27-Hydroxycholesterol, an Endogenous SERM, and Risk of Fracture in Postmenopausal Women: A Nested Case-Cohort Study in the Women's Health Initiative.

27-Hydroxycholesterol (27HC) is a purported, novel endogenous SERM. In animal models, 27HC has an anti-estrogen effect in bone, and 17ß-estradiol mitigates this effect. 27HC in relation to fracture risk has not been investigated in humans. Depending on the level of bioavailable 17ß-estradiol (bioE2 ), 27HC may increase fracture risk in postmenopausal women and modify the fracture risk reduction from menopausal hormone therapy (MHT). To test these a priori hypotheses, we conducted a nested case-cohort study of 868 postmenopausal women within the Women's Health Initiative Hormone Therapy (WHI-HT) trials. The WHI-HT tested conjugated equine estrogens versus placebo and separately conjugated equine estrogens plus progestin versus placebo. Fracture cases were 442 women who had an adjudicated incident hip or clinical vertebral fracture during the WHI-HT follow-up. The subcohort included 430 women randomly selected at WHI-HT baseline, four of whom had a subsequent fracture. Of the 868 women, 266 cases and 219 non-cases were assigned to the placebo arms. Cox models estimated hazard ratios for incident fracture in relation to pre-randomization circulating levels of 27HC and 27HC/bioE2 molar ratio. Models adjusted for age, race/ethnicity, total cholesterol, bioE2 , sex hormone-binding globulin, 25-hydroxyvitamin D, diabetes, osteoporosis, prior MHT use, BMI, falls history, and prior fracture. In women assigned to placebo arms, those in the middle and the highest tertiles of 27HC/bioE2 had an up to 1.9-fold (95% confidence intervals, 1.25 to 2.99) greater risk of fracture than women in the lowest tertile. In women assigned to MHT arms, fracture risk increased with continuous 27HC/bioE2 levels but not with categorical levels. 27HC levels alone were not associated with fracture risk. 27HC and 27HC/bioE2 did not modify the fracture risk reduction from MHT. In postmenopausal women, circulating levels of 27HC relative to bioE2 may identify those at increased risk of fracture. © 2018 American Society for Bone and Mineral Research.

A Study of the Potential Interaction Between Bazedoxifene and Atorvastatin in Healthy Postmenopausal Women.

An open-label, 3-period study was conducted in 30 healthy postmenopausal women (mean age, 58.4 years) who received a single oral dose of atorvastatin 20 mg on day 1 (period 1), multiple daily dosing of bazedoxifene 40 mg on days 4-11 (period 2), and coadministration of atorvastatin 20 mg + bazedoxifene 40 mg on day 12 (period 3). Serial blood samples were collected (24 hours after bazedoxifene and 72 hours after atorvastatin) and assayed for bazedoxifene, atorvastatin, and its ortho-hydroxy and para-hydroxy metabolites. Pharmacokinetic parameters were calculated using noncompartmental methods. Bazedoxifene exposure was not altered with coadministration of atorvastatin 20 mg (Cmax and AUCss were within bioequivalence limits). Similarly, atorvastatin and ortho-hydroxyatorvastatin exposure was equivalent with or without coadministration with bazedoxifene. Para-hydroxyatorvastatin concentrations were below the limit of quantitation under both conditions. Cmax for atorvastatin and ortho-hydroxyatorvastatin was 14% and 18% lower, respectively, and Tmax was 20% and 34% longer, respectively, with the combination compared with atorvastatin alone. There were no serious adverse events, and no subjects discontinued the study because of safety. No clinically significant pharmacokinetic interaction was observed between bazedoxifene and atorvastatin or its active metabolites, indicating they may be safely coadministered without dosage adjustment.

Transdermal delivery of raloxifene HCl via ethosomal system: Formulation, advanced characterizations and pharmacokinetic evaluation.

