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Fulvestrant.

Fulvestrant, a novel oestrogen receptor (ER) downregulator, is a pure anti-oestrogen which completely blocks the trophic actions of oestrogens without exerting any partial agonist effects. It reduces expression of oestrogen receptor, progesterone receptor and proliferative and cell turnover indices. The drug is well-tolerated with minimal systemic side effects. Large randomised trials have demonstrated similar efficacy to anastrozole in the treatment of postmenopausal advanced breast cancer. While results of a Phase III trial comparing fulvestrant with tamoxifen as first-line endocrine therapy for postmenopausal advanced breast cancer are awaited, future studies on its role in adjuvant and neoadjuvant settings, as well as in premenopausal women are required. With the role of tamoxifen as the gold standard of first-line therapy being challenged by the third generation aromatase inhibitors, direct comparison of the latter with fulvestrant in the first-line setting may also be worthwhile.

Animals↗

Chronic exposure to fulvestrant promotes overexpression of the c-Met receptor in breast cancer cells: implications for tumour-stroma interactions.

Our previous investigations using cell models of tamoxifen resistance have shown that the acquisition of an endocrine-insensitive state is accompanied by an invasive in vitro phenotype. In this study, we wished to determine whether this was specifically related to partial oestrogen receptor agonists or whether similar phenomena arise with the newer 'pure' anti-oestrogens, exemplified by fulvestrant. Our data demonstrate that the development of fulvestrant resistance in two breast cancer cell lines, MCF7 and T47D, is accompanied by an augmented migratory and invasive phenotype in vitro and overexpression of the HGF/SF receptor, c-Met. Importantly, upregulated c-Met expression in these cells facilitates their stimulation by HGF/SF-secreting stromal fibroblasts, leading to the activation of Src, Akt and ERK1/2 and a profound enhancement of their aggressive phenotype in vitro. These effects could be specifically attributable to activation of the c-Met receptor since the inclusion of neutralising antibodies to c-Met, or siRNA-mediated knockdown of c-Met expression, suppressed both invasion and migration stimulated by either exogenous HGF/SF, fibroblast-conditioned medium or following co-culture with fibroblast cells. Together, these in vitro data suggest that the development of fulvestrant resistance in vivo may confer a metastatic advantage to the cells by allowing their migratory and invasive behaviour to be augmented by surrounding stromal cells.

Antineoplastic Agents, Hormonal↗

Fulvestrant (AstraZeneca).

Fulvestrant (Faslodex) is an estrogen receptor (ER) downregulator under development by AstraZeneca for the potential treatment of breast cancer [172191], [237518], [314472], [349551]. In March 2001, an NDA was filed in the US for the second-line treatment of advanced breast cancer in postmenopausal women who have progressed on prior hormonal therapy [403574], [434825]; in December 2001, AstraZeneca was expecting to launch the compound in the US in thefirst half of 2002 [431887]. In August 2001, late-stage clinical trials were ongoing in Japan for breast cancer [422343]. Fulvestrant also has potential in the treatment of other estrogen-responsive tumors, such as uterine tumors [178081]. By 1997, fulvestrant was in phase II trials for uterine fibroids [272162], and by February 1999, it was reported that phase II trials for endometriosis were ongoing [314472], [336599]. However, no development has been reported for these indications since that time. In October 2001, Morgan Stanley expected launch in 2002, with estimated sales of $80 million in 2002 rising to $208 million in 2007 [429700]. Analysts at Lehman Brothers predicted in December 2001, that the product has a 90% chance of making it to market in 2002, with peak sales potential in this year of $800 million [434768].

Animals↗

Fulvestrant, an estrogen receptor downregulator, reduces cell turnover index more effectively than tamoxifen.

BACKGROUND: This study was performed to determine whether drug action on breast tumours could also be analysed using a cell turnover index (CTI), a composite measurement of both proliferation and apoptosis. MATERIALS AND METHODS: Data were obtained from a randomized, placebo-controlled trial comparing three single doses (50, 125 and 250 mg) of intramuscular fulvestrant (Faslodex, previously known as ICI 182,780) with oral tamoxifen 20 mg/day for 14-21 days in women with early, operable, ER-positive breast cancer. CTI was calculated as the ratio of the proliferation index to the apoptotic index. RESULTS: Fulvestrant 250 mg significantly reduced CTI compared with both placebo (p = 0.0003) and tamoxifen (p = 0.026). The effect on CTI with tamoxifen was not significantly different from that with placebo. CONCLUSION: This study suggests that CTI may be a useful indicator of drug action on breast tumour growth. A significant reduction in growth was found with fulvestrant 250 mg compared with tamoxifen.

