Progesterone antagonist therapy in a Pelizaeus-Merzbacher mouse model.

Pelizaeus-Merzbacher disease (PMD) is a severe hypomyelinating disease, characterized by ataxia, intellectual disability, epilepsy, and premature death. In the majority of cases, PMD is caused by duplication of PLP1 that is expressed in myelinating oligodendrocytes. Despite detailed knowledge of PLP1, there is presently no curative therapy for PMD. We used a Plp1 transgenic PMD mouse model to test the therapeutic effect of Lonaprisan, an antagonist of the nuclear progesterone receptor, in lowering Plp1 mRNA overexpression. We applied placebo-controlled Lonaprisan therapy to PMD mice for 10 weeks and performed the grid slip analysis to assess the clinical phenotype. Additionally, mRNA expression and protein accumulation as well as histological analysis of the central nervous system were performed. Although Plp1 mRNA levels are increased 1.8-fold in PMD mice compared to wild-type controls, daily Lonaprisan treatment reduced overexpression at the RNA level to about 1.5-fold, which was sufficient to significantly improve the poor motor phenotype. Electron microscopy confirmed a 25% increase in the number of myelinated axons in the corticospinal tract when compared to untreated PMD mice. Microarray analysis revealed the upregulation of proapoptotic genes in PMD mice that could be partially rescued by Lonaprisan treatment, which also reduced microgliosis, astrogliosis, and lymphocyte infiltration.

Ultrastructural changes of erythrocytes in whole blood after exposure to prospective in silico-designed anticancer agents: a qualitative case study.

BACKGROUND: Novel, in silico-designed anticancer compounds were synthesized in our laboratory namely, 2-ethyl-3-O-sulphamoyl-estra-1,3,5(10),15-tetraen-17-ol (ESE-15-ol) and 2-ethyl-3-O-sulphamoyl-estra-1,3,5(10)16-tetraene (ESE-16). These compounds were designed to have improved bioavailability when compared to their source compound, 2-methoxyestradiol. This theoretically would be due to their increased binding affinity to carbonic anhydrase II, present in erythrocytes. Since the novel compounds under investigation are proposed to be transported within erythrocytes bound to carbonic anhydrase II, the morphological effect which they may exert on whole blood and erythrocytes is of great significance. A secondary outcome included revision of previously reported procedures for the handling of the whole blood sample. The purpose of this study was twofold. Firstly, the ultrastructural morphology of a healthy female's erythrocytes was examined via scanning electron microscopy (SEM) after exposure to the newly in silico-designed compounds. Morphology of erythrocytes following exposure to ESE-15-ol and ESE-16 for 3 minutes and 24 hours at 22°C were described with the use of SEM. The haemolytic activity of the compounds after 24 hours exposure were also determined with the ex vivo haemolysis assay. Secondly, storage conditions of the whole blood sample were investigated by determining morphological changes after a 24 hour storage period at 22°C and 37°C. RESULTS: No significant morphological changes were observed in the erythrocyte morphology after exposure to the novel anticancer compounds. Storage of the whole blood samples at 37°C for 24 hours resulted in visible morphological stress in the erythrocytes. Erythrocytes incubated at 22°C for 24 hours showed no structural deformity or distress. CONCLUSIONS: From this research the optimal temperature for ex vivo exposure of whole blood samples to ESE-15-ol and ESE-16 for 24 hours was determined to be 22°C. Data from this study revealed the potential of these compounds to be applied to ex vivo study techniques, since no damage occurred to erythrocytes ultrastructure under these conditions. As no structural changes were observed in erythrocytes exposed to ESE-15-ol and ESE-16, further ex vivo experiments will be conducted into the potential effects of these compounds on whole blood. Optimal incubation conditions up to 24 hours for whole blood were established as a secondary outcome.

A phase I dose-escalation, safety and pharmacokinetic study of the 2-methoxyestradiol analog ENMD-1198 administered orally to patients with advanced cancer.

