Pronunciation: ZIL-brisk
Generic name: zilucoplan
Dosage form: subcutaneous injection (16.6 mg/0.416 mL, 23 mg/0.574 mL, 32.4 mg/0.81 mL.)
Drug class: Selective immunosuppressants

Medically reviewed by Melisa Puckey, BPharm. Last updated on Apr 6, 2025.

What is Zilbrysq?

Zilbrysq (zilucoplan) injection is a prescription medicine used for generalized myasthenia gravis (gMG) to help improve symptoms in patients who are AChR antibody positive (AChR-Ab+). Zilbrysq is the first once-daily, under-the-skin injection that can be self-administered by MG patients. Zilbrysq works by blocking a protein (C5) in the immune system that is involved with the symptoms of generalized myasthenia gravis. Zilbrysq (zilucoplan) is from the class of medicines called complement inhibitors and is a C5 inhibitor.

Zilbrysq became an FDA-approved medication on October 17, 2023, based on positive results from the 12-week phase 3 trial RAISE (NCT04115293). Zilbrysq is indicated for adult patients with generalized myasthenia gravis that is antiacetylcholine receptor (AChR) antibody positive. Zilbrysq showed rapid and clinically meaningful improvements in symptoms of MG, compared to a placebo, measured using the MG-ADL score.

What is myasthenia gravis?

Myasthenia gravis is a long-term (chronic) autoimmune disease that causes muscle weakness, leading to symptoms of double vision, drooping eyelids, trouble talking, breathing, and trouble walking. Myasthenia gravis is caused by antibodies from your immune blocking or attacking receptors between nerves and muscles,  which makes it harder for the muscles to contract. Many patients with myasthenia gravis have antibodies that attack the nicotinic acetylcholine receptors (AChR); these patients are called AChR antibody positive (AChR-Ab+).

Usually, the first and main symptom of MG is painless weakness of specific muscles that gets worse towards the end of the day. It may also become worse during physical activity and then improve after rest. MG symptoms often start with eye weakness; then, over a period of time, they may progress to a severe generalized form, with weakness in arms and legs or in muscles involved in swallowing and breathing.

The complement system is part of the immune system that becomes activated in MG, damaging the neuromuscular junction and causing symptoms of MG. 

How does Zilbrysq work?

Zilbrysq reduces complement-mediated damage to the junction between the nerves and muscles through its targeted mechanism of action of inhibiting complement component 5.  The complement system is part of the immune system and, when activated, drives myasthenia gravis. By Zilbrysq blocking the complement system, Zilbrysq helps improve myasthenia gravis symptoms.

Zilbrysq is a C5 inhibitor that works by suppressing the C5 protein in the immune complement system. This stops C5b-9 from being made and deposited at the neuromuscular junction. It is thought that the decrease in C5b-9 deposited at the neuromuscular junction causes generalized myasthenia gravis symptoms to improve.

Zilbrysq is not a monoclonal antibody,  so it can be used with intravenous immunoglobulin and plasma exchange without needing supplemental dosing.

Zilbrysq study 

The Zilbrysq study was a 12-week phase 3 study called RAISE (NCT04115293). It was a randomized, double-blind, placebo-controlled with 174 adults with anti-AChR-positive gMG. The effectiveness of Zilbrysq was measured using the MG-ADL score, which measures the impact of myasthenia gravis on daily functioning, a higher score meaning more severe symptoms. When the MG-ADL score decreases it means that myasthenia gravis symptoms have improved.

Zilbrysq Efficacy Results (MG-ADL Score at 12 Weeks)

• Zilbrysq Group: Average improvement in MG-ADL score: –4.4
• Placebo Group: Average improvement in MG-ADL score: –2.3

• Difference Between Groups: –2.1 points in favor of Zilbrysq

Zilbrysq study result/benefit

• Zilbrysq patients experienced greater clinically significant improvement in muscle weakness and daily function compared to placebo patients.

