Changes in bone and lipid metabolism in postmenopausal women with early breast cancer after terminating 2-year treatment with exemestane: a randomised, placebo-controlled study.

Aromatase inhibitors improve relapse-free survival in early breast cancer, but there is concern about possible detrimental effects on bone mineral density (BMD) and plasma lipids. This paper presents the results of a 2-year study evaluating the effects of exemestane versus placebo on BMD, bone markers, plasma lipids and coagulation factors, including a 1-year follow-up after termination of treatment in 147 patients. During treatment, the mean annual rate of loss of BMD in the lumbar spine was 2.17% in the exemestane group versus 1.84% in the placebo group (n.s.) and 2.72% versus 1.48%, respectively, in the femoral neck (P=0.024). A loss of BMD above that expected in both arms of this study could be due to low vitamin D status (88% of all patients had vitamin D levels <30 ng/ml). The changes observed with exemestane were partially reversed during a 1-year follow-up, with no significant difference between the two arms. Similarly, the moderate decrease in high-density lipoprotein (HDL)-cholesterol was reversed. The bone marker values decreased, although a difference at 6 months of follow-up was still recorded, in particular for the markers of bone synthesis.

Phase I and endocrine study of exemestane (FCE 24304), a new aromatase inhibitor, in postmenopausal women.

Aromatase inhibitors are a useful therapeutic option in the management of endocrine-dependent advanced breast cancer. A single-dose administration of exemestane (FCE 24304; 6-methylenandrosta-1,4-diene-3,17-dione), a new irreversible aromatase inhibitor, was investigated in 29 healthy postmenopausal female volunteers. The compound, given at p.o. doses of 0.5, 5, 12.5, 25, 50, 200, 400, and 800 mg (n = 3-4), was found to be a well tolerated, potent, long-lasting, and specific inhibitor of estrogen biosynthesis. The minimal dose which produced the maximum suppression of plasma estrogens was 25 mg, reducing plasma estrone, estradiol, and estrone sulfate to 35, 28, and 39% of basal values, respectively. This maximum suppression, observed at 3 days, persisted for at least 5 days after administration of a single dose. However, there was no interference on cortisol, aldosterone, 17-hydroxyprogesterone, or dehydroepiandrostenedione sulfate plasma levels. Peak plasma exemestane concentrations of 27, 221, 343, and 414 ng/ml were reached within 2 h after administration of 50, 200, 400, and 800 mg, respectively. Plasma concentrations declined rapidly and fell under the detection limit (10 ng/ml) at 4 (50 mg) or 24 h (200 and 400 mg). No clinically significant adverse events which could be attributed to the drug were reported. Apart from transient eosinophilia in 3 patients, all biochemical and hematological laboratory parameters were within 1.25-fold of the normal ranges.

Multicenter, phase II trial of exemestane as third-line hormonal therapy of postmenopausal women with metastatic breast cancer. Aromasin Study Group.

PURPOSE: To assess the antitumor activity, safety, and hormone-suppressive effects of the irreversible aromatase inactivator, exemestane (Aromasin, Pharmacia & Upjohn, Kalamazoo, MI), administered as third-line hormone therapy to postmenopausal women with metastatic breast cancer that is refractory to tamoxifen and megestrol acetate. PATIENTS AND METHODS: Exemestane was administered at a dose of 25 mg/d orally until patients experienced disease progression. The efficacy and safety of exemestane were clinically and radiographically evaluated. The impact of exemestane treatment on tumor-related signs and symptoms was assessed. The effect of exemestane on serum levels of estrogens and other steroidal hormones was determined. RESULTS: Ninety-one patients were treated. There were four complete responses (CR) and eight partial responses (PR), for an objective response rate of 13% in the entire treated population. The overall success rate (CR, PR, or stable disease [SD] >/= 24 weeks) was 30%. The median duration of response and overall success was 9 months and 8 months, respectively. Most patients with CR/PR (83%; 10 of 12 patients) and SD >/= 24 weeks (80%; 12 of 15 patients) had improved or stable tumor-related signs and symptoms. Mean levels of circulating estrone (E(1)), estradiol (E(2)), and estrone sulfate decreased to 11%, 22%, and 13% of baseline levels, respectively (at week 8 or 16 of treatment). One half of the patients had undetectable E(1) and E(2) levels during treatment, including at the time of disease progression. Mild nausea (20% of patients) and hot flashes (20%) were the most common drug-related adverse events and were generally grade 1. CONCLUSION: Exemestane is an active and well-tolerated third-line hormonal therapy that represents a new treatment option for postmenopausal patients with advanced breast cancer that has become refractory to standard first- and second-line hormonal therapies.

