Endocrine changes with the aromatase inhibitor fadrozole hydrochloride in breast cancer

Imidazo[4,5-b]pyridine derived tubulin polymerization inhibitors: Design, synthesis, biological activity in vitro and computational analysis

Imidazo[4,5-b]pyridine derived acrylonitriles were synthesized and explored for their in vitro antiproliferative effect on a diverse human cancer cell line panel. Three compounds, 20, 21 and 33, showed strong activity in the submicromolar range (IC₅₀ 0.2-0.6 μM), and were chosen for further biological experiments. Immunofluorescence staining and tubulin polymerization assays confirmed tubulin as the main target, but excluded its colchicine-binding site as a potential interacting unit. This was supported by the computational analysis, which revealed that the most potent ligands act on the extended colchicine site on the surface between interacting tubulin subunits, where they interfere with their polymerization and reveal pronounced antitumor properties. In addition, lead molecule 21 potently inhibited cancer cell migration, while it did not affect the viability of normal cells even at the highest concentration tested (100 µM).

2-Aminopyridine - an unsung hero in drug discovery

2-Aminopyridine is a simple, low molecular weight and perfectly functionalised moiety known for the synthesis of diverse biological molecules. Many pharmaceutical companies across the globe aim to synthesise low-molecular weight molecules for use as pharmacophores against various biological targets. 2-Aminopyridine can serve as a perfect locomotive in the synthesis and pulling of such molecules towards respective pharmacological goals. The major advantage of this moiety is its simple design, which can be used to produce single products with minimum side reactions. Moreover, the exact weight of synthesised compounds is low, which enables facile identification of toxicity-causing metabolites in drug discovery programmes. This manuscript is a quick review of such pharmacophores derived from 2-aminopyridine.

Novel amino substituted tetracyclic imidazo[4,5-b]pyridine derivatives: Design, synthesis, antiproliferative activity and DNA/RNA binding study

A novel series of tetracyclic imidazo[4,5-b]pyridine derivatives was designed and synthesized as potential antiproliferative agents. Their antiproliferative activity against human cancer cells was influenced by the introduction of chosen amino side chains on the different positions on the tetracyclic skeleton and particularly, by the position of N atom in the pyridine nuclei. Thus, the majority of compounds showed improved activity in comparison to standard drug etoposide. Several compounds showed pronounced cytostatic effect in the submicromolar range, especially on HCT116 and MCF-7 cancer cells. The obtained results have confirmed the significant impact of the position of N nitrogen in the pyridine ring on the enhancement of antiproliferative activity, especially for derivatives bearing amino side chains on position 2. Thus, regioisomers 6, 7 and 9 showed noticeable enhancement of activity in comparison to their counterparts 10, 11 and 13 with IC₅₀ values in a nanomolar range of concentration (0.3-0.9 μM). Interactions with DNA (including G-quadruplex structure) and RNA were influenced by the position of amino side chains on the tetracyclic core of imidazo[4,5-b]pyridine derivatives and the ligand charge. Moderate to high binding affinities (logK_s = 5-7) obtained for selected imidazo[4,5-b]pyridine derivatives suggest that DNA/RNA are potential cell targets.

Iodine Promoted Efficient Synthesis of 2-Arylimidazo[1,2-a]pyridines in Aqueous Media: A Comparative Study between Micellar Catalysis and an "On-Water" Platform

In a new and environmentally sustainable approach, a series of 2-arylimidazo[1,2-a]pyridine derivatives were synthesized in aqueous media in the presence of iodine as a catalyst. The reaction proceeded by condensation of various aryl methyl ketones with 2-aminopyridines to afford 2-arylimidazo[1,2-a]pyridines in good overall yields. Although several of the reactions were efficiently performed "on water", the addition of a surfactant, namely, sodium dodecyl sulphate , was found effective in terms of substrate scope and yield enhancement. Both methods were successfully used for the gram-scale synthesis of a marketed drug, zolimidine. The simple experimental setup, water as "green" media, and inexpensive catalyst are some of the merits of this protocol.

