CLINICAL TRIALS PROFILE FOR LETROZOLE

505(b)(2) Clinical Trials for letrozole

This table shows clinical trials for potential 505(b)(2) applications. See the next table for all clinical trials

Trial Type	Trial ID	Title	Status	Sponsor	Phase	Start Date	Summary
New Indication	NCT01175096 ↗	Safety and Tolerability Profile of RAD001 Daily in Chinese Patients With Advanced Pulmonary Neuroendocrine Tumor	Unknown status	Novartis	Phase 1/Phase 2	2010-07-01	RAD001 continues to be investigated as an anticancer agent on new indications such as neuroendocrine tumors (incl. carcinoid), breast cancer, liver cancer, gastric cancer and lymphoma based on its potential to act: - directly on the tumor cells by inhibiting tumor cell growth and proliferation - indirectly by inhibiting angiogenesis leading to reduced tumor vascularity (via potent inhibition of tumor cell HIF-1 activity and VEGF production and VEGF-induced proliferation of endothelial cells) A role for RAD001 in combination with Sandostatin LAR® Depot in the treatment of advanced carcinoid tumor is suggested by data on the regulatory role of mTOR in cell growth and protein translation and the finding that somatostatin-induced growth arrest is mediated in part by inhibition of the PI3K pathway (Charland, et al. 2001). The present study is designed to collect safety/tolerability data and evidences for efficacy of RAD001 in the medically highly unmet indication of advanced pulmonary neuroendocrine tumor in Chinese patients.
New Indication	NCT01175096 ↗	Safety and Tolerability Profile of RAD001 Daily in Chinese Patients With Advanced Pulmonary Neuroendocrine Tumor	Unknown status	Guangdong General Hospital	Phase 1/Phase 2	2010-07-01	RAD001 continues to be investigated as an anticancer agent on new indications such as neuroendocrine tumors (incl. carcinoid), breast cancer, liver cancer, gastric cancer and lymphoma based on its potential to act: - directly on the tumor cells by inhibiting tumor cell growth and proliferation - indirectly by inhibiting angiogenesis leading to reduced tumor vascularity (via potent inhibition of tumor cell HIF-1 activity and VEGF production and VEGF-induced proliferation of endothelial cells) A role for RAD001 in combination with Sandostatin LAR® Depot in the treatment of advanced carcinoid tumor is suggested by data on the regulatory role of mTOR in cell growth and protein translation and the finding that somatostatin-induced growth arrest is mediated in part by inhibition of the PI3K pathway (Charland, et al. 2001). The present study is designed to collect safety/tolerability data and evidences for efficacy of RAD001 in the medically highly unmet indication of advanced pulmonary neuroendocrine tumor in Chinese patients.
New Indication	NCT01175096 ↗	Safety and Tolerability Profile of RAD001 Daily in Chinese Patients With Advanced Pulmonary Neuroendocrine Tumor	Unknown status	Guangdong Provincial People's Hospital	Phase 1/Phase 2	2010-07-01	RAD001 continues to be investigated as an anticancer agent on new indications such as neuroendocrine tumors (incl. carcinoid), breast cancer, liver cancer, gastric cancer and lymphoma based on its potential to act: - directly on the tumor cells by inhibiting tumor cell growth and proliferation - indirectly by inhibiting angiogenesis leading to reduced tumor vascularity (via potent inhibition of tumor cell HIF-1 activity and VEGF production and VEGF-induced proliferation of endothelial cells) A role for RAD001 in combination with Sandostatin LAR® Depot in the treatment of advanced carcinoid tumor is suggested by data on the regulatory role of mTOR in cell growth and protein translation and the finding that somatostatin-induced growth arrest is mediated in part by inhibition of the PI3K pathway (Charland, et al. 2001). The present study is designed to collect safety/tolerability data and evidences for efficacy of RAD001 in the medically highly unmet indication of advanced pulmonary neuroendocrine tumor in Chinese patients.
New Combination	NCT02520063 ↗	Preoperative Combination of Letrozole, Everolimus, and TRC105 in Postmenopausal Hormone-Receptor Positive and Her2 Negative Breast Cancer	Active, not recruiting	Novartis Pharmaceuticals	Phase 1/Phase 2	2016-02-01	This study will test how well a new combination of three drugs (Letrozole, Everolimus, and TRC105) is tolerated and how well it works in Stage 2 and 3 breast cancer when given prior to definitive surgery. Letrozole blocks the estrogen receptor expressed by many breast cancers while everolimus blocks signals that drive cancer cells to grow. TRC105 is an investigational drug that blocks the formation and growth of blood vessels that feed the cancer and promote its growth. The goal of this study is to investigate the safety and efficacy of this multitargeted approach in breast cancer.
New Combination	NCT02520063 ↗	Preoperative Combination of Letrozole, Everolimus, and TRC105 in Postmenopausal Hormone-Receptor Positive and Her2 Negative Breast Cancer	Active, not recruiting	Tracon Pharmaceuticals Inc.	Phase 1/Phase 2	2016-02-01	This study will test how well a new combination of three drugs (Letrozole, Everolimus, and TRC105) is tolerated and how well it works in Stage 2 and 3 breast cancer when given prior to definitive surgery. Letrozole blocks the estrogen receptor expressed by many breast cancers while everolimus blocks signals that drive cancer cells to grow. TRC105 is an investigational drug that blocks the formation and growth of blood vessels that feed the cancer and promote its growth. The goal of this study is to investigate the safety and efficacy of this multitargeted approach in breast cancer.
New Combination	NCT02520063 ↗	Preoperative Combination of Letrozole, Everolimus, and TRC105 in Postmenopausal Hormone-Receptor Positive and Her2 Negative Breast Cancer	Active, not recruiting	University of Alabama at Birmingham	Phase 1/Phase 2	2016-02-01	This study will test how well a new combination of three drugs (Letrozole, Everolimus, and TRC105) is tolerated and how well it works in Stage 2 and 3 breast cancer when given prior to definitive surgery. Letrozole blocks the estrogen receptor expressed by many breast cancers while everolimus blocks signals that drive cancer cells to grow. TRC105 is an investigational drug that blocks the formation and growth of blood vessels that feed the cancer and promote its growth. The goal of this study is to investigate the safety and efficacy of this multitargeted approach in breast cancer.

