Therapeutic Small Interfering RNA Targeting Complement C3 in a Mouse Model of C3 Glomerulopathy

Alternative pathway complement dysregulation with abnormal glomerular C3 deposits and glomerular damage is a key mechanism of pathology in C3 glomerulopathy (C3G). No disease-specific treatments are currently available for C3G. Therapeutics inhibiting complement are emerging as a potential strategy for the treatment of C3G. In this study, we investigated the effects of <i>N</i>-acetylgalactosamine (GalNAc)-conjugated small interfering RNA (siRNA) targeting the C3 component of complement that inhibits liver C3 expression in the C3G model of mice with heterozygous deficiency of factor H (<i>Cfh</i> ^+/- mice). We showed a duration of action for GalNAc-conjugated C3 siRNA in reducing the liver C3 gene expression in <i>Cfh</i> ^+/- mice that were dosed s.c. once a month for up to 7 mo. C3 siRNA limited fluid-phase alternative pathway activation, reducing circulating C3 fragmentation and activation of factor B. Treatment with GalNAc-conjugated C3 siRNA reduced glomerular C3d deposits in <i>Cfh</i> ^+/- mice to levels similar to those of wild-type mice. Ultrastructural analysis further revealed the efficacy of the C3 siRNA in slowing the formation of mesangial and subendothelial electron-dense deposits. The present data indicate that RNA interference-mediated C3 silencing in the liver may be a relevant therapeutic strategy for treating patients with C3G associated with the haploinsufficiency of complement factor H.