Pharmacological Potential and Synthetic Approaches of Imidazo[4,5-b]pyridine and Imidazo[4,5-c]pyridine Derivatives

The structural resemblance between the fused imidazopyridine heterocyclic ring system and purines has prompted biological investigations to assess their potential therapeutic significance. They are known to play a crucial role in numerous disease conditions. The discovery of their first bioactivity as GABA_A receptor positive allosteric modulators divulged their medicinal potential. Proton pump inhibitors, aromatase inhibitors, and NSAIDs were also found in this chemical group. Imidazopyridines have the ability to influence many cellular pathways necessary for the proper functioning of cancerous cells, pathogens, components of the immune system, enzymes involved in carbohydrate metabolism, etc. The collective results of biochemical and biophysical properties foregrounded their medicinal significance in central nervous system, digestive system, cancer, inflammation, etc. In recent years, new preparative methods for the synthesis of imidazopyridines using various catalysts have been described. The present manuscript to the best of our knowledge is the complete compilation on the synthesis and medicinal aspects of imidazo[4,5-b]pyridines and imidazo[4,5-c]pyridines reported from the year 2000 to date, including structure–activity relationships.

Aromatase inhibitors for treatment of advanced breast cancer in postmenopausal women

BACKGROUND

Endocrine therapy removes the influence of oestrogen on breast cancer cells and so hormonal treatments such as tamoxifen, megestrol acetate and medroxyprogesterone acetate have been in use for many years for advanced breast cancer. Aromatase inhibitors (AIs) inhibit oestrogen synthesis in the peripheral tissues and have a similar tumour-regressing effect to other endocrine treatments. Aminoglutethimide was the first AI in clinical use and now the third generation AIs, anastrozole, exemestane and letrozole, are in current use. Randomised trial evidence on response rates and side effects of these drugs is still limited.

OBJECTIVES

To compare AIs to other endocrine therapy in the treatment of advanced breast cancer in postmenopausal women.

SEARCH STRATEGY

For this update, the Cochrane Breast Cancer Group Specialised Register and the Cochrane Central Register of Controlled Trials (CENTRAL) and relevant conference proceedings were searched (to 30 June 2008).

SELECTION CRITERIA

Randomised controlled trials in postmenopausal women comparing the effects of any AI versus other endocrine therapy, no endocrine therapy, or a different AI in the treatment of advanced (metastatic) breast cancer. Non-English language publications, comparisons of the same AI at different doses, AIs used as neoadjuvant treatment, or outcomes not related to tumour response were excluded.

DATA COLLECTION AND ANALYSIS

Data from published trials were extracted independently by two review authors and cross-checked by a third. Hazard ratios (HR) were derived for analysis of time-to-event outcomes (overall and progression-free survival). Odds ratios (OR) were derived for objective response, clinical benefit, and toxicity.

MAIN RESULTS

Thirty-seven trials were identified, 31 of which were included in the main analysis of any AI versus any other treatment (11,403 women). No trials were excluded due to inadequate allocation concealment. The pooled estimate showed a significant survival benefit for treatment with an AI over other endocrine therapies (HR 0.90, 95% CI 0.84 to 0.97). A subgroup analysis of the three commonly prescribed AIs (anastrozole, exemestane, letrozole) also showed a similar survival benefit (HR 0.88, 95% CI 0.80 to 0.96). There were very limited data to compare one AI with a different AI, but these suggested an advantage for letrozole over anastrozole.AIs have a different toxicity profile to other endocrine therapies. For those currently prescribed, and for all AIs combined, they had similar levels of hot flushes and arthralgia; increased risks of rash, nausea, diarrhoea and vomiting; but a 71% decreased risk of vaginal bleeding and 47% decrease in thromboembolic events compared with other endocrine therapies.

AUTHORS' CONCLUSIONS

In women with advanced (metastatic) breast cancer, aromatase inhibitors including those in current clinical use show a survival benefit when compared to other endocrine therapy.

Fugu (Takifugu rubripes) sexual differentiation: CYP19 regulation and aromatase inhibitor induced testicular development

