Squarunkin A hydrochloride is a potent and selective UNC119-cargo interaction inhibitor that inhibits the binding of a myristoylated peptide representing the N-terminus of Src kinase to UNC119A with an IC50 value of 10 nm and interferes with the activation of Src kinase in cells [1].

Treatment with Squarunkin A at concentrations of 2.5 μM, 0.625 μM, 0.078 μM, and 0.01 μM leads to a concentration-dependent decrease in Src phosphorylation [1]. Unlike other lipoprotein chaperones, such as PDE6d, AIPL1, and RhoGDI, which attach to S-prenylated proteins, Squarunkin A does not interact with their lipoprotein-binding sites. Instead, it targets and binds to UNC119 within cell lysates, thereby disrupting Src activation [1].