Antineoplastic Agents↗

Fulvestrant for the treatment of advanced breast cancer in postmenopausal women: a Japanese study.

BACKGROUND: Fulvestrant ('Faslodex') is a new type of oestrogen receptor (ER) antagonist that down-regulates the ER and has no known agonist effects. PATIENTS AND METHODS: In this open-label, Phase II trial, 30 postmenopausal Japanese women with hormone-sensitive advanced breast cancer, who had progressed on tamoxifen/toremifene following an initial response, received fulvestrant (250 mg; once-monthly intramuscular injection). Primary endpoints were objective tumour response rate (complete or partial response) and assessment of tolerability; secondary endpoints included clinical benefit (objective response, or stable disease > or = 24 weeks), duration of response and pharmacokinetic analysis. RESULTS: The objective response rate was 23.3% and 60.0% of patients experienced clinical benefit. Adverse events were generally mild; the most common were pharyngitis (26.7%), headache (23.3%) and nausea (20.0%). Pharmacokinetic data were similar to a Western study of postmenopausal patients. CONCLUSION: Fulvestrant 250 mg/month is effective and well-tolerated in Japanese patients who have relapsed after one prior endocrine treatment.

Adult↗

Clinical development of fulvestrant ("Faslodex").

This paper outlines the development of fulvestrant, the first in a new class of antioestrogen agents with no agonist effects, to be used for the treatment of hormone receptor-positive advanced breast cancer in postmenopausal women. The role of the oestrogen receptor in breast cancer growth and development and the evolution of pharmacological strategies to manipulate it are also discussed. Preclinical and clinical evidence for the efficacy of fulvestrant are also reviewed, along with the tolerability profile of this agent in relation to other endocrine therapies. Further research will define the role of this exciting new agent in the endocrine treatment of breast cancer.

Aged↗

Fulvestrant: an oestrogen receptor antagonist with a novel mechanism of action.

Due to their favourable tolerability profiles, endocrine therapies have long been considered the treatment of choice for hormone-sensitive metastatic breast cancer. However, the oestrogen agonist effects of the available selective oestrogen receptor modulators, such as tamoxifen, and the development of cross-resistance between endocrine therapies with similar modes of action have led to the need for new treatments that act through different mechanisms. Fulvestrant ('Faslodex') is the first of a new type of endocrine treatment--an oestrogen receptor (ER) antagonist that downregulates the ER and has no agonist effects. This article provides an overview of the current understanding of ER signalling and illustrates the unique mode of action of fulvestrant. Preclinical and clinical study data are presented in support of the novel mechanism of action of this new type of ER antagonist.

Animals↗

Fulvestrant antiestrogen for treatment of breast cancer.

Fulvestrant injection (Faslodex, AstraZeneca Pharmaceuticals LP, Wilmington, DE) is a novel estrogen receptor antagonist with no known agonist effects. Indicated for the palliative treatment of postmenopausal, endocrine-response, advanced breast cancer, the drug is well tolerated, and its most common side effect is mild gastrointestinal symptoms. Fulvestrant is administered as a once-a-month intramuscular injection in an outpatient setting. Its unique mechanism of action represents a new way to palliate breast cancer and may offer new options for women with advanced, endocrine-responsive disease.

Antineoplastic Agents, Hormonal↗

Fulvestrant (Faslodex): current status in the therapy of breast cancer.

Fulvestrant (Faslodex, formerly ICI 182,780) is a potent steroidal antiestrogen that mediates its effects by estrogen receptor downregulation. It appears to act as a pure antiestrogen and exhibits none of the negative side effects associated with the partial agonist activity of tamoxifen. It has been shown to be as effective as the oral aromatase inhibitor anastrozole in postmenopausal women with advanced breast cancer who have progressed on prior endocrine therapy, principally tamoxifen. It therefore provides the clinician with an alternative therapeutic strategy following the development of tamoxifen resistance. Fulvestrant might also have potential as a follow-on therapy after tamoxifen in an adjuvant setting and help alleviate some of the concerns surrounding long-term (up to 5 years) tamoxifen therapy.