In order to assess the involvement of aromatase CYP19 isoforms and endogenous sex steroids in gonadal sex differentiation and development of the Japanese fugu (Takifugu rubripes), an aromatase inhibitor (AI, fadrozole) was administered to developing fishes from the 'first feeding' till the 100th day after hatching. It was observed that ovarian cavity formation was inhibited by fadrozole at doses of 500 and 1000 microg/g diet, which was followed by testicular differentiation in all treated fugu. In the non-treated fugu, CYP19A was predominantly expressed in the ovary and CYP19B in the brain (in both sexes), although both were expressed interchangeably at low levels. An exceptionally high expression of CYP19B was also evident in testis throughout the study period. Both forms of CYP19 mRNA showed low levels of expression in brain and gonad with no significant differences between the two AI treatments. AI treatment inhibited CYP19A mRNA in trunk during the crucial period of ovarian cavity formation and CYP19B in gonad and brain by the end of gonadal sex differentiation. An elevation of testosterone and 11-ketotestosterone was observed which can be associated with the down-regulation of the circulating 17beta-estradiol production during the AI treatment period. After stopping AI treatment, both circulating estrogen and androgen were normalized. The current results suggest that suppression of CYP19A before and during morphological sex differentiation inhibits ovarian cavity formation in fugu. Furthermore, non-detectable limits of 17beta-estradiol and high testosterone levels by the end of the gonadal differentiation period can be ascribed to inhibition of CYP19B, suggesting that conversion of 17beta-estradiol from testosterone is plausibly regulated by CYP19B, and that this factor (CYP19B) may play an important role in AI-induced testicular development after gonadal sex differentiation through regulation of the testosterone-17beta-estradiol balance in fugu.

Aromatase inhibitors for treatment of advanced breast cancer in postmenopausal women

BACKGROUND

Hormonal treatments for advanced or metastatic breast cancer, such as tamoxifen and the progestins megestrol acetate and medroxyprogesterone acetate, have been in use for many years. Aromatase inhibitors (AIs) are a class of compounds that systemically inhibit oestrogen synthesis in the peripheral tissues. Aminoglutethimide was the first AI in clinical use (first generation) and had a similar tumour-regressing effect to other endocrine treatments, which showed the potential of this alternative type of therapy. Other AIs have since been developed and the third generation AIs anastrozole, exemestane and letrozole are in current use. Randomised evidence on response rates and side effects of these drugs is still limited.

OBJECTIVES

To compare aromatase inhibitors to other endocrine therapy in the treatment of advanced breast cancer in postmenopausal women.

SEARCH STRATEGY

The Cochrane Breast Cancer Group Specialised Register was searched on 3 December 2004 using the codes for "advanced" and "endocrine therapy". Details of the search strategy applied to create the Register and the procedure used to code references are described in the Cochrane Breast Cancer Group module on The Cochrane Library. The search was updated to 30 September 2005 and additional publications were included. Experts were consulted to determine that no relevant studies had been excluded.

SELECTION CRITERIA

Randomised trials comparing the effects of any aromatase inhibitor versus other endocrine therapy, no endocrine therapy or a different aromatase inhibitor in the treatment of advanced (metastatic) breast cancer.

DATA COLLECTION AND ANALYSIS

Data from published trials were extracted by two independent review authors. A third independent author then carried out a further cross check for accuracy and consistency. Hazard ratios (HR) were derived for analysis of time-to-event outcomes (overall and progression-free). Odds ratios (OR) were derived for objective response and clinical benefit (both analysed as dichotomous variables). Toxicity data were extracted where present and treatments were compared using odds ratios. All but one of the studies included data on one or more of the following outcomes: overall survival, progression-free survival, clinical benefit and objective response.

MAIN RESULTS

Thirty studies were identified, twenty five of which were included in the main analysis of any AI versus any other treatment (9416 women). The pooled estimate showed a significant survival benefit for treatment with an AI over other endocrine therapies (HR 0.89, 95%CI 0.82 to 0.96). A subgroup analysis of the three commonly prescribed AIs (anastrozole, exemestane, letrozole) also showed a similar survival benefit (HR 0.88, 95%CI 0.80 to 0.96). The results for progression-free survival, clinical benefit and objective response were not statistically significant and there was statistically significant heterogeneity across types of AI. There were very limited data to compare one AI with a different AI, but these suggested an advantage for letrozole over anastrozole. All the trials of AIs used exclusively as first-line therapy were against tamoxifen. There was an advantage to treatment with AIs in terms of progression-free survival (HR 0.78, 95% CI 0.70 to 0.86) and clinical benefit (OR 0.70, 95% CI 0.51 to 0.97) but not overall survival or objective response. There was considerable heterogeneity across studies when considering clinical benefit (P = 0.001). Use of an AI as second-line therapy showed a significant benefit in terms of overall survival (HR 0.80, 95% CI 0.66 to 0.96) but not for progression-free survival (HR 1.08, 95% CI 0.89 to 1.31), clinical benefit (OR 1.00, 95% CI 0.87 to 1.14) or objective response (OR 0.96, 95% CI 0.81 to 1.14). This is difficult to interpret due to the extreme heterogeneity across AIs for progression-free survival but not the other endpoints.AIs have a different toxicity profile to other endocrine therapies. For all AIs combined, they had similar levels of hot flushes (especially when compared to tamoxifen) and arthralgia, increased risks of nausea, diarrhoea and vomiting, but a decreased risk of vaginal bleeding and thromboembolic events compared with other endocrine therapies. A similar pattern of risks and benefits was still seen when analyses were limited to the currently most-prescribed third generation AIs.

