Abiraterone acetate (trade name Zytiga) is a prodrug to the abiraterone, steroidal compound with antiandrogen activity and a 17 α-hydroxylase/C17,20-lyase (CYP17) inhibitor. It is indicated in combination with prednisone for the treatment of patients with metastatic castration-resistant prostate cancer. Abiraterone acetate is converted in vivo to abiraterone which inhibits CYP17, enzyme expressed in testicular, adrenal, and prostatic tumor tissues and required for androgen biosynthesis. Administration of this agent may suppress testosterone production by both the testes and the adrenals to castrate-range levels. Androgen sensitive prostatic carcinoma responds to treatment that decreases androgen levels. Androgen deprivation therapies, such as treatment with GnRH agonists or orchiectomy, decrease androgen production in the testes but do not affect androgen production by the adrenals or in the tumor.

2S,4R ketoconazole or levoketoconazole is the 2S,4R enantiomer of ketoconazole, purified from racemic ketoconazole. Both enantiomers exerts antifungal activity. Ketoconazole activates AhR in gene reporter cell line and dose-dependently induces CYP1A1 mRNA and CYP1A1 protein in HepG2 cells, with enantiospecific pattern, i.e. 2R,4S ketoconazole was much more active as compared to 2S,4R ketoconazole. Levoketoconazole was shown to be a more potent inhibitor than the 2R,4S enantiomer of several enzymes in the steroidogenic pathway (CYP11B1, CYP17 and CYP21). Levoketoconazole was tested for the treatment of endogenous Cushing’s syndrome (Phase III) and type 2 diabetes mellitus (Phase II).

Seviteronel (VT-464) is a 17,20-lyase selective inhibitor of CYP17A1, which plays key roles in adrenal and intratumoral de novo biosynthesis of androgens. The inhibition of 17,20-lyase activity by seviteronel (VT-464) is enough to reduce androgen levels, and its preserving of 17alpha-hydroxylase activity largely avoids interference with the production of other steroidal hormones. Seviteronel (VT-464) also has shown AR-antagonist activity independent of CYP17 enzyme inhibition. It is currently in phase 2 clinical trials as a therapeutic for castration-resistant prostate cancer patients.

Galeterone (TOK-001, formerly called VN/124-1) is a potent anti-androgen with three modes of action. The compound acts as a specific androgen receptor antagonist, inhibits CYP17 lyase while conserving CYP17 hydroxylase function, and decreases overall androgen receptor levels in prostate cancer cells. Galeterone is a first in class, multi-targeted small-molecule drug that disrupts the growth and survival of prostate cancer cells. Tokai Pharmaceuticals is developing galeterone as an oral treatment for castration-resistant prostate cancer. Phase III clinical development of galeterone is underway in the US, Canada, Australia, Western Europe, Spain and the United Kingdom.

Orteronel (TAK-700) is a non-steroidal antiandrogen, discovered by Takeda Pharmaceutical Company Limited, that selectively inhibits the 17,20 lyase enzyme (CYP17A1). This enzyme, which is present in both the testes and adrenal glands, is central to the production of steroidal androgens. Synthesis of androgens outside the testes contributes to disease progression in castration-resistant prostate cancer (CRPC). In phase III of clinical trials for metastatic, hormone-refractory prostate cancer it wasn’t shown overall survival rates, and development was voluntarily terminated as a result.

Mono(ethylhexyl) phthalate (MEHP) is an active metabolite of Bis(2-ethylhexyl)phthalate (DEHP). DEHP is a widely used plasticizer. MEHP has been shown to be moderately toxic. Studies involving orally administered MEHP revealed the mild hepatic changes occurred but there was no bioaccumulation of the monoester. Studies of the rat and rabbit indicated that MEHP has no teratogenic effects. This compound was readily absorbed from the gastrointestinal tract. Radioactivity following intravenous administration of 14C-MEHP was rapidly distributed in tissues, with the highest levels occurring in the liver, kidney, and urinary bladder. Mono(ethylhexyl) phthalate is a member of a class of chemical compounds with known adverse effects on the male reproductive system.

Abiraterone acetate (trade name Zytiga) is a prodrug to the abiraterone, steroidal compound with antiandrogen activity and a 17 α-hydroxylase/C17,20-lyase (CYP17) inhibitor. It is indicated in combination with prednisone for the treatment of patients with metastatic castration-resistant prostate cancer. Abiraterone acetate is converted in vivo to abiraterone which inhibits CYP17, enzyme expressed in testicular, adrenal, and prostatic tumor tissues and required for androgen biosynthesis. Administration of this agent may suppress testosterone production by both the testes and the adrenals to castrate-range levels. Androgen sensitive prostatic carcinoma responds to treatment that decreases androgen levels. Androgen deprivation therapies, such as treatment with GnRH agonists or orchiectomy, decrease androgen production in the testes but do not affect androgen production by the adrenals or in the tumor.

2S,4R ketoconazole or levoketoconazole is the 2S,4R enantiomer of ketoconazole, purified from racemic ketoconazole. Both enantiomers exerts antifungal activity. Ketoconazole activates AhR in gene reporter cell line and dose-dependently induces CYP1A1 mRNA and CYP1A1 protein in HepG2 cells, with enantiospecific pattern, i.e. 2R,4S ketoconazole was much more active as compared to 2S,4R ketoconazole. Levoketoconazole was shown to be a more potent inhibitor than the 2R,4S enantiomer of several enzymes in the steroidogenic pathway (CYP11B1, CYP17 and CYP21). Levoketoconazole was tested for the treatment of endogenous Cushing’s syndrome (Phase III) and type 2 diabetes mellitus (Phase II).