An Open-label Study of Povetacicept (ALPN-303) in Autoimmune Kidney Diseases (RUBY-3)

Key Inclusion Criteria Summary: Biopsy-confirmed autoantibody-associated glomerular disease: immunoglobulin A nephropathy (IgAN), primary membranous nephropathy (pMN), or lupus nephritis (LN) Indication-specific criteria: IgAN Biopsy-confirmed diagnosis ≤10 years prior to the start of screening AND Screening UPCR ≥0.5 g/g. No background immunosuppression therapies. pMN A biopsy-confirmed diagnosis with positive anti-PLA2R1 antibodies or anti-THSD7A antibodies at screening or within 12 weeks prior to the start of screening AND Screening UPCR ≥1 g/g OR A biopsy-confirmed diagnosis ≤5 years prior to the start of screening with both serum and tissue negative for anti-PLA2R1 and anti-THSD7A antibodies AND Screening UPCR ≥3.5 g/g. Less than 50% reduction of proteinuria in the past 24 weeks prior to the start of screening despite on maximally tolerated angiotensin converting enzyme inhibitors (ACEis)/angiotensin II receptor blockers (ARBs) for more than 12 weeks No background immunosuppression therapies except for optional calcineurin inhibitors. LN A Biopsy-confirmed diagnosis of Class III, IV, or V LN ≤3 years prior to the start of screening AND Screening UPCR ≥1 g/g, with active urinary sediment OR additional criteria per protocol Positive anti-dsDNA at screening or within 12 weeks prior to the start of screening Positive anti-nuclear antibody On stable background immunosuppression ≥ 4 weeks prior to the start of screening On maximal dose or the maximally tolerated dose ACEis/ARBs for ≥12 weeks prior to study Day 1 Key Exclusion Criteria Summary: Prior diagnosis of, or fulfills diagnostic criteria for, another renal disease eGFR <30 mL/min/1.73m2 or rapidly progressive glomerulonephritis Recent serious or ongoing infection; risk or history of serious infection Receipt of B cell depleting therapies or anti-BAFF/APRIL therapies within 24 weeks.