Raloxifene HCl belongs to a class of selective estrogen receptor modulators (SERMs) which is used for the management of breast cancer. The major problem reported with raloxifene is its poor bioavailability which is only up to 2%. The main objective of the present work was to formulate raloxifene loaded ethosomal preparation for transdermal application and compare it with an oral formulation of the drug. Five ethosomal formulations with different concentrations of ethanol and a conventional liposomes formulation were prepared by rotary evaporation method. The prepared systems were characterised by high resolution transmission electron microscopy (HRTEM), force emission electron microscopy (FESEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and 31P NMR study. All these advanced characterization study established that the ethosome formulation was well defined by its size, shape and its bilayer formation. Transdermal flux of the optimized ethosome formulation was 22.14 ±â€¯0.83 µg/ml/cm2 which was 21 times higher when compared to the conventional liposomes. Confocal microscopy study revealed an enhanced permeation of coumarin-6 dye loaded ethosomes to much deeper layers of skin when compared with conventional liposomes. The gel was found to be pseudoplastic with elastic behaviour. In-vivo studies on rats showed a higher bioavailability of RXL (157% times) for ethosomal formulation when compared with the oral formulation. In conclusion, RXL loaded ethosomal formulation via transdermal route showed superior drug delivery properties as compared to oral formulation.

Pharmacokinetics and safety profile of single-dose administration of an estrogen receptor ß-selective phytoestrogenic (phytoSERM) formulation in perimenopausal and postmenopausal women.

OBJECTIVE: Selected estrogen receptor ß-selective phytoestrogen (phytoSERM), a preparation of genistein, daidzein, and S-equol, has an 83-fold selective affinity for estrogen receptor (ER) ß, and may promote neuronal survival and estrogenic mechanisms in the brain without exerting feminizing activity in the periphery. The aim of this study was to assess the safety, tolerability, and single-dose pharmacokinetics of the phytoSERM formulation in perimenopausal and postmenopausal women. METHODS: Eighteen women aged 45 to 60 years from a 12-week clinical trial evaluating cognitive performance and vasomotor symptoms were randomly assigned to placebo, 50 mg, or 100 mg phytoSERM treatment groups. Plasma levels of the three parent phytoestrogens and their metabolites were measured before and at 2, 4, 6, 8, and 24 hours after ingestion by isotope dilution high-performance liquid chromatography (HPLC) electrospray ionization tandem mass spectrometry. RESULTS: Plasma concentrations of genistein, daidzein, and S-equol peaked at 9, 6, and 4 hours, respectively, for the 50-mg dose, and at 6, 6, and 5 hours, respectively, for the 100-mg dose. The maximum concentration (Cmax) and area under the curve (AUC) for the three parent compounds were greater in the 100-mg dose group, indicating a dose-dependent change in concentration with the phytoSERM treatment. No adverse events were elicited. CONCLUSIONS: A single-dose oral administration of the phytoSERM formulation was well-tolerated and did not elicit any adverse events. It was rapidly absorbed, reached high plasma concentrations, and showed a linear dose-concentration response in its pharmacokinetics. These findings are consistent with previously reported parameters for each parent compound (Clinicaltrials.gov NCT01723917).

Pharmacokinetics, Dose Proportionality, and Bioavailability of Bazedoxifene in Healthy Postmenopausal Women.

PURPOSE: Bazedoxifene is a selective estrogen receptor modulator that has estrogen agonist effects on bone and lipid metabolism while having neutral or estrogen antagonist effects on the breast and endometrium. The present report describes findings from 3 Phase I clinical studies that evaluated the single-dose pharmacokinetics (study 1; n = 84), multiple-dose pharmacokinetics (study 2; n = 23), and absolute bioavailability (study 3; n = 18) of bazedoxifene. METHODS: All 3 studies enrolled healthy postmenopausal women who were either naturally postmenopausal or had undergone bilateral oophorectomy at least 6 months before the start of the study. FINDINGS: Study 1 showed that unconjugated and total (unconjugated and conjugated) bazedoxifene levels increased proportionally with ascending oral doses of bazedoxifene (through the dose range of 5-120 mg). Evaluation with or without food intake was conducted at the 10-mg dose, with no clinically relevant effect on pharmacokinetic parameters. Study 2 showed that bazedoxifene achieved steady state in 1 week and exhibited linear pharmacokinetics in doses of 5 to 40 mg with no unexpected accumulation over the dose range. In accordance with a linear pharmacokinetic profile, mean maximum plasma concentration values increased with increasing dose, with values of 1.6, 6.2, and 12.5 ng/mL for the 5-, 20-, and 40-mg doses, respectively. In study 3, tablet and capsule formulations of bazedoxifene formulations had an estimated oral bioavailability of ~6%. The clearance of bazedoxifene was 0.4 (0.1) L/h/kg based on intravenous administration. The oral formulations had comparable exposure profiles with respect to AUC and AUC0-t, and the 90% CIs for these values were within the bioequivalence limits of 80% to 125%. Bazedoxifene was safe and well tolerated in all 3 studies. IMPLICATIONS: These pharmacokinetic evaluations in healthy postmenopausal women found that bazedoxifene displayed linear pharmacokinetics with doses ranging from 5 to 40 mg, with no unexpected accumulation. Food did not seem to have any clinically relevant impact on pharmacokinetic parameters. Bazedoxifene had an estimated oral bioavailability of ~6% and was safe and well tolerated in the range of doses evaluated.

