Pemetrexed is a drug that belongs to a class of molecules termed folate antimetabolites and is used in the treatment of aggressive and late stage cancers. Pemetrexed inhibits three enzymes involved in the folate pathway: thymidylate synthase (TS), dihydrofolate reductase (DHFR), and glycinamide ribonucleotide formyltransferase (GARFT).
These enzymes are involved in purine and pyrimidine synthesis, molecules essential for DNA and RNA synthesis. Pemetrexed is approved for single use or in combination with cisplatin in non-squamous non-small cell lung cancer (NSCLC) and mesothelioma.
It is currently being tested for efficacy against other solid tumor types. Pemetrexed is considered to be a prodrug, meaning it is administered as an inactive form and converted to its active form inside the body. In order to ameliorate the side effects of this drug, folic acid and vitamin B12 are often supplemented with pemetrexed treatment.
Pemetrexed became FDA approved under the trade name Alimta in 2004 for malignant pleural mesothelioma in combination with cisplatin for inoperable tumors, in 2008 for advanced or metastatic non-squamous non-small cell lung cancer (NSCLC) in combination with cisplatin, and in 2009 for NSCLC tumors unresponsive to four cycles of platinum-based chemotherapy. This drug is manufactured through large-scale synthetic organic chemistry methods starting with abundant, commercially available precursors.