FDA-approved
Bones & muscles
Zilucoplan
Zilucoplan (Zilbrysq) is an FDA-approved peptide that blocks complement C5 in antibody-positive myasthenia gravis. Learn how it works and its risks.
- Reviewed by
- William Maish, MD MBA MPH, Clinical Product Lead
- Published
- October 5, 2026
- Last updated
- October 5, 2026
Key takeaway
Zilucoplan (sold as Zilbrysq) is a macrocyclic peptide that blocks complement protein C5, used to treat generalized myasthenia gravis in adults who carry a specific antibody. By preventing complement damage at the nerve-muscle junction, it improves daily function. It has been FDA-approved in the U.S. since 2023 and is a once-daily self-injection.
At a glance
| What it is | A complement C5 inhibitor, a macrocyclic peptide |
| Approved for | Generalized myasthenia gravis in adults who are anti-acetylcholine-receptor antibody positive |
| Key fact | In the RAISE trial it significantly improved myasthenia gravis daily-living scores versus placebo at 12 weeks |
| Route | Subcutaneous injection, once daily (self-administered) |
| Evidence strength | FDA approved |
What is zilucoplan?
Zilucoplan, sold under the brand Zilbrysq, is a synthetic macrocyclic (ring-shaped) peptide that inhibits complement component C5. It treats generalized myasthenia gravis (gMG), an autoimmune disease in which antibodies attack the connection between nerve and muscle, causing weakness. It is used specifically in patients whose disease is driven by antibodies to the acetylcholine receptor. It was developed under the code RA101495 and approved in the United States in 2023.
How does zilucoplan work?
Zilucoplan binds complement protein C5 and blocks its cleavage into the fragments C5a and C5b, which prevents assembly of the membrane attack complex, the complement structure that punches holes in cell membranes. In antibody-positive generalized myasthenia gravis, antibodies against the acetylcholine receptor recruit complement to the neuromuscular junction, and the resulting membrane attack complex damages the muscle's receptor-bearing surface, impairing signal transmission and causing weakness. By blocking C5, zilucoplan protects that junction from complement damage.
As a small peptide, it can be given as a simple once-daily subcutaneous injection that patients administer themselves, which is a practical contrast to intravenous complement therapies. In the phase 3 RAISE trial, zilucoplan significantly improved the myasthenia gravis activities-of-daily-living score1 compared with placebo at 12 weeks.
Is it FDA-approved?
Yes. Zilucoplan was approved2 by the FDA in 2023 for generalized myasthenia gravis in adults who are anti-acetylcholine-receptor antibody positive. It carries a boxed warning for serious meningococcal infections, requires meningococcal vaccination, and is dispensed only through a risk management program.
What is zilucoplan prescribed for?
Zilucoplan is prescribed for generalized myasthenia gravis in adults who test positive for antibodies to the acetylcholine receptor. It is self-injected once daily, offering an at-home option within the complement-inhibitor class.
What are the side effects?
According to the prescribing information, common side effects include:
- Injection-site reactions and bruising
- Upper respiratory tract infections
- Diarrhea
More serious considerations include:
- A boxed warning for serious meningococcal infections, requiring vaccination and a risk management program
- Other serious infections
- Pancreatitis and pancreatic cysts
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Sources: FDA prescribing information for Zilbrysq; the RAISE trial (Howard et al., The Lancet Neurology, 2023, DOI: 10.1016/S1474-4422(23)00080-71), indexed on PubMed. This document is educational and does not constitute medical advice.