Animals↗

Role of fulvestrant in sequential hormonal therapy for advanced, hormone receptor-positive breast cancer in postmenopausal women.

The introduction of antiendocrine agents with differing mechanisms of action now mandates the design of rational sequential hormonal regimens for breast cancer. The aromatase inhibitors (AIs), including the nonsteroidal compounds anastrozole and letrozole and the steroidal compound exemestane, are important alternatives or adjuncts to the antiestrogen agent tamoxifen in postmenopausal women with hormone receptor-positive breast cancer in the first-line management of advanced disease and in the adjuvant treatment of early-stage disease. These and other endocrine agents, including the newer estrogen receptor antagonist fulvestrant and also tamoxifen itself, have not been extensively evaluated within the context of hormonal sequencing. Based on a retrospective analysis of data from 3 phase III trials, patients treated with fulvestrant in the first- or second-line hormonal management of advanced breast cancer may derive further clinical benefit from subsequent treatment with an endocrine agent from another class. The need for prospective investigation of post-AI hormonal therapy is intensifying as a result of the increasing clinical use of the AIs. Sophisticated sequencing regimens designed to exploit different mechanisms of action have the potential to confer greater clinical benefit than the historical approach of selecting the agent with the next highest single-agent clinical activity upon disease progression.

Antineoplastic Agents, Hormonal↗

Screening of Estrogenic and Antiestrogenic Effects of Estradiol, Bisphenol A, and Fulvestrant Using 2D and 3D Breast Cancer Cell Systems With a Luciferase Reporter Gene Assay.

Endocrine-disrupting chemicals (EDCs) like bisphenol A (BPA) pose health risks by interfering with hormones. This study develops and utilizes in vitro 2D and 3D cell models to evaluate the estrogenic and antiestrogenic properties of compounds. Human breast cancer cell lines T47D and MCF7, stably transfected with a luciferase reporter gene (ERE-LUC), were first compared in 2D. Due to the significantly higher sensitivity and responsiveness observed in the T47D line during preliminary 2D screenings, this cell line was exclusively selected for the development of the 3D spheroid model. Cells were treated with 17β-estradiol (E2), BPA, and Fulvestrant (FUL) to assess cell viability and luciferase activity. In 2D models, T47D ERE-LUC cells showed higher responsiveness than MCF7 ERE-LUC, which failed to show significant luciferase induction with E2. In the 3D T47D model, cells exhibited significant and robust changes in luciferase activity in response to E2 and BPA, highlighting the enhanced fidelity of 3D cultures in replicating tissue conditions compared to their 2D counterparts. The study highlights the effectiveness of 3D models over 2D in evaluating estrogenic activity. Specifically, the 3D T47D ERE-LUC system serves as a superior, sensitive, and reliable platform for screening EDCs, offering benefits in cost, data speed, and reduced in vivo reliance.

Humans↗

Fulvestrant ('Faslodex'): extending the reach of endocrine therapy?

An effective option for estrogen receptor-positive breast cancer, endocrine therapy has had a significant role in improving the survival of women with postmenopausal breast cancer for more than 20 years. However, acquired resistance to disease by cancer cells is the repeated cause of relapse for patients. This supplement explores current thinking on resistance to endocrine therapy and, in particular, the potential role for fulvestrant ('Faslodex'), a novel endocrine therapy that possesses a unique mechanism of action.

Antineoplastic Agents, Hormonal↗

ICI 182,780 (Fulvestrant)--the first oestrogen receptor down-regulator--current clinical data.

ICI 182,780 (Fulvestrant) is the first in a new class of novel, steroidal, 'pure' antioestrogens--the oestrogen receptor (ER) down-regulators. Its unique mode of action and the absence of partial agonist activity make it a candidate for the treatment of advanced breast cancer in both pre- and postmenopausal women. Tamoxifen has been available for use over the past 25 years. However, its partial agonist activity has been associated with detrimental effects, particularly on the endometrium, and may be associated with the development of tamoxifen resistance. Other antioestrogen agents have previously been unable to demonstrate clinically relevant activity following the development of resistance to tamoxifen. In contrast, the unique mechanism of action of ICI 182,780 results in significant clinical activity in patients failing on tamoxifen therapy. Indeed, phase III clinical trials have demonstrated that ICI 182,780 is at least as effective as the aromatase inhibitor anastrozole in the treatment of postmenopausal patients with advanced disease who have progressed during threatment with prior enocrine therapy. As such, ICI 182,780 will provide a valuable addition to the armamentarium for the treatment of advanced breast cancer.

