FLI-06 is an inhibitor of Notch signaling. FLI-06 acts upstream of α-secretase and β-secretase cleavage, disrupting intracellular trafficking and processing of the Notch signaling pathway and inhibiting general secretion at a step before exit from the endoplasmic reticulum (ER). This inhibition is accompanied by a tubule-to-sheet morphological transition of the ER. FLI-06 does not act on the cytoskeleton, but causes a complete disruption of the Golgi in a manner different from that of Brefeldin A or Golgicide A. FLI-06 is the first compound acting that early in the secretory pathway.