All Clinical Trials for letrozole

Trial ID	Title	Status	Sponsor	Phase	Start Date	Summary
NCT00001521 ↗	Three Drug Combination Therapy Versus Conventional Treatment of Children With Congenital Adrenal Hyperplasia	Active, not recruiting	Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD)	Phase 2	1995-06-08	This study was developed to determine if a combination of four drugs (flutamide, testolactone, reduced hydrocortisone dose, and fludrocortisone) can normalize growth in children with congenital adrenal hyperplasia. The study will take 60 children, boys and girls and divide them into 2 groups based on the medications given. Group one will receive the new four- drug combination. Group two will receive the standard treatment for congenital adrenal hyperplasia (hydrocortisone and fludrocortisone). The boys in group one will take the medication until the age of 14 at which time they will stop taking the four drug combination and begin receiving the standard treatment for congenital adrenal hyperplasia. Girls in group one will take the four drug combination until the age of 13, at which time they will stop and begin receiving the standard treatment for congenital adrenal hyperplasia plus flutamide. Flutamide will be given to the girls until six months after their first menstrual period. All of the children will be followed until they reach their final adult height. The effectiveness of the treatment will be determined by measuring the patient's adult height, body mass index, and bone density. ...
NCT00003140 ↗	Letrozole After Tamoxifen in Treating Women With Breast Cancer	Completed	Cancer and Leukemia Group B	Phase 3	1998-08-24	RATIONALE: Estrogen can stimulate the growth of breast cancer cells. Hormone therapy using letrozole may fight breast cancer by reducing the production of estrogen. PURPOSE: This randomized phase III trial is studying letrozole to see how well it works in treating women with breast cancer who have received tamoxifen for at least 5 years.
NCT00003140 ↗	Letrozole After Tamoxifen in Treating Women With Breast Cancer	Completed	Eastern Cooperative Oncology Group	Phase 3	1998-08-24	RATIONALE: Estrogen can stimulate the growth of breast cancer cells. Hormone therapy using letrozole may fight breast cancer by reducing the production of estrogen. PURPOSE: This randomized phase III trial is studying letrozole to see how well it works in treating women with breast cancer who have received tamoxifen for at least 5 years.
NCT00003140 ↗	Letrozole After Tamoxifen in Treating Women With Breast Cancer	Completed	European Organisation for Research and Treatment of Cancer - EORTC	Phase 3	1998-08-24	RATIONALE: Estrogen can stimulate the growth of breast cancer cells. Hormone therapy using letrozole may fight breast cancer by reducing the production of estrogen. PURPOSE: This randomized phase III trial is studying letrozole to see how well it works in treating women with breast cancer who have received tamoxifen for at least 5 years.
NCT00003140 ↗	Letrozole After Tamoxifen in Treating Women With Breast Cancer	Completed	International Breast Cancer Study Group	Phase 3	1998-08-24	RATIONALE: Estrogen can stimulate the growth of breast cancer cells. Hormone therapy using letrozole may fight breast cancer by reducing the production of estrogen. PURPOSE: This randomized phase III trial is studying letrozole to see how well it works in treating women with breast cancer who have received tamoxifen for at least 5 years.
NCT00003140 ↗	Letrozole After Tamoxifen in Treating Women With Breast Cancer	Completed	National Cancer Institute (NCI)	Phase 3	1998-08-24	RATIONALE: Estrogen can stimulate the growth of breast cancer cells. Hormone therapy using letrozole may fight breast cancer by reducing the production of estrogen. PURPOSE: This randomized phase III trial is studying letrozole to see how well it works in treating women with breast cancer who have received tamoxifen for at least 5 years.
NCT00003140 ↗	Letrozole After Tamoxifen in Treating Women With Breast Cancer	Completed	North Central Cancer Treatment Group	Phase 3	1998-08-24	RATIONALE: Estrogen can stimulate the growth of breast cancer cells. Hormone therapy using letrozole may fight breast cancer by reducing the production of estrogen. PURPOSE: This randomized phase III trial is studying letrozole to see how well it works in treating women with breast cancer who have received tamoxifen for at least 5 years.

Clinical Trial Conditions for letrozole

Condition Name

Condition Name for letrozole
Intervention	Trials
Breast Cancer	234
Metastatic Breast Cancer	43
Infertility	36
Breast Neoplasms	33

Condition MeSH

Condition MeSH for letrozole
Intervention	Trials
Breast Neoplasms	414
Infertility	55
Polycystic Ovary Syndrome	52
Carcinoma	28

Clinical Trial Locations for letrozole

Trials by Country

Trials by Country for letrozole
Location	Trials
Italy	371
Spain	265
China	248
Canada	175
Japan	143

Trials by US State

Trials by US State for letrozole
Location	Trials
California	102
Texas	101
Florida	80
New York	75
Massachusetts	75

Clinical Trial Progress for letrozole

Clinical Trial Phase

Clinical Trial Phase for letrozole
Clinical Trial Phase	Trials
PHASE4	3
PHASE3	20
PHASE2	24

Clinical Trial Status

Clinical Trial Status for letrozole
Clinical Trial Phase	Trials
Completed	222
Recruiting	159
Active, not recruiting	78

Clinical Trial Sponsors for letrozole

Sponsor Name

Sponsor Name for letrozole
Sponsor	Trials
Novartis Pharmaceuticals	62
National Cancer Institute (NCI)	61
Pfizer	42

Sponsor Type

Sponsor Type for letrozole
Sponsor	Trials
Other	734
Industry	323
NIH	74

Letrozole (Femara and Generics) Clinical Trials Update, Market Analysis and Patent-Driven Projection

Last updated: May 21, 2026

Letrozole is an established oral aromatase inhibitor (AI) used for hormone receptor-positive (HR+) early breast cancer and metastatic breast cancer in postmenopausal women. Commercially, the drug is mature and largely generic outside of brand-specific periods. In parallel, clinical activity and label expansions have shifted toward guideline-aligned combination strategies, neoadjuvant/adjuvant sequencing refinements, and real-world evidence rather than novel monotherapy IP.

What clinical trials are evaluating letrozole in 2024–2026?

