Brain drug development is limited by the blood-brain barrier (BBB), which restricts the passage into the brain of >95% of all drug candidates intended for the CNS. The growth of future CNS drug development can be accelerated by fostering parallel growth in both CNS drug discovery and CNS drug delivery. One approach to solving the BBB problem is to target endogenous BBB transport systems, and to develop CNS drug delivery strategies that take advantage of these natural portals of entry into the brain.