Abiraterone Acetate (CB7630) is 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.

CYP17:72 nM

在啮齿动物模型中腹膜内给药后,发现Abiraterone具有快速脱乙酰化作用. 当作为其醋酸酯前药（CB7630）给药时,其抑制循环睾酮至检测不到的水平,并显著降低雄激素敏感器官的重量. Abiraterone具有良好的耐受性,实验中平均消除半衰期为27.6 h（因此可以每日一次给药）.使用Abiraterone的临床前研究显示CYP17下游雄激素生成减少,导致小鼠腹侧前列腺,睾丸和精囊的重量减轻.

Abiraterone抑制AR-阳性前列腺癌细胞的体外增殖和AR调控的基因表达,这可能是除了类固醇生成抑制作用外的AR拮抗作用造成的。Abiraterone阻断3β-羟化类固醇脱氢酶(3βHSD),这是一种合成生物活性雄激素所必需的酶。Abiraterone对3βHSD的抑制阻断DHT合成和雄激素受体响应。Abiraterone仅在SM1中表现出与血红素铁良好的络合作用。Abiraterone通过抑制CYP17A1,阻断雄激素的合成。Abiraterone抑制DHEA转化为Δ4-雄烯二酮。Abiraterone抑制Δ5-雄烯二醇转化为睾酮。Abiraterone在大鼠睾丸微粒体中抑制C17,20-裂解酶,IC50为5.8 nM。Abiraterone明显抑制睾酮分泌（-48％）,进而增加LH浓度（192％）。

C17,20-lyase activity assay: Microsomes are diluted to a final protein concentration of 50 μg/mL in the reaction mixture which contains 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, test compounds are 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 in our laboratory using a specific antibody against Δ4A and instructions provided by Biogenesis. 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 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.

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. (Only for Reference)