Romidepsin for the treatment of relapsed/refractory peripheral T-cell lymphoma: pivotal study update demonstrates durable responses

Background: Romidepsin is a structurally unique, potent, bicyclic class 1 selective histone deacetylase inhibitor approved by the US Food and Drug Administration for the treatment of patients with cutaneous T-cell lymphoma who have received >= 1 prior systemic therapy and patients with peripheral T-cell lymphoma (PTCL) who have received >= 1 prior therapy. Approval for PTCL was based on results (n = 130; median follow-up, 13.4 months) from the pivotal study of romidepsin for the treatment of relapsed/refractory PTCL. The objective is to present updated data (median follow-up, 22.3 months) and to characterize patients who achieved long-term responses (>= 12 months) to romidepsin. Methods: Patients with PTCL who relapsed from or were refractory to >= 1 prior systemic therapy received romidepsin 14 mg/m(2) as a 4-hour intravenous infusion on days 1, 8, and 15 every 28 days for up to 6 cycles; patients with response or stable disease could continue romidepsin beyond 6 cycles. The primary endpoint was rate of confirmed/unconfirmed complete response (CR/CRu) determined by an Independent Review Committee. Secondary endpoints included objective response rate (ORR) and duration of response (DOR). For patients who achieved CR/CRu, baseline characteristics by DOR (>= 12 vs < 12 months) were examined. Results: The ORR to romidepsin was 25%, including 15% with CR/CRu. The median DOR for all responders was 28 months (range, < 1-48+) and was not reached for those who achieved CR/CRu. Patients with lack of response or transient response to prior therapy achieved durable responses with romidepsin. Of the 19 patients who achieved CR/CRu, 10 had long-term (>= 12 months) responses; none of the baseline characteristics examined-including heavy pretreatment, response to prior therapy, or advanced disease-precluded long-term responses to romidepsin. With a median progression-free survival of 29 months, patients who achieved CR/CRu for >= 12 months had significantly longer survival vs those with CR/CRu for < 12 months or < CR/CRu. Extended treatment and longer follow-up did not affect the reported safety profile of romidepsin. Conclusions: Treatment with romidepsin leads to highly durable responses in a subset of patients with relapsed/refractory PTCL, with responses ongoing as long as 48 months.