Clinical investigation of RAD1901, a novel estrogen receptor ligand, for the treatment of postmenopausal vasomotor symptoms: a phase 2 randomized, placebo-controlled, double-blind, dose-ranging, proof-of-concept trial.

OBJECTIVE: The aim of the study was to assess the efficacy and safety of RAD1901, an oral estrogen receptor ligand, for the treatment of moderate-to-severe vasomotor symptoms of menopause. METHODS: This was a randomized, placebo-controlled, double-blind, dose-ranging, proof-of-concept trial. Postmenopausal women with a minimum of 7 moderate-to-severe, diary-reported hot flashes per day, or 50 per week, were randomized to one of five blinded dose groups (0 [placebo], 10, 25, 50, or 100 mg RAD1901 daily for 28 d). Efficacy endpoints included frequency and severity of hot flashes over 4 weeks of treatment. RESULTS: One hundred participants were randomized across the five treatment regimens. The frequency of moderate-to-severe hot flashes decreased in all groups over the treatment period (mean percent change from baseline at 4 wk, -54.1%, -77.2%, -51.8%, -53.8%, and -67.0% for placebo, 10, 25, 50, and 100 mg groups). The response in the 10 mg group was significantly different from placebo at 4 weeks (P = 0.024). No other dose group was significantly different from placebo. There were no statistically significant differences in severity of hot flashes between placebo and any dose group. Treatment was well tolerated; most treatment-emergent adverse events were mild to moderate in severity. CONCLUSIONS: Daily treatment with 10 mg RAD1901 over 4 weeks resulted in a statistically significant reduction in the frequency of moderate-to-severe hot flashes compared with placebo, with an acceptable safety profile. Further clinical trials are warranted to investigate RAD1901's utility as a potential treatment for vasomotor symptoms.

Population pharmacokinetic/pharmacodynamic assessment of pharmacological effect of a selective estrogen receptor ß agonist on total testosterone in healthy men.

BACKGROUND: LY500307 is a highly selective estrogen receptor ß (ERß) agonist, which loses its selectivity at high dose and leads to undesirable suppression of total testosterone (TT) concentration. The objective of the present analysis was to define the LY500307 dose with minimal effect on TT METHODS: LY500307 and TT concentrations were obtained from a single ascending-dose study in a total of 30 healthy male subjects. LY500307 (in the range of 0.5 to 500 mg) or placebo was administered orally as a single dose on 2 occasions with a 3-week washout period. A population pharmacokinetics/pharmacodynamics (PK/PD) model that integrated Fourier series in an indirect response model was developed to describe the circadian rhythm of TT and the exposure-response relationship of LY500307 on TT. RESULTS: The maximum TT suppression (Emax ) was approximately 28.6%. The potency (EC50 ) of LY500307 on TT suppression was approximately 1.69 ng/mL with a 95%CI of 0.871 to 4.44 ng/mL. This model could provide inferences on LY500307 dose levels that would result in various magnitudes of TT suppression. CONCLUSIONS: Population PK/PD modeling is a highly sensitive tool to detect exposure-response relationships on top of the complicated and highly variable circadian rhythm of TT.

