Conjugation with angiopep2 as a strategy for the brain delivery of a mitochondriotropic inhibitor of the potassium channel Kv_1.3

The voltage-gated potassium channels K_v1.3, expressed by the cells at the plasma membrane and mitochondria level, is highly expressed in several cancers such as melanoma, pancreatic cancer (PDAC), glioblastoma and neuroblastoma, thus turning out an interesting pharmacological target against cancer. Inhibition of the mitochondrial population of the channel leads to pro-apoptotic processes. PAPTP, one of the novel inhibitors of the mitoKv1.3, turned out to be highly effective against melanoma and PDAC in vivo and against glioblastoma cell lines in vitro. It cannot be exploited in orthotopic models of glioma because it is completely unable to cross the blood brain barrier (BBB). A possible approach to enhance the BBB permeability of drugs relies on the use of brain penetrating peptides. The aim of this study is to synthesize angiopep2-PAPTP and to evaluate its absorption into the brain in vivo. To design the conjugate as a pro-drug, the triphenylphosphonium (TPP⁺) moiety of PAPTP was modified adding a linker to one of the phenyl groups (PAPTPL), conjugated to angiopep2 through a bio-reversible carbamate bond. Angiopep2-PAPTP was administered to C57CL/6 mice (5 µmol/kg b.w.), which were sacrificed after 15 (n=5), 30 (n=4) and 60 (n=6) minutes. The results show that angiopep2-PAPTP is present in the brain at 15 and 30 minutes after the injection. The analysis of the liver showed that Angiopep2-PAPTP is mainly metabolized through the cleavage of the peptide chain. Summarizing, conjugation of PAPTP to angiopep2 represents a promising strategy to deliver PAPTP to the brain.