Study of Ravulizumab in Pediatric Participants With Primary IgAN

Inclusion Criteria: * Participant must be 2 to \< 18 years of age at the time of signing the informed consent or assent. * Stable and maximum allowed or tolerated RASI (ACEI and/or ARB) dose for ≥ 3 months prior to Screening with no planned change during Screening through Week 106. * UPCR ≥ 1.0 g/g from the mean of 3 first morning voids (FMV) collected within 1 week during the Screening Period * Estimated GFR ≥ 30 mL/min/1.73 m2 during Screening * Meningococcal infection vaccine * Haemophilus influenzae type b and Streptococcus pneumoniae vaccine * Participants who are receiving SGLT2i, DEARA (eg, sparsentan), MRA, ERA, or GLP-1 agonists must be on a stable and maximum allowed or tolerated dose for ≥ 3 months prior to Screening with no planned change in dose through Week 34. * Established diagnosis of primary IgAN diagnosis based on kidney biopsy within 3 years prior to Screening or during the Screening Period Exclusion Criteria: * Diagnosis of rapidly progressive glomerulonephritis * Secondary forms of IgAN not in the context of primary IgAN or IgAV * Concomitant clinically significant renal disease other than IgAN or IgAVN * Clinical remission of IgAN/IgAVN or clinically significant improvement in proteinuria within the last 6 months. * Uncontrolled diabetes mellitus with HbA1c \> 8.5% * History of kidney transplant or planned kidney transplant during the Primary Evaluation Period. * History of other solid organ (heart, lung, small bowel, pancreas, or liver) or bone marrow transplant * Splenectomy or functional asplenia * Participants with nephrotic syndrome receiving albumin infusions or with acute kidney injury requiring dialysis within the last 6 months prior to Screening. * Hemolytic uremic syndrome diagnosed any time prior to Screening. * Planned urological surgery expected to influence kidney function within the study time frame. * Congenital immunodeficiency * Active systemic bacterial, viral, or fungal infection within 14 days prior to enrollment * Received biologics for the treatment of IgAN or IgAVN within≤ 6 months prior to Screening