Provided are: a nucleic acid having an activity of inhibiting the expression of complement factor B； a medicinal composition comprising the nucleic acid； and a prophylactic or therapeutic agent, said agent comprising the nucleic acid, for atypical hemolytic uremic syndrome, paroxysmal nocturnal hemoglobinuria, age-related macular degeneration, membranoproliferative glomerulonephritis, C3 nephritis, membranous nephropathy, rapidly progressive glomerulonephritis (RPGN), acute kidney injury (AKI), ANCA associated vasculitis, lupus nephritis, asthma or an autoimmune disease.本發明提供一種具有補體B因子之表現抑制活性之核酸、包含該核酸之醫藥組合物以及包含該核酸之非典型溶血性尿毒症症候群、陣發性夜間血紅素尿症、老年性黃斑變性症、膜性增生性絲球體腎炎、C3腎炎、膜性腎病、快速進行性絲球體腎炎(RPGN)、急性腎衰竭(AKI)、ANCA相關血管炎、狼瘡性腎炎、哮喘或自體免疫疾病之預防或治療藥。
