Gliotoxin (CAS 67-99-2) is a small-molecule inhibitor targeting the chymotrypsin-like activity of the 20S proteasome farnesyltransferase (IC50 80 M) and geranylgeranyltransferase I (IC50 17 M) It modulates protein prenylation pathways and proteasomal function thereby regulating processes involved in tumor cell proliferation and immune cell functionality Gliotoxin exerts its biological activity primarily through inhibition of these enzymes and by modulating host-pathogen interactions including suppression of macrophage phagocytic function and facilitating Aspergillus internalization in lung epithelial (A549) cells via activation of host phospholipase D In vitro studies demonstrate growth inhibition of human breast cancer cells Based on these pharmacological properties gliotoxin holds research potential in cancer biology proteasome function fungal pathogen-host cell interaction and cellular signaling pathway studies