This research study is being done to compare the effectiveness and safety of frexalimab, a medication given as an injection under the skin every 4 weeks, with tacrolimus, a commonly used anti-rejection medication taken by mouth. The study will include adults ages 18 to 70 who are receiving their first kidney transplant and have a low to moderate risk of rejecting the transplanted kidney. Participants who qualify may take part in the study for up to 5 years.

The purpose of this Phase III study is to evaluate the efficacy and safety of iptacopan compared to placebo (both administered in combination with standard of care) in adult participants aged at least 18 years to ≤ 60 years and adolescents (12-17 years in non-EU countries and 16-17 years in EU countries) with idiopathic IC-MPGN. The study aims to demonstrate a reduction in proteinuria and stabilization in estimated glomerular filtration rate (eGFR) in participants treated with iptacopan compared to placebo. Change in patient-reported fatigue will also be evaluated. Alternative complement pathway (AP) dysregulation is believed to underlie the clinical manifestations and progression of IC-MPGN. Serum complement (C3) and other complement pathway biomarkers will be assessed to demonstrate that iptacopan reduces AP activity and targets the underlying cause of disease.