BACKGROUND: 2-methoxyestradiol (2ME2) is an estradiol-17ß metabolite with antiproliferative and antiangiogenic activities. ENMD-1198 is an analog of 2ME2 which was developed to decrease the metabolism and increase both the bioavailability and antitumor activities of the parent molecule. This first-in-human phase I study evaluated the tolerability, pharmacokinetics and preliminary evidence of activity of ENMD-1198 in advanced cancer patients. METHODS: Eligible patients received ENMD-1198 orally once daily in Part A (standard 3 + 3 dose escalation design), or in Part B (accelerated dose escalation design). Cycle 1 consisted of 28 days daily dosing followed by a 14-(Part A) or 7-(Part B) day observation period, then continuously in 28 day cycles thereafter. RESULTS: A total of 29 patients were enrolled in 12 dose cohorts (5 to 550 mg/m²)/d). The most common drug-related toxicities were Grade 1/2 fatigue (55%), nausea and vomiting (37%), and constipation (34%). Two DLTs (Grade 4 neutropenia) occurred at 550 mg/m²/day, and 425 mg/m²/d was declared the maximum tolerated dose. ENMD-1198 was absorbed rapidly with a T(max) of 1-2 h. Exposure to ENMD-1198 (C(max) and AUC0₋24 hr increased linearly with dose. The mean terminal half-life was 15 h. A 3-fold accumulation was found after multiple doses. Five patients achieved stabilization of disease for at least 2 cycles, three of whom (with neuroendocrine carcinoma of pancreas, prostate cancer and ovarian cancer) demonstrated prolonged stabilization ranging from 8-24.5 cycles. CONCLUSION: ENMD-1198 is well-tolerated with a pharmacokinetic exposure profile compatible with once daily dosing. The recommended phase II dose of ENMD-1198 is 425 mg/m²/d. Early evidence of prolonged disease stabilization in pre-treated patients suggests ENMD-1198 is worthy of additional investigation.

Daily Oral Administration of the Novel Androgen 11ß-MNTDC Markedly Suppresses Serum Gonadotropins in Healthy Men.

BACKGROUND: 11ß-methyl-19-nortestosterone (11ß-MNT) is a modified testosterone (T) with androgenic and progestational activity. A single oral dose of the prodrug, 11ß-MNT dodecylcarbonate (11ß-MNTDC), was well tolerated in healthy men. METHODS: We conducted a randomized, double-blind study at 2 academic medical centers. 42 healthy men (18-50 years) were randomized to receive oral placebo or 11ß-MNTDC, 200 or 400 mg daily, for 28 consecutive days. Primary outcome (safety and tolerability) measures were assessed twice per week. Subjects underwent serial blood sampling over 24 hours on days 1 and 28 to assess secondary outcomes: pharmacokinetics (serum drug concentrations); pharmacodynamics of 11ß-MNTDC (serum sex steroids and gonadotropins); and mood and sexual function (via validated questionnaires). RESULTS: There were no serious adverse events. No participants discontinued because of an adverse event or laboratory test abnormality. 11ß-MNTDC resulted in a dose-related increase in serum 11ß-MNTDC and 11ß-MNT concentrations sustained over 24 hours. Administration of 11ß-MNTDC resulted in a marked suppression of serum gonadotropins, T, calculated free T, estradiol, and SHBG over the treatment period (P < 0.01). Adverse effects that may be related to 11ß-MNTDC included weight gain, acne, headaches, fatigue, and mild mood changes, with 5 men reporting decreased libido and 3 decreased erectile/ejaculatory function. Serum low-density lipoprotein cholesterol, weight (~2 kg), hematocrit, and hemoglobin increased and serum high-density lipoprotein cholesterol decreased in both 11ß-MNTDC groups. CONCLUSION: Daily oral 11ß-MNTDC for 28 days in healthy men markedly suppressed serum gonadotropin and T concentrations without serious adverse effects. These results warrant further evaluation of 11ß-MNTDC as a potential male oral contraceptive.

Blood-brain barrier traversal by African trypanosomes requires calcium signaling induced by parasite cysteine protease.

