAR), we investigated if NES is metabolized to 3α, 5α-tetrahydronestorone (3α, 5α-THNES) in the brain and if this metabolite could interact with GABAAR. In female mice, low concentrations of reduced NES metabolites were identified by gas chromatography/mass spectrometry in both plasma and brain. Electrophysiological studies showed that 3α, 5α-THNES exhibited only limited activity to enhance GABAAR-evoked responses with WSS-1 cells and did not modulate synaptic GABAARs of mouse cortical neurons. Thus, the inability of reduced metabolite of NES (3α, 5α-THNES) to activate GABAAR suggests that the neuroprotective and myelin regenerative effects of NES are mediated via PR binding and not via its interaction with the GABAAR.

Single-dose pharmacokinetics of Nestorone, a potential female-contraceptive

A synthetic progestin Nestorone is being developed for female-contraception. This study was conducted to determine the distribution, metabolism, and excretion of tritium-labeled Nestorone ((3)H Nestorone) in adult female rats. Rats were injected subcutaneously (S.C.) with a single dose of 400 microCi (3)H Nestorone/kg BW. Its distribution and concentrations in blood, plasma and other tissues were determined at defined times. The excreta were examined for elimination of (3)H Nestorone. Radioactivity in all samples was analyzed by liquid scintillation counter. Metabolite profiling was performed by HPLC and LC/MS analysis of the plasma, urine, and feces samples. Following subcutaneous injection of (3)H Nestorone, the mean peak concentrations of radioactivity (C(max)) in the blood and plasma were 58.1 and 95.5 ng equiv. (3)H Nestorone/g, respectively, at 2-h postdose (T(max)). Thereafter, the concentration of drug steadily declined through 96-h postdose with a terminal elimination half-life (t(1/2)) of 15.6 h. (3)H Nestorone-derived radioactivity was widely distributed in most tissues by 0.5 h and attained a mean maximal concentration by 2-h postdose. Approximately, 81.4% and 7.62% of the administered dose was excreted via feces and urine, respectively. In vivo metabolism of (3)H Nestorone resulted into a total of 19 metabolites. Among them, two metabolites viz., 17alpha-deacetyl-Nestorone (M9) and 4,5-dihydro-17alpha-deacetyl-Nestorone (M19) were identified by HPLC and LC/MS analysis. Metabolite profiling of plasma samples showed that most of the circulating radioactivity was associated with unchanged parent drug, and M19. The M19 was a major metabolite in the profiled urine and feces samples. Presence of large proportion of drug/drug-related material in feces suggested that the biliary excretion is a main elimination route of (3)H Nestorone. The distribution, metabolism, and excretion profiles of (3)H Nestorone obtained in this study provide a fairly good insight about its fate in women.

Contraceptive vaginal rings releasing Nestorone and ethinylestradiol: a 1-year dose-finding trial

In a multicenter 1-year trial of contraceptive vaginal rings (rings) involving 150 women, three dose combinations of the progestin Nestorone (NES) and ethinylestradiol (EE) were compared with respect to effectiveness, safety and acceptability. Mean in vitro drug release rates for the three doses were 150 and 15, 150 and 20 and 200 and 15 microg/day of NES and EE, respectively. Each ring remained in situ for 21 days, removed for 7 days and then reinserted for a total of 13 cycles of use. We studied ring performance with respect to pregnancy and other termination events, adverse events, the extent of ovulation inhibition, serum drug levels and bleeding control. We also assessed the rings' effects on the vagina using a standardized colposcopy procedure. Seventy-two percent of the women completed the 1-year (> or = 350 days) study. In studied cycles, luteal activity (progesterone > or = 10 nmol/L) was noted in 17%, 7% and 12% of subjects with monitored cycles at the 150/15, 150/20 and 200/15 doses, respectively (p = .34). Two pregnancies occurred, both in subjects using the 200/15 microg/day ring. Breakthrough bleeding during ring use averaged about 2 days/year and breakthrough bleeding and spotting averaged about 7 days/year. In the entire trial, only two women discontinued because of bleeding problems. Medical conditions, chiefly vaginal problems, personal reasons and device loss or repeated expulsion were the principal reasons given for study discontinuation. Vaginal and cervical colposcopy, conducted with standardized techniques and standardized interpretations, revealed no elevated event incidence attributable to ring use. Clinical performance and adverse event profiles indicate that each of these 1-year NES/EE rings, used on a 21-day-in and 7-day-out regimen, provided women effective, acceptable and safe long-acting contraception under their own control.

