A folate analogue inhibitor of dihydrofolate reductase (DHFR) exhibiting high affinity for reduced folate carrier-1 (RFC-1) with antineoplastic and immunosuppressive activities. Pralatrexate selectively enters cells expressing RFC-1; intracellularly, this agent is highly polyglutamylated and competes for the folate binding site of DHFR, blocking tetrahydrofolate synthesis, which may result in depletion of nucleotide precursors; inhibition of DNA, RNA and protein synthesis; and apoptotic tumor cell death. Efficient intracellular polyglutamylation of pralatrexate results in higher intracellular concentrations compared to non-polyglutamylated pralatrexate, which is more readily effuxed by the MRP (multidrug resistance protein) drug efflux pump. RFC-1, an oncofetal protein expressed at highest levels during embryonic development, may be overexpressed on the cell surfaces of various cancer cell types. or A drug used in the treatment of peripheral T-cell lymphoma (a fast-growing form of non-Hodgkin lymphoma). It is also being studied in the treatment of other types of cancer. Pralatrexate may block the growth of cancer cells and cause them to die. It is a type of dihydrofolate reductase (DHFR) inhibitor. Also called FOLOTYN.