Exemestane

Hormone receptor-positive breast cancer is the main subtype of breast cancer in postmenopausal women, accounting for approximately 60% to 70% of all breast cancer cases. The growth of this type of tumor is highly dependent on the continuous stimulation of estrogen. As a third-generation aromatase inactivator, exemestane can irreversibly bind to the substrate binding site of aromatase to permanently block the catalytic activity of the enzyme, thereby significantly reducing the estrogen level in postmenopausal women and achieving the effect of inhibiting tumor growth. In clinical practice, it is mainly used for postmenopausal patients with advanced breast cancer whose disease progresses after adjuvant treatment with tamoxifen, and can also be used as a subsequent intensive adjuvant treatment regimen for patients with early-stage hormone receptor-positive breast cancer, which can significantly reduce the risk of postoperative recurrence, especially suitable for people who are intolerant to non-steroidal aromatase inhibitors.

At present, the global market size of exemestane is stable at around 1.2 billion US dollars, with a compound annual growth rate maintained at a steady level of 2.3%. The growth momentum mainly comes from the expansion of adjuvant treatment demand driven by the increased penetration rate of breast cancer screening in emerging markets. In terms of the domestic market, the annual sales of exemestane at the terminal of public medical institutions are approximately 1.1 billion yuan. After it was included in the National Medical Insurance Catalog in 2017, its clinical accessibility has been greatly improved, and the market share of generic drugs has exceeded 85%. At present, more than 15 domestic enterprises have obtained the approval documents for exemestane preparations, and the supply of API has basically achieved domestic substitution, with only a small number of high-end preparations still using imported API.

The original developer of exemestane is Pfizer, with the original brand name "Aromasin". The core compound patent of the original drug expired in the United States in 2016, and the Chinese compound patent expired in 2014. The main dosage form approved for the original drug is tablet, with a specification of 25mg. It has been included in the *Catalogue of Reference Preparations of Chemical Drugs* of China, and is also a reference preparation announced by the FDA. At present, nearly 20 domestic enterprises have completed the registration of exemestane API in CDE and obtained the A status label, and more than 20 exemestane preparation varieties have obtained domestic marketing approval. (Data as of September 2024, please refer to the official website of CDE for the latest information)

In response to the demand for impurity research in the process of R&D and quality control of generic exemestane, CATO can provide a full set of impurity reference standards for this API. Most of the products are in stock. Orders for in-stock products placed before 16:00 will be shipped on the same day. All reference standards meet the requirements of multiple regulatory systems such as Chinese Pharmacopoeia and FDA, and can fully meet the compliance needs of various R&D scenarios such as structural confirmation, content calibration and stability study.