A Study to Evaluate the Efficacy and Safety of Sefaxersen (RO7434656) in Participants With Primary Immunoglobulin A (IgA) Nephropathy at High Risk of Progression

The purpose of this study is to evaluate the efficacy, safety, and pharmacokinetics of sefaxersen (RO7434656), a novel Antisense Oligonucleotide (ASO) therapy in participants with primary IgA nephropathy (IgAN) who are at high risk of progressive kidney disease despite optimized supportive care.


Eligibility Criteria:
Inclusion Criteria:

* Primary IgAN, as evidenced by a kidney biopsy performed within 10 years prior to or during screening, without known secondary cause
* Treatment with maximum tolerated doses of angiotensin-converting enzyme (ACE) inhibitors or angiotensin II receptor blockers (ARBs) for at least 90 days immediately prior to screening, except for interruptions due to illness (not greater than 7 consecutive days), unless the potential participant is intolerant to these medications
* Urine Protein-to-Creatinine Ratio (UPCR) ≥ 1 gram per gram (g/g) or urine protein excretion ≥ 1 gram per day (g/day) (with UPCR ≥ 0.8 g/g), all measured from a 24-hour urine collection during screening
* eGFR ≥ 20 mL/min/1.73 m\^2, as calculated by the 2021 Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) creatinine equation (Inker et al. 2021a)
* Vaccination against Neisseria meningitidis, Streptococcus pneumoniae and Haemophilus influenzae according to national vaccination recommendations
* Female participants of childbearing potential must use adequate contraception

Exclusion Criteria:

* Pregnancy or breastfeeding, or intention of becoming pregnant during the study or within 12 weeks after the final dose of sefaxersen
* Histopathologic or other evidence of another autoimmune glomerular disease
* Presence of ≥ 50% crescents on kidney biopsy, sustained doubling of serum creatinine within 3 months prior to screening, or rapidly progressive glomerulonephritis in the opinion of the investigator
* History of kidney transplantation
* Glycated Hemoglobin (HbA1c) ≥ 6.5% or a clinical diagnosis of diabetes mellitus of any type
* Systolic blood pressure \>140 mmHg or diastolic blood pressure \>90 mmHg from the average of two measurements performed at least 1 minute apart during screening
* Initiation of SGLT2 inhibitors within 16 weeks prior to screening or during screening
* Initiation of endothelin receptor antagonists within 90 days prior to screening or during screening
* Initiation of mineralocorticoid receptor antagonists or non-dihydropyridine calcium channel blockers within 90 days prior to screening or during screening
* Use of herbal therapies within 90 days prior to or during screening
* Treatment with investigational therapy within 28 days prior to screening or 5.5 drug-elimination half-lives of that investigational product prior to screening
* Treatment with an investigational therapy planned during the treatment period
* Previous treatment with sefaxersen
* Treatment with oral or intravenous (IV) corticosteroids with a dose equivalent to ≥ 7.5 milligrams per day (mg/day) of prednisone for 7 days or equivalent to ≥ 5 mg/day of prednisone for 14 days within 90 days prior to screening
* Treatment with corticosteroids with systemic effects during screening
* Treatment with a systemic calcineurin inhibitor within 2 months prior to screening or during screening
* Treatment with anti-CD20 therapy within 9 months of screening or during screening
* Treatment with other systemic immunosuppressive agents within 6 months of randomization including, but not limited to, complement inhibitors, alkylating agents (e.g., cyclophosphamide or chlorambucil), azathioprine, or mycophenolate
* Planned major procedure or major surgery during screening or the study
* Substance abuse within 12 months prior to screening or during screening
* Any serious medical condition or abnormality in clinical laboratory tests that precludes an individual's safe participation in and completion of the study
* History of malignancy within \< 5 years prior to screening, with the exception of malignancies with a negligible risk of metastasis or death
* Usage of GLP-1-based therapy (i.e., GLP-1 mono-agonists, GLP-1/GIP dual agonists, etc.) within 90 days prior to screening or during screening, or intent to initiate during the study period