An UPLC-MS/MS method for separation and accurate quantification of tamoxifen and its metabolites isomers.

A selective and accurate analytical method is needed to quantify tamoxifen and its phase I metabolites in a prospective clinical protocol, for evaluation of pharmacokinetic parameters of tamoxifen and its metabolites in adjuvant treatment of breast cancer. The selectivity of the analytical method is a fundamental criteria to allow the quantification of the main active metabolites (Z)-isomers from (Z)'-isomers. An UPLC-MS/MS method was developed and validated for the quantification of (Z)-tamoxifen, (Z)-endoxifen, (E)-endoxifen, Z'-endoxifen, (Z)'-endoxifen, (Z)-4-hydroxytamoxifen, (Z)-4'-hydroxytamoxifen, N-desmethyl tamoxifen, and tamoxifen-N-oxide. The validation range was set between 0.5ng/mL and 125ng/mL for 4-hydroxytamoxifen and endoxifen isomers, and between 12.5ng/mL and 300ng/mL for tamoxifen, tamoxifen N-desmethyl and tamoxifen-N-oxide. The application to patient plasma samples was performed.

Effect of para halogen modification of S-3-(phenoxy)-2-hydroxy-2-methyl-N-(4-nitro-3-trifluoromethyl-phenyl)-propionamides on metabolism and clearance.

The purpose of this study was to better understand why para-halogen modifications of S-3-(4-halophenoxy)-2-hydroxy-2-methyl-N-(4-nitro-3-trifluoromethylphenyl) propionamide selective androgen receptor modulators (SARMs) had the opposite of expected effects on total clearance, in which electron-withdrawing groups generally protect benzene ring from hydroxylation. We determined the plasma protein binding of this series of halogen substituted SARMs and characterized the qualitative effects of B-ring halogen substitution on in vivo metabolism. In vivo metabolism of S-9, S-10, and S-11 were determined in rats using LC-MS(n) analysis. Intrinsic clearance was measured by in vitro metabolism using rat liver microsomes. Rat plasma protein binding was measured by equilibrium dialysis and drug concentrations after dialysis were analyzed by LC-MS. The major metabolic pathways of the halogen-substituted SARMs examined were very similar and included three major phase I pathways; (1) hydrolysis of the amide bond, (2) B-ring hydroxylation, and (3) A-ring nitro reduction to an aromatic amine. In plasma protein binding studies, S-1 (F, fu = 0.78 ± 0.17 %) showed the greatest unbound fraction, followed by S-9 (Cl, fu = 0.10 ± 0.04 %), S-10 (Br, fu = 0.03 ± 0.01 %), and S-11 (I, fu = 0.008 ± 0.001 %). The CLint values of S-1, S-9, S-10, and S-11 were 2.4, 2.5, 2.8, and 4.6 µL/min/mg, respectively. These findings suggest that as lipophilicity increased the free fraction was reduced thus compensating for metabolic liability and resulting in the apparent discrepancy between CLint and CL total of halogen-substituted SARMs series.

Preparation and evaluation of raloxifene-loaded solid dispersion nanoparticle by spray-drying technique without an organic solvent.

The aim of this study was to improve the physicochemical properties and bioavailability of a poorly water-soluble drug, raloxifene by solid dispersion (SD) nanoparticles using the spray-drying technique. These spray-dried SD nanoparticles were prepared with raloxifene (RXF), polyvinylpyrrolidone (PVP) and Tween 20 in water. Reconstitution of optimized RXF-loaded SD nanoparticles in pH 1.2 medium showed a mean particle size of approximately 180 nm. X-ray diffraction and differential scanning calorimetry indicated that RXF existed in an amorphous form within spray-dried nanoparticles. The optimized formulation showed an enhanced dissolution rate of RXF at pH 1.2, 4.0, 6.8 and distilled water as compared to pure RXF powder. The improved dissolution of raloxifene from spray-dried SD nanoparticles appeared to be well correlated with enhanced oral bioavailability of raloxifene in rats. Furthermore, the pharmacokinetic parameters of the spray-dried SD nanoparticles showed increased AUC(0-∞) and C(max) of RXF by approximately 3.3-fold and 2.3-fold, respectively. These results suggest that the preparation of RXF-SD nanoparticles using the spray drying technique without organic solvents might be a promising approach for improving the oral bioavailability of RXF.

