JH295 hydrate is a potent, irreversible and selective NIMA-related kinase 2 ( Nek2 ) inhibitor with an IC 50 of 770 nM. JH295 hydrate inhibits cellular Nek2 via alkylation of Cys22. JH295 hydrate is inactive against the mitotic kinases, Cdk1 , Aurora B or Plk1 , and does not perturb bipolar spindle assembly or the spindle assembly checkpoint. JH295 (hydrate) is a click chemistry reagent, it contains an Alkyne group and can undergo copper-catalyzed azide-alkyne cycloaddition (CuAAc) with molecules containing Azide groups.