Anastrozole. A review of its use in the management of postmenopausal women with advanced breast cancer

Partially Reversible Bilateral Papilledema in a Patient Using Anastrozole: A Case Study

Anastrozole is an endocrine-modifying agent used in the treatment of estrogen-sensitive breast cancer in the postmenopausal breast cancer population. Anastrozole is known for its side effect profile which includes an increased risk of osteoporosis. However, emerging evidence in the literature in the form of case studies demonstrates several potential ocular side effects due to the use of the medication. In our study, a 66-year-old female using anastrozole suffered severe bilateral papilledema that resolved after cessation of the medication. There is a growing body of evidence demonstrating the use of anastrozole and its impact on ocular health leading to deleterious side effects, such as papilledema.

Bone health in breast cancer

Early breast cancer is among the most common cancers worldwide. Recent advances continue to improve outcomes and increase long-term survivorship. However, therapeutic modalities are deleterious for patients' bone health. While antiresorptive therapy may partially negate this, consequent reduction in rates of fragility fractures remains unproven. Selective prescription of bisphosphonates or denosumab may be an amicable middle ground. Recent evidence also suggests a possible role of osteoclast inhibitors as adjuvant therapy, but the evidence is modest at best. In this narrative clinical review, we explore the impact of various adjuvant modalities on bone mineral density and fragility fracture rates of early breast cancer survivors. We also review optimal patient selection for antiresorptive agents, their impact on rates of fragility fractures, and the possible role of these agents as adjuvant therapy.

Management of Male Breast Cancer: The Journey so Far and Future Directions

Male breast cancer is now shown to be a unique entity and should be considered as a distinct disease. Given the relatively smaller number of cases, randomized controlled trials for treatment are extremely limited and majority of practices are derived from female breast cancer studies. This paper reviews available literature on surgical, radiation, and systemic therapies for male breast cancer, and discusses current practice recommendations.

Efficacy of anastrozole in the treatment of hypogonadal, subfertile men with body mass index ≥25 kg/m2

Background

Anastrozole is a non-steroidal fourth generation aromatase inhibitor that stops the conversion of testosterone to estradiol and has been used as empiric medical therapy for the treatment of male infertility in men with an abnormal testosterone-to-estradiol ratio <10 in order to increase endogenous testosterone levels. This study sought to evaluate the efficacy of anastrozole in the treatment of hypogonadal, subfertile men with body mass index greater than 25 mg/kg² with respect to hormonal profile, semen parameters and overall fertility status.

Methods

Retrospective chart review was performed of hypogonadal, subfertile men with body mass index ≥25 kg/m² who were treated with anastrozole (1 mg daily). Hormonal measurements and semen analysis prior to and after treatment was analyzed in 30 men. Total motile count was calculated from semen analysis. Clinical pregnancy rates were recorded.

Results

Men treated with anastrozole had increases in follicle stimulating hormone (4.8 versus 7.6 IU/L, P<0.0001), luteinizing hormone (3.4 versus 5.4 IU/L, P<0.0001), testosterone (270.6 versus 412 ng/dL, P<0.0001) and testosterone-to-estradiol ratio (9 versus 26.5, P<0.0001) and decrease in estradiol level (32 versus 15.9 pg/mL, P<0.01) after 5 months of therapy. Increases in sperm concentration (7.8 versus 14.2 million/mL, P<0.001), total motile count (12.6 versus 17.7 million, P<0.01) and strict morphology (3.0% versus 3.5%, P<0.05) was appreciated. Clinical pregnancy rate for our cohort was 46.6% (14 of 30), with 71.4% (10 of 14) conceiving through in vitro fertilization, 14.2% (2 of 14) through intrauterine insemination and 14.2% (2 of 14) through natural intercourse.

Conclusions

Anastrozole improves hormonal profiles and semen parameters in hypogonadal, subfertile men with body mass index over 25 kg/m² and may aid in achieving pregnancy especially in conjunction with assisted reproductive techniques.

Aromatase inhibitor use, side effects and discontinuation rates in gynecologic oncology patients

Objective.

Aromatase inhibitors (AI) are frequently prescribed in gynecologic oncology. We sought to define the frequency and duration of AI use, characterize AI side effects and determine the reasons for discontinuation in these patients.

Methods.

Uterine and ovarian cancer patients with AI use for gynecologic cancer therapy were identified retrospectively. Data were abstracted from the electronic medical record, including cancer type, stage, prior cancer treatments, body mass index, concurrent medications, prevalence of AI side effects before and during AI therapy, length of AI treatment and reason for AI discontinuation.

Results.

