Overview

Letrozole, or CGS 20267, is an oral non-steroidal type II aromatase inhibitor first described in the literature in 1990. It is a third generation aromatase inhibitor like exemestane and anastrozole, meaning it does not significantly affect cortisol, aldosterone, and thyroxine. Letrozole was granted FDA approval on 25 July 1997.

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 advanced breast cancer. Letrozole, given with ribociclib, is indicated to treat pre, peri, and postmenopausal women with HR+ and human epidermal growth factor 2 (HER2) negative advanced or metastatic breast cancer.

Associated Conditions

Advanced Breast Cancer
Anovulatory cycle
Epithelial Ovarian Cancer
HR+, HER2-, Advanced Breast Cancer
Stage I Breast Cancer
Metastatic HR + HER2 - breast cancer

Research Report

Published: Jul 10, 2025

Letrozole (DB01006): A Comprehensive Monograph on its Pharmacology, Clinical Efficacy, and Therapeutic Landscape

Executive Summary

Letrozole (DrugBank ID: DB01006) is a highly potent, selective, non-steroidal, third-generation aromatase inhibitor that represents a cornerstone in the management of hormone receptor-positive (HR+) breast cancer in postmenopausal women. Since its initial FDA approval in 1997, it has fundamentally altered the landscape of endocrine therapy, demonstrating superior efficacy over the previous standard of care, tamoxifen, across various clinical settings, including neoadjuvant, adjuvant, and advanced disease. Its mechanism of action involves the competitive inhibition of the aromatase enzyme (CYP19A1), which catalyzes the final step in estrogen biosynthesis. This leads to profound systemic estrogen deprivation, thereby inhibiting the growth of estrogen-dependent tumors.

Pharmacokinetically, letrozole is characterized by near-complete oral bioavailability, a long terminal half-life of approximately two days, and metabolism primarily via the CYP2A6 and CYP3A4 isoenzymes. A critical feature of its kinetics is the saturation of these metabolic pathways at the standard clinical dose of 2.5 mg daily, a phenomenon that underscores the importance of strict adherence to dosing schedules and caution regarding drug-drug interactions.

Continue reading the full research report

Clinical Trials

Title	Posted	Study ID	Phase	Status	Sponsor
Palazestrant in Combination With Ribociclib for the First-line Treatment of ER+/HER2- Advanced Breast Cancer	2025/07/25	NCT07085767	Not Applicable	Not yet recruiting	Olema Pharmaceuticals, Inc.
A Study to Test Inavolisib Treatments in Participants With Early-Stage, PIK3CA-Mutated Breast Cancer	2025/07/08	NCT07054190	Not Applicable	Not yet recruiting	Hoffmann-La Roche
Study of AVZO-023 as a Single Agent and in Combination With AVZO-021, and/or Endocrine Therapy in Advanced Solid Tumors	2025/05/31	NCT06998407	Phase 1	Not yet recruiting	Avenzo Therapeutics, Inc.
A Study of MK-5684 in People With Certain Solid Tumors (MK-5684-015/OMAHA-015)	2025/05/20	NCT06979596	Phase 2	Not yet recruiting	Merck Sharp & Dohme LLC
A Clinical Study of HRS-6209 in Combination With Letrozole in Patients With Breast Cancer	2025/05/16	NCT06974929	Phase 1	Recruiting	Jiangsu HengRui Medicine Co., Ltd.
Sirolimus for Injection (Albumin-bound) in Combination With Endocrine Therapy for HR+/HER2- Advanced/Metastatic Breast Cancer Patients Who Have Failed Standard Therapy	2025/05/04	NCT06957379	Phase 2	Active, not recruiting	CSPC ZhongQi Pharmaceutical Technology Co., Ltd.
Impact of Omitting Chemo Based on Patient's Selection for ER-Positive, HER2-Negative Breast Cancer With Ribociclib and Endocrine Therapy	2025/05/01	NCT06953882	Phase 2	Recruiting	Yale University
Non-interventional Study to Assess the Effectiveness and Safety of Ribociclib in the Adjuvant Therapy of Hormone Receptor Positive (HR+) HER2-negative Stage II and III Breast Cancer in Real Clinical Practice in Russia	2025/04/16	NCT06930859	N/A	Not yet recruiting	Novartis Pharmaceuticals
Implementation Study to Describe and Compare Retention Rate and Adherence to Adjuvant Therapy With Ribociclib With and Without Usage of Mobile Application in Patients With HR+ HER2-negative Stage II and III Breast Cancer in Real-world Practice	2025/04/01	NCT06905301	N/A	Not yet recruiting	Novartis Pharmaceuticals
Laboratory and Ultrasound Findings and Response to Letrozole in PCOS Patients	2025/03/06	NCT06861803	N/A	Not yet recruiting	Al-Azhar University

