UGT1A1 and neutropenia: Of the 84% of patients who received sacituzumab govitecan, and had UGT1A1 genotype results, the incidence of grade 4 neutropenia was 26% in patients homozygous for the UGT1A1*28 allele, 13% in patients heterozygous for the UGT1A1*28 allele, and 11% in patients homozygous for the wild type allele [9].