[Abiraterone acetate(ZYTIGA®)-development and literature review]

Abiraterone acetate(AA)has been approved in more than 80 countries for the treatment of patients with metastatic castration-resistant prostate cancer(mCRPC). In July 2013, a marketing approval application for AA was submitted to the Japanese Ministry of Health, Labour, and Welfare. AA is a selective inhibitor of CYP17A1, a crucial enzyme for androgen biosynthesis. AA exerts its anti-tumor activity by directly inhibiting androgen production at all three sources, i. e., the testes, adrenal glands, and tumor itself. Data from international phase III studies and phase I and II studies in Japan have indicated that AA improves the overall survival and quality of life(QoL)of patients with mCRPC. Herein, we have summarized the development of AA and the results of important international and local clinical trials in Japan. In addition, the effect of food on AA bioavailability, concomitant steroid use, and liver function test abnormalities have been discussed regarding the appropriate use of AA.

Androgen synthesis inhibitors in the treatment of castration-resistant prostate cancer

Suppression of gonadal testosterone synthesis represents the standard first line therapy for treatment of metastatic prostate cancer. However, in the majority of patients who develop castration-resistant prostate cancer (CRPC), it is possible to detect persistent activation of the androgen receptor (AR) through androgens produced in the adrenal gland or within the tumor itself. Abiraterone acetate was developed as an irreversible inhibitor of the dual functional cytochrome P450 enzyme CYP17 with activity as a 17α-hydroxylase and 17,20-lyase. CYP17 is necessary for production of nongonadal androgens from cholesterol. Regulatory approval of abiraterone in 2011, based on a phase III trial showing a significant improvement in overall survival (OS) with abiraterone and prednisone versus prednisone, represented proof of principle that targeting AR is essential for improving outcomes in men with CRPC. Inhibition of 17α-hydroxylase by abiraterone results in accumulation of upstream mineralocorticoids due to loss of cortisol-mediated suppression of pituitary adrenocorticotropic hormone (ACTH), providing a rationale for development of CYP17 inhibitors with increased specificity for 17,20-lyase (orteronel, galeterone and VT-464) that can potentially be administered without exogenous corticosteroids. In this article, we review the development of abiraterone and other CYP17 inhibitors; recent studies with abiraterone that inform our understanding of clinical parameters such as drug effects on quality-of-life, potential early predictors of response, and optimal sequencing of abiraterone with respect to other agents; and results of translational studies providing insights into resistance mechanisms to CYP17 inhibitors leading to clinical trials with drug combinations designed to prolong abiraterone benefit or restore abiraterone activity.

Abiraterone and metastatic prostate cancer: delays pain onset, cytotoxic therapy, and possibly death

When metastatic prostate cancer progresses despite androgen suppression but symptoms do not yet warrant cytotoxic therapy, abiraterone appears to prolong overall survival and to delay the onset of some cancer-related symptoms. But beware of cardiac and hepatic adverse effects that are inadequately documented.

The European medicines agency review of abiraterone for the treatment of metastatic castration-resistant prostate cancer in adult men after docetaxel chemotherapy and in chemotherapy-naive disease: summary of the scientific assessment of the committee for medicinal products for human use

