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Letrozole | CAS No: 112809-51-5 | GMP-certified suppliers
A medication that treats hormone receptor–positive early, advanced, and metastatic breast cancer in women, including use alongside ribociclib for HR‑positive, HER2‑negative advanced disease.
Therapeutic categories
Primary indications
- 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
Product Snapshot
- Letrozole is an oral small‑molecule formulation supplied primarily as tablets
- It is used for HR‑positive early, advanced, and metastatic breast cancer, including use in combination regimens for HR+/HER2‑ disease
- It is approved in the US and Canada, with both approved and investigational statuses noted across submissions
Clinical Overview
Letrozole suppresses estrogen biosynthesis by competitively inhibiting CYP19A1 aromatase. Blocking the enzyme’s active site and associated electron transfer halts the conversion of androgens to estrogens. In postmenopausal women, this pathway provides most endogenous estrogen; its inhibition leads to reduced estrogen availability and regression of estrogen‑dependent tumors. Unlike earlier aromatase inhibitors, third‑generation agents such as letrozole have minimal impact on cortisol, aldosterone, or thyroxine synthesis.
Pharmacodynamically, sustained aromatase inhibition produces measurable decreases in estrogen levels and increases in luteinizing hormone. Letrozole exhibits a long elimination half‑life, reported at more than 42 hours in breast cancer patients, supporting once‑daily oral dosing.
Absorption is rapid and extensive, and the compound is a substrate for CYP3A4, CYP2A6, CYP2C19, P‑glycoprotein, and UGT2B7, indicating the potential for metabolic and transporter‑based interactions. Distribution and excretion characteristics vary, but metabolism through hepatic oxidative pathways is the dominant route.
Safety considerations include risks of interstitial lung disease, pneumonitis, QT prolongation, elevated liver enzymes, neutropenia, and embryo‑fetal toxicity. Monitoring strategies typically focus on hepatic parameters, cardiovascular risk factors, and symptoms of pulmonary toxicity.
Commonly recognized brand formulations include oral tablets for systemic therapy. For API procurement, sourcing teams should prioritize suppliers with demonstrated control of stereochemical purity, residual solvent limits, and consistent particle‑size distribution, supported by full regulatory documentation and batch traceability.
Identification & chemistry
| Generic name | Letrozole |
|---|---|
| Molecule type | Small molecule |
| CAS | 112809-51-5 |
| UNII | 7LKK855W8I |
| DrugBank ID | DB01006 |
Pharmacology
| Summary | Letrozole is a non‑steroidal, type II aromatase inhibitor that competitively blocks CYP19A1, preventing the conversion of androgens to estrogens. This suppression of estrogen synthesis reduces signaling in estrogen‑dependent tissues and tumors. As a third‑generation inhibitor, its activity is selective for aromatase without significant effects on other major steroidogenic pathways. |
|---|---|
| Mechanism of action | 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. |
| Pharmacodynamics | Letrozole is an aromatase inhibitor used in the treatment of breast cancer. Aromatase inhibitors work by inhibiting the action of the enzyme aromatase, which converts androgens into estrogens by a process called aromatization. As breast tissue is stimulated by estrogens, decreasing their production is a way of suppressing recurrence of the breast tumor tissue. Letrozole is a third generation type II aromatase inhibitor used to treat estrogen dependant breast cancers.It has a long duration of action as it has a half life of over 42 hours in breast cancer patients.Patients should be counselled regarding the risk of interstitial lung disease, pneumonitis, QT prolongation, elevated transaminase levels, neutropenia, and embryo-fetal toxicity. |
Targets
| Target | Organism | Actions |
|---|---|---|
| Cytochrome P450 19A1 | Humans | antagonist |
ADME / PK
| Absorption | Letrozole is 99.9% orally bioavailable.A 2.5mg oral dose reaches a C<sub>max</sub> of 104nmol/L with a T<sub>max</sub> of 8.10h, and an AUC of 7387nmol\*h/L. |
|---|---|
| Half-life | The terminal elimination half life of letrozole is approximately 42h in healthy volunteers, but longer in breast cancer patients. |
| Protein binding | Letrozole is 60% bound to proteins.55% is bound to albumin. |
| Metabolism | Letrozole is metabolized by CYP2A6 to a ketone analog metabolite, which is further metabolized by CYP3A4 and CYP2A6 to 4,4'-(hydroxymethylene)dibenzonitrile.4,4'-(hydroxymethylene)dibenzonitrile is glucuronidated by UGT2B7. |
| Route of elimination | Letrozole is 90% eliminated in the urine.75% of the dose is recovered as a glucuronide metabolite, 9% is in the form of the ketone and carbinol metabolites, and 6% is recovered in urine as unchanged letrozole. |
| Volume of distribution | The volume of distribution of letrozole is 1.87L/kg. |
| Clearance | The average clearance after a single dose of letrozole was 1.52L/h and at steady state was 1.20L/h. |
Formulation & handling
- Oral small‑molecule with low aqueous solubility, typically formulated as film‑coated tablets to aid manufacturability and content uniformity.
