By studying drug mechanisms of actions in living cells, researchers have been able to show that the ocular toxicity of inhibitors of the beta-secretase beta-site APP-cleaving enzyme 1 (BACE1), which are in clinical trials for the treatment of Alzheimer's disease (AD), is due to inhibition of the related enzyme Cathepsin D. More broadly, they wrote in their paper, their results "underscore the power of chemical proteomics for discerning mechanisms of drug action."