Letrozole’s current clinical-trials footprint is dominated by:

• Combination regimens (with CDK4/6 inhibitors, SERDs, PI3K pathway agents, endocrine partners, or targeted agents) in HR+/HER2- disease and selected HR+ HER2+ settings.
• Neoadjuvant and perioperative strategies aimed at improving pathologic complete response rates or surrogate endpoints such as Ki-67 suppression.
• Biomarker-enriched studies (ESR1 mutations, ESR2 expression, PIK3CA alterations) to identify populations most likely to benefit from continued AI sensitivity.
• Comparative and adherence-focused studies addressing switching between endocrine agents, tolerability management, and dosing schedules.

Which trial types are most common for letrozole?

• Neoadjuvant endocrine therapy: letrozole as a baseline AI arm in “endocrine responsiveness” designs.
• Adjuvant sequencing trials: AI placement relative to surgery, ovarian suppression (OS) in select populations, or steroid suppression strategies where applicable.
• First-line metastatic studies: letrozole-based combinations, typically HR+/HER2-.
• Real-world and registry analyses: patterns of use, discontinuation reasons, and persistence in routine practice.

Where are the key development signals?

• Endocrine resistance stratification: trials increasingly stratify by ESR1 status and prior AI exposure, reflecting clinical practice.
• Treatment duration and switching: studies focus on time-to-switch triggers, adverse event management (bone health, arthralgia), and adherence.

How does letrozole market size and sales performance look globally by 2024?

Letrozole sits in the mature endocrine segment. The market is heavily impacted by:

• Broad generic availability across major geographies.
• Ongoing brand-to-generic substitution dynamics for Femara (brand) and its competitors.
• Indication mix: early-stage adjuvant use is stable but price is pressured; metastatic lines contribute episodic variability.

Market structure

• United States: generic penetration is high; brand revenue is largely residual and discount-driven.
• Europe: similar pattern with local price controls and competition from multiple generic manufacturers.
• Japan and select APAC markets: brand availability and reimbursement structures influence share, but generics tend to dominate over time.

Commercial drivers

• Incidence of HR+ breast cancer and adjuvant endocrine uptake.
• Guideline durability of AI-first strategy in postmenopausal patients.
• Bone health co-management (calcium/vitamin D, bisphosphonates/denosumab), which reduces discontinuation risk and supports persistence.

What is the price and reimbursement trajectory for letrozole as generics expand?

With mature patent status, the direction is typically:

• Continued erosion of average selling price (ASP) in markets where additional entrants launch.
• Shift from brand-led marketing to pharmacy-driven purchasing of generics.
• Pharmacy benefit design in the US (tiering, preferred generic lists) compresses pricing but can sustain volume.

What does “volume vs ASP” imply for revenue?

• Revenue growth is less likely from price and more likely from stable or rising treated patient volumes.
• In metastatic populations, use depends on sequencing against other AIs and SERDs, influencing short-cycle demand.

When does letrozole lose exclusivity, and what patents still matter?

Letrozole is a long-established active ingredient. For most planning purposes, the material question is not primary ingredient exclusivity but:

• formulation-specific or line-extension IP (rare at this point for a widely genericized API),
• method-of-use claims tied to specific dosing schedules, populations, or combinations (where enforceable),
• any remaining brand-protecting patents in specific jurisdictions.

Practical exclusivity reality

• Generic competition is already the dominant commercial state in the US and most EU markets.
• Any remaining barriers tend to be either:
  • weak in enforceability because of long passage of time and obviousness/anticipation challenges, or
  • narrow in scope and limited to specific formulation attributes (e.g., controlled release) or niche prescribing constraints.

What is the Orange Book status of letrozole in the United States?

Letrozole has longstanding generic listings in the FDA’s Orange Book for the relevant strengths and dosage forms. In a market where the active ingredient is widely generic, the Orange Book typically shows:

• a legacy brand reference (historically Femara),
• multiple generic ANDA products referencing the brand,
• patent lists that are often expired or close to expiry, with residual listed patents that may not block generic entry unless they remain enforceable and properly asserted.

How does letrozole compare with anastrozole and exemestane on efficacy, safety, and market risk?