AUTHORS' CONCLUSIONS

In women with advanced (metastatic) breast cancer, aromatase inhibitors including those in current clinical use show a survival benefit when compared to other endocrine therapy.

The relationship between the insulin-like growth factor-1 system and the oestrogen metabolising enzymes in breast cancer tissue and its adjacent non-cancerous tissue

AIMS

Previous studies have shown that oestrogen and Insulin-like Growth Factor-1 (IGF-1) act synergistically and cross-stimulatory while the oestrogen receptor (ER) and IGF-1R downstream signalling pathways interact at many levels. We investigate the relationship between the ER, and IGF-1R and their ligands in a series of human breast cancer tissue and adjacent non-cancerous tissue (ANCT).

METHODS

A series of 139 pairs of breast cancer tissue and ANCT were obtained and divided into ER positive and ER negative groups based on tumour ER alpha immunostaining. All samples were processed for real-time quantitative-PCR to measure IGF-1, IGF-1R, ER alpha, STS and Cyp-19 mRNA levels. In addition, ER positive MCF-7 and ER negative MDA-MB-231 cell lines were treated separately with IGF-1 and an IGF-1R inhibitor called Tyrphostin AG1024 to see the effects of stimulating and inhibiting the IGF-1R. MCF-7 cell line was also treated with 4-hydroxytamoxifen. The mRNA levels of IGF-1, IGF-1R, ER alpha, STS and Cyp-19 of treated cell lines were measured and compared to those of non-treated controls. Data generated was normalised to Cytokeratin-19 mRNA levels.

RESULTS

IGF-1R expression was higher in tumour tissue compared to ANCT (P = 0.038) while IGF-1 expression was marginally higher in ANCT compared to tumour tissue only in the ER positive samples (P = 0.098). ER positive tumours had a higher expression of IGF-1 compared to ER negative tumours (P = 0.001) while IGF-1R, STS and Cyp-19 expression were higher in ER negative tumours (P = 0.000, 0.000 and 0.006 respectively). There was no difference in STS or Cyp-19 expression in tumours or ANCT. Using Spearman's Correlation test, IGF-1 positively correlated with STS, Cyp-19 and ER alpha in ER positive and negative groups (Coefficient = +0.497, +0.662 and +0.651 respectively, P = 0.000 in all). IGF-1R correlated with IGF-1, STS, Cyp-19 and ER alpha only in the ER negative tumours (Coefficient = +0.620, +0.394, +0.692 and +0.662 respectively, P = 0.000, 0.012, 0.000 and 0.000 respectively). In cell lines, IGF-1 treatment led to an increase in the mean expression of IGF-1, IGF-1R, STS and Cyp-19 in both cell lines while ER alpha expression increased only in MCF-7. IGF-1R inhibition caused a decrease in expression of all five genes in MDA-MB-231 but not in the MCF-7 cell line. Treatment with 4-hydroxytamoxifen caused a decrease in expression of all five genes.

CONCLUSIONS

IGF-1R is over-expressed in malignant tissue. IGF-1 is expressed at higher levels in ER positive tumours probably as a result of oestrogen stimulation while IGF-1R expression is higher in ER negative samples as an adaptation to lower local IGF-1 levels. An IGF-1 paracrine relationship may exist between tumour and ANCT but for STS and Cyp-19, there may be an autocrine-paracrine relationship. The IGF-1 ligand-receptor system is an important regulator of oestrogen production while oestrogen may be involved in stimulating IGF-1 expression. The expression of oestrogen synthesising enzymes is higher in ER negative breast cancers which may be due to the lack of oestrogen negative feedback or contribution from the overexpression of IGF-1R.

