PARP1 and colorectal carcinoma: While olaparib caused a moderate decline in viability at the highest concentration, the other PARPi (veliparib, X17613, and X17618) had no effect on HCEC (Appendix A, Figure A4B) Taken together, the novel PARPi X17613 and X17618 did not trap PARP-1 and, similar to veliparib, induced no cytotoxicity in two different CRC cell models (MSI and MSS) and HCEC (Table 1).