146 women received AI therapy, with 68 for ovarian cancer (46.6%) and 78 for uterine cancer (53.4%). The majority (71.9%) had advanced stage disease at diagnosis. 54.1% noted AI-associated side effects within the first three visits after starting AI therapy. The most common side effects were arthralgias (29.5%), hot flashes (25.3%), new/worsening fatigue (16.4%), muscle or joint stiffness (8.2%) and myalgias (6.8%). The mean duration of therapy was 14.7 months. Gabapentin or selective serotonin reuptake inhibitor (SSRI) use was associated with decreased musculoskeletal side effects (gabapentin: p < .001, OR 0.88, 95% CI 0.83–0.94; SSRI: p < .001, OR 0.82, 95% CI 0.77–0.89). The most common reason for AI discontinuation was disease progression (87.9%), with 5.0% discontinuing due to side effects and 7.1% for other reasons.

Conclusion.

AI therapy for gynecologic cancers is frequently associated with musculoskeletal side effects, but rarely leads to treatment discontinuation. Thus, AI side effects should be assessed in gynecologic cancer patients to allow potential mitigation of symptoms through adjunct therapies.

New Crystal Forms for Biologically Active Compounds. Part 2: Anastrozole as N-Substituted 1,2,4-Triazole in Halogen Bonding and Lp-π Interactions with 1,4-Diiodotetrafluorobenzene

For an active pharmaceutical ingredient, it is important to stabilize its specific crystal polymorph. If the potential interconversion of various polymorphs is not carefully controlled, it may lead to deterioration of the drug’s physicochemical profile and, ultimately, its therapeutic efficacy. The desired polymorph stabilization can be achieved via co-crystallization with appropriate crystallophoric excipients. In this work, we identified an opportunity for co-crystallization of anastrozole (ASZ), a well-known aromatase inhibitor useful in second-line therapy of estrogen-dependent breast cancer, with a classical XB donor, 1,2,4,5-tetrafluoro-3,6-diiodobenzene (1,4-FIB). In the X-ray structures of ASZ·1.5 (1,4-FIB) co-crystal, different non-covalent interactions involving hydrogen and halogen atoms were detected and studied by quantum chemical calculations and QTAIM analysis at the ωB97XD/DZP-DKH level of theory.

Development of an intravaginal ring delivering simultaneously anastrozole and levonorgestrel: a pharmacokinetic perspective

Intravaginal rings (IVRs) are an option for continuous administration of drugs in women. As an attractive approach for the treatment of endometriosis-associated pelvic pain, IVRs delivering a combination of the aromatase inhibitor anastrozole (ATZ) and the progestin levonorgestrel (LNG) have been developed. This article describes the developmental pharmacokinetic (PK) aspects covering the characterization of in vitro release, preclinical IVR PK investigations in monkeys, and clinical PK considerations. An IVR for ATZ has been developed and investigated in healthy menstruating female cynomolgus monkeys showing effective in vivo release. PK data from the size-adapted IVR used in these animals can be translated into a human context as confirmed in human studies where predefined exposure levels of ATZ were reached. As ATZ may cause harm to the fetus, use of effective contraception has to be assured in women of childbearing potential. Therefore, the IVR delivers a low dose of LNG as a contraceptive. Although the daily dose differed strongly between both drugs (20 µg LNG/d to >1 mg ATZ/d), simultaneous delivery of ATZ and LNG in vitro and in vivo was observed with a high correlation between the in vitro release and PK profiles. The PK characteristics successfully guided the design of clinical studies investigating the drug–drug interaction (DDI) potential. No relevant DDI between both the investigated or other vaginally administered drugs were identified.

PEGylated liposomes of anastrozole for long-term treatment of breast cancer: in vitro and in vivo evaluation

The aim of present study was to develop conventional and PEGylated (long circulating), liposomes containing anastrozole (ANS) for effective treatment of breast cancer. ANS is a third-generation non-steroidal aromatase inhibitor of the triazole class used for the treatment of advanced and late-stage breast cancer in post-menopausal women. Under such disease conditions the median duration of therapy should be prolonged until tumor regression ends (>31 months). Liposomes were prepared by the thin film hydration method by using ANS and various lipids such as soyaphosphatidyl choline, cholesterol and methoxy polyethylene glycol distearoyl ethanolamine in different concentration ratios and evaluated for physical characteristics, in vitro drug release and stability. Optimized formulations of liposome were studied for in vitro cytotoxic activity against the BT-549 and MCF-7 cell lines and in vivo behavior in Wistar rats. Preformulation studies, both Fourier transform infrared study and differential scanning calorimetry analysis showed no interaction between the drug and the excipients used in the formulations. The optimized formulations AL-07 and AL-09 liposomes showed encapsulation efficiencies in the range 65.12 ± 1.05% to 69.85 ± 3.2% with desired mean particle size distribution of 101.1 ± 5.9 and 120.2 ± 2.8 nm and zeta potentials of -43.7 ± 4.7 and -62.9 ± 3.5 mV. All the optimized formulations followed Higuchi-matrix release kinetics and when plotted in accordance with the Korsemeyer-Peppas method, the n-value 0.5 < n < 1.0 suggests an anomalous (non-Fickian) transport. Likewise, the PEGylated liposomes showed greater tumor growth inhibition on BT-549 and MCF-7 cell lines from in vitro cytotoxicity studies (p < 0.05). Pharmacokinetic study of conventional and PEGylated liposomes in Wistar rats demonstrated a 3.33- and 20.28-fold increase in AUC(0-∞) values when compared to pure drug (p < 0.001). Among the formulations, PEGylated liposomes showed encouraging results by way of their long circulation and sustained delivery properties for effective treatment of breast cancer.

