OTS514 is a highly potent TOPK inhibitor, which inhibits TOPK kinase activity with a median inhibitory concentration (IC₅₀) value of 2.6 nM. OTS514 strongly suppresses the growth of TOPK-positive cancer cells^[1]. OTS514 induces cell cycle arrest and apoptosis^[2]. IC50 & Target: IC50: 2.6 nM (TOPK)^[1] In Vitro: OTS514 (1.5625-100 nM) induces cell cycle arrest and apoptosis at nanomolar concentrations in a series of human myeloma cell lines (HMCL) and prevents outgrowth of a putative CD138⁺ stem cell population from multiple myeloma (MM) patient-derived peripheral blood mononuclear cells^[2]. In Vivo: OTS514 (1-5 mg/kg; once a day for 2 weeks; intravenous administration) induces tumor regression in a xenograft model of A549 cells (TOPK-positive lung cancer cells)^[1].