On September 5, 2011, abiraterone was approved in the European Union in combination with prednisone or prednisolone for the treatment of metastatic castration-resistant prostate cancer (CRPC) in adult men whose disease has progressed on or after a docetaxel-based chemotherapy regimen. On December 18, 2012, the therapeutic indication was extended to include the use of abiraterone in combination with prednisone or prednisolone for the treatment of metastatic CRPC in adult men who are asymptomatic or mildly symptomatic after failure of androgen deprivation therapy in whom chemotherapy is not yet clinically indicated. Abiraterone is a selective, irreversible inhibitor of cytochrome P450 17α, an enzyme that is key in the production of androgens. Inhibition of androgen biosynthesis deprives prostate cancer cells from important signals for growth, even in cases of resistance to castration. At the time of European Union approval and in a phase III trial in CRPC patients who had failed at least one docetaxel-based chemotherapy regimen, median overall survival for patients treated with abiraterone was 14.8 months versus 10.9 months for those receiving placebo (hazard ratio, 0.65; 95% confidence interval 0.54-0.77; p < .0001). In a subsequent phase III trial in a similar but chemotherapy-naïve patient population, median radiographic progression-free survival was 16.5 months for patients in the abiraterone treatment arm versus 8.3 months for patients in the placebo arm (hazard ratio, 0.53; 95% confidence interval, 0.45-0.62; p < .0001). Abiraterone was most commonly associated with adverse reactions resulting from increased or excessive mineralocorticoid activity. These were generally manageable with basic medical interventions. The most common side effects (affecting more than 10% of patients) were urinary tract infection, hypokalemia, hypertension, and peripheral edema.

Sarcopenia and change in body composition following maximal androgen suppression with abiraterone in men with castration-resistant prostate cancer

BACKGROUND

Standard medical castration reduces muscle mass. We sought to characterize body composition changes in men undergoing maximal androgen suppression with and without exogenous gluocorticoids.

METHODS

Cross-sectional areas of total fat, visceral fat and muscle were measured on serial CT scans in a post-hoc analysis of patients treated in Phase I/II trials with abiraterone followed by abiraterone and dexamethasone 0.5 mg daily. Linear mixed regression models were used to account for variations in time-on-treatment and baseline body mass index (BMI).

RESULTS

Fifty-five patients received a median of 7.5 months abiraterone followed by 5.4 months abiraterone and dexamethasone. Muscle loss was observed on single-agent abiraterone (maximal in patients with baseline BMI >30, -4.3%), but no further loss was observed after addition of dexamethasone. Loss of visceral fat was also observed on single-agent abiraterone, (baseline BMI >30 patients -19.6%). In contrast, addition of dexamethasone led to an increase in central visceral and total fat and BMI in all the patients.

INTERPRETATION

Maximal androgen suppression was associated with loss of muscle and visceral fat. Addition of low dose dexamethasone resulted in significant increases in visceral and total fat. These changes could have important quality-of-life implications for men treated with abiraterone.

[Compassionate use of abiraterone and cabazitaxel: first experiences in docetaxel-pretreated castration-resistant prostate cancer patients]

OBJECTIVE

First clinical experiences with abiraterone and cabazitaxel for the treatment of metastatic castration-resistant prostate cancer patients following docetaxel chemotherapy are reported.

PATIENTS AND METHODS

We describe PSA response rates and disease control rates determined by imaging studies at 3 months as well as side effects in the daily routine. All patients were treated within the"compassionate use" programs of cabazitaxel and abiraterone or treated according to their inclusion and exclusion criteria at the "Technische Universität München".

RESULTS

Of 54 patients, 15 were treated with cabazitaxel and 39 with abiraterone. In patients treated with cabazitaxel, after 3 months of therapy the PSA reduction rate > 50% was 46.2%, the PSA progression rate was 15.4%, and the disease control rate was 83.3%. Main grade 3/4 hematotoxicities were neutropenia (40%) and anemia (20%). Febrile neutropenia was observed in 2 of 15 (13.3%) patients. Main non-hematological grade 3/4 toxicities were diarrhea (13.3%) and polyneuropathy (13.3%). In patients treated with abiraterone, after 3 months of therapy the PSA reduction rate >50% was 35.1%, the PSA progression rate was 46.0%, and the disease control rate was 47.1%. Main grade 3/4 hematotoxicities were anemia (5.1%) and thrombocytopenia (5.1%). Main non-hematological toxicities were fatigue (20.5%), sweating (17.9%), and constipation (10.3%).

CONCLUSION

Utilization of cabazitaxel and abiraterone in the daily routine show response rates comparable to their approval studies with acceptable side effects.

