Managing C3G: Comparing Conservative and Emerging Targeted Treatment Strategies

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Current Treatment Landscape and Eculizumab Efficacy

Patients with C3G treated with eculizumab often show an initial response followed by breakthrough disease progression after 1 to 2 years of therapy. This pattern occurs because:

• Eculizumab targets C5, blocking both C5a (an anaphylatoxin) and C5b
• The early response primarily stems from reduced inflammation through C5a inhibition
• Long-term disease control fails because eculizumab does not address the underlying dysregulation at the C3 convertase level

Evidence Base

Italian study data demonstrates the transient benefit pattern:

• Initial proteinuria reduction and albumin improvement
• Over time, proteinuria increases to above baseline
• Albumin levels eventually drop below baseline

Alternative Complement Inhibitors

Avacopan (C5a receptor antagonist) has been evaluated:

• Similar mechanistic limitations to eculizumab (targeting downstream of C3)
• Clinical trials (ACCOLADE study) failed to demonstrate adequate disease control

Treatment Paradigm Comparison

The situation parallels breakthrough hemolysis in paroxysmal nocturnal hemoglobinuria (PNH):

• Both conditions highlight the importance of targeting the appropriate level of the complement cascade
• In PNH, C3-targeting drugs have proven superior to C5-targeting drugs

Future Directions

For progressive C3G with high risk of kidney failure:

• C5 blockade appears insufficient for long-term disease control
• C3-targeting therapies may offer more effective disease modification

Transition from current eculizumab treatment to newer, upstream complement inhibitors will likely be necessary