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• description

  Abiraterone is a new type of hormone therapy. It is also called abiraterone acetate, CB7630 or Zytiga. It is used to treat prostate cancer that has spread to other parts of the body. It may help some men to live longer. It can also help control symptoms. Clinical trials are also using abiraterone for earlier stages of prostate cancer and advanced breast cancer. Abiraterone is associated with a not uncommon rate of serum enzyme elevation during therapy, but has not been clearly linked to cases of clinically apparent liver injury with jaundice.
  
  On April 28, 2011, the U.S. Food and Drug Administration approved abiraterone acetate (Zytiga Tablets, Centocor Ortho Biotech, Inc.) for use in combination with prednisone for the treatment of patients with metastatic castration-resistant prostate cancer (mCRPC) who have received prior chemotherapy containing docetaxel.
  
  Abiraterone is a steroidal compound with antiandrogen activity. it is a Cytochrome P450 17A1 Inhibitor. The mechanism of action of abiraterone is as a Cytochrome P450 17A1 Inhibitor, and Cytochrome P450 2D6 Inhibitor, and Cytochrome P450 2C8 Inhibitor 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.
  
  figure 1: Zytiga (abiraterone acetate);

• Therapeutic agent for prostate cancer

  Currently, for patients of advanced prostate cancer, androgen deprivation therapy including drugs and surgery is generally the preferred method of including drugs and surgery in order to reduce the testicular androgen synthesis. However, this treatment can’t suppress other parts of the body for yielding the male hormone.
  Abiraterone is a therapeutic agent for prostate cancer with the English name for Abiraterone. It has not yet been marketed in China. It is developed by researchers coming from the British Royal Marsden Hospital located in southwest (world-renowned cancer research treatment center). It is kind of drug which is able to repress any part of the body for androgen production. It can not only reduce the levels of the prostate-specific antigen (PSA) which represents the tumor activity, but also helps to shrink the tumor. It can also apply to cancer patients who have been subject to chemotherapy in the past, revealing treatment hope.
  Previously, the patent of the Abiraterone was owned by British Cougar biopharmaceutical Company. But in 2009 Johnson Pharmaceutical acquire the Cougar Biological Company with $ 970 million, and thus getting the permission of the drug. The phase III clinical trial results have showed that the goods can significantly prolong patients with advanced prostate cancer including those who had used one or two docetaxel chemotherapy but still got deteriorating lives with a small drug side effects and good safety.
  Abiraterone is an oral administrated cytochrome oxidase P450 (CYP450) c17 inhibitor which can decrease the androgen levels through inhibiting the key enzyme in the androgen synthesis--CYP450c17, and also has inhibitory effect on the androgens coming from testis and other body parts.
  The above information is edited by the chemicalbook of Dai Xiongfeng. ;

• How abiraterone works

  Hormones are substances produced naturally in the body. They act as chemical messengers and help control the activity of cells and organs. Hormonal therapies interfere with the way hormones are made or how they work in the body.
  Most prostate cancers need the hormone testosterone to grow. Almost all testosterone in men is made by the testicles. A very small amount is made by the adrenal glands, which sit above the kidneys.
  Abiraterone reduces the amount of testosterone made by your body. This reduces testosterone levels and may shrink the prostate cancer or stop it growing.
  References
  Abiraterone acetate (Zytiga®)
  Abiraterone acetate (often shortened to abiraterone) is a hormonal therapy drug used to treat advanced prostate cancer. It is also known as Zytiga®.;

• Mechanism of Action

  Abiraterone is an orally active inhibitor of the steroidal enzyme CYP17A1 (17 alpha-hydroxylase/C17,20 lyase). It inhibits CYP17A1 in a selective and irreversible manner via covalent binding mechanism. CYP17A1 is an enzyme that catalyzes the biosynthesis of androgen and is highly expressed in testicular, adrenal, and prostatic tumor tissue. More specifically, abiraterone inhibits the conversion of 17-hydroxyprognenolone to dehydroepiandrosterone (DHEA) by the enzyme CYP17A1 to decrease serum levels of testosterone and other androgens.
  References
  http://www.drugbank.ca/drugs/DB05812;

• side effects

  Like all treatments, abiraterone can cause side effects. Taking prednisolone as well as abiraterone will reduce the risk of side effects. Most men don’t have many problems with side effects. Possible side effects include:
  
  • fluid retention, which can cause swelling in your ankles or hands
  • High blood pressure during treatment happens in about 1 in 10 men (10%)
  • Abiraterone can also cause the level of potassium in your blood to drop. This could make you feel tired and you may be at risk of a fast, irregular heartbeat.
  • Tiredness (fatigue) and breathlessness from a drop in red blood cells (anaemia)
  • Swelling of the legs or feet due to fluid build up (known as peripheral oedema) affects about 3 in 10 men (30%)
  • Diarrhoea – drink plenty of fluids.
  • Bladder infections affect just over 1 in 10 men (10%)
  Occasional side effects
  Between 1 and 10 in every 100 people have one or more of these.
  
  • A mild effect on the liver that is unlikely to cause symptoms and will almost certainly go back to normal when you finish treatment.
  • Heart problems, including a faster heart beat, a change to the heart rhythm and chest pain.
  • Bone thinning (osteoporosis) can make bones more likely to break.
  • High fat (cholesterol) levels in your blood – your doctor will check for this.
  • An increased risk of getting an infection from a drop in white blood cells – it is harder to fight infections and you can become very ill. You may have headaches, aching muscles, a cough, a sore throat, or you may feel cold and shivery. If you have a severe infection this can be life threatening. Contact your treatment centre if you have any of these side effects or if your temperature goes above 38°C.
  • A skin rash – you may develop a rash, which can be itchy.
  Speak to your doctor if you notice anything unusual.;

• Biological Activity

  Description
  Abiraterone is a potent CYP17 inhibitor with IC50 of 2 nM in a cell-free assay.
  Features
  Approved for the treatment of docetaxel-treated castration-resistant prostate cancer.
  Targets  
  CYP17 [1](Cell-free assay) 2 nM
  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]
  
  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;

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