Nedosiran

Drug Overview

In the rapidly advancing field of Nephrology, the management of primary hyperoxaluria has been transformed by precision genetic medicine. Developed to address the severe systemic and renal consequences of oxalate overproduction, nedosiran represents a powerful Targeted Therapy. As a Next-Generation RNAi (RNA interference) therapeutic, this medication directly intervenes at the transcriptomic level to halt the metabolic production of oxalate, fundamentally altering the trajectory of the disease and preserving renal function.

• Drug Category: Nephrology / Genetic and Metabolic Diseases
• Drug Class: Next-Generation RNAi (Small interfering RNA)
• Generic Name: Nedosiran
• US Brand Names: Rivfloza
• Route of Administration: Subcutaneous (SC) Injection
• FDA Approval Status: FDA-approved to lower urinary oxalate levels in children (2 years of age and older) and adults with Primary Hyperoxaluria Type 1 (PH1) who have relatively preserved kidney function. 

Note: While heavily tested across all types of Primary Hyperoxaluria (PH1, PH2, and PH3), its current formal approval is strictly for PH1.

What Is It and How Does It Work? (Mechanism of Action)

Nedosiran is a double-stranded small interfering ribonucleic acid (siRNA) Biologic. To appreciate its broad potential across different types of hyperoxaluria, one must understand its unique enzymatic target in the hepatic metabolic pathway.

Unlike previous RNAi therapies that targeted upstream enzymes specific only to PH1, nedosiran was engineered to target the final common pathway of oxalate synthesis.

• Target Recognition: Nedosiran is conjugated to N-acetylgalactosamine (GalNAc) aminosugar residues. This acts as a highly specific homing mechanism, binding directly to asialoglycoprotein receptors (ASGPR) located exclusively on the surface of hepatocytes (liver cells).
• Molecular Silencing: Once inside the hepatocyte, nedosiran utilizes the body’s natural RNA interference pathway to bind to and degrade the messenger RNA (mRNA) responsible for producing the enzyme Lactate Dehydrogenase A (LDHA).
• Enzyme Inhibition: LDHA is the critical enzyme that catalyzes the final metabolic conversion of glyoxylate into toxic oxalate. Because this final step is common to all three types of primary hyperoxaluria (PH1, PH2, and PH3), inhibiting LDHA effectively shuts down the liver’s ability to produce oxalate, regardless of the upstream genetic defect.

FDA-Approved Clinical Indications

• Primary Indication: To lower urinary oxalate levels in children 2 years of age and older and adults with Primary Hyperoxaluria Type 1 (PH1) who have relatively preserved kidney function. As noted in the clinical inputs, it was extensively developed and tested as a pan-agent in all types of Hyperoxaluria (PH1, PH2, PH3) during the PHYOX clinical trials, primarily due to its LDHA-targeting mechanism.
• Other Approved Uses:
  • Currently, there are no FDA-approved indications for PH2 or PH3, as trial endpoints for those specific subtypes did not achieve the required statistical significance for regulatory approval.

Dosage and Administration Protocols

Nedosiran is administered as a once-monthly subcutaneous injection. Unlike other RNAi therapies in this space, it does not require a complex loading-dose phase; patients begin immediately on their maintenance dose based on actual body weight.

Dose Adjustments and Special Populations:

• Renal Insufficiency: No dosage adjustment is necessary for patients with mild-to-moderate renal impairment. It has not been heavily studied in patients with severe renal impairment (eGFR < 30 mL/min/1.73 m²).
• Hepatic Insufficiency: No dose adjustment is required for mild hepatic impairment. The safety and efficacy in moderate-to-severe hepatic impairment remain unstudied.
• Pregnancy: Animal studies utilizing high doses of nedosiran demonstrated potential fetal cardiovascular and skeletal malformations; its use during pregnancy must be carefully weighed against the risks of untreated hyperoxaluria.

