NSC 663284(DA-3003-10) is a potent, cell-permeable, and irreversible dual specificity phosphatase inhibitor of Cdc25, and exhibits an IC50 of 0.21 μM for Cdc25B2 and is 20 and 450-fold highly selective against Cdc25B2. NSC 663284 also inhibits NSD2 with an IC50 of 170 nM via a direct interaction with the catalytic SET domain.