C5 complement inhibitor (subcutaneous) Pregnancy: No available human data to evaluate drug-associated risk of major birth defects, miscarriage, or adverse maternal/fetal outcomes. Subcutaneous administration to pregnant monkeys increased embryofetal death at all doses tested (maternal exposures similar to human therapeutic exposures) in the absence of maternal toxicity. A pregnancy exposure registry exists (US label §8.1).

Zilucoplan

Brand names: Zilbrysq

Zilucoplan is a complement C5 inhibitor administered by subcutaneous injection for generalised myasthenia gravis in adults who are anti-acetylcholine receptor antibody positive.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Weight-banded once-daily dose: body weight less than 56 kg = 16.6 mg; 56 kg to less than 77 kg = 23 mg; 77 kg and above = 32.4 mg

Route: Subcutaneous injection only (abdomen, thighs, or back of the upper arms; rotate injection sites)

Frequency: Once daily, administered at approximately the same time each day

Max: Do not administer more than 1 dose per day; highest weight-band dosage is 32.4 mg once daily (77 kg and above)

US labelling (ZILBRYSQ, UCB Inc., label date 2026-02-03) — no UK SPC was available in the source bundle; dosing is by ACTUAL body weight. BEFORE INITIATION: obtain baseline lipase and amylase levels; vaccinate against meningococcal infection (serogroups A, C, W, Y and B) per current ACIP recommendations at least 2 weeks before the first dose — if urgent therapy is needed in a patient not up to date, give antibacterial prophylaxis and vaccinate as soon as possible. Prescribers must enrol in the ZILBRYSQ REMS. Prefilled syringes are single-dose; if refrigerated, allow to reach room temperature out of direct sunlight for 30–45 minutes before injecting (do not heat/microwave); may be stored at room temperature in the original carton for up to 3 months (do not return to the refrigerator thereafter). Do not use if the solution is cloudy or contains visible particles. Intended for use under the guidance and supervision of a healthcare professional; patients/caregivers may self-inject after training (upper outer arm injections should be given by a caregiver). MISSED DOSE: administer as soon as possible, then resume the regular schedule — do not give more than 1 dose per day. PAEDIATRICS: safety and effectiveness in paediatric patients have not been established (US label §8.4) — no paediatric dose is stated; verify against a children's formulary and specialist advice. ELDERLY: clinical studies did not include sufficient numbers of patients aged 65 and older to determine whether they respond differently. Source label relates to use in generalised myasthenia gravis (gMG). No renal dose adjustment statement was present in the fetched sections.

Dose auto-extracted from US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Contraindicated for initiation in patients with unresolved serious Neisseria meningitidis infection

Side effects

Injection site reactions (most common, ≥10%)
Upper respiratory tract infection (most common, ≥10%)
Diarrhoea (most common, ≥10%)
Serious meningococcal infections — septicaemia and/or meningitis, any serogroup including non-groupable strains; life-threatening and fatal cases have occurred in both vaccinated and unvaccinated patients on complement inhibitors
Pancreatitis and pancreatic cysts — discontinue if pancreatitis is suspected and manage until ruled out or resolved
Other systemic infections — use caution in patients with any other systemic infection

Clinical monograph

How it works

This macrocyclic peptide binds complement component C5, blocking its cleavage and preventing formation of the membrane attack complex, thereby protecting the neuromuscular junction from complement-mediated damage.

Prescribing in practice

By inhibiting terminal complement it markedly increases susceptibility to meningococcal and other encapsulated-organism infections, so meningococcal vaccination is required before starting and patients must be counselled to seek urgent care for signs of meningitis.
It is given as a daily self-administered subcutaneous injection and patients should be trained in proper technique.
It may be used alongside other myasthenia treatments under specialist supervision.

Monitoring

Ensure meningococcal vaccination is up to date and monitor for signs of serious infection and for clinical response of myasthenic symptoms.

Counselling the patient

Get any recommended meningococcal vaccinations and carry a patient safety card, seeking urgent care for fever, severe headache or neck stiffness.
Learn and follow the correct technique for the daily subcutaneous injection.

Evidence & guidelines

Its efficacy in anti-AChR-positive generalised myasthenia gravis was shown in the RAISE randomised controlled trial.

Reference: NICE HST25; SmPC; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways