Peripheral T-cell lymphomas (PTCL) represent about 12%–15% of non-Hodgkin lymphomas and are characterized for being a molecularly heterogenous group of diseases. The optimal treatment for PTCLs remains to be defined as they are usually refractory to existing therapies and carry a poor prognosis. Pralatrexate (PDX), a rationally designed antifolate drug, was granted FDA approval as a single agent for the treatment of relapsed/refractory PTCL in 2009. Because of its favorable toxicity profile and activity, Pralatrexate has become a major compound for patients with refractory PTCL.