Eculizumab Biosimilar Shows Durable Benefit in Long-Term aHUS

Long-term treatment with an eculizumab biosimilar (Elizaria; Generium) produced stable hematologic and safety outcomes in patients with atypical hemolytic uremic syndrome (aHUS), according to the results of a prospective, multicenter observational study published in Nephron.1

“The objective of a multicenter, prospective, observational study of an eculizumab biosimilar (Elizaria) was to analyze the efficacy and safety of long-term complement inhibitor therapy in patients with atypical hemolytic uremic syndrome (aHUS),” wrote the researchers of the study.

aHUS is a rare, life-threatening form of thrombotic microangiopathy (TMA) driven by uncontrolled activation of the complement alternative pathway, leading to microvascular thrombosis, hemolytic anemia, and progressive kidney injury.2 Without treatment, the condition carries a high risk of end-stage kidney disease and death. Terminal complement inhibition with eculizumab has been standard of care for more than a decade, transforming aHUS from a frequently fatal diagnosis into a manageable chronic condition. However, the reference product's cost has limited access in many health systems, spurring development of biosimilars intended to expand access while preserving efficacy and safety.

Consistent Efficacy Across Age Groups and Treatment Histories

The observational study enrolled 50 patients with aHUS aged 1 to 55 years, 42% of whom were under age 18.1 Patients received the eculizumab biosimilar in routine clinical practice over 56 weeks. Nineteen patients (38%) had previously been treated with reference eculizumab before enrolling, while 31 (62%) were naive to complement inhibitor therapy.

By the end of the study, mean (SD) platelet counts rose by 39.48 (21.7) × 109/L in treatment-naive patients and 33.61 (24.06) × 109/L in treatment-experienced patients. Nearly all patients achieved normal platelet counts—100% of treatment-naive patients and 96% of treatment-experienced patients. Mean lactate dehydrogenase activity, a marker of hemolysis, remained essentially unchanged, from 253.84 (122.22) U/L at screening to 245.24 (93.52) U/L at the end of the study, indicating that hemolytic activity was already controlled and stayed controlled.

63 Unrelated Adverse Events, Low Immunogenicity Reported

Investigators reported 63 adverse events judged unrelated to the biosimilar during the safety assessment period. No details on serious adverse events or discontinuations attributable to the study drug were disclosed in the published abstract. The authors characterized the overall safety profile as favorable, with low immunogenicity observed over the treatment course, a notable finding given ongoing concerns among clinicians about antidrug antibody formation with long-term biologic switching in rare disease populations.

Freedom from TMA events was reported in 77.6% of patients at week 21 and 80% at week 52. The proportion of patients achieving a complete TMA response increased significantly over the study period, reaching 8% (P = .046). Renal function also improved for a subset of patients: 12% had an estimated glomerular filtration rate gain of at least 15 mL/min/1.73 m2 by week 52.

The stability of platelet counts and TMA response rates across both treatment-naive and switch populations may support formulary strategies that favor biosimilar initiation or transition for eligible patients, provided ongoing pharmacovigilance continues to confirm low immunogenicity. As more eculizumab biosimilars gain global approval, comparative real-world evidence like this study will be important for utilization management decisions and prior authorization criteria in rare disease programs.

“Long-term complement inhibitor therapy with the eculizumab biosimilar in patients with aHUS has demonstrated a stable effect, a favorable safety profile, and low immunogenicity,” wrote the researchers.

References

1. Kotenko O, Kozlovskaya N, Emirova K, et al. Long-term therapy with eculizumab biosimilar in patients with atypical haemolytic uraemic syndrome: outcomes of a prospective observational study. Nephron. Published online June 12, 2026. doi:10.1159/000552914
2. Campbell P. FDA approves first interchangeable biosimilar to eculizumab for PNH and aHUS. HCPLive®. May 28, 2024. Accessed July 29, 2026. https://www.hcplive.com/view/fda-approves-first-interchangeable-biosimilar-to-eculizumab-for-pnh-and-ahus