17α-hydroxylase (IC50 = 2.5 nM); 17,20-lyase (IC50 = 15 nM)

Abiraterone (Abi) acetate is an ester prodrug of the anticancer drug Abiraterone, with IC50 values for 17,20-lyase and 17α-hydroxylase (CYP17 is a bifunctional enzyme) with 17,20-lyase and 17α-hydroxylase activity of 15 nM and 2.5 nM, respectively. Abiraterone has an IC50 of 27 nM for human 17,20-lyase and 30 nM for 17α-hydroxylase inhibition[1]. The proliferation of AR-positive prostate cancer cell lines LNCaP and VCaP can be considerably inhibited by abiraterone at doses ≥ 5 μM, as demonstrated by research [2]. With competitive Ki values of 2.1 and 8.8 μM, abiraterone inhibits the activity of recombinant human 3βHSD1 and 3βHSD2. In both cell lines, 5α-diketone and DHT production could be totally inhibited by 10 μM abiraterone. In the rapidly expanding subgroup, biratterone treatment dramatically slowed the evolution of CRPC, effectively containing tumor growth for the entire 4-week treatment period (P<0.00001) [3].

In prostate cancer that is resistant to castration, biratterone acetate (Abi) increases survival (CRPC). Abiraterone has been demonstrated to have an inhibitory dose of 0.5 mmol/kg/d, which results in serum concentrations of roughly 0.5 to 1 μM. It inhibits the consumption of [3H]-dehydroepiandrosterone (DHEA) and the buildup of Δ4-androstenedione (AD) in LNCaP with an IC50<1 μM. The control group's xenograft tumors showed a wide range of growth rates, with some growing slowly and only a few exhibiting vigorous growth [3].

Enzyme assays[3]
Incubations testing abiraterone as an inhibitor contained recombinant human 3βHSD1 or 3βHSD2 (in yeast microsomes, 3.2 or 25 μg protein per incubation, respectively), [3H]-pregnenolone (100,000 cpm, 1–20 μmol/L), and abiraterone (5–20 μmol/L) or ethanol vehicle in 0.2 to 1 mL of potassium phosphate buffer. After preincubation at 37°C for 1 to 3 minutes, NAD+ (1 mmol/L) was added, and the incubation was conducted at 37°C for 15 minutes. The reaction was stopped by addition of 1 to 2 mL ethyl acetate:isooctane (1:1) and extracting the steroids into the organic phase. The dried extracts were resolved either by TLC on plastic-backed silica gel plates using 3:1 chloroform:ethyl acetate or by HPLC. For TLC, regions of the plates containing steroids were identified with iodine vapor, excised with scissors, and quantitated by liquid scintillation counting as described. For HPLC, pregnenolone radioactivity was quantitated with BioSafeII scintillation cocktail. Incubations testing abiraterone as a substrate were carried out as above but substituting 0.1 to 5 μmol/L unlabeled abiraterone for pregnenolone and quantitating conversion by HPLC.

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Ligand-binding assay[2]
PC-3 cells transfected with WT or T877A mutant AR or LNCaP cells were seeded in 24-well plates and grown in CSS-supplemented phenol-red free media for 24 hours. To determine the kinetics of [3H]-R1881 binding to the WT and T877A AR, cells were treated with 0.25-25nM [3H]-R1881 for 2 hours, then washed, lysed and radioactivity was measured. Kd and Bmax were determined by nonlinear regression using Graphpad Prism™ software. When the concentration of [3H]-R1881 required to almost saturate AR in both WT and T877A AR mutant transfections was established (5nM), displacement of [3H]-R1881 by test compound was determined. The concentration at which 50% of [3H]-R1881 was displaced (EC50) was established using nonlinear regression

Cell viability[2]
LNCaP and VCaP cells were seeded in 96-well plates and grown in CSS-supplemented phenol red-free or FBS-supplemented media for 7 days. Cells were treated with compound at 24 and 96 hours after plating and cell viability was determined on day 7 by adding CellTiter Glo and measuring luminescence.

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Luciferase reporter assays[2]
We constructed a PSA-ARE3-luc luciferase reporter plasmid that was co-transfected with a human AR expression plasmid, F527-AR (wild-type (WT) or mutant as stated; mutations confirmed by sequencing) into PC-3 cells. These were seeded in white opaque 384-well plates and grown in 10% CSS-supplemented phenol red-free RPMI 1640 for 30 hours. Cells were then treated with the indicated concentration of compound and R1881 for 16 hours. Luciferase activity was determined by adding ONE Glo and measuring luminescence on a TopCount plate reader. Transfection efficiency and protein expression are shown in Supplemental Figure 1.