FDA Drug Approvals

Approved Product	Manufacturer	NDC Code	Route	Strength	Effective Date
Letrozole	Teva Pharmaceuticals USA, Inc.	0093-7620	ORAL	2.5 mg in 1 1	11/1/2020
LETROZOLE	Breckenridge Pharmaceutical, Inc.	51991-759	ORAL	2.5 mg in 1 1	12/31/2023
Letrozole	NuCare Pharmaceuticals,Inc.	68071-5264	ORAL	2.5 mg in 1 1	6/1/2020
Letrozole	ATLANTIC BIOLOGICALS CORP.	17856-0032	ORAL	2.5 mg in 1 1	1/13/2020
LETROZOLE	Chartwell RX, LLC	62135-491	ORAL	2.5 mg in 1 1	10/11/2023
Letrozole	Bryant Ranch Prepack	63629-7819	ORAL	2.5 mg in 1 1	11/7/2022
Letrozole	Natco Pharma Limited	63850-0025	ORAL	2.5 mg in 1 1	10/21/2020
Letrozole	Aurobindo Pharma Limited	59651-180	ORAL	2.5 mg in 1 1	9/16/2019
Letrozole	Dr. Reddy's Laboratories Limited	55111-646	ORAL	2.5 mg in 1 1	12/6/2018
LETROZOLE	AvPAK	50268-476	ORAL	2.5 mg in 1 1	1/9/2024

EMA Drug Approvals

Approved Product	Authorization Holder	Status	Issued Date
No EMA approvals found for this drug.

HSA Drug Approvals

Approved Product	Manufacturer	Approval Number	Dosage Form	Strength	Approval Date
LETROVITAE FILM-COATED TABLETS 2.5MG	SAG Manufacturing S.L.U.	SIN16037P	TABLET, FILM COATED	2.50mg	11/10/2020
LENTRONAT TABLETS 2.5 mg	Natco Pharma Limited - Pharma Division	SIN14825P	TABLET, FILM COATED	2.50mg	8/4/2015
Letara Film Coated Tablet 2.5mg	Douglas Manufacturing Ltd	SIN14470P	TABLET, FILM COATED	2.5mg	12/27/2013
ZATROLEX FILM-COATED TABLET 2.5MG	GENEPHARM S.A	SIN15739P	TABLET, FILM COATED	2.5mg	7/8/2019
LEZRA TABLET 2.5MG	S.C. SINDAN-PHARMA S.R.L.	SIN14826P	TABLET, FILM COATED	2.5 mg	8/13/2015
LETROZOLE SANDOZ FILM COATED TABLETS 2.5MG	Novartis Pharma Stein AG, Novartis Farma S.P.A. (Primary and Secondary packager)	SIN14565P	TABLET, FILM COATED	2.5mg	6/27/2014
LEBRETA FILM COATED TABLETS 2.5MG	Duopharma HAPI Sdn Bhd	SIN16602P	TABLET, FILM COATED	2.5 mg	9/12/2022
Letrozole Mevon Tablets 2.5mg	West Pharma - Producoes de Especialidades Farmaceuticas S.A., ATLAS PHARM, S.A.	SIN13916P	TABLET, FILM COATED	2.5mg	2/7/2011
LETERO (LETROZOLE) TABLETS 2.5 mg	Hetero Labs Limited	SIN14717P	TABLET, FILM COATED	2.500 mg	12/30/2014
Letrocord 2.5-Letrozole Tablets 2.5mg USP	INTAS PHARMACEUTICALS LIMITED	SIN16047P	TABLET, FILM COATED	2.5 mg	11/23/2020

NMPA Drug Approvals

Approved Product	Company	Approval Number	Drug Type	Dosage Form	Approval Date
No NMPA approvals found for this drug.

