Notably, targeted inhibition of key complement mediators (C3, C5, C5aR1) or upstream activators (C1q, C2) have shown consistent neuroprotective effects in preclinical models and early-phase clinical trials across multiple conditions, including AD, ALS, GBS, NMOSD, stroke, and even certain psychiatric models (Table 1). This evidence concerns the gene C5AR1 and Alzheimer disease.