Safety, immunogenicity, pharmacokinetics, and efficacy of degradation of anti‐HLA antibodies by IdeS (imlifidase) in chronic kidney disease patients

Safety, immunogenicity, pharmacokinetics, and efficacy of the IgG‐degrading enzyme of Streptococcus pyogenes (IdeS [imlifidase]) were assessed in a single‐center, open‐label ascending‐dose study in highly sensitized patients with chronic kidney disease. Eight patients with cytotoxic PRAs (median cytotoxic PRAs of 64%) at enrollment received 1 or 2 intravenous infusions of IdeS on consecutive days (0.12 mg/kg body weight ×2 [n = 3]; 0.25 mg/kg ×1 [n = 3], or 0.25 mg/kg ×2 [n = 2]). IgG degradation was observed in all subjects after IdeS treatment, with <1% plasma IgG remaining within 48 hours and remaining low up to 7 days. Mean fluorescence intensity values of HLA class I and II reactivity were substantially reduced in all patients, and C1q binding to anti‐HLA was abolished. IdeS also cleaved the IgG‐type B cell receptor on CD19(+) memory B cells. Anti‐IdeS antibodies developed 1 week after treatment, peaking at 2 weeks. A few hours after the second IdeS infusion, 1 patient received a deceased donor kidney offer. At enrollment, the patient had a positive serum crossmatch (HLA‐B7), detected by complement‐dependent cytotoxicity, flow cytometry, and multiplex bead assays. After IdeS infusion (0.12 mg/kg ×2) and when the HLA‐incompatible donor (HLA‐B7(+)) kidney was offered, the HLA antibody profile was negative. The kidney was transplanted successfully.