The present invention relates to a method of transporting a compound across the blood-brain barrier comprising administering to a patient an antibody or an antigen binding fragment thereof which binds with an affinity from about 20 nM to about 10 μM to a blood-brain barrier receptor (BBB-R) coupled to the compound such that the antibody transports the compound coupled thereto across the blood-brain barrier; to a polyspecific antibody or an antigen binding fragment thereof which comprises a first antigen binding site which binds the BBB-R and a second antigen binding site which binds a brain antigen; and to the use of said antibody for the manufacture of a medicament and for treating a neurological disorder.
VARIANTS OF AN ANTIBODY FOR TRANSPORTING A COMPOUND ACROSS THE BLOOD-BRAIN BARRIER