Zilbrysq side effects

Common Zilbrysq side effects

The most common Zilbrysq side effects were diarrhea (11%), injection site reactions (29%), upper respiratory tract infection (14%), urinary tract infections 8%, nausea or vomiting 8%, lipase increased (7%) and amylase increase (5%). These common side effects occurred in 5% or more of Zilbrysq patients and more frequently than patients taking the placebo in Study 1. 

Serious Zilbrysq side effects.

Serious Zilbrysq side effects may include:

Inflammation of the pancreas (pancreatitis) and other pancreatic problems. Pancreatitis and pancreatic cysts have occurred in people who use this medicine. Your healthcare provider will do blood tests (baseline lipase and amylase levels) to check your pancreas before you start treatment. 

Call your healthcare provider right away if you have pain in your stomach area (abdomen) that will not go away. Your healthcare provider will tell you if you should stop using this medicine if you are having problems with your pancreas. The pain may be severe or felt going from your abdomen to your back. The pain may happen with or without vomiting. These may be symptoms of pancreatitis.

Also, see the Warnings section.

Tell your healthcare provider about any side effect that bothers you or that does not go away. These are not all the possible side effects of Zilbrysq. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA1088.

Related/similar drugs

Warnings

Zilbrysq affects part of your immune system and may lower the ability of your immune system to fight certain infections, therefore increasing your chance of getting serious and life-threatening meningococcal infections.

• Meningococcal infections may become life-threatening or fatal if not recognized and treated early. You must complete or update two types of meningococcal vaccines (for both serogroup B infections and serogroup A, C, W, and Y infections) at least 2 weeks before your first dose of this medicine, if you have not already had these vaccines.
• If your healthcare provider decides that urgent treatment with Zilbrysq is needed, you should receive meningococcal vaccination(s) as soon as possible. 
• If you have not completed or updated vaccinations for meningococcal infections at least 2 weeks before your first Zilbrysq dose and therapy must be started right away, you must also receive antibiotics. 
• If you had a meningococcal vaccine in the past, you might need additional vaccination before starting this medicine. Your healthcare provider will decide if you need additional meningococcal vaccination. 
• Meningococcal vaccines do not prevent all meningococcal infections. Call your healthcare provider or get emergency medical care right away if you get any of these signs and symptoms of a meningococcal infection:  headache with nausea or vomiting, confusion,  headache and fever, muscle aches with flu-like symptoms, headache with a stiff neck or stiff back, eyes sensitive to light, fever,  and fever with a rash.

Your healthcare provider will give you a Patient Safety Card about the risk of meningococcal infection. Carry it with you at all times during treatment and for 2 months after your last dose. Your risk of meningococcal infection may continue for several weeks after your last dose of this medicine. It is important to show this card to any healthcare provider who treats you. This will help them diagnose and treat you quickly. 

Zilbrysq is only available through a program called the Zilbrysq REMS. Before you can receive this medicine, your healthcare provider must: 

• enroll in the Zilbrysq REMS. 
• counsel you about the risk of meningococcal infection. 
• give you the Patient Guide, including information about the signs and symptoms of meningococcal infection. 
• give you a Patient Safety Card about your risk of meningococcal infection, as discussed above. 
• make sure you are vaccinated with two types of meningococcal vaccine and, if needed, get revaccinated with the meningococcal vaccine. Ask your healthcare provider if you are unsure if you need to be revaccinated. 

Zilbrysq may also increase the risk of other types of serious infections. This injection may increase your chance of getting Streptococcus pneumoniae and Haemophilus influenzae type b. Your healthcare provider will tell you if you should receive the Streptococcus pneumoniae and Haemophilus influenzae type b vaccinations. 

Certain people may have an increased risk of gonorrhea infection. Talk to your healthcare provider about whether you are at risk for gonorrhea infection, about gonorrhea prevention, and about regular testing. 

Call your healthcare provider right away if you have new signs or symptoms of infection.

Who should not take Zilbrysq? 

You should not use this medicine if you have a Neisseria meningitidis infection.