Bilateral Optic Disc Swelling Following Anastrozole Therapy

A 56-year-old female with early-stage breast cancer, stage IA grade 1 endometrial cancer, and stage IC grade 1 ovarian cancer developed sudden-onset visual changes and right inferior visual field defect following anastrozole therapy. Examination revealed severe bilateral optic disc swelling and impaired visual acuity. Laboratory work-up was otherwise unremarkable. Anastrozole was discontinued and over the next month, patient had near-complete resolution of swelling in the right eye and improvement in the left eye. This is the only reported case of optic disc swelling following anastrozole therapy.

Sustained release optimized formulation of anastrozole-loaded chitosan microspheres: in vitro and in vivo evaluation

The purpose of this study was to develop sustained release formulation of anastrozole-loaded chitosan microspheres for treatment of breast cancer. Chitosan microspheres cross-linked with two different cross-linking agents viz, tripolyphosphate (TPP) and glutaraldehyde (GA) were prepared using single emulsion (w/o) method. A reverse phase HPLC method was developed and used for quantification of drug in microspheres and rat plasma. Influence of cross-linking agents on the properties of chitosan microspheres was extensively investigated. Formulations were characterized for encapsulation efficiency (EE), compatibility of drug with excipients, particle size, surface morphology, swelling capacity, erosion and drug release profile in phosphate buffer pH 7.4. EE varied from 30.4 ± 1.2 to 69.2 ± 3.2% and mean particle size distribution ranged from 72.5 ± 0.5 to 157.9 ± 1.5 μm. SEM analysis revealed smooth and spherical nature of microspheres. TPP microspheres exhibited higher swelling capacity, percentage erosion and drug release compared to GA microspheres. Release of anastrozole (ANS) was rapid up to 4 h followed by slow release status. FTIR analysis revealed no chemical interaction between drug and polymer. DSC analysis indicated ANS trapped in the microspheres existed in amorphous form in polymer matrix. The highest correlation coefficients (R (2)) were obtained for Higuchi model, suggesting a diffusion controlled mechanism. There was significant difference in the pharmacokinetic parameters (AUC(0-∞), Kel and t(1/2)) when ANS was formulated in the form of microspheres compared to pure drug. This may be attributed to slow release rate of ANS from chitosan microspheres and was detectable in rat plasma up to 48 h which correlates well with the in vitro release data.

Aromatase inhibitors in post-menopausal metastatic breast carcinoma

To summarise the advances in the hormonal treatment of post-menopausal metastatic breast cancer, this paper reviews the published literature regarding the randomised trials comparing aromatase inhibitors (AIs) versus tamoxifen as a first-line therapeutic choice, or AIs versus megestrole acetate (MEG) as a second-line option. The pooled analysis of these authors on AI versus MEG as a second-line option for post-menopausal metastatic breast cancer suggested that AIs do not add any significant benefit over MEG in terms of overall response rate (ORR) and time to progression. According to the Cochrane Database, use of an AI as a second-line therapy versus any other endocrine therapy (mostly MEG) has shown a significant benefit in terms of overall survival, but not for progression-free survival, clinical benefit (CB) or ORR. Concerning the authors' comparisons between AIs versus tamoxifen as a first-line endocrine option in post-menopausal women with metastatic breast carcinoma, AIs seem to be superior to tamoxifen, with a significant benefit in terms of ORR, CB and time to progression being observed in favour of AIs over tamoxifen with fixed effects estimates. According to the Cochrane Database, there was an advantage to the use of AIs over tamoxifen in terms of progression-free survival and CB, but not for overall survival or ORR. With regards to toxicity, AIs show similar levels of hot flushes and arthralgia, increased risks of nausea, diarrhoea and vomiting, but a decreased risk of vaginal bleeding and thromboembolic events compared with other endocrine therapies. Weight gain, dyspnoea and peripheral oedema seem to be more frequent with MEG. At present, there is no proved overall survival difference in patients who are treated first with an AI and then with tamoxifen compared with the opposite sequence. In the metastatic setting, results are limited and are based on retrospective analyses.

