The tankyrase inhibitor G007-LK inhibits small intestine LGR5+ stem cell proliferation without altering tissue morphology

Abstract Background The WNT pathway regulates intestinal stem cells and is frequently disrupted in intestinal adenomas. The pathway contains several potential biotargets for interference, including the poly-ADP ribosyltransferase enzymes tankyrase1 and 2. LGR5 is a known WNT pathway target gene and marker of intestinal stem cells. The LGR5+ stem cells are located in the crypt base and capable of regenerating all intestinal epithelial cell lineages. Results We treated Lgr5-EGFP-Ires-CreERT2;R26R-Confetti mice with the tankyrase inhibitor G007-LK for up to 3 weeks to assess the effect on duodenal stem cell homeostasis and on the integrity of intestinal epithelium. At the administered doses, G007-LK treatment inhibited WNT signalling in LGR5+ stem cells and reduced the number and distribution of cells traced from duodenal LGR5+ stem cells. However, the gross morphology of the duodenum remained unaltered and G007-LK-treated mice showed no signs of weight loss or any other visible morphological changes. The inhibitory effect on LGR5+ stem cell proliferation was reversible. Conclusion We show that the tankyrase inhibitor G007-LK is well tolerated by the mice, although proliferation of the LGR5+ intestinal stem cells was inhibited. Our observations suggest the presence of a tankyrase inhibitor-resistant cell population in the duodenum, able to rescue tissue integrity in the presence of G007-LK-mediated inhibition of the WNT signalling dependent LGR5+ intestinal epithelial stem cells.

Phase 1 dose escalation study of rigosertib by 2-, 4-, or 8-hour infusion twice-weekly in patients with advanced cancer.

CONTEXT: Rigosertib, a potent, multi-kinase inhibitor that selectively induces mitotic arrest and apoptosis in cancer cells and is non-toxic to normal cells, is being developed for the treatment of solid tumors and hematological malignancies. AIMS: To determine the safety, doselimiting toxicities, and clinical activity of rigosertib administered by 2-, 4-, or 8-hour continuous IV infusion twice-a-week for 3 weeks out of a 4-week cycle in patients with advanced solid tumor or hematological malignancies; and to confirm the safety and tolerability of the recommended phase 2 dose (RPTD). SETTINGS AND DESIGN: Phase 1, open-label, dose-escalation study in men and women ≥18 years of age. MATERIALS AND METHODS: An escalation phase optimized the duration of infusion (2, 4, or 8 hours) of 3200 mg rigosertib twice-a-week for 3 weeks of a 4-week cycle; an expansion phase confirmed the maximum tolerated dose (MTD). STATISTICAL ANALYSIS USED: All data summaries were descriptive. PK parameters were estimated using compartmental analysis. RESULTS: 25 patients (16 male, 9 female, 26- 66 years, all Asian) were treated with rigosertib, 16 in the escalation phase; 9 in the expansion phase. MTD was determined to be 3200 mg as a 4-hour infusion and 2400 mg over 4 hours was declared to be the RPTD. Best response was stable disease in 5 of 14 evaluable patients, with a mean (range) of 90 (43-108) days. CONCLUSIONS: 2400 mg rigosertib as a 4-hour infusion was identified as the RPTD. Five patients achieved stable disease lasting 6-16 weeks.