Bispecific antibodies are categorized into two groups: (a) pathology-targeting bispecific antibodies, which engage AD-related targets (like Aβ/tau, Aβ/TREM2) for synergistic effects; and (b) BBB-shuttling bispecific antibodies, which combine CNS-active antibodies with brain-penetrating modules (like TfR1, CD98hc) to improve delivery [125]. The gene discussed is MAPT; the disease is Alzheimer disease.