A Phase 2 Study to Evaluate the Safety, PD, PK, and Clinical Activity of ADX-097 in Participants With IgAN, LN or C3G

Key Inclusion Criteria: 1. Male or female participants aged ≥18 years. 2. Urine protein ≥ 0.75 g/24 hours or uPCR ≥ 0.5g/g 3. Screening eGFR ≥30 mL/min/1.73m2 calculated by the Chronic Kidney Disease Epidemiology Collaboration creatinine equation (CKD-EPI GFR). 4. Participants receiving a RAAS inhibitor must have been on a stable dose (at the maximum recommended dose according to local guidelines or maximum tolerated dose) for at least 12 weeks prior to Study Day 1 that is projected to remain stable during the study. 5. Participants receiving a sodium-glucose cotransporter-2 (SGLT2) inhibitor or sparsentan must have been on a stable dose for at least 12 weeks prior to Study Day 1 that is projected to remain stable during the study. 6. Kidney biopsy-proven diagnosis of IgAN within 52 week; LN within 12 weeks or C3G within 52 weeks of Day 1 and with evidence of C3 fragment deposition. Key Exclusion Criteria 1. A ≥50% decline in eGFR within 3 months before screening. 2. Concomitant significant renal disease other than IgAN, C3G, or LN. 3. Uncontrolled hypertension, defined as systolic blood pressure ≥150 mmHg and/or diastolic blood pressure ≥90 mmHg, despite antihypertensive treatment. 4. Kidney, other solid organs, or bone marrow transplantation prior to or expected to occur during the study.