In this episode, hosts Dr. Kenar Jhaveri and Dr. Koyal Jain are joined by Dr. Matt Sparks (co-creator of NephMadness) and Dr. Aarushi Varshney to discuss the evolving landscape of C3 Glomerulopathy (C3G). The conversation highlights the shift from traditional electron microscopy-based classifications to modern immunofluorescence-based diagnosis, as well as the groundbreaking arrival of two new FDA-approved targeted therapies.
The NephMadness Matchup
This episode focuses on the C3G bracket pitting two critical aspects of C3G against each other:
- Team Diagnosis: Focusing on the challenges of distinguishing C3G from infection-related GN or monoclonal gammopathy.
- Team Treatment: Highlighting the new era of factor B and C3 inhibitors that are revolutionizing patient outcomes.
Key Takeaways
1. Challenges in Diagnosis
- The "Two Orders of Magnitude" Rule: Modern diagnosis is based on immunofluorescence (IF) showing C3 deposition that is at least two orders of magnitude greater than any other immunoglobulin.
- C3G vs. PIGN: It can be difficult to distinguish C3G from Post-Infectious Glomerulonephritis (PIGN). Clinical clues include patient age, the persistence of low C3 levels after infection resolution, and the presence (or absence) of sub-epithelial humps on pathology.
- The Role of Monoclonal Gammopathy: In older patients, it is critical to rule out monoclonal gammopathy (using SPEP and free light chain assays) as a driver of complement activation.
2. The New Therapeutic Era
The panel discussed two landmark drugs that have recently shifted the C3G treatment paradigm:
- Iptacopan: An oral factor B inhibitor that showed a 30% reduction in proteinuria at six months in the APPEAR trial.
- Pegcetacoplan: A subcutaneous infusion (twice weekly) C3 inhibitor that demonstrated a nearly 70% reduction in proteinuria and stabilization of eGFR in the VALIANT trial.
- A "Hammer" Approach: Pegcetacoplan is described as a "larger hammer" because it acts at the crux of all three complement pathways (Classical, Lectin, and Alternative).
3. Safety & Monitoring
- Vaccination: Because these drugs inhibit the complement cascade, patients MUST be vaccinated against Neisseria meningitidis and Streptococcus pneumoniae at least two weeks before starting therapy.
- Prophylaxis: If urgent treatment is required, patients should start prophylactic antibiotics (such as Penicillin, Augmentin, or Ciprofloxacin).
Resources & Studies Mentioned
The hosts and guests of this GN in 10 episode do not have any disclosures to make relevant to the content of this episode.