Abiraterone. After prostate cancer treatment failure: 4-month survival advantage

There is no standard treatment for metastatic prostate cancer that progresses despite castration and cytotoxic chemotherapy. Abiraterone inhibits both testicular and extratesticular androgen synthesis. It has been approved in the European Union for use in this situation, in which treatment options are extremely limited. Clinical evaluation is based on a double-blind comparative trial of good methodological quality that included 1195 patients. The median overall survival time was 4 months longer in the group treated with abiraterone + prednisone (or prednisolone) than in the group treated with placebo + prednisone (or prednisolone): 15.8 versus 11.2 months. The addition of prednisone (or prednisolone) reduced but did not eliminate the effects of hyperaldosteronism induced by abiraterone; oedema occurred in 26.7% of patients, arterial hypertension in 8.5%, and hypokalaemia in 17.1%. Moderate hepatotoxicity was reported with abiraterone and needs to be better assessed. Abiraterone was also associated with cardiac arrhythmias (7.2% versus 4.6% with placebo) and heart failure (1% versus 0.3%). Abiraterone is metabolised by cytochrome P450 isoenzyme CYP3A4 and inhibits isoenzyme CYP2D6, resulting in a high potential for drug interactions. Treatment is somewhat inconvenient. Abiraterone must be taken between meals, serum potassium levels must be monitored, and care must be taken to avoid interactions. Overall, the known risks of abiraterone appear to be acceptable in view of its efficacy, but patients must be carefully monitored. Abiraterone is one option to discuss with patients with metastatic prostate cancer after other treatments fail.

Clinical and biochemical consequences of CYP17A1 inhibition with abiraterone given with and without exogenous glucocorticoids in castrate men with advanced prostate cancer

CONTEXT

Abiraterone acetate is a small-molecule cytochrome P450 17A1 (CYP17A1) inhibitor that is active in castration-resistant prostate cancer.

OBJECTIVE

Our objective was to determine the impact of abiraterone with and without dexamethasone treatment on in vivo steroidogenesis.

DESIGN AND METHODS

We treated 42 castrate, castration-resistant prostate cancer patients with continuous, daily abiraterone acetate and prospectively collected blood and urine before and during abiraterone treatment and after addition of dexamethasone 0.5 mg daily.

RESULTS

Treatment with single-agent abiraterone acetate was associated with accumulation of steroids with mineralocorticoid properties upstream of CYP17A1. This resulted in side effects, including hypertension, hypokalemia, and fluid overload, in 38 of 42 patients that were generally treated effectively with eplerenone. Importantly, serum and urinary androgens were suppressed by more than 90% from baseline. Urinary metabolites of 17-hydroxypregnenolone and 17-hydroxyprogesterone downstream of 17α-hydroxylase remained unchanged. However, 3α5α-17-hydroxypregnanolone, which can be converted via the backdoor pathway toward 5α-dihydrotestosterone, increased significantly and correlated with levels of the major 5α-dihydrotestosterone metabolite androsterone. In contrast, urinary metabolites of 11-deoxycortisol and active glucocorticoids declined significantly. Addition of dexamethasone to abiraterone acetate significantly suppressed ACTH and endogenous steroids, including 3α5α-17-hydroxypregnanolone.

CONCLUSION

CYP17A1 inhibition with abiraterone acetate is characterized by significant suppression of androgen and cortisol synthesis. The latter is associated with a rise in ACTH that causes raised mineralocorticoids, leading to side effects and incomplete 17α-hydroxylase inhibition. Concomitant inhibition of 17,20-lyase results in diversion of 17-hydroxyprogesterone metabolites toward androgen synthesis via the backdoor pathway. Addition of dexamethasone reverses toxicity and could further suppress androgens by preventing a rise in substrates of backdoor androgen synthesis.

