COMBINED USE OF CARBOXYL-DIRECTED PROTEIN PEGYLATION AND VECTOR-MEDIATED BLOOD-BRAIN-BARRIER DRUG-DELIVERY SYSTEM OPTIMIZES BRAIN UPTAKE OFBRAIN-DERIVED NEUROTROPHIC FACTOR FOLLOWING INTRAVENOUS ADMINISTRATION

Purpose. Peptide drug delivery to the brain requires optimization of ( a) plasma pharmacokinetics and (b) blood-brain barrier (BBB) permeabil ity. In the present studies, plasma pharmacokinetics are improved with protein pegylation and BBB transport is facilitated with the use of v ector-mediated drug delivery using the OX26 monoclonal antibody (MAb) to the rat transferrin receptor, which undergoes receptor-mediated tra nscytosis through the BBB in vivo. Methods. A conjugate of OX26 and st reptavidin (SA), designated OX26/SA, was prepared in parallel with the carboxyl-directed pegylation of brain-derived neurotrophic factor (BD NF). A novel bifunctional polyethyleneglycol (PEG) was used in which a hydrazide (Hz) was attached at one end and a biotin moiety was attach ed to the other end. This allowed for conjugation of BDNF-PEG-biotin t o OX26/SA. Results. The brain uptake of BDNF-PEG-biotin was increased following conjugation to OX26/SA to a level of 0.144+/-0.004% injected dose per g brain and a BBB permeability-surface area product of 2.0+/ -0.2 mu L/min/g. Conclusions. These studies demonstrate that peptide d rug delivery to the brain can be achieved with advanced formulation of protein-based therapeutics. The formulation is intended to (a) minimi ze rapid systemic clearance of the peptide, and (b) allow for vector-m ediated drug delivery through the BBB in vivo. Following this dual for mulation, the brain uptake of a neurotrophin such as BDNF achieves a v alue that is approximately 2-fold greater than that of morphine, a neu roactive small molecule.