|
Research Area
|
|
Description
|
Endocrinology |
|
Biological Activity
|
|
Description
|
Abiraterone (CB-7598) is a potent CYP17 inhibitor with IC50 of 2 nM. |
|
Targets
|
CYP17 |
|
|
|
|
|
|
IC50 |
2 nM [1] |
|
|
|
|
|
|
In Vitro
|
Abiraterone binds and inhibits wild-type and mutant androgen receptor (AR). Abiraterone inhibits in vitro proliferation and androgen receptor-regulated gene expression of androgen receptor-positive prostate cancer cells, which could be explained by androgen receptor antagonism in addition to inhibition of steroidogenesis. In fact, activation of mutant androgen receptor by eplerenone is inhibited by greater concentrations of Abiraterone. Abiraterone displaces ligand from both WT-AR and T877A with EC50 of 13.4 μM and 7.9 μM, respectively. [2]Abiraterone inhibits lyase activity with an IC50 of 5.8 nM in rat testis microsomes. Abiraterone acetate significantly inhibits T secretion (?48%) and in turn increased LH concentration (192%).[3] |
|
In Vivo
|
Abiraterone inhibits CYP17 with an IC50 of 72 nM, in human testicular microsomes. [4] Abiraterone fails to significantly reduce the size of any of the organs. [5] Abiraterone reduces the testosterone levels strongly, almost reaching the level of the orchiectomy control. The testosterone levels are reduced by Abiraterone for more than 95% compared to the control group. [6] |
|
Clinical Trials
|
Abiraterone acetate plus prednisone has entered in a phase II clinical trial in the treatment of prostate cancer. |
|
Features
|
Abiraterone has been approved for the treatment of docetaxel-treated castration-resistant prostate cancer (CRPC). |
|
Combination Therapy
|
|
Description
|
Abiraterone acetate in combination with Cabazitaxel and XRP6258 has entered a phase I clinical trial in the treatment of prostate cancer. |
|
Protocol
|
|
Kinase Assay
[3]
|
| C17,20-lyase activity assay |
Microsomes are diluted to a final protein concentration of 50 μg/mL in the reaction mixture which contained 0.25 M sucrose, 20 mM Tris–HCl (pH 7.4), 10 mM G6P and 1.2 IU/mL G6PDH. After equilibration at 37 °C for 10 minutes, the reaction is initiated by addition of βNADP to obtain a final concentration of 0.6 mM. Prior to the distribution of 600 μL of the reaction mixture in each tube, Abiraterone is evaporated to dryness under a stream of nitrogen and then are incubated at 37 °C for 10 minutes. After incubation with Abiraterone, 500 μL of the reaction mixture is transferred to tubes containing 1 μM of the enzyme substrate, 17OHP. After a further 10 minutes incubation, tubes are placed on ice and the reaction is stopped by addition of 0.1 ml NaOH 1N. Tubes are deep-frozen and stored at ?20 °C until assayed for Δ4A levels. A Δ4A RIA is developed and automated on a microplate format using a specific antibody against Δ4A. The separation of free and bound antigen is achieved with a dextran-coated charcoal suspension. After centrifugation, aliquots of the clear supernatant are counted in duplicates in a 1450 MicrobetaPlus liquid scintillation counter. The Δ4A concentrations of unknown samples are determined from the standard curve. The detection limit is 0.5 ng/mL and the within and between assay coefficients of variation are 10.7 and 17.6%, respectively at an assay value of 13 ng/mL. The rate of enzymatic reaction is expressed as pmol of Δ4A formed per 10 minutes and per mg of protein. The value of maximum activity without inhibitor (control) is set at 100%. The IC50 values are calculated using non-linear analysis from the plot of enzyme activity (%) against log of inhibitor concentration. |
|
Cell Assay
[2]
|
| Cell Lines |
LNCaP and VCaP cells |
| Concentrations |
0.1-5 μM |
| Incubation Time |
24 hours or 96 hours |
| Methods |
LNCaP and VCaP cells are seeded in 96-well plates and grown in CSS-supplemented phenol red-free or FBS-supplemented media for 7 days. Cells are treated with Abiraterone at 24 hours and 96 hours after plating and cell viability is determined on day 7 by adding CellTiter Glo and measuring luminescence. |
|
Animal Study
[5]
|
| Animal Models |
LAPC-4 xenograft mice |
| Formulation |
0.3% hydroxypropyl cellulose |
| Doses |
0.15 mmol/kg |
| Administration |
Administered via s.c. |
|
References |
|
[1] Attard G, et al. J Clin Oncol. 2008, 26(28), 4563-4571.
|
|
[2] Richards J, et al. Cancer Res. 2012, 72(9), 2176-2182.
|
|
[3] Duc I, et al. J Steroid Biochem Mol Biol. 2003, 84(5), 537-542.
|
|
[4] Hu Q, et al. J Med Chem. 2010, 53(15), 5749-5758.
|
|
[5] Bruno RD, et al. Steroids. 2011, 76(12), 1268-1279.
|
|
[6] Haidar S, et al. J Steroid Biochem Mol Biol. 2003, 84(5),555-562.
|
|