In this study we investigated why bloodstream forms of Trypanosoma brucei gambiense cross human brain microvascular endothelial cells (BMECs), a human blood-brain barrier (BBB) model system, at much greater efficiency than do T. b. brucei. After noting that T. b. gambiense displayed higher levels of cathepsin L-like cysteine proteases, we investigated whether these enzymes contribute to parasite crossing. First, we found that T. b. gambiense crossing of human BMECs was abrogated by N-methylpiperazine-urea-Phe-homopheylalanine-vinylsulfone-benzene (K11777), an irreversible inhibitor of cathepsin L-like cysteine proteases. Affinity labeling and immunochemical studies characterized brucipain as the K11777-sensitive cysteine protease expressed at higher levels by T. b. gambiense. K11777-treated T. b. gambiense failed to elicit calcium fluxes in BMECs, suggesting that generation of activation signals for the BBB is critically dependant on brucipain activity. Strikingly, crossing of T. b. brucei across the BBB was enhanced upon incubation with brucipain-rich supernatants derived from T. b. gambiense. The effects of the conditioned medium, which correlated with ability to evoke calcium fluxes, were canceled by K11777, but not by the cathepsin B inhibitor CA074. Collectively, these in vitro studies implicate brucipain as a critical driver of T. b. gambiense transendothelial migration of the human BBB.

Lymphatic transport of Methylnortestosterone undecanoate (MU) and the bioavailability of methylnortestosterone are highly sensitive to the mass of coadministered lipid after oral administration of MU.

The contribution of lymphatic transport to the oral bioavailability of methylnortestosterone (M) after oral administration of the lipophilic prodrug methylnortestosterone undecanoate (MU) has been evaluated, and the sensitivity of lymphatic MU transport to lymphatic lipid transport has been investigated. M and MU were administered intravenously and orally to greyhound dogs to determine absolute bioavailability after oral dosing of MU. MU was also administered orally with differing quantities of food (lipid) to lymph duct-cannulated greyhound dogs to investigate the relative roles of lymph versus blood transport on M bioavailability and the effect of lipid load on systemic exposure. The relationship between lymphatic lipid and MU transport was further investigated in anesthetized rats. The oral bioavailability of M after administration of MU was found to be highly dependent on coadministration of food, and the bioavailability of M increased approximately 700% in fed versus fasted animals. In both cases, lymph diversion resulted in negligible systemic exposure of M, indicating almost complete dependence on lymphatic transport of MU for systemic exposure of M. Lymphatic transport of MU was even more highly dependent on the quantity of coadministered lipid and increased more than 50-fold with increasing lipid load. Therefore, increasing the quantity of food or lipid coadministered with MU stimulated a significant increase in the lymphatic transport of MU and systemic exposure of M. The lipid sensitivity of lymphatic transport of MU is significantly higher than previously observed for more metabolically stable compounds, suggesting a role for coadministered lipid in promoting avoidance of enterocyte-based cleavage of MU.

Synthesis, antiproliferative, and pharmacokinetic properties of 3- and 17-double-modified analogs of 2-methoxyestradiol.

The syntheses of 21 analogs of 2-methoxyestradiol are presented, including ENMD-1198 which was selected for advancement into Phase 1 clinical trials in oncology. These analogs were evaluated for antiproliferative activity using breast tumor MDA-MB-231 cells, for antiangiogenic activity in HUVEC proliferation assays, and for estrogenic activity in MCF-7 cell proliferation. The most active analogs were evaluated for iv and oral pharmacokinetic properties via cassette dosing in rat and in mice pharmacokinetic models.

Significant antitumor activity in vivo following treatment with the microtubule agent ENMD-1198.

