MCL1 and cancer: Although computational protein design has been applied to discovery of BCL‐2 family selective binders,[67] to our knowledge non‐antibody based binding proteins have not previously been shown to differentiate between these proteins, specifically BCL‐xL and MCL‐1; this is noteworthy given the role of MCL‐1 in driving several cancers.[68, 69] We note the attrition rate that is a consequence of applying a variety of activity criteria as we progressed along this pipeline.