Figure 3.

Illustration showing the summarized considerations for obtaining effective brain antibody and protein delivery. Authors should consider first the choice of receptors, which include the RMT receptor is highly expressed at BBB and species-of-interest validation. In antibody engineering, authors should consider several factors, including avoiding fusion to naturally existing ligands, antibody fusion format engineering, antibody affinity, antibody effector function, no competition with natural ligands, endocytosis, and transcytosis confirmation, and unaltered biological activities upon fusion. At last, the in vivo evaluation is needed to validate the therapeutic efficacy and delivery efficiency, including blood circulation time, brain distribution verified by imaging, brain uptake quantification, and in vivo efficacy improvement.