Clinical studies using the microtubule-targeting agent 2-methoxyestradiol (2ME2; Panzem) in cancer patients show that treatment is associated with clinical benefit, including prolonged stable disease, complete and partial responses, and an excellent safety profile. Studies have shown that 2ME2 is metabolized by conjugation at positions 3 and 17 and oxidation at position 17. To define structure-activity relationships for these positions of 2ME2 and to generate metabolically stable analogues with improved anti-tubulin properties, a series of analogues was generated and three lead analogues were selected, ENMD-1198, ENMD-1200, and ENMD-1237. These molecules showed improved metabolic stability with >65% remaining after 2-h incubation with hepatocytes. Pharmacokinetic studies showed that oral administration of the compounds resulted in increased plasma levels compared with 2ME2. All three analogues bind the colchicine binding site of tubulin, induce G(2)-M cell cycle arrest and apoptosis, and reduce hypoxia-inducible factor-1alpha levels. ENMD-1198 and ENMD-1200 showed improved in vitro antiproliferative activities. Significant reductions in tumor volumes compared with vehicle-treated mice were observed in an orthotopic breast carcinoma (MDA-MB-231) xenograft model following daily oral treatment with all compounds (ANOVA, P < 0.05). Significantly improved median survival time was observed with ENMD-1198 and ENMD-1237 (200 mg/kg/d) in a Lewis lung carcinoma metastatic model (P < 0.05). In both tumor models, the high-dose group of ENMD-1198 showed antitumor activity equivalent to that of cyclophosphamide. ENMD-1198 was selected as the lead molecule in this analogue series and is currently in a phase I clinical trial in patients with refractory solid tumors.

Comparative estrogenicity of endogenous, environmental and dietary estrogens in pregnant women II: Total estrogenicity calculations accounting for competitive protein and receptor binding and potency.

Evaluating the biological significance of human-relevant exposures to environmental estrogens involves assessing the individual and total estrogenicity of endogenous and exogenous estrogens found in serum, for example from biomonitoring studies. We developed a method for this assessment by integrating approaches for (i) measuring total hormone concentrations by mass spectrometry (Fleck et al., 2018), (ii) calculating hormone bioavailable concentrations in serum and, (iii) solving multiple equilibria between estrogenic ligands and receptors, and (iv) quantitatively describing key elements of estrogen potency. The approach was applied to endogenous (E1, E2, E3, E4), environmental (BPA), and dietary Genistein (GEN), Daidzein (DDZ) estrogens measured in the serum of thirty pregnant women. Fractional receptor occupancy (FRO) based estrogenicity was dominated by E1, E2 and E3 (ER-α, 94.4-99.2% (median: 97.3%), ER-ß, 82.7-97.7% (median: 92.8%), as was the total response (TR), which included ligand specific differences in recruitment of co-activator proteins (RCA). The median FRO for BPA was at least five orders of magnitude lower than E1, E2 and E3, and three orders of magnitude lower than the fetal derived E4 and GEN and DDZ. BPA contributed less than 1/1000th of the normal daily variability in total serum estrogenicity in this cohort of pregnant women.

The in vivo properties of STX243: a potent angiogenesis inhibitor in breast cancer.

The steroidal-based drug 2-ethyloestradiol-3,17-O,O-bis-sulphamate (STX243) has been developed as a potent antiangiogenic and antitumour compound. The objective of this study was to ascertain whether STX243 is more active in vivo than the clinically relevant drug 2-methoxyoestradiol (2-MeOE2) and the structurally similar compound 2-MeOE2-3,17-O,O-bis-sulphamate (STX140). The tumour growth inhibition efficacy, antiangiogenic potential and pharmacokinetics of STX243 were examined using four in vivo models. Both STX243 and STX140 were capable of retarding the growth of MDA-MB-231 xenograft tumours (72 and 63%, respectively), whereas no inhibition was observed for animals treated with 2-MeOE2. Further tumour inhibition studies showed that STX243 was also active against MCF-7 paclitaxel-resistant tumours. Using a Matrigel plug-based model, in vivo angiogenesis was restricted with STX243 and STX140 (50 and 72%, respectively, using a 10 mg kg(-1) oral dose), thereby showing the antiangiogenic activity of both compounds. The pharmacokinetics of STX243 were examined at two different doses using adult female rats. The compound was orally bioavailable (31% after a single 10 mg kg(-1) dose) and resistant to metabolism. These results show that STX243 is a potent in vivo drug and could be clinically effective at treating a number of oncological conditions.

Dimethandrolone (7alpha,11beta-dimethyl-19-nortestosterone) and 11beta-methyl-19-nortestosterone are not converted to aromatic A-ring products in the presence of recombinant human aromatase.

