Letrozole is an aromatase inhibitor used to treat breast cancer in postmenopausal women. Letrozole, or CGS 20267, is an oral non-steroidal type II aromatase inhibitor first described in the literature in 1990.
- Mechanism
- Curator reviewed · 7 references
Letrozole is a non-steroidal type II aromatase inhibitor. It blocks the active site, and therefore the electron transfer chain of CYP19A1. This competitive inhibition prevents the conversion of androgens to estrogen. This action leads to a reduction in uterine weight and elevated leuteinizing hormone. In postmenopausal women, the action of aromatase is responsible for the majority of estrogen production. With reduced availability of estrogen, estrogen-dependant tumors regress. Third generation aromatase inhibitors do not significantly affect cortisol, aldosterone, and thyroxine levels.
- Primary indication
- Letrozole is indicated to treat postmenopausal women with hormone receptor (HR) positive early breast cancer, postmenopausal women with early breast cancer who have periviously been treated with tamoxifen, and postmenopausal women with HR+ or unknown...Curator reviewed · 7 structured indications
- Formula / weight
- C17H11N5 · 285.3027 g/mol (avg)
- First approval
- Canada, 1997 · United States, 1997
- Also known as
- Letrozol
- Code names
- CGS-20267
- Brand names
Resolves to
HPJKCIUCZWXJDR-UHFFFAOYSA-NSMILESN#CC1=CC=C(C=C1)C(N1C=NC=N1)C1=CC=C(C=C1)C#NWhat you can answer from here — as of September 20, 2026
Which drugs share a target with Letrozole, and which of those have an active Phase 3 trial?
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