This is a Phase 2, single arm, non-randomized, open-label, multi-center study designed to evaluate the safety and effectiveness of pralatrexate when administered with vitamin B12 and folic acid supplementation to patients with relapsed or refractory PTCL.~Pralatrexate will be given over 3-5 minutes intravenously (IV), which means through a vein. If pralatrexate is tolerated well, the patient will receive IV injections of pralatrexate every week for 6 weeks, followed by 1 week without receiving pralatrexate. These 7 week cycles will be repeated depending on response and tolerability.
Primary~• Determine the efficacy of pralatrexate with concurrent vitamin B12 and folic acid supplementation when administered to patients with relapsed or refractory peripheral T-cell lymphoma (PTCL)~Secondary~Determine the safety of pralatrexate with concurrent vitamin B12 and folic acid supplementation when administered to patients with relapsed or refractory PTCL~Determine the pharmacokinetic (PK) profile of pralatrexate when administered with vitamin B12 and folic acid supplementation