Reviewed by: HU Medical Review Board | Last reviewed: September 2023

The goal of treating myasthenia gravis (MG) is to reduce or improve muscle weakness. Drugs like acetylcholinesterase inhibitors (AChE) inhibitors, steroids, and other immunosuppressants are often used. However, these drugs do not always control symptoms.1

MG that gets worse or does not respond to drugs is called refractory MG. This happens in about 10 percent of cases. Biologic drugs (biologics) are a potential treatment option for people with refractory MG.1,2

Some antibody-based biologics may also be an option for adults with nonrefractory generalized MG. They must also have anti-acetylcholine receptor (AChR) antibodies. Eight out of 10 people with MG fit into this group.3

What are biologics?

Biologics are drugs made from living cells from animals or microorganisms. Biologics can prevent, treat, and cure disease.4

These are different from most traditional drugs. Traditional drugs are made in the lab from chemicals. Their ingredients are not directly produced by living cells. Traditional drugs similar in structure to known biologic drugs are called biosimilars.4

How do biologics work?

The biologics used most often to treat MG are monoclonal antibodies. Antibodies are proteins the immune system makes to fight germs. With autoimmune diseases, the antibodies attack healthy tissue instead of germs.1,2

Monoclonal antibodies drugs are lab-made molecules. They act like the healthy antibodies in the immune system. Some drugs like steroids impact the entire immune system. But monoclonal antibodies target one specific process. The process they target can help limit or prevent the disease.1,2

All monoclonal antibody drugs for MG target processes in the immune system. The specific targeting of these antibody therapies may help cause better results and fewer side effects. It can also be a way to avoid long-term therapy with steroids.1,2


Some antibody-based biologics are only approved for specific types of MG:3,5-12

  • Eculizumab (Soliris®) and efgartigimod (Vyvgart®) can treat people with anti-AchR antibodies and refractory MG.
  • Rituximab (Rituxan®) can treat people with anti-muscle-specific kinase (MuSK) antibodies and refractory MG.
  • Ravulizumab-cwvz (Ultomiris®) can treat people with anti-AChR antibodies and generalized MG (gMG).
  • Efgartigimod alfa and hyaluronidase-qvfc (Vyvgart® Hytrulo) can treat people with generalized MG with anti-AChR antibodies.
  • Rozanolixizumab-noli (Rystiggo®) can treat people with generalized MG (gMG) with anti-AChR or anti-MuSK antibodies.
  • Zilucoplan (Zilbrysq®) is used to treat generalized myasthenia gravis (gMG) in adults who are anti-acetylcholine receptor (AChR) antibody-positive.

If you are unsure what type of MG you have, talk with your doctor.

What are the possible side effects?

Side effects can vary depending on the specific biologic you are taking. Side effects may include:3,5-8

  • Fever or chills
  • Headache
  • Upper respiratory infection
  • Nausea or vomiting
  • Diarrhea
  • Swelling (edema)
  • Muscle or joint pain
  • Changes in white blood cell counts
  • Infections, including respiratory tract and urinary tract infections
  • Changes in electrolyte levels
  • Changes in liver function tests

People taking these antibody therapies for MG are monitored for infections. In some cases, these infections can be life-threatening. Before starting these drugs, tell your doctor if you have any signs of an infection, including:3,5-8

  • Headache
  • Fever
  • Chills
  • Muscle aches
  • Cough
  • Sore throat

Soliris, Ultomiris, and Zilbrysq target the same immune pathway, called the complement system. These biologics have a boxed warning, the strictest warning from the US Food and Drug Administration (FDA). The warnings are similar. People treated with these drugs have developed life-threatening infections including meningitis. Meningitis is a bacterial infection of the brain and spinal cord. It can be deadly if it is not quickly spotted and treated.8,13

It is recommended to get a meningococcal vaccine at least 2 weeks before your first dose of Soliris, Ultomiris, or Zilbrysq. You should get regular booster shots. Your doctor may also recommend antibiotics to avoid meningococcal disease.8,13

Rituxan also has a boxed warning from the FDA. It has this warning because it has been known to cause these serious and even fatal side effects:5

  • After a person received the drug (infusion reactions)
  • Reactions involving the skin and mucous membranes
  • Reactivated hepatitis B
  • Liver failure
  • Brain infection

These are not all the possible side effects of these drugs. Talk to your doctor about what to expect when taking these drugs. You should also call your doctor if you have any changes that concern you when taking these biologics.

Other things to know

Each biologic currently used in MG is different and has its own risks. Some may increase the risk of heart, kidney, or gut problems. Ask your doctor about any issues you may be at risk for and how to best monitor for these.3,5-8

Some biologic drugs can harm an unborn baby. If you or your partner can become pregnant, you should use birth control during treatment and for some time after your last dose.3,5-8

Starting some biologic therapies may impact your ability to receive certain vaccines. Tell your doctor about any vaccines you are scheduled to get before starting treatment.3,5-8

Biologic drugs are often given by IV. Allergic and infusion reactions can occur. Your doctor will monitor you for signs of these issues. If you have a severe reaction to an infusion, the drug may need to be stopped.3,6-8

Before beginning biologics for MG, tell your doctor about all your health conditions and any other drugs, vitamins, or supplements you take. This includes over-the-counter drugs.

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