The U.S. Food and Drug Administration (FDA) approved pegcetacoplan (Empaveli) as the first treatment for both C3 glomerulopathy (C3G) and primary immune complex membranoproliferative glomerulonephritis (IC-MPGN). Both are rare kidney diseases that can lead to serious complications, including kidney failure. The approval came in July.

How Pegcetacoplan Works

Pegcetacoplan is a type of medication known as a complement inhibitor. It works by preventing part of the immune system called the complement system from becoming overactive, which can result in damage to kidney tissue and inflammation. The drug helps prevent kidney damage and slow disease progression.

The drug is typically given twice weekly as a subcutaneous (under the skin) infusion, and it can be administered using an infusion pump or a specific type of injector device.

How the Drug Fared in Clinical Trials

The FDA approval was based on results from a clinical trial of people living with C3G or IC-MPGN. In this study, the drug:

• Reduced protein levels in the urine by about two-thirds compared with placebo (inactive treatment)
• Showed stabilized kidney function
• Led to a marked reduction in C3 deposits, with around 70 percent seeing a complete clearance of harmful C3 protein deposits in their kidney tissue

These benefits were consistent for both adults and adolescents, as well as people who had experienced remission (return of the disease) of C3G after a kidney transplant.

Common and Serious Side Effects

In clinical trials, the most common side effects — occurring in at least 10 percent of people — included:

• Infusion site reactions
• Fever
• Nasal congestion
• Flu
• Cough
• Nausea

Empaveli carries an FDA boxed warning because it can increase the risk of serious infections, especially those caused by certain bacteria, including Streptococcus pneumoniae (pneumococcus), Neisseria meningitidis (meningococcus), and Haemophilus influenzae type B. These infections can become life-threatening if not treated promptly.

Because of this risk, the drug is available only through a restricted Risk Evaluation and Mitigation Strategy (REMS) program, which helps ensure safe prescribing and monitoring.

Why This Approval Matters

C3G and IC-MPGN affect an estimated 5,000 people in the United States, and until recently, there were no medicines specifically approved to treat them. That began to change in March 2025, when the FDA approved iptacopan (Fabhalta) for adults with C3G and IgA nephropathy (IgAN). Iptacopan also works by blocking part of the complement system and helps lower protein levels in the urine. Iptacopan is one of a few medications approved for IgAN.

Pegcetacoplan is now one of only two FDA-approved therapies that directly target the complement system for C3G — and the first to also include IC-MPGN in its label. While it offers new hope for preserving kidney function, it also requires careful monitoring and vaccination before starting treatment.

If you’re living with a rare kidney disease and are curious about what treatments may be available — including whether this new approval might apply to you — speak with your doctor. Together, you can work on a treatment plan that meets your specific goals and diagnosis.

Learn more about current treatment options for C3G.

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