Flucytosine

Invasive fungal infection is a major inducing factor for the persistently high mortality rate in immunocompromised populations. As a pyrimidine antifungal drug, flucytosine exerts a selective antibacterial effect by inhibiting fungal nucleic acid synthesis, and is only sensitive to Cryptococcus, Candida and some dematiaceous fungi. It is mostly used clinically in combination with amphotericin B as the first-line treatment for cryptococcal meningitis and disseminated candidiasis, and is especially suitable for patients with immunodeficiency caused by AIDS, post-organ transplantation, long-term use of glucocorticoids, etc. Its characteristic of being prone to drug resistance when used alone also determines its core clinical positioning of combined medication.

The global market size of antifungal drugs has exceeded USD 17 billion in 2024, among which systemic antifungal drugs account for more than 65%. As a basic drug for antifungal combination therapy, the market size of flucytosine maintains a steady annual growth rate of about 4%, and its domestic sales in 2023 were approximately RMB 230 million. At present, the global API supply is dominated by manufacturers from China and India. Multiple domestic generic drug preparations have been approved, and it was included in the local list of drugs in shortage for monitoring in 2022, so the stability of clinical supply still needs to be guaranteed by upstream production capacity.

The original developer of flucytosine is Merck Sharp & Dohme, with the original brand name Ancobon, and its core compound patent in the United States expired as early as 1972. The dosage form approved for the original drug is oral tablet, with specifications of 250mg and 500mg, and it has been included in the FDA Reference Listed Drug Catalog. There is no imported original preparation approved in China yet. In terms of API registration, 8 domestic enterprises have obtained A-status registration numbers, and another 2 enterprises have registrations in I-status. Domestic preparations of two dosage forms, tablets and injections, have been approved for marketing. (Data as of May 2025, please refer to the official website of CDE for the latest information)

CATO provides a full set of impurity reference standards for flucytosine API, covering all relevant impurities and degradation products that may be generated during the synthesis process. Most of the products are in stock. For in-stock products, orders placed before 16:00 will be shipped on the same day. They fully comply with the regulatory requirements of the Chinese Pharmacopoeia, FDA and other regulations, and can directly support the full-process requirements of API quality research, stability investigation and registration declaration.