Activity of exemestane in metastatic breast cancer after failure of nonsteroidal aromatase inhibitors: a phase II trial.

PURPOSE: To evaluate the antitumor activity and toxicity of a new steroidal aromatase inactivator, exemestane, in postmenopausal women with metastatic breast cancer who had progressive disease (PD) after treatment with a nonsteroidal aromatase inhibitor. PATIENTS AND METHODS: In this phase II trial, eligible patients were treated with exemestane 25 mg daily (n = 241) followed, at the time PD was determined, by exemestane 100 mg daily (n = 58). RESULTS: On the basis of the intent-to-treat analysis by independent review, exemestane 25 mg produced objective responses in 6.6% of patients (95% confidence interval [CI], 3.8% to 10.6%) and overall success (complete response + partial response + no change for 24 weeks or longer) in 24.3% (95% CI, 19.0% to 30.2%). The median durations of objective response and overall success were 58.4 weeks (95% CI, 49.7 to 71.1 weeks) and 37.0 weeks (95% CI, 35.0 to 39.4 weeks), respectively. Increasing the dose of exemestane to 100 mg upon the development of PD produced one partial response (1.7%; 95% CI, 0.0% to 9.2%). Both dosages were well tolerated and were discontinued because of adverse events in only 1.7% of patients. CONCLUSION: Exemestane 25 mg once daily seems to be an attractive alternative to chemotherapy for the treatment of patients with metastatic breast cancer after multiple hormonal therapies have failed.

Exemestane is superior to megestrol acetate after tamoxifen failure in postmenopausal women with advanced breast cancer: results of a phase III randomized double-blind trial. The Exemestane Study Group.

PURPOSE: This phase III, double-blind, randomized, multicenter study evaluated the efficacy, pharmacodynamics, and safety of the oral aromatase inactivator exemestane (EXE) versus megestrol acetate (MA) in postmenopausal women with progressive advanced breast cancer who experienced failure of tamoxifen. PATIENTS AND METHODS: A total of 769 patients were randomized to EXE 25 mg/d (n = 366) or MA (n = 403) 40 mg four times daily. Tumor response, duration of tumor control, tumor-related signs and symptoms (TRSS), quality of life (QOL), survival, and tolerability were evaluated. RESULTS: Overall objective response (OR) rates were higher in patients treated with EXE than in those treated with MA (15.0% v 12.4%); a similar trend was noted in patients with visceral metastases (13.5% v 10.5%). Median survival time was significantly longer with EXE (median not reached) than with MA (123.4 weeks; P =.039), as were the median duration of overall success (OR or stable disease > or = 24 weeks; 60.1 v 49.1 weeks; P =.025), time to tumor progression (20.3 v 16.6 weeks; P =.037), and time to treatment failure (16.3 v 15.7 weeks; P =.042). Compared with MA, there were similar or greater improvements in pain, TRSS, and QOL with EXE. Both drugs were well tolerated. Grade 3 or 4 weight changes were more common with MA (17.1% v 7.6%; P =.001). CONCLUSION: EXE prolongs survival time, time to tumor progression, and time to treatment failure compared with MA and offers a well-tolerated treatment option for postmenopausal women with progressive advanced breast cancer who experienced failure of tamoxifen.

In vivo inhibition of aromatization by exemestane, a novel irreversible aromatase inhibitor, in postmenopausal breast cancer patients.

The effect of exemestane (6-methylenandrosta-1,4-diene-3,17-dione) 25 mg p.o. once daily on in vivo aromatization was studied in 10 postmenopausal women with advanced breast cancer. Aromatization was determined before treatment and after 6-8 weeks on therapy by administering a bolus injection of [3H]androstenedione (500 microCi) and [14C]estrone (5 microCi) followed by measurement of the isotope ratio of urinary estrogens after high-performance liquid chromatography purification. In addition, plasma endogenous estrogens were measured with highly sensitive radioimmunoassays after separation with high-performance liquid chromatography. Treatment with exemestane suppressed whole body aromatization from a mean pretreatment value of 2.059% to 0.042% (mean suppression of 97.9%). Plasma levels of estrone, estradiol, and estrone sulfate were found to be suppressed by 94.5%, 92.2%, and 93.2%, respectively. This is the first study revealing near total aromatase inhibition in vivo with the use of a steroidal aromatase inhibitor. The observation that exemestane is a highly potent aromatase inhibitor, together with the fact that the drug is administered p.o. and causes limited side effects, suggests that exemestane is a promising new drug for the treatment of hormone sensitive breast cancer.

