The blood-brain barrier (BBB) is the major obstacle to delivery of drugs to the brain for treating brain disorders (i.e., brain tumor, Alzheimer's, Parkinson's). The development of small and large molecules (i.e., peptides, proteins, and oligonucleotides) as anticancer agents has been hampered by the low permeation of these molecules through the BBB due to the presence of tight junctions and efflux pumps. Therefore, our long-term goal is to improve the in vivo delivery of anticancer drugs to the brain. Our central hypothesis is that modulating the adherens junction of the BBB using E-cadherin peptides can enhance the porosity of the intercellular junctions and, thus, enhance the paracellular permeation of small and large anticancer drugs. We found that an HAV peptide can improve the permeation of mannitol and an anticancer agent (daunomycin) into the brain using the in-situ brain perfusion rat model. In addition, a combination of HAV peptide and verapamil has a synergistic effect to improve the delivery of daunomycin to the brain. Therefore, the first aim of this project is to optimize the effect of HAV peptide in enhancing the delivery of paracellular markers into the brain. Second, the mechanism of transport of daunomycin upon modulation of the BBB with a combination of HAV peptide and verapamil will be investigated. Third, the BBB modulatory activity of HAV peptides will be improved by forming cyclic peptides. Fourth, the mechanism of action of HAV peptide in modulating cadherin-cadherin interactions in the intercellular junctions will be elucidated. Finally, the effects of HAV peptides on brain tumor responsiveness in vivo will be determined.