The effect of Nestorone on gonadotropic cells in pituitary of rats

The implant containing Nestorone is a promising long-acting contraceptive especially suitable for lactating women. In this study, two experiments were designed to observe the effect of Nestorone on the gonadotropic cells in pituitary of rats for analyzing its antiovulation mechanism. In the first experiment, the ED50 of Nestorone on inhibiting ovulation was found to be 1.32 mg/kg. The serum luteinizing hormone (LH) levels were significantly lower 60 h after being treated with Nestorone at 8:30-9:00 a.m. on Day 2 (D2) of estrus. Image analysis showed that the average size of the LH cells in groups treated with Nestorone at 2 or 4 mg/kg was larger than that of the control. In the group treated with 4 mg/kg, most of gonadotropic cells were regular round in shape. And, abundant granules in cytoplasm were found in those cells, which indicated that the LH stored in cells was not released. In the second experiment, the rats were treated with Nestorone at 5 mg/kg at 11:30-12:00 a.m. on D2 of estrus. The normal or higher expression of LHbeta mRNA in pituitary suggested that the synthesis of LH was not inhibited by the treatment with Nestorone. The expression of PR mRNA in pituitary was significantly lower than that of the control at 33 h after treatment. This might be a direct effect of Nestorone, since there were no differences in the serum E2 and P4 levels between the treated and the control group. It is concluded that Nestorone prevents ovulation through inhibition of LH secretion and it has no effect on synthesis of LH. Progesterone receptors in pituitary might be involved in this process, but further study is needed to gain more evidence.

Two-year performance of a Nestorone®-releasing contraceptive implant: a three-center study of 300 women

A 2-year trial of a single Nestorone (NES) rod implant was conducted at three Latin American centers, each enrolling 100 women. We studied the safety, effectiveness and acceptability of this progestin-releasing contraceptive implant. Three pregnancies occurred, the last at 18 months of use. Because no pregnancies were expected in the first 18 months, the trial was halted. At that time, 224 women had completed at least 18 months of use, and 99 women had used the implant for more than 24 months. Few participants used adjunctive contraception between the time the study was halted and the time they had their implant removed. No additional pregnancies occurred before the removal of the last implant. The 2-year cumulative pregnancy rate was 1.7 per 100 with a Pearl index of 0.6 per 100 for the 2-year period. The 1-year and 2-year continuation rates were 80.5 and 66.7 per 100, respectively. Menstrual and medical disturbances were the principal reasons for discontinuation, followed by planned pregnancy. Headache and weight gain frequently led to discontinuation. The NES implant had little important effect on most clinical chemistry and lipid parameters. Over the study course, the mean change in hemoglobin was <1%. Slight modification of the design of this single 2-year implant, restoring features previously examined in clinical trials, is likely to improve its effectiveness. A single NES implant appears to provide acceptable contraception for women.

An overview of nomegestrol acetate selective receptor binding and lack of estrogenic action on hormone-dependent cancer cells

