NCIt definition : A synthetic pyrimidine-based antifolate. Pemetrexed binds to and inhibits the enzyme
thymidylate synthase (TS), which catalyses the methylation of 2'-deoxyuridine-5'-monophosphate
(dUMP) to 2'-deoxythymidine-5'-monophosphate (dTMP), an essential precursor in DNA
synthesis.;