The purpose of the study is to evaluate safety, tolerability, and preliminary effectiveness following administration of PS-002 in adults with primary Immunoglobulin A (IgA) nephropathy. This will be a first-in-human study and will include participants at high risk of disease progression despite receiving current standard-of-care treatment.

Participants will be monitored for up to one year after receiving PS-002 and invited to take part in a long-term follow-up study (total follow-up: 5 years).

Inclusion Criteria:

• Diagnosis of primary IgA nephropathy (IgAN) as evidenced by renal biopsy.
• A historic kidney biopsy performed within 36 months prior to screening with reported evidence of complement component 3 (C3) deposition. If the participant had a kidney biopsy performed over 36 months prior to Screening, a new kidney biopsy should be carried out during the Screening period. This biopsy must exhibit signs of ongoing complement system activity.
• Proteinuria as assessed at the Screening visit by UPCR at least 1g/g (at least 1000 mg/g) OR total protein excretion at least 1 g/24 h (at least 1000 mg/24h) sampled from 24 h urine collection.
• eGFR calculated using the CKD-EPI formula at least 45 mL/min/1.73m^2.
• Sitting office systolic blood pressure equal to or less than 140 mmHg, diastolic blood pressure equal to or less than 90 mmHg.
• All participants must have been on best supportive care for IgAN, as per region-specific requirements defined in the protocol.

Exclusion Criteria:

• A participant has nephrotic syndrome, defined for this purpose as 24 h urine protein greater than 3.5g with concurrent hypoalbuminemia (serum albumin less than 3.0 g/dL [less than 30 g/L]).
• Any secondary IgAN defined as associated with gastrointestinal and liver disorders (liver cirrhosis, celiac disease, Crohn's disease, ulcerative colitis), autoimmune disorders (dermatitis herpetiformis, psoriasis, seronegative arthritis, systemic lupus erythematosus, rheumatoid arthritis), malignancy (IgA myeloma, lymphoma, lung cancer, renal cell cancer, cutaneous T-cell lymphoma), respiratory disorders (bronchiolitis obliterans, idiopathic pulmonary fibrosis) etc.
• Having a major concurrent non-IgAN-related disease that, in the opinion of the investigator, prevents the assessment of IgAN.
• History of malignancy; or bone marrow or organ transplant.
• History of, or currently active primary or secondary immunodeficiency, including known history of human immunodeficiency virus infection, and other severe immunodeficiency blood disorders.
• Presence of other significant medical conditions that would create an unacceptable procedure or anesthesia risk.
• Aspartate aminotransferase or alanine aminotransferase greater than 1.5 times the upper limit of normal.
• History of serious infection requiring parenteral antibiotics within the past 8 weeks prior to study drug administration.
• Participants previously treated with immunosuppressive/immunomodulatory agents such as, but not limited to, cyclophosphamide, infliximab, complement inhibitor, canakinumab, mycophenolate mofetil, mycophenolate sodium, cyclosporine, tacrolimus, everolimus, or systemic corticosteroids (exposure greater than 7.5mg/day prednisone/prednisolone equivalent) within 90 days (or 180 days for rituximab) prior to Screening. Participants previously or currently receiving oral budesonide (Kinpeygo/Tarpeyo) require wash out for 90 days prior to the study drug administration.
• Exposed to a live or attenuated vaccine within the 6 weeks prior to study drug administration.
• Participants with a known sensitivity or intolerance to corticosteroid therapy.
• Known hypersensitivity to study drug ingredients.
• Prior treatment with PS-002 or any other gene therapy, or participation in any other investigational trial during this study.
• Positive serology for hepatitis B or C, i.e., positive hepatitis B surface antigen or hepatitis C ribonucleic acid (RNA) viral load positive.
• Participants treated with potentially hepatotoxic medications unless they have been monitored in accordance with the drug label and have received a stable dose since >90 days prior to dosing without clinically significant liver enzyme fluctuations.

Note: Other protocol-defined inclusion/exclusion criteria may apply.

IPD data are not planned to be shared at this time due to patient privacy concerns with consideration of the small sample size for this open-label study