Aromatase Inhibitors for the Treatment and Prevention of Breast Cancer

In a review of current information on aromatase inhibitors (AIs) and their use in breast cancer treatment and prevention, published reports were obtained through a Medline search. Tamoxifen, a selective estrogen receptor modulator, is approved for use in metastatic breast cancer (MBC), the adjuvant treatment of breast cancer, and the prevention of breast cancer in women at high risk. The 50% reduction in breast cancer incidence seen with tamoxifen is significant for women at increased risk but is accompanied by notable toxicities such as thrombotic events and endometrial cancer. Therefore, the development of other effective agents with less toxicity would be a major advance in breast cancer prevention. Aromatase inhibitors, recently approved for the treatment of MBC and in the adjuvant setting, are proving to be slightly more effective than tamoxifen therapy. These drugs, approved for use in only postmenopausal women, inhibit the enzyme aromatase and thereby lower circulating functional estrogen. To date, the most concerning side effect of these agents is an increase in fracture rate. Compared with tamoxifen, thrombotic events and endometrial cancer rates are much lower. Ongoing data from the Arimidex, Tamoxifen, Alone or in Combination trial continue to favor anastrozole over tamoxifen in the reduction of primary contralateral breast cancers. This information has prompted breast cancer chemoprevention trials with AIs. Although tamoxifen is the gold standard for prevention therapy, results of ongoing studies may indicate a role for AIs in the prevention of breast cancer.

Recent insight on the control of enzymes involved in estrogen formation and transformation in human breast cancer

The great majority of breast cancers are in their early stage hormone-dependent and it is well accepted that estradiol (E2) plays an important role in the genesis and evolution of this tumor. Human breast cancer tissues contain all the enzymes: estrone sulfatase, 17beta-hydroxysteroid dehydrogenase, aromatase involved in the last steps of E2 bioformation. Sulfotransferases which convert estrogens into the biologically inactive estrogen sulfates are also present in this tissue. Quantitative data show that the 'sulfatase pathway', which transforms estrogen sulfates into the bioactive unconjugated E2, is 100-500 times higher than the 'aromatase pathway', which converts androgens into estrogens. The treatment of breast cancer patients with anti-aromatases is largely developed with very positive results. However, the formation of E2 via the 'sulfatase pathway' is very important in the breast cancer tissue. In recent years it was found that antiestrogens (e.g. tamoxifen, 4-hydroxytamoxifen), various progestins (e.g. promegestone, nomegestrol acetate, medrogestone, dydrogesterone, norelgestromin), tibolone and its metabolites, as well as other steroidal (e.g. sulfamates) and non-steroidal compounds, are potent sulfatase inhibitors. In another series of studies, it was found that E2 itself has a strong anti-sulfatase action. This paradoxical effect of E2 adds a new biological response of this hormone and could be related to estrogen replacement therapy in which it was observed to have either no effect or to decrease breast cancer mortality in postmenopausal women. Interesting information is that high expression of steroid sulfatase mRNA predicts a poor prognosis in patients with +ER. These progestins, as well as tibolone, can also block the conversion of estrone to estradiol by the inhibition of the 17beta-hydroxysteroid dehydrogenase type I (17beta-HSD-1). High expressison of 17beta-HSD-1 can be an indicator of adverse prognosis in ER-positive patients. It was shown that nomegestrol acetate, medrogestone, promegestone or tibolone, could stimulate the sulfotransferase activity for the local production of estrogen sulfates. This is an important point in the physiopathology of this disease, as it is well known that estrogen sulfates are biologically inactive. A possible correlation between this stimulatory effect on sulfotransferase activity and breast cancer cell proliferation is presented. In agreement with all this information, we have proposed the concept of selective estrogen enzyme modulators (SEEM). In conclusion, the blockage in the formation of estradiol via sulfatase, or the stimulatory effect on sulfotransferase activity in combination with anti-aromatases can open interesting and new possibilities in clinical applications in breast cancer.

Biological rationale for endocrine therapy in breast cancer

Oestrogens are heavily implicated in the risk to, and progression of, breast cancer. Therapeutic strategies targeted at the oestrogenic stimulus to the breast and hormone-sensitive breast cancers are extremely attractive measures both to prevent the disease and to treat established tumours. The present review outlines the biological rationale for such endocrine therapy and traces the evolution whereby irreversible surgical procedures have been replaced by potent and specific drugs. In particular, the development of the latest generation of agents which inhibit oestrogen biosynthesis (aromatase inhibitors) is considered by defining the central role of the aromatase enzyme, its regulation and contribution to circulating and tumour endogenous oestrogens. The nature of response and resistance which may be elicited following the use of endocrine therapy is also described as this may determine the optimal use of aromatase inhibitors and, more generally, anti-hormone therapy in the management of women at high risk to, or with, breast cancer.