Mouse xenograft studies[4]
Male NOD/SCID mice 6 to 8 weeks of age were used, and studies were conducted under an Institutional Animal Care and Use Committee–approved protocol. Mice were surgically orchiectomized and implanted with a 5 mg 90-day sustained release DHEA pellet to mimic CRPC with human adrenal physiology. Two days later, 7 × 106 LAPC4 cells were injected subcutaneously with Matrigel. Tumor dimensions were measured 2 to 3 times per week, and volume was calculated as length × width × height × 0.52. Once tumors reached 300 mm3, mice were randomly assigned to vehicle or Abiraterone treatment groups. Mice in the Abiraterone group were treated with 5 mL/kg intraperitoneal injections of 0.5 mmol/kg/d (0.1 mL 5% benzyl alcohol and 95% safflower oil solution) and control mice with vehicle only, once daily for 5 days per week over a duration of 4 weeks (n = 8 mice per treatment). Statistical significance between Abiraterone and vehicle treatment groups was assessed by ANOVA based on a mixed-effect model.

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Dissolved in 0.1 mL 5% benzyl alcohol and 95% safflower oil solution; 0.5 mmol/kg/d; s.c. injection

Male NOD/SCID mice with LAPC4 cells

Absorption
Geometric mean (± SD) Cmax was 73 (± 44) ng/mL and AUC0-∞ was 373 (± 249) ng x hr/mL following a single dose of 500 mg abiraterone acetate in overnight-fasted healthy subjects. Dose proportionality was observed in single doses of abiraterone acetate ranging from 125 mg to 625 mg. A group of patients with mCRPC received a daily dose of 1,000 mg: at steady-state, the mean (± SD) Cmax was 226 (± 178) ng/mL and AUC was 993 (± 639) ng x hr/mL. Following oral administration of abiraterone acetate to patients with metastatic castration-resistant prostate cancer, the median Tmax was two hours. _In vivo_, abiraterone acetate is converted to abiraterone. In clinical studies of other abiraterone acetate formulations, abiraterone acetate plasma concentrations were below detectable levels (< 0.2 ng/mL) in > 99% of the analyzed samples. Systemic exposure to abiraterone is increased when abiraterone acetate is administered with food. Abiraterone Cmax was approximately 6.5-fold higher, and AUC0-∞ was 4.4-fold higher when a single dose of abiraterone acetate 500 mg was administered with a high-fat meal (56-60% fat, 900-1,000 calories) compared to overnight fasting in healthy subjects. Given the normal variation in the content and composition of meals, taking abiraterone with meals has the potential to result in increased and highly variable exposures.

Route of Elimination
Following oral administration of 14C-abiraterone acetate, approximately 88% of the radioactive dose is recovered in feces: the major compounds present in feces are unchanged abiraterone acetate and abiraterone, accounting for approximately 55% and 22% of the administered dose, respectively. Approximately 5% of the dose is recovered in urine.

Volume of Distribution
The mean (± SD) apparent steady-state volume of distribution is 19,669 (± 13,358) L.

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Metabolism / Metabolites The conversion of abiraterone acetate to abiraterone, the active metabolite, is likely to be mediated by esterases, although specific esterases have not been identified. In human plasma, the two main circulating metabolites are abiraterone sulfate, which is formed by CYP3A4 and SULT2A1, and N-oxide abiraterone sulfate, which is formed by SULT2A1. These metabolites each account for about 43% of abiraterone exposure and are pharmacologically inactive.

Abiraterone has known human metabolites that include abiraterone sulfate. S73 | METXBIODB | Metabolite Reaction Database from BioTransformer | DOI:10.5281/zenodo.4056560

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Biological Half-Life
In patients with mCRPC, the mean (± SD) terminal half-life of abiraterone in plasma is 12 (± 5) hours.

Hepatotoxicity
Serum aminotransferase elevations occur in up to 13% of patients treated with abiraterone compared with 1% to 8% receiving placebo or a comparator drug, but the abnormalities are generally mild, transient and not associated with symptoms or jaundice. ALT elevations above 5 times the upper limit of normal (ULN) occur in 6% of abiraterone treated vs

Likelihood score: C (probable rare cause of clinically apparent liver injury).

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Protein Binding
Abiraterone is highly bound (>99%) to the human plasma proteins, albumin and alpha-1 acid glycoprotein.

[1]. Androgen synthesis inhibitors in the treatment of castration-resistant prostate cancer. Asian J Androl. 2014 May-Jun;16(3):387-400.

[2]. Interactions of abiraterone, eplerenone, and prednisolone with wild-type and mutant androgen receptor: a rationale for increasing abiraterone exposure or combining with MDV3100. Cancer Res. 2012 May 1;72(9):2176-82.

[3]. Abiraterone inhibits 3β-hydroxysteroid dehydrogenase: a rationale for increasing drug exposure in castration-resistant prostate cancer. Clin Cancer Res. 2012 Jul 1;18(13):3571-9.

[4]. Intracrine androgen biosynthesis in renal cell carcinoma. Br J Cancer. 2017 Mar 28;116(7):937-943.

[5]. Hormonal impact of the 17α-hydroxylase/C17,20-lyase inhibitor abiraterone acetate (CB7630) in patients with prostate cancer. British Journal of Cancervolume 90, pages2317–2325 (2004).

