Compounds may have similar affinity for a target while the association and dissociation rates of the drugs can differ. The figure below shows Aurora inhibitors with similar affinities for Aurora A and Aurora B (Willemsen-Seegers et al. 2017). Practically all inhibitors have affinities between 1 and 10 nM. Despite the comparable affinities, the figure shows that the association and dissociation kinetics of the compounds on Aurora A and B are clearly distinctive. The pan-Aurora inhibitor danusertib has similar affinity for Aurora A and B as shown in the table, while it has a 14-fold lower dissociation rate for Aurora B. This means that danusertib has much longer target residence time on Aurora B than Aurora A. In this context, it should also be noted that danusertib behaves as an Aurora B inhibitor in cell-based assays (Carpinelli et al. 2007). Especially for compounds of which the target residence time measurement exceeds the half-life in circulation, kinetic selectivity is more predictive for in vivo effect than determining selectivity on the basis of IC50 or KD.