Phase 2 trial of the histone deacetylase inhibitor romidepsin for the treatment of refractory multiple myeloma

Background: Epigenetic dysregulation is a hallmark of cancer, including multiple myeloma. Inhibitors of histone deacetylases (HDACs) induce DNA hyperacetylation by inhibiting removal of acetyl groups from amino tails on histone proteins, thereby uncoiling condensed chromatin favoring transcription of silenced genes, including tumor suppressor genes. Romidepsin is an HDAC inhibitor that exhibits antiproliferative and apoptotic effects against multiple myeloma cell lines. Methods: A phase 2 trial was performed of romidepsin in patients with multiple myeloma who were refractory to standard therapy. Treatment was comprised of romidepsin (13 mg/m²) given as a 4-hour intravenous infusion on Days 1, 8, and 15 every 28 days). Thirteen patients received a median of 2 cycles of therapy (range, 1-7 cycles). Results: Although no patients had an objective response, 4 of 12 patients with secretory myeloma exhibited evidence of M-protein stabilization, and several other patients experienced improvement in bone pain and resolution of hypercalcemia. Conclusions: The results of the current study demonstrate that romidepsin, as a single agent, is unlikely to be associated with a response rate of ≤30% in patients with refractory myeloma, although there was some clinical evidence suggesting a biological effect associated with therapy.