PPB Drug Approvals

Approved Product	Registration No.	Company	Licence No.	Strength	Registration Date
LOTUSENZA TABLETS 2.5MG	N/A	Lotus Pharmaceutical HK Limited	N/A	N/A	1/16/2025
LETRODAY 2.5 TABLETS 2.5MG	N/A	HANG LUNG TRADING CO	N/A	N/A	8/22/2024

TGA Drug Approvals

Approved Product	ARTG ID	Sponsor	Registration Type	Status	Registration Date
APO-LETROZOLE letrozole 2.5mg tablet bottle	163830	Arrotex Pharmaceuticals Pty Ltd	Medicine	A	1/20/2011
LETROZOLE-WGR letrozole 2.5mg film-coated tablet blister pack	236270	Cipla Australia Pty Ltd	Medicine	A	6/1/2016
CIPLA LETROZOLE letrozole 2.5mg film-coated tablet blister pack	236269	Cipla Australia Pty Ltd	Medicine	A	6/1/2016
ACCOZOLE letrozole 2.5 mg film-coated tablet blister pack	211121	Accord Healthcare Pty Ltd	Medicine	A	7/19/2013
GYNOTRIL letrozole 2.5 mg tablet blister pack	203379	Strides Pharma Science Pty Ltd	Medicine	A	5/20/2013
PHARMACOR LETROZOLE 2.5 letrozole 2.5 mg film-coated tablet blister pack	159589	Pharmacor Pty Ltd	Medicine	A	6/3/2010
LETROZOLE GH letrozole 2.5mg film-coated tablet blister pack	311016	Cipla Australia Pty Ltd	Medicine	A	3/12/2019
FEMARA letrozole 2.5mg tablet blister pack	60605	Novartis Pharmaceuticals Australia Pty Ltd	Medicine	A	10/30/1997
ARX-LETROZOLE letrozole 2.5 mg film-coated tablet blister pack	309249	Cipla Australia Pty Ltd	Medicine	A	12/17/2018
LETROZOLE ACTAVIS 2.5mg	176276	Medis Pharma Pty Ltd	Medicine	A	9/22/2011

Health Canada Drug Approvals

Approved Product	Company	DIN	Dosage Form	Strength	Market Date
FEMARA	novartis pharmaceuticals canada inc	02231384	Tablet - Oral	2.5 MG	8/18/1997
LETROZOLE	actavis pharma company	02348969	Tablet - Oral	2.5 MG	4/28/2010
JAMP LETROZOLE TABLETS	Jamp Pharma Corporation	02541912	Tablet - Oral	2.5 MG	8/20/2024
CO LETROZOLE	Cobalt Pharmaceuticals Company	02352052	Tablet - Oral	2.5 MG	N/A
MINT-LETROZOLE	mint pharmaceuticals inc	02508109	Tablet - Oral	2.5 MG	7/20/2021
AG-LETROZOLE	angita pharma inc.	02374439	Tablet - Oral	2.5 MG	2/3/2022
STASON-LETROZOLE	VPI Pharmaceuticals Inc	02431335	Tablet - Oral	2.5 MG	N/A
MYLAN-LETROZOLE	Mylan Pharmaceuticals ULC	02322544	Tablet - Oral	2.5 MG	N/A
LETROZOLE TABLETS	fresenius kabi canada ltd	02381958	Tablet - Oral	2.5 MG	N/A
TARO-LETROZOLE	sun pharma canada inc	02372282	Tablet - Oral	2.5 MG	10/4/2011

