Tazemetostat Plus CHOP in 1L T-cell Lymphoma

Inclusion Criteria: * Participants must have histologically or cytologically confirmed peripheral T cell lymphoma of one of the following subtypes: PTCL-NOS, Follicular helper T-cell lymphoma (ICC 2022) or Nodal T-follicular helper (TFH) cell lymphoma by (WHO 2022) which includes follicular helper T-cell lymphoma, AITL and follicular helper T cell lymphoma, follicular type, EATL, MEITL. All pathology will be reviewed at BWH. BWH review is not required prior to enrollment and patients may be enrolled based upon local pathology analysis. Ten blank slides will be required from outside tumor biopsy for correlative studies. * No prior treatment for T NHL with the exception of one cycle of CHOP or CHOEP or 7 days of corticosteroids at a dose of up to prednisone 60 mg or equivalent for palliation of disease related symptoms so long as the corticosteroids are discontinued prior to tazemetostat prephase or cycle 1 of treatment if not receiving the prephase. * At least one bi-dimensionally measurable lesion, defined as \>1.5 cm in its longest dimension as measured by CT. * Age ≥18 years. * ECOG performance status ≤2 (Karnofsky ≥60%, see Appendix A). * Participants must have adequate organ and marrow function as defined below: * absolute neutrophil count ≥1,000/mcL (750 mcl if bone marrow involvement with lymphoma) * platelets ≥75,000/mcL (25,000 if bone marrow involvement with lymphoma) * total bilirubin ≤ institutional upper limit of normal (ULN) * AST(SGOT)/ALT(SGPT) ≤3 × i…