Distorções causadas pelas ações judiciais à política de medicamentos no Brasil

OBJETIVO: Descrever os efeitos das ações judiciais que requerem o fornecimento de medicamentos, em relação a aspectos da política nacional de medicamentos. MÉTODOS: Pesquisa documental, com abordagem metodológica quali-quantitativa. Foram analisados todos os processos movidos por cidadãos contra a Secretaria Municipal de Saúde de São Paulo, referentes ao fornecimento de medicamentos, durante o ano de 2005. Utilizou-se formulário padronizado para a coleta de dados, realizando-se uma análise exploratória. RESULTADOS: Foram impetradas 170 ações contra a Secretaria requerendo o fornecimento de medicamentos. Os serviços do Sistema Único de Saúde originaram 59% das prescrições (26% municipais e 33% os demais). Câncer e diabetes foram as doenças mais referidas (59%). Faziam parte de listas de serviços 62% dos medicamentos solicitados itens solicitados. O gasto total foi de R$876 mil, efetuado somente para itens não selecionados (que não fazem parte da Relação Municipal de Medicamentos Essenciais), 73% dos quais poderiam ser substituídos. Do gasto total, 75% foram destinados à aquisição de antineoplásicos, cuja comprovação de eficácia necessita de mais ensaios clínicos. Dois desses medicamentos não estavam registrados no Brasil. CONCLUSÕES: A maioria das demandas por medicamentos geradas por ações judiciais poderia ser evitada se fossem consideradas as diretrizes do Sistema Único de Saúde, a organização do atendimento em oncologia e a observância das relações de medicamentos essenciais. A falta dessa observância compromete a Política Nacional de Medicamentos, a eqüidade no acesso e o uso racional de medicamentos no Sistema Único de Saúde.

Effect of an aromatase inhibitor on bmd and bone turnover markers: 2-year results of the Anastrozole, Tamoxifen, Alone or in Combination (ATAC) trial (18233230)

Aromatase inhibitors reduce estrogen levels in postmenopausal women with breast cancer. Residual estrogen is an important determinant of bone turnover. Adjuvant anastrozole was associated with significant BMD loss and increased bone remodeling, whereas tamoxifen reduced bone marker levels.

INTRODUCTION

In the Anastrozole, Tamoxifen, Alone or in Combination (ATAC) trial after a median follow-up of 68 months, a significant improvement in disease-free survival was observed with anastrozole treatment (hazard ratio [HR], 0.87; 95% CI, 0.78-0.97; p = 0.01). Anastrozole was also associated with tolerability benefits compared with tamoxifen, but with higher fracture rates. The HR of anastrozole compared with tamoxifen after 60 months of treatment was 1.49 (95% CI, 1.25-1.77).

MATERIALS AND METHODS

This prospectively designed subprotocol (n = 308) of ATAC assessed changes in BMD and bone turnover markers in postmenopausal women with invasive primary breast cancer receiving anastrozole 1 mg/day, tamoxifen 20 mg/day, or combination treatment with both agents for 5 years. Patients with osteoporosis were excluded (osteopenia permitted at the investigators discretion). Lumbar spine and total hip BMD was assessed at baseline and after 1 and 2 years; bone turnover markers (serum C-telopeptide, urinary N-telopeptide [NTX], free deoxypyridinoline, serum procollagen type-1 N-propeptide, bone alkaline phosphatase [ALP]) were assessed at baseline and after 3, 6, and 12 months. Results were expressed as median percentage change.

RESULTS

After 2 years of anastrozole treatment, BMD was lost at lumbar spine (median 4.1% loss) and total hip (median 3.9% loss) sites; increases of 2.2% and 1.2%, respectively, were observed with tamoxifen. After 1 year of anastrozole treatment, increased bone remodeling was observed (NTX, +15%; 95% CI, 3-25%; bone ALP, +20%; 95% CI, 14-25%); decreased bone remodeling was observed with tamoxifen (NTX, -52%; 95% CI, -62% to -33%; bone ALP, -16%; 95% CI, -24% to -11%).

CONCLUSIONS

Anastrozole is associated with significant BMD loss and a small increase in bone turnover, whereas tamoxifen (and the combination) is associated with increased BMD and decreased remodeling. These data may explain the increased fracture risk observed with anastrozole treatment in the ATAC trial. The impact of anastrozole on bone should be weighed against its overall superior efficacy and tolerability as observed in the main ATAC trial.

Aromatase Inhibitors in Breast Cancer: An Overview

We examined published reports on the use of aromatase inhibitors in postmenopausal patients with hormone receptor-positive breast cancer. Our data were obtained through a MEDLINE search of literature published in English. Current data indicate that aromatase inhibitors are equivalent or superior to tamoxifen as first-line therapy for metastatic breast cancer and as neoadjuvant treatment for primary breast cancer. In addition, randomized studies have shown that aromatase inhibitors can be administered instead of tamoxifen as a single agent for 5 years or sequentially with tamoxifen for 5 or 10 years. These choices should be discussed with the patient, considering the estimated risk for recurrence and other associated comorbid conditions such as osteoporosis and thromboembolism.