Antineoplastic Agents↗

Estrogen receptor antagonist fulvestrant (ICI 182,780) inhibits the anti-inflammatory effect of glucocorticoids.

The glucocorticoid receptor (GR) and estrogen receptor (ER) play important roles in both physiological and pathological conditions involving cell growth and differentiation, lipolysis, control of glucose metabolism, immunity, and inflammation. In fact, recent studies suggest that 17beta-estradiol, like glucocorticoids, may also have anti-inflammatory properties, even if the molecular mechanisms responsible for these activities have not yet been completely clarified. The present study was designed to gain a better understanding of the possible cross-talk between GR and ER in a model of lung inflammation (carrageenan-induced pleurisy). In particular, we have investigated whether fulvestrant (ICI 182,780), a selective ER-alpha antagonist, is able to attenuate the well known anti-inflammatory effect of dexamethasone (DEX), a synthetic glucocorticoid, in ovariectomized rats. We show that ICI 182,780, a selective ER-alpha antagonist, reverses the anti-inflammatory activity exhibited by DEX. Moreover, the coadministration of ICI 182,780 significantly inhibited the ability of DEX to reduce: 1) the degree of lung injury, 2) the rise in myeloperoxidase activity, 3) the increase of poly-(ADP-ribose) polymerase activity, tumor necrosis factor alpha, and interleukin-1beta levels, 4) inducible nitric-oxide synthase, 5) lipid peroxidation, 6) nitrotyrosine formation, 7) cyclooxygenase expression, and 8) the IkappaB-alpha degradation caused by carrageenan administration. In addition, quantitative PCR shows that DEX down-regulates GR and up-regulates glucocorticoid-induced leucine zipper levels, whereas ICI 182,780 does not counteract these effects. In conclusion, these results suggest that the in vivo anti-inflammatory property of DEX is also related to the ER-alpha.

Animals↗

Fulvestrant (ICI 182,780) down-regulates androgen receptor expression and diminishes androgenic responses in LNCaP human prostate cancer cells.

The androgen receptor (AR) plays a key role in the development and progression of prostate cancer. Targeting the AR for down-regulation would be a useful strategy for treating prostate cancer, especially hormone-refractory or androgen-independent prostate cancer. In the present study, we showed that the antiestrogen fulvestrant [ICI 182,780 (ICI)] effectively suppressed AR expression in several human prostate cancer cells, including androgen-independent cells. In LNCaP cells, ICI (10 micromol/L) treatment decreased AR mRNA expression by 43% after 24 hours and AR protein expression by approximately 50% after 48 hours. We further examined the mechanism of AR down-regulation by ICI in LNCaP cells. ICI did not bind to the T877A-mutant AR present in the LNCaP cells nor did it promote proteasomal degradation of the AR. ICI did not affect AR mRNA or protein half-life. However, ICI decreased the activity of an AR promoter-luciferase reporter plasmid transfected into LNCaP cells, suggesting a direct repression of AR gene transcription. As a result of AR down-regulation by ICI, androgen induction of prostate-specific antigen mRNA and protein expression were substantially attenuated. Importantly, LNCaP cell proliferation was significantly inhibited by ICI treatment. Following 6 days of ICI treatment, a 70% growth inhibition was seen in androgen-stimulated LNCaP cells. These data show that the antiestrogen ICI is a potent AR down-regulator that causes significant inhibition of prostate cancer cell growth. Our study suggests that AR down-regulation by ICI would be an effective strategy for the treatment of all prostate cancer, especially AR-dependent androgen-independent prostate cancer.

Androgens↗

Fulvestrant in postmenopausal women with advanced breast cancer.