Endocrine and clinical effects of exemestane (PNU 155971), a novel steroidal aromatase inhibitor, in postmenopausal breast cancer patients: a phase I study.

Clinical and endocrinological effects of exemestane (6-methylenandrosta-1,4-diene-3,17-dione; PNU 155971) were evaluated in an open Phase I study. Thirteen postmenopausal women suffering from advanced breast cancer received exemestane in escalating doses over a 12-week period. Starting on 5 mg once daily (o.d.), exemestane was subsequently escalated at 2-week intervals to 10, 25, 50, 100, and 200 mg o.d. Each patient subsequently continued treatment on the highest tolerated dose until time of progression. One patient terminated treatment after 6 days due to diarrhea that was probably not related to drug therapy, although a relationship could not be excluded. Apart from this, no serious side effects were seen during the dose escalation period. Exemestane (10 mg o.d.) caused maximal suppression of plasma estradiol (E2) and estrone (E1) to a mean of 14.6 and 5.8% of pretreatment levels, respectively, whereas 25 mg of exemestane o.d. suppressed estrone sulfate (E1S) to 8.9% of pretreatment levels. No fall in adrenal steroid levels was recorded. Exemestane (5 mg o.d.) suppressed urinary E2 and E1 to a mean of 11.9 and 12.2% of pretreatment levels, respectively. Administering exemestane at doses of 50-200 mg o.d. caused no further suppression of urinary E1, whereas urinary E2 fell to 6-7% of pretreatment levels. Median time to progression was 63 weeks. We conclude that exemestane is a well-tolerated aromatase inhibitor that effectively suppresses plasma and urinary estrogens in postmenopausal patients with breast cancer.

Combined treatment with the 5 alpha-reductase inhibitor PNU 157706 and the antiandrogen flutamide on the Dunning R3327 prostatic carcinoma in rats.

The steroid 5 alpha-reductase enzyme catalyzes the conversion of testosterone to the potent androgen 5 alpha-dihydrotestosterone (DHT). PNU 157706, a novel, potent and selective dual 5 alpha-reductase inhibitor, was reported to be effective in inhibiting the growth of established tumors in the Dunning R3327 rat prostatic carcinoma model. We have studied the efficacy of combined treatment with PNU 157706 and the antiandrogen flutamide in this prostatic tumor in rats. Rats with tumor diameters of about 1 cm were treated orally 6 days a week for 9 weeks with PNU 157706 (10 mg/kg per day) alone or in combination with flutamide (1 and 5 mg/kg per day). Animals were killed 24 h after the last treatment and ventral prostates were removed for testosterone and DHT determination. PNU 157706 reduced the growth of established tumors by 36%; flutamide showed a slight effect at 1 mg/kg per day (24% inhibition), while at the dose of 5 mg/kg per day it reduced tumor growth by 48%. The combination of PNU 157706 with the lower dose of flutamide caused an additive tumor growth inhibition (60%) and the combination with the higher dose of flutamide resulted in a better inhibition of tumor growth (68%) than did either treatment alone. Castration resulted in marked tumor growth inhibition (76%). Ventral prostate weight was more markedly reduced by PNU 157706 treatment than by flutamide; combined treatment was as effective as castration. Prostatic DHT content was markedly reduced by PNU 157706 (93%), whereas prostatic testosterone increased (137%). Concomitant treatment with flutamide partially antagonized the testosterone increase induced by PNU 157706 and did not modify the already considerable suppression of DHT. These data show that the inhibitory effects of PNU 157706 and flutamide on Dunning prostatic tumor growth are additive, thus supporting the rationale of this combination therapy in advanced prostate cancer, in order to achieve adequate androgen blockade with minimal side-effects.

Biochemical and pharmacogenetic dissection of human steroid 5 alpha-reductase type II.

