Zilbrysq (zilucoplan)

Zilbrysq is the brand name for zilucoplan, a once-daily injection under the skin for adults with generalized myasthenia gravis who test positive for antibodies against the acetylcholine receptor (AChR).

The disease: Myasthenia gravis is an autoimmune disease in which those antibodies disrupt the connection between nerves and muscles, causing weakness that gets worse with activity.

Maker: Zilbrysq is made by UCB and was the first complement inhibitor for this disease that patients can inject themselves at home.

Children: It has not been studied in children.

Source: FDA label for Zilbrysq, DailyMed, effective 2026-02-03

Zilucoplan is a small, ring-shaped peptide made of 15 amino acids that grabs onto complement protein C5, part of the immune system's complement cascade.

What blocking C5 does: By holding C5, it stops the protein from being split into C5a and C5b, which prevents the body from assembling the terminal complement complex (C5b-9), also called the membrane attack complex.

Why it helps: In AChR-positive myasthenia gravis, that complex is what the antibodies trigger to damage the junction where nerve meets muscle, so blocking it protects the connection.

What is known: The label notes the exact way this translates into stronger muscles is presumed rather than proven, but trial patients had 97.5% complement blockade by the end of the first week.

Source: FDA label for Zilbrysq, DailyMed, effective 2026-02-03

Injection site reactions were the most common side effect in the placebo-controlled trial, and the most serious risk is meningococcal infection.

Common side effects: In the 12-week placebo-controlled trial, the side effects reported more often on Zilbrysq than on placebo were injection site reactions (29% vs 16%), upper respiratory infections (14% vs 7%), diarrhea (11% vs 2%), urinary tract infections (8% vs 5%), nausea or vomiting (8% vs 7%), raised lipase (7% vs 0%), and raised amylase (5% vs 1%).

Pancreas: Lipase and amylase are pancreas enzymes, and the label warns that pancreatitis and pancreatic cysts have occurred.

Eosinophils: Some patients also had temporary rises in a type of white blood cell called eosinophils, which the label says is of uncertain importance.

Serious risk: The most serious risk, covered by a boxed warning, is life-threatening meningococcal infection.

Source: FDA label for Zilbrysq, DailyMed, effective 2026-02-03

Zilbrysq carries the FDA's strongest warning because blocking complement raises the risk of serious, sometimes fatal infections from Neisseria meningitidis, the bacteria that cause meningitis and blood infection.

Vaccines: You need meningococcal vaccines covering serogroups A, C, W, Y, and B at least 2 weeks before your first dose unless your doctor decides treatment cannot wait, in which case you get preventive antibiotics and the vaccines as soon as possible.

Warning signs: Vaccination lowers but does not remove the risk, so get emergency care for fever, fever with a rash, severe headache, stiff neck, confusion, or sensitivity to light.

REMS program: Because of this risk, Zilbrysq is only available through a restricted program called ZILBRYSQ REMS, and you must carry a Patient Safety Card during treatment and for 2 months after stopping.

Source: FDA label for Zilbrysq, DailyMed, effective 2026-02-03

Rash is not listed as a trial side effect of Zilbrysq, so a new rash deserves attention rather than reassurance.

Injection site reactions: The skin reaction the label does list is at the injection site (redness, pain, or a bump where you injected), reported by 29% of trial patients versus 16% on placebo; rotating sites on the belly, thighs, or backs of the upper arms helps.

Morphea: In long-term extension studies of 213 patients, 5% developed morphea, a patchy hardening and discoloration of the skin, usually more than 1 year after starting and mild to moderate in severity.

Fever with rash: Most important, a fever with a rash is one of the warning signs of meningococcal infection, so that combination means go to the emergency room right away.

Source: FDA label for Zilbrysq, DailyMed, effective 2026-02-03

The drug blocks complement within hours, but the label does not give a timeline for when muscle strength improves.

Complement blockade: In an earlier study, complement activity was 89.1% suppressed within 3 hours of the first injection, and in the main trial it was 97.5% suppressed by the end of week 1 and stayed there.

Blood levels: Blood levels of zilucoplan reach a steady state after about 4 weeks of daily dosing.

Symptom improvement: The label does not state how many days or weeks it takes for muscle strength or daily function to improve, because the trial measured its main results at 12 weeks. Your neurologist will usually judge your response over the first few months.

Source: FDA label for Zilbrysq, DailyMed, effective 2026-02-03

In the RAISE trial, Zilbrysq improved daily function and muscle strength more than placebo.

Trial design: The RAISE trial (called Study 1 on the label) enrolled 174 adults with AChR-positive generalized myasthenia gravis and gave them daily Zilbrysq or placebo for 12 weeks on top of their usual treatment.

MG-ADL results: On the MG-ADL scale, which scores 8 daily activities like talking, chewing, and breathing from 0 to 24, Zilbrysq patients improved by 4.39 points versus 2.30 on placebo, a difference of 2.09 points.

QMG results: On the QMG strength exam, scored 0 to 39, they improved by 6.19 points versus 3.25, a difference of 2.94 points.

Responder rates: Also, 73.1% of Zilbrysq patients had at least a 3-point MG-ADL improvement versus 46.1% on placebo, and 58% had at least a 5-point QMG improvement versus 33%.

Source: FDA label for Zilbrysq, DailyMed, effective 2026-02-03

Zilucoplan is a peptide with a long half-life that the body breaks down without using liver enzymes.