Development of raloxifene-solid dispersion with improved oral bioavailability via spray-drying technique.

The purpose of this study was to develop a raloxifene-loaded solid dispersion with enhanced dissolution rate and bioavailability via spray-drying technique. Solid dispersions of raloxifene (RXF) were prepared with PVP K30 at weight ratios of 1:4, 1:6 and 1:8 using a spray-drying method, and characterized by differential scanning calorimetry, X-ray powder diffraction, scanning electron microscopy, and solubility and dissolution tests. The bioavailability of the solid dispersion in rats was also evaluated compared to those of RXF powder and commercial product. Results showed that the RXF-loaded solid dispersion was in amorphous form with increased solubility and dissolution rate. The absorption of RXF from solid dispersion resulted in approximately 2.6-fold enhanced bioavailability compared to pure drug. Moreover, RXF-loaded solid dispersion gave similar AUC, C(max) and T(max) values to the commercial product, suggesting that it was bioequivalent to the commercial product in rats. These findings suggest that an amorphous solid dispersion of RXF could be a viable option for enhancing the oral bioavailability of RXF.

Quantification of tamoxifen and three of its phase-I metabolites in human plasma by liquid chromatography/triple-quadrupole mass spectrometry.

In view of future pharmacokinetic studies, a highly sensitive ultra performance liquid chromatography/tandem mass spectrometry (UPLC-MS/MS) method has been developed for the simultaneous quantification of tamoxifen and three of its main phase I metabolites in human lithium heparinized plasma. The analytical method has been thoroughly validated in agreement with FDA recommendations. Plasma samples of 200 µl were purified by liquid-liquid extraction with 1 ml n-hexane/isopropanol, after deproteination through addition of 50 µl acetone and 50 µl deuterated internal standards in acetonitrile. Tamoxifen, N-desmethyl-tamoxifen, 4-hydroxy-tamoxifen and endoxifen were chromatographically separated on an Acquity UPLC(®) BEH C18 1.7 µm 2.1 mm×100 mm column eluted at a flow-rate of 0.300 ml/min on a gradient of 0.2mM ammonium formate and acetonitrile, both acidified with 0.1% formic acid. The overall run time of the method was 10 min, with elution times of 2.9, 3.0, 4.1 and 4.2 min for endoxifen, 4-hydroxy-tamoxifen, N-desmethyl-tamoxifen and tamoxifen, respectively. Tamoxifen and its metabolites were quantified by triple-quadrupole mass spectrometry in the positive ion electrospray ionization mode. The multiple reaction monitoring transitions were set at 372>72 (m/z) for tamoxifen, 358>58 (m/z) for N-desmethyl-tamoxifen, 388>72 (m/z) for 4-hydroxy-tamoxifen and 374>58 (m/z) for endoxifen. The analytical method was highly sensitive with the lower limit of quantification validated at 5.00 nM for tamoxifen and N-desmethyl-tamoxifen and 0.500 nM for 4-hydroxy-tamoxifen and endoxifen, which is equivalent to 1.86, 1.78, 0.194 and 0.187 ng/ml for tamoxifen, N-desmethyl-tamoxifen, 4-hydroxy-tamoxifen and endoxifen, respectively. The method was also precise and accurate, with within-run and between-run precisions within 12.0% and accuracy ranging from 89.5 to 105.3%. The method has been applied to samples from a clinical study and cross-validated with a validated LC-MS/MS method in serum.

P-glycoprotein (ABCB1) transports the primary active tamoxifen metabolites endoxifen and 4-hydroxytamoxifen and restricts their brain penetration.

