API / Alfa Chemistry

ISO9001:2015 accredited

Online Inquiry


Product Information


Letrozole is a white to yellowish crystalline powder that is freely soluble in dichloromethane, slightly soluble in ethanol, and practically insoluble in water, which was approved by the FDA for the treatment of local or metastatic breast cancer. The chemical name of it is 4,4'-(1H-1,2,4-triazol-1-ylmethylene) dibenzonitrile. The structure is shown in fig. 1.

Structure of letrozole

Fig. 1 Structure of letrozole

Application in the treatment of breast cancer

  • Introduction of breast cancer

Breast cancer is a cancer that develops from breast tissue. Its signs may include breast lumps, altered breast shape, sunken skin, rejection of milk, fluid discharge from the nipple, and a red or scaly patch of skin. Breast cancer is the second leading cause of cancer death among women. In the United States, breast cancer will be diagnosed in 12% of all women over their lifetimes, and over 1.5 million women (25% of all women with cancer) are diagnosed with breast cancer every year throughout the world[1]. There are five important risk factors of breast cancer, including age, family history, reproductive factors, estrogen and life style. Breast cancer prevention is very important, and screening (mammography and MRI), chemoprevention (with SERMs and AIs) and biological prevention (using Herceptin and Pertuzumab) are most commonly used methods (Fig. 2)[2]. In addition, measures must be taken to aggressively treat breast cancer if diagnosed. Letrozole is an aromatase inhibitor that can be used to treat breast cancer.

Schematic diagram of risk factors and preventions of breast cancer

Fig. 2. Schematic diagram of risk factors and preventions of breast cancer

  • Mechanism of action

Breast cancer is primarily caused by estrogen, which is produced by the conversion of androgens through the activity of aromatase. Aromatase is a cytochrome P-450 enzyme localized to the endoplasmic reticulum of the cell and found in many tissues of premenopausal women, including ovary, liver, and breast. It catalyzes the aromatization of androstenedione and testosterone into estrone and estradiol that belong to estrogen. Letrozole is a third-generation aromatase inhibitor that effectively blocks estrogen synthesis, thereby inhibiting the growth or inducing the regression of hormone-responsive breast tumors[3].

  • Side effects

Common side effects of letrozole mainly include:



Bone fracture






Alfa Chemistry offers high quality letrozole. Please feel free to contact us for APIs or technical services.


  1. Adrienne, G., et al. Breast cancer treatment: a review. The Journal of the American Medical Association. 2019, 321(3): 288-300.
  2. Sun, Y.S., et al. Risk factors and preventions of breast cancer. International Journal of Biological Sciences. 2017, 13(11): 1387-1397.
  3. Bhatnagar, A.S. The discovery and mechanism of action of letrozole. Breast Cancer Research and Treatment. 2007, 105: 7-17.