Tankyrase (TNKS) inhibitor, with IC50 values to be 11 and 4 nM for TNKS1 and TNKS2 respectively; inhibiting Wnt / β-catenin signaling; XAV939 is a cell-permeable small molecule inhibitor of the Wnt / β-catenin pathway that inhibits tankyrase 1 and tankyrase 2, thus stabilizing axin and stimulating β-catenin degradation; Current research suggests that Wnt proteins act to maintain stem cells in an undifferentiated, self-renewing state. Wnt proteins act on a variety of stem cells that include neural, mammary and embryonic stem cells. In addition, XAV939 inhibits growth of DLD-1 cells, an APC-deficient colorectal cancer cell line.