Pegcetacoplan
Complement inhibitors
Complement inhibitors
A complement C3 inhibitor injected under the skin for PNH and some C3-driven kidney diseases; it raises the risk of meningococcal infection.
Quick facts
- Group
- Complement inhibitors
- Target
- Complement component C3 (plasma protein)
- Used for
- Paroxysmal nocturnal haemoglobinuria
- Key effects
- Diarrhoea · Injection-site redness or swelling · Joint
- ATC
- L04AJ03
No doses: the clinician sets them by the current guideline.
Mechanism of action
No structure with pegcetacoplan is available; the figure shows human C3c bound to compstatin, the peptide family pegcetacoplan belongs to (it is a compstatin-based peptide joined to polyethylene glycol).
Pegcetacoplan binds complement C3, upstream of C5. This blocks both the coating of red cells with C3 fragments (which leads to their removal in the liver and spleen) and the later formation of the membrane attack complex. It controls PNH but does not cure it.
- Pegcetacoplan binds complement C3
- C3 is not activated, so red cells are not coated with C3 fragments
- The downstream steps, including C5 and the lytic pore, are not reached
Indications
- Paroxysmal nocturnal haemoglobinuria Paroxysmal nocturnal haemoglobinuria →
- C3 glomerulopathy or primary immune-complex membranoproliferative glomerulonephritis
Adverse effects
Common
- Diarrhoea, abdominal pain, nausea
- Injection-site redness or swelling, bruising
- Headache, dizziness, tiredness
- Joint, muscle or back pain
- Cough, nasal congestion, nosebleeds, leg swelling
Contraindications
- Hypersensitivity to pegcetacoplan
- Certain active infections, including meningococcal infection
- Not vaccinated as required, unless antibiotic cover is given
Key interactions
- Vaccines against meningococcus and other encapsulated bacteria
- Required at least 2 weeks before starting; boosters may be needed
What is monitored
- Blood tests for haemolysis during treatment
- Monitoring for at least 8 weeks after stopping
- Pregnancy test before starting when relevant
Administration and safety
- Subcutaneous infusion with a pump or on-body injector, taught by a nurse or doctor
- Brought to room temperature without heating; injection sites rotated, avoiding scarred, bruised or tattooed skin
- Available only through a risk-management (REMS) programme; a Medication Guide comes with each supply
- Needles and devices go in a sharps container
Pregnancy and breastfeeding
It may harm the fetus: effective contraception is used during treatment and for a time after the last dose, and breastfeeding is avoided.
Nursing care
- Confirm vaccinations before the first dose
- Teach the warning signs of meningococcal infection and to seek care at once
- Teach the patient to carry the safety card during treatment and for 2 months after
- Warn that stopping without advice can trigger haemolysis and clots
Pharmacokinetics
- Absorption
- Subcutaneous infusion with a pump or on-body injector
Test yourself
Think of the answer, then tap the question to see it.
Which complement protein does pegcetacoplan block?
C3.
Why can a C3 inhibitor help PNH patients who stay anaemic on a C5 inhibitor?
It also stops the C3 coating that leads to red-cell removal outside the vessels.
How is pegcetacoplan given?
By subcutaneous infusion with a pump or on-body injector.
Connections
← Back to the class: Complement inhibitors
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Pegcetacoplan Injection: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2025); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026); 2QKI: Human C3c in complex with the inhibitor compstatin (RCSB Protein Data Bank, 2007).
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Representative model, for educational purposes only.