Xenoestrogen action in breast cancer: impact on ER-dependent transcription and mitogenesis

Several estrogen mimics (xenoestrogens) inappropriately activate the estrogen receptor (ER) in the absence of endogenous ligand. Given the importance of the ER in breast cancer growth and regulation, delineating the impact of these agents under conditions related to tumor treatment is of significant importance. We examined the effect of two prevalent xenoestrogens (bisphenol A and coumestrol) on ER activation and ER-dependent mitogenesis in breast cancer cells. We show that the ability of these agents to induce mitogenesis was restricted to conditions of estrogen depletion, and that these agents failed to cooperate with estradiol to induce MCF-7 breast cancer cell growth. These observations are consistent with the impact of each agent specifically on exogenous ER activation as monitored in HeLa cells, wherein the xenoestrogens activated the receptor in the absence of estradiol but failed to cooperate with estrogen. Tamoxifen blocked bisphenol A and coumestrol-mediated ER activation, indicating that exposure to these agents is unlikely to disrupt such therapeutic intervention. The response of tumor-derived ER alleles to these xenoestrogens was also examined. Although the xenoestrogens failed to alter ER-Y537S function, the ER-D351Y mutant demonstrated an enhanced response to bisphenol A. Moreover, tamoxifen enhanced the agonistic effects of xenoestrogens on ER-D351Y. Lastly, we examined the impact of ER co-activator overexpression on xenoestrogen response. Bisphenol A and coumestrol exhibited differential responses to co-activators with regard to ER activation. However, when using mitogenesis as an endpoint, these co-activators were insufficient to provide a significant growth advantage. Combined, these data demonstrate that bisphenol A and coumestrol can impact ER activity and ER-dependent proliferation in breast cancer cells, but the influence of these agents is restricted to conditions of estrogen depletion, selective mutation of the ER, and expression of specific co-activators.

Fulvestrant, a new treatment option for advanced breast cancer: tolerability versus existing agents

Owing to its favourable tolerability profile versus cytotoxic chemotherapy, endocrine therapy is the treatment of choice for postmenopausal women with hormone receptor-positive advanced breast cancer (ABC). However, tolerability concerns associated with some endocrine treatments and the potential for cross-resistance has helped to drive the need for new, effective and better-tolerated agents. Fulvestrant is a new type of oestrogen receptor antagonist with no agonist effects. In phase III trials, fulvestrant has been shown to be at least as effective as the third-generation aromatase inhibitor (AI) anastrozole in the treatment of postmenopausal women with ABC progressing on prior tamoxifen therapy. Fulvestrant is administered as a once-monthly 250 mg intramuscular injection into the gluteus muscle. Here we review the tolerability of fulvestrant in the treatment of postmenopausal women with hormone-sensitive ABC and compare it with that of the four most frequently prescribed endocrine treatments for advanced disease (tamoxifen, anastrozole, letrozole and exemestane). Compared with these agents, fulvestrant is well tolerated and is associated with a lower incidence of joint disorders compared with the non-steroidal AIs and none of the potential androgenic side-effects that are sometimes seen with steroidal AIs. It is also associated with hot flushes compared with tamoxifen. Fulvestrant therefore provides clinicians and patients with a useful, well-tolerated option for the treatment of hormone-sensitive ABC. Integration of such agents into the endocrine treatment sequence may extend the opportunity for using well-tolerated therapies before chemotherapy needs to be considered and thus may improve quality of life for patients with ABC. The overall safety profiles of newer agents such as fulvestrant will become increasingly clear with their ongoing use.

Estrogen receptors and their downstream targets in cancer

Estrogen has crucial roles in the proliferation of cancer cells in reproductive organs such as the breast and uterus. Estrogen-stimulated growth requires two estrogen receptors (ERalpha and ERbeta) which are ligand-dependent transcription factors. High expression of ERs is observed in a large population of breast tumors. In addition, the positive expression of ERs correlates with well-differentiated tumors, a favorable prognosis, and responsiveness to an endocrine therapy with anti-estrogen drugs in patients with breast cancer. Transcription activities of ERs can be regulated by interacting proteins such as coactivators and kinases as well as ligand-binding. Moreover, ER isoforms lacking an ability to transactivate are involved in breast cancer. Downstream target genes of ERs have important roles in mediating the estrogen action in breast cancer. We have isolated and characterized several novel estrogen-responsive genes to clarify the molecular mechanism of the estrogen action in target cells. Among these genes, the estrogen-responsive finger protein (Efp) was found to be highly expressed in breast cancer. Efp as a ubiquitin ligase (E3) is involved in the proteasome-dependent degradation of the 14-3-3sigma protein, one of cell cycle brakes, this degradation resulting in the promotion of breast cancer growth. A full understanding of the expression and function of ERs and their target genes could shed light on how estrogen stimulates the initiation and promotion of cancer, providing a new approach to diagnose and treat cancer.

Clinical and endocrine data for goserelin plus anastrozole as second-line endocrine therapy for premenopausal advanced breast cancer

A total of 16 premenopausal women with metastatic breast cancer (N=13) or locally advanced primary breast cancer (N=3) were treated with a combination of a gonadotropin-releasing hormone agonist goserelin, and a selective aromatase inhibitor anastrozole. All had previously been treated with goserelin and tamoxifen. In all, 12 patients (75%) achieved objective response or durable stable disease at 6 months, with a median duration of remission of 17+ months (range 6–47 months). Four patients still have clinical benefit. Introduction of goserelin and tamoxifen resulted in an 89% reduction in mean oestradiol levels (pretreatment vs 6 months=224 vs 24 pmol l⁻¹) (P<0.0001). Substitution of tamoxifen by anastrozole on progression resulted in a further 76% fall (to 6 pmol l⁻¹ at 3 months) (P<0.0001). Treatment with goserelin and tamoxifen led to a 90% fall in the mean follicle-stimulating hormone (P<0.001). This was reversed once therapy was changed to goserelin and anastrozole. A similar initial reduction was seen in the mean luteinising hormone levels, but substitution of tamoxifen by anastrozole on progression resulted in no significant change. Goserelin and tamoxifen did not lead to any significant change in testosterone and androstenedione levels. The combined use of goserelin and anastrozole as second-line endocrine therapy produces a significant clinical response of worthwhile duration, with demonstrable endocrine changes, in premenopausal women with advanced breast cancer, and offers them another therapeutic option. Further studies involving more patients and longer follow-up are indicated.

Effects of aromatase inhibition in elderly men with low or borderline-low serum testosterone levels

As men age, serum testosterone levels decrease, a factor that may contribute to some aspects of age-related physiological deterioration. Although androgen replacement has been shown to have beneficial effects in frankly hypogonadal men, its use in elderly men with borderline hypogonadism is controversial. Furthermore, current testosterone replacement methods have important limitations. We investigated the ability of the orally administered aromatase inhibitor, anastrozole, to increase endogenous testosterone production in 37 elderly men (aged 62-74 yr) with screening serum testosterone levels less than 350 ng/dl. Subjects were randomized in a double-blind fashion to the following 12-wk oral regimens: group 1: anastrozole 1 mg daily (n = 12); group 2: anastrozole 1 mg twice weekly (n = 11); and group 3: placebo daily (n = 14). Hormone levels, quality of life (MOS Short-Form Health Survey), sexual function (International Index of Erectile Function), benign prostate hyperplasia severity (American Urological Association Symptom Index Score), prostate-specific antigen, and measures of safety were compared among groups. Mean +/- SD bioavailable testosterone increased from 99 +/- 31 to 207 +/- 65 ng/dl in group 1 and from 115 +/- 37 to 178 +/- 55 ng/dl in group 2 (P < 0.001 vs. placebo for both groups and P = 0.054 group 1 vs. group 2). Total testosterone levels increased from 343 +/- 61 to 572 +/- 139 ng/dl in group 1 and from 397 +/- 106 to 520 +/- 91 ng/dl in group 2 (P < 0.001 vs. placebo for both groups and P = 0.012 group 1 vs. group 2). Serum estradiol levels decreased from 26 +/- 8 to 17 +/- 6 pg/ml in group 1 and from 27 +/- 8 to 17 +/- 5 pg/ml in group 2 (P < 0.001 vs. placebo for both groups and P = NS group 1 vs. group 2). Serum LH levels increased from 5.1 +/- 4.8 to 7.9 +/- 6.5 U/liter and from 4.1 +/- 1.6 to 7.2 +/- 2.8 U/liter in groups 1 and 2, respectively (P = 0.007 group 1 vs. placebo, P = 0.003 group 2 vs. placebo, and P = NS group 1 vs. group 2). Scores for hematocrit, MOS Short-Form Health Survey, International Index of Erectile Function, and American Urological Association Symptom Index Score did not change. Serum prostate-specific antigen levels increased in group 2 only (1.7 +/- 1.0 to 2.2 +/- 1.5 ng/ml, P = 0.031, compared with placebo). These data demonstrate that aromatase inhibition increases serum bioavailable and total testosterone levels to the youthful normal range in older men with mild hypogonadism. Serum estradiol levels decrease modestly but remain within the normal male range. The physiological consequences of these changes remain to be determined.

