TAPI-2 (TNF Protease Inhibitor 2) is a broad-spectrum inhibitor of matrix metalloprotease (MMP), tumour necrosis factorα-converting enzyme (TACE) and a disintegrin and metalloproteinase (ADAM), with an IC₅₀ of 20±10 μM for MMP. IC50 & Target: IC50: 20±10 μM (MMP)^[1] Ki: 1.5±0.27 nM (MMPs)^[1] In Vitro: The hydroxamate-based metalloprotease inhibitor TAPI-2 bounds to hmeprin with inhibition constants IC₅₀ 20±10 μM for hmeprin β subunit and 1.5±0.27 nM for hmeprin α subunit. Generally, hmeprin α is inhibited more strongly than the β subunit^[1]. Without affecting ADAM17 expression, TAPI-2 dramatically decreases the protein levels of NICD and its downstream target HES-1 in both HCP-1 and HT29 cells. Moreover, treating cells with TAPI-2 significantly decreases the CSC phenotype by -50% in both CRC cell lines. The dose-dependent effects of TAPI-2 on the sphere formation and protein levels of NICD and HES-1 confirm that the concentration used (20 μM) is within the effective dose range of TAPI-2 (5–40 μM)^[2].