In another approach, therapeutic pharmaceuticals are attached to molecules naturally transported across the barrier (i.e., viral vectors, nanoparticles, liposomes, exosomes), and by using transporter or receptor (e.g., transferrin receptor) ligands, such as how transport is done with an anti-amyloid-beta antibody modified into a bispecific format with the capacity to undergo transferrin receptor 1 (TfR1)-mediated transcytosis for Alzheimer’s disease [131]. The gene discussed is TFRC; the disease is Alzheimer disease.