Phthaladyn-23

Phthaladyn-23 is a cell-permeable phthalimide compound that is reported to inhibit Dynamin I and Dynamin II GTPase activity (IC₅₀ = 17.4 and 63 μM using purified sheep brain Dynamin I and recombinant Dynamin II, respectively) in a GTP-competitive manner. Phthaladyn-23 is shown to block K⁺-induced SVE (synaptic vesicle endocytosis) of FM4-64 dye into rat brain synaptosomes (IC₅₀ = 12.9 μM), while being ineffective at 30 μM against RME (receptor-mediated endocytosis) of transferrin into human osteosarcoma epithelial U2OS cells, presumably due to poor Dynamin II inhibitory potency and/or rapid efflux and/or limited permeability in this cell line.