An orally available inhibitor of maternal embryonic leucine zipper kinase (MELK) with potential antineoplastic activity. Upon administration, OTS167 binds to MELK, which prevents both MELK phosphorylation and activation; thus inhibiting the phosphorylation of downstream MELK substrates. This may lead to an inhibition of both cell proliferation and survival in MELK-expressing tumor cells. MELK, a serine/threonine kinase, is involved in cancer cell survival, invasiveness and cancer-stem cell formation and maintenance; it is highly upregulated in various types of cancer cells and absent in normal, healthy cells.