Before taking this medicine

Tell your healthcare provider about all of your medical conditions, including if you: 

• have an infection or fever.

Pregnancy

Tell your healthcare provider if you are pregnant or plan to become pregnant , as It is not known if Zilbrysq will harm your unborn baby. 

Breastfeeding

Tell your healthcare provider if you are breastfeeding or plan to breastfeed as it is not known if Zilbrysq  passes into your breast milk. Talk to your healthcare provider about the best way to feed your baby if you are using this medicine.

How should I use Zilbrysq?

Your doctor or healthcare provider will give you the detailed Instructions for Use that come with your injection. This has information on how to prepare and use this medicine and how to throw away the used prefilled syringes properly. Use this medicine exactly as prescribed by your healthcare provider after proper training on how to prepare and inject Zilbrysq.

Zilbrysq instructions

• Zilbrysq is given as a daily injection under the skin (subcutaneous) using a prefilled syringe. The daily dose should be administered at approximately the same time each day. 
• Zilbrysq is injected into areas of the abdomen, thighs, or back of the upper arms that are not tender, bruised, red, or hard. You should not inject into skin areas with scars or stretch marks. Only a caregiver can give Zilbrysq in the upper, outer arm.
• Rotate injection sites for each administration.

Your healthcare provider will decide the total daily dose depending on your body weight. 

Each prefilled syringe is for single-use only. Throw away the prefilled syringe after each use. Do not reuse. 

Zilbrysq Dosing Information 

The recommended adult Zilbrysq dose is based on actual body weight.

• Less than 56kg = 16.mg daily
• 56 kg to less than 77 kg = 23 mg daily
• 77 kg and above = 32.4 mg.

For more detailed dosing information, click on the link below.

What strengths is Zilbrysq available as?

Zilbrysq is available as prefilled syringes as 16.6 mg/0.416 mL, 23 mg/0.574 mL, or 32.4 mg/0.81 mL.

What should I do if I miss a dose?

If you miss your Zilbrysq dose, inject a dose as soon as possible. Then, inject your next dose at your regular scheduled time. Do not inject more than 1 dose each day. Call your healthcare provider if you are not sure what to do.

Interactions

Tell your healthcare provider about all the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements. Know the medicines you take and the vaccines you receive. Keep a list of them to show your healthcare provider and pharmacist when you get a new medicine.

Zilbrysq Prescribing Information

HCPs and patients often use the Zilbrysq Prescribing Information for more detailed information about this medicine. The Zilbrysq Prescribing Information contains more comprehensive information on Indications and Usage, Dosage and Administration, Clinical Pharmacology, Clinical Studies, Drug Interaction, and more. Discuss any medical questions you have with your HCP (health care professional). This is not all the information you need to know about this medicine for safe and effective use, and it does not take the place of talking to your doctor about your treatment.

The Prescribing Information is sometimes called Zilbrysq Package Insert or FDA label.

Storage

Pharmacy Prior to Dispensing 

• Prefilled syringes refrigerated at 2°C to 8°C (36°F to 46°F) in the original carton until dispensing. 
• Do not freeze. 

Storage for Patients or Caregivers After Dispensing

• Store at 2°C to 8°C (36°F to 46°F)  until expiration date on the carton.
• Store up to 30°C (86°F) for up to 3 months after removing from refrigerator or until expiration date on the carton, whichever occurs first. Write the date removed from the refrigerator in the space provided on the carton.
• Do not freeze. 
• Store prefilled syringes in the original carton to protect them from light until time of use.

Ingredients

Active ingredient: zilucoplan.

Inactive ingredients: dibasic sodium phosphate, anhydrous, monobasic sodium phosphate, monohydrate, sodium chloride, and water for injection.

Manufacturer

Manufactured for: UCB, Inc., Smyrna, GA 30080 ZILBRYSQ® is a registered trademark of the UCB Group of Companies. ©2023 UCB, Inc., Smyrna, GA 30080.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Medical Disclaimer