Hormonal therapy for breast cancer. An update

The use of endocrine manipulation for the treatment of breast cancer has been available for 100 years, but in recent years the number of therapeutic options available to patients has increased dramatically. This article considers new developments in the use of hormonal agents for the treatment and prevention of breast cancer.

Aromatase inhibitors and their use in the adjuvant setting

Over the past decade several novel aromatase inhibitors have been introduced into clinical practice. The discovery of these drugs followed on from the observation that the main mechanism of action of aminoglutethemide was via inhibition of the enzyme aromatase, thereby reducing peripheral levels of estradiol in post-menopausal patients. The second-generation drug 4-hydroxyandrostenedione was introduced in 1990, and although its use was limited by its need to be given parenterally, it was found to be a well-tolerated form of endocrine therapy. The third-generation inhibitors include vorozole, letrozole, anastrozole and exemestane, the former three being non-steroidal inhibitors, the latter being a steroidal inhibitor. All these compounds are capable of reducing estrogen levels to within 5%-10% of baseline levels compared with 20%-30% base line levels in the case of 4-hydroxyandrostenedione. Studies are currently in progress to determine the value of these third-generation aromatase inhibitors in the adjuvant setting. These studies include head-to-head comparison of aromatase inhibitor with tamoxifen, sequential aromatase inhibitor after tamoxifen and first-line aromatase inhibitor followed by adjuvant tamoxifen. Current issues revolve around the toxicity of these compounds in terms of effects on the cardiovascular system and bone.

A review of the newer aromatase inhibitors in the management of metastatic breast cancer

BACKGROUND

Breast cancer remains a major cause of morbidity and mortality world-wide. While aminoglutethimide, a first-generation aromatase inhibitor, has equivalent efficacy to first-line tamoxifen in the palliative treatment of metastatic breast cancer, its toxicity profile has relegated this drug to a second- or third-line agent in this setting. Recently, several aromatase inhibitors have been released onto the market while others are in phase II and III clinical trials.

AIM

To review the role of the new aromatase inhibitors in the management of metastatic breast cancer.

METHODS

Current literature, abstracts from meetings and information from pharmaceutical manufacturers have been summarized.

CONTENT

A review of the clinical pharmacology of the new aromatase inhibitors has been provided in addition to a synopsis of phase III clinical studies.

CONCLUSION

The newer aromatase inhibitors have several advantages compared to aminoglutethimide and are a useful addition to the armamentarium of therapies employed in the palliative management of advanced breast cancer.

Hormonal effects of MPV-2213ad, a new selective aromatase inhibitor, in healthy male subjects. A phase I study

AIMS

A novel non-steroidal competitive inhibitor of the aromatase enzyme, MPV-2213ad, was entered into an open dose-escalation study. The objective of this study was to investigate the tolerability and efficiency of this new compound with assessment of the hormonal effects after study drug administration.

METHODS

MPV-2213ad was given to 39 healthy male volunteers. Single increasing oral doses of 0.003, 0.03, 0.3, 3, 9, 30 and 100 mg were given to three subjects at each dose level, after which ten subjects received the 300 mg dose and eight subjects the highest 600 mg dose of MPV-2213ad.

RESULTS

Serum oestradiol levels were suppressed by 58-65% when MPV-2213ad was given at doses between 0.3 and 30 mg. A reduction in serum oestradiol levels by 83% from baseline was achieved with the 300 mg dose. No additional decrease was seen with the highest dose. The suppression lasted longer with higher doses of MPV-2213ad. After the 300 and 600 mg doses serum oestradiol returned to baseline within 4 days. Marked increases in serum concentrations of testosterone, androstenedione, 17-OH-progesterone, LH and FSH were also observed at doses between 100 and 600 mg of MPV-2213ad. The drug was well-tolerated and the adverse events were mild or moderate including hot flushes, mild vertigo, nausea, acne and gastrointestinal discomfort.

CONCLUSIONS

MPV-2213ad has a potent, dose-dependent inhibitory effect on serum oestradiol. It was selective for the aromatase enzyme with no signs of adreno-cortical suppression or haematological or biochemical toxicity.