P-glycoprotein (P-gp, ABCB1) is a highly efficient drug efflux pump expressed in brain, liver, and small intestine, but also in tumor cells, that affects pharmacokinetics and confers therapy resistance for many anticancer drugs. The aim of this study was to investigate the impact of P-gp on tamoxifen and its primary active metabolites, 4-hydroxytamoxifen, N-desmethyltamoxifen, and endoxifen. We used in vitro transport assays and Abcb1a/1b(-/-) mice to investigate the impact of P-gp on the oral availability and brain penetration of tamoxifen and its metabolites. Systemic exposure of tamoxifen and its metabolites after oral administration of tamoxifen (50 mg/kg) was not changed in the absence of P-gp. However, brain accumulation of tamoxifen, 4-hydroxytamoxifen, and N-desmethyltamoxifen were modestly, but significantly (1.5- to 2-fold), increased. Endoxifen, however, displayed a 9-fold higher brain penetration at 4 h after administration. Endoxifen was transported by P-gp in vitro. Upon direct oral administration of endoxifen (20 mg/kg), systemic exposure was slightly decreased in Abcb1a/1b(-/-) mice, but brain accumulation of endoxifen was dramatically increased (up to 23-fold at 4 h after administration). Shortly after high-dose intravenous administration (5 or 20 mg/kg), endoxifen brain accumulation was increased only 2-fold in Abcb1a/1b(-/-) mice compared with wild-type mice, suggesting a partial saturation of P-gp at the blood-brain barrier. Endoxifen, the clinically most relevant metabolite of tamoxifen, is a P-gp substrate in vitro and in vivo, where P-gp limits its brain penetration. P-gp might thus be relevant for tamoxifen/endoxifen resistance of P-gp-positive breast cancer and tumors positioned behind a functional blood-brain barrier.

Bioanalytical methods for determination of tamoxifen and its phase I metabolites: a review.

The selective estrogen receptor modulator tamoxifen is used in the treatment of early and advanced breast cancer and in selected cases for breast cancer prevention in high-risk subjects. The cytochrome P450 enzyme system and flavin-containing monooxygenase are responsible for the extensive metabolism of tamoxifen into several phase I metabolites that vary in toxicity and potencies towards estrogen receptor (ER) alpha and ER beta. An extensive overview of publications on the determination of tamoxifen and its phase I metabolites in biological samples is presented. In these publications techniques were used such as capillary electrophoresis, liquid, gas and thin layer chromatography coupled with various detection techniques (mass spectrometry, ultraviolet or fluorescence detection, liquid scintillation counting and nuclear magnetic resonance spectroscopy). A trend is seen towards the use of liquid chromatography coupled to mass spectrometry (LC-MS). State-of-the-art LC-MS equipment allowed for identification of unknown metabolites and quantification of known metabolites reaching lower limit of quantification levels in the sub pg mL(-1) range. Although tamoxifen is also metabolized into phase II metabolites, the number of publications reporting on phase II metabolism of tamoxifen is scarce. Therefore the focus of this review is on phase I metabolites of tamoxifen. We conclude that in the past decades tamoxifen metabolism has been studied extensively and numerous metabolites have been identified. Assays have been developed for both the identification and quantification of tamoxifen and its metabolites in an array of biological samples. This review can be used as a resource for method transfer and development of analytical methods used to support pharmacokinetic and pharmacodynamic studies of tamoxifen and its phase I metabolites.

Development and validation of a liquid chromatography-tandem mass spectrometry method for the simultaneous quantification of tamoxifen, anastrozole, and letrozole in human plasma and its application to a clinical study.