Abiraterone and increased survival in metastatic prostate cancer

BACKGROUND

Biosynthesis of extragonadal androgen may contribute to the progression of castration-resistant prostate cancer. We evaluated whether abiraterone acetate, an inhibitor of androgen biosynthesis, prolongs overall survival among patients with metastatic castration-resistant prostate cancer who have received chemotherapy.

METHODS

We randomly assigned, in a 2:1 ratio, 1195 patients who had previously received docetaxel to receive 5 mg of prednisone twice daily with either 1000 mg of abiraterone acetate (797 patients) or placebo (398 patients). The primary end point was overall survival. The secondary end points included time to prostate-specific antigen (PSA) progression (elevation in the PSA level according to prespecified criteria), progression-free survival according to radiologic findings based on prespecified criteria, and the PSA response rate.

RESULTS

After a median follow-up of 12.8 months, overall survival was longer in the abiraterone acetate-prednisone group than in the placebo-prednisone group (14.8 months vs. 10.9 months; hazard ratio, 0.65; 95% confidence interval, 0.54 to 0.77; P<0.001). Data were unblinded at the interim analysis, since these results exceeded the preplanned criteria for study termination. All secondary end points, including time to PSA progression (10.2 vs. 6.6 months; P<0.001), progression-free survival (5.6 months vs. 3.6 months; P<0.001), and PSA response rate (29% vs. 6%, P<0.001), favored the treatment group. Mineralocorticoid-related adverse events, including fluid retention, hypertension, and hypokalemia, were more frequently reported in the abiraterone acetate-prednisone group than in the placebo-prednisone group.

CONCLUSIONS

The inhibition of androgen biosynthesis by abiraterone acetate prolonged overall survival among patients with metastatic castration-resistant prostate cancer who previously received chemotherapy. (Funded by Cougar Biotechnology; COU-AA-301 ClinicalTrials.gov number, NCT00638690.).

Side-effects of topical androgenic and anabolic substances and steroids. A short review

There is an increasing interest, including androgenic and anabolic substances (AAS). The uncritical use may be associated with severe adverse effects. We observed five patients with different patterns of adverse reaction to AAS: two females and three males, they were identified when seeking medical help and advice. The following adverse effects from of AAS have been observed: deepening of the voice due to topical use of AAS in an anti-cellulite cream; circumscribed hypertrichosis and late onset acneiform eruptions due to testosterone replacement therapy after ovariectomy; homolateral gynecomastia and infertility, acne and striae distensae in males using injectable AAS.

CONCLUSIONS

ASS can trigger significant adverse effects. An interdisciplinary approach may be necessary for evaluation. The dermatologists should be familiar with the adverse effects.

Characterisation of the pharmacological profile of desoxymethyltestosterone (Madol), a steroid misused for doping

Desoxymethyltestosterone (DMT), also known as Madol, is a steroid recently identified to be misused as a doping agent. Since, the knowledge of functions of this substance is rather limited, it was our aim to characterise the pharmacological profile of DMT and to identify potential adverse side effects. DMT was synthesised, its purity was confirmed and its biological activity was tested. The potency of Madol (DMT) to transactivate androgen receptor (AR) dependent reporter gene expression was two times lower as compared to dihydrotestosterone (DHT). Receptor binding tests demonstrate that DMT binds with high selectivity to the AR, binding to the progesterone receptor (PR) was low. In vivo experiments in orchiectomised rats demonstrated that treatment with DMT resulted only in a stimulation of the weight of the levator ani muscle; the prostate and seminal vesicle weights remained unaffected. Like testosterone, administration of DMT resulted in a stimulation of IGF-1 and myostatin mRNA expression in the gastrocnemius muscle. In the prostate proliferation was stimulated by TP (testosteronepropionate), but remained unaffected by DMT. Remarkably, treatment with DMT, in contrast to TP, resulted in a significant increase of the heart weight. In the liver, DMT slightly stimulates the expression of the tyrosine aminotransferase gene (TAT). Our results demonstrate that DMT is a potent AR agonist with an anabolic activity. Besides the levator ani weight, DMT also modulates the gene expression in the musculus gastrocnemius. The observed stimulation of TAT expression in the liver and the significant increase of the heart weight after DMT treatment can be taken as an indication for side effects. Summarizing these data it is obvious that DMT is a powerful anabolic steroid with selective androgen receptor modulators (SARM) like properties and some indications for toxic side effects. Therefore, there is a need for a strict control of a possible misuse.