Absorption: After an injection under the skin, zilucoplan peaks in the blood about 3 to 6 hours later and more than 99% of it is bound to blood proteins.

Half-life: Its half-life, the time for the level to fall by half, is about 172 hours, or 7 to 8 days, which is why levels build up roughly 3-fold with daily dosing before settling at a steady state.

Breakdown: Because it is a peptide, the body breaks it down into smaller peptides and amino acids rather than using liver enzymes like CYP3A4, and less than 1% leaves in urine or stool.

Dose adjustments: No dose change is needed for kidney impairment or for mild to moderate liver impairment, and no interactions with other drugs are expected.

Source: FDA label for Zilbrysq, DailyMed, effective 2026-02-03

The FDA approved Zilbrysq in 2023 for adults with AChR antibody-positive generalized myasthenia gravis, making it the first complement inhibitor for the disease that can be self-injected.

Development: It was developed by Ra Pharmaceuticals under the code RA101495 and brought to market by UCB after UCB acquired that company.

Label updates: The label was most recently updated in February 2025 to revise the boxed warning, contraindication, and infection warnings.

Source: FDA label for Zilbrysq, DailyMed, effective 2026-02-03

The dose is based on your body weight and works out to about 0.3 mg per kilogram.

Dose by weight: You take 16.6 mg a day if you weigh less than 56 kg (red plunger), 23 mg if you weigh 56 to less than 77 kg (orange plunger), and 32.4 mg if you weigh 77 kg or more (dark blue plunger).

How to inject: You inject the full prefilled syringe under the skin of the belly, thigh, or back of the upper arm once a day at about the same time, rotating sites and avoiding scars, stretch marks, or bruised areas.

Self-injection: After training from your care team you can do this yourself at home, though injections in the upper outer arm should be done by a caregiver.

Missed dose: If you miss a dose, take it as soon as you remember and never inject more than 1 dose in a day.

Source: FDA label for Zilbrysq, DailyMed, effective 2026-02-03

The FDA label does not list a price, and we do not publish one because what you pay depends on your insurance.

What to expect: Zilbrysq is a specialty medicine dispensed through pharmacies certified in the REMS program, so expect prior authorization.

Support program: UCB runs a support program called ONWARD that pairs patients with medically trained care coordinators who review financial assistance options and help with treatment logistics; you can learn more at ucbonward.com.

What to do: Your neurologist's office can also help you enroll.

Source: UCB ONWARD patient support program

Yes, pancreatitis (inflammation of the pancreas) and pancreatic cysts have been reported.

Long-term studies: In long-term extension studies, 3.3% of patients had a pancreatic event, including 1.9% with pancreatitis and 1.4% with cysts.

Enzyme changes: In the 12-week trial, 6.9% of Zilbrysq patients had raised lipase and 4.7% had raised amylase versus 0% and 1.1% on placebo, and 7% had lipase more than 3 times the upper limit of normal.

What to do: Your doctor checks these 2 enzymes before you start, and severe stomach pain that spreads to your back, with or without vomiting, should be reported right away because the drug is stopped if pancreatitis is suspected.

Source: FDA label for Zilbrysq, DailyMed, effective 2026-02-03

Keep the prefilled syringes in the refrigerator at 36 to 46 degrees F (2 to 8 degrees C) in their original carton to protect them from light, and never freeze them.

Room temperature: You can also keep a carton at room temperature up to 86 degrees F (30 degrees C) for a single period of up to 3 months; write the date you took it out on the box and do not put it back in the fridge.

Before injecting: Let a refrigerated syringe sit out of direct sunlight for 30 to 45 minutes to warm up, and do not microwave or heat it.

Check the solution: It should be clear to slightly cloudy and colorless; do not use it if you see particles.

Source: FDA label for Zilbrysq, DailyMed, effective 2026-02-03

You need meningococcal vaccines against serogroups A, C, W, Y, and B, finished at least 2 weeks before your first dose.

Schedule: Follow the schedule the CDC's vaccine committee (ACIP) sets for people on complement inhibitors, which differs from the usual schedule.

Pneumococcal vaccine: The label also recommends pneumococcal vaccination, because blocking complement makes you more vulnerable to Streptococcus pneumoniae, Haemophilus influenzae, and to a lesser degree gonorrhea.

Boosters: Boosters are needed over time depending on how long you stay on treatment.

Limits: Vaccines reduce but do not erase the infection risk, so you still need to know the warning signs.

Source: FDA label for Zilbrysq, DailyMed, effective 2026-02-03

Both block complement protein C5, but they are very different molecules.

How they are given: Zilucoplan is a small synthetic peptide given as a daily injection under the skin that you can do yourself at home, while eculizumab is a large monoclonal antibody given as an IV infusion at an infusion center every 2 weeks.

Shared risk: The Zilbrysq label notes that life-threatening meningococcal infections have occurred with complement inhibitors as a class, so the vaccine requirements apply whichever one you use.

Choosing: The label does not compare the 2 drugs head to head, so the choice usually comes down to convenience and what your insurance covers.

Source: FDA label for Zilbrysq, DailyMed, effective 2026-02-03

They attack the disease at different points.

Zilucoplan: Zilucoplan blocks complement, the downstream immune machinery that the AChR antibodies use to damage the nerve-muscle junction.

FcRn inhibitors: FcRn inhibitors such as efgartigimod instead lower the overall amount of circulating antibodies, including the harmful ones.

Choosing: Because the mechanisms differ, your neurologist may prefer one or the other based on your antibody type, infection history, and how often you want to be treated.