Estrogen-responsive RING finger protein controls breast cancer growth

Most of the breast cancers initially respond to endocrine therapy that reduces the levels of estrogens or competes with estrogen for binding to its receptor. Most of the patients, however, acquire resistance to endocrine therapy with tamoxifen and aromatase inhibitors later. We assumed that identification of estrogen-responsive genes those regulate the growth of breast cancer is indispensable to develop new strategies targeting the genes and overcome the resistance to current endocrine therapy. Estrogen-responsive finger protein (Efp) is one of the estrogen receptor (ER)-target genes we have cloned using genomic binding site cloning. Efp features a structure of the RING-finger B-box coiled-coil (RBCC) motif. We postulated that Efp is a critical factor in proliferation of breast tumors. In a model system using MCF7 cells grown in xenografts, we showed that inhibition of Efp expression by antisense oligonucleotide reduced the tumor growth. MCF7 cells overexpressing Efp formed tumors in xenografts even in estrogen deprivation environment. By yeast two-hybrid screen, we identified that Efp interacts with 14-3-3sigma, which is known as a cell cycle brake that causes G2 arrest and expressed in normal mammary glands. In vitro studies have revealed that Efp functions as a ubiquitin-protein ligase (E3) that targets 14-3-3sigma. These data suggest that Efp controls breast cancer growth through ubiquitin-dependent proteolysis of 14-3-3sigma. Future studies may provide a new therapy to block breast tumor proliferation by targeting Efp.

Anastrozole: in early breast cancer

Anastrozole, a nonsteroidal selective aromatase inhibitor, has recently been approved in the US and several other countries for the adjuvant treatment of postmenopausal women with hormone receptor-positive early breast cancer. In the Arimidex, Tamoxifen alone or in Combination (ATAC) trial, anastrazole 1mg was significantly more effective than tamoxifen 20mg or combined treatment (17 and 19% relative risk reduction) for disease-free survival in postmenopausal women with early breast cancer. black triangle Anastrazole was also significantly more effective than tamoxifen for time to tumour recurrence and the odds of a primary contralateral tumour as a first event. During the first 2 years of treatment with anastrozole, tamoxifen or the combination, patient quality of life was similar in all treatment groups. Compared with tamoxifen, anastrozole was associated with a significantly lower incidence of vaginal bleeding, vaginal discharge, hot flushes, endometrial cancer, ischaemic cerebrovascular events, venous thromboembolic events and deep vein thrombosis including pulmonary embolism; tamoxifen was associated with a lower incidence of musculoskeletal disorders and fracture.

Anastrozole in the management of breast cancer

Anastrozole (Arimidex, AstraZeneca) is a third-generation aromatase inhibitor which rapidly reduces oestradiol concentrations to below detectable levels. It is both potent and selective for the aromatase enzyme, with near-maximal suppression of serum oestrogens occurring at the clinical dose of 1 mg/day in postmenopausal women with advanced breast cancer. Anastrozole has also been shown to be a potent suppressor of intratumoural oestrogens, with responses comparable to those in serum. The results of two large, identically designed, randomised trials in postmenopausal women with advanced breast cancer who had progressed on tamoxifen showed that oral anastrozole 1 mg/day produced a statistically significant survival advantage over megestrol acetate 40 mg q.i.d. The median duration of survival was 26.7 months for anastrozole versus 22.5 months for megestrol acetate. Anastrozole was as well-tolerated as megestrol acetate, while weight gain was significantly increased in the megestrol acetate group compared with the anastrozole group. In another Phase III clinical trial involving 1021 postmenopausal women with advanced breast cancer, anastrozole showed a statistically significant advantage over tamoxifen in median time to progression in a combined analysis of 611 patients who were known to be oestrogen receptor- or progesterone receptor-positive. Anastrozole was as well-tolerated as tamoxifen, with a low rate of withdrawals (2%) due to drug-related adverse events. In addition, anastrozole was associated with fewer thromboembolic events and episodes of vaginal bleeding than tamoxifen. For women with hormone receptor-positive tumours who progress on tamoxifen, anastrozole is superior to megestrol acetate. In addition, anastrozole is a reasonable alternative to tamoxifen for first-line endocrine therapy of advanced breast cancer. Recent data confirm an emerging role for anastrozole as adjuvant therapy for primary breast cancer in postmenopausal patients. Anastrozole is also being investigated in the neoadjuvant setting.

Nonsteroidal aromatase inhibitors: recent advances

Aromatase is the cytochrome P450 enzyme responsible for the last step of estrogen biosynthesis, and aromatase inhibitors constitute an important class of drugs in clinical use for the treatment of breast cancer. Nonsteroidal aromatase inhibitors (NSAIs) are competitive inhibitors of aromatase, which bind to the enzyme active site by coordinating the iron atom present in the heme group of the P450 protein. Presently, third generation NSAIs are in use, and research efforts are being carried out both to identify new molecules of therapeutic interest and to clarify the mechanism of action. In this article, we present a survey of the compounds that have been recently reported as NSAIs, to provide a broad view on the general structure-activity relationships of the class. Moreover, starting from the current knowledge of the mechanistic aspects of aromatase action and from recent theoretical work on the molecular modeling of both enzyme and inhibitors, we try to indicate a way to integrate these different studies in view of a more general understanding of the aromeatase-inhibitor system. Finally, some aspects regarding the possible future development of the field are considered briefly.