Human prostatic steroid 5alpha-reductase, encoded by the SRD5A2 gene on chromosome band 2p23, catalyses the irreversible conversion of testosterone to dihydrotestosterone (DHT), the most active androgen in the prostate, with NADPH as its cofactor. This enzyme has never been purified but a number of competitive inhibitors have been developed for this enzyme since increased steroid 5alpha-reductase activity may cause benign prostatic hypertrophy and prostate cancer. We report here the detailed biochemical and pharmacogenetic dissection of the human enzyme by analysing 10 missense substitutions and three double mutants which are all naturally found in humans. Nine of these 13 mutants reduce activity (measured as Vmax) by 20% or more, three increase steroid 5alpha-reductase by more than 15% and one results in essentially unaltered kinetic properties suggesting that it is a truly neutral ('polymorphic') amino acid substitution. Substantial pharmacogenetic variation among the mutants was also observed when three competitive inhibitors, finasteride, GG745 (dutasteride) and PNU157706, were investigated. Our studies not only define the substrate and cofactor binding sites of human steroid 5alpha-reductase, but also have significant consequences for the pharmacological usage of steroid 5alpha-reductase inhibitors in human patients treated for prostatic conditions.

Comparison of the effects of the irreversible aromatase inhibitor exemestane with atamestane and MDL 18962 in rats with DMBA-induced mammary tumours.

The antitumour activity of the steroidal aromatase inhibitors exemestane (FCE 24304), MDL 18962 and atamestane (SH 489) was evaluated on 7,12-dimethylbenzanthracene (DMBA)-induced mammary tumours in rats. The compounds were given subcutaneously at daily doses of 10 and 50 mg/kg for 4 weeks. Exemestane was also given orally, at daily doses of 100 and 200 mg/kg. Subcutaneous exemestane induced 30% (10 mg/kg) and 73% (50 mg/kg) regressions of established tumours and strongly reduced the appearance of new tumours. Conversely, atamestane, MDL 18962 and oral exemestane did not affect growth of established tumours nor influenced the appearance of new neoplasms. Aromatase activity of ovarian microsomes (OAA) was reduced by 85%-93% after subcutaneous exemestane and by 25%-59% after MDL 18962, and was unaffected after atamestane. Oral exemestane caused a reduction in OAA of 72%-74%. Serum luteinising hormone (LH) levels were reduced at both the subcutaneous doses of exemestane and at the higher dose of MDL 18962. Atamestane caused an increase in LH levels, while no effect was observed with oral exemestane. The LH-lowering effect of subcutaneous exemestane, the less marked effect of MDL 18962, and the ineffectiveness of oral exemestane were also observed after 10 days of treatment in ovariectomised rats. The antigonadotrophic effect of subcutaneous exemestane, which is probably due to its slight androgenic effect, could contribute to its antitumour activity in the DMBA tumour model in intact rats, through a counteraction of the negative feedback of oestrogens on gonadotropin secretion.

Third-line hormonal treatment with exemestane in postmenopausal patients with advanced breast cancer progressing on aminoglutethimide: a phase II multicentre multinational study. Exemestane Study Group.

In a European multicentre phase II study, 80 postmenopausal patients (pts) with advanced breast cancer progressing on aminoglutethimide (AG) at daily doses of > or = 500 mg were enrolled. Seventy-eight received exemestane (200 mg daily orally), including 33 pts resistant to prior AG, 39 pts who had progressed after an initial response to AG, and 6 pts whose response to AG was either unavailable or not evaluable. Three pts were pretreated with AG only, 69 with tamoxifen and AG, and 6 with tamoxifen, AG and other hormone therapies; 55% had also previously received chemotherapy. The predominant site of disease was visceral in 34 cases, bone in 27 and soft tissue in 17. Based on Peer Review assessment, the overall objective response rate (CRs plus PRs) was 26% (12% in pts resistant to AG and 33% in AG-responsive pts). Disease stabilisation > or = 24 weeks was achieved in an additional 13% of patients (15% of those resistant to AG and 13% of those AG-responsive), resulting in an overall success rate of 39% (28-50, 95% confidence interval). The median duration of objective response, overall success and median TTP were 59, 48 and 21 weeks, respectively. Toxicities were usually mild to moderate in severity, with hot flushes (21%), nausea (19%), dizziness (12%), weakness (12%), increased sweating (12%), androgenic symptoms (10%) and peripheral oedema (9%) as the most common side-effects. Only 2 pts (3%) discontinued treatment due to adverse events. These results are very promising considering that exemestane was administered as third- or fourth-line hormonal treatment in most cases and confirm previous observations about the lack of cross-resistance when steroidal aromatase inhibitors are sequenced with the non-steroidal aromatase inhibitor AG.

