Aminopterin

Aminopterin, a 4-amino derivative of folic acid (folic acid analogue) and a derivative of pterin with the molecular formula: C19H20N8O5. It is very similar in structure to methotrexate.

Aminopterin is actively transported into cells by the folate transporter. In the cell, it is converted by folyl polyglutamate synthase into a high molecular weight polyglutamate metabolite, which in turn binds to dihydrofolate reductase (DHFR) and inhibits its activity. Aminopterin polyglutamate is broken down intracellularly by γ-glutamyl hydrolase.

Aminopterin shows chemotherapeutic and immunosuppressive activities. Aminopterin was one of the first compounds to successfully induce remission in childhood leukemia and has been used clinically in the treatment of rheumatoid arthritis. However, the chemotherapeutic agent has since been replaced by methotrexate.