Treating a Rare Kidney Disease
Having complement 3 glomerulopathy (C3G) means having a rare kidney disease. But it also means you have several treatment options. These include FDA-approved C3G medicines, treatments for complications of C3G, and lifestyle and dietary changes that help manage risks associated with the disease. Review all of the different C3G treatment options with your nephrologist to determine what will work best for you.
"While these therapies remain the cornerstone of care, treatment must be individualized based on disease severity, underlying complement abnormalities, and rate of kidney function decline," says Fahad Aziz, MD, head of nephrology at the University of Wisconsin-Madison School of Medicine and Public Health.
Treatments Available for C3G Patients
You may already be taking some of these types of medications to control issues associated with your C3G. But it’s good to know what’s out there for you — and why you might need them.
Medications to control your blood pressure
Tiny blood vessels in your kidneys called glomeruli filter waste and excess fluids from your blood. But with C3G, the glomeruli don’t work properly. The breakdown products of the complement 3 proteins get stuck in the glomeruli, essentially clogging them. As a result,the kidneys don’t filter well. Fluid can build up and put pressure on your arteries, causing high blood pressure. You may need to control your blood pressure by taking medicine and monitoring your blood pressure at home.
Meds that reduce protein in your urine
Proteinuria means you have a higher level of protein than normal in your pee. That can make your pee look foamy or cloudy. It can be a sign that your kidneys are damaged, glomeruli aren't working properly, or your body isn't reabsorbing proteins properly. To control this problem, you may be prescribed blood pressure medicines, such as angiotensin-converting enzyme (ACE) inhibitors. These medicines lower the pressure on your glomeruli, so less protein enters your pee. If you also have high blood pressure, you could be prescribed medicines called renin-angiotensin system inhibitors that address both problems.
Meds to manage your cholesterol
You may develop high cholesterol when damage to your kidneys interferes with how your body processes cholesterol and fats. Having too much cholesterol in your blood vessels can lead to heart disease, which is the No. 1 cause of death in people with chronic kidney disease. Your doctor may prescribe statin medicines to help lower your cholesterol and protect your kidneys from further damage. Statins help lower cholesterol by slowing down production of LDL (bad) cholesterol in your liver and helping your liver remove LDL cholesterol from your blood.
Meds to control swelling
When you have C3G, it’s common for too much fluid to build up in your blood. This can lead to swelling in different areas of your body, also known as edema. Swelling tends to happen in your hands, legs, feet, and ankles. It can feel uncomfortable and interfere with your movement. You could also have swelling and puffiness around your eyes. Medicines called diuretics are an option for controlling and reducing swelling. They help your body get rid of excess fluid. Examples of diuretics include furosemide and spironolactone.
Meds that suppress your immune system
When you have C3G, a part of your immune system called the complement system is overactive. Your immune system’s complement pathway gets activated to fight against bacteria and viruses. But when it’s overactive, there are too many complement 3 proteins. When they break down, their debris gets stuck in your glomeruli, the blood vessels in your kidneys that filter wastes and fluids. Immunosuppressive drugs are sometimes used to calm the immune system. Corticosteroids, such as prednisone, are common examples. Another example of an immunosuppressive drug is mycophenolate mofetil, which may be used to prevent organ rejection after a kidney transplant. Depending on your body, you may not need immunosuppressive medicines or benefit from them.
Meds that slow down your immune system
Medicines called monoclonal antibodies have been used to treat C3G because they can slow down the complement system. Eculizumab is an example of a monoclonal antibody that's been used for treating rapidly progressive cases of C3G. But this medicine hasn’t been consistently effective, according to Aziz, because it targets a protein called C5 rather than C3.
Making changes to your diet
One way to manage your C3G outside of taking medication is to focus on your diet. The most important advice is to limit your sodium intake. With C3G, your kidneys have trouble filtering excess wastes as well as salt. When too much salt accumulates in your body, it can lead to high blood pressure and swelling. Your doctor may also advise eating foods low in potassium and phosphorus because your kidneys may not be able to filter extra nutrients from your blood. Always ask your doctor before making changes to your diet.
New Treatments on the Horizon
"Newer complement-targeted therapies are beginning to redefine the management landscape," Aziz says.
For example, in March 2025, the FDA approved the first-ever medicine for C3G, iptacopan (Fabhalta), which was already approved for other uses. The oral capsule is taken twice daily to treat proteinuria, the buildup of protein in urine. It works by blocking "activation of the complement pathway, addressing the disease at its source," Aziz says.
Another complement inhibitor that blocks the activity of C3 is pegcetacoplan (Empaveli). It was approved by the FDA in August 2025 to treat people aged 12 and older who have C3G. It’s given twice weekly either by infusion or an on-body injector that delivers the liquid under the skin over a 30- to 60-minute period.
"Together, these therapies mark a major shift from nonspecific immunosuppression toward precision, mechanism-based treatment, though long-term data on kidney survival and safety are still being gathered," Aziz says.
Diagnostic Tools Used Now
A kidney biopsy is "the gold standard" diagnostic tool for C3G, Aziz says. During the procedure, a doctor removes a small piece of your kidney using a needle or small incision. Then pathologists examine your sample at a lab to see if there is damage from C3 proteins in the glomeruli in your kidneys. The doctor will also look for dense deposits in the glomeruli that can help determine which type of C3G you have.
You may need blood and urine tests. Blood tests are done to look for abnormal complement proteins or excess wastes and can also tell if your glomeruli are filtering your blood well enough. Urine tests can show if there's any amount of protein or blood in your pee, which can be signs of C3G.
Diagnostic Tools Being Studied
Sometimes, genetic testing is done to find out what's causing your C3G, such as whether it runs in your family. These tests can also help doctors determine which treatments could work best for you, how serious the disease is, and how fast it could progress. Genetic testing is done by a geneticist and usually involves wiping the inside of your mouth with a cotton swab to get a sample of your cells. The sample is sent to a lab to be analyzed.
Other tools are still emerging and could make C3G diagnoses more detailed and personalized. For instance, next-generation sequencing panels analyze groups of genes to find abnormalities. These panels can be used to develop your treatment plan.
Research biomarkers that measure the activity of the complement system are also being used in some hospitals. These biomarkers, including complement proteins, can reveal more information that guides diagnosis and treatment.
What Advances Mean for C3G Patients
Clinical guidelines for C3G have not been updated to include recent advances in diagnostics and treatment. Doctors still rely on a 2013 consensus report and recent expert reviews, but "with the 2025 FDA approval of iptacopan, formal guidance is expected to evolve," Aziz says.
Kidney transplant numbers have been increasing in recent years. There were 27,759 kidney transplants in 2024, a 1.6 percent increase from 2023. Hispanic/Latino recipients saw the largest rate of increase at 6.5 percent.
Ongoing research efforts and rising kidney transplant numbers offer new hope for people with C3G. Waiting for new treatments to become available can be frustrating, so it’s important to find support. Leaning on friends and family and connecting with other C3G patients can help.
"Rare-disease uncertainty is stressful," Aziz says. "National kidney organizations host C3G pages, peer programs, and helplines that can be invaluable."