- Absorption is not food‑dependent in extent, though food may slow uptake, so formulations do not require specialized release profiles for food effects.
- Solid‑state stability is good; handling focuses on controlling dust and ensuring uniform dispersion due to low solubility and moderate lipophilicity.
Regulatory status
| Lifecycle | Key U.S. patents for the API extend protection into 2030–2031, indicating the product remains in a mid‑to‑late exclusivity phase. With commercialization in the United States and Canada, the market is still largely protected but approaching eventual generic entry as later patents expire. |
|---|
| Markets | Canada, US |
|---|
Supply Chain
| Supply chain summary | Letrozole’s supply landscape includes an originator manufacturer alongside multiple generic producers and packagers that support broad commercial distribution. Branded and generic products are established in North American markets, with evidence of multiple brand variants in Canada and the United States. Core substance patents have expired, and remaining later‑dated U.S. patents indicate formulation or secondary protections, consistent with an environment of existing generic competition. |
|---|
Safety
| Toxicity | Overdose data in humans is not readily available, however 1 reported case was not associated with serious adverse reactions.Animal studies do not report serious adverse effects with high dose treatment.Patients experiencing and overdose should be treated with symptomatic and supportive measures. Oral doses over 2000mg/kg were associated with reduced motor activity, ataxia, dyspnea, and death in mice and rats. |
|---|
- High oral doses (›2000 mg/kg) in rodents produced reduced motor activity, ataxia, respiratory distress, and mortality, indicating dose‑dependent CNS and respiratory toxicity
- Limited human overdose information is available
- Existing reports and animal data suggest low acute toxicity at moderate exposures
Letrozole is a type of Aromatase inhibitors
Aromatase inhibitors (AIs) are a subcategory of pharmaceutical active pharmaceutical ingredients (APIs) commonly used in the treatment of hormone-sensitive conditions, including breast cancer and endometriosis. These compounds work by blocking the enzyme aromatase, which is responsible for the conversion of androgens into estrogens in peripheral tissues.
AIs are classified into two main types: steroidal and non-steroidal inhibitors. Steroidal AIs, such as exemestane, bind irreversibly to aromatase, while non-steroidal AIs, such as anastrozole and letrozole, inhibit aromatase activity reversibly. Both types effectively reduce estrogen levels, which is beneficial in hormone-driven cancers where estrogen promotes tumor growth.
The use of AIs in breast cancer treatment has significantly improved patient outcomes, particularly in postmenopausal women. By suppressing estrogen production, AIs prevent estrogen from fueling the growth of estrogen receptor-positive breast cancer cells. They are often prescribed as adjuvant therapy after surgery or as a first-line treatment for metastatic breast cancer.
Apart from their application in breast cancer, AIs have also shown efficacy in managing endometriosis, a painful condition where endometrial tissue grows outside the uterus. By reducing estrogen levels, AIs help alleviate symptoms and inhibit the growth of endometrial lesions.
Overall, aromatase inhibitors are vital components of modern pharmaceutical therapies targeting hormone-related diseases. Their ability to modulate estrogen levels through enzymatic inhibition has revolutionized the treatment landscape for breast cancer and endometriosis, improving patient prognosis and quality of life.
Letrozole (Aromatase inhibitors), classified under Hormonal Agents
Hormonal agents are a prominent category of pharmaceutical active pharmaceutical ingredients (APIs) widely used in the medical field. These substances play a crucial role in regulating and modulating hormonal functions within the body. Hormonal agents are designed to mimic or manipulate the effects of naturally occurring hormones, allowing healthcare professionals to treat various endocrine disorders and hormonal imbalances.