Induction of abortion in early first trimester human pregnancy using epostane

The role of epostane (Sterling Winthrop, Guildford, UK), a competitive inhibitor of the 3 beta hydroxysteroid dehydrogenase enzyme system (3 beta-HSD), as an abortifacient agent in early human pregnancy has been studied in 54 women. All were less than 49 days from their last menstrual period. Thirty were treated with 200 mg of epostane every 8 h for 7 days and 24 were given 200 mg every 6 h for 7 days. This caused a sustained reduction in circulating progesterone concentrations, a smaller fall in 17 beta-oestradiol and no effect on serum cortisol. Abortion occurred in 21 women (70%) in the lower dosage group and in 20 women (87%) in the higher dosage group. Abortion was incomplete in 6 of these 41 women. A worsening of pregnancy nausea and vomiting was noted by 66% of women in the first group and 84% in the second. There was no delay in the resumption of normal menstruation following abortion. This study confirms the potential of epostane as an effective inhibitor of ovarian and placental steroidogenesis and as a potent abortifacient agent in early human pregnancy.

Epostane in nonpregnant females: effects on progesterone, 17 alpha-hydroxyprogesterone, and 17 beta-estradiol of two dose levels given for one month

So far, the use of epostane, a relatively new inhibitor of 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase enzyme system (3 beta-HSD), has been confined to short-term interference with luteal and placental function. This study explored whether epostane treatment from the beginning of the cycle for approximately 1 month would also inhibit ovarian follicular function. Twenty females with regular cycles received epostane 150 mg/day (ten healthy volunteers) or 600 mg/day (ten patients with endometriosis). Blood samples were drawn three times per week during control and treatment cycles. At 150 mg/day the mean total area under the serum concentration curve (AUC) of estradiol (E2) was somewhat higher than during the control cycles, despite apparently lower preovulatory E2 surges. During medication the highest value of E2 was found during the luteal phase. The mean AUC of progesterone (P) and 17 alpha-hydroxyprogesterone (17-OHP) during the luteal surge was decreased by approximately 45% each. At 600 mg/day all evaluable patients had lower AUC of E2 than during the control cycle. The mean decrease in AUC of P and 17-OHP was much more pronounced than in the lower dose group. Six of the ten patients showed no hormonal signs of follicular development and, consequently, anovulation. The capacity of epostane to modulate or inhibit, depending on the dose, ovarian follicular steroidogenesis and ovulation may prove valuable in a variety of clinical conditions.

Termination of early pregnancy by the 3 beta-hydroxysteroid dehydrogenase inhibitor epostane

