Pemetrexed belongs to the ‘folate antimetabolites’ class of chemotherapy agents, and it inhibits cell replication and tumor growth by inhibiting the activity of three enzymes involved in purine and pyrimidine synthesis: thymidylate synthase (TYMS), dihydrofolate reductase (DHFR) and glycinamide ribonucleotide formyl-transferase (GARFT) (37). Here, TYMS is linked to neoplasm.