Letrozole competes within the class of non-steroidal AIs (anastrozole) and steroidal AI (exemestane). Clinically, efficacy differences are modest across established adjuvant and metastatic settings. Market implications are driven by:

• generic pricing parity,
• switching patterns under tolerability,
• patient-specific adverse event profiles (arthralgia, bone density changes).

Key competitive distinctions

• All AIs carry class risks for bone mineral density loss, requiring monitoring and supportive care.
• Treatment choice often shifts based on tolerability and prior response.

What generic entry risks exist for letrozole, and how do Paragraph IV challenges affect pricing?

Given that letrozole is already widely genericized, new Paragraph IV opportunities are typically limited. When they occur, they mainly:

• accelerate additional generic entrants,
• compress ASP further in the affected strength/dosage and territory,
• create short-term supply and rebate shifts rather than meaningfully alter long-term penetration.

What litigations are most relevant for letrozole?

In a mature product, litigation tends to be:

• infrequent,
• usually tied to narrow, remaining patents,
• or settled through licensing/at-risk supply provisions.

How strong is the patent estate for letrozole today?

For investment and licensing, the patent estate strength is generally categorized as:

• low at the API level because the core compound era has long expired,
• mixed to weak in formulation/method-of-use space for a market that has sustained generic competition for years.

What does that mean for dealmaking?

• New licensing centered on broad exclusivity is unlikely to be compelling.
• Deals, if any, typically focus on narrow IP around a specific product configuration or combination regimen rather than letrozole alone.

What clinical endpoints have mattered for letrozole trials?

Across endocrine therapy studies, endpoints commonly include:

• Ki-67 suppression (neoadjuvant endocrine responsiveness),
• disease-free survival (DFS) and overall survival (OS) in adjuvant settings,
• objective response rate (ORR), clinical benefit rate (CBR), progression-free survival (PFS) in metastatic settings,
• safety and tolerability (bone-related events, arthralgia, discontinuation rates).

What is the likely market projection for letrozole through 2030?

Base case: revenue growth is modest and primarily volume-driven with continued price pressure.
Bear case: incremental substitution toward other endocrine options and evolving sequencing (including SERDs and targeted combinations) reduces AI monotherapy share in some subsegments.
Bull case: stable early-stage adjuvant use plus sustained guideline preference for AI-first strategies in postmenopausal populations supports volume.

Projection mechanics

Letrozole demand is mainly a function of:

• treated HR+ early breast cancer prevalence,
• metastatic endocrine sequencing patterns,
• adherence and persistence influenced by tolerability and bone-health management,
• generic supply stability.

How much of letrozole demand is “substitutable”?

• High substitutability exists within AIs (anastrozole and exemestane) because clinical efficacy is similar and pricing is compressed.
• Substitutability is lower when prescribers maintain patient-specific regimen continuity due to prior tolerability.

2030 direction

• Expect continued ASP erosion or stabilization at low levels depending on market entry waves and pharmacy contracting.
• Expect limited upside from new clinical indications unless a meaningful label expansion occurs that increases treated populations or restores branded differentiation, which is unlikely in a generic-dominant landscape.

Key Takeaways

• Letrozole is in a mature phase: generic-led pricing, stable but price-pressured demand, and clinical activity focused on combination strategies, sequencing optimization, and biomarker-enriched endocrine resistance designs.
• Market projection through 2030 trends toward low-growth revenue driven by volume rather than price, with substitution among AIs limiting share gains.
• Patent-driven upside is limited at the API level; any remaining enforceable exclusivity is likely narrow and not a broad barrier to generic competition.

FAQs

1. Are any new letrozole indications under FDA review?
2. Do ESR1 mutations change how clinicians use letrozole in metastatic disease?
3. How do CDK4/6 inhibitor combinations compare with AI monotherapy when letrozole is used first-line?
4. What is the bone health monitoring standard for patients on long-term letrozole?
5. Which generic manufacturers compete most strongly for letrozole in the US?

References

1. FDA. Orange Book: Approved Drug Products with Therapeutic Equivalence Evaluations. (Accessed 2026-05-21).
2. ClinicalTrials.gov. Search results for letrozole (last accessed 2026-05-21).
3. NCCN Clinical Practice Guidelines in Oncology: Breast Cancer. (Most recent version).
4. ESMO Clinical Practice Guidelines. (Most recent version).