Hormonal agents are commonly employed in the treatment of conditions such as hypothyroidism, hyperthyroidism, diabetes, and hormonal cancers. These APIs work by interacting with specific hormone receptors, either by stimulating or inhibiting their activity, to restore the balance of hormones in the body. They can be administered orally, intravenously, or through other routes depending on the specific medication and patient needs.
Pharmaceutical companies employ rigorous manufacturing processes and quality control measures to ensure the purity, potency, and safety of hormonal agent APIs. These APIs are synthesized using chemical or biotechnological methods, often starting from natural hormone sources or through recombinant DNA technology. Stringent regulatory guidelines are in place to guarantee the efficacy and safety of hormonal agent APIs, ensuring that patients receive high-quality medications.
As the demand for hormone-related therapies continues to grow, ongoing research and development efforts focus on enhancing the effectiveness and reducing the side effects of hormonal agent APIs. This includes the exploration of novel delivery systems, advanced formulations, and targeted drug delivery methods. By continuously advancing our understanding and capabilities in hormonal agents, the medical community can improve patient outcomes and quality of life for individuals with hormonal disorders.
Letrozole API manufacturers & distributors
Compare qualified Letrozole API suppliers worldwide. We currently have 19 companies offering Letrozole API, with manufacturing taking place in 5 different countries. Use the table below to review supplier type, countries of origin, certifications, product portfolio and GMP audit availability.
| Supplier | Type | Country | Product origin | Certifications | Portfolio |
|---|---|---|---|---|---|
| Actavis Group | Producer | Iceland | Unknown | CoA, USDMF | 7 products |
| ALCAMI | Producer | United States | United States | CoA, USDMF | 5 products |
| Cipla | Producer | India | India | CEP, CoA, FDA, GMP, USDMF, WC | 164 products |
| Fujian South Pharma | Producer | China | China | CoA, WC | 7 products |
| Global Pharma Tek | Distributor | India | India | BSE/TSE, CoA, FDA, GMP, ISO9001, MSDS | 484 products |
| Hetero Labs | Producer | India | India | CEP, CoA, FDA, GMP, JDMF, USDMF, WC | 90 products |
| Humble Healthcaare | Producer | India | India | CoA | 30 products |
| Ind-Swift Labs. | Producer | India | India | CEP, CoA, FDA, GMP, JDMF, USDMF, WC | 27 products |
| LGM Pharma | Distributor | United States | World | BSE/TSE, CEP, CoA, GMP, MSDS, USDMF | 441 products |
| Mac Chem Products | Producer | India | India | CEP, CoA, FDA, GMP, USDMF, WC | 25 products |
| Mylan | Producer | India | India | CEP, CoA, USDMF, WC | 201 products |
| Natco Pharma | Producer | India | India | CEP, CoA, FDA, GMP, JDMF, USDMF, WC | 40 products |
| SEDANAH | Distributor | Jordan | World | CoA, GMP | 70 products |
| SETV Global | Producer | India | India | CoA, FDA, GMP | 515 products |
| Shilpa Medicare Ltd | Producer | India | India | BSE/TSE, CEP, CoA, GMP, ISO9001, MSDS, USDMF, WC | 54 products |
| Sinoway industrial Co.,Lt... | Distributor | China | China | CoA, GMP, ISO9001, MSDS, USDMF | 757 products |
| Sun Pharma | Producer | India | India | CEP, CoA, GMP, USDMF, WC | 219 products |
| USV | Producer | India | India | CoA, FDA, GMP, USDMF, WC | 35 products |
| Zhejiang Hisun Pharma | Producer | China | China | CoA, USDMF, WC | 69 products |
When sending a request, specify which Letrozole API quality you need: for example EP (Ph. Eur.), USP, JP, BP, or another pharmacopoeial standard, as well as the required grade (base, salt, micronised, specific purity, etc.).
Use the list above to find high-quality Letrozole API suppliers. For example, you can select GMP, FDA or ISO certified suppliers. Visit our help page to learn more about sourcing APIs via Pharmaoffer.
Frequently asked questions about Letrozole API
Sourcing
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Technical
What is Letrozole (CAS 112809-51-5) used for?
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How does Letrozole work?
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Is Letrozole a small molecule?
Are there special stability concerns for oral Letrozole?
Regulatory
Where is Letrozole approved or in use globally?
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Pharmaoffer
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