Dimethandrolone undecanoate (DMAU: 7alpha,11beta-dimethyl-19-nortestosterone 17beta-undecanoate) is a potent orally active androgen in development for hormonal therapy in men. Cleavage of the 17beta-ester bond by esterases in vivo leads to liberation of the biologically active androgen, dimethandrolone (DMA), a 19-norandrogen. For hormone replacement in men, administration of C19 androgens such as testosterone (T) may lead to elevations in circulating levels of estrogens due to aromatization. As several reports have suggested that certain 19-norandrogens may serve as substrates for the aromatase enzyme and are converted to the corresponding aromatic A-ring products, it was important to investigate whether DMA, the related compound, 11beta-methyl-19-nortestosterone (11beta-MNT), also being tested for hormonal therapy in men, and other 19-norandrogens can be converted to aromatic A-ring products by human aromatase. The hypothetical aromatic A-ring product corresponding to each substrate was obtained by chemical synthesis. These estrogens bound with high affinity to purified recombinant human estrogen receptors (ER) alpha and beta in competitive binding assays (IC50's: 5-12 x 10(-9) M) and stimulated transcription of 3XERE-luciferase in T47Dco human breast cancer cells with a potency equal to or greater than that of estradiol (E2) (EC50's: 10(-12) to 10(-11) M). C19 androgens (T, 17alpha-methyltestosterone (17alpha-MT), androstenedione (AD), and 16alpha-hydroxyandrostenedione (16alpha-OHAD)), 19-norandrogens (DMA, 11beta-MNT, 19-nortestosterone (19-NT), and 7alpha-methyl-19-nortestosterone (MENT)) or the structurally similar 19-norprogestin, norethindrone (NET) were incubated at 50 microM with recombinant human aromatase for 10-180 min at 37 degrees C. The reactions were terminated by extraction with acetonitrile and centrifugation, and substrate and potential product were separated by HPLC. Retention times were monitored by UV absorption, and UV peaks were quantified using standard curves. Aromatization of the positive controls, T, AD, and 16alpha-OHAD was linear for 40-60 min, and conversion of T or AD was complete by 120 min. The nonsteroidal aromatase inhibitor, letrozole, demonstrated concentration-dependent suppression of T aromatization. Under the same conditions, there was no detectable conversion of DMA, 11beta-MNT, or NET to their respective hypothetical aromatic A-ring products during incubation times up to 180 min. Aromatization of MENT and 19-NT proceeded slowly and was limited. Collectively, these data support the notion that in the absence of the C19-methyl group, which is the site of attack by oxygen, aromatization of androgenic substrates proceeds slowly or not at all and that this reaction is impeded by the presence of a methyl group at the 11beta position.

A new micronized formulation of 2-methoxyestradiol-bis-sulfamate (STX140) is therapeutically potent against breast cancer.

UNLABELLED: There is a continued need for orally bioavailable anticancer compounds that exhibit good efficacy against breast cancer. STX140, a derivative of 2-methoxyestradiol (2-MeOE2), has been shown to have excellent oral bioavailability and significantly reduces tumor growth. A new micronized formulation of STX140 has now been developed and its pharmacokinetics (PK) in rats and effect on MDA-MB-231 breast cancer growth in nude mice was investigated. MATERIALS AND METHODS: For the PK studies, female Wistar rats were treated orally with STX140 in two separate vehicles (10% tetrahydrofuran (THF) in propylene glycol (PG) or 0.5% methyl cellulose (MC) in saline) and plasma samples taken for high performance liquid chromatography analysis over 48 h. For the tumor efficacy studies, female nude mice were inoculated with MDA-MB-231 breast cancer cells and then treated orally with a range of doses of STX140. RESULTS: The PK studies demonstrated that the THF/PG vehicle resulted in a greater oral bioavailability of STX140 compared to the 0.5% MC vehicle. However, this was not translated to the tumor efficacy studies where STX140 at 20 mg/kg in either vehicle caused a significant reduction in tumor volume. CONCLUSION: The new micronized formulation of STX140 is orally bioavailable and efficacious at inhibiting MDA-MB-231 breast tumor growth.

Discovery of Vilaprisan (BAY 1002670): A Highly Potent and Selective Progesterone Receptor Modulator Optimized for Gynecologic Therapies.

