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What is Letrozole? Research Information

Product Information:

  • Molecular mass – 285.30
  • Molecular formula – C17H11N5

Other names:

  • 112809-51-5
  • Femara
  • CGS-20267
  • 112809-51-5
  • Femara
  • Letrozol
  • CGS 20267
  • UNII-7LKK855W8I
  • 7LKK855W8
  • CHEMBL1444


Initially, in the year 1980, scientists from the Swiss company Ciba-Geigy AG (now known as Novartis AG) . This discovery was made while the scientists were screening for the ability of aromatase inhibition. Initially, this drug was developed for the treatment of hormone-dependent breast cancers in women (suffering from menopause). In past, most patients used to have surgery, chemotherapy or radiotherapy for the treatment of breast cancer at first. Letrozole comes as a tablet drug as an alternative to this first-line of treatments.

Mechanism of action:

is the drug (non-steroidal drug) related to the type-2 aromatase inhibitor class. It results in blocking the active sites and the blockage of CYP19A1 (electron transfer chain). This competitive inhibition through the letrozole prevents the androgen conversion to estrogen. This action of the drug leads to the specific reduction of uterine weight and also elevates the luteinizing hormone. Among post-menopausal women, the aromatase action is responsible for the production of estrogen. With the reduced estrogen availability, estrogen-dependent tumors tend to regress.

Clinical applications:

Female fertility:

(an aromatase inhibitor) was initially introduced as the potential drug for OI (ovulation Induction). According to a large number of studies, letrozole is beneficial for the ovulation indication for women suffering from PCOS (polycystic ovary syndrome), CC (clomiphene citrate) resistant women, the insemination (intrauterine), and also in the different protocols for mild stimulation (for intracytoplasmic sperm injection and in vitro fertilization). Letrozole is the best option (its oral consumption), having a shorter half-life and lesser side effects.

Anti-estrogen therapy for the selected ovarian cancer:

Ovarian cancer is the 5th most common cause of death in females. Most patients take different treatment approaches, such as surgical debulking, chemotherapy (platinum and taxane), and PFS (median progression-free survival). Endocrine therapies are invaluable treatments for metastatic breast cancer.

Letrozole is the most potent non-steroidal aromatase inhibitor, rapidly suppresses the circulating estrogens in the body. With letrozole, there are relatively no cases of partial remission in cancer patients. According to the evidence, letrozole is superior to several other hormonal agents in ovarian cancer treatment.


The information provided about Letrozole in this section is only for research advancement and disbursement of knowledge. The material collected in this article is meant for informational purposes about Letrozole. It is not to be considered instructional in any way. Moreover, we have further empathized with this by making sure no dosage information of Letrozole 2.5mg or recommendations about its way of consumption is mentioned. The information available in this article is a collection from different recognized studies and researches conducted by known experts and researchers in controlled medical facilities and institutions. Furthermore, the information provided in the article is not to encourage the reader to start its consumption or as an advertisement of the product. Administering any supplement or medication not FDA approved may be harmful and may cause serious illness.  Peptide Pros insist that none of their products be ingested under any circumstances.


  1. Bhatnagar, A. S. (2007). The discovery and mechanism of action of letrozole. Breast cancer research and treatment105(1), 7-17.
  2. Smyth, J. F., Gourley, C., Walker, G., MacKean, M. J., Stevenson, A., Williams, A. R., … & Langdon, S. P. (2007). Antiestrogen therapy is active in selected ovarian cancer cases: the use of letrozole in estrogen receptor–positive patients. Clinical Cancer Research13(12), 3617-3622.
  3. Kar, S. (2013). Current evidence supporting “letrozole” for ovulation induction. Journal of human reproductive sciences6(2), 93.
  4. Requena, A., Herrero, J., Landeras, J., Navarro, E., Neyro, J. L., Salvador, C., … & Graña-Barcia, M. (2008). Use of letrozole in assisted reproduction: a systematic review and meta-analysis. Human reproduction update14(6), 571-582.
  5. Haas, J., & Casper, R. F. (2017). In vitro fertilization treatments with the use of clomiphene citrate or letrozole. Fertility and sterility108(4), 568-571.
  6. Tatsumi, T., Jwa, S. C., Kuwahara, A., Irahara, M., Kubota, T., & Saito, H. (2017). No increased risk of major congenital anomalies or adverse pregnancy or neonatal outcomes following letrozole use in assisted reproductive technology. Human Reproduction32(1), 125-132.

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