CIMA AEMPS Drug Approvals

Approved Product	Company	Registration Number	Pharmaceutical Form	Prescription Type	Status
LETROZOL RATIOPHARM 2,5 mg COMPRIMIDOS RECUBIERTOS CON PELICULA EFG	Teva Pharma S.L.U.	71595	COMPRIMIDO RECUBIERTO CON PELÍCULA	Medicamento Sujeto A Prescripción Médica	Commercialized
LETROZOL EDIGEN 2,5 mg COMPRIMIDOS RECUBIERTOS CON PELICULA EFG	Aristo Pharma Iberia S.L.	70854	COMPRIMIDO RECUBIERTO CON PELÍCULA	Medicamento Sujeto A Prescripción Médica	Commercialized
LETROZOL ALTER 2,5 MG COMPRIMIDOS RECUBIERTOS CON PELICULA EFG	Laboratorios Alter S.A.	72124	COMPRIMIDO RECUBIERTO CON PELÍCULA	Medicamento Sujeto A Prescripción Médica	Commercialized
LETROZOL NORMON 2,5 mg COMPRIMIDOS RECUBIERTOS CON PELICULA EFG	Laboratorios Normon S.A.	69862	COMPRIMIDO RECUBIERTO CON PELÍCULA	Medicamento Sujeto A Prescripción Médica	Commercialized
LETROZOL PENSA PHARMA 2,5 MG COMPRIMIDOS RECUBIERTOS CON PELICULA EFG	Towa Pharmaceutical S.A.	81743	COMPRIMIDO RECUBIERTO CON PELÍCULA	Medicamento Sujeto A Prescripción Médica	Commercialized
LETROZOL CADIASUN 2.5 MG COMPRIMIDOS RECUBIERTOS CON PELICULA EFG	Cadiasun Pharma Gmbh	77900	COMPRIMIDO RECUBIERTO CON PELÍCULA	Medicamento Sujeto A Prescripción Médica	Not Commercialized
LETROZOL AUROVITAS SPAIN 2,5 mg COMPRIMIDOS RECUBIERTOS CON PELICULA EFG	Aurovitas Spain, S.A.U.	71123	COMPRIMIDO RECUBIERTO CON PELÍCULA	Medicamento Sujeto A Prescripción Médica	Not Commercialized
LETROZOL COMBIX 2,5 mg COMPRIMIDOS RECUBIERTOS CON PELICULA EFG	Laboratorios Combix S.L.U.	74256	COMPRIMIDO RECUBIERTO CON PELÍCULA	Medicamento Sujeto A Prescripción Médica	Commercialized
LETROZOL SANDOZ 2,5 mg COMPRIMIDOS RECUBIERTOS CON PELICULA EFG	Sandoz Farmaceutica S.A.	70933	COMPRIMIDO RECUBIERTO CON PELÍCULA	Medicamento Sujeto A Prescripción Médica	Commercialized
LETROZOL MABO 2,5 MG COMPRIMIDOS RECUBIERTOS CON PELICULA EFG	Mabo Farma S.A.	84689	COMPRIMIDO RECUBIERTO CON PELÍCULA	Medicamento Sujeto A Prescripción Médica	Commercialized

Philippines FDA Drug Approvals

Approved Product	Company	License Number	Dosage Form	Strength	Approval Date
No Philippines FDA approvals found for this drug.

Saudi SFDA Drug Approvals

Approved Product	Company	License Number	Dosage Form	Strength	Approval Date
No Saudi SFDA approvals found for this drug.

Malaysia NPRA Drug Approvals

Approved Product	Company	Registration Number	Dosage Form	Strength	Approval Date
No Malaysia NPRA approvals found for this drug.

UK EMC Drug Information

Medicine Name	MA Holder	MA Number	Pharmaceutical Form	Active Ingredient	Authorization Date
No UK EMC drug information found for this drug.

Related News

ROSALINE Trial: Neoadjuvant Letrozole/Entrectinib Shows Limited Efficacy in Invasive Lobular Breast Cancer

3 months ago

The phase 2 ROSALINE trial found that combining entrectinib with letrozole failed to meet its primary endpoint, with no efficacy-evaluable patients achieving residual cancer burden (RCB) of 0 or 1 in invasive lobular breast cancer.

Ribociclib-Letrozole Combo Shows Promising 24% Response Rate in Low-Grade Serous Ovarian Cancer Trial

5 months ago

• Phase 2 GOG 3026 trial demonstrates ribociclib plus letrozole achieves 24% response rate in low-grade serous ovarian cancer, surpassing current treatment options' efficacy. • The combination therapy shows favorable tolerability profile, building on established safety protocols from breast cancer treatment experience. • Researchers anticipate inclusion in NCCN guidelines, though optimal treatment timing and sequencing remain under investigation for future clinical trials.

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