Progesterone plays an important role in the female reproductive system. However, there is also evidence that gynecologic disorders/diseases such as uterine fibroids and endometriosis are progesterone-dependent. Steroidal and non-steroidal selective progesterone receptor modulators (SPRMs) have shown potential for the treatment of such diseases. Steroidal SPRMs, including mifepristone and ulipristal acetate, have proven effective in clinical trials. However, several steroidal SPRMs containing a dimethylamino substituent have been associated with elevated liver enzymes in patients. An earlier drug discovery program identified lonaprisan as a highly selective SPRM that did not show drug-related change in liver enzyme activity. Building on data obtained from that work, here we describe the research program that culminated in the discovery of a novel steroidal SPRM, vilaprisan, which combines an extremely high potency with very favorable drug metabolism and pharmacokinetic properties. Vilaprisan has entered clinical development and is currently undergoing phase 3 clinical trials.

In vitro activation of rat cardiac glucocorticoid antagonist- versus agonist-receptor complexes.

The synthetic antiglucocorticoid RU 38486 interacts with cardiac cytoplasmic glucocorticoid receptors and competes for in vitro binding with the potent agonist triamcinolone acetonide. In addition to binding to receptors with high affinity, RU 38486 also facilitates the in vitro conformational change in the receptor which is a consequence of the physiologically relevant activation step during which the receptor is converted from a non DNA- to a DNA-binding form. This ability of RU 38486 to promote receptor activation is reflected by both the appropriate shift in the elution profile of [3H]RU 38486-receptor complexes from DEAE-cellulose as well as by an increased binding of these complexes to DNA-cellulose. Although less effective than triamcinolone acetonide, RU 38486 promotes in vitro receptor activation under a variety of experimental conditions, including incubation of labeled cardiac cytosols at 25 degrees C for 30 min or at 15 degrees C for 30 min in the presence of 5 mM pyridoxal 5'-phosphate. Once thermally activated, the cardiac [3H]triamcinolone acetonide and [3H]RU 38486-receptor complexes bind to nonspecific DNA-cellulose with the same relative affinities, as evidenced by the fact that 50% of both activated complexes are eluted at approx. 215-250 mM NaCl. Thus, this pure antiglucocorticoid does promote, at least to some extent, many of the crucial in vitro events including high-affinity binding, activation, and DNA binding which have been shown to be required to elicit a physiological response in vivo.

Distribution of RU 486 and its demethylated metabolites in humans.

The concentrations of RU 486 and its demethylated metabolites were determined by RIA in samples of myometrium, abdominal adipose tissue, and serum, which were collected at hysterectomies performed 12-15 h after oral administration of 200 mg RU 486. The RU 486 concentrations in myometrium were similar in the five women studied, with a mean of 148 +/- 58 (+/- SD) ng/g (344 +/- 135 pmol/g). The adipose tissue RU 486 levels varied more, the mean concentration being 447 +/- 191 ng/g (1041 +/- 445 pmol/g). The serum RU 486 concentrations ranged from 175-899 ng/ml [mean, 396 +/- 259 ng/mL (922 +/- 603 nmol/L)]. In these women the nonprotein-bound fraction of [6,7-3H]RU 486 varied from 1.4-3.1% (mean, 2.3%). The approximate concentrations of the combined mono- and didemethylated metabolites of RU 486 were 1.4, 3.1, and 5.2 times higher in adipose tissue, myometrial tissue, and serum, respectively, than those of the parent RU 486. In vitro, rapid and nonsaturable accumulation of [6,7-3H]RU 486 from phosphate buffer into adipose tissue was inhibited by the addition of alpha 1-acid glycoprotein, the specific serum transport protein for RU 486, to the buffer medium. Accumulation of [6,7-3H]RU 486 in myometrial specimens was poor. The enterohepatic cycling of RU 486 was assessed in four normal subjects by repetitive intake of charcoal subsequent to ingestion of 200 mg RU 486. Compared to other normal subjects, the serum levels and areas under the concentration curves were lower and t1/2 values shorter in the group given charcoal, suggesting that in vivo RU 486 may be partly pooled in the enterohepatic cycle. Our studies suggest that despite the low volume of distribution and the effective serum binding of RU 486, the myometrial and adipose tissue concentrations of RU 486 and its metabolites were similar (approximately 10(-9)-10(-10) mol/g) after oral intake of RU 486.

