UGT1A1 and Decreased total neutrophil count: For example, low-activity UGT1A1 alleles (e.g., UGT1A1*28 and UGT1A1*6) are associated with an increased risk for severe or life-threatening neutropenia and myelosuppression during and after irinotecan administration [10,16,17,18,19,20,21].