Using reported glutathione S-transferase omega 1 (GSTO1-1) cocrystal structures, we designed and synthesized acrylamide-containing compounds that covalently bind to Cys32 on the catalytic site. Starting from a thiazole derivative 10 (GSTO1-1 IC50 = 0.6 μM), compound 18 was synthesized and cocrystallized with GSTO1. Modification on the amide moiety of hit compound 10 significantly increased the GSTO1-1 inhibitory potency. We solved the cocrystal structures of new derivatives, 37 and 44, bearing an amide side chain bound to GSTO1. These new structures showed a reorientation of the phenyl thiazole core of inhibitors, 37 and 44, when compared to 18. Guided by the cocrystal structure of GSTO1:44, analogue 49 was designed, resulting in the most potent GSTO1-1 inhibitor (IC50 = 0.22 ± 0.02 nM) known to date. We believe that our data will form the basis for future studies of developing GSTO1-1 as a new drug target for cancer therapy.