OTS514

OTS514, a thieno[2,3-c]quinolone compound, is a highly potent TOPK inhibitor with an IC50 value of 2.6 nM. The compound can inhibit TOPK kinase activity. TOPK (T-lymphokine-activated killer cell-originated protein kinase) is a protein that is found in a wide range of human cancers and is believed to work as an oncogene, promoting tumor growth.

It has been reported that OTS514 strongly inhibited the growth of the TOPK-positive cancer cell lines with low IC50 values ranging from 1.5 to 14 nM. While in HT29 cells, in which TOPK expression was little detectable, the IC50 value was 170 nM. Intravenous administration of free OTS514 at 1, 2.5, and 5mg/kg once a day for 2 weeks resulted in tumor growth Inhibition（TGI）of 5.7, 43.3, and 65.3% on day 15, respectively, without anybody weight loss. However, this inhibition also cause dysfunction in the differentiation process of hematopoietic stemcells (HSCs) to WBCs and RBCs but may enhance the differentiation of HSCs to megakaryocytes and platelets.

The antitumor effect of OTS514 in lung cancer xenograft model of LU-99 cells has also been investigated. OTS514 was administered to mice bearing LU-99 cancer cells after the tumor size reached about 200mm3. Intravenous administration of OTS514 (5 mg/kg) once a day for 2 weeks achieved good growth-suppressive effect with TGI of 104% without any body weight loss. However, the antitumor effect of OTS514 against LU-99 xenograft caused a significant reduction of WBCs.

References:
1. Matsuo Y, Park JH2, Miyamoto T, et al. TOPK inhibitor induces complete tumor regression in xenograft models of human cancer through inhibition of cytokinesis. ci Transl Med. 2014 Oct 22;6(259):259ra145.
2. Y. Nakamura, Y. Matsuo, S. Hisada, et al. Tricyclic compounds and PBK inhibitors containing the same. Patent WO/2011/123419 (2011)