Biowaivers for oral immediate-release products: implications of linear pharmacokinetics.

Bioequivalence of drug formulations plays an important role in drug development. Recently, the Biopharmaceutical Classification System (BCS) has been implemented for the purpose of waiving bioequivalence studies on the basis of the solubility and gastrointestinal permeability of drug substance. Using the rationale of the BCS, it can be argued that biowaivers can, however, also be granted on the basis of standard pharmacokinetic data. If a drug exhibits dose-linear pharmacokinetics and a sufficiently fast dissolution profile, it can be concluded that this drug appears to pose no problem with respect to absorption. It should be noted that a change of an immediate-release tablet formulation can only lead to a deviating rate and/or extent of absorption when release of the drug from the formulation is altered. Logically, the dissolution profiles of the different formulations should be equal to guarantee bioequivalency. Thus, both BCS and the alternative linear pharmacokinetics approach require an evaluation of dissolution profiles. The justification of BCS is found in the permeability classification of the compound, while those of the linear pharmacokinetics lie in the apparent lack of a permeability problem. For example, in this context P-glycoprotein-transported drugs form an interesting class of compounds, which may be treated likewise when complying to the aforementioned requirements. Furthermore, poorly soluble compounds may be less troublesome than expected. It is shown that linear kinetics can be explained by the solubilising activity of, for example, bile salts. In this instance, linear pharmacokinetics shows that elevated doses do not appear to exhibit a limiting role on the dissolution. Hence, a change in formulation without any effect on the dissolution profile is not expected to cause a change in availability. It is clear that the formulations to be compared should not contain excipients that display an effect on (presystemic) drug metabolism.

Mifegyne (mifepristone), a new antiprogestagen with potential therapeutic use in human fertility control.

PIP: Animal and human volunteer research involving the hormone antagonist Mifegyne (mifepristone) is reviewed. Studies in animals and humans show that the potent antiprogesterone, Mifegyne, causes pregnancy interruption by acting directly at the level of the endometrium. Pharmacokinetic studies indicate that gastrointestinal absorption is low (25%), but subcutaneous and intramuscular routes do not fare better than does oral administration. Experimental studies in women testing for antiprogesterone effects indicate that mifegyne does not affect menstrual cycle length in women with regular ovulatory cycles, except when using the highest doses (600 mg). Mifegyne inhibits gonadotrophin secretion in a dose-dependent way. In humans, mifegyne has some progestomimetic activity in the endometrium in the absence of progesterone. Researchers know that larger doses of mifegyne than those sufficient to induce uterine bleeding are required to cause antiglucocorticosteroid effects. Studies demonstrate that in 18% of patients studied the only significant side effect is prolonged uterine bleeding. In addition, mifegyne fails to cause an abortion in 15% of the cases. The success rate is 85% when mifegyne is given prior to the 5th week of amenorrhea. Due to the occurrence of failed abortions and prolonged uterine bleeding in some women, researchers advise close medical supervision. An added effect of mifegyne is that in both animal and human studies it is effective in inducing labor. Preliminary studies suggest that mifegyne taken once a month only on the expected date of individual menses could be used as a safe and effective form of fertility control.^ieng

Radioimmunoassay of 7 alpha-methyl-19-nortestosterone and investigation of its pharmacokinetics in animals.

A method for the measurement of 7 alpha-methyl-19-nortestosterone (7MENT) in serum/plasma by radioimmunoassay (RIA) is described. The antiserum, raised against 7 alpha-methyl-19-nortestosterone-3-O-oxime-bovine serum albumin, had a low titer (final dilution = 1:4500) and low affinity (Ka = 1.17 x 10(9) l/mol) but showed little or no cross-reactivity with several of the steroids tested. The sensitivity of the RIA was 28.2 pg/ml and the mean recovery of added cold steroid was 86 to 100%. Intra- and inter-assay coefficients of variation ranged from 4.3 to 7.3% and 7.3 to 8.4%, respectively. This RIA was used to follow plasma 7MENT levels after a single i.v. injection of the steroid in rats and rabbits. The metabolic clearance rates (MCR) of 7MENT as determined from the plasma disappearance curve for rats and rabbits were 50 l/day and 336 l/day, respectively. The MCR of 7MENT in rats and rabbits lies in the same range as for testosterone. When compared to other nortestosterone derivatives such as norethisterone, 7MENT is metabolized relatively faster.

