To determine whether these compounds inhibit KIF18A in cells, we treated chromosomally unstable triple-negative breast cancer (TNBC) MDA-MB-231 cells for 24 h with dimethyl sulfoxide (DMSO), 250 nM Compound 3 or Sovilnesib, control siRNA, or KIF18A siRNA and measured the chromosome alignment and spindle length (Figures 5C–E; Supplementary Figure S2). Here, KIF18A is linked to triple-negative breast carcinoma.