Enhanced delivery of doxorubicin into the brain via a peptide-vector-mediated strategy: Saturation kinetics and specificity

Doxorubicin delivery to the brain is often restricted because of the poor t ransport of this therapeutic molecule through the blood-brain barrier (BBB) . To overcome this problem, we have recently developed a technology, Pep: t rans, based on short natural-derived peptides that are able to cross effici ently the BBB without compromising its integrity. In this study, we have us ed the in situ mouse brain perfusion method to evaluate the brain uptake of free and vectorized doxorubicin. Doxorubicin was coupled covalently to sma ll peptide vectors: L-SynB1 (18 amino acids), L-SynB3 (10 amino acids), and its enantio form D-SynB3. We first confirmed the very low brain uptake of free radiolabeled doxorubicin, which is most likely due to the efflux activ ity of the P-glycoprotein at the level of the BBB. Vectorization with eithe r L-SynB1, L-SynB3, or D-SynB3 significantly increased the brain uptake of doxorubicin (about 30-fold). We also investigated the mechanism of transpor t of vectorized doxorubicin. We show that vectorized doxorubicin uses a sat urable transport mechanism to cross the BBB. The effect of poly( L-lysine) and protamine, endocytosis inhibitors, on the transport across the brain wa s also investigated. Both inhibitors reduced the brain uptake of vectorized doxorubicin in a dose-dependent manner. These studies indicate that the tr ansport of vectorized doxorubicin appears to occur via an adsorptive-mediat ed endocytosis.