Abiraterone acetate can cause developmental toxicity, female reproductive toxicity and male reproductive toxicity according to state or federal government labeling requirements.
Abiraterone acetate is a sterol ester obtained by formal condensation of the 3-hydroxy group of abiraterone with the carboxy group of acetic acid. A prodrug that is converted in vivo into abiraterone. Used for treatment of metastatic castrate-resistant prostate cancer. It has a role as a prodrug, an antineoplastic agent and an EC 1.14.99.9 (steroid 17alpha-monooxygenase) inhibitor. It is a sterol ester and a member of pyridines. It is functionally related to an abiraterone.
Abiraterone Acetate is an orally active acetate ester form of the steroidal compound abiraterone with antiandrogen activity. Abiraterone inhibits the enzymatic activity of steroid 17alpha-monooxygenase (17alpha-hydrolase/C17,20 lyase complex), a member of the cytochrome p450 family that catalyzes the 17alpha-hydroxylation of steroid intermediates involved in testosterone synthesis. Administration of this agent may suppress testosterone production by both the testes and the adrenals to castrate-range levels.
An androstene derivative that inhibits STEROID 17-ALPHA-HYDROXYLASE and is used as an ANTINEOPLASTIC AGENT in the treatment of metastatic castration-resistant PROSTATE CANCER.
See also: Abiraterone (has active moiety); Niraparib; abiraterone acetate (component of) ... View More ...

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Drug Indication
Abiraterone Mylan is indicated with prednisone or prednisolone for: the treatment of newly diagnosed high risk metastatic hormone sensitive prostate cancer (mHSPC) in adult men in combination with androgen deprivation therapy (ADT). the treatment of metastatic castration resistant prostate cancer (mCRPC) in adult men who are asymptomatic or mildly symptomatic after failure of androgen deprivation therapy in whom chemotherapy is not yet clinically indicated. the treatment of mCRPC in adult men whose disease has progressed on or after a docetaxel based chemotherapy regimen.
Abiraterone Krka is indicated with prednisone or prednisolone for: the treatment of newly diagnosed high risk metastatic hormone sensitive prostate cancer (mHSPC) in adult men in combination with androgen deprivation therapy (ADT) (see section 5. 1)the treatment of metastatic castration resistant prostate cancer (mCRPC) in adult men who are asymptomatic or mildly symptomatic after failure of androgen deprivation therapy in whom chemotherapy is not yet clinically indicated (see section 5. 1)the treatment of mCRPC in adult men whose disease has progressed on or after a docetaxel-based chemotherapy regimen.
Zytiga is indicated with prednisone or prednisolone for: the treatment of metastatic castration resistant prostate cancer in adult men who are asymptomatic or mildly symptomatic after failure of androgen deprivation therapy in whom chemotherapy is not yet clinically indicatedthe treatment of metastatic castration resistant prostate cancer in adult men whose disease has progressed on or after a docetaxel based chemotherapy regimen.

C26H33NO2

391.55

391.251

C, 79.76; H, 8.50; N, 3.58; O, 8.17

154229-18-2

Abiraterone;154229-19-3;Abiraterone acetate (Standard);154229-18-2;Abiraterone acetate-d4

9821849

White to off-white solid powder

1.1±0.1 g/cm3

506.7±50.0 °C at 760 mmHg

127-130°C

260.2±30.1 °C

0.0±1.3 mmHg at 25°C

1.584

6.55

0

3

3

29

739

6

CC(=O)O[C@H]1CC[C@@]2([C@H]3CC[C@]4([C@H]([C@@H]3CC=C2C1)CC=C4C5=CN=CC=C5)C)C

UVIQSJCZCSLXRZ-HMMZIKKISA-N

InChI=1S/C26H33NO2/c1-17(28)29-20-10-12-25(2)19(15-20)6-7-21-23-9-8-22(18-5-4-14-27-16-18)26(23,3)13-11-24(21)25/h4-6,8,14,16,20-21,23-24H,7,9-13,15H2,1-3H3/t20-,21?,23?,24?,25-,26+/m0/s1

[(3S,10R,13S)-10,13-dimethyl-17-pyridin-3-yl-2,3,4,7,8,9,11,12,14,15-decahydro-1H-cyclopenta[a]phenanthren-3-yl] acetate

Abiraterone Acetate; CB7630; CB 7630 ; CB-7630; trade name: Zytiga; Yonsa; UNII-EM5OCB9YJ6;

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

Solubility in Formulation 1: ≥ 1 mg/mL (2.55 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 10.0 mg/mL clear DMSO stock solution to 400 μL of PEG300 and mix evenly; then add 50 μL of Tween-80 to the above solution and mix evenly; then add 450 μL of normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 1 mg/mL (2.55 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 10.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 1 mg/mL (2.55 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 10.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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Solubility in Formulation 4: 5% DMSO+95% Corn oil: 30mg/mL

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 (Please use freshly prepared in vivo formulations for optimal results.)