The specific pharmacological profile of the 19-norprogestin nomegestrol acetate (NOMAC) is, at least in part, defined by its pattern of binding affinities to the different steroid hormone receptors. In the present study, its affinity to the progesterone receptor (PgR), the androgen receptor (AR) and the estrogen receptor (ER) was re-evaluated and compared to those obtained for progesterone (P) and several progestins. The characteristics of binding to the PgR in rat uterus were determined and Ki were found to be roughly similar with 22.8 and 34.3 nM for NOMAC and P, respectively. The binding characteristics of 3H-NOMAC were also determined and compared to that of 3H-ORG2058 with Kd of 5 and 0.6 nM, respectively for rat uterus and 4 and 3 nM, respectively for human T47-D cells. Structure-affinity and -activity relationships were studied on a variety of compounds related to NOMAC in order to assess its specificity as a progestin. The effects of NOMAC on the binding of androgen to the AR were investigated, using rat ventral prostate as target model. Contrary to what was observed for MPA, the RBA of NOMAC was found to decline with time, showing anti-androgenic rather than androgenic potential, a result that was confirmed in vivo. Regarding the ER, since none of the progestins were able to compete with estrogen for binding in rat uterus as well as in Ishikawa cells, the induction of alkaline phosphatase activity (APase) was used as an estrogen-specific response. It confirmed the intrinsic estrogenicity of progestins derived from 19-nor-testosterone (19NT), norethisterone acetate (NETA), levonorgestrel (LNG) or norgestimate (NGM) and others. In contrast, all P and 19-norP derivatives remained inactive. Finally, to complete this overview of NOMAC at the sex steroid receptor levels, the lack of estrogenic or estrogenic-like activity was checked out in different in vitro models. Data from this study have demonstrated that NOMAC is a progestin that has greater steroid receptor selectivity compared to MPA or some other synthetic progestins. It may provide a better pharmacological profile than those progestins currently in use in HRT and OC.

Recent developments in contraceptive implants at the Population Council

Development of contraceptive implant methods, when based on established or on new synthetic chemical entities, is a decadal or multi-decadal process. The process often requires the cooperation of numerous investigators for laboratory work, for early Phase II trials, for dose-finding trials, and for Phase III clinical trials. The Phase III work also requires cooperation with a commercial manufacturer and potential distributor of the product. The Population Council has recently completed developmental work on two levonorgestrel-releasing implants, with filings to regulatory agencies that support extended use of Jadelle implants for 5 years and Norplant implants for 7 years. When the developmental process includes establishing the clinical properties of a molecule not yet approved by regulatory agencies, the minimum development time appears to be two decades. The status and rationale of studies of a new Nestorone-releasing, single implant developed by the Population Council for a period of use of 2 years are presented.

Contraceptive implants and lactation

The safety and efficacy of four contraceptive implants, plant, Implanon, Nestorone and Elcometrine, have been evaluated during use in the postpartum period by lactating women. These implants provide highly effective contraceptive protection with no negative effect on breastfeeding or infant growth and development. Breastfeeding women initiating Norplant use in the second postpartum month experience significantly longer periods of amenorrhea than do untreated women or intrauterine device users. After weaning, the bleeding pattern is similar to that observed in non-nursing women. Norplant use does not affect bone turnover and density during lactation. Norplant and Implanon release orally active progestins while Nestorone and Elcometrine implants release an orally inactive progestin, which represents an advantage since the infant should be free of steroidal effects. The infant's daily intake of steroids (estimated from concentrations in maternal milk during the first month of use) range from 90 to 100 ng of levonorgestrel (Norplant), 75-120 ng of etonogestrel (Implanon), and 50 ng and 110 ng of Nestorone (Nestorone and Elcometrine implants, respectively). Nursing women needing contraception may use progestin-only implants when nonhormonal methods are not available or acceptable. Implants that deliver orally active steroids should only be used after 6 weeks postpartum to avoid transferring of steroids to the newborn.

Contraceptive efficacy and clinical performance of Nestorone implants in postpartum women

The objective of this study was to evaluate the contraceptive efficacy and clinical performance of a Nestorone subdermal implant (NES) in the postpartum period. NES (n = 100) and Copper T intrauterine device (T-Cu; n = 100) acceptors initiated contraception at 8 weeks postpartum and were followed at monthly intervals during the first year and at 3-month intervals thereafter. Pregnancy rates, breastfeeding performance, infant growth, bleeding pattern, and side effects were assessed. Blood and milk NES concentration were measured. No pregnancy occurred in 2195 and 2145 woman-months of NES implant and T-Cu use, respectively. No effect of NES on lactation and infant growth and no serious adverse events were observed. Lactational amenorrhea was significantly longer in NES users (353 +/- 20 days) than in T-Cu users (201 +/- 11 days). More NES users (55.8%) experienced prolonged bleedings than did T-Cu users (36.2%). Concentrations of NES in breast milk ranged between 54-135 pmol/liter. The Nestorone implant is a highly effective contraceptive, safe for breastfed infants because the steroid is inactive by the oral route.

Parenteral administration of progestin Nestorone to lactating cynomolgus monkeys: an ideal hormonal contraceptive at lactation?

