This is an open-label, investigator-initiated, single-arm pilot study. Patients with relapsed or refractory (R/R) peripheral T-cell lymphoma (PTCL) will receive Oncaspar® every 3 weeks up to a maximum of 8 courses or until disease progression or unacceptable toxicity. They will also receive dexamethasone 40mg daily for 4 days with every cycle. They will be restaged after 2 courses (6 weeks) and after 8 courses (24 weeks).