Exemestane improves survival compared with megoestrol acetate in postmenopausal patients with advanced breast cancer who have failed on tamoxifen. results Of a double-blind randomised phase III trial.

Exemestane is an aromatase inactivator. 769 Postmenopausal women with advanced breast cancer who had failed on tamoxifen were randomised to exemestane or megoestrol acetate in this double-blind trial. Objective response rate was similar between treatments. Median time to progression, time to treatment failure and overall survival was significantly longer with exemestane. Drug-related withdrawals and drug-related deaths were more common with megoestrol acetate.

High activity and tolerability demonstrated for exemestane in postmenopausal women with metastatic breast cancer who had previously failed on tamoxifen treatment.

This phase II, multicentre, open-label, clinical trial evaluated antitumoral efficacy, tolerability and endocrine effects following 25 mg of treatment with oral exemestane given daily to postmenopausal women with metastatic breast cancer. Eligibility criteria included oestrogen and/or progesterone positivity or a prior response to hormonal therapy if receptor status was unknown; prior failure to tamoxifen therapy; and progressive disease. Patients were divided into three strata: patients who did not respond to tamoxifen or progressed after disease stabilisation (SD) for less than 6 months (stratum 1); patients who, after an initial response or SD lasting at least 6 months, experienced disease progression whilst on tamoxifen (stratum 2); patients with recurrent metastatic disease during or within 12 months of discontinuing adjuvant tamoxifen (stratum 3). Of the 137 patients who received exemestane, 4 experienced a complete response (CR) and 28 a partial response (PR), for an overall response rate of 23%. Another 33 patients had SD for > or = 24 weeks, resulting in an overall success rate of 47%. The median time to objective response was 16.1 weeks (95% confidence interval (CI) 9.9-24.1). The median response duration was 69.4 weeks, the median duration of overall success 59.1 weeks, the median time to progression (TTP) 25.1 weeks and the median time to treatment failure (TTF) 24 weeks. Response to previous hormonal therapy had little effect on the results, except that there was a trend toward a higher overall success rate in patients who did not respond to previous hormonal therapy. After 8 weeks of therapy, serum levels of oestradiol (E2), oestrone (E1) and oestrone sulphate (E1S) were suppressed to 15.2%, 9.7% and 10.7% of baseline, respectively. The most common adverse events of drug-related or indeterminate cause were hot flushes (14%), dizziness (9%), nausea (8%) and increased sweating (5%). Exemestane had a favourable effect on performance status and tumour-related signs and symptoms, both of which improved or stabilised in approximately 67% and 68% of patients respectively. Exemestane is a unique therapy that is highly active and well tolerated as a new treatment for women with metastatic breast cancer.

Exemestane improves survival in metastatic breast cancer: results of a phase III randomized study.

We compared the efficacy and safety of the oral aromatase inactivator exemestane (EXE) with megestrol acetate (MA) in women with metastatic breast cancer. This phase III randomized, double-blind, multicenter study was conducted in 769 postmenopausal women who had experienced tamoxifen failure. Treatment arms consisted of EXE 25 mg once daily (n=366) or MA 40 mg four times daily (160 mg daily; n=403). Peer-reviewed, intent-to-treat analyses demonstrated that EXE induced a trend toward higher rates of complete response (CR)+partial response (PR) (15.0% vs. 12.4%) and of CR+PR+stable disease (SD)=24 weeks (37.4% vs. 34.6%), but differences were not statistically significant. Statistically significant differences favoring EXE were seen in median duration of CR+PR+SD=24 weeks (60.1 vs. 49.1 weeks; P=0.025), time to tumor progression (20.3 vs. 16.6 weeks; P=0.037), time to treatment failure (16.3 vs. 15.7 weeks; P=0.042), and overall survival (not reached vs. 123.4 weeks; P=0.039). Both treatments were well tolerated, but MA was associated with more grade 3 or 4 weight gain (8% vs. 17%, P=0.001); the pain score was sim-ilar in both groups. There was a trend toward superiority in treatment-related signs and symptoms (TRSS) with EXE. There was greater improvement in the pain score and TRSS in patients achieving an objective response with EXE vs. MA. Quality of life improved or was similar for EXE in most domains. Exemestane offers an important new treatment option for postmenopausal women with hormone-responsive breast cancer.