Pharmacodynamics of the antiprogesterone RU486 in women after oral administration.

The pharmacokinetic characteristics of RU486 and its acute effects on anterior pituitary hormone secretion after oral administration were examined in six normal women. Serum RU486 concentrations were determined by a radioimmunoassay. The absorption of RU486 was rapid with peak serum levels reached approximately 90 minutes after a single oral dose (4 mg/kg). The disappearance of RU486 and its metabolites conformed to a noncompartmental model with a mean apparent half-life of 53.7 +/- 6.9 hours. The mean apparent volume of distribution and clearance rate were 1.47 +/- 0.25 l/kg and 1.04 +/- 0.09 1/hour, respectively. In comparison with a control group of normal women (n = 9), there were significant elevations in transverse mean cortisol levels in the RU486 group (P less than 0.01). However, mean adrenocorticotropic hormone (ACTH) levels and the diurnal pattern of ACTH and cortisol secretion were not changed. RU486 induced a mild prolactin (PRL) elevation (P less than 0.01), whereas thyroid-stimulating hormone (TSH) and luteinizing hormone (LH) levels were not altered. In view of the relatively slow clearance rate for RU486 and its metabolites, our findings suggest that the pharmacologic action of RU486 is prolonged after a single oral dose.

Pharmacokinetics of 7 alpha-methyl-19-nortestosterone (MENT) delivery using subdermal implants in healthy men.

We studied the pharmacokinetics of 7 alpha-methyl-19-nortestosterone (MENT), a potent synthetic androgen, administered by subdermal implants. The implants contained 112 +/- 4 mg of MENT acetate in a polyethylene vinyl acetate copolymer. MENT acetate released from the implants is rapidly hydrolyzed to MENT in vivo. Fifteen healthy Finnish men were randomized to have either one, two, or four implants inserted in the medial aspect of the upper arm. The implants remained in place for 4 weeks. Blood samples were obtained before implant insertion, 1, 2, 3, and 4 weeks after insertion, and 1 and 2 weeks after removal. Serum MENT concentrations were determined by gas chromatography with mass selective detection. The MENT levels attained in each implant group remained at a steady level during the 4 weeks of implant use. The mean steady state MENT concentrations in the one, two, and four implant groups were 0.6, 1.4, and 2.3 nmol/L, respectively. Serum MENT concentrations during implant use were clearly dose dependent; the between-subject effect of implants as well as the differences between each pair of groups were all statistically significant. The release rate of MENT from one, two, and four implants was calculated to be approximately 0.3, 0.8, and 1.3 mg/day, respectively. This study suggests that MENT acetate implants are a promising method for long-term androgen administration in hypogonadism and male contraception.

PIP: The authors studied the pharmacokinetics of 112 +or- 4 mg of MENT acetate in a polyethylene vinyl acetate copolymer. MENT acetate released from the implants is rapidly hydrolyzed to MENT in vivo. 15 healthy Finnish men were randomized to have either 1, 2, or 4 implants inserted in the medial aspect of the upper arm. The implants remained in place for 4 weeks. Blood samples were obtained before implant insertion, 1, 2, 3, and 4 weeks after insertion, and 1 and 2 weeks after removal. Serum MENT concentrations were determined by gas chromatography with mass selective detection. The MENT levels attained in each implant group remained at a steady level during the 4 weeks of implant use. The mean steady state MENT concentrations in the 1, 2, and 4 implant groups were 0.6, 1.4, and 2.3 nmol/l, respectively. Serum MENT concentrations during implant use were clearly dose dependent; the between-subject effect of implants as well as the differences between each pair of groups were all statistically significant. The release rate of MENT from 1, 2, and 4 implants was calculated to be approximately 0.3, 0.8, and 1.3 mg/day, respectively. The study suggests that MENT acetate implants are a promising method for long-term androgen administration in hypogonadism and male contraception.