Niraparib in combination with irinotecan is more efficacious than irinotecan alone in the HCT16 (MSI) CRC and HT29 (MSS) models. (Data from this figure is from the same experiment as in Figure 4, but has been separated for ease of viewing.) In vivo efficacy of niraparib in combination with irinotecan in the A. HCT116 (MSI) and B. HT29 (MSS) xenograft models. Niraparib was dosed at 50, 25, or 10 mpk p.o. q.d., for 5 days a week (2 days off) and irinotecan was administered at 100 mpk i.p., on the 3rd day of every week for 4 weeks. Relative tumor size (% versus Day 0) is shown with SEM in error bars. C. and D. The 5-day dosing regimen was tolerated with 15% or less body weight loss in all combinations tested. Relative body weight (% versus Day 0) is shown. For each group, n = 7-10.