Table 2.

Affinity and selectivity of compounds for AURKA.

Cpd	IC50 (nM) AURKA AURKB		Fold-selectivity
MLN8237 (alisertib)	0.63	5.25	≥8.3a
PROTAC-D	3.58	77.2	21.6
PROTAC-DX	4.78	113	23.7
CpdA	6.17	95.4	15.5

Enzyme inhibition (IC₅₀) of different compounds in in vitro kinase assays. IC₅₀s are shown as geometric means of three repeats (MLN8237, PROTAC-D, -DX) or two (Cpd A). Fold-selectivity is expressed as the relative affinity for AURKA over AURKB.

^aMeasured IC50 for AURKA is at the lower limit of dose range and below the theoretical tight binding limit of the assay. Therefore true IC50 may be somewhat lower (and fold-selectivity higher).