To which drug class does methotrexate belong?

Methotrexate is a folic acid antagonist antineoplastic agent. It is primarily used to treat various types of acute leukemia—particularly acute lymphoblastic leukemia and malignant lymphoma—and also demonstrates therapeutic efficacy against several solid tumors, including lung cancer, breast cancer, and cervical cancer. However, this drug may cause adverse reactions, such as nausea, vomiting, abdominal pain, and diarrhea.