Clinical Efficacy and Research Results

Clinical efficacy data from the pivotal PHYOX2 and long-term PHYOX3 extension trials (spanning 2021-2026) demonstrated the robust capabilities of this Targeted Therapy:

• Urinary Oxalate Reduction: In the PH1 cohort, patients receiving the recommended monthly dose of nedosiran achieved a significant reduction in 24-hour urinary oxalate levels. The onset of action was rapid, with significant reductions observed at the first measurement (30 days post-dose), which were sustained over continuous therapy.
• Normalization Rates: A substantial proportion of PH1 patients achieved normal or near-normal urinary oxalate levels, effectively halting the progression of nephrocalcinosis and protecting the kidneys from crystalline damage.
• PH2 and PH3 Outcomes: While the drug successfully degraded LDHA mRNA, the clinical reduction in urinary oxalate for the PH2 and PH3 subgroups in the trials was mixed and did not consistently reach the primary efficacy endpoints required for a pan-hyperoxaluria approval.

Safety Profile and Side Effects

Note: Nedosiran does not carry a Black Box Warning.

Common Side Effects (>10%):

• Injection Site Reactions (ISRs): The most frequently reported adverse event, manifesting as localized pain, erythema, bruising, or mild swelling at the subcutaneous injection site (abdomen or upper thigh).

Serious Adverse Events:

• Immunogenicity: As with any oligonucleotide or Biologic, there is a potential for the formation of anti-drug antibodies (ADAs). However, clinical data indicates that nedosiran did not induce or boost ADAs in the vast majority of trial participants, and it did not clinically impact drug efficacy.

Management Strategies:

To mitigate injection site reactions, patients and caregivers should be instructed to rigorously rotate injection sites each month. Injections should not be administered into veins, scars, or bruised skin. If mild ISRs occur, they generally resolve spontaneously; topical cooling can provide symptomatic relief.

Research Areas

By effectively performing a “chemical liver transplant” via the silencing of the LDHA gene, nedosiran serves as a crucial bridge therapy in the broader context of regenerative medicine. Because primary hyperoxaluria is rooted in a hepatic genetic defect, continuous RNAi therapy protects the native kidneys from destruction while researchers investigate permanent cures. Current advanced research is exploring the intersection of these therapies with CRISPR-Cas9 gene editing and autologous hepatocyte infusions. The ultimate goal of this research is to permanently correct the genetic sequence in the patient’s liver stem cells, theoretically eliminating the need for lifelong RNAi suppression and preventing the requirement for dual liver-kidney transplantation.

Patient Management and Practical Recommendations

Pre-Treatment Tests:

• Baseline Oxalate Burden: Obtain a 24-hour urine collection to accurately quantify baseline urinary oxalate excretion, alongside plasma oxalate levels.
• Renal and Hepatic Panels: Assess baseline eGFR, serum creatinine, and comprehensive liver enzymes (AST, ALT, Bilirubin).

Precautions During Treatment:

• Hyperhydration: While nedosiran stops the production of new oxalate, it does not immediately clear existing systemic oxalate stores. Patients must maintain aggressive daily fluid intake (hyperhydration) to continuously flush the kidneys and prevent kidney stone formation.
• Missed Dose Protocol: Because this is a genetic silencer, maintaining steady-state enzyme suppression is critical. If a dose is missed within 7 days, administer it immediately. If missed by more than 7 days, administer it immediately and reset the monthly schedule from that new date.
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“Do’s and Don’ts”:

• DO store the prefilled syringes or vials in the refrigerator at 2°C to 8°C (36°F to 46°F).
• DO allow the medication to sit at room temperature for 30 minutes prior to injection to minimize discomfort.
• DON’T freeze the medication or expose it to direct heat or sunlight. If stored at room temperature, it must be used within 28 days.
• DON’T stop taking other supportive medications, such as oral potassium citrate or Vitamin B6, unless explicitly instructed by your nephrologist or geneticist.

Legal Disclaimer

The information provided in this guide is for educational and informational purposes only and does not constitute medical advice. It is not intended to be a substitute for professional medical consultation, diagnosis, or treatment. Always seek the advice of a qualified healthcare provider regarding a medical condition, changes in treatment, or prior to starting or stopping any medication.