An orally bioavailable inhibitor of the poly (ADP-ribose) polymerase (PARP) enzyme tankyrase, with potential antineoplastic activity. Upon administration, tankyrase inhibitor STP1002 selectively binds to and inhibits the activity of tankyrase. This may block the tankyrase-mediated poly(ADP-ribosyl)ation of multiple target proteins including various tumor suppressors. This may include the blockage of the poly(ADP-ribosyl)ation and destabilization of AXIN, a negative regulator of beta-catenin, and prevents Wnt/beta-catenin signaling. This may inhibit the activation of transcription of a wide range of target genes of Wnt/beta-catenin signaling, thereby preventing gene expression of many Wnt-related, pro-survival proteins and suppressing tumor cell growth. Tankyrase, a member of the PARP family, plays an important role in the regulation of the Wnt/beta-catenin signaling pathway, tumor suppressors, as well as telomere maintenance and mitosis regulation.