For example, irinotecan is commonly used for treating colorectal cancer (COAD), and its active metabolite, SN-38, is primarily glucuronidated by UGT1A1 with weak activity from all other UGT1As except UGT1A4 [101,102,103,104,105]. The gene discussed is UGT1A4; the disease is colon adenocarcinoma.