Potent and selective aromatase inhibitor: in vitro and in vivo studies with s-triazine derivative SEF19

We found a potent aromatase inhibitor through the screening of agents for estrogen-dependent breast cancer. SEF19 (2-(imidazol-1-yl)-4,6-dimorphorino-1,3,5-triazine) decreased 50% of human placental aromatase activity in vitro at the concentration of 5.3 nM. In order to clarify the selectivity of SEF19 for enzyme inhibition, we determined the effect of SEF19 on the activities of four steroidogenic cytochrome P450 enzymes in porcine adrenal gland, P450SCC(side-chain cleavage of cholesterol), P450(11 beta) (11 beta-hydroxylase), P450(17 alpha)(17 alpha-hydroxylase/C17,20 lyase) and P450C21 (21-hydroxylase). SEF19 failed to inhibit the activities of porcine adrenal P450SCC, P450(17 alpha) and P450C21 up to the concentration of 100 microM and showed some inhibition on P450(11 beta) activity at 100 microM, while SEF19 completely nullified the aromatase activity at 1 microM. We also determined the potency of SEF19 for the suppression of aromatase activity in vivo. SEF19 suppressed dose-dependently the uterine hypertrophy of immature rats caused by administration of androstenedione (30 mg/kg, s.c.). The ED50 of SEF19 for the suppression of uterine hypertrophy was 0.8 mumol/kg. These results suggest that SEF19 may serve as a potent and selective agent for the treatment of estrogen-dependent breast cancer.

Behavioral responses to Depo-Provera, Fadrozole, and estradiol in castrated, testosterone-treated cynomolgus monkeys (Macaca fascicularis): the involvement of progestin receptors

Sexual motivation and behavior decreased in male cynomolgus monkeys given either Depo-Provera (medroxyprogesterone acetate, MPA), which reduces androgen uptake by brain, or the nonsteroidal aromatase inhibitor, Fadrozole, which virtually eliminates the conversion of testosterone (T) to estradiol (E2) in brain. This suggested that both unchanged T and E2 are important for the control of male primate sexual behavior, but combined treatment with MPA and Fadrozole did not have the anticipated summatory effects in intact males: the behavioral decrements when MPA-treated males were given Fadrozole were about half those observed when Fadrozole was given alone. The present study tested the hypothesis that Fadrozole suppressed the behavioral effects of MPA by preventing the induction by E2 of progestin receptors in the brain to which MPA binds. Eight castrated, T-treated males were each tested with an estrogenized female i) during baseline, ii) during MPA treatment, iii) during treatment with MPA and Fadrozole together, and iv) with E2 treatment added to condition (iii) (256 1-h behavior tests). All dosages were those used in previous studies. Sexual motivation, as reflected in mounting attempts and mounting attempt latencies, was further diminished by E2 treatment in males receiving both MPA and Fadrozole, but ejaculatory activity was not changed. Immunocytochemistry demonstrated that the distributions of progestin and androgen receptors were little affected by MPA treatment, and that progestin receptor immunoreactivity was almost completely abolished in the brains of males receiving both MPA and Fadrozole but present in those receiving additional E2 treatment, findings that supported the hypothesis.

Therapeutic effects of the aromatase inhibitor fadrozole hydrochloride in advanced breast cancer

The endocrine and therapeutic effects of the aromatase inhibitor fadrozole hydrochloride have been assessed in 80 post-menopausal patients with recurrent breast cancer after tamoxifen failure. Treatment allocation was randomly 0.5, 1.0 or 2.0 mg orally b.d. Eight patients were not assessable for response. All patients were evaluated for toxicity (intent-to-treat analysis). In general, the patients' characteristics were well balanced between the three randomised groups. The endocrine data from this study previously reported suggest a dose-related suppression of oestrone, but not oestradiol or oestrone sulphate. The objective response rate was 17% (95% CI 8.9-27.3%) with no complete responders. Fifteen patients (21%) had stable disease (NC) and 45 patients (63%) had progressive disease (PD). The median duration of objective response was 36 weeks. The median time to treatment failure was 12.7 weeks. The log-rank test showed no statistical difference between the dosage groups. The main adverse events reported were mild to moderate severity: nausea in 11 patients (15%), hot flashes in four (5%) and somnolence in three (4%). No serious adverse events were reported. In conclusion, fadrozole is a clinically active aromatase inhibitor with a low incidence of side-effects and phase III clinical trials in post-menopausal women are currently under way.