Immunotherapy Drugs for Myasthenia Gravis

Myasthenia gravis (MG) is a chronic autoimmune disorder that causes certain muscles to become weak, especially after use. There is no cure for MG, but there are several drugs to help treat its symptoms and manage the underlying disease.

Acetylcholinesterase inhibitors are the first type of drug prescribed for people with MG. Acetylcholinesterase inhibitors quickly improve how the nerves transmit signals to the muscles. Some people with MG do not need to take another medicine to keep their symptoms under control.

However, many people with MG also need to take a drug that targets the immune system. These drugs can change how the immune system acts.¹

How do immunotherapy drugs work?

Immunosuppressants calm, or suppress, an overactive immune system. There are different forms of immunosuppressant drugs, including steroids and nonsteroidal immunosuppressants.¹

Another type of immune system-targeting drugs are called immunomodulators. Immunomodulators modulate (change) how the body’s immune system is working.¹

Examples

Steroids

Steroids (also called glucocorticoids) are usually the first add-on medicine a doctor will try if a person’s MG symptoms are not well-controlled by an acetylcholinesterase inhibitor. Prednisone is a common steroid often prescribed for people with MG. However, there are dozens of steroids on the market.

Steroids reduce inflammation by suppressing the immune system. This means that the body's immune system is less active and harmful antibodies are less likely to attack healthy tissue. However, this means the body is also less able to fight infections.¹

Many people with generalized MG need to take both an acetylcholinesterase inhibitor and a low-dose immunosuppressant long-term. Doctors try to prescribe the lowest steroid dose possible due to the many side effects of long-term use. However, large doses of steroids may be needed to quickly reduce severe symptoms. Large doses of steroids are often given in the hospital so the person can be watched closely.¹

Immunosuppressants

Steroids are an old and effective class of drugs used to calm the immune system. However, steroids often have many side effects when used long-term at high doses. That is why many people with MG transition to taking other immunotherapies.

Nonsteroidal immunosuppressants take longer than steroids to control symptoms. Thus, steroids are often combined with another immunotherapy until the immunosuppressant therapy starts working.

Examples of nonsteroidal immunosuppressants include:¹

• Azathioprine (brand names Azasan^®, Imuran^®)
• Cyclosporine (brand names Gengraf^®, Neoral^®, Sandimmune^®)
• Methotrexate (brand names Rheumatrex^®, Trexall^®)
• Mycophenolate mofetil (brand name Cellcept^®)
• Tacrolimus (brand names Astragraf^®, Envarsus^®, Prograf^®)

Antibody-based biologics

Biologics are drugs made from living cells. They can be derived from human or animal cells, tissues, or blood, among other sources. The process of making biologics turns products from living organisms into drugs that can prevent, treat, and cure diseases like MG. In MG, all the biologic drugs consist of antibodies made by cells. These antibodies target and suppress specific immune cells or immune pathways that are involved in MG. Examples of some antibody-based biologics used to treat MG include:

• Eculizumab (brand name Soliris^®)
• Efgartigimod alfa and hyaluronidase-qvfc (Vyvgart^® Hytrulo)
• Ravulizumab-cwvz (Ultomiris^®)
• Rituximab (brand names Rituxan^®, Ruxience^®, Truxima^®)
• Rozanolixizumab-noli (Rystiggo^®)

What are the possible side effects?

Side effects can vary depending on the specific drug you are taking. The most common side effects of immunosuppressants in general include:¹

• Increased risk of infection
• Nausea
• Vomiting

Other side effects may be more common to one type of immunosuppressant than another. For example, side effects common to steroids include:¹

• Cushing’s syndrome (redistribution of body fat)
• Cataracts
• Avascular necrosis (bone tissue death) in the hips and knees
• High blood pressure
• Insomnia
• Diabetes
• Osteoporosis (weakening of bones)
• Skin thinning and easy bruising
• Weight gain due to increased appetite

None of these drugs are likely to cause all of these side effects. The chance of a side effect depends on many factors, including the dose you take and the type of immunosuppressant you take.

These are not all the possible side effects of MG treatments. Talk to your doctor about what to expect or if you experience any changes that concern you during treatment with immunosuppressant drugs.

When are they prescribed?

Immunotherapies are sometimes used in combination with steroids. Other times they are used to replace steroids. Generally these drugs are given to people with MG who:¹

• Need more symptom control than steroids are providing
• Need to lower the amount or stop taking steroids altogether due to side effects

Nonsteroidal immunotherapies are more difficult to give to the patient and are more expensive than steroids. Each has different potential benefits and side effects.

Certain immunosuppressants are known to work better in some types of people with myasthenia gravis than others. For example:¹

• Azathioprine may be used in pregnant people with MG if acetylcholinesterase inhibitors and steroids do not fully control muscle weakness
• Older adults, especially those with kidney issues, may be given azathioprine or mycophenolate mofetil, instead of steroids
• Cyclosporine is usually not given to older adults with kidney issues due to potential kidney issues
• Rituximab and eculizumab may be used in people with refractory MG or severe disease

There are many other immune system drugs that may be prescribed off-label to people with MG. The theory is that these other immunosuppressants work for other autoimmune conditions and may also work for people with MG.¹

Other things to know

Most people with MG need to take a combination of an acetylcholinesterase inhibitor, a steroid, an immunotherapy drug, and/or a biologic. This is partly because these drugs attack muscle weakness in different ways and work at different speeds. And like everything else about myasthenia gravis, every person responds to a different combination of medicines.¹

For example, an acetylcholinesterase inhibitor begins to improve muscle weakness in 10 to 15 minutes, while plasma exchange takes days. A steroid begins to take effect in 2 to 3 weeks, and an immunosuppressant may take 6 months to a year. Thymectomy surgery improves symptoms after years.¹

While taking immunosuppressants, it is important to avoid crowds and people with contagious diseases and wash your hands often.¹

Other immune system treatments for MG

Two other treatments that help suppress the immune system include plasma exchange and IVIG (intravenous immune globulin). Plasma exchange is also called plasmapheresis. These treatments may be used to give steroids and other immune system drugs time to begin working.¹

Before beginning treatment for myasthenia gravis, tell your doctor about any other drugs, vitamins, or supplements you are taking. This includes over-the-counter drugs.