This clinical trial is for men and women age ≥ 18 years old who have been diagnosed with advanced rectum cancer. This is a phase 1b study to assess the safety and tolerability of the investigational study drug, E7046, in combination with preoperative radiotherapy and chemotherapy in the short course and long course radiotherapy settings. The primary objective of this study is to find a safe dose level of the investigational study drug, E7046 in combination with radiotherapy and chemotherapy. Other objectives of the study are to determine the maximum tolerated dose and/or recommended phase 2 dose of E7046 in combination with preoperative radiotherapy and chemotherapy. Currently available treatments are effective in some patients but many experience side effects. Therefore, there is a need to find more effective treatments with fewer side effects.