Antibody therapies in CNS diseases.

Therapeutic antibodies have essentially been banned from the central nervous system, and are so far limited to use mainly in multiple sclerosis. This is primarily due to the fact that antibody penetration across the blood-brain barrier is very limited, with about only 0.1% of circulating antibodies estimated to reach the brain at steady-state concentration. Nonetheless, advances are being made with conventional antibodies, showing that minimal exposure can act centrally to mediate therapeutic effects. Immunotherapy in Alzheimer's disease is a noteworthy example where antibodies against amyloid-β are able to reduce brain plaque pathology in preclinical models and humans. However, the advances in using antibodies directed at brain targets have also demonstrated impediments of low brain exposure in achieving clinical benefits, spurring increased attention in technologies designed to improve brain exposure of antibodies. Here we review antibodies in clinical trials for central nervous system disorders. Moreover, we describe some of the efforts to improve the therapeutic efficacy of antibodies by enhancing delivery across the blood-brain barrier. This article is part of the Special Issue entitled "Beyond small molecules for neurological disorders".