Pemetrexed is a new generation of anti-metabolic anticancer drug developed by Eli Lilly and Company, first approved by the U.S. Food and Drug Administration (FDA) in February 2004 for the treatment of malignant pleural mesothelioma, and then approved for the treatment of advanced non-small cell lung cancer, the English trade name Alimta®, Chinese trade name Libitai. Pemetrexed is a multi-targeted anti-cancer drug that acts on several key enzymes in the folate metabolism pathway, which can significantly affect DNA synthesis and cancer growth in cancer cells. Therefore, theoretically, pemetrexed should have a significant inhibitory effect on cancer and may be effective in treating multiple cancers. In fact, this is exactly what happened. Pemetrexed was first approved for the treatment of advanced pleural mesothelioma, a tumor with a high degree of malignancy, rapid progression, and poor efficacy against multiple therapies including radiotherapy, in which pemetrexed has shown positive efficacy. A large international multicenter phase III clinical study found that the combination of pemetrexed with cisplatin chemotherapy for inoperable pleural mesothelioma further improved the efficacy and prolonged survival of patients. Similarly, for patients with advanced non-small cell lung cancer, the efficacy of pemetrexed after failure of first-line chemotherapy is not inferior to that of the currently used doxorubicin, and some side effects are lower than those of the latter, as also concluded from a large-scale phase III clinical study in recent years. In fact, pemetrexed has also shown some efficacy in the treatment of a variety of malignancies, such as gastric cancer, breast cancer, pancreatic cancer, etc. Even in lung cancer and mesothelioma, the range of patients for whom it is indicated is expanding. As research progresses, it is believed that the scope of pemetrexed will be further expanded. Compared with many chemotherapeutic drugs, the side effects of pemetrexed are mild, mainly in the decrease of white blood cells, diarrhea, rash, mucositis, etc. Moreover, with the adoption of some preventive and therapeutic measures, such as the use of vitamins, folic acid and hormones, the incidence and severity of many side effects have significantly decreased, making pemetrexed safer for clinical use. In addition, medical doctors are exploring what kind of patients are more suitable for the use of pemetrexed. Preliminary results have shown that some genetic or protein differences can influence the therapeutic effects and side effects of pemetrexed, and it is believed that these results can also be applied to individualize patient treatment in the future. For example, by testing certain indicators in the same patients with advanced lung cancer who have failed first-line chemotherapy, doctors can predict which patients are more suitable for pemetrexed and which patients are more suitable for doxorubicin, or more suitable for targeted therapies such as eresart.