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Complement Inhibitors

Reviewed by: HU Medical Review Board | Last reviewed: September 2023

Geographic atrophy (GA) is the name for later stages of dry age-related macular degeneration (AMD). GA impacts your central vision and typically affects both eyes.1

Complement inhibitors are a type of drug that can treat many conditions. As of late 2023, 2 complement inhibitors have been approved to treat GA.1,2

How do complement inhibitors work?

The complement system is part of the immune system. It helps (“complements”) the antibodies of the immune system. The complement system assists the antibodies in doing their job fighting germs and protecting us.2

For some people, the immune system overreacts and causes too much inflammation. This reaction is the cause of many diseases.2

Some of these diseases are linked to an overactive complement system. Complement inhibitors work by controlling specific parts of the complement system. This control helps prevent this overreaction.2

We do not know what exactly causes GA. But scientists think the immune system may have a role. Some research shows that the complement system is linked to local inflammation, which can impact the eyes. Complement inhibitors may control this reaction and slow the damage associated with GA when given as an injection into the eyes.1


As of late 2023, there are 2 complement inhibitors approved to treat GA in the United States:3,4

What are the possible side effects?

Side effects can vary depending on the specific drug you use. Side effects of complement inhibitors include:3,4

  • Broken blood vessels in the eye
  • Eye pain or discomfort
  • Eye floaters
  • Blurry vision
  • High blood pressure within the eye
  • A different type of macular degeneration (called neovascular or wet AMD)

The use of complement inhibitors also increases your risk for retinal detachment and eye inflammation (endophthalmitis). These both can be very serious conditions. Proper administration of the drug can reduce this risk.2,3

These are not all the possible side effects of complement inhibitors. Talk to your doctor about what to expect after having an injection of complement inhibitors. You also should call your doctor if you have any changes that concern you while on complement inhibitors.

Other things to know

There is no cure for GA. Complement inhibitors can only slow the disease’s progression. Complement inhibitors for GA were approved because of results from clinical trials. The trials showed that complement inhibitors reduced how quickly GA advances.3,4

Complement inhibitors for GA are given as an injection into each affected eye. This injection must be given by a doctor. You will need to get injections every 30 to 60 days, depending on the drug. You will be monitored after the injection for signs of any complications. Depending on the drug, there may be a limit on how long you can safely receive injections.3,4

Complement inhibitors are not approved for children or people who are pregnant or breastfeeding. People with eye infections or active eye inflammation should not be given complement inhibitors3,4

Before beginning treatment for GA, tell your doctor about all your health conditions and any other drugs, vitamins, or supplements you take. This includes over-the-counter drugs.3,4

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