Nestorone (NES) progestin is highly effective for contraception following parenteral administration, but ineffective after oral ingestion due to rapid first-pass metabolism. Thus, NES might be ideal for lactational contraception; possible NES in milk should be metabolized by the nursing infant. We evaluated the distribution of NES, its endocrine effects and infant weight gain in five cynomolgus monkeys and their nursing infants. Nestorone implants, releasing approximately 40 microg NES/day in vitro, were placed s.c. in the mothers 3-4 months following delivery, where they remained in situ for 4 weeks. Sampling (blood daily from the mother; milk and blood from the infant at 3 day intervals) was initiated at 2 weeks prior to insertion, and continued for 2 weeks following removal of the implant. NES, oestradiol, progesterone and prolactin were measured by radioimmunoassays and the infants were weighed weekly. The (mean +/- SD) maternal serum and milk concentrations of NES were 337 +/- 90 and 586 +/- 301 pmol/l during the use of the implants. The ratio of milk/serum NES was 1.68 +/- 0.12 (mean +/- SE), and the serum and milk concentrations were significantly correlated (r = 0. 75, P < 0.001). NES was not detectable (<13 pmol/l) in any infant serum samples. Concentrations of prolactin (mean +/- SD) were 41.1 +/- 32, 26.7 +/- 7.6 and 26.3 +/- 9.5 ng/ml before, during and after the use of the implants respectively. The (mean +/- SE) infant weight increased from 643 +/- 54 g 1 week prior to insertion to 713 +/- 54 g 1 week following removal. These data confirm that NES in milk is rapidly metabolized by the suckling infant. Therefore, NES appears to be an ideal hormonal contraceptive for use during lactation.

Use of a single implant of elcometrine (ST-1435), a nonorally active progestin, as a long acting contraceptive for postpartum nursing women

Because of its unique features, the contraceptive effectiveness and tolerance during breast-feeding of 16-methylene-17 alpha-acetoxy-19-nor-4-pregnene-3,20-dione (elcometrine), delivered within a single subdermal capsule of medical grade polydimethylsiloxane, was investigated. Unlike other progestational steroids, elcometrine has no affinity for androgen and estrogen receptors and is inactive by the oral route. A total of 66 breast-feeding women receiving elcometrine by the subdermal route were enrolled in the study, and 69 women who elected to use Copper-T380 intrauterine devices (IUD) served as control subjects. The women and their infants were observed until the end of the first postpartum year. There were no significant differences in growth and development measurements among the infants in the elcometrine and control groups. The percentage of infants continuing to breast-feed at 3 and 6 months was significantly higher in the elcometrine group. There were no significant differences between the concentration of elcometrine in the mother's blood and milk. At 75 days, blood levels of elcometrine in the infants were near the undetectable and were significantly lower than the levels in maternal blood or milk (p < 0.01). In 15 of 25 infants, blood levels of elcometrine were at the limit of assay sensitivity or undetectable. Two pregnancies occurred in women using IUD, whereas none occurred in those using implants. There were menstrual bleeding irregularities in both groups. A single elcometrine capsule placed subcutaneously at 6-monthly intervals appears to be an effective method of contraception for lactating women and results in blood concentrations of nursing infants at or near undetectable levels.

Synthesis and progestational activity of 16-methylene-17 alpha-hydroxy-19-norpregn-4-ene-3,20-dione and its derivatives

16-Methylene-17 alpha-hydroxy-19-norpregn-4-ene-3,20-dione 1 and its 17 alpha-acylated derivatives were synthesized. The length of the 17 alpha-side-chain ranges from C2-C6. As anticipated, compound 1 did not show any progestational activity or receptor binding activity; whereas, the acylated compounds, especially the butyrate, showed remarkable ability to bind to progesterone receptors. These compounds also showed progestational activity in an in vitro T47D cell culture assay in which progestins increase alkaline phosphatase activity and in an in vivo ovulation inhibition assay. All of the compounds synthesized were without estrogenic activities. The results showed that acylation of 16-methylene-17 alpha-hydroxy-19-norprogesterone can increase progestational activity. The progestational activities of these compounds varied with the 17 alpha-side chain.