PURPOSE: Patients with hormone-sensitive breast cancer who have responded to tamoxifen (TAM) may receive additional benefit from a second endocrine agent after progression or relapse after TAM therapy. Fulvestrant (FVT; Faslodex; i.m. injection, ICI 182,780; AstraZeneca Pharmaceuticals, Wilmington, DE) was developed as a selective antagonist of estrogen. In postmenopausal women, FVT is reported to inhibit the proliferative effects of estrogen on sensitive tissues and has no apparent measurable estrogenic activity. In this report, we describe the data and analyses supporting marketing approval for FVT by the United States Food and Drug Administration (FDA). EXPERIMENTAL DESIGN: The FDA review of 16 clinical trials and 6 pharmacokinetic trials, as well as preclinical pharmacology and chemistry data, are described. The bases for marketing approval are summarized. RESULTS: Toxicology studies in the mouse, rat, and dog showed minimal toxicity except for antiestrogenic effects. Because of FVT aqueous insolubility, an i.m. formulation, given at monthly intervals, was selected for clinical studies. Pharmacokinetic studies demonstrated sustained concentrations with monthly injection. In in vitro studies FVT was extensively metabolized, primarily by hepatic cytochrome P450 3A4. Phase I studies showed minimal toxicity, and the maximal dose (250 mg) was limited by FVT solubility. In two Phase III trials, 851 patients were randomized to either 250 mg FVT i.m. monthly or to anastrozole (ANZ) 1 mg p.o. daily. Ninety-six percent of patients had received TAM previously for early (adjuvant treatment) or advanced breast cancer. Response rates (RR) were 17% for both FVT and ANZ study arms in the North American trial, and were 20% versus 15% for FVT versus ANZ, respectively, in the European trial. There were no observed differences between study arms with respect to time to progression or survival. The most common FVT adverse events reported as potentially treatment-related were injection site reactions and hot flashes. CONCLUSIONS: FVT was approved on April 25, 2002 by the FDA for the treatment of hormone receptor-positive metastatic breast cancer in postmenopausal women with disease progression after antiestrogen therapy. The recommended dose is 250 mg i.m. monthly as a single 5 ml injection or as two concurrent 2.5 ml injections into the buttocks. Approval was based on results of two randomized trials comparing response rates and time to progression of FVT- and ANZ-treated patients. Complete prescribing information is available on the FDA website.

Anastrozole↗

Persistent suppression of hepatic CYP2A1 expression and serum triiodothyronine levels by tamoxifen in intact female rats: dose-response analysis and comparison with 4-hydroxytamoxifen, fulvestrant (ICI 182,780), and 17beta-estradiol-3-benzoate.

Tamoxifen, a nonsteroidal antiestrogen, is used widely in the treatment of breast cancer and is undergoing evaluation as a chemopreventive agent. In this study, we investigated several long-term effects of tamoxifen in intact adult female rats following acute treatment at various dosages. The effects of tamoxifen on somatic growth, growth hormone (GH) levels, thyroid hormone levels, and on hepatic cytochrome P450 (P450) expression were compared with those of fulvestrant (ICI 182,780), 17beta-estradiol-3-benzoate, and 4-hydroxytamoxifen under the same experimental conditions. Each compound was injected s.c. for two consecutive days, and rats were killed 37 days after treatment. Tamoxifen decreased body weight and serum triiodothyronine (T3) levels at dosages ranging from 0.5 to 200 mg/kg. Ovary weight, uterus weight, peak plasma GH concentration, and hepatic CYP2A1 content were decreased 37 days after treatment with tamoxifen at a dosage of 20 mg/kg, but expression of other P450 enzymes was not affected. However, tamoxifen and 4-hydroxytamoxifen could not be detected in plasma by high performance liquid chromatography analysis at this time, which suggests that the effects of tamoxifen were mediated indirectly. 4-Hydroxytamoxifen exhibited effects similar to those of tamoxifen, indicating that this metabolite contributes to the in vivo activity of tamoxifen. Estradiol benzoate decreased CYP2A1 and increased CYP3A hepatic levels, but had no effect on serum T3 concentration. In contrast, treatment with ICI 182,780 had little or no effect on the endpoints measured. In summary, 2-day tamoxifen treatment of intact adult female rats resulted in persistent suppression of somatic growth, serum T3 levels, and hepatic CYP2A1 expression.

Animals↗