Progesterone is essential to sustain pregnancy in the first eight weeks. Its synthesis requires the enzyme 3 beta-hydroxysteroid dehydrogenase (3-HSD). We tested the efficacy of an orally administered 3-HSD inhibitor, epostane, in terminating unwanted early pregnancy. Fifty women in the fifth through eight weeks of pregnancy took epostane (200 mg orally every six hours) for seven days. By day 14, pregnancy had been terminated in 42 of the 50 patients (84 percent). Eight women (16 percent) did not abort and underwent dilation and curettage. Vaginal blood loss occurred on average on the third day of epostane treatment, and abortion on the fifth day. Two patients had incomplete abortions; one required a transfusion because of blood loss. Nausea was frequent (in 86 percent), but 76 percent of the participants concluded that epostane was preferable to dilation and curettage. The mean (+/- SD) pretreatment progesterone level (76 +/- 16 nmol per liter) decreased by day 7 (to 16 +/- 11 nmol per liter) and day 14 (to 10 +/- 9 nmol per liter) in those who aborted; levels of human chorionic gonadotropin also decreased from the mean at base line (73 +/- 72 kIU per liter) to 18 +/- 7 kIU per liter on day 7 and 9 +/- 5 kIU per liter on day 14. In those who did not abort after epostane treatment, progesterone levels decreased only slightly by day 7 (to 52 +/- 21 nmol per liter) and rose again (to 81 +/- 18 nmol per liter) by day 14. Among women who responded to epostane, normal menstrual periods had resumed by day 42 after the beginning of treatment in 72 percent. We conclude that epostane taken orally is an effective and safe method for the noninvasive termination of undesired early pregnancy.

Early pregnancy termination with antiprogestins: a comparative clinical study of RU 486 given in two dose regimens and Epostane

Mifepristone, (RU 486, Roussel Uclaf, Romainville, France), a progesterone (P) receptor blocking agent, and Epostane, (WIN 32,729, Sterling-Winthrop, Guildford, United Kingdom), a P synthesis inhibitor, were compared for their ability to terminate early human pregnancy. Seventy-eight healthy women, with a gestational length of less than 49 days from the last menstrual period and who requested termination of pregnancy, were recruited to the study. The patients were randomly allocated to three treatment regimens: (1) Mifepristone 25 mg bid for 7 days; (2) Mifepristone 50 mg bid for 7 days; and (3) Epostane 200 mg qid for 7 days. The results of the study confirmed that both compounds are potent abortifacients in early human pregnancy. No difference in efficacy was seen between the two dose regimens of Mifepristone, which both resulted in 61% complete abortions. Seventy-three percent aborted completely in the Epostane group. Subjective side effects, especially nausea, were more common in the women treated with Epostane, but no serious side effects were seen.

Termination of early human pregnancy with epostane

Fifty-six healthy women, with a gestational length of less than 49 days from the last menstrual period, who requested termination of pregnancy were treated with Epostane, a progesterone synthesis inhibitor. Epostane, which competitively inhibits the 3 beta-hydroxy steroid dehydrogenase enzyme system, was given in the dose 200 mg X 4 for seven days. Physical examination, routine laboratory screening and determination of hCG, progesterone, estradiol and cortisol was performed on days 0, 7 and 14. The treatment resulted in 84% complete abortions (90% among women completing therapy). Two women experienced vaginal bleeding only, while 7 were non-responders. Among subjective side effects nausea dominated totally and was also the reason for discontinuation in 4 cases. The average length of bleeding among women with complete abortions was 10.7 days and the decrease in hemoglobin and hematocrit was very slight. Routine laboratory values remained within the normal range. Cortisol levels were elevated on day 7 compared to days 0 and 14, but all single values were within the normal limits.

Effects of Epostane on progesterone synthesis in early human pregnancy

Healthy women requiring abortion in early normal pregnancy were recruited to study the abortifacient effects of different doses of Epostane, an inhibitor of 3 beta-hydroxy steroid dehydrogenase, that previously has been shown to interfere with progesterone production in the luteal phase of humans and to have abortifacient effects in animals. A single dose of 100 mg resulted in decreasing progesterone and estradiol, which rapidly recovered, and none of the women started to bleed. Repeated doses of 50 or 100 mg during one day resulted in a more pronounced decrease in both progesterone and estradiol, but no bleeding. When treatment was prolonged over several days with 100 mg X 4 for five days and 400 mg X 2 for four days, respectively, a suppression of progesterone and estradiol was found and two out of four and eight out of ten women started to bleed and subsequently aborted. The treatment was well tolerated by most of the women. Routine laboratory parameters remained unaltered throughout treatment. Cortisol levels remained within the normal range.