Effect of the dual 5alpha-reductase inhibitor PNU 157706 on the growth of dunning R3327 prostatic carcinoma in the rat.

PNU 157706 [N-(1,1,1,3,3,3-hexafluorophenylpropyl)-3-oxo-4-aza-5alpha-androst-1-ene-17beta-carboxamide] is a novel, potent and selective dual 5alpha-reductase inhibitor. We have investigated its effect on tumor growth, endocrine organ weights and prostatic dihydrotestosterone (DHT) content in rats bearing the androgen dependent Dunning R3327 prostatic carcinoma. Animals with tumor diameters of about 1 cm were treated orally for 9 weeks with PNU 157706 (2 and 10 mg/kg/day, 6 days a week) or they were castrated, to check the hormone responsiveness of the tumor. PNU 157706 was effective at both doses tested in reducing tumor growth (53 and 51% inhibition at 2 and 10 mg/kg/day, respectively), while castration caused higher inhibition (82%) of tumor growth. A marked reduction of ventral prostate weight occurred in rats treated with both doses of PNU 157706 (75 and 78%) or castrated (91%). Seminal vesicle weight was also reduced by PNU 157706 administration (56 and 61% inhibition), whereas testes, adrenal, thymus and pituitary weights were not affected. Prostatic DHT content was markedly suppressed (85 and 91%) in PNU 157706 treated rats, compared to 95% suppression caused by castration. These data support a possible role of dual 5alpha-reductase inhibitors in the hormonal therapy of prostatic cancer.

Inhibitory effect of combined treatment with the aromatase inhibitor exemestane and tamoxifen on DMBA-induced mammary tumors in rats.

The antitumor effect of exemestane (FCE 24304), an irreversible aromatase inhibitor, given alone or in combination with tamoxifen, was investigated in rats with 7,12-dimethylbenzanthracene (DMBA)-induced mammary tumors. The compounds were given once daily, 6 days a week for 4 weeks. Exemestane, given at the dose of 20 mg/kg/day s.c., induced 26% complete (CR) and 18% partial (PR) tumor regressions, compared to 0% CR and 6% PR observed in controls. Tamoxifen, given at 1 mg/kg/day p.o., induced 16% CR and 13% PR. The combined treatment caused 41% CR and 16% PR, thus resulting in a higher antitumor effect than either single treatment. The appearance of new tumors was reduced by each single treatment and almost totally prevented by the combined treatment. Serum prolactin (PRL) levels, assayed 4 h after the last dose, were unchanged in the group treated with the combination, whereas tamoxifen alone caused a slight increase of serum PRL. These results indicate that estrogen deprivation through aromatase inhibition and estrogen receptor antagonism causes a better inhibition of DMBA-induced mammary tumors than either treatment modality alone.

Hormonal effects of turosteride, a 5 alpha-reductase inhibitor, in the rat.

Turosteride [FCE 26073; 1-(4-methyl-3-oxo-4-aza-5 alpha-androstane-17 beta-carbonyl)-1,3- diisopropylurea] is a novel inhibitor of 5 alpha-reductase, the enzyme responsible for the conversion of testosterone (T) to 5 alpha-dihydrotestosterone (DHT). The compound caused inhibition of rat and human prostatic enzymes, with IC50 values of 55 and 53 nM, respectively. In addition, turosteride did not show any relevant binding affinity to the rat prostate androgen receptor (IC50 84 microM; relative binding affinity 0.004% of DHT). The endocrine effects of turosteride were evaluated in adult male rats, treated orally at daily doses of 3, 10 and 30 mg/kg for 20 days. At these doses, the compound reduced the ventral prostate weight by 10, 33 and 42% and the intraprostatic total DHT content by 61, 74 and 78%, respectively, whereas no change in the intraprostatic content of T was observed. Turosteride caused a 40% reduction of serum DHT levels which, however, did not reach statistical significance, whereas serum T levels were similar to control animals. No effect on serum luteinizing hormone or prolactin was observed. These results indicate that the antiprostatic effect of turosteride in the adult rat is related to inhibition of the conversion of T to DHT. However, at variance with other 5 alpha-reductase inhibitors (e.g. finasteride), turosteride caused a decrease in prostatic DHT not associated with a secondary increase in T content. This peculiarity of turosteride may represent an improvement of the compound over other inhibitors.

