The goal of treating myasthenia gravis (MG) is to reduce or improve muscle weakness. Drugs like acetylcholinesterase inhibitors (AChE) inhibitors, steroids, and other general immunosuppressants are often used. However, these do not always control symptoms.1
MG that gets worse or does not respond to these drugs is called refractory MG. This happens in about 10 percent of cases. Biologic drugs (biologics), specifically antibody-based medicines, are a potential immunosuppressive treatment option for people with refractory MG. Antibodies are proteins the body’s immune system makes to kill germs.1,2
Some biologics may also be an option for adults with nonrefractory generalized MG who have anti-acetylcholine receptor (AChR) antibodies. Eight out of 10 people with MG fit into this group.3
What are they?
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 the autoimmune disease MG are what are known as monoclonal antibodies. Antibodies are proteins the immune system naturally makes to fight germs. With an autoimmune disease, the body begins to attack healthy tissue instead of germs.1,2
Drugs that are monoclonal antibodies are lab-made molecules that act like healthy antibodies in the immune system. Rather than impacting the entire immune system the way steroids and other drugs do, these monoclonal antibodies are designed to target 1 specific process in the body. Unlike the bad antibodies in MG that cause disease, these monoclonal antibodies target a process in the body that can help limit or prevent disease. All of the monoclonal antibody drugs used to treat MG target processes in the immune system and so cause some form of immunosuppression. The specific targeting of these antibody therapies may help lead to better results and fewer side effects. It can also be a way to avoid long-term therapy with steroids, which has risks.1,2
Examples
Some antibody-based biologics are only approved for specific types of MG:3,5-8
- Eculizumab (Soliris®) and efgartigimod (Vyvgart®) may be used in people with AchR-positive refractory MG
- Rituximab (Rituxan®) may be used in people with MuSK-positive refractory MG
- Ravulizumab-cwvz (Ultomiris®) may be used in people with AChR-positive generalized MG
If you are unsure what type of MG you have, talk with your doctor.
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
Because they impact and suppress the immune system, 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 and Ultomiris target the same immune pathway, called the complement system. Both of 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.8,9
Health experts suggest you get a meningococcal vaccine at least 2 weeks before your first dose of Soliris or Ultomiris to decrease the risk of meningitis. You should get regular booster shots. Your doctor may also recommend antibiotics to avoid meningococcal disease.8,9
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 the last dose of your biologic. Talk to your doctor about options for birth control while taking these biologics.3,5-8
Starting immunosuppressive antibody-based biologic therapy 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 a biologic infusion, the drug may need to be stopped.3,6-8
Before beginning biologics for myasthenia gravis, tell your doctor about all your health conditions and any other drugs, vitamins, or supplements you take. This includes over-the-counter drugs.
