The invention is based, at least in part, on the finding that a dimeric version of a BBB-transmigrating antibody (e.g., the TMEM30A (CDC-50A) binding antibody, FC5) was found to greatly enhance transport across the BBB as compared to monovalent FC5 VHH. The invention provides, inter alia, molecules that increase transport of pharmacologically active agents across the blood brain barrier, methods for increasing transport across the blood brain barrier, and methods of treatment of disorders or diseases having a neurological component.
