The FDA-approved drug label for irinotecan hydrochloride (Camptosar®, Pfizer, NY, USA) [17] states that UGT1A1 PM patients experience increased systemic exposure to SN-38 (active metabolite of irinotecan), being at an increased risk for severe or life-threatening neutropenia and diarrhea during treatment. The gene discussed is UGT1A1; the disease is Decreased total neutrophil count.