GI254023X is a L-valine derivative that is 3-methyl-L-valine in which carboxy OH group is replaced by a methylnitrilo group and the one of the amino hydrogens is replaced by a (2R)-2-{(1S)-1-[formyl(hydroxy)amino]ethyl}-5-phenylpentanoyl group. It is a potent MMP9 and ADAM10 metalloprotease inhibitor with IC50 of 2.5 and 5.3 nM, respectively. It has a role as an antineoplastic agent, a matrix metalloproteinase inhibitor, an EC 3.4.24.* (metalloendopeptidase) inhibitor and an apoptosis inducer. It is an aldehyde, a member of hydroxylamines and a L-valine derivative.