How Effective Is Zilbrysq for Myasthenia Gravis? Plus, 5 Other Zilbrysq FAQs

There’s no cure for myasthenia gravis (MG), a condition that’s been historically difficult to treat. But, thankfully, there are new treatments available to help manage MG symptoms. This rare but serious autoimmune disorder causes muscle weakness in different parts of the body, especially the face, neck, and limbs.

In 2023, the FDA approved the first at-home, injectable treatment for MG. It’s called Zilbrysq (zilucoplan). Here, we’ll answer frequently asked questions about how Zilbrysq works, its benefits, the side effects it causes, and more.

1. How does Zilbrysq work?

With MG, the body's immune system can mistakenly create antibodies that attack acetylcholine receptors (AChR) on muscle cells. Acetylcholine (ACh) is a chemical messenger that normally attaches to these receptors and tells your muscles to move.

These anti-AChR antibodies can block or damage your AChRs. This prevents your brain and nerves from communicating with your muscles. Thus, your muscles don’t work the way they should.

Zilbrysq treats MG by blocking a protein called complement C5. Complement proteins play a role in creating these disruptive antibodies. By blocking complement C5, Zilbrysq is thought to lower the amount of anti-AChR antibodies attacking the body. But keep in mind that Zilbrysq can lower all types of antibodies, which increases the risk of getting infections.

EXPERT PICKS: WHAT TO READ NEXT

• How to tell if it’s myasthenia gravis: Myasthenia gravis has some hallmark symptoms. Learn about five early symptoms to look out for. 

• Navigating myasthenia gravis: Being diagnosed with myasthenia gravis can be unexpected. One woman shares her experience with being diagnosed and navigating a new life.

• Could it be genetic? Find out if you’re at a higher risk of developing myasthenia gravis based on your family history.

2. Who can take Zilbrysq?

Zilbrysq is only FDA approved for adults ages 18 years and older with MG who are anti-AChR antibody-positive. If you’re younger than 18 or don’t have this antibody, Zilbrysq won’t be the right MG treatment for you.

Good to know: About 85% of people that are diagnosed with MG test positive for anti-AChR antibodies. So while many people with MG are able to take Zilbrysq, this isn’t true for everyone. Your healthcare professional can do a blood test for anti-AChR antibodies to see if Zilbrysq is a treatment option for you.

3. How effective is Zilbrysq in treating myasthenia gravis?

Most of what we know about Zilbrysq’s effectiveness comes from the RAISE clinical trial. The RAISE trial was a randomized controlled trial in which some people received Zilbrysq and others received a placebo (an injection with no medication in it).

Researchers conducting the trial found that Zilbrysq was significantly more effective than a placebo in improving symptoms of MG in people who are anti-AChR antibody-positive. The trial looked at how well Zilbrysq improved MG symptoms in daily life. These symptoms included:

• Eye drooping

• Seeing double

• Trouble breathing

• Trouble talking

• Trouble chewing

• Trouble swallowing

• Difficulty with personal grooming

• Loss of independence

Everyone who participated in the RAISE trial was able to enter an extension of the trial called RAISE-XT. RAISE-XT is an “open-label” study in which all of the participants are knowingly receiving Zillbrysq. The RAISE-XT trial hasn’t been completed yet, but it has shown promising results so far.

4. How long is treatment with Zilbrysq?

Zilbrysq is a once-daily, subcutaneous (under the skin) injection. There are three doses of Zilbrysq available: 16.6 mg, 23 mg, and 32.4 mg. And the recommended dosage depends on your body weight.

Zilbrysq recommended dosages by weight are summarized in the chart below. 

Currently, there isn’t a set timeframe for how long Zilbrysq should be taken. But it’s considered to be a long-term maintenance medication. Your prescriber will put together a treatment plan based on your condition. Be sure to keep regular follow-up appointments with your prescriber so they can monitor your MG symptoms.

5. What are the side effects of Zilbrysq?

Like all medications, Zilbrysq has potential side effects to keep in mind.

The most common Zilbrysq side effects are:

• Injection site reactions, such as redness or itching

• Upper respiratory tract infections, such as sinus infections

• Diarrhea

• Urinary tract infections

• Nausea or vomiting

• Increased pancreatic enzymes

Zilbrysq REMS Program

Certain medications carry a risk of dangerous or life-threatening side effects. In these cases, the FDA often implements Risk Evaluation and Mitigation Strategy (REMS) medication safety programs to monitor for side effects. Zilbrysq has one of these programs in place.

Because Zilbrysq is a complement inhibitor, it carries a boxed warning (the FDA’s strictest warning) for rare but life-threatening meningococcal infections — also known as meningitis. Complement inhibitors can lower your amount of antibodies which weakens your immune system. This makes it more difficult for your body to fight off potential infections.

Anyone who receives Zilbrysq must enroll in the Zilbrysq REMS program (with their prescriber’s assistance). You must also be up-to-date on your meningococcal vaccinations before starting Zilbrysq. After starting treatment, your prescriber will closely monitor you for meningitis. If you experience any signs or symptoms of an infection, let your prescriber know right away.

6. What are the best alternatives to Zilbrysq for myasthenia gravis?

In addition to Zilbrysq, there are a few other FDA-approved medications for MG. Your healthcare professional can help you decide which MG treatment is best for you. They will review your medical history, insurance status, and personal preferences to help you make this decision.

Pyridostigmine (Mestinon) is the only oral treatment approved for MG. It’s a cholinesterase inhibitor that prevents the breakdown of ACh.

The other alternatives are injectable biologic medications that are made from living sources. These medications lower your levels of anti-AChR antibodies by suppressing your immune system in specific ways. The biologics used to treat MG are:

• Vyvgart (efgartigimod alfa)

• Vyvgart Hytrulo (efgartigimod alfa / hyaluronidase)

• Rystiggo (rozanolixizumab-noli)

• Ultomiris (ravulizumab)

Furthermore, medications such as steroids and immunosuppressants are often used off-label to treat MG. These medications are not approved to treat MG but are recommended by health experts anyway. This is because historically they’ve been helpful in managing MG symptoms.

How to save on Zilbrysq

There are ways to save on Zilbrysq, which is only available as a brand-name medication. GoodRx can help you navigate between your options, from copay savings cards and patient assistance programs, to help you save money on your prescription:

• Save with a copay savings card. If you have commercial insurance, you may be eligible to pay as little as $0 for Zilbrysq using a savings card from the manufacturer.

• Save with patient assistance programs. If you’re uninsured or underinsured, you may be eligible for Zilbrysq’s patient assistance program, which offers the medication free of charge for up to 1 year.

Why trust our experts?

Written by:

Sheila McAdoo, PharmD

Sheila McAdoo, PharmD, is a licensed pharmacist in Virginia, New York, and the District of Columbia. She has worked in the pharmacy industry for 12 years and currently works as a community pharmacist.

Edited by:

Joshua Murdock, PharmD, BCBBS

Joshua Murdock, PharmD, BCBBS, is a licensed pharmacist in Arizona, Colorado, and Rhode Island. He has worked in the pharmacy industry for more than 10 years and currently serves as a pharmacy editor for GoodRx.

Reviewed by:

Tegan Smedley, PharmD, APh

Tegan Smedley, PharmD, APh, has 10 years of experience as a pharmacist. She has worked in a variety of settings, including retail, hospital, and ambulatory care.

Our editorial standards

Meet our experts