There is substantial evidence that circulating estrogens promote the proliferation of breast cancer. Consequently, adjuvant hormonal treatment strategies targeting estrogen action have been established. Such hormonal therapies include selective estrogen receptor modulators, such as tamoxifen, which interfere at the estrogen receptors directly, or non-steroidal aromatase inhibitors, such as anastrozole and letrozole, which inhibit estrogen synthesis through blocking the aromatase, a key enzyme of estrogen production. Despite considerable therapeutic success, in several cases, the use of these drugs is limited by side effects that have been described to significantly impair the adherence of patients to endocrine treatment. However, objective data concerning patient adherence and its clinical relevance are limited. One promising approach to check patient-reported adherence is drug monitoring in human plasma. Therefore, a liquid chromatography-tandem mass spectrometry method to determine the plasma concentrations of tamoxifen, anastrozole, and letrozole has been developed and fully validated according to guidelines for clinical and forensic toxicology. The validation criteria evaluated were selectivity, linearity, accuracy and precision, limit of quantification, recovery and matrix effects, sample stability, and carryover. The six-point calibration curves showed linearity over the range of concentrations from 25 to 500 ng/ml for tamoxifen, 5 to 200 ng/ml for anastrozole, and 10 to 300 ng/ml for letrozole. The intra- and inter-day precision and accuracies were always better than 15%. The validated procedure was successfully applied to a clinical study (Patient-Reported Outcomes in Breast Cancer Patients undergoing Endocrine Therapy, PRO-BETh). A major aim of PRO-BETh study is the comprehensive evaluation of adherence to treatment in pre- and post-menopausal women with breast cancer. Plasma samples of 310 breast cancer patients undergoing anti-estrogen therapy were analyzed. Eight samples did not contain a quantifiable amount of drug, strongly indicating non-adherence of the corresponding patients to adjuvant breast cancer treatment. Furthermore, plasma concentrations at the lower end of the observed plasma level distribution might represent a hint but not a confirmation for non-adherence in terms of non-daily and irregular intake of the prescribed drug.

The growth-promoting action of individual women's sera on mammary carcinoma cells.

In vitro studies concerning the growth-stimulating effect of hormones, especially of estradiol and its metabolites, have mainly been performed using pure substances and breast cancer cell lines. In order to take into account the metabolism of inactive into active hormones or drugs and vice versa which occurs in several tissues, the influence of individual patients' sera on the growth of breast cancer cells in vitro was tested. Besides measuring the growth promoting action of several hormone replacement therapies, the antiestrogenic effect was determined by measuring the effect of 10(-10) M estradiol added to the culture medium (E2-sensitivity). Influence on proliferation and stimulatability was similar in MCF-7 and T47-D cells. Growth-promoting potential correlated significantly with patient age, being higher in young ladies than in older ones. The converse was true for E2 sensitivity. From the different steroid hormones tested, only higher estradiol levels were associated with increased growth stimulation and diminished E2 sensitivity. Hormone replacement therapy (HRT) of different types did not significantly increase growth potential of serum, however these results are preliminary. Treatment with tamoxifen of breast cancer patients led to a decrease of E2 sensitivity, whereas growth potential was not affected significantly. For the aromatase inhibitor Arimidex, a tendency towards growth inhibition and increased E2 sensitivity was observed. Our in vitro system allows identifying differences between individual persons and groups of women of different age or treatment with respect to stimulation of growth or influence on estrogen sensitivity of breast cancer cells by serum. It is speculated that results might reflect the personal risk or the risk under treatment to develop breast cancer.

Disposition of lasofoxifene, a next-generation selective estrogen receptor modulator, in healthy male subjects.

Disposition of lasofoxifene, a next-generation selective estrogen receptor modulator, was investigated in male volunteers after p.o. administration of a single 20-mg dose of [(14)C]lasofoxifene. Approximately 72% of the administered dose was recovered from the urine and feces, with majority of dose excreted in the feces, probably via bile. The absorption of lasofoxifene in humans was slow with T(max) values typically exceeding 6 h. The C(max) and area under plasma concentration-time profile from time 0 to the last quantifiable time point values of lasofoxifene were lower than those determined for total radioactivity, indicating presence of circulating metabolites. The primary clearance mechanisms for lasofoxifene in humans were direct conjugation (glucuronide and sulfate conjugates) and phase I oxidation, each accounting for about half of the metabolism. Several oxidative metabolites were identified by liquid chromatography/tandem mass spectrometry. The primary phase I metabolites were the result of hydroxylations on the tetraline moiety and the phenyl rings attached to the tetraline, and oxidation on the pyrrolidine moiety. Considering the numerous metabolites seen in vivo, additional in vitro studies using human liver and intestinal microsomes, recombinant cytochromes P450 (P450s), and UDP glucuronosyltransferases (UGTs) were performed. The turnover of lasofoxifene was very slow in liver microsomes, and only two metabolites were identified as two regioisomers of the catechol metabolite. The results from in vitro experiments with recombinant isoforms and P450 isoform-selective inhibitors suggested that the oxidative metabolism of lasofoxifene is catalyzed primarily by CYP3A and CYP2D6. In addition, its glucuronidation is catalyzed by UGTs that are expressed in both the liver (UGT1A1, UGT1A3, UGT1A6, and UGT1A9) and the intestine (UGT1A8 and UGT1A10).

