Pemetrexed, a multitargeted antifolate cytotoxic chemotherapy agent, which inhibits at least three target enzymes in the folate pathway (thymidylate synthase, dihydrofolate reductase, and glycinamide ribonucleotide formyl transferase), is approved as standard second-line treatment for advanced NSCLC [11,12]. The gene discussed is TYMS; the disease is non-small cell lung carcinoma.