Chemical toxins: a hypothesis to explain the global obesity epidemic

The number of obese people worldwide has escalated recently, revealing a complex picture of significant variations among nations and different profiles among adults and children, regions, and occupations. The commonly held causes of obesity-overeating and inactivity-do not explain the current obesity epidemic. There is evidence of a general decrease in food consumption by humans and a significant decline in their overall levels of physical activity. There is also more evidence to indicate that the body's natural weight-control mechanisms are not functioning properly in obesity. Because the obesity epidemic occurred relatively quickly, it has been suggested that environmental causes instead of genetic factors maybe largely responsible. What has, up to now, been overlooked is that the earth's environment has changed significantly during the last few decades because of the exponential production and usage of synthetic organic and inorganic chemicals. Many of these chemicals are better known for causing weight loss at high levels of exposure but much lower concentrations of these same chemicals have powerful weight-promoting actions. This property has already been widely exploited commercially to produce growth hormones that fatten livestock and pharmaceuticals that induce weight gain in grossly underweight patients. This paper presents a hypothesis that the current level of human exposure to these chemicals may have damaged many of the body's natural weight-control mechanisms. Furthermore, it is posited here that these effects, together with a wide range of additional, possibly synergistic, factors may play a significant role in the worldwide obesity epidemic.

Comparison of in vitro exemestane activity versus other antiaromatase agents

Anastrozole, letrozole, and exemestane are the most selective and potent oral antiaromatase agents currently available. However, in vitro and in vivo studies comparing these agents are lacking. Anastrozole and letrozole are reversible, competitive nonsteroidal type II inhibitors, whereas exemestane is an irreversible steroidal type I inactivator. The study was conducted to determine the impact of this characteristic on in vitro residual aromatase activity and protein levels after incubation of JEG-3 cells with aminoglutethimide (a type II inhibitor), anastrozole, exemestane, or letrozole. Aromatase activity was measured after various incubation times with each antiaromatase agent at a concentration 10 times higher than IC50 (concentration giving 50% inhibition). Only exemestane induced a residual inhibition of aromatase activity after its removal, without any change in the aromatase protein level. Aromatase activity increased after preincubation of JEG-3 cells with either aminoglutethimide or anastrozole without any change in the aromatase protein level. The aromatase protein level increased rapidly when cells were incubated with letrozole and aromatase activity inhibition disappeared immediately after removal of the drug. The breakthrough effects in aromatase activity or protein levels observed after treatment with reversible inhibitors may be a factor in therapeutic failure with these agents. These results suggest a possible advantage for exemestane because it is the only clinically available oral irreversible aromatase inactivator.

1-imidazolyl(alkyl)-substituted di- and tetrahydroquinolines and analogues: syntheses and evaluation of dual inhibitors of thromboxane A(2) synthase and aromatase

A series of 1-imidazolyl(alkyl)-substituted quinoline, isoquinoline, naphthalene, benzo[b]furan, and benzo[b]thiophene derivatives was synthesized as dual inhibitors of thromboxane A(2) synthase (P450 TxA(2)) and aromatase (P450 arom). Dual inhibition of these enzymes could be a novel strategy for the treatment of mammary tumors and the prophylaxis of metastases. The most potent dual inhibitors, 5-(2-imidazol-1-ylethyl)-7,8-dihydroquinoline (31) (P450 TxA(2): IC(50) = 0.29 microM; P450 arom: IC(50) = 0.50 microM) and its 5, 6-saturated analogue 30 (P450 TxA(2): IC(50) = 0.68 microM; P450 arom: IC(50) = 0.38 microM), showed a stronger inhibition of both target enzymes than the reference compounds (dazoxiben: IC(50) = 1.1 microM; aminoglutethimide: IC(50) = 18.5 microM). For the determination of the in vivo activity, the influence of selected compounds on serum TxB(2) concentration was examined in rats. Compound 30 (8.5 mg/kg body weight) led to a reduction of the TxB(2) serum level of 78%, 71%, and 51% after 3, 5, and 8 h, respectively (dazoxiben: 60%, 34%, and 36%). Selectivity was studied toward some enzymes of the steroidogenic and eicosanoid pathways. P450 17 was inhibited by selected compounds only at high concentrations. Compound 30 inhibited P450 scc by 13% (25 microM). Compound 31 did not affect cyclooxygenase and lipoxygenase.