Figure 1 –

Zafirlukast and montelukast are broad-spectrum thiol isomerase inhibitors. The structures of zafirlukast (A) and montelukast (B). Both zafirlukast (C) and montelukast (D) inhibit the thiol isomerases PDI, ERp5, ERp57, and ERp72 in a concentration-dependent manner when examined via the insulin turbidity assay. (E) The structure of a zafirlukast analogue missing the cyclopentyl moiety, decreasing or losing its affinity for the leukotriene receptor. (F) The analogue inhibits PDI, ERp5, ERp57, and ERp72 similarly to zafirlukast.