Similar to our earlier published results [19], all the hinge cysteine conjugates of thailanstatin displayed potent activity (IC50~1 nM) against the high Her2 (>600,000 receptors/cell) expressing N87 gastric cancer cell line but were not potent against moderate antigen expressing MDA-MB-361-DYT2 (361) breast cancer cell line (~150,000 receptors/cell). Here, ERBB2 is linked to breast carcinoma.