Endocrine properties of the testosterone 5 alpha-reductase inhibitor turosteride (FCE 26073).

Turosteride was tested in a series of studies for its effect on 5 alpha-reductase and for its possible influence on other steroidogenic enzymes and on steroid receptors. The compound was found to inhibit human and rat prostatic 5 alpha-reductases with IC50 values of 55 and 53 nM, respectively, whereas it caused a less marked inhibition of the dog enzyme (IC50 2.2 microM). Turosteride showed no relevant effect on rat adrenal C20,22-desmolase (IC50 254 microM) and human placental aromatase (IC50 > 100 microM), and only at relatively high concentrations it caused inhibition of human placental 5-ene-3 beta-hydroxysteroid dehydrogenase-isomerase (3 beta-HSD-I) (IC50 2.5 microM). Turosteride was found to be a selective 5 alpha-reductase inhibitor showing no noteworthy binding to receptors for androgens (relative binding affinity, RBA, 0.004%), estrogens (< or = 0.005%), progesterone (< 0.005%), glucocorticoids (< 0.01%) and mineralocorticoids (< 0.03%). Its biochemical profile was similar to that of finasteride, whereas 4-MA (17 beta-N,N-diethyl-carbamoyl-4-methyl-4-aza-5 alpha-androstan-3-one) was confirmed to be a non-selective 5 alpha-reductase inhibitor, showing a degree of binding affinity to the androgen receptor (RBA 0.1%) and a marked inhibition of 3 beta-HSD-I (IC50 32 nM). When given orally in immature castrated rats together with subcutaneous testosterone propionate (TP) for 7 consecutive days, turosteride reduced the ventral prostate and seminal vesicle growth promoting effect of TP, with IC50 values of approximately 5 and 6.7 mg/kg/day, whereas levator ani weight was unchanged. In comparison, 4-MA was approx. 3-fold less potent than turosteride in reducing the prostate and seminal vesicle weights and caused a marked reduction of levator ani weight, thus showing its unselectivity.

17 beta-acylurea derivatives of 4-azasteroids as inhibitors of testosterone 5 alpha-reductase.

A series of 17 beta-acylurea-4-aza-5 alpha-androstan-3-one derivatives has been assayed in vitro as inhibitors of testosterone 5 alpha-reductase, using the particulate fraction of human hyperplastic prostate and rat prostate as enzyme sources. The most active derivatives were 1-[4-methyl-3-oxo-4-aza-5 alpha-androstane-17 beta-carbonyl]- 1,3-dicyclohexylurea (compound 1) and 1-[4-methyl-3-oxo-4-aza-5 alpha-androstane-17 beta-carbonyl]- 1,3-diisopropylurea (compound 3) which demonstrated IC50 values of 41 and 55 nM for the human enzyme and of 83 and 53 nM for the rat enzyme, respectively. Neither compound showed any relevant binding affinity to the rat prostate androgen receptor (IC50 of approximately 100 and 84 microM). When given orally in immature castrated rats together with subcutaneous testosterone propionate (TP) for 7 consecutive days, compound 3 (laboratory code FCE 26073), at 3 mg/kg/day, significantly decreased the ventral prostate growth promoting effect of TP by 40-50%, whereas compound 1 was ineffective up to the dose of 10 mg/kg/day.

Effects of 5 alpha-reductase inhibitors on intraprostatic androgens in the rat.

FCE 27837 is a novel inhibitor of 5 alpha-reductase, the enzyme responsible for the conversion of testosterone (T) to 5 alpha-dihydrotestosterone (DHT). The compound caused inhibition of human and rat prostatic enzymes, with IC50 values of 51 and 60 nM, respectively. The in vivo effect of FCE 27837 on 5 alpha-reductase was evaluated in adult male rats, treated orally at 10 mg/kg/day for 10 days. The compound caused 33 and 42% reductions in ventral prostate and seminal vesicle weights, respectively. The prostatic content of DHT, measured 6 h after the 10th dose of FCE 27837, was reduced by 75%, whereas T content increased by 442%. Similar effects were observed with 10 mg/kg/day of finasteride, whereas epristeride, tested at the same oral dose, was found to be the least effective compound, decreasing prostate weight by 22% and DHT content by 46%. Castration caused > 90% reductions in prostatic weight and prostatic DHT.