Dysregulation of MCL1 isassociated with various cancers, and several small-molecule inhibitorsfor MCL1 have been designed for cancer therapy. MCL1–19G is a suitable model system for our purposefor several reasons: (i) MCL1 is a small protein (150 residues), (ii)the structure of the complex has been solved by X-ray crystallography, (iii) the MCL1–19G affinity has beenmeasured experimentally, and (iv) relativeAFE calculations have previously been performed for MCL1–19Gbinding., The gene discussed is MCL1; the disease is cancer.