Purpose: Romidepsin, a histone deacetylase inhibitor, has demonstrated activity in relapsed or refractory peripheral T-cell lymphoma (PTCL) as a single agent. Cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) therapy is widely used as first-line treatment of PTCL; however, it has limited efficacy. Results from a phase Ib and II study showed the feasibility of combining romidepsin with CHOP (Ro-CHOP)., Methods: This study is a randomized phase III study of Ro-CHOP versus CHOP in adult patients with previously untreated PTCL. All patients received CHOP in 3-week cycles for six cycles. Romidepsin, 12 mg/m 2 , was administered intravenously over a 4-hour period on days 1 and 8 of each 3-week cycle for six cycles. The primary end point was progression-free survival (PFS) according to International Working Group 1999 criteria., Results: Between January 2013 and December 2017, 421 patients were enrolled (Ro-CHOP, n = 211; CHOP, n = 210). The median PFS for Ro-CHOP versus CHOP was 12.0 months (95% CI, 9.0 to 25.8) versus 10.2 months (95% CI, 7.4 to 13.2) with a hazard ratio of 0.81 ( P = .096). In the Ro-CHOP versus CHOP arms, the median overall survival was 51.8 versus 42.9 months and the objective response rate was 63% versus 60% with complete response plus unconfirmed complete response rates of 41% versus 37% ( P > .1 in all comparisons), respectively. Grade 3 or 4 treatment-emergent adverse events occurring in ≥ 30% of patients in the Ro-CHOP arm included thrombocytopenia (50% v 10% in the Ro-CHOP v CHOP arms, respectively), neutropenia (49% v 33%), anemia (47% v 17%), and leukopenia (32% v 20%)., Conclusion: The addition of romidepsin to CHOP did not improve PFS, response rates, nor overall survival and increased the frequency for grade ≥ 3 treatment-emergent adverse events. Ro-CHOP does not represent a significant advance in the standard of care for patients with previously untreated PTCL., Competing Interests: Emmanuel BachyHonoraria: Gilead Sciences, Roche, Amgen, Janssen-CilagConsulting or Advisory Role: Roche, Gilead Sciences, Incyte, TakedaResearch Funding: Amgen Foundation (Inst)Travel, Accommodations, Expenses: Janssen-Cilag, Roche, Gilead Sciences, Incyte Vincent CamusHonoraria: Roche/Genentech, Incyte, Janssen, Gilead Sciences, NovartisConsulting or Advisory Role: RocheResearch Funding: iQone Healthcare (Inst)Travel, Accommodations, Expenses: Pfizer, Roche Catherine ThieblemontHonoraria: Celgene, AbbVie, Bayer, Janssen, Roche, Incyte, Novartis, Gilead SciencesResearch Funding: RocheTravel, Accommodations, Expenses: Roche, Janssen-Cilag, Kite/Gilead, Novartis David SibonConsulting or Advisory Role: Takeda, iQone Healthcare, Janssen, Roche, AbbVieTravel, Accommodations, Expenses: Takeda, Janssen René-Olivier CasasnovasHonoraria: Roche/Genentech, Takeda, Gilead Sciences, Bristol Myers Squibb, Merck, AbbVie, Celgene, Janssen, AmgenConsulting or Advisory Role: Roche/Genentech, Takeda, Gilead Sciences, Bristol Myers Squibb, Merck, AbbVie, Celgene, Janssen, IncyteResearch Funding: Roche/Genentech (Inst), Gilead Sciences (Inst), Takeda (Inst)Travel, Accommodations, Expenses: Roche/Genentech, Takeda, Gilead Sciences, Janssen Loïc YsebaertHonoraria: AbbVieConsulting or Advisory Role: AbbVie, Janssen-Cilag, Roche, Gilead SciencesResearch Funding: Roche (Inst), Janssen-Cilag (Inst), Gilead Sciences (Inst) Gandhi DamajConsulting or Advisory Role: Roche/Genentech, Takeda, iQoneResearch Funding: TakedaTravel, Accommodations, Expenses: PFIZEE, Roche/Genentech, AbbVie Stéphanie GuidezConsulting or Advisory Role: Kite/GileadTravel, Accommodations, Expenses: Janssen Marc AndréConsulting or Advisory Role: Takeda, BMSiResearch Funding: Takeda (Inst), Roche (Inst)Travel, Accommodations, Expenses: Roche, Celgene, Gilead Sciences Alejandro Martín García-SanchoHonoraria: Roche, Janssen-Cilag, Celgene, Servier, Gilead Sciences, TakedaConsulting or Advisory Role: Roche, Celgene, MorphoSys, Kyowa Hakko Kirin, iQone, EUSA Pharma, Gilead Sciences, Novartis, Servier, IncyteExpert Testimony: Gilead SciencesTravel, Accommodations, Expenses: Roche, Celgene¸ Servier Maria Jesus PenarrubiaHonoraria: AbbVie, Celgene, Servier, Takeda, RocheConsulting or Advisory Role: Gilead Sciences, Novartis, Celgene, AbbVie, Takeda, Clinigen GroupResearch Funding: CelgeneTravel, Accommodations, Expenses: Amgen, Servier, Novartis, Janssen, Celgene, Takeda Philipp B. StaberHonoraria: Roche, Amgen, Takeda, Abbott/AbbVie, Janssen Oncology, Incyte, Celgene, Bristol Myers Squibb/Pfizer, MSD Oncology, AstraZenecaResearch Funding: Roche (Inst) Judith TrotmanResearch Funding: BeiGene (Inst), Roche/Genentech (Inst), Pharmacyclics (Inst), Janssen-Cilag (Inst), Takeda (Inst), Celgene (Inst)Travel, Accommodations, Expenses: Roche/Genentech Andreas HüttmannHonoraria: TakedaConsulting or Advisory Role: TakedaTravel, Accommodations, Expenses: Roche Pharma AG Philippe GaulardHonoraria: Takeda, Gilead SciencesConsulting or Advisory Role: TakedaResearch Funding: Takeda (Inst), Innate Pharma (Inst), Sanofi (Inst)Travel, Accommodations, Expenses: Roche Marie-Helene Delfau-LarueHonoraria: Gilead Sciences, AmgenResearch Funding: Roche, CelgeneTravel, Accommodations, Expenses: Mundipharma Laurence de LevalHonoraria: Novartis (Inst)Consulting or Advisory Role: Lunaphore Technologies (Inst), Bayer (Inst) Michel MeignanHonoraria: RocheTravel, Accommodations, Expenses: Roche Ju LiEmployment: Bristol Myers Squibb/CelgeneStock and Other Ownership Interests: Bristol Myers Squibb/CelgeneResearch Funding: Bristol Myers Squibb/CelgeneTravel, Accommodations, Expenses: Bristol Myers Squibb/Celgene Franck MorschhauserConsulting or Advisory Role: Roche/Genentech, Gilead Sciences, Celgene, Bristol Myers Squibb, AbbVie, Epizyme, ServierSpeakers' Bureau: RocheExpert Testimony: Roche/Genentech Richard DelarueEmployment: Celgene/Bristol Myers Squibb, BeiGeneStock and Other Ownership Interests: Celgene/Bristol Myers Squibb, BeiGeneNo other potential conflicts of interest were reported.