Used primarily in chemotherapy, this compound is effective in treating non-small cell lung cancer and malignant pleural mesothelioma. It works by inhibiting multiple enzymes involved in folate metabolism, which are essential for DNA and RNA synthesis in rapidly dividing cancer cells. Administered intravenously, it is often combined with platinum-based agents to enhance therapeutic efficacy. Its use requires supplementation with folic acid and vitamin B12 to reduce toxicity and improve tolerability. Due to its mechanism, it selectively targets tumor cells with high metabolic demands, making it a valuable option in oncology for both first-line and maintenance therapy.