ATM and neoplasm: 83 At an oral dosageof 100 mg/kg QD, 23 was able to increase sensitivityto ionizing radiation in a HT29 xenograph mouse model.84 Both 23 and 24 wereable to enhance the efficacy of irinotecan in a SW620 mouse xenograftmodels, with 24 able to contribute to tumor regression.83,84 In line with other ATM inhibitors, 23 and 24 were ineffective without a DNA damaging agent to induce DSB.