This anti-tumor agent (FW = 342.38 g/mol; CAS 151720-43-3; Solubility: 13 mg/mL DMSO, methanol, acetonitrile, 10 mg/mL), also known as (2E)- 5-[3-[(phenylsulfonyl)amino]phenyl]-pent-2-en-4-ynohydroxamate, inhibits histone deacetylase. Oxamflatin shows antiproliferative activity in vitro against various mouse and human tumor cell lines, attended by drastic changes in the cell morphology and in vivo antitumor activity against B16 melanoma. Oxamflatin causes an elongated cell shape with filamentous protrusions as well as arrest of the cell cycle at the G1 phase in HeLa cells. These phenotypic changes in HeLa cells were similar to those induced by trichostatin A (TSA), a specific inhibitor of histone deacetylase (HDAC).