Pharmacokinetics of raloxifene in male Wistar-Hannover rats: influence of complexation with hydroxybutenyl-beta-cyclodextrin.

Raloxifene is a highly insoluble, highly metabolized serum estrogen receptor modulator approved for use in the treatment of osteoporosis. Hydroxybutenyl-beta-cyclodextrin (HBenBCD) is a novel solubility enhancer previously demonstrated to increase the oral bioavailability of tamoxifen, letrozole, and itraconazole. The current study evaluated the pharmacokinetics of raloxifene in oral and intravenous formulations with HBenBCD in male Wistar-Hannover rats. Analytical methodology to measure raloxifene and its metabolites was developed by measuring raloxifene metabolism in vitro. Formulation with HBenBCD significantly increased raloxifene oral bioavailability. Mean+/-S.D. oral bioavailabilities were 2.6+/-0.4% for raloxifene formulated with microcrystalline cellulose, 7.7+/-2.1% for a solid capsule formulation of raloxifene:HBenBCD complex, and 5.7+/-1.3% for a liquid-filled capsule formulation containing raloxifene:HBenBCD/PEG400/H(2)O. Relative to raloxifene/microcrystalline filled capsules, the presence of HBenBCD in the solid capsule formulation afforded: (i) a decrease in raloxifene T(max) (2.5+/-0.5h versus 4.0+/-0.5h); (ii) a two-fold increase in raloxifene C(max) and a three-fold increase in raloxifene AUC; and (iii) a 12-fold increase in raloxifene glucuronide C(max) and a 6.5-fold increase in raloxifene glucuronide AUC. Hence, these studies demonstrate that raloxifene formulations containing HBenBCD significantly increased the oral bioavailability in rats relative to formulations that did not contain HBenBCD.

131I labeling of tamoxifen and biodistribution studies in rats.

Tamoxifen [TAM ([Z]-2-[4-(1,2-diphenyl-1-di-butenyl)-phenoxy]-N,N-dimethylethanamine)] has been used as an antiestrogen drug for treatment and prevention of human breast cancer. Tamoxifen was labeled with 131I using iodogen as an oxidizing agent. Mass spectroscopy of the cold standard showed that the labeling occurs in ortho position to the phenyl ether position of TAM as expected. Quality control, radiochemical yield and stability were established using the radioelectrophoresis method. The radiolabeled compound maintained its stability throughout working period of 24 h. Scintigraphic imaging was performed and tissue distribution was determined in Albino Wistar rats. According to biodistribution and imaging experiments the radiolabeled compound presented estrogen receptor (ER) specificity and it was uptaken by endometrium as well as breast tissue.

27-Hydroxycholesterol is an endogenous SERM that inhibits the cardiovascular effects of estrogen.

The cardioprotective effects of estrogen are mediated by receptors expressed in vascular cells. Here we show that 27-hydroxycholesterol (27HC), an abundant cholesterol metabolite that is elevated with hypercholesterolemia and found in atherosclerotic lesions, is a competitive antagonist of estrogen receptor action in the vasculature. 27HC inhibited both the transcription-mediated and the non-transcription-mediated estrogen-dependent production of nitric oxide by vascular cells, resulting in reduced estrogen-induced vasorelaxation of rat aorta. Furthermore, increasing 27HC levels in mice by diet-induced hypercholesterolemia, pharmacologic administration or genetic manipulation (by knocking out the gene encoding the catabolic enzyme CYP7B1) decreased estrogen-dependent expression of vascular nitric oxide synthase and repressed carotid artery reendothelialization. As well as antiestrogenic effects, there were proestrogenic actions of 27HC that were cell-type specific, indicating that 27HC functions as an endogenous selective estrogen receptor modulator (SERM). Taken together, these studies point to 27HC as a contributing factor in the loss of estrogen protection from vascular disease.