apratoxin A

Apratoxin A is a potent cyclic depsipeptide natural product originally isolated from the marine cyanobacterium *Lyngbya majuscula*. It functions as a first-in-class inhibitor of the Sec61 translocon, the protein-conducting channel in the endoplasmic reticulum (ER) membrane. By binding to the Sec61α subunit, apratoxin A selectively blocks the co-translational translocation and biogenesis of a subset of secretory and integral membrane proteins, including essential growth factors and receptors such as VEGF, HER2, and MET. This mechanism leads to the induction of the unfolded protein response (UPR) and potent G1-phase cell cycle arrest and apoptosis in various cancer cell lines. While its high potency and broad-spectrum activity make it a compelling antineoplastic lead, its development has been challenged by systemic toxicity, leading to the exploration of synthetic analogs and targeted delivery strategies.